WO2006107049A1

WO2006107049A1 - Mask inspecting method and mask inspecting apparatus

Info

Publication number: WO2006107049A1
Application number: PCT/JP2006/307145
Authority: WO
Inventors: Masashi Ataka; Jun Nitta; Katuyuki Takahashi; Norimichi Anazawa; Ken-Ichi Kobayashi; Akira Yonezawa
Original assignee: Holon Co, .Ltd
Priority date: 2005-04-05
Filing date: 2006-04-04
Publication date: 2006-10-12
Also published as: JPWO2006107049A1

Abstract

[PROBLEMS] To automatically perform judgment as to a residue at a bottom portion of a contact hole, an adhesive residue or risen residue of a foreign material, judgment as to a growing foreign material, inspection of pattern roughness, inspection of a rounding shape of a pattern and inspection of pattern OPC, by image, by using an inspection method and a mask inspecting apparatus which are provided for performing inspection by generating an enlarged image of a surface of a mask, based on an emitted or absorbed signal obtained when the surface of the mask is surface-scanned with an electron beam by using a scanning electron microscope. [MEANS FOR SOLVING PROBLEMS] The mask inspecting method is provided with a step of acquiring an image of a mask region to be inspected; a step of obtaining a signal strength at a center of the acquired image and that at the periphery of the acquired image; and a step of comparing a ratio between both of the obtained signal strengths with a reference value, and judging the existence of the residue at the bottom portion of the contact hole, existence of the risen foreign material or the existence of the growing foreign material.

Description

Specification

Mask inspection method and mask inspection apparatus

Technical field

The present invention relates to an enlarged image of the surface of a mask based on a signal emitted or absorbed at that time by scanning the surface of the mask with an electron beam using a scanning electron microscope. The present invention relates to a mask inspection method and a mask inspection apparatus for generating and inspecting. Background art

Conventionally, a mask pattern defect inspection apparatus for a semiconductor LSI has performed pattern inspection by irradiating the mask with light. Defects are detected by converting the reflected or transmitted light when the light is applied to the mask into electrical signals and processing them. This process is automatically performed by the inspection apparatus. After the defect is detected, the stage on which the mask is mounted is moved to the coordinate position of the detected defect, and the operator confirms the defect on the mask. Judgment is made by distinguishing between dust on the part and metal film (residue). Judge that the dust can be removed in the final cleaning process and leave it to the cleaning process. On the other hand, the metal film (residue) on the glass part is removed by FIB (focused ion beam device) or laser device. Here, the method of distinguishing between dust and residue by the worker is that the residue of chrome metal, which is a light shielding mask material formed on the mask, appears black in transmitted light and shines white in reflected light. On the other hand, in the case of trash, the force that appears black in the transmitted light is the same as the chrome metal residue. In the reflected light, the trash is not as bright as the chrome metal residue. Separated. Further, when a mask material other than chromium metal is used, the same applies to a mask using chromium oxide and a phase shift mask using molybdenum silicide material, for example.

Disclosure of the invention

Problems to be solved by the invention

In recent years, the pattern size of LSI masks has been reduced, and in conventional inspections using light (inspection using an optical microscope, etc.), fine residues and dust, and residues at the bottom of contact holes There was a problem that they could not be recognized separately. Also, the mask dust residue There are so many places to be inspected, and it becomes impossible for the operator to make judgments. The targets of this inspection include not only the final mask product from which the resist has been stripped, but also the half mask product with a resist pattern that has been subjected to a development process during the patterning process of the mask.

Means for solving the problem

[0004] In order to solve these problems, the present invention acquires an image of a portion to be detected by a mask using a scanning electron microscope, and the signal intensity between the outside and inside of the contact hole on the acquired image. Automatically determine the presence or absence of residue at the bottom of the contact hole, determine the signal strength of the center and periphery of the foreign material on the image, and automatically determine the adhesive residue or floating residue of the foreign material on the image. For areas with and without a pattern, the signal strength is increased from the average signal strength by a predetermined signal strength !, is there! /, Is weak !, the area is detected to automatically determine growth foreign matter, and the roughness of the mask pattern on the image. Automatic inspection of rounded shape and OPC. Also, not only the final mask product but also the mask manufacturing process, for example, half mask product in the resist pattern state, a resist pattern is applied using a technique such as applying a charged particle acceleration voltage at a low pressure. Judge the unnecessary remaining state and the lack of resist pattern. In particular, it is effective to see the state of resist remaining or not in the hole shape part of the contact hole pattern.

The invention's effect

[0005] The present invention acquires an image of a portion to be inspected of a mask using a scanning electron microscope, and the presence or absence of a residue at the bottom of a contact hole, an adhesive residue of a foreign substance, or a floating surface on the acquired image. It is possible to automatically perform residue determination, growth foreign matter determination, pattern roughness inspection, pattern rounding shape inspection, and pattern OPC inspection. BEST MODE FOR CARRYING OUT THE INVENTION

[0006] In order to solve these problems, the present invention acquires an image of a portion to be detected by a mask using a scanning electron microscope, and the signal intensity between the outside and inside of the contact hole on the acquired image. Automatically determine the presence or absence of residue at the bottom of the contact hole, determine the signal strength of the center and periphery of the foreign material on the image, and automatically determine the adhesive residue or floating residue of the foreign material on the image. Average confidence about where the pattern is The signal intensity is strong by the predetermined signal intensity !, there is !, is weak !, the area is detected to automatically determine the growth foreign matter, and the mask pattern roughness, rounded shape, and OPC are automatically inspected on the image. .

Example 1

FIG. 1 shows a block configuration diagram of the present invention.

In FIG. 1, mask 1 is an LSI mask. For example, a chrome metal film is formed on a glass substrate, and a predetermined LSI pattern is exposed and developed. Here, the mask is fixed to the mask holder 2 for easy handling.

[0008] The mask holder 2 has a mask 1 fixed thereto.

The magazine 3 is a box for carrying a plurality of mask holders 2 to which the mask 1 is fixed and carrying it. The magazine 3 is a carrying box that is sealed so that no external force can enter the magazine 1.

[0009] The preliminary exhaust chamber 4 is a room (sealed space) for taking out the preliminary exhaust by inserting the mask holder 2 with the mask 1 fixed, taken out from the magazine 3.

[0010] The main chamber 5 is a state in which the mask holder 2 to which the mask 1 is fixed is placed on the stage 6, and here, the electron beam beam narrowed down from the electron optical system 6 is planarly scanned, and at that time, A secondary electron, reflected electron, light, etc., whose surface force has been released from the mask 1 is detected by a known detector (not shown) and modulated on its brightness (for example, secondary electrons) on the display. This is a room for displaying (image) (vacuum room of 10-6mmTorr or less).

The stage 6 is a mechanism for placing the mask holder 2 on which the mask 1 is fixed and moving it to a predetermined position in any direction (for example, the X direction and the Y direction) with high accuracy.

[0012] The electron optical system 7 generates a charged particle beam such as an electron beam, scans the surface of the mask 1 while irradiating the focused and finely focused beam on the surface of the mask 1, and generates 2 Secondary electrons, etc. are detected, a high-magnification image (for example, secondary electron image) is displayed on a display (not shown), a fine pattern on mask 1 is enlarged, and patterns at many specified positions are inspected. This is for automatic measurement. [0013] The personal computer 11 is a computer system that performs various controls according to a program. Here, the personal computer 11 mainly performs various controls for automatically determining the defect of the mask 1, and includes an image display unit 12, a measurement unit. 13, determination means 14, reference table 15, CAD data DB 16, result data table 17, display device 18, and input device 19.

The image display means 12 displays an enlarged image (for example, a secondary electron image) of the surface of the mask 1 on the screen of the display device 18.

[0015] The measuring means 13 measures the brightness and distance of the position of the pattern designated on the image.

[0016] The determination unit 14 determines a defect based on the brightness, distance, and the like at a predetermined position of the pattern measured by the measurement unit 13 (see FIGS. 2 to 16).

[0017] The reference table 15 is obtained by previously obtaining and registering various criteria for determining defects on an image (see FIGS. 2 to 16).

The CAD data DB 16 is original CAD data of a pattern formed on the mask 1.

The result data table 17 stores the result of the defect determined by the determination means 14.

The display device 18 displays a secondary electron image of the pattern of the mask 1 and the like.

The input device 19 is a device for an operator to input various instructions, and is a keyboard, a mouse, or the like.

Next, the overall defect determination will be described with reference to the flowchart of FIG.

FIG. 2 shows a flowchart (overall) for explaining the operation of the present invention.

In FIG. 2, S1 moves the mask coordinates to the defect inspection apparatus. This is because the coordinates of the mask (for example, the coordinates of the place where the defect appears to be present by comparing the pattern on the mask with the pattern of the CAD data using a device such as an optical microscope not shown) are sent to the defect inspection apparatus according to the present invention. Move the (coordinate of the mask found in advance) and notify the coordinates of the location that seems to be defective.

[0022] In S2, the operator confirms (finds) the pattern coordinates (pattern coordinates on the mask) of important points of interest with an optical microscope and notifies them. [0023] By receiving the above notification, the defect inspection apparatus according to the invention of the present application has coordinates such as coordinates that are considered to have defects on the mask 1 for each mask 1 and coordinates that need to be checked for the presence or absence of defects. This means that the coordinates (pattern coordinates) of the defect determination target have been received.

[0024] S3 inspects. This is based on the coordinates on the mask 1 notified by Sl and S2, and a secondary electron image is acquired and the defect is determined by referring to FIGS. 3 to 16 described later. The determination result of the defect is stored in the result data table 17.

[0025] In S4, the defect type is confirmed from each table. This is done by referring to the result data table 17 (table) in which the judgment results are stored according to the procedure in FIGS. 2 to 16 of S3, and confirming the type of defect for each coordinate on the mask 1.

[0026] S5 determines a defect. After checking the type of defect in Fig. 4, the decision is made whether the defect can be cleaned or can be corrected by FIB.

[0027] As described above, the defect inspection for the pattern to be inspected on the mask 1 will be described later.

From step 3 to Fig. 16, it is possible to make judgments such as cleaning and correction based on the result of the defect judgment. In the following, the inspection of S3 will be described in detail with reference to Figs.

Next, in accordance with the order of the flowchart of FIG. 3, with reference to FIG. 4, the presence / absence inspection of the bottom of the contact hole will be described in detail with reference to FIG.

FIG. 3 is a flowchart for explaining the operation of the present invention (part 1: contact hole).

In FIG. 3, S11 displays an image. This is shown, for example, in FIG.

Fig. 2 shows a secondary electron image of a contact hole to be inspected for defects specified on the mask 1

Displayed on the screen of 1 display device 18.

[0030] S12 measures the brightness of A. This measures the brightness (signal intensity A) of the chrome metal part around the contact hole on the image in Fig. 4 (d).

[0031] S13 measures the brightness of B. This measures the brightness B (signal intensity B) of the bottom part of the inside of the contact hole on the image in Fig. 4 (d).

[0032] S14 calculates BZA. Find the ratio (BZA) of B measured in S13 and A measured in S12.

In step S15, a threshold value T corresponding to the aspect ratio is obtained. This is the image of (d) in Fig. 4 (contour The threshold value T corresponding to the aspect ratio of the tato hole is obtained by referring to the reference table 15 created in advance in FIG. 4 (e) (for example, when the aspect ratio is 2.5 to 3.5) Find T = 0.43).

[0034] S 16 determines whether ΒΖΑ≥Τ. It is determined whether Β / Β obtained in S 14 is equal to or greater than the threshold Τ corresponding to the aspect ratio obtained in S 15. In the case of YES, it is determined that there is chromium (metal residue) at the bottom where the signal strength of the bottom force of the contact hole is large, and the product is judged as defective. On the other hand, in the case of NO, it is determined that there is no chromium (metal residue) at the bottom where the signal intensity from the bottom of the contact hole is small, and is judged as non-defective.

[0035] As described above, the signal strength B of the bottom force of the contact hole and the signal strength A of the edge are measured, and the threshold value T corresponding to the aspect ratio of the contact hole is obtained from the reference table 15, When BZA is larger than threshold value T, the aspect ratio of the contact hole changes by judging that it is defective with chrome (metal residue) at the bottom and judging that it is non-defective with no chrome (metal residue) at the bottom. However, it is possible to automatically determine the presence or absence of metal residue at the bottom of the hole with good accuracy.

FIG. 4 shows an explanatory diagram (part 1) of the present invention.

FIG. 4A shows a schematic diagram of a side cross-section of a contact hole on the mask.

[0037] FIGS. 4 (b) and 4 (c) are schematic side cross-sectional views in which the contact hole in FIG. 4 (a) is enlarged. Here, both have the same aspect ratio (ratio b / a where depth b of contact hole is equal to diameter a). (A) shows a non-defective product without chromium (metal residue) at the bottom of the contact hole, and (b) shows a defective product with chromium (metal residue) at the bottom of the contact hole.

[0038] Fig. 4 (d) shows a plane scan while irradiating an electron beam from the upper part of the contact hole in Fig. 4 (b) and (c), and detects the secondary electrons emitted at that time. The secondary electron image generated in this way is shown schematically. At this time, let B be the signal strength that detects the partial force at the bottom of the contact hole, and let A be the signal strength that also detects the partial force of the surrounding chromium. When the B 14 is larger than the threshold T obtained by referring to the reference table 15 in FIG. 4 (e) based on the aspect ratio (bZa) by the S 14 force and S 18 in FIG. It is possible to judge a defective product (with chrome at the bottom) and a non-defective product (without chrome at the bottom) when it is small. FIG. 4E shows an example of a reference table. The reference table 15 is used for determining that the bottom portion of the contact hole has chromium when the aspect ratio (bZa) is changed and the strength (ratio) of the detected signal exceeds the threshold value. The threshold (reference value) is obtained by experiment. Here, when the ratio (bZa) is less than the threshold, it is a small signal that is a signal from the glass of the mask (substrate) that chrome is exposed to, and when the ratio is greater than the threshold, it is a large signal from the chromium (metal residue). It represents. The reference table 15 shown in the figure is an example when the mask substrate is made of glass, and is used for other materials (or when the secondary electron image acquisition conditions (for example, acceleration voltage) have changed). The threshold T is a value that can distinguish the signal from the substrate at the bottom of the contact hole hole (mask substrate) and the signal from the metal residue at the bottom of the contact hole hole by changing the aspect ratio. Find and set by experiment.

Next, in accordance with the order of the flowchart of FIG. 5, with reference to FIG. 6, a detailed description will be given of the presence / absence of residual resist at the bottom of the contact hole under the configuration of FIG.

FIG. 5 is a flowchart for explaining the operation of the present invention (part 1: contact hole 2).

In FIG. 5, S111 displays an image. This is because, for example, as shown in FIG. 6B, which will be described later, the contact hole to be inspected for defects specified on the mask (semi-mask product) 1 is designated.

The secondary electron image is displayed on the screen of the display device 18 in FIG.

S121 measures the brightness of A. This measures the brightness (signal intensity A) of the resist pattern around the contact hole on the image in Fig. 6 (b).

[0043] S131 measures the brightness of B. This is because the bottom of the contact hole inside the hole (originally metal or molybdenum silicide force) in the image of Fig. 6 (b), there is no resist residue (residue) or resist residue. Brightness of the metal (chrome) part shown

Measure B (signal strength B).

[0044] S141 calculates BZA. Obtain the ratio (BZA) of B measured in S131 and A measured in S121.

[0045] In S151, a threshold value T corresponding to the aspect ratio is obtained. The threshold T corresponding to the aspect ratio of the image (contact hole) in FIG. 6B is obtained by referring to the reference table 15 created in advance in FIG. 6C (for example, the threshold T = 0. Here is the contour When there is a resist residue at the bottom of the hole in the hole, the bottom is very small compared to chromium, and in the experiment, T = 0. When it was 2 or less, it was used as a criterion for the presence or absence of residual resist on the bottom. If there is a resist type whose aspect ratio is related to threshold value Τ, the threshold value corresponding to the aspect ratio is obtained by experiment and set.

[0046] S161 determines whether ΒΖΑ≥Τ. It is determined whether or not ΒΖΑ determined in S141 is equal to or greater than the threshold Τ corresponding to the aspect ratio determined in S151. In the case of YES, it is judged that the original chromium is present at the bottom where the signal strength of the bottom force of the contact hole is large, and the product is judged as good. On the other hand, in the case of NO, the signal intensity from the bottom of the contact hole is small, and there is residual resist (residue) on the bottom (the bottom force of the contact hole of the half-mask product to be inspected above the original chromium) If there is a resist residue, the product is judged as defective.

[0047] As described above, the signal strength B of the bottom force of the contact hole and the signal strength A of the edge are measured, and the threshold value T corresponding to the aspect ratio of the contact hole is obtained from the reference table 15, When BZA is smaller than threshold T, there is resist residue at the bottom (there is resist residue on the original chrome) and it is judged as defective, and when it is larger, contact is judged as good without resist residue at the bottom. Even if the aspect ratio of the hole changes, the presence or absence of a resist residue (resist residue on the original chromium) at the bottom of the hole can be automatically determined with high accuracy.

FIG. 6 shows an explanatory diagram (part 1 2) of the present invention.

Fig. 6 (a) shows a schematic side sectional view of the contact hole on the mask (half mask product). Here, the aspect ratio is the ratio bZa when the contact hole depth b and diameter a are set. The contact hole on the left side of Fig. 6 (a) shows a non-defective product with no resist residue on the bottom (chrome), and the contact hole on the right side of Fig. 6 (a) has resist residue on the bottom (chrome). Indicates the state of the defective product.

[0049] (b) in FIG. 6 is a plane scan while irradiating an electron beam from the upper part of the left and right contact holes in FIG. 4 (a), and detects the secondary electrons emitted at that time. The secondary electron image generated in this way is shown schematically. At this time, the bottom part of the contact hole (original black Signal strength detected from the resist or resist residue) is B, and signal strength detected from the surrounding resist is A. When B ZA is smaller than the threshold value T obtained by referring to the reference table 15 in FIG. 6 (c) based on the aspect ratio (b / a) by S141 to S181 in FIG. It is possible to determine that the product is defective (having a resist residue at the bottom) and that it is good (when there is no resist residue at the bottom and chromium).

FIG. 6C shows an example of a reference table. When the aspect ratio (bZa) is changed, the reference table 15 determines that there is a resist residue at the bottom when the detected signal strength (ratio) is below the threshold. The threshold value (reference value) for this is determined by experiment. Here, when the bottom of the contact hole is a resist residue, in the experiment, BZA, which is not much related to the aspect ratio, was 0.2 or less. Since it was judged as a defective product, the threshold value T was uniformly set to 0.2. In the part described as chrome (bottom), as the aspect ratio (bZa) changes, the signal for detecting the original chrome force at the bottom changes as shown, and the BZA at that time is as shown in the figure. To change. In this experiment, if there is a resist residue on the original chrome at the bottom, the signal strength B detected for the resist residue force decreases rapidly, and the bottom is the original good chrome and defective products. To automatically determine the resist residue, the threshold value T = 0.2, which is not associated with the aspect ratio in the illustrated reference table 15, as shown in (1) in the figure. Two. You may set a threshold value that depends on the aspect ratio.

Next, in accordance with the order of the flowchart of FIG. 7, with reference to FIG. 8, the inspection of the floating foreign matter or adhesive foreign matter in the pattern will be described in detail with reference to FIG.

FIG. 7 is a flowchart for explaining the operation of the present invention (Part 2: Lifting).

In FIG. 7, S21 displays an image. This is because, for example, secondary electrons emitted upward when an electron beam is scanned in a plane from the upper direction shown in FIGS. 8A and 8B to be described later are detected and coordinates are designated on the mask 1. A secondary electron image of the pattern to be inspected for defect inspection is displayed on the screen of the display device 18 in FIG.

[0053] In S22, the central brightness A1 (or B1) is measured. This measures the brightness A1 (or B1) of the center of the pattern on the image in Fig. 8 (a) (or (b)). [0054] In step S23, ambient brightness A2 (or B2) is measured. This measures the brightness A2 (or B2) around the pattern on the image in Figure 8 (a) (or (b)).

[0055] S24 calculates the ratio of A2ZA1 or B2ZB1.

S25 determines whether A2 / A1 (or B2ZB1) ≥T2. This is to determine whether the ratio Α2 ZA1 (or B2ZB1) calculated in S24 is a reference value Τ2 (eg, Τ = 0.5 in FIG. Here, of A2ZA1 in Fig. 8 (a) or B2ZB1 in Fig. 8 (b), T2 = larger than 0.5! / ヽ (YES in S25) is the center and periphery of Fig. 8 (b) Are both adhered to the mask. In S26, it is determined as an adhesive residue, and it is determined as a defective product that is difficult to remove from the mask. On the other hand, if T2 = 0.5 (NO in S25), the center of (a) in Fig. 8 is found to be in close contact and the periphery is lifted. (Floating residue (good product)).

[0056] As described above, the threshold value T2 for measuring the signal strength A1 (B1) at the center of the pattern and the signal strength A2 (B2) around the pattern and determining the adhesion and lifting of the pattern from the reference table 15 (not shown). When A2 / A1 (B2 / B1) is greater than threshold T2, the adhesive residue is judged as a defective product, and when it is small, the lifted residue is judged as a non-defective product. Presence / absence can be automatically determined with good accuracy.

FIG. 8 shows an explanatory diagram (part 2) of the present invention.

Fig. 8 (a) shows the pattern center on the mask surface in close contact with the surrounding area. Assume that the signal intensity of the center secondary electron image at this time can be measured as A1, and the signal intensity at the periphery can be measured as A2. When the periphery rises, the ratio A2ZA1 between the central brightness A1 and the peripheral brightness A2 becomes small, for example, 0.5 or less.

FIG. 8B shows a state in which the center of the pattern on the mask surface is in close contact, and the force and the periphery are also in close contact. Assume that the signal intensity of the central secondary electron image at this time can be measured as B1, and the signal intensity at the periphery as B2. When both the center and the periphery are in close contact with the substrate, the brightness B1 at the center and the brightness B2 at the periphery are almost the same, and the ratio B2ZB1 becomes large, for example, 0.5 or more.

FIG. 8C shows an example of resist foreign matter and thin film foreign matter. The example shown in the figure shows an example where there is a resist or thin film particle between the pattern and the pattern. When this is enlarged, (c-1) Or (c 2).

FIG. 8 (c 1) shows an example in which the periphery is raised. The example (resist foreign matter, thin-film foreign matter) in which the periphery has risen corresponds to (a) in Fig. 8, and is an example in which NO is determined in S25 in Fig. 5 (A2ZA1 is the threshold T2 (for example, 0 5) In the following case), it is determined that the periphery is lifted up and is relatively easy to peel off, so it is judged as a non-defective product (S27 in Fig. 7).

FIG. 8 (c 2) shows an example in which the center and the periphery are in close contact. An example where the center and the periphery are in close contact

(Resist foreign matter, thin-film foreign matter) corresponds to (b) in Fig. 6 and is an example when S25 YES in Fig. 5 is already determined (when B2ZB1 is greater than or equal to threshold T2 (eg 0.5) It is determined that the center and the periphery are in close contact with each other, and the bottom of the foreign matter is in close contact with the substrate, so that it is difficult to peel off during the cleaning process. Fig. 7 S26).

Next, in accordance with the order of the flowchart of FIG. 9, with reference to FIG. 10, the inspection for the presence or absence of a growth foreign substance will be described in detail with the configuration of FIG.

FIG. 9 is a flowchart for explaining the operation of the present invention (part 3: growth foreign matter).

In FIG. 9, S31 displays an image. This is because, for example, as shown in FIGS. 10A and 10B, which will be described later, the secondary electrons emitted when the electron beam is scanned in a plane are detected, and the pattern of the defect inspection target coordinates designated on the mask 1 The secondary electron image is displayed on the screen of the display device 18 in FIG.

[0064] S32 extracts a noise component. This is because, for example, the part (the substrate part of the mask or the part without the fine pattern inside the large pattern) is not shown in (c) of FIG. The average value N1 of the noise component shown is extracted.

[0065] S33 sets a reference value. For example, when the average value of the noise component in (c) of FIG. 10 is N1, the reference value (N1 + α) that is slightly larger than the fluctuation amount of the noise component and larger than the illustrated α and the smaller reference value than the illustrated α Calculate the value (N1-α) and set it as the reference value.

[0066] In the case of the reference value (N1 + α), S34 extracts an image exceeding the reference value (N1 + α). For example, the image shown in (c) in Fig. 10 (c) that exceeds the signal strength (N1 + α) on the image is extracted.

[0067] In the case of the reference value (N1-α), S35 extracts an image having the reference value (N1-α) or less. The For example, in FIG. 10 (c), an image of the figure (mouth) below the signal intensity (N1-α) is extracted on the image.

[0068] In S36, it is determined whether there is an area of a predetermined pixel or more. This is to determine the force of the image extracted in S34 and S35 having a region of a predetermined pixel or more (for example, a region of 100 nm2 or more). In the case of YES, it is judged as a growth foreign substance in S37 as a defect because it is in the extent of hindering the mask (or the possibility of growing to a large extent). In the case of NO, it is determined that there is no growth foreign substance in S38, and it is determined as good.

[0069] As described above, the noise component N1 is extracted on the mask substrate (or on a large pattern) to extract an image of (N1 + α) or more, or an image of (N1 – α) or less, and a predetermined region or more. In this case, it is possible to determine that the foreign substance is a growth foreign substance and to automatically determine that it is defective and accurate.

FIG. 10 shows an explanatory diagram (part 3) of the present invention.

Fig. 10 (a) shows an example of an image of growth foreign matter (none), and Fig. 10 (b) shows an example of an image of growth foreign matter (existence). The growth foreign substance is a glass part or a chromium part or a phase shift part without a pattern, and the growth foreign substance part is characterized by being dim. Taking advantage of this feature, the noise component N1 is extracted according to the flowchart of FIG. 7 described above, the predetermined value α is determined by experiment, and images of (Nl + α) or more and images of (N1−α) or less are extracted. An image of a predetermined area or more is determined as a growth foreign substance and determined as a defective product.

[0071] (c) of FIG. 10 shows a signal example. This shows an example in which the signal intensity is plotted on the vertical axis for one line of the image when the growth foreign substance shown in FIG. 10 (b) is present. In this signal example, the average value of the noise component is N1 as shown. a is a value obtained by experiment, and is a value for identifying the noise component and the dark growth foreign substance in FIG. 10 (b) and extracting the growth foreign substance. In the figure, the part (i) is extracted as an image of (Nl + o or higher), and the part (mouth) is extracted as an image of (N1−α) or lower.

Next, in accordance with the order of the flowchart of FIG. 11, the inspection for the presence / absence of roughness will be described in detail with reference to FIG. 12 under the configuration of FIG.

FIG. 11 is a flowchart for explaining the operation of the present invention (part 4: roughness).

In FIG. 11, S41 displays an image. This is because, for example, as shown in FIGS. 12A and 12B, which will be described later, secondary electrons emitted when the electron beam is scanned in a plane are detected and the mask 1 is detected. 2 is displayed on the screen of the display device 18 shown in FIG.

[0074] S42 measures the roughness R of the linear portion of the pattern. As shown in Fig. 12 (b), the roughness R measures the deviation R from the straight line between the target area (here, LO (eg 50 µm)) for the edge of the specified pattern.

[0075] S43 determines whether R≥RO. Here, RO is a value that becomes a defect when the roughness shown in FIG. If YES, the roughness R of the obtained pattern is larger than the reference value RO, and the linearity is poor. On the other hand, in the case of N 2 O, the roughness R of the obtained pattern is smaller than the reference value RO, and the linearity is good.

[0076] As described above, the roughness R of the linear portion of the mask pattern is measured. If the roughness R is larger than the reference value RO, the linearity is bad and judged as a defective product, whereas if it is smaller than the reference value RO, It is possible to determine that the linearity is good and is a non-defective product, and to automatically determine with good accuracy.

FIG. 12 is an explanatory diagram (part 4) of the present invention.

FIG. 12 (a) shows an example of the straight line portion of the pattern.

FIG. 12B is a schematic diagram in which a portion indicated by a dotted line O in FIG. 12A is enlarged. When the pattern on the mask is formed like a solid line, each roughness (pattern linearity) R is measured on the image for each target region LO (for example, 50 nm). Then, for each measured target region LO, the roughness R is determined according to the flow chart shown in FIG. 11, and the roughness R is larger than the reference value RO and sometimes the linearity is poor. When a defective product is small, the linearity is good and a good product can be automatically determined.

Next, in accordance with the order of the flowchart of FIG. 13, with reference to FIG. 14, the inspection for the presence or absence of a rounded shape will be described in detail with the configuration of FIG.

FIG. 13 is a flowchart for explaining the operation of the present invention (No. 5: rounding shape).

In FIG. 13, S51 displays an image. For example, as shown in FIG. 14 to be described later, secondary electrons emitted when the electron beam is scanned in a plane are detected, and a secondary electron image of a pattern to be inspected for defects specified on the mask 1 is obtained. It is displayed on the screen of the display device 18 in FIG. In S52, the intersection point P is obtained by extending the pattern straight line in the X and Y directions. As shown in the image of Fig. 14, this is obtained by extending each side of the corner of the pattern to obtain the intersection P (coordinate of the intersection P).

In S53, the shortest distance M between P and the actual image is obtained. As shown in FIG. 14, the shortest distance M between the intersection point P obtained in S52 and the pattern on the actual image is obtained.

[0083] S54 determines whether M≥MO. Here, MO is a value that becomes a defect when the rounded shape shown in FIG. In the case of YES, it is determined that the corner of the pattern whose rounded shape value M is larger than the reference value MO is significantly rounded. On the other hand, in the case of NO, it is found that the corner of the pattern in which the obtained rounded shape value M is smaller than the reference value M0 is formed beautifully, so it is determined as non-defective in S56.

[0084] As described above, the value M of the rounded shape of the corner of the mask pattern is measured, and when it is larger than the reference value R0, the linearity is bad and judged as a defective product, whereas when it is smaller than the reference value R0 The linearity is good and it is judged as a non-defective product, and automatic judgment with good accuracy can be made.

FIG. 14 is an explanatory diagram (part 5) of the present invention.

FIG. 14 shows an example of a rounded pattern image. The rounded image is the corner of the pattern as shown. Although it is almost a right angle on the CAD data, the pattern corners are rounded as shown in the image after the pattern is actually exposed and developed on the mask based on the CAD data. In this case, the straight line is extended in the X and Y directions of the pattern to obtain the intersection P (find the corner in the original CAD data), and the intersection P and the actual solid line shown in the figure Measure the shortest distance M from the image. Then, when the measured shortest distance M is smaller than the reference value M0 (in the case of NO in S54 in FIG. 13 described above), it is determined that the rounded shape is good and is determined to be a non-defective product (S56 in FIG. 13).

Next, in accordance with the order of the flowchart of FIG. 15, with reference to FIG. 16, the OPC pass / fail inspection will be described in detail under the configuration of FIG.

FIG. 13 is a flowchart for explaining the operation of the present invention (part 6: OPC (optical pattern proximity effect correction)).

In FIG. 15, S61 displays an image. This is illustrated, for example, in FIG. Fig. 1 shows the secondary electron image of the area containing the defect inspection target (OPC) pattern specified on mask 1 by detecting the secondary electrons emitted when the electron beam is scanned in plane. Display on the screen of device 18.

[0089] S62 extracts an image of the OPC portion with reference to the CAD data. This extracts the actual image of the OPC part from the image displayed in S61 based on the CAD data. For example, the figure

As shown in Fig. 16 (c) or (d), the part of the actual image corresponding to the OPC part is extracted.

[0090] S63 measures the X direction dimension CX and the Y direction dimension CY of the OPC. This is an image of the OPC portion extracted in S62, for example, in the image of (c) or (d) in FIG. 16, the X-direction size CX and the Y-direction size CY of the OPC portion are measured.

[0091] S64 determines whether CX≥CXS or CY≥CYS. This is O measured by S63

PC part

• X direction dimension CX is equal to X direction reference value CXS!

• Determine whether Y-direction dimension CY is equal to or greater than Y-direction reference value C YS, or is NO. If either is smaller, NO is determined and a defective product is determined in S66. On the other hand, if YES, the size of the OPC part is sufficiently large.

[0092] As described above, the dimensions CX and CY in the X direction and Y direction of the OPC part of the mask are measured, and when one of them is smaller than the reference values CXS and CYS, it is determined as defective, and both are lower than the reference values. If it is too large, it is judged as a non-defective product, and OPC (Optical Pattern Proximity Effect Correction) can be automatically judged with high accuracy.

FIG. 16 shows an explanatory diagram (No. 6) of the present invention.

FIG. 16 (a) shows an example of an actual mask image, and FIG. 16 (b) shows an example of a CAD data image. Here, the X direction dimension of the OPC part on the CAD data image is CXS, and the Y direction dimension is CY S.

[0094] FIG. 16 (c) shows an example in which the dimension of the OPC portion is sufficiently large. In this case, the X-direction dimension of the OPC part on the image is CX and the Y-direction dimension is CY, both of which are reference values, here the reference value is • CAD data X direction dimension CXS X 2/3 = CXS

• Y dimension of CAD data CYS X 2/3 = CYS

And CX≥CXS and CY≥CYS (YES in S64, S65 in Fig. 15).

[0095] FIG. 16 (d) shows an example in which the size of the OPC portion is small. In this case, the X-direction dimension of the OPC part on the image is CX and the Y-direction dimension is CY, both of which are the reference values, here the reference value is

• CAD data X direction dimension CXS X 2/3 = CXS

• Y dimension of CAD data CYS X 2/3 = CYS

It shows that CX≥CXS and CY≥CYS (NO in S64, S66 in Fig. 15). Industrial applicability

[0096] The present invention acquires an image of a portion to be inspected of a mask using a scanning electron microscope, and the presence or absence of a residue at the bottom of a contact hole, an adhesive residue of a foreign substance, or a floating surface on the acquired image. It is possible to automatically perform residue determination, growth foreign matter determination, pattern roughness inspection, pattern rounding shape inspection, and pattern OPC inspection. Brief Description of Drawings

FIG. 1 is a block configuration diagram of the present invention.

FIG. 2 is a flowchart for explaining the operation of the present invention (overall).

FIG. 4 is an explanatory diagram (part 1) of the present invention.

FIG. 6 is an explanatory diagram (part 12) of the present invention.

FIG. 8 is an explanatory diagram (part 2) of the present invention.

FIG. 10 is an explanatory diagram (part 3) of the present invention.

FIG. 12 is an explanatory diagram (part 4) of the present invention. FIG. 13 is a flowchart explaining the operation of the present invention (part 5: rounded shape). FIG. 14 is an explanatory diagram (part 5) of the present invention.

FIG. 15 is a flowchart (part 6: OPC) for explaining the operation of the present invention.

FIG. 16 is an explanatory diagram (part 6) of the present invention.

Explanation of symbols

1: Mask

2: Mask Honoreda

3: Magazine

4: Preliminary exhaust chamber

5: Main chamber

6: Stage

7: Electron optics

11: PC

12: Image display means

13: Measurement means

14: Judgment means

15: Criteria table

16: CAD data

17: Result data table

18: Display device

19: Input device

Claims

The scope of the claims

[1] A scanning electron microscope is used to scan the surface of the mask with an electron beam and generate an enlarged image of the mask surface based on the signal emitted or absorbed at that time. The inspection method to perform

Obtaining an image of an area to be inspected on the mask;

The step of obtaining the signal intensity at the center of the acquired image and the signal intensity at the periphery, and comparing the ratio of the obtained signal intensity with the reference value, the presence or absence of residue at the bottom of the contact hole, the rise of foreign matter Steps to determine the presence or absence of growth foreign matter and

A mask inspection method comprising:

[2] A scanning electron microscope is used to scan the surface of the mask with the electron beam and generate an enlarged image of the mask surface based on the signal emitted or absorbed at that time. The inspection method to perform

Obtaining an image of an area to be inspected on the mask;

Measure the deviation of the linear force for the straight part of the pattern on the acquired image, measure the distance between the rounded shape of the corner of the pattern and the rounded shape of the corner, or the size of the minute pattern. Measuring step;

Determining pass / fail based on the measured value;

A mask inspection method comprising:

[3] obtaining a signal intensity B at the center of the contact hole of the acquired image and a signal intensity A of a portion forming the contact hole around the contact hole;

The signal strength ratio BZA of the two obtained above is compared with a reference value. When the ratio BZA is larger than the reference value, it is determined that there is a residue at the bottom of the contact hole. Determining that there is no residue at the bottom of the

The mask inspection method according to claim 1, further comprising:

[4] obtaining a signal intensity B at the center of the contact hole of the acquired image and a signal intensity A of a portion forming the contact hole around the contact hole;

Compare the signal strength ratio BZA of the two obtained with the reference value, and the ratio BZA is the reference value. Determining that there is residual resist at the bottom of the contact hole when it is smaller, and determining that there is no residual resist at the bottom of the contact hole when smaller.

The mask inspection method according to claim 1, further comprising:

[5] Steps for obtaining the signal strength A1 at the center of the acquired image and the signal strength A2 at the periphery of the image;

The ratio A2ZA1 between the two obtained signal strengths is compared with a reference value, and when the ratio A2ZA1 is larger than the reference value, it is determined as an adhesive residue, and when it is small, it is determined as a liftable residue.

The mask inspection method according to claim 1, further comprising:

[6] On the acquired image, an average signal strength is obtained for each of the inside of the pattern or the portion of the pattern, and a predetermined signal (a signal equal to or greater than X is obtained based on the obtained average signal strength). Strength is strong! Yes! / Is weak!

The mask inspection method according to claim 1, further comprising: determining a growth foreign material when the extracted area is a predetermined size or more.

[7] measuring a deviation of the linear force on a linear portion of the pattern on the acquired image;

Determining that the roughness is good when the measured deviation is less than a predetermined value, and determining that the roughness is bad when the measured deviation is greater than a predetermined value;

The mask inspection method according to claim 2, further comprising:

[8] measuring a distance between the rounded shape of the corner of the pattern and the rounded shape of the corner on the acquired image;

Determining that the rounded shape is good when the measured distance is less than or equal to a predetermined value, and determining that the rounded shape is defective when the measured distance is greater than or equal to a predetermined value;

The mask inspection method according to claim 2, further comprising:

[9] a step of measuring the dimensions of the OPC pattern in the X and Y directions on the acquired image;

When the measured dimensions in the X direction and Y direction are greater than a predetermined ratio than the dimensions in the X direction and Y direction on the CAD data, OPC is judged good. The step of judging PC failure and

The mask inspection method according to claim 2, further comprising:

[10] Using a scanning electron microscope, the surface of the mask is scanned with an electron beam, and an enlarged image of the mask surface is generated and inspected based on the signal emitted or absorbed at that time. To the inspection device that performs

Means for acquiring an image of an area to be inspected on the mask;

The means for determining the signal strength at the center of the acquired image and the signal strength of the surroundings, the ratio of the signal strengths of the two obtained and the reference value are compared, the presence or absence of residue at the bottom of the contact hole, and the rise of foreign matter Means for determining the presence or absence of growth foreign matter

A mask inspection apparatus.

[11] Using a scanning electron microscope, the surface of the mask is scanned with an electron beam, and an enlarged image of the mask surface is generated and inspected based on the signal emitted or absorbed at that time. To the inspection device that performs

Means for acquiring an image of an area to be inspected on the mask;

Measure the deviation of the linear force for the straight part of the pattern on the acquired image, measure the distance between the rounded shape of the no-turn corner and the rounded shape of the corner, or measure the size of the minute pattern Means to

Means for judging pass / fail based on the measured value;

A mask inspection apparatus.