JPH06283594A - Electrostatic chuck - Google Patents

Abstract

PURPOSE:To provide an electrostatic chuck which can prevent the peeling of a bonding part between a susceptor and a bonding member and of a bonding part between a mounting member and the bonding member, when the susceptor and the mounting member expand or contract on account of heat, and length difference is generated. CONSTITUTION:This electrostatic chuck for electrostatically attracting and holding an object 2 to be attracted on the mounting surface of a susceptor 10 is provided with a mounting member 31 whose thermal expansion coefficient is different from that of the susceptor 10 for mounting the object 2, and a bonding member 20 for bonding the mounting member 31 to the susceptor 10. The thickness of the bonding members 20 is constituted of an elastic body having elongation equal to or larger than the difference value of thermal expansion length or thermal contraction length between the susceptor 10 and the mounting member 31.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electrostatic chucks.

[0002]

2. Description of the Related Art A conventional electrostatic chuck for attracting and holding an object to be attracted, for example, a semiconductor wafer, is provided with a mounting member for mounting the semiconductor wafer, for example, a susceptor for mounting the semiconductor wafer and SiC having a different coefficient of thermal expansion. Then, a joining member for joining between the mounting member and the susceptor, for example, a polyimide film as an insulator is adhered. As a method of adhering this polyimide film to the susceptor and the mounting member,
Approximately 10 in advance on the front and back of the polyimide film
The polyimide-based adhesive applied in a thickness of μm was melted by heat and adhered to the susceptor and the mounting member. Similarly, when the mounting member is made of ceramics as an insulator, only the polyimide adhesive is applied between the ceramics and the susceptor, and the adhesive is melted and bonded by heat.

[0003]

However, a susceptor, for example, a lower electrode made of conductive metal Al and a mounting member for mounting a semiconductor wafer, for example, silicon carbide (S
iC) or a member made of ceramics or the like has a linear expansion coefficient different from that of the susceptor, a polyimide adhesive as a joining member for joining the susceptor and the placing member cannot provide a sufficient thickness. The difference in linear expansion length due to the heat of the mounting member could not be absorbed, which causes distortion, and the adhesive portion between the susceptor and the bonding member and the adhesive portion between the mounting member and the bonding member are separated. There was a problem. In addition, when only the polyimide adhesive is applied to the joining member between the mounting member and the susceptor, the adhesive is melted at a temperature of, for example, 120 ° C. or more, and the mixture is bonded and then returned to room temperature, bubbles are present on the bonding surface. There was a problem of being lost. Further, if the adhesive part between the susceptor and the bonding member and the adhesive part between the mounting member and the bonding member are peeled off, it becomes impossible to maintain the levelness of the mounting surface of the mounting member on which the semiconductor wafer is mounted. There was a problem. Further, if it becomes impossible to maintain the levelness of the mounting surface of the mounting member on which the semiconductor wafer is mounted, it becomes impossible to uniformly process the semiconductor wafer, and the yield of devices formed on the semiconductor wafer is reduced. There was a problem of lowering it.

An object of the present invention is to provide a space between the susceptor and the joining member and a space between the placing member and the joining member even if the susceptor and the placing member are expanded or contracted by heat and a difference in length occurs. An object of the present invention is to provide an electrostatic chuck capable of preventing the respective bonded portions of the same from peeling off.

[0005]

According to a first aspect of the present invention, there is provided an electrostatic chuck for adsorbing and holding an object to be adsorbed on a mounting surface of a susceptor by electrostatic force, and the susceptor on which the object to be adsorbed is mounted. A mounting member having a different coefficient of thermal expansion, and a bonding member for bonding and bonding the mounting member and the susceptor, the thickness of the bonding member is the thermal expansion or thermal contraction length of the susceptor and the mounting member. It is composed of an elastic body having an elongation substantially equal to or greater than the difference value. According to a second aspect of the present invention, the thickness of the elastic body is the difference in the thermal expansion or contraction length between the susceptor and the mounting member {(elongation rate of the joining member).
^{It has} a thickness substantially equal to or greater than the value divided by ² −1} 1/2. According to a third aspect of the present invention, the elastic body is made of liquid room temperature curable silicone rubber. According to a fourth aspect of the invention, the elastic body is composed of deacetone silicone rubber.

[0006]

In the present invention, since the joining member for joining the susceptor and the susceptor and the placing member having different linear expansion coefficients is made of an elastic body,
The elastic body expands or contracts due to heat of the susceptor and the mounting member, respectively, and even if a difference in length occurs, the elastic body expands according to the difference in the length. It is possible to prevent the respective joint portions between the member and the joint member from peeling off.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plasma etching apparatus to which an electrostatic chuck according to an embodiment of the present invention is applied will be described below with reference to the drawings.

As shown in FIGS. 1 to 3, in order to carry in or carry out an adsorbent, for example, a semiconductor wafer 2, into or out of the processing container 1, for example, an outer wall of the processing container 1, which is made of conductive aluminum. The opening 3 is provided, and the outer wall of the opening 3 is hermetically sealed with, for example, O.
A gate valve 4 that can be opened and closed through a ring is provided, and the processing container 1 is also provided through the gate valve 4.
Further, a load lock chamber (not shown) is continuously provided, and a transfer device (not shown) is provided in the load lock chamber, and the transfer device is configured to load or unload the semiconductor wafer 2 into or from the processing container 1. The wafer transfer system is constructed as described above.

A cylindrical susceptor support 5 made of a conductive material, for example, a metal such as aluminum is provided at the center of the bottom surface inside the processing container 1. 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. Discharge pipes 8 for discharging the vaporized N 2 of the liquid nitrogen are provided in the bottom surface of the processing container 1 so as to penetrate in an airtight manner. In addition, a conductive member as a lower electrode, for example, a metal such as aluminum (A
linear thermal expansion coefficient of 1; approximately 23.5 × 10 ⁻⁶ (cm / cm /
)) Is provided, and the susceptor 10 is mounted on the susceptor support base 5 by bolts (not shown).
Installed on. Further, the susceptor 10 is configured so that the cold heat of the refrigerant jacket 6 is conducted through the susceptor support 5 to be cooled. Further, the susceptor 10 is connected to a high frequency power source 12 of high frequency, for example 13.56 MHz or 40 MHz, through a blocking capacitor 11, and the susceptor 10 and the mounting member 31 are provided with a heat transfer medium such as an inert gas. A plurality of through holes 13a for uniformly supplying He gas as a gas to the back surface of the semiconductor wafer 2 are provided.
3a is connected to a gas storage chamber 13 for making the pressure of He gas applied to the through holes 13a uniform, and this gas storage chamber 13 is connected to a supply pipe 14 for introducing He gas from the outside of the processing container 1. It is connected.

Further, as shown in FIGS. 1 and 2, a joining member 20, for example, an RTV rubber which is a liquid and room temperature curable silicone rubber as an elastic body is attached to the upper portion of the susceptor 10. A mounting member 31 having a different coefficient of thermal expansion from the susceptor 10 is adhered to the upper portion of the joining member 20,
The semiconductor wafer 2 is mounted on the upper surface of the mounting member 31. Further, the mounting member 31 described above.
As shown in FIG. 3, is an insulating member, for example, made of ceramics (coefficient of linear thermal expansion: about 7.1 × 10 ⁻⁶ (cm / cm /
(.Degree. C.)), an electrode plate 31b and a heater 31a are provided inside, and the temperature of the semiconductor wafer 2 is increased to 200.degree. C. via the susceptor 10 by thermal cooling of the heater 31a and the coolant jacket 6. ~ -16
The temperature control device (not shown) is set to 0 ° C. so that the temperature can be set appropriately. In addition, the susceptor 10
As a method of joining the joining member 20 for joining between the mounting member 31 and the placing member 31, the joining surface 61 of the susceptor 10 and the joining member 20 or the joining surface 62 of the placing member 31 and the joining member 20 at approximately room temperature. The joining member 20 on at least one of the
As a liquid, room temperature curable silicone rubber is uniformly applied, the other joint surface is brought into contact, the levelness of the mounting member 31 is adjusted, and the thickness of the joint member 20 is changed with temperature. The thickness is adjusted according to the maximum difference in thermal expansion or thermal contraction length between the susceptor 10 and the mounting member 31, and the components are joined.

Further, as shown in FIG. 1, the electrode 31b
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).
The electrostatic chuck 9 is configured to be turned off or turned 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 2 and the high frequency power source 12 is turned on to generate plasma between the upper electrode 50 and the semiconductor wafer 2. The upper electrode 50 is electrically grounded via the wiring 53.

Further, the susceptor 10, the susceptor support 5, the joining member 20, the electrode 30, and the mounting member 31 are provided with a through hole 16 penetrating them.
A pin 15 that is electrically grounded through a resistance or an inductance is provided inside, and the pin 15 makes the processing container 1 airtight and expands and contracts a bellows 17.
It is connected to a vertically moving means, for example, an air cylinder 18 via. 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. In addition, an outlet 1 is provided at the bottom of the side wall of the processing container 1 to reduce the pressure inside the processing container 1.
9 is provided, and this gas discharge port 19 is connected to a vacuum exhaust device (not shown) such as a rotary pump or a turbo molecular pump through an open / close valve (not shown) such as a butterfly valve.

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, then lowers the pin 15, mounts the semiconductor wafer 2 on the mounting member, and is incorporated in the mounting member 31. An electrostatic force is generated by closing the switch 28 in order to supply a high voltage, for example, 500 V, to the electrode 31, and the electrostatic force causes the semiconductor wafer 2 to be adsorbed and held on the mounting surface of the mounting member 31.

Next, a heat transfer medium, for example, He gas as an inert gas is supplied from the supply pipe 14 to the gas reservoir chamber 13 once at a supply pressure, for example, in the range of several mTorr to 100 Torr, and this gas is supplied. An inert gas is supplied to the back surface of the semiconductor wafer 2 through the plurality of through holes 13a connected to the reservoir chamber 13, and the heater 31a and the cooling medium jacket 6 are cooled by heat, whereby the susceptor 1 is cooled.
The temperature of the semiconductor wafer 2 is set to, for example, 200
The temperature is controlled appropriately by a temperature adjusting device (not shown) to a desired temperature in the range of ° C to -160 ° C.

Next, as shown in FIG. 1, the upper electrode 5
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. And stabilize the high frequency power source 12 connected to the susceptor (lower electrode) 10
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.

At this time, when the semiconductor wafer 2 is moved from room temperature, for example, 20 ° C. to a processing temperature, for example, 170 ° C., as shown in FIG. 4, the susceptor 10 (the coefficient of linear thermal expansion of Al; Approximately 23.5 × 10 ^-6 (cm / cm / ° C))
Expands to a distance of 71 in the figure, and further, the mounting member 3
1, for example made of ceramics (coefficient of linear thermal expansion; approximately 7.1 × 1)
0 ⁻⁶ (cm / cm / ° C.) expands to a distance of 70 in the figure. If the difference between the expansion distance 71 of the susceptor 10 and the expansion distance 70 of the mounting member 31 is ΔL (72),
The thickness L1 (73) of the joining member 20 attached between the susceptor 10 and the placing member 31 is pulled to the length of L2 (74). Here, the difference between the expansion distance 71 of the susceptor 10 and the expansion distance 70 of the mounting member 31 is ΔL.
When the relation (72) is expressed by the equation (1), ΔL = (L / 2) × (T1−T0) × (α1−α2)
--- (1) where ΔL is the difference in distance due to thermal expansion, L is the distance of the bonded portion in the case of an 8-inch wafer, 200 mm, T1; 170 ° C., T0; 2
0 ° C. (room temperature) α1; susceptor 10 (coefficient of linear thermal expansion of Al; approximately 23.5 ×
10 ⁻⁶ (cm / cm / ° C.) α2; mounting member 31 (ceramic linear thermal expansion coefficient; approximately 7.1 × 10 ⁻⁶ (cm / cm / ° C.)), the difference in distance due to thermal contraction ( ΔL) ≈ 0.246
It also becomes mm.

Further, the relationship between the thickness L1 (73) and the thickness L2 (74) of the joining member 20 attached between the ΔL (72), the susceptor 10 and the placing member 31 is expressed by the equation (2). And (L1) ² + (ΔL) ² = (L2) ² ---
---------- (2) where ΔL is the difference in distance due to thermal expansion, L1 is the thickness of the joining member 20 at room temperature L2 is the elongation length of the joining member 20 due to thermal expansion, and L2 is the elongation rate Is η, L2 = η (L
Therefore, the equation (2) is represented by the following equation (3): (L1) ² + (ΔL) ² = η ² (L1) ² -----
--- (3) Therefore, the thickness L1 (73) of the joining member 20 attached between the susceptor 10 and the placing member 31 at room temperature is:
A value obtained by dividing the difference ΔL (72) in thermal expansion or contraction length between the susceptor 10 and the mounting member 31 by {(elongation rate of the bonding member) ² −1} 1/2 from the expression (3). The bonding surface 62 between the susceptor 10 and the bonding member 20 may be adjusted to a thickness substantially equal to or more than the above value and bonding, and even if the insulating film 20 is distorted due to the change of temperature with time. Also, peeling does not occur at the adhesive surface 61 between the placing member 31 and the joining member 20.

Further, the elongation rate η of the joining member 20 becomes η = {(ΔL / L1) ² +1} 1/2 from the equation (3), and the larger the value obtained from this becomes, The joining member 20 can be thinned, and the heat conduction efficiency from the susceptor 10 can be further increased. Further, as a member having a large elongation rate η and further adhering at room temperature, as described above, a liquid and room temperature curable silicone rubber is most suitable, and as a member that can withstand high temperature, heat resistance Silicone rubber, for example, deacetone silicone rubber, such as KE3417 (trade name) is preferable.

Next, the effect of this embodiment having the above-mentioned structure will be described. Even if the susceptor 10 and the mounting member 31 thermally expand or contract due to the difference in linear expansion coefficient between the susceptor 10, for example, Al as a conductive metal, and the mounting member 31, for example, silicon carbide (SiC) or ceramics. , A mounting member 31 having a coefficient of thermal expansion different from that of the susceptor 10.
The joining member 20 for adhering the space between the susceptor 10 and the mounting member 3
Since the thickness or elastic body is capable of absorbing the difference in linear expansion or contraction length of 1, the susceptor 10 and the joining member 2
The joining surface 62 between 0 and the mounting member 31 and the joining member 20
The peeling of the adhesive surface 61 between them can be suppressed. Also,
Since it is possible to suppress the peeling of the adhesive portion between the mounting member 31 and the joining member 20, it is possible to prevent moisture from accumulating on the peeled portion due to the change of the temperature with time, and to prevent moisture from accumulating. The corrosion of the electrode plate can be suppressed, and the attraction force of the electrostatic chuck 9 can be prevented from decreasing. Further, the semiconductor wafer 2 is pressed by the inert gas supplied from the back surface of the semiconductor wafer 2. Therefore, the semiconductor wafer 2 itself can be prevented from being damaged without bouncing on the mounting member 31. In addition, the adhesive portion 62 between the susceptor 10 and the joining member 20.
Since the peeling off of the adhesive portion 61 between the mounting member 31 and the joining member 20 is suppressed, the levelness of the mounting surface of the mounting member 31 on which the semiconductor wafer 2 is mounted can be maintained. Furthermore, since the levelness of the mounting surface of the mounting member 31 on which the semiconductor wafer 2 is mounted can be maintained, the semiconductor wafer 2 can be uniformly processed, and the devices formed on the semiconductor wafer 2 can be processed uniformly. It is possible to suppress a decrease in yield.

In this embodiment, the expansion of the joining member attached between the susceptor and the mounting member due to the thermal expansion has been described, but the same effect can be obtained in the thermal contraction regardless of the thermal expansion. However, the present invention is not limited to such an embodiment, and various modifications can be made within the scope of the gist of the present invention. Also,
Although the plasma etching apparatus has been described in the embodiment,
In addition to such a plasma etching apparatus, an electrostatic chuck that electrostatically attracts and holds an object to be attracted, such as the semiconductor wafer or LCD substrate, is not limited to the plasma etching apparatus and is a natural oxide film removing apparatus or an oxide film. The present invention is not limited to a single-wafer oxidation furnace for film deposition, an inspection device such as a wafer prober, a transfer device, and a heat treatment device such as CVD, and can also be used for a device under normal pressure, reduced pressure or positive pressure.

[0023]

According to the present invention, since the joining member for joining the susceptor and the mounting member having a different linear expansion coefficient to each other is made of an elastic body, the elastic body expands or contracts by heat of the susceptor and the mounting member, respectively. However, even if there is a difference in length, it expands according to this difference in length, so it is possible to prevent peeling of the respective joints between the susceptor and the joining member and between the mounting member and the joining member. Since it can be prevented and unevenness due to peeling does not occur, there is a remarkable effect that the horizontal state of the mounting member on which the attracted body is mounted can be maintained.

[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 the operation 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) 9 Electrostatic chuck 10 Susceptor (lower electrode) 20 Joining member 30 Electrode 31 Mounting member 72 ΔL (difference in thermal expansion or contraction length)

Claims (2)

[Claims] 1. An electrostatic chuck for attracting and holding an object to be adsorbed on a mounting surface of a susceptor by electrostatic force, comprising: a mounting member having a coefficient of thermal expansion different from that of the susceptor on which the object is mounted; The mounting member and a joining member for adhesively joining the susceptor are provided, and the thickness of the joining member is substantially the same as or more than the difference value of the thermal expansion or thermal contraction length difference between the susceptor and the mounting member. An electrostatic chuck comprising an elastic body having: 2. The thickness of the elastic body is approximately a value obtained by dividing a difference in thermal expansion or contraction length between the susceptor and the placing member by {(elongation rate of the joining member) ² −1} 1/2. The electrostatic chuck according to claim 1, wherein the electrostatic chuck has the same thickness or a thickness equal to or more than that value.