JPH09199488A - Processing equipment - Google Patents

Abstract

(57) Abstract: A processing apparatus capable of effectively controlling the temperature of a substrate during etching, film formation, and baking processing during semiconductor device manufacturing. A processing chamber (12) having an exhausting means for evacuating the interior, a lower electrode (29) installed in the processing chamber (12) and having a convex upper surface, and a convex shape of the lower electrode (29). An insulating material 30 for holding the substrate 19 in close contact with the upper surface thereof, and a solid / liquid reservoir 27 for supplying a cooling gas between the lower electrode 29 and the substrate 19 are provided. When a cooling gas is supplied between the lower electrode 29 and the substrate 19, the distance between the lower electrode 29 and the substrate 19 is about the same as the mean free path of the introduced cooling gas, or The convex shape of the upper surface of the lower electrode 29 was formed as follows.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing apparatus for performing processing such as dry etching, vapor deposition and sputtering on a substrate such as a semiconductor wafer.

[0002]

2. Description of the Related Art For example, in a semiconductor device manufacturing process, when vapor deposition or sputtering is performed as a film forming process, in order to obtain a good film quality with appropriate particle size, reflectance, specific resistance and hardness, the substrate is It is necessary to properly control the substrate temperature during baking and during film formation. In particular, the grain size and reflectance are greatly affected by the temperature of the substrate during film formation.

Further, it is necessary to control the temperature of the substrate 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. This is because by controlling the temperature of the substrate, it is possible to prevent thermal damage to the resist caused by the poor heat resistance of the resist and to etch a faithful pattern.

However, even if the temperature of the substrate is controlled so as to be the same as the temperature of the substrate support, the thermal contact between the substrate and the support is not sufficient in vacuum, so the temperature of the substrate is kept in vacuum. It is difficult to control.

Therefore, conventionally, the two of the substrate and the substrate support are provided.
In order to increase the thermal contact between the surfaces, a method has been proposed in which the substrate is mechanically pressed against the support base, or the substrate is attracted to the support base by electrostatic force. However, even by such a method, the thermal contact between the two surfaces of the substrate and the support is largely due to the gas molecules interposed between the two surfaces, and the heat exchange between the pure solids is caused by the above-mentioned pressing. Since the pressure is small enough to be ignored as compared with the heat exchange by gas molecules, a sufficient effect is not obtained.

In view of this, an apparatus for increasing thermal contact by interposing gas molecules between the substrate and the support is proposed and disclosed in Japanese Patent Laid-Open No. 56-103442.

As shown in FIG. 6, the substrate temperature control unit in this apparatus has a substrate 3 via a spacer 9 on a support base 5.
Are closely arranged and are supported by several clips 4.
The support base 5 is provided with a temperature control device 6 having a cooling or heating mechanism. The processing chamber 1 is exhausted through the exhaust port 2 so that the pressure becomes about 1 Pa.

At the same time, argon is introduced from the gas inlet 7, and this gas flows between the temperature control device 6 and the substrate 3,
It flows into the processing chamber 1 as shown by an arrow 8. At this time, the pressure in the space 10 between the substrate 3 and the temperature control device 6 is 10 to 10.
It is controlled to be 100 Pa.

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

[0010]

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention
When the temperature of a silicon substrate having a thickness of 0.45 mm and a temperature of 0.45 mm is controlled, the time constant becomes about 20 seconds. When dry etching with an applied power of 500 W is performed in such a situation, the temperature difference between the gas flowing out from the temperature control device and the surface of the silicon substrate becomes 130 ° C., the resist is thermally damaged, and good processing is performed. Can't do.

In view of the above circumstances, an object of the present invention is to perform etching, film formation, and baking treatments during the manufacture of semiconductor devices.
It is an object of the present invention to provide a processing apparatus capable of performing good processing by effectively controlling the substrate temperature during processing.

[0012]

In order to achieve the above object, in the present invention, a processing chamber provided with exhaust means for evacuating the interior thereof, and a top surface provided inside the processing chamber and having a convex shape. It is provided with the formed electrode means, a holding means for closely holding the substrate on the convex upper surface of the electrode means, and a gas supply means for supplying a cooling gas between the electrode means and the substrate. When the cooling gas is supplied from the gas supply means between the electrode means and the substrate, the distance between the electrode and the substrate is approximately the same as the mean free path of the introduced cooling gas, or The convex shape on the upper surface of the electrode means was formed so as to be less than that.

In order to reduce the temperature difference between the substrate and the electrode means and increase the response speed of the temperature control of the substrate, the amount of heat that flows between the substrate and the electrode means per unit time difference per unit temperature (hereinafter unit) It is necessary to increase the heat flow rate).
To increase the unit heat flow, increase the pressure and
The distance between the faces must be less than or equal to the mean free path of the gas under that pressure.

The substrate temperature during processing changes with time according to the following equation. (1) Tw = (1-exp (-kt / C)) Qi / k +
To Here, Tw is the substrate temperature, C is the heat capacity of the substrate, k is the unit heat flow rate, Qi is the constant amount of heat given to the substrate per unit time during processing, To is the temperature of the electrode means, t is the time, and t is the time.
= 0, Tw = To.

Further, when the temperature of the electrode means is at the steady value To and the initial temperature Two ≠ To of the substrate, the following equation is obeyed. (2) Tw = (Two−To) exp (−kt / C) +
In all cases above To, the response speed of the temperature control of the substrate is
It depends only on the heat capacity C of the substrate and the unit heat flow rate k between the two surfaces. The value of C is a value specific to the substrate, for example, a diameter of 100 m
m, about 6.2J · with a silicon substrate 0.45mm thick
It is K ~ ¹ . Therefore, in order to reduce the temperature difference between the substrate and the electrode means and increase the response speed of the temperature control of the substrate, it is necessary to increase the unit heat flow rate.

By the way, FIG. 5 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, the surface was covered with thin silicon oxide, and polished aluminum was used as the 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 the straight line passing through the origin, which proves that under these conditions the heat transfer purely between solids is negligible. That is, even if there is mechanical contact between the two surfaces of the solid, most of the thermal contact is due to gas interposed between the two surfaces. Further, it can be seen that when the pressure of the intervening gas is made larger than the value of 100 Pa in the conventional apparatus, the unit heat flow rate increases.

The above measured values are based on the following theoretical formula. That is, the amount of heat “dQ / dt” that passes between two surfaces per unit time follows the following equation. (3) dQ / dt = k ₁ (Tw-To) p (e << λ) (4) dQ / dt = k ₂ (Tw-To) e (e >> λ) where k ₁ and k ₂ are constants. , Tw and To are the temperatures of the substrate and the support, respectively, e is the distance between the two surfaces, p is the pressure of the intervening gas, and λ is the mean free path under that pressure. This formula shows that under low pressure and long mean free path,
"DQ / dt" 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 unit heat flow rate can be increased by increasing the pressure of the gas interposed between the two surfaces and by providing a mechanism for keeping the distance between the two surfaces equal to or less than the mean free path under the pressure.

In the conventional device, p is 1
The mean free path λ of Ar is about 50
μm. Therefore, it is desirable to reduce the interval to about 50 μm, but as shown in FIG.
The central portion of the substrate 3 swells as indicated by reference numeral 11 due to the pressure difference a. For example, in the case of a silicon wafer having a diameter of 100 mm and a thickness of 0.45 mm, the bulge amount at the center reaches 150 μm due to a pressure difference of 100 Pa. Therefore, the unit heat flow rate cannot be increased even if the pressure exceeds 50 μm which is the mean free path and the pressure is further increased.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. First, the principle of temperature control is illustrated in Fig. 1 using a substrate as an example.
It will be described based on. Support 17 for substrate 19 and substrate 1
In the substrate temperature control device having the holding means 23 for holding 9 and the gas introduction means 52 for introducing the gas into the space 20 formed by the substrate 19 and the support 17, the support 17 and the substrate 19 are provided. Is provided with a mechanism for keeping the distance below the mean free path of the gas under the pressure of the introduced gas, whereby the substrate temperature during the processing can be effectively controlled in the etching processing and the like during the semiconductor device manufacturing. .

An apparatus based on such a principle is basically a parallel plate type dry etching apparatus comprising 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 is connected to a vacuum exhaust system (not shown) via an exhaust port 13. A reaction gas is introduced into the processing chamber 12 through a gas inlet 24. Further, the processing chamber 12 is provided with an inlet / outlet 14 for taking in / out the substrate 20 at an appropriate position.

A high frequency power supply 25 is connected between the upper electrode 16 and the lower electrode 17. The lower electrode 17 is provided with a flow path 48 through which the liquid heat medium flows, a pump 42, and a temperature control device 43 for the liquid heat medium. Further, the gas reservoir 26 for the heat transfer gas is supplied through the orifice 21 and the valve 15.
Is provided. A gas cylinder 44 is provided in the gas sump 26 via a flow rate adjusting valve 45, and a flow rate adjusting valve 4 is also provided.
6, a rotary pump 47 is connected.

The substrate holding means 23 is made of an insulating material such as ceramic, and the ball screw 4 is inserted through a spring 39.
0 and the motor 41. An O-ring 18 is provided between the substrate 19 and the lower electrode 17, and the O-ring 18 is a space 2 formed by the substrate 19 and the lower electrode.
0 is sealed from the processing chamber 12.

In the above structure, the lower electrode 17 is kept at a constant temperature by circulating the liquid heat medium kept at an appropriate constant temperature. As a liquid heat carrier, 20
Although water kept at ° C. is used, a fluid other than water whose temperature is controlled may be used according to the purpose. Also, the lower electrode 17
May be controlled by using electric resistance.

The board 19 includes a motor 41 and a ball screw 40.
Then, the substrate is pressed against the lower electrode 17 by the substrate holding means 23 which moves up and down. At this time, the spring 39 is
, With a constant load, i.e., a mechanism for generating mechanical contact.

Further, the gas sump 26 is a flow rate adjusting valve 4
5, 46, a gas cylinder 44 and a rotary pump 47 always keep a constant pressure and are filled with a heat transfer gas. The space 20 contains a gas reservoir 26 and an orifice 2
A gas for heat transfer is introduced via 1. That is, the gas introduction means includes the gas reservoir 26 and the orifice 21 serving as a gas introduction port.

Next, how the temperature of the substrate is controlled during processing in the above apparatus, helium is used as a heat transfer gas, and the substrate has a diameter of 100 mm and a thickness of 0.45.
The description will be made by taking the case of a silicon substrate of mm as an example.

After the substrate 19 is placed, helium gas is introduced from the gas reservoir 26 at 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 at a height of about 800 μm. Further, the change amount w of the point located at a distance of r in the radial direction from the center of the substrate follows the following equation.

[0031]

[Equation 1]

Here, E and ν are 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 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-mentioned formula or a curved surface having more bulge. At this time, since the substrate 19 is pressed by the substrate support 23, it is deformed along the convex surface and has a stress.

At this time, the force exerted on the substrate 19 by the gas pressure is equal to or smaller than the stress possessed by the substrate 19, so that the substrate 19 does not generate a strain more than the strain already possessed by the gas pressure, and thus the substrate 19 It remains in mechanical contact along the electrode 17. The surface of the lower electrode 17 is polished to a surface roughness of 6-S or less. Therefore, the distance between the two surfaces is kept sufficiently smaller than the average free path of helium at 700 Pa of 30 μm over the entire surface.

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

Further, in the above apparatus, the orifice 21 is provided as an introducing means for introducing the heat transfer gas into the space 20. The diameter of the orifice 21 is about 40 μm so that the conductance with respect to helium is about 1 × 10 to ⁶ m ³ / sec. When the substrate 17 is not placed, the amount of gas flowing out of the gas reservoir 26 through the orifice into the processing chamber 12 having a pressure difference of 700 Pa is about 7 × 10 to ⁴ Pa · m ³ / sec.
This is sufficiently smaller than the reaction gas introduction amount 8 × 10 to ² Pa · m ³ / sec introduced from the reaction gas introduction port 24.
Therefore, even if leakage occurs in the sealing between the space 20 and the processing chamber 12, it does not adversely affect the processing.
The reliability of the temperature control mechanism according to this embodiment is improved. Also, by providing 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 space 2
The time required for 0 to reach the same pressure as the gas sump 26 must 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 reservoir 26 is Po, the pressure p of the space 20 follows the following equation.

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

In the above device configuration, 200 W to 50 W
FIG. 2 shows a temperature rise curve of the substrate 19 which is heated by the amount of heat received from the plasma when a high frequency power of 0 W is applied.
Here, the time constant of the response speed is about 3 seconds, which indicates a sufficiently good control characteristic. Further, the temperature difference with the lower electrode 17 is suppressed to 8 ° C and 20 ° C, respectively.

The heat resistant temperature of the resist is about 120 ° C.
Therefore, in this device, the additional high-frequency power is 2.5 K
That is, it can be increased to W.

An embodiment of the present invention will be described with reference to FIG. In this embodiment, the substrate 1 is formed by using electrostatic attraction disclosed in Japanese Patent Publication No. 57-47747.
The vapor in the liquid or the solid 37 in the liquid / solid reservoir 27 is used as the gas for heat transfer.

The device utilizing the attractive force of static electricity is composed of a plurality of (two in FIG. 3) electrodes 3 insulated from each other.
By applying DC voltages having different polarities from the DC power supply 38 between the electrodes 3 and 36, a closed circuit is formed between the substrate 19 and the two electrodes 33 and 36, and the substrate 19 is electrostatically charged without forming plasma. Can be adsorbed. Therefore, the substrate 19 can be electrostatically attracted even in the baking step of the substrate 19 without using plasma. Due to the attraction force due to the static electricity, the substrate 19 has about 10 gc
It is sucked by a force of m ~ ² , and mechanical contact occurs with the insulating material 30 over the entire surface.

At this time, the 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 the space 20. An orifice 21 is provided as a means for introducing gas into the. In the present embodiment, the insulating material 30 serves as a support.

Here, the liquid or solid is selected so that the vapor pressure of the gas or solid for generating the heat transfer gas is about 700 Pa when it is isothermal with the temperature-controlled lower electrode 29.

In this embodiment, since 1,1,2,2-tetrachloroethane is used as the heat transfer gas, the pressure 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 another liquid / solid having a vapor pressure.

Since the mean free path at this time is 3 μm, it is necessary to polish the surface of the insulator 30 to 0.8 S or less. Also, by using a soft organic compound for the insulating material 30 and flexibly deforming it along the shape of the lower 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 the mean free path of 3 μm of the gas at this time.
As a result, the thermal contact between the two surfaces is sufficiently large, and the unit heat flow is also large.

In addition, the space 20 is 700 in about 1 sec.
In order to achieve Pa, the orifices 1, 1, 2, 2-
Conductance to tetrachlorethane is 1 × 10
The diameter is set to 90 μm so as to be ~ ⁶ m ³ / sec.

The temperature rising curve of the substrate 19 in the above apparatus is shown in FIG. This is an example of a case where dry etching is performed by applying a high-frequency power of 300 W. 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 gas pressure of the heat transfer 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 base.

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 examples are examples in which the present invention is applied to a dry etching apparatus, the same effect is 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 present invention can be applied to other vacuum devices requiring electrode means and substrate temperature control.

According to the above embodiment, the gas pressure interposed between the substrate and the support is sufficiently raised, and the distance between the two surfaces is set smaller than the mean free path of the gas at that gas pressure. Therefore, the unit time, unit area, and heat flow rate per unit temperature difference between the two surfaces can be reduced from the conventional 50W ・ K ~ ¹・ m ~ ² to 250W.
・ It can be improved to 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 can be reduced to about one fifth of the conventional value.

Of course, the scope of the present invention is not limited to the above embodiments.

[0055]

According to the present invention, in etching, film formation, baking processing, etc. of a semiconductor device, the substrate temperature during processing can be effectively controlled, and good processing can be performed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a substrate processing apparatus according to the present invention.

FIG. 2 is a characteristic diagram showing a temperature rise curve of a substrate in the substrate processing apparatus shown in FIG.

FIG. 3 is a vertical sectional view showing another embodiment of the substrate processing apparatus according to the present invention.

4 is a characteristic diagram showing a temperature rise curve of a substrate in the substrate processing apparatus shown in FIG.

FIG. 5 is a characteristic diagram showing the relationship between the amount of heat flowing between two surfaces and the pressure of intervening gas.

FIG. 6 is a vertical sectional view of a conventional substrate temperature control device.

[Explanation of symbols]

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 chamber, 17 ... support base (lower electrode), 18 ... O-ring, 19 ... substrate, 20 ... space, 2
DESCRIPTION OF SYMBOLS 1 ... Gas inlet (orifice) 23 ... Holding means, 26 ...
No gas, 27 ... No liquid solid.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H01L 21/68 H01L 21/68 R H05H 1/46 H05H 1/46 M

Claims (3)

[Claims] 1. A processing chamber provided with exhaust means for evacuating the interior thereof, electrode means installed inside the processing chamber and having a convex upper surface, and a substrate on the convex upper surface of the electrode means. A holding means for closely holding and holding, and a gas supply means for supplying a cooling gas between the electrode means and the substrate,
When a cooling gas is supplied between the electrode means and the substrate by the gas supply means, the distance between the electrode and the substrate is approximately the same as the mean free path of the introduced cooling gas, or A processing apparatus characterized in that a convex shape on the upper surface of the electrode means is formed as described below. 2. The pressure of the cooling gas supplied from the gas supply means between the electrode and the substrate is 100 Pa.
The processing device according to claim 1, wherein the processing device is larger than the above. 3. A gas leaking into the processing chamber, of the cooling gas supplied from the gas supply means between the electrode and the substrate, is exhausted by the exhaust means. Item 1. The processing device according to Item 1.