JPH02253617A - Plasma treatment device - Google Patents

Abstract

PURPOSE:To improve uniformity of plasma treatment by allowing an equal magnetic field surface to vibrate in the axial direction of a magnetic field, applying AC current superposed by DC current to an electromagnet. CONSTITUTION:A semiconductor substrate 4 is installed within an reaction room 3 where a microwave guide tube 1 and a high vacuum discharge port 2 are connected. an electromagnet 5 is placed around the reaction room 3, and an AC power supply 6 and a DC power supply 7 are connected in series. Then, the DC power supply 7 allows current to flow to the electromagnet 5, an AC power supply 6 allows AC current to be superposed on DC current and applies it to the electromagnet 5, and then an ECR(Electron Cyclotron Reso nance) region 8 is formed within a reaction room 3, in this case, an equal mag netic field surface vibrates in the axial direction of magnetic field. a divergent magnetic field and hence a self potential also vibrates. and the distribution of the equal magnetic field surface also fluctuates. thus causing reaction to species fluctuate. Thus, it is possible to improve uniformity of plasma treatment as compared with the case when magnetic field was generated using only the DC current.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses ECR plasma to perform etching or C
The present invention relates to a plasma processing apparatus that performs VD.

Regarding conventional plasma processing apparatuses, ECR plasma processing apparatuses that utilize magnetic fields and microwaves are being put into practical use in place of parallel plate plasma processing apparatuses that have been widely used in the past.

The ECR plasma processing apparatus generates plasma under electron cyclotron resonance (ECR) conditions, where J = iB ω: microwave angular frequency, B: magnetic flux density, m: electron mass, q: electron charge. , chemically reactive species are formed to perform etching, CVD, etc.

Problems to be Solved by the Invention In conventional ECR plasma devices, an electromagnet is used to generate a magnetic field, and a constant DC current is passed to form an equimagnetic interface that satisfies the ECR conditions. However, it is difficult to form an isomagnetic interface with sufficiently uniform ECR conditions on a flat surface due to the problem of the device volume and the restriction on the diameter of the reaction chamber, and the isomagnetic interface is curved.

In addition, a divergent magnetic field is formed by this curved isomagnetic interface, and electrons flow out along this divergent magnetic field, forming a self-potential. Therefore, the second isomagnetic interface control is important, and it also improves controllability. This is a difficult technique. ECR plasma processing equipment utilizes the self-potential created by this divergent magnetic field, so in order to achieve anisotropy with ECR plasma alone, it is necessary to move the semiconductor substrate to be processed away from the reaction chamber and increase the self-potential. Ta. Furthermore, when the substrate is placed in the reaction chamber, it is difficult to achieve anisotropy because the ions generated by the ECR plasma alone do not generate a self-potential. It was necessary to forcibly generate a self-potential by applying a high-frequency bias to the substrate.

The present invention solves the above problems, and aims to provide a plasma processing apparatus that can improve the uniformity of plasma processing.

Means for Solving the Problems In order to solve the above problems, the present invention provides an electromagnet around a reaction chamber, and a power source for applying a DC current superimposed on an AC current to the electromagnet.

Effect With the above configuration, by applying a DC current superimposed with an AC current from the power source to the electromagnet, the isomagnetic interface vibrates in the axial direction of the magnetic field, and the divergent magnetic field and thus the self-potential also vibrate. Furthermore, since the distribution of the first isomagnetic surface also changes, the distribution of reactive species also changes. Therefore, the uniformity of plasma processing is improved compared to when a magnetic field is generated using only a DC current.

In addition, since the isomagnetic interface oscillates back and forth with respect to the substrate to be processed, the self-potential can be increased even when the substrate to be processed is closer to the reaction chamber than in the case of only DC current, and the deposition and Etching speed can be increased.

Example An embodiment of the present invention will be described below based on the drawings.

FIGS. 1(a) and 1(b) show an embodiment of the present invention.
FIG. 1 is a schematic plan view and a schematic cross-sectional view of a CR plasma processing apparatus. In FIGS. 1(a) and 1(b), a semiconductor substrate 4 is installed in a reaction chamber 3 to which a microwave introduction pipe 1 and a high vacuum exhaust port 2 are connected.

An electromagnet 5 is arranged around the reaction chamber 3, and an AC current 6 and a DC current g7 are connected in series to the electromagnet 5. The DC current 7 causes a DC current to flow through the electromagnet 5, and the AC current 6 is a few Hz expressed by I = Io cos ωt.
An AC current of several tens of KHz is superimposed on a DC current and applied to the electromagnet 5. An ECR region 8 is formed within the reaction chamber 3 .

In the above configuration, by applying an effective AC current to the electromagnet 5, for example, for a DC current of 2OA from the DC current 7,
The ECR region 8 vibrates with a width of ±0.7 cm. When the AC current is zero, the ECR region 8 is a microwave of 2.45 GHz.
It is adjusted so that it resonates in the TE□13 mode. By this AC current.

It was confirmed by changing the DC current that the self-potential fluctuated at a rate of ±2 V around -8 V. Furthermore, when etching polysilicon, the etching speed has increased from the conventional 70 nm/win to 12 nm/win.
Dramatically improved to 0nm/win, and the uniformity was better than the conventional ±
It improved from 5% to ±3%. Furthermore, since the control parameters for plasma generation have increased, the stability and reliability of the plasma processing apparatus has also improved.

Note that the magnitude and frequency of the AC current are set to optimal values depending on the size of the reaction chamber 3, the type of gas, the working pressure, and the installation position of the semiconductor substrate 4. Furthermore, as mentioned above, if the isomagnetic interface under ECR conditions is oscillated around a position that is an integer multiple of the microwavelength, a giant pulse-like ECR plasma can be generated like a laser using a Q switch, and deposition and Etching speed increases dramatically.

Effects of the Invention As described above, according to the present invention, since a superimposed AC current on a DC current is applied to the electromagnet, the isomagnetic interface vibrates in the axial direction of the magnetic field, improving the uniformity of plasma processing. The etching speed can be increased.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a schematic plan view and a schematic cross-sectional view of a plasma processing apparatus according to an embodiment of the present invention. 3...Reaction chamber, 4...Semiconductor substrate, 5...Electromagnet, 6...AC power supply, 7...DC power supply. 8...ECR area.

Claims (1)

[Claims] 1. A plasma processing apparatus equipped with an electromagnet around a reaction chamber and a power supply that applies a CD current superimposed on an AC current to the electromagnet.