JPH0451541A - Placing base for semiconductor substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a mounting table for semiconductor substrates.

(Prior Art) Conventionally, in the manufacture of semiconductor integrated circuits, etching equipment, ion implantation equipment, sputtering equipment, etc. have been used. In these equipment, a semiconductor wafer is fixed to a mounting table in a vacuum, and a thin film is formed. and high-density formation of fine patterns.

In order to prevent the semiconductor wafer from becoming hot and changing its physical properties during such processing, the semiconductor wafer is placed and fixed on the convex mounting surface of the mounting table using clamps, electrostatic adsorption, etc. Techniques for performing cooling are disclosed in JP-A-81-208225, JP-U-58-41722, JP-A-60-5540, JP-A-82-5708 [1], and the like.

(Problems to be Solved by the Invention) In any of the techniques disclosed in the above-mentioned publications, uniform contact between the semiconductor wafer and the mounting surface of the mounting table cannot be obtained, and it is difficult to control the temperature over the entire surface of the semiconductor wafer. There was a problem that uniformity could not be ensured.

For example, in an etching system, if a certain part of a semiconductor wafer is hotter than other parts,
This area is more likely to be etched, and there is an increasing demand for more uniform temperature on the semiconductor wafer in order to respond to the rapidly increasing miniaturization of processing in recent years.

Therefore, an object of the present invention is to uniformly bring the front side of the semiconductor substrate into close contact with the mounting table, and to partially change the amount of gas filled between the semiconductor substrate and the mounting surface. It is an object of the present invention to provide a mounting table for a semiconductor substrate that can uniformly control the temperature over the entire surface of the semiconductor substrate and ensure uniformity of processing.

[Structure of the Invention (Means for Solving the Problems) The present invention provides a semiconductor substrate mounting table on which a semiconductor substrate is placed and whose temperature is controlled, when the semiconductor substrate is pressed by a clamp. , a mounting surface curved with substantially the same curved surface as the curved surface on which the substrate deforms under uniformly distributed loads; a means for filling gas between the mounting surface and the substrate; and increasing temperature control efficiency of the substrate. and four parts formed on the placement surface so that a large amount of the gas is ensured at the location.

(Function) Fixing of the semiconductor substrate to the mounting surface is achieved by pressing the peripheral portion of the semiconductor substrate with a clamp. At this time, the curved surface of the semiconductor substrate when a uniformly distributed load is applied to the semiconductor substrate and the curved surface of the mounting surface that supports the semiconductor substrate are formed to have substantially the same curvature based on the pressing force of the clamp. Therefore, when the semiconductor substrate is pressed by the clamp, the back surface of the semiconductor substrate comes into close contact with the mounting surface. In the present invention, gas is filled between the mounting surface and the substrate, and the heat transfer between the two is improved by the convection of the gas.

According to the analysis by the present inventors, the shape of the mounting surface mentioned above,
It has been found that even if gas is filled, temperature uniformity over the entire surface of the semiconductor substrate cannot be ensured. Accordingly, in the present invention, in order to make the temperature distribution on the substrate uniform, recesses are formed on the mounting surface at positions corresponding to locations on the substrate where temperature control efficiency should be improved. With such a configuration, when gas is filled between the mounting surface and the substrate, the recessed portion ensures that a large amount of gas is filled in that portion. Although the pressure of the filled gas is uniform over the entire area, by increasing the amount of gas filled in some areas, heat convection by gas molecules is activated, making it possible to increase the efficiency of local temperature control. As a result, temperature uniformity over the entire surface of the semiconductor substrate is achieved.

(Example) Hereinafter, an example in which the semiconductor substrate mounting table of the present invention is applied to an etching apparatus will be specifically described with reference to the drawings.

First, the overall structure of this etching apparatus will be explained with reference to FIG.

In FIG. 3, in the upper part of a cylindrical vacuum container 10 made of AI and whose surface is anodized, there is a disk-shaped upper electrode 14 that can be raised and lowered via an electrode lifting mechanism 11 such as an air cylinder or a ball screw, and a connecting rod 12. is provided. This upper electrode 14 is made of Al and has a flat plate shape with an alumite-treated surface, and is connected to a reaction gas supply vibe 16 that introduces a reaction gas such as argon or freon from a gas supply source (not shown). Further, a large number of small holes (not shown) are provided on the lower surface of the upper electrode 14, and the reaction gas can flow out into the vacuum vessel 10 through these small holes. Moreover, the upper electrode 14 is for plasma generation and has a power of, for example, 50
It is connected to a high frequency power source 18 of about 300 kHz to 13 MHz with 0 to 150 ΩW, and a cooling liquid circulator (not shown) is installed on the upper electrode 14 side so that the upper electrode 14 can be cooled with a circulating cooling liquid such as water. A disk-shaped upper electrode cooling block 22 is provided in which a cooling liquid can be circulated through the cooling liquid vibrator 20 .

At the lower part of the vacuum vessel 10, a disk-shaped lower electrode cooling block 26 is provided which can circulate a cooling liquid, such as water, from a cooling liquid circulator (not shown) via a cooling vibe 24, similarly to the upper electrode 14. A flat lower electrode 28 made of Al and whose surface is alumite-treated is installed so as to be in contact with the upper surface of the lower electrode cooling block 26.
This lower electrode 28 also serves as a mounting table for a semiconductor substrate,
For example, electrically grounded. Alternatively, a voltage may be applied.

Here, the vacuum container 10 can be opened and closed by an opening/closing mechanism (not shown), such as a gate valve mechanism, and the semiconductor substrate 30 positioned inside is transported by a transport mechanism (not shown), such as a hand arm, and the semiconductor substrate 30 is placed on the lower electrode 28. Board 3
0 can be placed. Moreover, the vacuum container 10 is
When the opening/closing mechanism (not shown) is closed, it becomes airtight, and the inside is kept under the desired vacuum condition by a vacuum pump (not shown), for example, several tens of meters.
Torr to several tens of Torr is possible. Here, if a transport mechanism (not shown) is installed in the vacuum preliminary chamber and is airtightly connected to the vacuum container 10, the time required to bring the inside of the vacuum container 10 to a desired degree of vacuum with a vacuum pump (not shown) after transporting the semiconductor substrate 30 is shortened. can.

Then, on the upper outer periphery of the lower electrode 28, a clamp ring 32, which is made of Al and whose surface is alumite-treated, is capable of crimping the periphery of the mounted semiconductor substrate 30 to the lower electrode 28 with a desired clamping load. A ring raising/lowering mechanism 36, for example, an air cylinder or the like, is installed so that it can be raised and lowered. Further, inside the lower electrode 8 near the center, for example, three pins are connected to a pin lifting mechanism 40 such as an air cylinder via a connecting part 38 so that the semiconductor substrate 30 can be raised and lowered relative to the lower electrode 28. A lift pin 42 made of SUS is provided. This lift pin 42 is inserted into the lower electrode 28 using a portion of a hole 44 formed in the lower electrode 28.

The hole 44 is connected to a cooling gas supply pipe 46 so that a cooling gas such as helium gas from a cooling gas supply source (not shown) can be supplied directly to the semiconductor substrate 30 .

Further, between the lower electrode 28 and the surface on which the semiconductor substrate 30 is placed, a sheet-like synthetic polymer film 48, for example, is disposed so as to make the impedance between the semiconductor substrate 30 and the electrode holding the semiconductor substrate 30, that is, the lower electrode 28 uniform. Thickness 20μm
A heat-resistant polyimide resin with a thickness of about 100 μm is provided on the surface of the lower electrode 28 on which the semiconductor substrate 30 is placed by adhering it with a heat-resistant acrylic resin adhesive.

Further, an insulating shield ring 56 made of, for example, tetrafluoroethylene resin is provided around the outer periphery of the upper electrode 14 so that plasma can be generated to approximately the same size as the semiconductor substrate 30 held on the lower electrode 28.

Here, the lower electrode 28 also serves as a mounting table for the semiconductor substrate 30, and the clamping load applied to the periphery of the semiconductor substrate 30 by the crumbling 32 is evenly distributed on the mounting surface of the semiconductor substrate 30 by fixing the periphery of the semiconductor substrate 30. It is formed into a convex shape with substantially the same curved surface as the deformed curved surface of the semiconductor substrate 30 when it is assumed that a load is applied.

Next, details of the lower electrode 28 will be explained with reference to FIG. 1.

As shown in the figure, on the surface side of the lower electrode 28, there is a gas discharge port 44a that communicates with the hole 44 connected to the cooling gas supply vibe 46 and opens on the surface thereof.

44b is provided. The gas discharge ports 44g also serve as a lifting path for the lift pin 42, and are provided at four locations in the central region of the lower electrode 28. On the other hand, the gas discharge ports 44b are provided on the peripheral edge side of the lower electrode 28, and open at each position along the inner concentric circle and at each position along the outer concentric circle. As a characteristic feature of this embodiment, a ring-shaped groove 60, which is an example of a recessed section, is formed on the surface of the lower electrode 28. As shown in FIG. 2, which is a detailed cross-sectional view of part A in FIG.
A ring-shaped groove is formed across four widths, and the portion from the top end to the bottom surface is configured to smoothly continue with an inclined surface. The reason why the ring groove 60 has the above-described cross-sectional shape is that the above-described polymer film 48 is disposed in close contact with the ring groove 60 as well. This ring groove 60 and the outer gas discharge port 44b communicate with each other.

Next, the effect will be explained.

With the lift pins 42 raised, the semiconductor substrate 30 is carried into the vacuum container 10 and placed on the lift bin 42. Thereafter, by lowering the lift bin 42, the semiconductor substrate 30 is placed on the lower electrode 28. After that, the crumbling ring 32 is lowered, and the semiconductor substrate 30 is placed on the lower electrode 2.
8. Crimp on top.

Here, the lower electrode 28 also serves as a mounting table for the semiconductor substrate 30.
Since the semiconductor substrate 30 is formed with almost the same curved surface as the curved surface deformed by the uniformly distributed load, the clamping load 32 applies a clamping load of, for example, 2 kg to the periphery of the semiconductor substrate 30.
By applying approximately 3 kg, the peripheral edge of the semiconductor substrate 30 is forcibly displaced, for example, by approximately 0.7 am-0.8 mm, and the semiconductor substrate 30 is crimped onto the mounting surface of the lower electrode 28. As a result, the contact pressure with the mounting surface becomes uniform over the entire surface of the semiconductor substrate 30, making it possible to bring the entire surface of the semiconductor substrate 30 into close contact with the mounting surface.

At this time, the vacuum container 10 has already been sealed and is evacuated to a predetermined degree of vacuum using a vacuum pump (not shown). Furthermore, the upper electrode 14 is lowered by the electrode lifting mechanism 11 and the connecting rod 12, and the electrode distance from the lower electrode 28 is set to a desired distance, for example, about a few inches.

Next, a reaction gas such as argon gas is supplied from a gas supply source (not shown) to the upper electrode 14 through the gas supply pipe 16, and this reaction gas is supplied to the inside of the vacuum vessel 1° from a small hole (not shown) on the lower surface of the upper electrode 14. leaks into At the same time, a high frequency voltage is applied to the upper electrode 14 by the high frequency power supply 18 to generate plasma between it and the installed lower electrode 28, and the semiconductor substrate 3o on the lower electrode 28 is etched with this plasma.

At this time, the semiconductor substrate 3o is compressed to the lower electrode 28 by crumpling 32, but from a microscopic perspective, a gap exists between the lower electrode 28 and the semiconductor substrate 30 due to surface roughness, etc. . Due to the existence of this gap, particularly in a vacuum state, heat transfer between the semiconductor substrate 30 and the lower electrode 28 is not performed well, and even if the lower electrode 28 is cooled by circulating a cooling liquid through the cooling pipe 24, Even if the semiconductor substrate 30 is cooled effectively, it becomes impossible to cool the semiconductor substrate 30 effectively.

Therefore, gas is filled between the semiconductor substrate 30 and the lower electrode 28, more specifically between the semiconductor substrate 30 and the polymer film 48, and the convection of this gas ensures heat transfer between the two. . This gas, for example, He or the like is supplied at a predetermined pressure and flow rate, for example, about several cc/*1n. Such gas is transferred to the cooled lower electrode 28.
This ensures good heat transfer between the semiconductor substrate 30 and the semiconductor substrate 30 heated by the plasma, and cools the semiconductor substrate 30 by its own refrigerant action.

Here, the inventors have confirmed that, as a characteristic of such an etching apparatus, the temperature in the peripheral region of the semiconductor substrate 30 is higher than that in the central region. Therefore, in this embodiment, a ring groove 60 for supplying a heat transfer gas is formed in the peripheral portion of the lower electrode 28, which is a relatively variable temperature portion, for example, at a position about 10 degrees inward from the outer edge of the semiconductor substrate 30.
This ring groove 60 portion is configured to be filled with a relatively large amount of gas to achieve uniform cooling.

By filling a large amount of gas in the region corresponding to the periphery of the semiconductor substrate 30 in this way, variations in temperature distribution between the center and the periphery of the semiconductor substrate 30 can be suppressed, and the entire surface of the semiconductor substrate 30 can be It was possible to ensure temperature uniformity.

In FIG. 4, solid lines indicate the maximum and minimum temperatures of the semiconductor substrate when the filling pressure of the cooling gas is varied. The broken lines in the figure indicate the maximum temperature and the minimum temperature when a type of lower electrode 28 that does not have the ring groove 60 is used. As is clear from the figure, when the lower electrode 28 having the ring groove 60 is used, the semiconductor substrate 3
It was confirmed that the temperature of 0 was lowered. Moreover, in the case of the lower electrode 28 having the ring groove 60, the semiconductor substrate 3
It has been found that the difference between the maximum and minimum temperatures above 0 becomes smaller, that is, the temperature uniformity improves. It was confirmed that such an effect is more pronounced when the filling pressure of the cooling gas is 5°0 Torr or more, as shown in the figure.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible within the scope of the invention.

A plurality of concave ring grooves may be provided.

Although the above embodiment describes the case where the polymer film 48 is provided on the lower electrode 28, it is not necessary to provide such a polymer film 48.

Furthermore, the present invention is not necessarily applied to the above-mentioned plasma etching apparatus, but is also applicable to sputtering apparatus,
It can also be applied as a mounting table for an ion implanter or a CVD device.

[Effects of the Invention] As explained above, according to the present invention, the contact pressure between the semiconductor substrate and the mounting surface of the mounting table can be made uniform, and even when temperature uniformity cannot be obtained thereby, it is possible to By forming recesses at locations that increase temperature control efficiency, it is possible to ensure uniform temperature over the entire surface of the semiconductor substrate, and it is possible to ensure uniformity of processing.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a lower electrode in a plasma etching apparatus to which the present invention is applied, FIG. 2 is an enlarged cross-sectional view of part A in FIG. 1, and FIG. 3 is a plasma etching apparatus according to an embodiment. FIG. 4 is a characteristic diagram showing the maximum temperature and minimum temperature on the semiconductor substrate when the back pressure of the cooling gas is changed. 10... Vacuum container, 14... Upper electrode, 28...
Mounting table (lower electrode), 30... Semiconductor substrate, 32... Crumbling, 60... Recess (ring groove).

Claims (1)

[Claims] (1) In a semiconductor substrate mounting table on which a semiconductor substrate is placed and whose temperature is controlled, a curved surface that is almost the same as the curved surface on which the semiconductor substrate is deformed by an evenly distributed load when the semiconductor substrate is pressed by a clamp is used. A curved mounting surface; a means for filling gas between the mounting surface and the substrate; and a means for filling a large amount of the gas at a location where temperature control efficiency of the substrate is increased. , a recess formed in the above-mentioned mounting surface, and a mounting table for a semiconductor substrate.