KR101726473B1 - Isolation in micromachined single crystal Si using deep diffusion doping process - Google Patents

Abstract

In the fabrication of microstructure substrates using microelectromechanical systems (MEMS) technology, microstructures are formed on a bulk Si substrate without using conventional SOI (Si On Insulator) And the wiring process is performed, it is possible to manufacture the microstructure substrate so that the insulation between the electrodes and the electrical connection to the outside are performed. This can simplify the cap wafer manufacturing process and reduce the manufacturing cost, and can improve the manufacturing cost and yield by enlarging the kinds of wafer level bonding that can be selected, the size of the micro structure, the simplification / Improvement in manufacturing cost, improvement in performance / yield, and improvement in final package thickness.

Description

In a micromachining technique of a single crystal silicon, an isolation method using an impurity diffusion {

The present invention relates to a method of manufacturing a microstructure substrate by micro mechanical device electronic device technology, in which microstructures are formed on a bulk Si substrate without using a conventional SOI (Si On Insulator), insulation between electrodes is performed by impurity diffusion, And a microstructure structure and a fabrication method for forming interconnection between the electrodes and external connection to the microstructure substrate.

Recently, microelectromechanical systems (MEMS) technology has been expanding into the field of miniaturization of innovative systems which will lead various technology fields in mobile and automobile fields. Microelectromechanical and electronic device technologies are applied to a variety of existing semiconductor technologies such as thin film deposition, etching, photolithography, ion implantation and diffusion, Deep impurity diffusing technology, special plating technology, etc., are formed on a substrate such as a silicon substrate in a precise shape of a micro or nanometer unit by using a special silicon technology only for a micro-mechanical device.

In the structure fabricated by the micro mechanical device technology, electrodes for applying an electrical signal are formed, and each of the electrodes must be electrically insulated from each other. Various methods for electrical insulation between electrodes have been studied, and related related arts include a single crystal reactive etching and metallization (SCREAM) insulation method, a method using an SOI wafer, a method using a polysilicon structure and a wiring process Is known.

1 is a process diagram of a scrim insulation method as a prior art. In the scrim insulation method, an insulating oxide is deposited on the entire surface of a wafer including a surface of a structure through a plasma enhanced chemical vapor deposition (PECVD) process after a fine driving structure is formed, and a metal is deposited thereon to form an electrode to be. Although the process has a simple merit, there are limitations in the use of the inter-metallic bonding method, the need to form electrodes on the cap wafer, the need for additional processes to expose the pads after bonding, There are many disadvantages such as the necessity of using a more expensive SOI wafer and proceeding with the process.

2 is a process diagram of a method of using an SOI wafer as a prior art. In this method, a micro-driving structure is fabricated and a cap wafer on which an electrode is formed and Au-Si eutectic bonding are carried out and a process of exposing the electrode pad is performed. Although the process is simpler than the scrim insulation method, most of the disadvantages of the scrim insulation method are the same and the bonding method is further limited by eutectic bonding. Particularly, the dicing process, which is mainly used to expose electrode pads, has problems such as defects and design limitations.

3 is a technology for forming a fine driving structure and an electrode pad (for the purpose of inputting and outputting an electric signal to an electrode of a fine driving structure) on a microstructure substrate. In this method, polycrystalline silicon is formed on the bulk Si, an insulating layer is deposited and patterned, and polycrystalline silicon is deposited to a thickness of the structure. Cap wafer process is simple and various bonding method can be used. However, special deposition equipment of high price is needed for the deposition process of polycrystalline silicon with complicated manufacturing process of micro-driving structure and low internal stress, There is a drawback that it is not easy.

If an electrode pad (for inputting and outputting an electric signal to an electrode of a micro-driving structure) is formed by a simple process on the same wafer by using a process of manufacturing a micro-driving structure used in a scrim process method or a method using an SOI wafer, , Yield, process simplification, packaging size, and packaging process improvement.

SUMMARY OF THE INVENTION In order to solve the problems of the prior art described above, the present invention provides a structure in which fine driving structures and electrode pads (for inputting and outputting electric signals to electrodes of fine driving structure) are formed in a microstructure substrate and a method of manufacturing the same The purpose.

According to an aspect of the present invention, there is provided a microstructure substrate, including: a micro-structure on a front surface of a substrate; an impurity diffusion layer on the back surface; .

A method of fabricating a microstructure substrate according to an embodiment of the present invention includes: forming and floating a microstructure on a microstructure substrate; Bonding the cap wafer and the microstructure substrate; Back grinding the back surface of the microstructure substrate to a desired thickness; Forming a diffusion barrier layer on the back surface of the microstructure substrate after the backgrinding process, the diffusion barrier layer having an insulating property in a region other than a region to be diffused by impurities; Conducting impurity diffusion of a desired concentration and depth on the back surface of the microstructure substrate; Forming a region on the back surface of the microstructure substrate where a metal wiring and a metal electrode pad to which an electric signal can be applied are connected; And forming the metal wiring and the metal electrode pad.

Since the microstructure substrate according to the present invention can be stably manufactured by the devices and techniques set up for commercialization, the cap wafer does not need a wiring process and there is no need to electrically connect the cap wafer and the microstructure substrate, It is possible to improve yield, improve manufacturing cost, and improve performance stability. In addition, since the bulk Si is used, it is possible to use a substrate that is less expensive than SOI, and chip size can be reduced because wiring and electrode pads necessary for inputting and outputting electrical signals to the micro-drive structure are formed on the back surface of the microstructure substrate.

1 is a process diagram of a conventional scrim insulation method.
2 is a process diagram of a method of using a conventional SOI wafer.
3 is a process diagram of a method for forming a microdrive structure and an electrode pad on a microstructure substrate.
4 is a plan view of a part of a front surface of a microstructure substrate on which a fine driving structure is formed.
5 is a cross-sectional view of the microstructure substrate when cut in the vertical direction with reference to line segment A-A 'in FIG. 4;
6 is a cross-sectional view after proceeding with wafer level bonding with the cap substrate;
7 is a cross-sectional view of the back surface of the microstructure substrate after back grinding.
8 is a cross-sectional view after proceeding to form a diffusion barrier film pattern.
FIG. 9 is a cross-sectional view after proceeding with impurity diffusion; FIG.
10 is a cross-sectional view after forming a metal wiring and a metal electrode pad.
11 is a plan view after forming a metal wiring and a metal electrode pad.

Prior to the description of the concrete contents of the present invention, for the sake of understanding, the outline of the solution of the problem to be solved by the present invention or the core of the technical idea is first given.

According to an embodiment of the present invention, there is provided a micromechanical electronic device structure, including: a microstructure substrate on which a micro-driving structure is formed on a front surface of a ULK Si wafer; A cap substrate bonded to the microstructure substrate; An area where impurities of the opposite type to that of the substrate are diffused in some areas after the back side of the microstructure substrate is back-grounded; And a metal wiring layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art, however, that these examples are provided to further illustrate the present invention, and the scope of the present invention is not limited thereto.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which: It is to be noted that components are denoted by the same reference numerals even though they are shown in different drawings, and components of different drawings can be cited when necessary in describing the drawings. In the following detailed description of the operation principle of the preferred embodiment of the present invention, when it is determined that the description of the known function or configuration related to the present invention and other matters are unnecessarily obscured, A detailed description thereof will be omitted.

In addition, in the entire specification, when a part is referred to as being 'connected' to another part, it may be referred to as 'indirectly connected' not only with 'directly connected' . In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprises " or "comprising" when used herein should be interpreted as excluding the presence or addition of one or more other elements, steps, operations, or elements in addition to the stated element, step, I never do that.

4 is a plan view of a part of the front surface of the microstructure substrate on which the fine driving structure is completed. The fine driving structure is formed of at least three electrodes of the driving unit 11, the sensing unit 12, and the ground unit 13, and the electrodes must be insulated from each other.

5 is a cross-sectional view of the microstructure substrate when cut in the vertical direction with reference to line segment A-A 'in FIG. The micro-drive structure is exemplified by the case of the SBM (Sacrificial Bulk Micromachining) technology and can be processed by various technologies. It can be seen that the driving unit 11, the sensing unit 12, and the ground unit 13 are electrically connected through the substrate.

6 is a cross-sectional view of the cap substrate 14 after the wafer level bonding is proceeded to protect the microstructure from the influence of external impurities, external force, or the like. A part of the cap substrate 14 should be processed to keep a certain distance from the fine driving structure. If a transparent substrate is used, the process can be further simplified. The cap substrate 14 and the microstructure substrate may not be electrically connected to each other.

7 is a cross-sectional view of the back surface of the microstructure substrate after back grinding. The thickness of the microstructure substrate after back grinding can be determined to be as small as possible in consideration of differences between wafers and wafers such as etching process, initial thickness of cap substrate and microstructure substrate, back grinding process, and wafer warping characteristics.

FIG. 8 is a cross-sectional view after the diffusion barrier layer 15 is formed only in a region where the impurity diffusion of the opposite material to the microstructure substrate type is to proceed. The diffusion barrier layer 15 is mainly made of an oxide layer, but various materials can be used in consideration of the diffusion prevention effect and the subsequent process.
Here, the diffusion preventing film forming step has a melting point higher than the temperature of the impurity diffusion step, which will be described later, and prevents impurities from diffusing into the lower silicon during the impurity diffusion process, Use materials with easy properties. The material may be composed of a material such as, for example, silicon oxide, silicon nitride.
9 is a cross-sectional view after proceeding the impurity diffusion of the opposite material to the microstructure substrate type. N type impurities are implanted when the microstructure substrate is P type, and P type impurities are implanted when the substrate is N type. As shown in Fig. 9, the diffusion region of the impurity diffusion region 16 is determined so that insulation between the metal wiring and the metal electrode pad is achieved.

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FIG. 10 is a cross-sectional view of an example after metal wires 11 ', 12', 13 'and metal electrode pads 17 are formed so that an electric signal can be applied to the electrodes. The fine driving structure and the metal electrode are electrically connected between the electrode 11 and the metal electrode 11 ', between the electrode 12 and the metal electrode 12', between the electrode 13 and the metal electrode 13 ' . The diffusion preventing film 15 can be used as an insulating film between the metal wirings 11 ', 12', 13 'and the fine electrode substrate, thereby simplifying the process. The process sequence is to remove the oxide film in a part of the region where the microstructure electrode and the metal wiring are to be electrically connected, and to simultaneously form the metal wiring 11 ', 12', 13 'and the metal electrode pad 17 .

11 is a plan view of an example after forming the metal wires 11 ', 12', 13 'and the metal electrode pads 17 so that an electric signal can be applied to the electrodes. The metal electrode pad 17 can be electrically connected to the package pad through wire bonding, but the metal electrode pad 17 can be omitted when flip chip bonding is used.

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and specific embodiments and drawings. However, it should be understood that the present invention is not limited to the above- And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (10)

A microstructure substrate on which a fine driving structure is formed on a front surface of a bulk Si wafer;
A cap substrate bonded to the microstructure substrate;
An area of the back surface of the microstructure substrate after the backgrinding is progressively diffused in a part of the microstructure substrate in which impurities opposite to the type of the microstructure substrate are diffused; And
And a metal wiring and a metal electrode pad on the rear surface of the microstructure substrate after the back grinding process to allow electrical signals to be applied,
Type impurity is implanted when the type of the microstructure substrate is P-type, and P-type impurity is implanted in the opposite type of N-type when the type of the microstructure substrate is N-type. Microelectromechanical device structures.
The method according to claim 1,
Wherein the micro-driving structure is formed of at least two electrodes including a driving part of a movable structure and a sensing part of a fixed structure, which are manufactured by applying a SBM (Sacrificial Bulk Micromachining) technique, structure.
delete Forming and floating microstructures on the microstructure substrate;
Bonding the cap wafer and the microstructure substrate;
Back grinding the back surface of the microstructure substrate to a desired thickness;
Forming a diffusion barrier layer on the back surface of the microstructure substrate after the backgrinding process, the diffusion barrier layer having an insulating property in a region other than a region to be diffused by impurities;
Conducting impurity diffusion of a desired concentration and depth on the back surface of the microstructure substrate;
Forming a region to which a metal wiring and a metal electrode pad are to be connected so that an electric signal can be applied to the back surface of the microstructure substrate; And
And forming the metal wiring and the metal electrode pad.
5. The method of claim 4,
Wherein bonding the cap wafer and the microstructure substrate comprises:
Wherein bonding is performed using the cap wafer of the transparent wafer so that the alignment error is minimized and the rear surface alignment key formation process can be omitted.
delete 5. The method of claim 4,
The diffusion preventing film forming step may include:
It is possible to use a material having a melting point higher than the temperature of the impurity diffusion process and having a property of preventing impurities from diffusing into the lower silicon and diffusing impurities in the impurity diffusion process and easily forming a pattern by removing a desired region Wherein the microstructure substrate is formed by a method comprising the steps of:
5. The method of claim 4,
Wherein the impurity diffusing step comprises:
Type impurity is injected when the microstructure substrate is P-type, a P-type impurity is implanted when the microstructure substrate is N-type, and a diffusion region is determined such that insulation between the metal interconnection and the metal electrode pad is performed in a diffusion region of the impurity Of the substrate.
delete 5. The method of claim 4,
After forming the metal wiring and the metal electrode pad,
Further comprising the step of performing wire bonding or flip chip bonding through the metal electrode pad.

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