Wafer grinding method and wafer processing method

Abstract

The present application provides a method for grinding a wafer and a method for processing a wafer. The method for grinding a wafer includes: providing a wafer, the wafer including a device region and an edge region; performing a pre-thinning process on the back surface of the wafer; performing a drum grinding on the back surface of the wafer after the pre-thinning process, and after the drum grinding, a convex ring is formed in the edge region of the wafer. In the method for grinding a wafer of the present invention, a step of performing a pre-thinning process on the back surface of the wafer is added before performing the drum grinding on the back surface of the wafer. The final thickness of the finally obtained wafer can be flexibly adjusted by adjusting the thinning amount in the pre-thinning process, and wafers with a wider range of final thickness values can be obtained, which can meet the requirements of the process for wafers with different final thicknesses.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and particularly to a grinding method for wafers and a wafer processing method. Background Art

[0002] After the device is fabricated on the front side of the wafer, the back side of the wafer needs to be ground. In order to reduce the handling risk of the wafer and reduce the warping of the wafer, generally, the back side of the wafer is subjected to drum grinding; after drum grinding, a convex ring is formed on the edge of the wafer. However, due to the limitations of the drum grinding property and the thickness of the spacer fixture used to remove the convex ring after drum grinding, finally, only wafers with individual final thickness values can be obtained, which cannot meet the process requirements for wafers with different final thicknesses. Summary of the Invention

[0003] Based on the problem that only drum grinding is used to grind the back side of the wafer in the prior art, and finally only wafers with individual final thickness values can be obtained, which cannot meet the process requirements for wafers with different final thicknesses, it is necessary to provide a grinding method for wafers and a wafer processing method for the above problems.

[0004] In a first aspect, the present application provides a grinding method for wafers, including:

[0005] Providing a wafer, the wafer including a device region and an edge region;

[0006] Performing pre-thinning treatment on the wafer from the back side of the wafer;

[0007] Performing drum grinding on the back side of the wafer after pre-thinning treatment, and after the drum grinding, a convex ring is formed in the edge region of the wafer.

[0008] In the grinding method for wafers of the present invention, by adding a step of performing pre-thinning treatment on the back side of the wafer before performing drum grinding on the back side of the wafer, the final thickness of the finally obtained wafer can be flexibly adjusted by adjusting the thinning amount in the pre-thinning treatment, and wafers with a wider range of final thickness values can be obtained, which can meet the process requirements for wafers with different final thicknesses.

[0009] In one embodiment, the performing pre-thinning treatment on the wafer from the back side of the wafer includes:

[0010] Performing planar grinding on the back side of the wafer.

[0011] In a second aspect, the present invention further provides a wafer processing method, including:

[0012] Performing grinding treatment on the wafer by using the grinding method for wafers described in the first aspect;

[0013] Provide a mounting device, the mounting device includes a cutting ring and a cutting film, and the cutting film is adhered to the cutting ring;

[0014] Place the polished wafer on the surface of the cutting film, and the back surface of the wafer contacts the surface of the cutting film;

[0015] Remove the edge region and the convex ring of the wafer.

[0016] In the method for processing a wafer of the present invention, before performing drum grinding on the back surface of the wafer, a step of pre-thinning the back surface of the wafer is added. The final thickness of the finally obtained wafer can be flexibly adjusted by adjusting the thinning amount in the pre-thinning process. Wafer to be cut with a wider range of final thickness values can be obtained, which can meet the process requirements for wafers with different final thicknesses.

[0017] In one embodiment, the device region includes a plurality of chip regions arranged at intervals, and adjacent chip regions are isolated by cutting channels; devices are formed on the front surface of each chip region;

[0018] Before grinding the wafer by using the wafer grinding method as described in the first aspect, it further includes: forming a protective film on the front surface of the wafer, and the protective film covers at least the front surface of the device region;

[0019] After grinding the wafer by using the wafer grinding method as described in the first aspect, before placing the ground wafer on the surface of the cutting film, it further includes: removing the protective film.

[0020] In one embodiment, after performing drum grinding on the back surface of the pre-thinned wafer, the back surface of the wafer has rough lines; before removing the protective film after grinding the wafer, it further includes:

[0021] Remove the rough lines;

[0022] Form an electrode on the back surface of the wafer.

[0023] In the above embodiment, by removing the rough lines on the back surface of the wafer, the contact resistance between the electrode 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 fragmentation.

[0024] In one embodiment, dry etching or wet etching is performed on the back surface of the ground wafer to remove the rough lines.

[0025] In one embodiment, a cutting tool is used to cut and remove the edge region and the convex ring of the wafer.

[0026] In one embodiment, the cutting film is located on the back surface of the device region and the surface of the convex ring; removing the edge region and the convex ring of the wafer includes:

[0027] Providing a vacuum adsorption stage, the vacuum adsorption stage includes a stage body and a vacuum adsorption device located within the stage body, a gasket fixture is provided on the surface of the vacuum adsorption stage, and adsorption holes penetrating through the gasket fixture in the thickness direction are provided within the gasket fixture, and the adsorption holes are connected to the vacuum adsorption device;

[0028] Placing the mounting device with the wafer attached thereon on the vacuum adsorption stage, the cutting film located on the surface of the convex ring contacts the surface of the vacuum adsorption stage, and the cutting film located on the back surface of the device region contacts the surface of the gasket fixture;

[0029] Using the cutting tool to cut and remove the edge region and the convex ring.

[0030] In one embodiment, during the process of performing drum grinding on the back surface of the wafer after pre-thinning treatment, the thickness of the wafer removed is the same as the thickness of the gasket fixture.

[0031] In one embodiment, after removing the edge region and the convex ring of the wafer, it further includes: cutting the wafer to obtain a plurality of separated chips. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a flowchart of a grinding method for a wafer provided in an embodiment of the present application;

[0034] Figure 2 It is a schematic diagram of performing planar grinding on the back surface of a wafer in a grinding method for a wafer provided in an embodiment of the present application;

[0035] Figure 3 It is a schematic diagram of performing drum grinding on the back surface of a pre-thinned wafer in a grinding method for a wafer provided in an embodiment of the present application;

[0036] Figure 4 The flowchart of the processing method of the wafer provided in another embodiment of the present application;

[0037] Figure 5 The schematic diagram of removing the edge area and the convex ring of the wafer in the processing method of the wafer provided in another embodiment.

[0038] Explanation of reference numerals: 110, vacuum chuck; 120, protective film; 130, wafer; 1301, convex ring; 140, abrasive liquid delivery pipeline; 150, grinding head; 1601, cutting ring; 1602, cutting film; 1701, stage body; 1702, vacuum adsorption device; 180, gasket fixture; 1801, adsorption hole; 190, cutting tool. Detailed implementation manners

[0039] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0041] It can 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 the first element from another element.

[0042] It can be understood that "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if there is an electrical signal or data transmission between the connected circuits, modules, units, etc.

[0043] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "comprising", "including" or "having", etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0044] Semiconductor chips, such as power devices, power management, sensor chips, etc., are widely used in industrial control, automotive, power, energy and other fields. Taking the power device IGBT as an example, Insulated Gate Bipolar Transistor, that is, insulated gate bipolar transistor, is a composite power semiconductor device composed of BJT and MOSFET. It has the advantages of high switching speed, high input impedance, low control power, simple drive circuit, and low switching loss of MOSFET, as well as the advantages of low on-state voltage, large on-state current, and low loss of BJT. It has outstanding competitiveness in high voltage, large current, high speed, etc., and has become the mainstream development direction of switching devices in the field of power electronics.

[0045] Grinding is a very important process in the semiconductor chip manufacturing process. Grinding can achieve wafer thinning, wafer surface planarization, etc.

[0046] After the front side of the wafer is completed with device preparation, the back side needs to be ground. In order to reduce the handling risk of the wafer and reduce the warping of the wafer, the back side of the wafer is generally drum-grinded; after drum-grinding, a convex ring will be formed on the edge of the wafer. However, due to the limitations of the drum-grinding properties and the thickness of the gasket fixture used to remove the convex ring after drum-grinding, only wafers with individual final thickness values can be obtained finally, which cannot meet the process requirements for wafers with different final thicknesses.

[0047] Table 1. The final thickness of the wafer obtained after removing the convex ring based on different gasket fixtures after the back side of the wafer with an initial thickness of 725μm is drum-grinded.

[0048] Gasket fixture model Final thickness Final thickness range 655# 70μm 60μm - 80μm 610# 115μm 105μm - 125μm 500# 225μm 215μm - 235μm

[0049] Table 2. The final thickness of the wafer obtained after removing the convex ring based on different gasket fixtures after the back side of the wafer with an initial thickness of 735μm is drum-grinded.

[0050] Gasket fixture model Final thickness Final thickness range 655# 80μm 70μm - 90μm 610# 125μm 115μm - 135μm 500# 235μm 225μm - 245μm

[0051] The thickness of the spacer fixture for 500# in Table 1 and Table 2 is 500 μm, the thickness of the spacer fixture for 610# is 610 μm, and the thickness of the spacer fixture for 655# is 655 μm. As can be seen from Table 1 and Table 2, there are only three models of spacer fixtures used in the convex ring removal machine; after the back surface of the wafer with an initial thickness of 725 μm is subjected to drum grinding, the final thicknesses of the wafers obtained after removing the convex ring based on different spacer fixtures are only three values: 70 μm, 115 μm, and 225 μm; after the back surface of the wafer with an initial thickness of 735 μm is subjected to drum grinding, the final thicknesses of the wafers obtained after removing the convex ring based on different spacer fixtures are only three values: 80 μm, 125 μm, and 235 μm. Table 1 and Table 2 further confirm that only subjecting the wafer to drum grinding cannot meet the process requirements for wafers with different final thicknesses.

[0052] In one embodiment, please refer to Figure 1 , the present application provides a wafer grinding method, and the wafer grinding method may include the following steps:

[0053] S10: Provide a wafer, which includes a device area and an edge area;

[0054] S11: Perform a pre-thinning process on the back surface of the wafer;

[0055] S12: Perform drum grinding on the back surface of the pre-thinned wafer. After drum grinding, a convex ring is formed in the edge area of the wafer.

[0056] In the above wafer grinding method, by adding a step of performing a pre-thinning process on the back surface of the wafer before performing drum grinding on the back surface of the wafer, the final thickness of the finally obtained wafer can be flexibly adjusted by adjusting the thinning amount in the pre-thinning process, and wafers with a wider range of final thickness values can be obtained, which can meet the process requirements for wafers with different final thicknesses.

[0057] In step S10, please refer to Figure 1 in step S10 of Figure 2 , and provide a wafer 130, which includes a device area and an edge area.

[0058] In an optional example, the wafer 130 may include, but is not limited to, a silicon wafer, a gallium nitride wafer, a silicon carbide wafer, etc.

[0059] Specifically, the device area may include a plurality of chip areas arranged at intervals, and adjacent chip areas are isolated by dicing streets; devices are formed on the front surfaces of each chip area.

[0060] In order to protect the devices from being damaged by subsequent processes, a protective film 120 may be formed on the front surface of the wafer 130, as Figure 2 shown.

[0061] In step S11, refer to Figure 1 S11 in Figure 2 , and perform pre-thinning on the back surface of the wafer 130 from the back surface of the wafer 130.

[0062] In one example, in step S11, the back surface of the wafer 130 can be planar polished to thin the wafer 130.

[0063] Specifically, in step S11, the front and back surfaces of the wafer 130 can be thinned as a whole, and the thickness of the thinning can be flexibly adjusted according to the final thickness required for the wafer finally obtained later, and no limitation is made here.

[0064] In one example, in step S11, based on a planar polishing machine as shown in Figure 2 , the back surface of the wafer 130 is planar polished. Specifically, the planar polishing machine can include a vacuum chuck 110, a polishing liquid delivery pipeline 140, and a polishing head (not shown). The vacuum chuck 110 is used to adsorb the wafer 130, and the wafer 130 is adsorbed on the vacuum chuck 110 with the front surface facing down. At this time, the protective film 120 contacts the surface of the vacuum chuck 110. The polishing liquid delivery pipeline 140 is used to deliver the polishing liquid to the surface of the wafer 130, and the polishing head is used to perform planar polishing on the back surface of the wafer 130 based on the polishing liquid.

[0065] In step S12, refer to Figure 1 S12 in Figure 3 , and perform taiko polishing (i.e., execute the TAIKO process) on the back surface of the pre-thinned wafer 130. After the taiko polishing, a convex ring 1301 is formed in the edge region of the wafer 130.

[0066] In one example, in step S12, refer to Figure 3 , when using the polishing head 150 to perform taiko polishing on the back surface of the pre-thinned wafer 130, only the back surface of the device region is polished, and the edge region is not polished. In this way, after the taiko polishing, a convex ring 1301 is formed in the edge region of the wafer 130.

[0067] Specifically, the width of the convex ring 1301 can be about 3 mm.

[0068] In another embodiment, refer to Figures 1 to 3 in combination with Figure 4 , this application also provides a method for processing a wafer. The method for processing a wafer includes:

[0069] S20: Grind the wafer by using the wafer grinding method as described in the above embodiment;

[0070] S21: Provide a mounting device, which includes a cutting ring and a cutting film, and the cutting film is placed on the cutting ring.

[0071] S22: Place the polished wafer on the surface of the cutting film, and the back surface of the wafer contacts the surface of the cutting film.

[0072] S23: Remove the edge area and the convex ring of the wafer.

[0073] In the method for processing a wafer of the present invention, before performing drum grinding on the back surface of the wafer, a step of pre-thinning the back surface of the wafer is added. The final thickness of the finally obtained wafer can be flexibly adjusted by adjusting the thinning amount in the pre-thinning process, and wafers to be cut with a wider range of final thickness values can be obtained, which can meet the process requirements for wafers with different final thicknesses.

[0074] In step S20, please refer to Figures 1 to 3 and refer to Figure 4 step S20 in, and grind the wafer by using the wafer grinding method described in the above embodiment.

[0075] In an optional example, the device area includes a plurality of chip areas arranged at intervals, and adjacent chip areas are isolated by cutting channels; devices are formed on the front surfaces of each chip area. Before grinding the wafer 130, it may further include: forming a protective film 120 on the front surface of the wafer 130, and the protective film 120 at least covers 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 being damaged during subsequent grinding processes.

[0076] In an optional example, after grinding the wafer 130, before placing the ground wafer 130 on the surface of the cutting film, that is, between step S20 and step S21, it further includes: removing the protective film 120.

[0077] 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 can be removed by but is not limited to heating and other methods.

[0078] In an optional example, after performing drum grinding on the back surface of the pre-thinned wafer 130, the back surface of the wafer 130 has rough lines; before removing the protective film 120 after grinding the wafer 130, it further includes:

[0079] Removing the rough lines;

[0080] Forming an electrode on the back surface of the wafer 130.

[0081] In the above embodiments, by removing the rough texture on the back surface of the wafer 130, the contact resistance between the electrode 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 fragmentation.

[0082] Specifically, the electrode may include a metal electrode, and the electrode may be formed by, but not limited to, sputtering process, electroplating process or physical vapor deposition process. In this embodiment, the electrode is formed by physical vapor deposition process. More specifically, the material of the electrode may include at least one of aluminum, titanium, nickel and silver.

[0083] In an optional example, the back surface of the wafer 130 after grinding treatment may be dry etched to remove the rough texture, or the back surface of the wafer 130 after grinding treatment may be wet etched to remove the rough texture.

[0084] In step S21, please refer to Figure 4 the S21 step in Figure 5 , and a mounting device is provided. The mounting device includes a cutting ring 1601 and a cutting film 1602, and the cutting film 1602 is disposed on the cutting ring 1601.

[0085] Specifically, the cutting film 1602 may include a blue film, and the cutting film 1602 may cover the opening inside the cutting ring 1601.

[0086] In step S22, please refer to Figure 4 the S22 step in Figure 5 , and the wafer 130 after grinding treatment is placed on the surface of the cutting film 1602, and the back surface of the wafer 130 contacts the surface of the cutting film 1602.

[0087] It should be noted that the diameter of the wafer 130 should be smaller than the inner diameter of the cutting ring 1601 to ensure that the wafer 130 can be placed on the cutting film 1602.

[0088] In step S23, please refer to Figure 4 the S23 step in Figure 5 , and the edge region and the convex ring 1301 of the wafer 130 are removed.

[0089] In an optional example, a cutting tool 190 may be used to cut and remove the edge region and the convex ring 1301 of the wafer 130.

[0090] Specifically, the cutting tool 190 may include, but not limited to, a diamond blade.

[0091] In one example, the cutting film 1602 is located on the back surface of the device region and the surface of the convex ring 1301; in step S23, removing the edge region and the convex ring 1301 of the wafer may include:

[0092] S231: Provide a vacuum adsorption stage, which includes a stage main body 1701 and a vacuum adsorption device 1702 located inside the stage main body 1701. A gasket fixture 180 is provided on the surface of the vacuum adsorption stage. An adsorption hole 1801 penetrating through the gasket fixture 180 in the thickness direction is provided inside the gasket fixture 180, and the adsorption hole 1801 is connected to the vacuum adsorption device;

[0093] S232: Place the mounting device with the wafer 130 placed thereon on the vacuum adsorption stage. The dicing film 1602 on the surface of the convex ring 1301 contacts the surface of the vacuum adsorption stage, and the dicing film 1602 on the back surface of the device area contacts the surface of the gasket fixture 180;

[0094] S233: Use the dicing knife 190 to cut and remove the edge area and the convex ring 1301.

[0095] In an optional example, during the process of performing drum grinding on the back surface of the pre-thinned wafer 130, the thickness of the removed wafer 130 can be the same as the thickness of the gasket fixture 180.

[0096] In an optional example, the gasket fixture 180 can select the existing gasket fixture with the thinnest thickness. For example, the 500# gasket fixture among the three models of 500#, 610#, and 655# in Table 1 and Table 2 can be selected. Since the thickness of the removed wafer 130 during the drum grinding process is the same as the thickness of the gasket fixture 180, the thinner the thickness of the gasket fixture 180, the larger the thinning range left for pre-thinning the wafer 130. In this way, the thinning thickness during the pre-thinning process can be selected according to actual needs, so as to obtain the scheme of wafers with the most selectable final thicknesses.

[0097] Table 3. Data of wafers with an initial thickness of 725μm for the 500# gasket fixture after the wafer grinding method of the present application.

[0098]

[0099] As can be seen from Table 3, by adjusting the thinning thickness of the wafer 130 during the pre-thinning process, a relatively wide final thickness range can be obtained. That is, the thinning thickness during the pre-thinning process can be selected as 0 - 225μm, and the corresponding range of the final thickness of the wafer can also reach 0 - 225μm.

[0100] In an optional example, after removing the edge area of the wafer and the convex ring 1301, that is, after step S23, it further includes: dicing the wafer 130 to obtain multiple separated chips.

[0101] Specifically, but not limited to, a diamond blade can be used to cut the device area of the wafer 130 to obtain multiple separated and independent chips. Of course, in other examples, a laser can also be used to cut the device area of the wafer 130.

[0102] More specifically, the device area of the wafer 130 can be cut along the scribe line to avoid damaging the chips.

[0103] In the description of this specification, the descriptions referring to terms such as "one of the embodiments", "other embodiments", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0104] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0105] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A wafer processing method, characterized in that: include: Providing a wafer, wherein the wafer includes a device region and an edge region; performing a pre-thinning process on the wafer from the back side of the wafer, and adjusting the final thickness of the wafer obtained by adjusting the thinning amount in the pre-thinning process; Performing drum grinding on the back side of the pre-thinned wafer, wherein a convex ring is formed on the edge area of the wafer after the drum grinding, and the thickness of the wafer removed during the drum grinding is the same as the thickness of the gasket jig; A mounting device is provided, the mounting device comprising a cutting ring and a cutting film, the cutting film being mounted on the cutting ring; The polished wafer is placed on the surface of the dicing film, with the back side of the wafer in contact with the surface of the dicing film, and the dicing film on the back side of the device region of the wafer in contact with the surface of the gasket jig; A vacuum adsorption platform is provided, the vacuum adsorption platform comprising a platform body and a vacuum adsorption device located within the platform body, a gasket fixture is provided on the surface of the vacuum adsorption platform, the gasket fixture is provided with an adsorption hole penetrating the gasket fixture along the thickness direction, and the adsorption hole is connected to the vacuum adsorption device; Placing the mounting device with the wafer mounted thereon on the vacuum adsorption stage, wherein the dicing film on the surface of the convex ring contacts the surface of the vacuum adsorption stage, and the dicing film on the back side of the device area contacts the surface of the gasket jig; The edge area and the raised ring are cut away using a cutting knife.

2. The wafer processing method according to claim 1, wherein: The pre-thinning process of the wafer from the back side of the wafer includes: The back side of the wafer is plane-ground.

3. The wafer processing method according to claim 1, wherein: The device area includes a plurality of chip areas arranged at intervals, and adjacent chip areas are separated by cutting lines; a device is formed on the front side of each chip area; Before grinding the wafer, the method further includes: forming a protective film on the front surface of the wafer, wherein the protective film at least covers the front surface of the device area; After grinding the wafer and before attaching the ground wafer to the surface of the dicing film, the method further includes: removing the protective film.

4. The wafer processing method according to claim 3, wherein: After the back side of the wafer after the pre-thinning process is subjected to Taiko grinding, the back side of the wafer has rough texture; After the wafer is ground and before the protective film is removed, the method further includes: removing the rough texture; An electrode is formed on the back side of the wafer.

5. The wafer processing method according to claim 4, characterized in that: The back side of the wafer after the grinding process is dry-etched or wet-etched to remove the rough lines.

6. The wafer processing method according to claim 1, wherein: After removing the edge area and the convex ring of the wafer, the method further includes: cutting the wafer to obtain a plurality of separated chips.

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