Thick soft metal stripping process for reducing crushing and scratching of wafer

Abstract

The invention discloses a thick soft metal stripping process for reducing crushing and scratching of a wafer, and belongs to the technical field of LEDs and optical communication. The method comprises the following steps: (1) placing a wafer in a stripping unit, spraying liquid medicine to the center of the wafer at high pressure by using a high-pressure photoresist removing nozzle, and opening a small window in the center of the wafer; (2) spraying liquid medicine into the torn window by adopting a normal-pressure photoresist removing nozzle, and keeping the wafer to rotate at a relatively low rotating speed, so that a certain amount of liquid medicine is filled between the metal film layer of the wafer and the interlayer of the photoresist; and (3) a high-pressure photoresist removing nozzle is adopted to spray liquor medicine liquid to strip the metal film layer. According to the process, during stripping of electrode lead-out, the minimum metal scratch and crushing damage can be guaranteed to the maximum extent, the yield loss is reduced, and the conductivity of a product is improved.

Description

Technical Field

[0001] The invention relates to the technical field of LED and optical communication, and in particular to a thick soft metal stripping process for reducing wafer crushing and scratching. Background Art

[0002] In the field of LED optoelectronic devices, the electrode lead-out process for preparing light-emitting diodes is: first, the bottom PN junction of the wafer is exposed through the coating + development process, and then the conductive metal layer (Al) is made through the evaporation process. After the evaporation process is completed, the evaporated metal of certain special processes is thicker than the thickness of the photoresist (PR), resulting in the entire wafer being completely covered by the metal layer. The photoresist and the metal evaporated above the photoresist need to be stripped off. The traditional stripping process is thick soft metal electrode stripping technology, which is to adhere the blue film tape to the front of the wafer, and the back of the wafer is firmly sucked with a vacuum suction cup. The adhesion of the blue film tape is used to tear off part of the PR and the metal to be stripped by external force. If there is electrostatic breakdown or repeated pressure injuries during the tearing process, it will affect the conductivity and yield of the final product. Summary of the invention

[0003] In view of the problem that the inherent stripping process of the single-chip machine in the existing soft metal stripping process will cause scratches on the product's electrodes, the purpose of the present invention is to provide a thick soft metal stripping process that reduces wafer crushing and scratching. This process can minimize metal scratches and crushing during the stripping of electrode lead-out, reduce the loss of yield, and improve the product's conductive performance.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A thick soft metal stripping process for reducing wafer crushing and scratching, the process performs metal stripping on a wafer coated with photoresist and exposed, developed and prepared with a thick soft metal film layer, the metal stripping process is to place the wafer in a stripping unit for metal stripping; the method specifically comprises the following steps:

[0006] (1) Place the wafer on the wafer stage of the stripping unit, and use a high-pressure degumming nozzle to spray a high-pressure solution toward the center of the wafer. The solution destroys the thick soft metal film layer, thereby opening a small window in the center of the wafer;

[0007] (2) using a normal pressure degumming nozzle in a stripping unit to spray a liquid into the window torn in step (1), and keeping the wafer rotating at a relatively low speed so that a certain amount of liquid is filled between the metal film layer and the interlayer of the photoresist of the wafer;

[0008] (3) The metal film layer is stripped by spraying a high-pressure degumming nozzle in the stripping unit with a liquid medicine, wherein: the spray pressure is 10-15 MPa, the wafer rotation speed is 800-2000 r / min, and the high-pressure degumming nozzle performs a swing arm stripping action from the center to the edge of the wafer to achieve the stripping of the metal film layer and the removal of the photoresist;

[0009] Furthermore, the thick soft metal film layer of the present invention is one or more of aluminum, gold, nickel, silver and chromium, and has a thickness of 1-5 μm.

[0010] The stripping unit includes a degumming chamber, in which a rotatable wafer holding table and a high-pressure degumming nozzle and a normal-pressure degumming nozzle installed on the same swing arm are provided; wherein: the spraying direction of the normal-pressure degumming nozzle is perpendicular to the wafer surface, and the spraying direction of the high-pressure degumming nozzle has an angle of 10-30° with the vertical direction of the wafer.

[0011] The high-pressure degumming nozzle is a needle-shaped nozzle, and the normal-pressure degumming nozzle is a columnar nozzle.

[0012] In the above step (1), the high-pressure degumming nozzle is used to spray the liquid, and the jet of the high-pressure degumming nozzle is aimed at the center of the wafer, the wafer remains stationary, the liquid spraying time is 0.1-3s, and the liquid pressure is 3-15MPa. This process opens a small window in the center of the wafer. The liquid pressure and the instantaneous window opening spraying time should be adjusted to find the optimal balance parameter within the adjustment range according to the actual application situation to achieve the optimal window opening effect.

[0013] In the above step (2), the normal pressure degumming nozzle is used to spray the liquid, the spraying time is 5-30s, and the wafer rotation speed is 50-500r / min.

[0014] In the above step (3), the high-pressure degumming nozzle is used to spray the liquid medicine, and the spraying time is 10-100s.

[0015] Furthermore, after the metal film layer is stripped off in step (3), the wafer can be placed on a cleaning unit for wafer cleaning and wafer drying; the wafer cleaning is to place the wafer on a wafer stage of the cleaning unit, use a nozzle to swing from one edge of the wafer to the other edge and spray cleaning liquid (deionized water or other cleaning liquid) to achieve a more adequate cleaning effect; the wafer drying is to place the wafer on a wafer stage of the cleaning unit, use a nozzle to swing from one edge of the wafer to the other edge and spray nitrogen, and use a high-speed and long-term rotation method to dry the wafer.

[0016] The cleaning unit comprises a cleaning chamber, in which a rotatable wafer stage and two columnar nozzles respectively mounted on two swing arms are arranged; wherein: one columnar nozzle is used for spraying cleaning liquid, and the other columnar nozzle is used for spraying nitrogen, and the spraying directions of the two columnar nozzles are perpendicular to the wafer surface.

[0017] Preferably, during the spraying of the cleaning liquid, the wafer rotation speed is 300r / min-1000r / min, the spraying time is 10-60s, and the cleaning liquid flow rate is 500-1000ml / min.

[0018] Preferably, during the wafer drying process, nitrogen is sprayed on the front side of the wafer, the wafer rotation speed is 1000-2000r / min, the front side nitrogen spraying flow rate is 20-50L / min, and the time is 20-60s.

[0019] The advantages and beneficial effects of the present invention are as follows:

[0020] 1. The present invention adopts a high-pressure degumming nozzle to spray high-pressure liquid medicine, and avoids the electrostatic breakdown effect of the wafer to the greatest extent through the sol-gel ability and high-pressure force of the liquid medicine.

[0021] 2. When stripping soft metal electrodes, the present invention adopts a process of inclined high-pressure degumming nozzle + center window breaking + secondary stripping to achieve the effect of no scratches and no electrostatic breakdown on soft metals (such as aluminum electrodes). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the degumming chamber structure.

[0023] Figure 2 Schematic diagram of the cleaning chamber structure.

[0024] Figure 3 Comparison of metal stripping before and after in Example 1; wherein: (a) cross section before stripping; (b) cross section after stripping. DETAILED DESCRIPTION

[0025] In order to further understand the present invention, the present invention is described below in conjunction with examples, but the examples are only for further elaboration of the features and advantages of the present invention, rather than for limiting the claims of the present invention.

[0026] The invention provides a thick soft metal stripping process for reducing wafer crushing and scratching, the core of which is high pressure window opening + single stripping-High Press Center Fixing, Inject Chemical Liftoff-(CFIC); the process performs metal stripping treatment on wafers that have been coated with photoresist and exposed, developed and prepared (such as vapor deposition) with a thick soft metal film layer, and the metal stripping treatment is to place the wafer in a stripping unit for metal stripping, and then place the wafer in a cleaning unit for cleaning and drying after the metal stripping.

[0027] like Figure 1As shown, the stripping unit includes a degumming chamber, in which a rotatable wafer stage and a high-pressure degumming nozzle and a normal-pressure degumming nozzle mounted on the same swing arm are provided; wherein: the spraying direction of the normal-pressure degumming nozzle is perpendicular to the wafer surface, and the angle between the spraying direction of the high-pressure degumming nozzle and the vertical direction of the wafer is 10-30°. The high-pressure degumming nozzle is a needle-shaped nozzle with a nozzle tip diameter of 0.1-0.2 mm; the normal-pressure degumming nozzle is a columnar nozzle.

[0028] like Figure 2 As shown, the cleaning unit includes a cleaning chamber, in which a rotatable wafer stage and two columnar nozzles respectively installed on two swing arms are provided; wherein: the columnar nozzle installed on the DIW cleaning swing arm is used to spray cleaning liquid (such as deionized water or other cleaning liquids), and the columnar nozzle installed on the nitrogen drying swing arm is used to spray nitrogen, and the spraying directions of the two columnar nozzles are perpendicular to the wafer surface.

[0029] Embodiment 1:

[0030] Step 1: Place the wafer coated with photoresist, exposed, developed and evaporated with a 4.4μm aluminum film layer on the wafer stage of the stripping unit, and use a high-pressure degumming nozzle to spray high-pressure liquid on the wafer. The wafer remains stationary, the spray pressure is 8MPa, and the high-pressure liquid is sprayed on the center of the wafer for 2.5s to open a small tearing window with a diameter of about 9mm in the center of the wafer. In this embodiment, the spray direction of the high-pressure degumming nozzle is at an angle of 20° to the vertical direction of the wafer.

[0031] Step 2: Use the normal pressure degumming nozzle in the stripping unit to pour the liquid into the window opened in the first step. The process is carried out under normal pressure, with a wafer rotation speed of 100r / min, a liquid flow rate of 500mL / min, and spraying for 10s.

[0032] Step 3: Use a high-pressure degumming nozzle to slowly swing from the wafer window in the first step to the edge of the other side (to cater to the inclination angle of the nozzle), spray high-pressure liquid for 50 seconds, the wafer speed is 1500r / min, the high-pressure nozzle pressure is 15MPa, and swing back and forth 3 times.

[0033] Step 4: Transfer the wafer to the cleaning unit and spray deionized water at a fixed point in the center of the wafer. The wafer rotation speed is 300rpm, the deionized water flow rate is 800mL / min, and the spraying time is 50s.

[0034] Step 5: In the cleaning unit, the wafer is rotated at a high speed for a long time, and nitrogen is sprayed on the front of the wafer to dry it. The wafer rotation speed is 3000r / min, the front nitrogen spray flow rate is 30L / min, and the time is 30s.

[0035] After the above-mentioned stripping process is completed, the AOI microscope is used to observe the size of the pad and the degree of scratches / injuries, and to determine the undercut angle and the amount of metal residue at the edge.

[0036] Figure 3 This is a schematic diagram of the cross section of the wafer of this embodiment before and after the metal stripping process. The photoresist thickness is 3.2μm, the edge washing is 1mm, and a 4.4μm metal layer (Al) is evaporated, resulting in the aluminum film layer after evaporation to tightly cover the entire wafer. Stripping cannot be completed by simply immersing it. External force is applied to tear a window in the thick metal, and the drug solution is injected to dissolve its PR. The Al material is relatively soft and can be scratched by a slight scrape. By adjusting the mutual coordination of the process parameters, the pad is not scratched and there is no electrostatic breakdown during the rotating stripping process.

[0037] After stripping, scratch comparison was performed through AOI and OM, and the data showed that there was no loss in stripping yield through the process of the present invention, proving that the process of the present invention effectively avoids scratches / pressure damage / static breakdown of the Al metal pad, thereby avoiding adverse effects on the conductive properties of the product.

Claims

1. A thick soft metal stripping process for reducing wafer crushing and scratching, characterized by: The process performs metal stripping on a wafer coated with photoresist, exposed, developed and prepared with a thick soft metal film layer. The metal stripping process is to place the wafer in a stripping unit for metal stripping. The method specifically includes the following steps: (1) Place the wafer on the wafer stage of the stripping unit, and use a high-pressure degumming nozzle to spray a high-pressure solution toward the center of the wafer. The solution destroys the thick soft metal film layer, thereby opening a small window in the center of the wafer; (2) using a normal pressure degumming nozzle in a stripping unit to spray a liquid into the window torn in step (1), and keeping the wafer rotating at a relatively low speed so that a certain amount of liquid is filled between the metal film layer and the interlayer of the photoresist of the wafer; (3) The metal film layer is stripped by spraying liquid medicine with a high-pressure degumming nozzle in the stripping unit, wherein: the spray pressure is 10-15MPa, the wafer rotation speed is 800-2000r / min, and the high-pressure degumming nozzle performs a swing-arm stripping action from the center to the edge of the wafer to achieve the stripping of the metal film layer and the removal of the photoresist.

2. The thick soft metal stripping process for reducing wafer crushing and scratching according to claim 1 is characterized in that: The thick soft metal film layer is one or more of aluminum, gold, nickel, silver and chromium, and has a thickness of 1-5 μm.

3. The thick soft metal stripping process for reducing wafer crushing and scratching according to claim 1 is characterized in that: The stripping unit includes a degumming chamber, in which a rotatable wafer holding table and a high-pressure degumming nozzle and a normal-pressure degumming nozzle installed on the same swing arm are provided; wherein: the spraying direction of the normal-pressure degumming nozzle is perpendicular to the wafer surface, and the spraying direction of the high-pressure degumming nozzle has an angle of 10-30° with the vertical direction of the wafer.

4. The thick soft metal stripping process for reducing wafer crushing and scratching according to claim 3 is characterized in that: The high-pressure degumming nozzle is a needle-shaped nozzle, and the normal-pressure degumming nozzle is a columnar nozzle.

5. The thick soft metal stripping process for reducing wafer crushing and scratching according to claim 1 is characterized in that: In step (1), during the process of spraying the liquid medicine with a high-pressure degumming nozzle, the jet of the high-pressure degumming nozzle is aimed at the center of the wafer, the wafer remains still, the liquid medicine spraying time is 0.1-3s, and the liquid medicine pressure is 3-15MPa.

6. The thick soft metal stripping process for reducing wafer crushing and scratching according to claim 1, characterized in that: In step (2), during the process of spraying the liquid medicine using a normal pressure degumming nozzle, the spraying time is 5-30s and the wafer rotation speed is 50-500r / min; in step (3), during the process of spraying the liquid medicine using a high pressure degumming nozzle, the spraying time is 10-100s.

7. The thick soft metal stripping process for reducing wafer crushing and scratching according to claim 1, characterized in that: After the metal film layer is peeled off in step (3), the wafer is placed in a cleaning unit for wafer cleaning and wafer drying; the wafer cleaning is to place the wafer on a wafer holding table of the cleaning unit, use a nozzle to swing from one edge of the wafer to the other edge and spray cleaning liquid to achieve a more sufficient cleaning effect; the wafer drying is to place the wafer on a wafer holding table of the cleaning unit, use a nozzle to swing from one edge of the wafer to the other edge and spray nitrogen, and use a high-speed and long-term rotation method to dry the wafer.

8. The thick soft metal stripping process for reducing wafer crushing and scratching according to claim 7, characterized in that: The cleaning unit comprises a cleaning chamber, in which a rotatable wafer stage and two columnar nozzles respectively mounted on two swing arms are arranged; wherein: one columnar nozzle is used for spraying cleaning liquid, and the other columnar nozzle is used for spraying nitrogen, and the spraying directions of the two columnar nozzles are perpendicular to the wafer surface.

9. The thick soft metal stripping process for reducing wafer crushing and scratching according to claim 8, characterized in that: During the wafer cleaning process of spraying cleaning liquid, the wafer rotation speed is 300r / min-1000r / min, the spraying time is 10-60s, and the cleaning liquid flow rate is 500-1000ml / min.

10. The thick soft metal stripping process for reducing wafer crushing and scratching according to claim 8, characterized in that: During the wafer drying process, nitrogen is sprayed on the front side of the wafer. The wafer rotation speed is 1000-2000r / min, the front side nitrogen spraying flow rate is 20-50L / min, and the time is 20-60s.

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