JPWO2008108146A1 - Electrostatic chuck - Google Patents

Abstract

The present invention provides an electrostatic chuck that is capable of exchanging the attracting surface and has improved adhesiveness with a substrate such as a wafer to be attracted and held by making the replaceable resin sheet a flexible material. An adsorption electrode (6) such as copper or aluminum was included in the first insulating electrical conductor layer (3,4) of a resin such as polyimide or a silicone rubber such as fluorosilicone. Then, the second dielectric layer (5), which is a resin sheet such as polyimide, is attached on the upper layer (4) of the first insulating electric conductor layer so as to be exchangeable.

Description

  The present invention is used for plasma processing apparatuses such as etching processes and chemical vapor deposition (CVD) thin film formation used in semiconductor element manufacturing processes, electron exposure apparatuses, ion drawing apparatuses, ion implantation apparatuses, and liquid crystal panel manufacturing. This is a mechanism for an electrostatic chuck of a semiconductor wafer used in an ion doping apparatus to be used.

The chucking surface has the most influence on the life of the electrostatic chuck. Attracting surface of the electrostatic chuck is for holding the number 10 gf / cm ² when a large substrate of relatively hard material such as a semiconductor wafer or a glass considerable force, from the number of units per area gf / cm ^2. In addition, because the backside of the substrate, that is, the surface in contact with the suction surface, has dust or minute particles attached to it, or foreign substances floating from the walls of the processing chamber where the electrostatic chuck is installed directly touch the suction surface. The attracting surface of the electrostatic chuck is always worn and damaged.

  The electrostatic chuck attracting surface is made of a relatively hard material, such as ceramic, in order to reduce the influence of the wear and damage. Also in the case of resin, a material having a relatively high tensile strength, for example, a polyimide sheet called Ube Industries' Upilex (registered trademark of Ube Industries) is used. Although it is possible to increase the strength of the material and extend the life of the attracting surface of the electrostatic chuck, the flexibility of the attracting surface is lost, so the cooling characteristics of the substrate deteriorate. This is because both are made of a hard material, and the contact area between the suction surface and the substrate is reduced. Further, when hard materials rub against each other, the possibility of generating fine particles increases, and there is a concern about the problem of dust generation from the suction surface and the substrate itself.

  Japanese Patent Application Laid-Open No. 2003-45949, which is a patent document 1, discloses a method of processing a particle capturing sheet called an anti-adhesion sheet between a substrate and an adsorption surface of an electrostatic chuck used for forming a thin film. Yes. The anti-adhesion sheet is a consumable item and is said to be effective in reducing particles because it is replaced every time. Japanese Patent Application Laid-Open No. 10-209256, which is Patent Document 2, discloses that an electrode and a resin adsorption surface are attached to a ceramic insulating dielectric layer so that the electrode and the adsorption surface can be exchanged. Yes. Furthermore, in Japanese Patent Application Laid-Open No. 10-303286, which is Patent Document 3, an insulating dielectric layer made of ceramic is fixed to a substrate with an adhesive by an electrostatic chuck of a plasma etching apparatus, and the insulating dielectric layer is replaced. It is disclosed that it is possible.

JP 2003-45949 A JP-A-10-209256 JP-A-10-303286

Problems to be solved by the present invention are as follows.
The first problem is that the surface of the electrostatic chuck having an adsorption electrode on the insulating dielectric layer of a fluorine-silicone composite rubber such as a resin such as polyimide or fluorosilicone (also referred to as fluorosilicone) is coated with polyimide or the like. By attaching a resin sheet and making it possible to peel it off, the suction surface can be exchanged. A second problem is to improve the adhesion with a substrate such as a wafer to be sucked and held by making the replaceable resin sheet a flexible material.

In order to solve the above-mentioned problems, the invention of claim 1 is directed to an electrostatic chuck having an adsorption electrode inside a dielectric and adsorbing and holding a substrate by static electricity induced by a voltage applied to the adsorption electrode. The second dielectric layer can be attached to and peeled off from the first insulating dielectric layer having the structure, and the second dielectric layer can be exchanged.
Here, the material of the first insulating dielectric layer is not particularly limited. A resin such as polyimide or a fluorosilicone material that has a certain degree of electrical insulation and further has the purity, durability, and heat resistance of materials required for semiconductor manufacturing equipment is suitable. The first insulating dielectric layer made of polyimide or fluorosilicone has a thickness in the range of 50 to 200 μm, and is composed of a single layer or two or more layers of the same or different kinds of materials. When the thickness is relatively thin, it is appropriate to form it as a single layer, but when the thickness is large or when an adsorption electrode described later is contained, it is formed by bonding a plurality of polyimide sheets. The adsorption electrode is formed on the surface or inside of the first insulating dielectric layer. The material of the adsorption electrode is a material with high electrical conductivity such as copper or aluminum, or a material with high chemical and thermal resistance such as tungsten or tantalum. Furthermore, it is selected from those that are easy to process, such as nickel. The thickness is about 0.5 μm to 30 μm, but it is sometimes preferable to make it as thin as possible because the unevenness of the adsorption surface becomes small. Determined in consideration of durability and surface flatness. The adsorption electrode is formed by a method such as sputtering, plating, ion plating, vapor deposition, or adhesion of a thin film. When appropriate patterning is required, an etching method is used in combination. The second dielectric layer is formed of a polyimide resin. The thickness of the second dielectric layer is preferably in the range of 25 to 100 μm, and is formed as a single layer or multiple layers. In the case where the thickness is small, it is preferable in terms of production to form a single-layer sheet. The second dielectric layer is affixed to the first insulating dielectric layer with an adhesive, but it must have a suitable holding force and can be peeled off in order to have exchangeability.

According to a second aspect of the present invention, in the electrostatic chuck according to the first aspect, the second dielectric layer is attached to the first insulating dielectric layer with a silicon-based adhesive.
The pressure-sensitive adhesive used here needs to be made of a material that is as harmless as possible in the semiconductor manufacturing process. Since most of the adsorbing substrates are silicon substrates, the safety can be improved by using an adhesive of the same quality.

According to a third aspect of the present invention, in the electrostatic chuck according to the first or second aspect, the second dielectric layer is made of a material having higher flexibility than the first insulating dielectric layer, and has a Young's modulus. Is made of a polyimide resin having 2 to 6 GPa.
By making the second dielectric layer more flexible than the first insulating dielectric layer, it is possible to increase the contact area, that is, the adhesion between the substrate such as a wafer and the attracting surface of the electrostatic chuck. Young's modulus is a coefficient of how much displacement can be made with respect to the force applied to the material, and is an index indicating flexibility. The higher the coefficient, the harder the material. If the adhesion is increased, the heat from the wafer can be efficiently transferred by the electrostatic chuck, so that the cooling performance of the wafer is improved. Furthermore, since the contact resistance between the charges accumulated on the wafer and the electrostatic chuck is reduced, it can be efficiently eliminated.

  As described above in detail, according to the electrostatic chuck of the present invention, when the chucking surface of the electrostatic chuck has expired due to adhesion or damage of particles, only the second dielectric layer is replaced and regenerated. Can restore its function. This operation is more economical because it can be performed more easily than regenerating the insulating dielectric layer including the attracting electrode. In addition, by adhering a second dielectric layer on the surface of the electrostatic chuck having an insulating dielectric layer made of an existing resin, it is possible to regenerate the suction surface, and to cool the wafer. The performance can be improved.

It is a schematic sectional drawing of the electrostatic chuck which concerns on 1st Example of this invention. It is a schematic sectional drawing of the electrostatic chuck which concerns on 2nd Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base | substrate, 2 ... Cushion layer, 3 ... Lower layer of 1st insulating dielectric layer, 4 ... Upper layer of 1st insulating dielectric layer, 5 ... 2nd dielectric layer, 5a ... Adsorption surface 6 ... Adsorption electrode, 7 ... Cooling water channel, 8 ... Potential supply insulating part, 9 ... Potential supply terminal, 10 ... Power supply, 100, 101 ... Electrostatic chuck.

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

FIG. 1 is a schematic sectional view of an electrostatic chuck according to a first embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a base. The base 1 is made of a highly rigid aluminum metal. In the case of an electrostatic chuck for a wafer having a diameter of 300 mm, the base 1 has a diameter of 294 mm and a thickness of 10 mm. A cooling water channel 7 for cooling the base 1 is formed inside the base 1. The reason for cooling is to cool a substrate such as a wafer that is attracted and held on the electrostatic chuck by heat conduction indirectly by cooling the substrate 1.
An upper layer 4 of the first insulating dielectric layer is prepared. A polyimide resin having a thickness of 125 μm and a diameter of 294 mm is prepared. In this example, a product called Upilex (registered trademark of Ube Industries) was used.
Next, the adsorption electrode 6 is formed on one surface of the upper layer 4 of the first insulating dielectric layer. The material of the adsorption electrode 6 was copper. Aluminum, tungsten, tantalum, gold, and the like are also possible as other materials for the adsorption electrode 6. The adsorption electrode 6 was formed by plating using a thickness of 0.6 μm. Forming a film of the adsorption electrode 6 as thin as possible leads to a reduction in unevenness of the adsorption surface of the electrostatic chuck. Other methods for forming the adsorption electrode 6 include vapor deposition and sputtering. The adsorption electrode 6 was formed on the entire surface of one surface of the upper layer 4 of the first insulating dielectric layer, and was then patterned into a fan-shaped and bipolar type by an etching process. Various other electrode shapes such as comb and concentric circles are possible. As a method for forming the adsorption electrode 6, it is possible to form the adsorption electrode 6 only at a necessary portion by applying a mask.
The upper layer 4 of the first insulating dielectric layer on which the adsorption electrode 6 is formed is adhered to the lower layer 3 of the first insulating dielectric layer having a thickness of 125 μm so as to sandwich the adsorption electrode 6. For this bonding, a 20 μm thermoplastic polyimide adhesive sheet (not shown) is bonded.
In the bonding step, a method of forming a laminated form while defoaming by controlling temperature and pressure in a vacuum generally called press lamination is used. Next, the first insulating dielectric layer including the adsorption electrode 6 completed as described above is bonded to the substrate 1 through the cushion layer 2. At this time, a potential supply portion to the adsorption electrode 6 is also formed at the same time. Wiring to the potential supply terminal 9 for supplying a potential from the power source 10 to the adsorption electrode 6 is performed, but the potential supply terminal 9 is not in contact with other parts in order to maintain electrical insulation in the electrostatic chuck. Arranged inside the potential supply insulating portion 8. The cushion layer 2 is a silicon-based elastic body and has a thickness of 500 μm. The reason for providing this layer is to increase the contact ratio between the wafer and the attracting surface of the electrostatic chuck. This is because the adsorption electrode 6 and the wafer are adsorbed by static electricity, so that if the layers below the adsorption electrode 6 and the substrate 1 are flexible, the adsorption surface 5a comes into close contact with the surface state of the wafer.
Finally, the second dielectric layer 5 is attached to the upper layer 4 of the first insulating dielectric layer. The second dielectric layer 5 was a 25 μm polyimide resin called Kapton (registered trademark of Toray DuPont Co., Ltd.) with a 25 μm silicon adhesive.
Thus, the electrostatic chuck 100 of this embodiment is completed.

Evaluation of the wafer cooling characteristics of the electrostatic chuck 100 according to this example was carried out by being mounted on a medium current ion implantation apparatus. The conditions were set by implanting a phosphorous monovalent ion beam (energy 150 keV, beam current 3 mA, dose 1 × 10 ¹⁵ / cm ² ) into a 300 mm diameter silicon wafer. The temperature was measured at five points (center, left and right, top and bottom) of the wafer implantation surface, and showed good cooling characteristics even when the adsorption voltage was relatively lower than before. For example, when the adsorption voltage is 1000 V, the wafer surface temperature is in the range of 54 to 65 ° C., and even when the adsorption voltage is half of 500 V, the wafer surface temperature is in the range of 76 to 87 ° C. The results were satisfactory.

Next, a second embodiment of the present invention will be described.
FIG. 2 is a schematic sectional view of an electrostatic chuck according to the second embodiment of the present invention.
In this embodiment, the first insulating dielectric layer used in the first embodiment described above is not a polyimide but a fluorosilicone material, and has a lower layer 3 of the first insulating dielectric layer. do not do.
In FIG. 2, the substrate 1 is made of a hard aluminum metal, and in the case of an electrostatic chuck for a wafer having a diameter of 300 mm, the substrate 1 has a diameter of 294 mm and a thickness of 10 mm.
A cooling water channel 7 for cooling the base 1 is formed inside the base 1. The reason for cooling is to cool a substrate such as a wafer that is attracted and held on the electrostatic chuck by heat conduction indirectly by cooling the substrate 1.
An upper layer 4 of the first insulating dielectric layer is prepared. A fluorosilicone rubber having a thickness of 200 μm and a diameter of 294 mm is prepared.
Next, the adsorption electrode 6 is formed on one surface of the upper layer 4 of the first insulating dielectric layer. The material of the adsorption electrode 6 is a 30 μm copper foil. The attracting electrode 6 is formed on the entire surface of one surface of the upper layer 4 of the first insulating dielectric layer by a press laminating method equivalent to that in Example 1 through a silicon adhesive, and is divided into 10 fan shapes by an etching process. Patterned to be bipolar. The upper layer 4 of the first insulating dielectric layer on which the adsorption electrode 6 is formed is bonded to the substrate 1 with a silicon adhesive via the cushion layer 2 so as to sandwich the adsorption electrode 6. The potential supply portion is simultaneously formed. Wiring to the potential supply terminal 9 for supplying a potential from the power source 10 to the adsorption electrode 6 is performed, but the potential supply terminal 9 is not in contact with other parts in order to maintain electrical insulation in the electrostatic chuck. Arranged inside the potential supply insulating portion 8. The cushion layer 2 is a silicon-based elastic body and has a thickness of 650 μm.
Finally, the second dielectric layer 5 is attached to the upper layer 4 of the first insulating dielectric layer. The second dielectric layer 5 was a 25 μm polyimide resin called Kapton (registered trademark of Toray DuPont Co., Ltd.) with a 25 μm silicon adhesive.
The electrostatic chuck 101 of Example 2 is completed.
Since other configurations, operations, and effects are the same as those in the first embodiment, description thereof is omitted.

Finally, a third embodiment of the present invention will be described.
The method for regenerating the adsorption surface 5a is as follows.
When the adsorption surface 5a is deteriorated due to damage or other reasons, the second dielectric layer 5 is peeled off from the upper layer 4 of the first insulating dielectric layer. Since the adsorbing surface 5a and the upper layer 4 of the first insulating dielectric layer are pasted with an adhesive, the adhesive is relatively easily damaged without damaging the upper layer 4 of the first insulating dielectric layer. It can be peeled off with the help of other solubilizers. After the second dielectric layer 5 is peeled off, the upper layer 4 of the first insulating dielectric layer is washed with an organic solvent or the like, and a new second dielectric layer 5 is adhered again to the adsorption surface. Play 5a. Even when the second dielectric layer is attached to the existing electrostatic chuck, the same procedure as described above can be used.
Since other configurations, operations, and effects are the same as those in the first and second embodiments, description thereof is omitted.

Claims (3)

In an electrostatic chuck having an attracting electrode inside a dielectric and attracting and holding a substrate by static electricity induced by a voltage applied to the attracting electrode, a second insulating dielectric layer having the attracting electrode is provided on a second insulating dielectric layer. The dielectric layer can be applied and peeled off, and the second dielectric layer can be replaced.
An electrostatic chuck characterized by that. The second dielectric layer is attached to the first insulating dielectric layer with a silicon-based adhesive.
The electrostatic chuck according to claim 1. The second dielectric layer is made of a material having higher flexibility than the first insulating dielectric layer, and is made of a polyimide resin having a Young's modulus of 2 to 6 GPa.
The electrostatic chuck according to claim 1, wherein the electrostatic chuck is characterized in that:

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