JPS5837981B2 - Selective processing method for a metal layer made of or containing Cr attached to a semiconductor surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In recent years, semiconductor devices using group 1 semiconductors, particularly GaAs# conductors, have been widely used, for example, in the field of semiconductor lasers.

In such a semiconductor device, for example, G. A metal layer as an electrode or wiring layer on the surface of a semiconductor made of aAs? It is required to be attached.

In this case, if the semiconductor made of GaAs is P-type, the metal layer may have a metal layer made of Cr or containing Or that is formed in contact with the semiconductor for various reasons. is normal.

For example, a metal layer made of Or is formed on the surface of the semiconductor by depositing Or while the temperature of the semiconductor is at 500°C, and on top of that, Au is deposited while the temperature of the semiconductor is set at 200 to 350°C. It has a metal layer made of Au formed by.

By the way, Cr attached to the surface of such a semiconductor
When a metal layer made of or containing Or is later processed into a desired shape, conventionally, the metal layer made of or containing Cr is chemically selectively etched or mechanically etched. It was common for the target to be removed.

However, in the case of chemical selective etching treatment, for example, an etchant consisting of a hydrochloric acid solution is used, but in this case, the surface of the semiconductor that is exposed by selectively etching the metal layer made of or containing Or. However, the old man had problems such as getting rough things.

In addition, when mechanical selective removal treatment is performed, for example, ion ring is performed, but in this case, the removal treatment is finished immediately after the metal layer made of Cr or containing Or is selectively removed. However, the removal process has disadvantages such as causing roughness on the surface of the semiconductor exposed.

Therefore, the present invention aims to propose a new method that can selectively process a metal layer made of or containing Or attached to a semiconductor surface without the above-mentioned drawbacks. The etching unnecessary area on the metal layer made of or containing Or attached to the semiconductor surface is coated with a coating that is resistant to an electrolytic solution that can anodize the semiconductor surface. The method is characterized in that a metal layer containing Or is subjected to an electrolytic etching process using the above electrolytic solution.

Here, a metal layer made of or containing Or (hereinafter referred to as
For simplicity, the reason why a metal layer made of Or or containing Cr is simply referred to as a metal layer made of Or is because the following points were confirmed.

That is, if an electrolytic solution capable of anodic oxidizing the semiconductor surface is used as the electrolytic solution, the metal layer made of Or is selectively etched away by the electrolytic etching process, and the exposed surface of the semiconductor is anodized, and the surface of the semiconductor is anodized. Then, an oxide film of the material constituting the semiconductor is formed.

Therefore, even if the electrolytic etching process is not terminated immediately after the metal layer made of Or is selectively etched away, the surface of the semiconductor will not be etched unnecessarily.

Furthermore, when the oxide film formed on the surface of the semiconductor is removed and the surface is looked at, no roughness is found on the surface.

Furthermore, if the metal layer made of Or is selectively etched away, an oxide film is formed on the surface of the semiconductor exposed by the removal, as described above, and this causes interference of the oxide film. It can be determined by the color or by the change in voltage between the anode and cathode (if the electrolytic etching process is carried out at a constant current) or the change in the current passing between the anode and the cathode (if the electrolytic etching process is carried out by a constant voltage). Therefore, it can be immediately determined that the metal layer made of Or has been selectively etched away.

Therefore, the electrolytic etching process can be finished immediately, and the metal layer made of Or can be easily processed in a short time without wasting time.

Furthermore, since the oxide film formed as described above can be easily removed using an acid solution or an alkaline solution, if necessary, the metal layer made of Or processed according to the present invention may be removed on the semiconductor surface. The area other than the area marked with can be secured as a normal, rough surface, and if the oxide film formed as described above is not removed, this will cause the surface of the semiconductor to deteriorate. According to the invention, regions other than the region to which the metal layer made of processed Or is attached can be protected.

Moreover, as a coating that is resistant to electrolytes that can anodize the semiconductor surface, a photoresist coating, which is widely used in itself, can be applied, and therefore, the coating can be obtained finely. Therefore, the metal layer made of Or can be finely processed.

The above is the reason for processing the metal layer made of Cr attached to the semiconductor surface according to the features of the present invention.

Next, embodiments of the present invention will be described with reference to the drawings.

It is housed in a suitable container 1.

For example, the external connection lead 3 is led out into an electrolytic solution 2 using a solution in which a tartaric acid solution is mixed with ethylene glycol or propylene glycol at a ratio (volume ratio) of 1:2 to 4. For example, a cathode 4 made of platinum or gold is arranged.

Further, an external connection lead 5 is provided in the electrolytic solution 2, and on the surface of a semiconductor made of, for example, P-type GaAs.
A metal layer consisting of a metal layer made of Or formed in contact with this and a metal layer made of Au formed on it is attached, and on the area of the metal layer that does not require etching,
A sample 6, which was coated with a coating resistant to the electrolytic solution 2 using Photoresis 1- (AZ=1350, etc.), was placed.

Therefore, a constant current or constant voltage source 7 is connected to the sample 6 between the lead 3 of the external connection cathode 4 and the external connection lead 5 of the sample 6.
The two sides were connected as anodes and electrolytically etched.

In such a case, the uncoated region of the metal layer consisting of the metal layer made of Cr and the metal layer made of Au attached to the surface of the semiconductor in the sample 6 is thoroughly etched away, It was confirmed that an oxide film of GaAs constituting the semiconductor was formed on the region of the semiconductor layer where the metal layer was etched away.

After performing such etching treatment, the GaAs oxide film was removed using an acid solution such as hydrochloric acid or an alkaline solution such as sodium hydroxide.

In this case, it was confirmed that a clean, unroughed semiconductor surface was exposed.

Further, using the above-mentioned sample 6, a mixed solution of, for example, potassium iodide and iodine was applied to the metal layer made of Au.
Chemical etching was performed using an etchant to expose the metal layer made of Or, and then the sample in which the metal layer made of Or was exposed in this way was designated as the above-mentioned sample 6. A similar electrolytic etching process was performed.

In such cases, results similar to those described above were obtained.

However, in this case, the electrolytic etching treatment is carried out at 100~5o
It was performed at a current density of omA/7.

Further, after performing the electrolytic etching process in this manner, the oxide film formed on the surface of the semiconductor was removed in the same manner as described above.

In that case, a clean, unroughed semiconductor surface was obtained, as described above.

Furthermore, electrolytic etching treatment similar to that described above was carried out using a solution containing 3-polyboric acid solution and ethylene glycol or propylene glycol in a ratio (volume ratio) of 1:2 to 4 as electrolytic solution 2. I did it.

In such cases, results similar to those described above were obtained.

Furthermore, even if the sample 6 is a P-type semiconductor other than GaAs, especially a group 1 semiconductor, the metal layer attached in contact with the semiconductor surface may be The same electrolytic etching process as described above was applied to a metal layer containing other than Or, for example, a metal layer made of an alloy of Or and Au.

In this case, the same results as described above were obtained.

From the above, according to the present invention, it is possible to unnecessarily etch a metal layer made of Cr or containing Or attached to a semiconductor surface without having the drawbacks mentioned above at the beginning. easily, in a short time, without
Moreover, it is clear that it has the characteristic of being able to be processed finely and selectively.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an example of a method for selectively processing a metal layer made of or containing Or attached to a semiconductor surface according to the present invention. 1... Container, 2... Electrolyte, 4...
... cathode, 6 ... sample, 7 ... constant current source or constant voltage source.

Claims (1)

[Claims] 1. The etching unnecessary region on the metal layer made of or containing Or attached to the semiconductor surface is coated with a coating that is resistant to an electrolytic solution that can anodize the semiconductor surface. Or for a metal layer containing Or,
A method for selectively processing a metal layer made of Cr or containing Or attached to a semiconductor surface, the method comprising performing an electrolytic etching treatment using the above-mentioned electrolytic solution.