JPH0635664B2 - Thin film forming equipment by plasma processing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a thin film forming apparatus by plasma processing, and more particularly to a thin film forming apparatus using electron cyclotron resonance plasma.

[Conventional technology]

The apparatus of this type up to now, for example, as described in JP-A-56-155535, supplies a discharge gas to a plasma generation region where plasma is generated by electron cyclotron resonance due to the action of a microwave and a magnetic field. Is generated, and the reaction gas separately supplied by the generated plasma is decomposed to form a film on the substrate installed in the vacuum chamber.However, sufficient consideration has been given to the structure of these gas supply systems. There wasn't.

[Problems to be solved by the invention]

The above-mentioned conventional technique is excellent in that it can form a film over a large area while keeping the sample substrate at a low temperature. However, regarding the uniformity of the discharge gas concentration in the plasma generation region and the uniformity of the supply of the reaction gas in the sample plane direction, etc. However, there is a problem that the uniformity of the film formation rate is poor.

An object of the present invention is to solve these problems of the prior art, and a thin film forming apparatus comprising an electron cyclotron resonance plasma chemical vapor deposition apparatus in which the uniformity of the film forming rate is improved by specifying the structure of the gas supply system. To provide.

[Means for solving problems]

The above-mentioned object is to provide a magnetic field forming means and a microwave supply means for causing electron cyclotron resonance in at least a part of a vacuum chamber provided with a means for holding a sample substrate therein, and to discharge the vacuum chamber. In a thin film forming apparatus as an electron cyclotron resonance plasma chemical vapor deposition apparatus comprising a gas and a means for introducing a reaction gas, the means for introducing the reaction gas has a plurality of holes or holes for releasing the gas toward the sample surface. This is an annular structure having a slit, and the means for introducing the discharge gas is achieved by an annular structure having a plurality of holes or slits through which gas is emitted on the microwave supply side.

The characteristic points that are preferable conditions of the present invention will be listed below, and the configuration of the present invention will be described more specifically.

(1) A magnetic field forming means and a microwave supplying means are provided in a part of a vacuum chamber having a means for holding a sample substrate therein in order to cause electron cyclotron resonance, and a discharge gas and a microwave are supplied in the vacuum chamber. In a thin film forming apparatus comprising an electron cyclotron resonance plasma chemical vapor deposition apparatus provided with a means for introducing a reaction gas, the reaction gas introducing means has a plurality of ejection ports for releasing the reaction gas toward the center direction of the sample substrate surface. And a discharge gas introducing means, wherein the discharge gas introducing means is an annular structure having a plurality of ejection ports for discharging the discharge gas toward the microwave supply means opposite to the reaction gas introducing means. It is characterized by

(2) The size of the ring of the annular structure having the ejection port of the reaction gas is equal to or larger than that of the ring of the annular structure having the ejection port of the discharge gas, and the ejection port of the reaction gas An annular structure having an annular structure having a jetting outlet of the discharge gas in front of the microwave discharge part existing in a part of the vacuum chamber is provided in a region where plasma discharge is not generated on the sample substrate side. Characterize.

(3) The annular structure for supplying the reaction gas in the direction of the sample substrate is composed of a polygon including a circle, and the inner diameter is larger than the surface of the sample substrate.

(4) It is characterized in that the plurality of ejection ports for discharging the reaction gas have a tapered hole or slit structure with an enlarged opening diameter.

[Work]

The discharge gas is used to generate a plasma discharge by electron cyclotron resonance using a gas that does not cause film formation in the plasma discharge by itself. It has a great influence on the uniformity of the density of Pd, and as a result, it greatly affects the uniformity of the film formation rate on the sample substrate surface. For example, when the discharge gas is supplied from one inlet to the sample surface side as described in JP-A-56-155535, the concentration of the discharge gas is unevenly distributed and electrons in the plasma flow are distributed. Density is unevenly distributed, and it is difficult to obtain a uniform film formation rate. On the other hand, in the case of the present invention, the discharge gas is supplied to the microwave supply side from an annular structure having a plurality of holes or slits, and the discharge gas that is repelled by the wall surface is excited by plasma, The uniformity of electron density in the produced plasma stream is significantly improved.

The reactive gas refers to a gas species that causes film formation by its own plasma discharge, but in the present invention, the reactive gas is decomposed by the electrons in the plasma flow of the discharge gas and supplies the main constituent element of the thin film. JP-A-56-155535 shows an example in which a reaction gas is introduced through a supply port for a discharge gas, but this is not preferred in the present invention. In a pressure range of 10 m Torr or less, which is a general film forming condition, molecules do not collide with each other, and due to the difference in the mass of the reaction gas molecule and the electron, the reaction gas decomposition product changes its traveling direction even by electron collision. This is because in such a structure, film formation occurs on the microwave introduction path side and does not occur on the sample surface in the case of such a configuration. Therefore, in the present invention, it is necessary to supply the reaction gas toward the sample surface, and releasing it from the annular structure having a plurality of holes or slits has a great effect on improving the uniformity of the film formation rate. In this case, it is preferable that the hole or the slit-shaped gas outlet has a tapered shape or a double slit structure so that the gas discharge direction is restricted to the center direction of the sample substrate surface. In addition, the reaction gas blowing mechanism is located in a region where plasma discharge is not generated, plasma discharge due to the reaction gas does not occur, and the reaction gas is decomposed by electrons in the plasma flow of the discharge gas. It is effective for speed uniformity.
The inner diameter of the annular gas blowing mechanism for the reaction gas is larger than the film forming area of the sample substrate surface, which is effective for uniforming the film forming rate in the radial direction in the case of a circular sample substrate. When the inner diameter of the reaction gas blowing annular structure is small, the film forming rate in the central portion is large and the film forming rate in the peripheral portion is small, and uniform film formation is difficult, which is not preferable.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. First
The figure is an explanatory view of the structure of a thin film forming apparatus according to the present invention.

Reference numeral 1 is a magnetron, which normally generates a microwave of 0.1 to 10 GHz. The generated microwave is guided into the vacuum chamber 3 by the waveguide 2. Reference numeral 4 denotes a discharge tube, which is made of an insulating material (for example, quartz glass, ceramics such as alumina) in order to pass microwaves. Reference numeral 5 denotes a magnetic field generating means for forming a magnetic field in the vacuum chamber, which is composed of a solenoid coil. Reference numeral 6 is a sample substrate, and 7 is a sample table equipped with a heating mechanism. Reference numeral 8 denotes an exhaust port, to which a decompression pump (not shown) having a large exhaust speed such as a turbo molecular pump or an oil diffusion pump is connected. Reference numeral 9 is a discharge gas introduction pipe, and 10 is a reaction gas introduction pipe. A plurality of gas discharge portions of the discharge gas introduction pipe 9 are provided so as to discharge discharge gas in the direction of arrow 91 of the discharge pipe 4 to which microwaves are supplied. It has an annular structure with holes or slits. The gas releasing portion of the reaction gas introducing pipe 10 also has an annular structure having a plurality of holes or slits, but the reaction gas is emitted toward the sample surface as shown by arrow 101. Reference numerals 92 and 102 denote a discharge gas supply valve and a reaction gas supply valve, respectively. The above-mentioned reaction gas discharge portion is located at a position where it does not come into contact with the plasma flow of the discharge gas, that is, outside the contour line of magnetic force which comes into contact with the discharge tube open end. The gas outlet of the gas outlet of the reaction gas inlet pipe 10 is the second
As shown in the cross section in FIGS.
(Fig.) Or double slit-like structure (Fig. 3), and the emission direction of the reaction gas is restricted to the center of the sample substrate surface. Further, the inner diameter of the ring at the discharge portion of the reaction gas introducing pipe 10 is set to be larger than the film formation diameter of the sample substrate.

Next, the case where a SiO ₂ film is formed using this apparatus will be described. A silicon wafer is placed on the sample table 7 as the sample substrate 6, and oxygen is used as a discharge gas at a flow rate of 10 sccm (standard cc).
(abbreviation of per minute) was introduced through the discharge gas introduction tube 9, monosilane (SiH ₄ ) was introduced as a reaction gas through the discharge gas introduction tube at a flow rate of 5 sccm, and the pressure inside the vacuum chamber was set to 0.1 Pa. The maximum magnetic flux density of the discharge tube portion was set to 1500 Gauss, and 100 W of 2.45 GHz microwave was introduced to generate discharge to form a film. At this time, a SiO ₂ film could be formed with a uniformity of ± 3% in a region twice the cross-sectional area of the discharge tube. On the other hand, for comparison, when the discharge gas is introduced from the tip of the discharge tube to the sample substrate side, the uniformity is poor, and the area that satisfies ± 10% uniformity is narrower than the cross-sectional area of the discharge tube. When introduced from the side of the discharge tube in the lateral direction (that is, in the direction parallel to the sample substrate surface), the uniformity was even worse. Furthermore, the uniformity is poor even when the reaction gas is concentratedly introduced from one point of the introduction pipe, and only in the case of the embodiment of the present invention using a plurality of annular blowing portions, a uniform distribution with central symmetry is obtained. became. However, when the inner diameters of the plurality of annular blowing portions were smaller than that of the substrate 6, the area where uniform film formation was obtained was narrow. Further, when the blowing direction of the reaction gas was not directed to the center of the sample substrate surface, the film formation rate at the central portion was an M-shaped distribution.

Although the case of forming the SiO ₂ film has been described above, a similar tendency was obtained when nitrogen was used as the discharge gas to form the SiN film and when hydrogen was used as the discharge gas to form the amorphous silicon film.

〔The invention's effect〕

As described above, according to the present invention, it is possible to obtain a uniform film formation rate over a wide area of a sample substrate, which has the effects of improving productivity and quality, and makes a great contribution to industry.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an apparatus configuration according to an embodiment of the present invention, and FIGS. 2 and 3 are sectional views showing different embodiments of a reaction gas blowing portion. In the figure, 1 ... Magnetron, 2 ... Waveguide 3 ... Vacuum chamber, 4 ... Discharge tube 5 ... Solenoid coil, 6 ... Sample substrate 7 ... Sample stage, 8 ... Exhaust port 9 ... Discharge gas introduction pipes 9 and 10 ... Reaction gas introduction pipes

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Nakatani 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Hitachi, Ltd. Institute of Industrial Science (72) Inventor Tadashi Sonobe 3-chome, Hitachi-shi, Ibaraki No. 1 Stock company Hitachi Ltd. Hitachi factory

Claims (4)

[Claims] 1. A magnetic field forming means and a microwave supplying means for causing electron cyclotron resonance are provided in a part of a vacuum chamber having a means for holding a sample substrate therein, and a discharge is provided in the vacuum chamber. In a thin film forming apparatus comprising an electron cyclotron resonance plasma chemical vapor deposition apparatus provided with a gas and a means for introducing a reaction gas, the reaction gas introducing means includes a plurality of means for releasing the reaction gas toward the center direction of the sample substrate surface. An annular structure comprising an annular structure having jets, wherein the discharge gas introducing means has a plurality of jets for discharging the discharge gas to the microwave supply means side opposite to the reaction gas introducing means. An apparatus for forming a thin film by plasma treatment, comprising: 2. The size of the ring of the annular structure having the ejection port of the reaction gas is equal to or larger than that of the ring of the annular structure having the ejection port of the discharge gas, and An annular structure having an ejection port is provided in a region where plasma discharge is not generated on the sample substrate side through an annular structure having an ejection port of the discharge gas in front of a microwave discharge part which is a part of the vacuum chamber. An apparatus for forming a thin film by the plasma treatment according to claim 1. 3. The annular structure for supplying the reaction gas in the direction of the sample substrate is formed of a polygon including a circle, and the inner diameter of the annular structure is larger than the surface of the sample substrate. An apparatus for forming a thin film by the plasma treatment according to claim 1 or 2. 4. A plurality of jet outlets for discharging the reaction gas have a tapered hole or slit structure with an enlarged opening diameter. An apparatus for forming a thin film by the plasma treatment according to item 3.