JPS60115226A - Substrate temperature control method - Google Patents

Abstract

PURPOSE:To facilitate the transfer of substrate by causing at least the external circumference of substrate to be vacuum-processed for being attracted to the cooled substrate pedestal. CONSTITUTION:A lower electrode 20 which is formed as a substrate pedestal is electrically insulated and sealed through an insulator 11 to the bottom wall of a vacuum processing chamber 10. The lower electrode 20, the discharge space 30 and the upper electrode 40 vertically opposing to said lower electrode through the space are provided within the vacuum processing chamber 10. Corresponding at least to external circumference of rear surface of substrate 50 to be placed, an insulator 60 is buried at the surface of the lower electrode 60, and if a substrate is not placed, the lower electrode at the internal side of insulator 20 is formed with a groove 21 which is connected to the discharge space 30. A coolant path 22 is formed to the lower electrode 20 at the lower position of groove 21. The lower electrode 20 is respectively provided with a cooling gas supply path 23a and cooling gas exhaust path 23b communicating with the groove 21, and a coolant supply path 24a and coolant exhaust path 24b communicating with the coolant path 22.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a method for controlling the temperature of a substrate.

[Background of the invention]

One of the important uses of equipment for vacuum processing substrates, for example, dry etching equipment that utilizes high-frequency discharge, is the formation of fine patterns in the production of microscopic solid-state devices such as semiconductor integrated circuits. In the formation of this minute turn,
Usually, a pattern drawn by exposing a polymeric material called a resist coated on a material to be processed by ultraviolet rays and developing it is used as a mask and transferred to the material by dry etching.

However, because the mask and the substrate, which is the material to be processed, are heated by the chemical reaction heat with the plasma and the balanced incident energy of ions or electrons, sufficient heat dissipation cannot be obtained, that is, the temperature of the substrate cannot be maintained properly. If this is not controlled, the mask will be deformed and altered, resulting in the inability to form a correct pattern and making it difficult to remove the mask's substrate force remaining after dry etching. Therefore, various substrate temperature control methods that eliminate these disadvantages 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. 56-23
There is a method disclosed in Japanese Patent No. 853.

In Namiko's method, the substrate table to which the output of the Takaoka power supply is applied is water-cooled, the substrate to be processed is placed on the table via an insulator, and a DC voltage is applied to the electrodes to generate plasma. A device that applies a potential difference to the insulator through the insulator, and uses the resulting electrostatic adsorption force to attract the substrate to the substrate pedestal, reducing the thermal resistance between the substrate and the substrate pedestal and effectively cooling the substrate. It is. However, even with this method, there are only a few contact areas between the substrate and the insulator, and microscopically, there is a small gap. Further, a process gas enters this gap, and this gas acts as a thermal resistance.

In general, dry etching equipment usually uses 0. I To
The substrate is etched at a process gas pressure of about remains almost unchanged, and the effect increases as the contact area increases. Therefore, in order to reduce the thermal resistance between the substrate and the substrate stand and cool the substrate more effectively, a large electrostatic attraction force is required. Therefore, this method has the following problems.

(11) It becomes difficult for the substrate to separate from the substrate stand, so it takes time to transport the substrate after the etching process, and the substrate may be damaged.

(2)・Insulators,
In other words, it is necessary to apply a large potential difference to the substrate, but the larger the potential difference, the greater the damage to the elements within the substrate, so this requirement becomes stronger as the degree of integration of integrated circuits increases. The microfabrication of the thin gate film currently available does not provide sufficient throughput for device fabrication.

As a second example of the prior art, for example, Japanese Patent Application Laid-Open No. 57-14
There is a method as shown in Japanese Patent No. 5321. In this method, the substrate is directly cooled by gas. In such a method, the cooling efficiency of the substrate can be improved by using a cooling gas with excellent thermal conductivity such as helium gas (hereinafter abbreviated as GH). However, such a method has the following drawbacks.

(1) Since the cooling gas does not stay on the cooling surface side of the substrate but flows in large quantities into the vacuum processing chamber, even an inert gas like GHe has a large effect on the process (therefore, it cannot be used in all processes. Can not.

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

Egerton et al., 5solid 8tate Tec
hnology, Vol, 25°48, P84-8
7 (1982-8).

In this method, pressure is applied between the water-cooled substrate table and the substrate placed on the substrate table and secured around the outside with clamps.
The thermal resistance between the electrode and the substrate is reduced by circulating GHe of about 1 Torr, thereby effectively cooling the substrate. However, even with this method, GH
.

The outflow into the vacuum processing chamber is unavoidable, and therefore there are problems similar to those in the second example of the prior art described above, and the following problems also occur.

(1) A clamp is provided to secure the outer periphery of the board to prevent the board from floating up from the board stand.

Therefore, the area for fabricating elements within the substrate is reduced, and the transportation of the substrate becomes extremely complicated, resulting in an increase in the size of the device and a decrease in reliability.

(2) GHe is unevenly distributed in the gap between the back surface of the substrate and the substrate stand. [Object of the Invention] An object of the present invention is to provide a method for controlling the temperature of a substrate, which allows easy transportation of the substrate and reduces the influence on the process.

[Summary of the invention]

The present invention is advantageous in that at least the outer periphery of a substrate to be vacuum-processed is adsorbed to a substrate stand to be cooled, and the gap between the substrate and the substrate stand is filled with cooling gas, thereby eliminating the need for mechanical clamping means. , and attempts to suppress the outflow of the cooling gas into the vacuum processing chamber while minimizing the adsorption force. [Embodiment of the Invention] An embodiment of the present invention will be described with reference to FIG. 1.

FIG. 1 shows an example of a dry etching apparatus embodying the present invention.
A lower electrode I, which is a substrate stand, is electrically insulated and airtightly provided via the substrate 1. A vacuum processing chamber 10 is provided with the front of the lower electrode and the discharge space, and the front of the upper electrode is vertically opposed to each other.

When an insulator mark is embedded in the surface in front of the lower electrode corresponding to at least the outer periphery of the back surface between the substrates to be placed, and no part of the substrate is placed on the lower electrode row inside the insulator mark. ,
A groove 21 communicating with the discharge space is formed. Also,
A refrigerant flow path is formed in front of the lower electrode at a position below n421. Further, in front of the lower electrode, a cooling gas supply path 23a and a cooling gas discharge path 23b are connected to the groove 21, and a refrigerant supply path 24g and a refrigerant discharge path 24b are connected to the refrigerant flow path n.
are formed respectively. The cooling gas supply path 23g includes a conduit 70a connected to a cooling gas source (not shown).
A conduit 70b is connected to the cooling gas discharge path 23b.
One end of is connected. The conduit 70a is provided with a mass flow controller (hereinafter abbreviated as %MFC) n, and is connected to a conduit pipe for exhaust gas connected to the conduit 70a. The refrigerant supply path 24g includes a conduit 90 connected to a refrigerant source (not shown).
A is connected to the refrigerant discharge path 24b, and a refrigerant discharge conduit 90b is connected to the refrigerant discharge path 24b. In front of the lower electrode, a high frequency power supply IOT is connected via a matching box 100, and a DC power supply 1 is connected via a high frequency cutoff circuit 102.
03 is connected.

In addition, in front of the upper electrode, there is a gas discharge hole (not shown) that opens into the discharge space (9) and a gas flow M that communicates with the gas discharge hole.
(not shown) is formed, and a conduit (not shown) connected to a processing gas supply device (not shown) is connected to the gas flow path. Note that the vacuum processing chamber 10. High frequency power supply 1
01. The DC power supplies 103 are each grounded.

Here, the depth of the groove O is set to prevent the cooling gas from being unevenly distributed in the gap between the back surface of the substrate and the lower electrode, that is, between the groove and the insulator ω. The gap between the back surface of the substrate (material) and the bottom surface of the groove 21 is selected to be larger than the gap between the back surface of the substrate and the insulator ω when adsorbed to the lower electrode tube between the substrates. Furthermore, if the gap between the back surface between the substrates and the bottom surface of the groove 21 during adsorption is less than the mean free path length of the cooling gas, the heat transfer effect of the cooling gas will be reduced. The depth of the groove 4 is such that the gap between the back surface of the substrate and the bottom surface of the groove 21 is greater than the gap between the back surface of the substrate and the insulator ω, and preferably the depth is less than or equal to the mean free path length of the cooling gas. Select the In addition, the area of the part (hereinafter abbreviated as the adsorption part) that is adsorbed by the insulator ω on the back surface between the substrates is:
It is determined by the differential pressure between the cooling gas and the vacuum processing chamber 10 in order to prevent the substrates from floating from in front of the lower electrode due to the differential pressure between the cooling gas and the vacuum processing chamber 10. Select based on the required electrostatic adsorption force. For example, when the pressure of the cooling gas is ITorr and the pressure of the vacuum processing chamber 10 is 0.1
In the case of Torr, the floating IJ from the lower type i# addition between the substrates
The required electrostatic adsorption force to prevent this is approximately 1.3 f/c
tA, and from this, the area of the suction portion is selected to be approximately 1 of the area of the back surface between the substrates.

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

In Figures 2 and 3, cooling gas supply path Z3 a 1. t
In this case, it is formed of a conduit 25a, and in this case, the conduit 25a is provided so as to be movable up and down about the center of the substrate placement position in front of the lower electrode. A cooling gas discharge path 23b is formed outside the conduit 5a, and a conduit 25b is provided.
5b, a refrigerant supply path 24a is formed and a conduit 25 is formed.
A refrigerant discharge passage 24 is provided outside the conduit 25c.
A conduit 25d is disposed forming the b. Conduit 25b
The upper end is provided on the electrode upper plate, and a space is formed between the electrode upper plate portion, the electrode upper plate portion below the electrode upper plate portion, and the upper end portion of the conduit 25b. A dividing plate 4 is installed in the empty chamber path to form a refrigerant flow path n, and the end of the conduit 25c is installed in the dividing plate 4, and the upper end of the conduit 25d is installed in the electrode upper plate part n. ing. In this case, the surface of the electrode upper plate on which the substrate (not shown) is placed has a radial wave 21a and a circumferential WI21.
A plurality of strips are formed. The grooves 21g, 21b are of course in communication with the conduits 5a, 25b. An insulating film (not shown) is coated on the surface of the electrode upper plate on which the substrate is placed and where the grooves 21a and 21b are not formed. Here, the depth of the grooves 21a and 21b is as shown in FIG.
The depth has been selected as well. In addition, the suction part is the groove 21
It is divided into sections a and 21b, and the area is of course selected to be an area necessary to prevent the cooling gas from floating up from the bottom electrode between the substrates.

In addition, in FIGS. 2 and 3, 110 is an electrode cover that protects the surface of the electrode upper plates on which the substrate is not placed, 111 is an insulating cover that protects the lower electrode other than the surface of the electrode upper plates,
112 is a shield plate. Furthermore, at the upper end of the conduit 25a, three claws 113 are arranged at 120 degree intervals to support the substrate when the substrate is placed on the electrode upper plate and when the substrate is removed from the electrode upper plate. It is set up.

In FIG. 1, the substrates are transported into a vacuum processing chamber IO by a known transport device (not shown), and placed in front of the lower electrode with the outer periphery of the back surface corresponding to the insulator ω. After the completion of placing the substrates in front of the lower electrode, the processing gas is supplied from the processing gas supply device to the mega gas flow passage through the conduit, and after flowing through the gas flow passage, enters the discharge space from the gas discharge hole. released. At the same time, high-frequency power is applied from the high-frequency power source 101 to the lower electrode Shu, and the lower electrode is connected! A glow discharge occurs between #i beauty and the upper electrode shame. When plasma is generated by this glow discharge and etching begins, the gap between the substrates is
The insulator ω is attracted in front of the lower electrode by the electrostatic attraction force generated by the potential difference applied to both ends of the insulator ω. Thereafter, a cooling gas such as GH is supplied from a cooling gas source to the groove 21 to reduce the thermal resistance between the substrate and the front of the lower electrode, which is cooled by a refrigerant, such as water, flowing through the refrigerant flow path n. By reducing etching, the space between the substrates is effectively cooled. 0 When the end of etching approaches, the supply of GHa to the groove 21 is stopped, and as the etching ends, the processing gas is released to the discharge space blade, and the lower part Application of high frequency power and DC voltage to the electrodes is stopped. Thereafter, the electrostatic attraction force that continues to be generated between the substrates is released, and the lower mold f! It is removed from the top and carried out from the vacuum processing chamber 10.

The substrate temperature control method as in this embodiment provides the following effects.

11) Since the thermal resistance between the substrate and the lower electrode is lowered by GHe, which has good thermal conductivity, the effect of cooling the substrate is remarkable, and the contact area between the substrate and the lower electrode is increased by conventional electrostatic adsorption. Compared to the method of reducing thermal resistance, the electrostatic adsorption force can be as large as necessary to prevent the substrate from lifting due to the pressure difference between the GHt+ pressure and the vacuum processing chamber pressure. By reducing the pressure difference between the pressure of GH and the plasma pressure within the range allowed by thermal resistance, a sufficient substrate cooling effect can be obtained even if the electrostatic adsorption force is reduced.

(2) Since the electrostatic 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.

(3) 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, even with fine processing of a thin gate film, a sufficient throughput in device fabrication can be obtained.

(4) Since GH, which is a cooling gas, is suppressed from flowing into the vacuum processing chamber at the adsorption part, its influence on the process of Gl(e) is reduced, and it can be used in all processes.

(5) Since the floating of the substrate from the lower electrode is prevented by applying electrostatic adsorption force without using mechanical clamping means, it is possible to prevent a reduction in the area for manufacturing elements on the substrate, and to facilitate substrate transportation. As a result, it is possible to suppress the increase in size of the device and improve reliability.

(6) GHe in the gap between the back surface of the substrate and the lower electrode
can prevent uneven distribution of

By connecting an MFC that supplies 173 GH, with a process control computer, the supply amount of GHe can be controlled based on the relationship between the predetermined substrate temperature and the supply amount of GH, and the temperature of the substrate can be kept constant. Can be maintained at a temperature of

Such control is particularly effective when dry etching fvl-Cu-81 material, and can reduce the residue of the material to be etched by controlling the temperature to a high temperature within a range that does not damage the photoresist.

(8) When the plasma pressure is high, there are processes in which the etching rate increases as the substrate temperature rises. In such cases, when the substrate temperature exceeds a preset constant temperature, , GH, can be flowed to increase the cooling effect and reduce the etching time while preventing damage to the photoresist.

FIG. 4 shows another example of a dry etching apparatus embodying the present invention.
f! During the period, an optical path 120 is formed by communicating the outside of the vacuum processing chamber 10 and the discharge space, and the optical path 120 communicates with the outside of the vacuum processing chamber 1 and the discharge space.
A transparent window 121 is airtightly provided on the outside side.

Temperature measuring means, for example, an infrared thermometer 122, is provided outside the vacuum processing chamber 10 corresponding to the transparent window 121. The output of the infrared temperature 122 is input to the process control computer 124 via the amplifier 123. The command signal calculated by 24 is input to the NFC 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.

The substrate temperature control method as in this embodiment further provides the following effects.

(1) The temperature of the substrate can be controlled by adjusting the supply amount of GHe without measuring the temperature of the substrate.

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. In addition, if overetching is to be performed after the underlying material begins to be exposed, the supply of G He is stopped and the DC voltage is reversely applied to the lower electrode when the underlying material begins to be exposed. In this way, the electrostatic force remaining on the substrate at the end of etching can be further reduced, so the substrate will not be damaged when unloading the substrate, 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 by lowering it by the amount of temperature rise during over-etching. Further, as the cooling gas, a gas having good thermal conductivity such as hydrogen gas or neon gas may be used in addition to GHe.

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

〔Effect of the invention〕

As described above, the present invention has the following advantages: At least the outer periphery of a substrate to be vacuum processed is adsorbed to a substrate stand to be cooled, and cooling gas is supplied to the gap between the back surface of the substrate and the substrate stand. By satisfying the above requirements, mechanical clamping means are not required, the adsorption force can be reduced to the minimum necessary, and the outflow of cooling gas into the vacuum processing chamber can be suppressed, making it easy to transport substrates and minimizing the impact on the process. It has the effect of being able to do it0

[Brief explanation of the drawing]

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 cross-sectional view taken along line AA in FIG. Figure 4 is
FIG. 3 is a configuration diagram showing another example of a dry etching apparatus embodying the present invention. 10... Vacuum processing chamber, processing... Lower electrode, 21, 21a.

Claims (1)

[Claims] 1. A method for controlling the temperature of a substrate placed and held on a cooled substrate stand to be subjected to vacuum processing, comprising: adsorbing at least the outer periphery of the back surface of the substrate to the substrate stand;
A method for controlling the temperature of a substrate, characterized by filling a gap between the back surface of the substrate and a substrate stand with cooling gas. 2. The temperature control method for a substrate according to claim 1, wherein at least the outer periphery of the back surface of the substrate is electrostatically attracted to the substrate stand. 3. Preferably, the gap between the back surface of the substrate other than the back surface adsorbed on the substrate stand and the substrate stand is equal to or larger than the gap between the back surface of the substrate adsorbed on the substrate stand and the substrate stand. 3. The method of controlling the temperature of a substrate according to claim 1 or 2, wherein the mean free path length of the cooling gas is equal to or less than the mean free path length of the cooling gas.