JP5043771B2 - Electrostatic chuck - Google Patents

Description

  The present invention relates to an electrostatic chuck suitable for substrate processing in high-precision manufacturing processes such as ICs and LCDs. More specifically, the present invention dissipates heat from a substrate to be processed when a process that generates heat or requires heating is performed in a vacuum chamber. The present invention relates to an electrostatic chuck that holds the heat transferable state.

  Examples of processing that generates heat in the vacuum chamber include plasma processing such as etching and ashing, and examples of processing that requires heating include film formation processing such as plasma CVD. As an example of a plasma processing apparatus used for these processes, a pair of parallel plates serving as counter electrodes is provided, and a plasma processing space is formed between the parallel plates to target a substrate such as a silicon wafer. A so-called parallel plate type etcher (RIE) that performs an etching process, a parallel plate type PCVD that performs a film forming process, and the like are known.

  FIG. 2 (a) shows a longitudinal cross-sectional structure diagram. In a parallel plate type plasma processing apparatus, a pair of parallel plates are provided in a vacuum chamber, and plasma is formed in a plasma processing space formed between both plates. Is generated or introduced, and a predetermined processing gas or the like is also introduced into the plasma processing space. Then, a plasma reaction is performed in the plasma processing space, whereby an etching process or the like is performed on the substrate surface in the plasma processing space.

  An etcher will be described in detail. This apparatus includes a vacuum chamber in which a vacuum chamber lid 3 is attached on a vacuum chamber main body 2 so as to be openable and closable, and a substrate 1 that is an object of plasma processing is provided. Since it has a flat plate shape, the horizontally placed cathode portion 12 is provided in the center of the vacuum chamber main body 2, the upper surface of the cathode portion 12 is formed flat, and the substrate 1 is mounted thereon. It is possible to keep it. A cylindrical lower support 12a is vertically provided through the center of the inner bottom of the vacuum chamber main body 2. The cathode portion 12 is fixedly supported at the upper end of the lower support 12a and is constituted by these. The substrate support is implanted in a vacuum chamber and has an upper surface formed so that the substrate can be mounted.

  An anode portion 11 is suspended from the vacuum chamber lid portion 3 by a cylindrical upper support 11a at a substantially central position in the vacuum chamber lid portion 3 and above the cathode portion 12, and the anode portion 11, the cathode portion 12, When a high frequency is applied by the RF power source 31 with the electrodes facing each other, plasma is generated between the anode portion 11 and the cathode portion 12 under a predetermined vacuum pressure. When a predetermined processing gas is supplied thereto, plasma processing corresponding to the gas state or the like is performed on the substrate 1 placed on the upper surface of the cathode portion 12. As a result, a plasma processing space 13 is formed between the lower surface of the anode portion 11 and the upper surface of the cathode portion 12, and the plasma processing is performed on the surface of the substrate 1 placed there.

  The vacuum chamber main body 2 is formed with a suction port 2a penetrating the inside and outside in order to suck out the gas in the vacuum chamber and maintain an appropriate degree of vacuum. A gate valve 4a, a variable valve 4 and a vacuum pump are sequentially formed with respect to the suction port 2a. 5 are connected. The gate valve 4a is a manual valve for partitioning during maintenance or the like, and is opened during normal operation. The variable valve 4 inserted between this and a vacuum pump 5 such as a turbo pump is provided with a motor or the like that variably drives the valve opening, and is controlled by an electric signal to control the flow of fluid that can be remotely controlled. Functions as a variable aperture. Then, the throttle amount by the variable valve 4 is variably driven according to control of an appropriate PID control circuit or the like (not shown), so that the vacuum pressure in the vacuum chamber is automatically controlled to be a set pressure suitable for plasma processing.

  In such processing, in order to obtain a uniform processing result, it is necessary to maintain not only the vacuum pressure of the plasma processing space 13 but also the temperature of the substrate 1 at an appropriate set temperature. Moreover, it is necessary to keep the temperature of the entire substrate 1 as uniform as possible. However, under vacuum conditions, heat transfer by gas-mediated convection is hardly performed. Moreover, when viewed microscopically, not only the real contact area between the substrate 1 and the cathode portion 12 is small, but also the contact portions are randomly scattered. For this reason, relying on direct heat conduction and slight radiation results in insufficient heat dissipation and non-uniform heat distribution.

  Accordingly, the substrate 1 is placed on the substrate mounting surface of the processing substrate mounting electrode installed in the plasma processing space or the like in the vacuum chamber, that is, on the upper surface of the cathode portion 12 in the example of FIG. An electrostatic chuck 50 attracted by electrostatic force is provided in a thin and wide film shape (see FIG. 2B), and helium (He) or the like is provided between the electrostatic chuck 50 and the substrate 1 thereon. Cooling gas (heat transfer gas) is supplied.

  The cooling gas supply means includes a cathode portion through the inner cavity of the lower support 12a so that the cooling gas sent from the outside of the vacuum chamber main body 2 is blown out from the electrostatic chuck 50 side toward the lower surface and the back surface of the substrate 1. A cooling gas supply pipe 41 extending into or communicating with the substrate 12, a cooling gas supply cavity 42 formed in the cathode portion 12 having a width corresponding to the substrate mounting surface, and the electrostatic chuck 50. The cooling gas supply holes 43 are perforated so as to reach the cooling gas supply cavity 42, and are provided with cooling gas supply holes 43 scattered and scattered on the upper surface of the cathode portion 12. Thus, the electrostatic chuck 50 is provided on the substrate mounting surface (upper surface) of the electrode 12 in which the cooling gas supply hole 43 is formed.

  FIG. 3A shows a plan view of such a conventional electrostatic chuck 50, but grooves 51 are formed so as to connect the outermost peripheral ones among the many cooling gas supply holes 43. . The groove 51 is provided by being divided and separated into several arc portions so as to cover almost one round as a whole. FIG. 3B shows an enlarged schematic longitudinal sectional view of the portion of the groove 51 in which the cooling gas feed hole 43 is drilled. The electrostatic chuck 50 includes a conductive layer for charging static electricity, In order to prevent the static electricity from escaping, it has a pair of insulating layers that sandwich the conductive layer from above and below.

  Such an electrostatic chuck 50 is generally manufactured as follows. First, an upper insulating layer 57 made of an insulating resin sheet such as a polyimide film is attached to the upper surface of a conductive layer 55 such as a copper foil by an adhesive layer 56, and polyimide is also applied to the lower surface of the conductive layer 55. A lower insulating layer 53 made of an insulating resin sheet such as a film is attached with an adhesive layer 54 to form a single insulating sheet. Next, the groove 51 is punched out by a press or the like. Then, the adhesive layer 52 is attached to the upper surface of the cathode portion 12 while aligning the relative positions of the groove 51 and the cooling gas supply hole 43. Thus, the electrostatic chuck 50 having the groove 51 having a width W of 1 to 2 mm and a depth D of about 150 μm is completed.

  When the substrate 1 is placed on the cathode portion 12 having the electrostatic chuck 50 having such a structure, the substrate 1 is charged by charging the conductive layer 55 or charging due to the plasma processing. It is held with an urging force on the upper surface of the cathode portion 12 via the electrostatic chuck 50. When the cooling gas is sent into the cooling gas supply pipe 41, the cooling gas is supplied to the lower side of the substrate 1 through the cooling gas supply cavity 42 and the numerous cooling gas supply holes 43.

  Thus, even in a vacuum atmosphere, the substrate 1 is held on the electrostatic chuck 50 on the upper surface of the cathode portion 12, and the gap between the back surface and the lower surface of the substrate 1 and the electrostatic chuck 50 is filled with the cooling gas. Is done. This cooling gas spreads outward in the gap in the radial direction and is discharged into the plasma processing space 13 from a position immediately below the outermost periphery of the substrate 1, so that only a small amount is supplied so as not to affect the vacuum state.

  In such a flow, the cooling gas is set to the same pressure in the groove 51 and is distributed almost uniformly in the gap extending between the substrate 1 and the electrostatic chuck 50. Then, heat transfer is performed between the substrate 1 and the cathode portion 12 over almost the entire back surface of the substrate 1 using this cooling gas as a medium.

  However, in such a conventional electrostatic chuck, if there are voids or scratches in the resin sheet used for the upper insulating layer in the electrostatic chuck, the dielectric breakdown is likely to occur from that point, and once the dielectric breakdown has occurred. It can spread quickly and become unusable. Sheets having such voids and scratches are not used, but it is difficult to find even minute ones by inspection, and sheets having excellent insulating properties are easily damaged and difficult to handle. Therefore, even if it is impossible to desire a perfect electrostatic chuck with no voids or scratches, an electrostatic chuck that does not easily cause dielectric breakdown even if there are defects such as voids or scratches is devised. Is a problem.

  Further, in the conventional electrostatic chuck as described above, a groove is formed by punching in order to make the filling state of a heat transfer gas such as a cooling gas uniform. Since it is too large compared to the gap, the heat conduction by the heat transfer gas is deteriorated at the groove, so that the uniformity and uniformity of the heat distribution of the substrate is impaired. Moreover, since the electrode surface, which is a good conductor, is exposed at the bottom of the groove, abnormal discharge occurs in the groove, the bias voltage varies, and depending on the type of reactive gas used for plasma processing, etc. There was also a problem that the electrode surface was corroded. Therefore, how to form a groove that has a shallower groove depth and does not expose the electrode surface is a problem.

  Furthermore, in an electrostatic chuck in which grooves are formed by punching, some of the grooves are separated in order to avoid separation and separation of the portions surrounded by the grooves when the grooves are completely circled. It must be divided and formed. For this reason, the degree of freedom in design regarding the shape of the groove is limited, so that it is difficult to handle when attaching to the electrode, etc. There was dissatisfaction such as being easy to be different. Moreover, such non-uniform pressure distribution tends to be exacerbated when the depth of the groove is shallower than in the prior art. Thus, it is a further problem to improve the uniformity of the heat transfer gas pressure even if the depth of the groove is shallower than that of the prior art.

  The present invention has been made to solve such a problem, and an object of the present invention is to realize an electrostatic chuck that is difficult to break down. Another object of the present invention is to realize an electrostatic chuck having a shallow groove and good coverage. Another object of the present invention is to realize an electrostatic chuck with good uniformity of heat transfer gas pressure even if the groove is shallow.

  About the 1st thru | or 3rd solution means invented in order to solve such a subject, the structure and effect are demonstrated below.

[First Solution]
The electrostatic chuck of the first solving means is provided on a substrate mounting surface of an electrode (for mounting a substrate to be processed installed in a vacuum atmosphere such as a plasma processing space in a vacuum chamber), and includes a conductive layer and the conductive layer. In the electrostatic chuck having an insulating layer to be sandwiched, the insulating layer on the substrate side includes a plurality of thin film layers.

  In such an electrostatic chuck of the first solving means, even if the substrate-side insulating layer has a defect such as a void or a flaw in any of the plurality of thin film layers included in the insulating layer, If it is locally small, it rarely overlaps with a similar defect portion in other thin film layers laminated together, so that there is almost no defect that penetrates the front and back.

  As a result, even when an electrostatic chuck is made using a sheet having excellent insulating properties, an electrostatic chuck that is not easily damaged and has excellent insulation resistance is completed, and its life is greatly extended. Therefore, according to the present invention, it is possible to realize an electrostatic chuck that is difficult to break down.

[Second Solution]
The electrostatic chuck of the second solving means is an electrode on which a heat transfer gas supply hole is formed (which is an electrode for mounting a processing target substrate installed in a vacuum atmosphere such as a plasma processing space in a vacuum chamber). In the electrostatic chuck having a conductive layer and an insulating layer sandwiching the conductive layer provided on the substrate mounting surface of the substrate, the electrode has a groove communicating with the gas transfer hole for heat transfer formed on the substrate mounting surface. The conductive layer and the insulating layer are in close contact with the substrate mounting surface including the bottom of the groove and are penetrated by the heat transfer gas supply hole.

  In the electrostatic chuck of the second solving means, the conductive layer and the insulating layer are in close contact with the groove formed on the substrate mounting surface of the electrode in the same manner as in the absence of the groove. Therefore, a groove having substantially the same shape as the groove on the electrode surface appears on the surface of the electrostatic chuck. The heat transfer gas is supplied to the groove through the heat transfer gas supply hole.

  This makes it easy to make the groove on the surface of the electrostatic chuck shallower than the thickness of the electrostatic chuck if the groove to be carved into the electrode surface is shallow, and the groove bottom is not punched out. The layer of the electrostatic chuck that is bent and bent along the groove shape remains except for the through portion of the gas transfer hole for heat transfer. Therefore, according to the present invention, an electrostatic chuck that is shallow and has good coverage can be realized.

[Third Solution]
The electrostatic chuck of the third solving means is the electrostatic chuck of the second solving means described above, characterized in that the grooves are formed in a net shape (distributed and formed).

  In the electrostatic chuck of the third solving means, since it is not necessary to punch out the sheet of the electrostatic chuck, the grooves are distributed in a mesh shape based on the release from the restrictions on the distribution shape and the like of the grooves. Provided. And since the heat transfer gas is made the same pressure at the grooves distributed in a mesh shape, the pressure is equal everywhere, so the uniformity of the heat transfer gas is improved. Its function more than compensates for the increase in pressure gradient due to shallow grooves. Therefore, according to the present invention, it is possible to realize an electrostatic chuck with good uniformity of heat transfer gas pressure even if the groove is shallow.

As is clear from the above description, in the electrostatic chuck of the first solving means of the present invention, even if a part of the thin film layer is defective, the penetration is suppressed by the other thin film layer. Thus, there is an advantageous effect that an electrostatic chuck that is difficult to break down can be realized.
In the electrostatic chuck of the second solving means of the present invention, the groove shape carved on the electrode surface is transferred to the electrostatic chuck surface, so that the groove is shallow and the covering property is good. There is an advantageous effect that an electric chuck can be realized.

  Furthermore, in the electrostatic chuck of the third solving means of the present invention, since the grooves are formed in such a distributed state that the pressure gradient is eliminated, evenness of the heat transfer gas pressure can be achieved even if the grooves are shallow. However, there is an advantageous effect that a good electrostatic chuck can be realized.

  With regard to the electrostatic chuck of the present invention achieved by such a solution, a mode for carrying out the electrostatic chuck will be specifically described by way of examples.

  1A and 1B are schematic views illustrating the configuration of the first embodiment, in which FIG. 1A is a plan view and FIG. 1B is an enlarged longitudinal sectional view. 2 and FIG. 2 are also applicable to this example, and FIG. 1 corresponds to FIG. 3 of the conventional example. Since the same reference numerals are given, the repeated description is omitted, and hereinafter, the description will focus on differences from the conventional example.

  This electrostatic chuck 500 is different from the conventional electrostatic chuck 50 in that a plurality of radial straight lines intersect and communicate with each other in a plurality of concentric circles and have grooves 510 distributed in a net shape (FIG. 1A). (See FIG. 1 (b)). The upper insulating layer 57, which has conventionally been a single sheet, includes two sheets of a first thin film layer 571 and a second thin film layer 573.

  Such an electrostatic chuck 500 is formed on the upper surface (electrode mounting surface of the electrode) of the cathode portion 12 as follows. First, a first thin film layer 571 made of an insulating resin sheet such as a polyimide film, preferably less than half the thickness of the upper insulating layer 57 is attached to the upper surface of the conductive layer 55 such as copper foil by the adhesive layer 56. wear. Next, a second thin film layer 573 made of another insulating resin sheet such as a thin polyimide film is attached to the upper surface with an interlayer adhesive layer 572. As a result, voids and scratches in the first thin film layer 571 are closed by the second thin film layer 573, while voids and scratches in the second thin film layer 573 are closed by the first thin film layer 571. It is. Thereafter, the lower insulating layer 53 is also pasted as in the prior art, and a multilayer insulating sheet is formed in one sheet. In addition, the punching by the press etc. which was performed conventionally is not performed. In the insulating sheets (53 to 573) thus obtained, the upper insulating layer on the upper substrate 1 side includes a plurality of thin film layers 571 and 573.

  On the other hand, the upper surface of the cathode portion 12 is polished flat and then engraved therein to form a shallow groove having a width W of 1 to 2 mm and a depth D of about 10 to 50 μm. A large number of them are formed so as to form a net. Then, the insulating sheets (53 to 573) are attached to the upper surface of the cathode portion 12 with the adhesive layer 52 and pressed with high-pressure gas from above. This pasting operation can be easily performed because the insulating sheet has no cuts such as punch marks. As a result, the electrostatic chuck 500 having the conductive layer 55 and the insulating layers 53, 571, and 573 comes into close contact with the substrate mounting surface of the cathode portion 12 including the bottom of the groove.

  When the adhesive layer 52 is solidified, the grooves on the upper surface of the cathode portion 12 are transferred to the surface of the electrostatic chuck 500, and the grooves 510 distributed in the same net shape are formed. The groove 510 is shallow with a width W of 1 to 2 mm and a depth of about 20 to 50 μm. In addition, the cathode portion 12 is covered to the bottom of the groove.

  Finally, a large number of cooling gas supply holes 43 (heat transfer gas supply holes) that penetrate the electrostatic chuck 500 from above to the groove 510 and reach the cooling gas supply cavity 42 in the cathode portion 12 are formed. Wear. As a result, the groove on the substrate mounting surface of the cathode portion 12 communicates with the cooling gas supply hole 43, and the conductive layer and the insulating layer of the electrostatic chuck 500 are penetrated by the cooling gas supply hole 43. The surface groove 510 also leads to the cooling gas supply hole 43 everywhere.

  The use mode and operation of the electrostatic chuck of this embodiment will be described. When the substrate 1 is placed on the cathode portion 12 having the electrostatic chuck 500 having the above-described structure, the substrate 1 is statically charged by charging the conductive layer 55 or charging caused by the plasma treatment. It is held with an urging force on the upper surface of the cathode portion 12 via the electric chuck 500. Then, when the cooling gas (heat transfer gas) is fed into the cooling gas feed pipe 41, the cooling gas passes to the lower side of the substrate 1 through the cooling gas feed cavity 42 and the numerous cooling gas feed holes 43. Supplied. Even in a vacuum atmosphere, the substrate 1 is held on the electrostatic chuck 500 on the upper surface of the cathode portion 12, and a cooling gas is filled in the gap between the back and bottom surfaces of the substrate 1 and the electrostatic chuck 500. The

  As described above, the cooling gas is filled in the gap between the substrate 1 and the electrostatic chuck 500 through the cooling gas feed hole 43 in the conventional manner. However, when filling the cooling gas, the cooling gas enters the groove 510 from various places. Supplied and flows in the groove 510 in length and width to eliminate the pressure gradient. The cooling gas is distributed in a sufficiently uniform state in the gap extending between the substrate 1 and the electrostatic chuck 500.

  As a result, uniform heat transfer is performed between the substrate 1 and the cathode portion 12 over almost the entire back surface of the substrate 1 using the uniform cooling gas as a medium. Further, since the depth D of the groove is shallower than that in the conventional case at the groove 510, the heat transfer characteristic in the portion is improved, and almost uniform heat transfer is performed there. In this way, the temperature distribution is made uniform over the entire substrate 1.

  Further, since the upper surface of the cathode portion 12 is not exposed even in the groove 510 and is covered with the insulating electrostatic chuck 500, abnormal discharge is not induced between the back surface of the substrate 1. Even if an abnormal discharge occurs, it disappears quickly. Further, even when a corrosive gas or the like is mixed into the groove 510, the upper surface of the cathode portion 12 is not directly exposed to the gas, and the inconvenience that the upper surface of the cathode portion 12 is corroded by the corrosive gas is prevented. Therefore, various plasma treatments using any reactive gas can be freely selected.

It is a schematic diagram which shows the structure about one Example of the electrostatic chuck of this invention, (a) is a top view, (b) is a longitudinal cross-sectional enlarged view. It is a longitudinal cross-sectional schematic diagram which shows the usage example of an electrostatic chuck, (a) is a general view of a vacuum chamber, (b) is a lower electrode equipped with the electrostatic chuck. This is a conventional electrostatic chuck.

Explanation of symbols

1 Substrate (wafer, workpiece, target substrate)
2 Vacuum chamber body (vacuum chamber)
2a Suction port 3 Vacuum chamber lid (vacuum chamber)
4 Variable valves (variable throttle, pressure control mechanism, pressure control means)
4a Gate valve (gate valve)
5 Vacuum pump 11 Anode (one of parallel plates, upper electrode)
11a Upper support 12 Cathode part (the other parallel plate, lower electrode, substrate mounting electrode)
12a Lower support 13 Plasma processing space 31 RF power supply 41 Cooling gas supply pipe (heating medium, medium, gas transfer means for heat transfer, supply means)
42 Cooling gas supply cavity (heating medium, medium, gas transfer means for heat transfer, supply means)
43 Cooling gas supply hole (heat medium gas filling, medium gas supply, heat transfer gas supply hole)
50 Electrostatic chuck 51 Groove (dent, recess, means for uniformizing gas for heat transfer)
52 Adhesive layer 53 Lower insulating layer (electrode-side insulating layer)
54 Adhesive layer 55 Conductive layer (intermediate layer)
56 Adhesive layer 57 Upper insulating layer (substrate-side insulating layer)
500 Electrostatic chuck 510 Groove (recess, recess, means for equalizing gas pressure for heat transfer)
571 First thin film layer (laminated insulating layer, upper insulating layer, substrate-side insulating layer)
572 Interlayer adhesive layer (laminated insulation layer, upper insulation layer, substrate side insulation layer)
573 Second thin film layer (laminated insulating layer, upper insulating layer, substrate side insulating layer)

Claims (2)

Provided on the substrate side surface of the formed electrode of the heat transfer gas supply holes, the electrostatic chuck having a conductive layer and insulating layers sandwiching it,
The insulating layer includes a lower insulating layer disposed below the conductive layer and a plurality of upper insulating layers disposed above the conductive layer, wherein the plurality of upper insulating layers are respectively interposed via an adhesive layer. And the lowermost layer of the lower insulating layer and the upper insulating layer are respectively bonded to the conductive layer via an adhesive layer,
The electrode, the heat transfer gas supply holes width leads to 1 to 2 mm, Ri Contact the shallow groove depth 10~50μm formed on the substrate side surface, the conductive layer and the insulating layer, the including all surfaces of the shallow grooves are arranged on the substrate side surface, and an electrostatic chuck wherein the heat transfer gas supply holes is characterized in that through said conductive layer and the insulating layer. The electrostatic chuck before Kiasamizo is that connects to network, according to claim 1.

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