JPH0614520B2 - Processing equipment in low-pressure atmosphere - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a processing apparatus in a low-pressure atmosphere for performing processing such as etching, film formation, and baking processing on a substrate in the air.

Specifically, in a dry etching device, a device for cooling the substrate so that the photoresist on the substrate is not deteriorated by being heated by heat received from the plasma, and a substrate for degassing the substrate in the baking process. The present invention relates to a device for heating a substrate, and a temperature control device for the substrate necessary for controlling the grain size of the formed film, the optical reflectance, etc. in a vapor deposition, sputter vapor deposition device, etc. It is a thing.

[Background of the Invention]

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

Therefore, it is not possible to effectively control the temperature of the substrate simply by controlling the temperature of the substrate support.

Therefore, some methods are known for effectively increasing the transfer of heat between the two surfaces.

This conventional substrate temperature control device is constructed as shown in FIG. 1 as shown in JP-A-58-32410.

That is, this processing apparatus for sputtering or dry etching mainly comprises a vacuum chamber 10, a sputtering source 19, an anode 20, and a substrate support 12.

Then, the vacuum chamber 10 is exhausted to a low pressure by the exhaust device 18. A discharge is generated between the sputtering source 19 which is the cathode and the anode 20, and the generated ions are hit by the sputtering source 19 so that the molecules jump out, and the substrate 15 supported by the substrate support 12 is formed.
And a thin film made of the same material as the sputtering source is formed on the substrate 15.

Here, the conduit 11 is provided in the substrate support 12,
The temperature of the water controlled by the water supply device 2 flows through the pipe 5, so that the substrate support 12 is kept at an appropriate temperature.

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, and this gas chamber is sealed from the vacuum chamber 10 by the O-ring 17.

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

In the above conventional processing apparatus, the substrate 15 and the substrate support base are
By the gas molecules in the gas chamber provided between
Heat is transferred between the substrate 15 and the temperature-controlled substrate support, and the substrate temperature is controlled more effectively than when the substrate is simply placed on the substrate support 12.

However, this conventional processing device has the following problems.

That is, for example, when the substrate 15 is a silicon substrate having a thickness t = 0.5 mm and 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 gas. The amount of deformation Δγ at the position of γ in the radial direction from the center is subject to the deformation due to the pressure of the gas in the chamber 16 and follows the following equation (1).

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

At this time, the displacement amount δ ₀ at the substrate center, that is, at the position of γ = ₀
Is about 270 μm.

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

Furthermore, even with He having high thermal conductivity, a sufficient heat transfer effect due to the gas in the gas chamber 16 cannot be obtained, so a gas of the same type as the processing gas in the vacuum chamber 10 such as argon is used. If not, it is obvious that the high heat transfer effect seen in helium cannot be obtained.

As described above, in the conventional substrate temperature control method, sufficient heat transfer characteristics cannot be obtained even by using helium, which is a highly conductive gas, and the gas in the gas chamber 16 is of the same type as the gas in the vacuum chamber 10. However, in the case of using such a material, there is a problem that the effective heat transfer characteristics of the gas chamber 16 cannot be obtained in reality.

Further, it is impossible from the viewpoint of mechanical strength of the substrate to press down the substrate 15 to the crushed portion of the O ring where the sealing effect of the O ring occurs.

Therefore, if gas leaking occurs inevitably, and a gas different from the processing gas introduced into the vacuum chamber 10 is used as the heat transfer gas, the leaked heat transfer gas adversely affects the processing in the vacuum chamber 10. It also had the problem of affecting.

[Object of the Invention]

In view of the above-mentioned problems of the prior art, it is an object of the present invention to effectively and uniformly control the temperature of a substrate in an apparatus that performs processing such as etching, film formation and baking in a low pressure atmosphere. An object of the present invention is to provide a processing device in a low-pressure atmosphere that is made possible.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention provides a heat transfer amount between two surfaces at an arbitrary pressure within a range in which the gap distance between the substrate and the substrate support is smaller than the mean free path of the gas existing in the gap. It is effective by making the thickness of the gas layer smaller than the mean free path of the gas even when the substrate support is convex and the substrate is convexly deformed by the gas pressure. This is to improve the heat transfer characteristics between the two surfaces even in a gas other than the highly conductive gas.

Example of Invention

The present invention will be specifically described below based on the embodiments 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, when the pressure of the gas layer is changed, a unit time between two surfaces per unit time temperature difference,
FIG. 2 shows the change in the amount of heat passing through per unit area (heat transfer rate) measured by experiments for helium, nitrogen, and carbon tetrachloride.

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

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

The vacuum chamber 24 is evacuated to a low pressure by the exhaust system 41, and the vacuum gauge
The pressure is made constant by 39 and the control system 40, and for example, carbon tetrachloride as a processing gas is introduced from the processing gas inlet 25. Also,
Between the upper electrode 30 and the lower electrode 37 via the insulator 38,
A high frequency is applied from the high frequency power source 42, the processing gas is brought into a plasma state, and the surface of the substrate 34 on the lower electrode 37 is etched according to the pattern formed by the resist on the surface.

As is clear from this figure, when the thickness d of the gas layer is set to 10 μm or less, carbon tetrafluoride, oxygen and helium are used even if nitrogen and carbon tetrachloride are used in the gas layer up to a pressure of about 400 Pa. The same heat transfer rate as in the case can be obtained.

That is, the heat transfer effect is large when the thickness of the gas layer is constantly kept to about 10 μm or less.

The gas pressure depends on the type of gas, but if the thickness of the gas layer is about 10 μm (the limit of mechanical contact), it will be about 13
Even if it is more than 00Pa, the heat transfer rate does not increase and it is meaningless.

Furthermore, for example, a substrate having a radius of 50 mm receives a load of 1 kg from a gas of 1300 Pa, and if a load larger than this is applied, the substrate may be broken. Therefore, the limit is considered to be about 1300Pa.

In this figure, the straight line portion 21 is the case where the mean free path of the gas molecules is sufficiently larger than the thickness of the gas layer, the heat transfer rate increases linearly with the pressure of the gas, and the thickness of the gas layer and the type of gas vary. It doesn't matter.

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

The curved portion 23 is a transitional state in these two cases.

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

The substrate 34 is pressed with a total weight of 3 to 4 kg by a substrate supporting member 35 which is formed of an annular member provided with a spring 36 or a claw at 3 to 4 points and is driven by a driving system 29.

Further, the heat transfer gas is flown by the flow rate controller 46 and the vacuum gauge 45.
Is introduced into the lower electrode 37 from a gas reservoir 44 whose pressure is controlled by a conduit 47, and through a large number of gas introduction holes 31 with a diameter of about 1 mm provided on a circle 48 as shown in FIG. It is sent to the gap created by the lower electrode 37.

Further, the gas introduced into the vacuum chamber 24 through the gas introduction port 25 and the gas introduced into the vacuum chamber 24 through the lower electrode 37 are supplied together from a single conduit 28 and controlled by the flow rate control device 27, The total amount of gas supplied from the gas supply source 26 to the vacuum chamber is controlled.

The lower electrode 37 is processed into a convex shape, and the surface thereof is polished to a surface roughness of 3.2S.

At this time, the shape of the convex surface is processed according to the expression (1) or slightly larger than the expression (1). This is to prevent the substrate from being further deformed even when a load is applied from the back surface by introducing gas, and as a result, the substrate 34 adheres to the lower electrode 37 and does not deform the substrate more than necessary. .

A process of controlling the temperature of the substrate in the above device configuration will be described.

The gas introduced from the gas introduction hole 31 to the back surface of the substrate 34 is 2
While being evacuated into the vacuum chamber 24 through the surface gap, it is also introduced into the circle 48, and the gas pressure inside the circle 48 becomes the same value as the gas pressure in the gas introduction hole 31. It has been confirmed by experiments that the time required to reach the steady state does not take several seconds if the gap between the surface of about 3.2 S and the silicon substrate.

Further, at the stage of exhausting to the vacuum chamber 24 side, a pressure gradient is generated outside the circle 48. This is due to the conductance of this portion with the gap distance of 10 μm.

The radial pressure distribution of the gas layer 33 at this time is shown in FIG.

At this time, at many points on the substrate 34, the backside gas layer 33
Assuming that the pressure is set to, for example, 700 Pa, as is apparent from the graph shown in FIG. 2, gases such as helium, nitrogen, carbon tetrachloride (which is considered to be the same for other gases), etc. Heat transfer rate of 300 W / m ^{2 in all}
・ It shows a large value of deg.

Here, the pressure on the backside of the substrate is low in the area outside the circle 48, but the thermal conductivity of the substrate itself is sufficiently higher than the heat transfer coefficient of the gas layer, so the temperature difference from the substrate center is a problem. I won't.

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

Furthermore, when the amount of gas introduced into the vacuum chamber 24 through the lower electrode 37 is measured, a silicon substrate with a diameter of 100 mm is 3.2S.
Place it on the lower electrode that has been polished on the surface and set the pressure of the gas layer to 1000.
The amount of leak when introducing Pa from a gas introduction hole provided on the circumference of a radius of 45 mm is about 0.02 to 0.03 Pa · m ³ / sec, which is the normal reaction gas flow rate when performing dry etching. Compared with a certain 0.5 to 2 Pa · m ³ / sec, it is a value that is 1 to 2 orders of magnitude smaller, and microwave plasma processing by electron magnetic resonance is performed in a low pressure atmosphere of 10 ^-2 Pa to 10 ^-1 Pa. The flow rate of the reaction gas in the device 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).

Here, T ₀ and T _e 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, and c is the heat capacity of the substrate. Here, λ = 3.4W / deg, c = 5.8J / deg, T o
= 20 ℃, T _e = 400 ℃, it will rise to 360 ℃ in about 4 seconds. This value is almost the same even in experiments.

Furthermore, it will be apparent to those skilled in the art that the present invention can be applied to other process treatments not described in the present embodiment, which require substrate temperature control in vacuum.

〔The invention's effect〕

As described above, according to the present invention, a gas of about 700 Pa is interposed in the gap between the substrate and the substrate support, and the gap distance can be set to about 10 μm or less. Even if a process gas having a large molecular weight used as a process gas other than the above is used, the heat transfer rate between the substrate and the substrate support can be increased, whereby good temperature control characteristics can be obtained and a heat transfer gas can be obtained. In addition, since the same kind of gas as the processing gas can be used, there is an effect that the problem of leakage of the heat transfer gas can be solved. Further, the substrate transfers heat only to the substrate support through the heat transfer gas, and the heat transfer gas introduction part is formed by a small hole to transfer heat between the substrate and the substrate support. Since the influence on the distribution of the rate is made as small as possible, there is an effect that the substrate temperature can be controlled with a small distribution and excellent uniformity. In addition, by circulating a temperature-controlled fluid inside the substrate support and combining heat transfer between the substrate and the substrate support by heat transfer gas, it is possible to easily heat and cool the substrate. Have.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a conventional processing apparatus, FIG. 2 is a view showing the relationship between heat transfer rate and gas pressure, and FIG. 3 is a vertical cross-sectional view showing one embodiment of the present invention, FIG. Is a see-through view of the lower electrode and the substrate, and FIG. 5 is a view showing pressure distribution of the gas layer. 24 ... Vacuum chamber, 31 ... Gas introduction hole 33 ... Gas layer, 34 ... Substrate 35 ... Substrate support, 37 ... Lower electrode 44 ... Gas reservoir

Continuation of the front page (56) Reference JP 58-213434 (JP, A) JP 57-145321 (JP, A) JP 58-32410 (JP, A) JP 56-131931 (JP , A)

Claims (4)

[Claims] 1. A processing apparatus in a low-pressure atmosphere, comprising a support table for supporting a substrate to be processed in a processing chamber in a low-pressure atmosphere,
There is a pressing member that presses the substrate against the support table, the support table is provided with a flow path through which a temperature-controlled fluid flows, and the support surface of the support table that supports the substrate is convex with a high central portion. And having a large number of small holes in the supporting surface, and between the supporting base and the substrate pressed against the supporting base by the pressing member, 0.02 to
A processing apparatus in a low-pressure atmosphere, characterized in that a gas whose pressure is adjusted is introduced from the large number of small holes at a flow rate of 0.03 Pa · m ³ / S and exhausted from the processing chamber. 2. The large number of small holes are provided at a position close to the outer periphery of a substrate supported on the supporting surface of the support table, and the same kind of gas as the gas introduced into the low pressure processing atmosphere is introduced into the large number of small holes. The treatment device in a low pressure atmosphere according to claim 1, wherein the treatment device is introduced through the small hole between the substrate and the support surface. 3. The gas introduced between the supporting base and the substrate has a gap of 10 μm between the supporting base and the substrate.
The processing apparatus in a low-pressure atmosphere according to claim 2, wherein the pressure is adjusted as follows. 4. A low-pressure atmosphere according to claim 3, wherein a temperature-controlled fluid is controlled in a flow path provided inside the support base to control the temperature of the support base. Processing equipment.