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(11) | EP 0 787 562 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Double side polishing machine and method of polishing opposite sides of a workpiece using the same |
| (57) A double side polishing machine includes a disk-shaped carrier for holding an article
to be polished, and a sun gear and an internal gear which are meshed with external
teeth of the carrier. The tooth portions of the sun gear and the internal gear are
made of a hard resin material, such as polyimide sintered body or polyamide imide
resin, which has excellent wear resistance, sufficient self-lubricating performance,
and high shear resistance. Each tooth portion is formed as a single member, or is
formed by a plurality of separable segments. Alternatively, the internal and sun gears
are made of a metal such as steel and coated with a hard resin coating material. In
another double side polishing machine, each of the tooth portions of the internal
and sun gears is formed by a plurality of pins disposed at a predetermined pitches
and sleeves fit onto the pins. The sleeves are made of a resin. Alternatively, resin-coated
metallic sleeves may be used as the sleeves. The double side polishing machines can
prevent generation of metal powder, thereby suppressing generation of scratches and
metal contamination. |
BACKGROUND OF THE INVENTION
Field of the Invention:
[0001] The present invention relates to an improvement on a double side polishing machine for polishing opposite sides of a workpiece such as a semiconductor wafer. The present invention also relates to a method of polishing such a workpiece using an improved double side polishing machine.
Description of the Related Art:
[0002] Conventionally, a double side polishing machine has been used to polish opposite surfaces of a semiconductor wafer or the like. In such a double side polishing machine, there are provided a plurality of disk-shaped carriers, and a plurality of carrier holes are formed in each carrier so as to hold wafers. External teeth formed on the outer periphery of each carrier are meshed with a sun gear and an internal gear, so that the carriers revolve around the sun gear while rotating on their own axes. Wafers placed in the carrier holes are sandwiched between an upper polishing turn table and a lower polishing turn table. In this state, the top and bottom surfaces of the wafers are polished simultaneously.
[0003] With regard to carriers, there have been known metallic carriers, metallic carriers having resin coating on their surfaces (see Japanese Utility Model Application Laid-Open (Kokai) No. 58-4349), and carriers formed of laminated carbon-fiber plate into which resin is impregnated (see Japanese Patent Application Laid-Open (kokai) No. 58-143954).
[0004] Meanwhile, the sun gear and the internal gear are generally made of a metallic material such as steel.
[0005] In the case where the sun gear and the internal gear are made of a metallic material and the carriers are metallic carriers with or without resin coating, metal powder is produced from meshing portions where metallic surfaces are exposed, although the amount of produced metal power is small. When the metal powder enters the space between a polishing surface of a wafer and the upper or lower polishing turn table, scratches are formed on the surface of the wafer, or metal contamination is induced.
[0006] When the carriers are made of a resin, the external teeth of the carriers that are also made of the resin are meshed with the teeth of the metallic sun gear and the metallic internal gear, and are easily chipped and damaged. This shortens the service life of the carriers. In addition, if metal or resin powder enters the space between a polishing surface of a wafer and the upper or lower polishing turn table, scratches are formed on the surface of the wafer. Such scratches and metal contamination cause a fatal deficiency for semiconductor substrates, and yield of products decreases considerably.
[0007] The above-described problems also occur in other types of double side polishing machines; i.e., a double side polishing machine in which the teeth of the sun gear and the internal gear are formed by a plurality of pins provided at a predetermined pitch, and a double side polishing machine disclosed, for example, in Japanese Patent Application Laid-Open (kokai) No. 1-252356 in which the teeth of the sun gear and the internal gear are formed by rotatable rollers instead of pins so as to reduce wear caused by engagement with the external teeth of the carriers, thereby increasing durability.
[0008] That is, in the above-described two types of double side polishing machines, pins or rollers that form the teeth of the sun gear and the internal gear are made of a metal. Therefore, the pins or rollers wear when they are meshed with the external teeth of the carriers, so that metal powder is generated.
[0009] Accordingly, there has been demanded a polishing machine which can prevent generation of scratches and metal contamination which would otherwise occur while semiconductor wafers are being polished.
SUMMARY OF THE INVENTION
[0010] The present invention has been accomplished to solve the above-mentioned problems, and an object of the present invention is to provide an improved double side polishing machine that can prevent generation of metal powder, thereby suppressing generation of scratches and metal contamination.
[0011] Another object of the present invention is to provide a method of polishing opposite surfaces of a workpiece using the improved double side polishing machine.
[0012] In order to achieve the above-objects, the present invention provides a double side polishing machine which includes a disk-shaped carrier for holding an article to be polished (hereinafter referred to as a "workpiece"), a sun gear and an internal gear which are meshed with external teeth of the carrier, and upper and lower polishing turn tables that sandwich the workpiece so as to polish opposite surfaces of the workpiece, wherein at least the tooth portions of the sun gear and the internal gear are made of a hard resin material.
[0013] Alternatively, the sun gear and the internal gear are made of a metallic material, and at least the tooth portions of the sun gear and the internal gear are coated with a hard resin coating material.
[0014] Since the tooth portions of the sun gear and the internal gear are made of a hard resin or coated with a hard resin coating material, scratches can be suppressed, while the problem of metal contamination can be avoided. In addition, since the meshing engagement with the external teeth of the carrier becomes soft, the durability of the carrier can be enhanced.
[0015] The hard resin material is preferably a resin having excellent wear resistance, sufficient self-lubricating performance, and high shear resistance.
[0016] When the tooth portions are made of a hard resin material, each tooth portion is formed as a single member. Alternatively, each tooth portion is formed by a plurality of separable segments.
[0017] In the former case, work for attachment and replacement can be facilitated. In the latter case, when a portion of the tooth portion is broken, such a portion can be replaced individually. Therefore, it is economical, and molding cost can be decreased.
[0018] Preferably, the hard resin material and the hard resin coating material are selected from the group consisting of polyimide sintered body, polyether etherketone (PEEK), polyacetal, polyethylene terephthalate (PET), polyamide, and polyamide imide.
[0019] When such a resin is used as the hard resin material or the hard resin coating material, excellent characteristics can be provided, because the above-described resins have excellent wear resistance, sufficient self-lubricating performance, and high shear resistance.
[0020] Preferably, at least the external teeth of the carrier is made of a resin material. In this case, the resin material is preferably selected from the group consisting of glass epoxy material, laminated plate of resin-impregnated carbon fibers, and laminated plate of resin-impregnated alamido fibers.
[0021] The carrier may be made of a metallic material, and the surface of the carrier may be covered with a resin coating material.
[0022] When the carrier is made of a resin material, or is made of a metallic material and coated with a resin coating material, the teeth softly contact each other, so that no metallic powder is produced from the meshing surfaces. Accordingly, it becomes possible to prevent formation of scratches on wafer surfaces and metal contamination.
[0023] The present invention also provides a double side polishing machine which includes a disk-shaped carrier for holding a workpiece, a sun gear and an internal gear which are meshed with external teeth of the carrier, and upper and lower polishing turn tables that sandwich the workpiece so as to polish opposite surfaces of the workpiece, wherein each of the tooth portions of the sun gear and the internal gear is formed by a plurality of pins disposed at a predetermined pitch, and a sleeve made of a resin or a resin-coated metallic sleeve is fit onto the outer surface of each of the pins.
[0024] Since a sleeve made of a resin or a resin-coated metallic sleeve is fit onto the outer surface of each pin, no metal powder is produced due to friction, so that scratches on a workpiece and metal contamination can be considerably suppressed.
[0025] Preferably, the sleeve is made of a material having a bending strength equal to or greater than 1,000 kg/cm2, a shear strength equal to or greater than 800 kg/cm2, and a coefficient of friction equal to or less than 0.2.
[0026] It is said that a force above 500 kg/cm2 generally acts between the external teeth of the carrier and the pins (sleeves) during polishing. Accordingly, when the sleeves having the above-described properties are used, the durability of the sleeves can be increased.
[0027] When the sleeves are made of a resin, polyamide imide resin, polyamide resin, polyether etherketone resin or the like may be used.
[0028] The present invention further provides a method of polishing opposite sides of a workpiece through use of one of the double side polishing machines according to the present invention. The method makes it possible to polish the workpiece stably without fear of generating scratches or metal contamination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029]
FIG. 1 is a view schematically showing the structure of a double side polishing machine according to the present invention;
FIG. 2 is a top view as viewed from line A-A in FIG. 1;
FIG. 3 is a view showing grooves formed in a polishing surface of a polishing turn table;
FIGS. 4A and 4B are views showing first and second embodiments of the present invention, wherein FIG. 4A shows an internal gear, while FIG. 4B shows a sun gear;
FIGS. 5A and 5B are views showing a third embodiment of the present invention, wherein FIG. 5A shows an internal gear, while FIG. 5B shows a sun gear;
FIGS. 6A and 6B are views showing a fourth embodiment of the present invention, wherein FIG. 6A shows an internal gear, while FIG. 6B shows a sun gear;
FIG. 7 is a graph showing the results of comparison between the scratch generation ratio of Example 1 and that of Comparative Example 1;
FIG. 8 is a graph showing the results of comparison between the degree of metal contamination of Example 1 and that of Comparative Example 1;
FIGS. 9A and 9B are graphs showing the scratch generation ratio of Example 2, wherein FIG. 9A shows the result of comparison between Example 2 and Comparative Example 2, while FIG. 9B shows the result of comparison between Example 2 and Comparative Example 2 regarding the scratch generation ratio of each batch;
FIG. 10 is a partial cross section of a double side polishing machine according to a fifth embodiment of the present invention;
FIG. 11 is an enlarged view of a main portion of FIG. 10;
FIG. 12 is a top view showing a state in which wafers are held by carriers;
FIG. 13 shows the results of an experiment on the scratch generation ratio, wherein section A shows the results for the case of metallic sleeves, while section B shows the results for the case of resin sleeves according to the fifth embodiment; and
FIG. 14 shows the results of an experiment on metal contamination, wherein section A shows the results for the case of metallic sleeves, while section B shows the results for the case of resin sleeves according to the fifth embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0031] Among the drawings, FIG. 1 is a view schematically showing the structure of a double side polishing machine according to the present invention, FIG. 2 is a top view as viewed from line A-A in FIG. 1, and FIG. 3 is a view showing grooves formed in a polishing surface of a polishing turn table.
[0032] A double side polishing machine according to the present invention is structured as a machine for simultaneously polishing opposite surfaces of, for example, semiconductor wafers. As shown in FIGS. 1 - 3, the double side polishing machine includes a ring-shaped internal gear 1 fixed to a machine frame 7, a sun gear 2 rotatably about a rotational axis 2a, and three thin-plate-shaped carriers 3 meshed with the internal gear 1 and the sun gear 2. A tooth portion 1g is formed on the inner circumferential portion of the internal gear 1, and a tooth portion 2g is formed on the outer circumferential portion of the sun gear 2, respectively. External teeth 3g are formed on the outer circumferential portion of each carrier 3. The external gear 3g is meshed with the tooth portion 1g of the internal gear 1 and the tooth portion 2g of the sun gear 2. When the sun gear 2 is rotated, the carriers 3 revolve around the sun gear 2 while rotating on their own axes.
[0033] Each carrier 3 has carrier holes 3a at three positions, and wafers W are held within the carrier holes 3a. An upper polishing turn table 4 and a lower polishing turn table 5 are disposed such that the wafers W are sandwiched between the upper and lower polishing turn tables 4 and 5. The polishing turn tables 4 and 5 are respectively rotated about rotational axes 4a and 5a in opposite directions. As shown in FIG. 3, grid-like grooves m are formed in each of surfaces of the polishing turn tables 4 and 5 which face each other. Therefore, polishing agent supplied from a polishing agent supply nozzle 6, which will be described later, can be spread uniformly. Polishing pads 4c and 5c are bonded to the lower surface of the upper polishing turn table 4 and the upper surface of the lower polishing turn table 5, respectively.
[0034] Above the upper polishing turn table 4 is disposed the above-described polishing agent supply nozzle 6. Polishing agent supplied from the polishing agent supply nozzle 6 is supplied to the polishing surfaces of the wafers W via a polishing agent passage 4b formed in the upper polishing turn table 4.
[0035] The above-described double side polishing machine is operated as follows. After the upper polishing turn table 4 is moved upward, wafers W are placed into the carrier holes 3a. Subsequently, the upper polishing turn table 4 is moved downward, so that the wafers W are sandwiched between the upper polishing turn table 4 and the lower polishing turn table 5. While polishing agent is supplied from the polishing agent supply nozzle 6, the sun gear 2 is rotated. As a result, the carriers 3 revolve around the sun gear 2 and rotate on their own axes. Simultaneously with this, the upper polishing turn table 4 and the lower polishing turn table 5 are rotated in opposite directions so as to polish the top and bottom surfaces of the wafers W. In the present invention, the internal gear 1 and the sun gear 2 in particular have unique structures that prevent generation of metal powder or chips at portions where the internal gear 1 and the sun gear 2 mesh with the external teeth 3g of the carriers 3.
[0036] According to a first embodiment of the present invention, as shown in FIGS. 4A and 4B, each of the ring-shaped internal gear 1 (FIG. 4A) and the sun gear 2 (FIG. 4B) is made of a hard resin material as a single member. The hard resin material is selected from resins having excellent wear resistance, sufficient self-lubricating performance, and high shear resistance. For example, polyimide sintered body, polyether etherketone (PEEK), polyacetal, polyethylene terephthalate (PET), polyamide, and polyamide imide are suitable, and polyimide sintered body is most suitable.
[0037] When the internal gear 1 and the sun gear 2 are made of such a resin material, no metal powder is produced from the meshing portions, and no excessive force acts on the external teeth 3g of the carriers 3.
[0038] According to a second embodiment of the present invention, the internal gear 1 and the sun gear 2 shown in FIGS. 4A and 4B are made of a metallic material such as steel, and the tooth portions 1g and 2g and vicinities thereof are covered with a hard resin coating material. In this case, not only the tooth portions 1g and 2g and vicinities thereof, but also other portions of the internal gear 1 and the sun gear 2 may be covered with the hard resin coating material. In this case also, the hard resin material is preferably selected from resins having excellent wear resistance, sufficient self-lubricating performance, and high shear resistance, and the above-described resin materials are suitable.
[0039] According to a third embodiment of the present invention, as shown in FIGS. 5A and 5B, the internal gear 1 (FIG. 5A) is composed of an outer metallic member s and an inner resin member r that is disposed on the inner side of the outer metallic member s. The outer metallic member s is made of a metal such as steel. The inner resin member r is formed in a ring-like shape and has the tooth portion 1g. The sun gear 2 (FIG. 5B) is composed of a center metallic member s and an outer resin member r that is disposed to surround the center metallic member s. The center metallic member s is made of a metal such as steel. The outer resin member r is formed in a ring-like shape and has the tooth portion 2g. The metallic and resin members are fixed to each other through engagement between concave and convex surfaces, or through use of screws or the like.
[0040] According to a fourth embodiment of the present invention, as shown in FIGS. 6A and 6B, each of the resin members shown in FIGS. 5A and 5B is divided into a plurality of segments, such that all the segments have the same shape and the same size. These segments are fixed to a corresponding metallic member through engagement between concave and convex surfaces, or through use of screws. Therefore, each of the segments can be attached and removed individually.
[0041] Accordingly, when a portion of the tooth portion is broken, such a portion can be replaced individually. This is very convenient.
[0042] Next, a description will be given of test examples that were performed with the internal gears 1 and the sun gears 2 of the above-described embodiments, in which their tooth portions 1g and 2g are made of a hard resin or covered with a hard resin coating material.
Example 1:
[0043] The internal gear 1 and the sun gear 2 were made of polyimide sintered material, and steel carriers whose surfaces were coated with fluororesin were used as the carriers 3. Etched wafers (CZ P type, crystal orientation: <100>) each having a diameter of 200 mm were used as samples. Unwoven cloth (velour type) having a hardness of 80 (asker C hardness, JIS K-6301) was used as a polishing pad. Colloidal silica containing polishing agent (PH = 10.5) was used, and a polishing load of 150 g/cm2 and a polishing stock removal of 18 µm were selected as machining conditions.
[0044] 120 wafers were subjected to double side polishing under the above-described machining conditions, and these wafers were visually checked, under a collimated light in a dark room, whether scratches were formed on the surfaces of the wafers. The results are shown in FIG. 7. In FIG. 7, Example 1 is compared with Comparative Example 1, in which wafers were polished under the same machining conditions except that the internal gear 1 and the sun gear 2 were made of steel. FIG. 8 shows the comparison between Example 1 and Comparative Example 1 regarding the degree of metal contamination of polished wafer surfaces.
[0045] From the above-described results, it is understood that when the internal gear 1 and the sun gear 2 were made of steel, the scratch generation ratio became almost 100%, and that when the internal gear 1 and the sun gear 2 were made of polyimide sintered body as in the above-described embodiment, the scratch generation ratio decreased to 1.9%. It is further understood that the degree of metal contamination also decreased in general.
Example 2:
[0046] The internal gear 1 and the sun gear 2 were made of polyamide imide resin, and glass epoxy laminated plate and carbon epoxy laminated plate were used as the carriers 3. Etched wafers (CZ P type, crystal orientation: <100>) each having a diameter of 200 mm were used as samples. Unwoven cloth (velour type) having a hardness of 80 (asker C hardness) was used as a polishing pad. Colloidal silica containing polishing agent (PH = 10.5) was used, and a polishing load of 150 g/cm2 and a polishing stock removal of 18 µm were selected as machining conditions.
[0047] 105 wafers were subjected to double side polishing under the above-described machining conditions, and these wafers were visually checked, under a collimated light in a dark room, whether scratches were formed on the surfaces of the wafers. The results are shown in FIG. 9A. In FIG. 9A, Example 2 is compared with Comparative Example 2, in which wafers were polished under the same machining conditions except that the internal gear 1 and the sun gear 2 were made of steel. FIG. 9B shows the scratch generation ratio of each batch that included 15 wafers.
[0048] From the above-described results, it is understood that when the internal gear 1 and the sun gear 2 was made of polyamide imide resin, scratches on wafer surfaces can be considerably decreased.
[0049] When the cross sections of the external teeth of the carriers 3 used in Example 2 were examined by microphotography, it was found that when the internal gear 1 and the sun gear 2 were made of a polyamide imide resin, the degree of damage was lower as compared to the case in which the internal gear 1 and the sun gear 2 were made of steel. Therefore, in the present embodiment, the durability of the carriers can be enhanced.
[0050] Next, a fifth embodiment of the present invention will be described with reference to FIGS. 10 - 12. FIG. 10 is a partial cross section of a double side polishing machine according to the fifth embodiment of the present invention, FIG. 11 is an enlarged view of a main portion of FIG. 10, and FIG. 12 is a top view showing a state in which wafers are held by carriers.
[0051] A double side polishing machine according to the present embodiment is structured as a machine for simultaneously polishing opposite surfaces of, for example, semiconductor wafers. As shown in FIGS. 10 - 12, the double side polishing machine includes an internal gear 11 and a sun gear 12 which are meshed with external teeth G of carriers C. The double side polishing machine also includes an upper polishing turn table 13 and a lower polishing turn table 14 by which semiconductor wafers held by the carriers C are sandwiched. As shown in FIG. 12, three carriers C are meshed with the internal gear 11 and the sun gear 12.
[0052] The upper polishing turn table 13 and the lower polishing turn table 14 are individually driven, so that the upper and lower polishing turn tables 13 and 14 rotate about respective vertical axes. Polishing pads 13a and 14a are attached to surfaces of the polishing turn tables 13 and 14 which face each other. A polishing agent supply passage 17 is formed in the upper polishing turn table 13, and polishing agent supplied from a nozzle 18 is supplied to polishing surfaces via the polishing agent supply passage 17. Each carrier C has wafer holding holes h, as well as unillustrated polishing agent holes which allows the polishing agent to pass therethrough. The upper polishing turn table 13 can be moved upward so as to allow semiconductor wafers W to be placed in the wafer holding holes h of the carriers C.
[0053] The tooth portion of the internal gear 11 and the tooth portion of the sun gear 12 have the same structure. As shown in FIG. 11, which is an enlarged view of the tooth portion of the internal gear 11, the tooth portion is composed of a plurality of pins 15 that are embedded into the top surface of the gear base member 11a along the circumferential direction thereof, and sleeves 16 that are fit onto the pins 15 in a rotatable manner. The pitch of the pins 15 corresponds to the pitch of the external gears G of the carriers C. The sun gear 12 has a similar structure.
[0054] The pins 15 are made of metal such as SUS (stainless steel) The sleeves 16 fit onto the pins 15 are made of a polyamide imide resin having an excellent mechanical strength and wear resistance. The polyamide imide resin has a bending strength equal to or greater than 1,000 kg/cm2, a shear strength equal to or greater than 800 kg/cm2, and a coefficient of friction equal to or less than 0.2. This material is especially suitable for the tooth portion on which a large load acts while a force is transmitted between the external gears G of the carriers C and the tooth portion.
[0056] The above-described double side polishing machine is operated as follows. After the upper polishing turn table 13 is moved upward, semiconductor wafers W are placed into the wafer holding holes h of the carriers C. Subsequently, the upper polishing turn table 13 is moved downward, so that the wafers W are sandwiched between the upper polishing turn table 13 and the lower polishing turn table 14. As shown in FIG. 10, the thickness of the carriers C is smaller than the thickness of the semiconductor wafers W. When the sun gear 12 is rotated, the carriers C revolve around the sun gear 12 and rotate on their own axes.
Simultaneously with this, the upper polishing turn table 13 and the lower polishing turn table 14 are rotated in opposite directions so as to polish the top and bottom surfaces of the wafers W. At this time, polishing agent is supplied to the polishing surfaces.
[0057] During polishing, a load above 500 kg/cm2 generally acts between the sleeves 16 fit onto the pins 15 and the external teeth G of the carriers C, so that these parts cause considerable friction. However, since the sleeves 16 employed in the present embodiment have excellent wear resistance and strength, the amount of wear of the sleeves 16 can be decreased. In addition, even when the sleeves 16 wear out, no metal contamination occur, because the sleeves 16 are made of a resin. Moreover, scratches are hardly generated.
[0058] In order to confirm the effect of the resin sleeves 16, the scratch generation ratio and the degree of metal contamination were examined through tests and were compared with those in the case where metallic sleeves were used. FIGS. 13 and 14 show the results of the tests, wherein FIG. 13 shows the scratch generation ratio, and FIG. 14 shows the metal contamination. In each of the graphs shown in FIGS. 13 and 14, section A shows the results obtained in the case where metallic sleeves were used, and section B shows the results obtained in the case where resin sleeves according to the present embodiment were used.
[0059] In the test, the carriers C were made of a glass-fiber-reinforced resin, the metallic sleeves are made of SUS, and the resin sleeves are made of a polyamide imide resin.
[0060] Etched wafers (CZ P type, crystal orientation: <100>) each having a diameter of 200 mm were used as samples. Unwoven cloth (velour type) having a hardness of 80 (asker C hardness, JIS K-6301) was used as a polishing pad. Colloidal silica containing polishing agent (PH = 10.5) was used, and a polishing load of 150 g/cm2 and a polishing stock removal of 18 µm were selected as machining conditions.
[0061] From the test results, it was found that when metallic sleeves were used, the scratch generation ratio was 13% and that the scratch generation ratio decreased from 13% to 0.9% when the resin sleeves of the present embodiment were used. As shown in FIG. 14, it was also confirmed that when metallic sleeves were used, the surface concentrations of Cr and Ni exceeded respective DLs (Detection Limits) and that when resin sleeves of the present embodiment were used, the surface concentrations of Cr, Cu and Ni became lower than the DLs. The DLs are limits up to which a measuring apparatus can detects the concentrations, and when the concentrations are lower than the limits, which being represented as NDs, precise measurement is not guaranteed. Therefore, in the present embodiment, the metal contamination was reduced greatly.
[0062] The generation of scratches was checked visually under a collimated light. The degree of metal contamination was examined by ICP-MS after the polished wafers were cleaned with ammonia + H2O2 and NaOH + H2O2, followed by decomposition and correction of Cr, Cu, and Ni through use of HF (hydrofluoric acid).
[0063] In the fifth embodiment, the sleeves 16 are made of a resin. However, metal sleeves whose surfaces are coated with a resin may be used as the sleeves 16.
[0064] The present invention is not limited to the above-described embodiments. The above-described embodiments are mere examples, and other embodiments which have substantially the same structure as those defined in the appended claims and provide similar effects are included in the scope of the present invention.
1. A double side polishing machine comprising:
a disk-shaped carrier for holding a workpiece;
a sun gear and an internal gear which are meshed with external teeth of said carrier; and
upper and lower polishing turn tables that sandwich the workpiece so as to polish opposite surfaces of the workpiece,
characterized in that at least the tooth portions of said sun gear and said internal gear are made of a hard resin material.2. A double side polishing machine comprising:
a disk-shaped carrier for holding a workpiece;
a sun gear and an internal gear which are meshed with external teeth of said carrier; and
upper and lower polishing turn tables that sandwich the workpiece so as to polish opposite surfaces of the workpiece,
characterized in that said sun gear and said internal gear are made of a metallic material, and at least the tooth portions of said sun gear and said internal gear are coated with a hard resin coating material.3. A double side polishing machine according to Claim 1, characterized in that each tooth
portion is formed as a single member.
4. A double side polishing machine according to Claim 1, characterized in that each tooth
portion is formed by a plurality of separable segments.
5. A double side polishing machine according to any one of Claims 1, 3, and 4, characterized
in that said hard resin material is selected from the group consisting of polyimide
sintered body, polyether etherketone (PEEK), polyacetal, polyethylene terephthalate
(PET), polyamide, and polyamide imide.
6. A double side polishing machine according to Claim 2, characterized in that said hard
resin coating material is selected from the group consisting of polyimide sintered
body, polyether etherketone (PEEK), polyacetal, polyethylene terephthalate (PET),
polyamide, and polyamide imide.
7. A double side polishing machine according to any one of Claims 1 - 6, characterized
in that at least the external teeth of said carrier is made of a resin material.
8. A double side polishing machine according to Claim 7, characterized in that said resin
material is selected from the group consisting of glass epoxy material, laminated
plate of resin-impregnated carbon fibers, and laminated plate of resin-impregnated
alamido fibers.
9. A double side polishing machine according to any one of Claims 1 - 7, characterized
in that said carrier is made of a metallic material, and the surface of said carrier
is covered with a resin coating material.
10. A double side polishing machine comprising:
a disk-shaped carrier for holding a workpiece;
a sun gear and an internal gear which are meshed with external teeth of said carrier; and
upper and lower polishing turn tables that sandwich the workpiece so as to polish opposite surfaces of the workpiece,
characterized in that each of the tooth portions of said sun gear and said internal gear is formed by a plurality of pins disposed at a predetermined pitch, and a sleeve made of a resin or a resin-coated metallic sleeve is fit onto the outer surface of each of said pins.11. A double side polishing machine according to Claim 10, characterized in that said
sleeve is made of a material having a bending strength equal to or greater than 1,000
kg/cm2, a shear strength equal to or greater than 800 kg/cm2, and a coefficient of friction equal to or less than 0.2.
12. A method of polishing opposite sides of a workpiece by use of the double side polishing
machine according to any one of Claims 1 - 11.