A laser cutting post-processing method for multi-material layer chips

Abstract

The present invention discloses a post-laser cutting processing method for multi-material layer chips. The wafer comprises an InGap layer sandwiched between two GaAs layers. After laser cutting, a recast layer formed by the laser cutting adheres to the edge of the chip. A first etching step targeting the InGap layer and a second etching step targeting the GaAs layer are sequentially performed, and the first and second etching steps are repeated until the recast layer is removed. By performing alternating step-by-step etching, the problem of residual debris and burrs along the cutting path is resolved, preventing long residual material layers from breaking and forming sharp debris that could scratch the chip surface, thereby improving product yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor manufacturing processes, and in particular relates to a post-processing method for laser cutting of a multi-material layer chip. Background Art

[0002] In mass production, semiconductor devices typically involve depositing integrated circuit chips onto wafers, then dividing them into individual components before packaging and soldering them together. Wafer dicing technology plays a crucial role in improving yield and packaging efficiency. Laser dicing, with its advantages of high processing speed, narrow cutting grooves, non-contact operation, and high degree of automation, has gradually replaced traditional dicing methods and gained widespread adoption.

[0003] During the laser cutting process, the material being cut will vaporize and then redeposit on the surface of the cutting path and nearby to form a recast layer. For example, after laser cutting of GaAs-based HBT and pHEMT products, GaAs will exist in the form of a recast layer at the cutting edge, so it is usually necessary to use a chemical etching method suitable for GaAs to etch and remove the recast layer. However, the EPI of GaAs-based HBT and pHEMT both use InGaP as an etch stop layer. InGaP will also exist in the recast layer after laser cutting, and after conventional GaAs chemical etching is completed, a long InGaP layer will remain. The protruding part of InGaP is prone to breakage, forming sharp debris and scratching the chip surface, affecting device performance and production yield. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a post-processing method for laser cutting of a multi-material layer chip.

[0005] In order to achieve the above objectives, the technical solution of the present invention is:

[0006] A laser cutting post-processing method for a multi-material layer chip comprises the following steps:

[0007] 1) Laser cutting the wafer after the device process to form an independent chip, with a recast layer formed by laser cutting attached to the edge of the chip; the wafer is a GaAs-based wafer and has an InGap layer sandwiched between two GaAs material layers;

[0008] 2) using an etching solution of H3PO4:HCl=1:2-8 to perform a first etching on the InGap, and then cleaning it after etching;

[0009] 3) performing a second etching on GaAs using an etching solution of NH4OH:H2O2:H2O=0.5-3:0.5-3:10, and performing cleaning after etching;

[0010] 4) Repeating steps 2) and 3) in sequence until the recast layer is removed, wherein the total time of the first etching is 10 to 60 seconds, and the total time of the second etching is 30 to 120 seconds.

[0011] Optionally, the thickness of the InGap layer is 10 to 50 nm.

[0012] Optionally, the thicknesses of the two GaAs material layers from top to bottom are 500-2000 nm and 70-120 μm respectively.

[0013] Optionally, the etching time of the first etching in the subsequent step is shorter than the etching time of the first etching in the previous step; and the etching time of the second etching in the subsequent step is shorter than the etching time of the second etching in the previous step.

[0014] Optionally, the etching time of the first etching and the second etching decreases from early to late in the etching order, wherein the first etching decreases by 5 to 10 seconds each time, and the second etching decreases by 10 to 20 seconds each time.

[0015] Optionally, the process includes three first etchings in sequence, wherein the etching time of the first etching is 15 to 25 seconds; the etching time of the second etching is 10 to 18 seconds; and the etching time of the third etching is 3 to 8 seconds.

[0016] Optionally, the second etching process includes three times in sequence, wherein the etching time of the first second etching process is 25 to 45 seconds; the etching time of the second second etching process is 15 to 30 seconds; and the etching time of the third second etching process is 5 to 15 seconds.

[0017] Optionally, the chip is a GaAs-based HBT chip, including a sub-collector layer and a collector layer, and the InGap layer is provided between the sub-collector layer and the collector layer.

[0018] Optionally, the chip is a GaAs-based pHEMT chip, including a Schottky layer, and the InGap layer is located in the Schottky layer.

[0019] Optionally, the laser cutting is performed using an ultraviolet laser, and the cutting power of the ultraviolet laser is 1 to 10W.

[0020] The beneficial effects of the present invention are:

[0021] (1) After laser cutting of multi-material layer chips, the steps of etching away InGaP and etching away GaAs are performed in sequence, and step-by-step etching is performed through alternating cycles, which solves the problem of residual debris and burrs on the cutting path, prevents the material layer from breaking and forming sharp debris that scratches the chip surface, and improves the product yield;

[0022] (2) Through the alternating cycle etching method, the etching endpoint can be better controlled to obtain a high-quality etching surface, making the edge of the device smoother and avoiding the impact of burrs on device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the recast layer formed after chip cutting in Example 1;

[0024] Figure 2 Schematic diagram of step 2 of the laser cutting post-processing method of Example 1;

[0025] Figure 3 Schematic diagram of step 3 of the laser cutting post-processing method of Example 1;

[0026] Figure 4 This is a schematic diagram of the laser cutting post-processing method of Example 1 after etching is completed;

[0027] Figure 5 This is a schematic diagram of the comparative example after etching. DETAILED DESCRIPTION

[0028] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. The accompanying drawings are merely for illustration to facilitate understanding of the present invention, and their specific proportions may be adjusted according to design requirements.

[0029] Example 1

[0030] refer to Figure 1The GaAs-based wafer after device processing includes a first GaAs material layer 1, a second GaAs material layer 2, and an InGap layer 3 sandwiched between the two GaAs material layers, and also includes other semiconductor layers, passivation layers, metal layers, insulating layers, protective layers, etc. arranged on a platform above the second GaAs material layer 2. The first GaAs material layer 1 has a thickness of 70 to 120 μm, preferably 100 μm, the second GaAs material layer 2 has a thickness of 500 to 2000 nm, preferably 1500 nm, and the InGap layer 3 has a thickness of 10 to 50 nm, preferably 20 nm. The InGap layer 3 serves as an etch stop layer. The wafer that has undergone the device process is laser cut along the cutting path using a 4-6W UV laser and then separated into independent chips. Since the laser cutting portion includes the GaAs material layer and the InGap layer, the high temperature of the laser will turn the GaAs and InGap into gaseous form during the cutting process. After the cutting is completed, the gaseous GaAs and InGap will be redeposited on the cutting path and the surface of the wafer near the cutting path, forming a recast layer 4. The area where the chip is attached to the recast layer 4 is defined as the recast area. In the embodiment, a process of alternating and repeating the first etching for InGap and the second etching for GaAs is used to remove the recast layer 4 to obtain a smooth chip edge. The specific steps are as follows:

[0031] Step 1: Soak in surfactant solution

[0032] Immerse the chip in a surfactant solution for 30-200 seconds. The surfactant solution consists of one of the following: a) 3-5 wt% polyethylene glycol, 2-4 wt% polyethylene glycol octylphenyl ether, in water; b) 2-4 wt% polyoxypropylene / polyoxyethylene copolymer, 0.5-1.5 wt% polyoxyethylene compound, in water; c) 9-11 wt% polyvinyl alcohol, 3-5 wt% ethoxypropoxylated C6-12-alcohol, in water. The surfactant improves the wettability of the chip surface and reduces the chance of molten particles adhering to the chip surface during etching. It also helps to evenly distribute the etchant remaining on the chip surface after etching, suspending molten particles in the residual etchant and facilitating subsequent cleaning.

[0033] Step 2: First etching

[0034] refer to Figure 2 The chip was immersed in the first etching solution for 20 seconds. The first etching solution was a solution of H3PO4:HCl=1:5 to remove part of the InGap recast layer and part of the InGap layer 3 in the recast area. Then, the chip was transferred to a fast drain rinse tank and rinsed with DI water for 5 minutes.

[0035] Step 3: First and second etching

[0036] refer to Figure 3 , immerse the chip in the second etching solution for 40 seconds. The second etching solution is a solution of NH4OH:H2O2:H2O=1:1:10 to remove part of the GaAs material in the recast area, and then transfer it to a fast drain rinse tank and rinse with DI water for 5 minutes.

[0037] Step 4: Perform the second first etching

[0038] The chip was immersed in the first etching solution for 12 seconds. The first etching solution was a solution of H3PO4:HCl = 1:5. The remaining InGap recast layer and part of the InGap layer 3 in the recast area were further removed. Then, the chip was transferred to a fast drain rinse tank and rinsed with DI water for 5 minutes.

[0039] Step 5: Perform the second etching

[0040] The chip was immersed in a second etching solution for 25 seconds. The second etching solution was a solution of NH4OH:H2O2:H2O=1:1:10. Part of the GaAs material in the recast area was further removed. The chip was then transferred to a fast drain rinse tank and rinsed with DI water for 5 minutes.

[0041] Step 6: Perform the third first etching

[0042] The chip was immersed in the first etching solution for 5 seconds. The first etching solution was a solution of H3PO4:HCl=1:5. The InGap in the recast area was further removed. Then, the chip was transferred to a fast drain rinse tank and rinsed with DI water for 5 minutes.

[0043] Step 7: Perform the third second etching

[0044] Immerse the chip in the second etching solution for 10 seconds. The second etching solution is a solution of NH4OH:H2O2:H2O=1:1:10. Continue to remove the GaAs in the recast area. Then transfer it to the fast drain rinse tank and rinse with DI water for 5 minutes. Figure 4 The total length of the removed area is about 5 to 15 μm, preferably 10 μm.

[0045] In the embodiment, on the one hand, the GaAs and InGaP in the recast area are gradually removed through a repeated etching process that alternates between the two etching processes, thereby avoiding the problem of longer InGaP residues breaking and forming sharp debris; on the other hand, as the sequence progresses, the etching time gradually decreases, and the etching end point can be better controlled to obtain a smooth chip edge, thereby improving the problem of burrs and improving the yield rate of product shipment inspection.

[0046] As an application example, the chip is a GaAs-based HBT chip, including a GaAs sub-collector layer and a GaAs collector layer, and an InGap etching stop layer is provided between the sub-collector layer and the collector layer.

[0047] As another application example, the chip is a GaAs-based pHEMT chip, including a GaAs Schottky layer, and an InGap layer is located in the Schottky layer.

[0048] Comparative Example

[0049] refer to Figure 5 The difference between the comparative example and Example 1 is that only a solution of NH4OH:H2O2:H2O=1:1:10 is used to etch the recast layer of the chip once, and the etching time is 75s. The length of the residual InGap etching stop layer between the GaAs layers is about 5 to 15μm. The residual InGap etching stop layer breaks and forms sharp debris, which easily causes scratches on the wafer surface and burrs.

[0050] Compared with the comparative example, Example 1 uses three sections and two etching methods to gradually remove the material, avoiding a significant length difference between the two material layers, thereby avoiding the problem caused by the breakage of the residual material layer. In addition, according to actual needs, two or more sections can also be set to achieve this.

[0051] The above embodiments are only used to further illustrate a laser cutting post-processing method for a multi-material layer chip of the present invention, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the technical solution of the present invention.

Claims

1. A laser cutting post-processing method for a multi-material layer chip, characterized in that: The following steps are involved: 1) Laser cutting the wafer after the device process to form an independent chip, with a recast layer formed by laser cutting attached to the edge of the chip; the wafer is a GaAs-based wafer and has an InGap layer sandwiched between two GaAs material layers; 2) using an etching solution of H3PO4:HCl=1:2-8 to perform a first etching on the InGap, and then cleaning it after etching; 3) performing a second etching on GaAs using an etching solution of NH4OH:H2O2:H2O=0.5-3:0.5-3:10, and performing cleaning after etching; 4) Repeating steps 2) and 3) in sequence until the recast layer is removed, wherein the total time of the first etching is 10 to 60 seconds, and the total time of the second etching is 30 to 120 seconds.

2. The laser cutting post-processing method for a multi-material layer chip according to claim 1, characterized in that: The thickness of the InGap layer is 10 to 50 nm.

3. The laser cutting post-processing method for a multi-material layer chip according to claim 1, characterized in that: The thicknesses of the two GaAs material layers are 500-2000 nm and 70-120 μm respectively from top to bottom.

4. The laser cutting post-processing method for a multi-material layer chip according to claim 1, characterized in that: The etching time of the first etching in the subsequent step is shorter than the etching time of the first etching in the preceding step; the etching time of the second etching in the subsequent step is shorter than the etching time of the second etching in the preceding step.

5. The laser cutting post-processing method for a multi-material layer chip according to claim 4, characterized in that: The etching time of the first etching and the second etching decreases from the earliest to the last in the etching sequence, wherein the etching time of the first etching decreases by 5 to 10 seconds each time, and the etching time of the second etching decreases by 10 to 20 seconds each time.

6. The laser cutting post-processing method for a multi-material layer chip according to claim 5, characterized in that: The process includes three first etchings in order, wherein the etching time of the first etching is 15 to 25 seconds, the etching time of the second etching is 10 to 18 seconds, and the etching time of the third etching is 3 to 8 seconds.

7. The laser cutting post-processing method for a multi-material layer chip according to claim 5, characterized in that: The process includes three second etchings in order, wherein the etching time of the first second etching is 25 to 45 seconds, the etching time of the second second etching is 15 to 30 seconds, and the etching time of the third second etching is 5 to 15 seconds.

8. The laser cutting post-processing method for a multi-material layer chip according to claim 1, characterized in that: The chip is a GaAs-based HBT chip, comprising a sub-collector layer and a collector layer, wherein the InGap layer is provided between the sub-collector layer and the collector layer.

9. The laser cutting post-processing method for a multi-material layer chip according to claim 1, characterized in that: The chip is a GaAs-based pHEMT chip, comprising a Schottky layer, and the InGap layer is located in the Schottky layer.

10. The laser cutting post-processing method for a multi-material layer chip according to claim 1, characterized in that: The laser cutting is performed by using an ultraviolet laser, and the cutting power of the ultraviolet laser is 1 to 10W.

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