Polishing apparatus and wafer polishing method

Abstract

A polishing apparatus which is an index system polishing apparatus which includes a polishing head for holding a wafer, a plurality of turn tables to which polishing pads for polishing the wafer are attached, and a loading/unloading stage for loading the wafer to the polishing head or unloading the wafer from the polishing head, and which polishes the wafer while switching the turn tables to be used for polishing the wafer held at the polishing head by causing the polishing head to perform rotation movement, the polishing apparatus including a turn table upward and downward movement mechanism which allows the turn table to move upward and downward. With this polishing apparatus, it is possible to reduce an amount of displacement caused when moment load is applied on the polishing head during polishing.

Claims

1. An index system polishing apparatus comprising: a polishing head that holds a wafer; a plurality of turn tables to which polishing pads that polish the wafer are attached; and a loading/unloading stage that loads the wafer to the polishing head or unloads the wafer from the polishing head, and which polishes the wafer while switching the turn tables to be used for polishing the wafer held at the polishing head by causing the polishing head to perform rotation movement; a turn table upward and downward movement mechanism that allows the turn tables to move upward and downward; and a polishing head upward and downward movement mechanism that causes the polishing head to move upward and downward with a stroke width of 20 mm or less, wherein rotation movement of the polishing head and upward and downward movement of the turn tables and the polishing head are performed in parallel.

2. The polishing apparatus according to claim 1, wherein the polishing apparatus has a dressing mechanism at a position where the dressing mechanism does not interfere with a trajectory on which the polishing head performs rotation movement.

3. The polishing apparatus according to claim 2, wherein the turn table upward and downward movement mechanism adjusts height of the turn tables according to abrasion of the polishing pads when dressing of the polishing pads is performed by the dressing mechanism.

4. A wafer polishing method comprising providing the polishing apparatus according to claim 3, wherein switching of the turn tables to be used for polishing the wafer held at the polishing head is performed by the turn tables being moved downward and the polishing head being made to perform the rotation movement.

5. A wafer polishing method comprising providing the polishing apparatus according to claim 3, wherein switching of the turn tables to be used for polishing the wafer held at the polishing head is performed by the turn tables being moved downward and the polishing head being made to perform the rotation movement, and the method further comprises adjusting height of the turn tables according to abrasion of the polishing pads and dressing the polishing pads after polishing of the wafer is finished.

6. A wafer polishing method comprising providing the polishing apparatus according to claim 2, wherein switching of the turn tables to be used for polishing the wafer held at the polishing head is performed by the turn tables being moved downward and the polishing head being made to perform the rotation movement.

7. A wafer polishing method comprising providing the polishing apparatus according to claim 2, wherein switching of the turn tables to be used for polishing the wafer held at the polishing head is performed by the turn tables being moved downward and the polishing head being made to perform the rotation movement, and the method further comprises adjusting height of the turn tables according to abrasion of the polishing pads and dressing the polishing pads after polishing of the wafer is finished.

8. A wafer polishing method comprising providing the polishing apparatus according to claim 1, wherein switching of the turn tables to be used for polishing the wafer held at the polishing head is performed by the turn tables being moved downward and the polishing head being made to perform the rotation movement.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1A is a schematic side view illustrating a state where a turn table is located at a lowermost position of upward and downward movement in an example of a polishing apparatus of the present invention;

(2) FIG. 18B is a schematic side view illustrating a state where the turn table is located at an uppermost position of the upward and downward movement in an example of the polishing apparatus of the present invention;

(3) FIG. 2 is a schematic diagram illustrating an example of a turn table upward and downward movement mechanism in an example of the polishing apparatus of the present invention;

(4) FIG. 3A is a schematic top view when a wafer is polished in a state where the turn table is moved upward with the turn table upward and downward movement mechanism in an example of the polishing apparatus of the present invention;

(5) FIG. 3B is a schematic side view when the wafer is polished in a state where the turn table is moved upward with the turn table upward and downward movement mechanism in an example of the polishing apparatus of the present invention;

(6) FIG. 4A is a schematic top view when a polishing pad is dressed in a state where the turn table is moved downward with the turn table upward and downward movement mechanism in an example of the polishing apparatus of the present invention;

(7) FIG. 4B is a schematic side view when the polishing pad is dressed in a state where the turn table is moved downward with the turn table upward and downward movement mechanism in an example of the polishing apparatus of the present invention;

(8) FIG. 5 is a schematic top view illustrating an example of the polishing apparatus of the present invention;

(9) FIG. 6 is a flowchart illustrating an example of a wafer polishing method of the present invention;

(10) FIG. 7 is a schematic diagram illustrating a direction of moment load applied on a polishing head in simulation in Example 1;

(11) FIG. 8 is a schematic diagram illustrating a direction of load applied on a flange portion of the polishing shaft in simulation in Example 1;

(12) FIG. 9 is a schematic diagram illustrating a direction of load actually applied on the flange portion of the polishing shaft in Example 1;

(13) FIG. 10 is a diagram illustrating relationship between the number of times of dressing and change of a thickness of the polishing pad in Example 3 and Comparative Example 3;

(14) FIG. 11 is a schematic diagram illustrating an example of a typical one-side polishing apparatus;

(15) FIG. 12 is a schematic diagram illustrating an example of a typical index system wafer polishing apparatus;

(16) FIG. 13 is a flowchart illustrating an example of a typical index system wafer polishing method;

(17) FIG. 14A is a schematic diagram illustrating a state where a polishing head is located at a lowermost position of upward and downward movement in a conventional polishing apparatus;

(18) FIG. 14B is a schematic diagram illustrating a state where the polishing head is located at an uppermost position of the upward and downward movement in the conventional polishing apparatus;

(19) FIG. 15A is a schematic side view when the wafer is polished in a state where the polishing head is located at the lowermost position of the upward and downward movement in the conventional polishing apparatus; and

(20) FIG. 15B is a schematic side view when a polishing pad is dressed in a state where the polishing head is located at the uppermost position of the upward and downward movement in the conventional polishing apparatus.

DESCRIPTION OF EMBODIMENT

(21) Hereinafter, the embodiments of the present invention will be described, but the present invention is not limited to this embodiment.

(22) As described above, there is a problem that, in the case where moment load is applied on a polishing shaft while a wafer is polished, displacement occurs at the polishing shaft, which adversely affects quality of the wafer being polished.

(23) Therefore, the present inventors specifically investigated to solve such a problem. As a result, the present inventors conceived of providing a turn table upward and downward movement mechanism at the polishing apparatus. By allowing the turn table to move upward and downward with the turn table upward and downward movement mechanism, it is possible to shorten the length of the polishing shaft. By this means, stiffness of the polishing shaft is increased, so that it is possible to reduce an amount of displacement of the polishing shaft caused when moment load is applied during polishing.

(24) The present inventors examined the best mode for carrying out these and completed the present invention.

(25) First, the polishing apparatus of the present invention will be described with reference to FIG. 1A, FIG. 1B and FIG. 5.

(26) As illustrated in FIG. 5, the polishing apparatus 1 of the present invention includes polishing heads 2a to 2d for holding wafers, a plurality of turn tables 4a to 4c and a loading/unloading stage 12. Further, as illustrated in FIG. 1A and FIG. 1B, the polishing apparatus 1 includes a turn table upward and downward movement mechanism 5 which can move the turn tables 4a to 4c upward and downward. A polishing pad 3 for polishing the wafer W is attached to each of the turn tables 4a to 4c. The wafers W can be loaded on the polishing heads 2a to 2d or unloaded from the polishing heads 2a to 2d on the loading/unloading stage 12. Above the turn tables 4a to 4c, a polishing agent supplying mechanism 8 for supplying a polishing agent 7 on the turn tables 4a to 4c when the wafers W are polished is provided (see FIG. 3B and FIG. 4B).

(27) As illustrated in FIG. 5, the polishing apparatus 1 has a first polishing shaft 9a for attaching and rotating the polishing head 2a for holding the wafer W above the loading/unloading stage 12. In a similar manner, the polishing head 2d and the fourth polishing shaft 9d are provided above the first turn table 4a, the polishing head 2c and the third polishing shaft 9c are provided above the second turn table 4b, and the polishing head 2b and the second polishing shaft 9b are provided above the third turn table 4c.

(28) By respective polishing shafts 9a to 9d rotating at the same time, respective polishing heads 2a to 2d perform rotation movement, and polishing is performed while turn tables 4a to 4c to be used for polishing the wafer W are switched. Positions of the respective polishing heads 2a to 2d and polishing shafts 9a to 9d illustrated in FIG. 5 are initial positions, and, thereafter, the wafer W is polished, loaded and unloaded while the turn tables to be used for polishing are switched by rotation movement being repeated.

(29) Here, to simplify the explanation, two polishing heads are indicated with reference numerals 2a to 2d, and two polishing shafts are indicated with reference numerals 9a to 9d. That is, two polishing heads are assigned to one turn table.

(30) As a method for holding the wafer W with the polishing heads 2a to 2d, it is possible to use a vacuum contact method or a water filling method using a template.

(31) As illustrated in FIG. 2, the turn tables 4a to 4c and the turn table upward and downward movement mechanism 5 are located at a lower part of the polishing apparatus 1. In this manner, by providing the turn tables 4a to 4c and the turn table upward and downward movement mechanism 5 which are heavy goods at the lower part of the apparatus, it is possible to increase stiffness of the apparatus.

(32) The turn table upward and downward movement mechanism 5 can be, for example, configured using a ball screw. The turn table upward and downward movement mechanism 5 can move the turn tables 4a to 4c upward and downward and stop the turn tables 4a to 4c at desired arbitrary height positions. The turn table upward and downward movement mechanism 5 is configured to be able to move the turn tables 4a to 4c upward and downward independently. For example, at the polishing apparatus 1 illustrated in FIG. 1A and FIG. 1B, three independent turn table upward and downward movement mechanisms 5 respectively corresponding to the turn tables 4a to 4c are provided. The stroke widths of the turn tables 4a to 4c can be set at, for example, 100 mm.

(33) Note that, in FIG. 1A, FIG. 1B and FIG. 2, only a turn table, a polishing head and a polishing shaft with a suffix a are illustrated, and components with other suffixes are omitted. In FIG. 3A, FIG. 3B, FIG. 4A, FIG. 4B and FIG. 7, the polishing heads 2a to 2d are indicated with reference numeral 2. Further, in a similar manner, the turn tables 4a to 4c are indicated with reference numeral 4, and the polishing shafts 9a to 9d are indicated with reference numeral 9.

(34) As illustrated in FIG. 1A, positions where the turn tables 4a to 4c move downward to the lowermost position of the upward and downward movement can be set at positions of the turn tables 4a to 4c when the polishing pad 3 is dressed. In this manner, when the turn tables move downward, as illustrated in FIG. 4A and FIG. 4B, it is possible to dress (or brush) the polishing pad 3 at the dressing mechanism 6.

(35) Specifically, after the turn tables move downward to the lowermost position of the upward and downward movement, the dressing mechanism 6 moves from the initial position as illustrated in FIG. 3A to above the polishing pad 3 as illustrated in FIG. 4A and performs dressing.

(36) As illustrated in FIG. 1B, positions where the turn tables 4a to 4c move upward to the uppermost position of the upward and downward movement can be set as positions of the turn tables 4a to 4c when the wafer W is polished.

(37) With such a polishing apparatus, because it is not necessary to move the polishing head upward and downward with a long stroke width, it is possible to shorten the length of the polishing shaft. By this means, stiffness of the polishing shaft is increased, so that it is possible to reduce an amount of displacement of the polishing shaft caused when moment load is applied during polishing. By this means, it is possible to polish the wafer with high accuracy.

(38) As illustrated in FIG. 4A and FIG. 4B, the dressing mechanism 6 is preferably provided at a position where the dressing mechanism 6 does not interfere with a trajectory on which the polishing head 2 performs rotation movement.

(39) With such a configuration, it is possible to perform rotation movement of the polishing head and upward and downward movement of the turn tables in parallel without the polishing head interfering with the dressing mechanism. It is therefore possible to reduce takt time and improve productivity.

(40) At the polishing apparatus 1, a polishing head upward and downward movement mechanism (not illustrated) for moving the polishing heads 2a to 2d upward and downward can be provided. As described above, the polishing apparatus 1 of the present invention does not have to move the polishing heads 2a to 2d with a large stroke width and only has to have a minimum required stroke width for supporting various kinds of polishing heads. 20 mm or less is enough for this stroke width, and if the stroke width is 20 mm, the polishing head can also support polishing heads with different structures, such as a contact method and a water filling method. If the upward and downward movement width is equal to or less than 20 mm, it is possible to reliably suppress degradation of stiffness of the polishing shaft, so that it is possible to more reliably reduce an amount of displacement of the polishing shaft when moment load is applied during polishing.

(41) Further, when a polishing pad 3 with no groove is used, there is a case where the wafer W is adsorbed to the polishing pad 3, and, a phenomenon that the turn tables 4a to 4c are slightly lifted occurs when the polishing heads 2a to 2d are separated from the polishing pad 3. In this case, by respectively moving a plurality of polishing heads 2a to 2d assigned to one turn table upward with a time lag, it is possible to reduce adsorption force of the wafer W and the polishing pad 3 when the polishing heads 2a to 2d move upward. Further, because the polishing head upward and downward movement mechanism allows the polishing head to be easily changed, the polishing head upward and downward movement mechanism is also preferably provided at the polishing apparatus 1 having the turn table upward and downward movement mechanism 5.

(42) While, in the above mention, two polishing heads are assigned to one turn table, it is also possible to employ a configuration where one polishing head is assigned to one turn table. In this case, because it is not possible to perform operation for moving the polishing heads upward with a time lag as described above, while the polishing head upward and downward movement mechanism do not have to be provided, because the polishing head upward and downward movement mechanism allows the polishing head to be easily changed, the polishing head upward and downward movement mechanism is preferably provided.

(43) While the polishing heads 2a to 2d and the turn tables 4a to 4c typically employ a method in which rotation is performed with combination of a motor and a reducer 210 as illustrated in, for example, FIG. 14A and FIG. 14B, the polishing heads 2a to 2d and the turn tables 4a to 4c can be rotated using a direct drive motor. The polishing apparatus 1 illustrated in FIG. 1A and FIG. 1B use a direct drive motor 10, in which case, because ancillary facilities such as a reducer are not required, it is possible to design the turn table upward and downward movement apparatus in smaller space than in the case where a motor and a reducer are used.

(44) The polishing apparatus 1 can preferably perform rotation movement of the polishing heads 2a to 2d and upward and downward movement of the turn tables 4a to 4c and the polishing heads 2a to 2d in parallel.

(45) In this manner, because the both movement can be performed in parallel, it is possible to reduce takt time when the turn tables are switched or dressing is performed, so that it is possible to improve productivity.

(46) Further, the turn table upward and downward movement mechanism 5 preferably adjusts the height of the turn tables 4a to 4c according to abrasion of the polishing pad 3 or abrasion of dressing (or brushing) when dressing of the polishing pad 3 is performed at the dressing mechanism 6. As the polishing cycle increases, an abrasion amount of the polishing pad and dressing (or brushing) increases, relative positional relationship is displaced. In the present invention, because the turn tables 4a to 4c can be stopped at arbitrary height positions with the turn table upward and downward movement mechanism 5, by adjusting the height of the turn tables 4a to 4c as described above, it is possible to obtain a certain dressing effect even without adjusting the height of the dressing mechanism 6. Further, because such adjustment can be automated, it is possible to reduce process time, so that it is possible to improve productivity.

(47) A wafer polishing method using the polishing apparatus 1 of the present invention as described above will be described next.

(48) Here, specific flow of the wafer polishing method will be described based on the flowchart in FIG. 6 while motion of the polishing head 2a attached to the first polishing shaft 9a illustrated in FIG. 5 is mainly described.

(49) First, a wafer located on the loading/unloading stage 12 is loaded on the polishing head 2a and held at the polishing head 2a (SP1).

(50) The polishing head 2a holding the wafer rotates by 90 degrees (SP2) and moves to the first turn table 4a.

(51) Then, the first turn table 4a is moved upward to a position where the wafer contacts the polishing pad, and polishing is performed at the first turn table 4a by a polishing agent being supplied on the polishing pad from the polishing agent supplying mechanism, and a surface of the wafer being brought in sliding contact with the polishing pad while the first turn table 4a and the polishing head 2a being respectively rotated (SP3).

(52) After polishing is finished at the first turn table 4a, the first turn table 4a is moved downward, and the polishing head 2a rotates by 90 degrees (SP4), and moves to the second turn table 4b. Then, the second turn table 4b is moved upward to a position where the wafer contacts the polishing pad, and polishing is started again (SP5).

(53) After polishing is performed at the third turn table 4c while such operation is repeated (SP6 to SP7), the third turn table 4c is moved downward, and the first polishing head 2a is reversely rotated by 270 degrees (SP8), and returns to the loading/unloading stage 12, the wafer is unloaded from the polishing head 2a (SP9), thereby one cycle is finished.

(54) While the wafer is loaded/unloaded at the polishing head 2a of the first polishing shaft 9a, polishing is performed in parallel at each of the first to the third turn tables 4a to 4c at the polishing heads 2b to 2d of the second to the fourth polishing shafts 9b to 9d.

(55) According to such a wafer polishing method, because the polishing apparatus of the present invention which can reduce an amount of displacement of the polishing shaft when moment load is applied during polishing is used, it is possible to polish the wafer to obtain a wafer with favorable flatness. Further, it is possible to reduce takt time, so that it is possible to improve productivity.

(56) Further, after polishing of the wafer is finished, if the polishing pad is dressed after the height of the turn table is adjusted according to abrasion of the polishing pad, it is possible to always obtain a certain dressing effect as that described for the polishing apparatus of the present invention, and it is possible to reduce process time.

(57) Note that a timing at which dressing is performed is not particularly limited, and, for example, dressing may be performed every time polishing of the wafer is finished. However, because increase in a frequency of dressing leads to degradation of productivity, dressing is preferably performed at an appropriate timing according to the polishing pad or the polishing agent to be used.

EXAMPLES

(58) While the present invention will be more specifically described with examples of the present invention and Comparative Examples, the present invention is not limited to these examples.

Example 1

(59) The polishing apparatus of the present invention was prepared and shaft stiffness was evaluated. The prepared polishing apparatus supports polishing of a wafer having a diameter of 300 mm. The polishing head has a polishing head upward and downward movement mechanism for moving the polishing head upward and downward with a stroke width of 20 mm, and the turn table upward and downward movement mechanism has a stroke width of upward and downward movement of 100 mm.

(60) First, influence in the case where moment load is applied on the polishing head and the polishing shaft while the wafer is polished was analyzed through simulation. Note that the simulation was performed using Solidworks simulation.

(61) Concerning influence of the moment load, as illustrated in FIG. 7, an amount of displacement of the polishing head 2 in a parallel direction in the case where load F is applied on the polishing head 2 was obtained.

(62) As conditions of the simulation, it was assumed that load in a lateral direction of approximately 200 kgf was applied on the polishing head 2 upon polishing. As a result, as indicated in Table 1, the amount of displacement of the polishing head 2 in the parallel direction was 8.18 m.

(63) Further, as the shaft stiffness, as illustrated in FIG. 8, an amount of displacement of an end face of the flange portion of the polishing shaft 9 in a direction parallel to the load F in the case where load F was directly applied on the polishing shaft 9 in a direction of an arrow (lateral direction) as illustrated in FIG. 8 was obtained.

(64) As conditions of the simulation, it was assumed that load of approximately 15 kgf in the lateral direction was directly applied on the polishing shaft 9. As a result, the amount of displacement of the polishing shaft 9 was 0.15 m as indicated in Table 1.

(65) Subsequently, as illustrated in FIG. 9, not as the simulation, load of approximately 15 kgf in the lateral direction was actually applied on the flange portion of the polishing shaft 9 using a spring scale 11, and an amount of displacement of the end face of the flange portion was measured. At this time, the amount of displacement of the end face of the flange portion was measured using a laser displacement gauge.

(66) As a result, as indicated in Table 1, while the amount of displacement in the simulation was 0.15 m, the actual measured amount of displacement was 0.33 m.

(67) TABLE-US-00001 TABLE 1 Example 1 Actual Simulation measurement Lateral load 200 15 15 [kgf] Displacement 8.18 0.15 0.33 amount [m]

Comparative Example 1

(68) Simulation and evaluation of shaft stiffness using the spring scale 11 was performed as in Example 1 in a conventional polishing apparatus which does not have a turn table upward and downward movement mechanism of the present invention and whose stroke width of the polishing head upward and downward movement mechanism is 120 mm.

(69) As conditions of the simulation, as in Example 1, it was assumed that load of approximately 200 kgf in the lateral direction was applied on the polishing head during polishing. As a result, the amount of displacement of the polishing head in the parallel direction was 171. 90 m as indicated in Table 2.

(70) Further, the amount of displacement of the polishing shaft in the case where load of approximately 15 kgf in the lateral direction was applied on the polishing shaft was 3.8 m as indicated in Table 2.

(71) Subsequently, an actual measured value of the amount of displacement of the end face of the flange portion of the polishing shaft was measured while load was applied on the polishing shaft using the spring scale 11 as in Example 1. As a result, while the amount of displacement in the simulation was 3.8 m, as indicated in Table 2, the actual measured amount of displacement was 8.1 m.

(72) TABLE-US-00002 TABLE 2 Comparative Example 1 Actual Simulation measurement Lateral load 200 15 15 [kgf] Displacement 171.90 3.8 8.1 amount [m]

(73) From the results, because, in Example 1, it was possible to reduce the stroke width of the polishing head upward and downward movement mechanism from 120 mm to 20 mm and improve stiffness of the polishing shaft by providing the turn table upward and downward movement mechanism, it was possible to considerably reduce the amount of displacement of the polishing shaft due to the moment load compared to Comparative Example 1.

Example 2

(74) In the polishing apparatus of the present invention having the turn table upward and downward movement mechanism and the polishing head upward and downward movement mechanism, time required for the polishing head to move from the lowermost position to the uppermost position of the upward and downward movement was measured. Note that the stroke width of the polishing head upward and downward movement mechanism was set at 20 mm, and the upward and downward movement speed of the polishing head was set at 35 mm/second.

(75) As a result, moving time was 1.1 seconds on average including time required for acceleration and deceleration.

Comparative Example 2

(76) In the conventional polishing apparatus which does not have a turn table upward and downward movement mechanism of the present invention, time required for the polishing head to move from the lowermost position to the uppermost position of the upward and downward movement was measured. Note that the stroke width of the polishing head upward and downward movement mechanism was set at 120 mm, and the upward and downward movement speed of the polishing head was set at 35 mm/second as in Example 2.

(77) As a result, moving time was 3.8 seconds on average including time required for acceleration and deceleration.

(78) From the above results, in Example 2, it was possible to considerably reduce the moving time of the polishing head compared to Comparative Example 2.

Example 3

(79) The polishing pad was dressed using the polishing apparatus having the turn table upward and downward movement mechanism and the dressing mechanism of the present invention, and change of the thickness of the polishing pad through dressing was evaluated. As the polishing pad, a hard urethane foam polishing pad for which the thickness can be easily measured was used. Further, to allow the thickness of the polishing pad to easily change, a diamond dresser having a high removal effect of a polishing pad surface layer was used, a dressing period was extended, and dressing was repeatedly performed.

(80) Then, before each dressing was started, the height of the turn table was adjusted according to abrasion of the polishing pad. Specifically, an amount of displacement of the polishing pad due to dressing was obtained from the thickness of the polishing pad before and after the dressing, and dressing was repeatedly performed while increasing the height of the turn table by an amount corresponding to the amount of displacement. The measurement result at this time is illustrated in FIG. 10. FIG. 10 illustrates change of the thickness through repetition of the dressing when the thickness of the polishing pad before the first dressing is set at 1.0. The thickness of the polishing pad was measured by measuring a cutout portion for thickness measurement provided at an outer peripheral portion of the polishing pad using a laser displacement gauge.

(81) As illustrated in FIG. 10, it was confirmed that a change rate of the thickness of the polishing pad was substantially constant, and a certain dressing effect was maintained regardless of the thickness of the polishing pad.

Comparative Example 3

(82) Change of the thickness of the polishing pad through dressing was evaluated using the conventional polishing apparatus which does not have the turn table upward and downward movement mechanism of the present invention and whose height position of the turn table is fixed, as in Example 3, except that the height of the dressing mechanism was not adjusted. Note that the same polishing pad and dresser were used as those used in Example 3.

(83) As a result, as illustrated in FIG. 10, a change rate of the thickness of the polishing pad degrades as the dressing was repeated. This indicates that the dressing effect degrades.

Example 4

(84) Polishing of a silicon wafer of 300 mm and dressing of the polishing pad were actually performed using the polishing apparatus having the turn table upward and downward movement mechanism and the dressing mechanism of the present invention. The polishing head was made to perform rotation movement at the same time as picking up of the wafer during a polishing cycle.

(85) As a result, compared to the comparison result, it is possible to reduce cycle time by 3 seconds on average.

(86) Further, when the height of the turn table upon dressing was made to be automatically set by the turn table upward and downward movement mechanism according to abrasion of the brush and the polishing pad, it becomes not necessary to stop the polishing apparatus to adjust the height of the dressing mechanism, which leads to improvement in productivity by 5% in Example 4 compared to in Comparative Example 4 as well as reduction in cycle time as described above.

Comparative Example 4

(87) Polishing of a silicon wafer of 300 mm and dressing of the polishing pad were actually performed using the conventional polishing apparatus which does not have a turn table upward and downward movement mechanism of the present invention.

(88) Because the conventional polishing apparatus cannot perform rotation movement at the same time as picking up of the wafer, cycle time was longer by 3 seconds on average than that in Example 3.

(89) Further, because, with the conventional polishing apparatus, it is necessary to stop the polishing apparatus to adjust the height of the dressing mechanism according to abrasion of the brush and the polishing pad, productivity was lower by 5% as well as the cycle time was longer than that in Example 4.

(90) Note that the present invention is not limited to the embodiment. The embodiment is an example, and any embodiment which has substantially the same configuration as technical concept recited in claims of the present invention and which provides similar operational effects is incorporated in the technical scope of the present invention.