JP2000059014A - Manufacture of printed board and polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a printed board, which continues to laminate respectively and alternately insulating resin layers and signal wiring conductor layers on both surfaces of a base material and includes a polishing process, which can polish the surface of the insulating resin layer on one side of the insulating resin layers and the surface on one side of both surfaces of the base material into a roughly parallel surface. SOLUTION: Signal wiring conductor layers 23a and 23e of a desired pattern are respectively formed on the surfaces of a base material 21. The parts of the edges of the surfaces of the material 21 are left, and insulating resin layers 24a and 24b, which respectively cover the layers 23a and 23b, are formed. The layer 24b is polished in a state in that a polishing stopper member 14 of a polishing rate lower than those of the layers 24a and 24b is brought into contact with the part of the edge 61 on one side of the edges of the surfaces of the material 21. Thereby, the layer 24b is polished down to the thickness of the member 14, with the surfaces of the material 21 as a reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a printed circuit board, and more particularly to a method of flattening and polishing an interlayer insulating resin of a surface-mounted printed circuit board.

[0002]

2. Description of the Related Art A surface mount type printed circuit board is usually
Using a glass epoxy copper clad laminate for the base material, a photosensitive epoxy resin for the insulating layer, a copper plating layer etc. for the conductor layer,
It has a structure in which these are sequentially laminated. A general method of manufacturing a printed circuit board of a surface mounting method is described in, for example,
No. 53951. Here, FIG.
With reference to (a) to (f), a method for manufacturing a general surface mount type printed circuit board will be briefly described. First, a substrate in which copper layers 22a and 22b are adhered to the front and back of a substrate 21 made of glass epoxy is prepared (FIG. 7A).
2b is selectively patterned by etching to form signal wiring conductor layers 23a and 23b (FIG. 7).
(B)). Next, a photosensitive thermosetting resin is dissolved in a solvent and applied to both sides of the base material 21, and then the solvent is evaporated by a pre-curing to form insulating resin layers 24a and 24b. Usually, printing or a coater is used to apply the photosensitive thermosetting resin. Next, the insulating resin layer 24a,
Exposure and development are performed on 24b to form a photo via hole 25 (FIG. 7D). Next, the surfaces of the insulating resin layers 24a and 24b are polished to remove irregularities on the surface and flatten the surface (FIG. 7E). This removes irregularities generated on the surfaces of the insulating resin layers 24a and 24b due to the signal wiring conductor layers 23a and 23b, and irregularities generated on the surfaces of the insulating resin layers 24a and 24b due to uneven thickness of the insulating resin layers 24a and 24b. . Next, the flattened insulating resin layers 24a, 24
A copper layer is formed on the surface of b by copper plating, and this copper layer is patterned by photolithography and etching to form second signal wiring conductor layers 26a and 26b (FIG. 7 (f)). Thereafter, FIGS. 7 (c) to 7 (f)
By repeating the above steps and sequentially laminating the insulating resin layer and the signal wiring conductor layer, a printed board having a desired number of layers is formed.

In such a manufacturing method, FIG.
If irregularities remain on the surfaces of the insulating resin layers 24a and 24b after the polishing step, the second signal wiring conductor layer 2 shown in FIG.
Disconnection may occur in 6a and 26b. On the other hand, FIG.
In the polishing step (e), if the polishing amount is too large, the thickness of the insulating resin layers 24a and 24b becomes too thin, which impairs the reliability of interlayer insulation. Therefore, in the polishing step of FIG. 7E, it is important to control the amount of polishing.

As a polishing method in the polishing step of FIG. 7E, for example, a polishing method using a ceramic roll or a plane swing polishing method can be used. The ceramic roll polishing method is a method in which hard abrasive particles are combined with a binder to form a cylindrical abrasive, and the insulating resin layers 24a and 24b as the objects to be polished are formed.
It is a method of rolling and polishing on the surface of the substrate. On the other hand, the plane swing polishing method is a method in which pellets obtained by electrodepositing abrasive grains on a metal disk having a diameter of several mm are spread in a plate shape, or
This is a method in which a block of several mm square in which abrasive grains are bonded with a resin is spread in a plate shape and used as an abrasive, which is polished by being pressed against the surfaces of the insulating resin layers 24a and 24b while swinging. . For example, a ceramic roll manufactured by Ishii Co., Ltd. is known. As an apparatus for performing the plane swing polishing method, there is, for example, an overly sander (trade name, manufactured by Amitec Co., Ltd.).

[0005] Many polishing methods have been disclosed which can be used as a polishing method in the polishing step of FIG. For example, as disclosed in Japanese Patent Application Laid-Open No. 8-229808, while a surface of a workpiece to be polished is relatively rotated on a polishing pad attached to a surface of a rotating platen, There is a method in which polishing is performed by supplying a polishing liquid containing polishing abrasive grains between the polishing liquid and an object.
In this publication, a hollow portion is provided by stretching a diaphragm or the like horizontally on the back surface of a carrier holding a workpiece, and pressurized air is supplied to the hollow portion to make the contact pressure of the workpiece against the polishing pad uniform. Become Further, by pressing the retainer ring for preventing the workpiece from being detached from the carrier against the polishing pad with an appropriate pressure, deformation of the polishing pad due to the retainer ring is prevented, and the polishing amount at the outer peripheral portion of the workpiece is reduced.
It is also disclosed that the phenomenon of becoming larger than the central portion of the workpiece is suppressed, and the amount of polishing in the surface of the workpiece is made more uniform.

In Japanese Patent Application Laid-Open Nos. 6-15562 and 6-39705, a stopper is arranged on an outer peripheral portion of a holder holding a plate to be polished, and the stopper is projected from the holder by a predetermined amount. A polishing method is disclosed in which the polishing of the plate to be polished is stopped when the stopper comes in contact with the polishing platen.

[0007]

The above-mentioned insulating resin layer 2
The polishing steps 4a and 24b are performed by polishing the insulating resin layer 24 after polishing.
Ideally, the surfaces of a and 24b are planes parallel to the surface of the base member 21 as shown in FIG. However, in the conventional ceramic roll polishing method, the plane swing polishing method, and the polishing method disclosed in JP-A-8-229808, the entire surface of the insulating resin layers 24a and 24b has a substantially uniform thickness. As a result, even if the irregularities on the surface of the insulating resin layer can be removed, the insulating resin layers 24a, 24b
The thickness unevenness cannot be removed. For this reason, the surfaces of the insulating resin layers 24a and 24b cannot be made a plane parallel to the surface of the base 21 as shown in FIG.

In the polishing method described in JP-A-6-15562 and JP-A-6-39705, the back surface of the plate to be polished in contact with the surface of the holder is used as a reference surface, and a stopper is moved from the reference surface by a predetermined amount. Is projected, and the plate to be polished is polished to the predetermined thickness. When this method is applied to a printed circuit board (FIG. 7C) in which the insulating resin layers 24a and 24b are formed on both surfaces of the substrate 21, the surface of the insulating resin layer on the back side that is not polished is inclined. Since the undulating surface is the reference surface, the polished surface may be inclined with respect to the main plane of the substrate. Therefore, if this polishing method is used for manufacturing a printed circuit board, an insulating resin layer is formed only on one side in the step of FIG.
After polishing using the back surface on which the insulating resin layer is not formed as a reference surface, forming the insulating resin layer on the back surface side and polishing again, the forming process of the insulating resin layer and the polishing process are divided into two steps. Need to be done. In this case, the number of steps is about twice, so that the manufacturing efficiency is greatly reduced.

The present invention relates to a method for manufacturing a printed circuit board in which an insulating resin layer and a signal wiring conductor layer are laminated on both surfaces of a substrate, wherein the surface of the insulating resin layer is substantially parallel to the surface of the substrate. It is an object of the present invention to provide a manufacturing method including a polishing step capable of polishing a surface.

[0010]

In order to achieve the above object, according to the present invention, the following manufacturing method is provided.

That is, a first step of forming a signal wiring conductor layer having a desired pattern on a base material, and an insulating resin layer covering the signal wiring conductor layer while leaving an edge portion of the surface of the base material And polishing the insulating resin layer in a state where a polishing stopper member having a lower polishing rate than the insulating resin layer is brought into contact with the edge portion of the surface of the base material. And a third step of polishing the insulating resin layer to a thickness of the stopper member.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

A method of manufacturing a surface-mounted printed circuit board according to this embodiment will be described with reference to FIGS.

First, a substrate in which copper layers 22a and 22b are attached to the front and back of a substrate 21 made of glass epoxy is prepared (FIG. 6A). The copper layers 22a and 22b are selectively etched to be patterned into a desired wiring shape to form signal wiring conductor layers 23a and 23b (FIG. 6).
(B)). Next, a photosensitive thermosetting resin is dissolved in a solvent and applied to both sides of the base material 21, and then the solvent is evaporated by a pre-curing to form insulating resin layers 24a and 24b. Here, XP-9500CC manufactured by Shipley is used as the photosensitive thermosetting resin. When applying the photosensitive thermosetting resin, printing or a coater is used. At this time, the area for applying the photosensitive thermosetting resin is made slightly smaller than the area of the base material 21, and the insulating resin layer 24
a, 24b are not formed. This is because the stage of the printing apparatus or the coater is not soiled, and at the same time, the edge 61 serving as a reference surface is formed in a subsequent polishing process. Here, a 400 mm square substrate is used as the substrate 21, and the insulating resin layers 24 a and 24 b are 380 m long.
It was formed with m square. Therefore, around the base material 21, the width 10
The edge 61 where the insulating resin layers 24a and 24b are not formed in a strip shape in mm is left.

Next, the insulating resin layers 24a and 24b are exposed and developed to form photo via holes 25 in a desired arrangement (FIG. 6D). Further, the surfaces of the insulating resin layers 24a and 24b are polished to remove irregularities on the surface, and the surfaces of the insulating resin layers 24a and 24b are made substantially flat with the substrate 21 (FIG. 6E). Here, the polishing is performed so that the thickness of the polished insulating resin layers 24a and 24b is 50 μm in a portion where the signal wiring conductor layers 23a and 23b are not provided.

In this embodiment, this polishing step is performed by using a unique polishing apparatus (FIG. 6E). The configuration of the polishing apparatus will be described with reference to FIGS. In this polishing apparatus, the object to be polished 1 (the insulating resin layer 24a of FIG.
The substrate 21 with 24b is held by the chuck 2. The chuck 2 includes an upper plate 17 and a template 15.
It is composed of The upper plate 17 is a plate-like member whose central portion protrudes thickly in the shape of the base material 1. The template 15 is a frame having an opening 301 in the shape of the base material 21 and is formed so as to fit with a thick portion at the center of the upper plate 17 (FIG. 3). Here, the substrate 21 is
Since it is a square of 400 mm square and 0.5 mm in thickness, the opening 301 is also a square of approximately 400 mm square. A polishing stopper 14 made of a material having a lower polishing rate than the insulating resin layers 24a and 24b is fixed to the lower surface of the template 15 to stop polishing. The polishing stopper 14 has an opening 302 smaller than the opening 301. Therefore, when the polishing target 1 is inserted into the opening 301 of the template 15, the upper surface of the polishing stopper 14
It is configured to be in contact with the surface of the edge 61 of the object 1 to be polished. In addition,
Since the size of the opening 302 is set to be larger than the region where the insulating resin layers 24a and 24b are formed,
The polishing stopper 14 does not contact the insulating resin layer 24b,
It contacts only the surface of the edge 61 of the substrate 21.

As the material of the polishing stopper 14, for example, a metal material such as stainless steel or molybdenum, or a ceramic such as alumina can be used. In this embodiment, the polishing stopper 1 is made of stainless steel (SUS304).
4 are formed. The opening 3 of the polishing stopper 14
02 is 384 mm square here.

On the other hand, a backing member 18 made of an elastic material is attached to the center of the upper plate 17. Therefore, when the template 15 is fitted to the upper plate 17, the backing material 18 absorbs the unevenness of the insulating resin layer 24 a on the non-polished side of the object 1 to be polished, and
One edge 61 is pressed against the polishing stopper 14 to fix the substrate 21. As the material of the backing material 18, it is necessary to use an elastic material capable of sufficiently absorbing irregularities of the insulating resin layer 24a on the non-polished side of the object 1 to be polished.
In this embodiment, the backing material 18 is formed of urethane rubber having a thickness of 1 mm.

A plate thickness adjusting elastic body 16 is attached to a portion of the upper plate 17 which is in contact with the template 15 at the periphery. Since the plate thickness adjusting elastic body 16 is arranged, the object 1 to be polished having a wide range of thicknesses can be chucked by the chuck 2.
It is possible to hold with. Here, the plate thickness adjusting elastic body 16 is formed of urethane rubber having a thickness of 3 mm.

The upper plate 17 of the chuck 2 has
A shaft 201 is attached. The movable joint 19 is attached to the shaft 201, and the chuck 2 is supported by the shaft 201 so as to be free to tilt. A motor 3 for rotating the chuck 2 is connected to the shaft 201 as shown in FIG. 5, and a cylinder 7 is connected via a rotary joint 6. The motor 3 and the cylinder 7 are connected to the control device 8 by signal lines 9a and 9b, respectively. The chuck 2 is mounted on a polishing platen 4 on which a polishing pad 5 is attached on the upper surface. The polishing liquid 5 is supplied onto the polishing pad 5.

In the present embodiment using such a polishing apparatus, polishing is performed as shown in FIG. That is, the object to be polished 1 is sandwiched between the upper plate 17 of the chuck 2 and the template 15, and the chuck 2 is placed on the polishing platen 4. As a result, the insulating resin layer 24b to be polished is exposed from the opening 302 of the polishing stocker 14 as shown in FIG. 1, and the convex portion of the insulating resin layer 24b contacts the polishing pad 5. In this state, the insulating resin layer 24b is pressed against the polishing pad 5 by applying a predetermined pressure from the cylinder 7 under the control of the controller 8, and the chuck 2 is rotated by the motor 3. In addition, when the platen 4 is rotated to supply the polishing liquid 10 onto the polishing pad 5 (FIG. 5), the insulating resin layer 24b exposed from the polishing stopper 14 is polished.

The polishing of the insulating resin layer 24b is performed by using the insulating resin layer 2b.
It starts from the convex part of 4a. Then, when the thickness of a part of the insulating resin layer 24 b becomes equal to the thickness of the polishing stopper 14, the polishing stopper 14 at the periphery thereof comes into contact with the polishing pad 5. Then, in this portion, the progress of polishing is extremely suppressed by the polishing stopper 14, the polishing can be stopped by the thickness of the polishing stopper 14, and the polishing portion is formed in another portion of the insulating resin layer 24 a where polishing is easy. Move on. Therefore, the thickness of the polishing stopper 14 is set to a desired thickness of the insulating resin layer 24b, and the polishing is continued until all of the lower surface of the polishing stopper 14 comes into contact with the polishing pad 5. The thickness (thickness including the thickness of the signal wiring conductor layer 23b) can be made equal to the thickness of the polishing stopper 14 as shown in FIG. Polished insulating resin layer 24b
Is a plane substantially parallel to the surface of the substrate 21.

In this embodiment, the thickness of the polishing stopper 14 is set to 50 μm. The cylinder 7 was controlled so that the polishing pressure was 5.0 kPa, and the polishing liquid 10 used was one in which abrasive grains of green silicon carbide # 3000 were dispersed in a solvent. The polishing pad 5 was made of hard polyurethane.

While polishing is performed under these conditions, the in-plane distribution of the thickness of the insulating resin layer 24b (thickness including the thickness of the signal wiring conductor layer 23b) is measured on the way. The change in thickness difference (maximum difference) from the thin portion was determined, and the progress of polishing was checked. FIG. 8 shows the result. FIG.
As can be seen from the figure, the maximum in-plane difference in the thickness of the insulating resin layer 24b was about 18 μm before polishing, but decreased with the progress of polishing, and finally decreased to about 6 μm.
At this time, the final thickness of the insulating resin layer is 52 μm on average.
m. Further, the shape of the surface of the insulating resin layer 24b after polishing was measured.
b on the surface of the insulating resin layer 24b
It was also found that the step of μm became 0.5 μm or less after polishing. From these facts, by using the polishing apparatus of the present embodiment, the variation in the thickness of the insulating resin layer 24b can be suppressed to about 10% at the maximum, and the step is about 0.5 μm or less. It was confirmed that it could be made flat. Therefore, when the signal wiring conductor layer 26b is formed thereon in the next step, there is no possibility of disconnection due to a step or thickness distribution of the insulating resin layer 24b. In addition, there is no portion in the insulating resin layer 24b below the desired thickness of 50 μm,
High interlayer insulation reliability can be maintained.

After the polishing of the insulating resin layer 24b is completed, the object 1 to be polished is turned upside down and held on the chuck 2, thereby exposing the insulating resin layer 24a from the opening 302 of the polishing stopper 14, The insulating resin layer 24a is similarly polished to flatten the surface of the insulating resin layer 24a.

Next, the flattened insulating resin layers 24a, 24b
A copper layer is formed on the surface of the substrate by copper plating, and this copper layer is patterned by photolithography and etching to form second signal wiring conductor layers 26a and 26b (FIG. 6F). Thereafter, the steps of FIG. 6C to FIG. 6F are repeated, and the insulating resin layer and the signal wiring conductor layer are sequentially laminated, so that a desired number of signal wiring conductor layers and insulating resin layers are formed. Are formed to form a printed circuit board.

As described above, according to the manufacturing method of the present embodiment, the steps on the surfaces of the insulating resin layers 24a and 24b are eliminated by using the polishing apparatus shown in FIG. The thickness (thickness including the thickness of the signal wiring conductor layer 23b) can be made uniform. Therefore, it is possible to manufacture a printed circuit board having no risk of disconnection of the signal wiring conductor layer and having high interlayer insulation reliability. Polishing can be performed in this manner because the polishing apparatus shown in FIG. 1 is used as described above. The polishing apparatus shown in FIG. 1 has a configuration in which the polishing stopper 14 is brought into contact with the edge 61 of the substrate 21 so that the upper surface of the substrate is used as a reference for the polishing amount. In addition, the backing material 18 absorbs unevenness of the non-polished insulating resin layer 24a. Therefore, in the polishing apparatus of FIG. 1, the polishing amount is controlled by the polishing stopper 14 based on the upper surface of the substrate 21 instead of controlling the polishing amount using the stopper based on the back surface of the object 1 to be polished as in the related art. Can be. Thus, the insulating resin layer 24b can be accurately polished to a desired thickness without being affected by the unevenness of the insulating resin layer 24a on the non-polished side.

On the other hand, as a comparative example, in the above-described step of FIG. 6E, polishing was performed using a conventional method such as ceramic roll polishing, plane swing polishing, polishing polishing, and the like.
By the respective polishing methods, the unevenness on the surface of the insulating resin layer was removed to obtain a flat surface. However, since the feature of these polishing methods is to obtain a uniform polishing rate in the plane and not to cause unevenness in the polishing amount, the difference between the maximum value and the minimum value of the thickness of the insulating resin layer is very small before and after polishing. There was no change. Therefore, unlike this embodiment, the thickness of the insulating resin layer could not be basically made uniform by polishing, and the reliability of interlayer insulation was lower than that of this embodiment.

In the process shown in FIGS. 6A to 6D, when the insulating resin layer is laminated only on one side of the base material 21, the polishing material can be used even with a ceramic roll or a plane swing polishing method. If the parallelism of the support material of the object to be polished is high, it is considered that the thickness of the insulating resin layer can be made uniform by polishing because the back surface of the base material, which is somewhat flat, is used as a reference. However, since these polishing methods do not have a stopper as in the present invention,
Excessive polishing must be controlled by the number of passes or the time.In addition, since the surface of the insulating resin layer is polished in parallel to the back surface of the base material, the thickness of the insulating resin layer at the thicker portion of the base material becomes thinner. As a result, the thickness variation of the insulating resin layer cannot be suppressed more than the thickness variation of the base material. Therefore, the present invention in which the thickness of the resin is controlled based on the surface of the base material 21 can make the thickness of the insulating resin layer more uniform. Further, when the insulating resin layer and the signal wiring conductor layer are laminated only on one surface of the base material 21, the printed wiring board having the same number of laminations is compared with the case where the insulating resin layer and the signal wiring conductor layer are laminated simultaneously on both surfaces as in this embodiment. Approximately twice the number of steps are required to manufacture, and the manufacturing efficiency is low, and the manufacturing method of the present embodiment is excellent from the viewpoint of manufacturing efficiency.

[0030]

As described above, a method of manufacturing a printed circuit board in which an insulating resin layer and a signal wiring conductor layer are alternately laminated on both surfaces of a substrate, wherein the surface of the insulating resin layer is A polishing method capable of polishing to a surface substantially parallel to the surface of the substrate.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a support portion of a workpiece of a polishing apparatus used in a polishing step of a method of manufacturing a printed circuit board according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a configuration of a support portion of a workpiece of the polishing apparatus of FIG. 1;

FIG. 3 is a top view showing the configuration of a template 15 and a polishing stopper 14 of the polishing apparatus of FIG.

FIG. 4 is a sectional view showing a configuration of a template 15 and a polishing stopper 14 of the polishing apparatus of FIG. 1;

FIG. 5 is a block diagram showing the overall configuration of the polishing apparatus of FIG. 1;

FIGS. 6A to 6F are cross-sectional views illustrating steps of manufacturing a printed circuit board according to an embodiment of the present invention.

FIGS. 7A to 7F are cross-sectional views showing steps of manufacturing a conventional printed circuit board.

FIG. 8 is a graph showing a change in the maximum difference in the in-plane distribution of the thickness of the insulating resin layer as polishing proceeds in the polishing step of FIG. 6 (f).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... polishing object, 2 ... chuck, 3 ... motor, 4 ... rotating platen, 5 ... polishing pad, 6 ... rotary joint, 7
... Cylinder, 8 ... Control device, 9a, 9b ... Signal line, 1
0: Polishing liquid, 14: Polishing stopper, 15: Template, 16: Plate thickness adjusting elastic body, 17: Upper plate, 18 ...
Backing material, 19: movable joint, 21: base material, 22
a, 22b: copper layer, 23a, 23b: signal wiring conductor layer,
24a, 24b: insulating resin layer, 25: photo via hole, 26a, 26b: second signal wiring conductor layer, 61 ...
Edge, 201 ... axis.

Continuation of the front page (72) Inventor Masashi Miyazaki 1 Horiyamashita, Hadano-shi, Kanagawa F-term in the General-purpose Computer Division, Hitachi, Ltd. 5E314 AA27 BB12 CC01 DD01 DD05 FF01

Claims (8)

[Claims] 1. A first step of forming a signal wiring conductor layer having a desired pattern on a base material, and an insulating resin layer covering the signal wiring conductor layer except for an edge portion of a surface of the base material. And polishing the insulating resin layer in a state where a polishing stopper member having a lower polishing rate than the insulating resin layer is brought into contact with the edge portion of the surface of the base material. A third step of polishing the insulating resin layer to a thickness of the polishing stopper member. 2. The method of manufacturing a printed circuit board according to claim 1, wherein said polishing stopper member has a thickness set to a thickness at which said insulating resin layer is to be polished in said third step. A method for manufacturing a printed circuit board, comprising: 3. The method of manufacturing a printed circuit board according to claim 1, wherein in the third step, the polishing stopper member is arranged so as to surround the base material. Method. 4. The method of manufacturing a printed circuit board according to claim 1, wherein the first and second steps are steps of forming a signal wiring conductor layer and an insulating resin layer on both surfaces of the base material, respectively. In the third step, the insulating resin layers on both sides of the base material are polished one by one in order, and in order to absorb irregularities of the non-polished insulating resin layer, an elastic member is formed on the non-polished insulating resin layer. A method for manufacturing a printed circuit board, wherein polishing is performed in a state where the substrate is pressed. 5. A method for polishing a resin layer on a substrate, comprising: a polishing stopper member having a lower polishing rate than the resin layer on a portion of the surface of the substrate where the resin layer is not formed. A method for manufacturing a printed circuit board, wherein the insulating resin layer is polished to a thickness of the polishing stopper member by contacting and polishing the insulating resin layer in that state. 6. A polishing platen, and holding means for holding a substrate to be polished on the polishing platen, wherein the holding means is provided on an edge of a surface of a surface of the substrate to be polished. A polishing apparatus, comprising: a polishing stopper member disposed at a position in contact with a portion, wherein the polishing stopper member is made of a material having a lower polishing rate than a material constituting a surface to be polished of the substrate. 7. A polishing apparatus according to claim 6, wherein said holding means has a plate-like member for holding said substrate between said polishing stopper member and said plate-like member. A polishing apparatus, wherein an elastic member for absorbing irregularities on the back surface is attached to a portion of the substrate to be polished, where the back surface of the substrate contacts the back surface. 8. A polishing apparatus according to claim 6, wherein said polishing stopper is a frame-shaped member surrounding said substrate.