Gyro-sensor comprising a plurality of component units, and fabricating ...

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GYRO-SENSOR COMPRISING A
PLURALITY OF COMPONENT UNITS, AND
FABRICATING METHOD THEREOF

CROSS-REFERENCE TO RELATED 5
APPLICATIONS

This application claims the benefit of Korean Patent Application No. 2004-39680, filed on Jun. 1, 2004, in the Korean Intellectual Property Office, the disclosure of which 10 is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention 15 The present invention relates to a single chip including a

plurality of elements and a method of fabricating the same, and more particularly, to a subminiature single chip fabricated on a single substrate by fabricating a predetermined cavity in one of a plurality of elements and then positioning 20 another element in the cavity, and a method of fabricating the same.

2. Description of the Related Art

Recent developments in electronic technology have resulted in electronic devices that have various and excellent 25 functions and that are compact and light. In particular, such electronic devices have been made compact and light more rapidly due to advances in Micro Electro Mechanical System (MEMS) technology. In MEMS technology electrical and mechanical components are made on a single micro 30 body. In other words, MEMS technology combines micro scale mechanical and electrical structures to fabricate a system having a new function.

A plurality of structures and a plurality of circuit units fabricated using such MEMS technology can be intercon- 35 nected to develop various types of single chips.

FIGS. lAand IB are views illustrating the structure of a gyro-sensor as an example of such a single chip in which a plurality of structures and a plurality of circuit units are disposed on a plane. In other words, FIG. 1A is a plan view 40 of a gyro-sensor, and FIG. IB is a cross-sectional view of the gyro-sensor shown in FIG. 1A.

The gyro-sensor is an apparatus which detects a circular angular velocity using a principle of generating a Coriolis force in a third axis direction orthogonal to first and second 45 axis directions by receiving a rotation force of a constant angular velocity in the second axis direction perpendicular to a mass uniformly vibrating in the first axis direction. In other words, when the mass rotates toward the third axis direction due to the Coriolis force, the gyro-sensor changes 50 the displacement of the mass into a variation in capacitance to detect the circular angular velocity. Thus, the gyro-sensor requires a mass vibrating in a predetermined direction and a sensing electrode to generate and sense the Coriolis force. The mass and the sensing electrode can be fabricated using 55 MEMS technology.

Referring to FIG. 1A, in the gyro sensor, a MEMS structure 11, an analog Application Specific Integrated Circuit (ASIC) 12, and a digital ASIC 13 are disposed on a substrate 10 in a predetermined pattern. The MEMS struc- 60 ture 11 includes a mass, a sensing electrode, and the like. The analog ASIC 12 detects a variation in capacitance from the MEMS structure 11 and converts the variation into an analog voltage signal proportional to a circular angular velocity. Thus, the digital ASIC 13 converts the analog 65 voltage signal output from the analog ASIC 12 into a digital signal and outputs the digital signal to the outside.

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FIG. IB is a cross-sectional view of the gyro-sensor shown in FIG. 1A. Referring to FIG. IB, the MEMS structure 11 is electrically coupled to the analog ASIC 12 via conductive materials 14.

In the gyro-sensor shown in FIGS. 1A and IB, various structures and circuit units are disposed on a plane. Thus, the whole area of the single chip increases. Therefore, the gyro-sensor is not suitable for the recent tendency toward miniaturization.

FIGS. 2A and 2B illustrate the structure of a conventional gyro-sensor including a stack of a MEMS structure 21, an analog ASIC 22, and a digital ASIC 23. Referring to FIG. 2A, the MEMS structure 21 is formed on a substrate 20, and various circuit units such as the analog and digital ASICs 22 and 23 are formed on the MEMS structure 21. Next, the MEMS structure 21, the analog ASIC 22, and the digital ASIC 23 are electrically coupled to one another via wires 24. FIG. 2B is a cross-sectional view of the gyro-sensor shown in FIG. 2A.

As shown in FIGS. 2A and 2B, the whole area of the gyro-sensor may be more reduced than that of the gyrosensor in which elements are disposed on a plane. However, a plurality of elements are stacked, and then wire bonding is performed. Thus, the volume of the gyro-sensor is increased. Thus, the gyro-sensor is not suitable to be used in recent compact, light electric devices. Also, when the wire bonding is performed, loss of wires may occur.

SUMMARY OF THE INVENTION

Accordingly, the present general inventive concept has been made to address the above-mentioned disadvantages and/or problems, and an aspect of the present general inventive concept is to provide a single chip having a whole volume reduced by connecting and packaging a plurality of elements on a single substrate and a method of fabricating the same.

According to an aspect of the present invention, there is provided a gyro-sensor including: a substrate; a micro electro mechanical system structure including a surface including a predetermined area in which a cavity is formed and connected to an upper surface of the substrate to output a vibration signal proportional to an external rotation force; and a circuit unit positioned in the cavity, converting the vibration signal into a predetermined electric signal proportional to a circular angular velocity, and outputting the predetermined electric signal.

The circuit unit may include an analog application specific integrated circuit converting the vibration signal into a predetermined analog signal and a digital application specific integrated circuit converting the predetermined analog signal into a digital signal.

The micro electro mechanical system structure may be connected to the upper surface of the substrate so that the surface in which the cavity is formed faces the substrate.

The gyro-sensor may further include connectors electrically connecting the micro electro mechanical system structure and the circuit unit to the substrate. The connectors may be conductive bumps fabricated using a bumping method.

The micro electro mechanical system structure may be connected to the upper surface of the substrate so that the surface in which the cavity is formed faces a direction opposite to the substrate. The gyro-sensor may further include connectors electrically connecting the circuit unit to the cavity formed in the micro electro mechanical system structure. The connectors may be conductive bumps.

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The micro electro mechanical system structure may include: a lower glass substrate including a surface including a predetermined area in which the cavity is formed; a silicon layer connected to a surface opposite to the surface of the lower glass substrate in which the cavity is formed and 5 patterned in a predetermined vibration structure shape; a conductive layer formed on the lower glass substrate to be connected to the silicon layer; and an upper glass substrate connected to the silicon layer in an opposite direction to a direction along which the lower glass substrate is connected 10 to the silicon layer.

According to another aspect of the present invention, there is provided a single chip including: a first element including a surface comprising a predetermined area in which a cavity is formed; a second element positioned in the 15 cavity of the first element; and a substrate connected to the first and second elements via conductive materials to support the first and second elements.

According to still another aspect of the present invention, there is provided a method of fabricating a gyro-sensor, 20 including: fabricating a micro electro mechanical system structure outputting a vibration signal proportional to an external rotation force; etching a predetermined area of a surface of the micro electro mechanical system structure to form a cavity; connecting a circuit unit converting the 25 vibration signal into a predetermined electric signal proportional to a circular angular velocity and outputting the predetermined electric signal to an upper surface of a substrate; and connecting the micro electro mechanical system structure to the upper surface of the substrate to 30 position the circuit unit in the cavity.

According to yet another aspect of the present invention, there is provided a method of fabricating a gyro-sensor, including: fabricating a micro electro mechanical system structure outputting a vibration signal proportional to an 35 external rotation force; etching a predetermined area of a surface of the micro electro mechanical system structure to form a cavity; bonding a circuit unit converting the vibration signal into a predetermined electric signal proportional to a circular angular velocity and outputting the predetermined 40 electric signal to the cavity; and connecting the micro electro mechanical system structure to an upper surface of a substrate.

Fabricating the micro electro mechanical system structure may include: bonding a silicon layer to a first glass substrate 45 including a surface comprising an etched predetermined area; etching a predetermined area of the silicon layer to pattern the silicon layer in a predetermined vibration structure shape; bonding a second glass substrate including a space in which the predetermined vibration structure 50 vibrates to the silicon layer; and stacking a conductive layer electrically connecting the silicon layer to an external terminal.

BRIEF DESCRIPTION OF THE DRAWINGS 55

The above aspects and features of the present invention will be more apparent by describing certain embodiments of the present invention with reference to the accompanying go drawings, in which:

FIG. 1A is a plan view of a conventional single chip in which a plurality of structures are disposed on a plane;

FIG. IB is a cross-sectional view of the conventional single chip shown in FIG. 1A; 65

FIG. 2A is a plan view of a conventional single chip in which a plurality of structures are stacked;

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FIG. 2B is a cross-sectional view of the conventional single chip shown in FIG. 2A;

FIG. 3 is a cross-sectional view of a single chip according to an exemplary embodiment of the present invention;

FIG. 4 is a cross-sectional view of a gyro-sensor according to an exemplary embodiment of the present invention;

FIG. 5 is a cross-sectional view of a gyro-sensor according to another exemplary embodiment of the present invention;

FIGS. 6A through 6C are cross-sectional views illustrating a method of fabricating the gyro-sensor shown in FIG. 4 according to an exemplary embodiment of the present invention; and

FIGS. 7A through 7C are cross-sectional views illustrating a method of fabricating the gyro-sensor shown in FIG. 4 according to another exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY
EMBODIMENTS OF THE INVENTION

Certain embodiments of the present invention will be described in greater detail with reference to the accompanying drawings.

In the following description, the same drawing reference numerals are used for the same elements even in different drawings. Descriptions of certain items such as construction details and details of elements are only provided to assist in a comprehensive understanding of the invention. Thus, it is apparent that the present invention can be carried out without those details. Also, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

FIG. 3 is a cross-sectional view of a single chip according to an embodiment of the present invention. Referring to FIG. 3, the single chip includes a substrate 110, a first element 130, a second element 120, and connectors 140.

The substrate 110 is a general printed circuit board (PCB). A predetermined area of the first element 130 is etched to from a cavity. The second element 120 is positioned in the cavity. The first element 130 and the second element 120 are electrically connected to the substrate 110 via the connectors 140. Thus, the first and second elements 130 and 120 are interconnected via electric wires (not shown) formed in the substrate 110.

The connectors 140 may be fabricated by forming external protruding connectors having sizes of tens um to hundreds um of gold, solder, or other metallic materials on a pad (not shown) formed on the substrate 110, i.e., conductive bumps. If the connectors 140 are fabricated using such a bumping method, a path of an electric line is shortened. Thus, electric resistance and electric noise can be reduced so as to improve electric performance.

In a case where the gyro-sensor is embodied, the first element 130 may be a structure including a mass vibrating depending on a circular angular velocity and a sensing electrode, and the second element 120 may be an analog ASIC detecting the circular angular velocity from the first element 130, a digital ASIC, or the like.

Alternatively, the first element 130 may be an analog ASIC or a digital ASIC, and the second element 120 may be a structure including a mass, a sensing electrode, and the like. Such a structure may be arbitrarily determined by a manufacturer. As shown in FIG. 3, since the second element 120 is positioned in the cavity in the first element 130, the overall size of the single chip is reduced by the size of the second element 120.