JPS61119037A - Temperature controlling process and device of processed item in vacuum - Google Patents

Abstract

PURPOSE:To make it feasible to perform fine pattern etching, high quality filming and ion implanting process by a method wherein in case of vacuum processing of plasma etc., temperature control such as highly efficient wafer cooling etc. is performed having no effect upon the processing characteristics. CONSTITUTION:Processing gas supplied from a processing gas bomb 61 is pressure-regulated by a pressure regulating valve 62 and flow-controlled by a massflow controller 63 to be fed to a spare chamber 64. The processing gas at constant pressure is passed through a vacuum gauge 66 to be led to a gas leading-in port 65 while being constantly fedback to the mass controller 63. In such a constitution, a pressure P2 detected by a vacuum gauge 66 and another pressure P1 of refrigerant 70 (i.e. the pressure in refrigerant diaphragm chamber 48) are compared with each other to control the pressure of refrigerant 70 at high level making it higher than the pressure on a member 41 loaded with processed item. Through these procedures, the loading member 41 may be brought into close contact with backside of wafer regardless of any swell due to the pressure of wafer cooling gas and warping of wafer itself.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for controlling the temperature of a workpiece in vacuum processing. The present invention provides a method and apparatus for effectively controlling the temperature of a workpiece during dry etching using a plasma etching or reactive sputter etching device, or doping with impurities through ion implantation. can be used.

[Background of the invention]

2. Description of the Related Art In processing a workpiece (for example, a semiconductor wafer), for example, in a process for manufacturing an integrated circuit, the workpiece may be affected by an increase in temperature. - For example, during dry etching, a resist with poor heat resistance may melt or soften due to radiation from plasma or collisions with ions and electrons, causing the resist film to sag or shrink. For this reason, fine pattern etching cannot be performed,
Furthermore, it becomes difficult to remove the mask remaining after dry etching. Especially when the high frequency applied voltage is increased in order to accelerate the etching rate: this tendency is remarkable.

Another example is found in ion implantation of semiconductor wafers. When high-concentration ion implantation is performed during ion implantation, semiconductor ware may (1) be heated once more.6. S: “.Condition 1. The damage to the Yoji there were.

In the above case, it is necessary to lower the temperature of the object to be processed, such as a semiconductor wafer. Conventionally, for example, in the case of semiconductors, the temperature was controlled by circulating a cooling refrigerant through an electrode on which a semiconductor wafer was mounted. However, semiconductor wafers have warpage of approximately several tens of micrometers.

Because it is light, simply placing it on the workpiece placement surface does not provide sufficient thermal contact between the workpiece placement surface and the semiconductor wafer.
There was a problem that heat dissipation was not performed well. Therefore, methods for effectively increasing the exchange of heat between the two surfaces have been devised and disclosed. This method aims to improve thermal conductivity by introducing a gas pressurized by the pressure of the processing atmosphere between the semiconductor wafer and the processing object mounting surface (Japanese Patent Laid-Open No. 56-48132. According to this conventional example, gas molecules in a gas chamber provided between the semiconductor wafer and the workpiece mounting surface allow the semiconductor wafer and the workpiece mounting surface to be controlled in temperature. This allows for more effective temperature control than when the semiconductor wafer is simply placed on the workpiece placement surface. However, in this conventional example, the helium gas used for cooling may leak and mix with the plasma processing gas, inhibiting the plasma processing, and in order to prevent this, a gas other than helium gas is used. However, there is a problem that the cooling efficiency deteriorates.

This conventional plasma processing apparatus will be described in more detail with reference to FIG. 2 as follows.

The processing chamber 1 is provided with a substrate support 2, an electrode 3, a gas supply port 41 from a gas line (not shown), and an exhaust port 5 connected to an exhaust pump (not shown).

A high frequency power source 6 is connected to the electrode 3. The substrate support stand 2 has a cooling water passage 7, and a drain port 9 is connected to the supply port 8.
Cooling water passes through and cools the substrate support stand 2. Further, a substrate 10 is placed on this upper surface and is pressed against a substrate support stand by a substrate presser.

Helium gas for cooling is supplied between the substrate 10 and the substrate support 2 from a gas line 12.

The gas line 12 has a preliminary chamber 13. helium gas source 14;
Control valve 15, vacuum gauge 1 for pressure measurement in preliminary chamber 13
6. A control system 17 is provided. The preliminary chamber 13 feeds back the measured value of the vacuum gauge 16 to the control valve 15 to maintain a constant pressure.

When performing plasma processing with this apparatus at a pressure of about 10 pa in the processing chamber, helium gas of about 300 to 700 pa is supplied from the gas line 12. However, at this time, since this apparatus cannot completely seal between the substrate support stand 2 and the substrate 10, helium gas leaks into the processing chamber 1 as shown by the broken line A in the figure, causing the gas supply port to leak. Mix with the processing gas supplied from 4. As a result, plasma processing characteristics change.

This causes a problem of poor reproducibility. Furthermore, if a gas of the same type as the processing gas is supplied instead of helium gas in order to solve this problem, a problem arises in that the substrate IO is not sufficiently cooled.

As described above, the conventional substrate cooling method using gas cooling does not have sufficient performance for application to a plasma processing apparatus.

[Purpose of the invention]

The object of the present invention is to solve the above objectives. To provide a cooling method with sufficient performance that can be applied to plasma processing equipment, and to provide a cooling device that implements the method and is capable of controlling the temperature of a processed object in vacuum with higher performance. It is in.

[Summary of the invention]

The present invention was made based on the following findings. That is, as a result of investigating the heat transfer by gas between the substrate and the substrate support, it was found that the processing gas was CCΩ4-CF4-
It has been found that gases such as CaFa, which have large molecular weights, are greatly affected by the state of close contact between the substrate and the substrate support. In addition, since the substrate is generally around 0.5 mm thick, it was found that the pressure of the cooling gas caused the substrate to swell into a convex shape, creating a gap between the substrate and the substrate support. This was done after various studies on the effects of this, and the adhesion of the objects to be processed was controlled by controlling the pressure in the two spaces separated by the objects to be processed. As a result, it is possible to use the processing gas as the cooling gas.

The method for controlling the temperature of a workpiece according to the present invention includes placing the workpiece on a mounting surface of a workpiece mounting member when processing the workpiece in a vacuum atmosphere, and placing the workpiece on the mounting surface. At the same time, the workpiece mounting member is cooled by a cooling refrigerant, and gas is supplied between the workpiece and the workpiece mounting surface, and the pressure of the cooling refrigerant is reduced by the supplied gas. The feature is that it can be made higher than the pressure.

Further, the temperature control device for a processed object of the present invention is a device for controlling the temperature of the processed object when processing the processed object in a vacuum atmosphere, and is a device for controlling the temperature of the processed object when the processed object is placed and fixed. An object placement member, a cooling means for circulating a cooling refrigerant to cool the object placement member, and a gas feeding means for feeding gas between the object to be processed and the object placement surface. It is characterized in that it further comprises a control means for controlling the pressure of the cooling refrigerant to be higher than the feed gas pressure.

Since the present invention has the above configuration, the gap between the workpiece and the workpiece mounting surface can be made extremely small. As a result, a sufficient cooling effect can be obtained even when using a gas with a relatively large molecular weight, not necessarily helium, and thus cooling can be achieved using a desired gas. In other words, if the gap between the workpiece and the workpiece mounting surface is d, as the gap d becomes smaller, helium will also be absorbed by other materials such as CCA4.
As shown in FIG. 3, as d approaches O, the relationship between pressure p and thermal conductivity becomes close to that of CCA, HQ, and N2.

Therefore, if the present invention is used, sufficient effects can be obtained even if a cooling gas other than helium is used, and therefore temperature control can be performed effectively.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be specifically described with reference to FIG. FIG. 1 is a longitudinal sectional view of the temperature control device of this embodiment. In this example, the present invention is applied to temperature control of a semiconductor wafer during plasma processing.

A counter electrode 31 is built in the upper part of the processing chamber 30, and a processing gas line 33 is connected via an inlet 32 of the counter electrode 31.
A processing gas is supplied from the gas exhaust port 34, and the gas is exhausted from the gas exhaust port 34 by an exhaust vacuum pump 35. On the other hand, a lower electrode 40 is provided at the lower part, and a mounting member 41 made of a thin metal plate (for example, SUS with a thickness of about 50 μm) is placed on the upper surface of the lower electrode, and is fixed with a bolt 43 via a ring-shaped parent material 42 . The outer periphery of the semiconductor wafer 56 placed on the mounting member 41 is held and fixed by a workpiece presser 44 made of a quartz plate with bolts 45 . A cooling refrigerant inlet 046, an outlet 47, and a refrigerant diaphragm chamber 48 are formed in the lower part of the electrode, and a slide shaft 50 located below is connected by brazing 49 to the center of the workpiece mounting surface. Sliding guide 5
form 1. A refrigerant is sealed between the workpiece mounting member 41 and the lower electrode 40, and between the lower electrode 40 and the slide 1plh50 through rings 52 and 53 in the respective grooves, and the cooling refrigerant 70 is sent to the circulation pump 72. The refrigerant is sucked and circulated from the refrigerant tank 71 to the internal electrode diaphragm chamber 48 and flows through the refrigerant outlet 47 . At this time, the refrigerant 70 in the refrigerant tank
The pressure applied to the diaphragm (such as oil with low vapor pressure) is controlled by the pressure control valve 74 of the vacuum pump 73, and the temperature is maintained at a constant temperature by the temperature control unit 80. Further, the lower electrode is connected to a high frequency power source 54, and the vacuum container 30 is insulated from the electrode by an insulator 55.

On the other hand, a gas supply port 60 is opened in the slide shaft. The processing gas supplied from the processing gas cylinder 61 is sent to the preparatory chamber 64 after its pressure is adjusted by a pressure control valve 62 and its flow rate is adjusted by a mass flow controller 63 . A vacuum gauge 6 is used to keep the gas pressure constant and introduce it into the gas inlet 65.
6, feedback is constantly applied to the mass flow controller 63.

With this configuration, the pressure P2 detected by the vacuum gauge 66 and the pressure P of the cooling refrigerant 70 (therefore, the refrigerant diaphragm chamber 4
8), the pressure of the refrigerant flow O is controlled to be higher than the pressure above the processing object mounting member 41.

Specifically, this control is performed as follows.

That is, in the plasma processing apparatus shown above, Process 1: While supplying processing gas into the chamber 30, the chamber is evacuated by the exhaust vacuum pump 35 to a pressure of 10 to 20 pa, and the high frequency power source 54 is used to evacuate the chamber. A high frequency voltage is applied to generate plasma and processing is performed. Wafer 56 and a with it placed on it
Between the mounting members 41, 300 to 700
Supply a processing gas of pa.

Further, the refrigerant flowing through the diaphragm chamber 48 is controlled so that a pressure approximately 500 pa higher than that of the processing gas is applied to the diaphragm.

The thickness of the diaphragm's stainless steel plate is approximately 1/10 that of the 50 μm wafer 56, so the mounting member 41 is.

The diaphragm is pressed against the wafer 56 due to the pressure difference between the rain surfaces.

Therefore, the mounting member 41 and the back surface of the wafer can be brought into close contact with each other regardless of the bulge caused by the pressure of the processing gas for cooling the wafer or the warpage of the wafer itself.

In this way, the wafer 56, which is the object to be processed, and the mounting member 41 on which it is placed are brought into close contact with each other, and the gap between them is made extremely small, so that a sufficient cooling effect can be achieved without necessarily using helium gas. is obtained.

In this example, a processing gas was used as the cooling gas, but even in this case, it was as good as when helium was used.
Good cooling performance could be obtained. Furthermore, as a result of being able to use the processing gas as the cooling gas in this way, both gases are used in the opposite direction, so that no influence on the processing characteristics can be completely eliminated.

Although the present invention has been mainly described above with respect to the case where the processing gas is used as the cooling gas, the present invention is not limited to this. In other words, even with helium gas, which has excellent cooling performance, the adhesion between the wafer and the mounting surface is related to the cooling performance, and by improving the adhesion, when the same helium gas is used, it generates 1.5 times more heat than before. I was able to obtain the conductivity.

Therefore, it is clear that this can be applied to temperature control of a processed material in vacuum, such as in ion implantation.

〔Effect of the invention〕

According to the present invention, during vacuum self-processing such as plasma processing,
Temperature control such as high-performance wafer cooling can be performed without affecting the processing characteristics, and temperature control with good cooling performance can be performed in general, making it possible to perform fine pattern etching, high-quality film formation, and ion implantation. - It is possible to improve the yield in semiconductor product manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a temperature control device according to an embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of a conventional substrate temperature control device.
FIG. 3 is a diagram for explaining the present invention in detail. 40... Lower electrode, 41... Processed object mounting member, 4
4... Workpiece holding down, 44.47... Cooling refrigerant inlet and outlet, 48... Diaphragm chamber, 50...
- Slide shaft, 60... Gas supply port, 64... Preparation chamber, 80... Temperature control unit. Representative Patent Attorney Tadashi Akimoto Figure 1 Figure 2

Claims (4)

[Claims] 1. When processing the workpiece in a vacuum atmosphere, the workpiece is placed on the mounting surface of the workpiece mounting member, the workpiece is fixed to the mounting surface, and the workpiece mounting member is cooled. The cooling refrigerant is cooled by a cooling refrigerant, and gas is supplied between the workpiece and the workpiece mounting surface, so that the pressure of the cooling refrigerant can be made higher than the pressure of the supplied gas. A method for controlling the temperature of a processed object in vacuum processing. 2. 2. The method for controlling the temperature of a workpiece in vacuum processing according to claim 1, wherein the workpiece mounting member is formed of a thin plate having a rigidity lower than that of the workpiece. 3. Claim 1 or 2, characterized in that a gas of the same quality as the processing gas is used as the cooling refrigerant.
A method for controlling the temperature of a workpiece in vacuum processing as described in 2. 4. This is a device that controls the temperature of the workpiece when processing the workpiece in a vacuum atmosphere, and includes a workpiece mounting member on which the workpiece is placed and fixed, and a workpiece that circulates a cooling refrigerant to control the temperature of the workpiece. It is equipped with a cooling means for cooling the object placement member, and a gas supply means for feeding gas between the object to be processed and the object placement surface, and the pressure of the cooling refrigerant is adjusted to the feeding gas pressure. An apparatus for controlling the temperature of a processed object in a vacuum, characterized by comprising a control means for controlling the temperature at a higher temperature.