JP2956640B2 - Plasma processing equipment - Google Patents

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 microwave plasma apparatus suitable for use in plasma processing such as etching or thin film formation of a semiconductor element substrate used in a manufacturing process of an electronic device or the like. It relates to a processing device.

[0002]

2. Description of the Related Art In a vacuum reactor maintained at a low gas pressure,
By introducing microwaves, a gas discharge occurs,
A plasma processing apparatus that performs processing such as etching and thin film formation by irradiating the obtained plasma with a sample,
It is an indispensable device in the process of manufacturing highly integrated semiconductor elements and liquid crystals. In particular, a plasma processing apparatus that can independently control microwaves related to plasma generation and power for accelerating ions in generated plasma,
It is desired in dry etching technology and thin film formation technology.

FIG. 4 shows an example of the configuration of a conventional plasma processing apparatus, and schematically shows a plasma etching apparatus capable of independently controlling generation of plasma and acceleration of ions in the plasma. FIG. For example, reference (1) (T. Akimoto et al., JJ.
A. P., 33 (1994)), reference (2) (H. Mabuc
hiet al., Proc. 16th Symp. Dry Process,
P235 (1994)).

In FIG. 4, reference numeral 1 denotes a hollow rectangular reaction vessel. The reaction vessel 1 is formed of a metal such as aluminum and stainless steel. The upper part of the reaction vessel 1 has microwave permeability, low dielectric loss and heat resistance, for example, quartz glass or Al ₂ O _3.
Is sealed in an airtight state by a derivative plate 2 formed by using the above method.

[0005] Above the reaction vessel 1, a derivative line 3, which is opposed to the derivative plate 2 at a predetermined distance and is large enough to cover the derivative plate 2, is provided. This derivative line 3
The dielectric layer 3 includes a dielectric layer 3 made of a dielectric material such as a fluororesin having a small dielectric loss, and a metal plate 4 made of aluminum (Al) or the like provided on the upper surface of the dielectric layer 3. A microwave is introduced into the derivative line 3 from a microwave oscillator 5 via a waveguide 6, and the end of the derivative line 3 is sealed with a metal plate 4.

A sample table 8 having a sample holder 7 for holding a sample 20 to be processed is provided inside the reaction vessel 1. The sample holder 7 has a bias on the surface of the sample 20. A high frequency power supply 9 for generating a voltage is connected. Around the sample stage 8, a lower electrode cover A17 formed of a dielectric such as alumina or quartz in a link shape for insulating the side surface of the sample stage 8 from plasma.
Is installed.

Above the lower electrode cover A17, a plate-shaped lower electrode cover B18 made of a 2 mm-thick dielectric is provided above the lower electrode cover A17 in order to prevent plasma from directly touching the upper portion of the lower electrode cover A17. 1m gap
m.

On the lower surface of the dielectric plate 2 facing the sample 20, a microwave dispersion plate 11 made of aluminum, which is connected to the earth 10 via the reaction vessel 1 and is closely mounted, is provided.
A microwave introduction window 14 is formed in the microwave dispersion plate 11 so that microwaves can enter the reaction vessel 1. The microwave dispersing plate 11 made of aluminum makes the electric field intensity of the microwave in the reaction vessel 1 uniform by the size and the position of the microwave introduction window 14 provided on the dispersing plate 11, thereby generating a plasma. It is an indispensable part to achieve uniformity.

An exhaust pipe 12 connected to an exhaust device (not shown) for evacuating the reaction vessel 1 to a vacuum is connected to a lower wall of the reaction vessel 1. A gas supply pipe 13 is connected to supply necessary reaction gas into the reaction vessel 1.

Further, heaters 15 and 16 are installed in the reaction vessel 1 and the upper electrode, respectively, and the reaction vessel 1 and the upper electrode are heated in advance to prevent deposition. A heater power supply 19 for supplying electric power to each of the heaters 15 and 16 is provided.

In the plasma processing apparatus configured as described above, the plasma processing is performed on the surface of the sample 20 as follows.

First, the inside of the reaction vessel 1 is set to a predetermined pressure by exhausting air from the exhaust pipe 12.
The reaction gas is supplied from. Next, a microwave is oscillated in the microwave oscillator 5 and introduced into the dielectric line 3 via the waveguide 6. Then, an electric field is formed below the dielectric line 3 and passes through the microwave introduction window 14 to excite gas in the reaction vessel 1 to generate plasma. At the same time, to control the energy of the ions in the plasma,
A high-frequency power source 9 applies a high-frequency power source to the sample holder 7 on which the sample 20 is mounted, and generates a bias voltage on the surface of the sample 20. The bias voltage causes ions to be perpendicularly incident on the sample 20 and controls the energy of the ions incident on the sample 20.

[0013]

As described above, FIG.
In the conventional plasma processing apparatus shown in (1), in order to suppress the plasma from directly touching the upper portion of the lower electrode cover A17, a 2 mm-thick and 30 cm outer diameter dielectric material is provided above the lower electrode cover A17. Lower electrode cover B1
8 is provided so that the gap with the lower electrode cover A17 is 1 mm. Since the lower electrode cover A17 is made of a derivative and has a very large heat capacity, the temperature rise rate of the upper portion of the lower electrode cover A due to plasma irradiation is slow.

Table 1 shows a state in which the lower electrode cover B18 is removed by using an attachment-type temperature measurement plate.
The dependence of the upper temperature of the lower electrode cover A on the plasma irradiation time is shown.

[0015]

[Table 1]

The deposition generated by the plasma is:
The lower the temperature of the portion to be deposited, the easier the deposition is, for example, 160 ° C.
In the following, a film-like brown deposition is deposited thickly in about 5 minutes of plasma irradiation. On the other hand, as the temperature of the portion to be deposited is higher, the deposition is more difficult to deposit.
At 0 ° C. or higher, no deposition on the portion to be deposited is observed.

Therefore, immediately after the start of plasma irradiation (for example, irradiation time of 5 minutes), the upper part of the lower electrode cover A17 is kept at 45 ° C.
Due to the low temperature, deposition is deposited. However, when the plasma irradiation time is further extended and the temperature on the lower electrode cover A17 increases, the dissociation of the deposition deposited at a low temperature and the lower electrode cover A17 may occur.
Due to the difference in thermal expansion coefficient between the deposition and the deposition, the deposition deposited on the lower electrode cover A comes off and causes dust.

Therefore, in the conventional plasma processing apparatus shown in FIG. 4, a plate-like lower electrode cover B18 having a thickness of 2 mm is provided above the lower electrode cover A17 so that the distance from the lower electrode cover A17 is 1 mm. So that the upper part of the lower electrode cover A17 does not directly contact the plasma.

The lower electrode cover B18 has a thickness of 2 m.
m, and the heat capacity is reduced because the lower electrode cover A17 is installed at a distance of 1 mm from the lower electrode cover A17 having a large heat capacity.

Table 2 shows the results of measurement of the plasma temperature irradiation time dependence on the upper part of the lower electrode cover B18 in a state where the lower electrode cover B18 is installed above the lower electrode cover A17 using the attached temperature measuring plate.

[0021]

[Table 2]

The upper temperature of the lower electrode cover B reaches 170 ° C. in a short time after the plasma irradiation, for example, 5 minutes after the plasma irradiation, at which deposition hardly occurs. That is, the deposition is hardly deposited on the lower electrode cover B18 in any state during the plasma processing, so that the dust generated by the deposition can be suppressed.

However, in this conventional plasma processing apparatus, the lower electrode cover B18 and the lower electrode cover A17
It is found that since the gap between them is about 1 mm, the plasma wraps around the gap and deposits on the back surface of the lower electrode cover B18, and the deposition peels off and becomes dust.

FIG. 3 shows the result of investigation of the dependence of dust having a diameter of 0.2 μm or more on the number of processed wafers. In FIG. 3, the horizontal axis indicates the number of processed wafers, and the vertical axis indicates the number of dusts.
The measurement results are indicated by open triangles. As shown in FIG.
In the running of 00 wafers, the number often exceeded the allowable range of 50 wafers and was about 120 at the maximum. Furthermore, the dust was analyzed using an X-ray photoelectron spectrometer (ESCA), and as a result, it was found that the main component was fluorocarbon, which is a constituent molecule of deposition. No fluorocarbon-based deposition was observed in the reaction vessel 1 except for the back surface of the lower electrode cover B18.

The lower electrode cover B in a state where the lower electrode cover B18 is installed above the lower electrode cover A17.
The backside temperature of 18 was found to be 140 ° C. even with a plasma irradiation time of 40 minutes by a sticking-type temperature measurement plate.
It was proved that the deposition was deposited on the back surface.

Accordingly, the present invention has been made in view of such a problem, and has as its object to reduce the shape of the plate-like lower electrode cover B used in the above-described conventional plasma processing apparatus. Another object of the present invention is to provide a plasma processing apparatus that eliminates the plasma wraparound between the lower electrode cover B and the lower electrode cover A, thereby suppressing dust.

[0027]

To achieve the above object, the present invention provides a microwave oscillator, a waveguide for transmitting microwaves, and a dielectric line connected to the waveguide. a reaction vessel having a microwave introduction window, before
Serial and reaction sample holder provided for mounting a sample substrate to be processed in the container, means for applying a high frequency electric field or a DC electric field to the sample holder, microwaves disposed on the sample and the counter In a plasma processing apparatus provided with a window through which a microwave can be passed and provided with a microwave dispersion plate effective for controlling plasma uniformity , a first and a second dielectric material disposed around the sample holding unit and formed of a dielectric material Lower electrode cover
Comprises a two-division type bottom electrode cover that, with the first lower electrode cover, before being placed above the first lower electrode cover
Serial overlap the second lower electrode cover and each outer peripheral portion, between the first and second lower electrode cover, and having a structure such that the plasma does not wrap around.

[0028]

Embodiments of the present invention will be described below. According to a preferred embodiment of the present invention, a microwave oscillator (105 in FIG. 1), a waveguide for transmitting microwaves (106 in FIG. 1), and a dielectric line connected to the waveguide are opposed to each other. Reaction vessel (101 in FIG. 1) having a microwave introduction window to be processed, and a sample holding section (107 in FIG. 1) provided for placing a sample substrate (120 in FIG. 1) to be processed in the reaction vessel. ) And means for applying a high-frequency electric field or a DC electric field to the sample holder (109 in FIG. 1).
Etc.), and a window (114 in FIG. 1) through which microwaves are placed facing the sample are provided, and a microwave dispersion plate (111 in FIG. 1) effective for controlling plasma uniformity is provided. The lower electrode cover divided into two parts, that is, the first lower electrode cover A and the second lower electrode cover B are provided with a side wall at the outer peripheral end of the second lower electrode cover B, and the first lower electrode cover A The part is covered with the second lower electrode cover B.

In a preferred embodiment of the present invention, the first lower electrode cover A has a shoulder on the outer periphery thereof facing the open end of the side wall of the second lower electrode cover B,
A portion above the shoulder of the lower electrode cover A is housed in the side wall of the second lower electrode cover B.

In a preferred embodiment of the present invention, the second lower electrode cover B has a side wall at the outer peripheral end, and the open end of the side wall surrounds the outer periphery of the first lower electrode cover A. The first lower electrode cover A is entirely covered with the second lower electrode cover B.

As described above, in the embodiment of the present invention, the plasma does not enter the gap between the lower electrode cover A and the lower electrode cover B.
Deposition generated by plasma irradiation does not accumulate on the back surface, and as a result, dust caused by the deposition accumulated on the back surface of the lower electrode cover B can be suppressed.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. Hereinafter, an etching apparatus using a fluorine gas will be described as an example.

[Embodiment 1] FIG. 1 is a diagram showing a configuration of an embodiment of the present invention. In FIG. 1, reference numeral 101 denotes a hollow rectangular parallelepiped reaction vessel. The reaction vessel 101 is formed of a metal such as aluminum and stainless steel. The upper part of the reaction vessel 101 is microwave-permeable, has a low dielectric loss and has heat resistance, and is hermetically sealed by a dielectric plate 102 formed of, for example, quartz glass or Al ₂ O _3. Has been stopped.

Above the reaction vessel 101, the derivative plate 10
2 and a dielectric line 103 large enough to cover the dielectric plate 102 is mounted. The dielectric line 103 is composed of a dielectric layer 103 and a dielectric layer 10 made of a dielectric material such as fluororesin having a small dielectric loss.
3 and a metal plate 104 made of Al or the like placed on the upper surface of the third metal plate 3.

The microwave oscillator 1 is connected to the derivative line 103.
Microwaves are introduced through the waveguide 106 from the line 05, and the end of the dielectric line 103 is connected to the metal plate 1
04.

A sample stage 108 having a sample holder 107 for holding a sample 120 to be processed is provided inside the reaction vessel 101.
Is connected to a high-frequency power supply 109 for generating a bias voltage on the surface of the sample 120.

In addition, around the sample stage 108, the sample stage 1
A lower electrode cover A117 formed by molding a derivative of, for example, alumina or quartz into a ring shape is provided to insulate the side surface 08 from plasma.

Above the lower electrode cover A117, a tray-shaped lower electrode cover B118 made of a dielectric material is provided, and the ends of the lower electrode cover A117 and the lower electrode cover B11 are overlapped.
8 has a structure in which plasma is prevented from entering the gap.

A processing example of the plasma processing apparatus of the present embodiment configured as described above will be described below.

First, the interior of the reaction vessel 101 is set to a predetermined pressure by exhausting air from the exhaust pipe 112, and thereafter, a reaction gas is supplied from the gas supply pipe 113.

Next, a microwave is oscillated in the microwave oscillator 105 and introduced into the dielectric line 103 via the waveguide 106. Then, an electric field is formed below the derivative line 103, and the formed electric field passes through the microwave introduction window of the grounded microwave dispersion plate 111, further passes through the derivative plate 102, and generates plasma in the reaction vessel 101. At the same time, in order to control the ion energy in the plasma, the sample 120
A high frequency power supply is applied to the sample holding unit 107 on which is mounted, and a bias voltage is generated on the surface of the sample 120. With this bias voltage, ions are vertically incident on the sample 120, and processing on the wafer to be etched is performed while controlling the energy of the ions incident on the sample 120.

FIG. 3 shows the results obtained by examining the dependence of dust having a diameter of 0.2 μm or more on the number of processed wafers in the plasma processing apparatus of this embodiment. As can be seen from FIG. 3, in the plasma processing apparatus according to the present embodiment, dust is less than 10 during processing of 100 wafers, which is a significant improvement as compared with the conventional plasma processing apparatus shown in FIG. It was observed.

[Embodiment 2] FIG. 2 is a diagram showing a configuration of a second embodiment of the present invention. Referring to FIG. 2, the configuration of the plasma processing apparatus of the present embodiment except for the lower electrode cover B and the wafer processing method are the same as those of the first embodiment.

In this embodiment, the lower electrode cover B218
Has a structure that covers the entire lower electrode, and suppresses the plasma from wrapping around the lower electrode cover B back 218 surface.

Table 3 shows that, with the plasma processing apparatus of this embodiment, the lower electrode cover B218 was set on the lower electrode and the upper and side walls of the lower electrode cover B218 were attached to each other using a temperature measuring plate. The results are shown.

[0046]

[Table 3]

From Table 3, it can be seen that the deposition hardly deposits on the lower electrode cover B218.

Next, the results of actual dust measurement performed by the plasma processing apparatus of this embodiment will be described.

CF ₄ / CH ₂ F ₂ = 40/40 sccm,
100 dummy wafers are processed under the conditions of μ / RF = 1300/600 W and plasma irradiation time of 2 minutes, and immediately after that, plasma is generated while the dummy wafers are blown with gas under the condition of CF ₄ / CH ₂ F ₂ = 40/40 sccm. It was transported inside the chamber without doing so.

As a result, about 8 dust particles having a diameter of 0.2 μm or more were observed on a 6-inch wafer. Further, the dust was analyzed using an X-ray photoelectron spectrometer (ESCA), and as a result, it was found that the main component was fluorocarbon, which is a constituent molecule of deposition.

From the above results, it was found that this embodiment has a great effect in reducing dust.

[0052]

As described above, according to the present invention,
Dust can be significantly reduced, and as a result, the effect of significantly improving the reliability and productivity of device manufacturing is achieved. The reason is as follows.

That is, the generation of dust causes a reduction in yield in device manufacturing. In the conventional plasma processing apparatus shown in FIG. 4, there is a gap of 1 mm between the lower electrode cover B18 and the lower electrode cover A17, and the plasma wraps around the gap and deposits on the back surface of the lower electrode cover B18 to deposit. According to the present invention, the shape of the lower electrode cover B is changed and the lower electrode cover B is formed into a tray shape, thereby causing a problem that dust is generated due to the separation of the deposition. Eliminates plasma wraparound between the electrode covers B, suppresses deposition on the back surface of the lower electrode cover B,
Thus, it is possible to suppress dust caused by deposition deposited on the back surface of the lower electrode cover B.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a cross section of a plasma processing apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram schematically showing a cross section of a plasma processing apparatus according to another embodiment of the present invention.

FIG. 3 is a diagram showing a comparison between the embodiment of the present invention and the number of processed dust in the conventional plasma processing apparatus.

FIG. 4 is a diagram schematically showing a cross section of a conventional plasma processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction container 2 Derivative plate 3 Derivative line 4 Metal plate 5 Microwave power supply 6 Microwave waveguide 7 Sample holder 8 Sample table 9 High frequency power supply 10 Ground 11 Microwave dispersion plate 12 Exhaust pipe 13 Gas supply pipe 14 Microwave introduction window DESCRIPTION OF SYMBOLS 15 Heater 16 Heater 17 Lower electrode cover A 18 Lower electrode cover B 19 Heater power supply 20 Sample 101 Reaction vessel 102 Derivative plate 103 Derivative line 104 Metal plate 105 Microwave power supply 106 Microwave waveguide 107 Sample holder 108 Sample table 109 High frequency power supply Reference Signs List 110 ground 111 microwave dispersion plate 112 exhaust pipe 113 gas supply pipe 114 microwave introduction window 115 heater 116 heater 117 lower electrode cover A 118 tray-shaped lower electrode cover B 119 heater power supply 120 sample 201 reaction vessel 202 Derivative plate 203 Derivative line 204 Metal plate 205 Microwave power source 206 Microwave waveguide 207 Sample holder 208 Sample table 209 High frequency power source 210 Ground 211 Microwave dispersion plate 212 Exhaust pipe 213 Gas supply pipe 214 Microwave introduction window 215 Heater 216 Heater 217 Lower electrode cover A 218 Tray type lower electrode cover B 219 Heater power supply 220 Sample

Claims (4)

(57) [Claims] And 1. A microwave oscillator, a waveguide for transmitting the microwave, a reaction vessel having a microwave introducing window disposed opposite to the connected derivative line to the waveguide, into the reaction vessel a sample holder provided for mounting a sample substrate to be processed, means for applying a high frequency electric field or a DC electric field, a window microwaves disposed in the sample and the counter can pass provided in the sample holder It is, in the plasma processing apparatus having a valid microwave dispersion plate uniformity control of the plasma, is disposed around the sample holder it is formed of a dielectric
First, a second 2 division type bottom electrode cover made of a lower electrode cover, and the first lower electrode cover, the first that
And said second bottom electrode cover disposed above the lower electrode cover overlap each outer peripheral portion, between the first and second lower electrode cover, and characterized by having a structure such that the plasma does not wrap Plasma processing equipment. 2. The second lower electrode cover disposed above the first lower electrode cover has a side wall at an outer peripheral end thereof, and a part or the whole of the first lower electrode cover is formed in the second lower electrode cover.
The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is covered with a lower electrode cover. 3. A second lower electrode cover disposed above the first lower electrode cover has a side wall provided along an outer peripheral end, and the first lower electrode cover is provided with the second lower electrode cover. A shoulder portion facing the open end of the side wall portion is provided on an outer periphery, and a portion of the first lower electrode cover above the shoulder portion is accommodated in the side wall portion of the second lower electrode cover. The plasma processing apparatus according to claim 1, wherein 4. The second lower electrode cover disposed above the first lower electrode cover has a side wall at an outer peripheral end thereof, and an open end side of the side wall is an outer peripheral side of the first lower electrode cover. 2. The plasma processing apparatus according to claim 1, wherein the first lower electrode cover is entirely covered with the second lower electrode cover. 3.