A process for fabricating ultra-thin wafers with uniform stress release

Abstract

The present application relates to the technical field of ultra-thin wafer manufacturing, in particular to a stress-releasable ultra-thin wafer manufacturing process, which comprises the following steps: S1, first, complete the front high-temperature process of the wafer, bond the wafer front on the glass carrier plate, then thin the wafer back, and then bond the wafer back on the annular carrier plate; S2, take off the glass carrier plate of the wafer front, high-temperature temper the wafer, and use laser to perform the invisible cutting on the wafer back; S3, simultaneously electroplate metal layers on both sides of the wafer; S4, attach the wafer to the cutting mold frame, and cut into a granular shape along the invisible cutting path; the present application forms a groove-shaped cutting path on the wafer surface through laser cutting, due to the existence of the cutting path, the wafer can produce a small-angle bending to eliminate the stress generated by the wafer processing, the wafer is not easy to be damaged due to stress, and no excess loss of the wafer is generated.

Description

Technical Field

[0001] This invention relates to the field of ultrathin wafer fabrication technology, specifically an ultrathin wafer fabrication process that can uniformly release stress. Background Technology

[0002] A wafer is a silicon wafer used to manufacture silicon semiconductor circuits. Its raw material is silicon. After silicon crystal rods are ground, polished, and sliced, they are formed into silicon wafers, which are called wafers.

[0003] The wafer fabrication method, such as the IGBT wafer processing technology proposed in patent application number CN2021102739747, can perform ultra-thin IGBT wafer processing.

[0004] When wafers need to be cut into dies after they are fabricated, the fabricated wafers are usually cut directly. For example, the method for cutting wafers used to fabricate sensor chips into dies proposed in patent application number CN2011101068351 has the characteristic of high yield of diced dies.

[0005] In the prior art, such as the processing technology proposed in patent application number CN2021102739747 and the method proposed in patent application number CN2011101068351, wafer fabrication and dicing are separated into two independent parts. However, with the need to reduce the consumption of fabrication materials and the size of finished products, there is an increasing demand for thinner wafers. When fabricating ultra-thin wafers with a thickness of less than 60μm, the wafer is easily damaged due to stress during the wafer fabrication process and dicing. Summary of the Invention

[0006] The purpose of this invention is to provide an ultrathin wafer fabrication process that can uniformly release stress, so as to solve the problems mentioned in the background art.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] An ultrathin wafer fabrication process capable of uniformly releasing stress includes the following steps:

[0009] S1. First, complete the high-temperature process on the front side of the wafer, then flip it over and bond the front side of the wafer to the glass substrate. Then, thin the back side of the wafer and complete the corresponding back side process. Finally, bond the back side of the wafer to the ring substrate.

[0010] S2. By debonding the glass substrate, the glass substrate on the front side of the wafer is removed, the wafer is subjected to high-temperature tempering, then a ring of polyimide is coated on the sidewall of the front side of the wafer, and a laser is used to perform invisible cutting on the back side of the wafer to form an invisible cutting channel.

[0011] S3. By simultaneously electroplating the front and back sides of the wafer, metal layers are deposited on both the front and back sides of the wafer.

[0012] S4. The wafer is laser-cut along the polyimide to remove the annular carrier plate. The remaining wafer is then placed on the cutting die frame. The wafer is cut along the invisible cutting path to form dies and transferred to the next process for packaging.

[0013] Furthermore, in step S1, by applying an adhesive to the front side of the wafer, the front side of the wafer is bonded to the glass substrate by the adhesive; at the same time, after completing the back side process of the wafer, an adhesive is also applied to the back side of the wafer, and the back side of the wafer is bonded to the annular substrate by the adhesive.

[0014] Furthermore, in step S2, the maximum temperature during high-temperature tempering of the wafer is 1000°C.

[0015] Furthermore, in step S2, the glass carrier is debonded using UV light, and after the glass carrier is removed, solvent cleaning is used to remove the adhesive remaining on the wafer surface and the adhesive inside the ring carrier.

[0016] Furthermore, in step S4, a film expansion dicing method can also be used to allow the wafer to split along the invisible dicing path to form grains.

[0017] The beneficial effects of this invention are:

[0018] 1. Before high-temperature tempering and metal deposition processes, a hidden cleaving channel is formed on the wafer surface by laser cutting. During subsequent wafer processing, the presence of the hidden cleaving channel allows the wafer to bend at a small angle, eliminating the stress generated during processing. This makes it less prone to damage to wafers with a thickness of less than 60μm due to stress. Finally, the wafer is cracked along the direction of the hidden cleaving channel, without any unnecessary wafer loss.

[0019] 2. By using a ring-shaped carrier, the back side of the wafer is bonded to the ring-shaped carrier, while the front side of the wafer does not need to be bonded to any carrier. This allows for the simultaneous deposition of metal layers on both sides of the wafer without having to rotate the wafer around using a carrier, thus improving efficiency. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating step S1 of the present invention;

[0022] Figure 2 This is a flowchart illustrating step S2 of the present invention;

[0023] Figure 3 This is a flowchart illustrating step S3 of the present invention;

[0024] Figure 4 This is a flowchart illustrating step S4 of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Reference Figures 1-4 As shown, an ultrathin wafer fabrication process capable of uniformly releasing stress includes the following steps:

[0027] S1. First, complete the high-temperature process on the front side of the wafer, then flip it over and bond the front side of the wafer to the glass substrate. Then, thin the back side of the wafer so that the thickness of the wafer does not exceed 60μm and complete the corresponding back side process. Finally, bond the back side of the wafer to the ring substrate.

[0028] In this process, an adhesive is applied to the front side of the wafer, which then bonds the wafer to the glass substrate. Similarly, after the back side process is completed, an adhesive is applied to the back side of the wafer, which then bonds the wafer to the annular substrate.

[0029] S2. By debonding the glass substrate, the glass substrate on the front side of the wafer is removed, and the wafer is subjected to high-temperature tempering at a maximum temperature of 1000°. Then, a ring of polyimide is coated on the sidewall of the front side of the wafer, and a laser is used to perform invisible cutting on the back side of the wafer to form an invisible cutting channel.

[0030] The glass carrier was debonded using UV light, and after the glass carrier was removed, solvent cleaning was used to remove the adhesive residue on the wafer surface and the adhesive inside the ring carrier.

[0031] S3. By simultaneously electroplating the front and back sides of the wafer, metal layers are deposited on both the front and back sides of the wafer.

[0032] When depositing nickel, palladium, and gold on the front side of the wafer, chemical vapor deposition is used, and nickel, palladium, and gold are deposited sequentially.

[0033] Chemical vapor deposition was used to deposit Ti, Ni, and Ag on the back side of the wafer, and Ti, Ni, and Ag were deposited sequentially.

[0034] S4. The wafer is laser-cut along the polyimide to remove the annular carrier plate. The remaining wafer is then placed on the cutting die frame. The wafer is cut along the invisible cutting path to form dies and transferred to the next process for packaging.

[0035] Alternatively, a film splitting method can be used to allow the wafer to split along the invisible dicing path to form grains.

[0036] Before high-temperature tempering and deposition of Ti, Ni, Ag metals, and other related processes, a groove-shaped cutting channel is first laser-cut on the wafer surface. This allows the wafer to bend at a small angle during subsequent wafer processing due to the presence of the cutting channel, thus eliminating the stress generated during processing. This makes the wafer less prone to damage due to stress when manufacturing wafers with a thickness of less than 60μm. Finally, the wafer is cracked along the cutting channel direction, without generating unnecessary wafer loss.

[0037] By using a ring-shaped carrier, the back side of the wafer is bonded to the ring-shaped carrier, while the front side of the wafer does not need to be bonded to any carrier. This allows for the simultaneous deposition of metal layers on both sides of the wafer without having to rotate the wafer around using a carrier, thus improving efficiency.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A process for fabricating ultrathin wafers that can uniformly release stress, characterized in that, Includes the following steps: S1. First, complete the high-temperature process on the front side of the wafer, then flip it over and bond the front side of the wafer to the glass substrate. Then, thin the back side of the wafer and complete the corresponding back side process. Finally, bond the back side of the wafer to the ring substrate. S2. By debonding the glass substrate, the glass substrate on the front side of the wafer is removed, the wafer is subjected to high-temperature tempering, then a ring of polyimide is coated on the sidewall of the front side of the wafer, and a laser is used to perform invisible cutting on the back side of the wafer to form an invisible cutting channel. S3. By simultaneously electroplating the front and back sides of the wafer, metal layers are deposited on both the front and back sides of the wafer. S4. The wafer is laser-cut along the polyimide to remove the annular carrier plate. The remaining wafer is then placed on the cutting die frame. The wafer is cut along the invisible cutting path to form a die and then transferred to the next process for packaging. In step S2, the maximum temperature during high-temperature tempering of the wafer is 1000°C. In step S4, a film expansion and dicing method can also be used to allow the wafer to split along the invisible dicing path to form grains.

2. The ultrathin wafer fabrication process with uniform stress relief according to claim 1, characterized in that, In step S1, an adhesive is applied to the front side of the wafer, which then bonds the front side of the wafer to the glass substrate. Similarly, after the back side process is completed, an adhesive is applied to the back side of the wafer, which then bonds the back side of the wafer to the annular substrate.

3. The ultrathin wafer fabrication process with uniform stress relief according to claim 1, characterized in that, In step S2, the glass carrier is debonded by UV light, and after the glass carrier is removed, solvent cleaning is used to remove the adhesive remaining on the wafer surface and the adhesive inside the ring carrier.

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