JPH01194419A - Plasma processor - Google Patents

Abstract

PURPOSE:To operate a plasma over the whole face of a wafer and to uniformly process the whole wafer by connecting a rectangular waveguide through a tapered waveguide to a vacuum vessel thereby to generate the plasma in a state near a circular shape. CONSTITUTION:A microwave oscillated by an oscillator 1 is fed through a rectangular waveguide 2 and then fed through a tapered waveguide 10. The sectional shape of the electric field of the microwave is gradually deformed from a rectangular shape to a shape near a circular shape in response to the taped shape of the waveguide 10, and the sectional area of the electric field is gradually enlarged. In a generation chamber 3, a plasma having an electric field of the state substantially similar to that of the electric field in the outlet of the waveguide 10, i.e., an electric field of the state that its sectional area is large in the shape near a circular shape can be generated, and the plasma can be operated over the whole face of a wafer A formed in a circular shape by attaching a susceptor 9 in a reaction chamber 4. Accordingly, the whole face of the wafer can be uniformly etched, or processed by, such as CVD.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a plasma processing apparatus.

(Prior Art) In semiconductor manufacturing, a plasma processing apparatus used for ECR etching, ECR-CVD, etc. on semiconductor wafers has a microwave oscillator 1 connected to the oscillator 1, as shown in FIG. It is equipped with a vacuum vessel 5 having a waveguide 2, a plasma generation chamber 3 connected to the waveguide 2, and a reaction chamber 4 connected to the generation chamber 3, and further includes a magnetic field coil 6 surrounding the discharge chamber 3, and a plasma generation chamber 3 connected to the waveguide 2. A gas supply device 7 connected to the reaction chamber 4 and a vacuum pump 8 connected to the reaction chamber 4 are provided.

This equipment performs etching or CVD on semiconductor wafer A.
When performing this, the semiconductor wafer A is placed in the reaction chamber 4 inside the vacuum container 5 so as to face the generation chamber 3, and is held by a susceptor 9. In addition, the generation chamber 3 is
The inside of the reaction chamber 4 is vacuumed, and the gas supply device 7 supplies discharge gas to the inside of the generation chamber 3 and the reaction chamber 4. Then, the generation chamber 3 is
A uniform magnetic field is applied to the gas inside. Then, plasma is formed inside the generation chamber 3, and the electrons in the plasma move circularly around the lines of magnetic force.

The rotational frequency of this circular motion is inversely proportional to the weight of the electron, and proportional to the electric charge and magnetic field. On the other hand, the microwave oscillator 1 oscillates microwaves (electromagnetic waves), and the microwaves are transmitted to the waveguide 2.
It propagates inside the generation chamber 3 through. In this case, the frequency of the microwave is assumed to match the rotational frequency of the electrons moving circularly in the generation chamber 3, and the direction of the electric field of the microwave is relative to the direction of the magnetic field applied to the generation chamber 3 by the magnetic field coil 6. The directions are orthogonal. Then, the microwave is resonantly absorbed by the rotating electrons in the generation chamber 3, causing electron cyclotron resonance (Electron Cycltron Re5o).
nance.

It is abbreviated as ECR. ) phenomenon occurs. As a result, stable low-separation plasma is generated inside the generation chamber 3. The plasma generated in the generation chamber 3 acts on the wafer A provided in the reaction chamber 4, and a thin film is formed or etched on the surface of the wafer A by the reaction of the gas inside the reaction chamber 4.

Therefore, in the conventional plasma processing apparatus, a rectangular waveguide having a rectangular cross section, as shown in FIG. 6, is used throughout as the waveguide 2 connecting the oscillator 1 and the generation chamber 3. This is due to the following reason. In other words, rectangular waveguides can propagate microwaves efficiently, and it is easy to calculate the dimensions to determine the cross-sectional size according to the microwave frequency, making it possible to standardize products and reduce manufacturing costs. .

(Problems to be Solved by the Invention) However, when processing a wafer in a plasma processing apparatus, what is important is to perform the processing by applying plasma to the entire wafer.

However, when the rectangular waveguide 2 is used as in the prior art, there are the following problems. - Since the wafer A is numerically circular, the generation chamber 3 and the reaction chamber 4 have circular cross-sections so that the plasma can be applied to the entire wafer A. However, when using the rectangular waveguide 2,
As shown in FIG. 6, the rectangular waveguide 2 forms a circular generation chamber 3.
As a result, the cross-sectional shape of the passage through which the microwave passes rapidly changes from rectangular to circular at the connection between the waveguide 2 and the generation chamber 3. As shown in FIG. 7, the cross section of the electric field of the microwave that has passed through the rectangular waveguide 2 is rectangular. Therefore, even if a microwave with an electric field having a rectangular cross section enters the generation chamber 3 from the rectangular waveguide 2, the cross section of the electric field cannot suddenly change from a rectangular shape to a circular shape that matches the circular generation chamber 3; It only changes to a slightly distorted cross section.

As a result, the electric field of the plasma generated in the generation chamber 3 under the influence of the cross section of the electric field of this microwave also becomes a small form with a shape close to a rectangle, and a form that cannot act on the entire circular wafer A. will act on wafer A. Therefore, it is not possible to perform etching or CVD by applying plasma over the entire surface of the wafer A.
A situation has arisen where some parts remain that cannot be processed.

It is also conceivable to provide a waveguide converter between the rectangular waveguide 2 and the generation chamber 3, but in this case too, it is not expected to improve the uniformity of the microwave electric field much.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a plasma processing apparatus capable of performing etching or CVD processing over the entire surface of a semiconductor wafer.

[Structure of the Invention] (Means for Solving the Problem) In order to generate the above object, the plasma processing apparatus of the present invention includes a microwave oscillator, a rectangular waveguide connected to the microwave oscillator, and a rectangular waveguide connected to the microwave oscillator. A device comprising a vacuum vessel connected to a tube and into which discharge gas is introduced to form a plasma generation space, characterized in that the rectangular waveguide is connected to the vacuum vessel via a tapered waveguide. It is something.

(Operation) In the process of passing through the tapered waveguide, the microwave that has passed through the rectangular waveguide smoothly transforms the cross section of the electric field from a rectangle to a wide cross section close to a circle, and enters the plasma generation chamber. As a result, plasma is generated in a wide, nearly circular shape and acts over the entire surface of the wafer, making it possible to perform uniform processing over the entire surface of the wafer.

(Example) The present invention will be described in detail.

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the entire plasma processing apparatus, and the same parts as in FIG. 5 are designated by the same reference numerals, and their explanation will be omitted. In this embodiment, a tapered waveguide 10 is interposed between the rectangular waveguide 2 and the generation chamber 3 of the vacuum vessel 5. As shown in FIG. 2, this tapered waveguide 10 has an opening 1 at one end formed in a rectangular shape corresponding to the rectangular cross section of the rectangular waveguide 2, and an opening 12 at the other end formed into a circular shape of the generation chamber 3. It is formed into a circular shape with a size corresponding to the cross section, and this rectangular opening 1
A taper is formed in which the cross-sectional area gradually increases from 1 to the circular opening 12 while gradually transforming the rectangular cross-section into a circular cross-section. Then, the rectangular opening 11 of the tapered waveguide 10 is connected to the rectangular opening at the end of the rectangular waveguide 2,
The circular opening 12 is connected to the circular opening of the generation chamber 3 of the vacuum vessel 5.

In the plasma processing apparatus configured in this way, the microwave oscillated by the oscillator 1 passes through the rectangular waveguide 2 and then the tapered waveguide 10 . Here, in accordance with the tapered shape of the tapered waveguide 10, the cross-sectional shape of the electric field of the microwave is gradually transformed from a rectangular shape to a shape close to a circle, and the cross-sectional area of the electric field is gradually expanded. Finally, the form of the microwave electric field at the circular opening 2 which is the exit of the tapered waveguide 10 is as shown in FIG.

In this way, the electric field of the microwave is converted into a wide, nearly circular shape by the tapered waveguide 10, and the microwave enters the circular generation chamber 3. Therefore, in the generation chamber 3, the tapered waveguide 10
It is possible to generate a plasma with an electric field having a form that is approximately similar to the form of the electric field at the exit of the plasma, that is, an electric field having a shape close to a circle and a large cross-sectional area.This plasma is attached to the susceptor 9 in the reaction chamber 4. A circular wafer A provided with
can be applied over the entire surface. Therefore, uniform etching or CVD processing can be performed over the entire surface of the wafer A, and it is possible to prevent the occurrence of a situation where a portion of the wafer A is left unprocessed.

FIG. 4 shows another embodiment. This embodiment is formed by integrating a tapered waveguide 10 and a plasma generation chamber 3, and the generation chamber 3 has a height h and a diameter d determined from the design size of the vacuum vessel. Inside the generation chamber 3,
An inner container 14 is provided, which is made of a material capable of maintaining vacuum and transmitting microwaves, such as quartz, and has dimensions close to those of the reaction chamber 3 . This internal container 14 is for making plasma generation uniform over the wafer. This embodiment has the advantage that the uniformity of etching and CYD is good due to the presence of the inner container 14.

[Effects of the Invention] As explained above, according to the plasma processing apparatus of the present invention, etching and CVD processing can be performed satisfactorily by applying plasma over the entire surface of a semiconductor wafer.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the device of the present invention, FIG. 2 is a perspective view showing a rectangular waveguide and a tapered waveguide in the embodiment, and FIG. 3 is a tapered waveguide (this example). 4 is a sectional view showing another embodiment, FIG. 5 is a sectional view showing an example of a conventional device, and FIG. 6 is a diagram showing a rectangular waveguide in the same device. The perspective view shown in FIG. 7 is an explanatory diagram showing the electric field distribution of microwaves in a rectangular waveguide. 1...Microwave oscillator, 2... Rectangular waveguide, 3.
...Plasma generation chamber, 4...Reaction chamber, 5...Vacuum container, 10...Tapered waveguide. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] In an apparatus comprising a microwave oscillator, a rectangular waveguide connected to the microwave oscillator, and a vacuum vessel connected to the rectangular waveguide and into which a discharge gas is introduced to form a plasma generation space, the rectangular waveguide A plasma processing apparatus characterized in that the tube is connected to the vacuum vessel via a tapered waveguide.