JPS60175425A - Selective etching method - Google Patents

Abstract

PURPOSE:To finely machine a metal and a semiconductor by forming an Al layer and a resist material on an article to be etched, then selectively removing the material and the layer to form an Al pattern, and etching with the pattern as a mask. CONSTITUTION:Ti 11, Al 12 to be etched are bonded on an N type GaAs substate 10, and a positive type resist 13 is coated on the overall surface. Then, with the prescribed pattern as a mask it is exposed. Thus, the resist 13 is dissolved only at the exposed portion in a developer, the Al is simultaneously etched to obtain an Al pattern. Then, the resist 13 is removed, with the Al 13 as a mask the Ti 11 is removed by dry etching. Thus, fine and high density pattern can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for selectively etching metals, semiconductors, etc.

Conventional structure and its problems Wet etching methods using acids, alkalis, etc., which have been conventionally used for selective etching of metals and semiconductors, have difficulty controlling the amount of side etching and processing problems due to uneven wettability with the object to be etched. Due to poor shape reproducibility, it is unsuitable for high-density and miniaturization processes. In wet etching of titanium and molybdenum, which are particularly useful for Schottky electrodes, the etching rate increases exponentially with the etching time, making it extremely difficult to confirm the etching end point and making it impossible to perform wet etching with good reproducibility. In addition, in the dry etching method using radical gas, the high-molecular organic compound that serves as a mask is also etched. There were problems such as difficulty in resist removal.

OBJECTS OF THE INVENTION The present invention provides a selective etching method that overcomes these problems and facilitates the processing of metals and semiconductors.

Structure of the Invention The present invention provides an A7! This is a selective etching method in which the film is sandwiched, the resist material is developed after exposure, A/ is selected, targeted removal is performed, and after All is turned, the object to be etched is etched using this mura as a mask. be.

Description of examples The present invention will be specifically explained below with reference to examples.

FIG. 1 shows a schematic cross-sectional view of the processing steps of a semiconductor device processed using the present invention. 6000 layers of Ti11 and 6000 layers of A/12 were deposited on the n-type GaAs substrate 10 by EB evaporation method.
A positive resist 13 made of an organic polymer material is applied over the entire surface (FIG. 1(a)). Next, it is masked with a predetermined pattern and exposed. Here, since the resist 13 is a positive type resist, only the exposed portion is dissolved in the developer, and the rest remains. Since the developer for the positive resist 13 consists of a strong alkali, the A/12 exposed as a result of development is etched away during development, creating an Ad pattern without any additional process (see Figure 1 (b). ))
. Note that the Ag film thickness here was as thin as 500 mm, and there was almost no side etching when etching with this solution. Next, remove the remaining resist 13 with acetone,
Ti 11 is removed by dry etching using AL 12 as a mask. Dry etching uses low pressure plasma etching, using a mixed gas of CF4:02=1oO:1.
．． Etching was performed for 20 minutes in a 100 W plasma while maintaining the pressure at 3 torr.

Next, an Au-Sn alloy 14 (
Sn ratio 10%) was deposited by vacuum evaporation, and 400
' Alloyed with C (Fig. 1 (C)). A Schottky diode was obtained in the above manner.

FIG. 2 shows the relationship between the etching amount and etching time for positive type resist, ig, and Ti under the above conditions. A
e is not etched at all, whereas resist and Ti
770 people/min each.

It can be seen that etching is performed at a rate of 260 people/min.

If the resist 13 is left, it will harden during the plasma treatment as described above and cannot be easily removed, so it was removed before etching.

Thus, as shown in the present invention, by simultaneously forming an A6 pattern during pattern formation by photolithography, it has become possible to form a fine, high-density pattern in which etching of the mask itself during dry etching can be ignored.

Although the present invention has been described above in detail with reference to embodiments, the object to be etched is not limited to T1, but may also be metals such as Mo and Or, and semiconductors such as Si, Ge, and GaAs. The resist material is not limited to positive type, but may also be negative type.

Effects of the Invention As described above, the present invention enables microfabrication of the object to be etched by interposing the Ae layer between the object to be etched and the resist material, and has great practical effects. be.

[Brief explanation of drawings]

FIGS. 1(2) to (C) are process cross-sectional views according to embodiments of the present invention, and FIG. 2 is a positive resist, Ti, A7? FIG. 2 is a comparison diagram of etching rates in Plasmae and Nochi. 10-... n-type GaAs substrate, 11 .=-Tj-
, 12...A6, 13...Positive resist, 14...Au-Sn combination.

Claims (1)

[Claims] A step of sequentially forming an Ae layer and a resist material on the object to be etched, a step of selectively removing the resist stripping material and the Ae layer, and a step of etching the object using the A4 pattern formed by the removal as a mask. A selective etching method comprising the step of etching an object.