JPH02110926A - Temperature control of specimen and device thereof - Google Patents

Abstract

PURPOSE:To effectively control the temperature of a specimen to be vacuum-processed thereby lessening the effect of thermal conductive gas on the process by a method wherein the specimen is arranged on a specimen base provided with electric insulating material on the almost whole specimen arranging surface and then the specimen is electrostatically suction-held on the specimen base to feed the thermal conductive gas to the gap between the rear side of the specimen and the electric insulating material. CONSTITUTION:A specimen to be vacuum processed is arranged on a specimen base 20 provided with electric insulating material 60 on the almost whole specimen arranging surface through the intermediary of the said material 60; the arranged specimen is electrostatically suction-held on the specimen base 20; and then a thermal conductive gas is fed to a gap between the rear side of the suction-held specimen and the said electric insulating material 60. For example, He gas as the said thermal conductive gas is dispertion-fed to the gap between the rear side of the suction-held specimen and the electric insulating material 60 by dispersion grooves 21a, 21b provided on the said electric insulating material 60. Through these procedures, the gap amount between the rear side of the specimen and the specimen base 20 can be restrained from increasing thus enabling the specimen temperature to be effectively controlled simultaneously restraining the thermal conductive gas from running into the vacuum processing chamber to lessen the effect of the thermal conductive gas on the process.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method and apparatus for controlling the temperature of a sample.

The present invention relates to a sample temperature control method and apparatus particularly suitable for controlling the temperature of a substrate.

[Conventional technology]

JArli, for example, processes a sample using vacuum processing, for example, plasma (hereinafter abbreviated as plasma processing).

One of the important uses of dry etching equipment is the formation of fine patterns in the manufacture of minute solid-state devices such as semiconductor integrated circuits. The formation of this fine pattern is usually done by exposing a polymeric material called a resist to ultraviolet rays and developing it on a semiconductor substrate (hereinafter referred to as the substrate), which is the sample, and dry etching the substrate using the pattern as a mask. This is done by transcribing it into .

During such dry etching of a substrate, the mask and substrate are heated by the heat of chemical reaction with the plasma and the impact energy of ions or electrons in the plasma. Therefore, if sufficient heat dissipation is not obtained, that is, if the temperature of the substrate is not well controlled, the mask may become deformed or deteriorated, making it impossible to form a correct pattern, or making it difficult to remove the mask from the substrate after dry etching. This causes an inconvenience such as. Therefore, in order to eliminate these inconveniences, the following techniques have been conventionally used and proposed. These conventional techniques will be explained below.

A first example of the prior art is, for example, Japanese Patent Publication No. 56-53
As shown in Japanese Patent No. 853, a sample stage to which the output of a high-frequency power source is applied is water-cooled, and a material to be processed is placed on the sample stage via a dielectric film.

By applying a DC voltage to the sample stage, a potential difference is applied to the dielectric film via plasma, and the resulting electrostatic adsorption force causes the material to be processed to be attracted to the sample stage, creating a bond between the material to be processed and the sample stage. Some reduce thermal resistance and effectively cool the workpiece.

As a second example of the prior art, for example, Japanese Patent Application Laid-Open No. 57-14
．． As shown in Publication No. 5321.

Some methods cool the wafer directly by blowing gas from the back side of the wafer.

As a third example of the prior art, for example, E, J.

Egerton et al., 5solid 5tate Tec
hnology, Vow, 25.

No, 8. As shown in pages 84 to 87 (1982-8), an electrode, which is a water-cooled sample stage, and a substrate placed on the electrode and fixed by pressing the outer periphery to the electrode using mechanical clamping means. During this period, G with a pressure of about 6 Torr
Some devices allow He to flow to reduce the thermal resistance between the electrode and the substrate, thereby effectively cooling the substrate.

[Problem to be solved by the invention]

However, these prior art techniques do not give sufficient consideration to the effective cooling of the sample and the influence of the gas flowing on the backside of the substrate on the process, resulting in the following problems.

In the first conventional technique, even if the process is carried out as described above, the contact area between the material to be processed and the sample stage is still small, and there is a small gap when viewed microscopically. Further, a process gas enters this gap, and this gas acts as a thermal resistance. In general dry etching equipment, 1 usually 0.1T.
The material to be processed is etched using a process gas pressure of about 100 yen or more, and the gap between the material to be processed and the dielectric film is smaller than the mean free path length of the process gas, so the gap is reduced due to electrostatic adsorption force. There is almost no difference in terms of thermal resistance, and the effect increases as the contact area increases. Therefore, in order to reduce the thermal resistance between the material to be processed and the sample stage and cool the material to be processed more effectively, a large electrostatic adsorption force is required. For this reason,
Such technology has the following problems.

(1) The material to be processed becomes difficult to separate from the sample stage.
It takes time to transport the material to be processed after the etching process, and the material to be processed may be damaged.

(2) In order to generate a large electrostatic attraction force, it is necessary to provide a large potential difference between the dielectric film and the material to be processed. However, if this potential difference becomes large, the material to be processed, that is, the substrate This increases damage to the internal elements, resulting in poor yields, and the yield becomes even worse in microfabrication of thin gate films, which is becoming more demanding as the degree of integration of integrated circuits increases.

In the second conventional technology, helium gas (hereinafter referred to as G) I
By using a gas having excellent thermal conductivity such as (abbreviated as "e"), the cooling efficiency of the wafer can be improved.

However, such a technique has a first-order problem.

(1) Since a large amount of gas flows into the etching chamber rather than remaining on the cooling surface side of the wafer, even an inert gas like G11e has a large effect on the process, and therefore cannot be used in all processes.

In the third conventional technique described above, even if the outer periphery of the substrate is fixed with a clamp, leakage of Glee into the vacuum processing chamber is unavoidable, and therefore a problem similar to that in the second conventional technique described above is caused. Moreover, it also has the following problems.

(1) Since the outer periphery of the substrate is pressed by mechanical clamping means and the substrate is fixed to the electrode, the substrate is fixed to the circulating GH.
Due to the gas pressure e, it deforms into a convex shape with a middle height in a peripherally supported state. Therefore, the amount of gap between the back surface of the substrate and the electrode becomes large, and the heat conduction characteristics between the substrate and the electrode deteriorate accordingly. For this reason, the substrate cannot be cooled sufficiently effectively.

(2) Since the electrode is provided with a mechanical clamp that presses and fixes the outer periphery of the substrate, the device fabrication area within the substrate is reduced, plasma uniformity is inhibited, and one mechanical clamp During operation of the means, reaction products adhering to the mechanical clamping means fall off from the mechanical clamping means.

There is a risk of dust generation and, furthermore, substrate transport becomes extremely complicated, resulting in an increased size and reduced reliability of the device.

An object of the present invention is to provide a method and apparatus for controlling the temperature of a sample that can effectively control the temperature of a sample to be vacuum processed and reduce the influence of heat transfer gas on the process.

[Means to solve the problem]

The present invention provides a sample stand in which an electrical insulating material is provided on substantially the entire surface of the placement surface of a sample to be vacuum processed, and a suction means for electrostatically holding the sample placed on the sample stand via the electrical insulating material. And, it is held by suction by suction means.

A sample stage equipped with a gas supply means for supplying heat transfer gas to the gap between the back surface of the sample being held and the electrical insulating material, and the electrical insulating material is provided on substantially the entire surface of the surface on which the sample to be vacuum-treated is placed. The second method involves placing a sample through an electrically insulating material, holding the sample on a sample stage by electrostatic adsorption, and supplying heat transfer gas to the gap between the back surface of the sample and the electrically insulating material. This can be achieved by doing so.

[For production]

The sample is placed on a sample stand with an electric insulating material provided on substantially the entire surface of the placement surface of the sample to be vacuum processed, with the sample placed through the electric insulating material, and the placed sample is electrostatically attracted and held on the sample stand by an adsorption means. By supplying heat transfer gas by the gas supply means to the gap between the back surface of the sample held by suction and the electrical insulating material, deformation of the sample due to the gas pressure of the heat transfer gas is prevented, and the back surface of the sample held by suction and This suppresses the increase in the gap between the sample stage and the sample stage, effectively controlling the temperature of the sample to be vacuum processed, as well as suppressing the flow of heat transfer gas into the vacuum processing chamber, thereby reducing the amount of heat transfer gas imparted to the process. The impact can be reduced.

〔Example〕

Apparatus for vacuum processing, for example plasma processing, a sample include a dry etching apparatus, a plasma CVD apparatus, a sputtering apparatus, etc. Here, the present invention will be explained in detail by taking the dry etching apparatus as an example.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows the schematic structure of the dry etching apparatus. In this case, a lower electrode 20 serving as a sample stage is electrically insulated and airtightly provided on the bottom wall of the vacuum processing chamber IO via an insulator 11. The vacuum processing chamber 10 includes a discharge space 30 and an upper electrode 40 vertically opposed to the lower electrode 20.

An insulator 60, which is an electrical insulating material, is embedded in the surface of the lower electrode 20, which corresponds to the back surface of the substrate 50, which is a sample. Furthermore, a groove 21 is formed in the lower electrode 2o to form a supply path for heat transfer gas. The I@edge 60 and the groove 21 will be described in detail later with reference to FIGS. 2 and 3.

The lower electrode 20 has a gas supply path 23a communicating with the groove 21.
and a gas exhaust path 23b are formed. Furthermore, a coolant flow path 22 is formed within the lower electrode 20 . The lower electrode 20 has a refrigerant supply path 24a communicating with the refrigerant flow path 22.
and a refrigerant discharge path 24b are formed.

A conduit 70a connected to a gas source (not shown) is connected to the gas supply path 23a, and one end of a four-pipe 70b is connected to the gas discharge path 23b. The conduit 70a includes a mass flow controller (hereinafter referred to as MFC and l118) 7.
A regulating valve 72 is provided in the conduit 70b. The other end of the conduit 70b is connected to a conduit 12 for exhaust that connects the vacuum processing chamber 10 and the vacuum pump 80. The refrigerant supply path 24a includes a refrigerant source (not shown).
A conduit 9011 connected to the refrigerant discharge path 24 is connected to the refrigerant discharge path 24.
b is connected to a refrigerant discharge conduit 90b.

A high frequency power source 101 is connected to the lower electrode 20 through a matching box 100, and a DC power source 103 is connected through a high frequency cutoff circuit 102. Note that the vacuum processing chamber 10. High frequency power supply 101 and DC power supply 103 are each grounded.

Further, the upper electrode 40 is formed with a processing gas discharge hole (not shown) that opens into the discharge space 30 and a processing gas flow path (not shown) that communicates with the processing gas discharge hole. A conduit (not shown) connected to a processing gas supply device (not shown) is connected to the processing gas flow path.

Next, a detailed structural example of the lower electrode 20 shown in FIG. 1 will be explained with reference to FIGS. 2 and 3.

In FIGS. 2 and 3, the gas supply path 23a shown in FIG. It is installed so that it can move up and down. On the outside of the conduit 25a,
The gas discharge path 23b shown in FIG. 1 is formed to form the conduit 25b.
is installed. A conduit 25c is disposed outside the conduit 25b, forming the refrigerant supply j@24a shown in FIG. A conduit 25d is disposed outside the conduit 25c, forming a refrigerant discharge path 24b shown in FIG. The upper end of the conduit 25b is connected to the positive electrode upper plate 26, and the second end of the conduit 25d is the electrode temporary support 2 below the second class 26.
It is connected to 7. A cavity 28 is formed at the upper end of the conduit 25b by the electrode upper plate 26, the electrode-F temporary holder 27, and the conduit 25b. In the empty chamber 28, a dividing plate 29 is provided with a refrigerant flow path 2.
The upper end of the conduit 25c forms a dividing plate 29.
connected to.

The board (not shown) is drawn '11! Top plate 26
In this case, i7 for radial heat transfer gas distribution
, 721a and a plurality of circumferential heat transfer gas dispersion grooves 21b are formed. i:Hla for heat transfer gas dispersion,
21b is connected to conduits 25a and 25b.

Further, an insulator 60 is provided on the surface of the electrode upper plate 26 on which the substrate is placed (substantially the entire surface on which the substrate is placed). In this case, an insulating film is coated.

In addition, in FIGS. 2 and 3, 110 is an electrode cover that protects the surface of the electrode upper plate 26 in the part where the substrate is not placed;
11 is an insulating cover that protects the lower electrode 20 other than the surface of the electrode upper plate 26, and 112 is a shield plate. Further, at the upper end of the conduit 25a, there are pins 113 that support the substrate from the back surface side when the substrate is placed on the electrode upper plate 26 and when the substrate is removed from the electrode upper plate 26. Books are provided.

Further, the depth of the grooves 21a and 21b is determined by the gap between the back surface of the substrate and the bottom of the grooves 21a and 21b when the substrate is attracted
If the groove gap (hereinafter abbreviated as "groove gap") exceeds the mean free path length of the heat transfer gas, the heat transfer effect of the heat transfer gas will decrease. Groove 21a so as to be equal to or less than the path length.

It is better to select the depth of 21b.

In addition, the area of the part (hereinafter referred to as adsorption part) that is substantially in close contact with the insulating film by electrostatic adsorption on the back surface of the substrate is determined by the differential pressure between the gas pressure of the heat transfer gas and the pressure in the vacuum processing chamber 10. In order to prevent the substrate from floating up from the lower electrode 20, it is selected based on the required electrostatic adsorption force determined by the differential pressure between the gas pressure of the heat transfer gas and the pressure of the vacuum processing chamber 10. For example, the pressure of the heat transfer gas is I Torr and the pressure of the vacuum processing chamber 10 is 0.0 Torr. ITo
In the case of rr, the required electrostatic attraction force to prevent the substrate from floating from the lower electrode 20 is approximately 1.3 g/a+? and
Therefore, the area of the suction portion is selected to be approximately 115 times the area of the back surface of the substrate. It should be noted that this example is just an example, and it goes without saying that if the area of the attraction portion is increased to cover almost the entire back surface of the substrate, the electrostatic attraction force can be reduced accordingly.

In the dry etching apparatus of FIGS. 1 to 3 configured as described above, the substrate 50 is transported into the vacuum processing chamber 10 by a known transport device (not shown), and then the outer periphery of the back surface is insulated. It is placed on the lower electrode 20 in correspondence with the object 60. After the substrate 50 has been placed on the lower electrode 20 , the processing gas supplied from the processing gas supply device to the gas flow path via the conduit passes through the gas flow path and then flows into the discharge space 30 from the gas discharge hole of the upper electrode 40 . is released. Vacuum processing chamber 1
After adjusting the pressure within 0, a high frequency power source 101 is connected to the lower electrode 20.
Higher frequency power is applied, and a glow discharge occurs between the lower electrode 20 and the upper fQ pole 40. The processing gas in the discharge space 30 is turned into plasma by this glow discharge, and the etching process of the substrate 50 is started by this plasma. In addition, the lower electrode 20 also includes a DC power source 103.
DC voltage is applied. By starting the plasma etching process of the substrate 50, the self-bias voltage and DC power supply 103 generated by this plasma processing process are reduced.
With the DC voltage applied to the lower electrode 20 by
The substrate 50 is electrostatically attracted to the lower electrode 20 and is substantially closely attached and fixed. After that, in the grooves 21a and 21b,
A heat transfer gas, for example, is supplied from the gas source sequentially through the MFC 71 and the gas supply path 23a.

G11e is supplied. As a result, G1-1e is supplied from the grooves 21a and 21b over the entire small gap between the back surface of the substrate and the lower electrode 20, which are in substantially close contact with each other. At this time, GHe is supplied with the gas amount controlled by operating the MFC 71 and the adjustment valve 72.

Depending on the case, it is also possible to use GHe confined in the gap between the back surface of the substrate and the lower electrode 20, specifically, the insulator 60. As a result, the thermal resistance between the substrate 50 and the lower electrode 20, which is cooled by the refrigerant 1 flowing through the refrigerant flow path 22, such as water or low-temperature liquefied gas, is uniformly reduced over the entire back surface of the substrate, and is effectively cooled, ie, uniformly and efficiently.

In other words, the substrate can be effectively cooled by suctioning and holding substantially the entire back surface of the substrate. After that, as the etching approaches the end, G) is applied to the grooves 21a and 21b.
The supply of le is stopped, and upon completion of etching, the supply of processing gas to the discharge space 30 and the application of DC voltage and high frequency power to the lower electrode 20 are stopped. after that,
Subsequently, the electrostatic attraction force generated on the substrate 50 is released, and in this case, the pin 11, which is electrically maintained at the same potential as the electrode upper plate 26, is released.
3 comes into contact with the substrate 50, static electricity is removed, and the operation of the pin 113 causes the substrate 50 to contact the lower electrode 20.
removed from above. Thereafter, the substrate 50 is transported out of the vacuum processing chamber 10 by a known transport device. Further, static electricity can also be removed by stopping the application of the high-frequency power after stopping the application of the DC voltage.

As described above, according to this embodiment, the following effects can be obtained.

(1) Instead of pressing and fixing only the outer periphery of the substrate to the lower electrode as in the past, the substrate can be fixed in close contact with the lower electrode over a wide area (almost the entire surface on which the substrate is placed) by electrostatic adsorption. It is possible to prevent deformation of the substrate due to the gas pressure of GHe, and to suppress an increase in the amount of gap between the back surface of the substrate fixed to the lower electrode and the lower electrode. Therefore, it is possible to prevent deterioration of heat conduction characteristics between the substrate and the lower electrode, and to effectively cool the substrate.

(2) Since at least the outer periphery of the back surface of the substrate is adsorbed, Ga1e, which is a heat transfer gas, is suppressed from flowing into the vacuum processing chamber at the adsorption part, so the influence of GHe on the process is reduced, and all Can be used for processes.

(3) Compared to the conventional technology that uses electrostatic adsorption to increase the contact area between the substrate and the lower electrode to reduce thermal resistance, in this example, the magnitude of the electrostatic adsorption force is equal to the pressure of G1-18. The pressure difference between the GHe pressure and the plasma pressure can be controlled by the pressure difference between the back surface of the substrate and the lower electrode. By making it as small as the thermal resistance allows, a sufficient substrate cooling effect can be obtained even if the electrostatic adsorption force is made small.

(4) Since the D electric adsorption force is small, the substrate can be easily separated from the lower electrode, and the time for transporting the substrate after etching can be shortened, and damage to the substrate can be prevented.

(5) Since the electrostatic adsorption force may be small, the potential difference applied to the substrate is small and damage to elements within the substrate can be reduced. Therefore, there is no concern that the yield will deteriorate even in fine processing of a thin gate film.

(6) Since the substrate is fixed to the lower electrode by electrostatic adsorption force without using mechanical clamping means, it is possible to prevent a reduction in the element fabrication area within the substrate, maintain good plasma uniformity, and , there is no risk of dust being generated when placing the substrate on the lower electrode or removing the substrate from the lower electrode, and furthermore, it is possible to easily transport the substrate, and as a result, it is possible to suppress the size of the device and improve reliability. can be improved.

FIG. 4 shows another example of a dry etching apparatus embodying the present invention, in which the top wall of the vacuum processing chamber 10 and the upper electrode 4
0, an optical path 120 is formed to communicate the outside of the vacuum processing chamber 10 and the discharge space 30. A light-transmitting window 121 is airtightly provided on the outside of the vacuum processing chamber 10 in the optical path 120 . Outside the vacuum processing chamber 10 corresponding to the transparent window 121,
Temperature measuring means, for example an infrared thermometer 122, is provided. The output of the infrared a thermometer 122 is input to the process control computer 124 via the amplifier 123, and a command signal calculated by the process control computer 124 is input to the MFC 71. In addition, the same devices and the like as in FIG. 1 are indicated by the same reference numerals, and the description thereof will be omitted.

According to this embodiment, the following effects can also be obtained.

(1) Adjust the supply amount of G11e without measuring the temperature of the substrate. In other words, connect the MFC that supplies Ga1e to the process control computer, and calculate the relationship between the substrate temperature and the supply amount of G11e determined in advance. By controlling the supply amount of G11e, the temperature of the substrate can be maintained at a constant temperature. Such control is particularly effective when dry etching the AQ-Cu-8i material, and can reduce the residue of the etched material by controlling the temperature to a high temperature within a range that does not damage the photoresist.

(2) When the plasma pressure is high, there are processes in which the etching rate increases as the substrate temperature rises; in such cases, if the substrate temperature exceeds a preset constant temperature, By flowing G11e, the etching time can be shortened while increasing the cooling effect and preventing damage to the photoresist.

In the embodiments described above, electrostatic adsorption force is used to adsorb the substrate, but vacuum adsorption force can also be used in processes where the pressure of plasma gas is high. Alternatively, positive electrodes and negative electrodes may be arranged alternately on the lower surface of the insulator to apply electrostatic adsorption force to the substrate. Also, when over-etching is performed after the underlying material begins to be exposed.

When the underlying material begins to be exposed, the supply of GHe is stopped and a DC voltage is reversely applied to the lower electrode. In this way, the electrostatic force remaining on the substrate at the end of etching can be further reduced, so that the substrate is not damaged during unloading, and the time required for unloading the substrate can be shortened. However, in this case, it is necessary to control the temperature of the substrate during etching to be lowered by the amount of temperature rise during over-etching. In addition to GHe, a gas with good thermal conductivity such as hydrogen gas or neon gas may be used as the heat transfer gas.

Note that the present invention has a similar effect in controlling the temperature of a sample placed and held on a substrate stand to be cooled and subjected to vacuum processing.

〔Effect of the invention〕

As explained in Section 5 above, in the present invention, a sample is placed on a test ramp in which an electrical insulating material is provided on almost the entire surface of the placement surface of the sample to be vacuum-treated, and the placed sample is adsorbed. By electrostatically adsorbing and holding the sample on the sample stage using a gas supply means and supplying heat transfer gas to the gap between the back surface of the sample held by adsorption and the electrical insulating material, deformation of the sample due to the gas pressure of the heat transfer gas is prevented. It is possible to suppress the increase in the amount of gap between the back side of the sample and the sample stage, which is held by adsorption, effectively controlling the temperature of the sample being vacuum processed, and suppressing the outflow of heat transfer gas into the vacuum processing chamber. This has the effect of reducing the influence of heat transfer gas on the process.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a dry etching apparatus embodying the present invention, FIG. 2 is a detailed plan view of the lower electrode in FIG. 1, and FIG. 3 is a sectional view taken along line AA in FIG. FIG. 4 is a block diagram showing another example of a dry etching apparatus embodying the present invention. 10... Vacuum processing chamber, 20... Lower electrode, 21
．． 21a. 1 figure, 4 figures

Claims (1)

[Scope of Claims] 1. Place the sample on a sample stage with an electrical insulating material provided on substantially the entire surface of the sample placement surface to be vacuum-treated, with the sample placed through the electrical insulating material, and A method for controlling the temperature of a sample, comprising holding the sample by electrostatic adsorption on a sample stage, and supplying a heat transfer gas to a gap between the back surface of the sample held by adsorption and the electrical insulating material. 2. The heat transfer gas is distributed and supplied to the gap between the back surface of the sample held by suction and the electrical insulating material through dispersion grooves provided in the electrical insulating material.
Sample temperature control method described in Section 1. 3. A sample stand provided with an electrical insulating material on substantially the entire surface of the placement surface of the sample to be vacuum processed, and the sample placed on the sample stand via the electrical insulating material is electrostatically held on the sample stand. A sample temperature control device comprising an adsorption means and a gas supply means for supplying a heat transfer gas to a gap between the electrical insulating material and the back surface of the sample held by the adsorption means. 4. The close contact holding means is composed of a DC power source connected to the sample stage and a means for generating plasma during the vacuum processing, and the heat transfer gas supply means penetrates the sample stage and an electrical insulating material. and a supply path for the heat transfer gas that opens toward the back surface of the sample.
Sample temperature control device as described in Section 3. 5. The sample temperature control device according to claim 3, wherein the electrical insulating material has grooves for dispersing the heat transfer gas. 6. The sample temperature control device according to claim 5, wherein the depth of the dispersion groove is equal to or less than the mean free path length of the heat transfer gas. 7. The sample temperature control device according to claim 3, wherein the electrical insulating material is formed by coating the metal surface of the sample stage with an insulating film.