Wafer thinning device and wafer thinning method

Abstract

The invention provides a wafer thinning device. The wafer thinning device comprises a tank body used for containing corrosive liquid, a wafer fixing part and a slit generating part. Wherein the wafer fixing part and the slit generating part are both installed in the tank body, a wafer to be thinned is fixed through the wafer fixing part, and a slit is formed between the slit generating part and a corrosion surface of the wafer to be thinned. According to the wafer thinning device provided by the invention, the slit generation part is arranged, so that bubbles generated in the corrosion process of the wafer can be coalesced or broken near the corrosion surface of the wafer, micro-jet generated by bubble coalescing or breaking can generate pressure intensity of hundred MPa magnitude on the corrosion surface of the wafer, the corrosion rate of the wafer is greatly improved, and the yield of the wafer is improved. And meanwhile, the surface roughness of the corroded wafer is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and in particular to a wafer thinning device and a wafer thinning method. Background Art

[0002] With the development of the semiconductor industry, in order to meet the process requirements of integrated circuit chip packaging, the thickness of the chip is getting thinner and thinner. Therefore, it is inevitable to thin the wafer during the chip manufacturing process.

[0003] There are many processes for thinning wafers. Taking the most common silicon wafer as an example, common silicon wafer thinning processes include grinding, lapping, chemical mechanical polishing (CMP), electrochemical etching, wet etching, dry etching (DE), plasma etching (such as plasma assisted chemical etching PACE), etc. ， Plasma Assisted Chemical Etching; Atmospheric Pressure Plasma Etching (ADPE), etc. Among them, the wet etching process has the advantages of simple operation, low cost, fast etching rate, high reliability and high selectivity, and low damage to the surface state of the device, so it has become one of the most common wafer thinning processes.

[0004] The basic principle of wet etching of silicon wafers is to place the silicon wafer to be etched in an etching solution, and to achieve thinning of the silicon wafer by controlling the effective concentration and temperature parameters of the etching solution. However, a large number of hydrogen bubbles will be generated during the thinning process. These bubbles will adhere to the surface of the silicon wafer in the early stage of generation, and the bubbles staying on the surface of the silicon wafer will hinder the contact between the etching solution and the silicon wafer, resulting in a low corrosion rate on the surface of the silicon wafer, uneven corrosion rates at different positions, and high surface roughness. In the prior art, methods such as adding surfactants, mechanical stirring or ultrasound are usually used during the etching process to make the bubbles separate from the etching surface of the silicon wafer as soon as possible, but the effects are limited. There are similar problems when using wet etching processes to thin other types of wafers (such as gallium arsenide, silicon carbide, etc.). Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to overcome the defects of the prior art in that the etching rate is low when etching the wafer surface and the surface roughness of the wafer after etching is high, thereby providing a wafer thinning device and a wafer thinning method with high etching rate and good etching effect.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a wafer thinning device, comprising: a tank 101 for containing a corrosive liquid, a wafer fixing component 102, and a slit generating component 103; wherein:

[0008] The wafer fixing component 102 and the slit generating component 103 are both installed inside the tank 101 , and the wafer 104 to be thinned is fixed by the wafer fixing component 102 , and a slit 106 is formed between the slit generating component 103 and the etched surface of the wafer 104 to be thinned.

[0009] In the above technical solution, the tank body 101 is a closed container and is connected to the vacuum pump 108 .

[0010] In the above technical solution, a mechanical stirring component 109 and / or an ultrasonic component 110 are also installed.

[0011] In the above technical solution, the slit generating component 103 is a fixed position component.

[0012] In the above technical solution, the slit generating component 103 is a position-adjustable component.

[0013] In the above technical solution, the wafer fixing component 102 includes a base 201 and an upper pressure ring 202, and the wafer to be thinned is placed on the base 201 and fixed by the upper pressure ring 202;

[0014] The slit generating component 103 includes a bridge plate 203 and a core plate 204 . The bridge plate 203 is fixedly mounted on the upper pressure ring 202 . The core plate 204 is mounted on the bridge plate 203 . The relative position between the bridge plate 203 and the core plate 204 is adjustable.

[0015] The present invention also provides a wafer thinning method implemented based on the wafer thinning device, comprising:

[0016] Step 1: Mount the wafer 104 to be thinned on the wafer fixing component 102;

[0017] Step 2, installing a slit generating component 103 above the wafer fixing component 102, and ensuring that the width of the slit 106 formed between the slit generating component 103 and the upper surface of the wafer is within a preset width range;

[0018] Step 3, injecting the etching liquid 107 into the tank 101 in which the wafer fixing component 102 and the slit generating component 103 are placed. After the etching liquid 107 is injected, the liquid level of the etching liquid 107 is higher than the height of the slit generating component 103;

[0019] Step 4: The wafer 104 is corroded and thinned in the etching solution 107. When the thickness of the wafer 104 reaches a preset value, the etching process is terminated and the wafer 104 is taken out.

[0020] In the above technical solution, between step 3 and step 4, the method further includes:

[0021] The tank body 101 is evacuated by a vacuum pump 108 so that the air pressure in the tank body 101 reaches a preset value;

[0022] In step 4, the terminating corrosion process comprises:

[0023] The air pressure value in the tank body 101 is gradually restored to the standard atmospheric pressure.

[0024] In the above technical solution, between step 3 and step 4, the method further includes:

[0025] Start the mechanical stirring component 109 and / or the ultrasonic component 110;

[0026] In step 4, the terminating corrosion process comprises:

[0027] The mechanical stirring component 109 and / or the ultrasonic component 110 are stopped.

[0028] In the above technical solution, taking out the wafer includes:

[0029] The wafer fixing component 102 with the thinned wafer 104 mounted thereon is taken out from the etching solution 107 , and then is immersed and rinsed in warm water, and finally the thinned wafer 104 is taken out from the wafer fixing component 102 .

[0030] The present invention adopts the above technical solution, which has the following advantages:

[0031] The wafer thinning device provided by the present invention is provided with a slit generating component, so that bubbles generated by the wafer during the etching process can be aggregated or collapsed near the etching surface of the wafer, so that the microjets generated by the aggregation or collapse of the bubbles can generate a pressure of the order of hundreds of MPa on the etching surface of the wafer, thereby greatly improving the wafer etching rate and reducing the surface roughness of the wafer after etching.

[0032] The wafer thinning device provided by the present invention also has the advantages of simple structure and convenient operation, and has low manufacturing cost and can be reused, thereby greatly reducing the production cost of rapid etching of large-size wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 It is a schematic diagram of the principle of wet etching technology in the prior art;

[0035] Figure 2 It is a schematic diagram of the principle of using slits to accelerate the corrosion rate and reduce the roughness of the corrosion surface;

[0036] Figure 3 It is a schematic structural diagram of a wafer thinning device of the present invention;

[0037] Figure 4 is a schematic structural diagram of a wafer thinning device according to an embodiment of the present invention;

[0038] Figure 5 It is a schematic structural diagram of a wafer fixing component and a slit generating component included in the wafer thinning device of the present invention in one embodiment;

[0039] Figure 6 is a schematic structural diagram of a base included in a wafer thinning device of the present invention in one embodiment;

[0040] Figure 7 is a schematic structural diagram of an upper pressure ring included in the wafer thinning device of the present invention in one embodiment;

[0041] Figure 8 is an oblique view of a bridge included in a wafer thinning device of the present invention in one embodiment;

[0042] Fig. 9 is an oblique view of a bridge included in the wafer thinning device of the present invention after being inverted in one embodiment;

[0043] Fig.10 is a schematic structural diagram of a screw included in the wafer thinning device of the present invention in one embodiment;

[0044] Fig.11 is a schematic structural diagram of a core plate included in a wafer thinning device of the present invention in one embodiment;

[0045] Fig.12 is a flow chart of a wafer thinning method provided by the present invention;

[0046] Fig.13 This is a picture of the thinned wafer sample under uniform backlight;

[0047] Fig.14 It is a schematic diagram of the surface roughness of the wafer sample after thinning. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0049] Before describing the wafer thinning device and the wafer thinning method of the present invention in detail, the relevant principles are first described.

[0050] According to the existing wet etching technology, the wafer to be etched is placed in the etching solution for thinning. During the thinning process, bubbles are generated and attached to the wafer surface. The bubbles can be separated from the etching surface of the wafer by using surfactants, mechanical stirring or ultrasound, but there is a defect that the effect of bubbles separating from the etching surface of the wafer is not good. In addition, reference Figure 1 In the prior art, when a bubble detaches from the wafer corrosion surface, the detachment process is as follows: either it rises rapidly; or when the bubble reaches a certain distance from the wafer corrosion surface, it merges with other bubbles to form a new bubble and then rises rapidly; or when the bubble reaches a certain distance from the wafer corrosion surface, the bubble collapses to form two or more new bubbles, and each of the new bubbles rises rapidly.

[0051] The applicant has found through research that bubbles can generate microjets when they coalesce or break. Figure 2 As shown, if the bubbles generated during the wafer etching and thinning process can be allowed to coalesce or collapse near the wafer etching surface, the microjets generated by the coalescence or collapse can produce a pressure of the order of hundreds of MPa on the wafer etching surface, which is equivalent to introducing additional stress, which can greatly increase the wafer etching rate while reducing the surface roughness of the wafer after etching.

[0052] Based on the above principle, the present invention proposes a wafer thinning device and a wafer thinning method.

[0053] Figure 3 Schematic diagram of the structure of the wafer thinning device of the present invention, as shown in Figure 3 As shown, the wafer thinning device of the present invention comprises: a tank 101, a wafer fixing component 102, and a slit generating component 103; wherein,

[0054] The wafer fixing component 102 and the slit generating component 103 are both installed inside the tank 101 . The wafer 104 to be thinned is fixed by the wafer fixing component 102 . A slit 106 is formed between the slit generating component 103 and the etched surface of the wafer 104 to be thinned.

[0055] The tank 101 is a place for etching and thinning the wafer, and is used to contain the etching liquid 107, and the wafer fixing component 102 and the slit generating component 103 are installed inside the tank 101. The tank 101 is made of corrosion-resistant materials, such as PVDF polytetrafluoroethylene, PP polypropylene, fluoroplastics, stainless steel, glass containers (not applicable to frosted glass), etc.

[0056] The wafer fixing component 102 is used to install the wafer 104 to be thinned. The wafer 104 includes a front side to be etched and a back side to be protected. When the wafer 104 is fixedly installed, the wafer fixing component 102 seals and protects the back side of the wafer 104 and opens the front side of the wafer 104 to the outside, so that the etching liquid 107 can only etch the front side of the wafer 104.

[0057] The slit generating component 103 is used to generate a slit 106. After the wafer 104 to be thinned is mounted on the wafer fixing device 102, the slit generating component 103 is then mounted above the front surface of the wafer 104, so that a slit 106 is formed between the front surface of the wafer 104 and the opposite surface of the slit generating component 103. The width of the slit 106 should be within a certain range, such as 0.3-5mm. If the slit width is too large, the bubbles formed on the wafer surface during the etching process will still coalesce or collapse at a distance from the etching surface of the wafer; if the slit width is too small, the bubbles generated on the wafer surface during the etching process will aggregate in the slit and be difficult to be discharged, hindering the wafer from continuing to erode.

[0058] The wafer thinning device provided by the present invention is provided with a slit generating component, so that bubbles generated by the wafer during the etching process can be coalesced or collapsed near the etching surface of the wafer, so that the micro jets generated by the coalescence or collapse of the bubbles can generate a pressure of the order of 100 MPa on the etching surface of the wafer, greatly improving the etching rate of the wafer, while reducing the surface roughness of the wafer after etching. The wafer thinning device provided by the present invention also has the advantages of simple structure and convenient operation, and has low manufacturing cost and can be reused, which greatly reduces the production cost of fast etching of large-size wafers.

[0059] Based on any of the above embodiments, in another embodiment of the present invention, the tank body 101 is a closed container and is connected to the vacuum pump 108 .

[0060] The ideal gas state equation is expressed as:

[0061] pV=nRT

[0062] Among them, p represents the gas pressure, V represents the gas volume, n represents the amount of substance in the gas, R represents the molar gas constant, and T represents the thermodynamic temperature of the gas.

[0063] From the force analysis of the bubbles, it can be seen that the critical volume of the bubbles when they detach from the wafer surface is constant, that is, V is constant. From the ideal gas state equation, it can be known that during the wafer corrosion process, if the gas pressure of the atmospheric environment decreases, the amount of gas molecules that reach the critical volume of gas floating will also decrease accordingly; if the gas molecule generation rate is regarded as constant, reducing the gas pressure in the wafer corrosion environment can accelerate the detachment of bubbles from the wafer surface and improve the wafer corrosion uniformity and corrosion rate.

[0064] Based on the above principle, in this embodiment, the tank 101 is set as a closed container and connected to the vacuum pump 108. By evacuating the tank 101 by 108, a low-pressure environment can be created for the wafer etching process, thereby accelerating the detachment of bubbles from the wafer surface and improving the wafer etching uniformity and etching rate. Figure 4 Schematic diagram of the structure of the wafer thinning device in this embodiment.

[0065] The wafer thinning device provided by the present invention can create a low-pressure environment for the wafer etching process by setting the tank body as a closed container and connecting it to a vacuum pump, thereby accelerating the detachment of bubbles from the wafer surface and improving the wafer etching uniformity and etching rate.

[0066] Based on any of the above embodiments, in another embodiment of the present invention, the wafer thinning device is further equipped with a mechanical stirring component 109 and / or an ultrasonic component 110 .

[0067] In this embodiment, the etching liquid is stirred by the mechanical stirring component 109, and / or the ultrasonic component 110 emits ultrasound to act on the etching surface of the wafer, so that the bubbles generated during the wafer etching process are separated from the etching surface of the wafer as soon as possible.

[0068] In one embodiment, the mechanical stirring component 109 can be installed outside the tank body 101, a hole is opened on the surface of the tank body 101, and a sealing structure is added at the contact point between the transmission rod of the mechanical stirring component 109 and the tank body 101, so as to stir the corrosive liquid in the tank body 101.

[0069] In another embodiment, the ultrasonic component 110 may be installed outside the tank 101, and the ultrasound emitted by the ultrasonic component 110 may act on the etching surface of the wafer.

[0070] The structures of the mechanical stirring component 109 and the ultrasonic component 110 are common knowledge to those skilled in the art, and thus will not be described in detail in this embodiment.

[0071] The wafer thinning device provided by the present invention uses a mechanical stirring component and / or an ultrasonic component to enable bubbles generated during wafer etching to separate from the wafer etching surface as quickly as possible, thereby avoiding the defect that bubbles stay on the wafer surface and hinder the contact between the etching liquid and the wafer surface.

[0072] Based on any of the above embodiments, in another embodiment of the present invention, the slit generating component 103 is a position-fixed component.

[0073] The slit generating component 103 is used to form a slit 106 with one of the surfaces (etched surface) of the wafer 104 to be thinned. As a feasible implementation, the slit generating component 103 is a fixed position component, that is, after being installed in the tank 101, its position remains fixed.

[0074] For example, the slit generating component 103 is a flat component with a vent hole 105, which is fixedly installed at a certain position in the tank 101 by means of a buckle. The installation position should ensure that after the slit generating component 103 is fixed, the distance between the slit generating component 103 and the etched surface of the wafer 104 meets the slit width requirement.

[0075] The slit generating component 103 is a fixed position component, which has the advantages of simple structure and low implementation cost, but also has the problem of insufficient position flexibility and inability to flexibly adjust the slit width.

[0076] Based on any of the above embodiments, in another embodiment of the present invention, the slit generating component 103 is a position-adjustable component.

[0077] The slit generating component 103 is used to form a slit 106 with one of the surfaces (etched surface) of the wafer 104 to be thinned. As a preferred implementation, the slit generating component 103 is a position-adjustable component, that is, after it is installed in the tank 101, its position can be flexibly adjusted within a certain range.

[0078] For example, the slit generating component 103 is a flat component, on which a vent hole 105 is provided, and a thread is provided on its edge, and corresponding threads are also provided on certain areas of the inner wall of the tank body 101. After the slit generating component 103 is installed in the tank body 101, the position of the slit generating component 103 can be adjusted as needed. When the distance between the wafer surface and the lower surface of the slit generating component 103 changes due to corrosion (that is, the slit width changes), the position of the slit generating component 103 can be adjusted in real time, so that the slit width remains unchanged or within a preset width range. In addition, the etching speed of the wafer can be adjusted by adjusting the slit width.

[0079] The wafer thinning device provided by the present invention has the function of adjusting the slit width by setting the slit generating component as a position-adjustable component. The wafer etching rate can be flexibly adjusted by adjusting the slit width, and the wafer surface roughness can be reduced at the same time.

[0080] Based on any of the above embodiments, in another embodiment of the present invention, the wafer fixing component 102 includes a base 201 and an upper pressure ring 202, and the wafer to be thinned is placed on the base 201 and fixed by the upper pressure ring 202;

[0081] The slit generating component 103 includes a bridge plate 203 and a core plate 204 . The bridge plate 203 is fixedly mounted on the upper pressure ring 202 . The core plate 204 is mounted on the bridge plate 203 . The relative position between the bridge plate 203 and the core plate 204 is adjustable.

[0082] In this embodiment, a specific implementation of the wafer fixing component 102 and the slit generating component 103 is provided. Figure 5 Schematic diagram of the structure of the wafer fixing component and the slit generating component. Figure 5 As shown, the wafer fixing component 102 includes a base 201 and an upper pressure ring 202 that cooperate with each other to clamp the wafer. The wafer includes a front side to be etched and a back side to be protected. The base 201 is used to seal the back side of the wafer, and the upper pressure ring 202 is annular and is used to seal the edge of the front side to be etched of the wafer. The base 201 contacts the wafer through a lower sealing ring 206, and the upper pressure ring 202 contacts the wafer through an upper sealing ring 207. The wafer is placed on the base 201 through a rubber protective pad 205.

[0083] Figure 6 is a schematic diagram of the structure of the base. Figure 6 As shown, the upper side of the base 201 is an upper convex truncated platform structure. The shape of the convex platform 301 is consistent with the shape of the wafer to be etched. The diameter of the convex platform 301 is the standard diameter of the wafer minus the corresponding standard tolerance. Through the convex platform 301, the back of the wafer can be evenly supported. Accordingly, the diameter of the convex platform 301 is slightly smaller than the concave structure 401 of the upper pressure ring (the concave structure 401 of the upper pressure ring is Figure 7 The diameter of the base 201 is marked in the figure to ensure that the base 201 and the upper pressure ring 202 can be assembled smoothly without relative shaking. The height of the boss 301 is less than the depth of the inner concave of the upper pressure ring 202 to avoid hard contact between the main structure of the wafer fixing component 102 and the wafer. The periphery of the base 201 is 8 M10 threaded holes 302 for fixing the wafer fixing component 102; the side of the base 201 is provided with a transverse threaded hole 303 for facilitating the removal of the clamp.

[0084] Figure 7 Figure 2 is a schematic diagram of the structure of the upper pressure ring. Figure 7As shown, the middle part of the upper pressure ring 202 is a concave structure 401, the shape of the concave structure 401 is consistent with the shape of the wafer to be etched, and the diameter is the standard diameter of the wafer plus the corresponding standard tolerance, ensuring that all wafers can be smoothly assembled in the upper pressure ring but avoiding large shaking. In one embodiment, the wafer is a four-inch silicon wafer with a diameter of 100±0.5mm, and the diameter of the concave structure 401 is set to 100.6mm. The concave structure 401 has a sinking film-taking groove 402 near the wafer cutting edge to facilitate tweezers to assemble the wafer. The inner and outer sides of the sinking film-taking groove 402 are respectively an upper sealing groove 403 for fixing the upper sealing ring 207 and a lower sealing groove 404 for fixing the lower sealing ring 206. The periphery of the lower sealing groove 404 is a group of M11 through holes 405 corresponding to the base threaded holes 302, and two M10 threaded holes 406 for fixing the upper pressure ring 202 and the bridge plate 203.

[0085] Figure 8 This is an oblique view of the plate bridge in the slit generation component. Fig. 9 This is an inverted oblique view of the bridge in the slit generating component. Figure 8 and Fig. 9 As shown, the bridge plate 203 is used in conjunction with the upper pressure ring 202. There is a lower convex ring 501 at the bottom of the bridge plate 203. The diameter of the lower convex ring 501 is the inner diameter of the open area 407 of the upper pressure ring 202 minus the corresponding standard tolerance; the lower convex ring 501 is only used as a limit structure between the bridge plate 203 and the upper pressure ring 202. The height can be set according to actual needs. In one embodiment, its height is 1mm. The outer diameter 502 of the central ring of the bridge plate 203 is more than 5mm smaller than the radius of the open area 407 of the upper pressure ring to reserve sufficient space for the flow of the etching liquid and the discharge of gas products during the etching process. In this embodiment, the inner diameter 503 of the center ring of the bridge plate and the outer diameter of the core plate 204 are tightly matched using M60*2mm threads, and the width of the slit between the bottom surface of the core plate and the wafer is adjusted by rotating the core plate 204; 80 notches are evenly distributed on the upper surface of the center ring of the bridge plate, serving as core plate rotation angle marks 504; the bridge plate 203 and the upper pressure ring 202 correspond one-to-one with the M11 through holes 505 and the M10 threaded holes 406 of the upper pressure ring, and are fixed using M10 external hexagonal screws 208.

[0086] Fig.10 The schematic diagram of the structure of the screw used in the slit generating component is shown in FIG. Fig.10 As shown, the top of the screw 208 is an outer hexagonal shape 601 with a lifting ear. The outer hexagonal shape 601 is compatible with a torque wrench, which can quantitatively represent the assembly pressure of the fixture and facilitate hand tightening during the assembly process.

[0087] Fig.11 The schematic diagram of the structure of the core plate in the slit generating component is shown in Figure 2. Fig.11As shown, the core plate 204 and the bridge plate 203 are tightly matched through the M60 external thread 701; the lower surface 702 of the core plate is a plane parallel to the surface of the wafer to be etched, and the gap between the plane and the wafer is the width of the slit used to accelerate the etching; the center of the core plate 204 is a symmetrical sinking structure, and the core plate handle 703 in the center of the core plate is used to rotate the core plate 204; the core plate mark 704 corresponds to the core plate rotation angle mark 504 on the bridge plate, and by rotating the core plate 204, the core plate 204 moves upward or downward, thereby adjusting the width of the slit. In this embodiment, the core plate mark 704 rotates through a bridge plate notch, and the slit width increases or decreases by 25um.

[0088] In this embodiment, all parts except the seal are made of acid-resistant, alkali-resistant and high-temperature-resistant hard polytetrafluoroethylene; the sealing rubber ring and the sealing gasket are made of corrosion-resistant and elastic fluororubber. Accordingly, inventions using the same material properties but different materials should be included in the protection scope of the present invention.

[0089] This embodiment provides a specific implementation method of a wafer thinning device, which has the advantages of accelerating the wafer etching rate, reducing the wafer surface roughness, and adjusting the wafer etching rate.

[0090] Fig.12 A flowchart of a wafer thinning method provided by the present invention, which is implemented based on the wafer thinning device provided by any of the above embodiments, and includes:

[0091] Step 1201, mounting the wafer 104 to be thinned on the wafer fixing component 102;

[0092] Step 1202, installing a slit generating component 103 above the wafer fixing component 102, and ensuring that the width of the slit 106 formed between the slit generating component 103 and the upper surface of the wafer is within a preset width range;

[0093] Step 1203, injecting the etching liquid 107 into the tank 101 in which the wafer fixing component 102 and the slit generating component 103 are placed. After the etching liquid 107 is injected, the liquid level of the etching liquid 107 is higher than the height of the slit generating component 103;

[0094] Step 1204 , the wafer 104 is corroded and thinned in the etching solution 107 . When the thickness of the wafer 104 reaches a preset value, the etching process is terminated and the wafer 104 is taken out.

[0095] This embodiment describes the specific implementation steps of the wafer thinning method, which is implemented based on the wafer thinning device described in the previous embodiment.

[0096] Before thinning the wafer, the wafer 104 to be thinned needs to be mounted on the wafer fixing component 102; then the slit generating component 103 is mounted, and the width of the gap between the slit generating component 103 and the surface of the wafer to be etched is ensured to be within a preset value range. As an implementation method, the wafer fixing component 102 can be placed in the tank 101 first, and then the wafer 104 is mounted on the wafer fixing component 102, and then the slit generating component 103 is placed in the tank 101 and mounted above the wafer fixing component 102. In another implementation method, the wafer 104 can be mounted on the wafer fixing component 102 first, and then the slit generating component 103 is mounted above the wafer fixing component 102, and finally the combination of the wafer fixing component 102 and the slit generating component 103 is placed in the tank 101.

[0097] Next, the etching liquid can be injected into the tank 101 on which the wafer fixing component 102 and the slit generating component 103 are installed, and it is ensured that the liquid level of the etching liquid is higher than the height of the upper surface of the slit generating component 103 .

[0098] The etching liquid etches the etching surface of the wafer 104, and bubbles are continuously generated during the etching process; under the action of the slit, the bubbles coalesce or break near the etching surface of the wafer 104, and the micro jets generated by the coalescence or breakage generate a pressure of the order of hundreds of megapascals on the etching surface of the wafer 104, which greatly increases the etching rate of the wafer 104 and reduces the surface roughness of the etching wafer 104. During the etching process, the thickness of the wafer 104 is continuously reduced. When the thickness reaches a preset value, the etching process is stopped and the etching wafer 104 is taken out.

[0099] The wafer thinning method provided by the present invention sets a slit near the wafer etching surface so that bubbles generated during the etching process are aggregated or collapsed near the wafer etching surface, thereby improving the etching rate of the wafer and reducing the surface roughness of the wafer after etching.

[0100] Based on any of the above embodiments, in an embodiment of the present invention, between step 1203 and step 1204, the method further includes:

[0101] The tank body 101 is evacuated by the vacuum pump 108 so that the air pressure in the tank body 101 reaches a preset value;

[0102] In step 1204, the terminating corrosion process includes:

[0103] The air pressure value in the tank body 101 is gradually restored to the standard atmospheric pressure.

[0104] According to the ideal gas state equation, reducing the gas pressure in the wafer corrosion environment can accelerate the bubbles to leave the wafer surface, and improve the wafer corrosion uniformity and corrosion rate. Therefore, in this embodiment, the tank 101 is slowly evacuated by the vacuum pump 108, and the gas pressure in the tank 101 is reduced from the standard atmospheric pressure to 3 / 4 standard atmospheric pressure in about 5 minutes; during the crystal corrosion process, the gas generated by the corrosion process is slowly discharged, so that the atmospheric pressure in the tank 101 is constant at about 3 / 4 standard atmospheric pressure.

[0105] After the corrosion process is completed, in order to avoid a sudden change in pressure that may cause the wafer 104 to break, before taking out the wafer, the air pressure in the tank 101 needs to be slowly restored to the standard atmospheric pressure, such as gradually restoring the air pressure in the tank 101 to the standard atmospheric pressure within 5 minutes.

[0106] The wafer thinning method provided by the present invention improves the wafer corrosion uniformity and corrosion rate by reducing the gas pressure in the wafer corrosion environment, and reduces the surface roughness of the wafer after corrosion.

[0107] Based on any of the above embodiments, in an embodiment of the present invention, between step 1203 and step 1204, the method further includes:

[0108] Start the mechanical stirring component 109 and / or the ultrasonic component 110;

[0109] In step 1204, the terminating corrosion process includes:

[0110] The mechanical stirring component 109 and / or the ultrasonic component 110 are stopped.

[0111] Mechanically stirring the etching liquid and / or emitting ultrasound to the etching surface of the wafer helps the bubbles generated during the etching process of the wafer to separate from the etching surface of the wafer as soon as possible. Therefore, in this embodiment, before the etching process begins, the mechanical stirring component 109 and / or the ultrasonic component 110 need to be started; and after the etching process ends, the mechanical stirring component 109 and / or the ultrasonic component 110 are stopped.

[0112] The frequency of the ultrasound used in this embodiment is between 20-40 kHz, and the power of the ultrasound is between 240-360 w.

[0113] The wafer thinning method provided by the invention increases the wafer etching rate by stirring the etching liquid or using ultrasonic action, reduces the surface roughness of the wafer after etching, and improves the uniformity of wafer etching.

[0114] Based on any of the above embodiments, in this embodiment, taking out the wafer includes:

[0115] The wafer fixing component 102 with the thinned wafer 104 mounted thereon is taken out from the etching solution 107 , and then is immersed and rinsed in warm water, and finally the thinned wafer 104 is taken out from the wafer fixing component 102 .

[0116] In this embodiment, in order to avoid wafer breakage caused by rapid temperature changes, when taking out the wafer, the wafer fixing component 102 containing the wafer 104 is taken out from the etching solution and first immersed in warm water (such as warm water with a temperature range of 45-55°C) for rinsing and then slowly cooled down. When the cooling time reaches a preset value or the wafer temperature reaches a preset value, the thinned wafer 104 is taken out from the wafer fixing component 102.

[0117] The wafer thinning method provided by the present invention first slowly cools down the wafer and then takes the wafer out, thereby effectively avoiding the problem of wafer breakage caused by rapid temperature changes.

[0118] Based on any of the above embodiments, in this embodiment, between step 1202 and step 1203, the method further includes:

[0119] A spacer for adjusting the tilt angle is placed under the wafer fixing member 102 .

[0120] In this embodiment, a pad for tilting angle is placed under the wafer fixing component 102, so that the wafer and the slit adjacent to the wafer are tilted at a certain angle to the horizontal plane. With this tilting angle, the bubbles generated during the etching process can be discharged faster, avoiding the gas layer formed by a large amount of gas agglomeration to hinder the contact between the etching solution and the wafer.

[0121] The wafer thinning method provided by the present invention can accelerate the discharge of bubbles generated during the etching process by setting the tilt angle, thereby preventing the gas layer formed by agglomeration of a large amount of gas from hindering the contact between the etching liquid and the wafer.

[0122] In another embodiment, Figure 5-Figure 11 Taking the device shown as an example, the wafer thinning method of the present invention is described.

[0123] First, place the upper pressure ring 202 upside down, then install sealing rings of corresponding sizes in the upper sealing groove 403 and the lower sealing groove 404, and ensure that the thickness of the sealing ring is greater than the depth of the sealing groove; then place the protective surface of the wafer 104 upward on the concave part of the upper pressure ring 202, and pay attention to aligning the wafer cut edge; then place the rubber protection pad 205 on the wafer protection surface; then invert the base 201, match it tightly with the upper pressure ring 202, and tighten the wafer fixing device from the bottom with screws 208; turn over the tightened wafer fixing device, and measure the height difference between the upper surface of the upper pressure ring 202 and the surface of the wafer; then according to the height Differentially adjust the core plate 204 to set the slit width to an ideal value; place the assembled wafer fixing device and the slit generating component in a corrosion solution in a constant temperature water bath of 70-80°C, and tilt them at a fixed inclination angle to facilitate the slit structure to discharge the bubbles generated by corrosion, apply 20-40kHz ultrasound to the corrosion liquid container with a power of 240-360w, and after the wafer is thinned to the target thickness, take out the assembled wafer fixing device and the slit generating component, place them in warm water to rinse the alkaline solution, and after the wafer slowly cools to room temperature, disassemble the wafer fixing device and the slit generating component, take out the wafer, and perform thickness and roughness tests on it.

[0124] In order to compare the difference between the wafer thinning method of the present invention and the wafer thinning method in the prior art in terms of etching rate and etching area uniformity, in a comparative example, a 4-inch wafer sample is taken, a slit is set in the central area thereof, and no slit is set in the outer ring area thereof. Then, the entire wafer sample is thinned using an etching solution.

[0125] Fig.13 This is a picture of the wafer sample after thinning under uniform backlight. The orange-red area in the center of the wafer corresponds to the slit area, and the dark red area on the outer ring of the wafer corresponds to the corrosion area without slits. Due to the construction of the slit structure, the bubbles are guided to gather and break near the wall of the wafer, generating microjets and introducing additional stress. Therefore, the silicon corrosion rate in the slit corrosion area, i.e., the center area of ​​the wafer, is greatly increased compared to the open corrosion area without a slit structure. Therefore, after the same corrosion process, the thickness of the slit corrosion area in the center of the wafer is 13um, which is significantly lower than 25um in the outer ring area. As a result, the light transmittance in the center area of ​​the wafer is higher and appears orange-red, while the light transmittance in the open corrosion area on the outer ring of the wafer is lower and appears dark red. Through this picture, it can be intuitively demonstrated that the wafer thinning method of the present invention is faster in corrosion rate than the wafer thinning method in the prior art.

[0126] Fig.14 The schematic diagram of the surface roughness of the wafer sample after thinning. As shown in the figure, the surface roughness of the wafer in the narrow slot etching area in the center of the wafer is significantly lower than that of the open area around the outer ring of the wafer.

[0127] Combination Fig.13 and Fig.14It can be seen that in the wafer sample, the corrosion rate of the slit accelerated corrosion area is 51um / h, and the corrosion rate of the open corrosion area without slit structure is 37um / h, which increases the corrosion rate by more than 35%. The surface roughness of the slit accelerated corrosion area is 21.5nm, and the roughness of the open corrosion area is 31.7nm, and the surface roughness is reduced by more than 33%.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wafer thinning device, characterized in that: include: A tank (101) for containing a corrosive liquid, a wafer fixing component (102), and a slit generating component (103); wherein: The wafer fixing component (102) and the slit generating component (103) are both installed inside the tank body (101); the wafer (104) to be thinned is fixed by the wafer fixing component (102); and a slit (106) is formed between the slit generating component (103) and the etched surface of the wafer (104) to be thinned.

2. The wafer thinning device according to claim 1, characterized in that: The tank body (101) is a closed container and is connected to a vacuum pump (108).

3. The wafer thinning device according to claim 1 or 2, characterized in that: A mechanical stirring component (109) and / or an ultrasonic component (110) are also installed.

4. The wafer thinning device according to claim 1 or 2, characterized in that: The slit generating component (103) is a position-fixed component.

5. The wafer thinning device according to claim 1 or 2, characterized in that: The slit generating component (103) is a position-adjustable component.

6. The wafer thinning device according to claim 5, characterized in that: The wafer fixing component (102) comprises a base (201) and an upper pressure ring (202); the wafer to be thinned is placed on the base (201) and fixed by the upper pressure ring (202); The slit generating component (103) comprises a bridge plate (203) and a core plate (204); the bridge plate (203) is fixedly mounted on the upper pressure ring (202); the core plate (204) is mounted on the bridge plate (203); and the relative position between the bridge plate (203) and the core plate (204) is adjustable.

7. A wafer thinning method implemented by the wafer thinning device according to any one of claims 1 to 6, characterized in that: include: Step 1: Mounting a wafer (104) to be thinned on a wafer fixing component (102); Step 2, installing a slit generating component (103) above the wafer fixing component (102), and ensuring that the width of the slit (106) formed between the slit generating component (103) and the upper surface of the wafer is within a preset width range; Step 3, injecting a corrosive liquid (107) into the tank (101) in which the wafer fixing component (102) and the slit generating component (103) are placed, and after the injection of the corrosive liquid (107), the liquid level of the corrosive liquid (107) is higher than the height of the slit generating component (103); Step 4: The wafer (104) is corroded and thinned in the corrosive liquid (107). When the thickness of the wafer (104) reaches a preset value, the etching process is terminated and the wafer (104) is taken out.

8. The wafer thinning method according to claim 7, characterized in that: Between step 3 and step 4, the method further includes: Performing a vacuum operation on the tank body (101) by means of a vacuum pump (108) so that the air pressure value in the tank body (101) reaches a preset value; In step 4, the terminating corrosion process comprises: The air pressure value in the tank body (101) is gradually restored to the standard atmospheric pressure.

9. The wafer thinning method according to claim 7 or 8, characterized in that: Between step 3 and step 4, the method further includes: Starting the mechanical stirring component (109) and / or the ultrasonic component (110); In step 4, the terminating corrosion process comprises: The mechanical stirring component (109) and / or the ultrasonic component (110) are stopped.

10. The wafer thinning method according to claim 7, characterized in that: The step of taking out the wafer comprises: The wafer fixing component (102) on which the thinned wafer (104) is mounted is taken out from the etching liquid (107), then immersed and rinsed in warm water, and finally the thinned wafer (104) is taken out from the wafer fixing component (102).

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