KR0170413B1 - Mount for supporting substrates and plasma processing apparatus using the same - Google Patents

Abstract

The wafer mounting table is disposed in the process chamber of the plasma etching apparatus. The periphery of the susceptor, which is the mounting base body, is formed in a bent shape with a large radius of curvature. An electrostatic sheet is disposed on the susceptor, and the seam folding extends downward in a bent shape so as to run away from the last portion of the semiconductor wafer, that is, along the bend circumference of the susceptor. The conductive film of the electrostatic chuck sheet is extended in the same direction by the shorter the horizontal component of the length of the seam fold. This increases the electrostatic and thermal bonding between the conductive film and the wafer.

Description

Mounting stage of substrate to be processed and plasma processing apparatus using the same

1 is a partial cross-sectional view showing a conventional wafer mounting table.

FIG. 2 is a partial cross-sectional view showing the Shumilray ray model used to calculate the graph shown in FIG.

3 is a graph showing the relationship between the transmissive amount of the wafer from the electroconductive chuck sheet of the electroconductive film and the temperature of the wafer.

4 is a cross-sectional view showing the overall configuration of a single wafer plasma etching apparatus according to an embodiment of the present invention.

FIG. 5 is an exploded perspective view showing the mounting table in the embodiment shown in FIG.

FIG. 6 is an enlarged fragmentary sectional view showing the mounting table in the embodiment shown in FIG.

7 is an enlarged fragmentary sectional view showing a modification of the mounting table.

8 is an enlarged partial sectional view showing another modification of the mounting table.

* Explanation of symbols for main parts of the drawings

2,22,102: wafer 4,20,20y, 106: electrostatic chuck sheet

10: reaction vessel 11a: outer support frame

11b: inner support frame 12: susceptor support

12a: cooling cover 12b, 12c: through hole

14,14y, 100: susceptor 14a: wafer placement unit

14b: flange portion 14c: circumference of the mounting surface

14yc: side 14d: through hole

16: introduction pipe 18: discharge pipe

20a, 20b: insulating polymer resin film

20c, 20yc: conductive film 20d, 20yd, 106a: rim

20e: through hole 24: insulated cable

26: electric supply rod 28: DC power

30: high frequency power supply 32: focus ring

34: upper electrode 35: small hole

36: gas supply pipe 38: exhaust pipe

39: exhaust pump 104: focus ring

108,110 polyimide resin film 112 conductive film

114: gap 116: circumference of the susceptor mounting surface

R: Excess Rx: Distance of last part

Ry: Horizontal component

TECHNICAL FIELD The present invention relates to a mounting table of a substrate to be processed and a plasma processing apparatus using the same, and more particularly, to an improvement of the mounting table of a semiconductor wafer.

In a single wafer type semiconductor processing apparatus, one semiconductor wafer is placed on a conductive base called a susceptor in a vacuum reaction vessel, and predetermined processing is performed on the surface of the wafer. In recent years, an electrostatic chuck type structure has been adopted in which a wafer is adsorbed and held on a susceptor with a constant power without using mechanical holding means such as a clamp.

The original one of this kind of electrostatic chuck is formed by oxidizing the surface of the susceptor to form an insulating film. A high voltage is applied to the susceptor, and the insulating film is polarized on the susceptor surface. As a result, static electricity is generated at the interface with the semiconductor wafer, and the wafer is adsorbed and held by the coulomb force. In this structure, sufficient polarization was not applied to the insulating film on the susceptor surface, and the electrostatic adsorption force was insufficient. Therefore, in recent years, the structure in which the electrostatic chuck sheet is provided on the susceptor has become mainstream.

Fig. 1 shows the structure of a recent electrostatic chuck having a wafer mounting table of a single wafer plasma etching apparatus. In this structure, the susceptor 100 is provided with a focus ring 104 for in-plane uniformity processing of the semiconductor wafer 102, and the electrostatic chuck sheet 106 is disposed at the top.

The electrostatic chuck sheet 106 overlaps a pair of polyimide resin films 108 and 110 and encapsulates a thin conductive film 112 such as a copper foil therein. The sheet 106 is formed in a circular shape in accordance with the upper surface (mounting surface) of the susceptor 100. The sheet 106 is formed with a plurality of through holes (corresponding to the holes 20e in FIG. 5), through which the inert gas, between the susceptor 100 and the wafer 102 and the sheet 106, He is supplied, for example, and the thermal conductivity between both members is secured.

The conductive film 112 of the sheet 106 is smaller in diameter than the polyimide resin films 108 and 110, and the rim 106a of the sheet is seam welded to both polyimide resin films 108 and 110. It is wealth. This seam seam 106a is inevitable from the structure of the electrostatic chuck sheet which encloses a conductive film between two overlapping films, but the conductive film 112 is exposed and short-circuited with the exterior (especially susceptor). It is responsible for the insulation function to prevent it.

The diameter of the wafer mounting surface of the susceptor 100 and the diameter of the sheet 106 are set smaller than the diameter of the wafer 102 as shown in FIG. This is to prevent reactive ions from entering only the surface of the wafer 102 and not from entering the wafer placing surface. For example, in the case of plasma etching, when reactive ions enter the mounting portion of the susceptor 100 in the plasma, the mounting surface is also etched at the incident portion, which is undesirable.

However, the problem described below arises in the wafer mounting stand of the structure mentioned above.

By making the diameter of the mounting surface of the susceptor 100 smaller than the diameter of the wafer 102, the outer periphery of the wafer 102 is pushed out to some extent (ra) out of the mounting surface of the susceptor 100. However, with respect to the conductive film 112 of the sheet 106, the wafer 102 is attached to the seam fold 106a of the sheet 106 as well as the portion ra which is pushed out from the mounting surface of the susceptor 100. The part in contact with it (rb) is also pushed out. Therefore, in the last part of the wafer 102 over the distance R which added both, the adsorption force from the electrically conductive film 112 of the sheet 106 becomes weak. For this reason, the thermal conductivity between the sheet 106 and the last part of the wafer 102 worsens, and the crack property of the wafer deteriorates. As described above, the seam seam 106a of the sheet 106 is inevitable and technical in both sides of sheet production and short circuit prevention, and there is a limit to shortening.

In addition, the focus ring 104 is fitted to the setter 100 so that the gap 114 becomes 0.1 to 0.3 mm in order to protect the susceptor 100 from plasma. However, when the voltage applied to the susceptor 100 is very high, or when the plasma concentration is very high, discharge occurs at the susceptor edge 116 and the susceptor 100 and the electrostatic chuck sheet 106 are disconnected. Destroy it.

It is therefore an object of the present invention to provide an adsorption holding force on a substrate to be processed, a mounting table of the substrate to improve the temperature uniformity of the substrate, and a plasma processing apparatus using the same.

Another object of the present invention is to provide a mounting table of a substrate to be prevented from discharge from a susceptor and a plasma processing apparatus using the same.

An apparatus for plasma processing a wafer-shaped substrate according to the present invention; A process chamber, exhaust pump means capable of setting the chamber in a high pressure reduction state, means for supplying a processing gas to be plasma into the chamber, means for converting the process gas into plasma, and supporting the substrate during plasma processing The mounting base body and the mounting base body having a convex shape and having a support surface facing the substrate, and a side surface formed to continuously and at an angle with respect to the support surface. And an electrostatic chuck sheet for adsorbing and holding the substrate at a constant power, and the electrostatic chuck sheet has a support surface of the mounting base body so that a figure extends on the side surface of the mounting base body. It covers and is provided.

In a preferable embodiment, the electrostatic chuck sheet is composed of a conductive film and two insulating resin films which are larger in size than the conductive film and sandwich the same. The resin film has a portion pushed out of the conductive film is bonded to each other, thereby forming the rim.

In the present invention, the rim of the electrostatic chuck sheet is bent or bent in the direction of running away from the last portion of the substrate to be processed, and overlaps the side of the mounting body, that is, the susceptor, or the bent or bent circumference. As a result, the radial length component of the seam fold of the electrostatic chuck sheet is shortened, and the edge portion of the conductive film of the electrostatic chuck sheet can be brought close to the edge portion of the substrate to be processed.

For this reason, the electrostatic adsorption force of the electrostatic chuck sheet with respect to the to-be-processed board | substrate increases, and the temperature difference between the last part of a to-be-processed board | substrate and a center part can be made small.

Moreover, when the peripheral part of the mounting surface of the susceptor is formed as a bending surface, and the rim of the electrostatic chuck sheet is formed as a bending surface so as to overlap the bending circumference of the susceptor, the electric field concentration to the peripheral part of the susceptor is prevented, Damage to the susceptor, burnout of the sheet, and insulation breakdown can be prevented.

In order to investigate the relationship between the excess amount of the wafer from the electrostatic chuck sheet of the electroconductive film and the temperature of the wafer, the temperature distribution of the wafer was calculated using the shumulation model shown in FIG.

The calculation conditions are as shown below.

150 mm in diameter of the wafer 2

Thermal Conductivity 150W / mK of Wafer 2

200 W input RF power to the wafer (2)

Seam fold length of the electrostatic chuck sheet 4 1.5mm

25 ° C uniform surface temperature of the electrostatic chuck sheet (4)

Supply gas He, P = 7,5 Torr between the surface of the wafer 2 and the sheet 4

Thermal Conductance between Wafer 2 and Sheet 4 Surface 34 x PW / m ² K

Based on the above conditions, the temperature distribution of the wafer 2 was calculated using the excess field R as 6, 4, 2, 1 mm, as shown in FIG. 3 as R 6, R 4, R 2, and R 1, respectively. A curve was obtained. In the calculation, since radiation and heat conduction from the wafer to the outside were small, they were ignored.

As shown in FIG. 3, it can be seen that the in-plane uniformity of the temperature of the wafer deteriorates as the excess amount R increases. In excess amount R = 6,4,2,1 mm, the temperature difference (DELTA) T between the center of a wafer and the position of 10 mm inside from an edge was 11.9 degreeC, 7.1 degreeC, 3.2 degreeC, and 1.6 degreeC, respectively.

In this invention, since the excess amount R from the electroconductive film of an electrostatic chuck sheet can be made substantially small, the in-plane uniformity of the temperature of a wafer can be improved.

EXAMPLE

In the single wafer type plasma etching apparatus shown in FIG. 4, an outer cylindrical frame and a conductive outer support frame 11a are formed integrally with the vessel 10 at the center of the bottom surface of the reaction vessel 10. And the insulating support frame 11b is fitted. In the support frame 11b, a cylindrical susceptor support 12 is disposed, and the susceptor 14 is attached by the bolt 15 on the susceptor support 12. The susceptor 14 and the susceptor support 12 are both made of a conductive metal such as aluminum. The cooling cover 12a is formed in the susceptor support 12, and the cooling liquid supplied into the cooling cover 12a through the introduction pipe 16 passes through the discharge pipe 18 and is discharged to the outside of the apparatus.

As shown in FIG. 5, the susceptor 14 is a disk body formed by six-integrating a thick wafer mounting portion 14a and a thin flange portion 14b, that is, the upper surface of the wafer placing portion 14a. As shown in the figure, the periphery 14c of the mounting surface is formed of a large bending surface having a radius of curvature. The susceptor support 12 and the susceptor 14 are formed with through holes 12c and 14d for supplying cooling heat exchange gases such as Ar, He, and O _{2 to the} back surface of the semiconductor wafer 22.

The electrostatic chuck sheet 20 is overlaid on the wafer mounting surface of the susceptor 14, and the wafer 22 is placed on the sheet 20. The mounting surface of the susceptor 14 and the diameter of the sheet 20 are set to be smaller than the diameter of the wafer 22. The sheet 20 is formed by enclosing a conductive film 20c such as copper foil between two insulating polymer resin films 20a and 20b, as specified in FIG. The rim 20d of the sheet 20 is formed in a curved surface with a large radius of curvature so as to overlap the peripheral portion 14c of the wafer placing surface. Also in this sheet 20, as shown in FIG. 5, a through hole 20e for supplying a cooling gas such as He or Ar to the back surface of the wafer 22 is formed.

As shown in FIG. 4, the conductive film 20c of the electrostatic chuck sheet 20 includes conductive wires covered by the insulated cable 24 embedded in the susceptor 14 and through-holes of the susceptor support 12. It is connected to the DC power supply 28 via the electricity supply rod 26 inserted in 12b. In addition, a high frequency power supply 30 is connected to the susceptor support 12.

On the flange portion 14b of the susceptor 14, an annular focus ring 32 that surrounds the wafer 22 is disposed. The focus ring 32 is made of an insulating material or a conductive material such as SiC and C, and is used to uniformly process the wafer 22. The upper surfaces of the focus ring 32 and the wafer 22 become uniform.

The upper electrode 34 is disposed above the susceptor 14. The upper electrode 34 is supplied with an etching gas such as plasma gas, for example, CF ₄ , through a gas supply pipe. The etching gas is blown downward from the plurality of small holes 35 formed in the electrode surface of the upper electrode 34.

The upper electrode 34 is grounded, and high frequency power, for example, 380 KHz, 1.5 KW from the high frequency power supply 30 is applied between the upper electrode 34 and the susceptor (lower electrode) 14. Plasma is generated under the upper electrode 34 by the high frequency power, and reactive ions generated by the plasma are incident perpendicularly to the surface of the wafer 22 to cause a chemical reaction with the workpiece on the surface of the wafer, and etching is performed. Lose. By etching, the raw reaction product is discharged by the exhaust pump 39 through the exhaust pipe 38 connected to the lower side wall of the reaction vessel 10. The reaction vessel 10 is set to a high pressure reduction state necessary for plasma treatment by the exhaust pump 39.

The high voltage DC voltage, for example 2.0 KV, is applied from the DC power supply 28 to the conductive film 20c of the electrostatic chuck sheet 20. Thereby, the static electricity by polarization generate | occur | produces on the surface of the sheet | seat 20, and the wafer 22 is attracted to the sheet | seat 20 by the coolon force.

As indicated in FIG. 6, the seam fold 20d of the electrostatic chuck sheet 20 is formed as following the bend circumference 14c of the susceptor 14. In other words, the rim 20d extends downward in a bent shape so as to escape from the last of the wafer 22.

Therefore, even if the length of the seam fold 20d itself is the same as the conventional one, the horizontal component of the length is shortened. For this reason, the conductive film 20c of the sheet 20 can be formed so as to approach the edge portion of the wafer 22 as much as the horizontal component of the length of the seam fold 20d is shortened.

Therefore, the distance Rx of the marginal portion of the wafer 22 pushed out of the conductive film 20c of the electrostatic chuck sheet 20 is the last portion distance R of the conventional electrostatic chuck shown in FIG. Shorter than

As a result, the electrostatic and thermal coupling between the conductive film 20c of the electrostatic chuck sheet 20 and the wafer 22 increases, and the electrostatic adsorption force on the last portion of the wafer 22 increases, As described along with FIG. 3, the temperature difference between the last portion of the wafer 22 and the central portion of the wafer 22 becomes small.

As in the plasma etching apparatus, when the high frequency power is very high, for example, 380 KHz, 1.5 KW, or when the plasma concentration is very high, in the conventional structure as shown in FIG. The electric field concentrates on the circumference 116 to cause discharge, which may damage the susceptor 14 and cause a breakdown. However, according to the configuration in which the circumferential portion 14c of the mounting surface of the susceptor 14 is formed into a bent surface having a large radius of curvature, as in the present embodiment shown in FIG. 6, the circumferential portion of the mounting surface of the susceptor There is no concern for the electric field to concentrate on. In the conventional structure of FIG. 1, the periphery part 116 of the susceptor mounting surface is formed in substantially right angle with curvature radius only 0.8 mm. In contrast, the radius of curvature of the susceptor placing surface shown in FIG. 6 and the rim 20d of the electrostatic chuck sheet 20 are 3.0 mm in curvature.

In addition, in this embodiment, the seam fold 20d of the electrostatic chuck sheet 20 is formed in the same bent surface to cover the bend circumference portion 14c of the susceptor 14, so that this seam fold 20d is provided. By the insulation breakdown voltage of, the concentration of the electric field on the susceptor circumference can be prevented more effectively. For example, when the aramid resins before the crystallization having a thickness of 50 mm are used as the films 20a and 20b of the sheet 20, since the dielectric breakdown voltage of the copper resin is 230 KV / mm, the rim 20d of this sheet is about 2.3. Insulation breakdown voltage of KV / mm can be obtained.

7 shows a modification of the wafer mounting table according to the present invention. In this modification, the periphery of the mounting surface of the susceptor 14y is formed in each shape, and the seam fold 20yd of the electrostatic chuck sheet 20y is folded to overlap the side surface 14yc of the susceptor 14y. It is bent and processed. According to this structure, the seam fold 20yd of the electrostatic chuck sheet 20y extends downward in the substantially vertical direction, and the horizontal component Ry of the length becomes quite short. As a result, the diameter of the conductive film 20yc of the electrostatic chuck sheet 20 can be further increased, and the electrostatic and thermal coupling between the conductive film 20yc and the last portion of the wafer 22 can be further increased. Can be.

In addition, even if the periphery of the susceptor mounting base is not formed to an angle substantially close to the right angle as in this modified example, it is formed at an angle of about 120 degrees at an angle, so that the rim of the electrostatic chuck sheet 20 is about 120 degrees in accordance with the angle. It may be bent and processed by bending.

In addition, when the conductive film of the electrostatic chuck sheet extends to the bent portion, the electrostatic and thermal coupling between the conductive film and the last portion of the wafer can be further increased.

In this way, the electrostatic chuck sheet 20 has a three-dimensional shape that is bent or bent in the seam fold 20d. As a material of the polymer films 20a and 20b for this purpose, aramid resin or polyimide resin before crystallization is suitable. The aramid resin before crystallization is a swelling gel film before drying and heat treatment, and is not subjected to crystallization of the polymer, so that the die draw molding can be performed. Therefore, when this resin is used for the electrostatic chuck sheet, the rim can be bent or bent at any curvature radius or angle.

8 shows another modification of the wafer mounting base according to the present invention.

As shown in this modification, the circumferential portion 14c of the mounting surface of the susceptor 14 is bent even when the electrostatic chuck sheet is omitted and the wafer 22 is directly placed on the mounting surface of the susceptor 14. By forming it in a shape, the electric field concentration to the circumference part 14c can be eliminated, and the breakage of the susceptor 14 can be prevented.

In addition, although the above-described embodiment relates to a plasma etching apparatus, the mounting table according to the present invention is applicable to other processing apparatuses such as ashing apparatus, CVD apparatus, and the like.

Claims (14)

When processing a wafer-shaped substrate in the process chamber, a mounting table for placing the substrate, the support surface facing the substrate in a convex shape and the side formed to be continuous and angled with respect to the support surface A support body of the mounting base body, which is sandwiched between the mounting base body and the substrate and sucks and holds the substrate at a constant power, and covers a support surface of the mounting body so that a figure extends to the side of the mounting body. A mounting table of a substrate to be processed, comprising an electrostatic chuck sheet. The mounting table according to claim 1, wherein the supporting surface and the side surface (14yc) of the mounting table main body are connected by a bending surface. The insulating electrostatic chuck sheet (2) according to claim 1, wherein the electrostatic chuck sheet (4) has a larger dimension than the conductive films (20c) and (20yc) and the conductive films (20c) and (20yc). 20b), wherein the resin film is bonded to each other, wherein the portions pushed out from the conductive films (20c) (20yc) form the rims (20d) (20yd). 4. The mounting table of a to-be-processed substrate according to claim 3, wherein the resin film is made of aramid resin or polyimide resin before crystallization. 2. The focus ring 32 is disposed around the mounting base body and the electrostatic chuck sheet 4, and the upper surface of the ring 32 is substantially the upper surface of the substrate mounted on the sheet. A mounting table of a substrate to be processed, characterized in that uniformity. An apparatus for plasma processing a wafer-like substrate, comprising: a process chamber, exhaust pump means (39) capable of setting the chamber in a high pressure reduction state, means (36) for supplying a processing gas of plasma into the chamber; A mounting table main body having means for converting the processing gas into plasma, a support surface which supports the substrate during plasma processing, forms a convex shape and faces the substrate, and a side surface that is formed continuously and at an angle with respect to the support surface. And an electrostatic chuck sheet sandwiched between the mounting body and the substrate, the electrostatic chuck sheet covering the supporting surface of the mounting body so that the substrate is adsorbed and held at an electrostatic force and the figure extends to the side of the mounting body. Plasma processing apparatus, characterized in that. The plasma processing apparatus according to claim 6, wherein the support surface and the side surface of the mounting base body are connected by a bending surface. 7. The electrostatic chuck sheet according to claim 6, wherein the electrostatic chuck sheet is composed of conductive films 20c and 20yc, and two insulating resin films 20a and 20b which are larger in size than the conductive film and sandwich the same. And the portions pushed out from the conductive films 20c and 20yc are bonded to each other to form the rim. The plasma processing apparatus according to claim 8, wherein the resin film is made of aramid resin or polyimide resin before crystallization. The method of claim 6, wherein the focus ring 32 is disposed around the mounting body and the electrostatic chuck sheet, and the upper surface of the ring 32 is substantially uniform with the upper surface of the substrate mounted on the sheet. Plasma processing apparatus characterized by. An apparatus for plasma processing a wafer-like substrate, comprising: a process chamber, exhaust pump means capable of setting the chamber in a high pressure reduction state, means for supplying a process gas to be plasma into the chamber, and plasma processing of the process gas; A mounting table having means, a support surface for supporting the substrate during plasma processing, forming a convex shape and opposing the substrate, and a side surface formed continuously and at an angle through a curved surface with respect to the support surface; And a focus ring disposed around the mounting table and having an upper surface substantially uniform with an upper surface of the substrate mounted on the mounting target. The mounting table main body according to claim 11, wherein the mounting table has a convex shape and a support surface facing the substrate, and a side surface formed continuously and at an angle through the bending surface with respect to the support surface; A plasma between the main body and the substrate, the electrostatic chuck sheet being provided on the support surface of the mounting base body so that the substrate is attracted and held by the electrostatic force and the figure extends to the side of the mounting base body. Processing unit. The electrostatic chuck sheet according to claim 12, wherein the electrostatic chuck sheet is made of a conductive film and two insulating resin films larger in size than the conductive film and sandwiched therebetween, and the resin film is bonded to each other by a portion protruding from the conductive film. And forming the rim. The plasma processing apparatus according to claim 13, wherein the resin film is made of aramid resin or polyimide resin before crystallization.