JPH09148567A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which can form an LDD spacer without damaging a gate oxide film and a silicon substrate, in a process for forming an LDD spacer in a semiconductor device. SOLUTION: A gate oxide film 2 is formed by oxidizing substrate silicon, a polycrystalline silicon film 3 is formed on the gate oxide film 2, insulating material is formed on the polycrystalline silicon film 3, patterning is performed by using photolithography technique, and then a gate electrode is formed by working in order the insulating material and the polycrystalline silicon. By exposing the gate electrode to inert gas plasma, an LDD spacer 7 can be formed without damaging the gate oxide film 2 and a silicon substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming an LDD spacer.

[0002]

2. Description of the Related Art Conventional LDD in the manufacture of semiconductor devices
As one of spacer processing techniques, there is a semiconductor dry etching technique (Tokuyama Unbiased) shown on page 113.

A conventional technique will be described with reference to FIG. After cleaning the surface of the substrate silicon 12 with dilute hydrofluoric acid, a silicon oxide film 13 as a gate oxide film is formed with a film thickness of 8 nm by a thermal oxidation method, and a 250 nm film is formed as an upper wiring layer of the ultrathin silicon oxide film 13. A thick polycrystalline silicon film 14 was formed by thermal decomposition of monosilane (SiH ₄ ) and patterned with a photoresist 15 (FIG. 3a), and then polycrystalline silicon was etched to form a gate electrode (FIG. 3b). . After forming the gate electrode, a silicon oxide film 16 of about 200 nm is formed on the upper layer of the gate electrode by a thermal oxidation method (FIG. 3c), and the silicon oxide film 16 is etched by anisotropic etching to form an LDD spacer 17. (Fig. 3d). At this time, damage 1 to the silicon substrate
8 is formed. FIG. 4 is a schematic view of a dry etching apparatus usually used for forming a LDD spacer 17 by etching a conventional silicon oxide film 16, which is a parallel plate type reactive ion etching apparatus having an upper electrode 19 and a lower electrode 20. is there. 30 SCCM of CF4 and 20 SCCM of CHF3 were introduced from the gas inlet 21, the pressure in the reaction chamber was set to 0.10 Torr, and a high frequency power of 1000 W was applied from the high frequency power supply 22. The etching end point of the silicon oxide film 16 is determined by observing the change in the emission intensity of silicon during etching. For example, the etching end point of the silicon oxide film 16 is set when the emission intensity rises by 30% from the minimum value.

[0004]

As described above, in the conventional method, anisotropic etching is used in etching the silicon oxide film, so that a thin gate oxide film of about 8 nm is etched and damages the substrate. Will give. Further, in a terrible case, the substrate may be etched, which may cause an abnormal shape.

[0005]

According to the method of manufacturing a semiconductor device of the present invention, in the step of forming an LDD spacer in a semiconductor device, a step of oxidizing a substrate silicon to form a gate oxide film, and a step of forming a gate oxide film on the gate oxide film are performed. At least a step of forming a conductive film to be a gate electrode, a step of forming an insulator on the conductive film, and a step of exposing the conductive film and the insulating film to plasma of an inert gas after patterning. . The method for manufacturing a semiconductor device of the present invention is characterized by using a silicon oxide film as the insulator.

The method of manufacturing a semiconductor device of the present invention is characterized in that argon is used as the inert gas.

[0007]

According to the method of the present invention, the LDD spacer can be formed by utilizing the insulating film on the gate electrode without damaging the gate oxide film and the silicon substrate by exposing to the plasma of the inert gas. It has the effect of being able to.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

FIG. 2 is a schematic view of a plasma device used to form an LDD spacer in this embodiment, which is a downstream type plasma device having an upper electrode 8 and a lower ground electrode 9.

As an example, an LDD spacer was formed by the following process shown in FIG. After cleaning the surface of the substrate silicon 1 with dilute hydrofluoric acid, a silicon oxide film 2 is formed as a gate oxide film by a thermal oxidation method to a film thickness of 8 nm, and a 250 nm film is formed as a wiring layer above the ultrathin silicon oxide film 2. A thick polycrystalline silicon film 3 was formed by thermal decomposition of monosilane (SiH ₄ ), and a 200 nm thick silicon oxide film 4 was further deposited on this upper layer by plasma CVD and patterned with a photoresist (FIG. 1 a). After that, the silicon oxide film 4 and the polycrystalline silicon film 3 were sequentially etched to form a gate electrode (FIG. 1).
b).

Next, the wafer is placed in the plasma apparatus of FIG. 2, 50 SCCM of argon gas is introduced from the gas inlet 10, the pressure is set to 0.10 Torr, and the high frequency power source 1 is set.
A high frequency of 1000 W was applied from 1 to turn argon gas into plasma, and argon ions were generated. 2 in time
Applied for about a minute. As a result, the silicon oxide film 4 above the gate electrode was physically removed by argon ions (FIG. 1c) and redeposited on the side wall of the gate electrode below to form the LDD spacer 7 (FIG. 1d). As a result, the LDD spacer 7 could be formed without scraping the gate oxide film 2 and without damaging the silicon substrate 1.

Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the etching conditions and the apparatus described above.

[0013]

INDUSTRIAL APPLICABILITY The present invention has an effect that the LDD spacer can be formed without damaging the gate oxide film and the silicon substrate in the step of forming the LDD spacer in the semiconductor device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a process in an example of the present invention.

FIG. 2 is a schematic view of a plasma device used in an example of the present invention.

FIG. 3 is a sectional view of a step in an example of the related art.

FIG. 4 is a schematic view of a dry etching apparatus used in an example of the prior art.

[Explanation of symbols]

 1. Silicon substrate 2 Silicon oxide film (gate oxide film) 3 Polycrystalline silicon film 4 Silicon oxide film 5・ ・ Photoresist film 6 ・ ・ ・ ・ ・ ・ Argon ion 7 ・ ・ ・ ・ ・ ・ ・ ・ LDD spacer 8 ・ ・ ・ ・ Upper electrode 9 ・ ・ ・ ・ Lower electrode 10 ・ ・ ・ ・ ・ ・ ・ ・ Gas introduction Mouth 11 ... High-frequency power source 12 Silicon substrate 13 Silicon oxide film (gate oxide film) Polycrystalline silicon film 15 .. Photoresist film 16 .. Silicon oxide film 17 .. LDD spacer 18 .. Damaged part 19 .. Upper electrode 20 .. Lower part Electrode 21: Gas inlet 22: High frequency power source

Claims (3)

[Claims] 1. A step of forming a gate oxide film on a semiconductor substrate, a step of forming a conductive film to be a gate electrode on the gate oxide film, a step of forming an insulator on the conductive film, A method of manufacturing a semiconductor device, comprising: at least a step of patterning a conductive film and the insulating film into a desired shape and then exposing the conductive film and plasma to an inert gas plasma. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a silicon oxide film is used as the insulator. 3. The method of manufacturing a semiconductor device according to claim 1, wherein argon is used as the inert gas.