Patent Application
20070267145
Hereinafter, one embodiment of the present invention will be described with reference to
The overall construction of a vacuum processing apparatus used in a plasma processing apparatus will be described in
The following describes a concrete structure of the vacuum processing, chamber 106 with reference to
A processing gas is supplied from a gas supplying unit such as a storage tank (not shown) via a path such as a piping with a predetermined flow rate and mixture ratio to the processing chamber 200 through a through hole 262 for gas introduction provided in a shower plate 260 disposed in opposed relation above a wafer mounting surface, and pressure within the processing chamber 200 is controlled by a vacuum evacuation valve 204 including plural rotatable flaps varying an opening area of communication, and the evacuation pump 203.
Via a high frequency power source 221 and a match box 222 mounted outside the vacuum vessel 210, a high-frequency power is applied to the antenna 201 and introduced to the processing chamber 220 using the plasma. At the same time, plasma is generated by interaction between a magnetic field generated by a magnetic field generating unit 202 and the high-frequency power, and the wafer 220 is etched. The through hole 262 is disposed in a region substantially equal in area to or larger than the sample mounting surface on which the wafer 220 is mounted.
The sample table 250 includes a dielectric film 255 forming a sample mounting surface on which the wafer 220 is mounted, and a DC voltage is applied to the dielectric film 255 via a DC power supply 206 and a filter circuit 256 disposed outside the processing chamber 200, and the wafer 220 is absorbed to the sample mounting surface and held by static electricity. Furthermore, He gas is supplied to the back surface of the wafer 220 via a gas introduction adjustment valve 214 for adjusting a gas supply amount from a He gas source 213 disposed outside the processing chamber 200 to cool the wafer 220.
RF bias is applied to a metallic block 251 constituting the sample table 250 via a matching box 208 from an RF bias supply 207 disposed outside the processing chamber 200, and ion in plasma is induced onto the wafer 220 to assist etching reaction. The metallic block 251 constituting the sample table 250 is provided with a flow path 254, and a coolant is introduced to the flow path 254 by the temperature adjusting unit 209 disposed outside processing chamber 200 to control the temperature.
Specifically, although the wafer 220 receives incoming heat from plasma during processing and incoming heat by RF bias, the heat of the He gas, the dielectric film 255, and the metallic block 251 is transferred and is cooled. To electrically insulate the metallic block 251 against plasma, and to protect it from being exhausted due to sputter and etching by the plasma, a ceramic cover 253 is installed.
The following describes a detailed structure of the sample table 250 with reference to
The flow path 254 through which a coolant flows is disposed in the upper metallic block 251a. He introduction paths 310 and 311 for introducing He to a wafer back surface are provided in the center and outer circumference of the metallic block 251. In this example, He introduction portions are referred to as the center and the outer circumference, but He may be introduced from other portions. The metallic block 251 has a pusher 257 for vertically conveying the wafer 220 in a middle portion, and includes an introduction terminal 308 for applying voltage to a metallic film incorporated in the dielectric film 255 to electrostatically chuck the wafer, and an introduction terminal 309 for applying a bias to a metallic block 305.
The metallic block 305 is electrically conducted to the metallic blocks 251a and 251b by a bolt 304. Instead of applying a bias to the metallic block 305, a bias may be directly applied to the metallic blocks 251a and 251b. In this embodiment, the case where the dielectric film 255 contains a metallic film, that is, a dipole electrostatic chucking apparatus is shown. However, the metallic block 251a or 251b without a metallic film, or a monopole electrostatic chucking apparatus that applies voltage to the metallic block 305 may be used. 306 designates an insulation plate and 307 designates a base.
Details of the inside of the sample table 250 are shown in
The heat insulating layer 401 is a ring-shaped space comprised by connection between grooves respectively disposed in the blocks 251a and 251b. Preferably, the space should be in a evacuated atmosphere to increase heat insulation effect. In this example, the metallic block 251b is provided with a hole 407 to establish a route for enabling evacuation by the evacuation pump 203. Specifically, a minor gap exists between the lower surface of the metallic block 251b and the upper surface of the insulating plate 306, and between the lower surface of the metallic block 305 and the upper surface of the insulating plate 306, and the gap communicates with the heat insulating layer 401 via the hole 407.
At the same time, the gap communicates with the space of the processing chamber 200 via gaps on the inner side of the ceramic cover 253 and on the upper surface of the insulation plate 306, and on the upper surface and side of the base 307. In other words, a sealing unit does not exist for the gaps. Therefore, as the processing chamber 200 is evacuated by the evacuation pump 203 and decompressed, the heat insulating layer 401 turns into a evacuated atmosphere via the minor gaps and the hole 407. The above-described minor gap blocks heat transfer among blocks constituting the gaps, and absorbs thermal deformation of the metallic block.
The height of the heat insulating layer 401 is almost equal to or higher than the height of the coolant grooves 254a and 254b. To further increase the heat insulation effect of the heat insulating layer 401, it is effective to enlarge the heat insulating layer 401. In this example, the height of the heat insulating layer 401 is about twice the size of the coolant grooves 254a and 254b.
The metallic block 251b below the heat insulating layer 401 is constructed to be thin and large in thermal resistance in diameter direction. To seal the insulating layer 401, O rings 404 and 405 are disposed between the metallic blocks 251a and 252b in the vicinity of the heat insulating layer 401. To seal coolant flowing through the coolant groove 254b, an O ring 402 is disposed between the metallic blocks 251a and 251b outside the coolant groove 254b, and an O ring is also disposed between the metallic block 251b and the metallic block 305. Furthermore, to seal the fastening locations of bolts 302, O rings 406 are respectively disposed in positions across from the bolt 302, and between the metallic blocks 251a and 251b. The O ring 404 composes a sealed shaft structure but may have a flat seal structure.
A ring-shaped groove is disposed in a position corresponding to the He introduction path 311 in the upper portion of the metallic block 305, and He is introduced therein from below. The He is guided to an He introduction path 311.
In the sample table 250 having such a structure, the lowest portion of strength in the metallic blocks 254a and 254b is naturally the heat insulating layer 401, and the bolts 301 & 302 are disposed across the heat insulating layer 401 each other.
The bolts 301 are disposed in 16 locations in the circumferential direction and the bolts 302 are disposed in nine locations in the circumferential direction. However, any number of bolts for obtaining a required strength determined by a bolt size and a bolt material may be used. Furthermore, in this drawing, the bolts 303 are disposed in four locations in the central portion so that the metallic blocks 254a and 254b do not deflect in the central portion and the parallelism of the wafer mounting surface is not impaired.
A means increasing heat efficiency includes changing the metallic block 251b to a member having a heat conduction suppression effect such as ceramic instead of metal.
The range of arranging positions are set for reasons described with reference to
As shown in this drawing, the percentage positions of the arranging positions of the pusher pins for the wafer radius value are the minimum at about 62%. The inventors appreciated that equivalent stress generated in the wafer during pushup exerts no serious influence on the wafer by disposing the pusher pins within a range of ±15% at around 62%.
As shown in this drawing, a deflection amount of the sample table (deformation amount in vertical direction of upper member) is smaller than values in both sides in a predetermined range of the percentage of bolt fastening positions, and particularly becomes minimum in a percentage position at about 65%. The inventors appreciated that a deflection amount of the sample table occurring when upper and lower members are fastened by the bolts exerts no serious influence on the results of processing the wafer surface by disposing bolts within a range of about ±15% at around 65%.
The positions of vacuum heat insulating slits disposed within the sample table are usually disposed within a range of 70% to 85% of the cylindrical sample table in the radial direction. In this embodiment, gas is introduced from a gas introduction hole serving as a through hole disposed in a shower plate disposed above the sample to below the sample, and plasma is generated within space inside the processing chamber above the sample table to process the sample, and discharged through a space between the outer side of the sample table and the inner wall within the processing chamber. In this construction, when the distribution of reaction products adhered to the sample surface in an upper portion of the sample is taken into account, the positions of vacuum heat insulating slits are within the above-described range.
In the above-described embodiment, a processing shape of the sample surface is influenced by the distribution of the amount and density of adhesive substances such as reaction products adhered to the sample surface, and the adhesion of deposits such as the reaction product primarily depends on temperatures. Therefore, by properly adjusting the temperature of the sample, a processing shape of the sample surface is accurately adjusted. Based on the knowledge that the distribution of the reaction product within space above the sample surface is large in the center of the sample and becomes rapidly small in the outer circumference, the inventors, to make a temperature distribution within the sample table larger in the center of the sample and smaller in the outer circumference, disposes a concentric or spiral passage through which the heat exchange medium having high temperature flows in the center within the sample table, and a concentric or spiral passage through which heat exchange medium having cool temperature flows in the outer circumference, and disposes vacuum heat insulating slits between the passages for suppressing heat transfer. The inventors know that, in the construction of the above-described embodiment, the distribution of deposits on the wafer becomes smaller rapidly at the range of 70-85% and more in the radial direction of the sample table, and disposes the vacuum heat insulating slits within the range.
In summary, in the sample table in which a heat insulating layer evacuated is manufactured by a fastening, that is, a non-bonding method, when the vacuum heat insulating slits are disposed in the center of the sample table (e.g., position of 70%), a proper bolt disposition range with a deflection of the surface of the sample table taken into account is a range of a central portion in a vertical direction of
Furthermore, a proper range to dispose the pusher pins is a range of 47 to 68% in a sample radial direction, and the range is shown in an upper portion of
In this embodiment, in these ranges, the pusher pins and the bolts are disposed on a circle circumference of a same radius within the range of 47 to 68% in which a proper range of bolt disposition and a proper range of pusher pin disposition agree with each other.
In view of these points, as shown in
Specifically, in this embodiment, the pusher pins and the bolts are disposed in positions of percentage positions 47 to 68% to the wafer radius from the center axis of the sample table to the outer circumference, and a passage for a heat exchange medium is disposed in the center of the sample table across the region. The heat exchange medium in the center is not disposed to extend to the outer circumference of the sample table to surround or bypass the pusher pins or bolts. In other words, the heat exchange medium is disposed concentrically or spirally even in positions at the center of the sample table in the vicinity of the pusher pins or bolts.
The vacuum heat insulating slits are disposed from the radial direction to the outer circumference of the sample table in which the pusher pins and bolts are concentrically disposed, and a passage for heat exchange medium is disposed in the outer circumference of the sample table. The pusher pins and the bolts are disposed with a predetermined diameter, and with a margin in addition to this diameter, passages for heat exchange medium are disposed in the center and the outer circumference of the sample table. The passage for heat exchange medium at the outer circumference, like the passage at the center, is disposed concentrically or spirally without bypassing or surrounding the pusher pins or the bolts.
Thus, on the inside of the sample table, passages for heat exchange medium are disposed in the center and the outer circumference sandwiching a region in which the pusher pins and the bolts are disposed on a circle circumference of a same radius. In the region in which the pusher pins and the bolts are disposed, if space permits, or according to specifications, mechanical and electrical structures vertically disposed such as lines and connectors for energizing electrodes in an upper portion of the sample table, a socket, and a passage for gases supplied to the sample table surface can be disposed. Thus, in the above-described embodiment, the inside of the sample table includes plural concentric doughnut-shaped (or ring-shaped) regions comprising a region in which a central passage for a heat exchange medium is disposed, a region which vertically extending structures are disposed outside the region, and a region in which vacuum heat insulating slits and a passage for heat exchange medium in the outer circumference disposed outside the region are disposed.
By such the construction, efficiently disposed within the sample table, the sample table can be made small in size. Moreover, since the passage for heat exchange medium is disposed meanderingly in the radial direction from the concentric or spiral shapes because of the disposition of the vertical structures, a local bias in a temperature distribution within the sample table, an uneven temperature distribution in the circumferential direction at the center of the sample table, and an uneven processing shape are suppressed.
According to this embodiment, since the sample table has a heat insulating layer of a evacuated atmosphere manufactured by fastening, when the sprayed film has come to an end of its life and must be replaced by a new one, only the metallic block provided with the sprayed film has to be replaced, and running costs are reduced. Furthermore, since the upper and lower metallic blocks can be removed from the processing chamber in a fastened state, and the two metallic blocks can be integrally removed from the processing chamber, the replacement operation is easy.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-140079 | May 2006 | JP | national |
