WO2015155268A1

WO2015155268A1 - Method for detaching a growth substrate of a semiconductor component

Info

Publication number: WO2015155268A1
Application number: PCT/EP2015/057670
Authority: WO
Inventors: Joachim Hertkorn; Thomas LEHNHARDT
Original assignee: Osram Opto Semiconductors Gmbh
Priority date: 2014-04-11
Filing date: 2015-04-09
Publication date: 2015-10-15
Also published as: DE102014105208A1

Abstract

The invention relates to a method for producing a nitride compound semiconductor component, having the following steps: - providing a structured growth substrate (3) which has a surface structure, wherein the surface structure has elevations (31) which do not adjoin one another, and the growth substrate has a flat surface in intermediate spaces (32) between the elevations (31), - growing a first layer (1), which has GaN and which does not completely cover the surface structure, - growing a second layer (2), which has Al_xGa_1-xN, where 0 < x ≤ 1, on the first layer (1), - carrying out an etching process in which the first layer (1) is partly removed at least at a surface bordering the growth substrate (3), - growing at least one additional nitride compound semiconductor layer (4), and - detaching the growth substrate (3).

Description

description

METHOD FOR DISCONNECTING A WAXING SUBSTRATE OF A SEMICONDUCTOR COMPONENT

The invention relates to a method for producing a nitride compound semiconductor device, in particular an optoelectronic nitride compound semiconductor device.

This patent application claims the priority of German Patent Application 10 2014 105 208.0, the disclosure of which is hereby incorporated by reference.

For manufacturing nitride compound semiconductor devices such as LEDs or semiconductor lasers, the functional layers of the device typically become

epitaxially on a suitable growth substrate

deposited. Sapphire substrates are particularly suitable for growing nitride compound semiconductor layers. The growth substrate for epitaxially growing the

Nitride compound semiconductor layers does not have to

necessarily have a flat surface. Rather, it has been found to be advantageous

textured sapphire substrate (PSS, patterned sapphire

Substrates), in particular an increased

Luminous efficacy at a radiation-emitting

to achieve optoelectronic component.

It has also been found to be advantageous in a nitride compound semiconductor based

Component to connect the epitaxial layer sequence at a side opposite the growth substrate side with a carrier and then detach the growth substrate. In this embodiment is advantageous between the epitaxial layer sequence and the carrier a

inserted reflective layer. An LED made in this way is called a thin-film LED.

To detach the growth substrate from a

Nitride compound semiconductor device can be used in particular a per se known laser lift-off method. However, it has been found that when using structured sapphire substrates a detachment of the

Growth substrate by laser lift-off or others

Method is not readily possible or to a

Damage to the epitaxial semiconductor layer sequence leads. An object to be solved is therefore to provide an improved method for producing a nitride compound semiconductor device, wherein a structured

Growth substrate is used, which can be peeled off in a relatively simple manner.

This object is achieved by a method according to independent claim 1. Advantageous embodiments and

Further developments of the invention are the subject of the dependent claims.

In the method, according to at least one embodiment, a structured growth substrate is provided, which has a surface structure. The surface structure of the growth substrate advantageously has elevations which do not adjoin one another. Between the surveys, the

Growth substrate preferably has a flat surface. The surface structure of the growth substrate may in particular be formed by a plurality of elevations, which in a predetermined arrangement, in particular in a periodic arrangement, on the surface of the

Growth substrate are arranged. The elevations may in particular in a grid arrangement, for example in a hexagonal grid, on the surface of

be arranged structured growth substrate.

According to at least one embodiment is on the

Growth substrate, a first layer of a

Grown nitride compound semiconductor material, which preferably comprises GaN or consists of GaN, and the

Surface structure not completely covered.

According to at least one embodiment, in a further method step, a second layer of a

Nitride compound semiconductor material, which preferably comprises or consists of Al _x Ga _] __ _x N with 0 <x -S 1, grown on the first layer. The second layer has a

Aluminum content x, which is greater than the aluminum content of the first layer, wherein the first layer preferably contains no aluminum.

In accordance with at least one embodiment, an etching process is subsequently carried out in which the first layer is at least partially removed at an interface with the structured growth substrate. The etching process is preferably done in situ, i. in one for growing up

Nitride compound semiconductor layers used

Coating plant. The growing up of

Nitride compound semiconductor layers can be carried out in particular by means of organometallic vapor phase epitaxy (MOVPE). In this case, the etching is advantageously carried out in the MOVPE system. In a subsequent step, at least one further nitride compound semiconductor layer or, preferably, several further nitride compound semiconductor layers are grown. In particular, it can be provided that the others

Nitride compound semiconductor layers functional

Layer sequence of a semiconductor device, in particular an optoelectronic semiconductor device form. The further nitride compound semiconductor layers, which are grown after the etching process, may in particular be a light-emitting diode layer sequence.

According to at least one embodiment, according to the

Growing up the at least one more

Nitride compound semiconductor layer detached the growth substrate from the semiconductor layer sequence thus produced. The detachment of the growth substrate is advantageously simplified in the method described here in that the first layer was at least partially removed in the previous etching process at an interface to the growth substrate. The adhesion between the first layer and the

Growth substrate is advantageously reduced in this way.

In accordance with at least one embodiment of the method, the growth substrate is a structured sapphire substrate (PSS). The elevations which form the surface structure of the growth substrate preferably have a cross-section which tapers with increasing distance from the surface. Starting from a base area, the surveys are therefore in a of the

Growth substrate pointing away direction narrower. The

Elevations may in particular have a dome-like shape, preferably the shape of a cone or a truncated cone. The Base areas of the surveys advantageously do not border

to each other, so that between the surveys spaces are formed on the surface of the growth substrate. As the first layer grows, it initially grows substantially between the elevations, that is, in the planar spaces.

In the method, the growth of the first layer is advantageously terminated when the first layer covers about 50% to 90% of the surface of the growth substrate. In other words, the growth of the first layer is stopped before the first layer completely overgrows the elevations of the surface structure.

It turned out that the first layer at

Growing up in the interstices between the elevations does not grow up with a completely planar surface, but rather that the first layer rather first areas, in the crystallographic c-plane of the

Nitride compound semiconductor material and having second regions which are not oriented in the c-plane. The c-plane oriented regions have a surface that is parallel to the growth substrate. This corresponds in particular to a (0001) crystal surface of the nitride compound semiconductor material.

The surface regions of the first layer which are not oriented in the c-plane are formed by crystal facets which do not run parallel to the growth substrate. These obliquely oriented crystal facets occur during the growth of the first layer, in particular at the interfaces between the first layer and the elevations of the surface structure. Advantageously, therefore, the second areas, the not oriented in the c-plane, to the elevations of the surface structure.

The elevations preferably have a width on average

between 1 ym and 4 ym. The height of the elevations is preferably on average between 0.5 ym and 2.5 ym.

The elevations preferably have on average a distance between 0.2 ym and 0.8 ym. Below the distance the

Surveys are here and below the shortest distance between the bases of two adjacent surveys to understand.

The second layer, which has AlGaN and is applied to the first layer, advantageously has a thickness of between 2 nm and 50 nm, preferably a thickness of between 5 nm and 10 nm. For example, the second layer may be about 5 nm thick. The comparatively thin second layer substantially conforms to the first layer, that is, it replicates the surface contour of the first layer. Like the first layer, the second layer also has first areas oriented in the c-plane and second areas not oriented in the c-plane and the peaks

adjoin, on.

The second layer advantageously has an aluminum content x> 0. The aluminum content x in the second layer is preferably between 0.05 and

including 0.1. It has been found that the first regions of the second layer, which on the c-plane oriented first regions of the first layer grow, have a larger aluminum content than the second regions, which grow on the obliquely to the growth substrate oriented second regions of the first layer. In other words, when the nitride compound semiconductor material of the second layer grows, it becomes oblique when grown on the non-c-plane material

Crystal facets of the first layer less aluminum

installed as on the parallel to the growth substrate

extending in c-plane oriented crystal facet. This circumstance is in the subsequent process step for

Implementation of a selective etching process exploited.

According to at least one embodiment is in the

Etching process, which is preferably carried out in situ, uses an etchant whose etch rate increases with

Aluminum content of the etched

Nitride compound semiconductor material decreases. In particular, an etchant is used, which for AlGaN a

has a lower etch rate than GaN. As a result, the second regions of the second layer, which have a lower aluminum content than the first regions, are etched faster than the first regions. Of the

The etching process is advantageously carried out such that the first regions of the second layer are not complete

be removed. The second regions with the lower aluminum content are preferably completely removed due to the larger etching rate, so that the etching process continues in the underlying second regions of the first layer.

After the removal of the second regions of the second layer, in particular those regions of the first layer are removed which are below the second regions of the second layer Layer are arranged. The first layer is therefore

especially in the areas adjacent to the surveys areas removed. In particular, it can be achieved in this way that the first layer is substantially no longer connected to the side surfaces of the elevations of the surface structure. A contact between the first layer and the growth substrate is therefore advantageous in the

Essentially only in a part of the interstices

between the surveys. In this way, the adhesion between the first layer and the growth substrate becomes

significantly reduced, which makes detachment of the growth substrate essential in a subsequent process step

facilitated . In accordance with at least one embodiment of the method, the etching process takes place by means of hydrogen. An etching process carried out by means of hydrogen has in particular the property that the etching rate during the etching of a

Nitride compound semiconductor material with increasing

Aluminum content decreases. The etching process can be carried out in particular by the fact that in the growth of the

Nitride compound semiconductor layers used

Coating plant is generated a hydrogen-rich atmosphere.

The detachment of the growth substrate is preferably carried out by means of a laser lift-off process. Alternatively, it is also possible, the growth substrate by a wet chemical

Method, by the application of ultrasound, by the generation of mechanical shear forces, for example by a temperature treatment, or by mechanical

Replace force. In one embodiment of the method, the layer sequence of the previously on the growth substrate

applied layers before detachment of the growth substrate at a side opposite the growth substrate side connected to a carrier. The carrier may in particular comprise silicon. The comparatively expensive growth substrate compared to silicon, which in particular has sapphire, can advantageously be used again after detachment. The at least one further layer, which is grown on the second layer, can in particular a

Include light-emitting diode layer sequence. The method is particularly suitable for producing a thin-film LED, in which the light-emitting diode layer sequence is detached from the structured growth substrate. For the production of

Light-emitting diode layer sequence can be advantageous per se

known epitaxy methods are used, the

Production of thin-film LEDs on flat substrates can be used.

In another preferred embodiment of the method, the at least further layer grown on the second layer is a GaN layer, which preferably has a thickness of between 500 μm and 1000 μm inclusive. After the detachment of the growth substrate, this comparatively thick GaN layer can be used in particular as a self-supporting substrate, for example for the production of an optoelectronic component. On the self-supporting GaN layer thus produced can in particular a

Semiconductor laser to be grown. Since with increasing layer thickness of the GaN layer, mechanical stresses in the layer system increase, it is possible in this embodiment that the GaN layer by itself of the Growth substrate separated without one of the previously

described separation method is applied.

The invention will be described below with reference to

Embodiments explained in more detail in connection with the figures 1 to 9.

1 to 9 show a schematic representation of a

Embodiment of the method based on intermediate steps.

Identical or equivalent components are each provided with the same reference numerals in the figures. The

Components shown and the proportions of the components with each other are not to be regarded as true to scale. In the following FIGS. 1 to 9, only a section of the growth substrate 3 is shown for the sake of simplicity

shown.

The growth substrate 3 shown schematically in cross section in FIG. 1 in a perspective view and in FIG. 2 in accordance with an exemplary embodiment is a structured one

Sapphire substrate having a surface structure. The surface structure is formed by a plurality of protrusions 31 which are not adjacent to each other and through

Interspaces 32 are separated from each other. The elevations 31 are advantageous in a predetermined two-dimensional arrangement on the surface of the growth substrate 3

arranged. In the illustrated embodiment are the elevations 31 each conical. Alternatively, the surveys could take a different form from the one of

Growth substrate 3 of tapered cross-section, for example, the shape of a truncated cone. In the

Gaps 32 between the elevations 31 has the

Aufwachsubstrat 3 advantageously a flat surface.

The elevations 31 preferably have on average a width between 1 ym and 4 ym. Height of the elevations 31 is preferably on average between 0.5 ym and 2.5 ym. The

Elevations 31 preferably have on average a distance d between 0.2 ym and 0.8 ym, wherein the distance d is the shortest distance between the bases of two

adjacent elevations 31 is.

In the intermediate step illustrated in FIG. 3, a first layer 1 of a nitride compound semiconductor material has been grown on the structured growth substrate 3. The first layer 1 is preferably a GaN layer. Before applying the first layer 1 may optionally be a thin nucleation layer, preferably of AlN, on the

Growth substrate 3 are applied (not shown). The first layer 1 is grown on the growth substrate 3 in such a way that it does not completely cover the elevations 31. In particular, the tips of the conical elevations 31 protrude out of the first layer 1.

The first layer 1 has on its surface first regions 11, which in the c-plane of

Nitride compound semiconductor material are oriented and parallel to the growth substrate. Furthermore, the first layer 1 adjacent to the elevations 31 second Areas 12 which extend obliquely to the growth substrate 3 and are not grown in the c-plane.

In the intermediate step shown in Figure 4 is a second layer on the first layer 1 has been grown 2 which Al _x _Ga] __ N _x with x> 0, preferably 0.05 ^ x ^ 0.1, comprising. The second layer 2, which contains aluminum, is a comparatively thin layer whose thickness is between 2 nm and 50 nm, preferably between 5 nm and 10 nm. The thickness of the second layer 2 may be, for example, 5 nm.

The first layer 1 is separated from the second layer 2

Advantageously overgrow substantially conforming, so that the second layer 2 is substantially the same

Surface contour as the first layer 1 has.

In particular, the surface of the second layer 2 has first regions 21, which are oriented in the crystallographic c-plane, and second regions 22 adjoining the elevations 31, which run obliquely to the growth substrate 3 and are not oriented in the c-plane.

It turned out that when growing up

Nitride compound semiconductor material of the second layer 2 is incorporated in the second regions 22 less aluminum than in the first regions 21, which in the c-plane

Orientation grow on the first layer 1. The second layer 2 therefore has in its edge regions 22, which adjoin the elevations 31, a lower aluminum content than in the first regions 21, which over the

Gaps 32 of the growth substrate 3 are arranged.

The in the second regions 22 of the second layer 2

Diminished aluminum content is in a subsequent Etching step, the result of which is shown schematically in Figure 5, exploited. In this process step, parts of the first layer 1 and the second layer 2 are etched with an etchant whose etching rate is lower, the higher the aluminum content of the

Nitride compound semiconductor material is.

An etchant suitable for carrying out such an etching process is in particular hydrogen. During the etching process by means of hydrogen, the second regions 22 of the second layer 2 are removed faster than the first regions 21 because of their lower aluminum content. Preferably, the first regions 21 of the second layer are not complete and the second regions 22 are complete

ablated. After the removal of the second regions 22, the etching process continues in the first layer 1. Since the first layer 1 does not comprise aluminum, the etch rate of the etchant in the first layer is even greater than in the second regions 22 of the second layer. Since the etching of the first layer 1 starts in the regions adjacent to the elevations 31, the first layer 1 is partially removed, in particular at the interface with the elevations 31.

As shown schematically in FIG. 5, the etching process can be carried out, for example, until the first

Layer 1 is at least partially removed to the gaps 32 at the surface of the growth substrate 3. The etching process is then stopped, in particular by the

Etch hydrogen is removed from the reactor. In the production of the nitride compound semiconductor layers by means of MOVPE, H ₃ is generally introduced into the coating system. The NH ₃ feed is preferably interrupted during the etching process and upon completion of the etching process resumed.

In the method step illustrated in FIG. 6, a further nitride compound semiconductor layer 41 is grown on the second layer 2, which has a sufficiently large thickness that it overgrows the regions of the second layer 2 which are separated from one another by the elevations 31 and grows into a closed layer. The others

In particular, nitride compound semiconductor layer 41 may be a GaN layer.

In a further method step illustrated in FIG. 7, further nitride compound semiconductor layers are formed

grown, for example, a light-emitting diode layer sequence 42 for an LED. The light-emitting diode layer sequence 42 may in particular comprise an n-doped semiconductor region 43, an active layer 44 and a p-doped semiconductor region 45. The only simplified

Light-emitting diode layer sequence 42 may be composed of a plurality of individual layers, such

Layer sequences are known per se and therefore not explained in detail.

In the intermediate step illustrated in FIG. 8, the light-emitting diode layer sequence 42 has been connected to a carrier 7 on a side opposite the growth substrate 3. The carrier 7 may in particular be a silicon wafer. The carrier 7 may be provided with a bonding layer 6 such as a solder layer with the

Light emitting diode layer sequence 42 are connected. Advantageously, the light-emitting diode layer sequence 42 is provided with a mirror layer 5 prior to connection to the carrier 7, in order in the finished nitride compound semiconductor device in FIG Direction of the carrier 7 emitted radiation for

to reflect the opposite radiation exit surface and improve in this way the radiation efficiency. In the intermediate step shown in FIG. 9, the growth substrate 3 is detached from the produced layer sequence. The growth substrate 3 can be detached from the layer sequence in particular by a laser lift-off process. Alternatively, the growth substrate 3, for example by application of ultrasound, by a wet chemical

Method, are replaced by the generation of shear forces, in particular by a temperature treatment, or by purely mechanical force. The detachment of the growth substrate 3 is advantageously facilitated in the method that the attached to the

Waxing substrate 3 adjacent first layer 1 was at least partially removed by the etching process, in particular at the adjacent to the elevations 31 areas of

Surface of the growth substrate 3. The one described here

Therefore, the method makes it possible in particular for the structured growth substrate 3 to be derived from the layer sequence of the

Dissolve nitride compound semiconductor device, which would otherwise be difficult or even impossible.

In an alternative variant of the method, in the method step illustrated in FIG. 6, a very thick further nitride compound semiconductor layer 41, in particular a thick GaN layer, whose thickness is preferably between 500 .mu.m and 1000 .mu.m, is grown. This can be done before

Growing a light emitting diode layer sequence of the

Growth substrate 3 are replaced and due to their large thickness as a cantilever substrate for growing another Layers, in particular a laser diode structure or a light-emitting diode structure, act.

The invention is not limited by the description with reference to the embodiments. Rather, the includes

Invention every new feature as well as every combination of

Features, which includes in particular any combination of features in the claims, even if this feature or this combination itself is not explicitly in the

Claims or embodiments is given.

Claims

Process for producing a

Nitride compound semiconductor component, comprising the steps:

- Providing a structured growth substrate (3) which has a surface structure, the surface structure having elevations (31) which do not adjoin one another, and wherein the

The growth substrate has a flat surface in the spaces (32) between the elevations (31),

- Growing a first layer (1), which is GaN

and does not completely cover the surface structure,

- Growing a second layer

(2), which has Al _x Gai- _x N with 0 <x -S 1, on the first layer (1), carrying out an etching process in which the first layer (1) at least at an interface to

Growing substrate

(3) is partially removed,

- Growing up at least one more

Nitride compound semiconductor layer

(4), and

- Removing the growth substrate (3).

Method according to claim 1,

wherein the structured growth substrate (3).

structured sapphire substrate.

Method according to one of the preceding claims, wherein the elevations (31) have the shape of a cone or a truncated cone.

Method according to one of the preceding claims, wherein the elevations (31) have an average width between 1 ym and 4 ym.

5. Method according to one of the preceding claims,

wherein the elevations (31) have an average height of between 0.5 ym and 2.5 ym.

6. Method according to one of the preceding claims,

wherein the elevations (31) have an average distance between 0.2 ym and 0.8 ym.

7. Method according to one of the preceding claims,

wherein the first layer (1) and the second layer (2) each have first areas (11, 21) that are oriented in the c-plane and second areas (12, 22) that are not oriented in the c-plane , exhibit.

8. Method according to claim 7,

wherein the second areas (12, 22) adjoin the elevations (31) of the surface structure.

9. Method according to one of the preceding claims,

wherein the second layer (2) has a thickness of 2 nm to 50 nm.

10. Method according to one of the preceding claims,

where the second layer (2) has Al _x Gai- _x N with 0.05 < x ^ 0.1.

11. Method according to one of the preceding claims,

the etching process is carried out using hydrogen.

12. Method according to one of the preceding claims,

wherein the growth substrate (3) is removed by means of Laser lift-off occurs.

13. The method according to any one of the preceding claims, wherein the at least one further layer is connected to a carrier (7) before the growth substrate (3) is detached.

14. The method according to any one of the preceding claims, wherein the at least one further layer

Light-emitting diode layer sequence (42).

15. Method according to one of claims 1 to 13,

wherein the at least one further layer comprises a GaN layer (41) with a thickness of 500 μm to 1000 μm.