Patent Application
20240278381
This application claims the benefit of priority to Japanese Patent Application No. 2021-099930 filed on Jun. 16, 2021, which is expressly incorporated herein by reference in its entirety.
The present invention relates to a polishing head, a polishing device, and a method of manufacturing a semiconductor wafer.
The devices for polishing the surface of a work such as a semiconductor wafer include a one-side polishing device for polishing one side of a work, and a both-side polishing device at the time of polishing both sides of a work. With the one-side polishing device, normally, while pressing the surface to be polished of a work held by a polishing head against a polishing pad bonded to a surface plate, the polishing head and the surface plate are rotated, respectively, thereby bringing the surface to be polished of the work and the polishing pad into sliding contact with each other. By supplying an abrasive to between the surface to be polished and the polishing pad thus coming in sliding contact with each other, it is possible to polish the surface to be polished of the work.
As the method of pressing the work held by the polishing head against the polishing pad in the one-side polishing device as described above, a rubber chuck system is known (see WO 2020/202682 and Japanese Patent No. 4833355, which are expressly incorporated herein by reference in their entirety).
With the polishing head of the rubber chuck system, by introducing a gas such as air into the space at the back surface of a membrane (which is referred to as a rubber film in Japanese Patent No. 4833355), and thereby swelling the membrane, it is possible to press the work.
With the polishing head described in WO 2020/202682, the space is partitioned into two spaces, and the amounts of the gas to be introduced into respective spaces are adjusted, respectively, thereby enabling independent control of the polished surface pressure to be applied to the outer circumferential region of the surface to be polished of the work and the polished surface pressure to be applied to the central part (see paragraph 0009 of WO 2020/202682, and the like). Japanese Patent No. 4833355 also discloses a polishing head with the space partitioned into two spaces (see FIG. 1 of Japanese Patent No. 4833355, and the like). Below, the polishing head with the space at the back surface of the membrane partitioned into two spaces will be referred to as a two-zone membrane head. The present inventors studied the two-zone membrane head described in WO 2020/202682, and the two-zone membrane head described in Japanese Patent No. 4833355, and proved that it is difficult to combine the control of the polishing amount of the outer circumferential region of the surface to be polished of the work, and the suppression of local fluctuations in polishing amount at the surface to be polished.
One aspect of the present invention provides for a two-zone membrane head capable of combining the control of the polishing amount of the outer circumferential region of the surface to be polished of the work, and the suppression of local fluctuations in polishing amount at the surface to be polished.
One aspect of the present invention relates to:
With the polishing head (two-zone membrane head) in accordance with one aspect of the present invention, it is possible to combine control of the polishing amount of the outer circumferential region of the surface to be polished of the work, and the suppression of local fluctuations in polishing amount at the surface to be polished. The presumption by the present inventors regarding this point is as follows.
When a work is polished using the polishing head shown in WO 2020/202682, the outer circumferential region of the surface to be polished of the work is situated vertically under the connection part between the partition for partitioning the space at the back surface of the membrane and the membrane (see, for example, FIG. 1 of WO 2020/202682). The pressure to be applied vertically downward from the two spaces divided with the partition can be controlled by the amount of a gas to be introduced into each region. However, it is not easy to control the pressure to be applied vertically downward of the partition, which is normally smaller than the pressures to be applied vertically downward from the two spaces, respectively. This can be considered to be the reason why the local fluctuations in polishing amount (specifically, the local reduction of the polishing amount vertically under the connection part) tends to be caused with the work polished using the polishing head shown in WO 2020/202682.
In contrast, with the polishing head in accordance with one aspect of the present invention, the inside diameter of the bottom annular connection part, which is the connection part of the annular partition wall for dividing the two spaces with the membrane, is larger than the inside diameter of the second annular member. Therefore, when polishing is performed using the polishing head, vertically under the bottom annular connection part, the second annular member is situated, and the outer circumferential region of the surface to be polished of the work is not situated. The present inventors consider this point as the reason why the surface to be polished of the work can be polished while suppressing the local reduction of the polishing amount vertically under the connection part by using the polishing head.
Further, with the polishing head in accordance with one aspect of the present invention, for the connection part of the annular partition wall, the outer circumferential region of the setting position of the work to be polished is situated vertically under the top annular connection part, and the inside diameter of the bottom annular connection part is larger than the inside diameter of the second annular member. For these reasons, the second annular member is situated vertically under the bottom annular connection part. In contrast, with the polishing head shown in FIG. 1 of Japanese Patent No. 4833355, the inside diameter of the connection part of the partition with the membrane is smaller than the inside diameter of the second annular member. As compared with the polishing head with such a configuration, with the polishing head in accordance with one aspect of the present invention, it is possible to more effectively control the pressure to be applied downward from the outside space by adjusting the amount of the gas to be introduced into the outside space divided by the annular partition wall. As a result, it becomes possible to easily control the polishing amount of the outer circumferential region of the surface to be polished of the work by adjusting the amount of the gas to be introduced into the outside space. This is presumed by the present inventors. Although the presumption by the present inventors is described in the present specification, the present invention is not limited to such presumption.
In one embodiment, the annular partition wall can include a side surface shape selected from the group consisting of an inclined shape and a horizontal shape in the cross-sectional shape. Vertically under at least a part of the side surface shape, the inside circumferential end of the second annular member and the outside circumferential end of the setting position of the work to be polished can be situated.
In one embodiment, the closing member can include a top disk-shaped member and a bottom disk-shaped member with a smaller outside diameter than that of the top disk-shaped member. The annular partition wall can be configured such that the top annular connection part is connected to the side surface of the bottom disk-shaped member.
In one embodiment, the polishing head can further have a back pad between the membrane and the second annular member.
In one embodiment, the polishing head can have an introduction path which introduces a gas into the inside space, and an introduction path which introduces a gas into the outside space.
One aspect of the present invention relates to:
Another aspect of the present invention relates to a method of manufacturing a semiconductor wafer, including: polishing the surface of a semiconductor wafer to be polished with the above polishing device to form a polished surface.
In accordance with one aspect of the present invention, it becomes possible to provide a two-zone membrane head capable of combining control of the polishing amount of the outer circumferential region of the surface to be polished of the work and suppression of local fluctuations in polishing amount at the surface to be polished.
A polishing head in accordance with one aspect of the present invention has a first annular member, a closing member which closes the upper surface side opening of the opening of the first annular member, a membrane which closes the lower surface side opening of the opening of the first annular member, and a second annular member situated under the membrane and having an opening which holds a work to be polished. In the polishing head, with the direction toward the center of the opening of the first annular member assumed as the inside, and with the other direction assumed as the outside, the space, which is formed by closing the opening of the first annular member with the closing member and the membrane, is partitioned into an inside space and an outside space with an annular partition wall having a top annular connection part connected to the closing member and a bottom annular connection part connected to the membrane, the inside diameter of the bottom annular connection part of the annular partition wall is larger than the inside diameter of the second annular member, and the outer circumferential region of the setting position of the work to be polished is situated vertically under the top annular connection part of the annular partition wall.
Below, the polishing head will be further described in details. In the present invention and in the present specification, the expressions of “lower surface”, “under”, “upper surface”, “top”, “bottom”, and the like mean “lower surface”, “under”, “upper surface”, “top”, “bottom”, and the like when the polishing head is placed in a state in which a polishing process is performed. In the present invention and in the present specification, for the expressions “inclined” and “horizontal”, the case where the polishing head is inclined with respect to the horizontal direction when the polishing head is placed in a state in which a polishing process is performed is referred to as “inclined”, and the case where the polishing head is in parallel with such a horizontal direction is referred to as “horizontal”. Further, the direction toward the center of the opening of the first annular member is referred to as inside, and the other direction is referred to as outside. The term “annular” means the shape having an opening, and the shape of the opening in a plan view can be a circular shape. Below, the present invention will be described by way of the accompanying drawings. However, the embodiments shown in the drawings are illustrative, and the present invention is not limited to such embodiments. Further, the same portions are given the same reference numerals and signs in the drawings.
In each drawing of
The lower surface of the first annular member 11 is covered with a membrane 13. The membrane 13 may close at least the lower surface side opening of the first annular member 11. From the viewpoint of suppressing the occurrence of misalignment when the membrane 13 is swollen, and the viewpoint of suppressing mixing of an abrasive into the opening of the first annular member 11, the entire annular lower surface of the first annular member 11 is also preferably covered with the membrane 13. The membrane 13 can be bonded with the annular lower surface of the first annular member 11 by a known method such as use of an adhesive. Further, as shown in each drawing of
In each drawing of
In each of
In each drawing of
In each drawing of
As for the annular partition wall, the cross-sectional shape of the annular partition wall preferably at least partially includes the side surface shape selected from the group consisting of an inclined shape and a horizontal shape, and vertically under at least a part of such a side surface shape, a region including the inside circumferential end of the second annular member and the outside circumferential end of the setting position of the work to be polished is more preferably situated. Having such a configuration can lead to the following: upon introducing a gas into the outside space at the time of polishing, at least a part of the inner wall surface of the annular partition wall comes in contact with the upper surface of the membrane. This can contribute to facilitating the following: by changing the amount of the gas to be introduced into the outside space, the polishing amount in the plane (especially, the outer circumferential region) of the work to be polished is controlled. At the time of polishing, normally, a gas is introduced into both of the outside space and the inside space. A polishing head can have a configuration such that when a gas is introduced into the outside space at the time of polishing, at least a part of the inner wall surface of the annular partition wall comes in contact with the upper surface of the membrane. This can be confirmed by, for example, the following: when a gas is introduced into only the outside space without introducing a gas into the inside space, the upper surface of the membrane and at least a part of the inner wall surface of the partition wall come in contact with each other.
As the specific examples of the cross-sectional shape, in the example shown in
One aspect of the present invention relates to a polishing device having the above polishing head, a polishing pad, and a surface plate which supports the polishing pad.
Further, another aspect of the present invention relates to a method of manufacturing a semiconductor wafer, including polishing the surface of a semiconductor wafer to be polished by the above polishing device to form a polished surface.
Below, the present invention will be described by way of Examples. However, the present invention is not limited to the embodiments shown in Examples. The polishing pressure Pe described below is the pressure to be applied from the outer circumferential region of the membrane 13 downward due to swelling of the outer circumferential region of the membrane 13 caused by introduction of a gas into the outside space 16b through the gas introduction path 17b. The polishing pressure Pc is the pressure to be applied from the central part of the membrane 13 downward due to swelling of the central part of the membrane 13 caused by introduction of a gas into the inside space 16a through the gas introduction path 17a. The polishing pressures Pe and Pc are experimental values.
The polishing head (the two-zone membrane head of the rubber chuck system) of Example 1 is the polishing head with the configuration shown in
The polishing head of Example 2 is the polishing head with the same configuration as that of the polishing head of Example 1, except that d3 is set as the value shown in Table 1.
With each polishing head of Example 1 and Example 2, the inside diameter d1 of the bottom annular connection part Clower of the annular partition wall 15A is larger than the inside diameter d2 of the second annular member, and the outer circumferential region of the setting position W of the work to be polished is situated vertically under the top annular connection part Cupper of the annular partition wall 15A. For the polishing heads of Example 1 and Example 2, it has been confirmed as follows: when a gas is introduced into only the outside space without introducing a gas into the inside space, at least a part of the inner wall surface of the partition wall (particularly, a part of or the whole of the inner wall surface of the portion in a bottom horizontal shape in a cross-sectional shape) comes in contact with the upper surface of the membrane.
Each polishing head of Comparative Example 1 and Comparative Example 2 is a polishing head with the same configuration as that of the polishing head of Example 1, except that d1 and d3 are set as the values shown in Table 1.
With the polishing head of Comparative Example 1, the inside diameter d1 of the bottom annular connection part Clower of the annular partition wall 15A is smaller than the inside diameter d2 of the second annular member (d1<d2). Therefore, at the time of polishing, the second annular member 12 is situated vertically under the bottom annular connection part Clower of the annular partition wall 15A.
With the polishing head of Comparative Example 2, although the inside diameter d1 of the bottom annular connection part Clower of the annular partition wall 15A is roughly equal to the inside diameter d2 of the second annular member, the relationship of “d1<d2” is satisfied. Therefore, at the time of polishing, the second annular member 12 is situated vertically under the bottom annular connection part Clower of the annular partition wall 15A.
In the following polishing process, a plurality of silicon wafers cut out under the same cutting conditions from the same single crystal silicon ingot, and subjected to various processings under the same conditions were subjected to a one-side polishing process as the finish polishing step of the final step.
As the polishing device of Example 1, a polishing device with the configuration shown in
A polishing device of Example 2 was the same as the polishing device of Example 1, except that the polishing head was set as the polishing head of Example. With the polishing device, three silicon wafers were respectively subjected to a one-side polishing process by the method described for Example 1.
Also for Comparative Example 1 and Comparative Example 2, similarly, using the polishing head of each Comparative Example as the polishing head, three silicon wafers were respectively subjected to a one-side polishing process by the method described for Example 1.
As for each silicon wafer subjected to a polishing process in Example 1, Example 2, Comparative Example 1, and Comparative Example 2, using a geometric measurement system WaferSight manufactured by KLA-Tencor Co., as a measuring device,
As for each silicon wafer subjected to a polishing process, the difference in polishing amount was calculated as “difference in polishing amount=wafer center thickness−wafer outer circumference thickness”.
As for each silicon wafer subjected to a polishing process in Example 1, Example 2, Comparative Example 1, and Comparative Example 2, using a geometric measurement system WaferSight manufactured by KLA-Tencor Co., as a measuring device, ESFOR of the index for the outer circumferential region flatness of the wafer was determined. The ESFOR is the abbreviation of Edge site flatness front reference least square range (abbreviation obtained by connecting the underlined letters). The ESFOR is determined as the value obtained in the following manner: with the measuring device, a site is set in the outer circumferential region of the wafer surface subjected to a polishing process; the site is radially divided into a plurality of sectors; and the minimum displacement is added to the maximum displacement from the best fit surface at the site. The dividing conditions for the sector were set as 72 sectors, a Length of 15 mm, and a Width of 5°.
From the results described above, it can be confirmed as follows. In the polishing process with the polishing devices of Example 1 and Example 2, it is possible to control the polishing amount of the outer circumferential region of the surface to be polished of the work by changing the polishing pressure Pe, and it is also possible to suppress fluctuations in local polishing amount at the surface to be polished.
One aspect of the present invention is useful in the technical field of a semiconductor wafer such as a silicon wafer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-099930 | Jun 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/018384 | 4/21/2022 | WO |
