Wafer thinning processing method and wafer

Abstract

The invention provides a wafer thinning processing method and a wafer, and the wafer thinning processing method comprises the following steps: providing a wafer which comprises a front surface and a back surface which are oppositely arranged, and bonding the front surface of the wafer to a slide through a first bonding glue layer; carrying out first-time processing treatment on the back surface of the wafer; carrying out de-bonding on the wafer and the slide glass so as to separate the wafer from the slide glass; bonding the front surface of the wafer to a slide through a second bonding glue layer; processing the back surface of the wafer for the second time; wherein the temperature tolerance of the second bonding adhesive layer is greater than that of the first bonding adhesive layer, and the process temperature of the second processing is greater than that of the first processing. According to different bonding requirements of different processes, multiple bonding is adopted, and bonding glue with different requirements is selected at different process nodes, so that thinning and automatic transmission and transfer of the ultrathin wafer can be met, process requirements of high-temperature annealing, metallization and the like at high temperature can be met, and the performance of the device is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor processing and relates to a wafer thinning processing method and a wafer. Background Art

[0002] Power device chips use back metallization as electrodes. In order to improve device performance, it is necessary to use back thinning to reduce the thickness of the chip, thereby reducing the on-resistance between the front and back sides and reducing energy loss. Since the front side processing of the wafer is complex and involves many steps, it is easy to break if thin sheets are used, resulting in a sharp drop in the yield rate. Therefore, the technology uses a process flow of first front side processing and then back side processing.

[0003] The back-side processing of the wafer involves processes such as back-side thinning, back-side ion implantation, back-side cleaning, and back-side metallization. The thinned wafer has reduced strength, which leads to problems of warping and breakage. Since automated wafer transfer has high requirements on wafer strength, wafers with a thickness of less than 150 microns are generally difficult to transfer using automated equipment due to their own warping.

[0004] The Taiko process can reduce the warpage of the wafer. The principle is to thin only the middle part of the wafer during wafer thinning, and keep the original thickness of the 3-4 mm part of the edge of the wafer. In this way, the warpage of the wafer can be controlled within 1 mm to achieve automatic handling and operation of automated equipment. With the further improvement of process technology, the thickness requirements for wafers will also be thinner. When the performance of the device requires the wafer thickness to be ≤80 microns, the breakage rate of the Taiko process will surge, which is not suitable for automated handling and operation of wafers. For this reason, people have invented wafer-level temporary bonding technology, which bonds the wafer and the carrier together with bonding glue, and then The wafer is thinned (the wafer thickness will be ≤80 microns), and the carrier and wafer are involved in the subsequent process together to ensure that the ultra-thin wafer can be transferred by automated equipment and will not break in the subsequent process. When the product process is completed, the carrier and the wafer are separated. Among them, the wafer thinning process has high requirements on the bonding quality, and it is necessary to use bonding glue with good bonding effect, such as acrylic resin and propylene glycol methyl ether acetate solvent, etc. However, these materials have poor high temperature resistance and will decompose at high temperature to produce acrylic acid, propylene, propane, carbon black and other organic substances, which limits the maximum process temperature of the bonded wafer in the subsequent process (annealing, metallization) and reduces the device performance.

[0005] Therefore, how to provide a wafer thinning processing method and a wafer that can meet both wafer thinning requirements and high temperature process requirements has become a technical problem that needs to be urgently solved by technical personnel in this field.

[0006] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a wafer thinning processing method and a wafer, so as to solve the problem that the temperature resistance of the bonding glue in the wafer processing process in the prior art cannot meet the high temperature process requirements.

[0008] To achieve the above-mentioned object and other related objects, the present invention provides a wafer thinning method, comprising the following steps:

[0009] Providing a wafer, wherein the wafer comprises a front side and a back side that are arranged opposite to each other, and bonding the front side of the wafer to a first carrier through a first bonding adhesive layer;

[0010] Performing a first processing on the back side of the wafer, wherein the first processing includes thinning;

[0011] Debonding the wafer and the first carrier to separate the wafer and the first carrier;

[0012] Bonding the front side of the wafer to the second carrier through a second bonding adhesive layer;

[0013] Performing a second processing on the back side of the wafer;

[0014] The temperature tolerance of the second bonding adhesive layer is greater than the temperature tolerance of the first bonding adhesive layer, and the process temperature of the second processing is greater than the process temperature of the first processing.

[0015] Optionally, after the first processing is performed on the back side of the wafer, the thickness of the wafer does not exceed 80 μm.

[0016] Optionally, the thinning method comprises chemical mechanical polishing.

[0017] Optionally, the material of the first bonding adhesive layer includes acrylic resin and propylene glycol methyl ether acetate solvent.

[0018] Optionally, the second processing includes one or more of annealing and back side metallization.

[0019] Optionally, before performing the second processing on the back side of the wafer, the back side of the wafer is further cleaned and ion implanted.

[0020] Optionally, the process temperature of the second processing is greater than 280°C.

[0021] Optionally, the material of the second bonding adhesive layer includes one or more of epoxy resin, polyurethane, and polyimide.

[0022] Optionally, after the second processing is performed on the back side of the wafer, the method further includes debonding the wafer and the second carrier.

[0023] The present invention also provides a wafer, which is manufactured by any of the wafer thinning methods described above.

[0024] As described above, in the wafer thinning processing method and wafer of the present invention, multiple bonding is adopted according to different bonding requirements of different processes, and bonding glues with different requirements are selected at different process nodes. This can not only meet the thinning and automated transmission and transportation of ultra-thin wafers, but also meet the process requirements of high-temperature annealing and metallization at higher temperatures, effectively expanding the window of semiconductor process technology and improving device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Shown is a schematic diagram of a wafer thinning processing method.

[0026] Figure 2 Shown is a flow chart of a wafer thinning method according to an embodiment of the present invention.

[0027] Figure 3 It is a schematic diagram showing that a wafer and a first carrier are bonded via a first bonding adhesive layer in an embodiment of the present invention.

[0028] Figure 4 It is a schematic diagram showing the back side of the wafer after the first processing in an embodiment of the present invention.

[0029] Figure 5 Shown is a schematic diagram of debonding the wafer and the first carrier in an embodiment of the present invention.

[0030] Figure 6 It is a schematic diagram showing that a wafer and a second carrier are bonded via a second bonding adhesive layer in an embodiment of the present invention.

[0031] Figure 7 A schematic diagram showing the back side of a wafer after a second processing is performed according to an embodiment of the present invention.

[0032] Component number description

[0033] 1 Wafer

[0034] 2 First bonding layer

[0035] 3 First slide

[0036] 4 Second bonding layer

[0037] 5 Second slide

[0038] Steps S1 to S5 DETAILED DESCRIPTION

[0039] like Figure 1 As shown, it is a schematic diagram of a wafer thinning method, including: coating an adhesive layer on the surface of the wafer, coating a release layer on the surface of the carrier → bonding the wafer and the carrier → thinning the back of the wafer → cleaning the back of the wafer, ion implantation, annealing, metallization → debonding the wafer and the carrier. The bonding process will use the coating of the adhesive layer and the release layer. These two layers of materials are bonding glue. The main components of these glues are acrylic resin and propylene glycol methyl ether acetate (PMA) solvent, which can form a high bonding quality and meet the thinning process requirements. However, its high temperature resistance is poor. At a high temperature of more than 280°C, it will decompose to produce organic substances such as acrylic acid, propylene, propane, and carbon black. This limits the maximum process temperature of the bonded wafer in the subsequent process. During the annealing and metallization process, a process temperature greater than 300°C may be used. The maximum tolerance temperature of the bonding glue cannot meet the process temperature requirements.

[0040] Therefore, the purpose of this application is to provide a new wafer thinning processing method that can meet both wafer thinning requirements and high temperature process requirements.

[0041] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0042] See also Figures 2 to 7 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0043] This embodiment provides a wafer thinning method. Figure 2 , including the following steps:

[0044] S1: providing a wafer, wherein the wafer comprises a front side and a back side which are arranged opposite to each other, and bonding the front side of the wafer to a first carrier through a first bonding adhesive layer;

[0045] S2: performing a first processing on the back side of the wafer, wherein the first processing includes thinning;

[0046] S3: debonding the wafer and the first carrier to separate the wafer and the first carrier;

[0047] S4: bonding the front side of the wafer to the second carrier through a second bonding adhesive layer;

[0048] S5: performing a second processing on the back side of the wafer.

[0049] The wafer thinning method of this embodiment is described in detail below with reference to specific drawings.

[0050] First, see Figure 3 , perform step S1: provide a wafer 1, wherein the wafer 1 includes a front side and a back side that are arranged opposite to each other, and bond the front side of the wafer 1 to a first carrier 3 through a first bonding adhesive layer 2.

[0051] As an example, the wafer 1 may be a silicon wafer, a germanium wafer, a gallium arsenide wafer, a silicon carbide wafer, a gallium nitride wafer or any other suitable wafer, which may be selected according to actual needs.

[0052] As an example, before the front side of the wafer 1 is bonded to the first carrier 3, the step of processing the front side of the wafer 1 is also included. After the front side processing of the wafer 1 is completed, the front side of the wafer 1 is bonded to the first carrier 3 through the first bonding adhesive layer 2 for processing the back side of the wafer 1.

[0053] As an example, the first carrier 3 may be a glass carrier, a metal carrier, a semiconductor carrier or any other suitable carrier. Preferably, in order to avoid the introduction of impurities, a carrier made of the same material as the wafer is preferably used.

[0054] As an example, in this embodiment, the subsequent first processing is a thinning process, and the thinning process has high requirements for bonding quality, that is, the bonding effect of the first bonding adhesive layer 2 is relatively high, such as the thickness uniformity of the bonding glue applied to the wafer and the carrier, the particles and bubbles in the glue, the holes after bonding, the strength after bonding, etc. In this embodiment, the material of the first bonding adhesive layer 2 includes acrylic resin and propylene glycol methyl ether acetate solvent, etc., which can form a high bonding quality and meet the requirements of the subsequent thinning process, among which acrylic resin mainly provides good adhesion and mechanical strength, and propylene glycol methyl ether acetate solvent helps to improve the leveling of the bonding glue and improve the thickness uniformity and adhesion of the bonding adhesive layer.

[0055] Next, see Figure 4, executing step S2: performing a first processing on the back side of the wafer 1, wherein the first processing includes thinning.

[0056] As an example, the back side of the wafer 1 is thinned to reduce the thickness of the wafer 1, thereby reducing the on-resistance of the front and back sides of the device and reducing energy loss. Specifically, in this embodiment, the thickness of the wafer 1 after thinning is ≤80 microns, forming an ultra-thin wafer.

[0057] As an example, the back side of the wafer 1 is thinned by chemical mechanical polishing or any other suitable method, wherein the process temperature of the thinning process is low, and even if the temperature tolerance of the first bonding adhesive layer 2 is low, it will not decompose to produce organic substances such as acrylic acid, propylene, propane, carbon black, etc.

[0058] Next, see Figure 5 , executing step S3: debonding the wafer 1 and the first carrier 3 to separate the wafer 1 and the first carrier 3.

[0059] As an example, the method for debonding the wafer 1 and the first carrier 3 includes thermal sliding debonding, chemical wet debonding, thermal decomposition debonding, laser debonding or any other suitable debonding method. After debonding the wafer 1 and the first carrier 3, the front side of the wafer 1 is separated from the first carrier 3.

[0060] Next, see Figure 6 , executing step S3: bonding the front side of the wafer 1 to the second carrier 5 through the second bonding adhesive layer 4 .

[0061] As an example, the second carrier 5 and the first carrier 3 can be the same carrier to reduce costs, or new carriers can be provided in different bonding steps, depending on the needs.

[0062] As an example, the subsequent second processing is a high-temperature process, and the second bonding adhesive layer 4 is made of a material with high temperature tolerance, such as epoxy resin, polyurethane, polyimide, etc.

[0063] Next, see Figure 7 , execute step S3: perform secondary processing on the back side of the wafer 1.

[0064] As an example, the second processing includes high-temperature processes such as annealing and back metallization. Before the second processing, the back side of the wafer 1 is cleaned and ion implanted, and then high-temperature processes such as annealing and back metallization are performed. Since the second bonding layer 4 has high temperature tolerance, it can withstand high-temperature processes of 400 degrees or even higher, that is, it can increase the process temperature of the second processing, effectively enlarging the window of semiconductor process technology and improving device performance.

[0065] As an example, after the back side of the wafer 1 is processed for the second time, that is, after the back side process of the wafer 1 is completed, the wafer 1 and the second carrier 5 are debonded, and then subsequent process steps such as testing, cutting, packaging, etc. are performed according to needs. Among them, the method of debonding the wafer 1 and the second carrier 5 includes thermal sliding debonding, chemical wet debonding, thermal decomposition debonding, laser debonding or any other suitable debonding method.

[0066] As an example, processes such as wafer thinning have high requirements on the quality of bonding, and annealing and metallization processes have high requirements on the temperature tolerance of the bonding sheet. Currently, there is no bonding glue that matches both "high bonding quality" and "high temperature tolerance". In this application, multiple bonding methods are adopted. According to the different bonding requirements of different processes, bonding glues with different requirements are selected at different process nodes. It can not only meet the thinning and automated transmission and transportation of ultra-thin wafers, but also meet the process requirements of high temperature annealing and back metallization at higher temperatures, effectively expanding the window of semiconductor process technology and improving device performance.

[0067] It should be noted that this embodiment only lists a wafer thinning processing method with two bondings, and is not limited to this embodiment. Three bondings, four bondings or even more bondings can be performed according to needs, wherein bonding glues with different performances are selected according to different process nodes to adapt to different process requirements.

[0068] As an example, the present application also provides a wafer, which is manufactured by the above-mentioned wafer thinning processing method.

[0069] In summary, the wafer thinning processing method and wafer of the present invention adopt multiple bonding according to different bonding requirements of different processes, and select bonding glues with different requirements at different process nodes, which can not only meet the thinning and automatic transmission and transportation of ultra-thin wafers, but also meet the process requirements of high-temperature annealing and metallization at higher temperatures, effectively enlarging the window of semiconductor process and improving device performance. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0070] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A wafer thinning method, characterized in that: The following steps are involved: Providing a wafer, wherein the wafer comprises a front side and a back side that are arranged opposite to each other, and bonding the front side of the wafer to a first carrier through a first bonding adhesive layer; Performing a first processing on the back side of the wafer, wherein the first processing includes thinning; Debonding the wafer and the first carrier to separate the wafer and the first carrier; Bonding the front side of the wafer to the second carrier through a second bonding adhesive layer; Performing a second processing on the back side of the wafer; The temperature tolerance of the second bonding adhesive layer is greater than the temperature tolerance of the first bonding adhesive layer, and the process temperature of the second processing is greater than the process temperature of the first processing.

2. The wafer thinning method according to claim 1, characterized in that: After the first processing is performed on the back side of the wafer, the thickness of the wafer does not exceed 80 μm.

3. The wafer thinning method according to claim 1, characterized in that: The thinning method includes chemical mechanical polishing.

4. The wafer thinning method according to claim 1, characterized in that: The material of the first bonding adhesive layer includes acrylic resin and propylene glycol methyl ether acetate solvent.

5. The wafer thinning method according to claim 1, characterized in that: The second processing includes one or more of annealing and back side metallization.

6. The wafer thinning method according to claim 5, characterized in that: Before the second processing is performed on the back side of the wafer, the back side of the wafer is cleaned and ion implanted.

7. The wafer thinning method according to claim 5, characterized in that: The process temperature of the second processing is greater than 280°C.

8. The wafer thinning method according to claim 5, characterized in that: The material of the second bonding adhesive layer includes one or more of epoxy resin, polyurethane, and polyimide.

9. The wafer thinning method according to claim 1, characterized in that: After the second processing is performed on the back side of the wafer, the method further includes debonding the wafer and the second carrier.

10. A wafer, characterized in that: The wafer is manufactured by the wafer thinning method described in any one of 1-9.

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