IGBT wafer processing technology

Abstract

The present invention relates to the field of semiconductor processing technology, and specifically to an IGBT wafer processing process. The present invention comprises S1, completing a process before a metal process on the front side of the wafer; S2, thinning the back side of the wafer; S3, etching the back side of the wafer to form a gentle slope; S4, completing the process on the back side of the wafer; S5, coating polyimide on the back side and bonding to a glass carrier; S6, completing the process on the front side of the wafer; S7, completing cutting by etching and laser to remove the polyimide on the front side; S8, cutting the edge of the wafer; S9, attaching the cut wafer to a first cutting mold frame and washing off the polyimide on the back side; the present invention can provide stress support at the edge by performing a gentle slope treatment on the back side of the wafer, and at the same time, the back side of the wafer of the present invention is coated with polyimide and bonded to a glass carrier, which can buffer the stress of the metal thick film and ensure that the thin wafer will not be warped or damaged after being coated with a thick metal film.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor processing, and in particular to an IGBT wafer processing technology. Background Art

[0002] An IGBT is a fully controlled, voltage-driven, composite power semiconductor device composed of a BJT (bipolar junction transistor) and a MOS (insulated gate field-effect transistor). It combines the high input impedance of a MOSFET (metal-oxide semiconductor field-effect transistor) with the low on-state voltage drop of a GTR (power transistor). A GTR offers a low saturation voltage drop and high current density, but also high drive currents. A MOSFET offers low drive power and fast switching speeds, but also high on-state voltage drop and low current density. The IGBT combines the advantages of both devices, offering low drive power and low saturation voltage drop. It is ideally suited for applications in power conversion systems with DC voltages of 600V and above, such as AC motors, inverters, switching power supplies, lighting circuits, and traction drives.

[0003] The current IGBT wafer production process first completes the front-side wafer process, then bonds the front side to a glass carrier, thins the back side, and completes subsequent back-side wafer processing. However, due to the high-temperature steps involved in the back-side process, the adhesive is a polymer material that can only withstand a maximum heating temperature of 350°C. Furthermore, the front side has already undergone metal processing, and Al or Cu can only withstand a maximum heating temperature of 560°C. Therefore, this process cannot be implemented on wafers bonded to a glass carrier. The debonded wafer is prone to breakage and damage. Summary of the Invention

[0004] The object of the present invention is to provide an IGBT wafer processing technology to solve the problems raised in the above background technology.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] An IGBT wafer processing process includes the following steps:

[0007] S1, complete the process before the metal process on the front side of the wafer;

[0008] S2, adhering a grinding tape to the front side of the wafer, thinning the back side of the wafer, then removing the grinding tape, and adsorbing the front side of the wafer onto a first glass carrier with adsorption holes;

[0009] S3: Sealing the sidewalls of the wafer, then etching the center of the back of the wafer to form a gentle slope at the edge of the wafer;

[0010] S4, complete the wafer backside process;

[0011] S5. Coating polyimide on the back of the wafer to flatten the back, then adsorbing the back of the wafer onto a second glass carrier with adsorption holes, then cutting the edge seal of the wafer using a laser, and removing the first glass carrier together with the cut edge seal of the wafer;

[0012] S6, flipping the wafer to the front side, coating polyimide on the front side of the wafer, and exposing the PAD growth gap and cutting path after development, curing, and etching;

[0013] S7, first make the front metal PAD process, then use plasma etching to cut the road to the back metal layer, and then use laser to cut the back metal;

[0014] S8, coating the edge of the front side of the wafer with photoresist, washing away the polyimide at the center of the front side of the wafer, and then cutting the edge of the wafer with a laser;

[0015] S9. Turn the cut wafer over so that the front side is attached to the cutting mold frame, remove the second glass carrier together with the cut wafer, and wash away the polyimide on the back side of the wafer.

[0016] Furthermore, the processes before the front metal process in S1 include trench, ILD and contact hole processes.

[0017] Furthermore, the edge sealing in S3 adopts SOG technology, CVD technology or carbon deposition technology.

[0018] Furthermore, the carbon deposition technology specifically includes:

[0019] S3.1. Using a carbon deposition reaction, a carbon deposition layer is formed on the back of the wafer, and the front of the wafer is bonded to the first glass carrier.

[0020] S3.2. Coat the edge of the back side of the wafer with photoresist, and then use laser to etch the carbon on the back side of the wafer.

[0021] Furthermore, the back metal process includes photolithography, ion implantation, back metal and annealing processes.

[0022] Beneficial effects of the present invention:

[0023] 1. The present invention first seals the edge of the back of the wafer through edge sealing technology, then makes a gentle slope treatment, and then can use laser cutting to directly remove the edge of the wafer, making it easier to remove the wafer. At the same time, although it is an ultra-thin wafer, the edge can still contact the contact point or edge of the mechanical transfer arm of the heating and metal-related process equipment, so as not to cause fragmentation or localized cracks on the edge, and at the same time overcome the limitation of the back tempering temperature;

[0024] 2. The back of the wafer of the present invention is coated with polyimide and then bonded to the glass carrier. The bonding area is mainly the edge of the wafer, which can buffer the stress generated by the front metal thick film and the electroplating and chemical plating processes. The edge of the wafer is then directly cut off by cutting to facilitate the separation of the wafer and the carrier. The back polyimide is then removed to ensure that the thin wafer will not warp or break after the thick metal coating.

[0025] 3. The present invention coats polyimide on the front side, then develops, cures, and etches to expose the cutting path. It can automatically align on the front side, first etches the cutting path and then laser cuts off the back metal, thus overcoming the problem of difficult alignment in traditional wafer backside cutting. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0027] Figure 1 Schematic diagram of the molding process step S1 of the present invention;

[0028] Figure 2 Schematic diagram of the molding process of step S2 of the present invention;

[0029] Figure 3 Schematic diagram of the molding process step S3 of the present invention;

[0030] Figure 4 Schematic diagram of the molding process step S4 of the present invention;

[0031] Figure 5 Schematic diagram of the molding process step S5 of the present invention;

[0032] Figure 6 Schematic diagram of the molding process step S6 of the present invention;

[0033] Figure 7 Schematic diagram of the molding process of step S7 of the present invention;

[0034] Figure 8 Schematic diagram of the molding process step S8 of the present invention;

[0035] Figure 9 It is a forming schematic diagram of process step S9 of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] Reference Figures 1-9 As shown, an IGBT wafer processing process includes the following steps:

[0038] S1. Complete the process before the metal process on the front side of the wafer, including trench, ILD and contact hole processes;

[0039] S2, adhering a grinding tape to the front side of the wafer, thinning the back side of the wafer, then removing the grinding tape, and adsorbing the front side of the wafer onto a first glass carrier plate having adsorption holes, thereby fixing the wafer;

[0040] S3: Sealing the sidewalls of the wafer, then etching the center of the back of the wafer to form a gentle slope at the edge of the wafer;

[0041] The edge sealing technology mainly includes SOG technology, CVD technology and carbon deposition technology.

[0042] If carbon deposition technology is used, it specifically includes:

[0043] S3.1. Using a carbon deposition reaction, a carbon deposition layer is formed on the back of the wafer, and the front of the wafer is bonded to the first glass carrier.

[0044] S3.2. Coat the edge of the back side of the wafer with photoresist, and then use laser to etch the carbon on the back side of the wafer.

[0045] S4: Complete the wafer backside process, including photolithography, ion implantation, backside metallization and annealing process;

[0046] The edge of the back of the wafer is sealed through edge sealing technology, and then a gentle slope is made. After that, laser cutting can be used to directly remove the edge of the wafer to facilitate wafer removal. At the same time, although it is an ultra-thin wafer, the edge can still contact the contact point or edge of the mechanical transmission arm of the heating and metal-related process equipment, so as not to cause fragmentation or local cracks on the edge, and at the same time overcome the limitation of the back annealing temperature.

[0047] S5. Coating polyimide on the back of the wafer to flatten the back, then adsorbing the back of the wafer onto a second glass carrier with adsorption holes, then cutting the edge seal of the wafer using a laser, and removing the first glass carrier together with the cut edge seal of the wafer;

[0048] S6, flipping the wafer to the front side, coating polyimide on the front side of the wafer, and exposing the PAD growth gap and cutting path after development, curing, and etching;

[0049] S7, first make the front metal PAD process, then use plasma etching to cut the road to the back metal layer, and then use laser to cut the back metal;

[0050] By coating polyimide on the front side, developing, curing, and etching to expose the PAD growth gap and cutting path, the front metal PAD process is first completed in the growth gap; the cutting path can be automatically aligned on the front side, and the cutting path is first etched and then the back metal is cut off by laser, overcoming the problem of difficult alignment in traditional wafer backside cutting.

[0051] S8, coating the edge of the front side of the wafer with photoresist, washing away the polyimide at the center of the front side of the wafer, and then cutting the edge of the wafer with a laser;

[0052] The back of the wafer is coated with polyimide and then bonded to a glass carrier. The bonding area is mainly at the edge of the wafer, which can buffer the stress generated by the thick metal film on the front and the electroplating and chemical plating processes. The edge of the wafer is then directly cut off by cutting to facilitate separation of the wafer from the carrier. Removing the polyimide on the back ensures that the thin wafer will not warp or break after thick metal coating.

[0053] S9. Turn the cut wafer over so that the front side is attached to the cutting mold frame, remove the second glass carrier together with the cut wafer, and wash away the polyimide on the back side of the wafer.

[0054] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. An IGBT wafer processing process, characterized in that: The following steps are involved: S1, complete the process before the metal process on the front side of the wafer; S2, adhering a grinding tape to the front side of the wafer, thinning the back side of the wafer, then removing the grinding tape, and adsorbing the front side of the wafer onto a first glass carrier with adsorption holes; S3: Sealing the sidewalls of the wafer, then etching the center of the front side of the wafer to form a gentle slope at the edge of the wafer; S4, complete the wafer backside process; S5. Coating polyimide on the back of the wafer to flatten the back, then adsorbing the back of the wafer onto a second glass carrier with adsorption holes, then cutting the edge seal of the wafer using a laser, and removing the first glass carrier together with the cut edge seal of the wafer; S6, flipping the wafer to the front side, coating polyimide on the front side of the wafer, and exposing the PAD growth gap and cutting path after development, curing, and etching; S7, first make the front metal PAD process, then use plasma etching to cut the road to the back metal layer, and then use laser to cut the back metal; S8, coating the edge of the front side of the wafer with photoresist, washing away the polyimide at the center of the front side of the wafer, and then cutting the edge of the wafer with a laser; S9, flipping the cut wafer so that the front side is attached to the cutting mold frame, removing the second glass carrier together with the cut wafer, and washing away the polyimide on the back side of the wafer; The processes before the front metal process in S1 include trench, ILD and contact hole processes; The edge sealing in S3 adopts SOG technology, CVD technology or carbon deposition technology; The back metal process includes photolithography, ion implantation, back metal and annealing processes.

2. The IGBT wafer processing process according to claim 1, characterized in that: The carbon deposition technology specifically includes: S3.

1. Using a carbon deposition reaction, a carbon deposition layer is formed on the back of the wafer, and the front of the wafer is bonded to the first glass carrier. S3.

2. Coat the edge of the back side of the wafer with photoresist, and then use laser to etch the carbon on the back side of the wafer.

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