A wafer wet etching immersion device and immersion method

Abstract

The application belongs to the technical field of piezoelectric quartz wafer processing, and discloses a wafer wet etching infiltration device and method, which comprises a fixed plate, a double-output-shaft motor fixedly connected to the fixed plate, a hollow shaft as an output shaft of the double-output-shaft motor, a fixed seat installed at an output end of the double-output-shaft motor, a suction cup arranged on a lower surface of the fixed seat and used for adsorbing a wafer, and a rotary joint connected to a tail end of the double-output-shaft motor and connected to a vacuum generator negative pressure source through an air pipe. The wafer is horizontally placed, and two surfaces of the wafer are infiltrated respectively, so that the time difference of infiltration etching time at each position on the wafer can be eliminated, and the etching consistency at each position on the wafer can be maintained. Based on the infiltration device and method, the problem of differences in product sizes on the same wafer is improved, the overall size consistency is improved from a deviation of ±5 μm to ±1.5 μm, and the performance requirement of high-end crystal vibration is met.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric quartz wafer processing technology, specifically, it relates to a wet etching apparatus and wet etching method for wafers. Background Technology

[0002] With the rapid development of electronic terminal devices towards miniaturization, low power consumption, and high stability, piezoelectric quartz crystal oscillators, as the timing and clock signal reference source for these devices, are facing increasingly stringent requirements regarding the processing precision, morphological consistency, and performance stability of quartz wafers, as device sizes continue to shrink and operating frequencies continue to increase. Traditional mechanical grinding processes for quartz wafers are no longer sufficient to meet the performance specifications of ultra-high frequency devices in terms of dimensional accuracy and morphological controllability. Therefore, ultra-high frequency quartz wafers fabricated using photolithography are gradually becoming the mainstream technology in the industry.

[0003] In the manufacturing process of photolithographic quartz wafers, the functional morphology pattern of the wafer is mainly transferred through the process path of "surface coating - photoresist coating - exposure and development - wet etching". Among them, the development and gold-chromium etching stages require immersion in etching solution. At present, the wet etching process in mass production generally adopts a basket-type batch operation method: the wafers to be etched are vertically loaded into a batch in a special basket, and a robotic arm drives the basket to be immersed in a tank containing etching solution from top to bottom. After the preset etching time is reached, the robotic arm lifts the basket out of the etching solution to complete the etching operation.

[0004] In the aforementioned wafer etching process, the basket is immersed in the etching solution from top to bottom. The lower region of the wafer contacts the etching solution first, followed by the upper region. After etching is complete, the upper region detaches from the etching solution first, followed by the lower region. Therefore, there is a significant difference in the immersion time of different regions on the same wafer in the etching solution. This results in variations in the product size and appearance of different regions, affecting product consistency. For ultra-high frequency quartz crystal wafers, micron-level dimensional deviations directly lead to significant dispersion in core electrical parameters such as device resonant frequency and impedance, significantly reducing product yield and failing to meet the performance requirements of high-end crystal oscillators. Summary of the Invention

[0005] The purpose of this invention is to provide a wet etching apparatus and method for wafer wet etching, which solves the technical problem in the prior art where the different immersion times of different parts of the wafer with the etching solution lead to different etching degrees on different parts of the wafer, resulting in the inability of the same wafer product to meet the performance requirements of high-end crystal oscillators.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An immersion apparatus for wet etching of wafers includes a fixing plate; A dual-output-shaft motor is fixedly connected to the fixing plate, and the output shaft of the dual-output-shaft motor is a hollow shaft. A mounting base is installed at the output end of the dual-output-shaft motor; A suction cup is disposed on the lower surface of the mounting base for adsorbing wafers; A rotary joint is connected to the tail end of the dual-output shaft motor and connected to the vacuum generator negative pressure source via an air pipe; The suction cup is connected to the vacuum generator negative pressure source through the fixed base, the hollow shaft of the dual-output shaft motor and the rotary joint; An ultrasonic transducer is mounted on the fixed plate; An oscillating probe, connected to the output end of the ultrasonic transducer, is used to disrupt the surface tension of the etching solution.

[0007] Furthermore, the fixed plate includes a horizontal part and a vertical part connected to each other, wherein a dual-output shaft motor is connected to the end of the horizontal part of the fixed plate, and the vertical part is used to connect an actuator that drives the fixed plate to move.

[0008] Furthermore, the ultrasonic transducer is fixedly mounted in the middle of the horizontal part of the fixed plate; the oscillating probe penetrates to the bottom of the fixed plate and extends to the bottom of the wafer gripped by the suction cup.

[0009] Furthermore, the suction cup is divided into three concentric layers from the inside out: an inner layer suction cup, a middle layer suction cup, and an outer layer suction cup. The three layers of suction cups are adapted to wafers of different sizes and specifications. One inner layer suction cup is provided and corresponds to the center position of the wafer. Four middle layer suction cups and four outer layer suction cups are provided. The middle layer and the outer layer suction cups are evenly arranged along a ring array.

[0010] Furthermore, each of the suction cups is equipped with an independent miniature one-way valve, which includes a steel ball, a spring, and a sealing ring. When the suction cup is not covered by the wafer, atmospheric pressure pushes the steel ball to block the air passage and cut off the negative pressure. After the suction cup is attached to the wafer surface, the pressure difference is eliminated, and the one-way valve automatically opens to connect the negative pressure air passage, so that only the suction cup in contact with the wafer generates adsorption force.

[0011] Furthermore, the negative pressure air path is as follows: a suction cup that is attached to the wafer, the inner cavity of the fixed base, the inner cavity of the output shaft of the dual-axis motor, a rotary joint, an air pipe, and a vacuum generator.

[0012] A wet etching method for wafers, comprising the following steps: A100: The fixing plate moves downward. During the downward movement, the position of the fixing plate is adjusted so that the fixing seat is concentric with the wafer to be immersed in the etching solution, until the chuck contacts the wafer. A200: Start the vacuum generator. The suction cups covering the wafer will generate negative pressure, which will adsorb the wafer under the mounting base. A300: Move the fixing plate above the etching solution tank, and then slowly lower the wafer while keeping it horizontal until the lower surface of the wafer contacts the surface of the etching solution. Start counting the etching time from the contact surface. A400: After the etching time reaches the target etching time, the wafer is taken out horizontally and placed in a basket for wafer flipping. Then, the above steps are repeated to etch the other side.

[0013] Furthermore, in step A400, after the etching time reaches the target etching time, the ultrasonic transducer is activated, and the oscillating probe is used to oscillate the etching solution, thereby breaking the surface tension of the etching solution and removing the adsorption effect of the etching solution on the wafer. Then, the wafer is removed horizontally by fixing the board upward.

[0014] Furthermore, in step A400, after the wafer is removed while remaining horizontal, the dual-axis motor is started to drive the wafer to rotate, thereby using centrifugal force to remove the residual etching solution from the wafer surface.

[0015] Furthermore, in the A400 step, after the wafer is spun dry with the etching solution, it is cleaned with a mist of pure water to further remove the residual etching solution, and then the wafer is rotated again to spin dry the residual water.

[0016] The beneficial effects of this invention are: 1. This invention employs a horizontal placement method for the wafer, immersing both sides of the wafer separately. This eliminates the time difference in immersion etching across different areas of the wafer, maintaining etching consistency throughout. Based on this immersion device and method, the problem of dimensional differences between different products on the same wafer is improved, increasing the overall dimensional consistency from a deviation of ±5μm to ±1.5μm, meeting the performance requirements of high-end crystal oscillators.

[0017] 2. This invention uses an oscillating probe to disrupt the surface tension of the etchant in advance, thereby removing the adsorption force exerted on the wafer by the etchant surface, ensuring that the wafer is not damaged when it is removed, and improving the yield and production efficiency.

[0018] 3. By setting up inner, middle and outer three-layer suction cups to correspond to wafers of different sizes, this invention can perform suction and clamping on wafers of different sizes at different points, and balance the suction force applied by the etching solution surface on different parts of the wafer. This avoids the large wafer being held by a small area suction cup and removed from the etching solution, which would cause the periphery of the large wafer to break due to the suction force, thus improving product yield. Attached Figure Description

[0019] Figure 1 This is a front view of the overall structure of the present invention; Figure 2 This is a bottom view of the overall structure of the present invention; Figure 3 This is a flowchart of the wafer wetting process of the present invention.

[0020] In the diagram: 100, fixing plate; 200, dual-shaft motor; 300, rotary joint; 400, air pipe; 500, fixing base; 600, suction cup; 700, ultrasonic transducer; 800, oscillation probe; 900, wafer. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figures 1-2 As shown, a wet etching apparatus for wafers includes a fixed plate 100 capable of performing a transfer function. The fixed plate 100 is composed of a vertical part and a horizontal part. The vertical part is used to connect an actuator, such as a robotic arm, that drives the fixed plate 100 to move, thereby realizing the transfer function of the entire apparatus. The horizontal part is mainly used to install components for picking up wafers 900.

[0023] A dual-output shaft motor 200 is fixedly connected to the horizontal end of the fixed plate 100, and the output shaft of the dual-output shaft motor 200 is a hollow shaft; the tail end of the dual-output shaft motor 200 ( Figure 1 The upper end shown is connected to a rotary joint 300; an air pipe 400 is connected to the rotary joint 300, and the other end of the air pipe 400 is connected to a vacuum generator (negative pressure source); the output end of the dual-shaft motor 200 ( Figure 1 The lower end shown is equipped with a mounting base 500; the lower surface of the mounting base 500 is connected to multiple suction cups 600 for adsorbing and gripping the wafer 900.

[0024] like Figure 2As shown, the suction cup 600 has three layers from the inside out: inner, middle, and outer. These layers correspond to different specifications of wafers 900, such as wafer 900-1, wafer 900-2, and wafer 900-3 shown in the figure. The inner layer suction cup 600 has one unit corresponding to the center of the wafer 900, while the middle and outer layers each have four units arranged in a circular array. Each suction cup 600 has a built-in independent miniature one-way valve, which mainly consists of a steel ball, a spring, and a sealing ring. Its working principle is as follows: when the nozzle is not covered by a workpiece, atmospheric pressure pushes the valve closed, cutting off the vacuum passage; when covered by a workpiece, the pressure difference disappears, the valve opens, connecting to negative pressure, thus only the nozzle in contact with the workpiece generates suction. The purpose of setting up an independent micro check valve is to enable the suction cup 600 to automatically adapt to wafers 900 of different sizes. When gripping small wafers 900, the suction cup 600 used to grip large wafers 900 can automatically close the air path to avoid affecting the stable gripping of wafers 900.

[0025] The flow path of the negative pressure air circuit is as follows: suction cup 600 covered by wafer 900, inner cavity of fixed seat 500, inner cavity of output shaft of dual output shaft motor 200, rotary joint 300, air pipe 400, and vacuum generator.

[0026] An ultrasonic transducer 700 is also fixed on the upper surface of the horizontal part of the fixing plate 100; the output end of the ultrasonic transducer 700 is connected to an oscillating probe 800, and the oscillating probe 800 extends through to the lower part of the horizontal part of the fixing plate 100, with its end extending down to the lower part of the wafer 900 being gripped. The function of the oscillating probe is to disrupt the surface tension of the etching solution.

[0027] Please see Figure 3 Based on the above-provided wet etching apparatus for wafers, in some embodiments, the present invention also provides a wet etching method for wafers, the steps of which are as follows: S100: The fixing plate 100 moves downward. During the downward movement, the position of the fixing plate 100 is adjusted so that the fixing seat 500 is concentric with the wafer 900 to be immersed in the etching solution, until the suction cup 600 contacts the wafer 900. S200: Start the vacuum generator. The suction cup 600, which is covered by the wafer 900, generates negative pressure and adsorbs the wafer 900 under the mounting base 500. S300: The fixed plate 100 is moved above the etching solution tank, and then the wafer 900 is slowly lowered while keeping it horizontal until the lower surface of the wafer 900 contacts the surface of the etching solution. The etching time is calculated from the point of contact with the surface of the solution. S400: After the etching time reaches the target etching time, the ultrasonic transducer 700 is activated, and the oscillating probe 800 is used to oscillate the etching solution to break the surface tension of the etching solution and remove the adsorption effect of the etching solution on the wafer 900. Then the fixing plate 100 moves upward to keep the wafer 900 horizontal and take it out. S500: The fixed plate 100 moves upward and starts the dual output shaft motor 200. The dual output shaft motor 200 drives the wafer 900 to rotate. The centrifugal force is used to throw off the residual etching solution on the surface of the wafer 900, so as to prevent the residual etching solution from continuing to play an etching role. S600: After the etching solution is spun dry on wafer 900, wafer 900 is cleaned with a mist of pure water to further remove residual etching solution and ensure the cleanliness of the wafer 900 surface. Then, wafer 900 is rotated again to spin dry the residual water. One purpose is to maintain the adsorption force of the subsequent suction cup 600 on wafer 900, and the other purpose is to avoid contaminating the etching solution when the other side of wafer 900 is immersed. S700: Place the wafer 900 in a basket for wafer flipping (i.e., swapping the front and back sides), and then repeat the above steps to etch the other side.

[0028] It is worth noting that: due to the tension between the wafer 900 and the surface of the etching solution, there is an adsorption force, and the wafer 900 itself is brittle and fragile. Therefore, one of the innovations of this invention is how to separate the product from the liquid in a timely, accurate and non-destructive manner when one side of the wafer 900 reaches the set reaction time with the etching solution. This invention uses an oscillating probe 800 to break the surface tension of the liquid in advance, thereby removing the adsorption force generated by the etching solution on the wafer 900, ensuring that the wafer 900 is not damaged when it is taken out, and improving the product yield and production efficiency.

[0029] This invention employs a horizontal placement of the wafer 900 and wets both sides of the wafer 900 separately, eliminating time differences in wetting and etching times across different areas of the wafer 900 and maintaining etching consistency throughout. Based on this wetting device and method, the problem of dimensional differences between different products on the same wafer 900 is improved, reducing the overall dimensional consistency from a deviation of ±5μm to ±1.5μm, meeting the performance requirements of high-end crystal oscillators.

[0030] This invention, by setting up inner, middle and outer three-layer suction cups 600 to correspond to wafers 900 of different specifications, can perform suction and clamping on wafers 900 of different specifications at various points, and balance the suction force applied by the etching solution surface on each part of the wafer 900. This avoids the large-size wafer 900 being held by the small-area suction cups 600 and removed from the etching solution, and prevents the periphery of the large-size wafer 900 from breaking due to the suction force, thereby improving product yield.

[0031] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A wet etching apparatus for wafers, comprising a fixing plate (100); characterized in that: Also includes: A dual-output shaft motor (200) is fixedly connected to the fixed plate (100), and the output shaft of the dual-output shaft motor (200) is a hollow shaft; A mounting base (500) is installed at the output end of the dual-output-shaft motor (200); A suction cup (600) is disposed on the lower surface of the fixture (500) for adsorbing the wafer (900). A rotary joint (300) is connected to the tail end of the dual-output shaft motor (200) and connected to the vacuum generator negative pressure source through an air pipe (400); The suction cup (600) is connected to the vacuum generator negative pressure source through the fixed base (500), the hollow shaft of the dual-output shaft motor (200) and the rotary joint (300); An ultrasonic transducer (700) is mounted on the fixed plate (100); An oscillating probe (800) is connected to the output end of the ultrasonic transducer (700) and is used to disrupt the surface tension of the etching solution.

2. The immersion apparatus for wet etching of wafers according to claim 1, characterized in that: The fixed plate (100) includes a horizontal part and a vertical part connected to each other, wherein a dual-output shaft motor (200) is connected to the end of the horizontal part of the fixed plate (100), and the vertical part is used to connect an actuator that drives the fixed plate (100) to move.

3. The wet etching apparatus for wafers according to claim 2, characterized in that: The ultrasonic transducer (700) is fixedly disposed in the middle of the horizontal part of the fixed plate (100); the oscillating probe (800) penetrates to the bottom of the fixed plate (100) and extends to the bottom of the wafer (900) gripped by the suction cup (600).

4. The wet etching apparatus for wafers according to claim 1, characterized in that: The suction cup (600) is divided into three concentric layers: an inner suction cup (600), a middle suction cup (600), and an outer suction cup (600). The three layers of suction cups (600) are adapted to wafers (900) of different sizes and specifications. There is one inner suction cup (600) and it corresponds to the center position of the wafer (900). There are four middle suction cups (600) and four outer suction cups (600). The middle and outer suction cups (600) are evenly arranged along a ring array.

5. The wet etching apparatus for wafers according to claim 4, characterized in that: Each of the suction cups (600) is equipped with an independent miniature one-way valve, which includes a steel ball, a spring, and a sealing ring. When the suction cup (600) is not covered by the wafer (900), atmospheric pressure pushes the steel ball to block the air passage and cut off the negative pressure. After the suction cup (600) is attached to the surface of the wafer (900), the pressure difference is eliminated, and the one-way valve automatically opens to connect the negative pressure air passage. Only the suction cup (600) in contact with the wafer (900) generates adsorption force.

6. The wet etching apparatus for wafers according to claim 5, characterized in that: The negative pressure airflow path is as follows: The chuck (600) that fits against the wafer (900), the inner cavity of the mounting base (500), the inner cavity of the output shaft of the dual-axis motor (200), the rotary joint (300), the air pipe (400), and the vacuum generator.

7. A wet etching method for wafers, applicable to the wet etching apparatus for wafers as described in any one of claims 1-6, characterized in that: The steps of the impregnation method are as follows: A100: During the downward movement of the fixing plate (100), the position of the fixing plate (100) is adjusted so that the fixing seat (500) is concentric with the wafer (900) to be immersed in the etching solution, until the suction cup (600) is in contact with the wafer (900); A200: Start the vacuum generator. The suction cup (600) on the part covered by the wafer (900) generates negative pressure, which adsorbs the wafer (900) under the fixture (500). A300: The fixed plate (100) is moved above the tank containing the etching solution, and then the wafer (900) is slowly lowered while keeping it horizontal until the lower surface of the wafer (900) contacts the surface of the etching solution. The etching time is calculated from the point of contact with the surface of the solution. A400: After the etching time reaches the target etching time, the wafer (900) is taken out horizontally and placed in a basket for wafer flipping. Then, the above steps are repeated to etch the other side.

8. The wet etching method for wafers according to claim 7, characterized in that: In step A400, after the etching time reaches the target etching time, the ultrasonic transducer (700) is activated, and the oscillating probe (800) is used to oscillate the etching solution to break the surface tension of the etching solution and remove the adsorption effect of the etching solution on the wafer (900). Then, the fixing plate (100) moves upward to remove the wafer (900) while keeping it horizontal.

9. The wet etching method for wafers according to claim 8, characterized in that: In step A400, after the wafer (900) is taken out horizontally, the dual output shaft motor (200) is started. The dual output shaft motor (200) drives the wafer (900) to rotate, thereby shaking off the residual etching solution on the surface of the wafer (900).

10. The wet etching method for wafers according to claim 9, characterized in that: In step A400, after the wafer (900) is spun dry with the etching solution, it is cleaned with a mist of pure water to remove the residual etching solution, and then the wafer (900) is rotated again to spin dry the residual water.

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