JP2679816B2 - Plasma processing method - Google Patents

Description

The present invention relates to a plasma processing method and a plasma processing apparatus.

(Prior Art) In integrated circuit technology, 1M memory is already on the market, and 4M and 16M are the focus in development, always pursuing high integration. Silicon trench etching is required as one of the development factors for achieving this super integration. This silicon trench etching has become a technique absolutely necessary for device isolation or reduction of the two-dimensional area of a capacitor cell as the integration degree of IC is improved.
It is well known to those skilled in the art that a triode etcher has received attention as a means for this trench etching. For example, it is described in Japanese Patent Publication No. 57-44749.

(Problems to be Solved by the Invention) However, when trench etching with a high aspect ratio is performed, there are problems such as undercut, Si black, side wall roughness, and bowing.
Further, regarding the shape, it is necessary to satisfy the desired trench shape such as controlling the taper angle and round etching.

The present invention has been made in consideration of the above points, and provides a plasma processing method capable of performing a favorable trench etching shape while maintaining a high etching rate and a high selection ratio.

[Configuration of the invention]

(Means for Solving the Problems) According to claim 1 of the present invention, a first electrode and a second electrode are provided in a vacuum container so as to face each other, and a high-frequency power source and a pulse oscillator are connected to the first electrode and the second electrode, respectively. The third electrode is grounded between the electrode and the second electrode, and the high frequency power supplied from the high frequency power source is supplied to the first and second electrodes based on the pulse oscillation of the pulse oscillator. Plasma is generated to plasma-process the silicon on the second electrode,
A plasma treatment method is characterized in that silicon is etched by a gas containing SF ₆ while repeating generation and stop of plasma at substantially equal intervals of 5 milliseconds to 7.5 milliseconds.

(Function and effect) By generating the plasma intermittently, it is possible to set a replacement time for the by-products and residual gas inside the trench and the main etchant gas. Therefore, the influence of by-products and residual gas can be reduced. By supplying a fresh main etchant gas to the inside of the trench which can be reduced, it is possible to control the trench shape of the trench etching to a desired good shape.

(Example) Next, an example in which the present invention is applied to dry etching by a triode etcher will be described with reference to the drawings.

Airtight container as a vacuum container (1) For example, a rectangular container made of Al is used. This container (1) is surface-treated such as alumina (Al ₂ O ₃ ) so that it does not respond to the reaction gas.
It is processed on the surface. In such a container (1), three electrodes (2), (3) and (4) as a first electrode, a second electrode and a third electrode are arranged to face each other in order to generate plasma. That is, disc-shaped first and second electrodes (2) and (3) are provided in the vertical direction, and these electrode plates (2)
An intermediate electrode (4) is arranged between (3). The first and intermediate electrodes (2) and (4) have a mesh structure,
It has a structure that allows gas to pass through. An operating voltage is applied to each of the electrodes (2), (3) and (4) from outside the airtight container (1). For example, high frequency power, for example 13.56 MHz, is applied between the first and second electrodes (2) and (3) and the intermediate electrode (4). This high frequency power is supplied by high frequency power supplies (5) and (6) connected to the first and second electrodes (2) and (3), respectively. Further, pulse generators (7) and (8) are connected to the high-frequency power supplies (5) and (6), respectively, and each electrode (2) is based on the pulse generated by the pulse oscillators (7) and (8). It is controlled so that the high frequency power is applied to (3) and (4). Further, a gas introduction pipe (9) is connected to the container (1) so that a gas or the like that contributes to etching is supplied between the electrodes (2), (3) and (4). The first and intermediate electrodes (2) and (4) have a mesh structure, and the gas supplied through the gas introduction pipe (9) is the first and intermediate electrodes (2) and (4) having the mesh structure. ), And can be supplied to the surface of the silicon (hereinafter referred to as the wafer (10)) placed on the second electrode (3). Further, in order to exhaust the gas in the container (1), the exhaust duct (11) is connected to the container (1) to form a triode etcher.

Further, when the wafer (10) is loaded onto the second electrode (3) and is unloaded from the electrode (3), the electrode (3) is
Also, the structure may be relatively movable so as to widen the interval between the intermediate electrodes (4). Furthermore, in order to increase the adhesion ratio between the wafer (10) and the surface of the second electrode (3), the second electrode (3) has a structure in which the surface center portion of the second electrode (3) has a protruding curvature, and the peripheral portion is Alternatively, the ring-shaped pressing mechanism may be pressed from above.

Next, the etching method using the triode etcher will be specifically described.

The wafer (10) is loaded onto the second electrode (3).
Next, from the gas introduction pipe (9), etching reaction gas such as SF ₆ gas flow rate 100SCCM, O ₂ gas flow rate 80SCCM, and Kr
A gas flow rate of 150 SCCM is supplied into the container (1) to keep the internal pressure of the airtight container (1) at a constant pressure, for example, 0.6 TORR. At this time, the supply gas passes through the first electrode (2) as described above, further passes through the intermediate electrode (4), and is supplied to the wafer (10) on the second electrode (3). Exhausted by (11). Also, at this time, the first and second electrodes (2) and (3) with respect to the intermediate electrode (4), high-frequency power of 13.56 MHz, respectively, for example, 400 W for the first electrode (2) and the second electrode (3) To 200W
Is applied from the high frequency power supplies (5) and (6). The high-frequency power is controlled by the pulse oscillators (7) and (8), respectively, so that the output time and the stop time of the high-frequency power are respectively desired as shown in FIG.

A trench etching shape due to the influence of this intermittent operation is shown in FIG.

(A) figure shows the case where plasma is continuously generated, (b) figure repeats operation of plasma generation for 3.8 msec, plasma stop for 3.8 msec, (c) figure similarly, for example Plasma generation 5msec, plasma stop 5m
sec, (d) figure shows plasma generation 7.5msec, stop 7.5ms
The case where each operation of ec is repeated is shown. In the figure (a), undercut and Si black are generated. Next, as shown in Figure (b), undercutting and reduction of Si black were observed by performing pulse discharge.
In the figure (c), the Si black disappeared, but some undercut still occurred. Furthermore, in FIG.
Undercut and Si black disappear, and good shape is obtained.

As can be seen from this figure, anisotropic trench etching using low-temperature plasma is performed by etching silicon with a gas containing SF ₆ while repeating plasma generation and stop at approximately equal intervals of 5 ms or more and 7.5 ms or less. The trench shape can be improved.

In the above embodiment, the intermittent discharge of the plasma by the pulse control is explained as the duty ratio of 1: 1 (generation of plasma: stop of plasma), but the invention is not limited to this, and the first electrode, the second electrode Although the electrodes were pulse-controlled at the same time, only one electrode may be controlled, and the optimum value can be freely determined by adapting to various processes.

As described above, according to this embodiment, during the process of converting the etching gas into plasma and etching, by generating the above-mentioned plasma intermittently by controlling by pulse oscillation or the like, by-products and residuals inside the trench are generated. It is possible to set a replacement time between the gas and the main etchant gas, so that the effects of by-products and residual gas can be reduced, and by constantly supplying a fresh main etchant gas inside the trench, the trench shape for trench etching can be reduced. Can be controlled to a desired good shape.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a trench etcher for explaining one embodiment of the method of the present invention, FIG. 2 is an explanatory diagram of an output waveform of a pulse oscillator for a high frequency power source in FIG. 1, and FIG. 3 is a trench according to the method of FIG. It is a groove shape explanatory view of etching. 1 ... Container, 2,3,4 ... Electrodes 5,6 ... High frequency power supply, 7,8 ... Pulse oscillator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 60-201631 (JP, A) JP 62-276829 (JP, A) JP 61-8925 (JP, A) JP 62- 163326 (JP, A) JP 62-128526 (JP, A) JP 61-190944 (JP, A)

Claims (1)

(57) [Claims] 1. A first electrode and a second electrode are provided to face each other in a vacuum container, a high frequency power source and a pulse oscillator are connected to each, and a third electrode is provided between the first electrode and the second electrode. The electrode is grounded, and high-frequency power supplied from a high-frequency power source is supplied to the first and second electrodes based on pulse oscillation of the pulse oscillator to generate plasma to generate plasma on the second electrode. Plasma treatment of the silicon, and etching the silicon with a gas containing SF ₆ while repeating plasma generation and stop at substantially equal intervals of 5 milliseconds to 7.5 milliseconds.