Patent Application
20240109161
The present invention relates to a polishing apparatus and a polishing method for polishing a flat portion of a substrate, such as a wafer.
Devices, such as a memory circuit, a logic circuit, and an image sensor (e.g., a CMOS sensor) are becoming more highly integrated these days. In a process of forming such devices on a substrate, such as a wafer, foreign matter, such as fine particles or dust, or an unwanted film, may adhere to the substrate. Foreign matter adhering to a substrate can cause defects, such as a molding failure, or a damage of the device. Therefore, in order to enhance a reliability of the device, it is necessary to remove the foreign matter on the substrate.
There has been provided a polishing apparatus configured to polish a substrate using a polishing tool in order to remove foreign matter on the substrate, such as a wafer. Such a polishing apparatus is configured to polish a substrate by bringing a polishing tool into sliding contact with the substrate. The polishing apparatus polishes the substrate by pressing the polishing tool against the substrate with a polishing head.
An example of the polishing apparatus is configured to polish a substrate by pressing a polishing tool, such as a polishing tape, against the substrate with a polishing head, while rotating the substrate and advancing the polishing tool in one direction.
One possible solution to the above problem is to change a material of the polishing blade 340 in order to reduce a friction coefficient, but the dynamic friction force cannot be reduced to zero. Another possible solution is to adjust a tilt angle of the polishing blade 340 so as to equalize pressing forces at the pressing point P1 and the pressing point P2 without applying the universal joint to the polishing head 310. However, it is difficult to adjust the tilt angle of the polishing head 310 according to a change in tension applied to the polishing tape 303.
It is therefore an object of the present invention to provide a polishing apparatus and a polishing method capable of uniformly polishing a flat portion of a substrate without affecting pressing force of a polishing head due to dynamic friction force generated between the polishing head and a polishing tape.
In an embodiment, there is provided a polishing apparatus for polishing a flat portion of a substrate, comprising: a substrate holder configured to hold a substrate and rotate the substrate; a polishing-tape feeding mechanism configured to advance a polishing tape in its longitudinal direction; and at least one polishing head arranged near a flat portion of the substrate, wherein the polishing head has a fluid pressing structure configured to press the polishing tape with fluid against the flat portion of the substrate, and the fluid pressing structure has a fluid supply port arranged so as to face a back surface of the polishing tape.
In an embodiment, the fluid pressing structure comprises a slit nozzle having the fluid supply port in a slit shape.
In an embodiment, the fluid pressing structure comprises an area pad having a pressing surface and the fluid supply port, the pressing surface having a recess formed in the center of the pressing surface, and the fluid supply port being located in the recess.
In an embodiment, the fluid comprises a fluid mixture of gas and liquid.
In an embodiment, a proportion of the gas in the fluid mixture is higher than a proportion of the liquid in the fluid mixture.
In an embodiment, the flat portion of the substrate comprises an edge portion located in a periphery of the substrate, and the fluid pressing structure has an arc shape having a curvature substantially the same as a curvature of a peripheral shape of the substrate.
In an embodiment, there is provided a polishing method for polishing a flat portion of a substrate, comprising: holding a substrate and rotating the substrate by a substrate holder; and advancing a polishing tape in its longitudinal direction by a polishing-tape feeding mechanism, while pressing the polishing tape with fluid against a flat portion of the substrate by supplying the fluid from a fluid supply port formed in a fluid pressing structure of a polishing head toward a back surface of the polishing tape.
In an embodiment, the fluid pressing structure comprises a slit nozzle having the fluid supply port in a slit shape.
In an embodiment, the fluid pressing structure comprises an area pad having a pressing surface and the fluid supply port, the pressing surface having a recess formed in the center of the pressing surface, and the fluid supply port being located in the recess.
In an embodiment, the fluid comprises a fluid mixture of gas and liquid.
In an embodiment, a proportion of the gas in the fluid mixture is higher than a proportion of the liquid in the fluid mixture.
In an embodiment, the flat portion of the substrate comprises an edge portion located in a periphery of the substrate, and the fluid pressing structure has an arc shape having a curvature substantially the same as a curvature of a peripheral shape of the substrate.
According to the present invention, pressing the polishing head against the polishing tape with the fluid can uniformly polish the flat portion of the substrate without generating dynamic friction force between the polishing head and the polishing tape.
Further, according to the present invention, friction heat generated between the substrate and the polishing tape during polishing can be cooled by the fluid, so that a polishing rate can be improved.
Furthermore, the fluid flows to the polishing point of the substrate, so that polishing debris can be removed from a substrate surface.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The substrate holder 110 includes a plurality of rollers 111 which can contact a periphery of the wafer W, and a roller rotating mechanism (not shown) configured to rotate the plurality of rollers 111 about their respective own axes. The polishing head 10 is disposed below the wafer W held by the substrate holder 110. In
In this embodiment, the first surface 1 of the wafer W is a back surface of the wafer W on which no device is formed or device is not to be formed, i.e., a non-device surface. A second surface 2 of the wafer W, which is opposite the first surface 1, is a surface on which devices are formed or devices are to be formed, i.e., a device surface. In this embodiment, the wafer W is held by the substrate holder 110 horizontally with the first surface 1 facing downward.
The roller rotating mechanism is configured to rotate the four rollers 111 at the same speed in the same direction. During polishing of the first surface 1 of the wafer W, the periphery of the wafer W is held by the rollers 111. The wafer W is held horizontally, and is rotated about its own axis by the rotations of the rollers 111. During the polishing of the first surface 1 of the wafer W, the four rollers 111 rotate about their respective own axes, while positions of the rollers 111 themselves remain stationary.
As shown in
A protective-liquid supply nozzle 128 configured to supply a protective liquid (e.g., pure water) onto the second surface 2 of the wafer W is disposed above the wafer W held by the substrate holder 110. The protective-liquid supply nozzle 128 is coupled to a not-shown protective-liquid supply source. The protective-liquid supply nozzle 128 is oriented toward the center of the second surface 2 of the wafer W. The protective liquid is supplied from the protective-liquid supply nozzle 128 to the center of the second surface 2 of the wafer W, and the protective liquid spreads over the second surface 2 of the wafer W by centrifugal force. The protective liquid prevents the rinsing liquid containing polishing debris and foreign matter generated in the polishing of the wafer W from contacting the second surface 2 of the wafer W. As a result, the second surface 2 of the wafer W can be kept clean.
The polishing head 10 is supported by a supporting member 131, and the supporting member 131 is fixed to a movable plate 120. Therefore, the entire polishing head 10 can move together with the movable plate 120. The supporting member 131 has a not-shown through-hole, and the polishing tape 3 extends through this through-hole.
The polishing head 10 is configured to press the polishing tape 3 with fluid against the first surface 1 of the wafer W. The polishing head 10 is coupled to a fluid supply line 30, and the fluid is supplied from a not-shown fluid supply source to the polishing head 10. Details of the polishing head 10 will be described later.
The polishing-tape feeding mechanism 141 includes a tape feeding reel 143 configured to feed the polishing tape 3, and a tape take-up reel 144 configured to collect the polishing tape 3. The tape feeding reel 143 and the tape take-up reel 144 are coupled to tension motors 143a and 144a, respectively. The tension motors 143a and 144a are fixed to a reel base 142. The reel base 142 is fixed to the movable plate 120, so that the entire polishing-tape feeding mechanism 141 can move together with the movable plate 120.
The polishing tape 3 is advanced or fed from the tape feeding reel 143 to the tape take-up reel 144 via the polishing head 10 in a direction indicated by arrows by rotating the tape take-up reel 144 in a direction indicated by an arrow. The polishing tape 3 is fed to a position over the polishing head 10 such that a polishing surface 3a of the polishing tape 3 faces the first surface 1 of the wafer W. The tension motor 143a can apply tension to the polishing tape 3 by applying a predetermined torque to the tape feeding reel 143. The tension motor 144a is controlled such that the polishing tape 3 is advanced at a constant speed. An advancing speed of the polishing tape 3 can be changed by changing a rotating speed of the tape take-up reel 144. In one embodiment, the advancing direction of the polishing tape 3 may be opposite to the direction indicated by the arrow shown in
The polishing apparatus 100 further includes a plurality of guide rollers 153a, 153b, 153c, and 153d configured to support the polishing tape 3. The polishing tape 3 is guided so as to surround the polishing head 10 by these guide rollers 153a, 153b, 153c, and 153d. The polishing head 10 polishes the first surface 1 of the wafer W by pressing the polishing tape 3 from its back side with the fluid against the first surface 1 of the wafer W. The guide rollers 153b and 153c arranged above the polishing head 10 guide the polishing tape 3 such that the polishing tape 3 advances in a direction parallel to the first surface 1 of the wafer W. The guide rollers 153a, 153b, 153c, and 153d are fixed to a not-shown holding member, and this holding member is fixed to the movable plate 120.
In order to bring the polishing tape 3 into contact with a region ranging from the center O1 to an outermost portion of the first surface 1 of the wafer W, the polishing apparatus 100 of this embodiment includes a polishing-head moving mechanism 191 configured to translate the polishing head 10 relative to the substrate holder 110. The polishing-head moving mechanism 191 is configured to move the polishing head 10 between the center O1 of the first surface 1 of the wafer W and the outermost portion of the first surface 1.
A plurality of linear-motion guides 195 are fixed to a lower surface of the movable plate 120, and the movable plate 120 is supported by the plurality of linear-motion guides 195. The plurality of linear-motion guides 195 are disposed on a mounting surface 197. The movable plate 120 is moved by the polishing-head moving mechanism 191, and the linear-motion guide 195 restricts the movement of the movable plate 120 to a linear motion in a radial direction of the wafer W.
The polishing-head moving mechanism 191 includes a ball-screw mechanism 193 and a motor 194 configured to drive the ball-screw mechanism 193. A servo motor can be used as the motor 194. The movable plate 120 is coupled to a screw shaft 193a of the ball-screw mechanism 193. When the polishing-head moving mechanism 191 operates, the polishing head 10, the polishing-tape feeding mechanism 141, and the guide rollers 153a, 153b, 153c, and 153d are moved in the radial direction of the wafer W relative to the substrate holder 110.
During the polishing of the wafer W, the polishing-head moving mechanism 191 moves the polishing head 10 between the center O1 of the first surface 1 of the wafer W and the outermost portion of the first surface 1. The polishing apparatus 100 further includes an operation controller 180 configured to control operations of each component of the polishing apparatus 100. The polishing-head moving mechanism 191 is electrically connected to the operation controller 180, so that operations of the polishing-head moving mechanism 191 are controlled by the operation controller 180. When the polishing-head moving mechanism 191 operates, the polishing head 10, the polishing-tape feeding mechanism 141, and the guide rollers 153a, 153b, 153c, and 153d are moved together.
During the polishing of the first surface 1 of the wafer W, the positions of the rollers 111 themselves remain stationary, and the rollers 111 are arranged at positions where the rollers 111 do not contact the polishing head 10 when the polishing head 10 moves from the center side of the wafer W to the outer side of the wafer W. Therefore, the polishing tape 3 can polish the entire first surface 1 including the outermost portion of the wafer W.
The polishing head 10 is coupled to the fluid supply line 30, and the fluid is supplied from the not-shown fluid supply source to the polishing head 10. More specifically, the fluid supply line 30 has a liquid supply line 31 to which a liquid (e.g., pure water, carbonated water, alkaline chemical liquid, etc.) is supplied from a not-shown liquid supply source, and a gas supply line 32 to which a gas (e.g., dry air, inert gas, etc.) is supplied from a not-shown gas supply source. In one embodiment, the fluid supply line 30 may have either the liquid supply line 31 or the gas supply line 32.
The polishing head 10 has a fluid pressing structure 12, a flow passage 14, and a fluid mixing chamber 15. In the polishing head 10 of this embodiment, the fluid pressing structure 12 is constituted of a slit nozzle. The fluid pressing structure 12 is arranged in an upper portion of the polishing head 10. As shown in
The flow passage 14 communicates with the fluid supply port 13 and the fluid mixing chamber 15. The fluid mixing chamber 15 is coupled to the fluid supply line 30, i.e., the liquid supply line 31 and the gas supply line 32. The liquid flowing through the liquid supply line 31 and the gas flowing through the gas supply line 32 are mixed in the fluid mixing chamber 15 to form a fluid mixture. This fluid mixture flows through the flow passage 14, and is supplied as a two-fluid jet from the fluid supply port 13 toward a back surface of the polishing tape 3. The fluid supply port 13 is arranged so as to face the back surface of the polishing tape 3, so that the polishing tape 3 can be pressed against the first surface 1 of the wafer W by the fluid mixture (two-fluid jet) supplied from the fluid supply port 13.
The liquid supply line 31 is provided with a liquid supply valve 33 configured to open and close a flow passage of the liquid supply line 31, a flow-rate controller 35 configured to regulate a flow rate of the liquid flowing through the liquid supply line 31, and a flow meter 37 configured to measure the flow rate of the liquid flowing through the liquid supply line 31. The liquid supply valve 33 is arranged upstream of the flow-rate controller 35 and the flow meter 37 in a flowing direction of the liquid. An example of the flow-rate controller 35 includes a flow-rate control valve or a mass flow-rate controller. A pressure sensor (not shown) may be provided between the flow meter 37 and the fluid mixing chamber 15.
The gas supply line 32 is provided with a gas supply valve 34 configured to open and close a flow passage of the gas supply line 32, a flow-rate controller 36 configured to regulate a flow rate of the gas flowing through the gas supply line 32, and a flow meter 38 configured to measure the flow rate of the gas flowing through the gas supply line 32. The gas supply valve 34 is arranged upstream of the flow-rate controller 36 and the flow meter 38 in a flowing direction of the gas. An example of the flow-rate controller 36 includes a flow-rate control valve or a mass flow-rate controller. A pressure controller configured to regulate a pressure of the gas flowing through the gas supply line 32 may be provided instead of the flow-rate controller 36. An example of the pressure controller includes an electro-pneumatic regulator. A pressure gauge configured to measure the pressure of the gas flowing through the gas supply line 32 may be provided instead of the flow meter 38. A flow meter and a pressure gauge may be provided together between the flow-rate controller 36 (or the pressure controller) and the fluid mixing chamber 15.
In one embodiment, a proportion of the gas in the fluid mixture is higher than a proportion of the liquid in the fluid mixture. In general, when comparing the same amount of liquid (e.g., pure water, carbonated water, chemical liquid, etc.) with gas (e.g., dry air, inert gas, etc.), the gas is less expensive. Therefore, cost can be reduced by making the proportion of the gas in the fluid mixture higher than the proportion of the liquid. The proportions of the gas and the liquid in the fluid mixture can be regulated by the flow-rate controller 35 and the flow-rate controller 36 (or the pressure controller).
In this embodiment, the liquid and the gas are mixed in the fluid mixing chamber 15 in the polishing head 10 to produce the fluid mixture, while in one embodiment, the fluid supply line 30 through which a fluid mixture mixed in advance flows may communicate with the flow passage 14 without passing through the fluid mixing chamber 15, and the fluid mixture may be directly supplied to the fluid pressing structure 12. In one embodiment, one of the liquid supply line 31 and the gas supply line 32 may communicate with the flow passage 14 without passing through the fluid mixing chamber 15, and only one of the liquid and the gas may be supplied to the fluid pressing structure 12. In both cases, the polishing head 10 can supply the fluid from the fluid supply port 13 toward the back surface of the polishing tape 3.
Angles of the fluid pressing structure 12 and the fluid supply port 13 of the present invention with respect to the advancing direction of the polishing tape 3 are not limited to the embodiment shown in
Next, operations of the polishing apparatus 100 of this embodiment will be described. The operations of the polishing apparatus 100 described below are controlled by the operation controller 180 shown in
The operation controller 180 is composed of at least one computer. The operation controller 180 includes a memory 180a and an arithmetic device 180b. The arithmetic device 180b includes a CPU (central processing unit) or a GPU (graphic processing unit) configured to perform arithmetic operations according to instructions contained in programs stored in the memory 180a. The memory 180a includes a main memory (e.g., a random access memory) accessible by the arithmetic device 180b, and an auxiliary memory (e.g., a hard disk drive or a solid state drive) storing data and the programs therein.
The wafer W to be polished is held by the rollers 111 of the substrate holder 110 with the first surface 1 facing downward, and is rotated about the axis of the wafer W. Specifically, the substrate holder 110 rotates the wafer W by rotating the plurality of rollers 111 about the respective their own axes while the plurality of rollers 111 are in contact with the periphery of the wafer W with the first surface 1 of the wafer W facing downward. Next, the rinsing liquid is supplied onto the first surface 1 of the wafer W from the rinsing-liquid supply nozzle 127, and the protective liquid is supplied onto the second surface 2 of the wafer W from the protective-liquid supply nozzle 128. The rinsing liquid is supplied for cleaning the processing point on the first surface 1 of the wafer W and/or preventing area(s) other than the processing point from drying. The protective liquid spreads over the entire second surface 2 of the wafer W by centrifugal force.
The polishing-head moving mechanism 191 moves the polishing head 10 to a position below the center O1 of the first surface 1 of the wafer W. The operation controller 180 drives the polishing-tape feeding mechanism 141 to advance the polishing tape 3 in its longitudinal direction at a predetermined speed while applying a predetermined tension to the polishing tape 3. Next, the operation controller 180 instructs the liquid supply valve 33 and the gas supply valve 34 to open to thereby supply the fluid to the polishing head 10. The polishing head 10 brings the polishing surface 3a of the polishing tape 3 into contact with the first surface 1 of the wafer W by the fluid, and starts polishing the first surface 1 of the wafer W in the presence of the rinsing liquid. Further, the polishing-head moving mechanism 191 moves the polishing head 10, the polishing-tape feeding mechanism 141, and the guide rollers 153a, 153b, 153c, and 153d outwardly in the radial direction of the wafer W, while the polishing tape 3 is pressed against the first surface 1 of the wafer W by the fluid emitted from the polishing head 10. The operation controller 180 can regulate a pressing force of the fluid against the polishing tape 3 by controlling a flow rate supplied to the polishing head 10 by the flow-rate controller 35 and the flow-rate controller (or pressure controller) 36. During the polishing of the wafer W, the rinsing-liquid supply nozzle 127 and the protective-liquid supply nozzle 128 continue supplying the rinsing liquid and the protective liquid to the wafer W.
When the polishing head 10 reaches the outermost portion of the first surface 1 of the wafer W, the operation controller 180 instructs the polishing apparatus to terminate polishing of the wafer W. Specifically, the liquid supply valve 33 and the gas supply valve 34 are closed to stop supplying the fluid to the polishing head 10, so that the polishing tape 3 is separated from the first surface 1 of the wafer W. Thereafter, the operation controller 180 instructs the substrate holder 110, the rinsing-liquid supply nozzle 127, the protective-liquid supply nozzle 128, and the polishing-tape feeding mechanism 141 to stop their operations, so that the polishing of the wafer W is terminated. In one embodiment, the polishing-head moving mechanism 191 may reciprocate the polishing head 10 between the outermost portion and the center O1 of the first surface 1 of the wafer W.
According to the above-described embodiment, since the polishing head 10 presses the polishing tape 3 with the fluid without contacting the back surface of the polishing tape 3, no dynamic friction force is generated between the polishing tape 3 and the polishing head 10 when the polishing tape 3 is advanced during polishing of the wafer W. Therefore, the polishing tape 3 can be uniformly pressed against the flat portion of the wafer W by adjusting the pressure of the fluid supplied from the fluid pressing structure 12 of the polishing head 10 such that the pressing force is uniform, and as a result, the flat portion of the wafer W can be uniformly polished.
In particular, in this embodiment, a fluid mixture of the liquid and the gas is used as the fluid for pressing the polishing tape 3. This fluid mixture is emitted as a two-fluid jet from the polishing head 10 onto the back surface of the polishing tape 3. The fluid mixture can press the polishing tape 3 against the wafer W with a greater pressing force than the liquid alone.
In addition, the fluid supplied from the polishing head 10 to the back surface of the polishing tape 3 can cool friction heat generated between the wafer W and the polishing tape 3 when the wafer W is polished. Generally, the friction heat generated at the polishing point of the wafer W may cause a decrease in polishing performance of the polishing tape 3, and as a result, a polishing rate may be lowered. Therefore, the polishing rate can be improved by cooling the friction heat with the fluid.
Furthermore, the fluid supplied from the polishing head 10 to the back surface of the polishing tape 3 flows over to the polishing point of the wafer W, so that polishing debris can be removed from the first surface 1 of the wafer W.
The polishing head 10 has a fluid pressing structure 12, a flow passage 14, and a fluid mixing chamber 15. In the polishing head 10 of this embodiment, the fluid pressing structure 12 is constituted of an area pad. The fluid pressing structure 12 is arranged in the upper portion of the polishing head 10, and as shown in
A fluid mixture produced in the fluid mixing chamber 15 flows through the flow passage 14, is supplied from the fluid supply port 18 into the recess 17 to fill the recess 17, and further flows out toward an outside of the fluid pressing structure 12. The fluid supply port 18 and the recess 17 are arranged so as to face the back surface of the polishing tape 3. A gap between the pressing surface 16 of the fluid pressing structure 12 and the back surface of the polishing tape 3 is filled with the fluid, so that the polishing tape 3 can be pressed against the first surface 1 of the wafer W with the entire pressing surface 16 including the recess 17.
In the embodiments shown in
The polishing tape 3 fed to the polishing-head assembly 11A is supported by guide rollers 163a, 163b, 163c, and 163d, and the polishing tape 3 fed to the polishing-head assembly 11B is supported by guide rollers 173a, 173b, 173c, and 173d. Configurations of the polishing-tape feeding mechanisms 141A and 141B, the supporting members 131A and 131B, the guide rollers 163a, 163b, 163c, and 163d, and the guide rollers 173a, 173b, 173c, and 173d are the same as those of the polishing-tape feeding mechanism 141, the supporting member 131, and the guide rollers 153a, 153b, 153c, and 153d described with reference to
The polishing head 10A corresponds to the polishing head 10 described with reference to
During polishing, the polishing-tape feeding mechanism 141A advances the polishing tape 3 in a direction indicated by an arrow F shown in
The plurality of polishing heads 10A and 10B are configured to be operable independently of each other. The polishing heads 10A and 10B of the polishing-head assembly 11A are aligned with a gap along the advancing direction F of the polishing tape 3 (i.e., the longitudinal direction of the polishing tape 3). The polishing heads 10A and 10B of the polishing-head assembly 11B are aligned with a gap along the advancing direction G of the polishing tape 3 (i.e., the longitudinal direction of the polishing tape 3). Each of the plurality of fluid pressing structures 12, 12A, and 12B of this embodiment extends obliquely with respect to the advancing directions F and G of the polishing tapes 3. When viewed from the advancing direction F or the advancing direction G of the polishing tape 3, the plurality of fluid pressing structures 12, 12A, and 12B are continuously aligned along a direction perpendicular to the advancing directions F and G of the polishing tapes 3. Furthermore, when viewed from the advancing direction F or the advancing direction G of the polishing tape 3, the plurality of fluid pressing structures 12, 12A, and 12B are continuously arranged without gaps.
Although the plurality of fluid pressing structures 12, 12A, and 12B are not aligned on a straight line, the plurality of fluid pressing structures 12, 12A, and 12B are located at different distances from the axis CP of the substrate holder 110, so that when the wafer W is rotating, each region of the first surface 1 of the wafer W passes through one of the plurality of fluid pressing structures 12, 12A, and 12B. Therefore, the polishing tapes 3 can be pressed against the entire first surface 1 of the wafer W by the fluid supplied from the plurality of fluid pressing structures 12, 12A, and 12B.
Angles of the fluid pressing structures 12, 12A, and 12B and the fluid supply ports 13, 13A, and 13B with respect to the advancing directions of the polishing tapes 3 are not limited to the embodiment shown in
In one embodiment, the polishing head 10A may be the polishing head 10 having the fluid pressing structure 12 described with reference to
According to the above-described embodiment, since the polishing heads 10A and 10B press the polishing tape 3 with the fluid without contacting the back surface of the polishing tape 3, no dynamic friction force is generated between the polishing tapes 3 and the polishing heads 10A and 10B when the polishing tapes 3 are advanced during polishing of the wafer W. Therefore, the polishing tapes 3 can be uniformly pressed against the flat portion of the wafer W by adjusting the pressure of the fluid supplied from the fluid pressing structures 12 of the polishing heads 10A and 10B such that the pressing forces are uniform. As a result, the flat portion of the wafer W can be uniformly polished.
Further, the fluid supplied from the polishing heads 10A and 10B to the back surfaces of the polishing tapes 3 can cool friction heat generated between the wafer W and the polishing tapes 3 when the wafer W is polished. Generally, the friction heat generated at the polishing point of the wafer W may cause a decrease in polishing performance of the polishing tape 3, and as a result, a polishing rate is lowered. Therefore, the polishing rate can be improved by cooling the friction heat with the fluid.
Furthermore, the fluid supplied from the polishing heads 10A and 10B to the back surfaces of the polishing tapes 3 flows over to the polishing points of the wafer W, so that polishing debris can be removed from the first surface 1 of the wafer W.
Referring back to
The polishing head 10, the holding stage 204, the lower-side supply nozzle 222, and the upper-side supply nozzle 230 are arranged in an interior of a partition wall 260. The interior of the partition wall 260 constitutes a polishing chamber in which the wafer W is to be polished. The partition wall 260 is located on a base plate 265. The shaft 205 extends through the base plate 265.
The holding-stage driving mechanism 207 includes a motor 214 as a stage rotating device configured to rotate the holding stage 204, and an air cylinder 217 configured to vertically move the holding stage 204. The motor 214 is fixed to a lower surface of the base plate 265. The holding stage 204 is rotated by the motor 214 via the shaft 205, a pulley 211a coupled to the shaft 205, a pulley 211b attached to a rotating shaft of the motor 214, and a belt 212 riding on these pulleys 211a and 211b. The rotating shaft of the motor 214 extends parallel to the shaft 205. With such a configuration, the wafer W held on an upper surface of the holding stage 204 is rotated by the motor 214. The shaft 205 is coupled to the air cylinder 217 via a rotary joint 216 attached to a lower end of the shaft 205, so that the air cylinder 217 can raise and lower the shaft 205 and the holding stage 204.
The wafer W is placed on the upper surface of the holding stage 204 by a not-shown transfer mechanism such that the center O1 of the wafer W is located on the axis Cr of the holding stage 204. The wafer W is held on the upper surface of the holding stage 204 with a device surface of the wafer W facing upward. With such a configuration, the substrate holder 210 can rotate the wafer W about the axis Cr of the holding stage 204 (i.e., an axis of the wafer W), and can raise and lower the wafer W along the axis Cr of the holding stage 204.
The polishing head 10 is configured to press the polishing tape 3 against the edge portion of the wafer W with fluid. The polishing head 10 is coupled to a fluid supply line 30, and the fluid is supplied from a not-shown fluid supply source. Details of the polishing head 10 will be described later.
The polishing apparatus 200 further includes a polishing-tape feeding mechanism 242 configured to feed the polishing tape 3 to the polishing head 10 and collect the polishing tape 3 from the polishing head 10. The polishing-tape feeding mechanism 242 is disposed outside the partition wall 260. The polishing-tape feeding mechanism 242 includes a tape feeding reel 243 configured to feed the polishing tape 3 to the polishing head 10, and a tape take-up reel 244 configured to collect the polishing tape 3 that has been used in polishing of the wafer W. The polishing tape 3 is advanced or fed from the tape feeding reel 243 via a fluid pressing structure 12 of the polishing head 10 in a direction indicated by an arrow depicted in the tape take-up reel 244 by rotating the tape take-up reel 244 in the direction indicated by the arrow.
Not-shown tension motors are coupled to the tape feeding reel 243 and the tape take-up reel 244, respectively. A tension motor coupled to the tape feeding reel 243 can apply a predetermined torque to the tape feeding reel 243 to apply tension to the polishing tape 3. A tension motor coupled to the tape take-up reel 244 is controlled so as to advance the polishing tape 3 at a constant speed. An advancing speed of the polishing tape 3 can be changed by changing a rotating speed of the tape take-up reel 244. In one embodiment, the advancing direction of the polishing tape 3 may be opposite to the direction indicated by the arrow shown in
The polishing tape 3 is fed to the polishing head 10 such that the polishing surface of the polishing tape 3 faces the periphery of the wafer W. The polishing tape 3 is fed from the tape feeding reel 243 to the polishing head 10 through an opening 260a formed in the partition wall 260, and the used polishing tape 3 is collected by the tape take-up reel 244 through the opening 260a. The polishing-tape feeding mechanism 242 further includes a plurality of guide rollers 245, 246, 247, and 248 configured to support the polishing tape 3. The advancing direction of the polishing tape 3 is guided by the guide rollers 245, 246, 247, and 248.
The polishing head 10 has a plurality of guide rollers 253, 254, 255, 256, 257, 258, and 259 configured to guide the polishing tape 3 from the tape feeding reel 243 (see
The polishing head 10 has the fluid pressing structures 12A and 12B including two slit nozzles, a flow passage 14, and a fluid mixing chamber 15. The fluid pressing structure 12A and the fluid pressing structure 12B are arranged in parallel, and arranged symmetrically with respect to a center line Ct. Slit-shaped fluid supply ports 13A and 13B are formed in the two fluid pressing structures 12A and 12B, respectively. The two fluid pressing structures 12A and 12B and the two fluid supply ports 13A and 13B are curved inwardly toward the center line Ct. More specifically, the fluid pressing structures 12A and 12B and the fluid supply ports 13A and 13B each has an arc shape having a curvature substantially the same as a curvature of a peripheral shape of the wafer W (not shown in
The flow passage 14 communicates with the fluid supply ports 13A and 13B and the fluid mixing chamber 15. The fluid mixture mixed in the fluid mixing chamber 15 flows through the flow passage 14 and is supplied from the fluid supply ports 13A and 13B toward the back surface of the polishing tape 3. The fluid supply ports 13A and 13B are arranged so as to face the back surface of the polishing tape 3, so that the polishing tape 3 can be pressed against the edge portion of the wafer W by the fluid supplied from the fluid supply ports 13A and 13B.
In this embodiment, liquid and gas are mixed in the fluid mixing chamber 15 in the polishing head 10 to produce the fluid mixture, while in one embodiment, the fluid supply line 30 through which a fluid mixture mixed in advance flows may communicate with the flow passage 14 without passing through the fluid mixing chamber 15, and the fluid mixture may be directly supplied to the fluid pressing structures 12A and 12B. In one embodiment, one of the liquid supply line 31 and the gas supply line 32 may communicate with the flow passage 14 without passing through the fluid mixing chamber 15, and only one of the liquid or the gas may be supplied to the fluid pressing structures 12A and 12B.
The polishing head 10 may further have a pressing pad (or a bevel pad) 270 disposed between the fluid pressing structure 12A and the fluid pressing structure 12B. The pressing pad 270 is made of closed-cell form material, such as silicone rubber, which has elasticity. When the polishing head 10 is moved toward the wafer W by a not-shown pressing mechanism, the pressing pad 270 presses the polishing tape 3 from its back side against the bevel portion of the wafer W, so that the polishing head 10 polishes the bevel portion of the wafer W. In order to reduce friction with the back surface of the polishing tape 3, a sheet whose surface is covered with fluororesin may be attached to a front surface (or a pressing surface) of the pressing pad 270. The pressing pad 270 is detachable with a bolt or the like.
The polishing apparatus 200 further includes a not-shown tilting mechanism. The polishing apparatus 200 can polish the periphery of the wafer W while changing a tilt angle of the polishing head 10 by the tilting mechanism.
As shown in
The polishing apparatus 200 includes an operation controller 280 configured to control operations of each component of the polishing apparatus 200. The polishing head 10, the liquid supply valve 33, the gas supply valve 34, the flow-rate controller 35, the flow-rate controller (pressure controller) 36, the substrate holder 210, the lower-side supply nozzle 222, the upper-side supply nozzle 230, the polishing-tape feeding mechanism 242, and the tilting mechanism are electrically connected to the operation controller 280. Operations of the polishing head 10, the liquid supply valve 33, the gas supply valve 34, the flow-rate controller 35, the flow-rate controller (pressure controller) 36, the substrate holder 210, the lower-side supply nozzle 222, the upper-side supply nozzle 230, the polishing-tape feeding mechanism 242, and the tilting mechanism are controlled by the operation controller 280. During polishing, the operation controller 280 instructs the polishing-tape feeding mechanism 242 to operate so as to advance the polishing tape 3 in its longitudinal direction at a predetermined speed while applying a predetermined tension to the polishing tape 3.
The operation controller 280 is composed of at least one computer. The operation controller 280 includes a memory 280a, and an arithmetic device 280b. The arithmetic device 280b includes a CPU (central processing unit) or a GPU (graphic processing unit) configured to perform arithmetic operations according to instructions contained in programs stored in the memory 280a. The memory 280a includes a main memory (e.g., a random access memory) accessible by the arithmetic device 280b, and an auxiliary memory (e.g., a hard disk drive or a solid state drive) storing data and the programs therein.
The fluid pressing structure 12A and the fluid pressing structure 12B are arranged symmetrically with respect to the center line Ct (see
In one embodiment, the fluid pressing structures 12A and 12B of the polishing head 10 may include the area pads described with reference to
Further, in one embodiment, if the polishing head 10 is intended to polish one of the top edge portion and the bottom edge portion, the polishing head 10 may include only one of the two fluid pressing structures 12A and 12B. Furthermore, in one embodiment, the polishing apparatus 200 may include a plurality of polishing heads 10 arranged in a circumferential direction of the holding stage 204.
The previous description of embodiments is provided to enable a person skilled in the art to make and use the present invention. Moreover, various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles and specific examples defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope as defined by limitation of the claims.
The present invention is applicable to a polishing apparatus and a polishing method for polishing a flat portion of a substrate, such as a wafer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-021042 | Feb 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/001028 | 1/14/2022 | WO |
