JPH06275708A - Electrostatic chuck - Google Patents

Abstract

PURPOSE:To provide an electrostatic chuck in which peeling of adhered parts of a susceptor and an insulating film or a resistor layer and the film due to change in thermal expansions or contractions of the susceptor and the layer can be suppressed. CONSTITUTION:An electrostatic chuck for attracting to hold an element 2 to be attracted at a mount surface of a susceptor 10 by an electrostatic force comprises a resistor layer 31 as a mount surface for attracting to mount the element 2 to be attracted, and an insulating film 20 arranged between the layer 31 and the susceptor 10, wherein an adhered part 21 of the film 20 to the layer 31 is formed to be asymmetrical to an adhered part 22 of the film 20 to the susceptor 10.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electrostatic chucks.

[0002]

2. Description of the Related Art As a conventional electrostatic chuck for attracting and holding an object to be attracted, for example, a semiconductor wafer as an object to be treated by electrostatic force, one surface of a polyimide film as an insulating film is formed on substantially the entire upper surface of a susceptor. Is adhered with a polyimide adhesive, and the other surface of the polyimide film opposite to the susceptor is attached to the substantially entire surface of the non-mounting surface side of the semiconductor wafer of the resistor layer as a mounting surface for adsorbing and mounting the semiconductor wafer. The polyimide film and the susceptor are bonded to each other with a polyimide adhesive, and the contact part between the insulating film and the resistor layer is bonded substantially symmetrically with the insulating film sandwiched therebetween. Further, in order to hold the semiconductor wafer by suction, a DC power source is applied to the electrode plate provided on the lower surface of the resistor layer side, and the contact potential difference between the semiconductor wafer and the resistor layer causes
The semiconductor wafer was held by suction on the suction holding surface of the resistor layer by electrostatic force.

[0003]

However, the susceptor is appropriately cooled to a cooling temperature, for example, -10 ° C. or lower by the cooling means, and the adsorbed body is cooled by the cooling of the susceptor.
For example, a resistor layer as a mounting surface on which a semiconductor wafer as an object to be processed is sucked and mounted is also cooled to a temperature substantially equal to that of the susceptor through an insulating film, and sucked and held on the mounting surface side of the resistor layer. The semiconductor wafer is also cooled to substantially the same temperature. Here, due to the difference in linear expansion coefficient between the susceptor, for example, Al as a conductive metal, and the resistor layer, for example, silicon carbide (SiC), the insulating film attached between the susceptor and the resistor layer is distorted and the susceptor is distorted. There is a problem that the adhesive portion between the insulating film and the insulating film and the adhesive portion between the resistor layer and the insulating film are peeled off.
Further, when the adhesive portion between the resistor layer and the insulating film is peeled off, dew condensation occurs in the peeled portion as the temperature changes with time, water is accumulated, and the electrode plate provided on the resistor layer is corroded. There is a problem that the attraction force of the electrostatic chuck is reduced. Further, if the adhesive part between the susceptor and the insulating film and the adhesive part between the resistor layer and the insulating film are peeled off, it becomes impossible to maintain the levelness of the mounting surface on which the semiconductor wafer of the resistor layer is mounted. There was a problem. Furthermore, if it becomes impossible to maintain the levelness of the mounting surface on which the semiconductor wafer of the resistor layer is mounted, it becomes impossible to uniformly process the semiconductor wafer, and the yield of devices formed on the semiconductor wafer will be reduced. There was a problem of lowering it.

An object of the present invention is to hold an electrostatic chuck capable of suppressing the peeling of the adhesive portion between the susceptor and the insulating film or between the resistor layer and the insulating film due to the change in thermal expansion or contraction of the susceptor and the resistive layer. To provide.

[0005]

SUMMARY OF THE INVENTION The present invention is an electrostatic chuck for attracting and holding an object to be adsorbed on a placing surface of a susceptor by electrostatic force, as a placing surface for adsorbing and placing the object to be attracted. A resistor layer; and an insulating film disposed between the resistor layer and the susceptor, wherein the insulating film and the resistor layer are bonded together, and the insulating film and the susceptor are bonded together. It is asymmetrical.

[0006]

According to the present invention, since the adhesive portion between the insulating film and the resistor layer and the adhesive portion between the insulating film and the susceptor are asymmetrical, even if thermal expansion or thermal contraction length of the susceptor and the resistor layer occurs, Since the change in the thermal expansion or contraction length of the susceptor and the resistor layer does not interfere with the adhesive part between the insulating film and the resistor layer and the adhesive part between the insulating film and the susceptor, the susceptor and the insulator film or the resistor layer and the insulator film are not It is possible to suppress peeling of each adhesive portion.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the accompanying drawings by an embodiment applied to a plasma etching apparatus.

As shown in FIGS. 1 to 3, an object to be treated as an object to be adsorbed, for example, a semiconductor wafer 2 is carried into the processing container 1 on an outer wall of a processing container 1, for example, a container made of conductive aluminum. Alternatively, an opening 3 for carrying out is provided, and a gate valve 4 that can be opened and closed via a sealing body that hermetically seals, for example, an O-ring, is provided on the outer wall of the opening 3.
And a load lock chamber (not shown) is laid in the processing container 1 via the gate valve 4, and the semiconductor wafer 2 is transferred to the processing container 1 by a transfer device (not shown) provided in the load lock chamber. A wafer transfer system is configured to carry in or carry out.

Further, a conductive member, for example, a metal such as aluminum (a coefficient of linear thermal expansion of Al; approximately 23 × 10 ⁻⁶ (cm / cm / ° C.)) is formed in the center of the bottom surface inside the processing container 1. For example, a columnar susceptor support 5 is provided as cooling means for cooling the susceptor 10. A coolant jacket 6 for accumulating a cooling medium, for example, liquid nitrogen, is formed inside the susceptor support 5. The coolant jacket 6 includes an introduction pipe 7 and a coolant jacket 6 for introducing the liquid nitrogen into the coolant jacket 6. Exhaust pipes 8 for exhausting the vaporized N ₂ of liquid nitrogen are provided in the bottom surface of the processing container 1 in an airtight and insulating manner to cool the susceptor 10. Further, the liquid nitrogen is thermally cooled in the coolant jacket 6 to control the temperature of the semiconductor wafer 2 via the susceptor 10 to be appropriately settable to, for example, 0 ° C. to −120 ° C. by a temperature adjusting device (not shown). Is configured to. Further, a conductive member as a lower electrode, for example, a susceptor 10 made of a metal such as aluminum is attached to the upper part of the susceptor support 5 by a bolt (not shown).
Is a high frequency power source 1 of high frequency, for example, 13.56 MHz or 40 MHz via the blocking capacitor 11.
2 is connected to the susceptor support 5 and the susceptor 10 by a heat transfer medium such as He as an inert gas.
Gas, or when this He gas is not desirable to mix with the processing gas when processing the semiconductor wafer 2, a gas equivalent to the processing gas for processing the semiconductor wafer 2 is supplied to the back surface of the semiconductor wafer 2. A hole portion, for example, a through hole 13 connected to the supply pipe 14 is formed.

As shown in FIGS. 1 and 2, an insulating layer 20 is formed on the susceptor 10 such as a sheet of polyimide film (coefficient of linear thermal expansion of polyimide film; approximately 2).
0 to 22 × 10 ⁻⁶ (cm / cm / ° C.)) is adhered, and an electrode 30 made of a conductive paste, for example, a paste made of silver or copper, is applied to the upper surface of the insulating layer 20 and is applied to the lower surface of the resistor. The body layer 31 is adhered, and the resistor layer 31
The semiconductor wafer 2 is mounted on the upper part of the. The resistance layer 31 has a resistance value between an insulator and a conductor, specifically, for example, 1 × 10 6 Ω ⁻¹ cm.
^-1 or more and a semiconductor having a volume resistivity of 1 × 10 12 Ω ^-1 cm ^-1 or less, for example, silicon carbide (SiC) (linear thermal expansion coefficient of SiC; approximately 3.0 to 4.0 × 10 ^-6 (cm / cm /
C.)) and its thickness is, for example, 5 mm or less.
The electrodes 30 may be formed by screen-printing silver or palladium on the surface of the resistor layer 31 instead of applying the silver or copper paste. Further, the insulating layer 20 is bonded to the insulating layer 20 by bonding. An adhesive, for example, a polyimide-based adhesive having a thickness of about 10 μm is applied to the surface of the polyimide film, and the polyimide film is fixedly brought into contact with the adhesive member, and the temperature is raised to, for example, 120 ° C. or more to melt and bond the adhesive. It is what makes me.

Further, as shown in FIGS. 3 and 4, the adhesive between the resistor layer 31 and the insulating film 20 is the adhesive portion 21.
(A in FIG. 4), and the peripheral edge portion 21 on the upper portion of the susceptor 10 is formed into a convex curved surface, and the peripheral edge portion 21 of the convex curved surface prevents the adhesion between the insulating film 20 and the susceptor 10. Adhesive part 22 which is the outer periphery of the symmetry plane of said adhesive part 21
4B, and the adhesive portion 21 between the resistor layer 31 and the insulating film 20 and the adhesive portion 22 between the insulating film 20 and the susceptor 10 are bonded to each other with the insulating film 20 sandwiched therebetween. It is configured so that the adhesive parts do not overlap via the insulating film,
The electrostatic chuck 9 is configured as described above.

Further, as shown in FIG.
Is connected to the electrode 30 at one end side of a conductive wire 25 whose periphery is covered with an insulating member such as Teflon, and the other end side is connected to the electrode 31 at a high voltage, for example, 200V to 3KV. A power supply means for supplying a voltage, for example, a power supply rod 26 made of copper, is connected to the bottom surface of the processing container 1 in an airtight and insulated manner, and switches to a high voltage power supply 27. For example, they are connected via an electromagnetic switch 28. The electromagnetic switch 28 is turned on by a control signal for controlling a device (not shown).
It is configured to be N or OFF.

An upper electrode 50 is provided above the susceptor 10 and above the processing container 1,
A processing gas, for example, a processing gas such as CHF ₃ or CF ₄ , or an inert gas is supplied to the upper electrode 50 through a gas supply pipe 51, and a plurality of radial holes are formed on the bottom wall of the upper electrode 50. The processing gas is discharged from the small holes 52 toward the semiconductor wafer, and when the high frequency power source 12 is turned on, plasma is generated between the upper electrode 50 and the semiconductor wafer 2. The electrode 50 is grounded by a wiring 53 for electrically grounding.

Further, a through hole 16 penetrating the susceptor 10, the susceptor support 5, the insulating film 20, the electrode 30 and the resistor layer 31 is provided, and the through hole 16 is electrically connected through a resistance or an inductance. A grounded pin 15 is provided, and this pin 15 is connected to an up-and-down moving means, for example, an air cylinder 18 via a bellows 17 that makes the processing container 1 airtight and can expand and contract.
Further, the pin 15 transfers the semiconductor wafer 2 from the transfer device in the load lock chamber, and moves vertically by the air cylinder 18 when the semiconductor wafer 2 is brought into contact with or separated from the resistor layer 31. Has been done. A discharge port 19 is provided at the bottom of the side wall of the processing container 1 to reduce the pressure inside the processing container 1. The gas discharge port 19 is an open / close valve (not shown), such as a butterfly valve. Is connected to a vacuum exhaust device (not shown), such as a rotary pump or a turbo molecular pump.

Next, the operation of the plasma etching device configured as described above will be described.

First, the gate valve 4 is opened, and the semiconductor wafer 2 is loaded into the processing container 1 and delivered to the pins by the transfer device provided in a load lock chamber (not shown). The transfer device moves into the load lock chamber, closes the gate valve 4, and then the pin descends to place the semiconductor wafer 2 on the resistor layer.

Next, the process of electrostatically attracting and holding the semiconductor wafer 2 to the resistor layer 31 will be described. As shown in FIG. 1, a high voltage is applied to the electrode 31 coated on the resistor layer 31. For example, when the switch 28 is closed to supply power of 500 V, as shown in FIG. 4, there is a slight gap A in the contact surface between the semiconductor wafer 2 and the resistor layer 31, and the resistor layer 31 is a semiconductor. Since the voltage drop is small, a large potential difference occurs between the potential V3 on the lower surface of the semiconductor wafer 2 and the potential V2 on the upper surface of the resistor layer 31. Therefore, a large electrostatic force is generated due to this potential difference, that is, a contact potential difference, so that the semiconductor wafer 2 is attracted to the resistor layer 31. In addition, V
1 and V2 are potentials on the lower surface of the resistor layer 31 and the surface of the semiconductor wafer 2, respectively.

Next, as shown in FIG.
The processing gas is supplied from the gas supply pipe 51 connected to 0, the processing gas is introduced into the processing container 1 through the small hole 52, and the internal pressure of the processing container 1 is set to a set value, for example, 10 mTorr to 10 Torr. The heat transfer medium, for example, He gas as an inert gas, is supplied to the back surface of the semiconductor wafer 2 at a predetermined pressure from a hole connected to the supply pipe 14, for example, a through hole 13, Two
Is maintained at a temperature of 0 ° C. to −120 ° C. and the high frequency power source 12 connected to the susceptor (lower electrode) 10 is turned off.
Then, plasma is generated in the processing container 1 and between the upper electrode 50 and the semiconductor wafer 2, and the semiconductor wafer 2 is etched by the plasma.

Further, the semiconductor wafer 2 is exposed to the ambient temperature,
For example, from 20 ° C to the processing temperature, for example -100 ° C,
Further, when the processing temperature, for example, −100 ° C. is changed to the atmospheric temperature, for example, 20 ° C., the susceptor 10 (the coefficient of linear thermal expansion of Al; approximately 23 × 10 ⁻⁶ (cm / cm / ° C.)) and the resistance. Body layer 31, for example silicon carbide (SiC) (Si
Linear thermal expansion coefficient of C: approximately 3.0 to 4.0 × 10 ⁻⁶ (cm / c
m / ° C.)) causes thermal expansion or thermal contraction. Here, the conventional electrostatic chuck 9 is shown in FIG.

As shown in [A], the insulating film 20 provided between the susceptor 10 and the resistor layer 31 is substantially symmetrical to the susceptor 10 and the resistor layer 31 and is adhered over the entire surface by an adhesive agent. It is bonded at the bonding portion 35. As described above, when they are adhered to each other substantially symmetrically and substantially over the entire surface, the linear thermal expansion coefficient of the resistor layer 31 is calculated from the thermal expansion or thermal contraction distance 36 due to the linear thermal expansion coefficient of the resistor layer 31. Since the thermal expansion or contraction distance 37 due to the linear expansion coefficient is larger than the linear expansion coefficient, the insulating film 20 is distorted, and the adhesive portion between the susceptor 10 and the insulating film 20 and between the resistor layer 31 and the insulating film 20 is formed. It was peeled off at 35. The difference in distance between the susceptor 10 and the resistor layer 31 due to thermal expansion or contraction is represented by the formula (1) by taking thermal contraction as an example. ΔL = (L / 2) × (T1−T0) × (α1−α2) −−− (1) where ΔL is the difference in distance due to heat shrinkage, L is the distance of the bonded portion is 200 mm for an 8-inch wafer, T1; -100
C, T0; 20 ° C., α1; susceptor 10 (Al linear thermal expansion coefficient; approximately 23 × 10 −6 (cm / cm / ° C.) α2; resistor layer 31 (SiC linear thermal expansion coefficient; approximately 3.0) ×
10 ⁻⁶ (cm / cm / ° C.)), the difference in distance due to heat shrinkage (ΔL) = 0.24 m
m, and the insulating film 20 changes as the temperature changes with time.
Causes distortion, and peeling progresses at the adhesive portions 35 between the susceptor 10 and the insulating film 20 and between the resistor layer 31 and the insulating film 20.

Further, in FIG.

As shown in [B], the susceptor 10 and the insulating film 2
0 adhesive layer 22, the resistor layer 31 and the insulating film 2
Since the bonding portion 21 between 0 is asymmetrical with the insulating film 20 sandwiched therebetween, the insulating film 20 is only pulled by the susceptor 10 and the resistor layer 31, respectively.
Therefore, in order to prevent the peeling, the expansion and contraction of the insulating film 20 is a difference in distance (ΔL) =
It suffices to endure 0.24 mm. Further, as shown in FIG. 3, when a heat transfer medium, for example, a gas equivalent to the processing gas for processing the semiconductor wafer 2 is supplied to the back surface of the semiconductor wafer 2, the same gas as this processing gas is applied to the electrode 30. In order to prevent corrosion of the electrodes, it is preferable that the resistance layer 31 and the insulating film 20 be bonded so as to cover the electrode 30.

Next, the effect of this embodiment having the above-mentioned structure will be described. Due to the difference in linear expansion coefficient between the susceptor 10, for example, Al as a conductive metal and the resistor layer 31, for example, silicon carbide (SiC), the insulating film attached between the susceptor and the resistor layer is distorted, and It is possible to suppress peeling of the adhesive portion between the insulating films and the adhesive portion between the resistor layer and the insulating film. In addition, the resistor layer 31 and the insulating film 2
When the adhesive portion between 0s is peeled off, it is possible to prevent the peeled portion from corroding the electrode 30 provided on the resistor layer 31 due to dew condensation due to the change of temperature with time, and to suppress the attraction force of the electrostatic chuck 9. Can be suppressed. Also,
It is possible to suppress peeling of the adhesive portion 22 between the susceptor 10 and the insulating film 20 and the adhesive portion between the resistor layer 31 and the insulating film 20, so that the mounting surface of the resistor layer 31 on which the semiconductor wafer 2 is placed is mounted. The levelness can be maintained more. Furthermore, since the mounting surface of the resistor layer 31 on which the semiconductor wafer 2 is mounted can be kept more horizontal, the semiconductor wafer 2 can be processed uniformly, and the semiconductor wafer 2 can be processed uniformly. It is possible to improve the yield of the device formed on the substrate.

In this embodiment, the adhesive between the insulating film and the resistor layer is provided on the outer periphery of the symmetry plane with the insulating film sandwiched between the insulating film and the susceptor. It is needless to say that the adhesive part between the insulating film and the susceptor may be attached to the inner periphery of the symmetrical surface with the insulating film sandwiching the insulating film, and the present invention is not limited to such an embodiment. Various modifications can be made within the scope of the present invention. In addition, although the plasma etching apparatus has been described in the embodiment, an electrostatic chuck that electrostatically attracts and holds an object to be attracted, such as the semiconductor wafer or the LCD substrate, is used in addition to the plasma etching apparatus. A natural oxide film removing device, a single-wafer oxidation furnace for depositing an oxide film, an inspection device such as a wafer prober, a transfer device, C
The present invention is not limited to a heat treatment apparatus such as VD, but can be used for an apparatus under normal pressure, reduced pressure or positive pressure.

[0023]

According to the present invention, since the bonding portion between the insulating film and the resistor layer and the bonding portion between the insulating film and the susceptor are asymmetrical, thermal expansion or thermal contraction length of the susceptor and the resistor layer occurs. In addition, since the change in the thermal expansion or contraction length of the susceptor and the resistance layer does not interfere with the adhesion part of the insulation film and the resistance layer and the adhesion part of the insulation film and the susceptor, the susceptor and the insulation film or the resistance layer Since it is possible to suppress the occurrence of unevenness due to peeling of the respective adhesive portions of the insulating film, there is a remarkable effect that the horizontal state of the attracted body held by the electrostatic chuck by suction can be kept more horizontal.

[0024]

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a plasma etching device to which a first embodiment according to the present invention is applied.

FIG. 2 is an exploded perspective view showing a configuration of a main part of the electrostatic chuck of FIG.

FIG. 3 is a partial cross-sectional view showing a configuration of a bonding portion of the electrostatic chuck of FIG.

FIG. 4 is a partial cross-sectional view showing a configuration of an adhesive portion of an electrostatic chuck on which the attracted body of FIG. 1 is placed.

5 is a partial cross-sectional view showing the action of the electrostatic chuck for mounting the attracted body of FIG.

[Figure 6]

FIG. 9A is a partial cross-sectional view showing the action of a conventional electrostatic chuck on which an object to be attracted is placed.

FIG. 3B is a partial cross-sectional view showing the action of the electrostatic chuck on which the attracted body of FIG. 1 is placed.

[Explanation of sign]

 DESCRIPTION OF SYMBOLS 1 Processing container 2 Adsorbent (semiconductor wafer) 5 Susceptor support (cooling means) 9 Electrostatic chuck 10 Susceptor (lower electrode) 20 Insulating films 21, 22 Adhesive part 30 Electrode 31 Resistor layer

Claims (1)

[Claims] 1. An electrostatic chuck for attracting and holding an object to be adsorbed on a placing surface of a susceptor by electrostatic force, a resistor layer as a placing surface on which the object to be attracted is attached, and the resistor. A layer and an insulating film disposed between the susceptor, wherein the insulating film and the resistor layer have an asymmetrical adhesive portion, and the insulating film and the susceptor have an asymmetrical adhesive portion. An electrostatic chuck that does.