JPH03166377A - Electron cyclotron resonance plasma cvd device - Google Patents

Abstract

PURPOSE:To uniformize the density of plasma flowing into a reaction chamber and to simultaneously attain the uniformity in film thickness and homogeneity by providing an impeller to be rotated by a plasma current in the plasma current. CONSTITUTION:A rotating stirrer 12 as the impeller is set between a plasma producing chamber 10 and the reaction chamber 30 in the electron cyclotron resonance plasma CVD device. The plasma current proceeding to the reaction chamber 30 from the plasma producing chamber 10 collides with the blade 12b of the stirrer 12 to rotate the stirrer 12, and agitated by the rotation. The density distribution of the plasma introduced into the reaction chamber 30 is uniformized by the agitation. Since the opening 12a of the stirrer 12 is rotated and moved by the rotation of the stirrer 12, the plasma current is not shadowed, and the uniformity in the film quality is unaffected.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an electron cyclotron resonance plasma CVD apparatus used for shaping glabellar insulating films and passive basin films during the manufacture of integrated circuits. Electron cyclotron resonance plasma CV with homogenizing means
Regarding D device.

[Conventional technology]

Most of the glabella insulating films and passivation films currently used in integrated circuits are formed by plasma CVD using plasma discharge.

However, in this plasma CVD method, it is necessary to raise the substrate temperature in order to ensure film quality and coverage of the stepped portions of the substrate, so the elements formed on the substrate are affected by thermal stress during temperature rise and fall. There was a problem as damage could occur.

Therefore, recently, electron cyclotron resonance (ElectronCyc), which can obtain good film quality even at low substrate temperatures, has been developed.
1 o tron Resonance) Braz 7
CVD method is beginning to be used. This method generates plasma by utilizing the highly efficient absorption of microwave energy by electrons due to the electron cyclotron resonance phenomenon, and generates a higher plasma density than the normal plasma CVD method. A high quality film can be obtained even when the substrate temperature is below 200''C.

A device for forming a silicon nitride film using this electron cyclotron resonance plasma CVD method will be explained with reference to FIG. The electron cyclotron resonance plasma CVD apparatus has a plasma generation chamber 10 and a reaction chamber 30. A microwave waveguide 20 is connected to the plasma generation chamber 10 through a microwave introduction window 21, and an excitation tube is placed outside of the microwave waveguide 20. A coil 40 is arranged. Further, a substrate 51 is provided inside the reaction chamber 30.
A sample stand 50 on which a sample is placed is installed, and an exhaust port 61 connected to an exhaust system 60 is provided on the back side of this sample stand 50.

Next, a method of forming a silicon nitride film using this apparatus will be explained.

The N2 gas introduced from the first gas introduction system 11 resonates and absorbs the microwaves incident through the microwave introduction window 21 in the magnetic field generated by the excitation coil 40 in the plasma generation chamber 10, and is excited and becomes a plasma state. The plasma thus generated is drawn out by the magnetic field gradient of the divergent magnetic field formed by the excitation coil 40 and flows into the reaction chamber 30, decomposing the SiHn (silane) gas introduced from the second gas introduction system 31. Then, a silicon nitride film is formed on the substrate 51.

At this time, Ar gas is introduced into the device and the base +
By applying a high frequency bias 52 to 1i51 and utilizing the self-bias effect of the substrate, a bias sputtering method is adopted in which sputtering and film formation are performed in parallel, making it possible to flatten the coating on the substrate step. has also been proposed.

(Problems to be Solved by the Invention) However, the above electron cyclotron resonance plasma CVD apparatus has the following problems.

The density of plasma generated by electron cyclotron resonance has a unique distribution resulting from the resonance mode of the microwave and the intensity distribution of the magnetic field within the plasma generation chamber 10, which serves as a cavity resonator for the introduced microwave. The plasma density often tends to decrease from the center of the plasma generation chamber 10 toward the outside. Therefore, the thickness of the film formed when this plasma reaches the surface of the substrate 51 also reflects the plasma density, and its uniformity deteriorates.

In particular, when bias sputtering is employed, if a high frequency bias 52 is applied to the substrate 5l, stress on the shaped film may increase and film peeling may occur. Therefore, in order to prevent this, it is necessary to increase the gas pressure within the apparatus, but when the gas pressure is increased in this way, the uniformity of the film thickness distribution generally deteriorates further.

On the other hand, there are also attempts to make the film thickness distribution uniform by arranging a fixed shielding plate or the like on the path of the plasma flow.

However, with this method, the plasma density itself is not made uniform, but the deposition rate on the substrate is averaged as a result by changing the flow path of the plasma flow, so the film thickness is made uniform. Even if this is done, properties such as denseness and acid resistance of the film will change in areas that will be in the shadow of the shielding plate and areas that will not be in the shadow of the shielding plate, and the homogeneity will deteriorate.

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned problems, and its object is to provide a means to automatically equalize the density of plasma flowing into the reaction chamber without requiring any external operation. An object of the present invention is to provide an electron cyclotron resonance plasma CVD apparatus that can simultaneously achieve film thickness uniformity and homogeneity.

[Means to solve the problem]

In order to solve the above problems, in an electron cyclotron resonance plasma CVD apparatus having a plasma generation region and a reaction region, the means taken by the present invention is such that the plasma flow is It is equipped with an impeller that can be rotated by the plasma flow flowing from the generation region to the reaction region.

Furthermore, in this case, the impeller is equipped with an opening through which the plasma flow flowing from the plasma generation region to the reaction region passes, but the distribution of the aperture ratio on concentric circles extending from the rotation center of the impeller in the centrifugal direction is This is set so that the distribution of plasma density generated within the plasma generation region in the centrifugal direction has a tendency opposite to that of the distribution. For example, if the plasma density in the plasma generation region has a distribution that monotonically decreases in the centrifugal direction of the impeller, then the aperture ratio on the concentric circles of the impeller has a distribution that monotonically increases in the centrifugal direction. do.

[Effect]

According to this means, when the plasma generated in the plasma generation region flows into the reaction region, the plasma flow collides with an impeller installed in the middle of the path of the plasma flow,
The reaction drives the impeller to rotate, and the rotating impeller also agitates the plasma flow itself, making the density of the plasma in the reaction region that has passed through the impeller uniform. be done.

In addition, as long as the plasma flow exists, the impeller continues to rotate, so the path through which the plasma flow passes also rotates.
Since the plasma channel is not affected by the shadows that would occur if a fixed shielding plate is installed in the apparatus, the quality of the shielding film will not be non-uniform.

Therefore, the plasma stream having a uniform density formed in the reaction region by the impeller reaches the substrate surface, resulting in a uniform and homogeneous film formation.

Note that since the impeller described above rotates naturally due to the plasma flow, there is no need to drive it to rotate from the outside, so a drive mechanism is not required.

Furthermore, regarding the shape of the opening formed in the impeller,
When the aperture ratio distribution in the centrifugal direction of the impeller is set to have a tendency opposite to the plasma density distribution in the plasma generation region, that is, the plasma raw $. If the aperture ratio is made smaller in parts of the region with high plasma density and increased in parts with low plasma density, the flow rate of the plasma flowing into the reaction region will change in the centrifugal direction depending on the distribution of this aperture ratio. In other words, the amount of plasma flowing into the area where the aperture ratio is small is small, and the amount of plasma flowing into the area where the aperture ratio is large is large.

Therefore, the bias in the centrifugal direction of the plasma density introduced into the reaction region through this opening is alleviated and made uniform by the change in the inflow amount with the opposite tendency in the centrifugal direction. The effect of this aperture ratio distribution works in conjunction with the above-mentioned stirring by the impeller, and even if there is a large deviation in the plasma density in the plasma generation region in the radial direction, the density of the plasma flowing into the reaction chamber is more easily homogenized.

〔Example〕

Next, embodiments of the present invention will be described based on the accompanying drawings.

FIG. 1 is a schematic diagram of an electron cyclotron resonance plasma CVD apparatus according to a first embodiment of the present invention.

This electron cyclotron resonance plasma CVD apparatus has a plasma generation chamber 10 and a reaction chamber 30, and a rotating stirrer 12 is installed as an impeller between the plasma generation chamber 10 and the reaction chamber 30. Here, the plasma generation chamber 10
A waveguide 20 for transmitting microwaves is connected through a microwave introduction window 21, and a first gas introduction system 11 is also installed. Further, an excitation coil 40 surrounds the plasma generation chamber 10. On the other hand, the reaction chamber 30 has a second
A gas introduction system 31 is installed, and an exhaust system 6 for gas discharge is installed.
An exhaust port 61 connected to 0 is connected. This reaction chamber 3
A sample stand 50 is installed inside o, and a high frequency voltage 52 can be applied to a substrate 51 placed on this sample stand 50.

The rotating stirrer 12 is attached to a support base 1 fixed to the main body of the device.
3 is rotatably supported. FIG. 2(a) shows a plan view of this rotating stirrer 12, and FIG. 2(b) shows a side view. The rotating stirrer 12 has a disc shape with an opening 12a extending in the radial direction and a blade 12b diagonally protruding toward the plasma generation chamber 1o, and the center thereof extends above and below the rotating stirrer 12. It is supported by an arm 13a of a support base 13 and can freely rotate about this support part as a rotation axis. The openings 12a are arranged in a radial shape centered on the rotation axis of the autorotating stirrer 12, and have a fan shape whose opening width becomes wider in the centrifugal direction.

Next, referring again to FIG. 1, the effects of this electron cyclotron resonance plasma CVD apparatus will be explained in the case where a silicon nitride film is formed.

Introducing N2 or NH3 or a mixture thereof into the plasma generation chamber 10 from the first gas introduction system 11,
Microwaves are introduced from the waveguide 20 through the microwave introduction window 21 . When this microwave energy is absorbed by electron cyclotron resonance, these gases are excited and high-density plasma is generated. The conditions for this electron cyclotron resonance to occur are, for example, when the microwave frequency is 2450 MHz, the magnetic flux density formed by the excitation coil 40 is 875 gau.
It is ss. A divergent magnetic field is created in the plasma generation chamber 10 by the excitation coil 40, and the gradient of this magnetic field draws plasma toward the reaction chamber 30 side.

The plasma flow that advances from inside the plasma generation chamber 10 to the reaction chamber 30 side collides with the blade 12b of the rotating stirrer 12, and at the same time, the rotating stirrer 12 is rotated by the reaction, and at the same time, it is stirred by the rotating starch l2. By this stirring, the density distribution of the plasma introduced into the reaction chamber 30 is made uniform. Referring to FIG. 3, which shows the plasma density on a sample where a film is formed, even if the high-density part of the plasma is concentrated in the center as in the conventional device shown by the dotted line, the stirring by the rotating stirrer 12 As shown by the solid line, the plasma density within the reaction chamber 30 is made uniform.

Further, the plasma flow passes through the opening 12a and enters the reaction chamber 30.
However, since the opening 12a rotates and moves with the rotation of the rotating stirrer 12, there is no shadow in the plasma flow as in the case where a fixed shielding plate is installed, so that the film quality is uniform. There is no effect on sexuality.

The plasma flow introduced into the reaction chamber 30 decomposes the SiH<(silane) gas introduced from the second gas introduction system 31 and forms a silicon nitride film on the substrate 5l. Here, the inside of the reaction chamber 30 is 1o-3 to 10-'T by the exhaust system 60.
The substrate 51 is heated to about 50-150''C by the energy of the plasma flow.

The silicon nitride film formed in this way on the substrate 51 has uniformity in film thickness and film quality over the entire surface of the substrate because the plasma flow introduced into the reaction chamber 30 is made uniform. Become something.

Furthermore, in order to improve coverage, the pressure inside the reaction chamber 30 is reduced to about 10
- When forming a film by applying a high frequency bias 52 to the substrate 51 at a high Torr, the stirring action of the above-mentioned rotating stirrer is exerted in the same way even if the gas pressure is increased, which deteriorates the uniformity of the film thickness. It is possible to planarize the film formed on the step of the substrate without causing any unevenness.

In the embodiments described above, the openings and blades of the rotating stirrer can have other shapes, such as windmills, ventilation fans, turbines, etc., as long as the rotating stirrer is rotated by the plasma flow. In addition to the method described in the above embodiment, the rotating stirrer may be supported by an arm only on the upper side of the rotating stirrer via the central axis, and the width of the arm of the support base is approximately 2 to 3 mm. If there is, it does not seem to affect the uniformity of the shaped membrane.
Further, the material of the rotating stirrer 12 and the support base l3 may be metal or a heat-resistant insulating material.

Next, other embodiments of the present invention will be described with reference to FIGS. 4 to 6.

FIG. 4(a) shows a plan view of a rotating stirrer according to the second embodiment. The structure of the device other than the rotating stirrer is the same as that of the first embodiment, so a description thereof will be omitted. In this case, the rotating stirrer 14 is provided with an opening 14a that becomes wider in the centrifugal direction. Opening width a. The relationship between the aperture ratio a/2πr and the distance r is shown in FIG. 5(a), with the ratio of the sum a being the aperture ratio. Unlike the rotating stirrer 12 of the first embodiment in which the aperture ratio is constant, the rotating stirrer 1
The aperture ratio increases monotonically toward the outer periphery of No. 4.

According to the rotating stirrer 14, the flow rate of plasma passing through the stirrer 14 increases as it goes to its outer periphery, so the plasma density distribution in the reaction chamber 30 after passing through the stirrer 14 increases compared to the plasma density distribution in the plasma generation chamber 10 before passing through the stirrer 14. The distribution becomes small near the center of the rotating stirrer 14 and becomes high at the outer periphery. Therefore, as shown in FIG. 5(b), when the distribution of plasma density in the plasma generation chamber 10 monotonically decreases toward the outer periphery and the deviation in the center is large, the Although it is conceivable that sufficient uniformity of plasma density cannot be obtained by the stirring action alone, by using this rotating stirrer 14, the distribution of plasma density in the centrifugal direction can be relaxed and made uniform.

Further, FIG. 4(b) shows a rotating stirrer 16 in a third embodiment. Also in this case, the structure of the device other than the rotating stirrer is the same as in the first embodiment. In this rotating stirrer 16, the opening 1 has two types of opening widths.
6a and 16a', both of which have a constant opening width in the centrifugal direction, and the distribution of the opening ratio is monotonous toward the outer periphery, as shown in FIG. 6(a). has decreased to

As shown in FIG. 6(b), if the plasma density distribution within the plasma generation chamber 10 increases monotonically toward the outer periphery and the deviation is large, by using the rotating stirrer 16, The distribution of plasma density in the centrifugal direction can be relaxed and made uniform.

Rotating stirrer 1 explained in the second and third embodiments
In addition to 4.16, the reaction chamber 3
It is possible to make the plasma density uniform within 0.

Various embodiments other than those described above are possible. For example, it is also possible to install a plurality of rotating stirrers, which are impellers, in parallel or perpendicular to the plasma flow path. Further, these plurality of rotating stirrers can be a combination of those having the same rotation direction or opposite rotation directions.

〔Effect of the invention〕

The present invention is characterized in that an impeller is rotatably installed in the middle of the plasma flow path in an electron cyclotron resonance plasma CVD apparatus, and therefore, the following effects are achieved.

(2) The impeller rotates under the action of the plasma flow itself, and the rotation of the impeller agitates the plasma flow, so that the density of the plasma flowing into the reaction region is made uniform. Therefore, a uniform plasma flow reaches the substrate surface, and it is possible to easily obtain in-plane uniformity in the thickness and quality of the shaped film.

- Since the impeller is rotationally driven by the plasma flow itself, there is no need for an external rotation drive device, and there is no need to adjust the rotation speed.

■ If the shape of the impeller aperture is such that the aperture ratio distribution has a tendency opposite to the plasma density distribution in the plasma generation chamber in the centrifugal direction, the impeller It is possible to alleviate the bias in plasma density in the centrifugal direction of the car. Therefore, even if the plasma density in the plasma generation chamber has a particularly large deviation in the centrifugal direction, the plasma density in the reaction chamber can be made uniform.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the structure of an electron cyclotron resonance plasma CVD apparatus according to an embodiment of the present invention. FIG. 2(a) is a plan view of the rotating stirrer according to the first embodiment, and FIG. 2(b) is a side view thereof. FIG. 3 is a graph showing the plasma density distribution on the surface of the sample (substrate) in the electron cyclotron resonance plasma CVD apparatus according to the embodiment of the present invention. FIG. 4(a) is a plan view of a rotating stirrer according to a second embodiment, and FIG. 4(b) is a plan view of a rotating stirrer according to a third embodiment. FIG. 5(a) is a graph showing the aperture ratio in the centrifugal direction of the rotating stirrer according to the second embodiment, and FIG. 5(b) is a graph showing the centrifugal aperture ratio of the generated plasma density to which the second embodiment is applied. It is a graph diagram showing distribution of directions. FIG. 6(a) is a graph showing the aperture ratio in the centrifugal direction of the rotating stirrer according to the third embodiment, and FIG. 6(b) is a graph showing the centrifugal aperture ratio of the generated plasma density to which the third embodiment is applied. It is a graph diagram showing distribution of directions. Figure 7 shows conventional electron cyclotron resonance plasma CVD.
FIG. 2 is a schematic diagram showing the structure of the device. [Explanation of symbols] 10... Plasma generation chamber 11... First gas introduction system 12, 14. 16... Rotating stirrer 13... Support bases 12a, 14a, 16a, 16a'... Openings 12b, 14b. 16b, 16b'...play 20...waveguide 21...microwave introduction window 30...reaction chamber 31...second gas introduction system 40...excitation coil 50...sample stand 5l... Board 52... High frequency voltage 60... Exhaust system 6I... Exhaust port.

Claims (2)

[Claims] (1) In an electron cyclotron resonance plasma CVD apparatus having a plasma generation region and a reaction region, a blade is installed in the middle of the path of the plasma flow flowing from the plasma generation region to the reaction region so as to be rotatable by the plasma flow. An electron cyclotron resonance plasma CVD apparatus characterized by being equipped with a vehicle. (2) In claim 1, the impeller is provided with an opening through which the plasma flow flowing from the plasma generation region to the reaction region passes, and the impeller has a concentric circle extending in the centrifugal direction from the rotation center of the impeller. An electron cyclotron resonance plasma CVD apparatus characterized in that the above distribution of aperture ratio has a tendency opposite to the distribution of generated plasma density in the centrifugal direction.