Method for removing residual liquid medicine on edge of crystal back based on front cleaning

Abstract

The invention relates to a method for removing residual liquid medicine on the edge of a wafer back based on front cleaning, which is formed by starting from a Malangori effect mechanism aiming at the special condition that a wafer and a back spraying device are almost attached due to a narrow distance and considering factors that the surface tension of a cleaning reagent is smaller than that of liquid medicine to be removed and the like. After etching or chemical cleaning of the front surface of the wafer is completed, deionized water on the front surface of the wafer is attracted and flows back to a liquid medicine residue position on the edge of the back surface of the wafer through water washing of the front surface of the wafer in cooperation with wafer revolution number change and opening and closing of a back spraying device for spraying nitrogen in combination with the Malangori effect; and residual liquid medicine at the edge of the crystal back is fully diluted and cleaned, so that the cleanness of the crystal back is ensured to the greatest extent, the pollution risk of subsequent measurement and processing procedures is avoided, and the method does not need to modify existing equipment and is convenient to implement.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a method for removing residual chemicals from the back edge of a crystal based on front-side cleaning. Background Technology

[0002] In existing single-wafer wet etching and chemical cleaning technologies, during the wafer front-side processing, the chemical solution on the wafer front flows back to the edge of the wafer back (0-5mm) due to surface tension. Traditionally, water spraying on the back side diluted and removed the residual chemical solution at the wafer back edge to ensure cleanliness after the wafer back process. However, to minimize chemical evaporation and subsequent gas contamination of the wafer back, the space between the wafer back and the Chuck (clamping fixture) is reduced, essentially only providing back-side gas protection. Furthermore, the distance between the wafer back and the back spraying device is extremely narrow, almost touching, making it impossible to add back-side water washing components. Therefore, it is impossible to clean and remove the chemical solution from the wafer back edge, which poses a risk of contamination to subsequent measurement and processing instruments.

[0003] Patent CN105513994B discloses a mechanism for preventing back-side contamination of wafers. This mechanism addresses the issue of small amounts of liquid flowing from the wafer edge to the back side. It incorporates a fan-shaped structure on the lower surface of the suction cup. During rotation, the fan-shaped structure creates an upward airflow on the lower surface of the suction cup. This airflow changes direction upon encountering the lower surface and flows along it to the edge, thus guiding liquid flowing from the back-spray device and the wafer front to the wafer edge, forming an airflow protection system to prevent liquid from flowing to the back side of the wafer. However, this fan-shaped structure occupies considerable installation space and is not suitable for situations where the distance between the wafer back and the back-spray device is small.

[0004] Patent CN106711059B discloses a liquid protection structure for the back side of a wafer. This structure has a protective ring below the back side of the wafer. The protective ring prevents chemicals from continuing to flow to the back side of the wafer. When chemicals come into contact with the protective ring below the back side of the wafer, they are stopped at the working gap due to the surface tension of the liquid, preventing them from flowing further into the center of the wafer. However, the protective ring in this structure also requires a certain amount of installation space and is not suitable for situations where the distance between the wafer back and the back spraying device is small. Summary of the Invention

[0005] The purpose of this invention is to provide a method for removing residual chemicals from the back edge of a wafer based on front-side cleaning. This method is specifically designed for the special case where the distance between the wafer and the back spray device is very small and they are almost touching. It only involves water washing on the front side of the wafer, combined with changes in wafer rotation speed and the opening and closing of the back spray device. By combining the Marangoni effect, the deionized water on the front side of the wafer is attracted back to the residual chemicals at the back edge of the wafer, thereby achieving the cleaning and removal of residual chemicals at the back edge of the wafer. Furthermore, this invention does not require modification of existing equipment and is easy to implement.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for removing residual chemicals from the back edge of a wafer based on front-side cleaning includes a back-spraying device, a wafer carrier stage, a deionized water swing arm, a nitrogen swing arm, and a chemical swing arm. The lower end of the wafer carrier stage is connected to a rotary drive device, and its upper end passes through the middle of the back-spraying device. The wafer is placed on the wafer carrier stage. The method for removing residual chemicals from the back edge of a wafer based on front-side cleaning includes the following steps:

[0008] Step 1: Place the wafer on the wafer carrier stage, start the back spray device to spray nitrogen gas, and at the same time, start the nozzle at the end of the liquid spray arm to spray liquid onto the front of the wafer. The wafer carrier stage drives the wafer to rotate at a speed of V1, and the spraying time is T1.

[0009] Step 2: The liquid spraying arm stops spraying, the back spray device remains on, the deionized water spraying arm starts spraying deionized water onto the front of the wafer, the wafer carrier stage drives the wafer to maintain a rotation speed of V1, and the spraying time is T2.

[0010] Step 3: With the back spray device and deionized water swing arm in the same state, the wafer carrier stage increases the rotation speed of the wafer from V1 to V2 for a duration of T3.

[0011] Step 4: The back spray device and the deionized water swing arm remain in the same state, and:

[0012] Step 4.1: The wafer carrier stage reduces the wafer rotation speed from V2 to V3, and at the same time, the back spray device is turned off for a duration of T4.

[0013] Step 4.2: Then the wafer carrier stage drives the wafer rotation speed to increase from V3 to V4, and at the same time the back spray device is turned on for a duration of T5;

[0014] Step 4.3: Repeat steps 4.1 and 4.2 until the set number of times is reached;

[0015] Step 5: The back spray device is turned on, and the deionized water swing arm sprays deionized water onto the front of the wafer. The wafer carrier stage drives the wafer to maintain a rotation speed of V5, and the spraying time is T6.

[0016] Step 6: The wafer carrier stage increases the wafer rotation speed from V5 to V6. The deionized water swing arm and back spray device are both turned off. The nozzle at the end of the nitrogen swing arm sprays nitrogen onto the front of the wafer for a time of T7.

[0017] Step 7: After completing the above steps, use a damp pH test paper to wipe the edge of the crystal back to determine whether it is clean.

[0018] In step one, the nozzle at the end of the liquid spraying arm swings from one side of the wafer to the other to spray the liquid. The rotation speed of V1 is 100 to 800 rpm, and the spraying time T1 is 30 to 120 seconds.

[0019] In step two, the nozzle at the end of the deionized water swing arm swings from one edge of the wafer to the other edge to spray deionized water.

[0020] In step three, the speed range of V2 is 500 to 1500 rpm, and the duration of T3 is 2 to 10 seconds.

[0021] In step 4.1, the speed range of V3 is 50 to 500 rpm, and the duration T4 is 10 to 30 seconds; in step 4.2, the speed range of V4 is 600 to 1500 rpm, and the duration T5 is 2 to 15 seconds; in step 4.3, steps 4.1 and 4.2 are repeated 2 to 5 times.

[0022] In step five, the V5 speed range is 500-1500 rpm, and the spraying time T6 is 10-60 seconds.

[0023] In step six, the V6 speed range is 1500-2500 rpm, and the nitrogen spraying time T7 is 20-120 seconds.

[0024] The advantages and positive effects of this invention are as follows:

[0025] 1. This invention addresses the special situation where the wafer and the back-spray device are almost touching with a very small gap. Considering that the surface tension of the cleaning reagent (often DIW, IPA, etc.) is less than that of the solution to be removed, this invention is based on the Marangoni effect mechanism. After etching or chemical cleaning is completed on the front side of the wafer, this invention only uses water washing on the front side of the wafer, combined with changes in wafer rotation speed and the opening and closing of the back-spray device. Combined with the Marangoni effect, the deionized water on the front side of the wafer is attracted back to the solution residue at the edge of the back side, which fully dilutes and cleans the residual solution at the edge of the back side, thereby maximizing the cleanliness of the back side and avoiding the risk of contamination in subsequent measurement and processing processes.

[0026] 2. This invention only uses water washing on the front side of the wafer, combined with changes in wafer rotation speed and the opening and closing of the back spray device, and combined with the Marangoni effect to attract the deionized water on the front side of the wafer back to the chemical residue at the edge of the wafer. Therefore, no modification to existing equipment is required, making it easy to implement. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the method of the present invention.

[0028] Figure 2 This is a schematic diagram of the device structure targeted by the present invention.

[0029] Figure 3 for Figure 2 Top view of the device

[0030] Figure 4 This is a schematic diagram of the working state of the method of the present invention. Figure 1 ,

[0031] Figure 5 This is a schematic diagram of the working state of the method of the present invention. Figure 2 .

[0032] Among them, 1 is a wafer, 2 is a back-spraying device, 3 is a wafer carrier stage, 4 is a deionized water swing arm, 5 is a nitrogen swing arm, and 6 is a chemical solution swing arm. Detailed Implementation

[0033] The invention will now be described in further detail with reference to the accompanying drawings.

[0034] like Figures 2-3 As shown, the device structure targeted by this invention includes a back spraying device 2, a wafer carrier stage 3, a deionized water swing arm 4, a nitrogen swing arm 5, and a chemical solution swing arm 6. The lower end of the wafer carrier stage 3 is connected to a rotary drive device, and its upper end passes through the middle of the back spraying device 2 and carries the wafer 1. The back spraying device 2 is a known technology in the art, used to spray nitrogen gas; for example, see the back spraying disk structure in patent CN105513994B. However, currently, to minimize the contamination of the back of the wafer by chemical solution evaporation gases, such as... Figure 2 As shown, the gap between wafer 1 and back-spray device 2 is extremely narrow, almost touching, making it impossible to add back-washing components or other structures. The deionized water swing arm 4, nitrogen swing arm 5, and pharmaceutical swing arm 6 are all technologies known in the art. They are driven to rotate and swing by a motor or other device, and nozzles are provided at the ends of the swing arms. In this embodiment, the arrangement of the above-mentioned swing arms is as follows... Figure 3 As shown.

[0035] To address the issue of the chemical solution on the front side of wafer 1 flowing back to the 0-5mm edge of the back side due to surface tension, and in the absence of a back-side water washing component or other structure, this invention alters the rotational speed of wafer 1 and coordinates with the activation or deactivation of the back spray device 2. This allows deionized water from the front side to flow back to the edge of the back side of the wafer, contacting the chemical solution to be removed. Utilizing the Marangoni effect (the effect of liquid tension gradient difference), the deionized water on the front side of wafer 1 is attracted back to the chemical residue area at the back edge, repeatedly diluting and cleaning the residual chemical solution at the back edge. This maximizes the removal of residual chemical solution at the back edge, ensuring that both the front and back sides of the wafer are free of contamination and preventing contamination of subsequent measurement and processing equipment.

[0036] like Figure 1 As shown, the method of the present invention includes the following steps:

[0037] Step 1: Place wafer 1 on wafer carrier stage 3, activate back spray device 2 to spray nitrogen gas, and simultaneously, the nozzle at the end of the chemical liquid swing arm 6... Figure 4 The liquid is sprayed from one side of wafer 1 to the other. The wafer carrier stage 3 drives wafer 1 to rotate at a speed of V1, and the speed range of V1 is 100 to 800 rpm. The liquid flow rate is 200 to 1500 mL / min, and the spraying time T1 is 30 to 120 seconds.

[0038] Step Two: The liquid spraying arm 6 stops spraying, the back spray device 2 remains open, the deionized water spraying arm 4 starts and the end nozzle swings from one edge of wafer 1 to the other edge, spraying deionized water (for smaller wafers of 2, 3, and 4 inches, deionized water can be sprayed only at the center point, such as...). Figure 5 As shown), the wafer carrier stage 3 drives the wafer 1 to maintain a rotational speed of V1.

[0039] This step mainly involves using deionized water to fully dilute and remove the chemical solution on the front side of wafer 1, so as to achieve a thorough front cleaning effect and at the same time block the etching chemical action of the chemical solution in step one.

[0040] In this step, the deionized water flow rate is adjusted to 600–1500 mL / min, and the spraying time T2 is 10–60 seconds.

[0041] Step 3: With the back spray device 2 and the deionized water swing arm 4 remaining unchanged, the wafer carrier stage 3 drives the wafer 1 to increase its rotational speed from V1 to V2, and the rotational speed of V2 is in the range of 500 to 1500 rpm, with a duration of 2 to 10 seconds for T3.

[0042] The purpose of this step is to increase the rotation speed of wafer 1 to fling out the chemical solution from the back edge of the wafer, thereby reducing the amount of residual chemical solution and facilitating subsequent cleaning.

[0043] Step 4: The back spray device 2 and the deionized water swing arm 4 remain in the same state, and:

[0044] Step 4.1: The wafer carrier stage 3 drives the wafer 1 to reduce its rotation speed from V2 to V3, while the back spray device 2 is turned off. The rotation speed range of V3 is 50 to 500 rpm, and the duration T4 is 10 to 30 seconds.

[0045] Step 4.2: Then the wafer carrier stage 3 drives the wafer 1 to rotate from V3 to V4, and at the same time the back spray device 2 is turned on. The rotation speed of V4 is 600 to 1500 rpm, and the duration T5 is 2 to 15 seconds.

[0046] Step 4.3: Repeat the above process a set number of times. In this embodiment, the above process is repeated 2 to 5 times to fully dilute and clean the residual drug solution at the edge of the crystal back.

[0047] In this step, the wafer 1 rotation speed is repeatedly increased and decreased, and the back spray device 2 is repeatedly started and stopped. This allows the deionized water on the front side to flow back to the edge of the back side of the wafer, where it comes into contact with the solution to be removed. The Marangoni effect is utilized to better attract the deionized water on the front side of wafer 1 back to the solution residue area at the back edge. The Marangoni effect is an interfacial convection phenomenon caused by a surface tension gradient. For example, patent CN111739829B induces the Marangoni effect by spraying drying gas onto the surface of a wafer with an attached liquid film, thus achieving the backflow of the attached liquid and obtaining a fully dried wafer. This invention induces the Marangoni effect through the changing rotation speed of wafer 1 and the repeated starting and stopping of the back spray device 2. Furthermore, this method does not require structural modifications to existing equipment and does not need to consider installation space issues related to the structure, therefore it is suitable for… Figure 2 The diagram shows a situation where the gap between wafer 1 and back-spray device 2 is very small and they are almost touching.

[0048] Step 5: Activate the back spray device 2. The nozzle at the end of the deionized water swing arm 4 swings from one edge of wafer 1 to the other edge, spraying deionized water. (For smaller wafers of 2, 3, and 4 inches, deionized water can be sprayed only at the center point.) Figure 5 As shown), the wafer carrier stage 3 drives the wafer 1 to maintain a rotation speed of V5. The rotation speed range of V5 is 500 to 1500 rpm, the deionized water flow rate is adjusted in the range of 600 to 1500 mL / min, and the spraying time T6 is 10 to 60 seconds.

[0049] Step Six: Wafer 1 is rotated at high speed for an extended period of time, and nitrogen is sprayed onto the front side of wafer 1 to dry the wafer. Specifically, wafer carrier stage 3 drives wafer 1 to rotate at a speed from V5 to V6, with V6 speed ranging from 1500 to 2500 rpm. Deionized water swing arm 4 and back spray device 2 are both closed. The nozzle at the end of nitrogen swing arm 5 sprays nitrogen onto the front side of wafer 1. The nitrogen flow rate is adjusted from 10 to 60 L / min, and the spraying time T7 is 20 to 120 seconds.

[0050] Step 7: After completing the above steps, wipe the edge of the crystal back with a damp pH test paper. If the test paper does not change color (no acid reaction), it means that it is clean.

[0051] Through numerous application examples, this invention has been verified to show that, by comparing pH test strips before and after application, all application examples showed no change in pH, proving that the process method of this invention can effectively clean the residual solution on the edge of the crystal back, ensuring the cleanliness of the crystal back after the operation.

Claims

1. A method for removing residual pharmaceutical solution from the edge of a crystal back based on front-side cleaning, characterized in that: The device includes a back spraying device (2), a wafer carrier stage (3), a deionized water swing arm (4), a nitrogen swing arm (5), and a chemical solution swing arm (6). The lower end of the wafer carrier stage (3) is connected to a rotary drive device, and the upper end passes through the middle of the back spraying device (2). The wafer (1) is placed on the wafer carrier stage (3). The method for removing chemical solution residues from the back edge of the wafer based on front cleaning includes the following steps: Step 1: Place the wafer (1) on the wafer carrier stage (3), start the back spray device (2) to spray nitrogen gas, and at the same time, the nozzle at the end of the liquid swing arm (6) starts to spray liquid onto the front of the wafer (1). The wafer carrier stage (3) drives the wafer (1) to rotate at a speed of V1, and the spraying time is T1. Step 2: The liquid spraying arm (6) stops spraying, the back spraying device (2) remains open, the deionized water arm (4) starts spraying deionized water onto the front of the wafer (1), the wafer carrier stage (3) drives the wafer (1) to maintain a rotation speed of V1, and the spraying time is T2. Step 3: The back spray device (2) and the deionized water swing arm (4) remain unchanged. The wafer carrier stage (3) drives the wafer (1) to increase its rotation speed from V1 to V2 for a duration of T3. Step 4: The back spray device (2) and the deionized water swing arm (4) remain in the same state, and: Step 4.1: The wafer carrier stage (3) drives the wafer (1) to reduce its rotation speed from V2 to V3, and at the same time, the back spray device (2) is turned off for a duration of T4. Step 4.2: Then the wafer carrier stage (3) drives the wafer (1) to increase its rotation speed from V3 to V4, and at the same time the back spray device (2) is turned on for a duration of T5; Step 4.3: Repeat steps 4.1 and 4.2 until the set number of times is reached; Step 5: The back spray device (2) is turned on, the deionized water swing arm (4) sprays deionized water onto the front of the wafer (1), the wafer carrier stage (3) drives the wafer (1) to maintain a speed of V5, and the spraying time is T6. Step 6: The wafer carrier stage (3) drives the wafer (1) to increase its rotation speed from V5 to V6. The deionized water swing arm (4) and the back spray device (2) are both closed. The nozzle at the end of the nitrogen swing arm (5) sprays nitrogen onto the front of the wafer (1) for a time of T7. Step 7: After completing the above steps, use a damp pH test paper to wipe the edge of the crystal back to determine whether it is clean.

2. The method for removing residual pharmaceutical solution from the edge of the crystal back based on front-side cleaning according to claim 1, characterized in that: In step one, the nozzle at the end of the liquid spray arm (6) sprays liquid from one side of the wafer (1) to the other side. The rotation speed of V1 is 100 to 800 rpm and the spraying time T1 is 30 to 120 seconds.

3. The method for removing residual pharmaceutical solution from the edge of the crystal back based on front-side cleaning according to claim 1, characterized in that: In step two, the nozzle at the end of the deionized water swing arm (4) swings from one edge of the wafer (1) to the other edge to spray deionized water.

4. The method for removing residual pharmaceutical solution from the edge of the crystal back based on front cleaning according to claim 1, characterized in that: In step three, the speed range of V2 is 500 to 1500 rpm, and the duration of T3 is 2 to 10 seconds.

5. The method for removing residual pharmaceutical solution from the edge of the crystal back based on front cleaning according to claim 1, characterized in that: In step 4.1, the speed range of V3 is 50 to 500 rpm, and the duration T4 is 10 to 30 seconds; in step 4.2, the speed range of V4 is 600 to 1500 rpm, and the duration T5 is 2 to 15 seconds; in step 4.3, steps 4.1 and 4.2 are repeated 2 to 5 times.

6. The method for removing residual pharmaceutical solution from the edge of the crystal back based on front-side cleaning according to claim 1, characterized in that: In step five, the V5 speed range is 500-1500 rpm, and the spraying time T6 is 10-60 seconds.

7. The method for removing residual pharmaceutical solution from the edge of the crystal back based on front-side cleaning according to claim 1, characterized in that: In step six, the V6 speed range is 1500-2500 rpm, and the nitrogen spraying time T7 is 20-120 seconds.

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