JPH0757465B2 - Method and apparatus for polishing thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polishing method and a polishing apparatus for a thin film sample in which a thin film having a constant film thickness such as SOI (Silicon on insulator) is formed on a substrate. is there.

[Problems to be Solved by Prior Art and Invention]

As a polishing method for this kind of main conductor substrate and the like, there is a method proposed by the present applicant in Japanese Patent Application No. 63-18729.
In this method, the thickness of the thin film is preliminarily measured on a substrate on which a thin film to be polished is formed, and a processing region having a certain area centered on this measurement point is defined, and the processing region is smaller than the processing region. Move the polishing pad whose diameter of the contact surface is set to be the area along the zigzag-shaped path in the processing area and adjust the contact pressure of the polishing pad according to the film thickness measurement value of the processing area. The polishing process is sequentially performed for each processing region. According to this method, since the polishing processing amount is adjusted according to the film thickness measurement value of each processing region, the film thickness can be made extremely uniform.

However, in such a conventional method, it is difficult to reduce the processing time because a single relatively small polishing pad is used, and there is a problem particularly in the processing efficiency.

In view of such circumstances, an object of the present invention is to provide a polishing method and a polishing apparatus for a thin film of this kind, which can form a uniform thin film and can improve the processing efficiency.

[Means and Actions for Solving the Problems]

In the polishing method according to the present invention, a plurality of processing regions are set on the substrate, the film thickness of the thin film is measured for each processing region, and a plurality of polishing pads arranged in a row are provided on the substrate in a predetermined path. The contact pressure of the polishing pad is changed in accordance with the film thickness of each processing region when simultaneously moving along. Further, the polishing apparatus according to the present invention comprises a pad group consisting of a plurality of polishing pads arranged in a row corresponding to a plurality of processing regions set on the substrate, each polishing pad comprising:
The polishing pads are polygonal and adjacent to each other, and the adjacent polishing pads are arranged such that the sides and the corners of the respective polygons face each other and rotate in opposite directions.

Therefore, by simultaneously operating a plurality of polishing pads arranged in a row corresponding to the processing region of the substrate, it is possible to perform polishing processing over a wide range of the substrate at one time. Further, depending on the cross-sectional shape and arrangement of the polishing pads, it is possible to rotate the plurality of polishing pads in close proximity without interfering with each other.

〔Example〕

An embodiment of the thin film polishing method and polishing apparatus according to the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 shows an example of the structure of a polishing apparatus used for carrying out the method of the present invention. In the figure, 1 is a frame of the apparatus, 2 is a biaxial orthogonal direction on a pace plate 1a of the frame 1 ( The table 3 is mounted so as to be movable in the X and Y directions and can support the substrate P in a fixed position, and 3 is the supporting arms 1b, 1 of the frame body 1.
A plurality of shafts 4 rotatably supported by b ′ and movably in a direction orthogonal to the table 2 are attached to the tip of the shaft 3 to form a square having a side of about 8 mm, and an artificial leather on the lower surface thereof. It is a polishing pad to which a polishing pad (not shown) is attached and is arranged so as to face the upper surface of the substrate P on the table 2. Each polishing pad 4 constitutes a pad group, but here, on the substrate P, at regular intervals as shown in FIG.
24 film thickness measurement points a, ..., a are preset, and 24 film processing areas are centered on each of these film thickness measurement points a.
A, ..., A is defined. Of these processing areas A, 16 processing areas A, ...
Area A indicated by a dotted line in the figure. 2), the polishing pads 4 of the pad group are arranged in 4 rows and 4 columns. As is apparent from FIG. 2, the polishing pads 4 are arranged such that the rotation angles of the adjacent polishing pads 4 in the row direction and the column direction deviate from each other by 45 °, that is, one side portion of the polishing pad 4 and the other side thereof are adjacent to each other. Are arranged so as to face each other. Further, 5 is a gear attached to each shaft 3 to connect the shafts 3 to each other and one of them is connected to a rotation driving means (not shown), and 6 is a shaft bearing 3 via a thrust bearing 7. Pneumatic cylinders each of which is independently operable. In the above case, the processing area A of the substrate P can take all positions along the X and Y directions by moving the table 2. Therefore, the relative positional relationship between each processing region A and each polishing pad 4 can be freely set.

Next, a specific example of a polishing method using the polishing apparatus having the above configuration will be described. As the substrate P, two silicon single crystal plates each having a diameter of about 5 cm are oxidized and bonded together, and one of the single crystal plates is polished by the conventional method to have a thickness of about 5 μm. Such a film thickness distribution of the substrate P was found to be varied in the range of 2 to 7 μm as the initial film thickness value according to the measurement by the interference type film thickness meter. In this case, the interval w between the measurement points a and the width W of the unit processing area A shown in FIG. 3 are set to w = 8 mm and W = 8 mm in the X and Y directions. The substrate P placed on the table 2 along the X and Y directions
When the table 2 is moved so that the area A ₀ (see FIG. 3) and the pad group are aligned, the polishing pad 4 and each processing area A
Correspond to each other, and each polishing pad 4 is lowered by the operation of the pneumatic cylinder 6 and rotated. As a result, each processing area A has a corresponding polishing pad 4
Then, the polishing process is performed all over the area A ₀ all at once. In this case, taking the arbitrary processing area A'shown in FIG. 4 as an example, the movement of the polishing pad 4 corresponding to this processing area A'is such that the locus at its center is the pitch p.
To form the zigzag shape of the processing area A '
The contact pressure of the polishing pad 4 with respect to is determined so as to be proportional to the difference between the film thickness measurement value at the film thickness measurement point a ′ representing the film thickness of the processing region A ′ and the desired film thickness target value. . The contact pressure is kept constant by the pneumatic cylinder 6 during the polishing of the processing area A ', but since the polishing pad 4 and the amount of polishing by the polishing pad 4 have a certain proportional relationship,
By thus determining the contact pressure of the polishing pad 4, the processing efficiency can be improved. Such polishing processing in the processing area A ′ is similarly performed in all the other processing areas A, so that the uniform film thickness is achieved in the area A ₀ . In this case, all the polishing pads 4 rotate at the same time via the gears 5, but the polishing pads 4 are adjacent to each other because they are rotated by 45 ° from each other and rotate in opposite directions, so that they collide with each other. Smooth operation can be guaranteed without Therefore, since the polishing pads 4 can be arranged close to each other, the surface of the substrate P after polishing is in an extremely smooth state with no processing unevenness. In the above case, the rotation speed of each polishing pad 4 is
It is carried out at 440 rpm and using colloidal silica as the polishing liquid.

Since the polishing method and the polishing apparatus according to the present invention are configured as described above, as a result of performing the polishing process over the entire region of the substrate P, a maximum film thickness reduction of 1 μm can be obtained within the processing time of about 3 minutes. Was given. Further, based on the film thickness distribution obtained at this time, the contact pressure of the polishing pad 4 for polishing each processing region A is determined in the same manner as described above, polishing is performed, and this is repeated 5 times in total. As a result, an SOI layer having a uniform film thickness of 1 ± 0.2 μm can be obtained in the end in a processing time of 18 minutes.
The processing efficiency is remarkably improved as compared with the above-described conventional polishing processing method, which requires a processing time of about 500 minutes in order to obtain an equivalent to such an SOI layer.

The polishing pad 4 in the above embodiment may be any polygon such as a quadrangle or a pentagon, and the number of processing areas A to be defined is not limited to that in the above embodiment and may be set appropriately. In that case, the size of the polishing pad 4 may be set corresponding to each processing region A.

〔The invention's effect〕

As described above, according to the present invention, there is an excellent advantage that the seed substrate can be efficiently polished and the film thickness can be made uniform.

[Brief description of drawings]

FIG. 1 is a sectional view of a polishing apparatus used for carrying out the method of the present invention, FIG. 2 is a plan view showing a positional relationship between a polishing pad and a substrate, and FIG. 3 is a processing region defined on the substrate. FIGS. 4 and 5 are plan views showing a setting example, and FIGS. 4 and 5 are a plan view and a partially enlarged plan view of a substrate for explaining a specific example of a polishing method in a unit processing region. 1 ... Frame, 2 ... Table, 3 ... Shaft, 4 ...
Polishing pad, 5 ... Gear, 6 ... Pneumatic cylinder, 7
...... Thrust bearing, A, A '... Processing area, a, a' ... Film thickness measurement point.

Claims (2)

[Claims] 1. A method of polishing a thin film, wherein a polishing pad is rotated and moved while being pressed against the surface of a substrate on which a thin film to be polished is formed. While setting the processing area, the film thickness of the thin film is measured for each processing area, and when the polishing pads having a plurality of rows are simultaneously moved along the predetermined path on the substrate, the polishing A method of polishing a thin film, characterized in that the contact pressure of the pad is changed according to the film thickness of each of the processing regions. 2. A thin film polishing apparatus for performing polishing processing by moving a polishing pad while pressing it while rotating it on the surface of a substrate on which a thin film to be polished is formed. The pad group is composed of a plurality of polishing pads arranged corresponding to the plurality of processing areas set by, each polishing pad has a polygonal shape,
Adjacent polishing pads are arranged such that the sides and corners of each of the polygons face each other and rotate in opposite directions, and each of the polishing pads can adjust the contact pressure on the substrate. The thin film polishing apparatus is characterized by being supported as described above.