JP3357991B2 - Electrostatic suction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for electrostatically adhering an object to be processed to a substrate and performing, for example, a sputtering process. The present invention relates to an electrostatic suction device suitable for obtaining conduction.

[0002]

2. Description of the Related Art Conventionally, for example, FIG.
An electrostatic chuck 3 for electrostatically fixing an object 5 to be processed on an upper portion of a base 1 provided with a cooling mechanism 1a such as a cooling water pipe as shown in FIG. And a rubber-like insulator 4b that is in close contact with the workpiece 5 above the electrode 2 is known.

Further, as shown in FIG. 2, an electrostatic chuck 3 for electrostatically fixing an object 5 to be processed on an upper portion of a base 1 provided with a cooling mechanism 1a is connected to an electrode 2 connected to a DC power source 6 and And an arc-shaped groove 8 connected to a gas supply hole 7 penetrating through the insulator 4 and the base 1 on the suction surface of the electrostatic chuck 3 on the object 5 to be processed. And
It is also known that a gas is caused to flow from the groove 8 to a gap between the workpiece 5 and the insulator 4.

FIG. 1 shows an object 5 to be processed.
Is placed on the electrostatic chuck 3 and a voltage is applied to the electrode 2.
A suction force of F = ε · (S / d ² ) · (V / 2) ² acts on the object 5, and the object 5 comes into close contact with the rubber-like insulator 4 b. Here, ε is the dielectric constant of the rubber-like insulator 4b, d
Is the thickness of the rubber-like insulator 4b, S is the area of the surface of the electrode 2 facing the workpiece 5, and V is the voltage of the DC power supply 6. Next, when the substrate 1 made of a metal such as aluminum having good heat conductivity is cooled by a cooling mechanism 1a by circulation of a coolant or the like, heat of the object 5 is transferred through the rubber-like insulator 4b and the insulator 4a. 1, and the object 5 is cooled. Therefore, for example, when the etching process is performed on the object 5, the temperature of the object 5 can be kept low even if the thermal load of the etching plasma is applied to the object 5. However, at this time, the rubber-like insulator 4b is deteriorated by being eroded by a reactive etching gas or the like. When the DC power source 6 is turned off and the workpiece 5 is detached from the electrostatic chuck 3 after the processing, the workpiece 5 However, there arises a problem that the rubber adheres to the rubber-like insulator and is hardly peeled off.

In the conventional example shown in FIG. 2, the above-described problem occurs because a rigid material such as ceramics is used for the insulator 4 of the electrostatic chuck 3 on which the workpiece 5 is placed. However, when a voltage is applied to the electrode 2 to fix the workpiece 5 on the insulator 4 by suction, for example, when the aluminum base 1 is cooled by the cooling mechanism 1a, the insulator 4 is cooled by heat conduction. Even if the object 5
Because the insulator 4 is rigid and makes contact with the insulator 4 in a point contact state, there is an average interval of about 10 μ between the workpiece and the insulator, and heat of the workpiece 5 is applied to the insulator 4. Not easily transmitted. Therefore, a gas is further flowed from the groove 8 provided in the suction surface area of the workpiece 5 of the electrostatic chuck 3 at the above-mentioned interval, and the heat of the workpiece is transferred to the insulator through the gas to remove the workpiece. I'm trying to cool. Therefore, even if a thermal load such as etching plasma is applied to the object, the temperature of the object can be kept low.

[0006]

As described above, in the electrostatic chuck of the type shown in FIG. 2 in which a gas is passed through a gap between an object and an insulator as one means for cooling the object, the gap is reduced. When less than or about the same as the mean free path of the gas, the heat transfer Q per unit area is: Q = (3/2) · κ · α ₁ · (T−Tg) · Γ where Γ = (1/4) · n · υ = (1/4) · P / (κ · Tg) · ｛8 · κ · Tg / (π · m )} 1/2 Tg = (α 1 · T + α 2 · T 0) is a _{/ (α 1 + α 2)} . Here, κ is Boltzmann's constant, α ₁ is the coefficient of thermal adaptation of the gas molecules to the adsorption surface of the electrostatic chuck, T is the temperature of the object, T ₀ is the temperature of the insulator, and Tg is the temperature of the gas molecules. Temperature, Γ is the surface density of gas molecules incident on the adsorption surface of the workpiece of the electrostatic chuck, n is the density of gas molecules, υ is the average velocity of gas molecules, m is the mass of gas molecules, P is the electrostatic chuck. The pressure of the gas on the adsorption surface of the processing object is shown. From the above equation, it can be seen that the heat transfer Q per unit area is proportional to the gas pressure P on the workpiece suction surface of the electrostatic chuck. In addition, when dry etching is performed on an object to be processed, an inert gas is preferably used as a gas, and helium gas is particularly advantageous because heat transfer is large. In the conventional electrostatic adsorption apparatus shown in FIG. 2, when helium gas of, for example, about 10 Torr is ejected from the groove of the object adsorption surface, the conductance of the groove is small. There is a problem in that the pressure drop increases toward the temperature, and the temperature of the outer periphery of the processing object increases. Further, the thickness of the insulator provided on the upper surface of the electrode 2 of the electrostatic chuck 3 is as thin as about 200 to 300 μm. If a large groove is formed in the insulator to increase the conductance, the surface insulating layer becomes thinner and dielectric breakdown occurs. There is a risk of starting.
For example, when the object to be processed is a 6-inch wafer and the groove is provided near the center of the suction surface, the gas pressure distribution becomes low near the outer periphery of the wafer as shown in FIG. In this case, the pressure of the helium gas in the groove is 9.6 Torr, and the atmosphere around the wafer is 0.01 Torr. In this state, 1.18 W /
When a thermal load of cm ² is applied, the temperature distribution of the wafer becomes as shown in FIG. 4 even when heat conduction in the wafer is taken into consideration, and the temperature near the outer periphery of the wafer increases. The temperature in the vicinity of the outer periphery increases as the thermal load increases. For example, in the case of dry etching, the selectivity and the etching shape are not uniform, and the resist film on the wafer is burned.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and disadvantages and to provide an electrostatic attraction device in which the heat conductivity of the attraction surface of an object to be treated becomes uniform.

[0008]

According to the present invention, there is provided a substrate cooled by a cooling mechanism.
An electrostatic chuck having at least one pair of electrodes covered with a ceramic insulator for electrostatically adhering and fixing the object to be processed, and an electrostatic chuck adhered to the substrate; A gas ejection hole for ejecting a gas for transmitting heat of the processing object to the electrostatic chuck, and a gas ejection hole formed in a ceramic insulator connected to the gas ejection hole and covering a back surface of an electrode of the electrostatic chuck. It has a and the distribution space of the gas, the above-mentioned
The insulator covering the electrodes of the electrostatic chuck is a thin ceramic plate
Consisting of a single ceramic thin plate
And the back side is covered with multiple ceramic sheets.
Layer, and the inside of the multilayer sheet on the back side
When the thin plate is stacked by forming a long hole in the thin plate of the interlayer
It is characterized in that a space is formed . The flow space is formed at a location corresponding to the vicinity of the outer periphery of the area of the adsorption surface, and a gas supply port and a plurality of gas ejection holes provided at substantially equal intervals in the vicinity of the outer periphery are provided so as to be connected to the flow space. The flow space is formed in a volume capable of holding the pressure of the space formed between the electrostatic chuck and the object to be processed,
The insulator covering the electrodes of the electrostatic chuck is made of a ceramic thin plate. The surface side of the electrode is covered with one ceramic thin plate, and the back side is covered with a plurality of ceramic thin plates in multiple layers. When a long hole is formed in the middle layer thin plate among the multilayer thin plates on the back side and the thin plates are stacked, the above-mentioned flow space is formed.

[0009]

The gas ejected from the gas ejection holes diffuses into the gap between the object to be processed and the insulator adsorbed on the suction surface of the electrostatic chuck, and the gas ejection holes enter the flow space formed inside the insulator. Since it is connected, gas can be ejected at a high pressure, and good heat transfer from the object to be processed to the electrostatic chuck can be performed. As the pressure of the gas to be jetted increases, the pressure on the outer peripheral side also increases, and it is possible to prevent the temperature from increasing on the outer peripheral side of the workpiece. Further, since the flow space is formed in the insulator covering the back surface of the electrode of the electrostatic chuck, the thickness of the insulator on the electrode surface is not impaired, and the dielectric breakdown does not occur.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
FIGS. 5 to 7 show an embodiment of an electrostatic suction device provided in a vacuum chamber of a dry etching device. In this example, an alumina substrate 1 provided with a cooling mechanism 1a such as a cooling water pipe is provided with an alumina substrate. Electrostatic chucks 3 are formed by covering a pair of semicircular disc-shaped electrodes 2 with an insulator 4 made of stainless steel. When a potential is applied to each electrode 2 from a DC power supply 6, static electricity is applied to the electrostatic chucks 3. Then, an object to be processed such as a 6-inch wafer is adsorbed on the surface. The back surface of the electrostatic chuck 3 is adhered to the substrate 1, the front surface of the electrode 2 is covered with a disk-shaped insulator 4c made of a thin plate having a thickness of 300 μm, and five thin plates of the same shape and thickness are stacked. The back surface of the electrode 2 was covered with the insulator 4d.
The diameter of the pair of electrodes 2 is configured to be slightly smaller than the diameter of the insulators 4c and 4d. The suction surface of the electrostatic chuck 3 is almost equal to the diameter of the electrode 2 and is 10 mm from the outer periphery of the suction surface.
Twelve gas ejection holes 7 for ejecting, for example, helium gas are formed at equal intervals on the inside, and the ejected gas flows through the gap between the workpiece 5 and the suction surface of the electrostatic chuck 3. An arc-shaped flow space 9 is formed inside the insulator 4 d covering the back surface of the electrode 2 when viewed from above, and the gas ejection holes 7 are formed so as to communicate with the flow space 9. 10
Is a gas supply port for supplying gas to the circulation space 9.

The flow space 9 is formed at a location corresponding to the vicinity of the outer periphery of the area of the suction surface of the electrostatic chuck 3, and the cross-sectional area of the flow space 9 is formed larger than the cross-sectional area of the gas ejection holes 7. . The circulation space 9 is formed by forming an arc-shaped long hole by punching or the like on some of the thin plates of the intermediate layer among the thin plates of ceramics covering the back side of the electrode 2, and laminating and bonding the thin plates. Can be formed.

In this embodiment, when a workpiece 5 is placed on the electrostatic chuck 3 and then a voltage is applied to the electrode 2,
The workpiece 5 is attracted and fixed by the static electricity generated in the electrostatic chuck 3. Next, when the substrate 1 is cooled by the cooling mechanism 1a, the insulator 4 is cooled by heat conduction. Further, when helium gas is ejected from the gas ejection holes 7, heat of the object 5 is transferred to the insulator 4 via the helium gas. And consequently,
The workpiece 5 is cooled. At this time, the pressure distribution of the helium gas on the adsorption surface is such that the gas is supplied from the large-volume circulation space 9 to the gas ejection holes 7, as shown in FIG. Helium pressure on the order of about 5 Torr is maintained up to this point. The pressure of the helium gas in the gas ejection hole 7 in this case is 7 Torr, the atmosphere surrounding the object to be treated 5 is 0.01 Torr, the flow rate of the helium leaking to atmosphere 1.61 × 10 ^{- 2} Torr · liter / sec It is. FIG. 9 shows the temperature distribution when a thermal load of 1.18 W / cm ² is uniformly applied to the workpiece 5 in order to etch the wafer of the workpiece 5. The temperature from the part to the vicinity of the outer periphery was kept low.

The insulator 4 has another ceramic having good heat conductivity.
If the leakage of helium gas does not matter, the gas ejection hole 7 can be further provided near the outer periphery of the adsorption surface. The workpiece 5 may be something other than a wafer. Further, in the above-described embodiment, the gas is ejected from the gas ejection holes. However, the same effect can be obtained by ejecting the gas from the slit-shaped gas ejection grooves 11 as shown in FIG.

[0014]

As described above, in the present invention, the gas ejection hole of the electrostatic chuck is formed by a ceramic covering the back surface of the electrode.
Connection with the flow space formed in the insulator of the electrostatic chuck, it is possible to flow high-pressure gas even near the outer periphery of the workpiece suction surface of the electrostatic chuck, and there is a danger of dielectric breakdown.
The outer periphery near to uniform the thermal conductivity of the suction surface of the object is also able to be cooled well without causing,
For example, when the object to be processed is dry-etched, the selectivity and the uniformity of the etched shape can be improved. Thus, since it can be formed relatively easily, there are effects such as good manufacturability.

[Brief description of the drawings]

FIG. 1 is a cutaway side view of a conventional example.

FIG. 2 is a sectional side view of another conventional example.

FIG. 3 is a pressure distribution diagram of helium gas in the conventional example of FIG.

FIG. 4 is a temperature distribution diagram of an object to be processed in the conventional example of FIG. 2;

FIG. 5 is a cutaway side view of an embodiment of the present invention.

FIG. 6 is a cutaway plan view taken along line 6-6 of FIG. 5;

FIG. 7 is an enlarged sectional view of a main part of FIG. 5;

FIG. 8 is a pressure distribution diagram of helium gas in the embodiment of FIG.

FIG. 9 is a temperature distribution diagram of an object to be processed in the embodiment of FIG.

FIG. 10 is a cutaway plan view of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 1a Cooling mechanism 2 Electrode 3 Electrostatic chuck 4, 4c, 4d Insulator 5 Workpiece 6 DC power supply 7 Gas ejection hole 9 Flowing space

Continuing on the front page (72) Inventor Toshio Hayashi 2500 Hagizono, Chigasaki-shi, Kanagawa Prefecture Inside Japan Sky Technology Co., Ltd. (72) Inventor Kazuo Noda 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Nippon Special Ceramic Company (56) reference Patent flat 2-98957 (JP, a) JP Akira 63-300517 (JP, a) JP flat 2-67745 (JP, a) (58 ) investigated the field (Int.Cl. ⁷ , DB name) H01L 21/68 C23C 14/50

Claims (2)

(57) [Claims] A substrate cooled by a cooling mechanism, and at least one pair of electrodes covered with a ceramic insulator for electrostatically adsorbing and fixing an object to be processed; A chuck, a gas ejection hole for ejecting a gas for transmitting heat of the processing object adsorbed on the adsorption surface of the electrostatic chuck to the electrostatic chuck, and an electrode of the electrostatic chuck connected to the gas ejection hole. rear possess a circulation space of said gas formed in the insulating material of the ceramic covering, insulator covering the electrode of the electrostatic chuck ceramic
It consists of a thin plate, and the surface side of the electrode is
Cover with a thin plate, the back side of which is made of multiple ceramic thin plates
To cover multiple layers, and of the multilayer sheet on the back side
When a thin plate is laminated by forming a long hole in the thin plate of the intermediate layer
An electrostatic suction device, wherein a circulation space is formed . 2. The flow space is formed at a position corresponding to the vicinity of the outer periphery of the area of the suction surface, and a gas supply port and a plurality of gas ejection holes provided at substantially equal intervals in the vicinity of the outer periphery are formed by the flow space. The electrostatic space according to claim 1, wherein the flow space is formed to have a volume capable of holding a pressure of a space formed between the electrostatic chuck and the workpiece. Suction device.