News Column

Patent Application Titled "Mounting Table Structure and Method of Holding Focus Ring" Published Online

June 17, 2014



By a News Reporter-Staff News Editor at China Weekly News -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventor Uchida, Yohei (Kurokawa-gun, JP), filed on November 26, 2013, was made available online on June 5, 2014.

The assignee for this patent application is Tokyo Electron Limited.

Reporters obtained the following quote from the background information supplied by the inventors: "In a manufacturing process of a semiconductor device, a processing target object, i.e., a wafer is attracted to and held on an electrostatic chuck of a mounting table, and a plasma process such as etching process or film forming process is performed on the wafer. In general, the mounting table includes the electrostatic chuck; and a base member configured to support the electrostatic chuck. The base member is provided with a temperature control unit configured to control the temperature of the wafer. In order to perform the plasma process uniformly on an entire region of the wafer, a focus ring is provided on the base member to surround the wafer.

"To perform the process uniformly on the entire region of the wafer, a temperature of the focus ring needs to be controlled with high precision. In order to control the temperature of the focus ring precisely, heat resistance between the base member of the mounting table and the focus ring needs to be reduced. For the purpose, conventionally, there has been employed a mounting table structure in which a sheet having elasticity and thermal conductivity is provided between the base member and the focus ring. An Example of such a mounting table structure is described in Japanese Patent Laid-open Publication No. 2002-016126 (Patent Document 1).

"The mounting table structure in the Patent Document 1 includes a base member (mounting table), a ring-shaped member and a pressing member. The base member has a mounting surface, a ring-shaped mounting surface and a protruding part. An electrostatic chuck is provided on the mounting surface. The ring-shaped mounting surface is provided outside the mounting surface, and a focus ring is disposed on the ring-shaped mounting surface with a sheet having elasticity and thermal conductivity therebetween. The protruding part is provided outside the ring-shaped mounting surface. The ring-shaped member is fastened to the protruding part by a screw. The pressing member is fastened to the ring-shaped member by a screw with a bottom surface of the pressing member in contact with the ring-shaped member. Further, a flange of the pressing member comes into contact with a thin portion of the focus ring from above to press the focus ring against the ring-shaped mounting surface. In this mounting table structure, as the focus ring is pressed downward by the pressing member, a thickness of the sheet is reduced and the sheet is brought into firm contact with the focus ring and the base member. As a result, thermal resistance between the base member and the focus ring may be reduced.

"Patent Document 1: Japanese Patent Laid-open Publication No. 2002-016126

"In the mounting table structure described in Patent Document 1, a thickness decrement of the sheet is determined depending on various factors such as the thickness of the sheet, a thickness of the ring-shaped member, a thickness of the thin portion of the focus ring, a distance between the bottom surface of the pressing member and the flange in a height direction, and so forth. Therefore, it may be difficult to adjust the thickness decrement of the sheet. Further, the thickness decrement of the sheet may be varied depending on variations of the aforementioned sizes resulted from manufacturing errors. If the thickness decrement of the sheet is small, the thermal resistance between the base member and the focus ring would be increased, so that the temperature of the focus ring to which heat is transferred from plasma would also be increased. Meanwhile, if the thickness decrement of the sheet is large, a great force would be applied on the components pressing the sheet, i.e., the focus ring and the pressing member, so that these components may be damaged.

"In order to adjust the thickness decrement of the sheet in the mounting table structure described in Patent Document 1, a distance between the ring-shaped member and the pressing member needs to be adjusted. For example, the pressing member needs to be fastened to the ring-shaped member by a screw while spaced apart from the ring-shaped member. In this configuration, the pressing member may be fastened to the ring-shaped member by controlling the torque of the screw precisely. Since, however, the torque of the screw changes with the lapse of time, the thickness decrement of the sheet may not be maintained constant."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventor's summary information for this patent application: "In view of the foregoing, example embodiments provide a technique capable of adjusting a thickness decrement of a sheet serving as a heat transfer medium, and capable of maintaining a set thickness decrement of the sheet.

"In one example embodiment, a mounting table structure includes an electrostatic chuck at a central region thereof and a base member that mounts thereon a focus ring along a periphery of the electrostatic chuck. The mounting table structure includes a sheet, having elasticity and thermal conductivity, provided between the focus ring and the base member; a pressing member provided along a periphery of the focus ring, and configured to press the focus ring toward the base member to contract the sheet; and a supporting member connected to the base member. Further, the pressing member includes a pressing surface that presses the focus ring toward the base member and a multiple number of contact surfaces that face downward and are arranged at a preset interval in a circumferential direction thereof. The supporting member includes first contact surfaces and second contact surfaces. The first contact surfaces are arranged at the preset interval in the circumferential direction, and the second contact surfaces are arranged at the preset interval in the circumferential direction such that the second contact surfaces and the first contact surfaces are alternately arranged. Furthermore, the first contact surfaces are located at a position different from that of the second contact surfaces in a height direction, and the contact surfaces of the pressing member are protruded from portions of the pressing member at a distance larger than distances of the first contact surfaces and the second contact surfaces in the height direction. Moreover, a thickness decrement of the sheet is set by contacting the pressing member with the supporting member.

"In this mounting table structure, by selecting a position of the pressing member on the supporting member connected to the base member in the circumferential direction, the contact surfaces of the supporting member that would make contact with multiple contact surfaces of the pressing member can be selected from the first contact surfaces and the second contact surfaces. Accordingly, a position of the pressing surface in the height direction can be determined, and a distance between the pressing surface of the pressing member and the base member in the height direction can be adjusted. As a result, a thickness decrement of the sheet provided between the base member and the pressing surface can be adjusted. By way of example, when the thickness decrement of the sheet is large, the contact surfaces of the pressing member would be brought into contact with the contact surfaces of the supporting member located at a higher position. Meanwhile, if the thickness decrement of the sheet is small, the contact surfaces of the pressing member would be brought into contact with the contact surfaces of the supporting member located at a lower position. In this way, the thickness decrement of the sheet can be adjusted. Further, since the pressing member is fastened to the supporting member while the pressing member is in contact with the supporting member, it may be possible to firmly fasten the pressing member to the supporting member without being affected by loosening of screws, or the like. As a consequence, a set thickness decrement of the sheet can be maintained.

"In the example embodiment, the supporting member may further include third contact surfaces. The third contact surfaces may be arranged at the preset interval in the circumferential direction and are located at a position different from those of the first contact surfaces and the second contact surfaces in the height direction, and the contact surfaces of the pressing member may be protruded from the portions of the pressing member at a distance larger than distances of the first contact surfaces, the second contact surfaces and the third contact surfaces in the height direction. In this configuration, by way of example, among the first contact surfaces, the second contact surfaces and the third contact surfaces, the position of the contact surfaces located at a midway position in the height direction may be set to correspond to a design value of the thickness decrement of the sheet, and a distance between the contact surfaces of the supporting member can be set to correspond to an adjustment range of the thickness decrement of the sheet. With this configuration, if an actual thickness decrement of the sheet is larger than the design value, the contact surfaces of the pressing member may be brought into contact with the contact surfaces of the supporting member located at a higher position. Meanwhile, if an actual thickness decrement of the sheet is smaller than the design value, the contact surfaces of the pressing member may be brought into contact with the contact surfaces of the supporting member located at a lower position. As a result, the thickness decrement of the sheet can be made to be approximate to the design value.

"In the example embodiment, the supporting member and the base member may serve as a single body. In this configuration, the number of constituent components of the mounting table structure can be reduced, and a manufacturing cost can be cut.

"In another example embodiment, a method of holding a focus ring in a mounting table structure includes an electrostatic chuck at a central region thereof and a base member that mounts thereon a focus ring. The method includes mounting the focus ring along a periphery of the electrostatic chuck such that a sheet having elasticity and thermal conductivity is provided between the base member and the focus ring; adjusting a distance between a pressing surface of a pressing member contacted to the focus ring and the base member in a height direction by determining a position in the height direction where the pressing member comes into contact with a supporting member connected to the base member by selecting a position of the pressing member on the supporting member in a circumferential direction; and fastening the pressing member to the supporting member while the pressing member is in contact with the supporting member at the determined position in the height direction.

"In this method, by selecting a position of the pressing member on the supporting member connected to the base member in a circumferential direction, a distance between the pressing surface of the pressing member and the base member in the height direction can be adjusted. As a result, a thickness decrement of the sheet provided between the base member and the pressing surface of the pressing member can be adjusted. Further, since the pressing member is fastened to the supporting member while the pressing member is in contact with the supporting member, it may be possible to firmly fasten the pressing member to the supporting member without being affected by loosening of screws, or the like. As a consequence, a set thickness decrement of the sheet can be maintained

"In the adjusting of the distance between the pressing surface of the pressing member and the base member in the height direction, the position in the height direction where the pressing member comes into contact with the supporting member is determined such that a decrement of a thickness of the sheet falls within a range from about 10% to about 20% of the thickness of the sheet. In this configuration, if there is a manufacturing error in the size of the sheet or the like, a temperature variation of the focus ring during a plasma process can be reduced.

"In accordance with the various aspects and example embodiments, the thickness decrements of the sheet as the heat transfer medium can be adjusted, and a set thickness decrement of the sheet can be maintained.

"The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

"In the detailed description that follows, embodiments are described as illustrations only since various changes and modifications will become apparent to those skilled in the art from the following detailed description. The use of the same reference numbers in different figures indicates similar or identical items.

"FIG. 1 is a cross sectional view schematically illustrating an example plasma processing apparatus;

"FIG. 2 illustrates a mounting table structure when viewed from above;

"FIG. 3 is a cross sectional view taken along a line III-III of FIG. 2;

"FIG. 4 is a plane view illustrating a base member including a supporting member;

"FIG. 5 is a plane view of a pressing member;

"FIG. 6 is a cross sectional view taken along a line VI-VI of FIG. 2;

"FIG. 7A and FIG. 7B are conceptual diagrams for describing a method of adjusting a thickness decrement of a sheet;

"FIG. 8A and FIG. 8B are conceptual diagrams for describing the method of adjusting a thickness decrement of a sheet;

"FIG. 9 is a chart showing a relationship between a thickness decrement of a sheet and a temperature of a focus ring;

"FIG. 10 is a flowchart for describing a method of holding a focus ring in accordance with an example embodiment;

"FIG. 11 is a cross sectional view illustrating a mounting table structure in accordance with another example embodiment; and

"FIG. 12 is a plane view illustrating a supporting member of the mounting table structure in accordance with the another example embodiment."

For more information, see this patent application: Uchida, Yohei. Mounting Table Structure and Method of Holding Focus Ring. Filed November 26, 2013 and posted June 5, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=3719&p=75&f=G&l=50&d=PG01&S1=20140529.PD.&OS=PD/20140529&RS=PD/20140529

Keywords for this news article include: Asia, Japan, Tokyo Electron Limited.

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Source: China Weekly News


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