JPH0521567A - Evaluation method of silicon substrate surface irregularities - Google Patents

Abstract

(57) [Summary] [Structure] A silicon substrate is immersed in a mixed solution of hydrochloric acid (HCl) and hydrogen peroxide solution (H ₂ O ₂ ) to measure the amount of chlorine (Cl) taken in on the surface of the silicon substrate by X-ray analysis, etc. The surface roughness is quantitatively evaluated from the Cl amount by measuring a wide range at once. According to the measuring method of the present invention, it becomes possible to evaluate the atomic level unevenness on the surface of the silicon substrate at a time over a wide range of 10,000 times or more compared with the conventional method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atomic level unevenness evaluation method for a silicon substrate surface.

[0002]

2. Description of the Related Art Surface irregularities of a silicon substrate cause deterioration of the dielectric strength of an oxide film, and it is necessary to control the surface irregularities at the atomic level in a highly integrated circuit manufacturing process. Conventionally, the surface unevenness of a silicon substrate is obtained by observing the cross section of the substrate with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), a scanning tunneling microscope (STM) that scans the substrate surface with a probe, or an atom. Force microscope (A
It has been evaluated by measurement using FM).

[0003]

In the conventional measuring method,
There is a problem that the area where the surface irregularities can be evaluated becomes extremely narrow. For example, when evaluating surface irregularities at the atomic level using SEM and TEM, the cross-sectional area that can be observed at one time is about several hundred Å, and even in the case of STM and AFM that scans the surface with a probe, it is several tens of μm square. Only the area can be measured, and it is difficult to evaluate the surface unevenness at the atomic level over a wide range.

An object of the present invention is to provide a method for evaluating the surface unevenness of the surface of a silicon substrate at the atomic level over a wide range at once.

[0005]

The method of the present invention for evaluating the surface irregularities of the surface of a silicon substrate at the atomic level in a wide range at one time is a method using hydrochloric acid (HCl) and hydrogen peroxide solution (H).
₂ O ₂ ) A silicon substrate is immersed in a mixed solution, the amount of chlorine (Cl) taken into the surface of the silicon substrate is measured in a wide range at once by X-ray analysis, etc., and the surface roughness is quantitatively evaluated from the amount of Cl. It is a thing.

[0006]

[Function] In a mixed solution of hydrochloric acid (HCl) and hydrogen peroxide solution (H ₂ O ₂ ), the surface of the silicon substrate is oxidized by H ₂ O ₂ and
A natural oxide film of about Å is formed, but at this time chlorine (Cl) is taken into the natural oxide film. Since the surface area of the formed native oxide film increases as the surface irregularities increase, the amount of Cl taken in per unit area of the substrate increases as the surface irregularities increase. Therefore, it becomes possible to evaluate the surface irregularities by measuring the amount of Cl taken into the surface.

[0007]

[Example] It is known that when a silicon substrate is immersed in a mixed solution of nitric acid (HNO ₃ ) + hydrofluoric acid (HF) + pure water (H ₂ O), the surface roughness of the silicon substrate increases as the immersion time increases. There is. After immersing the silicon substrate in HNO ₃ + HF + H ₂ O mixed solution (composition ratio HNO ₃ : HF: H ₂ O = 45: 1: 70), hydrochloric acid (HCl) + hydrogen peroxide solution (H ₂ O ₂ ) + pure water (H ₂ O) mixed liquid (composition ratio HCl: H ₂ O ₂ : H ₂ O =
After being immersed in 1: 1: 5) for 10 minutes, washed with water, and dried, the amount of chlorine (Cl) incorporated in the surface of 1 cm ² was measured by total reflection fluorescent X-ray analysis. HNO ₃ + HF + H ₂ O
The relationship between the immersion time in the mixed solution and the amount of Cl is shown in FIG. H
It was confirmed that the amount of Cl taken into the surface of the silicon substrate during the immersion of the HCl + H ₂ O ₂ + H ₂ O mixed solution increased as the immersion time in the NO ₃ + HF + H ₂ O mixed solution increased, and the surface irregularities can be evaluated. I was able to confirm that That is, the surface roughness can be quantitatively evaluated by the chlorine content.

[0008]

According to the measuring method of the present invention, it is possible to evaluate the atomic level unevenness on the surface of a silicon substrate at a time over a wide range of 10,000 times or more compared with the prior art.

[Brief description of drawings]

FIG. 1 HNO ₃ + HF + H ₂ O mixed solution (HNO ₃ : H
After dipping the silicon substrate in F: H ₂ O = 45: 1: 70), a mixed solution of HCl + H ₂ O ₂ + H ₂ O (HCl: H ₂ O ₂ :
_{H 2 O = 1: 1:} 5) silicon substrate which is a diagram showing a Cl surface concentration after immersing 10 minutes.

Claims (1)

Claim: What is claimed is: 1. A silicon substrate is immersed in a mixed solution of hydrochloric acid and hydrogen peroxide solution, and the surface roughness is quantitatively analyzed based on the amount of chlorine taken into the surface of the silicon substrate. Evaluation method of substrate surface irregularities.