RU2539872C1 - Microwave plasma processing device - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to etching and deposition of metal, semiconductors, dielectrics and lower pressures and can be used in production of solid-state device of high integration level. Proposed device comprises waveguide circuit enveloping reaction chamber sidewall. Several discharge tubes extend through waveguide circuit wide wall centre, perpendicular to the chamber. Magnetic field is applied to discharge tube inlet and outlet in waveguide circuit to induce conditions for electron cyclotron resonance. To allow identical plasma parameters, circular waveguide circuits are arranged and reaction chamber in tiers with the shift of discharge tubes in tiers relative to each other. Additionally, extra gas feed electrode is used.

EFFECT: better uniformity of silicon plate treatment, simplified plasma adjustment in every discharge tube.

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Description

The invention relates to microwave plasma systems for conducting etching and deposition of layers of metals, semiconductors, dielectrics at reduced pressures and can be used in technological processes for creating semiconductor devices with a high degree of integration.

A device for microwave plasma processing of materials at reduced pressures is known, consisting of a microwave generator, a rectangular waveguide tract intersected perpendicular to its wide wall with a quartz discharge tube connected to a reaction chamber, in turn, connected to a vacuum post. Reaction gases are supplied from special flowmeters to both the quartz tube and the area of the plate being processed. The other end of the waveguide path (opposite from the microwave generator) is connected to either a matched load or a short-circuit piston. Accordingly, either the traveling wave mode and the plasmatron on the traveling wave, or the standing wave mode and the plasmatron on the standing wave, are realized [“Theoretical and Applied Plasma Chemistry”. Polak L.S. and others, Science, 1975, p.21]. However, in this device it is difficult (impossible) to control (tune) the uniformity of processing plates of large diameter (more than 40 mm).

Known microwave plasma installation of the waveguide type of processing materials at reduced pressures, consisting of a microwave generator, a waveguide tract enveloping the reaction chamber and ending with a short-circuit piston or matched load. In several places, a wide wall of the waveguide path is crossed by quartz discharge tubes perpendicular to its surface, one end of which enters the reaction chamber, and gas (or gases) is supplied through the other. At the places of entry and exit of quartz tubes in the waveguide tract, a magnetic field is superimposed, and the conditions of electron cyclotron resonance (ECR) are realized. Plasma is ignited in the discharge tubes, which is “injected” into the reaction chamber, in which silicon wafers are processed (etched, deposited layers and films) [“Device for microwave plasma processing of large-diameter wafers” Collection of materials “3rd International Symposium on Theoretical and Applied plasmochemistry. ”- Ivanovo, 2002, volume 2, p. 472-474]. The disadvantages of the analogue are:

- it is difficult to adjust the same plasma burning in each discharge tube (the plasma density of the discharges in each tube is different);

- it is practically difficult to control the uniformity of processing on the plate (although it is possible).

The closest analogue (prototype) is known, a plasma processing device [RU 2368032 C1, H01L 21/3065, 09/20/2009], consisting of a reaction vacuum chamber with inputs of microwave plasma sources, the amount of which is unregulated, located perpendicular to the side wall, and located in the reaction a vacuum chamber of a heated or cooled pedestal for substrates having the possibility of vertical movement and the possibility of electric displacement relative to the plasma. Outside the chamber, above the placement of the substrates, an RF inductor is located on the pedestal, and the chamber wall, in the place where it adjoins the inductor, is made of a material transparent to the RF electromagnetic field. The main disadvantage of the device is the uneven processing of the plates (approximately 2%), which is especially true when switching to nanoscale thicknesses of functional layers and nanoscale topological elements.

The technical result of the invention is to improve the uniformity of the processing of silicon wafers, simplifying the setting of plasma combustion in each discharge tube.

The invention is illustrated in figure 1 and figure 2.

The technical result is achieved due to the fact that the waveguide path 1, enveloping the side wall of the reaction chamber 2, is circular and is excited from two diametrically opposite sides by means of waveguide tees. The waves in the opposite shoulders of the tees differ in phase by 180 ° and do not “see” each other. Therefore, the excitation of the ECR plasma in each discharge tube 3 passing through the center of the wide wall of the waveguide path and perpendicular to it, by applying a magnetic field using electromagnets 4 and magnetic circuits 5 at the points of entry and exit from the waveguide path, is performed from two microwave sources. The reflected waves coincide in phase with the incident wave in the opposite shoulder of the tee, that is, there is a “feed” of each source due to the reflected wave and, thereby, the efficiency of microwave energy of the generator and the uniformity of plasma burning in each discharge tube (plasma density in each discharge tube is almost the same). Thus, plasma is “injected” into the reaction chamber from all the discharge tubes with almost the same density into solid angles that intersect, and a region of decaying plasma is formed with a high degree of uniformity of plasma parameters into which the plate is placed. When processing plates up to 76 mm in diameter, the unevenness of processing is about 2 ÷ 3%. When processing plates up to 150 mm in diameter, the unevenness of processing is up to 5%. To reduce this uneven processing, the claimed invention consists of several tiers of plasma excitation in the reaction chamber, and the inlet of the discharge tubes into the reaction chamber of one tier are displaced relative to the other tier and are located exactly in the middle of the gap between the tubes of the adjacent tier. Thus, the uniformity of the parameters of the “technological” plasma in the reaction chamber increases and allows processing plates with a diameter of up to 150 mm with an unevenness of 1 ÷ 1.5%.

In order to be able to control the plasma parameters (technological process) using a constant or high-frequency bias field, an additional electrode 6, isolated from the body of the reaction chamber, is introduced into the reaction chamber. The heated stage 7 for accommodating the processed plates 8 is also isolated from the body of the reaction chamber.

To expand the technological capabilities of the device, the additional electrode mentioned above is made in the form of a “shower” 6 through which additional gases are introduced. To solve the same problem, a ring electrode (gas distributor) 9 is placed near the stage.

Claims (1)

A microwave plasma processing device containing a waveguide path enveloping the side wall of the reaction chamber, several discharge tubes pass perpendicular to the chamber through the center of the wide wall of the waveguide path, and a magnetic field is applied at the points of entry and exit of the waveguide path to create conditions for electron cyclotron resonance, characterized in that the waveguide paths, made circular, are located on the wall of the reaction chamber in tiers with the offset of the discharge tubes in tiers relative to each other, and an electrode is additionally introduced through which gases are introduced.

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