RU2461091C1 - Method of determining irregularities in semiconductor material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: in the method of determining irregularities in semiconductor material, involving anodic oxidation of the surface of a solid-state body made of semiconductor material in an aqueous electrolyte solution and subsequent visual determination of the location of irregularities on the surface of the solid-state body, according to the invention, the aqueous electrolyte solution used is aqueous phosphoric acid solution with concentration from 0.05 to 0.1 M; the electrolysis process is carried out for 0.5-5.0 s at constant voltage of 30-130 V, wherein the location of irregularities on the solid-state body made of semiconductor material is determined from the location of areas on the surface whose colour or colour hue is different from that the rest of the surface of the solid-state body.

EFFECT: aggressive chemical agents are not used when realising the method.

Description

The invention relates to the field of electronic technology and can be used to control the quality of conductive layers and surfaces of semiconductor films used in the manufacture of microelectronics products, for example light-emitting diodes and photodetectors.

Known methods for determining inhomogeneities in semiconductor materials due to defects in their structure, foreign inclusions, the presence of areas with uneven doping, which are based on electrochemical oxidation of the surface of the investigated film.

A known method for determining inhomogeneities in semiconductor films [JP 57056941], which includes the formation of a thin conductive film on the studied semiconductor film and subsequent electrolysis in a solution of phosphoric, acetic, nitric acid using the studied semiconductor film as the anode. In the process of electrolysis, an oxide film is formed in those parts of the formed thin conductive film that are located on top of the locations of the inhomogeneities present in the test film, since these areas have a higher electrical conductivity. At the same time, under the influence of an acid used as an electrolyte, etching of sections of a thin conductive film that is not protected by an oxide film occurs. Then, the localization of inhomogeneities in the studied semiconductor film is visually determined, which corresponds to the localization on its surface of the areas covered by the oxide film.

The method under consideration is complex, which is associated with the need for preliminary application of a thin conductive film to the studied film.

A known method for determining inhomogeneities in a semiconductor material, in particular in a crystalline film of silicon carbide [JP 63025943], which is selected by the authors as the closest analogue.

The method under consideration includes anodic oxidation of the surface of a semiconductor film in an aqueous electrolyte solution. An aqueous solution of hydrofluoric acid is used as an aqueous electrolyte solution, the electrolysis process is carried out for 30 s to 10 min at a constant voltage of 5 to 15 V. At the same time, the formed oxide film is etched under the influence of hydrofluoric acid used as an electrolyte. Then examine the etched surface of the investigated semiconductor film using an optical microscope and visually determine the location of inhomogeneities in it.

The disadvantage of this method is the need to use special optical equipment, namely a microscope, which complicates the method. In addition, for the etching of the oxide film in the considered method, an aggressive chemical agent is used - hydrofluoric acid, which refers to harmful compounds.

The task of the invention is the creation of a new method for determining inhomogeneities in a semiconductor material.

The essence of the claimed invention lies in the fact that in the method for determining inhomogeneities in a semiconductor material, comprising anodic oxidation of a solid surface of a semiconductor material in an aqueous electrolyte solution and subsequent visual determination of the location of inhomogeneities on the surface of a solid, according to the invention, an aqueous electrolyte solution is used phosphoric acid solution with a concentration of from 0.05 to 0.1 M, the electrolysis process is carried out for from 0.5 to 5.0 s at tinuous voltage of from 30 to 130, wherein the irregularities on the locations of the solid body of semiconductor material is judged by its location on the surface portions, the color or color tone is different from the color or hue of the remaining surface of the solid.

In the inventive method, as a result of electrolysis, an oxide film is formed from the semiconductor material on the surface of the solid under study. In the course of experimental studies, the authors selected an electrolyte and anodic oxidation regimes in which an oxide film of small thickness (not more than 1 μm) is formed on the surface of a solid. The color of said thin oxide film is determined by its optical thickness, which is directly proportional to the film thickness. The surface areas with higher electrical conductivity corresponding to the locations of inhomogeneities in the solid under study oxidize faster, the oxide film above these areas has a greater thickness and, accordingly, differs in color tone from the color tone of the oxide film on the rest of the surface. In this case, the oxide film formed over inhomogeneities, which are inclusions of a substance of a different chemical nature, may have a different color than the color of the oxide film over the rest of the surface.

That is, by the presence and location of sections of the oxide film, the color tone or color of which differs from the color or color tone of the remaining surface of the oxide film, we can visually judge the presence and location of heterogeneities present in the studied solid. In this case, the visual determination of inhomogeneities can be carried out with the naked eye or, in the case of studies of relatively small solid bodies, using an optical microscope.

When the electrolysis time is more than 5.0 s, the optical properties of the resulting oxide film are equalized by its volume, which reduces the sensitivity of the visual determination of inhomogeneities.

If the voltage exceeds 130 V, breakdown of the oxide film may occur, which leads to disruption of the anodic oxidation process.

When the electrolysis time is less than 0.5 s, the oxide film available for observation does not have time to form on the surface of the investigated solid.

Important in the claimed method is the choice as an electrolyte of an aqueous solution of phosphoric acid with a concentration of 0.05 to 0.1 M, which provides sufficient conductivity for the electrochemical process and does not have a destructive effect on the oxide film.

When the concentration of phosphoric acid in the aqueous solution is less than 0.05 M, the electrolyte conductivity becomes too low. At a concentration of phosphoric acid in an aqueous solution of more than 0.1 M, due to an increase in the viscosity of the electrolyte, the movement of reagents near the surface of the oxidized solid slows down, and the oxide film does not have time to form during the indicated electrolysis time.

Thus, the technical result achieved by using the claimed invention is the creation of a new method for determining inhomogeneities in a semiconductor material based on the visual determination on the surface of the investigated solid body of areas whose color tone or color differs from the color tone or the color of the rest of the solid surface.

The inventive method is as follows.

An electrochemical process is carried out to oxidize the test solid from a semiconductor material in an electrolyte solution, which is used as an aqueous solution of phosphoric acid with a concentration of from 0.05 to 0.1 M, while the test solid serves as an anode. As the cathode material, for example, platinum, graphite can be used. The process is conducted at a constant voltage of 30-130 V for 0.5-5.0 s. During electrolysis, an oxide film forms on the surface of the test solid.

At the end of the electrolysis process, surface areas of the solid under study are visually determined, the color or hue of which differs from the color or color tone of the remaining surface of the solid, and the presence and locations of these sections are used to judge the presence and locations of heterogeneities present in the solid under study. In this case, the visual determination of inhomogeneities can be carried out with the naked eye or, in the case of studies of relatively small solid bodies, using an optical microscope.

The possibility of implementing the proposed method is shown in examples of specific performance.

Example 1

The presence of heterogeneities in gallium arsenide was determined.

Anodic oxidation of the test sample was carried out in an aqueous solution of phosphoric acid with a concentration of 0.05 M.

The electrolysis process was conducted at a constant voltage of 30 V for 0.5 s. During electrolysis, an oxide film formed on the surface of the test solid film. At the end of the process, the oxidized surface of the test film was visually examined. It was found that most of the surface of the film had a light blue color, while surface areas having a yellow color were observed. The presence and location of sites with yellow color were used to judge the presence and location of heterogeneities present in the gallium arsenide film.

Example 2

The presence of heterogeneities in the gallium antimonide sample was determined.

Anodic oxidation of the test film was carried out in an aqueous solution of phosphoric acid with a concentration of 0.05 M.

The electrolysis process was conducted at a constant voltage of 130 V for 0.5 s. During electrolysis, an oxide film formed on the surface of the test solid film. At the end of the process, the oxidized surface of the test film was visually examined. It was found that most of the surface of the film was cyan, with surface portions having a darker blue color being observed. The presence and location of areas with a darker blue color were used to determine the presence and location of heterogeneities present in the gallium antimonide sample.

Example 3

The presence of heterogeneities in the sample of indium antimonide was determined.

Anodic oxidation of the test film was carried out in an aqueous solution of phosphoric acid with a concentration of 0.1 M.

The electrolysis process was conducted at a constant voltage of 100 V for 5.0 s. During electrolysis, an oxide film formed on the surface of the test solid film. At the end of the process, the oxidized surface of the test film was visually examined. It was found that most of the surface of the film had a light blue color, while surface portions having a darker blue color were observed. In addition, dotted areas of red color were observed. The presence and location of areas with darker blue and red areas were judged on the presence and location of heterogeneities present in the indium antimonide film.

Claims (1)

A method for determining inhomogeneities in a semiconductor material, including anodic oxidation of a solid surface from a semiconductor material in an aqueous electrolyte solution and subsequent visual determination of the location of inhomogeneities on the solid surface, characterized in that an aqueous solution of phosphoric acid with a concentration of from 0 is used as an aqueous electrolyte solution , 05 to 0.1 M, the electrolysis process is carried out for from 0.5 to 5.0 s with a constant voltage of 30 to 130 V, while eniya inhomogeneities in the solid semiconductor material is judged by its location on the surface portions, the color or color tone is different from the color or hue of the remaining surface of the solid.