Polishing pad with adjusted elastic recovery force and manufacturing method thereof

Abstract

The present invention relates to a polishing pad with an adjustable elastic restoring force and a method for manufacturing the same. The polishing pad according to the present invention comprises a polishing layer for polishing a wafer surface; and a support layer attached to the lower surface of the polishing layer to support the polishing layer, wherein a plurality of through holes are formed in the support layer for fine adjustment of the elastic restoring force.

Description

Technology Field

[0001] The present invention relates to a polishing pad and a method for manufacturing the same, and more specifically, to a polishing pad with adjusted elastic recovery force and a method for manufacturing the same. Background Technology

[0002] Chemical Mechanical Polishing (CMP) refers to a semiconductor process that flattens a wafer using chemical reactions and mechanical force. As high-performance semiconductor chips require more layers to be deposited and finer circuits to be etched onto the wafer, the CMP PAD, or polishing pad, plays an important role in the CMP process, which is used for the purpose of wide-area flattening of the wafer.

[0003] Generally, a polishing pad consists of a polishing layer that comes into direct contact with the wafer and a support layer that supports the polishing layer from underneath.

[0004] In the CMP process, the removal rate (RR) and uniformity of the wafer are important. The polishing layer (i.e., the top pad) comes into direct contact with the wafer and plays a major role in the removal rate, while the support layer (bottom pad) plays a major role in the uniformity of the wafer.

[0005] In other words, the abrasive layer is a high-hardness material composed of polyurethane or similar substances, and as the area where the wafer directly contacts and polishing takes place, it directly affects the amount of polishing (RR) because it is the section where the wafer, slurry, and conditioner work.

[0006] The support layer receives the strong force acting during the polishing process and disperses the force during CMP operation, thereby performing the function of minimizing damage to the wafer.

[0007] To perform this function, a material having a predetermined compressive modulus may be selected for the support layer.

[0008] In other words, the support layer must be configured to have appropriate elastic restoring force.

[0009] For reference, elastic recovery force can be briefly explained as the ability of a material to return to its original shape after the deformation or stress applied from the outside is removed.

[0010] Simply put, it refers to the property of a material to return to its original shape or size when force or stress is removed after it has been deformed.

[0011] This is one of the properties primarily used to represent elasticity. Elasticity refers to the ability of a material to return to its original state after temporarily changing shape in response to an external force. Since elastic recovery indicates how effectively deformation is removed even after the material's elastic limit, it plays an important role in material engineering and design.

[0012] Generally, elastic restoring force is evaluated by measuring deformation after applying a load and observing how quickly the material returns to its initial state after removing the load; it is considered an important material property that provides information for predicting the quality, durability, and performance in the operating environment of a material.

[0013] As such, the elastic recovery force of the support layer is determined by the compressive elasticity of the support layer, and wafer uniformity control is possible during the CMP process depending on this compressive elasticity of the support layer.

[0014] However, the support layer has a planar shape and controls the compressive modulus by adjusting its own hardness through the selection of an appropriate material, but this presents a problem in that fine-tuning of the compressive modulus is difficult.

[0015] However, the restoring force due to the compressive modulus of the support layer affects the RR and uniformity of the wafer according to the ratio of the restoring force that restores the shape of the PAD to its original state when a wafer with a constant load and rotational speed (rotation) rotates once during the rotation (revolution) process of the PAD, depending on the rotational speed of the Platen (PAD).

[0016] In this case, if the support layer is strong, it may be advantageous for RR, but the flatness-related uniformity may decrease; conversely, if the support layer is too weak, the edge or center may be excessively polished depending on the minute location of the wafer pressure load during the CMP operation, which causes a decrease in product quality and yield.

[0017] Currently, bottom pads used in the market utilize pads made of non-woven fabric impregnated with polyurethane (SUBA Type), polyurethane foam pads (Poron foam), or low-hardness urethane pads; however, all of these have limitations in changing the hardness of the bottom pad and consequently, there is a problem in that the compressive modulus cannot be finely adjusted.

[0018] In other words, the reality is that it is difficult to make adjustments other than the intrinsic properties (elastic recovery force) of the support layer, and finely controlling these intrinsic properties is also difficult due to the interplay with material selection. Prior art literature

[0019] Published Patent No. 10-1598556 The problem to be solved

[0020] Accordingly, the present invention has been devised to solve the aforementioned conventional problems, and its purpose is to provide a polishing pad that finely adjusts the magnitude of elastic restoring force even under the same material, and a method for manufacturing the same. means of solving the problem

[0021] To achieve the above objective, the polishing pad according to the present invention comprises a polishing layer for polishing a wafer surface; and a support layer attached to the lower surface of the polishing layer to support the polishing layer, wherein a plurality of through holes for fine adjustment of elastic restoring force may be formed in the support layer.

[0022] In addition, to achieve the above-mentioned purpose, the polishing pad according to the present invention comprises a polishing layer for polishing a wafer surface; and a support layer attached to the lower surface of the polishing layer to support the polishing layer, wherein at least one groove may be formed on the upper surface of the support layer for fine adjustment of elastic restoring force.

[0023] In addition, to achieve the above-mentioned purpose, the method for manufacturing a polishing pad according to the present invention may include the steps of: identifying the type of wafer; placing a support layer that supports the polishing layer and has a plurality of through holes formed corresponding to the type of wafer to be polished; applying or attaching an adhesive layer on the support layer; and placing a polishing layer for polishing the wafer on the adhesive layer.

[0024] In addition, to achieve the above-mentioned purpose, the method for manufacturing a polishing pad according to the present invention may include the steps of: identifying the type of wafer; placing a support layer that supports the polishing layer and has a plurality of grooves formed corresponding to the type of wafer to be polished; applying or attaching an adhesive layer on the support layer; and placing a polishing layer for polishing the wafer on the adhesive layer. Effects of the invention

[0025] As explained above, according to the present invention, by adjusting the hole size or the width / depth / pitch of the groove formed in the support layer, the density can be varied to provide a compressive modulus suitable for the wafer condition. Brief explanation of the drawing

[0026] FIG. 1 is a schematic diagram of an overall CMP device including a polishing pad according to one embodiment of the present invention, and FIG. 2 is a configuration diagram of the polishing pad of FIG. 1, and FIGS. 3 and 4 are configuration diagrams of a conventional polishing pad, and FIGS. 5 to 9 are configuration diagrams of a polishing pad according to an embodiment of the present invention, and FIGS. 10 to 14 are diagrams showing the configuration of a polishing pad according to another embodiment of the present invention. Specific details for implementing the invention

[0027] The present invention will be described in detail below with reference to the attached drawings.

[0028] The following embodiments according to the present invention are merely examples to aid in understanding the invention, and the present invention is not limited to these embodiments. In particular, the present invention may be composed of a combination of at least one of the individual components, individual functions, or individual steps included in each embodiment.

[0029] In particular, for convenience, some claims in the scope of claims have included alphabets such as '(a)', but these alphabets do not define the order of each step.

[0030] A schematic configuration of a Chemical Mechanical Polishing (CMP) device including a polishing pad (1) according to one embodiment of the present invention is as shown in FIG. 1.

[0031] As shown in FIG. 1, in a CMP device, after fixing a polishing pad (1) to a rotatable support disk called a platen, a semiconductor wafer is mounted on a planetary disk called a polishing head.

[0032] At this time, by the mutual rotational movement of the platen and the disk, a polishing slurry in which fine particles (polishing particles) are suspended is injected into the gap between the polishing pad (1) and the semiconductor wafer, thereby polishing and flattening the semiconductor wafer.

[0033] When the wafer surface rotates on the polishing pad (1), the polishing slurry particles are pressed and adhered to the wafer surface at the contact point, so the processing surface is polished by the dynamic frictional action between the wafer surface and the polishing slurry particles, and this polishing process is called CMP polishing.

[0034] An example of the specific configuration of the polishing pad (1) according to the present embodiment is as shown in FIG. 2.

[0035] As illustrated in the drawing, a polishing pad (1) according to one embodiment of the present invention may be composed of a polishing layer (100), an adhesive layer (200), a support layer (300), and an attachment layer (400). FIG. 2 illustrates the components constituting the polishing pad (1) according to the present invention, and a more detailed description of the shape of each component will be provided later.

[0036] Here, the polishing layer (100) performs the function of polishing the surface of the semiconductor wafer by coming into direct contact with the semiconductor wafer as shown in FIG. 1, and a groove (110) may be formed on its upper surface to facilitate the movement of the slurry.

[0037] In the CMP process, uniform polishing is possible only when the slurry is evenly distributed on the pad surface, and the groove (110) formed in the polishing layer (100) performs the function of spreading the slurry evenly.

[0038] In other words, if the slurry accumulates in one place or there is a shortage of it, the uniformity of the polishing may be reduced, but thanks to the groove (110) formed on the upper surface of the polishing layer (100), the slurry can flow smoothly across the entire pad.

[0039] In addition, when material on the wafer surface is removed during the polishing process, the particles remain in the slurry. However, if there is a groove (110) on the upper surface of the polishing layer (100), the removed particles can be easily discharged together with the slurry, so that the pad does not get clogged, and as a result, the pad lifespan is extended and the polishing quality can be improved.

[0040] Furthermore, when polishing, a thin water film formed by a slurry is generated between the wafer and the pad. If there is no groove (110) on the upper surface of the polishing layer (100), the water film becomes thicker and the polishing efficiency decreases. However, the thickness of the water film is maintained at a constant height due to the shape of the groove (110), so that accurate polishing can be achieved.

[0041] In particular, the CMP pad gradually wears down over time, and if it does not wear evenly with respect to the wafer surface due to the amount of pad wear, the uniformity of polishing decreases. However, if a groove (110) is formed on the upper surface of the polishing layer (100), the surface of the pad wears down uniformly, allowing the pad to be used for a longer lifespan, and there is also an advantage that uniform regeneration is possible, especially during the conditioning process.

[0042] As described above, the groove (110) on the upper surface of the polishing layer (100) that performs various functions can be formed in various patterns such as straight grooves, spiral grooves, grid grooves, and circular grooves. Forming the groove (110) on the upper surface of the polishing layer (100) in this manner is a known technique and is not a feature unique to the present invention.

[0043] The adhesive layer (200) performs the function of firmly bonding the polishing layer (100) and the support layer (300) to each other.

[0044] For example, the adhesive layer (200) may be composed of a hot melt tape, wherein the hot melt tape is made based on a thermoplastic resin and melts at a certain temperature to strongly bond the polishing layer (100) and the support layer (300).

[0045] As such, the adhesive layer (200) serves to prevent separation between the polishing layer (100) and the support layer (300) during polishing, and the adhesive material may be any known material.

[0046] In this way, when the polishing layer (100) and the support layer (300) are firmly fixed to each other by the adhesive layer (200), the performance of the polishing pad (1) can be maintained consistently.

[0047] Meanwhile, the support layer (300) is attached to the lower surface of the polishing layer (100) and performs the function of supporting the polishing layer (100).

[0048] That is, the support layer (300) is located below the polishing layer (100) and serves to increase the mechanical strength of the pad and mitigate shock, thereby maintaining constant pressure during the polishing of the semiconductor wafer and contributing to extending the lifespan of the polishing pad (1).

[0049] This support layer (300) may be composed of a combination of a high-density polymer or soft polyurethane.

[0050] The reason the polishing pad (1) is configured to include a polishing layer (100) and a support layer (300) in this manner is due to reasons such as maintaining polishing uniformity, securing mechanical strength, and extending the lifespan of the polishing pad (1).

[0051] If only the polishing layer (100) is present, the pressure distribution under load is not uniform, which may result in uneven polishing. Also, if the polishing layer (100) is too flexible, the pad may easily deform, so a support layer (300) is required to prevent this.

[0052] In particular, the pad wears out during the polishing process, but if there is a support layer (300), the wear resistance of the polishing layer (100) is increased, so that the usage time can be extended.

[0053] A separate cushion layer may be added between the polishing layer (100) and the support layer (300).

[0054] A feature that differs from the conventional feature in this embodiment is that a plurality of through holes (310) are formed in this support layer (300).

[0055] That is, the support layer (300) can be formed from a specific material as previously described, but in this embodiment, a plurality of through holes (310) are formed to finely adjust the elastic restoring force of the support layer (300).

[0056] The through holes (310) formed in the support layer (300) may be formed along a plurality of virtual concentric circles.

[0057] In another embodiment, a plurality of grooves (320) may be formed in the support layer (300) for fine adjustment of the elastic restoring force.

[0058] That is, the groove (320) formed in the support layer (300) is formed to adjust the elastic restoring force of the support layer (300), and performs a completely different function from that formed in the polishing layer (100).

[0059] Meanwhile, an attachment layer (400) may be formed on the lower part of the support layer (300).

[0060] The attachment layer (400) performs the function of allowing the polishing pad (1) to be attached to the platen, and may be made of, for example, Removal Tape.

[0061] That is, the polishing pad (1) is attached to the polishing equipment (polishing head), and when removing it after use, it can be easily removed if this removal tape is present.

[0062] This attachment layer (400) can be made to adhere strongly during polishing work but be cleanly separated when removed by using a special adhesive layer (200). Since the material or physical properties of the attachment layer (400) correspond to known technology, a more detailed description is omitted.

[0063] Below, the structure of a conventional polishing pad (1) and a polishing pad (1) according to various embodiments of the present invention will be compared and explained by illustrating their surfaces and cross-sections.

[0064] First, FIG. 3 shows an example of a cross-sectional view of a conventional polishing pad (1').

[0065] As illustrated in the drawing, a conventional polishing pad (1') is composed of a polishing layer (10), an adhesive layer (20), a support layer (30), and an attachment layer (40), wherein a plurality of grooves (11) are formed on the upper surface of the polishing layer (10) as illustrated.

[0066] FIG. 4 shows a cross-sectional view of the polishing pad (1') corresponding to the surface condition of the polishing layer (10) and the support layer (30) constituting the conventional polishing pad (1').

[0067] That is, FIG. 4(a) shows the upper surface of the polishing layer (10) of the polishing pad (1'), FIG. 4(c) shows the upper surface of the support layer (30) of the polishing pad (1') (i.e., the surface attached to the lower surface of the polishing layer (10)), and FIG. 4(b) shows a vertical cross-sectional view of the polishing pad (1').

[0068] In this way, conventionally, a groove (11) is formed in the polishing layer (10) of the polishing pad (1'), but no hole or groove is formed in the support layer (30).

[0069] In contrast, a polishing pad (1) according to one embodiment of the present invention has a plurality of through holes (310) (i.e., holes) formed in the support layer (300) for fine adjustment of elastic restoring force, as shown in FIGS. 5 to 9.

[0070] First, in FIG. 5, it can be seen that through holes (310) are evenly formed across the entire surface of the support layer (300).

[0071] FIG. 6 shows an example in which through holes (310) are formed along virtual concentric circles on the upper surface of a support layer (300), in particular, an example in which more virtual concentric circles (i.e., concentric circles that serve as the standard for forming through holes (310)) are densely packed as they go toward the center of the support layer (300).

[0072] FIG. 7 shows an example in which fewer virtual concentric circles are densely packed from the middle part of the support layer (300) toward the center or toward the outside, and FIG. 8 shows an example in which more virtual concentric circles are densely packed from the middle part of the support layer (300) toward the center or toward the outside.

[0073] Finally, Fig. 9 shows an example in which more virtual concentric circles are densely packed from the center of the support layer (300) outward.

[0074] A polishing pad (1) according to another embodiment of the present invention is illustrated in FIGS. 10 through 14.

[0075] In these drawings, unlike the previous embodiment, a through hole (310) is not formed in the support layer (300), but rather at least one groove (320) (indented groove) is formed.

[0076] First, looking at FIG. 10, it can be seen that a plurality of grooves (320) are formed in a concentric shape on the upper surface of the support layer (300) of the polishing pad (1) (i.e., the surface that is attached to the lower surface of the polishing layer (100) through the adhesive layer (200)). At this time, the spacing between the concentric circles is the same.

[0077] Next, looking at FIG. 11, it can be seen that a plurality of grooves (320) are formed in a concentric shape on the upper surface of the support layer (300) of the polishing pad (1), and the spacing of the concentric circles decreases as they go from the center of the support layer (300) outward.

[0078] In contrast to Fig. 11, Fig. 12 shows that the spacing of the concentric circles of the groove (320) formed on the upper surface of the support layer (300) of the polishing pad (1) increases from the center of the support layer (300) outward.

[0079] FIG. 13 shows an example in which the spacing of the concentric circles of the groove (320) formed on the upper surface of the support layer (300) of the polishing pad (1) decreases as it goes from the middle part of the support layer (300) to the center or to the outside, and FIG. 14 shows an example in which the spacing of the concentric circles of the groove (320) formed on the upper surface of the support layer (300) of the polishing pad (1) increases as it goes from the middle part of the support layer (300) to the center or to the outside.

[0080] In this way, by forming a through hole (310) or a groove (320) in the support layer (300) of the polishing pad (1), it is possible to form a support layer (300) having a compressive elastic modulus relative to the support layer (300) of the same material, and accordingly, the elastic restoring force of the polishing pad (1) can be finely adjusted.

[0081] Meanwhile, when grooves (110) are formed along a plurality of concentric circles on the upper surface of the polishing layer (100), it is preferable that the ratio of the location where the grooves (110) of the polishing layer (100) are formed to the location where the through holes (310) or grooves (320) of the support layer (300) are formed be 70% or less.

[0082] For example, if a groove (320) of the support layer (300) is formed at the same location as a groove (110) formed in the polishing layer (100), the corresponding ratio is 100%, and if a groove (320) of the support layer (300) is formed at a location opposite to the groove (110) formed in the polishing layer (100), the corresponding ratio is 0%, and the ratio must be kept 70% or less.

[0083] An example of a specific method for calculating such a correspondence ratio is to assume that the groove (110) formed in the polishing layer (100) has completely penetrated the polishing layer (100) (also known as the ‘groove (320) hole’), and to first calculate the area where the groove (320) (or through hole (310)) formed in the support layer (300) is visible through the groove (110) hole of the polishing layer (100) that has completely penetrated, and then to secondly calculate the total area of ​​the groove (320) (or through hole (310)) formed in the support layer (300), and then to calculate the correspondence ratio by using the area calculated in the first calculation as the numerator and the area calculated in the second calculation as the denominator.

[0084] This is because if the response ratio exceeds 70%, the stability of the support layer (300) is adversely affected by the influence of the groove (110) formed in the polishing layer (100).

[0085] As a result of repeated experiments, when the response ratio exceeded 70%, the variation in the removal rate (RR) and uniformity of the semiconductor wafer increased by 40% compared to when it did not.

[0086] The polishing pad (1) according to the above-described embodiment is intended to allow the use of a polishing pad (1) in which the elastic recovery force is optimally adjusted according to the type of semiconductor wafer (a concept including the state) as previously described.

[0087] Accordingly, when a semiconductor wafer is selected, after confirming the type of the wafer (a concept including the state), a support layer (300) having a plurality of through holes (310) (or grooves (320)) formed corresponding to the confirmed type of wafer is selected and placed, and after applying or attaching an adhesive layer (200) on the placed support layer (300), a polishing layer (100) for polishing the wafer is placed on the adhesive layer (200), thereby manufacturing an optimal polishing pad (1) that is suitable for the polishing conditions of the selected wafer.

[0088] Of course, at this time, an attachment layer (400) can be formed on the lower surface of the support layer (300).

[0089] In this way, in the polishing pad (1), the size of the hole formed in the support layer (300) or the width / depth / pitch of the groove (320) can be adjusted to change the density and provide a compressive elasticity suitable for the wafer condition.

[0090] Meanwhile, it goes without saying that the process of carrying out each of the above-described embodiments may be performed by a program or application stored on a predetermined recording medium (e.g., computer-readable). Here, the recording medium includes all electronic recording media such as RAM (Random Access Memory), magnetic recording media such as hard disks, optical storage recording media such as CDs (Compact Disks), etc.

[0091] Furthermore, the present invention is not limited to the specific embodiments described above, but can be implemented with various modifications and variations within the scope of the essence of the invention. It will be obvious that such modifications and variations are included in the present invention if they fall within the scope of the appended claims. Explanation of the symbols

[0092] 1 : Polishing pad 100 : Polishing layer 200: Adhesive layer 300: Support layer 400 : Adhesion layer

Claims

Claim 1 A polishing pad comprising a polishing layer for polishing a wafer surface; and a support layer attached to the lower surface of the polishing layer to support the polishing layer, wherein a plurality of through holes are formed in the support layer, the plurality of through holes are formed independently of a groove formed on the upper surface of the polishing layer, and the elastic restoring force is adjusted as the density of the support layer changes due to the formation of the plurality of through holes. Claim 2 A polishing pad according to claim 1, characterized in that the plurality of through holes formed in the support layer are formed along a plurality of imaginary concentric circles. Claim 3 A polishing pad according to claim 1, characterized in that the through holes are formed with different densities depending on the position of the support layer. Claim 4 A method for manufacturing a polishing pad comprising: (a) a step of identifying the type of wafer; (a) a step of placing a support layer that supports the polishing layer and has a plurality of through holes formed corresponding to the type of wafer to be polished; (b) a step of applying or attaching an adhesive layer on the support layer; and (c) a step of placing a polishing layer for polishing the wafer on the adhesive layer, wherein the plurality of through holes are formed independently of a groove formed on the upper surface of the polishing layer, and the elastic restoring force is adjusted as the compressive elastic modulus of the support layer changes by causing a change in the density of the support layer. Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete

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