JPS6156613B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a stepped mesa structure in an electronic device having a mesa side surface consisting of multiple steps with a large width/height ratio.

In general, a method for forming a mesa on the surface of an electronic device material such as a metal or a semiconductor is as shown in FIG. A mesa is formed by chemically selectively etching the surface of the electronic material 11 using a method [FIG. 1a]. The slope of the mesa side surface according to such a conventional method is large, and therefore, in an electronic device having a mesa of the conventional structure, when wiring 13 is run vertically across the mesa side surface, there is a problem that wire breakage occurs on the steeply sloped mesa side surface. Figure 1b] was found.

The present invention was made in order to eliminate the problems that occur with the conventional structure as described above, and its purpose is to:
To provide a method for forming a stepped mesa structure in an electronic device, in which the mesa side surface is made into a structure consisting of a large number of steps with a large width/height ratio, the slope of the mesa side surface is made gentle, and disconnection on the mesa side surface is prevented. It is in.

According to the present invention, an oxide layer is selectively formed on the surface of the electronic device material by an anodic oxidation method using a film having low adhesion to an electronic device material such as a metal or a semiconductor as a mask, and then the formed oxidized layer is A method for forming a stepped mesa structure in an electronic device is obtained, which is characterized by repeating the oxidation/removal process many times to remove all the oxide layer.

The present invention will be described below as an electronic device material.
An example using GaAs will be explained with reference to the drawings.
FIG. 2 is a diagram for explaining one embodiment of the present invention. First, it was heated at 80℃ for 30 minutes.
Photoresist OMR-30CP (product name) is deposited on the GaAs wafer 21 using a commonly used spinner.
was applied at a rotational speed of 3000rpm for 20 seconds, exposed and developed using a normal exposure method, and then exposed to 150°C.
The mask 22 is formed by sintering for one hour (FIG. 2a). Next, by anodic oxidation, an oxide layer 23 is formed on the exposed GaAs surface using the GaAs wafer 21 partially masked with photoresist as an anode. At this time, the electrolytic solution for anodic oxidation enters the interface between the end of the mask 22 and the GaAs wafer 21, so an oxide layer 13 is also formed on the surface of the GaAs wafer 21 under the mask 22 that is in contact with the electrolytic solution, and along with this, the oxidized layer 13 is Since the thickness of the layer 23 increases to about 1.5 times the depth of the consumed GaAs wafer, the mask 22, which has a small adhesion to the GaAs wafer 21, rises as the oxide layer 23 grows, and as a result, the area near the oxide layer increases. A gap is created at the interface, and the electrolytic solution further penetrates into the gap at the interface between the master 22 and the GaAs wafer 21, forming an oxide layer on the surface of the GaAs wafer 21 there as well (FIG. 2b). The oxide layer selectively formed on the surface of the GaAs wafer as described above can be easily removed using, for example, an aqueous HCl solution without etching the GaAs (FIG. 2c).
Next, anodic oxidation is performed again using the above mask 22 [FIG. 2 d], and the oxide layer 23 is removed [FIG. 2 e]. By repeating the oxidation and removal steps as described above and then removing the mask 22, a mesa consisting of a large number of steps with a large width/height ratio is provided on the surface of the GaAs wafer 21 [FIG. 2 f] I can do it. Next, by vacuum evaporation method,
The wiring metal 2 is placed vertically across the side of the mesa.
4 (Fig. 3g) does not cause any disconnection. Note that the width/height ratio of the steps formed in one step of oxidation and removal is 4.6 to 4.7 times, but the width/height ratio of the steps can be changed arbitrarily depending on the mask formation conditions. For example, the above OMR
By applying two coats of 30CP and doubling the mask thickness, this ratio can be changed to 4.1-4.2.

As explained above, the electronic device having the structure of the present invention can eliminate wiring breaks. Further, the idea of the present invention is effective not only for measures against wire breakage, but also for electronic devices that require stairs that are wide and low in height. Although GaAs was explained in the examples, other electronic device materials that can be anodized may also be used.
It goes without saying that the same effect can be obtained with Al, Ta, Si, etc., and although we used photoresist OMR-30CP as a mask, it goes without saying that the same effect can be obtained with other similar films. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining a conventional mesa structure and its manufacturing method, and FIG. 2 is a sectional view for explaining an embodiment of the present invention, showing each main process. In the figure, 11 is an electronic device material, 12 is a mask, 13 is a wiring metal, 21 is a GaAs wafer, 2
2 is a photoresist film, 23 is an oxide layer, and 2
4 indicates wiring metal.

Claims (1)

[Claims] 1. An oxide layer is selectively formed on the surface of an electronic device material such as a metal or a semiconductor by an anodic oxidation method using a film with low adhesion to the electronic device material as a mask, and then the formed oxide layer is A method for forming a stepped mesa structure in an electronic device, characterized by repeating an oxidation/removal process for removing layers many times.