JP3804117B2 - Substrate polishing method and polishing apparatus used for the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate polishing method, and more particularly to a substrate polishing method for polishing a substrate on a surface basis, and a polishing apparatus used for the method.
[0002]
[Prior art]
A semiconductor wafer (hereinafter simply referred to as a wafer) is used as a starting material when manufacturing a semiconductor device such as an IC or LSI. In each manufacturing process of the semiconductor device, since various processes for forming circuit elements are performed on the surface of the wafer, it is necessary to polish the surface of the wafer in advance so as to be flat. Or this grinding | polishing may be performed in the middle of each manufacturing process as needed. Such polishing is performed using a dedicated polishing apparatus.
[0003]
FIG. 4 is a cross-sectional view showing a conventional polishing apparatus. In the figure, reference numeral 1 denotes a wafer to be polished, and this wafer 1 is disposed between a surface plate 2 and a wafer holder (substrate holder) 3. 4 is a polishing pad affixed to the surface of the surface plate 2, and 5 is a nozzle that supplies the polishing liquid 6 to the polishing pad 4.
[0004]
The wafer holder 3 is composed of the following parts. Reference numeral 7 is a reference plate, which is disposed so as to face the back surface of the wafer 1 and has a pressure reducing and pressurizing small hole 8 for supplying a gas such as air, and is fixed to the support plate 10 by a reference plate set screw 9. ing. 11 is a universal joint provided between a pair of upper plates 18 and 18 above the support plate 10, and 12 is a large hole for pressure reduction and pressurization provided at the center of the support plate 10 and the upper plates 18 and 18. Reference numeral 13 denotes a decompression and pressurization groove for communicating the decompression and pressurization small hole 8 of the reference plate 7 with the decompression and pressurization large hole 12 of the support plate 10. Reference numeral 14 denotes a seal provided around the decompression and pressurization groove 13. A ring 15 is a backing pad attached to the surface of the reference plate 7. A retainer ring 16 for preventing the wafer 1 from popping out is provided around the reference plate 7, and the retainer ring 16 is fixed to the support plate 10 by a retainer set screw 17.
[0005]
In such a polishing apparatus, when the wafer 1 is polished, the wafer 1 is disposed below the backing pad 15 constituting the wafer holder 3, and the decompression and pressurizing small holes 8, the decompression and pressurizing grooves are provided. 13 and the reduced pressure and pressure large holes 12 are used to perform vacuum suction from the outside, and the back surface of the wafer 1 is adsorbed to the backing pad 15 surface. Next, the wafer holder 3 is placed above the surface plate 2 with the wafer 1 adsorbed, and the surface of the wafer 1 is held in a reduced pressure or normal pressure state so that the surface of the wafer 1 is the polishing pad 4 of the surface plate 2. Press on. Subsequently, the surface of the wafer 1 is polished by rotating both the surface plate 2 and the wafer holder 3 while supplying the polishing liquid 6 from the nozzle 5 to the polishing pad 4.
[0006]
[Problems to be solved by the invention]
By the way, in the polishing method using the conventional polishing apparatus, the unevenness of the thickness of the backing pad 15 directly becomes the unevenness of the polishing pressure, so that there is a problem that the surface which becomes the polishing surface of the wafer 1 is not uniformly polished.
[0007]
That is, instead of the surface reference polishing required for the polishing surface of the wafer 1, the back surface reference polishing depends on the unevenness of the thickness of the backing pad 15. Accordingly, since in-plane uniformity is insufficient particularly for planarization polishing of a wafer having a step on the surface, a polishing method capable of surface-based polishing is required.
[0008]
The present invention has been made to solve such problems, and pressurizes the back surface of the substrate with a gas and polishes the surface of the substrate while supplying a polishing liquid to the surface of the substrate through a polishing pad. In this case, it is an object to enable the substrate to be polished with good in-plane uniformity with respect to the surface.
[0009]
[Means for Solving the Problems]
In the substrate polishing method of the present invention, a substrate is placed between a surface plate and a substrate holder, the back surface of the substrate is pressurized with a gas supplied from the substrate holder side, and the surface of the substrate is passed through the polishing pad from the surface plate side. A substrate polishing method for polishing a surface of a substrate by rotating both a surface plate and a substrate holder while supplying a polishing liquid, the retainer ring surrounding the side surface of the substrate, and the retainer ring and the substrate holder. A retainer-free screw for connecting the retainer and a free screw clamp capable of pressing the retainer-free screw are provided, the substrate is placed on the substrate holder, and suctioned under reduced pressure from the substrate holder side. By lowering the free screw clamp and pushing down the retainer free screw, the retainer ring protrudes downward from the board, The substrate holder and the substrate are moved onto the polishing pad, the position of the substrate holder is fixed at a position where the retainer ring and the polishing pad are in contact, and the substrate is separated from the substrate holder by gas, and the substrate is pressed against the polishing pad, Next, by raising the free screw clamp, the retainer ring is raised to the same height as the surface of the substrate, and the surface of the substrate is polished in this state.
[0010]
Therefore, according to the substrate polishing method of the present invention, the surface of the substrate is polished by the substrate holder in a state where the back surface of the substrate is lifted from the substrate holder except for the outer peripheral portion. Accordingly, since a conventional backing pad is not necessary, the substrate can be polished with in-plane uniformity with respect to the surface.
[0011]
The polishing apparatus according to the present invention includes a surface plate provided with a polishing pad on a contact surface with a substrate to be polished, a reference plate having a hole for supplying gas disposed so as to face the back surface of the substrate, and a reference plate fixed Support plate, a cushion for sealing which is arranged to be shrinkable in the height direction around the reference plate and holds the outer periphery of the back surface of the substrate, and is arranged to be movable in the height direction around the seal cushion The retainer ring that surrounds the side surface of the substrate, the retainer cushion that is disposed so as to be contractible in the height direction in contact with the retainer ring and moves the retainer ring as described above, and the retainer ring and the support through the retainer cushion fixing of the surface plate retainer-free screw that connects the plate, the pressing can free thread clamping the retainer-free screw at least provided And a substrate holder that supplies the gas from the reference plate of the pores of the substrate holder, characterized by comprising as to position in a state of being spaced apart through the gas space of the substrate from the reference plate.
[0012]
Therefore, according to the polishing apparatus of the present invention, the reference plate that is arranged so as to face the back surface of the substrate and has a hole for supplying gas, the support plate to which the reference plate is fixed, and the peripheral portion of the reference plate in the height direction A cushion for sealing that is disposed in such a manner that the outer periphery of the back surface of the substrate is held, a retainer ring that is disposed movably in the height direction around the sealing cushion and surrounds the side surface of the substrate, and the retainer ring. A retainer cushion that is disposed so as to be contractable in the height direction and moves the retainer ring as described above, a retainer-free screw that connects the retainer ring and the support plate via this retainer cushion, and presses the retainer-free screw since it constitutes a substrate holder at least provided a possible free screw clamps, by supplying a gas from the pores of the reference plate It is possible to position the substrate from the reference plate while being spaced apart through the gas space. Accordingly, since a conventional backing pad is not necessary, the substrate can be polished with in-plane uniformity with respect to the surface.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail according to embodiments shown in the drawings.
[0014]
FIG. 1 is a sectional view showing a polishing apparatus used for carrying out the substrate polishing method of the present invention, FIG. 2 is a sectional view showing a wafer holder 3 which is a main part of the polishing apparatus, and FIG. 3 is a bottom view showing the wafer holder 3.
[0015]
1 to 3, 1 is a wafer to be polished, 2 is a surface plate, 3 is a wafer holder, and the wafer 1 is disposed between the surface plate 2 and the wafer holder 3. 4 is a polishing pad affixed to the surface of the surface plate 2, and 5 is a nozzle that supplies the polishing liquid 6 to the polishing pad 4.
[0016]
The wafer holder 3 is composed of the following parts. Reference numeral 7 is made of a rigid material such as ceramic or glass, and is arranged so as to face the back surface of the wafer 1, and has a reference plate having a small hole 8 for decompression and pressurization for supplying a gas such as air. The reference plate 7 is a support plate made of a material such as ceramic or the like and fixed by a reference plate set screw 9.
[0017]
11 is a universal joint provided between a pair of upper plates 18 above the support plate 10, 12 is a large hole for decompression and pressurization provided in the center of the support plate 10 and the upper plate 18, and 13 is a reference plate 7. Reference numeral 14 denotes a pressure reduction and pressurization groove for communicating the pressure reduction and pressurization small hole 8 with the pressure reduction and pressurization large hole 12 of the support plate 10, and reference numeral 14 denotes a seal ring provided around the pressure reduction and pressurization groove 13. A peripheral portion of the reference plate 7 is made of a highly elastic material such as soft silicone rubber, and a sealing cushion 19 is disposed so as to be contractible in the height direction. The sealing cushion 19 is in contact with the support plate 10. The sealing cushion 19 functions to hold the outer peripheral portion of the back surface of the wafer 1.
[0018]
A retainer ring 16 is arranged around the seal cushion 19 so as to be movable in the height direction, which is made of, for example, Delrin (registered trademark) or epoxy resin. The retainer ring 16 is interposed by a retainer-free screw 20 via a retainer cushion 21. It is fixed to the support plate 10. The retainer cushion 21 is made of, for example, a highly elastic material such as soft silicone rubber, and is disposed so as to be shrinkable in the height direction. The retainer ring 16 is moved in the height direction by the elastic force of the retainer cushion 21 and functions to prevent the wafer 1 from protruding in the side surface direction.
[0019]
A free screw clamp 22 is provided around the upper plate 18, and this free screw clamp 22 is disposed such that its protruding end 22 a can move up and down in the insertion hole 23 of the retainer free screw 20. The screw 20 can be pressed.
[0020]
Next, a substrate polishing method using such a substrate polishing apparatus will be described.
[0021]
First, as shown in FIG. 3, the wafer 1 to be polished is set to the sealing cushion 19 constituting the wafer holder 3 so that the orientation flat 1a has a predetermined positional relationship. As shown in FIG. 2, the outer periphery of the back surface of the wafer 1 is sucked from outside through the decompression and pressurization small holes 8, the decompression and pressurization grooves 13 and the decompression and pressurization large holes 12. The portion is adsorbed on the surface of the reference plate 7 in a state where the sealing cushion 19 is compressed. At this time, as shown by an arrow in FIG. 2, the free screw clamp 22 is lowered and pushes down the retainer free screw 20 so that the retainer ring 16 is positioned at the lowermost end. In this state, the bottom of the retainer ring 16 protrudes downward from the surface of the wafer 1 by 50 to 500 μm (preferably 100 to 200 μm).
[0022]
Next, as shown in FIG. 1, the wafer holder 3 holding the wafer 1 is placed on the surface plate 2 and fixed at a position where the retainer ring 16 contacts the polishing pad 4. Subsequently, when a gas such as air is supplied from the outside via the decompression and pressurizing small hole 8, the decompression and pressurizing groove 13, and the decompression and pressurizing large hole 12, the back surface of the wafer 1 is heated by the gas. As a result, the polishing pad 4 is pressed away from the surface of the reference plate 7. Reference numeral 24 denotes a gas space formed between the reference plate 7 and the wafer 1. As a result, the wafer 1 is pressed by the gas space 24 without using the backing pad as in the prior art.
[0023]
Next, as shown in FIG. 1, when the free screw clamp 22 is raised as shown by an arrow, the retainer free screw 20 is not pressed, so the retainer ring 16 compresses the retainer cushion 21 and the surface of the wafer 1. Ascend to the same height. As a result, the retainer-free screw 20 is also raised by this amount of compression. Subsequently, the surface of the wafer 1 is polished by rotating both the surface plate 2 and the wafer holder 3 while supplying the polishing liquid 6 from the nozzle 5 to the polishing pad 4. In such a polishing state, the compression amount of the sealing cushion 19 changes corresponding to the fluctuation of the surface pressure during polishing, but the sealing cushion 19 is made of a highly elastic material such as soft silicone rubber. The sealing effect against gas is always maintained. As described above, the followability of the vertical movement is good, but since the frictional force is large with respect to the lateral force, the wafer 1 does not rotate or shift with respect to the sealing cushion 19. Accordingly, the wafer 1 rotates in synchronization with the rotation of the wafer holder 3.
[0024]
Further, even if the wafer 1 is displaced during polishing, the retainer ring 16 in contact with the surface of the polishing pad 4 prevents the wafer 1 from protruding in the side surface direction. Further, even if the wafer 1 is wavy or warped, the polishing surface of the wafer 1 is pressed against the surface of the polishing pad 4 by back pressure, so that the wafer 1 can be polished almost on the basis of the surface. For this reason, for example, when performing planarization polishing of a wafer having an interlayer film step in an intermediate process of manufacturing MOSIC, the pattern step can be removed with good in-plane uniformity.
[0025]
As described above, according to the substrate polishing method of the present invention, the surface of the wafer 1 is polished by positioning the back surface of the wafer 1 with the gas space separated from the wafer holder 3 except for the outer peripheral portion. Effects can be obtained.
[0026]
(1) Since the surface reference polishing of the wafer 1 can be performed, in-plane uniformity is improved.
[0027]
(2) As the in-plane uniformity is improved, the polishing pad 4 made of a hard material can be used, so that the level difference can be easily flattened.
[0028]
(3) Since the back surface of the wafer 1 can be polished without contact, the back surface is not damaged.
[0029]
(4) Since the outer peripheral portion of the back surface of the wafer 1 is always sealed with a sealing cushion 19 made of a highly elastic material, gas leakage due to pressurization can be prevented, and the applied pressure is stabilized.
[0030]
(5) Polishing can be performed with almost no influence of warpage, waviness, thickness unevenness, etc. existing on the wafer 1.
[0031]
In the description in the text, an example has been described in the case of polishing a semiconductor wafer as an example. However, the present invention is not limited to this, and the present invention can be similarly applied to a case of polishing a wafer-like substrate. Further, the polishing has been described by taking an example in the case of performing a single wafer, but it can also be applied to the case of polishing a plurality of wafers simultaneously. Further, the specific materials of the parts constituting the wafer holder are not limited to those exemplified in the text, but can be similarly used as long as they have equivalent functions.
[0032]
【The invention's effect】
As described above, according to the present invention, since the back surface of the substrate is positioned in a state where it is separated from the substrate holder via the gas space except for the outer peripheral portion, the surface of the substrate is polished. Polishing can be performed with good in-plane uniformity.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a polishing apparatus used for carrying out a substrate polishing method of the present invention.
FIG. 2 is a cross-sectional view showing a substrate holder which is a main part of a polishing apparatus used for carrying out the substrate polishing method of the present invention.
FIG. 3 is a bottom view showing a substrate holder which is a main part of a polishing apparatus used for carrying out the substrate polishing method of the present invention.
FIG. 4 is a cross-sectional view showing a conventional polishing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Wafer (substrate), 2 ... Surface plate, 3 ... Wafer holder (substrate holder), 4 ... Polishing pad, 5 ... Nozzle, 6 ... Polishing liquid, 7 ... Reference plate, 10 ... Support plate, 14 ... Seal ring, 16 Retainer ring, 19 ... Seal cushion, 20 ... Retainer free screw, 21 ... Retainer cushion, 22 ... Free screw clamp, 24 ... Gas space.

Claims (3)

A substrate is disposed between the surface plate and the substrate holder, and the back surface of the substrate is pressurized with a gas supplied from the substrate holder side, and a polishing liquid is supplied from the surface plate side to the surface of the substrate through a polishing pad. However, the substrate polishing method for polishing the surface of the substrate by rotating both the platen and the substrate holder,
The substrate holder is provided with a retainer ring so as to surround a side surface of the substrate, a retainer-free screw that connects the retainer ring and the substrate holder, and a free screw clamp that can press the retainer-free screw ,
By placing the substrate in the substrate holder and sucking the substrate from the substrate holder side under reduced pressure, the substrate is sucked into the substrate holder,
By lowering the free screw clamp and pushing down the retainer free screw, the retainer ring protrudes downward from the substrate,
Next, the substrate holder and the substrate are moved onto the polishing pad, the position of the substrate holder is fixed at a position where the retainer ring and the polishing pad are in contact, and the substrate holder is separated from the substrate holder by gas. Pressing the substrate against the polishing pad;
Next, by raising the free screw clamp, the retainer ring is raised to the same height as the surface of the substrate, and the surface of the substrate is polished in this state. A retainer cushion is provided between the substrate holder and the retainer ring so as to be in contact with the retainer ring and contractible in a height direction, and the retainer cushion is expanded and contracted by raising and lowering the free screw clamp and the retainer free screw. The substrate polishing method according to claim 1, wherein the retainer ring is raised and lowered. A surface plate provided with a polishing pad on the contact surface with the substrate to be polished;
A reference plate arranged to face the back surface of the substrate and having a hole for supplying gas;
A support plate to which the reference plate is fixed,
A cushion for sealing that is arranged to be shrinkable in the height direction around the reference plate and holds the outer peripheral portion of the back surface of the substrate;
A retainer ring that surrounds the side surface of the substrate and is movably disposed in the height direction around the sealing cushion.
And a retainer cushion which is disposed so as to be contractible in the height direction in contact with the retainer ring and moves the retainer ring as described above,
A retainer-free screw that connects the retainer ring and the support plate via the retainer cushion;
A substrate holder that is fixed on the polishing pad by providing at least a free screw clamp capable of pressing the retainer-free screw,
A polishing apparatus, wherein a gas is supplied from a hole of a reference plate of the substrate holder, and the substrate is positioned in a state of being separated from the reference plate.

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