JP2000202763A - Polishing device and polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly make flatness in the total surface of a semiconductor substrate, and attain uniform polishing up to in the vicinity of a wafer edge, in a polishing device or a polishing pad for use in a mechanical flatting process smoothing by polishing a surface of an insulation layer or metal wiring formed on the semiconductor substrate. SOLUTION: In this polishing device, a semiconductor substrate is fixed to a polishing head, a polishing layer of at least 70 degrees micro rubber A hardness and 1 MPa to 500 MPa tensile elastic modulus secured through a cushion layer of at least 60 MPa volume modulus and 0.1 MPa to 20 MPa tensile elastic modulus to a polishing surface plate is pressed to the semiconductor substrate, and the polishing head or the polishing surface plate or both thereof are rotated, so as to polish the semiconductor substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus and a polishing pad for a semiconductor substrate, and more particularly to a method for mechanically flattening the surface of an insulating layer formed on a semiconductor substrate such as silicon and the surface of metal wiring. To a polishing apparatus and a polishing pad.

[0002]

2. Description of the Related Art Large-scale integrated circuits (LSI) typified by semiconductor memories have been increasingly integrated year by year, and accordingly, the technology for manufacturing large-scale integrated circuits has been increasing. Further, with the increase in the density, the number of stacked semiconductor device manufacturing locations has also increased. Due to the increase in the number of layers, unevenness of the main surface of the semiconductor wafer caused by stacking, which has not been a problem in the past, has become a problem. As a result, for example, Nikkei Microdevice July 1994 Issue 50
As described on page 57, chemical mechanical polishing (CMP) is performed for the purpose of compensating for a lack of depth of focus at the time of exposure due to unevenness caused by laminating, or for improving wiring density by flattening through holes. : Chemical
The planarization of a semiconductor wafer using a mechanical polishing technique has been studied.

In general, a CMP apparatus includes a polishing head for holding a semiconductor substrate as an object to be processed, a polishing pad for performing a polishing process on the object to be processed, and a polishing platen for holding the polishing pad. Then, in the polishing process of the semiconductor substrate, a protruding portion of the layer on the surface of the semiconductor substrate is removed by moving the semiconductor substrate and the polishing pad relative to each other using a slurry composed of an abrasive and a chemical solution, thereby smoothing the layer on the substrate surface. It is to be. The polishing rate at the time of polishing the semiconductor substrate, for example, in the case of a silicon oxide (SiO2) film formed on one main surface of the semiconductor substrate, is substantially proportional to the relative speed and load between the semiconductor substrate and the polishing pad. Therefore, in order to uniformly polish each part of the semiconductor substrate, it is necessary to make the load applied to the semiconductor substrate uniform.

However, the surface of the semiconductor substrate held by the polishing head often undulates as a whole, for example, due to the original deformation of the semiconductor substrate such as warpage. Therefore, in order to uniformly apply a load to each part of the semiconductor substrate, it is desirable to use a soft polishing pad from the viewpoint of bringing the polishing pad into contact with the undulation of the semiconductor substrate as described above. However, when a polishing process for flattening irregularities such as an insulating layer formed on one main surface of a semiconductor substrate is performed using a soft polishing pad, the followability to the undulation of the semiconductor substrate can be improved. In addition, the flatness of local irregularities on the surface of the semiconductor substrate deteriorates. For example, there is a problem that partial unevenness of the layer on the surface of the semiconductor substrate is polished, that is, the polished surface is rounded and not flat. On the other hand, when polishing a semiconductor substrate similarly using a hard polishing pad,
Contrary to the case of using the above-mentioned soft polishing pad, it is possible to improve the flatness of the local unevenness on the surface of the semiconductor substrate, but it becomes worse from the viewpoint of followability to the entire undulation of the semiconductor substrate, for example, In each part of the entire undulation of the semiconductor substrate surface, the unevenness of the part where the undulation is protruded is polished a lot, and the unevenness of the part where the undulation is recessed is almost left without being polished. I will. Such non-uniform polishing processing exposes the aluminum wiring and the thickness of the silicon oxide insulating film surface after polishing differs from part to part, so that, for example, irregularities in through-hole diameters and unevenness due to lamination cannot be flattened. This causes insufficient depth of focus at the time of exposure.

As a prior art relating to a polishing pad for satisfying the conflicting demands of improving the partial flatness and the overall followability, a two-layer pad disclosed in JP-A-6-21028 has been tried. Was. JP-A-6-210
No. 28, the two-layer pad has a bulk modulus of 4 p.
250 psi / psi over a stress range of si to 20 psi
The polishing layer in direct contact with the semiconductor substrate supported by the cushion layer described below has a larger volume elastic modulus. The purpose is to allow the cushion layer to absorb the entire undulation of the semiconductor substrate, while allowing the polishing layer to withstand a curvature greater than a certain area (eg, greater than the die spacing). Unfortunately, such conventional two-layer pads still remain challenging in terms of polishing performance.
First of all, even if the polishing layer has a bulk modulus higher than that of the cushion layer, the flatness of the local unevenness on the surface of the semiconductor substrate may be deteriorated, and the local flatness is reduced by the bulk elasticity of the polishing layer. It is not always correlated with rates. Second, the bulk modulus of the cushion layer is 4 psi to 20 ps.
Since the stress range of i is 250 psi / psi, the undulation followability of the entire semiconductor substrate is poor, and as a result, uniformity (uniformity) of the flatness over the entire semiconductor substrate cannot be obtained. In addition, as described in pages 177 to p183 of CMP Science published by Science Forum Co., Ltd., it is also an issue how close planarization is required to the edge of the wafer within the wafer plane. It is hard to say that there is. Accordingly, there is a need for an improved polishing apparatus or polishing pad that overcomes the above disadvantages.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing apparatus or a polishing apparatus for use in a mechanical flattening step for smoothing the surface of an insulating layer or a metal wiring formed on a semiconductor substrate by polishing. An object of the present invention is to provide a technique for uniformly polishing the entire surface of a semiconductor substrate in a polishing pad.

[0007]

Means for Solving the Problems As means for solving the problems, the present invention has the following constitution.

As a first invention, "a semiconductor substrate is fixed to a polishing head and fixed to a polishing platen via a cushion layer having a volume elastic modulus of 60 MPa or more and a tensile elasticity of 0.1 MPa to 20 MPa or less. Micro rubber A
Polishing the semiconductor substrate by rotating the polishing head or the polishing platen or both with the polishing layer having a hardness of 70 degrees or more and a tensile elastic modulus of 1 MPa or more and 500 MPa or less pressed against the semiconductor substrate. A method for polishing a semiconductor substrate, comprising: As a second invention, there is provided a polishing head, a polishing pad facing the polishing head, a polishing platen for fixing the polishing pad, and a polishing device including a driving device for rotating the polishing head, the polishing platen or both of them. An apparatus wherein the polishing pad has a bulk modulus of 60.
MPa or more and tensile modulus of elasticity is 0.1 MPa or more 2
A polishing apparatus comprising a cushion layer having a hardness of 0 MPa or less and a polishing layer having a micro rubber A hardness of 70 degrees or more and a tensile modulus of elasticity of 1 MPa or more and 500 MPa or less in a direction of a polishing head. As a third invention, "a polishing layer having a micro rubber A hardness of 70 degrees or more and a tensile modulus of 1 MPa or more and 500 MPa or less, a bulk modulus of 60 MPa or more, and a tensile modulus of 0.1
A polishing pad comprising: a cushion layer having a pressure of not less than 20 MPa and not more than 20 MPa. ".

[0009]

Embodiments of the present invention will be described below.

First, the micro rubber A hardness referred to in the present invention will be described. The micro rubber A hardness means a value evaluated by a micro rubber hardness meter. This device is manufactured by Kobunshi Keiki Co., Ltd.
Supplied as Micro Rubber Hardness Tester MD-1. The micro rubber hardness tester MD-1 realizes the hardness measurement of thin and small samples, which was difficult to measure with a conventional hardness tester, and is a spring-type rubber hardness tester (durometer).
Since it is designed and manufactured as a reduced model of about 1/5 of the A type, its measured value can obtain a value almost coincident with the hardness of the spring type rubber hardness meter A type. The micro rubber hardness tester MD-1 has a diameter of 0.16 mm in diameter and a height of 0.5 mm. The load method is a cantilever type leaf spring, and the spring load is 2.24 m at 0 point.
N is 33.85 mN at 100 points. The descending speed of the needle is measured by controlling the range of 10 to 30 mm / sec with a stepping motor. In a normal polishing pad, the thickness of the polishing layer or the hard layer is less than 5 mm, and cannot be evaluated by a spring type rubber hardness meter A type because it is too thin. Therefore, the evaluation can be performed by the micro rubber hardness meter MD-1.

The polishing pad of the present invention includes a polishing layer having a function of polishing a semiconductor substrate and a cushion layer disposed on a side to be fixed. The polishing layer of the present invention comprises a micro rubber A
It is a polishing layer having a hardness of 70 degrees or more and a tensile modulus of 1 MPa or more and 500 MPa or less. The micro rubber A hardness of the polishing layer needs to be 70 degrees or more, preferably 80 degrees or more, and more preferably 90 degrees or more. If the micro rubber A hardness is less than 70 degrees, the flatness of the local unevenness of the semiconductor substrate becomes poor, which is not preferable. Tensile modulus is applied to the polishing layer in a dumbbell shape and tensile stress is applied.
Tensile strain (= change in tensile length / original length) is 0.
Measure the tensile stress in the range from 01 to 0.03,
Tensile modulus = ((tensile stress when tensile strain is 0.03)-(tensile stress when tensile strain is 0.01)) / 0.02. As a measuring device, Orientec Tensilon Universal Tester RTM
-100 and the like. The measurement conditions were as follows: the test speed was 5 cm / min, the test piece shape was 5 mm wide, and the sample length was 50 m.
m dumbbell shape. The tensile modulus is preferably 1 MPa or more and 500 MPa or less. Tensile modulus of elasticity is 1M
If it is less than Pa, it is not preferable because of poor flatness.
If the pressure exceeds 0 MPa, it is not preferable because the flatness of the entire semiconductor substrate cannot be uniform. The more preferable range of the tensile elastic modulus of the polishing layer is 10 MPa or more and 300 MPa.
Hereinafter, a more preferable range is 20 MPa to 100 MPa.
a or less.

It is preferable that the polishing layer has closed cells in order to enhance the retention of the abrasive and to increase the polishing rate. The closed cell diameter is preferably 1000 μm or less because the flatness of the local unevenness of the semiconductor substrate is good. The more preferable diameter of the closed cell is 500 μm or less, and the more preferable diameter is 300 μm or less.

The polishing layer preferably has a density in the range of 0.70 to 0.90. If the density is less than 0.70, the polishing rate is low, which is not preferable. If the density exceeds 0.90, the polishing rate is low, which is not preferable. A more preferable range of the density is 0.74 or more and 0.86 or less. A more preferred range is from 0.75 to 0.82.

A preferable material for the polishing layer contains polyurethane as a component. A more preferable material is 0.8 to 3.8 times the content of the polymer polymerized from the vinyl compound with respect to the content of polyurethane. The following are included. The polyurethane is a polymer synthesized based on a polyaddition reaction or a polymerization reaction of a polyisocyanate. The compound used as the symmetry of the polyisocyanate is an active hydrogen compound, that is, a compound containing two or more polyhydroxy or amino groups. Examples of the polyisocyanate include, but are not limited to, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Polyol is typical as polyhydroxy, but as polyol, polyether polyol, polytetramethylene ether glycol, epoxy resin-modified polyol,
Examples include polyester polyol, acrylic polyol, polybutadiene polyol, and silicone polyol.

The vinyl compound in the present invention is a compound having a vinyl group having a carbon-carbon double bond. Specifically, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, methacrylic acid, glycidyl methacrylate, ethylene glycol dimethacrylate, fumaric acid, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, maleic acid, Dimethyl maleate, diethyl maleate, dipropyl maleate,
Acrylonitrile, acrylamide, vinyl chloride, styrene, α-methylstyrene and the like can be mentioned. The polymer polymerized from the vinyl compound in the present invention is a polymer obtained by polymerizing the above vinyl compound, and specifically, polymethyl methacrylate, polyethyl methacrylate, poly (n-butyl methacrylate), Isobutyl methacrylate, poly (2-ethylhexyl methacrylate), polyisodecyl methacrylate, poly (n-lauryl methacrylate), poly (2-hydroxyethyl methacrylate), poly (2-hydroxypropyl methacrylate), poly (2-hydroxyethyl acrylate) , Poly (2-hydroxypropyl acrylate),
Poly (2-hydroxybutyl methacrylate), polydimethylaminoethyl methacrylate, polydiethylaminoethyl methacrylate, polymethacrylic acid, polyglycidyl methacrylate, polyethylene glycol dimethacrylate, polyfumaric acid, polydimethyl dimethyl fumarate, diethyl polyfumarate, dipropyl polyfumarate, polymaleic acid Dimethyl polymaleate, diethyl polymaleate, dipropyl polymaleate, polyacrylonitrile, polyacrylamide, polyvinyl chloride, polystyrene, poly (α-methylstyrene) and the like. The content of the polymer polymerized from the vinyl compound in the present invention is 0.8 times or more to 3.8 times the content of the polyurethane.
It is preferably at most twice. If the content of the polymer polymerized from the vinyl compound is less than 0.8 times the content of the polyurethane, it is not preferable because the slurry adsorption characteristics of the polyurethane are not improved. If the content of the polymer to be polymerized from the vinyl compound exceeds 3.8 times the content of the polyurethane, the elasticity of the polyurethane is undesirably impaired. The ratio of the content of the polymer polymerized from the more preferable vinyl compound to the content of the polyurethane is preferably 1.5 to 1.5.
It is not less than twice and not more than 3.0 times.

A preferred method of forming the polishing layer of the present invention is to swell a vinyl compound on a foamed polyurethane sheet having closed cells of 1000 μm or less in advance and a density of 0.70 to 0.90 in advance. After that, the method of polymerizing the vinyl compound in the foamed polyurethane sheet is a polishing pad obtained because the blend of the polymer to be polymerized from the polyurethane and the vinyl compound is microscopically uniform with a structure having closed cells. Is preferable because the flatness of the local unevenness can be improved. The proton relaxation time of the polishing layer containing 0.8 to 3.8 times the content of the polymer polymerized from the vinyl compound with respect to the content of the polyurethane obtained in the present invention in this manner is set to Observation by T _1H measurement method by solid-state NMR,
Since the relaxation time of the foamed polyurethane is almost the same, it has been found that the polymer polymerized from the polyurethane and the vinyl compound is compatible with each other to such an extent that a domain of several tens nm or more is not formed. For the foamed polyurethane sheet, it is necessary to determine the combination and optimum amount of the polyisocyanate and the polyol, the catalyst, the foam stabilizer and the foaming agent depending on the hardness, the cell diameter and the density.

As a method of polymerizing the vinyl compound in the foamed polyurethane sheet after the vinyl compound is swollen into the foamed polyurethane sheet, the vinyl compound is swollen together with a photodegradable radical initiator, and then the polymer is exposed to light and polymerized. Examples of the method include a method of swelling a vinyl compound together with a thermally decomposable radical initiator and then applying heat to polymerize the same, and a method of swelling the vinyl compound and then polymerizing by emitting an electron beam or radiation.

The cushion layer according to the present invention has a bulk modulus of 6
It is necessary that it is 0 MPa or more and the tensile elastic modulus is 0.1 MPa or more and 20 MPa or less. The bulk modulus is measured by applying an isotropic applied pressure to an object whose volume is measured in advance and measuring the change in volume. Bulk modulus =
It is defined as applied pressure / (volume change / original volume).
For example, the original volume is 1 cm 3, and when the applied pressure is 0.07 MPa isotropically applied, the volume change is 0.00
If it is 005 cm ³ , the bulk modulus is 1400 MPa. As one method of measuring the bulk modulus, for example, the volume of an object to be measured is measured in advance, then the object to be measured is immersed in water placed in a container, the container is placed in a pressure vessel, and the applied pressure is increased. In addition, there is a method of measuring a change in volume of an object to be measured and an applied pressure from a change in the height of water in a container inside. The liquid to be immersed is preferably one that does not swell or destroy the object to be measured, and is not particularly limited as long as it is a liquid, and examples thereof include water, mercury, and silicon oil. The tensile modulus of elasticity is determined by applying a tensile stress to the cushion layer in a dumbbell shape and a tensile strain (= change in tensile length / original length) of 0.01 to 0.
The tensile stress was measured in the range up to 03, and the tensile elastic modulus = ((tensile stress when tensile strain was 0.03) −
(Tensile stress at a tensile strain of 0.01)) / 0.
02. Examples of the measuring device include Tensilon Universal Tester RTM-100 manufactured by Orientec. As the measurement conditions, the test speed was 5 cm /
The shape of the test piece is a dumbbell shape with a width of 5 mm and a sample length of 50 mm.

The cushion layer must have a bulk modulus of 60 MPa or more. When the pressure is less than 60 MPa, the uniformity of the flatness over the entire surface of the semiconductor substrate is deteriorated, which is not preferable. A more preferable range of the bulk modulus is 200 MPa or more. Further, the tensile elastic modulus of the cushion layer needs to be 0.1 MPa or more and 20 MPa or less. Tensile modulus is 0.1MPa
If it is less than 1, the uniformity of the flatness over the entire surface of the semiconductor substrate (uniformity) is deteriorated, which is not preferable.
It is not preferable that the tensile modulus exceeds 20 MPa, because the uniformity of the flatness of the entire surface of the semiconductor substrate is impaired. A more preferable range of the tensile modulus is from 0.5 MPa to 10 MPa. Such cushion layers include natural rubber, nitrile rubber,
Non-foamed elastomers such as neoprene rubber, polybutadiene rubber, polyurethane rubber, and silicone rubber can be used, but are not particularly limited thereto. The preferred thickness of the cushion layer is in the range of 0.1 to 100 mm. If the thickness is less than 0.1 mm, the uniformity of the flatness over the entire surface of the semiconductor substrate (uniformity) is deteriorated, which is not preferable. If it exceeds 100 mm, local flatness is impaired, which is not preferable. A more preferable range of the thickness is 0.2 mm or more and 5 mm or less. A more preferable range is 0.5 mm or more and 2 mm or less.

In the present invention, fixing the polishing layer to the polishing platen via the cushion layer means that the cushion layer is fixed from the polishing platen so as not to shift during polishing, and the polishing layer does not shift from the cushion layer. It is fixed. Examples of the method of fixing the polishing platen and the cushion layer include a method of fixing with a double-sided adhesive tape, a method of fixing with an adhesive, and a method of fixing the cushion layer by suctioning from the polishing platen, but are particularly limited. is not. As a method of fixing the cushion layer and the polishing layer, a method of fixing with a double-sided adhesive tape, a method of fixing with an adhesive, and the like can be considered, but are not particularly limited. When the polishing layer and the cushion layer are fixed with a double-sided adhesive tape or an adhesive layer, the tensile elastic modulus of the obtained polishing pad is measured in a state where a double-sided adhesive tape or the like is not attached to the back side of the cushion layer which is not the polishing layer side. It is preferable that the measured value be 150 MPa or less because the uniformity of the flatness over the entire surface of the semiconductor substrate (uniformity) is not impaired. Further preferred tensile modulus is 100 MPa or less. The tensile elasticity is determined by applying a tensile stress to a polishing pad in a dumbbell shape without applying a double-sided adhesive tape or the like to the back side of the cushion layer which is not the polishing layer side, and applying a tensile strain (= tensile length change / original tension). The tensile stress was measured when the length was in the range of 0.01 to 0.03, and the tensile elastic modulus = ((tensile stress when tensile strain was 0.03) − (tensile stress when tensile strain was 0.01) )) / 0.02. Examples of the measuring device include Tensilon Universal Tester RTM-100 manufactured by Orientec. As the measurement conditions, the test speed was 5 cm / min, the test piece shape was a dumbbell shape having a width of 5 mm and a sample length of 50 mm.

Preferred as a double-sided adhesive tape or adhesive layer for bonding the polishing layer and the cushion layer is Sumitomo 3
Double-sided adhesive tape 463, 465, 9204 of M Corporation
Nitto Denko Corporation double-sided adhesive tape No. Acrylic adhesive transfer tape without base material such as 591, Sumitomo 3M Co., Ltd.
And a double-sided adhesive tape using a soft vinyl chloride base material such as 447DL of Sumitomo 3M Co., Ltd. as a base material.

In the polishing apparatus of the present invention, when it is necessary to replace the polishing layer after polishing because the polishing rate cannot be obtained, the polishing layer is fixed to the polishing platen with the cushion layer fixed thereto. It is also possible to remove and replace it from the cushion layer. Since the cushion layer is more durable than the polishing layer, replacing only the polishing layer is preferable in terms of cost.

Hereinafter, a method for polishing a semiconductor substrate using the polishing pad of the present invention will be described.

By using the polishing pad of the present invention, using a silica polishing agent, an aluminum oxide polishing agent, a cerium oxide polishing agent, or the like as a polishing agent, the unevenness of an insulating film and the unevenness of metal wiring on a semiconductor substrate are reduced. It can be planarized. First, a polishing apparatus having a polishing head, a polishing platen for fixing a polishing pad, and a means for rotating the polishing head, the polishing platen or both of them is prepared. Then, the polishing pad of the present invention is fixed to the polishing platen of the polishing apparatus so that the polishing layer faces the polishing head. The semiconductor substrate is fixed to the polishing head by a method such as a vacuum chuck. The polishing table is rotated, and the polishing head is rotated in the same direction as the rotation of the polishing table, and pressed against the polishing pad. At this time, the polishing agent is supplied from a position where the polishing agent enters between the polishing pad and the semiconductor substrate. The pressing pressure is usually performed by controlling the force applied to the polishing head. As the pressing pressure, 0.01 to 0.2 MPa is preferable because local flatness can be obtained.

According to the polishing apparatus and the polishing pad of the present invention, it is possible to achieve uniformity (uniformity) of the flatness over the entire surface of the semiconductor substrate.

[0026]

The present invention will be described below in further detail with reference to examples. In this example, each characteristic was measured by the following method.

Micro rubber A hardness: Polymer Instruments Co., Ltd.
It is measured with a micro rubber hardness tester MD-1 (location: Nishiiri, Shirumatemachi, Kamigyo-ku, Kyoto-shi).

The structure of the micro rubber hardness tester MD-1 is as follows. 1. Sensor part (1) Load method: cantilever leaf spring (2) Spring load: 0 point 2.24 gf 100 points 33.85 gf (3) Spring load error: ± 0.32 gf (4) Needle dimensions: diameter: 1.6 mm cylindrical height 0.5 mm (5) Displacement detection method: strain gauge type (6) Pressing leg dimensions: outer diameter 4 mm inner diameter 1.5 mm Sensor drive unit (1) Drive method: Vertical drive by stepping motor Lowering speed control by air damper (2) Vertical movement stroke: 12 mm (3) Lowering speed: 10 to 30 mm / sec (4) Height adjustment range: 0 to 67 mm ( (Distance between sample table and sensor pressing surface) Sample stage (1) Sample stage size: diameter 80 mm (2) Fine movement mechanism: fine movement by XY table and micrometer head Stroke both X-axis and Y-axis 15 mm (3) Level adjuster: body leg for level adjustment and round level

Example 1 A 5 mm thick foamed polyurethane sheet (Micro Rubber A
Hardness = 50 degrees, density: 0.77, closed cell average diameter: 11
0 μm) is immersed in methyl methacrylate to which 0.1 parts by weight of azobisisobutylnitrile is added for 24 hours.
The foamed polyurethane sheet swollen with methyl methacrylate is sandwiched between glass plates and heated at 70 ° C. for 24 hours. After heating, remove from the glass plate and perform vacuum drying at 50 ° C. This was ground to obtain a polishing layer having a thickness of 1.2 mm. The micro rubber A hardness of this polishing layer is 98 degrees,
The density was 0.79, the average diameter of the closed cells was 150 μm, and the content of polymethyl methacrylate was 2.6 times the content of polyurethane. The tensile modulus is 3
It was 5 MPa. A cushion layer of 1 mm of nitrile rubber (volume modulus = 140 MPa, tensile modulus = 4.5 MPa) and the polishing layer are combined with the Nitto Denko double-sided adhesive tape N.
o. At 591, a polishing pad was prepared. The tensile elastic modulus of the polishing pad was 15 MPa. 0.25μm width and 1.2μm height on 6 inch silicon wafer
Was formed at intervals of 0.5 mm, and a semiconductor substrate was further formed thereon by forming an insulating film having a thickness of 3 μm by CVD using tetraethoxysilane. The unevenness of the surface of the insulating film on the semiconductor substrate before polishing is 11,000 angstroms at the center of the wafer and 11000, 11500, 11200, and 11400 at four peripheral portions.
Angstrom. The present semiconductor substrate was mounted on a polishing head of a polishing machine and rotated at 37 rpm. The polishing pad was fixed to a platen of the polishing machine, and was rotated at 36 rpm in the same direction as the rotation direction of the polishing head. The silica polishing agent was 225 ml / min. Polishing pressure is 0.
Polishing was performed at 05 MPa for 7 minutes. The unevenness of the surface of the insulating film on the semiconductor substrate after polishing is 10% at the center of the wafer.
0 Angstrom, 200, 30 in 4 surrounding areas
0, 250, and 400 angstroms. The thickness of the insulating film at the center of the wafer was 1.5 μm, and the thickness of the insulating film 3 mm from the wafer edge was 1.4 μm. As described above, uniformity of the flatness over the entire surface of the semiconductor substrate of 6 inches is obtained, and uniform polishing is achieved near the wafer edge.

Example 2 A 5 mm thick foamed polyurethane sheet (Micro Rubber A
Hardness = 50 degrees, density: 0.81, average diameter of closed cells: 30
0 μm) is immersed in styrene containing 0.1 part by weight of azobisisobutylnitrile for 24 hours. 7 Insert the foamed polyurethane sheet with styrene swelling
Heat at 0 ° C. for 24 hours. After heating, remove from the glass plate and perform vacuum drying at 50 ° C. This was ground to obtain a polishing layer having a thickness of 1.2 mm. The micro rubber A hardness of the polishing layer was 98 degrees, the density was 0.82, the average diameter of closed cells was 330 μm, and the content of polystyrene was 1.6 times the weight of polyurethane. The tensile modulus was 40 MPa. 2 mm polyurethane rubber (bulk modulus = 100 MPa, tensile modulus = 10M
Pa) was prepared as a cushion layer, and the polishing layer and the cushion layer were adhered to each other with a double-sided adhesive tape Y-4913 of Sumitomo 3M Co., Ltd. to prepare a polishing pad. The tensile elastic modulus of the polishing pad was 18 MPa. Al wirings having a width of 0.25 μm and a height of 1.2 μm are formed on a 6-inch silicon wafer at intervals of 0.5 mm, and furthermore, an insulating film is formed thereon by CVD using tetraethoxysilane so as to have a thickness of 3 μm. Formed. The steps of the irregularities on the surface of the insulating film were 11,000 angstroms at the center of the wafer and 11000, 11500, 11200, and 11400 angstroms at four peripheral portions. The substrate is mounted on a polishing head of a polishing machine and rotated at 37 rpm. The polishing pad is fixed to a platen of the polishing machine, and the polishing pad is rotated at 36 rpm in the same direction as the rotation direction of the polishing head. Polishing pressure 0.05MPa while supplying
Was polished for 6 minutes. The unevenness of the surface of the insulating film after polishing was 700 angstroms at the central portion of the wafer and 600, 800, 700, and 700 angstroms at four peripheral portions. The thickness of the insulating film at the center of the wafer was 1.6 μm, and the thickness of the insulating film 3 mm from the edge of the wafer was 1.5 μm. As described above, uniformity of the flatness over the entire surface of the semiconductor substrate of 6 inches is obtained, and uniform polishing is achieved near the wafer edge.

Example 3 78 parts by weight of a polyether-based urethane polymer (Adiprene L-325 manufactured by Uniroyal Co.) and 4,4'-methylene-
Bis-2-chloroaniline 20 parts by weight and hollow polymer microspheres (Expancel 551 DE manufactured by Chemo Nobel)
1.8 parts by weight were mixed by a RIM molding machine and discharged into a mold to prepare a polymer molded body. This polymer molded body was sliced with a slicer to a thickness of 1.2 mm to form a polishing layer. The micro rubber A hardness of this polishing layer is 98 degrees and the density is:
0.80, average diameter of closed cells: 33 μm. The tensile modulus was 35 MPa. 1 mm neoprene rubber (bulk modulus = 100 MPa, tensile modulus =
12 MPa) as a cushion layer, and the polishing layer and the cushion layer are double-sided adhesive tape Y-94 manufactured by Sumitomo 3M Co., Ltd.
9 to form a polishing pad. The tensile elastic modulus of the polishing pad was 25 MPa. Al wirings having a width of 0.25 μm and a height of 1.2 μm are formed at intervals of 0.5 mm on a 6-inch silicon wafer, and a silicon oxide insulating film having a thickness of 3 μm is formed thereon by CVD using tetraethoxysilane as a raw material. It was formed so that it might be. The irregularities on the surface of the insulating film were 11,000 angstroms at the center of the wafer and 11000, 11500 at four peripheral portions.
11200 and 11400 angstroms. This substrate was mounted on a polishing head of a polishing machine and rotated at 37 rpm. The polishing pad was fixed to a polishing platen of the polishing machine, and was rotated at 36 rpm in the same direction as the rotation direction of the polishing head. Polishing was carried out at a polishing pressure of 0.05 MPa for 6 minutes while supplying the pressure in minutes.
The unevenness of the surface of the insulating film after polishing is 7% at the center of the wafer.
00 angstrom, 800, 50 in 4 surrounding areas
0, 400, and 500 angstroms. The thickness of the insulating film at the center of the wafer was 1.3 μm, and the thickness of the insulating film 3 mm from the edge of the wafer was 1.2 μm. As described above, uniformity of the flatness over the entire surface of the semiconductor substrate of 6 inches is obtained, and uniform polishing is achieved near the wafer edge.

Comparative Example 1 The polishing layer used in Example 3 was prepared. The micro rubber A hardness of the polishing layer was 98 degrees, the density: 0.80, and the average diameter of closed cells: 33 μm. The tensile modulus is 35MP
a. 1.2 mm thickness obtained by impregnating a polyurethane solution of a nonwoven fabric as a cushion layer and then performing wet film formation
(Polyurethane foam) (volume modulus = 3 MPa, tensile modulus = 50 MPa) was prepared. The polishing layer and the cushion layer are made of Sumitomo 3M Co., Ltd. double-sided adhesive tape 442J.
(Double-sided adhesive tape based on polyester film)
To produce a polishing pad. The tensile elastic modulus of the polishing pad was 215 MPa. 0.25μm width, 1.2μm height Al on 6 inch silicon wafer
Wirings were formed at an interval of 0.5 mm, and a tetraethoxysilane was further formed thereon by CVD to form an insulating film having a thickness of 3 μm. The step of the unevenness on the surface of the insulating film is 11,000 angstroms at the center of the wafer and 4
11000, 11500, 11200, 1140
It was 0 angstroms. The substrate is attached to a polishing head of a polishing machine and rotated at 37 rpm. The polishing pad is fixed to a platen of the polishing machine, and the polishing pad is rotated at 36 rpm in the same direction as the rotation direction of the polishing head. Polishing pressure 0.05 while supplying
Polishing was performed at 7 MPa for 7 minutes. The surface unevenness of the polished insulating film was 1200 angstrom at the center of the wafer and 200, 500, 1200 and 14 at four peripheral portions.
00 angstroms. The thickness of the insulating film at the center of the wafer was 1.3 μm, and the thickness of the insulating film 3 mm from the edge of the wafer was 0.8 μm. The uniformity of the flatness over the entire surface of the semiconductor substrate (uniformity) is insufficient, and uniform polishing near the wafer edge is not achieved.

[0033]

According to the polishing apparatus and polishing pad of the present invention, it is possible to achieve uniformity (uniformity) of local unevenness on the entire surface of a semiconductor substrate, and achieve uniform polishing near the wafer edge. It is possible to do.

Claims (10)

[Claims] 1. A micro rubber A hardness fixed to a polishing head by fixing a semiconductor substrate to a polishing head, and fixed to a polishing platen through a cushion layer having a bulk elastic modulus of 60 MPa or more and a tensile elastic modulus of 0.1 MPa to 20 MPa. Polishing the semiconductor substrate by rotating the polishing head or the polishing platen or both in a state where the polishing layer having a tensile modulus of 70 ° or more and a tensile elastic modulus of 1 MPa or more and 500 MPa or less is pressed against the semiconductor substrate. A method for polishing a semiconductor substrate, comprising: 2. The thickness of the cushion layer is 0.1 or more and 100 or more.
2. The polishing method according to claim 1, wherein the thickness is not more than mm. 3. The polishing method according to claim 1, wherein the polishing layer contains polyurethane as a main component, and has a density of 0.70 or more and 0.90 or less. 4. The polishing layer has a content of a polymer which is polymerized from a vinyl compound in an amount of 0.
The polishing method according to any one of claims 1 to 2, wherein the polishing method contains 8 to 3.8 times, has closed cells of 1000 µm or less, and has a density in a range of 0.70 to 0.90. . 5. A polishing apparatus comprising: a polishing head, a polishing pad facing the polishing head, a polishing platen for fixing the polishing pad, and a driving device for rotating the polishing head, the polishing platen or both of them. The polishing pad has a bulk modulus of 60 MPa or more and a tensile modulus of 0.1 M.
A polishing apparatus comprising: a cushion layer having a pressure of Pa to 20 MPa and a polishing layer having a micro rubber A hardness of 70 degrees or more and a tensile modulus of elasticity of 1 MPa to 500 MPa in a direction of a polishing head. 6. The polishing apparatus according to claim 5, wherein the polishing head has means for fixing the semiconductor substrate. 7. A polishing layer having a micro rubber A hardness of 70 degrees or more and a tensile modulus of 1 MPa or more and 500 MPa or less, and a cushion layer having a volume modulus of 60 MPa or more and a tensile modulus of 0.1 MPa or more and 20 MPa or less. A polishing pad comprising: 8. The cushion layer has a thickness of 0.1 or more and 100 or more.
The polishing pad according to claim 7, wherein the thickness is not more than mm. 9. The polishing pad according to claim 7, wherein the polishing layer contains polyurethane as a main component and has a density of 0.70 or more and 0.90 or less. 10. The polishing layer contains a content of a polymer polymerized from a vinyl compound at a content of 0.8 to 3.8 times the polyurethane content, has closed cells of 1000 μm or less, and The polishing pad according to any one of claims 7 to 8, wherein the density is in a range of 0.70 or more and 0.90 or less.