JPH09219442A - Electrostatic chuck and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability and durability and ensure uniformity of processing within a plane of a sample substrate, by working a groove in a form appropriate for achieving uniform in-plane temperature distribution for an electrostatic chuck. SOLUTION: In an electrostatic chuck 19 which is used by charging a gas between a sample substrate and a chuck main frame and is adapted for attracting a sample substrate 11 by an electrostatic force, a groove 22 having a depth not greater than an average free path under a charging pressure of the gas is worked on a surface of the chuck main frame which contacts the sample substrate. It is preferred that the depth of this groove 22 is not greater than 10μm and that the uniformity of depth is within an error range of ±10%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck used in a semiconductor manufacturing apparatus and a method for manufacturing the electrostatic chuck, and more particularly to a method for machining a groove on a chuck surface.

[0002]

2. Description of the Related Art When a sample substrate such as a semiconductor substrate is processed in a vacuum by a semiconductor manufacturing apparatus, an electrostatic chuck is used for precisely controlling the temperature of the sample substrate. In this case, the electrostatic chuck needs to be intimately thermally coupled to the sample substrate to be processed, and therefore, in order to promote heat conduction with the sample substrate, the electrostatic chuck and the sample substrate are usually connected to each other. A gas such as He is filled between the substrate and the substrate. By the way, the in-plane temperature distribution state of the semiconductor substrate is an important factor for uniformly plasma-treating the semiconductor substrate. Therefore, as shown in Japanese Patent Laid-Open No. 6-318566, which is one of typical prior arts, a gas is filled between a semiconductor substrate (sample substrate) and an electrostatic chuck, and a semiconductor substrate to be processed and a static substrate are statically charged. The temperature of the semiconductor substrate is controlled by promoting heat conduction between the electric chucks.

[0003]

In the gas filling method as described above, in order to promote the flow of the gas introduced between the sample substrate and the electrostatic chuck, conventionally, the gas is contacted with the sample substrate of the electrostatic chuck. A plurality of grooves are provided on the surface (chuck surface), but the groove of the electrostatic chuck that is currently used is deeper than necessary, which causes non-uniform temperature distribution in the surface of the sample substrate. In the case of using the mechanical processing, there is a problem that microcracks are easily generated during the groove processing and the product reliability is poor.

On the other hand, as disclosed in Japanese Unexamined Patent Publication No. 6-318566, a large number of grooves are required because the size of the grooves is small and especially the depth and width of the grooves are small. Therefore, the manufacturing process is complicated, such as the formation of a cross-hatch pattern groove, and the disadvantages such as an increase in the device cost cannot be avoided.

The present invention has been made in order to solve the above problems, and an object of the present invention is to make the in-plane temperature distribution uniform for this type of electrostatic chuck. An object of the present invention is to provide an electrostatic chuck capable of improving the reliability and durability by processing a groove in an appropriate mode and contributing to ensuring the uniformity of processing within the surface of the sample substrate.

[0006]

The present invention has the following configuration to achieve the above object. That is, the present invention is an electrostatic chuck in which a gas is filled between a sample substrate and a chuck body, and the sample substrate is attracted by an electrostatic force. A groove having a depth equal to or less than the mean free path in is processed.

The present invention is also characterized in that, in the electrostatic chuck, the depth of the groove processed on the surface of the chuck body in contact with the sample substrate is 10 μm or less. Further, the present invention is characterized in that, in the electrostatic chuck, the uniformity of the depth of 10 μm or less of the groove processed on the surface of the chuck body in contact with the sample substrate is within an error range of ± 10%.

Further, according to the present invention, a gas is filled between the sample substrate and the chuck body for use, and the surface of the electrostatic chuck that adsorbs the sample substrate by electrostatic force is in contact with the sample substrate and is etched by a chemical or plasma. hand,
A method of manufacturing an electrostatic chuck, characterized in that a groove having a depth equal to or smaller than an average free path at a filling pressure of the used gas is processed on the surface.

[0009]

According to the present invention having the above-mentioned means, when a sample substrate such as a semiconductor substrate is processed, gas is introduced between the electrostatic chuck and the semiconductor substrate by a groove on the surface which is the chuck surface of the electrostatic chuck. Can be quickly filled. The heat transfer dynamics of the gas in this case are roughly classified into three according to the ratio of the mean free path according to the pressure of the gas and the representative length between the two objects filled with the gas.

The first is the manner in which gas transfers heat in the same manner as solids. That is, if the distance between two bodies is longer than the mean free path of the gas, heat will first be transferred from one body to the gas and then between the molecules of the gas, then to the other body. Will be told. The second is a general heat transfer mode by gas convection. And the third is heat transfer dynamics when the mean free path of gas, which is heat transfer in a vacuum, is longer than between two objects, and at this time, collisions between molecules of the gas are reduced,
Since the gas collides between two objects, the adaptation coefficient, which is the efficiency with which heat is transferred to the object when the gas hits the object, is related to the magnitude of heat transfer. This heat transfer is represented by the following formula (1).

Assuming the following equation (1), the distance between two objects may be much shorter than the mean free path of gas.
If the distance between the two objects is longer than the mean free path of the gas, gas molecules tend to collide with each other and the heat transfer efficiency decreases. When the distance between two substances is shorter than the mean free path of the gas filled between the two substances, heat conduction is related to the distance between these substances as shown in equation (1). It is not constant.

[0012]

## EQU1 ## G = (a1 * a2 * .LAMBDA. * P) / {a1 + a2-(a1 * a2)} ... (1) where Λ = 3.5 * 10 < ^-3 > * M- ^0.5 * {([gamma] +1) / (Γ−1)} × (273 / T) ^0.5 a1, a2: adaptation coefficient γ: specific heat ratio of gas M: molecular weight of gas P: pressure of gas T: absolute temperature of gas

That is, here, it is a premise that the depth of the groove is shorter than the mean free path of the gas so as not to reduce the heat conduction, and this is an important point. Also,
Fig. 5 shows the relationship between pressure and mean free path. From Fig. 5, the mean free path of He at about 1300 Pa (10 Torr) is 10 µm, and at about 4000 Pa (30 Torr) 4.5.
μm. Here, the gas filled between the semiconductor substrate and the electrostatic chuck need not be limited to He, and (1)
When the physical properties of other gases are applied to the equation, oxygen and nitrogen have higher heat conduction, and the heat conduction efficiency can be actually increased.

The gap between the electrostatic chuck and the semiconductor substrate that it chucks is usually about 1 μm, the pressure of the gas used as the cooling gas is about 1300 Pa, and the mean free path in that case is about 10 μm. The conditions are met. On the other hand, the depth of the groove of the electrostatic chuck according to the present invention being 10 μm or less means that the difference in the heat conduction efficiency between the portion having the groove and the portion not having the groove is minimized and the heat conduction is uniform in the surface. The groove depth should be shallower than the mean free path at the pressure of the gas used, since the purpose is to achieve this. Therefore, the groove having such a condition is shorter than the mean free path of the gas, and thus never lowers the heat conduction.

Further, since the depth of the groove is shallow, the attraction force of the electrostatic chuck is hardly reduced as compared with that without the groove. Furthermore, since the depth of the groove is shallow and uniform, the impedance change in the groove portion is small even when performing plasma processing, so that the semiconductor substrate can be uniformly processed without being affected by the groove. It is possible.

In the manufacturing method according to the present invention,
By using etching with a chemical solution or plasma, it is easy to make the groove depth uniform. further,
Since no damage such as microcracks is given to the electrostatic chuck, there is an advantage that the reliability and durability of the device are improved.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows one of the basic structures of an etching apparatus using an electrostatic chuck according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a microwave oscillator that generates microwaves, and specifically, 2.45 GHz
The output of 0 to 1 kW is used at the frequency of. 2
Is a matching circuit for efficiently absorbing microwaves into plasma, 3 is a waveguide for propagating the microwaves, and 4 is an element for circularly polarizing the microwaves.

Reference numeral 7 denotes a vacuum container for accommodating a semiconductor wafer 11, which is a sample substrate, and is provided with a microwave introduction window 5, an exhaust chamber 8, a load lock chamber 9, etc., and the microwave introduction window 5 is a vacuum. In a state where the vacuum state in the container 7 is maintained, the microwave that has passed through the waveguide 3 and the element 4 is evacuated to the vacuum container
It is provided so as to propagate inside, and is made of quartz glass or ceramic. Reference numeral 6 is a pipe for introducing the processing gas into the vacuum container 7.

Reference numeral 10 denotes an electromagnetic coil which can generate a magnetic field in the vacuum container 7 which satisfies the ECR condition (electron cyclotron resonance condition: 875 Gauss in this case). That is, by introducing the microwave into the vacuum container 7 under the magnetic field application, EC
R plasma is generated. The semiconductor wafer 11 is held horizontally, for example, by a holding device 12 in the vacuum container 7. The structure of this holding device 12 is shown in FIG.

In the holding device 12, the electrostatic chuck 19 is adhered and fixed on the electrode block 13 which is made of aluminum and is cooled by the cooling medium 16, and the semiconductor wafer 11 is held thereon. A ring 25 made of quartz or ceramic is arranged around the electrostatic chuck 19. The conductive layer of the electrostatic chuck 19 is connected to a DC power supply 18 for the electrostatic chuck 19 via a filter 24 for cutting high frequencies.

The electrostatic chuck 19 is for adjusting the temperature when the semiconductor wafer 11 is subjected to plasma processing. During the plasma processing, the DC power supply 18 is applied to attract the semiconductor wafer 11 to the chuck surface and to remove gas. Gas is introduced between the semiconductor wafer 11 and the electrostatic chuck 19 from the introduction unit 15 to promote heat conduction between the electrostatic chuck 19 and the semiconductor wafer 11, and thus the electrode on which the semiconductor wafer 11 is cooled. It is possible to keep a constant temperature difference with respect to the temperature of the block 13. Further, the electrode block 13 is insulated from another vacuum container 26 by an insulator 14 made of ceramic or the like, and a high frequency power source (100
The high frequency power from (for 2 kHz to 2 MHz) 21 is applied through the matching box 20.

In FIG. 3, the groove 22 in the electrostatic chuck 19 is shown.
The chuck surface provided with is shown as a plane. In the figure, the electrostatic chuck 19 has a diameter of 196 mm and is for an 8-inch wafer. A hatched portion is a groove 22. The groove 22 passes through the center axis of the electrostatic chuck 19 and three ring-shaped grooves having a groove width of 2 mm arranged concentrically with the center axis as a center and the center axis. Radially along the diameter 3
It is formed by eight straight grooves having a groove width of 2 mm extending between the ring-shaped grooves of the strip. In this apparatus, since the pressure of the He gas to be filled is about 4000 Pa (30 Torr), the groove 22 is processed to have a depth of 10 μm ± 10%.

A method of processing the groove 22 is shown in a process chart of FIG. First, a mask having a groove pattern (see FIG. 3) provided on the electrostatic chuck 19 is manufactured. In FIG. 4, each of (a) to (d) is a step of manufacturing a mask for etching the groove pattern. In step (a), S
OG (spin-on-glass) is applied to the entire upper surface of the electrostatic chuck 19, and in step (b), a resist is further applied thereon, and then in step (c), the resist is applied using the mask. After exposure to light and development, the process proceeds to step (d) to etch SOG by plasma etching or etching with a hydrofluoric acid solution. The mask on the electrostatic chuck 19 is completed up to this point.

After that, etching is performed with a chemical solution or plasma. In this etching process, as shown by steps (e) and (f) in FIG. 4, after the electrostatic chuck 19 in the masked state is etched in the step (e), the step (f) is performed. ) And remove the mask. In this way, the groove 22 having a predetermined pattern
Is completed. Note that etching with a chemical solution or etching with plasma depends on a material to be etched. Since alumina is used for the chuck body of the electrostatic chuck 19 here, it is processed by using plasma etching. As the gas in this case, a plasma etching process is performed using a mixed gas of chlorine and hydrogen.

[0025]

As described above, according to the electrostatic chuck and the method of manufacturing the same according to the present invention, the manufacturing reproducibility of the electrostatic chuck is excellent, and the durability is improved. By using a chuck, it promotes heat conduction during processing of a sample substrate such as a semiconductor substrate, and
It is possible to stably improve the uniformity of processing within the surface of the sample substrate.

[Brief description of drawings]

FIG. 1 is a schematic basic structure diagram of an etching apparatus using an electrostatic chuck according to an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a holding device 12 in FIG.

3 is a plan view showing a chuck surface of an electrostatic chuck 19 in FIG.

4A to 4C are process diagrams sequentially showing a method of forming a groove 22 on the electrostatic chuck 19 in FIG.

FIG. 5 is a mean free path diagram of various gases.

[Explanation of symbols]

 11 ... Sample substrate 19 ... Electrostatic chuck 22 ... Groove

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kouki Ikeda 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Co., Ltd. Kobe Research Institute (72) Inventor Kanemaru Moriga Nishi-ku, Kobe-shi, Hyogo Prefecture 1-5-5 Takatsukadai, Kobe Research Institute of Kobe Steel, Ltd. (72) Inventor Takashi Onishi 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel Institute of Kobe Steel, Ltd.

Claims (4)

[Claims] 1. In an electrostatic chuck, which is used by filling a gas between a sample substrate and a chuck body and adsorbs the sample substrate by electrostatic force, a surface of the chuck body in contact with the sample substrate is filled with the working gas at a filling pressure. An electrostatic chuck characterized in that a groove having a depth equal to or smaller than the mean free path is processed. 2. The electrostatic chuck according to claim 1, wherein the depth of the groove processed on the surface of the chuck body in contact with the sample substrate is 10 μm or less. 3. The electrostatic chuck according to claim 2, wherein the uniformity of the depth of the groove processed on the surface of the chuck body in contact with the sample substrate is within an error range of ± 10%. 4. A surface of the electrostatic chuck, which is used by being filled with a gas between the sample substrate and the chuck body and which adsorbs the sample substrate by electrostatic force, is etched with a chemical solution or plasma to etch the surface. A method of manufacturing an electrostatic chuck, characterized in that a groove having a depth equal to or less than an average free path at a filling pressure of a used gas is processed on the surface.