JP3084466B2 - 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 for performing processes such as etching and thin film formation, and more particularly to a structure of a microwave introduction unit for generating and maintaining the plasma.

[0002]

2. Description of the Related Art Microwaves are introduced into a vacuum vessel under reduced pressure and low gas pressure to generate gas discharge to generate plasma, and the plasma is irradiated on the surface of a sample substrate to perform etching. Research has been conducted on devices which perform processes such as thin film formation and the like as indispensable for the production of highly integrated semiconductor elements and the like. In particular, as a device that can generate highly active plasma in the low gas pressure range,
Promising are magnetic field microwave plasma devices and devices that generate plasma by electron cyclotron resonance excitation.

FIG. 8 is a longitudinal sectional view of a conventional plasma processing apparatus utilizing an electron cyclotron resonance excitation using a microwave, which is configured as an etching apparatus. In FIG. 8, reference numeral 31 denotes a plasma generation chamber constituting a vacuum vessel; Denotes a sample chamber.

The plasma generating chamber 31 has a cooling water flow chamber 31a having a double wall around its periphery, and a microwave inlet 31b having a microwave inlet window 31b sealed with quartz glass at the center of the upper wall. 31c, and a plasma extraction window 31 at the center of the lower wall at a position facing the microwave introduction port 31c.
d. One end of a waveguide 32 whose other end is connected to a microwave oscillator (not shown) is connected to the microwave introduction port 31c, and a sample chamber 33 is provided facing a plasma extraction window 31d. An exciting coil 34 is disposed concentrically with the generation chamber 31 and a waveguide 32 connected thereto so as to surround one end of the waveguide.

In the sample chamber 33, the plasma extraction window 31d is provided.
A sample table 37 is disposed at a position opposite to the sample chamber 33, on which a sample S such as a wafer is mounted as it is or detachably mounted by means such as electrostatic suction. An exhaust port 33a connected to an exhaust device (not shown) is opened in the wall. 31g is a gas supply system connected to the plasma generation chamber 31, 33g is a gas supply system connected to the sample chamber 33, and 31h and 31i are supply and discharge systems of cooling water.

In such an etching apparatus, after the inside of the plasma generation chamber 31 and the sample chamber 33 are evacuated to a required pressure, a required gas pressure is obtained in the plasma generation chamber 31 through a gas supply system 31g. As described above, a microwave is introduced into the plasma generation chamber 31 through the microwave waveguide 32 while forming a magnetic field with the excitation coil 34, and the gas is resonantly excited using the plasma generation chamber 31 as a cavity resonator. Generate plasma. The generated plasma is drawn out around the sample S in the sample chamber 33 by a diverging magnetic field whose magnetic flux density decreases toward the sample chamber 33 formed by the exciting coil 34, and etches the surface of the sample S in the sample chamber 33. (JP-A-57-133636).

In the above-described conventional apparatus, the microwave introduction port 31c opened in the upper wall of the plasma generation chamber 31 is hermetically sealed by a microwave introduction window 31b made of a quartz glass plate that allows microwave transmission. However, the microwave introduction window 31b is disposed at the end of the microwave introduction port 31c so as to cover the microwave introduction port 31c, and is fixed together with a stopper 32b in a state where the microwave introduction window 31b overlaps the flange 32a at the end of the waveguide 32. ing.

Therefore, when viewed from the side of the plasma generation chamber 31 which functions as a cavity resonator for microwaves, the inside of the microwave introduction port 31c is a space, and
As a result of the formation of a step between the inner wall surface and the inner wall surface of the 31, there is a problem that microwaves are abnormally reflected at this portion and the uniformity of the plasma distribution is deteriorated due to this.

As a countermeasure, an apparatus as shown in FIG. 9 has been filed by the present applicant (Japanese Patent Application Laid-Open No. 63-318099).
. FIG. 9 is a partial cross-sectional view of a conventional plasma apparatus according to the application of the present applicant, in which a microwave introduction port 31c opening to the plasma generation chamber 31 is filled with the inner wall surface of the plasma generation chamber 31 so as to be filled. A microwave introduction window 48 made of a microwave transmitting material is provided so as to be flush. Other configurations are substantially the same as those of the device shown in FIG. 7, and corresponding portions are denoted by the same reference numerals.

The microwave introduction window 48 in FIG. 9 is constructed by providing a larger rectangular or circular flange portion 48b above a disk portion 48a substantially equal to the diameter and the axial length of the microwave introduction port 31c. The disk portion 48a is fitted tightly into the microwave inlet 31c, and the flange portion 48a is
b is brought into contact with the outer peripheral edge of the microwave introduction port 31c with an O-ring or the like (not shown) interposed therebetween, and the lower end surface of the disc portion 48a is positioned so as to be flush with the inner wall surface of the plasma generation chamber 31. I have.

In such a conventional apparatus, the microwave introduction port 31c opened in the upper wall of the plasma generation chamber 31 is filled with the microwave introduction window 48, which is a microwave transmitting material, without any gap. As a result, abnormal reflection of microwaves does not occur, abnormal reflection of microwaves is reduced accordingly, and generation of plasma is made uniform.

However, in such a conventional apparatus, a rectangular TE ₁₀ mode or a circular TE
_{Since the eleven} modes are used, and these electric field distributions are strong in the central part, there is a problem that the generated plasma density also has a strong distribution at the center of the plasma generation chamber. Therefore, in order to equalize the distribution of microwaves in the plasma generation chamber, a microwave diffusing means such as a concave lens is provided in the microwave introduction window to make the microwave electric field distribution uniform and the plasma generation chamber uniform. (Japanese Patent Laid-Open Publication No. Hei 3-
244123).

This is because the commonly used microwave is circular
Focusing on the strong electric field distribution at the center in the TE ₁₁ mode, a concave lens is used for the microwave introduction window to achieve uniform introduction of microwaves. However, the electric field distribution of the circular TE ₁₁ mode differs depending on the direction as shown in FIG. Figure
Figure 10 (a) shows the outline of the electric and magnetic field distributions in the waveguide.
10 (b) and 10 (c) are shown in the center of Fig. 10 (a).
Direction, which is the direction of the electric field, the direction orthogonal to the direction of the electric field
It is a distribution diagram of the electric field strength (E) in each of the x-directions.
As is clear from FIG. 10 (b), the center and the periphery in the y direction
There is no large change in the electric field strength between. On the other hand, FIG.
As can be seen, the electric field strength is highest at the center in the x direction.
Strength decreases rapidly as you move toward the periphery
You. In other words, from the viewpoint of uniform introduction of microwaves,
The uniformity in the y direction is good, but the uniformity in the x direction is
Low, resulting in poor plasma uniformity
Was.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric field distribution of a microwave introduced into a plasma generation chamber due to a microwave mode. An object of the present invention is to provide a plasma processing apparatus capable of improving nonuniformity, uniformly introducing microwaves into a plasma generation chamber, and stably and efficiently generating plasma having a uniform density.

[0015]

According to the present invention, there is provided a plasma processing apparatus, comprising: a microwave introduction portion for introducing a microwave from a microwave waveguide into a plasma generation chamber; and a connection between the microwave waveguide and the plasma generation chamber. Dielectric near the part
In the plasma processing apparatus is provided, wherein the dielectric is in the microwave tube a plane perpendicular to the propagation direction of the microwave propagating through the center of the plane surrounded by the inner surface wall of the microwave guide direction and the straight intersects the direction of the electric field
Whether the cross-sectional shape in the (x direction) is the corresponding both ends of the cross-section
Tapered shape that becomes thinner continuously or stepwise toward the center
And the cross-sectional shape in the direction of the electric field (y direction) is the electric field.
Wherein the <br/> be in the form that is different from the direction of the cross-sectional shape perpendicular to the direction of.

[0016]

According to the present invention, the dielectric material includes the microphone
Perpendicular to the propagation direction of the microwave propagating in the waveguide
A surface surrounded by an inner wall of the microwave waveguide.
Direction perpendicular to the direction of the electric field at the center in the plane (x direction
Direction) from the periphery to the center of the section
Tapered shape that becomes thinner continuously or stepwise.
The cross-sectional shape in the direction (y-direction) is orthogonal to the direction of the electric field
Is different from the cross-sectional shape in the
Even when the electric field distributions in the direction and the y direction are different, the electric field distribution can be effectively made uniform.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a longitudinal sectional view of a plasma processing apparatus according to one embodiment of the present invention. As in the conventional apparatus, the vacuum vessel includes a plasma generation chamber 1 and a sample chamber 3.

The plasma generation chamber 1 has a hollow cylindrical shape with a cooling water flow chamber 1a having a double surrounding wall, and is formed so as to constitute a cavity resonator for microwaves. A microwave introduction port 1c is provided at the center of the upper wall of the plasma generation chamber 1, and a microwave introduction window 8 made of a microwave transmitting material is provided here. The microwave introduction window 8 is formed at the center of the lower wall. A plasma extraction window 1d is provided at a position opposed to.

One end of the waveguide 2 is connected to the outer surface of the microwave introduction window 8, and a sample chamber 3 is disposed in the plasma extraction window 1d so as to face the one end. An excitation coil 4 is provided around one end of the generation chamber 1 and one end of the waveguide 2 connected thereto.

The other end of the waveguide 2 is connected to a microwave oscillator (not shown), and the generated rectangular TE ₁₀ mode microwave is introduced into the plasma generation chamber 1 to form an electric field therein. . The exciting coil 4 is connected to a DC power supply (not shown) to form a magnetic field for generating plasma in the plasma generating chamber 1 by passing a DC current, and to reduce the magnetic flux density toward the sample chamber 3 side. A divergent magnetic field is formed, and the plasma generated in the plasma generation chamber 1 by the divergent magnetic field is introduced into the sample chamber 3.

The sample chamber 3 is provided with an exhaust port 3a connected to an exhaust device (not shown) on the bottom wall facing the plasma extraction window 1d. The sample stage 7 is provided by
A sample S is disposed on the upper surface so as to face the plasma extraction window 1d.

FIG. 2A is an enlarged perspective view of the microwave introduction window 8 constituting the microwave introduction window 8, and FIG. 2B is a side view thereof. A lens portion 8b having a larger diameter is formed integrally with the upper surface of the microwave introduction window 8a, the disc portion 8a is closely fitted to the microwave introduction window 8, and the periphery of the circular lens portion 8b is formed by the microwave introduction window. An O-ring or the like (not shown) is interposed on the outer peripheral edge of the upper portion 8 in an airtight state, and the flange portion of the waveguide 2 as shown in FIG.
It is fixed together with the metal fitting 2b together with 2a.

In this state, the lower end surface of the disk portion 8a is plasma
It is substantially flush with the inner wall surface of the generation chamber 1. Microwave conduction
The lens portion 8b of the entrance window 8 is directed toward one diameter R side of the surface.
Tapered surfaces 8c, 8 that slope gently downward from both sides
c, and the direction of the diameter R is defined as yIn the direction
It is attached to the microwave inlet 1c. By this
TE₁₁Mode in microwavex directionField strength
It can be kept uniform. The disk 8a and the lens 8b
May be formed separately.

As the microwave transmitting material, quartz glass (
Dielectric constant ε _r = 3.8), alumina (AI ₂ O ₃ dielectric constant ε _r = 8.
5) Materials with relatively large dielectric constant, such as, BN, SiN, and other heat-resistant polymer materials (Teflon, polyimide) are used.

When such a material is changed from a disk shape to a concave shape or a convex shape, microwaves are also diffused and focused just as light is diffused and focused by a lens. However, this effect is not as strong as light because the wavelength of the microwave is longer than light and about the same as the size of the lens.

That is, the circular TE ₁₁ that is often used is usually used.
As shown in FIG. 10, the electric field distribution of the mode is the distribution that is strongest at the center and weaker at the periphery, and is less uniform in the x direction than in the y direction . Therefore, by using a dielectric having a lens effect in the microwave introduction part, x
Since direction of direction is larger degree of concave shape than in the y direction
The degree of diffusion is greater in the x direction than in the y direction ,
The non-uniformity due to the direction of the TE ₁₁ mode is eliminated, and the microwave can be introduced into the plasma generation chamber with high uniformity. The shape of this dielectric is designed according to the propagation mode of the microwave in the circular waveguide. The thickness of the dielectric is preferably 20 mm or more in consideration of problems such as mechanical strength and interference.

In the figures, 1g is a gas supply system connected to the plasma generation chamber 1, 3g is a gas supply system connected to the sample chamber 3, 1h,
1i is a cooling water supply system and a discharge system. In the plasma processing apparatus having such an apparatus of the present invention, the sample S is placed on the sample stage 7 in the sample chamber 3 and the inside of the plasma generation chamber 1 and the sample chamber 3 are set to a required degree of vacuum. , Gas supply pipe 1g, 3
g, gas is supplied into the plasma generation chamber 1 and the sample chamber 3, and in this state, a DC current flows through the excitation coil 4, and the inside of the plasma generation chamber 1 passes through the waveguide 2 and the microwave introduction window 8. To be introduced. As a result, the gas is efficiently ionized to generate plasma, and the generated plasma is generated by the diverging magnetic field formed by the exciting coil 4.
Then, the gas in the sample chamber 3 is activated, and etching or thin film formation on the surface of the sample S is performed.

A comparative test of such a device of the present invention will be described. Note the diameter of the microwave introducing window 8 and 120 mm, also as a comparative example using a microwave introducing window in the conventional projection type as shown in FIG. 9, and x direction on the sample table 7
The distribution of the ion saturation current density in the y direction was compared.
The test conditions were evaluated with plasma under an Ar gas pressure of 1 mtorr.

The results are as shown in FIG. FIG. 3 shows the radial position (mm) on the horizontal axis and the saturated ion current density on the vertical axis. In the graph, ○ and Δ indicate the case where the apparatus of the present invention was used, and ● and × indicate the case where the conventional apparatus was used.
○ and ● correspond to the distribution in the x direction, and △ and × correspond to the distribution in the y direction. As is apparent from FIG. 3, the uniformity of the ion saturation current density in the x-direction in the apparatus of the present invention is improved as compared with the conventional apparatus.

[0030] In the embodiment of FIG. 2 shows a configuration of changing only the shape and thickness to have the x-direction Nitsu microwave introduction windows 8 independently along the electric field distribution in the y direction in the y-direction shape -The thickness may be designed.

FIG. 4 shows another example of the microwave introducing window 8, FIG. 4 (a) is an enlarged perspective view thereof, and FIG. 4 (b) is a side view thereof. In this embodiment, the surface of the lens portion 8b in the x-direction is formed in a tapered shape which is gradually inclined downward from both sides toward the diameter R side.

FIG. 5 is a perspective view showing still another example of the microwave introduction window, and FIGS. 6 (a), 6 (b) and 6 (c) are a plan view, a front view and a side view of FIG. is there. In this embodiment, the tapered surface is gently inclined downward from both sides toward the diameters R ₁ and R ₂ in the x direction and the y direction orthogonal to each other. As a result, the shape and thickness of the surface of the lens portion 8b change independently in the x direction and the y direction , respectively.
A uniform electric field distribution can be obtained in both the direction and the y direction .

FIG. 7 is an enlarged cross-sectional view showing still another example of the microwave introduction window. In this embodiment, only the lens portion 9 is made of a microwave transmitting material, which is the conventional lens shown in FIG. The configuration is such that the microwave introduction window 48 and the microwave introduction window 10 having the same shape are combined. Microwave introduction window 8
Is the same as the conventional configuration. The lens section 9 has substantially the same shape as the lens section 8b of the microwave introduction window 8 shown in FIG. Only the lens portion of each microwave introduction window shown in FIGS. 4 and 5 is separately formed to form a microwave introduction window 48 shown in FIG.
Needless to say, it may be combined with.

The thickness distribution and shape of the lens unit 9 in the x and y directions are such that the characteristics of the plasma generated by the magnetic field intensity distribution, gas pressure, etc., ie, the plasma density, the plasma dielectric constant, and the plasma impedance change. Since the optimum thickness and the optimum shape change depending on the values, the numerical value and the shape may be set in accordance with these.

In the above embodiment, the apparatus of the present invention is etched,
The case where the film forming apparatus is configured has been described. However, the present invention is not limited to this, and can be applied to, for example, a sputtering apparatus.

[0036]

As described above, according to the present invention, the dielectric
The body is a member of the microwave propagating in the microwave waveguide.
A plane perpendicular to the direction of propagation, the plane of the microwave waveguide
Direction perpendicular to the direction of the electric field at the center in the plane surrounded by the inner wall
Cross section in the direction (x direction)
Tapered shape that becomes thinner continuously or stepwise toward the center
And the cross-sectional shape in the direction of the electric field (y direction) is
The shape is different from the cross-sectional shape in the direction perpendicular to the direction , so that the uniformity of the microwave electric field strength is improved, and thereby the uniform plasma distribution corresponding to the propagation mode in the waveguide. And an excellent effect that uniform etching, film formation, and the like can be performed on the sample can be achieved.

[Brief description of the drawings]

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

2 is an enlarged perspective view and a side view of the plasma introduction window shown in FIG.

FIG. 3 is a graph showing test results of the plasma processing apparatus according to the present invention.

FIG. 4 is an enlarged perspective view showing another example of the plasma introduction window used in the plasma processing apparatus according to the present invention.

FIG. 5 is an enlarged perspective view showing still another example of the plasma introduction window used in the plasma processing apparatus according to the present invention.

6 is a plan view, a front view, and a side view of the plasma introduction window shown in FIG.

FIG. 7 is a longitudinal sectional view showing still another example of the plasma introduction window used in the plasma processing apparatus according to the present invention.

FIG. 8 is a longitudinal sectional view of a conventional plasma processing apparatus.

FIG. 9 is a partially enlarged sectional view of the same.

10A is a distribution diagram of the electric field and the magnetic field of the microwave of the circular TE ₁₁ mode in the waveguide, and FIG. 10B is the center of the waveguide .
Of the electric field in the y direction, which is the direction of the electric field in the part
(C) is the distribution of the electric field at the center of the waveguide.
It is a distribution diagram which shows the electric field strength in the x direction orthogonal to the direction .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generation room 3 Sample room 4 Excitation coil 8 Microwave introduction window 8a Disk part 8b Lens part 8c Tapered surface 9 Lens part 10 Microwave introduction window

Claims (1)

(57) [Claims] A dielectric is provided near a connection between the microwave waveguide and the plasma generation chamber in a microwave introduction portion for introducing microwaves from the microwave waveguide to the plasma generation chamber.
In the plasma processing apparatus provided with a body, it said dielectric body, said a plane perpendicular to the propagation direction of the microwave propagating the microwave tube, the microwave within a plane surrounded by the inner surface wall of the tube phase sectional shape of the electric field direction and the straight direction orthogonal (x-direction) in the center of the cross section
Continuous or stepwise from the corresponding ends to the center
It has a tapered shape that becomes thinner and cuts in the direction of the electric field (y direction).
The plasma processing apparatus, wherein the surface shape and the direction of the cross-sectional shape perpendicular to the direction of the electric field is a shape that different <br/>.