CN115083889A - Wafer grinding method and wafer processing method - Google Patents

Abstract

The application provides a wafer grinding method and a wafer processing method. The grinding method of the wafer comprises the following steps: providing a wafer, wherein the wafer comprises a device area and an edge area; carrying out pre-thinning treatment on the wafer from the back side of the wafer; and carrying out Taiko grinding on the back of the wafer subjected to the pre-thinning treatment, wherein after the Taiko grinding, a convex ring is formed in the edge area of the wafer. According to the method for grinding the wafer, the step of pre-thinning the back surface of the wafer is added before the step of grinding the back surface of the wafer too drum, the final thickness of the finally obtained wafer can be flexibly adjusted by adjusting the thinning amount in the pre-thinning treatment, the wafer with the final thickness in a wider numerical range can be obtained, and the requirements of the process on the wafers with different final thicknesses can be met.

Description

Wafer grinding method and wafer processing method

technical field

The present application relates to the field of semiconductor technology, and in particular, to a method for grinding wafers and a method for processing wafers.

Background technique

The front side of the wafer needs to be ground after the device is fabricated. In order to reduce the risk of wafer handling and reduce the warpage of the wafer, the backside of the wafer is generally subjected to drum grinding; after the drum grinding, a convex ring will be formed on the edge of the wafer. However, due to the limitation of the grinding properties of the drum and the thickness of the shim jig used to remove the convex ring after the drum grinding, only wafers with a final thickness of individual values can be obtained, which cannot meet the requirements of the process for wafers with different final thicknesses. demand.

SUMMARY OF THE INVENTION

Based on the existing technology that only uses a drum grinder to perform drum grinding on the back of the wafer, only wafers with a final thickness of an individual value can be obtained, which cannot meet the requirements of the process for wafers with different final thicknesses. It is necessary to provide a method for grinding wafers and a method for processing wafers in response to the above problems.

In a first aspect, the present application provides a method for grinding a wafer, comprising:

providing a wafer including a device area and an edge area;

pre-thinning the wafer from the backside of the wafer;

The back surface of the wafer after the pre-thinning treatment is subjected to drum grinding. After the drum grinding, a convex ring is formed on the edge area of the wafer.

In the wafer grinding method of the present invention, the step of pre-thinning from the back of the wafer is added before the drum grinding of the back of the wafer, which can be flexibly adjusted by adjusting the amount of thinning in the pre-thinning process The final thickness of the finally obtained wafer can be obtained with a wider numerical range of the final thickness of the wafer, which can meet the requirements of the process for wafers with different final thicknesses.

In one embodiment, the pre-thinning process on the wafer from the backside of the wafer includes:

Plane grinding is performed on the backside of the wafer.

In a second aspect, the present invention also provides a method for processing a wafer, comprising:

The wafer is ground by the grinding method of the wafer described in the first aspect;

A placement device is provided, the placement device includes a dicing ring and a dicing film, and the dicing film is attached to the dicing ring;

The wafer after grinding treatment is attached to the surface of the dicing film, and the back of the wafer is in contact with the surface of the dicing film;

The edge region and the raised ring of the wafer are removed.

In the wafer processing method of the present invention, a step of pre-thinning from the backside of the wafer is added before the drum grinding of the backside of the wafer, which can be flexibly adjusted by adjusting the amount of thinning in the pre-thinning process The final thickness of the finally obtained wafer can obtain the wafer to be cut with a wider range of final thicknesses, which can meet the requirements of the process for wafers with different final thicknesses.

In one embodiment, the device region includes a plurality of chip regions arranged at intervals, and adjacent chip regions are separated by dicing lanes; devices are formed on the front surface of each chip region;

Before performing the grinding process on the wafer using the wafer grinding method as described in the first aspect, the method further includes: forming a protective film on the front surface of the wafer, the protective film covering at least the front surface of the device region ;

After grinding the wafer by using the wafer grinding method described in the first aspect, and before attaching the polished wafer to the surface of the dicing film, the method further includes: removing the protective film.

In one embodiment, after performing drum grinding on the back of the wafer after the pre-thinning process, the back of the wafer has rough textures; after grinding the wafer, remove the Before the protective film, also include:

removing the rough texture;

Electrodes are formed on the backside of the wafer.

In the above embodiment, by removing the rough texture on the backside of the wafer, the contact resistance between the electrodes and the wafer can be reduced; at the same time, the stress formed in the wafer due to grinding can also be released, thereby reducing the risk of debris.

In one embodiment, dry etching or wet etching is performed on the back surface of the wafer after grinding to remove the rough texture.

In one embodiment, the edge region and the raised ring of the wafer are removed by dicing using a dicing knife.

In one embodiment, the dicing film is located on the back surface of the device area and the surface of the convex ring; removing the edge area and the convex ring of the wafer includes:

A vacuum adsorption stage is provided. The vacuum adsorption stage includes a stage main body and a vacuum adsorption device located in the stage main body. A gasket fixture is provided on the surface of the vacuum adsorption stage. The gasket fixture An adsorption hole is arranged inside the gasket fixture along the thickness direction, and the adsorption hole is communicated with the vacuum adsorption device;

Place the mounting device on which the wafer is attached on the vacuum suction stage, and the dicing film on the surface of the convex ring and the surface of the vacuum suction stage are located in the device area The dicing film on the back side is in contact with the surface of the gasket fixture;

The edge region and the collar are removed by cutting with the cutting knife.

In one embodiment, the thickness of the removed wafer is the same as the thickness of the spacer fixture during the drum grinding of the back surface of the wafer after the pre-thinning process.

In one embodiment, after removing the edge region and the convex ring of the wafer, the method further includes: dicing the wafer to obtain a plurality of separated chips.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the traditional technology, the following briefly introduces the accompanying drawings that are used in the description of the embodiments or the traditional technology. Obviously, the drawings in the following description are only the For some embodiments of the application, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

1 is a flowchart of a method for grinding a wafer provided in an embodiment of the present application;

2 is a schematic diagram of plane grinding the backside of the wafer in the wafer grinding method provided in one embodiment of the present application;

3 is a schematic diagram of drum grinding performed on the back surface of a pre-thinning wafer in a method for grinding a wafer provided in an embodiment of the present application;

FIG. 4 is a flowchart of a wafer processing method provided in another embodiment of the present application;

FIG. 5 is a schematic diagram of removing the edge region and the convex ring of the wafer in the processing method of the wafer provided in another embodiment.

Description of reference numerals: 110, vacuum chuck; 120, protective film; 130, wafer; 1301, convex ring; 140, polishing liquid delivery pipeline; 150, grinding head; 1601, cutting ring; 1602, cutting film; 1701, Stage main body; 1702, vacuum adsorption device; 180, gasket fixture; 1801, adsorption hole; 190, cutting knife.

Detailed ways

In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the related drawings. Embodiments of the present application are presented in the accompanying drawings. However, the application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of the application are for the purpose of describing specific embodiments only, and are not intended to limit the application.

It will be understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element.

It can be understood that the "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between them.

As used herein, the singular forms "a," "an," and "the/the" can include the plural forms as well, unless the context clearly dictates otherwise. It should also be understood that the terms "comprising/comprising" or "having" etc. designate the presence of stated features, integers, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more Possibilities of other features, integers, steps, operations, components, parts or combinations thereof.

Semiconductor chips, such as power devices, power management, sensor chips, etc., are widely used in industrial control, automotive, electric power, energy and other fields. Taking power device IGBT as an example, Insulated Gate Bipolar Transistor, namely insulated gate bipolar transistor, is a composite power semiconductor device composed of BJT and MOSFET. It has both high switching speed of MOSFET, high input impedance, low control power, and drive circuit. It has the advantages of simplicity and low switching loss, and has the advantages of low on-state voltage, large on-state current, and low loss of BJT. It has outstanding competitiveness in high voltage, high current, and high speed, and has become the mainstream of switching devices in the field of power electronics. Direction of development.

Grinding is a very important process in the semiconductor chip manufacturing process. Grinding can achieve thinning of the wafer, flattening of the wafer surface, and so on.

The front side of the wafer needs to be ground after the device is fabricated. In order to reduce the risk of wafer handling and reduce the warpage of the wafer, the backside of the wafer is generally subjected to drum grinding; after the drum grinding, a convex ring will be formed on the edge of the wafer. However, due to the limitation of the grinding properties of the drum and the thickness of the shim jig used to remove the convex ring after the drum grinding, only wafers with a final thickness of individual values can be obtained, which cannot meet the requirements of the process for wafers with different final thicknesses. demand.

Table 1. The final thickness of the wafer after the backside of the wafer with an initial thickness of 725 μm has been drum-polished, and the convex ring has been removed based on different shim fixtures.

Gasket fixture model final thickness Final thickness range 655# 70μm 60μm～80μm 610# 115μm 105μm～125μm 500# 225μm 215μm～235μm

Table 2. The final thickness of the wafer after the backside of the wafer with an initial thickness of 735 μm was drum-polished and the convex ring was removed based on different shim fixtures.

Gasket fixture model final thickness Final thickness range 655# 80μm 70μm～90μm 610# 125μm 115μm～135μm 500# 235μm 225μm～245μm

In Table 1 and Table 2, the thickness of the 500# gasket jig is 500μm, the thickness of the 610# gasket jig is 610μm, and the thickness of the 655# gasket jig is 655μm. As can be seen from Table 1 and Table 2, there are only three types of spacer fixtures used in the convex ring removal machine; The final thicknesses of the obtained wafers are only 70 μm, 115 μm and 225 μm; after the backside of the wafer with an initial thickness of 735 μm is subjected to drum grinding, the final thickness of the wafer obtained after removing the convex ring based on different gasket fixtures There are only three values of 80 μm, 125 μm and 235 μm. Tables 1 and 2 further confirm that only drum grinding of wafers cannot meet the requirements of the process for wafers with different final thicknesses.

In one embodiment, referring to FIG. 1 , the present application provides a method for grinding a wafer, and the method for grinding a wafer may include the following steps:

S10: Provide a wafer, the wafer includes the device area and the edge area;

S11: pre-thinning the wafer from the backside of the wafer;

S12 : performing drum grinding on the back surface of the pre-thinned wafer, and after the drum grinding, a convex ring is formed on the edge area of the wafer.

In the above-mentioned wafer grinding method, the step of pre-thinning from the back of the wafer is added before the drum grinding of the back of the wafer, which can be flexibly adjusted by adjusting the amount of thinning in the pre-thinning process. The final result is obtained. The final thickness of the wafer can be obtained with a wider range of final thicknesses, which can meet the requirements of the process for wafers with different final thicknesses.

In step S10 , referring to step S10 in FIG. 1 and FIG. 2 , a wafer 130 is provided, and the wafer 130 includes a device region and an edge region.

In an alternate example, wafer 130 may include, but is not limited to, silicon wafers, gallium nitride wafers, or silicon carbide wafers, among others.

Specifically, the device region may include a plurality of chip regions arranged at intervals, and adjacent chip regions are separated by dicing lines; devices are formed on the front surface of each chip region.

In order to protect the device from being damaged by subsequent processes, a protective film 120 may be formed on the front surface of the wafer 130 , as shown in FIG. 2 .

In step S11 , referring to S11 in FIG. 1 and FIG. 2 , the wafer 130 is pre-thinned from the backside of the wafer 130 .

In one example, in step S11 , the backside of the wafer 130 may be plane-ground to achieve thinning of the wafer 130 .

Specifically, in step S11 , the front and back sides of the wafer 130 may be thinned as a whole, and the thickness of the thinning may be flexibly adjusted and set according to the final thickness required for the subsequent final wafer, which is not limited here.

In one example, in step S11 , the backside of the wafer 130 may be plane-polished based on the plane-grinding machine as shown in FIG. 2 . Specifically, the plane grinding machine table may include a vacuum suction cup 110 , a polishing liquid conveying pipeline 140 and a grinding head (not shown). The vacuum suction cup 110 is used for sucking the wafer 130 , and the wafer 130 is adsorbed on the vacuum suction cup 110 face down. , at this time, the protective film 120 is in contact with the surface of the vacuum chuck 110 . The polishing and conveying pipeline 140 is used for conveying the polishing liquid to the surface of the wafer 130 , and the polishing head is used for plane-grinding the back surface of the wafer 130 based on the polishing liquid.

In step S12 , referring to S12 in FIG. 1 and FIG. 3 , drum grinding is performed on the back surface of the wafer 130 after the pre-thinning process (ie, a TAIKO process is performed). Ring 1301.

In an example, in step S12 , referring to FIG. 3 , when the grinding head 150 is used to perform drum grinding on the backside of the wafer 130 after the pre-thinning process, only the backside of the device area is ground, without the edge grinding. In this way, after the drum grinding, a convex ring 1301 is formed in the edge region of the wafer 130 .

Specifically, the width of the convex ring 1301 may be about 3 mm.

In another embodiment, please refer to FIG. 4 in conjunction with FIG. 1 to FIG. 3 , the present application further provides a method for processing a wafer, and the method for processing a wafer includes:

S20: using the wafer grinding method described in the above embodiment to perform grinding processing on the wafer;

S21: Provide a mounting device, the mounting device includes a cutting ring and a cutting film, and the cutting film is attached to the cutting ring;

S22: the ground wafer is placed on the surface of the dicing film, and the back of the wafer is in contact with the surface of the dicing film;

S23: Remove the edge region and the convex ring of the wafer.

In the wafer processing method of the present invention, a step of pre-thinning from the backside of the wafer is added before the drum grinding of the backside of the wafer, which can be flexibly adjusted by adjusting the amount of thinning in the pre-thinning process The final thickness of the finally obtained wafer can obtain the wafer to be cut with a wider range of final thicknesses, which can meet the requirements of the process for wafers with different final thicknesses.

In step S20 , please refer to step S20 in FIG. 4 with reference to FIG. 1 to FIG. 3 , and use the wafer grinding method as described in the above-mentioned embodiment to grind the wafer.

In an optional example, the device region includes a plurality of chip regions arranged at intervals, and adjacent chip regions are separated by dicing lines; devices are formed on the front surface of each chip region. Before grinding the wafer 130 , the method may further include: forming a protective film 120 on the front surface of the wafer 130 , and the protective film 120 covers at least the front surface of the device area. By forming the protective film 120 on the front surface of the wafer 130, the device can be protected from damage during the subsequent grinding process.

In an optional example, after grinding the wafer 130 , before attaching the ground wafer 130 to the surface of the dicing film, that is, between steps S20 and S21 , the process further includes: removing the protective film 120 .

Specifically, the protective film 120 may include, but is not limited to, a UV-curable adhesive layer or a hot-melt adhesive layer. The protective film 120 may be removed by, but not limited to, heating or the like.

In an optional example, after performing drum grinding on the backside of the wafer 130 after the pre-thinning process, the backside of the wafer 130 has rough textures; after grinding the wafer 130 and before removing the protective film 120, further include:

remove rough texture;

Electrodes are formed on the backside of the wafer 130 .

In the above embodiment, by removing the rough texture on the backside of the wafer 130, the contact resistance between the electrodes and the wafer 130 can be reduced; at the same time, the stress formed in the wafer 130 due to grinding can also be released, thereby reducing the risk of debris .

Specifically, the electrode may include a metal electrode, and the electrode may be formed by, but not limited to, a sputtering process, an electroplating process or a physical vapor deposition process. In this embodiment, a physical vapor deposition process is used to form the electrode. More specifically, the material of the electrode may include at least one of aluminum, titanium, nickel and silver.

In an optional example, dry etching may be performed on the backside of the ground wafer 130 to remove rough textures, or wet etching may be performed on the backside of the ground wafer 130 to remove the roughness. Rough texture.

In step S21 , referring to step S21 in FIG. 4 and FIG. 5 , a mounting device is provided. The mounting device includes a dicing ring 1601 and a dicing film 1602 , and the dicing film 1602 is attached on the dicing ring 1601 .

Specifically, the cutting film 1602 may include a blue film, and the cutting film 1602 may cover the opening in the cutting ring 1601 .

In step S22 , referring to step S22 in FIG. 4 and FIG. 5 , the polished wafer 130 is placed on the surface of the dicing film 1602 , and the backside of the wafer 130 is in contact with the surface of the dicing film 1602 .

It should be noted that the diameter of the wafer 130 should be smaller than the inner diameter of the dicing ring 1601 to ensure that the wafer 130 can be placed on the dicing film 1602 .

In step S23 , referring to step S23 in FIG. 4 and FIG. 5 , the edge region of the wafer 130 and the convex ring 1301 are removed.

In an alternative example, the edge region of the wafer 130 and the raised ring 1301 may be removed by dicing using a dicing knife 190 .

Specifically, the cutting blade 190 may include, but is not limited to, a diamond blade.

In one example, the dicing film 1602 is located on the backside of the device area and the surface of the convex ring 1301; in step S23, removing the edge area of the wafer and the convex ring 1301 may include:

S231 : providing a vacuum adsorption stage, the vacuum adsorption stage includes a stage main body 1701 and a vacuum adsorption device 1702 located in the stage main body 1701 , a gasket jig 180 is provided on the surface of the vacuum adsorption stage, and the gasket jig 180 There is an adsorption hole 1801 penetrating the gasket fixture 180 along the thickness direction, and the adsorption hole 1801 is communicated with the vacuum adsorption device;

S232: Place the mounting device on which the wafer 130 is attached on the vacuum suction stage, the dicing film 1602 on the surface of the convex ring 1301 and the surface of the vacuum suction stage, and the dicing film 1602 and the pad on the back of the device area The surfaces of the wafer jig 180 are in contact;

S233 : Use the cutting knife 190 to cut and remove the edge region and the convex ring 1301 .

In an optional example, the thickness of the removed wafer 130 may be the same as the thickness of the spacer jig 180 during the drum grinding process on the back surface of the pre-thinned wafer 130 .

In an optional example, the gasket jig 180 can be selected from the existing gasket jig with the thinnest thickness. 500# gasket fixture. Since the thickness of the wafer 130 removed in the drum grinding process is the same as the thickness of the spacer jig 180 , the thinner the thickness of the spacer jig 180 is, the more thinning range is left for the pre-thinning process of the wafer 130 . In this way, the thickness to be thinned during the pre-thinning process can be selected according to actual needs, so that the wafer scheme with the most final thickness can be selected.

Table 3. Various data of wafers with an initial thickness of 725 μm selected for a 500# gasket fixture after the wafer grinding method of the present application.

It can be seen from Table 3 that by adjusting the thinning thickness of the wafer 130 in the pre-thinning process, a wider final thickness range can be obtained, that is, the thinning thickness in the pre-thinning process can be selected to be 0-225 μm, which corresponds to The final thickness of the wafer can also range from 0 to 225 μm.

In an optional example, after removing the edge region of the wafer and the convex ring 1301 , that is, after step S23 , the method further includes: dicing the wafer 130 to obtain a plurality of separated chips.

Specifically, the device area of the wafer 130 may be cut, but not limited to, using a diamond blade to obtain a plurality of separate and independent chips. Of course, in other examples, a laser may also be used to cut the device region of the wafer 130 .

More specifically, the device area of the wafer 130 may be diced along the dicing lines to avoid chip damage.

In the description of this specification, description with reference to the terms "one of the embodiments", "the other embodiment", etc. means that a particular feature, structure, material or feature described in connection with that embodiment or example is included in at least one implementation of the invention example or example. In this specification, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

The technical features of the above-described embodiments can be combined arbitrarily. To simplify the description, all possible combinations of the technical features of the above-described embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the description in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (10)

1. a grinding method of wafer, is characterized in that, comprises: providing a wafer including a device area and an edge area; pre-thinning the wafer from the backside of the wafer; The back surface of the wafer after the pre-thinning treatment is subjected to drum grinding. After the drum grinding, a convex ring is formed on the edge area of the wafer. 2. The grinding method of a wafer according to claim 1, wherein the pre-thinning process performed on the wafer from the backside of the wafer comprises: Plane grinding is performed on the backside of the wafer. 3. a processing method of wafer, is characterized in that, comprises: The wafer is subjected to a grinding process using the method for grinding a wafer according to claim 1 or 2; A placement device is provided, the placement device includes a dicing ring and a dicing film, and the dicing film is attached to the dicing ring; The wafer after grinding treatment is attached to the surface of the dicing film, and the back of the wafer is in contact with the surface of the dicing film; The edge region and the raised ring of the wafer are removed. 4. The wafer processing method according to claim 3, wherein, The device area includes a plurality of chip areas arranged at intervals, and adjacent chip areas are separated by dicing lanes; the front side of each chip area is formed with devices; Before using the wafer grinding method according to claim 1 or 2 to perform the grinding process on the wafer, the method further comprises: forming a protective film on the front surface of the wafer, the protective film covering at least the device area. front; After the wafer is ground by the method for grinding a wafer according to claim 1 or 2, the wafer after the grinding process is placed on the surface of the dicing film, further comprising: removing the the protective film. 5. The processing method of a wafer according to claim 4, wherein the back surface of the wafer after the pre-thinning process is subjected to drum grinding, the back surface of the wafer has rough texture; After the wafer is ground, before removing the protective film, it also includes: removing the rough texture; Electrodes are formed on the backside of the wafer. 6 . The wafer processing method according to claim 5 , wherein dry etching or wet etching is performed on the back surface of the polished wafer to remove the rough texture. 7 . 7 . The wafer processing method according to claim 1 , wherein the edge region and the convex ring of the wafer are removed by cutting with a dicing knife. 8 . 8 . The wafer processing method according to claim 7 , wherein the dicing film is located on the back surface of the device region and the surface of the convex ring; the edge region and all the edges of the wafer are removed. 9 . The convex ring, including: A vacuum adsorption stage is provided. The vacuum adsorption stage includes a stage main body and a vacuum adsorption device located in the stage main body. A gasket fixture is provided on the surface of the vacuum adsorption stage. The gasket fixture An adsorption hole is arranged inside the gasket fixture along the thickness direction, and the adsorption hole is communicated with the vacuum adsorption device; Place the mounting device on which the wafer is attached on the vacuum suction stage, and the dicing film on the surface of the convex ring and the surface of the vacuum suction stage are located in the device area The dicing film on the back side is in contact with the surface of the gasket fixture; The edge region and the collar are removed by cutting with the cutting knife. 9. The wafer processing method according to claim 8, wherein, in the process of performing drum grinding on the back of the wafer after the pre-thinning process, the thickness of the removed wafer is the same as the thickness of the wafer. The thickness of the gasket jig is the same. 10 . The wafer processing method according to claim 8 , wherein after removing the edge region and the convex ring of the wafer, the method further comprises: cutting the wafer to obtain multiple separate chips.

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