JPH05226462A - Electrostatic chuck - Google Patents

Abstract

PURPOSE:To provide an electrostatic chuck structure which keeps a wafer uniform in temperature distribution in plasma, where the electrostatic chuck holds a processed substrate such as a wafer or the like by suction in a treatment process. CONSTITUTION:Two or more electrodes 3 are separately buried in an electrostatic chuck 1, and dielectric layers are made to vary in thickness for each electrode 3 so as to locally control a attracting force between the electrodes 3 and a wafer 5, whereby the wafer 5 is kept uniform in temperature distribution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an electrostatic chuck for attracting and fixing a wafer in the process of treating a wafer which is an attracted substrate.

In recent years, in the wafer process of semiconductor devices, epitaxial, CVD, sputtering, vacuum deposition, etc.
More and more processes using vacuum chambers are used. Therefore, a fixing method in a vacuum atmosphere that does not damage the wafer surface is required.

[0003]

2. Description of the Related Art FIG. 7 is an explanatory view of a conventional example. In the figure, 11 is an electrostatic chuck, 12 is a dielectric, 13 is an electrode, 14 is a DC power supply, and 15 is a wafer.

In the wafer process, as a method of fixing the wafer, a vacuum chuck method of applying backside exhaust to fix the wafer to the chuck, a method of electrically fixing the wafer using an electrostatic chuck, and a machine using claws and arms. For example, there is a method of fixing the wafer.

Among them, the method of electrically fixing a wafer by using an electrostatic chuck is, in terms of manufacturing a semiconductor device,
It is used in a wide range because it is not in contact with the surface of the wafer and can be applied in vacuum.

As shown in FIG. 7 (a), a conventionally used electrostatic chuck 11 has a single electrode 13 provided in a dielectric 12 and a DC voltage from a DC power supply 14 between the electrode 13 and the wafer 15. Or a plurality of electrodes 13 are embedded in the dielectric 12 and a DC voltage is applied between the electrodes 13 and the other electrodes 13 to act between the wafer 15 and the electrodes 13 as shown in FIG. 7B. Wafer 15 is electrostatically chucked by dielectric 12 and electrode 13 by Coulomb force
It is adsorbed on 11.

Since the distance between the electrode 13 of the electrostatic chuck 11 and the wafer 15 is uniform, a uniform attracting force acts on the wafer 15 on the electrode 13. In addition, of course, the adsorption force does not work on the part where the electrode 13 is not present.

[0008]

In dry etching using plasma, the etching rate needs to be uniform at any position on the wafer. This etching rate greatly depends on the temperature. In other words, it is important to make the temperature distribution on the wafer uniform in order to make the etching rate on the wafer uniform.

In practice, a method of cooling the electrostatic chuck with water, gas or the like is used in order to make the temperature distribution on the wafer uniform, but as a practical matter, the temperature distribution of the wafer in the plasma is Appear concentrically.

An object of the present invention is to provide an electrostatic chuck having a structure that makes the temperature distribution of a wafer in plasma uniform.

[0011]

FIG. 1 is an explanatory view of the principle of the present invention, and FIGS. 2 to 6 are explanatory views of an embodiment of the present invention. In the figure, 1 is an electrostatic chuck, 2 is a dielectric, 3 is an electrode, 4
Is a DC power supply, 5 is a substrate to be attracted, 6 is a wafer, 7 is a chamber, 8 is plasma, and 9 is a water cooling tube.

The temperature of the electrostatic chuck 1 is lower than that of the wafer 6, which is the substrate 5 to be attracted, in plasma. Therefore, when the temperature of a part of the wafer 6 in the plasma is higher than that of the other part, if the attraction force between the wafer 6 and the electrostatic chuck 1 in the part having the higher temperature is increased, the thermal conductivity of the part is improved. The heat of the wafer 6 is dissipated to the electrostatic chuck 1 and the temperature is lowered.

The attraction force between the wafer 6 and the electrostatic chuck 1 is based on the Coulomb force. Coulomb force is inversely proportional to the square of distance. Therefore, the electrostatic chuck 1 is formed such that the thickness of the dielectric 2 between the electrode 3 and the wafer 6 where the attraction force is desired to be increased is thin, and the portion where the attraction force is desired to be increased is increased. To do.

Such a structure of the dielectric 2 can be obtained relatively easily by stacking the dielectric layers 2'provided with the electrodes 3. Further, in this method, even if there is only one voltage source, the distance between the electrode 3 and the wafer 6 is different for each electrode, so that the attraction force of the electrostatic chuck 1 to the wafer 6 is different for each electrode.

In the case of the conventional electrostatic chuck 1 having two or more electrodes 3, the attraction force did not work at the boundary between the electrodes 3A and 3B. However, with the structure in which the electrodes 3 are stacked, there is no planar gap at the boundary between the electrode 3A and the electrode 3B, and it is possible to eliminate the part where the adsorption force does not work, and more localized adsorption force control is possible. ..

As a practical matter, the wafer 6 in the plasma is
Since the temperature distribution of 1 appears concentrically, the shape of the electrode 3 is concentric, and the attraction force between the wafer 6 and the electrostatic chuck 1 is concentrically distributed.

That is, as shown in FIG. 1, the object of the present invention is to change the thickness of the dielectric layer between the electrode 3 in the dielectric and the attracted substrate 5 in the electrostatic chuck 1. This means that at least two electrodes 3 are provided in the dielectric 2.
More specifically, by embedding independently, by varying the thickness of the dielectric layer for each electrode 3, and partially controlling the attraction force between the electrode 3 and the substrate 5 to be attracted, As shown in FIG. 2, the electrostatic chuck 1 has electrodes 3 embedded in the surface thereof, and as shown in FIG. 5, the electrodes 3 are concentric, and at least two or more electrodes 3 are positively connected. Can be achieved by having a mechanism for applying a positive voltage and a negative voltage alone.

[0018]

According to the present invention, the partial attraction force of the electrostatic chuck can be variously changed with a constant voltage, and the temperature distribution of the wafer in the plasma can be controlled.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of the principle of the present invention, and FIGS. 2 to 6 are explanatory views of an embodiment of the present invention. The electrostatic chuck 1 shown in a plan view in FIG. 1A and a sectional view in FIG.
As shown in (a) to (d), four disk-shaped dielectric layers 2A, 2B, 2C, and 2D are stacked on the respective surfaces in which the rectangular electrodes 3 are embedded at different positions.

As shown in FIG. 1B, a silicon wafer is placed on the electrostatic chuck 1 as a substrate 5 to be attracted.
A voltage of 1,000 V was applied from the DC power source 4 to each electrode 3 to examine the partial adsorption force.

The distance between the attracted substrate 5 and each electrode 3, that is,
The result is that the attraction force increases as the thickness of the dielectric layer 2'decreases. Adsorption force 2A>2B>2C> 2D. Therefore, if the suction force is large, the temperature of the wafer is lowered as described above, so that the wafer temperature is lower than D in the direction A as shown in FIG.

As described above, it was confirmed that the attraction force can be controlled by changing the thickness of the dielectric layer 2 '. As a comparative example with the present invention, the structure of a conventional bipolar electrostatic chuck is shown in FIG.
FIG. 3A is a plan view and FIG. 3B is a sectional view.

Alumina ceramic is used as the dielectric 12. The electrode 3A at the center of the electrostatic chuck 11
The wafer is fixed by applying a voltage of 1,000 V and +1,000 V to the electrode 3B on the outer peripheral portion. The electrostatic chuck 1 is set in the parallel plate type RIE device shown in the schematic sectional view of FIG.

The plasma formation conditions are as follows: Argon (Ar) gas flow rate 100 sccm, chamber gas pressure 0.15 Torr, RF power 500
W went. Electrostatic chuck by flowing 20 ℃ water from the water cooling tube
As shown in the plan view of the wafer in FIG. 4B, the wafer temperature at the time of cooling 11 and generating plasma is higher in the vicinity of the outer periphery than in the central portion of the wafer 6. The difference between the maximum value and the minimum value is 30 ℃, and it is observed that there is a considerable temperature difference.

Therefore, in order to suppress the temperature rise of the outer peripheral portion, as shown in FIG. 5, an electrostatic chuck 1 is prepared in which the attracting force of the outer peripheral portion of the wafer 6 is larger than that of the central portion. did.

As shown in FIG. 6, the dielectric 2 of the electrostatic chuck 1 has an electrode 3A that covers the outer peripheral portion of the wafer.
It has a structure in which a disk-shaped dielectric layer 2A in which is embedded and a disk-shaped dielectric layer 2B in which an electrode 3B covering the central portion of the wafer is embedded are concentrically stacked.

As a result of conducting an experiment similar to the above-mentioned conventional example using this electrostatic chuck 1, the temperature of the outer peripheral portion of the wafer 6 is somewhat higher than that of the central portion of the wafer 6, The difference between the maximum value and the minimum value was 11 ° C, and the temperature distribution of the wafer 6 was improved considerably.

From the results of this experiment, the number of electrodes 3 is increased,
If the difference in the thickness of the dielectric layer 2'is enlarged, a more improved temperature distribution can be obtained.

[0029]

As described above, according to the present invention,
The attraction force between the substrate to be attracted such as a wafer and the electrostatic chuck tube is partially changed by the difference in the electrostatic force corresponding to the distance between the wafer and the electrode to control the heat conduction between the wafer and the electrostatic chuck and The distribution of the wafer temperature inside was able to be made uniform.

Therefore, it becomes possible to obtain a constant etching rate on the entire surface of the wafer, which largely contributes to the technical improvement of the wafer process.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention (No. 1)

FIG. 2 is an explanatory diagram of the principle of the present invention (No. 2)

FIG. 3 is an explanatory diagram of an embodiment of the present invention (No. 1)

FIG. 4 is an explanatory diagram of an embodiment of the present invention (No. 2)

FIG. 5 is an explanatory diagram of an embodiment of the present invention (part 3).

FIG. 6 is an explanatory view of an embodiment of the present invention (No. 4).

FIG. 7 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 1 Electrostatic Chuck 2 Dielectric 3 Electrode 4 DC Power Supply 5 Adsorbed Substrate 6 Wafer 7 Chamber 8 Plasma 9 Water Cooling Tube

Claims (5)

[Claims] 1. An electrostatic chuck (1) comprising a dielectric (2)
An electrostatic chuck characterized in that a thickness of a dielectric layer between an electrode (3) inside and a substrate (5) to be attracted is changed. 2. At least two or more electrodes (3) are independently embedded in the dielectric (2), the thickness of the dielectric layer is changed for each electrode (3), And the substrate to be attracted
The electrostatic chuck according to claim 1, wherein the attraction force between (5) and (5) is partially controlled. 3. The electrostatic chuck (1) according to claim 2, wherein at least two or more dielectric layers (2 ′) having the surface embedded with the electrodes (3) are superposed on each other. Electrostatic chuck. 4. The electrostatic chuck according to claim 1, wherein the electrode (3) has a concentric circular shape. 5. A mechanism for applying only a positive voltage, or a positive voltage and a negative voltage, to the at least two or more electrodes (3), 1. Alternatively, the electrostatic chuck according to item 4.