JPH1197197A - Plasma treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a plasma having high uniformity over a wide area and heighten the intra-plane uniformity in the plasma treatment. SOLUTION: Microwaves of 2.45 GHz are in TM mode introduced through a waveguide tube 3 into the first vacuum chamber 21, and a magnetic field of 875 Gauss is formed so that a film formation gas is turned in a plasma by means of electron cyclotron resonance, and a SiOF film is formed on a wafer. Therein the condition 0.75<=D2/D1<=0.85 should be met, where D1 is inside diameter of the first vacuum chamber 21 while D2 is the inside diameter of the microwave inlet part of the vacuum chamber 21. According to this configuration, the transmission of microwaves is disturbed in the part where the inside diameter of the first vacuum chamber 21 enlarges steeply to cause generation of the higher-order mode of the TM mode, and thereby the electric field distribution becomes uniform in the plane opposing to the wafer W, and the plasma density becomes uniform within the plane, so that the intra-plane uniformity of plasma treatment is heightened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ECR (Electron) for a substrate to be processed such as a semiconductor wafer.
The present invention relates to a plasma processing apparatus that forms a thin film such as an SiOF film or a SiO ₂ film by a plasma process such as a cyclotron resonance process.

[0002]

2. Description of the Related Art Aluminum wiring is mainly used as a wiring pattern of an integrated circuit, and an SiOF film or a SiO ₂ film is used as an interlayer insulating film for insulating the aluminum wiring. As a method, ECR plasma processing for generating high-density plasma by combining a microwave and a magnetic field tends to be adopted because of good film quality.

FIG. 9 shows a conventional plasma processing apparatus for performing this ECR plasma processing. For example, in this apparatus, for example, 2.45 GHz is installed in a plasma generation chamber 1A.
Is supplied through the transmission window 12 by the waveguide 11 and a magnetic field of, for example, 875 gauss is applied by a combination of the main electromagnetic coil 13 and the auxiliary electromagnetic coil 14, and the interaction between the microwave and the magnetic field is performed. (Electron Cyclotron Resonance) Plasma gas such as Ar gas or O ₂ gas is converted into high-density plasma, and this plasma is used to form the
For example, a film forming gas such as a SiH ₄ gas or a SiF ₄ gas introduced into the inside is activated to form ionic species, and
A thin film is formed on a semiconductor wafer (hereinafter, referred to as “wafer”) W placed on the semiconductor wafer 5.

The waveguide 11 comprises a rectangular waveguide 11a,
The microwave generated by the microwave generator 16 and transmitted in the TE ₁₀ mode in the rectangular waveguide 11a is constituted by combining the conical waveguide 11b gradually expanding toward the lower side. conical waveguide 11b in TE ₁₁ mode - is converted to de, as it is conical waveguide 11b TE ₁₁ mode - are introduced into and transmitted by de plasma generating chamber 1A.

Here, the TE ₁₁ mode will be described with reference to FIG. FIG. 10A is a sectional view in the diameter direction of a cylindrical waveguide having an inner diameter of 2a, for example, and FIG.
FIG. 3A is a cross-sectional view taken along the line AA in FIG. 3A. In this mode, the electric field indicated by a solid line in the figure exists in the diameter direction of the waveguide. The chain line in the figure indicates the magnetic field, and FIG.
The middle circle indicates the state where the electric field goes to the inside of the paper, and the solid circle indicates the state where the electric field goes to the outside of the paper.

[0006]

In [0005] However the above-described plasma processing apparatus, the microwave is TE ₁₁ mode - because they are introduced into the plasma generating chamber 1A by de density of the cross-section of the electric line of force of the wafer upward, It is high at the center and becomes smaller as it approaches the periphery, resulting in an uneven electric field distribution. Here, since the density of the plasma generated in the plasma generation chamber 1A is substantially proportional to the electric field distribution, the film thickness of the thin film formed by the plasma processing becomes thinner at the periphery corresponding to the electric field distribution, and the film thickness is high. It has become difficult to ensure in-plane uniformity.

On the other hand, US Pat. No. 5,234,526 discloses TM
A plasma processing apparatus utilizing the ₀₁ mode is disclosed. This device, TE ₁₀ mode - the end for example inside diameter of the rectangular waveguide to transmit de connects to the cylindrical waveguide 109 mm, microwave TM ₀₁ mode - introduced into the plasma generation chamber in de It is configured as follows.

Here, the TM01 _mode will be described with reference to FIG. 11. FIG. 11A is a sectional view of a cylindrical waveguide having an inner diameter of 2a, for example, in the diameter direction, and FIG. It is sectional drawing in AA of FIG.11 (a). This mode
In the figure, the electric field indicated by the solid line in the figure propagates along the tube wall while changing its direction every half wavelength so as to pass from the tube wall of the waveguide to the center and return to the tube wall. Also in this figure, the dashed line indicates the magnetic field, and in FIG. 11B, は indicates that the electric field is directed toward the inside of the paper, and • indicates that the electric field is directed toward the outside of the paper.

In such an apparatus, when processing a 6-inch wafer, for example, the inner diameter of the cylindrical waveguide is 109.
mm, uniformity of the electric field distribution in a certain cross section on the upper side of the wafer can be secured. However, in recent years, the diameter of a wafer tends to increase from an 8-inch size to a 12-inch size. When the wafer becomes larger than the inner diameter of the cylindrical waveguide, the area of the waveguide outlet facing the peripheral portion of the wafer is increased. The electric field intensity becomes extremely small, and the in-plane uniformity of the film thickness eventually deteriorates.

The present invention has been made under such circumstances, and it is an object of the present invention to improve the in-plane uniformity of plasma processing by generating highly uniform plasma over a wide area. It is an object of the present invention to provide a plasma processing apparatus and a method thereof.

[0011]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a cylindrical vacuum chamber having a circular plate-shaped transmission window at one end for transmitting high frequency, and a mounting table for a substrate to be processed is provided inside. A vacuum vessel provided; magnetic field forming means for forming a magnetic field in the vacuum vessel;
Mode - de e.g. TM ₀₁ mode - and a high-frequency supply means for supplying through said transparent window in de, electron cyclotron resonance by the processing gas between the high-frequency and magnetic fields into a plasma, the substrate to be processed by the plasma In a plasma processing apparatus that performs processing on the other hand, when the inside diameter of the vacuum chamber is D1, and the diameter of the high-frequency outlet of the transmission window is D2, 0.75 ≦ D2 / D1 ≦ 0.85. And

[0012]

1 is a sectional view showing an embodiment of a plasma processing apparatus according to the present invention, FIG. 2 is a perspective view of a part thereof, and FIG. 3 is an enlarged sectional view of a main part thereof. . 2 in the figure
Is a vacuum container formed of, for example, aluminum. The vacuum vessel 2 includes a first vacuum chamber 21 located above and generating plasma, and a second vacuum chamber 22 connected and connected below. These vacuum chambers 2
The first and second vacuum chambers 21 and 22 are formed in a cylindrical shape.
The inner diameter D1 is set to, for example, 250 mm (see FIG. 3), and the second vacuum chamber 22 is set to have an inner diameter larger than that of the first vacuum chamber 21. The vacuum vessel 2 is grounded and has a zero potential.

The upper end of the vacuum vessel 2 is opened, and a high frequency (microwave) transmitting member such as aluminum nitride (AlN) is formed in this portion, and the diameter A1 is 2
A 30 mm circular plate-shaped transmission window 23 is provided in an airtight manner. The transmission window 23 has an outer peripheral edge hermetically supported by a support ring 24 made of, for example, aluminum. The vacuum state in the vacuum vessel 2 is maintained by the transmission window 23 and the support ring 24.

The support ring 24 is provided at the upper end of the vacuum vessel 2, and is configured such that the inner peripheral surface protrudes below the lower surface of the transmission window 23.
The microwave inlet has an inner diameter narrower than other portions. For example, in this embodiment, the diameter D2 of the transmission window 23 on the microwave outlet side, that is, the inner diameter D2 of the microwave inlet portion of the first vacuum chamber 21 is set to about 200 mm based on experimental results described later.
The thickness of the support ring 24 below the transmission window 23 is set to about 5 mm.

[0015] On the outside of the transmission window 23, the plasma chamber 21 for example a microwave of 2.45 GHz TM mode - de e.g. TM ₀₁ mode - is the waveguide 3 for supplying at de like are provided. For example, as shown in FIG. 2, the exit side end of the rectangular waveguide 31 is connected to the upper side side of the cylindrical waveguide 32 at right angles to the lower end of the cylindrical waveguide 32. The side is connected to the upper end of a conical waveguide 33 formed in a tapered shape so as to gradually expand toward the lower side.

The conical waveguide 33 has, for example, an inner diameter A2 of an exit side opening set to 200 mm, and the end of the exit side opening is connected to the upper surface of the transmission window 23. The entrance end of the rectangular waveguide 31 is connected to a high-frequency power supply 34 for generating plasma, and the microwave generated by the high-frequency power supply 34 is guided by the waveguide 3 to pass through the transmission window 23. It can be introduced into the plasma chamber 21. In the present embodiment, the high-frequency power supply unit and the rectangular waveguide 31, the cylindrical waveguide 32, and the conical waveguide 33 constitute a high-frequency supply unit.

A gas nozzle 41 for supplying, for example, a plasma gas is provided evenly along the circumferential direction on the upper side of the side wall that defines the first vacuum chamber 21. A plasma gas source is connected, and a plasma gas such as an Ar gas or an O ₂ gas can be uniformly supplied to the upper portion in the first vacuum chamber 21 without unevenness. Although only two gas nozzles 41 are shown in the figure to avoid complication of the drawing, more gas nozzles 41 are actually provided.

On the other hand, the upper part of the second vacuum chamber 22, ie, the first
A ring-shaped film-forming gas supply unit 42 is provided in a portion communicating with the vacuum chamber 21 of the first embodiment, and a gas supply port 42a is formed in the inner peripheral surface. One end of a gas supply pipe 43 whose other end is connected to a film-forming gas source (not shown) is connected to the film-forming gas supply section 42, and a film-forming gas such as SiH ₄ gas or SiF ₄ gas is used as the gas. The gas is blown out from the supply port 42a.

A ring-shaped main electromagnetic coil 51 is arranged on the outer periphery of the side wall defining the first vacuum chamber 21 so as to approach the outer periphery and surround the vacuum chamber 21. A ring-shaped auxiliary electromagnetic coil 52 is arranged below the vacuum chamber 22, and is used for the first vacuum chamber 2.
A magnetic field B extending from the top to the bottom, for example, 875 gauss, from the first to the second vacuum chamber 22 can be formed.

In the second vacuum chamber 22, a mounting table 6 for mounting the wafer W is provided so as to be movable up and down between a processing position and a transfer position of the wafer W. The mounting table 6 is provided with a dielectric plate 62 having a built-in heater and electrodes on a main body 61 made of, for example, aluminum, and the surface is configured as an electrostatic chuck. A DC power supply (not shown) for an electrostatic chuck is connected to the electrodes, and a high-frequency power supply unit 63 is connected to apply a bias voltage for drawing ions into the wafer W. Further, an exhaust pipe 25 is connected to the bottom of the film forming chamber 22.

Next, a method for forming an interlayer insulating film made of, for example, a SiOF film on a wafer W to be processed by using the above-described plasma processing apparatus will be described. First, vacuum vessel 2
A gate valve (not shown) provided on the side wall is opened, and, for example, a wafer W of, eg, an 8-inch size having an aluminum wiring formed on its surface is loaded from a load lock chamber (not shown) by a transfer arm (not shown). 6. Place on top.

Subsequently, after closing the gate valve to seal the inside, the mounting table 6 is raised to the processing position, the internal atmosphere is exhausted by the exhaust pipe 25, and the interior is evacuated to a predetermined vacuum degree. A gas such as an Ar gas and an O ₂ gas are introduced at a predetermined flow rate, and a film forming gas such as a SiF ₄ gas is introduced from the film forming gas supply unit at a predetermined flow rate. Then, the inside of the vacuum vessel 2 is, for example, 0.15 Pa
And a bias voltage of 13.56 MHz and 2500 W is applied to the mounting table 6 by the high frequency power supply unit 63, and the surface temperature of the mounting table 6 is set to, for example, 40.
Set to 0 ° C.

In the first vacuum chamber 21, a high-frequency power source 3
2. A high frequency (microwave) M of 2.45 GHz and 2700 W from FIG. 4 is first transmitted through the rectangular waveguide 31 in the TE ₁₁ mode, and then the rectangular waveguide 31 and the cylindrical waveguide 32 are connected. parts around at TM ₀₁ mode - is converted to de, TM ₀₁ mode while it is expanding the field region of the conical wave guide 33 - it is transmitted by the de reach the ceiling portion of the vacuum vessel 2, via a transmission window 23 It is introduced into the first vacuum chamber 21.

On the other hand, a magnetic field B is formed in the vacuum vessel 2 by the main electromagnetic coil 51 and the auxiliary electromagnetic coil 52.
At the point where the intensity of the magnetic field becomes 875 gauss, the interaction between the magnetic field and the microwave causes electron cyclotron resonance, and the resonance turns the plasma gas into plasma and increases the density. The use of a plasma gas stabilizes the plasma.

The generated plasma flows from the first vacuum chamber 21 to the second vacuum chamber 22 as a plasma flow, and the SiF ₄ gas supplied here is activated (plasmaized) by the plasma flow. Thus, active species (plasma) are formed. On the other hand, the plasma ions are drawn into the wafer W by the bias voltage, and the corners of the SiOF film deposited on the pattern (concave portion) on the surface of the wafer W are scraped off by the plasma ion sputter etching to widen the frontage, thereby forming the SiOF film. It is filmed and embedded in the recess.

In such a plasma processing apparatus, the inner diameter of the first vacuum chamber 21 is set to 200 m at the microwave inlet.
m, which is rapidly increased to 250 mm immediately below, so that the thickness of the formed SiOF film can be made substantially uniform in the plane of the wafer W.

The reason is presumed as follows. That microwaves are transmitted with an increasing electric field region a conical waveguide 33 as described above, through the transmission window 23 TM ₀₁ mode -
The inside of the first vacuum chamber 21 is rapidly introduced into the first vacuum chamber 21, but the inside diameter of the first vacuum chamber 21 is rapidly increased. Thus TM ₀₁ mode - microwave propagating waveguide 3 and the inlet portion of the first vacuum chamber 21 along the tube wall in de is disturbed by this rapidly larger moiety, for example, in FIG order as shown mode - generates de, its mode - - de e.g. TM ₀₂ mode is considered to continue to transmit the left in the first vacuum chamber 21 of the de.

In such a high-order mode, an electric field is generated not only in the tube wall but also in the central portion of the vacuum vessel 2. An electric field will be present at Therefore, a uniform plasma region can be secured over a wide area in the plane, and as a result, the Si formed by the plasma
It is assumed that the thickness of the OF film becomes substantially uniform in the plane of the wafer W.

Here, the occurrence of such a higher-order mode is presumed to be related to the ratio of the inner diameter D1 of the first vacuum chamber 21 to the inner diameter D2 of the inlet from experimental results described later. Is done. That is, if D2 / D1 is too large, that is, if the inner diameter D1 is not much larger than the inner diameter D2, the disturbance of the propagation of the microwave is considered to be too small, and the transmission will end up in the TM01 _mode .

[0030] The TM ₀₁ mode - since microwaves in soil propagates with an increasing electric field region along the tube wall of the conical waveguide 33, inner diameter than the upper end of the conical waveguide 33 In the large first vacuum chamber 21, the electric field exists in the inner wall portion but does not exist in the central portion. For this reason, the electric field intensity is considerably reduced at the central portion, and it is considered that it is difficult to increase the in-plane uniformity of the plasma density.

On the other hand, if D2 / D1 is too small, that is, if the inside diameter D1 is too large, the propagation of the microwave is disturbed too much at the portion where the inside diameter D1 becomes large, and a mode that is not axially symmetric is easily excited. It is considered that the in-plane uniformity of the plasma density deteriorates.

Next, an experimental example performed by the present inventors to optimize D2 / D1 in relation to the in-plane uniformity of the film thickness will be described. Using the plasma processing apparatus shown in FIG. 1 described above, the inner diameter D1 = Ar gas and O ₂ gas at a predetermined flow rate.
While being introduced into the first vacuum chamber 21 of 250 mm,
An iF ₄ gas is introduced into the second vacuum chamber 22 at a predetermined flow rate, and the high-frequency power is 2500 W and the bias power is 2700.
W, the deposition temperature is 400 ° C., the pressure in the vacuum vessel 2 is 0.1
At 5 Pa, the size of the inner diameter D2 on the inlet side of the first vacuum chamber 21 was changed, and a SiOF film was formed on an 8-inch wafer W under the same process conditions as in the above-described embodiment. Was measured for in-plane uniformity. Here, the in-plane uniformity of the film thickness was measured by an optical probe. The same experiment was performed when the inner diameter D1 of the first vacuum chamber 21 was 275 mm and 300 mm.

The results are shown in FIGS. 5 to 8, wherein FIG. 5 shows the case where the inner diameter D1 of the first vacuum chamber 21 is 250 mm.
6 shows the case of 275 mm, FIG. 7 shows the case of 300 mm, and in FIG.
75 mm and □ indicate 300 mm, respectively.

According to this result, regardless of the size of the inner diameter D1 of the first vacuum chamber 21, when the ratio (D2 / D1) of the size of the inner diameter D2 of the inlet to the inner diameter D1 is about 0.8, The in-plane uniformity of the thickness of the SiOF film is best,
It was recognized that the in-plane uniformity became worse as the value was increased.

In order to generate a highly uniform plasma over a wide area in the first vacuum chamber 21,
It has been confirmed that an optimum relationship exists between the inner diameter D1 of the first vacuum chamber 21 and the inner diameter D2 of the inlet of the first vacuum chamber 21, and the in-plane uniformity of the film thickness is reduced to 20% or less. In order to
It was recognized that it was sufficient to set about 0.75 ≦ D2 / D1 ≦ 0.85.

In the above, in the present invention, the waveguide for transmitting the TM mode is not limited to the configuration described in the embodiment, but a configuration in which a rectangular waveguide and a plurality of cylindrical waveguides having different inner diameters are combined. The higher order mode of the TM _mode is not limited to the TM02 _mode , but may be the _TM03 mode or the like. Further, the present invention is not limited to the film forming process of the SiOF film, and may be applied to a film forming process of, for example, a SiO ₂ film or a CF film (a fluorine-added carbon film), or may be applied to an etching process. You may make it.

[0037]

According to the plasma processing apparatus of the present invention, since highly uniform plasma can be generated over a wide area, the in-plane uniformity of the plasma processing can be improved.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing an example of a waveguide used in the plasma processing apparatus.

FIG. 3 is a cross-sectional view of the vicinity of a microwave inlet of the plasma processing apparatus.

FIG. 4 is a cross-sectional view for explaining propagation of a microwave.

FIG. 5 is a characteristic diagram showing the relationship between D2 / D1 and the in-plane uniformity of film thickness when D1 = 250 mm.

FIG. 6 is a characteristic diagram showing a relationship between D2 / D1 and in-plane uniformity of film thickness when D1 = 275 mm.

FIG. 7 is a characteristic diagram showing the relationship between D2 / D1 and the in-plane uniformity of film thickness when D1 = 300 mm.

FIG. 8 is a characteristic diagram showing a relationship between D2 / D1 and in-plane uniformity of film thickness.

FIG. 9 is a sectional view showing a conventional plasma processing apparatus.

FIG. 10 is a cross-sectional view for explaining a TE ₁₁ mode.

FIG. 11 is a cross-sectional view for explaining a _TM01 mode.

[Explanation of symbols]

 2 Vacuum Vessel 21 First Vacuum Chamber 22 Second Vacuum Chamber 23 Transmission Window 24 Support Ring 3 Waveguide 31 Rectangular Waveguide 32 Cylindrical Waveguide 33 Conical Waveguide 34 High Frequency Power Supply 54 Main Electromagnetic Coil 6 Mounting table W Semiconductor wafer

Claims (2)

[Claims] A vacuum container having a cylindrical vacuum chamber provided at one end with a circular plate-shaped transmission window for transmitting high frequency, and a mounting table for a substrate to be processed provided therein; and the vacuum container. A magnetic field forming means for forming a magnetic field therein; and a high frequency supply means for supplying a high frequency into the vacuum chamber in the TM mode through the transmission window, wherein electron cyclotron resonance between the high frequency and the magnetic field is provided. In a plasma processing apparatus that converts a processing gas into a plasma by the method described above and performs processing on a substrate to be processed by the plasma, if the inside diameter of the vacuum chamber is D1, and the diameter of the high-frequency outlet portion of the transmission window is D2, 0. 75 ≦ D2 / D1 ≦
A plasma processing apparatus, wherein the ratio is 0.85. 2. The plasma processing apparatus according to claim 1, wherein said TM mode is a TM01 _mode .