JPH08316299A - Electrostatic chuck - Google Patents

Abstract

PURPOSE: To prevent turn-round of plasma discharge by a method wherein a metal exposure part of a junction part side face is enclosed and screened with an insulator ring integrally attached to a periphery of an electrostatic attraction mechanism part. CONSTITUTION: A dielectric ceramic 1 and a skirt portion are integrally processed from ceramic of which main components are alumina, silicon nitride, silicon carbide or the like, and a layer portion of a dielectric is processed to be in a thickness 0.1 to 2mm. A pedestal 3 is a metal excellent in heat conductivity such as Al, Cu, etc., and soldered across an intermediate layer 2 of which a coefficient of thermal expansion is 4 to 8×10<-6> , and which is composed of Mo, titanium, niobium, tantalum, WC-Co, 42%Ni alloy, etc. A soldered layer 4 serves as an electrode 5 as it is. Thus, it is possible to completely prevent damages in a metal of the pedestal 3 and an electrode junction part due to permeation of plasma gas, and also a surface of the dielectric ceramic 1 is extremely effectively cooled to obtain an electrostatic chuck excellent in etching characteristics and film formation characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck, and more particularly to a structure which is excellent in cooling characteristics of a dielectric ceramic surface and can prevent abnormal wraparound of plasma discharge.

[0002]

2. Description of the Related Art Electrostatic chucks are often used for adsorption and fixation when plasma processing semiconductor substrates. A dielectric ceramic disk is adhered on a pedestal that is structurally excellent in heat conduction, and the back surface of the pedestal is usually cooled or heated to a constant temperature, except in special cases. The pedestal is made of a material with excellent heat conduction such as aluminum or aluminum nitride, and the pedestal and the ceramic are usually bonded together with an organic adhesive. It is difficult to keep the treated substrate adsorbed on the body ceramic surface at a uniform temperature. Therefore, the present inventors have succeeded in greatly improving the heat transfer ability of the joint by first metallurgically joining the pedestal and the ceramic. At this time, the electrodes were joined at the same time as the metallurgical joining by joining the electrodes in the pattern shape (Japanese Patent Application No. 6-
240492). As a result, the temperature control of the treated substrate became uniform, and the etching characteristics and film forming characteristics were significantly improved. However, here, during the operation, there was a problem that the plasma discharge went around to the exposed portion of the brazing material in the gap of the brazing portion.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a new structure for the above-mentioned brazing type electrostatic chuck capable of solving the problem of plasma discharge wraparound. Is intended to be provided.

[0004]

The above problems can be solved by the following means. That is, 1. In an electrostatic chuck having a structure in which an electrostatic chucking mechanism is directly or indirectly brazed on a pedestal, an exposed metal part on the side surface of the bonding part is integrally attached around the electrostatic chucking mechanism. An electrostatic chuck characterized by being surrounded and shielded by a body ring. 2. In an electrostatic chuck having a structure in which an electrostatic chucking mechanism is directly or indirectly brazed on a pedestal, an exposed metal part on the side surface of the bonding part is integrally attached around the electrostatic chucking mechanism. Surrounded by a body ring, shielded,
A step-like step is provided on the outer circumference of the ring, and when the electrode cover is placed on the ring and set, the horizontal surface of the step of the ring is further outside the inner circumference of the electrode cover. Characteristic electrostatic chuck. 3. The insulator ring is integrally formed of the same material on the dielectric ceramic plate of the electrostatic attraction mechanism section.
2. The electrostatic chuck according to 2.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a metal or ceramic material having excellent heat conduction characteristics as a pedestal material, and the electrostatic adsorption mechanism is directly or indirectly brazed to this pedestal. .

There is at least a gap corresponding to the thickness of the brazing material in the brazing part sandwiched between the electrostatic adsorption mechanism part and the pedestal,
This part is exposed to the outside, and plasma discharge may wrap around here. An insulator ring attached around the electrostatic adsorption mechanism hides this gap and prevents the plasma discharge from wrapping around. Also, at this time, a structure is provided in which a step-like step is provided on the outer peripheral portion of the insulator ring, and when the electrode cover is placed and set on the ring, the horizontal surface of the ring is further outside the inner peripheral surface of the electrode cover, that is, If the structure is such that the outer diameter of the horizontal surface of the step formed on the ring is larger than the diameter of the inner peripheral surface of the electrode cover, the plasma will go straight from above and get lost in the minute gap between the ring and the electrode cover. Collides with the stepped surface of the ring and is reflected, and the wraparound of the plasma is completely blocked. Further, the surface on which the electrode cover is placed does not necessarily have to be the stepped surface, and it may be placed on another surface. The point is that the horizontal plane of this step has only to reflect the plasma traveling straight.

The shape of the insulator ring is like wearing a sickle around the electrostatic attraction mechanism portion, and it is better to extend it down to at least the portion where the gap at the joint portion is hidden. The insulator ring does not have to be made entirely of the same insulating ceramic material. At least the surface exposed to the outside should be an insulator. Since it is often costly to integrally manufacture the rotary hook portion of an insulator ceramic or a dielectric ceramic, the disk and surrounding rotary hook portion are made of metal, and the insulator ceramic (dielectric Body ceramic) (which may be body ceramic) to form the insulating ring portion. Alternatively, a structure may be adopted in which a dielectric ceramic disk is bonded onto a disk and the rotary hook is covered with an insulating ceramic (or a dielectric ceramic). Alternatively, the disc and the surrounding frame are formed of metal, the surface is covered with an insulating ceramic, the dielectric electrode layer is further formed on the insulating ceramic, and the dielectric ceramic layer is further formed on the electrode layer. It may have a structure that does. Alternatively, only the hook portion may be formed of metal, and the exposed surface and the joint portion may be covered with an insulating ceramic.

Here, the electrostatic attraction mechanism section is a generic term for a structure having a dielectric ceramic and a structure including an electrostatic induction electrode formed on the back surface of the ceramic as a main section. That is, in the single-pole type electrostatic chuck, a combination of a dielectric ceramic and an electrostatic induction electrode formed on the back surface of the ceramic, or a ceramic insulating plate for insulating the back surface of the electrode was combined. The structure is the main part, and in the bipolar system, the main part is the structure consisting of a dielectric ceramic, an electrostatic induction electrode formed on the back surface of this ceramic, and a ceramic insulating plate lining the back surface of this electrode. The structure serves as the adsorption mechanism.

As described above, the insulator ring may be integrally made of the same material as the dielectric ceramic portion of the electrostatic attraction mechanism section, or integrally made of the same material as the ceramic insulating plate. May be. Alternatively, the same material or different materials may be separately formed and mechanically fitted or joined. Alternatively, the structure may be such that a metal is covered with an insulator. In the case of joining, it is preferable to adhere with an insulating or plasma-resistant organic or inorganic adhesive, especially an inorganic adhesive. As the material of the surface portion of the insulator ring, any ceramic can be used as long as it is a ceramic material that is insulative and plasma resistant and is not harmful to the semiconductor.

The dielectric ceramic is a sintered body of the dielectric ceramic, or a film of the dielectric ceramic, that is, a film of the dielectric ceramic formed by thermal spraying, or a film formed by thin film processing such as sputtering or CVD. Alternatively, any one formed by another film forming process can be selected. Here, the dielectric ceramics are not limited to ceramics having a particularly high dielectric constant. In view of the phenomenon that the attraction force increases even if the thickness of the ordinary electrical insulating ceramic is reduced, the general electrical insulating ceramics are included in the category of the “dielectric ceramic” in the present invention. Insulator ceramics such as high dielectric constant ceramics such as alumina titanate and barium titanate, silicon nitride, aluminum nitride, alumina, sapphire, silicon carbide, and diamond formed into a film are included in this category.

When the electrostatic attraction mechanism section and the pedestal are brazed, the difference in thermal expansion between the joining surface material of the attraction mechanism section and the pedestal material becomes a problem. When the pedestal material is metal and the joining surface material of the adsorption mechanism is ceramic, the ceramics on the joining surface are often destroyed by thermal stress when directly brazed. Especially in the case of aluminum, the ceramic material is almost cracked. In such a case, it is advisable to insert a single intermediate layer or a plurality of intermediate layers into the joint to reduce the thermal stress. The term "indirect joining" of the present invention refers to the case where an intermediate layer is inserted into this joining portion to join. Any metal or ceramic material can be used as the intermediate layer. If the pedestal material is copper or aluminum and the ceramic is an alumina-based material or a material containing these as the main components, that is, the coefficient of thermal expansion is 7 to 8
× For ^{10 -6,} a thermal expansion coefficient of 4 to 12 × ^{10 -6} material, for example, W, Mo, Nb, Cr , 42% Ni alloy, 42Ni-6Cr, Ti, Ni , WC-Co cemented carbide, TiC-Ni cermet, carbon steel, special steel, and composite materials such as W-Cu, W-AL, Mo-Cu, and Mo-AL can be appropriately used. Especially 4-6 × 10 ⁻⁶
Having a coefficient of thermal expansion of 42% Ni alloy, 4
2% Ni-6% Cr alloy, Mo, W, or alloys containing these as main components can be preferably used. If the ceramic is silicon carbide, aluminum nitride, or a material containing these as the main components, that is, the coefficient of thermal expansion is 4 to 5
× For ^{10 -6,} a thermal expansion coefficient of 3 to 7 × ^{10 -6} material, for example, W, Mo, Nb, Cr , 42% Ni alloy, WC-Co cemented carbide, TiC-Ni cermet further W-Cu , W-AL, Mo-Cu, Mo-AL, and other composite materials can be used as appropriate. Especially 4-6 × 10
Kovar, 42% Ni alloy, 42% Ni-6% Cr alloy, Mo, W, or alloys containing these as the main components, which have a coefficient of thermal expansion of ⁻⁶ , can be preferably used.

When a metal / ceramic or metal / metal composite material is used as the pedestal material to reduce the coefficient of thermal expansion of the pedestal portion, it is effective in stress relaxation. Examples of the composite material include ceramics such as silicon carbide and aluminum nitride, or aluminum and aluminum alloys (Al-Si, Al-T) in porous materials of low expansion metals such as Mo, W, Invar and Amber.
(i alloy, etc.), a material impregnated with a metal having a high thermal conductivity such as copper, or a material obtained by mixing and sintering these powders is suitable. The linear expansion coefficient of these materials is 4 to 8 × 10.
^-6 is suitable for joining with a material such as silicon carbide, aluminum nitride or alumina.

In the electrostatic chuck, an electrode is always formed on the back side of the dielectric ceramic. The electrode is formed by metallizing the back side of the ceramic, but in the present invention, the brazing metal layer at the joint may be used as it is as an electrode. That is, in the monopolar system, the electrostatic adsorption mechanism is a combination of only dielectric ceramic and electrodes,
When a metal material is used for the intermediate layer and the ceramic and the intermediate layer and the intermediate layer and the pedestal are brazed, the brazing material layer, the intermediate layer, and the pedestal portion all become electrodes. Further, when the ceramic and the pedestal are brazed without the intermediate layer, the brazing material layer, the pedestal part, and all become electrodes. In the bipolar method, when the dielectric ceramic and the ceramic insulator are brazed to the pattern shape of the electrode, the brazing material layer becomes the electrode as it is.

In the case of brazing the electrostatic adsorption mechanism and the base material, or brazing in the electrostatic adsorption mechanism, the joint may be metallized in advance and then brazed, or the ceramic fusion bonding material may be used. You may braze directly with a brazing material. For the metallization, all ordinary metallizing methods such as plating, sputtering, paste baking, and fusion of active metal can be applied. In the case of direct brazing, so-called active metal brazing material can be appropriately used. The main components of the active metal brazing material are Cu, Ag, Au, Ni, Co, AL, Si, S
It is an alloy containing a trace amount to several percent of an active metal in an alloy containing a metal component having a low vapor pressure such as n and In. At this time, as the active metal, Ti, Zr, Nb, Ta, V, and other Ti group and V group elements, Cr, Mn, Y, AL, and the like, all of which are normally used for this purpose, can be used. .

Next, an embodiment will be described with reference to the drawings. FIG.
[FIG. 3] is an explanatory view of a case where a rotary hook portion (insulator ring) is formed of the same material as a dielectric ceramic in a monopolar electrostatic chuck. FIG. 2 is an explanatory diagram of a case where the hook portion (insulator ring) and the dielectric ceramic are formed of different materials. FIG.
[FIG. 4] is an explanatory view of a case where a hook-shaped portion (insulator ring) and a dielectric ceramic are formed of different materials and integrally sintered. FIG. 4 is an explanatory diagram of a case where the hook portion (insulator ring) is made of another material and is joined to the suction mechanism body. FIG. 5 shows an example of a bipolar type in which the hook portion (insulator ring) is made of the same material as the dielectric ceramic, and the pedestal is made of the insulating ceramic. Fig. 6 shows an example of a bipolar type, in which the hook portion (insulator ring) and the dielectric ceramic are the same material, and the pedestal is metal. FIG. 7 is an example of a bipolar type, in which the hook portion (insulator ring) and the dielectric ceramic are different materials and the pedestal is metal. FIG. 8 is an example of a hook having a laminated structure of a metal base material and an insulating film. FIG. 9 shows an example in which a dielectric electrode and a dielectric ceramic are formed by a film forming method. 10 and 11 are explanatory views of the structure of the portion of the lift pin hole. In FIG. 1, the dielectric ceramic 1 and the rotary hook portion (insulator ring) are integrally processed from a ceramic containing alumina, silicon nitride, silicon carbide or the like as a main component, and the dielectric layer portion is 0. It is processed into a thickness of 1 to 2 mm. The pedestal 3 is a metal having good thermal conductivity such as aluminum or copper, and is formed of the intermediate layer 2 having a thermal expansion coefficient of 4 to 8 × 10 ⁻⁶ such as Mo, titanium, niobium, tantalum, WC-Co, or 42% Ni alloy. It is brazed in between. The brazing layer 4 also serves as the dielectric electrode 5 as it is. FIG. 2 shows a structure in which the insulator ceramic 6 forms a hook portion (insulator ring), the monopolar electrode 5 is formed on the insulator ceramic, and the dielectric ceramic 1 is attached on the electrode. . An insulating material is filled between the dielectric ceramic 1 and the insulating ceramic 6 (a gap where the electrode exists) to completely fill the gap. Insulator ceramic 6
The pedestal 3 and the pedestal 3 are brazed with the intermediate layer 2 in between, as in the case of FIG. FIG. 3 shows a structure in which a dielectric ceramic portion 1 forming an upper layer of an electrode, an electrode layer 5, and an insulating ceramic layer 6 forming a lower layer are integrally sintered. The electrodes are formed by printing a tungsten paste or the like, sintering it, and bonding it. In FIG. 4, the hook portion is formed of an insulating sleeve 7, and this is joined with an inorganic adhesive or the like around an electrostatic attraction body having a structure in which the dielectric ceramic 1, the insulating ceramic 6, and the electrode 5 are integrally sintered. It is a structure. FIG. 5 shows a bipolar structure in which the pedestal 3 is an insulator ceramic, and the brazing metal layer is in the shape of an electrode.
Join. FIG. 6 shows the structure of FIG. 5, in which the pedestal 3 is made of metal, and in this case, the electrically insulating ceramic intermediate layer 2 is inserted and joined between the electrode 5 and the pedestal 3. FIG. 7 shows a bipolar structure in which the dielectric ceramic 1 and the rotary hook material (insulator ceramic 6) are different materials. The bipolar is formed between the dielectric ceramic and the hook material. Insulator ceramic 6
The pedestal 3 and the pedestal 3 are joined together with the intermediate layer 4 interposed therebetween. FIG.
Is a metal disk having a rotary hook with a dielectric ceramic layer coated on its outer surface by a film-forming method such as thermal spraying, sputtering, CVD, sol-gel method, or ceramic paste coating baking. Is. The metal disk serves not only as the electrode 5 but also as an intermediate layer for buffering stress when joining with the pedestal. At least the portion where the metal surface is exposed to the outside is essential for the portion that covers the insulating film, and it is more preferable that the bottom surface of the hook portion shown in the figure, and more preferably, the inner peripheral surface of the hook, should also be covered.
In FIG. 9, an electrode 5 is formed by thermal spraying, sputtering, or the like on the insulating ceramic 6 in the hook portion by a film forming method, and a layer of the dielectric ceramic 1 is also formed on the electrode 5 by a film forming method. 10 and 11 show a structure in which a hook 9 is formed so that plasma is not inserted from the lift pin hole. FIG. 10 shows the same material as the dielectric ceramic 1 integrally processed, and FIG. 11 shows the separately processed hook 9 inserted into the dielectric ceramic portion as shown in FIG. 1 to 11 are representative embodiments of the present invention, and it is a matter of course that the present invention is not limited to this example. Further, it is also of course held that the intermediate layer described in this example may be unnecessary if the material of which the thermal expansion characteristic of the pedestal material is similar to the material of the joint portion of the electrostatic attraction mechanism portion is unnecessary. Also,
In the present invention, the dielectric ceramic, the intermediate layer, the pedestal, or the dielectric ceramic and the pedestal are all brazed, but if only the plasma is prevented from wrapping around, the organic adhesive can sufficiently serve the purpose. You can As the organic adhesive, an epoxy adhesive, a silicone adhesive or the like is particularly suitable.

[0016]

【Example】

Example 1 Structure shown in FIG. 12 Dielectric ceramic: SiC-based dielectric ceramic (φ150 × 2t) having the shape shown in FIG. 12 was used. The electrodes were metallized by applying Si-20Ti powder on the back surface of a unipolar dielectric ceramic and heating in vacuum (2 × 10 ⁻⁵ Torr) at 1450 ° C. for 5 minutes. The metallization thickness is about 10 microns. The metallized surface was further plated with Ni. Pedestal: Aluminum was used to form the shape shown in FIG. The joint surface is Ni-plated. Middle layer: A Mo plate with a thickness of 2 mm and φ150 is used. Both sides of Mo are plated with Ni. The dielectric ceramic and the intermediate layer and the intermediate layer and the pedestal were joined so as to be hidden by the hook portion of the dielectric ceramic as shown in the figure. A low melting point In solder was used for the brazing material to bond the solder. As a result, cracking and peeling were not observed at the joint. Usage status DC voltage (700V) was applied to the pedestal to electrostatically adsorb the silicon wafer. It was actually used for the plasma etching process of a silicon wafer. No abnormal discharge of plasma was observed. After testing for a total of 5,000 hours, there was no trace of plasma entering the gap between the ceramic electrode cover and the dielectric ceramic. In addition, this structure is much better cooled than the one in which the dielectric ceramic and the pedestal are bonded together with an adhesive, and depending on the operating conditions, it is about 30-
It was confirmed that the temperature of the ceramic surface decreased by about 50 ° C.

Example 2 Structure shown in FIG. 13 Dielectric ceramic: Alumina-titania ceramic (φ100 × 0.2 mmt) having the shape shown in FIG. 13 was used.
The electrode is a monopolar dielectric ceramic with Ti sputtering on the back surface and Ni sputtering on Ti. Electroless Ni plating (10 micron) on Ni sputter pedestal: Aluminum was used to form the shape shown in FIG. The joint surface is Ni-plated. Intermediate layer: 42% Ni with a thickness of 3 mm and φ100
Uses alloy plate. The dielectric ceramic and the intermediate layer and the intermediate layer and the pedestal were joined so as to be hidden by the hook portion of the dielectric ceramic as shown in the figure. Sn-Ag solder is used for the brazing material. As a result, cracking and peeling were not observed at the joint. In actual use, the bottom of the pedestal was covered with a cover (alumina) as shown in the figure to cover and hide the exposed part. DC voltage (800 V) was applied to the pedestal to electrostatically adsorb the silicon wafer. It was actually used for the plasma etching process of a silicon wafer. No abnormal discharge of plasma was observed. After conducting a test for a total of 100 hours, there was no trace of plasma intrusion inside.

Example 3 Dielectric ceramic: Aluminum nitride (φ100 × 0.2 mmt) having the shape shown in FIG. 5 was used. The electrode is a bipolar pedestal: aluminum nitride ceramic
It processed into the shape shown in. The dielectric ceramic and the pedestal are brazed in a bipolar pattern with Ag-Cu-3% Ti alloy. As a result, cracking and peeling were not observed at the joint. Usage status DC voltage (800V) was applied to the pedestal and the silicon wafer could be electrostatically adsorbed. It was actually used for the plasma etching process of a silicon wafer. Abnormal plasma discharge was not observed at all even after testing for a total of 100 hours.

Example 4 Dielectric ceramic: shape shown in FIG. 8 A 2 mm thick Ni plate was used to form a metal electrode (φ100) having a shape shown in FIG. 8 having a hook. The surface of the dielectric ceramic was made of alumina / titania dielectric ceramic. Two
mm spraying. The electrode was monopolar pedestal: aluminum and processed into the shape shown in FIG. The joint surface is Ni-plated. Except for the joints, insulation treatment is performed by alumina spraying. The dielectric ceramic and pedestal are joined with In alloy solder. As a result, cracking and peeling were not observed at the joint. Usage status DC voltage (800V) was applied to the pedestal and the silicon wafer could be electrostatically adsorbed. It was actually used for the plasma etching process of a silicon wafer. Abnormal plasma discharge was not observed at all even after testing for a total of 100 hours.

[0020]

As described above in detail, the present invention can completely prevent damage to the pedestal metal and the electrode joint portion due to the penetration of plasma gas, and at the same time, the ceramic surface is cooled very effectively. However, the etching characteristics and the film forming characteristics have extremely excellent characteristics, and make a great contribution to the improvement of the quality of semiconductor substrate processing.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a case where a hook portion (insulator ring) is formed of the same material as a dielectric ceramic in a monopolar electrostatic chuck.

FIG. 2 is an explanatory view of a case where a hook portion (insulator ring) and a dielectric ceramic are formed of different materials.

FIG. 3 is an explanatory view of a case where a rotary hook portion (insulator ring) and a dielectric ceramic are made of different materials and integrally sintered.

FIG. 4 is an explanatory view of a case where the hook portion (insulator ring) is formed of another material and is joined to the suction mechanism body.

FIG. 5 is a bipolar type and has a hook portion (insulator ring).
Is made of the same material as the dielectric ceramic, and the pedestal is an insulator ceramic.

FIG. 6 is an example of a bipolar type, in which a hook part (insulator ring) and a dielectric ceramic are the same material and a pedestal is a metal.

FIG. 7 is a bipolar type, a hook part (insulator ring).
An example in which the dielectric ceramic is a different material and the pedestal is a metal.

FIG. 8 is an example of a hook having a laminated structure of a metal base material and an insulating film.

FIG. 9 is an example in which a dielectric electrode and a dielectric ceramic are formed by a film forming method.

FIG. 10 is an explanatory diagram of a structure of a lift pin hole portion.

FIG. 11 is an explanatory diagram of a structure of a lift pin hole portion.

FIG. 12 is a view for explaining the structure of the embodiment in FIG.

FIG. 13 is a drawing for explaining the structure of the embodiment in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Dielectric ceramic 2 ... Intermediate layer 3 ... Pedestal 4 ... Layer with brazing 5 ... Electrode 6 ... Insulator ceramic 7 ... Insulation sleeve 8 ... Lift pin hole 9 ... Hama

Claims (3)

[Claims] 1. In an electrostatic chuck having a structure in which an electrostatic chucking mechanism is directly or indirectly brazed on a pedestal, a metal exposed part on the side surface of the bonding part is integrated around the electrostatic chucking mechanism. An electrostatic chuck characterized in that it is surrounded and shielded by an insulator ring that has been attached. 2. An electrostatic chuck having a structure in which an electrostatic chucking mechanism is directly or indirectly brazed on a pedestal, and a metal exposed portion on a side surface of the bonding portion is integrally formed around the electrostatic chucking mechanism. It is surrounded and shielded by an insulator ring that is attached dynamically, and when a step-like step is provided on the outer periphery of the ring and the electrode cover is placed on the ring and set, the horizontal surface of the step of the ring is the electrode cover. An electrostatic chuck characterized by having a structure such that it is located further outside than the inner peripheral surface. 3. The electrostatic chuck according to claim 1, wherein the insulator ring is integrally formed on the dielectric ceramic plate of the electrostatic attraction mechanism portion with the same material.