WAFER POLISHING APPARATUS AND METHOD

Abstract

Wafer polishing device comprising: a housing (111) providing a predetermined pressure space thereunder; a drive ring (112) flatly connected to a lower part of the housing (111), the drive ring (112) having a central part that is vertically variable in shape; a head assembly (110) disposed at a lower portion of the drive ring (112), the head assembly (110) including a wafer mounting member having a lower surface to which a wafer (W) is mounted; a head lifting unit (130) arranged at an upper part of the housing (111) for vertically lifting the head assembly (110) according to a control pressure; a sensor (140) arranged on a central part of the drive ring (112) for measuring a distance of the central part of the drive ring from the housing (111); and an additional head lifting unit (150) arranged on the head lifting unit (130) for adjusting a height of the head assembly (110) according to a distance value measured by the sensor (140) such that the central part of the drive ring (112) is flat during a wafer polishing process.

Description

background

[0001] The present disclosure relates to a wafer polishing apparatus capable of maintaining a drive ring in a flat state and a wafer polishing method.

[0002] Generally, a mirror polishing process is performed in a wafer manufacturing process to improve the planarization of a wafer, and the most important technology among planarization technologies is chemical mechanical polishing (CMP).

[0003] In CMP, a semiconductor wafer is polished in contact with a polishing surface while a suspension, which is a chemical abrasive, is supplied to the polishing surface.

[0004] The polishing apparatus includes a polishing table having a polishing surface provided with a polishing pad, and a pressing head for pressing a semiconductor wafer. When the semiconductor wafer is polished using the polishing apparatus, a predetermined pressure is applied to allow the semiconductor wafer to contact the polishing pad of the polishing table, while the pressing head presses the semiconductor wafer. Here, the polishing table and the pressing head move relatively to allow the semiconductor wafer to contact the polishing surface, so that a surface of the semiconductor wafer is planarized and polished into a mirror surface.

[0005] Japanese Laid-Open Patent Publication No. 2001-105305, published under the application number JP 2001-105305 A, discloses a head assembly structure of a polishing apparatus comprising a housing and a combustible drive ring for forming a pressing chamber in which a predetermined pressure is applied to a lower part of a spindle shaft to lightly support a substrate and adsorb a wafer to a bottom surface thereof through various components arranged below the drive ring.

[0006] The document DE 600 20 759 T2 relates to a polishing device with a tiltable wafer carrier. The wafer carrier is coupled to a drive shaft via a universal coupling, allowing it to be tilted relative to the drive shaft. Tilting of the wafer carrier can be detected by sensors. A pressing force on the wafer carrier is controlled depending on the tilting. The document DE 103 93 369 T5 describes a wafer polishing device. This device comprises a chuck for holding a polishing target material and a retaining ring arranged around the chuck, wherein the retaining ring and the chuck can be oscillated independently of one another. The document DE 11 2009 002 112 B4 describes a polishing head for holding a workpiece to be polished on a rubber foil, as well as a polishing device equipped with the polishing head.

[0007] The Fig. 1A to 1B are views illustrating deformation of a drive ring of a head assembly according to the prior art.

[0008] As in the Fig. 1A and Fig. As shown in Fig. 1B, in the prior art head assembly, a polishing operation is performed while the wafer and the polishing pad rotate in directions opposite to each other after the wafer descends to a polishing pad placed on a carrier plate in a state where the wafer is adsorbed.

[0009] Generally, the polishing pad used for a final polishing process consists of a nap layer and a felt base material pad. As the polishing process progresses, the base material pad and nap layer decrease in thickness.

[0010] The head assembly lowers a set height to allow the wafer to contact the polishing pad, performing the final polishing process. While the drive ring within the head assembly is initially held in a flat shape, the drive ring within the head assembly changes shape as the polishing pad changes thickness.

[0011] When the polishing pad decreases in thickness due to the repeated polishing process, a central part of the drive ring 12 is deformed into a concave shape as shown in Fig. 1A. As a result, a gap may occur between a sleeve and a flange constituting a wafer fixing member 13, and also, a central axis of the wafer fixing member 13 may move horizontally during the polishing process.

[0012] On the other hand, when the polishing pad is newly replaced to increase the thickness, the central part of the drive ring 12 is deformed into a convex shape as shown in Fig. 1B. Consequently, a load can be concentrated in an edge region of the wafer mounting member 13 to increase a polishing height at the edge region of the wafer mounting member 13.

[0013] As described above, in the prior art wafer polishing apparatus, when the polishing pad thickness changes, the drive ring 12 may be deformed to compensate for the wafer fixing part 13. Therefore, it may be difficult to maintain uniform wafer polishing quality, and the polishing performance may also deteriorate. Summary

[0014] Embodiments provide a wafer polishing apparatus capable of detecting deformation of a drive ring to automatically adjust ascending / descending positions of a head assembly, thereby maintaining the drive ring in a flat state, and a wafer polishing method.

[0015] In one embodiment, a wafer polishing apparatus comprises: a housing providing a predetermined pressure space thereunder; a drive ring flatly connected to a lower part of the housing, the drive ring having a central part that is vertically variable in shape; a head assembly disposed at a lower part of the drive ring, the head assembly including a wafer mounting part having a lower surface to which a wafer is attached; a head lifting unit disposed at an upper part of the housing for vertically lifting the head assembly according to a control pressure; a sensor disposed at a central part of the drive ring for measuring a distance of the central part of the drive ring from the housing;and an additional head lifting unit arranged on the head lifting unit for adjusting a height of the head assembly according to a distance value measured by the sensor such that the center part of the drive ring is flat during a wafer polishing process.;

[0016] In another embodiment, a wafer polishing method in which a wafer adsorbed on a head assembly having a wafer fixing portion balanced according to a flat shape of a drive ring is polished using a polishing pad placed on a support plate comprises: a first process of allowing the wafer to contact the polishing pad as the head assembly descends while applying a predetermined pressure thereto; a second process of measuring a shape of the center portion of the drive ring while the wafer is in contact with the polishing pad in the first process; and a third process of adjusting a height of the head assembly such that a shape of the center portion of the drive ring is flat according to a value measured by a sensor. Short description of the drawings Fig. 1A to 1B are views illustrating deformation of a drive ring of a head assembly according to the prior art. Fig. 2 is a view of a wafer polishing apparatus according to an embodiment. Fig. 3 is a view showing a Fig. 2 represents the applied head assembly. Fig. 4 is a view showing a Fig. 2 represents the head lifting unit used. Fig. Fig. 5 is a view showing a sensor for detecting deformation of a drive ring used in Fig. 2 is applied. Fig. 6 is a flowchart of a wafer polishing method according to an embodiment. Detailed description of the embodiments

[0017] Hereinafter, embodiments will be described in detail with reference to the attached drawings. The scope of the concept of the embodiment can be determined from the content disclosed in the embodiment, and the concept of the embodiment can include all implementation changes, such as additions, removals, and modifications of components, with respect to the proposed embodiment.

[0018] Fig. 2 is a view illustrating a wafer polishing apparatus according to an embodiment.

[0019] The wafer polishing apparatus according to an embodiment comprises a support plate 101 on which a polishing pad P is placed, and a head assembly 110 to which a wafer W is adsorbed, as shown in Fig. 2. The support plate 101 and the head assembly 110 are rotatably mounted.

[0020] The support plate 101 has a disc shape. A drive shaft 102 is arranged at a center of a lower surface of the support plate 101, and a separate drive motor 103 is arranged on one side of the drive shaft 102 to rotate the drive shaft 102.

[0021] The head assembly 110 can be rotatably mounted by a head rotation unit 120. The head assembly 110 can be vertically lifted by the head lifting unit 130 and automatically fine-adjusted in vertical height by an additional head lifting unit 150.

[0022] The head assembly 110 vacuum-adsorbs a wafer W at a lower part thereof, and this will be described in detail below.

[0023] The head rotating unit 120 includes a rotating shaft 121 disposed above the head assembly 110, a rotating motor 122 for providing rotating power to the rotating shaft 121, and a pulley and belt 123 for transmitting power from the rotating motor 122 to the rotating shaft 121.

[0024] A lifting shaft 131 of the head lifting unit 130, which will be described in detail below, is directly connected to an upper part of the head assembly 110, and the rotating shaft 121 is arranged surrounding the lifting shaft 131.

[0025] Here, the lifting shaft 131 is mounted within the rotating shaft 121. Likewise, the lifting shaft 131 can be installed rotatably together with the rotating shaft 121.

[0026] Fig. 3 is a view showing the Fig. 2 represents the applied head assembly.

[0027] The head assembly 110 has a shape capable of adsorbing a wafer by vacuum. As shown in Fig. 3, the head assembly 110 includes a housing 111, a drive ring 112 fixed by a collet 112a and a flange 113a to cover a lower surface of the housing 111, and a wafer fixing member configured to be fitted to a lower part of the drive ring 112.

[0028] The housing 111 has a predetermined pressure space 111a thereunder and has an open lower side and a stepped space at a periphery of a lower end thereof.

[0029] Of course, a separate pressure application unit is connected to the housing 111 to provide a predetermined pressure in the housing 111 and its detailed description is omitted.

[0030] The clamping sleeve 112a is mounted to engage the stepped end of the lower end of the housing 111, and the flange 113a is mounted to engage a lower part of an outer periphery of the clamping sleeve 112a. An outer peripheral end of the drive ring 112 is fixed between the clamping sleeve 112a and the flange 113a.

[0031] The drive ring 112 is mounted to cover the open bottom side of the housing 111 and has a plurality of disc-shaped holes for transmitting a predetermined pressure. Likewise, the drive ring 112 is formed of a soft material, so that a central portion thereof is vertically elevated.

[0032] The wafer fixing member includes a sleeve 113, a ceramic block 114, a die assembly 115, and a guide member 116. A passage through which a vacuum pressure is transmitted between the housing 111 and the drive ring 112 is defined in the sleeve 113 and the ceramic block 114.

[0033] The sleeve 113 contacts a lower surface of the drive ring 112 and is adapted to engage with a lower part of an inner peripheral surface of the flange 113a.

[0034] The ceramic block 114 is arranged at a lower part of the sleeve 113 to reinforce the strength of the sleeve 113.

[0035] The die assembly 115 may be in the form of a non-slip pad formed from a material such as polyurethane. The die assembly 115 is arranged under the ceramic block to adsorb or press the wafer W.

[0036] The guide member 116 is arranged on a periphery of a lower surface of the die assembly 115 to guide a peripheral part of the wafer W.

[0037] Accordingly, when the vacuum pressure is supplied to a pressure space 111a of the housing 111, the pressure is transmitted to the wafer fixing part through the drive ring 112 and thus the wafer W is adsorbed to the lower surface of the die assembly 115.

[0038] Fig. 4 is a view showing the Fig. 2 represents the head lifting unit used.

[0039] The head lifting unit 130 may be a type of cylinder. As shown in Fig. 4, it is installed such that a lifting shaft 131 is arranged within the cylinder housing 132 for lifting.

[0040] The lifting shaft 131 can be directly connected to an upper part of the head assembly (see reference 110 in Fig. 2) and can be connected together with the rotary shaft (see reference 121 in Fig. 2) rotate as described above.

[0041] The cylinder housing 132 may have a predetermined pressure chamber therein and supply a separate pressure to the pressure chamber.

[0042] Here, the cylinder housing 132 accommodates an upper end of the lifting shaft 131 therein such that at least one sealing member 133 disposed on a periphery of the lifting shaft 131 engages with an inner wall of the cylinder housing 131.

[0043] Although the sealing member 133 is arranged between the lifting shaft 131 and the cylinder housing 132, the upper end of the lifting shaft 131 is liftable within the cylinder housing 132.

[0044] A manual adjustment element 134 configured to engage the lifting shaft 131 may be disposed at a lower portion of the cylinder housing 132. The manual adjustment element 134 may be manually adjusted to adjust a height of the lifting shaft 131.

[0045] Furthermore, an additional head lifting unit 150 may be arranged on one side of the cylinder housing 132 to automatically adjust a height of the lifting shaft 131.

[0046] In detail, the additional head lifting unit 150 comprises upper / lower nozzles 151 and 152 for providing pressure into the cylinder housing 132 and a pressure control part 153 for controlling the pressure provided to the upper / lower nozzles 151 and 152. The additional head lifting unit 150 is controlled during operation by a value supplied by a sensor 140 for measuring the shape of the above-described drive ring (see reference numeral 112 in Fig. 3) is entered.

[0047] The upper nozzle 151 is arranged at an upper part of the cylinder housing 132 above the sealing part 133. Accordingly, the lifting shaft 131 lowers when pressure is applied from the upper nozzle 151 because the pressure in the upper space of the housing 132 is relatively high with respect to the sealing part 133.

[0048] The lower nozzle 152 is arranged at a lower part of the cylinder housing 132 below the sealing part 133. Accordingly, the lifting shaft 131 rises when pressure is applied from the lower nozzle 152 because the pressure in the lower space of the housing 132 is relatively high with respect to the sealing part 133.

[0049] The pressure control part 153 controls a pressure supplied to the upper / lower nozzles 151 and 152 according to a value supplied from the sensor 140.

[0050] In detail, when the drive ring has the concave shape measured by the sensor 140, the pressure control part 153 controls the pressure so as to provide the pressure to the upper nozzle 151, and when the ring has the convex shape measured by the sensor 140, the pressure control part 153 controls the pressure so as to provide the pressure to the lower nozzle 152.

[0051] Fig. 5 is a view showing the sensor detecting the deformation of the Fig. 2 applied drive ring.

[0052] The sensor 140 may be provided as an optical linear scale type. As shown in the Fig. 3 and Fig. 5, the sensor 140 includes a light emitting part 141, a light receiving part 142, a linear scale 143, and an amplifier 144.

[0053] Of course, the sensor 140 may be mounted on the sleeve disposed over the center portion of the drive ring 112.

[0054] The light-emitting part 141 and the light-receiving part 142 are arranged at a predetermined distance from each other in the horizontal direction. A light-generating LED can be used as the light-emitting part 141, and a light-detecting photodiode can be used as the light-receiving part 142.

[0055] The linear scale 143 is arranged vertically movable between the light emitting part 141 and the light receiving part 142 and includes a measuring scale through which light passes.

[0056] Here, the linear scale 143 may be in contact with the housing 111. The linear scale 143 may be arranged to measure a distance with respect to an inner top surface of the housing 111 while the center portion of the drive ring 112 is lifted.

[0057] The amplifier 144 detects and amplifies data transmitted to the light receiving part 143 to measure even a fine movement.

[0058] Thus, when the center portion of the drive ring 112 rises / lowers, an amount of light passing through the dimensional scale continuously changes while the linear scale 143 moves with respect to the inner top surface of the housing 111, thereby measuring a height of the drive ring 112 with respect to the housing 111 and detecting a shape of the center portion of the drive ring 112.

[0059] Here, when the center portion of the drive ring 112 rises to have the concave shape, a distance between the housing 111 and the drive ring 112 is measured that is smaller than a reference value. On the other hand, when the center portion of the drive ring 112 descends to have the convex shape, a distance between the housing 111 and the drive ring 112 is measured that is larger than the reference value.

[0060] Fig. 6 is a flowchart of a wafer polishing method according to an embodiment.

[0061] The wafer polishing method according to an embodiment is applied at a time when a wafer W of a head assembly 110 is just touching a polishing pad P of a support plate 101 before a polishing operation starts. A process in which the head assembly 110 is automatically adjusted in height to allow a drive ring 112 to be maintained in a flat state will be described below with reference to Fig. 2, Fig. 3 and Fig. 6 are described.

[0062] When a predetermined pressure P0 is applied to a head lifting unit 130, the head assembly 110 lowers to a predetermined initial position in operations S1 and S2.

[0063] Of course, when the wafer W of the head assembly 110 lowers to the initial position, the wafer W may touch the polishing pad P of the carrier plate 101.

[0064] However, if the polishing pad P decreases in height due to repeated use, the wafer W of the head assembly 110 may not touch the polishing pad P of the support plate 101 even if the wafer W of the head assembly 110 descends to the initial position. Thus, the drive ring 112 within the head assembly 110 may be deformed into a convex shape.

[0065] Likewise, when the polishing pad P is newly replaced to increase in height, the wafer W of the head assembly 110 may lower to the initial position to excessively contact the polishing pad P of the support plate 101. Thus, the drive ring 112 within the head assembly 110 may be deformed into a concave shape because an excessive load is applied to a peripheral part of the head assembly 110.

[0066] In an operation S3, a height of a center portion of the drive ring 112 is measured using a sensor 140.

[0067] Here, the sensor 140 may be provided as an optical linear scale type. As described above, a light-emitting part and a light-receiving part rise / fall together with the center part of the drive ring 112, but a linear scale may contact the housing 111.

[0068] Thus, when the center portion of the drive ring 112 rises / falls, the light-emitting portion and the light-receiving portion rise / fall with respect to the linear scale, and thus the light passing through the linear scale can change. Consequently, the height of the drive ring 112 can be measured according to the change in the light passing through the linear scale.

[0069] In operations S4 and S5, the polishing process starts when the height h of the drive ring 112 corresponds to a reference value h0.

[0070] Of course, the height h of the drive ring 112 may be previously supplied to the reference value h0 in a state where the drive ring 112 is flat in order to compare the height h of the drive ring 112 measured by the sensor 140 with the reference value h0.

[0071] Here, when the height h of the drive ring 112 corresponds to the reference value h0, it is determined that the head assembly 110 is balanced because the drive ring 112 is flat, and thus the polishing operation is carried out without separately adjusting a position of the head assembly 110.

[0072] On the other hand, when the height h of the drive ring 112 does not correspond to the reference value h0, the lifting / lowering of the head assembly 110 is adjusted by an additional head lifting unit 150 in operations S4 and S6.

[0073] Here, if the height h of the drive ring 112 does not correspond to the reference value h0, it is determined that the head assembly 110 is not balanced because the drive ring 112 is deformed into a convex or concave shape, and thus the head assembly 110 is automatically adjusted in position.

[0074] Specifically, when the drive ring 112 has a height h smaller than the reference value h0, it is determined that the center part of the drive ring 112 rises to be deformed into the concave shape, and thus the additional head lifting unit 150 sets an initial lowering position of the head assembly 110 to finely rise.

[0075] On the other hand, when the drive ring 112 has a height h0 larger than the reference value h0, it is determined that the central part of the drive ring 112 descends to be deformed into the convex shape, and thus the additional head lifting unit 150 adjusts the initial lowering position of the head assembly 110 to finely descend.

[0076] By repeating the above-described operations, the balance of the head assembly 110 can be automatically adjusted at the initial lowering position to improve the comfort of a worker. Additionally, the polishing operation can be performed in the state where the wafer W of the head assembly 110 contacts the polishing pad of the support plate 101 at a uniform pressure to maintain uniform polishing quality and improve polishing efficiency.

[0077] In the wafer polishing apparatus and method according to one embodiment, when the head assembly moves to the initial lowering position by the wafer lifting unit, the shape of the drive ring within the head assembly can be measured using the sensor, and thus the polishing operation can be performed in the state where the lowering position of the head assembly is automatically adjusted using the additional head lifting unit to keep the drive ring in a flat state.

[0078] Therefore, since the wafer polishing operation is carried out in the state where the balance of the wafer fixing part is automatically adjusted using the drive ring, the polishing quality of the wafer can be uniformly maintained and also the polishing efficiency can be improved.

Claims

[1] Wafer polishing device comprising: a housing (111) providing a predetermined pressure space thereunder; a drive ring (112) flatly connected to a lower part of the housing (111), the drive ring (112) having a central part that is vertically variable in shape; a head assembly (110) disposed at a lower portion of the drive ring (112), the head assembly (110) including a wafer mounting member having a lower surface to which a wafer (W) is mounted; a head lifting unit (130) arranged at an upper part of the housing (111) for vertically lifting the head assembly (110) according to a control pressure; a sensor (140) arranged on a central part of the drive ring (112) for measuring a distance of the central part of the drive ring from the housing (111); and an additional head lifting unit (150) arranged on the head lifting unit (130) for adjusting a height of the head assembly (110) according to a distance value measured by the sensor (140) such that the central part of the drive ring (112) is flat during a wafer polishing process. [2] The wafer polishing apparatus according to claim 1, wherein the head assembly (110) further comprises a sleeve (113) disposed above the central portion of the drive ring (112), and the sensor (140) is provided as an optical linear scale type disposed above the sleeve (113). [3] A wafer polishing apparatus according to claim 2, wherein the sensor (140) comprises: a light-emitting part (141) arranged above the sleeve (113); a light-receiving part (142) horizontally spaced a predetermined distance from the light-emitting part; and a linear scale (143) movably disposed between the light-emitting part (141) and the light-receiving part (142) for measuring a distance from the housing (111). [4] The wafer polishing apparatus according to claim 3, wherein the sensor (140) further comprises an amplifier (144) that detects data transmitted to the light receiving part (142) to amplify the detected data. [5] A wafer polishing apparatus according to claim 1, wherein the head lifting unit (130) comprises: a lifting shaft (131) connected to an upper part of the housing (111); a cylinder housing (132) connected to an upper end of the lifting shaft (131) for lifting the lifting shaft (131) while providing pressure thereto; at least one sealing part (133) arranged on a circumference of the lifting shaft (131), wherein the at least one sealing part (133) engages with an inner wall of the cylinder housing (132). [6] The wafer polishing apparatus according to claim 5, wherein the additional head lifting unit (150) has an upper nozzle (151) that provides pressure into the cylinder housing (132) from an upper side with respect to the sealing member (133). [7] The wafer polishing apparatus according to claim 5, wherein the additional head lifting unit (150) has a lower nozzle (152) that provides pressure into the cylinder housing (132) from a lower side with respect to the sealing member (133). [8] A wafer polishing method in which a wafer (W) adsorbed on a head assembly (110) having a wafer fixing member balanced according to a flat shape of a drive ring (112) is polished using a polishing pad (P) placed on a support plate (101), the wafer polishing method comprising: a first operation that allows the wafer (W) to contact the polishing pad (P) as the head assembly (110) lowers while providing a predetermined pressure thereto; a second process for measuring a shape of the central part of the drive ring (112) while the wafer (W) is in contact with the polishing pad (P) in the first process; and a third process of adjusting a height of the head assembly (110) such that a shape of the central part of the drive ring (112) is flat according to a value measured by a sensor (140). [9] The wafer polishing method according to claim 8, wherein the first process comprises setting a lowering position of the head assembly (110) using a reference value at which the drive ring (112) is in a flat state. [10] The wafer polishing method according to claim 9, wherein the second process comprises comparing the height of the central portion of the drive ring (112) with the reference value. [11] The wafer polishing method according to claim 10, wherein in the third process, when the height of the central part of the drive ring (112) is larger than the reference value, the height of the head assembly (110) is set to lower, and when the height of the central part of the drive ring (112) is smaller than the reference value, the height of the head assembly (110) is set to rise. [12] The wafer polishing method according to claim 10, wherein in the third process, the height of the head assembly (110) is adjusted such that the height of the central part of the drive ring (112) corresponds to the reference value.

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