A CMP polishing pad for improving polishing flatness and its preparation process

Abstract

The present invention discloses a CMP polishing pad for improving polishing flatness and its preparation process, belonging to the technical field of CMP polishing. A CMP polishing pad for improving polishing flatness includes a hard polishing layer and a soft polishing layer. A plurality of inner pad ring supports are arranged between the hard polishing layer and the soft polishing layer, and the inner pad ring supports are distributed in a circular array on the surface of the soft polishing layer. The soft polishing layer can shrink and assist when the upper hard polishing layer is affected by pressure. To solve the problem that in the existing CMP polishing, the particles generated by friction on the surface of the object and the polishing pad during polishing will also mix into the liquid. Once the liquid flow rate is limited and the impurities cannot be effectively discharged, it will affect the subsequent surface polishing accuracy. The polishing liquid generated during the friction polishing process between the wafer and the hard polishing layer will enter the liquid guiding holes, and finally be discharged from the drainage flow grooves at the bottom after being filtered by the soft polishing layer.

Description

Technical Field

[0001] The present invention relates to the field of CMP polishing technology, and specifically provides a CMP polishing pad for improving polishing flatness and its preparation process. Background Art

[0002] The CMP technology is a process in which the surface of the material to be polished reaches the required flatness under the combined action of chemistry and mechanics. The chemical components in the polishing liquid react with the material surface to form a softening layer that is easy to polish. The abrasive particles in the polishing pad and the polishing liquid perform physical and mechanical polishing on the material surface to remove the softening layer. The polishing head presses the surface of the wafer to be polished against the rough polishing pad, and global planarization is achieved through the coupling of polishing liquid corrosion, particle friction, and polishing pad friction.

[0003] In the existing CMP polishing process, the polishing liquid flows through the texture structure on the surface of the polishing pad. However, during polishing, particles generated by friction between the object and the polishing pad surface will also mix into the liquid. Once the liquid flow rate is limited and impurities cannot be effectively discharged, it will affect the subsequent surface polishing accuracy. Summary of the Invention

[0004] The purpose of the present invention is to provide a CMP polishing pad for improving polishing flatness and its preparation process. The polishing liquid generated during the friction polishing process between the wafer and the hard polishing layer will enter the liquid guiding holes, and finally be discharged from the drainage flow grooves at the bottom after being filtered by the soft polishing layer, which can solve the problems in the prior art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A CMP polishing pad for improving polishing flatness, including a hard polishing layer and a soft polishing layer. A plurality of inner pad supports are arranged between the hard polishing layer and the soft polishing layer. The inner pad supports are distributed in a circular array on the surface of the soft polishing layer. The soft polishing layer can contract and assist when the upper hard polishing layer is affected by pressure, which can effectively avoid excessive wear between the hard polishing layer and the wafer. The inner pad supports can play an auxiliary supporting role to ensure the flatness of the hard polishing layer and prevent the soft polishing layer from collapsing under the influence of long-term pressure;

[0006] A wafer is arranged above the hard polishing layer, and a pressure carrier is arranged above the wafer. Among them, the pressure carrier is in contact with the wafer.

[0007] Further, a fine polishing mesh surface is provided on the outer surface of the hard polishing layer. Among them, cross-grid grooves are provided on the outer surface of the fine polishing mesh surface, and the cross-grid grooves extend to the outer edge of the hard polishing layer. A plurality of locking buckle grooves are provided on the outside of the hard polishing layer. The polishing pad structure can be fixed above the polishing table by using the locking buckle grooves. The cross-grid grooves are responsible for transporting and containing the polishing liquid. During the polishing process, the polishing liquid can flow through the cross-grid grooves, so as to transport the polishing liquid between the wafer and the fine polishing mesh surface.

[0008] Further, a retaining ring is provided between the cross-grid grooves. The retaining ring and the hard polishing layer adopt an integral molding process. Liquid guiding holes are provided inside the retaining ring. An internal pressure groove is provided below each liquid guiding hole. The inner pad ring support is installed inside the internal pressure groove. The liquid guiding holes and the internal pressure grooves communicate with each other. The retaining ring is set as a convex structure. The convexity of the retaining ring can prevent the polishing liquid from entering the liquid guiding holes when flowing at non-polishing gaps.

[0009] Further, a plastic cover surface is provided on the outer surface of the soft polishing layer. A plurality of integral hole columns are provided on the outer surface of the plastic cover surface. Among them, the hole columns are distributed in a circular array. The inside of the soft polishing layer is set as an irregular pore structure. The plastic cover surface thermally seals the pores in the surface area of the soft polishing layer, so as to prevent the polishing liquid from directly entering the pores inside the soft polishing layer after penetrating the hard polishing layer. The pore design is retained in the internal space of the hole columns. The irregular pore structure can absorb the polishing liquid and preliminarily filter it at the same time. The pore structure adsorbs the impurity particle structure generated by polishing in the polishing liquid. The particle size of these polishing impurities is larger than that of the polishing liquid particles.

[0010] Further, an inner ring hole is provided on the inner side of the inner pad ring support. The inner pad ring support is installed on the outside of the hole column through the inner ring hole. An enclosing bladder cavity and a central bladder cavity are provided inside the inner pad ring support. Among them, the enclosing bladder cavity is distributed around the central bladder cavity. Both the enclosing bladder cavity and the central bladder cavity are vacuum-sealed structures. The compressive capacity of the inner pad ring support can be improved through the enclosing bladder cavity and the central bladder cavity. At the same time, the deformation operation of the inner pad ring support under pressure can also be realized.

[0011] Further, a connecting rib partition is provided between the enclosing bladder cavity and the central bladder cavity. The connecting rib partition and the inner pad ring support adopt an integral molding process. The connecting rib partition divides the inside of the inner pad ring support into five independent space regions.

[0012] Further, the bottom of the hard polishing layer is attached to the plastic cover surface on the surface of the soft polishing layer. Among them, the hole column extends into the internal pressure groove. The upper and lower sides of the inner pad ring support are respectively attached to the hard polishing layer and the soft polishing layer.

[0013] Furthermore, a filter storage tank is provided inside the pore column, and the filter storage tank corresponds to the liquid guide hole. Part of the polishing liquid is introduced into the filter storage tank through the liquid guide hole, so that a large amount of polishing liquid can be avoided from accumulating on the surface of the hard polishing layer.

[0014] Furthermore, a drainage trough is provided at the bottom of the soft polishing layer, and the drainage trough extends through and extends to the outer edge of the soft polishing layer. With the help of the drainage trough, part of the polishing liquid absorbed by the soft polishing layer can be discharged under pressure, thereby realizing recycling.

[0015] A preparation process of a CMP polishing pad with improved polishing flatness comprises the following steps:

[0016] Step 1: Align the inner ring hole inside the inner pad ring support with the hole column on the surface of the soft polishing layer;

[0017] Step 2: After the inner ring support is installed, the hard polishing layer is pressed on the top of the soft polishing layer so that the inner ring support is embedded in the inner pressure groove at the bottom;

[0018] Step 3: Place the assembled polishing pad structure on the polishing table and use the locking grooves around it to lock and fix it. The wafer is pressed and adhered to the surface of the hard polishing layer by the pressure carrier.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. In the present invention, the interior of the soft polishing layer is set to an irregular pore structure, and the plastic cover is used to heat-seal the pores in the surface area of ​​the soft polishing layer, so that the polishing liquid can be prevented from directly entering the pores inside the soft polishing layer after penetrating the hard polishing layer. The pore design is retained in the internal space of the pore column. The irregular pore structure can be used to initially filter the polishing liquid while absorbing it, and the impurity particle structure generated by polishing in the polishing liquid is adsorbed by the pores. The particle size of these polishing impurities is larger than that of the polishing liquid particles. In this way, most of the impurity particles can be trapped inside the soft polishing layer, and the filtered polishing liquid can be directly recycled for secondary use. After the polishing operation is completed, the soft polishing layer only needs to be disassembled, cleaned or replaced;

[0021] 2. In the present invention, the retaining ring is configured as a convex structure, and the convexity of the retaining ring can prevent the polishing liquid from entering the liquid guide hole when flowing in the non-polishing gap. The inner pad ring support will deform when squeezed, and the deformed inner pad ring support can squeeze the hole column. At this time, the inner diameter of the filter storage tank inside the hole column is reduced under the influence of pressure. At the same time, the retaining ring in the contact area between the wafer and the hard polishing layer will also shrink under the action of pressure. At this time, the polishing liquid generated by the wafer and the hard polishing layer during the friction polishing process will enter the liquid guide hole, and then enter the filter storage tank through the liquid guide hole, and finally be discharged from the drainage trough at the bottom after being filtered by the soft polishing layer;

[0022] 3. In the present invention, the soft polishing layer can assist in shrinking when the upper hard polishing layer is affected by pressure, which can effectively avoid excessive wear between the hard polishing layer and the wafer. The inner pad ring support can play a role in auxiliary support to ensure the flatness of the hard polishing layer and prevent the soft polishing layer from collapsing under the influence of long-term pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the overall front view of the present invention;

[0024] Figure 2 is the schematic structural view of the hard polishing layer of the present invention;

[0025] Figure 3 is the schematic view of the overall exploded structure of the present invention;

[0026] Figure 4 is the schematic structural view of the inner pad ring support of the present invention;

[0027] Figure 5 is the schematic cross-sectional structural view of the inner pad ring support of the present invention;

[0028] Figure 6 is the schematic cross-sectional structural view of the whole of the present invention;

[0029] Figure 7 is Figure 6 the enlarged structural view of part A of

[0030] Figure 8 is Figure 7 the schematic structural view of the extrusion state of A-1 of

[0031] Figure 9 is the schematic structural view of the soft polishing layer of the present invention.

[0032] In the figure: 1. Hard polishing layer; 2. Soft polishing layer; 3. Inner pad ring support; 4. Wafer; 5. Pressure carrier; 101. Fine polishing mesh surface; 102. Cross grid grooves; 103. Retaining ring; 104. Inner pressure groove; 105. Locking buckle groove; 1031. Liquid guiding hole; 201. Drainage flow groove; 202. Hole column; 203. Plastic cover; 2021. Storage and filtration groove; 301. Inner ring hole; 302. Surrounding capsule cavity; 303. Connecting rib partition; 304. Central capsule cavity. DETAILED DESCRIPTION OF THE INVENTION

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] To solve the problem that the existing polishing pad is extruded for a long time during the polishing process, resulting in uneven depressions on the surface of the polishing pad and thus affecting the polishing efficiency; please refer to Figures 1-7 , the following technical solutions are provided in this embodiment:

[0035] A CMP polishing pad for improving polishing flatness includes a hard polishing layer 1 and a soft polishing layer 2 provided with a plurality of inner pad ring supports 3 between the hard polishing layer 1. During the process of contact friction between the hard polishing layer 1 and the wafer 4, polishing processing can be performed on the wafer 4. Among them, the inner pad ring supports 3 are distributed in a circular array on the surface of the soft polishing layer 2. The soft polishing layer 2 can contract and assist when the upper hard polishing layer 1 is affected by pressure, so as to effectively avoid excessive wear between the hard polishing layer 1 and the wafer 4. The inner pad ring supports 3 can play a role in auxiliary support to ensure the flatness of the hard polishing layer and prevent the soft polishing layer 2 from collapsing under the influence of long-term pressure.

[0036] In addition, a fine polishing mesh surface 101 is provided on the outer surface of the hard polishing layer 1. Among them, a cross grid groove 102 is provided on the outer surface of the fine polishing mesh surface 101, and the cross grid groove 102 extends to the outer edge of the hard polishing layer 1. The cross grid groove 102 is responsible for transporting and accommodating the polishing liquid. During the polishing process, the polishing liquid can flow through the cross grid groove 102, so as to transport the polishing liquid between the wafer 4 and the fine polishing mesh surface 101.

[0037] Specifically, a plurality of locking buckle grooves 105 are provided on the outer side of the hard polishing layer 1, and a retaining ring 103 is provided in the space between the cross grid grooves 102. The retaining ring 103 and the hard polishing layer 1 are made by an integral molding process, and the locking operation between the polishing pad and the polishing table can be realized through the locking buckle grooves 105.

[0038] Specifically, a liquid guiding hole 1031 is provided inside the retaining ring 103, and an internal pressure groove 104 is provided below each liquid guiding hole 1031. The inner pad ring support 3 is installed inside the internal pressure groove 104. The liquid guiding hole 1031 and the internal pressure groove 104 are mutually communicated. The retaining ring 103 is set as a convex structure, and the convexity of the retaining ring 103 can prevent the polishing liquid from entering the liquid guiding hole 1031 when flowing at the non-polishing gap.

[0039] To solve the problem that in the existing CMP polishing, particles generated by friction on the surface of the object and the polishing pad will also mix into the liquid during polishing. Once the liquid flow rate is limited and impurities cannot be effectively discharged, it will affect the subsequent surface polishing accuracy. Please refer to Figures 4-9 , the following technical solutions are provided in this embodiment:

[0040] In this embodiment, a plastic cover 203 is provided on the outer surface of the soft polishing layer 2. A plurality of integral hole columns 202 are provided on the outer surface of the plastic cover 203. The inside of the soft polishing layer 2 is set as an irregular pore structure. The plastic cover 203 thermally seals the pores in the surface area of the soft polishing layer 2, which can prevent the polishing liquid from directly entering the internal pores of the soft polishing layer after penetrating the hard polishing layer 1. The internal space of the hole column 202 retains the pore design. The irregular pore structure can absorb the polishing liquid and preliminarily filter it at the same time, and use the pores to adsorb the impurity particle structure generated by polishing in the polishing liquid. The particle size of these polishing impurities is larger than that of the polishing liquid particles, so that most of the impurity particles can be intercepted inside the soft polishing layer 2. The filtered polishing liquid can be directly recycled for the second time. After the polishing operation is completed, only the soft polishing layer 2 needs to be disassembled, cleaned or replaced.

[0041] In addition, an inner ring hole 301 is provided on the inner side of the inner pad ring support 3. The inner pad ring support 3 is installed on the outer side of the hole column 202 through the inner ring hole 301. The inner pad ring support 3 will deform when being squeezed. The deformed inner pad ring support 3 can squeeze the hole column 202. At this time, the inner diameter of the storage filter groove 2021 inside the hole column 202 is reduced under the influence of pressure.

[0042] Specifically, an enclosing bladder cavity 302 and a central bladder cavity 304 are provided inside the inner pad ring support 3. A connecting rib partition 303 is provided between the enclosing bladder cavity 302 and the central bladder cavity 304. The connecting rib partition 303 and the inner pad ring support 3 are made by an integral molding process. The compressive capacity of the inner pad ring support 3 can be improved through the enclosing bladder cavity 302 and the central bladder cavity 304, and at the same time, the deformation operation of the inner pad ring support 3 under pressure can be realized.

[0043] Specifically, the bottom of the hard polishing layer 1 is attached to the plastic cover 203 on the surface of the soft polishing layer 2. Among them, the hole column 202 extends into the inner pressure groove 104. The upper and lower sides of the inner pad ring support 3 are respectively attached to the hard polishing layer 1 and the soft polishing layer 2. A storage filter groove 2021 is provided inside the hole column 202. The storage filter groove 2021 corresponds to the liquid guiding hole 1031. With the help of the liquid guiding hole 1031, the polishing liquid remaining on the surface of the hard polishing layer 1 can be downwardly introduced into the storage filter groove 2021.

[0044] Specifically, a liquid drainage groove 201 is provided at the bottom of the soft polishing layer 2. The liquid drainage groove 201 extends through to the outer edge of the soft polishing layer 2. The design of the liquid drainage groove 201 is conducive to discharging the polishing liquid inside the soft polishing layer 2 from the bottom.

[0045] Working principle: Align the inner ring hole 301 inside the inner pad ring support 3 with the hole column 202 on the surface of the soft polishing layer 2 for sleeving. After the inner pad ring support 3 is installed, press-fit the hard polishing layer 1 above the soft polishing layer 2, so that the inner pad ring support 3 is embedded into the inner pressure groove 104 at the bottom. Place the assembled polishing pad structure on the polishing table and lock and fix it using the locking buckle grooves 105 around. The wafer 4 is pressed and adhered to the surface of the hard polishing layer 1 through the pressure carrier 5. The inside of the soft polishing layer 2 is set as an irregular pore structure. The plastic cover 203 thermally seals the pores in the surface area of the soft polishing layer 2, which can prevent the polishing liquid from directly entering the internal pores of the soft polishing layer 2 after penetrating the hard polishing layer 1. The internal space of the hole column 202 retains the pore design. Through the irregular pore structure, the polishing liquid can be absorbed and preliminarily filtered at the same time. The pore structure adsorbs the impurity particle structure generated by polishing in the polishing liquid. The particle size of these polishing impurities is larger than that of the polishing liquid particles, so that most of the impurity particles can be intercepted inside the soft polishing layer 2. The filtered polishing liquid can be directly recycled. After the polishing operation is completed, only the soft polishing layer 2 needs to be disassembled, cleaned or replaced.

[0046] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprises", "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device.

[0047] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention.

Claims

1. A CMP polishing pad for improving polishing flatness, characterized in that: It comprises a hard polishing layer (1) and a soft polishing layer (2), wherein a plurality of inner ring supports (3) are arranged between the hard polishing layer (1) and the soft polishing layer (2), and the inner ring supports (3) are distributed in a ring array on the surface of the soft polishing layer (2); The outer surface of the soft polishing layer (2) is provided with a plastic cover (203), the outer surface of the plastic cover (203) is provided with a plurality of integrated pore columns (202), and the interior of the soft polishing layer (2) is provided with an irregular pore structure; An inner ring hole (301) is provided on the inner side of the inner ring support (3), and the inner ring support (3) is installed on the outer side of the hole column (202) through the inner ring hole (301). A surrounding cavity (302) and a central cavity (304) are provided inside the inner ring support (3).

2. A CMP polishing pad for improving polishing flatness according to claim 1, characterized in that: The outer surface of the hard polishing layer (1) is provided with a fine polishing mesh surface (101), wherein the outer surface of the fine polishing mesh surface (101) is provided with a cross-shaped groove (102), the cross-shaped groove (102) extends to the outer edge of the hard polishing layer (1), and the outer side of the hard polishing layer (1) is provided with a plurality of locking buckle grooves (105).

3. A CMP polishing pad for improving polishing flatness according to claim 2, characterized in that: A retaining ring (103) is arranged between the cross-shaped grooves (102); the retaining ring (103) and the hard polishing layer (1) are formed by an integral molding process; a liquid guide hole (1031) is arranged inside the retaining ring (103); an internal pressure groove (104) is arranged below each liquid guide hole (1031); the inner pad ring support (3) is installed inside the internal pressure groove (104); and the liquid guide hole (1031) and the internal pressure groove (104) are interconnected.

4. A CMP polishing pad for improving polishing flatness according to claim 3, characterized in that: A connecting rib partition (303) is provided between the surrounding cavity (302) and the central cavity (304), and the connecting rib partition (303) and the inner cushion ring support (3) are formed in one piece.

5. A CMP polishing pad for improving polishing flatness according to claim 4, characterized in that: The bottom of the hard polishing layer (1) is bonded to the plastic cover (203) on the surface of the soft polishing layer (2), wherein the hole column (202) extends to the inside of the internal pressure groove (104), and the upper and lower sides of the inner pad ring support (3) are respectively bonded to the hard polishing layer (1) and the soft polishing layer (2).

6. A CMP polishing pad for improving polishing flatness according to claim 5, characterized in that: A filter storage tank (2021) is provided inside the pore column (202), and the filter storage tank (2021) corresponds to the liquid guide hole (1031).

7. A CMP polishing pad for improving polishing flatness according to claim 6, characterized in that: A drainage trough (201) is provided at the bottom of the soft polishing layer (2), and the drainage trough (201) extends through and to the outer edge of the soft polishing layer (2).

8. A process for preparing a CMP polishing pad with improved polishing flatness, based on the CMP polishing pad with improved polishing flatness according to claim 7, characterized in that: The steps include: Step 1: Align the inner ring hole (301) inside the inner pad ring support (3) with the hole column (202) on the surface of the soft polishing layer (2) for installation; Step 2: After the inner ring support (3) is installed, the hard polishing layer (1) is pressed onto the soft polishing layer (2) so that the inner ring support (3) is embedded into the inner pressure groove (104) at the bottom; Step 3: Place the assembled polishing pad structure on the polishing table and use the locking buckle grooves (105) around it to lock and fix it.

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