JP7399220B2 - polishing equipment - Google Patents

Description

The present invention relates to a polishing apparatus for polishing wafers.

In the semiconductor manufacturing field, a polishing apparatus is known that polishes a semiconductor wafer (hereinafter referred to as a "wafer") such as a silicon wafer and then polishes the wafer to remove a remaining clutch.

In the polishing apparatus described in Patent Document 1, the polishing surface of the polishing pad formed to have a larger diameter than the wafer is in contact with the entire surface of the wafer, and the feeding means moves the polishing pad in the -Z direction while rotating the wafer and the polishing pad. This is a polishing device that polishes the top surface of a wafer by moving the wafer.

Japanese Patent Application Publication No. 2015-134383

However, in the polishing apparatus described in Patent Document 1, when the polishing pad does not abut parallel to the upper surface of the wafer, for example, when the polishing pad is tilted with respect to the wafer so that the part protruding from the wafer falls down, the polishing pad There is a problem in that the polishing surface may come into contact with only a portion of the wafer, resulting in variations in the amount of polishing of the wafer.

Therefore, a technical problem arises that must be solved in order to uniformly polish the entire surface of the wafer, and it is an object of the present invention to solve this problem.

In order to achieve the above object, a polishing apparatus according to the present invention includes: a polishing head having a polishing pad for polishing the upper surface of a wafer; a spindle shaft for rotating the polishing head; A central pressing means for pressing the polishing head downward via a spindle shaft, an outer pressing means for pressing the polishing head downward on an outer peripheral side of the spindle shaft, and connecting the polishing head and the spindle shaft. and an elastic member that bends so that the polishing head follows the upper surface of the wafer.

According to this configuration, the central pressing means presses the center of the polishing pad, and the outer pressing means presses the outer peripheral side of the spindle shaft, so that the polishing pad is tilted so as to follow the top surface of the wafer, so that the wafer can be completely covered. Polishing can be performed with the polishing pad in contact with the surface. In addition, by pressing the outer circumferential side of the spindle shaft with the outer pressing means, pressure escape that tends to occur on the outer circumferential side of the polishing pad is suppressed, and variations in the pressing force distribution that tend to be concentrated in the center of the polishing pad are alleviated. can do.

Further, in the polishing apparatus according to the present invention, the elastic member includes at least one first joint part joined to the spindle shaft and at least one second joint part joined to the polishing head. Preferably.

Further, in the polishing apparatus according to the present invention, it is preferable that the first joint portion and the second joint portion are arranged so as not to overlap when viewed from at least one of the above and the below.

Further, in the polishing apparatus according to the present invention, it is preferable that the elastic member is formed in a triangular shape when viewed from at least one of an upper side and a lower side.

Further, in the polishing device according to the present invention, the first joint portion is provided at the apex portion of the elastic member when viewed from at least one of above and below, and the second joint portion is provided at the apex portion of the elastic member when viewed from at least one of above and below. It is preferable that the elastic member is provided at a central portion of a side of the elastic member when viewed from one side.

Further, in order to achieve the above object, a polishing apparatus according to the present invention includes a fixed body and a rotating body that is provided with a polishing pad for polishing a wafer and rotates relative to the fixed body. a polishing head, a spindle shaft that is arranged inside the fixed body and rotates the rotating body, a first pressing means that presses the polishing head toward the wafer via the spindle shaft, and the fixed body. and a second pressing means for pressing the polishing head toward the wafer, and a tilt-allowing connection means for connecting the rotating body to the spindle shaft in a freely tiltable manner.

In the present invention, the central pressing means presses the center of the polishing pad, and the outer pressing means presses the outside of the spindle shaft, so that the polishing pad is tilted to follow the top surface of the wafer. Polishing can be performed while the two are in contact with each other. In addition, by pressing the outer circumferential side of the spindle shaft with the outer pressing means, pressure escape that tends to occur on the outer circumferential side of the polishing pad is suppressed, and variations in the pressing force distribution that tend to be concentrated in the center of the polishing pad are alleviated. can do.

1 is a perspective view schematically showing a polishing apparatus according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view schematically showing the internal structure of the polishing device. FIG. 3 is a vertical cross-sectional view schematically showing the main parts of the polishing head. A plan view and a perspective view showing a part of an elastic member and a rotating body. FIG. 3 is a schematic diagram showing the positional relationship of pressing areas that act on a wafer. FIG. 3 is a schematic diagram showing a state in which a polishing pad follows and contacts an inclined wafer. FIG. 3 is a diagram showing the analysis results of the pressing force distribution over the entire surface of the wafer. FIG. 7 is a schematic diagram showing the positional relationship of pressing areas that act on a wafer in a polishing apparatus according to a modification of the present invention.

Embodiments of the present invention will be described based on the drawings. In addition, in the following, when referring to the number, numerical value, amount, range, etc. of constituent elements, the term is limited to that specific number, unless it is specifically specified or it is clearly limited to a specific number in principle. It doesn't matter if it's more than or less than a certain number.

In addition, when referring to the shape or positional relationship of constituent elements, etc., unless it is specifically specified or it is clearly considered that it is not the case in principle, etc., we refer to things that are substantially similar to or similar to the shape, etc. include.

Further, in the drawings, characteristic parts may be enlarged or exaggerated in order to make the features easier to understand, and the dimensional ratios of the constituent elements are not necessarily the same as in reality. Further, in the cross-sectional views, hatching of some components may be omitted in order to make the cross-sectional structure of the components easier to understand.

FIG. 1 is a perspective view schematically showing a polishing apparatus 1 according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the internal structure of the polishing apparatus 1. As shown in FIG. FIG. 3 is a sectional view showing the main parts of the polishing head 10. The polishing apparatus 1 polishes the upper surface of the wafer W held by the wafer chuck 2 to remove a damaged layer including microcracks generated during the grinding process.

The wafer chuck 2 is rotatably provided around a rotation axis a1 passing through the center of the wafer chuck 2. The wafer chuck 2 has an adsorbent (not shown) made of a porous material such as alumina embedded in the upper surface. The wafer chuck 2 is equipped with a conduit (not shown) extending through the inside and extending to the surface. The pipe line is connected to a vacuum source, compressed air source, or water supply source via a rotary joint (not shown). When the vacuum source is activated, the wafer W placed on the wafer chuck 2 is attracted and held by the wafer chuck 2. Further, when the compressed air source or the water supply source is activated, the adsorption between the wafer W and the wafer chuck 2 is released. Note that the wafer chuck 2 may be provided with a tilt mechanism (not shown) that tilts the rotation axis a1.

The wafer W is suction-held by the wafer chuck 2 while being mounted on a bag grind tape, a support substrate such as a glass substrate, a silicon substrate, or the like. In particular, as the wafer W becomes thinner and has a larger diameter, a support substrate is often used.

The polishing apparatus 1 includes a polishing head 10 provided above a wafer chuck 2. The polishing head 10 is configured to be rotatable by a polishing spindle 20.

The polishing spindle 20 includes a motor 21, a spindle shaft 22 connected to the motor 21, a casing 23 housing the spindle shaft 22, and a bearing 24 interposed between the spindle shaft 22 and the casing 23. ing. The spindle shaft 22 is rotated by the motor 21 around the rotation axis a2. Note that reference numeral 3 is a guide that restricts the vertical movement of the polishing spindle 20.

The polishing apparatus 1 includes a feed mechanism (not shown) that vertically moves the polishing head 10 up and down. The feeding mechanism is, for example, a known ball screw slider mechanism. The feeding mechanism seats the polishing surface 31 of the polishing pad 30 on the upper surface of the wafer W before starting processing, and retracts the polishing head 10 to a predetermined standby position after finishing processing.

The polishing head 10 includes a rotating body 11, a fixed body 12, and a bearing 13.

A polishing pad 30 is horizontally attached to the lower end of the rotating body 11. The polishing pad 30 is formed to have a larger diameter than the wafer W. For example, the diameter of the polishing pad 30 is set to 450 mm for the wafer W having a diameter of 300 mm.

The rotating body 11 has a U-shaped cross section, and is connected to the lower end of the spindle shaft 22 via an elastic member 14. The fixed body 12 is formed into a disk shape and is housed in the rotating body 11 via a bearing 13. As a result, as the spindle shaft 22 rotates, the rotating body 11 and the elastic member 14 rotate together relative to the fixed body 12.

As shown in FIG. 4, the elastic member 14 has a substantially equilateral triangular shape in plan view. The elastic member 14 is formed into a flexible shape, and is preferably made of tempered steel. Since the elastic member 14 is interposed between the rotating body 11 and the spindle shaft 22, the rigidity of the polishing head 10 in the prying direction is reduced, so that the polishing pad 30 is not tilted so as to swing in the vertical direction. I can do it. The elastic member 14 includes an upper joint part 15 and a lower joint part 16.

One upper joint portion 15 is provided on the upper surface of the elastic member 14 near each vertex of the elastic member 14 . The upper joints 15 are respectively joined to the spindle shafts 22 .

One lower joint portion 16 is provided on the lower surface of the elastic member 14 near the center of each side of the elastic member 14 . The lower joint portions 16 are respectively joined to the rotating body 11 . In this way, the upper joint parts 15 and the lower joint parts 16 are arranged alternately along the circumferential direction of the elastic member 14.

The polishing apparatus 1 includes a first air cylinder 40 as a central pressing means and a second air cylinder 50 as an outer pressing means.

In the first air cylinder 40, a cylinder 41 is attached to the column 4, and a piston 42 is attached to the upper surface of the casing 23. Further, the first air cylinder 40 is arranged on the rotation axis a2 and is configured to evenly press the entire casing 23 downward.

Two second air cylinders 50 are provided on the upper part of the fixed body 12. Specifically, the cylinder 51 is attached to the lower surface of the flange 25 erected from the side surface of the casing 23, and the piston 52 is attached to the upper surface of the fixed body 12. Further, the second air cylinders 50 are provided one by one at symmetrical positions across a straight line connecting the center of rotation of the polishing head 10 and the center of the wafer W when viewed from above. Further, the rotation axis a2 and the two second air cylinders 50 are arranged so as to form the vertices of an equilateral triangle when viewed from a plane. Note that the arrangement of the second air cylinder 50 is not limited to that described above.

Note that the central pressing means and the outside pressing means are controlled by known pneumatic pressure control in which the piston moves forward and backward by compressed air supplied into the cylinders, as in the first air cylinder 40 and the second air cylinder 50 as described above. The device is not limited to the device, and any structure that can apply a pressing force to the wafer W may be used, for example, a diaphragm or an air bag.

The operation of the polishing apparatus 1 is controlled by a control device 60. The control device 60 controls each component constituting the polishing device 1. The control device 60 includes, for example, a CPU, a memory, and the like. Note that the functions of the control device 60 may be realized by controlling using software, or may be realized by operating using hardware. Further, the control device 60 also functions as a pressure control means that controls the pressing force of the first air cylinder 40 and the second air cylinder 50.

Next, the operation of the polishing apparatus 1 will be explained based on the drawings.

As shown in FIG. 5, in the polishing apparatus 1, the polishing pad 30 covers the entire surface of the wafer W, the rotating directions of the polishing pad 30 and the wafer W match, and the outer periphery of the polishing pad 30 and the outer periphery of the wafer W are aligned at one point. Perform polishing so that they overlap. As a result, the velocity vectors in the plane of the wafer W match. In addition, the polishing pad 30 always covers the entire surface of the wafer W during processing, so that the entire surface of the wafer W is always in contact with the polishing pad 30.

During the polishing process, the first air cylinder 40 and the second air cylinder 50 each press the polishing pad 30 downward with a predetermined pressing force. Specifically, the pressing force from the first air cylinder 40 is transmitted to the casing 23 , the bearing 24 , the spindle shaft 22 , the elastic member 14 , and the rotating body 11 in this order, so that the polishing is performed immediately below the first air cylinder 40 . Pad 30 is pressed onto the top surface of wafer W.

Further, the pressing force from the second air cylinder 50 is transmitted to the fixed body 12, the bearing 13, and the rotating body 11 in this order, so that the polishing pad 30 is pressed against the upper surface of the wafer W directly under the second air cylinder 50. . As a result, as shown in FIG. 5, the first air cylinder 40 presses the center of the polishing pad 30, and the second air cylinder 50 presses the center of the polishing pad 30. Press.

In this way, when the second air cylinder 50 presses a location away from the rotation center of the polishing head 10, the elastic member 14 interposed between the rotating body 11 and the spindle shaft 22 is bent, and the polishing The pad 30 tilts to swing in the vertical direction.

As a result, the polishing pad 30 tends to tilt so that the part of the polishing pad 30 that is not supported by the wafer W falls downward, or as shown in FIG. 6, the rotation axis a1 of the wafer chuck 2 is tilted. Even when polishing is performed in a state where the polishing pad 30 is tilted so as to follow the wafer W and the polishing pad 30 is brought into contact with the entire surface of the wafer W, polishing can be performed.

Further, the two second air cylinders 50 are symmetrical with respect to a straight line connecting the rotation center of the polishing head 10 and the center of the wafer W, and the rotation axis a2 and the two second air cylinders 50 are symmetrical with respect to the plane. By being arranged so as to form the vertices of an equilateral triangle when viewed, the attitude of the polishing head 10 can be smoothly corrected.

Further, when pressing the polishing pad 30 against the wafer W by pressurizing only the center of the polishing pad 30 as in the past, as shown in FIG. 7(a), the pressing force acting on the wafer W is While it is large near the rotation axis of the polishing pad 30, it becomes small near the outer periphery of the polishing pad 30, and so-called pressure escape occurs at the outer periphery of the polishing pad 30, which may cause variations in the pressure force distribution within the surface of the wafer W. there were. Note that in FIG. 7A, the dark-colored area on the right side of the page is the area where the pressing force is the largest, and the pressing force decreases in the order of the light-colored area and the dark-colored area toward the left side of the page.

However, while pressing with the first air cylinder 40, the second air cylinder 50 locally presses between the rotation center of the polishing head 10 and the outer periphery of the polishing pad 30, that is, the polishing pad 30 is By applying pressure at multiple points at the center and outside of the rotation axis a2, as shown in FIG. 7(b), escape of pressure at the outer peripheral portion of the polishing pad 30 is suppressed, and the distribution of pressing force within the surface of the wafer W is improved. Variations can be alleviated.

Note that the pressing force of the first air cylinder 40 and the second air cylinder 50 may be maintained at a value set in advance before the start of processing during processing, or may be changed as appropriate during processing. It doesn't matter if it's something you do.

For example, the wafer chuck 2 is provided with a plurality of pressure sensors that measure the pressing force acting on the wafer W during processing, and the control device 60 calculates the pressing force distribution within the wafer W based on the measured values of each pressure sensor. However, by adjusting the pressing force of the second air cylinder 50, variations in the pressing force distribution within the surface of the wafer W may be alleviated while processing. Note that the pressure sensor may be, for example, a load cell provided to support the wafer chuck 2.

In the above-described embodiment, the case where two second air cylinders 50 are provided as the outer pressing means has been described, but it is also possible to provide one second air cylinder 50. In this case, the second air cylinder 50 is provided on a straight line connecting the center of rotation of the polishing head 10 and the center of the wafer W when viewed from above, as shown in FIG.

As a result, the second air cylinder 50 disposed on the opposite side of the rotation center of the polishing head 10 across the center of the wafer W presses the outer peripheral side of the spindle shaft 22 downward, so that the polishing pad 30 is attached to the wafer W. The attitude of the polishing head 10 can be corrected to follow.

In the embodiment described above, the elastic member 14 connecting the rotary body 11 and the spindle shaft 22 was explained as an example of the tilt-permitting connection means. For example, it may be a gimbal mechanism or the like.

Below, some examples of polishing devices will be added.
[1] A wafer polishing apparatus, which includes a polishing head having a polishing pad for polishing the upper surface of the wafer, a spindle shaft for rotating the polishing head, and an inclination for connecting the polishing head to the spindle shaft in a tiltable manner. A permissible connection means, a central pressing means for pressing the polishing head downward through the spindle shaft, and an outer pressing means provided on the outer circumferential side of the spindle shaft for pressing the polishing head downward. polishing equipment.
According to this configuration, the central pressing means presses the center of the polishing pad, and the outer pressing means presses the outer peripheral side of the spindle shaft, so that the polishing pad is tilted so as to follow the top surface of the wafer, so that the wafer can be completely covered. Polishing can be performed with the polishing pad in contact with the surface. In addition, by pressing the outer circumferential side of the spindle shaft with the outer pressing means, pressure escape that tends to occur on the outer circumferential side of the polishing pad is suppressed, and variations in the pressing force distribution that tend to be concentrated in the center of the polishing pad are alleviated. can do.

[2] The polishing head includes a rotating body connected to the spindle shaft via the tilt-permitting connection means and having the polishing pad attached to a lower end thereof, and the polishing head is arranged inside the rotating body, and the outer pressing means is connected to the spindle shaft. The polishing device according to [1], comprising a fixed body attached to the rotating body and a bearing interposed between the rotary body and the fixed body.
According to this configuration, the pressing force of the outer pressing force is transmitted to the fixed body, the bearing, and the rotating body in this order, so that the pressing force that presses the polishing pad against the upper surface of the wafer is locally applied directly below the outer pressing force means. be able to.

[3] The polishing apparatus according to [1] or [2], further comprising pressure control means for controlling the pressing force applied by the central pressing means or the outer pressing means.
According to this configuration, the pressure control device adjusts the pressing force of the central pressing means or the outer pressing means, thereby making it possible to alleviate variations in the pressing force distribution within the wafer surface.

[4] Further comprising a plurality of measuring means for measuring the pressing force within the wafer, the pressure controlling means controlling the pressing force applied by the central pressing means or the outer pressing means according to the measured value of the measuring means. The polishing apparatus according to [3].
According to this configuration, the pressure control device adjusts the pressing force of the central pressing means or the outer pressing means based on the pressing force distribution within the wafer surface calculated from the measurement value of the measuring means, thereby applying pressure within the wafer surface. Variations in pressure distribution can be further alleviated.

[5] The polishing apparatus according to [1], wherein one of the outer pressing means is provided on a straight line connecting the center of rotation of the polishing head and the center of the wafer when viewed from above.
According to this configuration, the outer pressing means placed on the opposite side of the center of rotation of the polishing pad across the center of the wafer presses the outer peripheral side of the spindle shaft downward, thereby polishing the polishing pad so that it follows the wafer. The posture of the head is corrected so that polishing can be performed with the polishing pad in contact with the entire surface of the wafer, and variations in the pressing force distribution are alleviated by suppressing pressure escape on the outer circumferential side of the polishing pad. I can do it.

[6] The outer pressing means is provided at a symmetrical position across a straight line connecting the rotation center of the polishing head and the center of the wafer when viewed from a plane, and the rotation center of the polishing head and the outer pressing means are The polishing device according to [1], wherein one polishing device is provided on each vertex of a regular polygon when viewed from a plane.
According to this configuration, the plurality of external pressing means press the polishing pad in a well-balanced manner, so that the posture of the polishing head is smoothly corrected so that the polishing pad follows the wafer, and the polishing pad is brought into contact with the entire surface of the wafer. Polishing can be performed in a state in which the polishing pad is held in place, and it is also possible to suppress pressure escape on the outer circumferential side of the polishing pad, thereby alleviating variations in the pressing force distribution.

Further, the present invention can be modified in various ways other than those described above without departing from the spirit of the invention, and it goes without saying that the present invention extends to such modifications.

1 ... Polishing device 2 ... Wafer chuck 3 ... Guide 4 ... Column 10 ... Polishing head 11 ... Rotating body 12 ... Fixed body 13 ... Bearing 14 ... Elasticity Components (tilt-permissible connection means)
15 ... Upper joint part 16 ... Lower joint part 20 ... Polishing spindle 21 ... Motor 22 ... Spindle shaft 23 ... Casing 24 ... Bearing 30 ... Polishing pad 31 ... - Polishing surface 40...first air cylinder (center pressing means)
50...Second air cylinder (outer pressing means)
60...Control device W...Wafer a1...Rotation axis a2 (of wafer chuck)...Rotation axis (of polishing head)

Claims (6)

a polishing head having a polishing pad for polishing the top surface of the wafer;
a spindle shaft that is not connected to the polishing head on the rotation axis and is provided to allow the polishing head to rotate around the rotation axis;
central pressing means disposed above the polishing head and pressing the polishing head downward via the spindle shaft;
outer pressing means for pressing the polishing head downward on the outer peripheral side of the spindle shaft;
An elastic body formed of a continuous body surrounding the rotation axis when viewed from at least one of above and below, connecting the polishing head and the spindle shaft, and bending so that the polishing head follows the upper surface of the wafer. parts and
A polishing device characterized by comprising: The elastic member is
at least one first joint joined to the spindle shaft;
at least one second joint joined to the polishing head;
The polishing apparatus according to claim 1, further comprising: 3. The polishing apparatus according to claim 2, wherein the first joint part and the second joint part are arranged so as not to overlap when viewed from at least one of above and below. 4. The polishing apparatus according to claim 3, wherein the elastic member has a triangular shape when viewed from at least one of an upper side and a lower side. The first joint portion is provided at an apex portion of the elastic member when viewed from at least one of above and below,
5. The polishing apparatus according to claim 4, wherein the second joint portion is provided at a central portion of a side of the elastic member when viewed from at least one of above and below. The polishing head includes a fixed body and a rotating body that is provided with a polishing pad for polishing a wafer and rotates relative to the fixed body ,
The spindle shaft is arranged inside the fixed body ,
The polishing apparatus according to claim 1 , wherein the outer pressing means is provided on the fixed body .