JPH0936092A - Microwave plasma treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly, easily, and positively prevent a charge-up damage from occurring without decreasing an ashing speed by providing means for supporting the reverse side of a material so that it does not directly contact a grounded sample stand on the sample stand in a microwave plasma treating device. SOLUTION: A sample stand 14 with conductivity is provided in a reaction room 43 and a grounding pin 14a is connected to the sample stand 14. Also, a plurality of supporting means 19 with nearly pin shape are provided on the sample stand 14 and a sample S is placed at the supporting means 19. In this manner, in a microwave plasma treating device 10, the sample stand 14 connected to a ground 14a is placed at the reverse side of the sample S, namely at the downstream side of a reaction gas, thus attracting a charged particle to the side of the sample stand 14 with a high conductance when the charged particle exists around the sample S and supporting the sample S by the supporting means 19 away from the sample stand 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave plasma processing apparatus, and more particularly, it utilizes plasma generated by introducing microwaves to perform etching processing, ashing processing, etc. on a semiconductor element substrate or the like. The present invention relates to a microwave plasma processing device used as an applying device.

[0002]

2. Description of the Related Art In the manufacturing process of LSI, various processes are often performed by using plasma generated when energy is externally applied to a reaction gas. In particular, dry etching technology using plasma is
It has become an indispensable technology in the SI manufacturing process.

Generally, the excitation means for generating plasma uses microwaves and RF (Radio Frequency).
cy) in some cases. When using microwave,
Compared to the case of using RF, there are advantages that plasma can be obtained at a lower temperature and a higher density, contamination by electrodes is less, and the device configuration and its operation are simple. However, in the conventional plasma processing apparatus using microwaves,
The area of the plasma generation region is small, and it is difficult to uniformly generate plasma in this plasma generation region, and thus it is difficult to uniformly process a large-diameter semiconductor substrate.

A device using a dielectric line is known as a device capable of uniformly generating microwave plasma with a large area of plasma generation region.
(JP-A-65-2600 and JP-A-6-2755)
No. 66). FIG. 4 is a sectional view schematically showing a conventional microwave plasma processing apparatus of this type using a dielectric line, and reference numeral 41 in the drawing denotes a reactor. The reactor 41 is formed using a metal such as stainless steel, the peripheral wall 41a of the reactor 41 has a double structure, a cooling water passage 41b is formed therein, and a cooling water passage 41b is formed inside. Has a plasma generation chamber 42 and a reaction chamber 43 having a horizontal cross-sectional shape of about 290 × 290 mm. The plasma generation chamber 42 and the reaction chamber 43 are partitioned by a conductive partition plate 45 having a plurality of holes 45a.
A gas supply pipe 42b for supplying a required reaction gas into the reactor 41 is connected to one side wall of the reactor 2. The upper part of the plasma generation chamber 42 is hermetically sealed by a microwave introduction window 42a, and the microwave introduction window 42a is transparent to microwaves, has a small dielectric loss, and is heat resistant quartz glass, It is formed by using a dielectric plate such as alumina. A sample stand 44 for mounting the sample S is arranged in the reaction chamber 43, and an exhaust port 43a connected to an exhaust device (not shown) is formed in the lower wall of the reaction chamber 43. There is.

On the other hand, the dielectric line 4 is provided above the reactor 41.
6 is provided, a frame 46a formed by using a metal plate such as aluminum is provided on the upper and side portions of the dielectric line 46, and a fluorine with small dielectric loss is provided on the lower surface of the frame 46a. A dielectric layer 46b made of resin, polyethylene, polystyrene or the like is provided. A microwave oscillator 48 is connected to the dielectric line 46 via a waveguide 47.
The microwave from 8 is transmitted through the waveguide 47 to the dielectric line 4
It will be introduced in 6. These reactors 41,
Microwave introduction window 42a, sample stage 44, dielectric line 4
The microwave plasma processing apparatus 40 is configured to include 6, the waveguide 47, the microwave oscillator 48, and the like.

When the microwave plasma processing apparatus 40 configured as described above is used to perform ashing processing on the surface of the sample (wafer) S placed on the sample stage 44, first, exhaust is performed from the exhaust port 43a. After setting the plasma generation chamber 42 and the reaction chamber 43 to a required degree of vacuum, the reaction gas is supplied from the gas supply pipe 42b. In addition, the cooling water is circulated in the cooling water passage 41b, and the plasma generation chamber 42 and the reaction chamber 4 are
Maintain 3 at the desired temperature. Next microwave oscillator 4
8 oscillates a microwave and introduces the microwave into the dielectric line 46 via the waveguide 47, an electric field is formed below the dielectric line 46, and the formed electric field passes through the microwave introduction window 42a. It is transmitted and supplied to the plasma generation chamber 42, and plasma is generated. Then, neutral particles such as radicals in the generated plasma are mainly holes 45a.
And the neutral particles ash the resist on the sample S in the reaction chamber 43.

[0007]

In recent years, high quality and low cost have been demanded for LSIs. With regard to the resist ashing technique, not only the processing speed is improved but also charge-up damage caused by plasma is prevented. Prevention is required. When charge-up damage occurs, MOSFET (Metal Oxide Semiconduc
(Tor Field Effect Transistor) or the insulation film of the MOS capacitor insulation breakdown may occur, and the LSI may not operate normally.

The above microwave plasma processing apparatus 40
In the above, when the material of the microwave introducing window 42a is alumina, the occurrence of charge-up damage is suppressed, while in the case of quartz, this may occur. Therefore, the material of the microwave introducing window 42a causes charge-up damage. There is a problem that is easily affected.

Further, by controlling parameters such as the size of the hole 45a of the partition plate 45 and the plasma generation chamber 42, it is possible to prevent charge-up damage. It is troublesome to change each time, and as a result, there is a problem that it is difficult to reliably prevent charge-up damage from occurring at all times.

The present invention has been made in view of the above problems, and provides a microwave plasma processing apparatus capable of always and easily and reliably preventing the occurrence of charge-up damage without lowering the ashing speed. The purpose is to do.

[0011]

In order to achieve the above object, a microwave plasma processing apparatus according to the present invention comprises a microwave oscillator, a waveguide for transmitting microwaves, and a waveguide connected to the microwave oscillator. In a microwave plasma processing apparatus provided with a dielectric line, a reactor having a microwave introduction window arranged opposite to the dielectric line, and a sample stage, the back surface of the sample does not directly contact the grounded sample stage. It is characterized in that a supporting means for supporting in a state is arranged on the sample table.

The above-mentioned charge-up damage is generated when the sample is mainly irradiated with charged particles (ions) in microwave plasma. According to the microwave plasma processing apparatus having the above-described configuration, since the grounded sample stage is arranged on the back surface side of the sample, that is, on the downstream side of the reaction gas, even if charged particles exist around the sample. Even when the charged particles are attracted to the sample stage side having high conductance,
Since the sample is supported by the supporting means apart from the sample table, the charged particles are prevented from being irradiated and accumulated on the sample. As a result, charge-up damage can be always and easily prevented from occurring in the sample, and the ashing reaction is rate-controlled by the neutral particles (radicals) in the plasma. Therefore, the ashing process can be surely performed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a microwave plasma processing apparatus according to the present invention will be described below with reference to the drawings. Note that components having the same functions as those of the conventional example are denoted by the same reference numerals. FIG. 1 is a sectional view schematically showing a microwave plasma processing apparatus according to an embodiment, and 43 in the drawing shows a reaction chamber similar to that shown in FIG. A sample table 14 having conductivity is arranged in the reaction chamber 43, and the sample table 14 is connected to a ground 14a. A plurality of substantially pin-shaped supporting means 19 are arranged on the sample table 14, and the sample S is placed on the supporting means 19. Other configurations are the same as those shown in FIG. 4, and therefore detailed description thereof will be omitted here. The microwave plasma processing apparatus 10 is configured to include the sample stage 14, the ground 14a, the supporting means 19, the reactor 41, the microwave introduction window 42a, the dielectric line 46, the waveguide 47, the microwave oscillator 48, and the like. There is.

When the microwave plasma processing apparatus 10 having the above-mentioned structure is used to perform the ashing process on the surface of the sample S placed on the supporting means 19, first, the exhaust port 43a.
Then, the plasma generation chamber 42 and the reaction chamber 43 are set to a required degree of vacuum, and then the reaction gas is supplied from the gas supply pipe 42b. Further, the cooling water is circulated through the cooling water passage 41b to maintain the plasma generation chamber 42 and the reaction chamber 43 at a predetermined temperature. Next, when a microwave is oscillated in the microwave oscillator 48 and this microwave is introduced into the dielectric line 46 through the waveguide 47, an electric field is formed below the dielectric line 46, and the formed electric field is the microwave. The plasma is generated by passing through the introduction window 42a and being supplied to the plasma generation chamber 42. Then, mainly neutral particles such as radicals in the generated plasma pass through the holes 45a, and the neutral particles ash the resist on the sample S placed on the supporting means 19. On the other hand, some of the charged particles that have passed through the holes 45a flow toward the sample table 14 side without being irradiated onto the sample S.

[0015]

EXAMPLES AND COMPARATIVE EXAMPLES Below, the results of evaluating the charge-up damage by subjecting the sample S to ashing treatment using the microwave plasma processing apparatus 10 according to the embodiment and measuring the flat band voltage shift amount are shown. explain.

The charge-up damage evaluation method based on the flat band voltage shift amount is generally used, and the charge up amount due to charged particles or the like is monitored as the flat band voltage shift amount during the processing step during device fabrication. Is the way to do it. As the device 10,
The horizontal sectional shape of the reaction chamber 43 and the plasma generation chamber 42 is about 290 × 290 mm, and the number of supporting means 19 is four.
Aluminum is used as the material of the supporting means 19, and the distance L ₁ between the lower surface of the microwave introduction window 42a and the partition plate 45 is set to about 7.
mm, the distance between the partition plate 45 and the sample S was set to about 46 mm, and the distance between the sample S and the sample table 14 was set to about 10 mm. The ashing process conditions are shown in Table 1 below.

[0017]

[Table 1]

FIG. 2 shows the MNO as the sample S used in the experiment.
FIG. 2 is a sectional view schematically showing an S (Metal Nitride Oxide Semiconductor) capacitor, in which 21 is a diameter of about 1
A 50 mm p-type Si substrate is shown. p-type Si substrate 2
1 has a thickness t ₁ of about 2.5 nm on the surface of the SiO ₂ film 22.
Is formed, and the thickness t ₂ is about 40 n on the SiO ₂ film 22.
m of the Si ₃ N ₄ film 23 is formed, and PolySi having a thickness t ₃ of about 400 nm is formed at a predetermined position on the Si ₃ N ₄ film 23.
The film 24 is formed. These p-type Si substrate 21, S
iO ₂ film 22, Si ₃ N ₄ film 23 and PolySi film 2
4 constitutes an MNOS capacitor as an experimental sample S.

As a comparative example, the case where the sample S was directly placed on the sample table 44 as shown in FIG. 4 was selected. In this case, the distance L ₂ between the sample S and the partition plate 45 is about 56 mm.
Set to.

FIG. 3 shows a case where the apparatus of the embodiment and the comparative example is used for M
FIG. 9 is a plot diagram showing the result of continuously measuring the amount of each flat band voltage shift in the diameter X direction by subjecting the NOS capacitor to ashing treatment, and in the figure, the symbol □ indicates that the material of the microwave introduction window 42a is quartz. In the case of, the circle indicates the case of alumina, the black square indicates the comparative example when the material of the microwave introducing window 42a is quartz, and the triangle indicates the comparative example of alumina. There is.

As is apparent from FIG. 3, in the case of the device 40 according to the comparative example, the flat band voltage shift occurs when the material of the microwave introduction window 42a is quartz, whereas the device according to the example. In the case of No. 10, flat band voltage shift did not occur regardless of the material of the microwave introduction window 42a. Further, the distance L ₂ between the partition plate 45 and the sample S is different between the comparative example and the example, but the example is easier to charge up,
The difference in the flat band voltage shift shown in FIG. 3 is not due to the difference in this parameter.

It has been confirmed that even when the ashing process conditions shown in Table 1 are changed, substantially the same results as those shown in FIG. 3 are obtained.

Further, the distance L ₃ between the sample S and the sample table 14 is not limited to 10 mm at all, and if the distance is as small as possible, substantially the same result as that shown in FIG. 3 can be obtained. It has been confirmed.

As is clear from the above results, in the microwave plasma processing apparatus 10 according to the embodiment, the ground 14a is used.
Since the sample stage 14 connected to the sample S is arranged on the back surface side of the sample S, that is, on the downstream side of the reaction gas, even if charged particles exist around the sample S, the charged particles have high conductance. The sample S is attracted to the sample stage 14 side and is supported by the support means 19 apart from the sample stage 14, so that the charged particles are prevented from being irradiated and accumulated on the sample S. As a result, the occurrence of charge-up damage in the sample S can be always and easily prevented, while the ashing reaction is limited by the neutral particles in the plasma, so that the ashing speed is not reduced. The ashing process can be reliably performed on the.

In the above embodiment, the case where a conductive material is used as the material of the supporting means 19 has been described.
In other embodiments, non-conductive materials may be used.

In the above embodiment, the case where the supporting means 19 is fixedly arranged on the sample table 14 has been described, but in order to prevent interference with the conveying means (not shown) for the sample S, The support means may be arranged so as to be movable in the vertical direction.

In the above embodiment, the case where the conductive sample stage 14 is connected to the ground 14a has been described, but in another embodiment, the conductive reactor 41 is used.
The bottom of the may be connected to the ground 14a.

[0028]

As described in detail above, in the microwave plasma processing apparatus according to the present invention, since the grounded sample stage is arranged on the back surface side of the sample, that is, on the downstream side of the reaction gas, Even if charged particles are present around the sample, the charged particles are attracted to the side of the sample table having a high conductance, and the sample is supported by the support means away from the sample table. The irradiation and accumulation of the charged particles on the sample is prevented. As a result, the occurrence of charge-up damage in the sample can be constantly and easily prevented, and the ashing reaction is rate-controlled by the neutral particles in the plasma. The ashing process can be reliably performed.

[Brief description of drawings]

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

FIG. 2 is a sectional view schematically showing a MNOS capacitor as a sample S used in an experiment.

FIG. 3 is a plot diagram showing the results of measuring the amount of each flat band voltage shift in the diameter X direction by subjecting an MNOS capacitor to an ashing process using the devices of Examples and Comparative Examples. The mark shows an example when the material of the microwave introduction window is quartz, the ○ mark shows an example when it is alumina, the black □ mark shows a comparative example when the material of the microwave introduction window is quartz, and the Δ mark shows alumina. Comparative examples in the case of are respectively shown.

FIG. 4 is a sectional view schematically showing a conventional microwave plasma processing apparatus using a dielectric line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Microwave plasma processing apparatus 14 Sample stage 14a Earth 19 Supporting means 41 Reactor 42a Microwave introduction window 44 Sample stage 46 Dielectric line 47 Waveguide 48 Microwave oscillator

Claims (1)

[Claims] 1. A reactor having a microwave oscillator, a waveguide for transmitting microwaves, a dielectric line connected to the waveguide, and a microwave introduction window arranged to face the dielectric line. In the microwave plasma processing apparatus including the sample table, a supporting means for supporting the back surface of the sample without directly contacting the grounded sample table is provided on the sample table. Wave plasma processing equipment.