JPS59155143A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To realize a simple alumina film isolation method by a method wherein a substrate is selectively etched using an etching-resistant film as the mask, an alumina layer is directly provided on the whole surface of the substrate and the etching-resistant film and the alumina film are simultaneously removed according to a life-off method. CONSTITUTION:A buffer layer 2 and an N type active layer 3 are continuously grown epitaxially on a semiinsulative GaAs substrate 1. Then, a photoresist 8 is coated, the element active region is patterned and a substrate surface 10 to become an insulating isolation region is made to expose. An etching is performed on the buffer layer 2 from the substrate surface 10. Alumina is made to stick on the whole surface in a thickness equal to the etching depth. The photoresist 8 and an alumina layer 9' on the element active region are removed. A heat treatment is performed for increasing the adhesion between an aumina layer 9 and the buffer layer 2. Then, the electrodes of a gate 4, a source 5 and a drain 6 are formed and each of the electrodes are led out on the alumina layer 9.

Description

[Detailed Description of the Invention] The present invention provides aluminum oxide (hereinafter referred to as alumina)
The present invention relates to an alumina membrane separation method that electrically isolates between electrodes and between elements.

For example, as shown in FIG.
Electrical element isolation of the FET is achieved by etching the area other than the active layer 3 into the buffer layer 2, which is an electrically insulating layer, to a certain depth to form a mesa structure, and forming a gate 4. A method is adopted in which the electrodes of the source 5 and drain 6 are metalized and wiring is drawn from the surface of the active layer 3 to the mesa etched region. However, according to this method, the thickness of the electrode wiring is 0.5 to 0.8
Since the mesa etching depth is 1.0 μm or more compared to 1.0 μm, there is a drawback that the electrode wiring is easily disconnected at the mesa step portion 7.

Therefore, in order to prevent the step difference caused by etching, the etched area is filled with a dielectric material. Silicon oxide and organic materials are normally used as dielectrics, but the use of alumina has been proposed to solve problems with their heat resistance and formation methods.

In other words, an aluminum layer is formed on the entire surface of the substrate including the selectively etched areas, and the aluminum layer filling the etched areas is selectively aluminized and the rest is removed, or the entire aluminum layer is replaced with an alumina layer. It was converted and selectively removed by etching. However, this method requires at least the steps of removing the etching mask, forming the aluminum layer, converting it to an alumina layer, and selectively removing the alumina layer or the aluminum layer.

Unfortunately, the manufacturing process becomes longer.

An object of the present invention is to provide an alumina membrane separation method with simple steps.

The present invention is characterized in that the substrate is selectively etched using the etching-resistant film as a mask, an alumina layer is directly provided on the entire surface, and the etching-resistant film and the alumina film thereon are simultaneously removed by a lift-off method.

The present invention will be explained below with reference to the drawings.

FIG. 2 shows a G a A s V which is an embodiment of the present invention.
FIG. 1 is a cross-sectional view in the manufacturing process of a one-piece barrier game.

First, as shown in FIG. 2(a), a semi-insulating GaAs substrate 1 having a (100) plane as a main surface is coated with 1013 to 1014 c.
Buffer layer 2 with a carrier concentration of WL-3 is 3 to 7μ
On the m1 layer, an n-type active layer 3 having a carrier concentration of 0.5 to 1.5×10”f−3 is epitaxially grown continuously to a thickness of 0.5 to 0.9 μm.

Next, as shown in FIG. 2(b), a photoresist 8 is applied, and the device operating area is patterned using ordinary lithography technology to form a substrate surface that will become an insulating isolation area.

Next, as shown in FIG. 2 1c), 1, for example, sulfuric acid H! S0
4 and hydrogen peroxide H20! The mixed solution is etched from the substrate surface 10 until approximately 2000 to 3000 A is injected into the buffer layer 2.

Thereafter, as shown in FIG. 2 (di), sialumina is deposited on the entire surface by sputtering to a thickness equal to the etching depth. At this time, no alumina film is formed on the side surfaces of the photoresist 8. , Figure 2 (
As shown in e), the photoresist 8 on the device operating area and the alumina layer 9' thereon are removed using an organic solvent, and a slight lift-off is performed. 7 is formed when the sides of the photoresist 8 are misted out.

Next, in order to increase the adhesion between the alumina layer 9 and the buff 7 layer 2, hydrogen H! Heat treatment is performed under a gas atmosphere or an inert gas (Ar, N2) atmosphere. After this, as shown in FIG. 2, gate 4. Source 5° and drain 6 electrodes are formed, and each electrode is drawn out onto the alumina layer 9 to form an electrode pad.

According to the above manufacturing method, since the surface of the alumina layer and the surface of the active layer are at the same height, the surface of the element is flattened.
Therefore, disconnection of the electrode wiring does not occur. Moreover, the alumina layer can be directly formed and unnecessary alumina layers can be removed using the lift-off method.

The process is also simplified.

As explained above in detail, according to the present invention, by providing an alumina layer around the active layer, it is possible to prevent disconnection of electrode wiring and to provide high electrical insulation between each electrode and the active layer. This has the effect of obtaining stable characteristics (enabling electrical insulation separation between electrode pads).

It should be noted that the present invention can be applied not only to discrete devices but also to insulation isolation between IC- elements, and other semiconductor materials such as St can be used as the substrate material.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional semiconductor device, and FIG. 2 (at to (f)) are cross-sectional views showing a manufacturing method according to an embodiment of the present invention. Insulating GaAs substrate, 2...
Buffer layer, 3...N-type active layer, 4...
・Gate, 5... Source, 6... Drain, 7... Mesa step, 8... Photoresist, 9... Alumina , 10...
・Substrate surface.

Claims (1)

[Claims] selectively forming an etching-resistant mask in an element formation region of a semiconductor substrate; selectively etching the semiconductor substrate using the etching-resistant mask; forming an aluminum oxide layer over the entire surface; A method for manufacturing a semiconductor device, comprising the step of simultaneously removing the etching-resistant mask and the aluminum oxide layer on the etching-resistant mask.