Polishing pad casting mold, polishing pad processing method, and polishing pad
By designing a tilted casting point and a heat-controlled polishing pad casting mold, the problem of uneven density of polyurethane polishing pads was solved, improving production yield and wafer polishing quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI XINQIAN INTEGRATED CIRCUIT CO LTD
- Filing Date
- 2022-12-29
- Publication Date
- 2026-06-26
AI Technical Summary
In existing technologies, the density of polyurethane polishing pads and the expansion ratio of microspheres are not uniform, leading to low production yield and scratches during wafer polishing.
A polishing pad casting mold with a sandwich structure is designed with casting points composed of inclined surfaces. Temperature uniformity is controlled by heating to ensure that the polishing pad material slides down the inclined surfaces to fill the inner groove, avoiding the formation of air bubbles and achieving consistency in density and porosity.
This improved the uniformity of polishing pad density and microsphere expansion ratio, increased polishing pad production yield, and reduced the risk of scratches during wafer polishing.
Smart Images
Figure CN116512144B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical mechanical polishing, and in particular to polishing pad casting molds, polishing pad processing methods, and polishing pads. Background Technology
[0002] The semiconductor industry is the core of the modern electronics industry, and the foundation of the semiconductor industry is the silicon material industry. Although various new semiconductor materials are constantly emerging, more than 90% of semiconductor devices and circuits, especially very large-scale integration circuits (VLSI), are fabricated based on high-purity, high-quality silicon single-crystal polished wafers and epitaxial wafers. Currently, with the further miniaturization of feature linewidths in VLSI, higher requirements are placed on the planarization of silicon wafer surfaces. Chemical mechanical polishing (CMP) is widely recognized as the best global material planarization method in the VLSI stage. This method can obtain a more perfect surface and a higher polishing rate, and has basically replaced traditional techniques such as thermal flow, rotating glass method, etch-back method, and electron all-around resonance method.
[0003] Polishing pads are indispensable consumables in the chemical mechanical polishing (CMP) process of integrated circuit manufacturing. The main function of polishing pads in CMP is to hold and distribute the polishing slurry evenly, while simultaneously providing mechanical friction between the pad and the wafer surface, thereby removing excess layers and achieving wafer surface planarization.
[0004] CMP polishing pads, also known as CMP abrasive pads, are primarily used for polishing semiconductor wafers and sapphire wafers. CMP polishing pads are composed of polyurethane material containing filler to control the pad's hardness. The micro-protrusions on the surface of the polishing pad directly contact the wafer, generating friction to mechanically remove the polishing layer. Under centrifugal force, polishing fluid is evenly sprayed onto the surface of the polishing pad, chemically removing the polishing layer and carrying the reaction products out of the pad. The properties of the polishing pad directly affect the surface quality of the wafer and are one of the direct factors related to the planarization effect.
[0005] Currently, the substrate of CMP pads is polyurethane. The main production process involves vacuum dehydrating polyether polyols (or polyester polyols, polypropylene ether glycol, etc.), adding isocyanate, and preparing a prepolymer. A portion of the polyol is mixed with chain extenders and foaming agents, stirred to foam, and then added to a prepolymer tank, injected into a mold, cooled, and sliced.
[0006] It has been proven that casting polyurethane into a cake and then slicing the cake into thin polishing pads is an effective method for manufacturing polishing pads with constant and reproducible polishing properties. Existing technology has demonstrated that a "cake" casting method can produce polyurethane sheets suitable for slicing. However, a disadvantage is that uneven casting and heat distribution during the casting and gelation process lead to inconsistent microsphere expansion, resulting in uneven density distribution from the center to the periphery of the system. This makes it impossible for the molded polyurethane cake to achieve uniform density and microsphere expansion ratios throughout the entire process. This results in two adverse consequences: first, a low yield rate in polishing pad production; the yield of polyurethane cakes produced using existing casting methods that can be used as qualified polishing pads after slicing is low; second, during wafer polishing, the inability to perform full inspection during production leads to missed microsphere distributions, resulting in residues that cannot be effectively removed in time, causing irreversible scratches on the wafer surface. Summary of the Invention
[0007] To address the aforementioned technical problems, the present invention aims to overcome the technical defect that the molded polyurethane cake body cannot achieve uniform density and microsphere expansion ratio in every part, and provides a polishing pad casting mold, a polishing pad processing method, and a polishing pad.
[0008] To solve the above-mentioned technical problems, the polishing pad casting mold of the present invention includes two casting pieces. Each casting piece is provided with a bonding strip on both sides and the bottom edge. The bonding strips of the two casting pieces are connected to each other, so that a polishing pad generating inner groove is formed between the two casting pieces. The top edge of each casting piece is provided with a first inclined surface as a casting point. The polishing pad processing material can slide down along the casting point to fill the polishing pad generating inner groove.
[0009] In another preferred embodiment, the top of the bonding strip located on both sides of each casting sheet is provided with a second inclined surface.
[0010] In another preferred embodiment, at least one of the first inclined surface and the second inclined surface is a convex arc surface.
[0011] In another preferred embodiment, the bonding strip is provided with a ventilation groove and a fixing hole for a locking screw to pass through.
[0012] In another preferred embodiment, the bonding strip is provided with positioning holes for passing through positioning pins.
[0013] The polishing pad processing method includes the following steps:
[0014] Step S1: Prepare polishing pad processing material; specifically, step S11: Mix the prepolymer and microsphere filler evenly to form an intermediate material;
[0015] Step S12: Place the intermediate material into the casting machine tank and stir it at a uniform speed;
[0016] Step S13: Place the curing agent into the casting machine tank and stir it at a uniform speed;
[0017] Step S14: Mix the intermediate material with the curing agent to form a polishing pad processing material.
[0018] Step S2: Heat the polishing pad casting mold to 50-70 degrees Celsius. Specifically, heat the polishing pad casting mold to 50-70 degrees Celsius and let it stand for 10-20 minutes.
[0019] Step S3: Pour the polishing pad processing material into the polishing pad generating inner groove of the polishing pad casting mold; specifically including: Step S31: Set the casting pipe at the casting point of the polishing pad generating inner groove;
[0020] Step S32: Pour the polishing pad material into the polishing pad casting mold along the pouring point through the pouring pipe;
[0021] Step S33: Remove the pouring pipe;
[0022] Step S34: Use the hole cover to cover the polishing pad of the casting mold to create an inner groove.
[0023] Step S4: The polishing pad material is vulcanized in the polishing pad casting mold to form a solid, thus completing the processing.
[0024] A polishing pad, wherein the polishing pad is manufactured by a polishing pad manufacturing method.
[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0026] 1. The present invention provides a sandwich structure for casting a polishing pad, and designs a casting point composed of inclined surfaces on the polishing pad casting mold. When the polishing pad processing material is poured in, the liquid processing material can slowly slide down the inclined surface to the side wall of the mold, and slide down the side wall of the mold to the bottom of the mold at the same speed until the polishing pad is filled and an inner groove is formed. This effectively avoids air bubbles at the bottom caused by excessively fast vertical falling and improves the uniformity of the microsphere expansion ratio.
[0027] 2. In the process of this invention, the polishing pad casting mold is preheated to 50-70 degrees Celsius before the polishing pad material is poured in. This allows for better control of the polyurethane cake formed by the polishing pad material, controlling the temperature and reaction rate from all directions and positions, ensuring that the entire "cake" has the same density and porosity. Therefore, it will not have a negative impact on wafers with low-K patterns during wafer polishing. Attached Figure Description
[0028] Figure 1This is a schematic diagram of the structure of the polishing pad casting mold of the present invention.
[0029] Figure 2 This is a schematic diagram of the main structure of a single cast-in-place piece.
[0030] Figure 3 This is a side view of a single cast-in-place section.
[0031] Figure 4 This is a three-dimensional perspective diagram of a single cast-in-place section.
[0032] Figure 5 This is a three-dimensional cross-sectional view of the polishing pad casting mold of the present invention.
[0033] Figure 6 Microscopic view of an existing polishing pad.
[0034] Figure 7 This is a microscope view of the polishing pad of the present invention.
[0035] Reference numerals in the attached drawings: 1-Pouring sheet; 11-Adhesive strip; 12-Ventilation groove; 13-Fixing hole; 14-Positioning hole; 2-Hole cover; 31-First pouring point; 32-Second pouring point; 41-First inclined surface; 42-Second inclined surface; 5-Locking screw; 6-Positioning pin. Detailed Implementation
[0036] Unless otherwise defined, the technical or scientific terms used in this specification and claims shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.
[0037] All the values listed in this article, ranging from the lowest to the highest, refer to all values obtained by incrementing the lowest and highest values by one unit when the difference between the lowest and highest values is more than two units.
[0038] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0039] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.
[0040] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0041] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that, in order to keep the description of these embodiments brief, this specification cannot provide a detailed description of all features of the actual embodiments.
[0042] Example
[0043] like Figure 1 As shown, the polishing pad casting mold includes two casting plates 1 and one hole cap 2, wherein the two casting plates 1 have symmetrical and identical structures. Specifically, as shown... Figures 2-5 As shown: Each casting piece 1 has a rectangular structure, with bonding strips 11 on both sides and the bottom edge. The bonding strips 11 of two casting pieces 1 are connected and bonded together, thus forming a polishing pad generating inner groove with three sides between the two casting pieces 1. The top of this polishing pad generating inner groove is the opening groove. A first casting point 31 and a second casting point 32 are provided at both ends of the opening groove for casting polishing pad processing material. Both the first casting point 31 and the second casting point 32 are structures composed of three inclined surfaces. In this way, when the polishing pad processing material slides down along the casting points to fill the polishing pad generating inner groove, the liquid processing material can slowly slide down along the inclined surfaces to the side wall of the mold, and slide down along the side wall of the mold at the same speed to the bottom of the mold until the polishing pad generating inner groove is filled. This effectively avoids air bubbles at the bottom caused by excessively rapid vertical falling and improves the uniformity of the microsphere expansion ratio.
[0044] like Figure 5 As shown, the first pouring point 31 and the second pouring point 32 have the same structure, both including two first inclined surfaces 41 and one second inclined surface 42. The first inclined surface 41 is the chamfer at the top of the pouring piece 1, and the second inclined surface 42 is the chamfer at the top of the two side bonding strips 11. The inclination of the chamfer is generally 5 to 45 degrees relative to the vertical surface, preferably 30 degrees.
[0045] In another preferred embodiment, both the first inclined surface 41 and the second inclined surface 42 can be slightly convex arc surfaces, so that the liquid processing material can decelerate and then accelerate before falling on the inclined surface, which makes it easier to control the fall.
[0046] In another preferred embodiment, such as Figures 2-4 As shown, venting grooves 12 are evenly distributed on the bonding strip 11. When the bonding strips 11 of two casting pieces 1 are bonded together, the corresponding venting grooves 12 form an exhaust hole to discharge the gas generated during the molding process. Fixing holes 13 are also provided on the bonding strip 11. Locking screws 5 pass through the fixing holes 13 of the two casting pieces 1 to fix them together. To facilitate the installation of the two casting pieces 1, positioning holes 14 can also be provided on the bonding strip 11. Before fixing with locking screws 5, positioning pins 6 are used to pass through the positioning holes 14 to position the casting pieces 1 relative to each other.
[0047] The specific steps for processing the polishing pad using the polishing pad casting mold of this embodiment are as follows:
[0048] Step S1: Prepare polishing pad material; In this embodiment, the polishing pad material comprises a cast polyurethane polymer material formed by a prepolymer reaction. The prepolymer reaction refers to the isocyanate-terminated reaction product generated by the reaction of prepolymer polyol and polyfunctional aromatic isocyanate. The aliphatic isocyanate content in the polyfunctional aromatic isocyanate should be less than 11% by weight, and the isocyanate-terminated reaction product contains 4.5-9.6% by weight of unreacted NCO. The curing agent is a polyamine, polyol, or alcohol amine mixture curing agent for curing. The polishing pad contains at least 0.01% microsphere filler.
[0049] Step S2: In this embodiment, the two casting plates of the polishing pad casting mold are assembled and installed. After assembly, they are simultaneously heated to 50-70 degrees Celsius and left to stand for 10-20 minutes (all vents on the upper part are opened before heating). The preferred operation is: observe the external temperature controller, and after all temperature sensors reach 65 degrees, continue heating and leave for 15 minutes to ensure uniform temperature distribution within the mold cavity.
[0050] Step S3: Pour the polishing pad material into the inner groove of the polishing pad casting mold along the two pouring points, and then cover the opening groove with a hole cap.
[0051] Step S4: After the polishing pad material is vulcanized at 65-100 degrees Celsius for 5-15 hours in the polishing pad casting mold, the mixture in the mold becomes solidified. Remove the mold cover and then remove the annular sidewall. The solidified cylindrical polymer can be removed. Cut the solidified cylindrical polymer into circular polishing pad slices of about 2 cm. The resulting slices have a uniform surface color and density.
[0052] By continuing the above steps, polishing pad slices with stable quality, uniform color, and uniform density can be obtained.
[0053] In step S1 above, the polishing pad material also includes:
[0054] Step S11: Mix the prepolymer and microsphere filler evenly to form an intermediate material;
[0055] Step S12: Place the intermediate material in a casting machine tank at a temperature of 50-110 degrees Celsius and stir it at a uniform speed.
[0056] Step S13: Place the curing agent in a casting machine tank at a temperature of 50-120 degrees Celsius and stir it at a uniform speed.
[0057] Step S14: Mix the intermediate material with the curing agent to form a polishing pad processing material.
[0058] In step S3 above, the pouring of the polishing pad material specifically includes:
[0059] Step S31: Place the pouring pipe at the pouring point of the inner groove generated by the polishing pad;
[0060] Step S32: Pour the polishing pad material into the polishing pad casting mold along the pouring point through the pouring pipe;
[0061] Step S33: Remove the pouring pipe;
[0062] Step S34: Use the hole cover to cover the polishing pad of the casting mold to create an inner groove.
[0063] The polishing pad produced by the polishing pad casting mold of this embodiment is compared with the polishing pad manufactured in a conventional manner:
[0064] like Figure 6 As shown, traditionally manufactured polishing pads, under a microscope at a set magnification, exhibit a porous structure resulting from uneven heating and foaming (the varying sizes and uneven distribution of the pores are clearly visible). For example... Figure 7 As shown, the polishing pad manufactured by this invention has a porous structure that is uniformly foamed when heated, as indicated by a microscope at the same magnification.
[0065] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.
Claims
1. A polishing pad casting mold, characterized in that, The device includes two casting plates, each with adhesive strips on both sides and the bottom edge. The adhesive strips of the two casting plates are connected and face each other, forming a polishing pad and generating an inner groove between the two casting plates. Each casting plate has a casting point at its top edge, which is a structure composed of three inclined surfaces, including two first inclined surfaces and one second inclined surface. Polishing pad material can slide down along the casting point to fill the polishing pad and generate the inner groove. Each casting plate has a rectangular structure. The second inclined surface is located at the top of the adhesive strips on both sides of each casting plate. The first inclined surface is the chamfer at the top of the casting sheet, and the second inclined surface is the chamfer at the top of the two side bonding strips. The inclination of the chamfer is 5 to 45 degrees relative to the vertical surface. At least one of the first and second inclined surfaces is a convex arc surface, allowing the liquid processing material to decelerate and then accelerate before falling onto the inclined surface; vent grooves are evenly distributed on the bonding strip, and when the bonding strips of two casting sheets are bonded together, the corresponding vent grooves form an exhaust hole to discharge the gas generated during the molding process; the bonding strip is also provided with fixing holes for the locking mechanism to pass through; and positioning holes are provided on the bonding strip for positioning pins to pass through. The polishing pad material comprises a cast polyurethane polymer formed by the reaction of a prepolymer.
2. A method for processing a polishing pad, characterized in that, The molding process using the polishing pad as described in claim 1 includes the following steps: S1. Making polishing pad processing materials; S2. Heat the polishing pad casting mold to 50-70 degrees Celsius; S3. Pour the polishing pad processing material into the inner groove of the polishing pad forming mold; S4. The polishing pad material is vulcanized in the polishing pad casting mold to form a solid, thus completing the processing.
3. The polishing pad processing method according to claim 2, characterized in that, In step S2, the polishing pad casting mold is heated to 50-70 degrees Celsius and left to stand for 10-20 minutes.
4. The polishing pad processing method according to claim 2, characterized in that, Step S3 includes: S31. Place the pouring pipe at the pouring point where the inner groove of the polishing pad is generated; S32. The polishing pad material is poured into the polishing pad casting mold along the pouring point through the pouring pipe. S33. Remove the pouring pipe; S34. The polishing pad of the casting mold is formed by covering the polishing pad with the hole cover to create an inner groove.
5. The polishing pad processing method according to claim 2, characterized in that, Step S1 includes: S11. Mix the prepolymer and microsphere filler evenly to form an intermediate material; S12. Place the intermediate material into the casting machine tank and stir it at a uniform speed; S13. Place the curing agent in the casting machine tank and stir at a uniform speed; S14. Mix the intermediate material with the curing agent to form a polishing pad processing material.
6. A polishing pad, characterized in that, The polishing pad is manufactured by the polishing pad processing method according to any one of claims 2 to 5.