Semiconductor CMP retaining ring and bonding method thereof

Abstract

The invention provides a semiconductor CMP retaining ring and a bonding method thereof, the semiconductor retaining ring comprises a PPS annular layer and a stainless steel annular layer, and the two layers are cured and bonded by a two-component epoxy adhesive at 20-30 DEG C; and the two-component epoxy glue is coated on the bonding surface along the annular structure of the retaining ring to form a ring shape. According to the technical scheme, the formed CMP retaining ring is not prone to degumming and resistant to acid and alkali, and the problem that in the subsequent wafer mill polishing process, the particle content is high due to falling of glue seams is solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a semiconductor CMP retaining ring and its bonding method. Background Technology

[0002] In the chemical mechanical polishing (CMP) process, the retaining ring is an important consumable component. It surrounds the wafer directly and presses the wafer onto the polishing pad for grinding. Its main function is to fix, constrain and protect the wafer, while ensuring polishing uniformity.

[0003] The inner diameter of the retaining ring is generally slightly larger than the wafer diameter, providing a precise constraint space for the wafer. It should not be too tight (jamming) or too loose (causing the wafer to slide or jump out). Its bottom usually has grooves or toothed structures. These grooves help to evenly deliver the polishing fluid under the wafer and remove polishing debris. The bottom is in direct contact with the polishing pad and is the part that suffers the most wear. Its top has a precision mechanical interface for connecting to the carrier or backing film of the CMP equipment head to ensure that the pressure can be evenly transmitted.

[0004] The retaining ring is a consumable. Its bottom will gradually thin due to continuous friction with the polishing pad. Long-term contact with chemical slurry may cause material denaturation or deformation, so it needs to be replaced regularly.

[0005] In summary, the CMP retainer ring is a precision-critical consumable that affects the uniformity of polishing and the defect rate. Without a well-designed, stable retainer ring, the global planarization required by modern chip manufacturing cannot be achieved.

[0006] The existing technology for bonding retainer rings involves sandblasting the bonding surfaces, cleaning and drying them, applying multiple strips of adhesive to the bonding surfaces, applying a weight after the bonding surfaces are joined, and finally curing the adhesive in an oven. Due to poor adhesive bonding, CMP retainer rings used in wafer fabs frequently experience high particle counts (particles falling into the adhesive seams), and in severe cases, even delamination (PPS and stainless steel separating), causing wafer contamination or scrapping. Therefore, improving the bonding process is crucial and urgent in the industry. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a bonding method for semiconductor CMP retaining rings, which solves the problems of delamination and adhesive removal that occur when retaining rings are used in wafer fabs in the prior art.

[0008] To achieve the above and other related objectives, the present invention is implemented by including the following technical solutions.

[0009] The first aspect of this invention provides a method for bonding a semiconductor CMP retaining ring, wherein the semiconductor retaining ring comprises a PPS annular layer and a stainless steel annular layer, and the two layers are bonded together by curing a two-component epoxy adhesive at 20-30°C; the two-component epoxy adhesive is applied in a ring shape along the annular structure of the retaining ring on the bonding surface. Preferably, during application, the two-component epoxy adhesive is a closed ring without gaps or intervals in the application direction; and there are no gaps or intervals in the radial direction of the retaining ring.

[0010] The PPS annular layer in this application is made of polyphenylene sulfide.

[0011] In this application, the stainless steel is SUS316L or 316L.

[0012] Preferably, the two-component epoxy adhesive is Alolada 2014-2.

[0013] Preferably, the curing time is at least 8 hours.

[0014] Preferably, the curing process involves fixing the material with upper and lower clamping plates and tightening it with screws. The screw tightening torque is 3~6 N•m. More preferably, it is 4~5 N•m, such as 4 N•m, 4.5 N•m, or 5 N•m.

[0015] More preferably, pressure is applied during curing using a clamp comprising an upper annular plate and a lower annular plate, which are detachably connected by two vertically embedded, spaced-apart screws. During operation, a retaining ring is positioned between the two annular plates and between the two screws. More preferably, one annular plate has a through threaded hole, and the other annular plate has a corresponding threaded blind hole. More preferably, the spacing between the two vertically embedded, spaced-apart screws is 5-10 mm larger than the difference between the inner and outer diameters of the retaining ring. More preferably, the torque of each screw is 3-6 N•m. In a more specific embodiment, 10-15 sets of screws are used for locking, with each set of screws spaced along the same radial direction, such as 10, 11, 12, 13, 14, or 15 sets.

[0016] Preferably, after curing, the thickness of the adhesive layer is 0.05~0.1mm, such as 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm or 0.1mm.

[0017] Preferably, apply a sufficient amount of adhesive, to the point that the adhesive slightly overflows. Alternatively, the approximate amount of adhesive can be estimated based on the specific structure, gap size, and bonding surface area of ​​the PPS and stainless steel ring layers to ensure sufficient adhesive application.

[0018] Preferably, before applying the two-component epoxy adhesive, the bonding surfaces are sandblasted, cleaned, and dried. More preferably, the sandblasting abrasive is #24 white corundum (particle size 850-710μm), achieving a surface roughness Ra of 4-8μm. Cleaning can be done with pure water, or ultrasonic cleaning with pure water. Drying is also done by heating, such as using an oven. The oven drying temperature can be set according to actual conditions, such as less than 90℃, or 85℃, 80℃, 70℃, 60℃, 50℃, 40℃, 30℃, 20℃, or 10℃.

[0019] The second aspect of the present invention uses a CMP retaining ring formed by any of the bonding methods described above, which consists of a stainless steel layer, a two-component epoxy adhesive curing layer, and a PPS layer from bottom to top; and the thickness of the two-component epoxy adhesive layer is 0.05~0.1mm.

[0020] The third aspect of the present invention also discloses the use of a two-component epoxy adhesive for bonding a double-layer CMP retaining ring, wherein the upper layer of the CMP retaining ring is a PPS ring and the lower layer is a stainless steel ring.

[0021] Preferably, the two-component epoxy adhesive is Alolata 2014-2. Compared to heat-curing adhesives, this room-temperature curing adhesive avoids the problem of material expansion and contraction caused by heating, thus preventing the adhesive from peeling off. If the curing temperature is too high, such as above 45°C, it will cause deformation of the PPS layer due to thermal expansion and contraction, resulting in poor bonding effects such as delamination.

[0022] As described above, the bonding method for a semiconductor CMP retaining ring of the present invention has the following beneficial effects:

[0023] This application utilizes a two-component epoxy adhesive that cures at room temperature, combined with a coating process, to prevent gaps or delamination between the two layers of the retainer ring. It also avoids air bubbles in the adhesive layer. A specialized clamping device is used for reinforcement, resulting in a more uniform adhesive thickness and a more stable bond. The selected two-component epoxy adhesive cures at room temperature. The resulting CMP retainer ring is not only resistant to delamination and acids / alkalis, but also avoids the problem of high particle content caused by adhesive gaps falling off during subsequent wafer fab polishing processes. Attached Figure Description

[0024] Figure 1 The diagram shown illustrates the adhesive application method of the present invention.

[0025] Figure 2 The diagram shown is a structural schematic of the fixing clamp of the present invention.

[0026] Figure 3 The image shown is an illustration of the degummed product in the comparative example of this invention.

[0027] Figure 4 The image shown is an effect diagram of the seepage product in the comparative example of this invention.

[0028] Figure 5 The diagram shown is a schematic representation of the degumming effect observed under a microscope in Comparative Example 3.

[0029] Figure 6 The image shown is a microscopic observation of the degumming results in Example 1. Detailed Implementation

[0030] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0031] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0032] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0033] In this application, the applicant discovered that for dual-material CMP retaining rings formed from PPS and stainless steel, conventional adhesives often resulted in delamination issues reported by downstream wafer foundries, leading to a high number of product defects. Therefore, a specific two-component epoxy resin adhesive was selected and combined with a specific application method to solve this problem. Specifically, the two-component epoxy resin adhesive is Alolada 2014-2. The specific application method is as follows: Figure 1 As shown, during coating, the two-component epoxy adhesive is a closed loop with no gaps or gaps in the coating direction; and there are no gaps or gaps in the radial direction of the retaining ring. Figure 1More specifically, the two-component epoxy adhesive is applied in only one ring. It should be noted that this ring of adhesive can extend to the entire bonding surface (applying sufficient adhesive, even to the point of slight overflow. Alternatively, the approximate amount of adhesive can be estimated based on the specific structure of the PPS and stainless steel ring layers, gap dimensions, and bonding surface area to ensure adequate adhesive application). More specifically, applying a continuous, closed-loop layer of adhesive to the bonding surface effectively improves the removal of air bubbles during bonding, thus avoiding problems caused by… Figure 1 The middle left image shows poor air release caused by multiple layers of adhesive and adhesive defects caused by air bubbles.

[0034] The specific structure of the CMP retaining ring used in this embodiment is as follows: the upper layer is a ring-shaped layer made of PPS material, and the lower layer is a ring-shaped layer made of stainless steel, specifically SUS316L stainless steel; the inner diameter of the retaining ring is 301±0.1mm; the outer diameter of the retaining ring is 360.4±0.1mm; and the thickness of the retaining ring (i.e., the width of the bonding surface) is 25mm. In practice, the bonding surface of the CMP retaining ring has different structural characteristics depending on the reagent process or equipment; for example, a liquid reservoir is formed at the bonding surface of the upper PPS layer to store a certain amount of adhesive liquid. The number of liquid reservoirs (e.g., 2-3) and their structure can be designed according to the actual situation, as long as there is enough adhesive to cover and diffuse the entire bonding surface after applying pressure in one ring. Specifically, the adhesive application avoids the liquid reservoir. When the applicant actually uses the two-component epoxy adhesive in this application for bonding, a good bonding effect can be achieved by applying a ring of CMP retaining ring with different bonding surface structures and fixing it with a curing clamp. Compared with the multi-ring adhesive application process in the prior art, it has better sealing performance.

[0035] The retaining ring in the above technical solution of this application can be used for retaining rings with wafer sizes of 8 inches or 12 inches.

[0036] This application provides a specific curing fixture for applying uniform pressure after applying adhesive to complete the curing process. Specifically, as shown in the embodiments below... Figure 2 As shown, the fixing clamp in this application includes an upper annular plate and a lower annular plate, which are detachably connected by two vertically embedded, spaced-apart screws. During operation, the retaining ring is located between the two annular plates and between the two screws. More preferably, one annular plate has a through threaded hole, and the other annular plate has a corresponding threaded blind hole. More preferably, the spacing between the two vertically embedded, spaced-apart screws is 10 mm larger than the difference between the inner and outer diameters of the retaining ring. More preferably, the torque of each screw is 5 N•m. Using... Figure 2The special clamp shown is tightened with screws in 12 sets (24 screws), each screw with a torque of 5 N•m. This ensures that the product is evenly stressed, the glue thickness is more uniform, and the bonding effect is more stable.

[0037] The adhesive used in the embodiments and comparative examples of this application is Alolada 2014-2.

[0038] Example 1

[0039] In this embodiment, only one ring of adhesive is applied, and the specific application method is as follows: Figure 1 As described above, the bonding temperature is 25℃, the curing time is 10 hours, and the aforementioned fixing clamps are used for locking and securing during curing. The thickness of the cured adhesive layer is 0.05mm.

[0040] Example 2

[0041] In this embodiment, only one ring of adhesive is applied, and the specific application method is as follows: Figure 1 As described above, the bonding temperature is 20℃, the curing time is 10 hours, and the aforementioned fixing clamps are used for locking and securing during curing. The thickness of the cured adhesive layer is 0.05mm.

[0042] Example 3

[0043] In this embodiment, only one ring of adhesive is applied, and the specific application method is as follows: Figure 1 As described above, the bonding temperature is 30℃, the curing time is 10 hours, and the aforementioned fixing clamps are used for locking and securing during curing. The thickness of the cured adhesive layer is 0.05mm.

[0044] Example 4

[0045] In this embodiment, only one ring of adhesive is applied, and the specific application method is as follows: Figure 1 As described above, the bonding temperature is 30°C, the curing time is 10 hours, and the curing is achieved using the aforementioned fixing clamps. The locking torque is reduced compared to Example 3. The thickness of the cured adhesive layer is 0.1 mm.

[0046] After bonding and curing the CMP retaining ring using the technical solution described in this application, an adhesive thickness of 0.05~0.1mm is optimal considering factors such as bonding strength, acid and alkali resistance, and leakage. Excessive adhesive thickness increases the risk of delamination and adhesive particle shedding during wafer fab polishing.

[0047] Comparative Example 1

[0048] The only difference from Example 1 is that it does not employ, as in Example 1. Figure 2 The fixing fixture shown.

[0049] The results showed that the adhesive layer thickness was uneven, with some areas being thicker and others thinner, and the thickness distribution ranged from 0.02 to 0.3 mm.

[0050] Comparative Example 2

[0051] The only difference from Example 1 is that the curing time is 5 hours.

[0052] Result: The adhesive did not fully cure, and the PPS and stainless steel separated during subsequent machining.

[0053] Comparative Example 3

[0054] The only difference from Example 1 is the application of two rings of glue spaced apart.

[0055] Result: There was obvious glue shortage at the glue layer, resulting in poor adhesion and sealing.

[0056] Thirty CMP retaining rings each formed by the processes in Examples 1-4 and Comparative Examples 1-3 were subjected to heating tests and acid and alkali resistance tests to observe degumming.

[0057] The heating test was conducted by heating 10 samples in an oven at 60°C for 3 hours, and then observing the degumming process.

[0058] The acid and alkali resistance tests were conducted as follows: 10 samples were soaked in an HCl aqueous solution with a pH of 1 for 3 days, and 10 samples were soaked in a sodium hydroxide aqueous solution with a pH of 14 for 3 days.

[0059] The corrosion and degumming conditions were observed, and the specific results are shown in Table 1 below.

[0060] Specifically, in this application, the debonding situation can be observed under a microscope (200-300x magnification). Specifically, after curing (without separating the PPS and stainless steel rings from the overall appearance), visual inspection of the adhesive joint will reveal obvious gaps if debonding occurs, indicating separation of the PPS and stainless steel. For example... Figure 5 The demonstration, using a microscope to observe the delamination at the bonding points in Comparative Example 3, revealed significant delamination. Obvious gaps were observed between the PPS layer and the cured two-component epoxy adhesive layer, as well as between the stainless steel layer and the cured two-component epoxy adhesive layer. Figure 6 This is an example of delamination at the adhesive joint in Example 1. It shows the unobserved delamination gaps. The PPS layer and the stainless steel layer are tightly bonded together by the cured adhesive layer.

[0061] Because obvious corrosion can still be observed after degumming and acid / alkali soaking. For example, after peeling off the degummed product under a microscope, observe the bonding surface of the PPS ring. By observing the color change at the bonding point in the darker areas (the cured adhesive adhering to the PPS), one can determine whether corrosion has occurred. If the color of the darker areas changes, such as a change in blackness or grayness (generally becoming lighter), it is determined to be corrosion. Specifically... Figure 3 As shown, Figure 3 In Comparative Example 3, the stainless steel ring and the PPS ring were separated. The dark area was a two-component epoxy resin adhesive. Observation revealed light and dark variations in the dark area, with areas showing signs of corrosion and becoming lighter in color. Figure 3 It can be seen that when acidic or alkaline liquids enter the product, they cause varying degrees of corrosion to the adhesive, resulting in patches of varying depths.

[0062] For gaps and other imperfections that cannot be observed under a microscope, further leakage testing is conducted to assess the adhesion and sealing performance. Leakage testing involves applying a red marker to the adhesive seam without opening the bond (after the PPS and stainless steel layers have cured and are not separated). After application, the bond is opened (peeled) for destructive analysis. If significant pigment penetration into the bonded surface is observed, it is considered leakage, indicating poor adhesive sealing. Figure 4 The product in Comparative Example 1 was subjected to a leakage test. A distinct red marker ink color was observed on the bonding surfaces of both the PPS layer and the stainless steel layer, indicating leakage.

[0063] Table 1

[0064]

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for bonding a semiconductor CMP retaining ring, characterized in that, The semiconductor retaining ring comprises a PPS annular layer and a stainless steel annular layer, which are bonded together by a two-component epoxy adhesive cured at 20~30℃; the two-component epoxy adhesive is applied in a ring shape along the annular structure of the retaining ring on the bonding surface.

2. The bonding method according to claim 1, characterized in that, During coating, the two-component epoxy adhesive is a closed loop with no gaps or gaps in the coating direction; and there are no gaps or gaps in the radial direction of the retaining ring.

3. The bonding method according to claim 1, characterized in that, The curing time is at least 8 hours.

4. The bonding method according to claim 1, characterized in that, The curing process involves fixing the product with upper and lower clamping plates and tightening it with screws. The screw tightening torque is 3~6 N•m.

5. The bonding method according to claim 4, characterized in that, The clamp includes an upper annular plate and a lower annular plate, which are detachably connected by two vertically embedded, spaced screws. During operation, the retaining ring is located between the two annular plates and between the two screws.

6. The bonding method according to claim 5, characterized in that, One of the annular plates has a through threaded hole, and the other annular plate has a threaded blind hole at the corresponding location; and / or, the screw is vertically embedded in the upper and lower annular plates, and the interval between the two turns is 5 to 10 mm larger than the difference between the inner and outer diameters of the retaining ring; and / or, the torque of each screw is 3 to 6 N∙m; and / or it is locked with 10 to 15 sets of screws.

7. The bonding method according to claim 1, characterized in that, After curing, the adhesive layer thickness is 0.05~0.1mm.

8. The bonding method according to claim 1, characterized in that, Before applying the two-component epoxy adhesive, the bonding surfaces are sandblasted, cleaned, and dried until the surface roughness Ra value reaches 4~8μm.

9. A CMP retaining ring formed by the bonding method according to any one of claims 1 to 8, wherein from bottom to top, it comprises a stainless steel layer, a two-component epoxy adhesive curing layer, and a PPS layer; and the thickness of the two-component epoxy adhesive layer is 0.05 to 0.1 mm.

10. The use of a two-component epoxy adhesive for bonding a double-layer CMP retainer ring, wherein the upper layer of the CMP retainer ring is a PPS ring and the lower layer is a stainless steel ring; the two-component epoxy adhesive is Alolada 2014-2.

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