JP2010129845A - Electrostatic chuck and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic chuck having a structure in which plasma erosion against a silicone adhesive can be almost completely prevented and which allows smooth plasma treatment with no trouble to a work such as a wafer, and a method for manufacturing the same. <P>SOLUTION: The electrostatic chuck 1 comprises a base 2, a ceramic plate 3, and an adhesive part 4. The adhesive part 4 is constituted of a silicone adhesive 41, an epoxy adhesive 42 and a polyimide film 43. Specifically, the silicone adhesive 41 is applied on a surface 20a of a pedestal 20, and the epoxy adhesive 42 and the polyimide film 43 are installed in a broad gap 40 constituted by a step part 20b of the pedestal 20 and the peripheral lower surface of the ceramic plate 3. Thereby, the adhesive part 4 has a structure in which the outer peripheral surface of the silicon adhesive 41 is covered with the epoxy adhesive 42, and the outer peripheral surface of the epoxy adhesive 42 is covered with the polyimide film 43. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrostatic chuck for holding a workpiece such as a semiconductor wafer and a manufacturing method thereof.

Conventionally, this type of electrostatic chuck has a ceramic plate for mounting a workpiece such as a wafer, a metal base on which the ceramic plate is mounted, and the base and the ceramic plate bonded together. (For example, an apparatus described in Patent Document 1).
FIG. 13 is a schematic sectional view showing such a conventional electrostatic chuck.
As shown in FIG. 13, the conventional electrostatic chuck 100 has a structure in which a ceramic plate 101 is bonded onto an aluminum base 102 using an adhesive portion 103.
The bonding portion 103 has a structure in which the silicon adhesive 104 is interposed between most of the back surface 101b of the ceramic plate 101 and the surface 102a of the base 102, and the epoxy adhesive 105 is filled outside the silicon adhesive 104. It has become.
Accordingly, the silicon adhesive 104 prevents adverse effects due to the difference in thermal expansion between the ceramic plate 101 and the base 102, and the epoxy adhesive 105 prevents erosion of the silicon adhesive 104 during plasma processing. Yes.

JP-A-3-335573

However, in the conventional electrostatic chuck 100 described above, the epoxy adhesive 105 may be eroded when used for a long time in plasma processing or the like. The epoxy adhesive 105 is excellent in workability, such as being curable at room temperature, and is therefore frequently used as a plasma erosion inhibitor, but its durability is not long. It is about three times the endurance time of the silicon adhesive 104, and is not suitable for use in a semiconductor manufacturing apparatus or the like for processing a large amount of wafers by performing a plasma treatment for a long time.
That is, when the electrostatic chuck 100 is used for a long time, as shown in FIG. 14, after the epoxy adhesive 105 is eroded by plasma, the silicon adhesive 104 is also eroded. When the wafer is operated under a high-temperature environment such as plasma processing, an air passage 106 for passing a cooling gas G for cooling the wafer passes through the silicon adhesive 104 and the ceramic plate 101. It is provided in the electrostatic chuck 100 so as to open on the surface 101a. However, when the silicon adhesive 104 is eroded as described above, there is a problem that the air passage 106 is broken and the cooling gas G leaks to the outside of the electrostatic chuck 100.

  The present invention has been made to solve the above-described problems, and has a structure capable of almost completely preventing plasma erosion of the silicon adhesive so that a smooth plasma processing operation without hindrance to a workpiece such as a wafer can be performed. It is an object of the present invention to provide an electrostatic chuck and a manufacturing method thereof.

In order to solve the above-mentioned problems, the invention of claim 1 includes a ceramic plate having an adsorption electrode for adsorbing a workpiece such as a wafer, and a metal base on which the ceramic plate is placed. An electrostatic chuck comprising an adhesive portion for bonding the base and the ceramic plate, wherein the adhesive portion includes a silicon adhesive that occupies most of the gap between the base and the ceramic plate, and the silicon adhesive. An epoxy adhesive that is airtightly provided around the outer gap and a band-shaped polyimide film that is airtightly provided so as to wind the epoxy adhesive from the outside to the outer gap of the epoxy adhesive.
With this configuration, when a workpiece such as a wafer is placed on the ceramic plate and the suction electrode is turned on, the workpiece is attracted to the surface of the ceramic plate by the electrostatic force of the suction electrode.
When plasma processing is performed on the workpiece in this state, the entire electrostatic chuck is immersed in the plasma atmosphere, and active plasma particles attempt to erode the bonded portion.
However, in this invention, the adhesive part is composed of a silicon adhesive, an epoxy adhesive that is provided around the outer side of the silicon adhesive, and a polyimide film that is provided around the epoxy adhesive so as to be wound from the outside. The part is not eroded in a short time. That is, since the epoxy adhesive is covered from the outside by a polyimide film that is more durable than the epoxy adhesive against the plasma, the plasma particles are in direct contact with the polyimide film, but are in direct contact with the epoxy adhesive. There is no. Therefore, compared with the conventional electrostatic chuck in which the epoxy adhesive is arranged on the outermost side and exposed, the defense against the silicon adhesive is higher and it can withstand long-time use.

According to a second aspect of the present invention, in the electrostatic chuck according to the first aspect, a stepped portion is formed along the peripheral portion of the surface of the base, and an epoxy adhesive is formed in a gap between the stepped portion and the peripheral portion of the ceramic plate. And a polyimide film is hermetically attached to the outside of the epoxy adhesive.
With this configuration, the epoxy adhesive and the polyimide film are mounted in a wide gap between the stepped portion formed along the surface peripheral portion of the base and the peripheral portion of the ceramic plate, so that the mounting operation is easy. .

  According to a third aspect of the present invention, in the electrostatic chuck according to the first or second aspect, the polyimide film is any one of Kapton, Upilex, Apical, and Midfil.

  According to a fourth aspect of the present invention, in the electrostatic chuck according to any one of the first to third aspects, the gap between the stepped portion and the peripheral portion of the ceramic plate is set to about 2.5 mm, and the width of the polyimide film is set. The gap is set equal to the gap, and the thickness is set to a thickness in the range of 25 μm to 250 μm.

According to a fifth aspect of the present invention, there is provided an electrostatic chuck for manufacturing an electrostatic chuck by adhering a ceramic plate having an adsorption electrode for adsorbing a workpiece such as a wafer to the surface of a metal base through an adhesion portion. In the method of manufacturing the electric chuck, the step of forming the bonding portion includes a first step of bonding the base and the ceramic plate with a silicon adhesive interposed between the base and the ceramic plate. The second step of inserting a band-shaped polyimide film having a width equal to the outer gap of the silicon adhesive into the gap so as to wind the silicon adhesive, and filling the epoxy adhesive into the gap from the outer side of the polyimide film In this state, by reducing the pressure in the gap, the gas between the polyimide film and the silicon adhesive is released outside the gap through the epoxy adhesive. A third step, by pressure increase the epoxy adhesive from the outside, and a structure and a fourth step of advancing the epoxy adhesive between the polyimide film and silicone adhesive.
With this configuration, the electrostatic chuck can be manufactured by bonding the ceramic plate to the surface of the metal base through the bonding portion. At this time, by performing the first step, the silicon adhesive is interposed between the base and the ceramic plate to bond the base and the ceramic plate, and the second step is performed. Then, a strip-like polyimide film having a width equal to the gap on the outside of the silicon adhesive is inserted into the gap so as to wind the silicon adhesive. Then, by executing the third step, in the state where the epoxy adhesive is filled in the gap from the outside of the polyimide film, the pressure in the gap is reduced, and the gas between the polyimide film and the silicon adhesive is reduced. Released through the epoxy adhesive to the outside of the gap. Furthermore, by executing the fourth step, the epoxy adhesive is pressurized from the outside, and the epoxy adhesive enters between the polyimide film and the silicon adhesive. Thereby, a desired adhesion part is formed.

According to a sixth aspect of the present invention, in the method for manufacturing an electrostatic chuck according to the fifth aspect, the step of recessing along the peripheral edge of the surface of the base is formed so that the gap outside the silicon adhesive is made of the silicon adhesive. The thickness is made larger than the thickness, and the second to fourth steps are executed.
With this configuration, the epoxy adhesive and the polyimide film can be mounted in a wide gap, so that the mounting operation is facilitated.

  As described above in detail, according to the electrostatic chuck of the present invention, the adhesive portion is configured to cover the epoxy adhesive from the outside with a highly durable polyimide film. Can be almost completely prevented. As a result, by using the electrostatic chuck of the present invention, there is an excellent effect that it is possible to perform a smooth plasma processing operation without hindrance to a workpiece such as a wafer.

  In particular, according to the invention of claim 2, since the epoxy adhesive and the polyimide film can be easily mounted in the gap, it is possible to improve the manufacturing workability.

  Further, according to the method for manufacturing an electrostatic chuck of the present invention, there is an effect that an electrostatic chuck having high plasma durability and usable for a long time can be manufactured.

  In particular, according to the invention of claim 6, a technique with high manufacturing workability can be provided.

  The best mode of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing an electrostatic chuck according to a first embodiment of the present invention, and FIG. 2 is a schematic sectional view of the electrostatic chuck.
The electrostatic chuck 1 of this embodiment is a device that sucks and holds a semiconductor wafer W as a workpiece, and includes a base 2, a ceramic plate 3, and an adhesive portion 4 as shown in FIG. 1.

  The base 2 is a metal disc body, and has a pedestal portion 20 on which the ceramic plate 3 is placed. In this embodiment, the base 2 having the base portion 20 having a radius R20 of 148 mm and a height H20 of 2 mm on a main body having a radius R2 of 170 mm and a thickness H2 of 5 mm is formed of aluminum.

The ceramic plate 3 is a disc body on which a wafer W having a diameter of 298 mm is placed, and has suction electrodes 31a and 31b for suctioning the wafer W by electrostatic force.
In this example, the radius R3 of the ceramic plate 3 was set to 149 mm, and the thickness H3 was set to 1 mm.
As shown in FIG. 2, the ceramic plate 3 is attached to the surface of the base 2, that is, the surface 20 a of the pedestal portion 20 via the adhesive portion 4.

The bonding portion 4 includes a silicon adhesive 41, an epoxy adhesive 42, and a polyimide film 43 provided in a gap between the base portion 20 of the base 2 and the ceramic plate 3.
Here, the bonding portion 4 will be described in detail.
A stepped portion 20b is formed at the peripheral portion of the surface 20a of the base portion 20 of the base 2 and is recessed about 2 mm below the surface 20a.
The silicon adhesive 41 is applied to the surface 20a of the pedestal portion 20 excluding the stepped portion 20b, and occupies most of the pedestal portion 20 and the ceramic plate 3. In this example, the thickness T41 (see FIG. 1) of the silicon adhesive 41 was set to 0.5 mm.
Accordingly, the size H40 of the gap 40 between the stepped portion 20b and the lower surface of the peripheral edge portion of the ceramic plate 3 is 2.5 mm, and the epoxy adhesive 42 and the polyimide film 43 are disposed in the gap 40. ing.
Specifically, the epoxy adhesive 42 was hermetically filled in the gap 40 outside the silicon adhesive 41. Then, after inserting a polyimide film 43 having a width of 1 mm equal to the size H40 of the gap 40 into the gap 40, the polyimide film 43 was mounted in an airtight manner so as to wind the outside of the epoxy adhesive 42.
The thickness t43 of the polyimide film 43 is set within a range of 25 μm to 250 μm. In order to secure the waist strength of the polyimide film 43, the thickness t43 is preferably set to 105 μm to 250 μm.
As such a polyimide film 43, Kapton, Upilex, Apical, midfill and the like can be applied.
That is, the adhesive part 4 covers the outer peripheral surface of the silicon adhesive 41 that would be exposed if the epoxy adhesive 42 and the epoxy adhesive 42 are absent, and is exposed if the polyimide film 43 is not present. The outer peripheral surface of the wax epoxy adhesive 42 is covered with a polyimide film 43.

  The electrostatic chuck 1 having the above-described structure of the bonding portion 4 is provided with a ventilation path 5 for allowing the cooling gas G to pass therethrough, and each ventilation path 5 penetrates the ceramic plate 3 from the lower side of the base 2. Opening is made on the surface 3 a of the ceramic plate 3. Although not shown, a cooling water channel is also provided in the base 2.

Next, a method for manufacturing the electrostatic chuck 1 will be described.
3-8 is a figure which shows each process of the manufacturing method of the electrostatic chuck 1, FIG. 3 is a schematic sectional drawing which shows a 1st process, FIG. 4 is a schematic which shows a 2nd process. FIG. 5 is a schematic sectional view showing a third step before decompression, FIG. 6 is a schematic sectional view showing a third step after decompression, and FIG. FIG. 8 is a schematic cross-sectional view showing a process, and FIG. 8 is a schematic cross-sectional view showing a state after execution of the fourth process.

The electrostatic chuck 1 can be manufactured by executing the first to fourth steps.
That is, as shown in FIG. 3, after the first step is performed and the base 2 having the pedestal portion 20 formed with the stepped portion 20 b is arranged on the lower side, the silicon adhesive 41 of the bonding portion 4 is placed on the pedestal portion. The base 2 and the ceramic plate 3 are bonded to each other by being interposed between the front surface 20a of the 20 and the back surface 3b of the ceramic plate 3.
And as shown in FIG. 4, a 2nd process is performed and the polyimide film 43 is inserted in the gap | interval 40 so that the silicon adhesive 41 may be wound from the outer side. At this time, a space S in which air is accumulated is generated between the silicon adhesive 41 and the polyimide film 43.
Therefore, as shown in FIG. 5, the third step is executed.
Specifically, the epoxy adhesive 42 is accommodated in the bowl-shaped jig 6, and the jig 6 is disposed outside the gap 40, so that the epoxy adhesive 42 is removed from the polyimide film 43 from the outside of the gap 40. Fill the inside. In this state, the gap 40 is depressurized.
Then, due to this pressure reducing action, the air in the space S reaches the epoxy adhesive 42 side from the gap between the upper end of the polyimide film 43 and the back surface of the ceramic plate 3 and the gap between the lower end of the polyimide film 43 and the surface of the step portion 20b. It is discharged to the outside of the gap 40 from between the adhesive 42 and the jig 6.
As a result, as shown in FIG. 6, the polyimide film 43 is attracted to the outer peripheral surface of the silicon adhesive 41, and the space S between the silicon adhesive 41 and the polyimide film 43 disappears.
Then, the fourth step is executed to increase the pressure of the epoxy adhesive 42 from the outside. Then, as shown in FIG. 7, the epoxy adhesive 42 enters the silicon adhesive 41 side through the gap between the polyimide films 43. When the epoxy adhesive 42 enters a desired amount between the polyimide film 43 and the silicon adhesive 41, the fourth step is terminated, and as shown in FIG. 8, the epoxy adhesive 42 and the polyimide film 43 Can be mounted in the gap 40 wider than the thickness of the silicon adhesive 41.
As a result, the bonding portion 4 is formed between the base 2 and the ceramic plate 3, and thereafter, the air passage 5 and the like (see FIG. 2) are formed, whereby the electrostatic chuck 1 is completed.

Next, operations and effects of the electrostatic chuck 1 of this embodiment will be described.
FIG. 9 is a schematic view showing a state in which the electrostatic chuck 1 is disposed in the plasma chamber, FIG. 10 is a schematic cross-sectional view showing a suction state of the wafer W, and FIG. It is a schematic fragmentary sectional view which shows the state which collides with.
When the electrostatic chuck 1 is used for, for example, a plasma etching process, the electrostatic chuck 1 is disposed in a chamber 7 of a plasma etching apparatus as shown in FIG. Place on the electric chuck 1.
Then, as shown in FIG. 10, the switch 33 for supplying power to the adsorption electrodes 31 a and 31 b is closed and applied to the adsorption electrodes 31 a and 31 b of the DC power supply 32. Then, a positive charge is collected right above the adsorption electrode 31a, and a negative charge is collected right above the adsorption electrode 31b. The wafer W is attracted and fixed to the surface 3a of the ceramic plate 3 by the electrostatic force of these charges and the charges induced on the wafer W.

  In this state, the wafer W is subjected to the plasma etching process in the chamber 7 shown in the module body 9. During this process, the chamber 7 is in a high temperature environment, and as shown in FIG. The wafer W is cooled using the gas G. Specifically, the cooling gas G is supplied into the gas in the ventilation path 5 by a pump (not shown). Then, the cooling gas G flows out from the upper end of the ventilation path 5 opened to the surface 3 a of the ceramic plate 3 to cool the wafer W.

In this state, a plasma etching process is performed. Then, the entire electrostatic chuck 1 in the chamber 7 is immersed in the plasma atmosphere, and the active plasma particles A etch the wafer W into a predetermined shape.
At the same time, however, the plasma particles A go around to the bonding portion 4 side and try to erode the bonding portion 4.
However, in the bonding part 4 applied to this embodiment, as shown in FIG. 11, the outer peripheral surface of the silicon adhesive 41 is covered with an epoxy adhesive 42, and the outer peripheral surface of the epoxy adhesive 42 is covered with a polyimide film 43. Therefore, the polyimide film 43 prevents the plasma particles A from entering the gap 40. Under the same plasma environment, the plasma durability of the polyimide film 43 is much higher than that of the epoxy adhesive 42, and it takes a considerably long time for the polyimide film 43 to be eroded by the active plasma particles A. . After the polyimide film 43 is eroded, the plasma particles A are prevented from entering the silicon adhesive 41 by the epoxy adhesive 42. Therefore, it takes a very long time for the plasma particles A to erode the polyimide film 43 and the epoxy adhesive 42 and directly contact the silicon adhesive 41.
That is, by using the electrostatic chuck 1 of this embodiment, the defense against the silicon adhesive is higher than that of the above-described conventional electrostatic chuck in which the epoxy adhesive 42 is arranged on the outermost side and exposed. Can be used for a considerable time.
In addition, a polyimide film 43 and an epoxy adhesive 42 are mounted in the gap 40 so that they do not protrude outside the electrostatic chuck 1. For this reason, when performing the down-flow anisotropic etching process with the active plasma particles A, as shown in FIG. 11, the plasma particles A fall almost vertically downward from the upper side of the chamber 7, so that they fall at a high speed. The plasma particles A that do not collide directly with the outermost polyimide film 43, and most of the plasma particles A that collide with the polyimide film 43 are low-speed plasma particles A reflected at other sites. Also, the durability time of the polyimide film 43 becomes longer.

Next explained is the second embodiment of the invention.
FIG. 12 is a schematic sectional view showing an electrostatic chuck 1 according to the second embodiment of the present invention.
This embodiment does not provide a wide gap 40 for mounting the epoxy adhesive 42 and the polyimide film 43 of the bonding portion 4, and an epoxy adhesive is provided in the gap 40 ′ having the same width as the gap indicated by the silicon adhesive 41. The point which attached 42 and the polyimide film 43 differs from the said 1st Example.
That is, as shown in FIG. 12, the stepped portion 20 b is not provided on the pedestal portion 20 of the base 2, and the entire surface 20 a of the pedestal portion 20 is formed flat.
The silicon adhesive 41 is applied to most of the inside of the surface 20 a, and the epoxy adhesive 42 is hermetically filled in the gap outside the silicon adhesive 41. A polyimide film 43 is attached in an airtight manner so as to wind the outside of the epoxy adhesive 42.
Since other configurations, operations, and effects are the same as those in the first embodiment, description thereof is omitted.

1 is an exploded perspective view showing an electrostatic chuck according to a first embodiment of the present invention. It is a schematic sectional drawing of an electrostatic chuck. It is a schematic sectional drawing which shows a 1st process. It is a schematic sectional drawing which shows a 2nd process. It is a schematic sectional drawing which shows the 3rd process before pressure reduction. It is a schematic sectional drawing which shows the 3rd process after pressure reduction. It is a schematic sectional drawing which shows a 4th process. It is a schematic sectional drawing which shows the state after 4th process execution. It is the schematic which shows the state which has arrange | positioned this electrostatic chuck in a plasma chamber. It is a schematic sectional drawing which shows the adsorption | suction state of a wafer. It is a general | schematic fragmentary sectional view which shows the state which a plasma particle collides with a polyimide film. It is a schematic sectional drawing which shows the electrostatic chuck which concerns on 2nd Example of this invention. It is a schematic sectional drawing which shows this conventional electrostatic chuck. It is a schematic sectional drawing which shows the erosion state of an epoxy adhesive or a silicon adhesive.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrostatic chuck, 2 ... Base, 3 ... Ceramic plate, 3a ... Front surface, 3b ... Back surface, 4 ... Adhesion part, 5 ... Air passage, 6 ... Jig, 7 ... Chamber, 20 ... Base part, 20a ... Surface 20b: Stepped part, 31a, 31b ... Adsorption electrode, 32 ... DC power supply, 33 ... Switch, 40 ... Gap, 41 ... Silicone adhesive, 42 ... Epoxy adhesive, 43 ... Polyimide film, A ... Plasma particle, G ... Cooling gas, W ... wafer.

Claims (6)

A ceramic plate having a suction electrode for sucking a workpiece such as a wafer, a metal base on which the ceramic plate is placed, and an adhesive portion for bonding the base and the ceramic plate An electrostatic chuck comprising:
A silicon adhesive that occupies most of the gap between the base and the ceramic plate, an epoxy adhesive that is hermetically surrounded in a gap outside the silicon adhesive, and an outer side of the epoxy adhesive. It was composed of a band-shaped polyimide film that was airtightly wound around the gap to wind the epoxy adhesive from the outside,
An electrostatic chuck comprising: The electrostatic chuck according to claim 1,
A stepped portion is formed along the peripheral edge of the surface of the base, and the epoxy adhesive is hermetically filled in a gap between the step and the peripheral edge of the ceramic plate, and a polyimide film is formed outside the epoxy adhesive. Attached airtight,
An electrostatic chuck characterized by that. The electrostatic chuck according to claim 1 or 2,
The polyimide film is one of Kapton, Upilex, Apical and Midfil.
An electrostatic chuck characterized by that. The electrostatic chuck according to any one of claims 1 to 3,
The gap between the step and the peripheral edge of the ceramic plate is set to about 2.5 mm,
While setting the width of the polyimide film equal to the gap, the thickness was set to a thickness in the range of 25 μm to 250 μm.
An electrostatic chuck characterized by that. This is an electrostatic chuck manufacturing method for manufacturing an electrostatic chuck by adhering a ceramic plate having an adsorption electrode for adsorbing a workpiece such as a wafer to the surface of a metal base through an adhesion portion. And
The step of forming the adhesive portion includes
A first step of interposing a silicon adhesive in a large portion between the base and the ceramic plate to bond the base and the ceramic plate;
A second step of inserting a band-like polyimide film having a width equal to the outer gap of the silicon adhesive into the gap so as to wind the silicon adhesive;
In the state where the epoxy adhesive is filled in the gap from the outside of the polyimide film, the pressure in the gap is reduced, so that the gas between the polyimide film and the silicon adhesive is passed through the epoxy adhesive in the gap. A third step of releasing to the outside;
And a fourth step of causing the epoxy adhesive to enter between the polyimide film and the silicon adhesive by increasing the pressure of the epoxy adhesive from the outside. In the manufacturing method of the electrostatic chuck according to claim 5,
By forming a stepped portion that is recessed along the peripheral edge of the surface of the base, the gap outside the silicon adhesive is made wider than the thickness of the silicon adhesive, and the second to fourth steps are performed. Execute,
A method of manufacturing an electrostatic chuck.

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