JPH06252116A - Formation of game insulating film - Google Patents

Abstract

PURPOSE:To form a gate insulating film having excellent characteristics, such as the breakdown field intensity, TDDB, etc. CONSTITUTION:After exposing the clean surface of a single-crystal Si substrate 11 by removing an unnecessary layer 12, such as a contaminated layer, natural oxide film, etc., on the substrate 11, the substrate 11 is transferred to a process for forming an insulating film 13 and the film 13 is formed on the substrate 11 while the surface of the substrate 11 is maintained in a clean state. Since the existence of the unnecessary layer 12, such as the contaminated layer, natural oxide film, etc., is completely eliminated from the process for forming the gate insulating film 13, the characteristics of the gate insulating film 13, such as the breakdown field intensity, TDDB, etc., of the film 13 are remarkably improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a gate insulating film used in a miniaturized MOS integrated circuit.

[0002]

2. Description of the Related Art Conventionally, a gate insulating film has been formed by performing necessary pre-cleaning in a cleaning tank and then forming the gate insulating film in a high temperature oxidation furnace.

[0003]

However, in the conventional method for forming a gate insulating film, the gate insulating film is formed in a high temperature oxidation furnace after once removing unnecessary layers such as a contaminated layer and a natural oxide film in a cleaning process. By the time it is started, single crystal Si
There is a problem that an unnecessary layer such as a natural oxide film is formed on the substrate and the quality of the gate insulating film is deteriorated.

[0004]

In order to solve the above problems, the present invention removes a contaminated layer on a single crystal Si substrate, an unnecessary layer such as a natural oxide film, and exposes a clean single crystal Si substrate surface. After that, the process proceeded to the gate insulating film forming step while keeping the surface in a state of clean single crystal Si, and the gate insulating film was formed.

[0005]

In a miniaturized MOS integrated circuit, especially a MOS integrated circuit designed by the submicron design rule, a very thin gate insulating film having a film thickness of 200 Å or less is used. In the case of such an extremely thin gate insulating film, even if it is an extremely thin layer of several 10 Å or less before its formation,
If an unnecessary layer such as a natural oxide film remains, it affects the characteristics of the gate insulating film.

Since the contaminated layer and the unnecessary layer such as the natural oxide film are formed unintentionally in the cleaning liquid, in the atmosphere, etc., it is very difficult to strictly control the contamination and accurately control the film quality and the film thickness. . The presence of such an unnecessary layer such as a natural oxide film deteriorates the characteristics after the gate insulating film is formed. By completely eliminating the existence itself of the contaminated layer, the natural oxide film and the like from the process of forming the gate insulating film, the film properties such as the breakdown electric field strength and the TDDB property are significantly improved.

[0007]

1 (a) to 1 (c) are sectional views showing schematic views in the order of steps of a method for forming a gate insulating film according to the present invention. Figure 1
In (a), 11 is a single crystal Si substrate, 12 is a contamination layer,
Indicates an unnecessary layer such as a natural oxide film. FIG. 1B shows a state in which the unnecessary layer is removed and the clean single crystal Si substrate surface is exposed.

FIG. 1 (c) shows a structure in which the gate insulating film 13 is formed on the surface of a clean single crystal Si substrate when the unnecessary layer 12 is formed.
It shows a state in which the existence of is completely eliminated.

[0009]

As described above in detail, the method of forming a gate insulating film according to the present invention eliminates the influence of an unwanted layer such as a contaminated layer or a natural oxide film, and greatly improves the characteristics of the gate insulating film. It has excellent features that make things possible.

[Brief description of drawings]

1A, 1B, and 1C are cross-sectional views schematically showing the order of steps of a method for forming a gate insulating film according to the present invention.

[Explanation of symbols]

 11 Single crystal Si substrate 12 Contamination layer, unnecessary layer such as natural oxide film 13 Gate insulating film

Claims (5)

[Claims] 1. A method for forming a gate insulating film used in a MOS transistor, wherein a contamination layer existing on a single crystal Si substrate, an unnecessary layer such as a natural oxide film, is removed to expose a clean single crystal Si substrate surface. A method of forming a gate insulating film, comprising the step of forming a gate insulating film while maintaining a state in which a clean single crystal Si substrate surface is exposed. 2. The unnecessary layer according to claim 1, wherein the method for removing the unwanted layer such as the contaminated layer and the natural oxide film includes a step of performing a high temperature heat treatment in a vacuum or reduced pressure atmosphere. Removal method. 3. The method for removing the contaminated layer, the unnecessary layer such as a natural oxide film, includes a step of performing high temperature heat treatment in an atmosphere having a reducing action such as hydrogen, or in a reduced pressure atmosphere thereof. 5. The method for removing an unnecessary layer according to claim 1. 4. As a method of shifting to the step of forming a gate insulating film while maintaining the state where the clean single crystal Si substrate surface is exposed, removal of an unnecessary layer in the same chamber shielded from the outside air. The method for forming a gate insulating film according to claim 1, wherein a series of steps from the step of forming the gate insulating film to the step of forming the gate insulating film are performed. 5. As a method for shifting to the step of forming a gate insulating film while maintaining the state where the clean single crystal Si substrate surface is exposed, as a method, a plurality of chambers isolated from outside air and between the chambers are provided. The method for forming a gate insulating film according to claim 1, wherein a series of steps from removal of the unnecessary layer to formation of the gate insulating film are performed in an apparatus having a wafer transfer mechanism.