JP2581026B2 - Processing method and apparatus in low pressure atmosphere - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for processing in a low-pressure atmosphere for performing processes such as etching, film formation and baking on a substrate in a processing chamber in a low-pressure atmosphere.

More specifically, in a dry etching apparatus, an apparatus for cooling a substrate so that the photoresist on the substrate is not deteriorated by heating the substrate by heat received from plasma, and a baking process for degassing the substrate. In, it is necessary to heat the substrate effectively,
The present invention relates to an apparatus for heating a substrate, a method for controlling a temperature of a substrate required for controlling a particle diameter of a formed film, an optical reflectance, and the like in a vapor deposition or sputter vapor deposition apparatus, and a device therefor.

[0003]

2. Description of the Related Art It is known that, in a processing apparatus in a low-pressure atmosphere, the transfer of heat between a substrate and a substrate support is not sufficiently performed like the transfer of heat at normal pressure. this is,
This is because intervening gas molecules play a large role in transfer of heat between the two surfaces.

For this reason, simply controlling the temperature of the substrate support cannot effectively control the temperature of the substrate.

There are known several methods for effectively increasing the transfer of heat between two surfaces.

This conventional substrate temperature control apparatus is disclosed in
It is configured as shown in FIG. 1 as shown in 8-32410.

That is, the processing apparatus such as sputtering or dry etching mainly comprises a vacuum chamber 10, a sputter source 19,
It comprises an anode 20 and a substrate support 12.

[0008] The vacuum chamber 10 is evacuated to a low pressure by an exhaust device 18. A discharge is generated between the sputtering source 19, which is a cathode, and the anode 20, and the generated ions are hit by the sputtering source 19, whereby the molecules jump out, and reach the substrate 15 supported by the substrate support 12, and the substrate 15 A thin film of the same material as the sputter source is formed on 15.

Here, a conduit 11 is provided in the substrate support table 12, and water whose temperature is controlled is flown from the water supply device 2 through the pipe 5, so that the substrate support table 12 has an appropriate temperature. Is kept.

The substrate 15 is pressed by a substrate support 13 provided with a spring 14 with a uniform load over the entire circumference.
At this time, an O-ring 17 is provided between the substrate 15 and the substrate support 12.
And a gas chamber 16 is created, which is
It is sealed from the vacuum chamber 10 by a ring 17.

Here, in the gas sump 4, the gas inflow from the gas supply source 1 is controlled by the gas pressure gauge 8, the control system 9 and the valve 3. A gas chamber 16 formed in a gap between the substrate 15 and the substrate support 12 is connected to the gas reservoir 4 through a valve 6 and a gas pipe 7, and is constantly controlled at a constant pressure.

In the conventional processing apparatus described above, the substrate 15
Heat is exchanged between the substrate 15 and the temperature-controlled substrate support by gas molecules in a gas chamber provided between the substrate support 12 and the substrate, and the substrate is simply placed on the substrate support 12. Thus, more effective substrate temperature control is performed.

However, the conventional processing apparatus has the following problems.

That is, for example, when the thickness of the substrate 15 is t = 0.5 m
m, a silicon substrate having a radius a = 50 mm, the pressure p in the gas chamber 16 is 1000 Pa, and the pressure in the vacuum chamber 10 is sufficiently smaller than p, the substrate is deformed by the pressure of the gas in the gas chamber 16. , The amount of deformation δr at a position r in the radial direction from the center
Follows the following (Equation 1).

[0015]

(Equation 1)

Here, E and V are the longitudinal modulus of elasticity and Poisson's ratio of silicon, respectively, E = 13.1 × 10 ¹⁰ (N /
m ² ) and V ≒ 0.3.

At this time, the displacement δ ₀ at the center of the substrate, ie, at the position of r = 0, is about 270 μm.

This value greatly exceeds the appropriate thickness of the gas chamber 16 of 134 μm when He is used as the gas.
That is, the effect as designed cannot be obtained.

Furthermore, even if He has a high thermal conductivity, a sufficient heat transfer effect cannot be obtained by the gas in the gas chamber 16, so that the same kind of processing gas as the processing gas in the vacuum chamber 10, such as argon, is used. Obviously, the use of gas does not provide the high heat transfer effect found in helium.

[0020]

As described above, in the conventional substrate temperature control method, sufficient heat transfer characteristics cannot be obtained even when helium, which is a highly conductive gas, is used. When a gas of the same type as the gas in the vacuum chamber 10 is used, there is a problem that an effective heat transfer characteristic of the gas chamber 16 cannot be obtained in practice.

Further, it is impossible to press the substrate 15 to the extent that the O-ring seals the O-ring to produce a sealing effect from the viewpoint of the mechanical strength of the substrate.

Therefore, if a gas different from the processing gas introduced into the vacuum chamber 10 is used as the heat transfer gas, a leaked heat transfer gas is generated.
There was also a problem that processing in step 10 was adversely affected.

An object of the present invention is to provide an apparatus for performing processes such as etching, film formation, and baking in a low-pressure atmosphere in view of the above-mentioned problems of the prior art, so that the temperature of a substrate can be effectively controlled. To provide a processing apparatus in a low-pressure atmosphere.

[0024]

According to the present invention, in order to attain the above object, the present invention provides a method in which the distance between the substrate and the substrate support is smaller than the mean free path of the gas present in the gap.
Focusing on the fact that the amount of heat transferred between surfaces does not depend on the type of gas at an arbitrary pressure, the thickness of the gas layer is maintained even when the substrate is deformed to be convex due to the gas pressure when the substrate support is made convex. The point is that the heat transfer characteristic between the two surfaces is improved even in gases other than the highly conductive gas by making the mean free path smaller than the gas.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on an embodiment shown in the drawings.

That is, the features of the present invention will be specifically described with reference to FIG.

Assuming that the thickness of the gas layer between the substrate and the substrate support is d, and the pressure of the gas layer is changed, the amount of heat that passes between two surfaces per unit time per unit temperature difference per unit time per unit area (heat transfer rate) FIG. 2 shows the results of measurement of helium, nitrogen, and carbon tetrachloride by experiment.

Further, an embodiment of the present invention will be specifically described with reference to FIGS. 3, 4 and 5. FIG.

The present embodiment is a parallel plate type dry etching apparatus mainly comprising a vacuum chamber 24, an upper electrode 30, a lower electrode 37, and a high frequency power supply 42.

The vacuum chamber 24 is evacuated to a low pressure by an evacuation system 41, and is evacuated to a constant pressure by a vacuum gauge 39 and a control system 40, and a processing gas such as carbon tetrachloride is introduced from a processing gas inlet 25.

High frequency power is applied from a high frequency power supply 42 between the upper electrode 30 and the lower electrode 37 via the insulator 38, and the processing gas is in a plasma state. Is etched according to the pattern formed by the resist.

As is apparent from this figure, when the thickness d of the gas layer is set to 10 μm or less, even if nitrogen and carbon tetrachloride are used in the gas layer up to a pressure of about 400 Pa, for example, carbon tetrafluoride, oxygen, helium The same heat transmittance as in the case of using is obtained. That is, if the thickness of the gas layer is always set to about 10 μm or less, the heat transfer effect is large.

Although the gas pressure depends on the type of gas, if the thickness of the gas layer is about 10 μm (the limit of mechanical contact), the heat transmission rate does not increase even at about 1300 Pa or more. ,
meaningless.

Further, for example, a substrate having a radius of 50 mm is 1300P
The load received from the gas a is 1 kg, and applying a load greater than this may cause the substrate to break.
Therefore, about 1300 Pa is considered to be the limit.

In this figure, the straight line portion 21 is a case where the mean free path of the gas molecules is sufficiently larger than the thickness of the gas layer, and the heat transmittance increases linearly with the pressure of the gas, and the thickness and the gas Regardless of the type.

On the other hand, the linear portion 22 is a case where the mean free path of the gas molecules is sufficiently smaller than the thickness of the gas layer, and the heat transmittance decreases as the thickness of the gas layer increases. At this time, the heat transmission rate does not change even if the pressure increases as long as the gases are of the same type.

The curved portion 23 is in an excessive state in these two cases.

Here, the lower electrode 37 is provided with the conduit 32 inside, and a fluid maintained at a set temperature is supplied from a fluid supply source 43 to be maintained at the set temperature. The method of keeping the lower electrode 37 at the set temperature is not limited to the method of flowing a fluid,
A method using a heat pipe and a cooling source or a heating wire may be used.

The substrate 34 is pressed with a total weight of 3 to 4 kg by a substrate support 35 which is formed by an annular or 3 to 4 point pawl provided with a spring 36 and driven by a driving system 29.

Further, a heat transfer gas is introduced into the lower electrode 37 from the gas reservoir 44, the pressure of which is controlled by the flow control device 46 and the vacuum gauge 45, through the conduit 47, and as shown in FIG. Is supplied to a gap formed by the substrate 34 and the lower electrode 37 through a number of gas introduction holes 31 having a diameter of about 1 mm provided in the substrate.

The gas introduced into the vacuum chamber 24 through the gas inlet 25 and the gas introduced into the vacuum chamber 24 through the lower electrode 37 are supplied from a single conduit 28 together. It controls the total amount of gas supplied from the gas supply source 26 to the vacuum chamber.

The lower electrode 37 is processed into a convex shape. The surface is polished to a surface roughness of about 3.2S.

At this time, the shape of the convex surface is determined according to equation (1) or
(1) Processed slightly larger. This is to prevent the substrate from being further deformed even when a gas is introduced and the substrate receives a load from the back surface. .

The process of controlling the temperature of the substrate in the above-described apparatus configuration will be described.

The gas introduced from the gas introduction hole 31 to the back surface of the substrate 34 is exhausted into the vacuum chamber 24 through the gap between the two surfaces, and is also introduced into the circle 48, and the gas inside the circle 48 is removed. The pressure becomes the same value as the pressure of the gas in the gas introduction hole 31.
It has been experimentally confirmed that the time required to reach the steady state does not take several seconds if the gap is about 3.2 S between the surface and the silicon substrate.

At the stage when the air is evacuated to the vacuum chamber 24 side,
Outside of 48, a pressure gradient is created. This is the gap distance
This is due to the conductance of this part of 10 μm.

FIG. 5 shows the pressure distribution in the radial direction of the gas layer 33 at this time.

At this time, at many points on the substrate 34, if the pressure of the gas layer 33 on the back surface is set to a set pressure, for example, 700 Pa, as is clear from the graph shown in FIG. All gases such as carbon chloride (this is considered to be the same for other gases) show a large value of 300 W / m ² · deg.

Here, the pressure on the back surface of the substrate is low at the portion outside the circle 48, but since the thermal conductivity of the substrate itself is sufficiently larger than the heat transmittance of the gas layer, the temperature difference from the center of the substrate is low. Does not matter.

Here, when a power of about 200 W is applied by the high-frequency power supply 42 and the aluminum film on the silicon substrate is dry-etched, the temperature of the substrate is about 30 ° C. when the lower electrode is set at 20 ° C. Was. This is an extremely good value compared to a value of 250 ° C. when the substrate is simply placed.

Further, when the amount of gas introduced into the vacuum chamber 24 through the lower electrode 37 was measured, a silicon substrate having a diameter of 100 mm was placed on the lower electrode polished to a 3.2S surface, and the pressure of the gas layer was measured. Is set to 1000 Pa, and the amount of leak when the gas is introduced from a gas introduction hole provided on a circumference with a radius of 45 mm is about 0.02 to
It is about 0.03 Pa · m ³ / sec, which is 0.5 to 2 Pa · m ³ / se, which is a normal reaction gas flow rate when performing dry etching.
The value is one to two orders of magnitude smaller than c, and 10 to ²
Reactant gas flow rate in microwave plasma processing equipment by electron magnetic resonance processing in low pressure atmosphere of Pa ~ ¹⁰ ~ ¹ Pa
The value is less than 0.04 to 0.06 Pa · m ³ / sec. Therefore, it can also be used as a substrate temperature control device in a plasma processing apparatus using microwave discharge.

When the substrate support is used for baking the substrate while being heated to 400 to 500 ° C., the substrate temperature T rises according to the following (Equation 2).

[0053]

(Equation 2)

Here, To and Te are the initial temperature of the substrate, the temperature of the electrodes, λ is the amount of heat passing through the entire surface of the substrate, c
Is the heat capacity of the substrate. Here, λ = 3.4 W / deg, c =
5.8 J / deg, To = 20 ℃, Te = 400 ℃, about 4
It will rise to 360 ° C in seconds. This value is almost the same even in experiments.

Further, it will be apparent to those skilled in the art that the present invention can be applied to other processing which is not described in this embodiment and requires control of the substrate temperature in a vacuum.

[0056]

As described above, according to the present invention, since a gas of about 700 Pa is interposed in the gap between the substrate and the substrate support, the gap distance can be reduced to about 10 μm or less. Even when using a process gas having a high molecular weight used for a process gas other than helium, which is a neutral gas, the heat transfer rate between the substrate and the substrate support can be increased, and
Good temperature control characteristics can be obtained, and a gas of the same type as the processing gas can be used as the heat transfer gas, so that there is an effect that the problem of the leak of the heat transfer gas can also be solved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a conventional processing apparatus.

FIG. 2 is a diagram showing a relationship between a heat transmittance and a gas pressure.

FIG. 3 is a longitudinal sectional view showing one embodiment of the present invention.

FIG. 4 is a perspective view of a lower electrode and a substrate.

FIG. 5 is a diagram showing a pressure distribution of a gas layer.

[Explanation of symbols]

24… Vacuum chamber 31… Gas introduction hole 33… Gas layer
34 ... substrate 35 ... substrate support 37 ... lower electrode 44 ... gas reservoir.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location H01L 21/302 E

Claims (8)

(57) [Claims] A temperature of a support provided in a processing chamber in a low-pressure atmosphere is controlled by flowing a temperature-controlled fluid into the support, and a substrate to be processed is supported on the temperature-controlled support. A gas whose pressure is adjusted to 700 Pa or more is introduced between the supported substrate and the support table, and the gas is exhausted from the processing chamber to thereby obtain 300 W / m ² · deg.
A processing method in a low-pressure atmosphere, wherein the temperature of the substrate is controlled by the heat transmission rate. 2. The gas, wherein the pressure is adjusted to 700 Pa or more, is supplied from a plurality of small holes provided at a position near an outer periphery of a substrate supported on the support surface of the support table. Item 6. A method for processing in a low-pressure atmosphere according to Item 1. 3. A processing gas is introduced into the processing chamber in the low-pressure atmosphere, and the gas supplied from the plurality of small holes and adjusted to a pressure of 700 Pa or more is the same kind of gas as the processing gas. The method for treating in a low-pressure atmosphere according to claim 1, wherein: 4. The gas introduced between the support and the substrate has a gap of 10 μm between the support and the substrate.
2. The method according to claim 1, wherein the pressure is adjusted to be as follows. 5. A processing chamber maintained in a low-pressure atmosphere, and a substrate on which a substrate to be processed is mounted in the processing chamber, and a flow path through which a temperature-controlled fluid flows therein are provided. Supporting means having a plurality of small holes, pressing means for pressing the substrate against the mounting surface, pressure from the plurality of small holes between the substrate and the mounting surface pressed by the pressing means. Gas introducing means for introducing a gas adjusted to 700 Pa or more, and exhaust means for exhausting the processing chamber, wherein the gas introducing means introduces the gas between the mounting surface and the substrate by the gas introducing means. By exhausting gas from the processing chamber by the exhaust means, 300 W / m ² · de
A processing apparatus in a low-pressure atmosphere, wherein the temperature of the substrate is controlled with a heat transmittance of at least g. 6. The processing chamber has processing gas introducing means for introducing a processing gas into the low-pressure atmosphere, and the gas introduced between the substrate and the mounting surface from the plurality of small holes is supplied to the processing chamber. 6. The processing apparatus in a low-pressure atmosphere according to claim 5, wherein the processing gas is the same kind of gas as the processing gas introduced into the processing chamber from the processing gas introduction unit. 7. The supporting means, wherein the mounting surface is formed in a convex shape, and the plurality of small holes are provided at positions near an outer periphery of a substrate mounted on the mounting surface. The processing apparatus in a low-pressure atmosphere according to claim 5. 8. A processing apparatus in a low-pressure atmosphere according to claim 5, wherein a temperature-controlled fluid is caused to flow through a flow path provided inside said support means to control the temperature of said support means. .