JPS6179229A - Formation of electrode - Google Patents

Abstract

PURPOSE:To form the extra minute pattern having a little plasma damages on a wafer effectively by causing the radical excited by microwaves and the radical excited by laser beams to act on a polycrystalline semiconductor layer. CONSTITUTION:A plasma and the radical which is electrically neutral are produced by introducing an Si(CH3)4 gas from an opening of a transportation pipe 5 and using a microwave for a periphery of a plasma generating chamber 7 from a microwave waveguide 8. Those plasma and radical are introduced into a crystal container 1 in which a semiconductor wafer 3 is placed with being in parallel to the wafer 3 through the transportation pipe. Also, Cl2 gas is introduced into the container 1 through a gas line. Then an etching plane of the wafer 3 is irradiated with vertical laser beams. As a result, the competitive reaction between the deposition action by the radical whose life is prolonged by the microwave and the etching action excited by the laser beams attains the extra minute anisotropic etching of a little damages.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a method for forming electrodes such as gate electrodes suitable for VLSI manufacturing processes, and particularly for efficiently etching ultrafine patterns in the submicron region to obtain high anisotropy. This invention relates to an electrode forming method.

(Background technology and its problems) Currently, in order to form fine patterns with a line width of 2 μm or less required for processing gate electrodes and wiring parts in the VLSI process,
Anisotropic etching is performed by reactive ions accelerated by an electric field in plasma, and this etching is performed using RIE (Reactive Ion E).
It is called tchino). The surface of the silicon semiconductor substrate or gate oxide film will be severely damaged by the impact of reactive ions accelerated by this electric field.

In order to explain this phenomenon, FIGS. 3(a) and 3(b) show
The answer is yes to form a gate electrode, and first a gate oxide film 10 is formed on the surface of the silicon semiconductor wafer 3. Next, a polycrystalline silicon layer 20 is deposited on the surface of the gate oxide film 1o, and a resist 30 is selectively formed thereon (FIG. 3(a)). Using this resist 30 as a mask, the polycrystalline silicon layer 20 is deposited. 20 is dry-etched using reactive ions, and the polycrystalline silicon 20 under the resist 30 is used as a gate electrode. (Figure 3(b)). In this etching process, the surface of gate oxide film 10 is damaged by the impact of reactive ions.

In addition, a phenomenon of destruction of the gate oxide film 20, which is thought to be caused by the charging of reactive ions, has been reported, and more recently, J Damage has also been reported.

For this reason, etching with radicals excited by ultraviolet rays has been proposed as one method for realizing etching that does not cause plasma damage. However, it is not possible to perform anisotropic etching by simply generating radicals through ultraviolet irradiation. To achieve anisotropic etching, an electric field perpendicular to the surface to be etched is applied to drive the reactive ions vertically. However, in this method, the wafer surface is damaged by the impact of reactive ions.

As an anisotropic etching device using this optical excitation, the one shown in FIG. 2 has been proposed. In the figure, a wafer 3 as an object to be etched placed on a support stand 2 is loaded in a quartz container 1. As shown in FIG. This wafer 3 has, for example, a silicon substrate on which polycrystalline silicon is deposited. A photoresist 4 is selectively formed on the surface of the wafer 3 as a mask for etching. Further, a mercury lamp 5 is provided outside the quartz container 1, and its irradiation light is set to be parallel to the wafer 3.

In such an apparatus, CI2+ S i (
CH3)4/H(+ mixed gas is introduced, and the introduced mixed gas is decomposed by irradiating mercury lamp light (wavelength 253.7 nm) parallel to the material surface of polycrystalline silicon 3 from mercury lamp 4, While a thin film is deposited to form a sidewall protective film, etching of the polycrystalline silicon 3 progresses due to optically excited radicals by irradiating the sample surface of the polycrystalline silicon 3 with laser light (wavelength 308nl) perpendicularly at the same time. Etching progresses due to a competitive reaction between this etching and the thin film deposition, and on the etched sidewalls, this thin film acts as a protective film to prevent undercuts and achieve anisotropic etching.

However, such etching methods suffer from non-uniform competitive reactions due to wafer warpage and steps that occur in the latter half of the wafer process. The reason for this is that deposition caused by lateral ultraviolet irradiation increases the height of photodecomposition due to wafer warping or steps, and changes the deposition rate. It is also stated that the deposition rate is faster on the surface.

For this reason, it is difficult to uniformly etch the entire surface of a wafer, and many control elements are required to control the competing reactions in step operations such as those found in reduction projection exposure apparatus.

(Purpose) The present invention has been made in view of the problems of the etching methods already proposed as described above, and is based on the deposition effect of radicals excited by microwaves and having a longer life, and on the etching of semiconductors. To provide a method for forming electrodes by fine anisotropic dry etching, which causes less plasma damage seen in normal etching using plasma, due to competitive reaction with etching caused by radicals excited by laser light irradiated perpendicularly to the surface. It is something.

(Example) Hereinafter, the present invention will be described in detail using etching of polycrystalline silicon in a gate electrode as an example.

FIG. 1 shows a manufacturing apparatus according to the etching method of the present invention. In the figure, a transport pipe 6 extends from the left side of a quartz container 1, and its end is open.

Further, a plasma generation chamber 7 is provided near the end of the transport pipe 6, and a microwave waveguide 8 is attached around the plasma generation chamber 7.

In this configuration, 5t (CI-
13>4 gas is introduced, and a microwave (2,45
GHz) to generate plasma and electrically neutral radicals. While plasma excited by microwaves has a relatively long life, radicals have a long life, and are transported through a transport pipe 5 into a quartz container 1, which is a reaction chamber loaded with a semiconductor wafer 3. It is introduced parallel to C3. On the surface of wafer 3, there is a
As shown in the figure, the stratum corneum is formed. Further, a gas line is provided in the container 1 separately from the transport pipe 5, and C12 gas is introduced through this line. Then, a laser beam (X
e C (wavelength: 308 nm) is irradiated. Then, ultrafine anisotropic etching with little damage can be achieved through a competitive reaction between the deposition action of radicals whose lifetime has been extended by microwaves and the etching action of radicals excited by laser light.

The long-lived radicals introduced into the reaction chamber at this time are uniformly distributed within the chamber, which solves the problems of wafer warpage and step shape, and enables uniform anisotropic dry etching over the entire wafer surface. In addition, in the case of direct etching with a laser beam without using a resist in the apparatus shown in FIG. According to such a method, a stepping operation seen in a reduction projection exposure apparatus may be applied.

Furthermore, in FIG. 1, the generated radicals are introduced from the lateral direction to the wafer 3, but in order to improve uniformity, the radicals may be introduced from above. In that case, the laser Quartz 1, avoiding the part that is irradiated with light.
By irradiating from the surrounding area, the influence of the irradiation direction can be suppressed.

(Effects) As described above, according to the present invention, it is possible to efficiently form an ultra-fine pattern with less plasma damage on a semiconductor wafer to be etched.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of an etching device according to the formation method of the present invention, FIG. 2 is a diagram showing a conventionally proposed etching device, and FIGS. 3(a) and (b) are diagrams showing a method for forming a gate electrode. These are cross-sectional views in the order of steps. 1... Quartz container 2... Support stand 3... Semiconductor wafer 4... Mask 5... Mercury lamp 6...・Transport pipe 7...Plasma generation chamber 8...Microwave introduction pipe 9...Gas line 10...Gate oxide film 20... Polycrystalline silicon 30...Resist

Claims (1)

[Claims] An electrode forming method in which an oxide film is formed on a semiconductor wafer, a polycrystalline semiconductor layer is deposited on the oxide film, and then the polycrystalline semiconductor layer is selectively etched and the remaining polycrystalline semiconductor layer is used as an electrode. As the etching means, radicals excited by microwaves are applied to the polycrystalline semiconductor layer, and the anisotropic property is created by a competitive reaction with the deposition action of the radicals excited by the microwaves. A method for forming an electrode, characterized in that etching is performed.