JPS63291423A - Low temperature dry-etching equipment - Google Patents

Abstract

PURPOSE:To realize a dry-etching equipment with which the accuracy of temperature setting can be improved while the temperature range is expanded by a method wherein a means which controls the liquid level of liquefied gas to regulate the temperature and reduces the thermal contact resistance between a sample table and a substrate is provided. CONSTITUTION:Liquefied gas 12 is supplied into a liquefied gas container 4 provided in a vacuum chamber in accordance with the signal of a level sensor 11 to control the liquid surface level. The container 4 itself is linked with a movable flange 6. A heater 13 is provided in a sample table 2 and the temperature of a substrate 3 is monitored by a thermocouple 14 while the temperature is thermally balanced by the liquefied gas 12 and the heater 13. A temperature regulator 15 receives the signal of the thermocouple 14 and controls the power applied to the heater 13. The flange 6 linked with the sample table 2 is coupled with the vacuum chamber 1 through a bellows 16. If the flange 6 is moved at the time of etching, the substrate 3 is strongly pressed against a fixed ring 17 and the contact area between the substrate 3 and the sumple table 2 to reduce a thermal contact resistance so that the thermal conduction effect can be improved and the cooling capability of the liquefied gas to the substrate 3 can be improved.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a low temperature dry etching device.

In particular, the present invention relates to a low temperature dry etching apparatus suitable for anisotropic dry etching with little side etching.

(Conventional technology) Efficiently performing highly accurate etching processing on semiconductor substrates is an essential technology for ultra-LS 1% manufacturing.
Various new techniques related to anisotropic etching with less undercut have been developed and researched, and in particular, Japanese Patent Application No. 11945/1982 and Japanese Patent Application No. 260738/1983 regarding methods and devices for cooling the substrate to be etched on a sample stage have been developed. has been filed as prior art.

(Problem to be Solved by the Invention) The former of the above-mentioned prior art uses a heat pipe as a cooling mechanism to cool the substrate to a temperature of several tens of degrees Celsius or lower, thereby preventing side etching. However, there was a problem in that the temperature controllable range was -196 to 160°C, and the control range was narrow. The latter solves the former problem by controlling the cooling of the sample stage by using a heater in combination with a heat pipe.6 The present invention utilizes the technology of the prior application described above, and furthermore, the present invention utilizes the technology of the prior application described above, and furthermore, By increasing the heat absorption capacity of the etching process and efficiently absorbing the heat generated during etching, we have expanded the temperature range to set the optimum temperature for each substrate material and etching gas in the range of 0 to -196°C. At the same time, it is equipped with a sample cooling mechanism that can improve the accuracy of the set temperature. It is an object of the present invention to provide a low temperature dry etching apparatus suitable for anisotropic dry etching with little side etching.

(Means for Solving the Problems) The above purpose is achieved by providing a heater on a sample stage above a cooling container that is placed in a vacuum chamber and into which liquefied gas is introduced.

AM is achieved by adjusting the temperature by controlling the liquid level of the liquefied gas and by providing means for reducing the contact thermal resistance between the sample stage and the substrate. The low temperature control means for the sample stage may include a low temperature gas controller or a Peltier device.

(Function) The heat generated during etching can be reduced by using a heater and controlling the liquid level of the liquefied gas in the cooling container.
When controlling the temperature of the substrate to a relatively low temperature range of ℃,
The liquid level of the liquefied gas is raised, and conversely, when the temperature of the substrate is controlled to a relatively high temperature range of 0° C., the liquid level of the liquefied gas is lowered. By reducing the contact thermal resistance between the sample stage and the substrate, the heat absorption capacity of the sample stage is increased and its temperature can be adjusted over a wide range. When using low-temperature gas, control the current of the heater and the flow rate of low-temperature gas. In the case of a Peltier element, by changing the current, the substrate can be heated from 0 to -180 under adiabatic conditions in vacuum. Temperature control is selectively performed within a range of °C.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 is a diagram showing an embodiment of the low-temperature dry etching apparatus according to the present invention, in which a liquefied gas container 4 provided in a vacuum chamber 1 is provided with a large number of fins with good thermal conductivity. Liquefied gas 12 is introduced into the liquefied gas container 4 from a separately provided replenisher 9 via a supply hose 10 and further through a supply pipe 8, and the liquefied gas is automatically supplied by a signal from a liquid level sensor 11. 12 is replenished into the liquefied gas container 4 and is configured to control the liquid level. Also, the liquefied gas container 4 itself is indicated by the arrow 5u.
, 5d. A heater 13 is disposed inside the sample stage 2, and the temperature of the substrate 3 is monitored with a thermocouple 14 while keeping a thermal balance between the liquefied gas 12 and the heater 13, and a temperature controller 15 receives and receives this signal.
controls the power of the heater 13.

The flange 6 connected to the sample stage 2 is connected to the vacuum chamber 1 via a bellows 16, and during etching, the flange 6 is
As shown in FIG. 2, by moving in the direction, the substrate 3 is strongly pressed against the fixing ring 17, the contact area between the substrate 3 and the sample stage 2 increases, the contact thermal resistance decreases, and the heat conduction effect increases. , the cooling capacity of the substrate 3 by the liquefied gas increases. Etching is performed by applying a high frequency voltage between the sample stage 2 and the upper mold @18.

Further, a sample introduction chamber 20 is provided on the side surface of the vacuum chamber 1 via a valve 19, and the structure is such that the substrate 3 can be replaced without opening the vacuum chamber 1 to the atmosphere.

<Second Embodiment> FIG. 3 shows a second embodiment of the present invention. The figure shows that by interposing a soft thin plate 21 between the sample stage 2 and the substrate 3, the thermal contact between the substrate 3 and the sample stage 2 is increased (the contact thermal resistance is decreased). It is possible to control the temperature with high precision. As the soft thin plate material, Teflon, silicone rubber, etc. are preferable because they do not have the problem of contamination with foreign matter during etching. The holding ring 17 is fixed to the vacuum chamber 1 via a spring 22, and is attached to the arrow 5 of the liquefied gas container 4.
It is configured such that the pressing force can be adjusted by the moving distance for pressing in the U direction.

<Third Embodiment> FIG. 4 shows a third embodiment of the present invention. In this case, the surface of the sample stage 2 for mounting the sample is formed into an upwardly convex arc shape, and the substrate 3 is placed on top of this with the soft thin plate 21 sandwiched between them. Move the liquefied gas container 4 in the direction of the arrow 5u,
When the fixing ring 17 and the outer peripheral edge of the substrate 3 come into contact with each other and are pressed, the substrate 3 deforms into an arc shape and comes into close contact with the sample stage 2 .

This increases the thermal contact between the substrate 3 and the sample stage 2 (decreases the contact thermal resistance), and the heat generated during etching is efficiently transferred to the liquefied gas, controlling the temperature of the substrate 3 with high precision. be able to.

<Fourth Embodiment> FIG. 5 shows a fourth embodiment of the present invention. This embodiment is specifically designed to keep the substrate 3 at a low temperature, and is designed so that the liquid level of the liquefied gas occupies a higher position than the back surface 24 of the sample stage so that the back surface 24 of the sample stage is always in contact with the liquefied gas 4. It is composed of As a result, the etching heat is easily transferred to the liquefied gas 12, making it possible to maintain the substrate 3 at a low temperature.

<Fifth Embodiment> FIG. 6 is a diagram showing an embodiment using low-temperature gas of the present invention, in which a substrate 3 is placed on a sample stage 2 placed in a vacuum container 1, and a cooling gas A block 34 is installed. A large number of fins 35 are arranged inside the cooling block 34, and a low temperature gas introduced through a pipe 36 removes heat from the substrate 3. A cooling gas (for example, dry nitrogen gas)
is stored in a cylinder 37 and introduced into the cooling block 37 through a pipe 38. It passes through a container 40 containing liquefied gas 39, where the gas at room temperature is cooled to a low temperature. A high frequency voltage is applied between the upper electrode 18 and the sample stage 2 in the vacuum chamber 1, and etching is performed.

When the temperature of the substrate 3 rises due to the heat generated at this time, the temperature controller 15 receives the measurement signal measured by the thermocouple 14, opens the flow rate valve 45 of the low temperature gas, increases the flow rate of the low temperature gas, and cools the substrate 3. The cooling capacity of the block 34 is increased to maintain the temperature of the substrate 3 at a low temperature. Fig. 7 shows a heater 1 on the sample stage 2 of the embodiment shown in Fig. 6.
3, the temperature of the sample stage 2 is controlled by keeping the flow rate of cooling gas constant and changing the current value of the heater 13.

<Sixth Embodiment> FIG. 8 shows a sixth embodiment of the present invention. cooling block 3
A flow path 50 for a cooling gas (for example, Freon) sent from a refrigerator 55 is formed within the cooling gas 4, and heat exchange with the heat generated during etching is performed here. The temperature of the substrate 3 is detected by a thermocouple 14, and the refrigerator 55 is controlled based on the signal from the thermocouple 14 so that the temperature of the substrate 3 remains constant even when heat is input. . After heat exchange within the cooling block 34, the cooling gas returns to the refrigerator 55 and is cooled.

<Seventh Example> FIG. 9 shows an example using the Peltier element of the present invention. A Peltier element 51 is disposed at the bottom of the sample stage 2, and by changing the current value that drives it, the heat absorption ability can be varied, and by reversing the direction of the applied current, it can be selectively Both heating and cooling operations can be performed. The Peltier element is controlled by a controller 52 so that the temperature of the substrate 3 is constant. The temperature of the board 3 is measured by a thermocouple 14, and a fan 53 is provided below the Peltier element 51 for the purpose of dissipating the heat absorbed from the board 3 into the atmosphere, and is configured to blow air in the direction of the arrow 5u. As a result of controlling the temperature of the substrate using this example, it was possible to control the temperature within the range of 20 to -120°C with an accuracy of ±3°C.

In particular, even if there is a heat input of 50 watts to the substrate 3 during etching, the overshoot value is only around 5°C, and is approximately 1.
The temperature could be controlled to the original set temperature in 0 seconds. Also, when etching was performed using a Si wafer as the substrate, -
It was found that 80 to -120°C is the optimum temperature.

Comprehensive experiments conducted by the inventors in each of the above embodiments show that the temperature of the substrate can be controlled to an accuracy of ±3°C in the range of 30 to -150°C, and that the temperature of the substrate 3 can be controlled at a temperature of -50°C or more. By lowering the liquid level of the liquefied gas when controlling the temperature in a relatively high temperature range, the input power of the heater was 100 W, and the consumption of liquid nitrogen used as the liquefied gas was as small as 30 dl'/min. . Furthermore, when the Si wafers used in these examples were subjected to plasma etching, the results were -80 to -1.
Good etching was achieved at a temperature of 20° C., and this temperature range was determined to be the optimum temperature for low-temperature etching of silicon.

To summarize the above, the main subject of the present invention is a low-temperature dry etching apparatus characterized by having means for increasing/decreasing thermal resistance by controlling the liquid level of liquefied gas and for reducing contact thermal resistance between a substrate and a sample stage. .

(Effects of the invention) By controlling the liquid level of the liquefied gas and arranging the container in the vacuum chamber according to the present invention, a mechanical load is applied to the outer edge of the substrate to be etched to bring the substrate into close contact with the sample stage. As a result of highly accurate temperature control with a small amount of liquefied gas and heater power, there is no side etching and etching can be performed only in the depth direction, which has a remarkable effect on reducing manufacturing costs and improving reliability of the substrate to be etched. played.

[Brief explanation of the drawing]

1 and 2 are views showing one embodiment of a low temperature dry etching apparatus according to the present invention, and FIGS. 3 to 9 are views showing other embodiments of the present invention.

Claims (1)

[Scope of Claims] 1. A low-temperature dry etching apparatus in which a substrate to be etched is placed on a sample stage whose temperature is controlled to a low temperature in a vacuum chamber, and the surface of the substrate is treated by plasma excited in the vacuum chamber, A temperature control device for the substrate, including means for adjusting a liquid level height of liquefied gas introduced into a cooling container in which the sample stage is placed, and means for reducing contact thermal resistance between the substrate and the sample stage. A low-temperature dry etching device comprising: 2. As a means for reducing the contact thermal resistance, a mechanical load is applied to the outer peripheral surface of the substrate to be etched placed on the sample stage. The low temperature dry etching device described. 3. The low temperature dry etching apparatus according to claim 1, wherein a soft thin plate is inserted between the substrate and the sample stage as means for reducing the contact thermal resistance. 4. The low temperature dry etching apparatus according to claim 1, wherein the surface of the sample stage is formed in an upwardly convex arc shape as means for reducing the contact thermal resistance. 5. The low-temperature dry etching apparatus according to claims 1 to 4, wherein the sample stage is equipped with a cooling block for introducing low-temperature gas instead of liquefied gas and a temperature control device. 6. The low-temperature dry etching apparatus according to claims 1 to 4, wherein the sample stage is configured to use a Peltier element instead of liquefied gas to control the temperature.