JPH06275395A - Plasma treatment device - Google Patents

Abstract

PURPOSE:To maintain the stable performance of a plasma treatment device by constituting the microwave lead-in window of a reactor by plural heat resistant plates. CONSTITUTION:The microwave treatment window 19 of a plasma treatment device is formed on the upper part of a plasma formation chamber 20 to make gas, led into the upper part of a reactor 11 from a gas feed pipe 13, plasma by the chamber 20. The window 19 is composed of the heat resistant plate 19a of a first layer and the heat resistant plate 19b of a second layer, and the plates 19a and 19b consist of a quarts glass plate and an alumina plate respectively. Airtightness is maintained by the plate 19b capable of transmitting a microwave. The microwave generated in a microwave oscillator 16 enters in a dielectric line 12 via a waveguide 15 to pass the window 19 to enter the formation chamber 20. While gas fed from a gas feed pipe 13 is led into the chamber 20 to form plasma by irradiation of the microwave, and a radical in the plasma transmits a partitioning plate 17 to be expanded in a reaction chamber 21 to treat a specimen S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus suitable for etching and resist removing processes.

[0002]

2. Description of the Related Art A reaction gas and a microwave are introduced into a container whose pressure is reduced to near vacuum, a gas discharge is caused to generate plasma, and this plasma is guided to the surface of a substrate to perform etching, resist removal (ashing), etc. Plasma processing apparatuses for performing processing have become indispensable for manufacturing highly integrated semiconductor elements and the like.

FIG. 4 is a sectional view schematically showing a conventional plasma processing apparatus of this type. In the figure, reference numeral 11 denotes a hollow rectangular parallelepiped reactor. The reactor 11 is made of metal such as stainless steel, and its peripheral wall has a double structure, and the inside thereof is a cooling water flow chamber 18.
During the operation of the apparatus, the cooling water flows through the cooling water flow chamber 18 to cool the periphery of the reactor 11. The upper part of the reactor 11 is a plasma generation chamber 20, and the upper part of the plasma generation chamber 20 has microwave permeability and a small dielectric loss.
And heat-resistant quartz glass, Pyrex glass,
It is hermetically sealed by a microwave introduction window 22 formed by using a dielectric plate such as alumina ceramics. A reaction chamber 21 is formed below the plasma generation chamber 20 via a partition plate 17 having a mesh structure, and a sample S is placed in the reaction chamber 21 at a position facing the microwave introduction window 22. A sample table 23 is provided. An exhaust port 14 connected to an exhaust device (not shown) is formed in the lower wall of the reaction chamber 21, and a gas for supplying a required reaction gas into the reactor 11 is provided on one side wall of the plasma generation chamber 20. The supply pipe 13 is connected.

On the other hand, the dielectric line 1 is provided above the reactor 11.
2 is provided, a metal plate 12a formed of aluminum (Al) or the like is provided above the dielectric line 12, and a dielectric layer 12b is fixed to the lower surface of the metal plate 12a with bolts or the like. Has been done. The dielectric layer 12b is made of fluororesin, polyethylene, polystyrene or the like, which has a small dielectric loss. A microwave oscillator 16 is connected to the dielectric line 12 via a waveguide 15,
The microwave from the microwave oscillator 16 is introduced into the dielectric line 12 through the waveguide 15.

When the surface of the sample S mounted on the sample table 23 is subjected to ashing using the plasma processing apparatus having the above-described structure, first, the inside of the reactor 11 is exhausted by exhausting air from the exhaust port 14. After the vacuum degree is set to, the reaction gas is supplied from the gas supply pipe 13 into the plasma generation chamber 20. During operation of the device, the cooling water is supplied to the cooling water flow chamber 18
To cool the periphery of the reactor 11. Then, the microwave oscillator 16 is operated to oscillate the microwave, and this microwave is introduced into the dielectric line 12 via the waveguide 15. Thereby, an electric field is formed below the dielectric line 12, and the formed electric field is introduced into the plasma generation chamber 20 through the microwave introduction window 22. On the other hand, the gas supplied from the gas supply pipe 13 is introduced into the plasma generation chamber 20 and turned into plasma by irradiation with microwaves. Of the plasma, electrically neutral radicals mainly permeate through the mesh-shaped partition plate 17 and spread uniformly in the reaction chamber 21, reach the surface of the sample S mounted on the sample table 23, and are ashed. Is performed.

[0006]

In the plasma processing apparatus described above, quartz glass, Pyrex glass, and alumina, which have microwave permeability, small dielectric loss, and heat resistance, are provided above the plasma generation chamber 20. A microwave introduction window 22 formed by using a dielectric plate such as ceramics (hereinafter referred to as alumina) is formed, and the hermeticity of the reactor 11 is maintained by this, but this microwave introduction window 22 is conventionally used. Was composed of a single heat-resistant plate.

When a single alumina plate is used as the microwave introduction window 22, the alumina plate is heated by the heat inside the reactor to generate thermal stress, and the outside of the reactor 11 is at atmospheric pressure. On the other hand, since the inside of the reactor 11 is under a reduced pressure, there is a problem that the alumina plate is stressed due to the difference in pressure, which may result in damage. Further, when the alumina plate is heated and its temperature rises, it becomes difficult for microwaves to pass therethrough, which causes a problem that, for example, the ashing processing speed is lowered, or the uniformity of the ashing speed on the processing surface is deteriorated.

On the other hand, when a single glass plate such as quartz glass is used as the microwave introduction window 22, the above-mentioned problem is unlikely to occur because the coefficient of thermal expansion is small, but the radiant heat causes the glass plate to move. The dielectric layer 12b that is made of resin and is transmitted therethrough is heated, and the dielectric layer 12b is also heated by heat conduction, so that thermal deformation occurs, and microwaves are attenuated to deteriorate process performance. was there. A similar tendency was observed in the alumina plate with respect to the decrease in process performance due to the increase in heat in the vicinity of the dielectric layer 12b.

The present invention has been made in view of the above problems, and is provided with a microwave introduction window that is excellent in heat insulation performance, is less likely to cause a failure such as damage due to heat, and does not cause a reduction in processing capacity. Thus, it is an object of the present invention to provide a plasma processing apparatus capable of maintaining stable performance.

[0010]

In order to achieve the above object, a plasma processing apparatus according to the present invention comprises a waveguide for transmitting microwaves, a dielectric line connected to the waveguide, and a dielectric line. A reactor having a microwave introduction window hermetically sealed and arranged opposite to the body line, the reactor being separated into a plasma generation chamber and a reaction chamber by a partition plate having a plurality of holes, and the reaction chamber In the plasma processing apparatus provided with a sample table on which the object to be processed is mounted, the microwave introduction window is constituted by a plurality of heat resistant plates.

As a material for forming the microwave introduction window, a material having microwave transparency and a small dielectric loss is preferable, but especially the first layer (layer close to the plasma generation chamber).
The heat-resistant plate (1) is preferably one that is not easily damaged by thermal stress or the pressure of gas from the outside, and the second layer (layer near the dielectric line) is preferably one that blocks heat rays to some extent.

As a specific combination of the plurality of heat resistant plates, when the first layer is a glass plate such as quartz glass and the second layer is an alumina plate, both the first layer and the second layer are alumina plates. In some cases, a combination of two heat-resistant plates may be mentioned, such as a case where both the first layer and the second layer are glass plates such as quartz glass, but in addition, a combination of three or more heat-resistant plates. It doesn't matter. Further, among the above combinations, a combination in which the first layer is a quartz glass plate and the second layer is an alumina plate is preferable.

When the microwave introduction window is composed of two layers of heat resistant plates, the thickness of the alumina plate is 0.5.
Approximately 5 mm is preferable, and the thickness of the quartz glass plate is 12
It is preferably about 20 mm. The plurality of heat-resistant plates may be in close contact with each other, but it is preferable to provide a space between the heat-resistant plates in order to prevent heat conduction.

[0014]

According to the above structure, due to the presence of the microwave introduction window composed of the plurality of heat resistant plates, the radiant heat generated from the plasma is reflected at the interface of the combined heat resistant plates, and the dielectric line is formed. The amount of radiant heat reaching the dielectric layer that constitutes the element is reduced. There is also an air layer between each heat resistant plate, and this layer blocks heat transfer. Therefore, the dielectric layer forming the dielectric line is hard to be heated, and microwave attenuation due to thermal deformation of the dielectric layer is prevented.

Furthermore, since there are a plurality of heat resistant plates constituting the microwave introduction window, it is difficult for external pressure to directly act on the heat resistant plate of the first layer, and the thickness of the heat resistant plate is large. By thinning, the strain due to the thermal stress acting on the heat resistant plate is also reduced. Therefore, breakage of the heat resistant plate forming the microwave introduction window is less likely to occur.

In particular, when the microwave introduction window is formed by a combination of the first layer of quartz glass plate and the second layer of alumina plate, the first layer of quartz glass has a small coefficient of thermal expansion, and therefore, is subject to thermal strain. Damage and the like are less likely to occur, while the temperature of the alumina plate of the second layer is less likely to rise due to the presence of the first layer, so the thermal stress that acts on it becomes less and less likely to damage.
Moreover, it has excellent radiant heat blocking performance. Further, even with the above-described configuration, the microwave introduction window has excellent microwave transmission properties and does not cause deterioration in microwave transmission performance.

Therefore, the plasma processing apparatus according to the present invention is excellent in stability, and in the processing such as etching and ashing, the process performance such as the uniformity of the processing surface and the processing speed becomes stable for a long time. Further, the dielectric layer is less likely to be thermally deformed, so that the life of the dielectric layer is significantly extended.

[0018]

EXAMPLES AND COMPARATIVE EXAMPLES Examples and comparative examples of the plasma processing apparatus according to the present invention will be described below with reference to the drawings. It should be noted that components having the same functions as those of the conventional example are designated by the same reference numerals.

FIG. 1 is a sectional view schematically showing a plasma processing apparatus according to the embodiment, in which 19 denotes a microwave introduction window.

The plasma processing apparatus according to this embodiment is the same as the conventional apparatus except for the microwave introduction window 19, so the description will focus on this microwave introduction window 19 and the other portions. Is omitted.

In the plasma processing apparatus according to the embodiment,
The microwave introduction window 19 is formed in the upper part of the plasma generation chamber 20, and this plasma generation chamber 20 is provided in the upper part of the reactor 11 to turn the gas introduced from the gas supply pipe 13 into plasma. The microwave introduction window 19 is composed of a heat-resistant plate 19a of the first layer and a heat-resistant plate 19b of the second layer. As the heat-resistant plate 19a of the first layer near the plasma generation chamber 20, the length and width are 380 mm. A quartz glass plate with a thickness of 20 mm is used as the second layer heat-resistant plate 19b.
An alumina plate having the same length and width of 380 mm and a thickness of 2 mm is used. In the microwave introduction window 19 having such a configuration, the heat-resistant plate 19a made of quartz glass as the first layer keeps the airtight state, and the heat-resistant plate 19b made of alumina as the second layer capable of transmitting microwaves. Can block heat.

Next, the operation of the thus-configured plasma processing apparatus will be described. The microwave oscillated by the microwave oscillator 16 passes through the waveguide 15 and the dielectric line 1
2 is introduced into the plasma generation chamber 20 through the microwave introduction window 19 composed of the two layers of heat resistant plates 19a and 19b. On the other hand, the gas supplied from the gas supply pipe 13 is introduced into the plasma generation chamber 20 and plasma is formed by irradiation with microwaves.

Of the plasma, a radical mainly passes through the partition plate 17 having a mesh structure and uniformly spreads in the reaction chamber 21 to reach the sample S for processing.

Using the above-described plasma processing apparatus, the ashing process was performed on the resist formed on the sample S using a silicon wafer. Ashing process is O ₂ + N ₂
Is used as a gas species, and the gas flow rate ratio is O ₂ :
N ₂ = 95: 5 is set, and the pressure in the reactor 11 is set to 1
Torr was set at a gas flow rate of 1 slm, and the mixed gas was allowed to flow in the reactor 11. The microwave power at this time was set to 1.5 kW.

As a comparative example, the ashing process was performed under the same conditions using the plasma processing apparatus described in the section "Prior Art".

The results are shown in FIGS. 2 and 3. Figure 2
6 is a graph showing the relationship between the elapsed time and the ashing rate when the plasma processing apparatuses according to Examples and Comparative Examples were continuously operated. As is clear from the results of FIG. 2, in the plasma processing apparatus according to the example, the ashing processing speed equivalent to that of the plasma processing apparatus according to the comparative example was obtained in the initial process, and in the comparative example, the ashing processing speed after 100 minutes elapsed. Is remarkably reduced, while in the example, 1
Even after 70 minutes, the ashing process speed hardly changed, indicating that the ashing process was performed stably.

FIG. 3 is a graph showing the relationship between the elapsed time and the uniformity of the processed surface when the plasma processing apparatus is continuously operated. As is clear from FIG. 3, the uniformity of the treatment showing the variation with respect to the average ashing treatment speed at each point on the treatment surface was lower than 10% at the beginning in the comparative example, and showed excellent uniformity, but 90
In contrast to the fact that after a lapse of about a minute, the temperature rises sharply to indicate that the treatment is uneven, whereas in the embodiment, the uniformity does not deteriorate even after a lapse of about 170 minutes, and the entire surface is maintained for a long time. It can be seen that the ashing treatment is uniformly applied to the.

As described above, in the plasma processing apparatus according to the embodiment, the ashing processing speed and the uniformity of the ashing processing on the processing surface can be kept constant over a long period of time. Further, even if such a treatment is performed for a long time, thermal deformation or the like does not occur in the dielectric layer 12b, and the life of the dielectric layer 12b can be greatly extended.

In the above embodiment, the case where the ashing process is performed has been described, but the same effect can be obtained when the etching process is performed.

[0030]

As described in detail above, in the microwave plasma processing apparatus according to the present invention, a waveguide for transmitting microwaves, a dielectric line connected to the waveguide, and a dielectric line A reactor having a microwave introduction window hermetically sealed and arranged opposite to the body line, the reactor being separated into a plasma generation chamber and a reaction chamber by a partition plate having a plurality of holes, and the reaction chamber In the plasma processing apparatus provided with a sample table on which the processing target is placed, since the microwave introduction window is composed of a plurality of heat resistant plates, the microwave introduction window has durability and heat insulation performance. Will be excellent.

Therefore, in the processing such as etching and ashing, the process performance such as the uniformity of the processing surface and the processing speed can be made stable for a long time. Further, since the dielectric line is not thermally deformed, the life of the dielectric line can be significantly extended.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between an elapsed time and an ashing rate when the plasma processing apparatuses according to the example and the comparative example are continuously operated.

FIG. 3 is a graph showing the relationship between the elapsed time and the uniformity of the processed surface when the plasma processing apparatuses according to the example and the comparative example are continuously operated.

FIG. 4 is a sectional view schematically showing a conventional plasma processing apparatus.

[Explanation of symbols]

 11 Reactor 12 Dielectric line 15 Waveguide 17 Partition plate 19 Microwave introduction window 19a First layer heat resistant plate 19b Second layer heat resistant plate 20 Plasma generation chamber 21 Reaction chamber 23 Sample stage

Claims (1)

[Claims] 1. A reactor having a waveguide for transmitting microwaves, a dielectric line connected to the waveguide, and a microwave introduction window which is arranged to face the dielectric line and is hermetically sealed. In the plasma processing apparatus, wherein the reactor is separated into a plasma generation chamber and a reaction chamber by a partition plate having a plurality of holes, and the reaction chamber is provided with a sample table for mounting an object to be processed, The plasma processing apparatus, wherein the microwave introduction window is composed of a plurality of heat resistant plates.