JPH06260449A - Plasma processor - Google Patents

Abstract

PURPOSE:To provide a plasma processor with a mounting base structure that causes no damage to an electrostatic chuck when the mounting base having the electrostatic chuck is adjusted at a specific cooling temperature. CONSTITUTION:Within the plasma processor wherein an electrostatic chuck 8 holding a work 12 by electrostatic suction is junctioned on an electrostatic block 13, a mounting base 9 provided with a cooling mechanism is arranged in a vacuum vessel to plasma-process the work 12 using plasma produced in the vacuum vessel, the electrode block 13 is composed of a material in the thermal expansion coefficient having a little difference from that of the electrostatic chuck 8. In such a constitution, simultaneously with the acceleration of the thermal conduction by junctioning the electrostatic chuck 8 with the electrode block 13, the stress due to the difference in the thermal expansion coefficient imposed on said junction surface in the low temperature cooling time can be suppressed. Through these procedures, since no damage is caused to the junction surface due to the stress imposition even in the low temperature cooling time, the mounting base 9 can be controlled at specific cooling temperature thereby enabling the plasma processing such as etching step, etc., to be performed with high precision.

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 for irradiating an object to be processed with plasma particles generated by plasma to perform precision processing such as etching, sputtering and CVD.

[0002]

2. Description of the Related Art An electron cyclotron resonance device (hereinafter referred to as an ECR device) can be shown as a typical example of a plasma processing device. As is well known, the ECR device introduces a high-frequency electric field and a processing gas into a vacuum container to which a magnetic field is applied, and performs processing by electron cyclotron resonance caused by three elements of the magnetic field, the high-frequency electric field and electrons in the processing gas atom. By processing the gas into plasma and irradiating the object to be treated with ions and radicals generated at that time, processing such as etching and deposition can be performed. A conventional configuration of an ECR plasma processing apparatus that performs plasma processing on a semiconductor substrate by this ECR apparatus will be described below. A plasma processing apparatus 30 shown as a schematic diagram in FIG. 3 has magnetic coils 10 a and 10 b for applying a magnetic field inside the vacuum container 7 with the vacuum container 7 as a center.
Are arranged concentrically with the central axis of the vacuum container 7, and a microwave introduction window 2 is provided at the upper end on the central axis of the vacuum container 7 to allow microwaves from the microwave power source 5 to pass through the vacuum container 7
The waveguide 6 to be introduced therein is connected. Vacuum container 7
A substrate 12 for etching processing is placed on a mounting table 11 installed inside, and the inside of the vacuum container 7 is evacuated from the exhaust port 4 to be kept in a predetermined vacuum state.
When the processing gas is introduced from the gas introduction port 3 into the vacuum container 7 to which the magnetic field and the high frequency electric field are applied as described above, the processing gas is turned into plasma by electron cyclotron resonance and plasma particles such as ions and radicals are generated. . The plasma particles flow in the direction of the lines of magnetic force and irradiate the substrate 12 mounted on the mounting table 11, so that plasma processing can be performed on the substrate 12. Plasma treatment 30
In the above, since the substrate 12 placed on the placing table 11 is heated by being irradiated with plasma particles, the temperature rises and the plasma processing is adversely affected. Therefore, in order to suppress the temperature rise of the substrate 12, the mounting table 11 is provided with a temperature adjusting means. FIG. 4 shows an enlarged sectional view of the mounting table 11. As shown in the figure, an electrode block 20 to which a high frequency bias voltage for improving the processing speed is applied is provided on the upper surface of the mounting table 11 on which the substrate 12 is mounted, and the electrode block 20 is supplied from the coolant supply path 16. The temperature is adjusted to a constant temperature by refluxing a coolant such as liquid nitrogen. Further, an electrostatic chuck 19 for holding the substrate 12 by electrostatic attraction is arranged on the electrode block 20, and in order to enhance heat conduction between the substrate 12 and the electrostatic chuck 19, a gas introduction path is provided therebetween. Introducing a gas that transfers heat from 15
The temperature is adjusted so that heat is effectively conducted from the substrate 12 to the electrode block 20. These structures are disclosed in JP-B-57-44747 or JP-A-63-30051.
No. 7, etc.

[0003]

However, in the structure of the mounting table 11 having the above-mentioned conventional structure, the coefficient of thermal expansion of the materials forming the electrostatic chuck 19 and the electrode block 20 which are in contact with each other is not taken into consideration. There were the following problems. That is, as shown in FIG. 4, the electrostatic chuck 19 is configured by sandwiching a conductor to which a high voltage is applied from the electrostatic attraction power supply 18 between dielectrics (ceramics). The electrode block 20 is made of aluminum or stainless steel. When the electrode block 20 is cooled with liquid nitrogen, stress is generated on the adhesive surface due to the difference in the coefficient of thermal expansion between the material forming the electrostatic chuck 19 and the material forming the electrode block 20, and The adhesive surface of 1 may be peeled off or the electrostatic chuck 19 may be destroyed. Because of this problem, the cooling temperature of the mounting table 11 is -60 in the conventional configuration.
There was a situation in which the cooling temperature of -100 ° C or lower, which is required for controlling the radical reaction in which the chemical reaction is active, cannot be achieved because the temperature is limited to about ° C. Therefore, as a conventional means adopted to achieve the above-mentioned low temperature control, an object to be processed such as a substrate is clamped by mechanical means without using an electrostatic chuck. However, in this case, there are problems such as contamination of the clamp position and deterioration of the etching state due to the pressing by the mechanical clamp, and the situation is that it cannot be used as a mass production machine. The present invention has been made in view of the above problems, and an object of the present invention is not to damage the electrostatic chuck even when the mounting table equipped with the electrostatic chuck is adjusted to a required cooling temperature. It is to provide a plasma processing apparatus having a mounting table structure.

[0004]

In order to achieve the above-mentioned object, the means adopted by the present invention is such that an electrostatic chuck for holding an object to be processed is bonded onto an electrode block by electrostatic attraction.
A mounting table having a cooling structure for cooling the object to be processed is disposed in the electrode block in a vacuum container, and the mounting table is mounted on the mounting table by plasma generated in the vacuum container. In a plasma processing apparatus for plasma-processing an object to be processed, the electrode block is made of a material having a coefficient of thermal expansion that is small in difference from a coefficient of thermal expansion of a material forming the electrostatic chuck. Configured as a device. As a specific constituent material of the above configuration, when the constituent material of the electrostatic chuck is ceramic, titanium can be used as the constituent material of the electrode block.

[0005]

[Function] Plasma treatment is to physically and chemically treat an object to be treated with ions or radicals, but in order to control a radical reaction in which a chemical reaction is active, the object to be treated is -100 ° C. or less. It is required to cool to the maximum and to control the temperature with high accuracy. To meet this requirement, hold the workpiece with an electrostatic chuck,
It is necessary to cool the mounting table equipped with the electrostatic chuck to −100 ° C. or lower, and to efficiently conduct the temperature of the object to be processed to the mounting table. According to the present invention, the electrostatic chuck is bonded to the electrode block on the mounting table to promote heat conduction, and at the same time, the generation of stress due to the difference in coefficient of thermal expansion generated on the bonding surface during low temperature cooling is suppressed. Adopted. That is, since the electrode block is made of a material having a coefficient of thermal expansion that has a small difference from the coefficient of thermal expansion of the material forming the electrostatic chuck, the electrode block between the electrode block and the electrostatic chuck forming the bonding surface is Generation of stress due to difference in coefficient of thermal expansion is suppressed,
Even when cooled at a low temperature, the fracture of the joint surface due to stress generation does not occur. Therefore, control to the required cooling temperature is achieved, and plasma processing such as etching is performed accurately. As a specific material for forming the bonding surface, when the constituent material of the electrostatic chuck is ceramic, by using titanium as the constituent material of the electrode block, the cooling temperature of the mounting table is cooled to −100 ° C. or less. It becomes possible to do.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. still,
The following example is an example embodying the present invention and does not limit the technical scope of the present invention. Figure 1
FIG. 2 is a cross-sectional configuration diagram showing the configuration of a mounting table in an example ECR etching apparatus that performs dry etching by an ECR apparatus, which is an example of a plasma processing apparatus, and FIG. 2 is a configuration of an example ECR etching apparatus provided with the mounting table shown in FIG. It is a schematic diagram which shows. The same elements as those of the conventional configuration are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 2, the ECR etching apparatus 1 uses the magnetic coils 10a and 10b in the vacuum chamber 7 to perform ECR conditions (875 gauss).
The magnetic field that satisfies the
Microwaves supplied from (2.45 GHz, 0 to 1 kW) are applied from the microwave introduction window 2, the processing gas introduced from the gas introduction port 3 is turned into plasma by electron cyclotron resonance, and ions and radicals generated by the plasma A substrate 1 which is an object to be processed placed on a mounting table 9.
It is configured so that the etching treatment can be performed by irradiating the two. The mounting table 9 in the ECR etching apparatus configured as described above is configured as shown in FIG. The mounting table 9 is configured by disposing the electrode block 13 on the upper end of the support column 17 so as to be insulated from the support column 17 by the insulator 14, and by bonding the electrostatic chuck 8 on the electrode block 13. A high frequency bias voltage from a high frequency power source 21 is applied to the electrode block 13, and liquid nitrogen is circulated from the refrigerant gas supply passage 16 to cool the electrode block 13. Further, the electrostatic chuck 8 has a conductor sandwiched between ceramics, and a high voltage is applied to the conductor from the electrostatic attraction power supply 18, so that a substrate (a substrate to be mounted) mounted on the electrostatic chuck 8 is The processed product 12 is electrostatically adsorbed and held. Further, in order to promote heat conduction from the substrate 12 to be mounted to the electrode block 13, a gas introduction path 15 is provided between the substrate 12 and the electrostatic chuck 8.
A gas for heat transfer is introduced from. The mounting table 9 configured as described above can suppress the heat generation of the substrate 12 through the electrostatic chuck 8 by cooling the electrode block 13 with liquid nitrogen, and control it so that a desired etching reaction is performed. . Titanium is adopted as a constituent material of the electrode block 13 having the above structure. When the electrode block 13 is made of titanium and the joint surface of the electrostatic chuck 8 to be joined thereto is ceramic, the difference in the coefficient of thermal expansion between them is small, so that the coefficient of thermal expansion during low temperature cooling is small. Generation of stress due to the difference is suppressed.

Here, a case where titanium which is a constituent material of the electrode block 13 of the present embodiment is combined with a ceramic which is a constituent material of the electrostatic chuck 8 and a conventional constituent material such as aluminum or stainless steel is combined. The effect of the combination of the ceramic and titanium according to the present embodiment will be demonstrated by comparing with the case. Table 1 shows the amount of strain (for a diameter of 200 mm) caused by the difference in the coefficient of thermal expansion between aluminum, stainless steel (SUS), and titanium, which are combined with ceramics.
This is a comparison in the state of 00 ° C and -200 ° C. Table 2 shows the stress generated between the ceramic and each of the metal materials to be joined at the time of cooling at -100 ° C and at the time of cooling at -200 ° C.

[Table 1]

[Table 2] It can be seen from Tables 1 and 2 that the combination of ceramic and titanium is the best, and that other combinations (conventional structure) cannot generate low temperature cooling due to the generation of large stress. It is understood that -60 ° C is the limit. The combination of ceramic and titanium has a great difference from the other combinations, and cooling at -100 ° C or lower is possible. Therefore, by using titanium as the constituent material of the electrode block 13 in this embodiment and joining it to the ceramic constituting the electrostatic chuck 8, -100 ° C.
The following cooling is possible. As shown in Table 2, -100
The stress generated at a diameter of 200 mm at ℃ is 4.9.
kg / mm ² , whereas the strength of ceramics is 20
Since it is kg / mm ² , it can be used even at -200 ° C. As mentioned above, by enabling low temperature cooling,
Even when the chemical reaction in plasma etching is active, it is possible to obtain a highly accurate etching shape without undercut. Further, since the electrostatic chuck can be used even at low temperature cooling which is impossible with the conventional configuration, the etching performance is improved and the yield of devices formed on the substrate is significantly improved. The following is the execution data of the etching process of the resist formed on the silicon substrate 12 by the ECR etching apparatus 1 having the above configuration. The electrode block 13 is cooled to −100 ° C., oxygen is introduced into the vacuum container 7 as a processing gas,
Etching was carried out at a microwave power of 250 W and a high frequency bias voltage of 200 V applied to the mounting table 9. As a result, the etching rate of the resist was 10,000 Å / min, the selection ratio to SiO _{2 was} 100, the dimensional error of the etching shape to the mask was 0.02 μm, and the uniformity of the etching rate within the surface of the substrate 12 was ± 5% (6 inches). An etching treatment was obtained. The embodiment described above is an example of application of the present invention to an ECR etching apparatus, but the present invention is applicable not only to ECR but also to any plasma processing apparatus, not limited to etching.

[0008]

As described above, according to the present invention, the object to be processed can be cooled to a temperature of −100 ° C. or lower by using the electrostatic chuck for holding the object to be processed on the mounting table. Therefore, it is possible to control the active radical reaction in the plasma treatment, and it is possible to improve the processing shape and the selection ratio and reduce the contamination in the etching treatment, and it is possible to perform uniform plasma treatment on the surface to be treated. As a result, the yield of device formation is greatly improved.

[Brief description of drawings]

FIG. 1 is a sectional configuration diagram showing a configuration of a mounting table adopted in an ECR etching apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an ECR etching apparatus according to an embodiment.

FIG. 3 is a schematic diagram showing a configuration of an ECR etching apparatus according to a conventional example.

FIG. 4 is a cross-sectional configuration diagram showing a configuration of a mounting table according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... ECR etching apparatus (plasma processing apparatus) 2 ... Microwave introduction window 3 ... Gas introduction port 4 ... Exhaust port 5 ... Microwave power supply 6 ... Waveguide 7 ... Vacuum container 8 ... Electrostatic chuck 9 ... Mounting table 10a , 10b ... Magnetic coil 12 ... Substrate (object to be processed) 13 ... Electrode block 16 ... Refrigerant supply path 18 ... Electrostatic attraction power supply

Claims (2)

[Claims] 1. A mounting table comprising an electrostatic chuck for holding an object to be processed by electrostatic attraction, the electrode block being bonded to the electrode block, and the electrode block having a cooling structure for cooling the object to be processed. In the plasma processing apparatus, which is disposed in a vacuum container and plasma-processes an object to be processed placed on the mounting table by plasma generated in the vacuum container, a material in which the electrode block constitutes the electrostatic chuck. A plasma processing apparatus comprising a material having a coefficient of thermal expansion that has a small difference from the coefficient of thermal expansion. 2. The plasma processing apparatus according to claim 1, wherein titanium is used as a constituent material of the electrode block when the constituent material of the electrostatic chuck is ceramic.