CN108183065A - A kind of method and compound substrate for eliminating silicon wafer warpage - Google Patents

Abstract

The invention discloses a method for eliminating wafer warping and a composite substrate, the method comprising the following steps: S1: selecting a warped wafer (1); S2: depositing a wafer on the back side of the wafer (1) A stress compensation film (2) with stress inside, so that the internal stress of the stress compensation film (2) and the internal stress of the wafer (1) cancel each other out to obtain a flat composite substrate; the wafer (1) Silicon carbide-based silicon carbide wafers or silicon-based gallium nitride wafers. The composite substrate includes a wafer (1) and a stress compensation film (2), the stress compensation film (2) covers the back of the wafer (1), and the stress compensation film (2) The internal stress of the wafer (1) cancels out each other; the wafer (1) is a silicon carbide-based silicon carbide wafer or a silicon-based gallium nitride wafer. The invention deposits a layer of stress compensation film with internal stress on the back of the warped wafer, so that the internal stress of the stress compensation film and the internal stress of the wafer cancel each other, thereby eliminating the warping phenomenon.

Description

A method for eliminating wafer warpage and composite substrate

technical field

The invention belongs to the technical field of semiconductor micro-nano processing, and in particular relates to a method for eliminating wafer warpage and a composite substrate prepared by the method.

Background technique

Silicon carbide (SiC) and gallium nitride (GaN) are two wide bandgap semiconductor materials. They have the advantages of high critical breakdown electric field strength, high saturation electron mobility, high thermal conductivity, etc., and are especially suitable for applications in microwave and high-power In the field of power transmission and energy conversion, microwave devices and power electronic devices prepared with it can carry high voltage and high current, and can work stably in harsh application environments such as high radiation and high temperature.

When the ingot of the silicon carbide substrate grows, the internal stress formed by the silicon carbide crystal is relatively large. When the silicon carbide ingot is cut into wafer slices, the internal stress is likely to cause warpage, and the warpage remains after epitaxy growth.

When gallium nitride is epitaxially grown on a silicon substrate, it is also easy to cause warpage due to internal stress.

The warping of silicon carbide-based silicon carbide wafers and silicon-based gallium nitride wafers will bring difficulties to subsequent device processing, which is manifested in:

One is that warpage prevents smooth focused exposure of the entire wafer during the photolithography process.

The second is that warpage makes it difficult for a large number of semiconductor equipment including exposure machines to automatically carry wafers. This is manifested as: the wafer cannot be effectively vacuum-adsorbed by the transfer pallet, and it is easy to slip and fall off from the transfer pallet; and the wafer cannot be positioned in the equipment chamber by vacuum adsorption.

In the prior art, the method used to overcome the warpage of SiC-based SiC wafers is to increase its thickness. In the case of the same internal stress of the SiC wafer, the greater the thickness of the SiC wafer, the smaller the warpage.

The shortcoming of the above-mentioned method of prior art is:

One is to increase the cost of devices based on silicon carbide materials. The greater the thickness of the silicon carbide substrate, the more materials consumed by a single wafer, and the higher the cost;

The second is that the process is cumbersome and complicated, the efficiency is low, and the yield rate is lost. The thicker the silicon carbide-on-silicon carbide wafer, the greater the on-resistance of the device. Before dicing, it needs to be thinned from the back of the silicon carbide-based silicon carbide wafer by grinding. At this time, the device on the front side of the silicon carbide-based silicon carbide wafer has been completed, and it needs to be covered and protected. The front side of the silicon wafer is strongly bonded to the surface of the grinding device to protect the devices on the front side of the silicon carbide-based silicon carbide wafer from damage during the high-speed and high-intensity back grinding process. The silicon carbide-based silicon carbide wafer is then removed from the surface of the grinding device, and the overlay protection is removed. The entire "cover-bond-grind-debond-decap" process is cumbersome and leads to inefficiency and yield loss.

In the prior art, the method for overcoming the warping phenomenon of GaN-on-Si wafers is to try to change the process parameters of its epitaxial growth. Since the setting of process parameters for epitaxial growth mainly needs to consider other factors, such as defects, growth rate, etc., it is often impossible to effectively control warpage, which leads to a large range of warpage in GaN-on-Si wafers, increasing the difficulty of device process .

Contents of the invention

The first technical problem to be solved by the present invention is to provide a method for eliminating wafer warpage.

The second technical problem to be solved by the present invention is to provide a composite substrate prepared by the above method.

In order to solve the above-mentioned first technical problem, the invention adopts the following technical solutions:

The invention provides a method for eliminating wafer warpage, comprising the steps of:

S1: Select a warped wafer;

S2: Depositing a layer of stress compensation film with internal stress on the back of the wafer, so that the internal stress of the stress compensation film and the internal stress of the wafer cancel each other to obtain a flat composite substrate;

The wafer is a silicon carbide-based silicon carbide wafer or a silicon-based gallium nitride wafer.

Preferably, when the wafer is a silicon carbide-based silicon carbide wafer, the method further includes the following step: S3: Depositing an internal stress-free auxiliary film on the back of the stress compensation film.

Preferably, the type and size of the internal stress are regulated by adjusting the pressure, temperature, composition ratio, and deposition rate of the stress compensation film deposited.

Preferably, the material of the stress compensation film is silicon oxide, silicon nitride or metal.

Preferably, the internal stress of the stress compensation film is compressive stress, no stress or tensile stress.

In order to solve the above-mentioned second technical problem, the present invention provides a composite substrate, including a wafer and a stress compensation film, the stress compensation film covers the back of the wafer, and the inside of the stress compensation film The stress and the internal stress of the wafer cancel each other; the wafer is a silicon carbide-on-silicon carbide wafer or a gallium nitride-on-silicon wafer.

Preferably, when the wafer is a silicon carbide-based silicon carbide wafer, the composite substrate further includes an internal stress-free auxiliary film, and the auxiliary film covers the back surface of the stress compensation film.

Preferably, the material of the stress compensation film is silicon oxide, silicon nitride or metal.

Preferably, the internal stress of the stress compensation film is compressive stress, no stress or tensile stress.

Preferably, the material of the auxiliary film is silicon oxide, silicon nitride, metal, TEOS or glass for semiconductor; the glass for semiconductor is glass prepared by SOG or CVD. Any range recited in the present invention includes the endpoints and any value between the endpoints and any sub-range formed by the endpoints or any value between the endpoints.

Unless otherwise specified, each raw material in the present invention can be purchased commercially, and the equipment used in the present invention can be carried out by using conventional equipment in the field or referring to the prior art in the field.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The method of the present invention deposits a layer of internal stress compensation film with stress on the back of the warped wafer, so that the internal stress of the stress compensation film and the internal stress of the wafer cancel each other, thereby eliminating the warping phenomenon and obtaining a smooth wafer. Composite substrates make high-precision photolithography possible.

(2) The method of the present invention can reduce the light transmittance of the silicon carbide wafer by depositing the stress compensation film and the auxiliary film, thereby making the silicon carbide wafer easier to identify and locate. Due to the low light transmittance of the material of the stress compensation film (such as silicon oxide, silicon nitride, metal, etc.) and the material of the auxiliary film (such as silicon oxide, silicon nitride, metal, TEOS or semiconductor glass, etc.), The stress compensation film and the auxiliary film can reduce the light transmittance of the silicon carbide wafer. In this way, the shading performance of the silicon carbide wafer is enhanced, and it is easier to be identified and positioned.

(3) The method of the present invention can eliminate the warping phenomenon and obtain a flat composite substrate. The flat composite substrate can be effectively vacuum-adsorbed by the conveying pallet, and is not easy to slip off from the conveying pallet, so that the semiconductor device is relatively stable. Automatic wafer handling is easier.

(4) The method of the present invention can increase the thickness of the silicon carbide wafer by depositing the stress compensation film and the auxiliary film, so that the silicon carbide wafer can be handled more easily in semiconductor equipment, while reducing the probability of fragmentation or cracking.

Description of drawings

Below in conjunction with accompanying drawing, specific embodiment of the present invention is described in further detail

1 is a schematic diagram of a warped wafer in Example 1 of the present invention;

2 is a schematic diagram of depositing a stress compensation film on the back side of a wafer according to Embodiment 1 of the present invention;

3 is a schematic diagram of a warped wafer according to Embodiment 2 of the present invention;

FIG. 4 is a schematic diagram of depositing an auxiliary film on the back of the stress compensation film according to Embodiment 3 of the present invention.

Detailed ways

In order to illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not limit the protection scope of the present invention.

Example 1

This implementation provides a method for eliminating wafer warpage, the method comprising the steps of:

S1: Select a warped wafer 1;

S2: Deposit a layer of stress compensation film 2 with internal stress on the back of the wafer 1, so that the internal stress of the stress compensation film 2 and the internal stress of the wafer 1 cancel each other out to obtain a flat composite substrate.

The above-mentioned wafer 1 is a silicon carbide-based silicon carbide wafer or a silicon-based gallium nitride wafer.

The material of the stress compensation film 2 is preferably silicon oxide, silicon nitride or metal.

The internal stress of the above-mentioned stress compensation film 2 is compressive stress, no stress or tensile stress. Those skilled in the art can adjust the type of internal stress (compressive stress, no stress or tensile stress) of the deposited stress compensation film 2 by adjusting the process parameters of the deposited stress compensation film 2, such as gas pressure, temperature, composition ratio, deposition rate, etc. and size.

In this embodiment, in the above step S1, for example, the wafer 1 that is bent upward in the middle is selected, that is, the front side of the wafer 1 is convex, as shown in FIG. 1; in the above step S2, for example, in the warped wafer A layer of stress compensation film 2 with internal compressive stress is deposited on the back of 1, so that the internal stress of the stress compensation film 2 and the internal stress of the wafer 1 cancel each other, thereby eliminating the warping of the wafer 1 and obtaining a flat composite substrate. as shown in picture 2.

In this embodiment, the composite substrate includes a wafer 1 and a stress compensation film 2 .

Example 2

This implementation provides a method for eliminating wafer warpage, the method comprising the steps of:

S1: Select a warped wafer 1;

S2: Deposit a layer of stress compensation film 2 with internal stress on the back of the wafer 1, so that the internal stress of the stress compensation film 2 and the internal stress of the wafer 1 cancel each other out to obtain a flat composite substrate.

The above-mentioned wafer 1 is a silicon carbide-based silicon carbide wafer or a silicon-based gallium nitride wafer.

The material of the stress compensation film 2 is preferably silicon oxide, silicon nitride or metal.

The internal stress of the above-mentioned stress compensation film 2 is compressive stress, no stress or tensile stress. Those skilled in the art can adjust the type of internal stress (compressive stress, tensile stress or no stress) of the deposited stress compensation film 2 by adjusting the process parameters of the deposited stress compensation film 2, such as gas pressure, temperature, composition ratio, deposition rate, etc. and size.

In this embodiment, in the above step S1, for example, the wafer 1 that is bent downward in the middle is selected, that is, the front surface of the wafer 1 is concave, as shown in FIG. 3; in the above step S2, for example, in the warped wafer 1 A layer of stress compensation film 2 with internal tensile stress is deposited on the back of circle 1, so that the internal stress of stress compensation film 2 and the internal stress of wafer 1 cancel each other, thereby eliminating the warping of wafer 1 and obtaining a flat composite substrate ,as shown in picture 2.

In this embodiment, the composite substrate includes a wafer 1 and a stress compensation film 2 .

Example 3

This implementation provides a method for eliminating wafer warpage, the method comprising the steps of:

S1: Select a warped wafer 1;

S2: Depositing a layer of stress compensation film 2 with internal stress on the back of the wafer 1, so that the internal stress of the stress compensation film 2 and the internal stress of the wafer 1 cancel each other out to obtain a flat composite substrate;

S3: Depositing an auxiliary film 3 with no internal stress on the back of the above stress compensation film 2 .

The above-mentioned wafer 1 is a silicon carbide-based silicon carbide wafer.

The material of the stress compensation film 2 is preferably silicon oxide, silicon nitride or metal.

The internal stress of the above-mentioned stress compensation film 2 is compressive stress, no stress or tensile stress. Those skilled in the art can adjust the type of internal stress (compressive stress, zero stress or tensile stress) and size.

In this embodiment, in the above step S1, for example, the silicon carbide wafer 1 that is bent downward in the middle is selected, that is, the front side of the silicon carbide wafer 1 is convex or concave; in the above step S2, for example, in the warped A stress compensation film 2 with compressive or tensile stress is deposited on the back of the silicon carbide wafer 1, so that the internal stress of the stress compensation film 2 and the internal stress of the silicon carbide wafer 1 cancel each other out, thereby eliminating the stress compensation of the silicon carbide wafer 1. warping to obtain a flat silicon carbide composite substrate; in the above step S3, deposit an internal stress-free auxiliary film 3 on the back of the silicon carbide composite substrate obtained in the above step S2, that is, the back of the stress compensation film 2, to obtain The final flat silicon carbide composite substrate is shown in FIG. 4 .

In this embodiment, the silicon carbide composite substrate further includes an auxiliary film 3 , that is, the finally obtained silicon carbide composite substrate includes a silicon carbide wafer 1 , a stress compensation film 2 and an auxiliary film 3 .

The aforementioned auxiliary film 3 is used for light shielding, and is also used for increasing the thickness of the silicon carbide composite substrate to a required thickness value.

The material of the auxiliary film 3 is preferably silicon oxide, silicon nitride, metal, ethyl silicate (TEOS) or semiconductor glass. The semiconductor glass is glass prepared by SOG (spin on glass coating-spin coating glass) or CVD (Chemical VaporDeposition-chemical vapor deposition).

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. All the implementation manners cannot be exhaustively listed here. All obvious changes or variations derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims (10)

1. a method for eliminating wafer warpage, is characterized in that, comprises the steps: S1: Select a warped wafer (1); S2: Deposit a layer of stress compensation film (2) with internal stress on the back of the wafer (1), so that the internal stress of the stress compensation film (2) and the internal stress of the wafer (1) are mutually Offset to obtain a flat composite substrate; The wafer (1) is a silicon carbide-based silicon carbide wafer or a silicon-based gallium nitride wafer. 2. The method for eliminating wafer warpage according to claim 1, wherein when the wafer (1) is a silicon carbide-based silicon carbide wafer, the method further comprises the steps of: S3: Depositing an internally stress-free auxiliary film (3) on the back of the stress compensation film (2). 3. The method for eliminating wafer warpage according to claim 1 or 2, characterized in that, the type of internal stress is controlled by adjusting the pressure, temperature, composition ratio and deposition rate of the deposited stress compensation film (2) and size. 4. The method for eliminating wafer warpage according to claim 1 or 2, characterized in that the material of the stress compensation film (2) is silicon oxide, silicon nitride or metal. 5. The method for eliminating wafer warpage according to claim 1 or 2, characterized in that, the internal stress of the stress compensation film (2) is compressive stress, no stress or tensile stress. 6. A composite substrate, characterized in that it comprises a wafer (1) and a stress compensation film (2), the stress compensation film (2) covers the back side of the wafer (1), and the The internal stress of the stress compensation film (2) and the internal stress of the wafer (1) cancel each other; the wafer (1) is a silicon carbide-based silicon carbide wafer or a silicon-based gallium nitride wafer. 7. The composite substrate according to claim 6, characterized in that, when the wafer (1) is a silicon carbide-based silicon carbide wafer, the composite substrate also includes an internal stress-free auxiliary film ( 3), and the auxiliary film (3) covers the back of the stress compensation film (2). 8. The composite substrate according to claim 6 or 7, characterized in that, the material of the stress compensation film (2) is silicon oxide, silicon nitride or metal. 9. The composite substrate according to claim 6 or 7, characterized in that the internal stress of the stress compensation film (2) is compressive stress, no stress or tensile stress. 10. The silicon carbide composite substrate according to claim 7, characterized in that, the material of the auxiliary film (3) is silicon oxide, silicon nitride, metal, TEOS or semiconductor glass; the semiconductor glass is Glass prepared by SOG or CVD.