Method for processing compound semiconductor wafer

Abstract

The application discloses a processing method of a compound semiconductor wafer, which comprises the following steps: attaching the compound semiconductor wafer to a carrier film, fixing the carrier film in a fixing ring, and packaging the edge of the carrier film through the fixing ring to form a bearing assembly; and performing a cutting process, a film expanding process, an etching process and a carrier film retraction process in the form of the bearing assembly. In the continuous process, the wafer is maintained in the form of a bearing assembly, the distance between the crystal grains is expanded after pre-expanding, so that the side wall of the cutting path can be etched clean, the yield rate meets the standard, then the carrier film is retracted to the initial state and is suitable for subsequent process steps, the bearing structure of the wafer does not need to be replaced, the process is simplified, the production cost is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of semiconductors, and specifically relates to a method for processing compound semiconductor wafers. Background Technology

[0002] In recent years, the applications of III-V compound semiconductors have become increasingly widespread. To significantly reduce costs and improve manufacturing efficiency, integrated circuit chips or circuit element structures are often fabricated on wafers in mass production, then divided into individual units, and finally packaged and soldered. Laser cutting technology, with its advantages of high processing speed, high wafer utilization, non-contact processing, and high degree of automation, has been widely adopted. However, laser-cut chips often have laser-melted recast material at the edges, which needs to be etched away; otherwise, the chip yield will be affected.

[0003] Because the spacing between chips after dicing is only the distance of the dicing line, etching is difficult. To ensure clean etching, the distance between the chips needs to be increased. However, the introduction of the expansion process leads to the need to replace the wafer support structure due to size changes. For example, expansion rings and other components need to be used to replace the iron rings used in other process equipment for support. Subsequent processes need to replace the iron rings again. This increases the complexity of the process and the consumables such as expansion rings, affecting production costs and efficiency. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a method for processing compound semiconductor wafers.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for fabricating a compound semiconductor wafer, comprising:

[0007] Step 1) Attach the compound semiconductor wafer to the carrier film, stretch the carrier film in the fixing ring and seal the edges through the fixing ring to form a carrier component;

[0008] Step 2) Move the carrier component into the dicing process to cut the wafer into several grains along the dicing path;

[0009] Step 3) Place the carrier component in the film expander to pre-expand the carrier film to increase the spacing between the grains to a first spacing;

[0010] Step 4) Move the carrier component into the etching process to etch the sidewalls of the grain's cutting path;

[0011] Step 5) Place the carrier component in a nitrogen purging machine and purge the surface of the carrier film with high-temperature nitrogen. The temperature of the high-temperature nitrogen is ≥150℃, the distance between the air outlet and the film surface is 5cm~25cm, the purging time is ≥30s, and after cooling, the carrier film shrinks back to its initial state, so that the spacing between the grains shrinks back.

[0012] Optionally, the carrier film is a PVC blue film with a thickness of 50–100 μm.

[0013] Optionally, the retaining ring is a stainless steel ring.

[0014] Optionally, in step 1), the cutting is laser cutting; in step 3), wet etching is used to remove the laser-cut recast material attached to the edge of the grain.

[0015] Optionally, the film expanding machine includes a film expanding fixture, which includes a pre-expanding ring and a base. The pre-expanding ring is disposed on the base and there is a height difference between the top surface of the pre-expanding ring and the base. The outer diameter of the pre-expanding ring is smaller than the inner diameter of the fixed ring. In step 2), the fixed ring is sleeved on the outside of the pre-expanding ring for film expansion.

[0016] Optionally, the height difference is ≥2cm, and the first spacing after expansion is ≥30μm.

[0017] Optionally, in step 4), the temperature of the high-temperature nitrogen gas is 150℃~500℃, the nitrogen gas flow rate is in the range of 5L / min~15L / min, the purging time is 30s~300s, and after cooling, the spacing between the grains shrinks to less than 15um.

[0018] Optionally, step 5) involves placing the carrier component in a crystal picking machine for crystal picking.

[0019] A method for shipping a compound semiconductor wafer, wherein the compound semiconductor wafer is processed using the above-described processing method and then shipped in the form of the carrier component.

[0020] Optionally, the carrier component enters the crystal picking process after being shipped to the packaging plant.

[0021] The beneficial effects of this invention are as follows:

[0022] In continuous processes, the wafer is maintained in the form of a carrier component. After pre-expansion, the distance between the dies is increased to facilitate the clean etching of the dicing sidewalls, so that the yield meets the standards. Then the carrier film is shrunk back to the initial state and is suitable for subsequent process steps. There is no need to replace the carrier structure of the wafer, which simplifies the process, reduces production costs, and improves production efficiency. Attached Figure Description

[0023] Figure 1This is a schematic diagram of the structure of the support component in the processing method of the compound semiconductor wafer of Example 1;

[0024] Figure 2 This is a schematic diagram of the expansion fixture used in the processing method of the compound semiconductor wafer in Example 1;

[0025] Figure 3 This is a schematic diagram of the film expansion process for the compound semiconductor wafer fabrication method of Example 1;

[0026] Figure 4 for Figure 2 A schematic diagram of the decomposition process;

[0027] Figure 5 This is a schematic diagram of the grain spacing before (5a), after (5b), and after (5c) pre-expansion in the processing method of the compound semiconductor wafer of Example 1.

[0028] Figure 6 The images show enlarged views of the etched grain sidewalls of Example 1 and the comparative example.

[0029] Figure 7 The figure shows the strength of the etched grains in Example 1 and the comparative example, where 75µm and 100µm represent the grain thickness.

[0030] Figure 8 The images show the actual shipment formats of Example 2 and the comparative example. Detailed Implementation

[0031] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. The accompanying drawings are merely illustrative to facilitate understanding of the invention, and their specific proportions can be adjusted according to design requirements. The vertical relationships of relative elements and the definitions of front / back in the graphics described herein should be understood by those skilled in the art to refer to the relative positions of the components; therefore, they can all be flipped to present the same component, and all of this should fall within the scope disclosed in this specification.

[0032] Example 1

[0033] The following describes in detail a method for processing a compound semiconductor wafer according to Example 1. The compound semiconductor wafer may be, for example, a gallium arsenide-based wafer or an indium phosphide-based wafer, which has already undergone conventional device manufacturing processes and is about to enter the dicing process.

[0034] refer to Figure 1A compound semiconductor wafer 11 is attached to a carrier film 12, which is stretched in a retaining ring 13 and its edges are encapsulated by the retaining ring 13, forming a carrier component 1. The carrier film 12 is an 80μm thick PVC UV film, the wafer 11 is a 6-inch wafer, and the retaining ring 13 is a 12-inch iron ring made of SUS420 stainless steel, serving as a frame for fixing the workpiece during subsequent cutting and processing.

[0035] The carrier component 1 is moved into a laser cutting machine, and the wafer 11 is cut into several grains along the cutting path using a laser cutting process. For example, for GaAs-based wafers, ultraviolet laser is used for cutting. Thermal stress is generated during laser cutting, and laser-melted recast material exists at the edges of the divided grains.

[0036] Place the carrier assembly 1 into the film expander. (Reference) Figure 2 The expanding fixture 2 of the expanding machine includes a base 21 and a pre-expanding ring 22. The pre-expanding ring 22 is disposed on the base 21, and there is a height difference between the top surface of the pre-expanding ring 22 and the base 21, the height difference being ≥2cm. The outer diameter of the pre-expanding ring 22 is smaller than the inner diameter of the fixing ring 13 but larger than the size of the wafer 11. (Reference) Figure 3 The expanding fixture 2 is placed on the machine platform of the expanding machine. The fixing ring 13 is sleeved outside the pre-expanding ring 22 for expanding the film, and the carrier film 12 is then covered on the surface of the pre-expanding ring 22. In this embodiment, the outer diameter of the pre-expanding ring 22 is approximately 200 mm, the ring width is ≥8 mm, and it has an arc-shaped chamfer with a chamfer ≤10° to provide support for the carrier film 12 during the expanding process and reduce the probability of film breakage.

[0037] For details, please refer to Figure 4 The base 21 is also annular, with several protrusions 211. Each protrusion 211 has a groove 212, into which the pre-expansion ring 22 is embedded. The top surface of the pre-expansion ring 22 protrudes beyond the top surface of the protrusion 211, and the outer periphery of the top surface of the protrusion 211 is inclined to reduce film breakage during expansion. The pre-expansion ring 22 and the protrusion 211 can also be configured to rotate relative to each other. Specifically, the inner wall of the pre-expansion ring 22 has an annular groove 221 extending radially outward. At least one limiting member 213 is fixed on the side wall of the groove 212. The other end of the limiting member 213 is inserted into the annular groove 221 and slides with it, enabling relative rotation between the pre-expansion ring 22 and the base 21. When the base 21 rotates, relative movement will occur between the two, greatly reducing the dynamic friction between the pre-expansion ring 22 and the carrier film 12, and reducing the probability of film breakage.

[0038] The base 21 also includes a slot 212 for engaging the fixing ring 13. During film expansion, the cylindrical expanding device of the expanding machine descends, causing the fixing ring 13 to descend as well, until the fixing ring 13 abuts against the surface of the base 21. The expanding fixture can then be embedded into the inner cavity of the cylindrical expanding device, allowing the carrier film 12 to cover the surface of the fixture and expand. The base 21 is then driven to rotate. The pre-expanding ring 22 remains stationary or rotates only a small angle due to static friction with the carrier film 12, and the slot 212 engages with the outer periphery of the fixing ring 13. Then, the cylindrical expanding device is controlled to rise back to its original position, completing the film expansion. After film expansion, the inter-grain spacing is ≥30μm. (Reference) Figure 5 ,in Figure 5 a represents the grain spacing before film expansion. Figure 5 b represents the grain spacing after film expansion.

[0039] After the film expansion is completed, the carrier component is moved into the etching process. A chemical wet etching process is used to etch the sidewalls of the die's dicing channels to remove the recast layer attached to the die edges. The etching can be performed using conventional processes. In this embodiment, for GaAs-based wafers, the etching solution uses a ratio of NH4OH+H2O2+H2O or HCl+H2O2+H2O for chemical wet etching to completely remove the recast layer attached to the die edges.

[0040] After etching, the carrier component is placed in a nitrogen purging machine. High-temperature nitrogen (450°C) is used to purge the surface of the carrier film. The distance between the outlet and the film surface is 10cm, and the temperature of the nitrogen reaching the product surface is 85-90°C. The purging time is 180 seconds, and the nitrogen flow rate is 10L / min. This softens the carrier film, and after natural cooling, the carrier film shrinks back to its initial state, reducing the spacing between the grains. (Reference) Figure 5 c represents the grain spacing after retraction. The grain spacing can be retracted to its initial state, approximately 10µm. Once the carrier film is returned to its stretched state on the fixing ring, it can be used for subsequent crystal picking processes on a crystal picking machine.

[0041] As is commonly known, the process includes routine steps such as cleaning and drying, which will not be elaborated upon.

[0042] Comparative Example

[0043] The difference between the comparative processing method and Example 1 lies in the following: In the post-cutting film expansion process, a conventional film expansion fixture is used. An inner expansion ring is placed on the worktable. After expansion, the carrier film is in a stretched state. An outer expansion ring is used to fix the carrier film onto the inner expansion ring. Then, a cutter is used to cut the carrier film along the outside of the outer expansion ring, causing the wafer and carrier film to detach from the original fixing ring. The wafer is then supported on the carrier film stretched by the expansion ring and transferred to other processes. Since the expansion ring is usually made of POM (polyoxymethylene resin), it may not be suitable for subsequent processes. In the subsequent wafer picking process, the wafer on the expansion ring is cut off and attached to the aforementioned fixing ring to fit the wafer picking machine.

[0044] refer to Figure 6 and Figure 7 Using the same etching process, Example 1 and the comparative example can achieve similar etching effects. In terms of appearance, their sidewalls are flat and there is no side etching, and the grain strength is not much different, which meets the yield requirements.

[0045] Compared to the comparative example, Example 1 has the following advantages:

[0046] 1) No expansion ring is needed, reducing material consumption;

[0047] 2) It avoids the risk of scratches, fragments, etc. during cutting;

[0048] 3) It enables continuous processes to be carried on the same fixed ring without conversion, which simplifies the process, improves efficiency, and increases yield.

[0049] Example 2

[0050] A method for shipping compound semiconductor wafers involves processing the wafer using the method described in Example 1, and then shipping it in the form of the original carrier component. Specifically, the diced and etched dies are arranged on a carrier film with dicing spacing, and the carrier film is stretched in a fixing ring. Example 2 is applicable to inbound and outbound shipments between upstream and downstream manufacturers. Packaging manufacturers can directly use the wafers mounted on the fixing ring for a die-picking machine for die-picking processes. (Refer to...) Figure 8 Compared to the comparison model, there is no need to cut the wafer and transfer it to the fixing ring, which simplifies the customer's process steps, increases the customer's packaging flexibility, and enables diversified delivery methods.

[0051] This invention maintains the wafer in a carrier component form during a continuous process. The continuous process includes laser cutting, film expansion, etching of the die sidewalls through melting and recasting, film shrinkage, and die picking (or other processes). By pre-expanding, the distance between the dies is increased to facilitate the clean etching of the dicing sidewalls, ensuring the yield meets the standards. Then, the carrier film is shrunk back to its initial state and is suitable for subsequent process steps. This eliminates the need to replace the wafer's carrier structure, simplifying the process, reducing production costs, and improving production efficiency.

[0052] The above embodiments are only used to further illustrate a method for processing compound semiconductor wafers according to the present invention. However, the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for processing a compound semiconductor wafer, characterized in that, include: Step 1) The compound semiconductor wafer is attached to the carrier film, the carrier film is stretched in the fixing ring and the edges are sealed by the fixing ring to form a carrier component; Step 2) Move the carrier component into the cutting process, and use laser cutting to cut the wafer into several grains along the cutting path; Step 3) Place the carrier component in the film expansion machine, which includes an expansion fixture, a pre-expansion ring and a base, with the pre-expansion ring disposed on the base; and fit the fixing ring over the pre-expansion ring to pre-expand the carrier film to increase the spacing between the grains to a first spacing. Step 4) Move the carrier component into the etching process, and use wet etching to etch the sidewalls of the grain cutting path to remove the laser-cut recast material attached to the edge of the grain. Step 5) Place the carrier component in a nitrogen purging machine and purge the surface of the carrier film with high-temperature nitrogen. The temperature of the high-temperature nitrogen is ≥150℃, the distance between the air outlet and the film surface is 5cm~15cm, the purging time is ≥30s, and after cooling, the carrier film shrinks back to its initial state, so that the spacing between the grains shrinks back.

2. The method for processing compound semiconductor wafers according to claim 1, characterized in that: The carrier film is a PVC UV film with a thickness of 50~100 μm.

3. The method for processing compound semiconductor wafers according to claim 1, characterized in that: The retaining ring is a stainless steel ring.

4. The method for processing compound semiconductor wafers according to claim 1, characterized in that: There is a height difference between the top surface of the pre-expanding ring and the base, and the outer diameter of the pre-expanding ring is smaller than the inner diameter of the fixed ring; the height difference is ≥2cm, and the first spacing after expansion is ≥30μm.

5. The method for processing compound semiconductor wafers according to claim 1, characterized in that: In step 4), the temperature of the high-temperature nitrogen gas is 150℃~500℃, the nitrogen gas flow rate is in the range of 5L / min~25L / min, and after cooling, the spacing between the grains shrinks to less than 15um.

6. The method for processing a compound semiconductor wafer according to claim 1, characterized in that, It also includes: step 5) placing the carrier component in a crystal picking machine for crystal picking process.

7. The method for processing compound semiconductor wafers according to claim 1, characterized in that: The base is annular and has several protrusions, each protrusion having a groove; the pre-expansion ring is embedded in the groove, and the top surface of the pre-expansion ring protrudes outward from the top surface of the protrusion; the outer periphery of the top surface of the protrusion is inclined.

8. The method for processing compound semiconductor wafers according to claim 7, characterized in that: The pre-expanding ring and the base are configured to rotate relative to each other; the inner wall of the pre-expanding ring is provided with an annular groove extending radially outward, and at least one limiting member is fixed on the side wall of the groove, the other end of the limiting member is inserted into the annular groove and slides in cooperation with the annular groove.

9. A method for shipping a compound semiconductor wafer, characterized in that: The compound semiconductor wafer is processed using the processing method described in any one of claims 1 to 8 and then shipped in the form of the carrier component.

10. The shipping method according to claim 9, characterized in that: After the carrier component is shipped to the packaging plant, it enters the crystal picking process.

Images