JPS62237730A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the yield of a completed semiconductor element without damaging a semiconductor substrate by forming a 2-layer of an insulating protective film which can be selectively etched, and removing without mechanical vibration overhangs of the protective film of the 2-layer structure formed by mesa etching with a mesa etching mask. CONSTITUTION:An oxide film 21 is formed over the entire surface by a CVD method on a semiconductor substrate 1, a nitride film 22 is then formed, the surface is coated with a photoresist film 3, the films 3 and 21, 22 on the substrate 1 to be removed to form a mesa structure are selectively removed, and the film 3 is thereafter all removed. The substrate 1 is mesa etched, and overhangs 4 formed at this time are composed of the film 22 and part of the film 21 having smaller etching rate than the substrate 1 at mesa etching. Only the oxide film portions of the overhangs 4 are selectively removed by etching with an etchant of fluoric acid type. The film 22 on the top of the mesa is eventually selectively removed by etching with phosphoric acid.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a semiconductor device that prevents chips, cracks, etc. that occur around the top of a mesa structure.

(conventional technology) is often used. This mesa structure reduces stray capacitance, enables effective operation at high frequencies, eliminates the need for leakage current on the element surface compared to planar types, and achieves high breakdown voltage. It is also sometimes used as a means of element isolation.

A conventional method for manufacturing the mesa structure is shown in FIG. 2(a).

The process shown in (b) is generally used.

First, as shown in FIG.
ical vapor deposition, hereinafter referred to as CVD. ) method to form the protective film 2. Next, a photoresist film 3 is formed on the protective film 2, and the photoresist film 3 and the protective film 2 on the semiconductor substrate 1 in the area to be etched away are selectively removed by photolithography. After that, the photorenost film 3 is completely removed.

Next, as shown in FIG. 2(b), mesa etching is performed to form a mesa structure. At this time, the protective film 2 used as a mask for mesa etching remains as it is, and the eaves 4 are formed.

(Problems to be Solved by the Invention) In the conventional method for forming a mesa structure, the semiconductor substrate 1 is immersed in a liquid and subjected to ultraviolet treatment in order to remove the eaves 4 formed as shown in FIG. 2(b). When sonic vibration is applied, a collision occurs, and the insulating protective film on the eaves portion 4 remains in the form of a piece. At the same time, there was a problem in that chips and cracks occurred around the top of the mesa of the semiconductor substrate 1.

These chips and cracks are damage to a part of the semiconductor substrate 1, and cause leakage current and characteristic deterioration.

Further, in the subsequent metal film wiring process, normal wiring could not be obtained, which was a factor in reducing yield.

The present invention was made to solve the above problems,
An object of the present invention is to provide a method for removing an eave formed by mesa etching without damaging a semiconductor substrate.

(Means for Solving the Problems) In order to achieve the above object, the present invention forms two layers of insulating protective films that can be selectively etched on a semiconductor substrate. Here, the lower protective film may have the same etching properties as the semiconductor substrate, and the upper protective film is formed of a material having different etching properties from those of the lower protective film and the semiconductor substrate. By using this two-layer protective film as a mask for mesa etching, a mesa structure without eaves is finally obtained.

(Embodiment) An embodiment of the present invention is shown in FIG. An insulating protective film (e.g., oxide film) that may have the same etching properties as the substrate 1 (e.g., silicon); 22 denotes the semiconductor substrate 1 and the insulating protective film 2;
This is an insulating protective film (for example, a nitride film) having a different etching property from No. 1.

In FIG. 1(a), an oxide film 21 is formed over the entire surface of the semiconductor substrate 1 on the active layer region side (the active layer region is not shown; the same applies hereafter) by the CVD method, and then the oxide film is removed by chipping. A photoresist film 3 and a protective film 21 on the semiconductor substrate 1.
22 is selectively removed. After that, the entire photoresist film 3 is removed.

In FIG. 1(b), mesa etching is performed on the semiconductor substrate 1 from which the protective film has been selectively removed.
This shows that it is composed of a part of the oxide film 21 having a lower etching rate.

(FIG. 1(c)) shows a state in which only the oxide film portion of the eaves 4 has been selectively etched away using a hydrofluoric acid-based etching solution.

FIG. 1 (dl shows the state in which the nitride film 22 at the top of the mesa has been selectively etched away with phosphoric acid.

(Effects of the Invention) As explained above, according to the present invention, the eaves formed in mesa etching are removed without being subjected to mechanical vibration, so that the semiconductor substrate is not damaged and can be used for subsequent processing. This has the effect of improving the yield and reliability of semiconductor devices completed after the process.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, and is a sectional view showing a method for manufacturing a semiconductor device in order of steps, and FIG. 2 is a sectional view showing a conventional manufacturing method in order of steps. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2, 21. 22... Insulating protective film, 3... Photoresist film, 4... Eaves.

Claims (1)

[Claims] a step of forming a first protective film on the semiconductor substrate; a step of forming another second protective film on the first protective film; a first protective film formed on the semiconductor substrate; A step of selectively removing the second protective film to form an etched region for forming a mesa structure, and a step of etching away the semiconductor substrate in the region exposed in the photoetching step to form a mesa structure. a step of removing the first protective film around the top of the mesa exposed by the mesa etching; and a step of removing all the second protective film of the mesa pattern formed in the photoetching step. A method of manufacturing a semiconductor device, comprising: