Process method for cleaning flux of wafer product for HBM packaging

Abstract

The invention belongs to the field of 3D advanced packaging, and particularly relates to a technological method for cleaning flux of a wafer product for HBM packaging. The method comprises the following steps that a wafer product to be cleaned and packaged by the HBM is placed in a soaking unit casset containing a flux cleaning agent to be soaked, and the casset is vibrated up and down during soaking; the soaked wafer product is conveyed to a high-pressure photoresist removing unit, a flux cleaning agent is sprayed at high pressure, and the wafer product does reciprocating forward and reverse rotation motion along the axis of the circle center during spraying; the wafer after high-pressure spraying cleaning is conveyed to a normal-pressure cleaning unit, IPA is sprayed on the surface of the wafer, and during spraying, the wafer product does reciprocating forward and reverse rotation motion along the axis of the circle center; and the wafer product after IPA cleaning rotates at a high speed and is matched with N2 for drying at the same time. By adopting the cleaning method disclosed by the invention, the flux in the tiny gap between the Die can be efficiently cleaned, no cleaning agent residue is generated, a high-quality packaging effect is ensured, and the cost is relatively low.

Description

Technical Field

[0001] The present invention belongs to the field of 3D advanced packaging, and in particular relates to a process method for cleaning flux of HBM packaged wafer products. Background Art

[0002] In the HBM (High Bandwidth Memory) packaging process for 3D advanced packaging, eight layers of DRAM dies (dynamic random access memory) are sequentially bonded to a substrate. Flux is first applied between each layer of DRAM dies, followed by hot-pressing the bumps to bond each layer together. After the eight layers are bonded, the flux cleaning process is required. The gaps between each DRAM die layer and between the bumps reach less than 20μm, making cleaning the flux from these tiny gaps without leaving any residual cleaning fluid a challenge.

[0003] Existing single-chip flux cleaning technology typically utilizes a vacuum chamber to reduce resistance to the cleaning fluid entering tiny gaps, displacing the flux. IPA (isopropyl alcohol) is then used to displace the cleaning fluid. However, this cleaning technology not only increases equipment costs but also struggles to achieve ideal cleaning results. Summary of the Invention

[0004] To address the technical difficulties in the prior art, the present invention provides a process for effectively cleaning flux from HBM-packaged wafers. The cleaning equipment includes an immersion unit (IMM), a high-pressure cleaning unit (ST), and a normal-pressure cleaning unit (SR). The wafer is first placed in the immersion unit containing flux cleaning agent. The wafer then enters the high-pressure degumming unit, where high-pressure cleaning agent is sprayed to displace the flux. Finally, the wafer enters the IPA normal-pressure cleaning unit. By adjusting the wafer's forward and reverse rotation, centrifugal force displaces the cleaning agent and spins it dry, achieving a clean, residue-free cleaning and reducing costs.

[0005] The technical solutions of the present invention are as follows:

[0006] A process for cleaning flux from HBM packaged wafer products, the method comprising the following steps:

[0007] (1) Place the HBM packaged wafer product to be cleaned in a cassette containing a flux cleaning agent and immerse it in the cassette while shaking the cassette up and down. During the shaking process, the cassette remains in the cleaning agent.

[0008] (2) The soaked wafer product is transferred to the high-pressure degumming unit, where flux cleaning agent is sprayed at high pressure. While spraying, the wafer product performs reciprocating forward and reverse motion along the central axis;

[0009] (3) The wafer product after high-pressure spray cleaning is transferred to the normal pressure cleaning unit, and IPA is sprayed on the surface of the wafer product. While spraying, the wafer product performs reciprocating forward and reverse motion along the central axis;

[0010] (4) The wafer product after IPA cleaning is rotated at high speed and dried with N2 at the same time.

[0011] Furthermore, the flux cleaning agent temperature in step (1) is 40-90° C., the soaking time is 30-60 min, the oscillation amplitude is 5-10 cm, and the oscillation is performed every 1-10 s.

[0012] Furthermore, the shaking process of step (1) is specifically as follows: every 5 to 10 minutes of shaking, the immersion unit cassette is pulled up from the cleaning agent, and after staying for 5 to 15 seconds, it is continued to be placed in the cleaning agent and shaken up and down.

[0013] Furthermore, the high-pressure spraying of flux cleaning agent in step (2) is specifically as follows: a fan-shaped high-pressure nozzle is used with the end of its swing arm away from the wafer product as the rotation center, and the swing arm length is used as the radius to swing from one edge of the wafer product to the other edge and spray the cleaning agent; during the swinging process, the vertical distance between the fan-shaped high-pressure nozzle and the surface of the wafer product is 15 to 30 mm, the angle formed by the axis of the fan-shaped high-pressure nozzle and the plane where the wafer product is located is 5° to 45°, the high-pressure pressure is 5 to 16 MPa, the spraying flow rate is 300 to 500 mL / min, and the swing rate of the fan-shaped high-pressure nozzle is 1° to 20° / s.

[0014] Furthermore, when the wafer product performs reciprocating forward and reverse motion in step (2), the speed and time of one cycle are set as follows: the wafer product rotates clockwise at a speed of 50-300 rpm for 15-30 s → the wafer product rotates counterclockwise at a speed of 50-300 rpm for 15-30 s → the wafer product rotates clockwise at a speed of 50-300 rpm for 15-30 s → the wafer product rotates counterclockwise at a speed of 500-1000 rpm for 30-50 s → the wafer product rotates counterclockwise at a speed of 50-300 rpm for 15-30 s; and 5-20 cycles are repeated.

[0015] Furthermore, the spraying of IPA described in step (3) is specifically as follows: using a normal pressure nozzle with the end of its swing arm away from the wafer product as the rotation center, vertically swinging from one edge of the wafer product to the other edge with the length of the swing arm as the radius and spraying IPA, during the swinging process, the vertical distance between the normal pressure nozzle and the surface of the wafer product is 15 to 30 mm, the normal pressure is 0.2 to 0.5 MPa, the spraying flow rate is 100 to 1000 mL / min, and the swing rate of the normal pressure nozzle is 1° to 20° / s.

[0016] Furthermore, when the wafer product performs reciprocating forward and reverse motion in step (3), the speed and time of one cycle are set as follows: the wafer product rotates clockwise at a speed of 50-200 rpm for 15-30 s → the wafer product rotates clockwise at a speed of 500-3000 rpm for 5-20 s → the wafer product rotates counterclockwise at a speed of 500-3000 rpm for 5-20 s → the wafer product rotates counterclockwise at a speed of 500-200 rpm for 15-30 s → the wafer product rotates counterclockwise at a speed of 500-3000 rpm for 5-20 s → the wafer product rotates clockwise at a speed of 500-3000 rpm for 5-20 s; and 5-20 cycles are repeated.

[0017] Furthermore, the high-speed rotation speed in step (4) is 2000-3000 rpm, the rotation time is 2-5 min, the N2 temperature is 50-70°C, and the N2 flow rate is 20-40 L / min.

[0018] Furthermore, the flux is Indium NC699 soldering flux; and the flux cleaning agent is ZESTRON FA+.

[0019] Advantages and beneficial effects of the present invention

[0020] 1. The immersion unit (IMM) has the function of continuously oscillating the wafer up and down. The continuous oscillation of the immersion tank makes it easier for the FA+ cleaning agent to penetrate into the tiny gaps of the flux.

[0021] 2. The high-pressure cleaning unit (ST) uses multiple cycles of forward and reverse speed rinsing to fully replace the FA+ cleaning agent with the flux.

[0022] 3. The normal pressure cleaning unit (SR) uses multiple cycles of forward and reverse speed cleaning to quickly replace the FA+ cleaning agent.

[0023] The present invention combines the above three means to efficiently clean the flux in the tiny gaps between dies without generating cleaning agent residue, thereby ensuring high-quality packaging effects and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the oscillation curve of the immersion unit cassette;

[0025] Figure 2 This is the curve of the wafer speed changing with time in the high-pressure cleaning unit;

[0026] Figure 3 This is the curve of wafer rotation speed changing with time in the atmospheric pressure cleaning unit;

[0027] Figure 4 The MUF filling result of the wafer after cleaning in Example 1;

[0028] Figure 5 This is the MUF filling result of the wafer after cleaning in Comparative Example 1;

[0029] Figure 6 This is the OM observation result of the wafer after cleaning in Example 1;

[0030] Figure 7 This is the OM observation result of the wafer after cleaning in Comparative Example 1;

[0031] Figure 8 This is a structural diagram of the soaking unit of the cleaning equipment;

[0032] Figure 9 A structural diagram of a high-pressure cleaning unit of a cleaning device;

[0033] Figure 10 This is the structural diagram of the atmospheric pressure cleaning unit of the cleaning equipment. DETAILED DESCRIPTION

[0034] The present invention provides a process for effectively cleaning flux for HBM packaged wafer products. The type of flux cleaned in the present invention is IndiumNC699 solder flux. The cleaning equipment used in the present invention is a KS-S300-6FCL cleaning machine, which includes an immersion unit, a high-pressure cleaning unit (high-pressure degumming unit) and a normal-pressure cleaning unit (including an IPA cleaning swing arm and an N2 swing arm). Figure 8-10 shown.

[0035] Example 1

[0036] The first step is to place the wafer to be cleaned (12-inch HBM packaged wafer product) in a solution containing flux cleaning agent ( The wafers were immersed in an immersion unit cassette (wafer box) containing FA+cleaning solution at a cleaning agent temperature of 70°C. At the same time, the immersion unit cassette was oscillated up and down. During the oscillation process, the cassette was always in the cleaning agent with an oscillation amplitude of 6 cm and an oscillation every 2 seconds. Every 10 minutes, the immersion unit cassette was lifted up from the cleaning agent solution, stayed there for 10 seconds, and then continued to be placed in the cleaning agent solution and oscillated up and down. The total immersion time was 40 minutes.

[0037] In the second step, the soaked wafer is transferred to the high-pressure degumming unit, and a fan-shaped high-pressure nozzle is used to rotate from one edge of the wafer product to the other edge with the arm length as the radius, and the cleaning agent is sprayed ( FA+ cleaning liquid), the specific structure of the fan-shaped high-pressure nozzle: the shape is cylindrical, the outlet shape is linear, and the sprayed liquid is fan-shaped. During the swing process, the vertical distance between the fan-shaped high-pressure nozzle and the surface of the wafer product is 20mm, and the angle formed by the axis of the fan-shaped high-pressure nozzle and the plane of the wafer product is 30°. The high-pressure pressure at the outlet of the fan-shaped high-pressure nozzle is set to 14Mpa, the flow rate is set to 400mL / min, the nozzle swing rate is 5° / s, and the swing time is 20min. During this period, the wafer performs reciprocating forward and reverse motions, such as Figure 2 As shown, the wafer rotates at +200 rpm (25 s) → -200 rpm (25 s) → +200 rpm (25 s) → -800 rpm (20 s) → -200 rpm (25 s) as one cycle (the wafer rotates clockwise at 200 rpm for 25 s, then counterclockwise at 200 rpm for 25 s, then counterclockwise at 200 rpm for 20 s, then counterclockwise at 200 rpm for 25 s), and the cycle is repeated 10 times.

[0038] In the third step, the wafer is transferred from the high-pressure degumming unit to the IPA normal-pressure cleaning unit. A normal-pressure nozzle is used with the end of its swing arm away from the wafer product as the rotation center, and the swing arm length is used as the radius to vertically swing in an arc from one edge of the wafer to the other edge and spray IPA. The structure of the normal-pressure nozzle is: the outer shape is truncated cone, the outlet shape is circular, and the sprayed liquid is cylindrical. During the swinging process, the vertical distance between the atmospheric pressure nozzle and the wafer surface is 20 mm, the atmospheric pressure is set to 0.2 MPa, the flow rate is set to 500 mL / min, and the nozzle swing rate is 10° / s. During this period, the wafer performs reciprocating forward and reverse motions. The wafer speed and time are set in sequence: +50 rpm (20 s) → +1500 rpm (5 s) → -1500 rpm (5 s) → -50 rpm (20 s) → -1500 rpm (5 s) → +1500 rpm (5 s). The above is one cycle, and the cycle lasts for a total of 10 minutes (the wafer rotates clockwise at 50 rpm for 20 s, then rotates clockwise at 1500 rpm for 5 s, then rotates counterclockwise at 1500 rpm for 5 s, then rotates counterclockwise at 50 rpm for 20 s, then rotates counterclockwise at 1500 rpm for 5 s, and then rotates clockwise at 1500 rpm for 5 s).

[0039] In the fourth step, after the wafer is cleaned with IPA, the liquid film is gradually thinned by gradually increasing the rotation speed until it is dried at high speed. The increase rate is 500 rpm / s. After increasing from 1500 rpm at the end of the third step to 2000 rpm, the rotation speed is maintained for 150 seconds. At the same time, hot N2 is used to fully dry the laminate gap. The N2 temperature is 60°C and the flow rate is set to 30 L / min.

[0040] Comparative Example 1

[0041] The first step is to place the wafer to be cleaned in a solution containing flux cleaning agent ( The sample was immersed in a cassette containing FA+cleaning liquid at a cleaning agent temperature of 70°C for 40 minutes (the cassette was not shaken up and down during the immersion process).

[0042] Steps 2 to 4 are the same as those in Example 1.

[0043] Comparative Example 2

[0044] The first step is the same as the first step in Example 1.

[0045] In the second step, the soaked wafer is transferred to the high-pressure degumming unit, and a fan-shaped nozzle is tilted (30°) with the end of the swing arm away from the wafer product as the rotation center, and the swing arm length is used as the radius to swing from one edge of the wafer product to the other edge and spray the cleaning agent ( FA+cleaning liquid), during the swinging process, the vertical distance between the fan-shaped high-pressure nozzle and the wafer product surface is 20 mm, the high-pressure pressure at the fan-shaped high-pressure nozzle outlet is set to 14 MPa, the flow rate is set to 400 ml / min, the nozzle swing rate is 5° / s, and the swing time is 20 minutes. During this period, the wafer rotates clockwise at a speed of 200 rpm.

[0046] The third and fourth steps are the same as those in Example 1.

[0047] Comparative Example 3

[0048] The first step is the same as the first step in Example 1.

[0049] The second step is the same as the second step in Example 1.

[0050] In the third step, the wafer is transferred from the high-pressure degumming unit to the IPA normal-pressure cleaning unit. A normal-pressure nozzle is used with the end of its swing arm away from the wafer product as the rotation center, and the swing arm length is used as the radius to vertically swing in an arc from one edge of the wafer to the other edge and spray IPA. During the swinging process, the normal-pressure nozzle is 20 mm vertically away from the wafer surface, the normal pressure is set to 0.2 MPa, the flow rate is set to 500 ml / min, the nozzle swing rate is 10° / s, and the swing time is 10 min. During this period, the wafer rotates clockwise at a speed of 500 rpm.

[0051] The fourth step is the same as the fourth step in Example 1.

[0052] Test results

[0053] According to the methods of Example 1 and Comparative Examples 1-3, two wafers were cleaned using each method, one of which was tested using Method 1 and the other was tested using Method 2.

[0054] Method 1: The wafers cleaned in Example 1 and Comparative Examples 1-3 were continued to be taped out and baked, and then MUF filling (molded bottom filling) was performed. SAT (scanning acoustic microscope) ultrasonic detection of the existing voids and gaps was used. The surface of the wafers cleaned by the method of Example 1 was clean and free of flux residue (such as Figure 4 ); After the wafers cleaned by the methods of Comparative Examples 1-3, the filling material was blocked from entering the gaps between the laminates due to the incomplete cleaning of the flux. Figure 5 Shown is the result after MUF filling of the wafer cleaned by the method of comparative example 1.

[0055] Method 2: Place the cleaned wafers of Example 1 and Comparative Examples 1-3 on a hot plate at 245°C. After the bump column melts, use tweezers to pull out the laminated die layer by layer. Use OM (optical microscope) to observe the die surface. The surface of the wafer cleaned by the method of Example 1 is clean and has no flux residue (such as Figure 6 ), after cleaning by the methods of Comparative Examples 1-3, there is obvious flux residue on the surface of the wafer. Figure 7 Shown is the wafer surface after cleaning using the method of Comparative Example 1.

[0056] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A process for cleaning flux from HBM packaged wafer products, characterized by: The method comprises the following steps: (1) Place the HBM packaged wafer product to be cleaned in a cassette containing a flux cleaning agent and immerse it in the cassette while shaking the cassette up and down. During the shaking process, the cassette remains in the cleaning agent. (2) The soaked wafer product is transferred to the high-pressure degumming unit, where flux cleaning agent is sprayed at high pressure. While spraying, the wafer product performs reciprocating forward and reverse motion along the central axis; (3) The wafer product after high-pressure spray cleaning is transferred to the normal pressure cleaning unit, and IPA is sprayed on the surface of the wafer product. While spraying, the wafer product performs reciprocating forward and reverse motion along the central axis; (4) The wafer product after IPA cleaning is rotated at high speed and dried with N2 at the same time.

2. The process according to claim 1, wherein: The flux cleaning agent temperature in step (1) is 40-90° C., the soaking time is 30-60 min, the oscillation amplitude is 5-10 cm, and the oscillation is performed every 1-10 s.

3. The process according to claim 1 or 2, characterized in that: The shaking process of step (1) is specifically as follows: every 5 to 10 minutes of shaking, the immersion unit cassette is pulled up from the cleaning agent, and after staying for 5 to 15 seconds, it is continued to be placed in the cleaning agent and shaken up and down.

4. The process according to claim 1, characterized in that: The high-pressure spraying of flux cleaning agent described in step (2) is specifically as follows: using a fan-shaped high-pressure nozzle with the end of its swing arm away from the wafer product as the rotation center and the length of the swing arm as the radius, swinging from one edge of the wafer product to the other edge and spraying the cleaning agent; during the swinging process, the vertical distance between the fan-shaped high-pressure nozzle and the surface of the wafer product is 15 to 30 mm, the angle formed by the axis of the fan-shaped high-pressure nozzle and the plane where the wafer product is located is 5° to 45°, the high-pressure pressure is 5 to 16 MPa, the spraying flow rate is 300 to 500 mL / min, and the swing rate of the fan-shaped high-pressure nozzle is 1° to 20° / s.

5. The process according to claim 1, characterized in that: When the wafer product performs reciprocating forward and reverse motion in step (2), the speed and time of one cycle are set as follows: the wafer product rotates clockwise at a speed of 50-300 rpm for 15-30 s → the wafer product rotates counterclockwise at a speed of 50-300 rpm for 15-30 s → the wafer product rotates clockwise at a speed of 50-300 rpm for 15-30 s → the wafer product rotates counterclockwise at a speed of 500-1000 rpm for 15-30 s → the wafer product rotates counterclockwise at a speed of 50-300 rpm for 15-30 s; repeat 5-20 cycles.

6. The process according to claim 1, characterized in that: The spraying of IPA described in step (3) is specifically as follows: using a normal pressure nozzle with its swing arm away from the end of the wafer product as the rotation center, vertically swinging from one edge of the wafer product to the other edge with the swing arm length as the radius and spraying IPA, during the swinging process, the vertical distance between the normal pressure nozzle and the surface of the wafer product is 15 to 30 mm, the normal pressure is 0.2 to 0.5 MPa, the spraying flow rate is 100 to 1000 mL / min, and the swing rate of the normal pressure nozzle is 1° to 20° / s.

7. The process according to claim 1, characterized in that: When the wafer product performs reciprocating forward and reverse motion in step (3), the speed and time of one cycle are set as follows: the wafer product rotates clockwise at a speed of 50-200 rpm for 15-30 s → the wafer product rotates clockwise at a speed of 500-3000 rpm for 5-20 s → the wafer product rotates counterclockwise at a speed of 500-3000 rpm for 5-20 s → the wafer product rotates counterclockwise at a speed of 500-200 rpm for 15-30 s → the wafer product rotates counterclockwise at a speed of 500-3000 rpm for 5-20 s → the wafer product rotates clockwise at a speed of 500-3000 rpm for 5-20 s; repeat 5-20 cycles.

8. The process according to claim 1, characterized in that: The high-speed rotation speed described in step (4) is 2000-3000 rpm, the rotation time is 2-5 min, the N2 temperature is 50-70°C, and the N2 flow rate is 20-40 L / min.

9. The process according to claim 1, wherein: The flux is Indium NC699 soldering flux; the flux cleaning agent is ZESTRON FA+.

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