Wafer cutting method

Abstract

The present invention provides a wafer cutting method, comprising: S1, providing a wafer, coating a photoresist on the surface of the wafer; S2, patterning the photoresist, using a mask to expose and develop the photoresist, the patterned photoresist covers the effective chip area of ​​the wafer and exposes the cutting path of the wafer; S3, cutting the wafer along the cutting path; S4, sorting the cut single chip and fixing it to the mucous membrane of the peripheral band frame; S5, exposing the patterned photoresist on the chip fixed on the mucous membrane, and developing to remove the patterned photoresist and stains. Foreign matter such as silicon scraps and metal particles generated during the cutting process can only fall on the patterned photoresist and cannot contact the pixel area on the chip surface, thereby effectively protecting the chip surface. It can effectively prevent the splash generated during chip cutting from damaging the chip surface and reduce the pressure damage to the chip surface caused by the suction nozzle during chip sorting, avoid the contaminants from adhering to the chip surface during the cutting process, and improve the yield of wafer reconstruction.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated circuit manufacturing, and in particular relates to a wafer cutting method. Background Art

[0002] With the development of semiconductor technology, the integration of chips is getting higher and higher, while the corresponding chip size is getting smaller and smaller. In the semiconductor process, the wafer needs to be cut into individual chips, and then these chips are made into different semiconductor packaging structures. Wafer cutting is a key process in the semiconductor packaging process. However, the splashes such as silicon slag or metal particles generated during the wafer cutting process will damage the chip surface; in addition, during chip sorting, the silicon slag generated by the chip adheres to the suction nozzle, causing the surface of the chip sucked by the subsequent suction nozzle to be crushed; in addition, there are silicon powder generated during the cutting process and oil particles generated during the movement of components on the chip surface, which are difficult to remove. Therefore, the surface of the chip after cutting is damaged by splashes, crushed by the suction nozzle, and difficult to remove pollutants, which cause the chip surface to be damaged and the yield to decrease. Summary of the invention

[0003] The purpose of the present invention is to provide a wafer cutting method, in which foreign matter such as silicon scraps and metal particles generated during the cutting process can only fall on the patterned photoresist and cannot contact the pixel area on the chip surface, thereby effectively protecting the chip surface. It can effectively prevent the splash generated during chip cutting from damaging the chip surface and reduce the pressure damage to the chip surface caused by the suction nozzle during chip sorting, avoid the contaminants from adhering to the chip surface during the cutting process, and improve the yield of wafer reconstruction.

[0004] The present invention provides a wafer cutting method, comprising:

[0005] S1. providing a wafer, and coating a photoresist on the surface of the wafer;

[0006] S2, patterning the photoresist, exposing and developing the photoresist using a mask, wherein the patterned photoresist covers the chip effective area of ​​the wafer and exposes the cutting path of the wafer;

[0007] S3, cutting the wafer along the cutting path;

[0008] S4, sorting the cut single chips and fixing them on the mucosa with a surrounding frame;

[0009] S5, exposing the patterned photoresist on the chip fixed on the mucous membrane, and developing to remove the patterned photoresist and stains.

[0010] Furthermore, the wafer includes an image sensor wafer, which includes a substrate, a circuit layer, a filter layer and a microlens layer from bottom to top; a plurality of photodiodes are formed in the substrate, and the plurality of photodiodes are arranged in rows and columns of a pixel array; and metal wiring is formed in the dielectric layer for connecting pixel signals.

[0011] Furthermore, step S3 specifically includes: using a laser and / or a blade to cut the wafer, first using a laser to cut the wafer line by line along the cutting path, and in the thickness direction of the wafer, the laser sequentially cuts the microlens layer, the filter layer and the circuit layer until the substrate is exposed; then using the blade to cut through the substrate line by line.

[0012] Furthermore, the laser cutting specifically includes: providing a laser beam machine, the laser beam machine includes a laser emitter, a chuck table and a moving mechanism; the chuck table fixes the wafer, and the moving mechanism drives the wafer fixed on the chuck table to move.

[0013] Furthermore, the blade cutting specifically includes: providing a cutting machine, the cutting machine including a motor, a main shaft, and a hub and the blade which are sequentially sleeved on the main shaft; the blade is fixed to the radial circumferential edge of the hub, the motor drives the main shaft to rotate, and drives the blade to rotate through the hub to cut through the substrate.

[0014] Furthermore, step S4 specifically includes: after the cutting is completed, sorting the chips to separate qualified chips from unqualified chips; fixing the qualified chips to the mucous membrane of the peripheral belt frame.

[0015] Furthermore, after step S5, the method further includes: step S6, performing automatic optical inspection on all chips on the mucosa after removing the patterned photoresist.

[0016] Furthermore, the automatic optical inspection is divided into four optical inspections, the first optical inspection is wafer inspection, the second optical inspection is particle appearance defect inspection, the third optical inspection is chip / wire bonding inspection, and the fourth optical inspection is plastic packaging appearance inspection.

[0017] Furthermore, there are multiple cutting lanes, and the multiple cutting lanes extend along a first direction and a second direction that are perpendicular to each other respectively; the multiple cutting lanes are staggered in a tic-tac-toe pattern; and the area surrounded by the staggered cutting lanes is the effective area of ​​the chip.

[0018] Furthermore, the wafer includes an integrated circuit wafer or a force-sensitive device wafer.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a wafer cutting method, comprising: S1, providing a wafer, coating a photoresist on the surface of the wafer; S2, patterning the photoresist, using a mask to expose and develop the photoresist, the patterned photoresist covers the effective chip area of ​​the wafer and exposes the cutting path of the wafer; S3, cutting the wafer along the cutting path; S4, sorting the cut single chip and fixing it to the mucous membrane of the peripheral band frame; S5, exposing the patterned photoresist on the chip fixed on the mucous membrane, and developing to remove the patterned photoresist and stains. Foreign matter such as silicon scraps and metal particles generated during the cutting process of the present invention can only fall on the patterned photoresist and cannot contact the pixel area on the chip surface, thereby effectively protecting the chip surface. It can effectively prevent the splash generated during chip cutting from damaging the chip surface and reduce the pressure damage to the chip surface caused by the suction nozzle during chip sorting, avoid the adhesion of pollutants to the chip surface during the cutting process, and improve the yield of wafer reconstruction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic flow chart of a wafer cutting method according to an embodiment of the present invention.

[0022] Figure 2 The figure is a schematic diagram of a wafer cutting method according to an embodiment of the present invention.

[0023] Figure 3 Schematic diagram of laser cutting in a wafer cutting method according to an embodiment of the present invention.

[0024] Figure 4 Schematic diagram of blade cutting in a wafer cutting method according to an embodiment of the present invention.

[0025] Figure 5 This is a schematic diagram of sorting and fixing chips onto a mucous membrane after cutting in a wafer cutting method according to an embodiment of the present invention.

[0026] The reference numerals are as follows:

[0027] 11-substrate; 12-circuit layer; 13-filter layer; 14-microlens layer. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are in a very simplified form and use an inaccurate scale, which is only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0029] For ease of description, some embodiments of the present application may use spatially relative terms such as "above", "below", "top", "below", etc. to describe the relationship between one element or component and another (or other) elements or components as shown in the various figures of the embodiments. It should be understood that in addition to the orientations described in the drawings, the spatially relative terms are also intended to include different orientations of the device in use or operation. For example, if the device in the drawings is turned over, the elements or components described as being "below" or "below" other elements or components will subsequently be positioned as being "above" or "above" other elements or components. The terms "first", "second", etc. below are used to distinguish between similar elements and are not necessarily used to describe a specific order or time sequence. It is to be understood that these terms used in this way are interchangeable where appropriate.

[0030] The embodiment of the present invention provides a wafer cutting method, such as Figure 1 As shown, including:

[0031] S1. Provide a wafer and coat a photoresist on the surface of the wafer;

[0032] S2, patterning the photoresist, using a mask to expose and develop the photoresist, the patterned photoresist covers the chip effective area of ​​the wafer and exposes the wafer cutting path;

[0033] S3, cutting the wafer along the cutting path;

[0034] S4, sorting the cut single chips and fixing them on the mucosa with a surrounding frame;

[0035] S5. Exposing the patterned photoresist on the chip fixed on the mucous membrane, and developing to remove the patterned photoresist and stains.

[0036] The steps of the wafer cutting method according to the embodiment of the present invention are described in detail below with reference to the accompanying drawings.

[0037] like Figure 2 and Figure 3As shown, S1, provide a wafer, and coat the surface of the wafer with photoresist. The wafer is, for example, an image sensor wafer, and the wafer includes a substrate 11, a circuit layer 12, a filter layer 13, and a microlens layer 14 from bottom to top. A plurality of photodiodes are formed in the substrate 11, and the plurality of photodiodes are arranged in rows and columns of a pixel array. The circuit layer 12 includes a dielectric layer and a metal layer located in the dielectric layer. The dielectric layer is, for example, a low dielectric insulating film formed by a film of an inorganic material such as SiOF or BSG (SiOB), or a film of an organic material such as a polyimide-based or polyparaxylene-based polymer. Metal wiring is formed in the dielectric layer for connecting the pixel signal. The filter layer 13 covers the circuit layer 12, and the filter layer includes a red filter, a green filter, and a blue filter; the red filter, the green filter, and the blue filter are correspondingly arranged above the photodiode. The microlens layer 14 is located above the filter layer 13, and the microlens is configured to guide the incoming light through the corresponding filter to reach the corresponding photodiode. The present invention does not limit the type of wafer. In other examples, the wafer may be various device wafers, such as integrated circuit wafers and force-sensitive MEMS (micro-electromechanical systems) device wafers.

[0038] Semiconductor photoresist spraying equipment is used to coat the wafer surface with photoresist, and soft baking and hard baking are performed. Soft baking is to make the photoresist swell during the exposure process, thereby improving the laser-induced thin film separation effect. Hard baking is to make the photoresist maintain good stability when the laser is irradiated. The baking temperature and time are adjusted according to the properties of the photoresist.

[0039] S2, patterning photoresist, using a mask to expose and develop the photoresist, the patterned photoresist covers the effective chip area of ​​the wafer and exposes the wafer's cutting path; the cutting path is clearly exposed, which is obviously convenient for alignment cutting. Looking down at the wafer, there are multiple cutting paths, and the multiple cutting paths extend along a first direction and a second direction that are perpendicular to each other; the multiple cutting paths are staggered in a tic-tac-toe shape.

[0040] S3, cutting the wafer along the cutting path; the wafer can be cut by laser and / or blade. For example, Figure 3 As shown, the laser can be used to cut the wafer line by line along the cutting path. In the thickness direction of the wafer, the laser cuts the microlens layer 14, the filter layer 13 and the circuit layer 12 in sequence until the substrate 11 is exposed. Then, as shown in FIG. Figure 4 As shown, the blade on the tool is used to cut through the substrate 11 row by row. During laser and / or blade cutting in this step, foreign matter such as silicon chips / metal particles can only fall on the patterned photoresist and cannot contact the pixel area on the chip surface, thereby effectively protecting the chip surface.

[0041] Laser cutting specifically includes: providing a laser beam machine, the laser beam machine includes a laser emitter, a chuck table and a moving mechanism; the chuck table fixes the wafer, and the moving mechanism drives the wafer fixed on the chuck table to move. In the steps of laser cutting, exemplary process parameters include: laser wavelength: 300nm ~ 400nm; laser output power: 1.0W ~ 4.0W; repetition frequency: 40kHz ~ 200kHz; pulse width: 8ns ~ 13ns; the cutting supply speed of the laser beam and the wafer moving relative to each other is: 50mm / sec ~ 400mm / sec.

[0042] The blade cutting specifically includes: providing a cutting machine, the cutting machine includes a motor, a main shaft, and a hub and a blade sequentially mounted on the main shaft; the blade is fixed to the radial peripheral edge of the hub, the motor drives the main shaft to rotate, and the hub drives the blade to rotate to cut through the substrate 11. Exemplarily, in the blade cutting step, the blade: the outer diameter is 40mm to 60mm, the width is 70μm to 90μm; the number of revolutions of the blade is: 25000rpm to 50000rpm; the cutting feed speed of the blade and the wafer moving relative to each other is: 20mm / sec to 40mm / sec.

[0043] S4, such as Figure 5 As shown, the cut single chips are sorted and fixed to the mucosa of the surrounding belt frame. After the cutting is completed, the chips need to be sorted to separate qualified chips from unqualified chips. The qualified chips are fixed to the mucosa of the surrounding belt frame. Sorting is usually performed using a sorting machine, which classifies and separates the chips according to certain rules through optical detection and mechanical sorting.

[0044] S5. Exposing the patterned photoresist on the chip fixed on the mucus film, and developing and removing the patterned photoresist and stains on the surface of the wafer.

[0045] S6. Perform automatic optical inspection on all chips on the mucous film after removing the patterned photoresist. The automatic optical inspection is divided into four optical inspections. The first optical inspection is wafer inspection, the second optical inspection is particle appearance defect inspection, the third optical inspection is chip / wire bonding inspection, and the fourth optical inspection is plastic packaging appearance inspection.

[0046] The present invention is a new photoresist coating method for chip wafer reconstruction, which can effectively prevent the splashes generated during chip cutting from damaging the chip surface and reduce the pressure damage to the chip surface caused by the suction nozzle during chip sorting, thereby improving the yield of wafer reconstruction. Wafer reconstruction is a general term for several processes in the chip industry. The present invention can effectively protect the chip surface, increase the surface yield of the product in the cutting and sorting processes to 100%, reduce yield loss, and improve product yield. The reduction in cutting cleaning time and the reduction in pressure damage in the sorting process help improve the production capacity of wafer reconstruction.

[0047] In summary, the present invention provides a wafer cutting method, including: S1, providing a wafer, coating a photoresist on the surface of the wafer; S2, patterning the photoresist, using a mask to expose and develop the photoresist, the patterned photoresist covers the effective chip area of ​​the wafer and exposes the cutting path of the wafer; S3, cutting the wafer along the cutting path; S4, sorting the cut single chip and fixing it to the mucous membrane of the peripheral band frame; S5, exposing the patterned photoresist on the chip fixed on the mucous membrane, and developing to remove the patterned photoresist and stains. Foreign matter such as silicon chips and metal particles generated during the cutting process of the present invention can only fall on the patterned photoresist and cannot contact the pixel area on the chip surface, thereby effectively protecting the chip surface. It can effectively prevent the splash generated during chip cutting from damaging the chip surface and reduce the pressure damage to the chip surface caused by the suction nozzle during chip sorting, avoid the adhesion of pollutants to the chip surface during the cutting process, and improve the yield of wafer reconstruction.

[0048] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the method disclosed in the embodiment, since it corresponds to the device disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0049] The above description is only a description of the preferred embodiment of the present invention, and is not any limitation on the scope of rights of the present invention. Any technical personnel in this field can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A wafer cutting method, characterized in that: include: S1. providing a wafer, and coating a photoresist on the surface of the wafer; S2, patterning the photoresist, exposing and developing the photoresist using a mask, wherein the patterned photoresist covers the chip effective area of ​​the wafer and exposes the cutting path of the wafer; S3, cutting the wafer along the cutting path; S4, sorting the cut single chips and fixing them on the mucosa with a surrounding frame; S5, exposing the patterned photoresist on the chip fixed on the mucous membrane, and developing to remove the patterned photoresist and stains.

2. The wafer cutting method according to claim 1, characterized in that: The wafer includes an image sensor wafer, which includes a substrate, a circuit layer, a filter layer and a microlens layer from bottom to top; a plurality of photodiodes are formed in the substrate, and the plurality of photodiodes are arranged in rows and columns of a pixel array; and metal wiring is formed in the dielectric layer for connecting pixel signals.

3. The wafer cutting method according to claim 2, characterized in that: Step S3 specifically includes: using a laser and / or a blade to cut the wafer; first using a laser to cut the wafer line by line along the cutting path, and in the thickness direction of the wafer, the laser sequentially cuts the microlens layer, the filter layer and the circuit layer until the substrate is exposed; then using the blade to cut through the substrate line by line.

4. The wafer cutting method according to claim 3, characterized in that: The laser cutting specifically includes: providing a laser beam machine, the laser beam machine including a laser emitter, a chuck table and a moving mechanism; the chuck table fixes the wafer, and the moving mechanism drives the wafer fixed on the chuck table to move.

5. The wafer cutting method according to claim 3, characterized in that: The blade cutting specifically includes: providing a cutting machine, the cutting machine including a motor, a main shaft, and a hub and the blade which are sequentially sleeved on the main shaft; the blade is fixed on the radial circumferential edge of the hub, the motor drives the main shaft to rotate, and drives the blade to rotate through the hub to cut through the substrate.

6. The wafer cutting method according to claim 1, characterized in that: Step S4 specifically includes: after the cutting is completed, sorting the chips to separate qualified chips from unqualified chips; fixing the qualified chips to the mucous membrane of the peripheral belt frame.

7. The wafer cutting method according to claim 1, characterized in that: After step S5, the method further includes: step S6, performing automatic optical inspection on all chips on the mucous membrane after removing the patterned photoresist.

8. The wafer cutting method according to claim 7, characterized in that: The automatic optical inspection is divided into four optical inspections. The first optical inspection is wafer inspection, the second optical inspection is particle appearance defect inspection, the third optical inspection is chip / wire bonding inspection, and the fourth optical inspection is plastic packaging appearance inspection.

9. The wafer cutting method according to claim 1, wherein: There are multiple cutting paths, and the multiple cutting paths extend along a first direction and a second direction that are perpendicular to each other respectively; the multiple cutting paths are staggered in a tic-tac-toe pattern; and the area surrounded by the staggered cutting paths is the effective area of ​​the chip.

10. The wafer cutting method according to claim 1, wherein: The wafer includes an integrated circuit wafer or a force-sensitive device wafer.

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