JPH0693446B2 - Processor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a processing apparatus for controlling a processing substrate temperature to perform etching, film formation or baking.

[Background of the Invention]

Currently, in the manufacture of semiconductor devices, when performing vapor deposition or sputtering as a film forming means, in order to obtain good film quality with appropriate particle size, reflectance, specific resistance and hardness, during baking of the substrate There is a need to effectively control the substrate temperature in the film. In particular, the grain size and reflectance are greatly affected by the substrate temperature. Further, it is necessary to control the substrate temperature also when a resist pattern is formed on the film by exposure and development and the film is etched according to the resist pattern by dry etching. By controlling the substrate temperature,
This is because it is possible to prevent thermal damage to the resist caused by poor heat resistance of the resist and to etch a faithful pattern.

However, it is difficult to control the temperature of the substrate in vacuum. This is because even if the temperature of the substrate is controlled to the same temperature as that of the temperature-controlled substrate support, the thermal contact between the substrate and the support is insufficient in vacuum.

Therefore, conventionally, in order to increase the thermal contact between the two surfaces of the substrate and the substrate supporting base, the substrate is mechanically pressed against the supporting base, or the substrate is attracted to the supporting base by electrostatic force. Methods such as how to make it have been devised. However, even such a method does not produce a sufficient effect. That is, the thermal contact between the two surfaces of the solid is largely due to the gas molecules interposed between the two surfaces, and the heat exchange between the pure solids is about the above-mentioned holding pressure as compared with the heat exchange by the gas molecules. It is so small that it can be ignored.

Therefore, an apparatus for increasing the thermal contact by interposing gas molecules between the substrate and the support was devised and is disclosed in JP-A-56-103442.

The substrate temperature controller of this device is shown in FIG.

The substrate 3 is supported by several clips 4 in close proximity to the support base 5 via a spacer 9. A temperature control device 6 having a cooling or heating mechanism is provided on the support base 5. The processing chamber 1 is exhausted from the exhaust port 2.
At the same time, argon is introduced from the gas introduction port 7, and this gas enters the processing chamber 1 as a flow 8 between the temperature control device 6 and the substrate 3. At this time, the pressure in the space 10 between the substrate 3 and the temperature control device 6 is controlled to be 10 to 100 Pa, and the pressure in the processing chamber 1 is exhausted to about 1 Pa.

Therefore, the temperature of the substrate 3 is controlled by the temperature control device 6 by the heat conduction of the intervening gas having a pressure of about 100 Pa.

However, even in this type of device, the temperature control of the substrate 3 is not sufficient. For example, when controlling the temperature of a silicon substrate with a diameter of 100 mm and a thickness of 0.45 mm, the time constant is as long as 20 seconds, and when dry etching with an applied power of 500 W is performed, the temperature difference with the temperature controller becomes 130 ° C and the resist Suffers thermal damage. Therefore, it is impossible to apply power of about 500 W or more. There is another problem with this type of device. In other words, by leaking the heat conduction gas, the mechanism is also used as the treatment gas, so that the heat conduction gas leaks even when it is desired to introduce a treatment gas other than the heat conduction gas into another flow path. There is a problem that it cannot be eliminated.

The present inventor has earnestly studied to solve the above problems, and has obtained the following findings.

First, in order to reduce the temperature difference between the substrate and the support table and increase the response speed of the substrate temperature control, the amount of heat that flows between the substrate and the support table per unit time and unit temperature difference (hereinafter referred to as unit heat flow rate). It is necessary to increase. In order to increase the unit heat flow, it is necessary to increase the pressure and at the same time make the distance between the two surfaces equal to or less than the mean free path of the gas under the pressure.

The substrate temperature during processing changes with time according to the following equation.

(1) T _w = (1-exp (-kt / C)) Q _i / k + T ₀ where T _w is the substrate temperature, C is the heat capacity of the substrate, k is the unit heat flow rate, and Q _i is the unit time during processing. Per constant amount of heat given to the substrate, T ₀ is the temperature of the support, t is time, and t = 0
In, T _w = T ₀ .

Further, when the temperature of the support is at a steady value T ₀ and the initial temperature of the substrate T _w0 ≠ T ₀ , the following formula is obeyed.

(2) T _w = (T _w0 −T ₀ ) exp (−kt / C) + T ₀ or more, in either case, the response speed of the substrate temperature control is the heat capacity C of the substrate and the unit heat flow rate between the two surfaces. Only depends on k. The value of C is a value peculiar to the substrate, for example, a diameter of 100 mm,
For a silicon substrate with a thickness of 0.45 mm, it is about 6.2 J · K ^-1 . Therefore, in order to reduce the temperature difference between the substrate and the support and increase the response speed of the substrate temperature control, it is necessary to increase the unit heat flow rate.

By the way, FIG. 2 shows measured values showing how the unit heat flow rate changes when nitrogen is interposed between the two surfaces and the pressure thereof is changed. The substrate was covered with silicon and the surface was covered with thin silicon oxide, and polished aluminum was used as a supporting material.
The surface was thoroughly washed and a load of 1 kg per 100 mm diameter was applied between the two surfaces. The curve is close to a straight line passing through the origin, which proves that under these conditions heat transfer only between solids can be neglected. That is, even if there is mechanical contact between the two surfaces of the solid, most of the thermal contact is due to the gas present between the two surfaces. Also, it can be seen that the unit heat flow rate increases when the pressure of the intervening gas is made larger than the value of 100 Pa in the conventional device.

The above measured values are based on the following theoretical formula. That is, the amount of heat that passes between the two surfaces per unit time "dQ / dt"
Follows the formula:

(3) dQ / dt = k ₁ (T _w −T ₀ ) p (e << λ) (4) dQ / dt = k ₂ (T _w −T ₀ ) e (e >> λ) where k ₁ , k ₂ is a constant, T _w and T ₀ are the temperature of the substrate and the substrate support, e is the distance between the two surfaces, p is the pressure of the intervening gas, λ
Is the mean free path under that pressure. This equation is calculated as “dQ / dt” under the condition of low pressure and long mean free path.
Is proportional to p, and "dQ / dt" is proportional to e when the pressure is high and the mean free path is sufficiently short.

Therefore, the pressure of the gas interposed between the two surfaces is increased, and
The unit heat flow rate can be increased by providing a mechanism for making the distance between the surfaces equal to or less than the mean free path under the pressure.

By the way, in the conventional apparatus, p is about 100 Pa, so the mean free path λ of Ar is about 50 μm. Therefore, it is desirable to reduce the distance to about 50 μm, which is impossible with this device. That is, the central portion of the substrate 3 bulges due to the pressure difference of 100 Pa as shown in FIG. For example, in a silicon wafer having a diameter of 100 mm and a thickness of 0.45 mm, the bulge amount at the central portion reaches 150 μm due to the pressure difference of 100 Pa. Therefore,
It has already exceeded the mean free path of 50 μm, and the unit heat flow rate cannot be increased even if the pressure is further increased.

[Object of the Invention]

The present invention effectively controls the substrate temperature during processing in etching, film formation, and baking during semiconductor device manufacturing,
It is an object of the present invention to provide a processing apparatus which is capable of performing etching faithful to a pattern, forming a film having a good film quality, or performing a good baking.

[Outline of Invention]

The present invention relates to a processing apparatus that performs processing of a substrate in a processing chamber held at a vacuum or a pressure close to a vacuum while controlling the temperature of the substrate, and has a predetermined supporting surface for supporting the substrate. A support table, the temperature of which is controlled to a constant temperature, gas introducing means for introducing a gas for heat transfer of a predetermined pressure between the convex surface of the support table and the substrate, and the substrate on the convex surface of the support table. The distance between the convex surface and the substrate by pressing with a predetermined load, the holding means for holding the same or less than the mean free path of the gas under the pressure of the introduced gas, and the gas introduction means for the heat transfer The gas introduced into the space between the convex surface and the substrate is configured to have a sealing means that seals the space to the extent that the gas can leak into the processing chamber. In the processing chamber maintained at a close pressure In a processing apparatus for processing a substrate while controlling the temperature of the substrate, the temperature is controlled to a predetermined constant temperature by using an electrode to which a DC voltage is applied and an insulating material that insulates the electrode from the substrate. Support base, gas introduction means for introducing a heat transfer gas of a predetermined pressure between the insulating material on the support base and the substrate, and electrostatic force generated by applying a DC voltage to the electrodes. Holding means for sucking the substrate onto the insulating material by means of and holding the distance between the substrate and the insulating material to the same or less than the mean free path of the gas under the pressure of the introduced gas. It is configured.

A mechanism for keeping the distance between the support and the substrate below the mean free path of the introduced gas under the pressure of the gas is achieved, for example, as follows.

The surface of the support table facing the substrate is made convex according to the amount of displacement of the substrate. Alternatively, the support or the surface of the support is made of a soft organic material.

With the above configuration, the substrate temperature during the processing can be effectively controlled in the etching processing and the like at the time of manufacturing the semiconductor device.

Example of Invention

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

First, the essence of the embodiment will be described with reference to FIG.

In this embodiment, a support 17 for the substrate 19, a holding means 23 for holding the substrate 19, and a gas introduction means 52 for introducing a gas into the space 20 formed by the substrate 19 and the support 17. The substrate temperature control device has a mechanism for keeping the distance between the support 17 and the substrate 19 below the mean free path of the introduced gas under the pressure of the gas.

As a result, in the etching process at the time of semiconductor device manufacturing,
The substrate temperature during processing can be effectively controlled.

First Embodiment A first embodiment will be described with reference to FIG.

The apparatus according to the present embodiment is basically a parallel plate type dry etching apparatus including a processing chamber 12, a lower electrode 17 and a upper electrode 16 each having a polished surface and a convex surface. In this embodiment, the lower electrode 17 serves as a support.

The processing chamber 12 has a vacuum exhaust system (not shown) through the exhaust port 13.
It is connected to the. A reaction gas is introduced into the processing chamber 12 through the gas introduction port 24. Further, the processing chamber 12 is provided with a loading / unloading port 14 for loading / unloading the substrate 19 at an appropriate position.

A high frequency power supply 25 is connected between the upper electrode 16 and the lower electrode 17.

In the lower electrode 17, the liquid heat medium flow channel 48, the pump 42,
A liquid heat medium temperature control device 43 is provided. Also,
A gas reservoir 26 for heat transfer gas is provided through an orifice 21 and a valve 15. A gas cylinder 44 is connected to the gas reservoir 26 via a flow rate adjusting valve 45, and a rotary pump 47 is connected to the gas reservoir 26 via a flow rate adjusting valve 46.

The substrate holding means 23 is made of an insulating material such as ceramic, and is connected to the ball screw 40 and the motor 41 via a spring 39.

An O-ring 18 is provided between the substrate 19 and the lower electrode 17, and the O-ring 18 seals a space 20 formed by the substrate 19 and the lower electrode from the processing chamber 12.

In the above device, the lower electrode 17 is kept at a constant temperature by circulating the liquid heat medium kept at an appropriate constant temperature. As the liquid heat medium, water kept at 20 ° C. is used, but a fluid other than water whose temperature is controlled may be used depending on the purpose. The temperature of the lower electrode 17 may be controlled by using electric resistance.

The substrate 19 is pressed against the lower electrode 17 by the substrate holding means 23 that moves up and down by the motor 41 and the ball screw 40.
At this time, the spring 39 serves to press the substrate 19 with a constant load, that is, a mechanism that causes mechanical contact.

The gas sump 26 is constantly kept at a constant pressure by the flow rate adjusting valves 45 and 46, the gas cylinder 44 and the rotary pump 47, and is filled with the heat transfer gas. The heat transfer gas is introduced into the space 20 from the gas sump 26 through the orifice 21. That is, the gas introduction means is composed of the gas sump 26 and the orifice 21 serving as a gas introduction port.

Next, how the substrate temperature control during processing in the present embodiment is performed, helium is used as a heat transfer gas, and the substrate is a silicon substrate having a diameter of 100 mm and a thickness of 0.45 mm will be described as an example. .

After the substrate 19 is placed, helium gas is introduced from the gas reservoir 26 having a pressure of about 700 Pa, which is one digit larger than that of the conventional example.
When a gas having a pressure of 700 Pa is introduced, the center of the substrate 19 bulges to a convex shape of about 800 μm. Further, the amount of change w at a point at a distance r from the center of the substrate in the radial direction complies with the following equation.

Here, E and ν are the Young's modulus and Poisson's ratio of silicon, h and a are the thickness and radius of the substrate 19, respectively, and p is the gas pressure.

Therefore, the convex surface of the lower electrode 17 is preliminarily processed into a curved surface having a shape conforming to the above formula, or a curved surface having more bulge. At this time, since the substrate 19 is pressed by the holding means 23, it deforms along the convex surface and has stress.

At this time, the force that the substrate 19 receives due to the gas pressure is equal to or smaller than the stress that the substrate 19 has, so that the substrate 19 does not generate more strain than it already has due to the gas pressure. Along 17 the mechanical contact remains. The surface of the lower electrode 17 has a surface roughness of 6-S.
It is polished below. Therefore, the average free path of helium at 700 Pa is 30μ across the entire surface.
It is kept sufficiently smaller than m.

Here, considering that the thermal contact between the solids can be neglected, the thermal contact is uniform over the entire surface. Therefore, sufficient thermal contact can be realized, and the unit heat flow can be sufficiently increased.

Further, in this embodiment, an orifice 21 is provided as an introducing means for introducing the heat conducting gas into the space 20. This orifice 21 has a diameter of about 40 μm so that the conductance for helium is about 1 × 10 ^-6 m ³ / sec.
I am doing it.

When the substrate 17 is not placed, the amount of gas flowing from the gas sump 26 through the orifice into the processing chamber 12 having a pressure difference of 700 Pa is about 7 × 10 ⁻⁴ Pa · m ³ / sec. This is the amount of reaction gas introduced from the reaction gas inlet 24 8 × 10 ^-2
Small enough for Pa · m ³ / sec. Therefore, even if leakage occurs in the sealing between the space 20 and the processing chamber 12, it does not adversely affect the processing, so the reliability of the temperature control mechanism according to the present embodiment is improved. Further, by attaching this orifice, it is possible to eliminate the sealing by the O-ring 18, and at the same time, even if the substrate 19 is carried in and carried out without breaking the vacuum of the processing chamber 12, the valve 15 becomes unnecessary. Become.

Here, after the substrate 19 is placed, the time required for the space 20 to reach the same pressure as the gas sump 26 needs to be sufficiently short. When the volume of the space 20 is V, the conductance of the orifice is C, and the pressure in the gas sump 26 is P ₀ , the pressure p of the space 20 is p.
Follows the formula:

(6) p = P ₀ (1-exp (−Ct / V)) Here, since the space 20 is a cylinder having a thickness of at most 100 μm, V = 7.8 × 10 ⁻⁷ m ³ The response time constant of is about 1 sec, which is a sufficiently fast response.

FIG. 4 shows a temperature rising curve of the substrate 19 which is heated by the amount of heat received from the plasma when a high frequency power of 200 W to 500 W is applied in the above device configuration. Here, the time constant of the response speed is about 3 seconds, which shows a sufficiently good control characteristic. Also,
The temperature difference with the lower electrode 17 is also kept at 8 ° C and 20 ° C, respectively.

Further, since the heat resistant temperature of the resist is about 120 ° C., this device can increase the added high frequency power to 2.5 KW.

Second Embodiment Next, a second embodiment will be described with reference to FIG.

Only the parts different from the first embodiment will be described.

In the second embodiment, the substrate 19 is supported by utilizing the suction by the electrostatic force disclosed in Japanese Patent Publication No. 57-44747, and the heat transfer gas is stored in the liquid solid reservoir 27. The feature is that it uses the liquid or solid 37 vapor.

The device utilizing the attractive force of static electricity has a mechanism capable of applying a DC voltage from a DC power supply 38 between the two insulated electrodes 33, 36. Because of this electrostatic attraction, the substrate
19 is sucked with a force of about 10 gcm ^-2 over the entire surface, and mechanical contact occurs with the insulating material 30 over the entire surface. At this time, an O-ring 18 for sealing the space 20 formed between the substrate 19 and the insulating material 30 on the lower electrode 29 and the processing chamber 12 is provided, and a gas into the space 20. As in the first embodiment, an orifice 21 is provided as a means for introducing the. In this embodiment, the insulating material 30 serves as a support.

Here, the liquid or solid that generates the heat transfer gas is
When it is isothermal with the temperature-controlled lower electrode 29, its vapor pressure is 70
Select a liquid or solid that gives a pressure of about 0Pa.

In this embodiment, since 1,1,2,2-tetrachloroethane is used, the temperature is about 700 Pa at room temperature. Here, the liquid / solid to be used is not limited to 1,1,2,2-tetrachloroethane and may be a liquid solid having another vapor pressure.

Since the mean free path at this time is 3 μm, the surface of the insulator 30 needs to be polished to 0.8 S or less. Also, by using a soft organic compound for the insulating material 30 and flexibly deforming along the shape of the surface of the substrate 19, the distance between the two surfaces can be made smaller than the mean free path.

At this time, vaporized gas is present between the two surfaces that are mechanically in contact with each other, and the distance between the two surfaces is sufficiently smaller than 3 μm, which is the mean free path of the gas at this time. As a result, 2
The thermal contact between the faces becomes large enough, and the unit heat flow also becomes large.

Further, in order to set the space 20 to 700 Pa in about 1 sec, the diameter of 90 μm is set so that the conductance of the orifice 21 with respect to 1,1,2,2-tetrachloroethane is 1 × 10 ⁻⁶ m ³ / sec.

The temperature rising curve of the substrate 19 in the above apparatus is shown in FIG.
This is an example when dry etching is performed by adding high-frequency power of 300W. The time constant is 5 seconds, which is a sufficient value. Further, this device has an advantage that the structure is simple because it is not necessary to control the gas flow and the gas pressure of the heat conduction gas.

The same effect can be expected by using the wafer temperature control device disclosed in Japanese Patent Laid-Open No. 56-131930 as a device for reducing the distance between the substrate 19 and the support.

Further, forming the support or the surface of the support from a soft organic compound is very effective in reducing the distance between the two surfaces.

Although the above two embodiments are examples in which the present invention is applied to a dry etching apparatus, the same effect can be expected when applied to a film forming apparatus such as sputtering or vapor deposition or a substrate baking apparatus. It can be easily inferred that the method can be applied to a vacuum apparatus that requires the substrate temperature control.

According to the above embodiment, the gas pressure between the substrate and the support is sufficiently raised, and the distance between the two surfaces can be made smaller than the mean free path of the gas at the gas pressure. Heat flow rate per unit time, unit area, unit temperature difference of
It is possible to improve the 50WK ^-1 m ^-2 to 250W · K ^-1 · m ^-2. As a result, the temperature difference between the substrate and the support during processing and the time constant for controlling the substrate temperature are each reduced to 1/5 of the conventional value.
It can be made as small as possible.

As a matter of course, the scope of the present invention is not limited to the above embodiments.

〔The invention's effect〕

According to the present invention, the substrate temperature during processing can be effectively controlled in etching, film formation, baking processing, etc. of a semiconductor device, and pattern faithful etching, film formation of good film quality or good baking is performed. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a conventional substrate temperature control device, FIG. 2 is a graph showing the relationship between the amount of heat flowing between two surfaces and intervening gas pressure, and FIG. 3 is a vertical cross-sectional view of the first embodiment. FIG. 4 is a graph showing a temperature rise curve of the substrate according to the first embodiment, FIG. 5 is a vertical sectional view of the second embodiment, and FIG. 6 is a temperature rise curve of the substrate according to the second embodiment. It is the graph shown. 1 ... Processing chamber, 3 ... Substrate, 4 ... Clip, 5 ... Support base, 6 ... Temperature control device, 7 ... Gas inlet, 8 ...
Flow, 9 ... Spacer, 10 ... Space, 12 ... Processing room, 17
…… Supporting base (lower electrode), 18 …… O-ring, 19 …… Substrate, 20 …… Space, 21 …… Gas inlet (Olyphus), 23
…… Holding means, 26 …… Gas reservoir, 27 …… Liquid solid reservoir.

Claims (6)

[Claims] 1. A processing apparatus for processing a substrate in a processing chamber, which is held at a vacuum or a pressure close to a vacuum, while controlling the temperature of the substrate, and has a predetermined supporting surface for supporting the substrate. A support table, the temperature of which is controlled to a constant temperature, gas introducing means for introducing a gas for heat transfer of a predetermined pressure between the convex surface of the support table and the substrate, and the substrate on the convex surface of the support table. The distance between the convex surface and the substrate by pressing with a predetermined load, the holding means for holding the same or less than the mean free path of the gas under the pressure of the introduced gas, and the gas introduction means for the heat transfer A processing apparatus, comprising: a sealing unit that seals the space introduced between the convex surface and the substrate to such an extent that the gas can leak into the processing chamber. 2. The convex shape of the support table is formed in advance so as to conform to the shape of a substrate which is deformed by the gas pressure introduced into the space by the heat transfer gas introducing means. The processing device described. 3. The heat transfer gas introducing means forms an orifice in the gas introducing portion of the space, and the conductance of the orifice is a reaction in which the amount of gas introduced into the space is introduced into the processing chamber. It is set to a value that is so small as to be significantly less than the amount of gas, and that the pressure in the space is a time constant that allows a response so that the pressure of the gas introduced is in a very short time. The processing apparatus according to claim 1. 4. In a processing apparatus for processing a substrate in a processing chamber, which is maintained at a vacuum or a pressure close to a vacuum, while controlling the temperature of the substrate, an electrode to which a DC voltage is applied and the electrode are insulated from the substrate. A support table having an insulating material for controlling the temperature to a predetermined constant temperature, and a gas introducing means for introducing a heat transfer gas having a predetermined pressure between the insulating material on the support table and the substrate. And attracting the substrate onto the insulating material by an electrostatic force generated by applying a DC voltage to the electrode, the distance between the substrate and the insulating material,
A processing device comprising: holding means for holding the same as or less than the mean free path of the introduced gas under the pressure of the introduced gas. 5. A reaction in which the heat transfer gas introducing means forms an orifice in the gas introducing portion of the space, and the conductance of the orifice is the amount of gas introduced into the space introduced into the processing chamber. It is set to a value that is so small as to be significantly less than the amount of gas, and that the pressure in the space is a time constant that allows a response so that the pressure of the gas introduced is in a very short time. The processing apparatus according to claim 4. 6. The processing apparatus according to claim 4, wherein the heat transfer gas is a liquid or solid vaporized gas which has a predetermined pressure when the heat transfer gas is isothermal.