JPS60121778A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device, which operates in a ultra-high frequency region, with high reliability and less in skin effect loss, by coating a P-N junction section as a boundary section between an epitaxial layer and a diffusion layer with an insulating film and forming a metallic film on the surface of a substrate. CONSTITUTION:An epitaxial layer 2 having the same conduction type as a low- resistivity semiconductor substrate 1 is formed on the substrate 1, and an epitaxial layer or a diffusion layer 3 having a conduction type reverse to the epitaxial layer 2 is shaped on the epitaxial layer 2. An electrode metal 4 is formed on the layer 3. The substrate 1 is mesa-etched so as to obtain desired electrical characteristics while using the electrode metal 4 as a mask. An insulating film 6 is formed on the substrate 1. A positive group resist is applied and the whole surface is exposed and developed, thus leaving a resist 7 under the overhang section of the electrode 4. The insulating film 6 is etched while using the photo-resist 7 as a mask, thus leaving the insulating film 6 under the overhang section of the electrode 4. A P-N junction section as a boundary section between the layers 2 and 3 is coated with the insulating film 6. A proper metal is vapor deposited on the surface of the substrate 1 to form a metallic layer 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a semiconductor device for ultra-high frequencies.

(Prior art) Semiconductor devices used at high frequencies such as millimeter waves have to have smaller dimensions to increase Q, making it difficult to process electrodes, etc., so simple mesas are often used.

Various backbation methods have been used to reduce the loss due to the skin effect and increase the reliability of the Me'I11 diode.

As a method of reducing the loss due to the skin effect, a configuration as shown in FIG. 1 has been adopted. In Fig. 1, l is a low resistivity semiconductor substrate %, 2 is an epitaxial layer with the same conductivity as the semiconductor substrate l, 3 is an epitaxial layer or diffusion layer of a different conductivity type from the semiconductor substrate l, and 4 is an electrode metal. % 5
is a metal layer.

That is, after performing mesa etching using the electrode metal 4f as a mask, the metal layer 5 is deposited on the semiconductor substrate to reduce loss due to the skin effect.

In addition, in order to increase the reliability, after performing mesa etching on the electrode metal 4-metal mask, and coating the semiconductor substrate with an insulating film by the CVD method, a positive photoresist is applied. Fully exposed,
Reliability is improved by leaving an insulating film 6 under the outer ring portion of the electrode metal 40 and covering the PN junction with the insulating film.

However, as mentioned above, in high-frequency semiconductor devices, the dimensions become smaller in order to increase Q, making it difficult to process electrodes, etc., and inevitably the structures shown in FIGS. 1 and 2 have been manufactured.

However, although the loss due to the V skin effect can be reduced by attaching the metal layer 5 to the bottom surface of the semiconductor substrate shown in FIG. 1, there is a drawback that reliability is lacking because no insulating film is formed on the PN junction surface.

On the other hand, in the backbation method shown in Figure 2, reliability is improved by protecting the PN junction, but the drawback is that it is not possible to reduce loss due to the skin effect because no metal layer is formed. There was.

Furthermore, as mentioned above, since the dimensions are small, it has been strongly desired to adopt a self-aligning method in order to solve these problems.

(Objective of the Invention) An object of the present invention is to eliminate the above-mentioned problems and provide a method for manufacturing a highly reliable semiconductor device that operates at ultra-high frequency and has little loss due to the skin effect, using a relatively simple process. It is in.

(Structure of the Invention) A method for manufacturing a semiconductor device of the present invention includes a step of forming an epitaxial layer having the same conductivity type as the semiconductor substrate on a semiconductor substrate having conductivity, and forming an epitaxial layer on the epitaxial layer having a conductivity type opposite to that of the epitaxial layer. a step of forming an epitaxial layer or a diffusion layer of the opposite conductive wall, a step of forming a metal electrode on the epitaxial layer or the diffusion layer of the reverse conductive wall, and a semiconductor substrate on which the epitaxial layer etc. is formed by using a mask on the metal electrode. A step of mesa-etching the metal electrode and forming an overhang portion of the metal electrode, forming an insulating film on the surface of the mesa-etched semiconductor substrate, and using a photo-etching technique to form an insulating film under the overhang portion of the electrode. a step of depositing metal on the semiconductor substrate and forming a metal layer on the surface of the semiconductor substrate except for the portion above the metal electrode and under the overhang portion using a photo-etching technique; and forming an ohmic electrode on the back surface of the semiconductor substrate. The structure includes a step of forming.

(Example) Two examples of the present invention will be described below with reference to the drawings.

FIGS. 3(a) to 3(e) are cross-sectional views showing the process order for detailed explanation of the present invention.

As shown in FIG. 3 18), an epitaxial layer 2 of the same conductivity type as the substrate is formed on a low resistivity semiconductor substrate l, and then an epitaxial layer 2 or an epitaxial layer of a conductivity opposite to that of the epitaxial layer 2 is formed on the epitaxial layer 2. A diffusion layer 3 is formed. Next, metal is deposited on the epitaxial layer or diffusion layer 3, and an electrode metal 4 is formed using a photoetching technique.

Next, as shown in FIG. 3(b), the semiconductor substrate is mesa-etched using a sulfuric acid-based etching solution using the electrode metal 4 as a mask so as to obtain desired electrical characteristics. At this time, the bottom of the electrode metal 4 is over-etched to form an overhang portion. The lateral depth of the overetching is preferably approximately the sum of the thicknesses of the insulating film and the photoresist.

Next, as shown in FIG. 3(C), CV
An insulating film 6 is formed by method D. Next, a positive resist is applied, exposed to light over the entire surface, and developed, so that the resist 7 under the overhang portion of the electrode 4 remains, and all other resists are removed.

Next, as shown in FIG. 3(d), 71 ft of photoresist
: By etching the insulating film using an appropriate etching solution as a mask, the insulating film 6 under the overhang portion of the electrode 4 can be left. This insulation film 6 covers the PN junction which is the boundary between the epitaxial layer 2 and the epitaxial or diffusion layer 3. Next, a suitable metal is deposited on the surface of the conductor substrate to form a metal layer 8.

Next, as shown in FIG. 3(e), the back surface of the semiconductor substrate is mechanically or chemically etched to a predetermined thickness, and then an ohmic electrode 9t is formed.

As described above, a semiconductor device according to an embodiment of the present invention is obtained. In this embodiment, the P-N junction portion is completely covered with the insulating film 6, so that reliability can be improved.

Since the metal layer 8 is deposited on the surface of the low resistivity layer 1, loss due to the skin effect can be reduced.

Furthermore, since the main steps of these manufacturing methods can be carried out in a self-aligned manner, small-walled semiconductor devices can be reliably manufactured.

(Effects of the Invention) As described above, according to the present invention, it is possible to obtain a highly reliable semiconductor device that operates at ultra-high frequency power and has little loss due to the collective skin effect, through a relatively simple process.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of a conventional ultra-high frequency semiconductor device, and FIGS. 3(a) to 3(e) are cross-sectional views shown in the order of steps for explaining an embodiment of the present invention. . ■・・・・・・−・Low resistivity semiconductor substrate, 2・・・・・・l
Epitaxial layer with the same conductivity as 3... 13 epitaxial layer or diffusion layer different from 2, 4...
...Electrode metal, 5.8...-Metal layer, 6...
...-Insulating film, 7... Photoresist, 9...
...Ohmic electrode. Mine 1st year graduate 2nd year old v-3rd time

Claims (1)

[Claims] a step of forming an epitaxial layer of the same conductivity as the semiconductor substrate on a semiconductor substrate of one conductivity type, a step of forming an epitaxial layer or a diffusion layer of conductivity opposite to the epitaxial layer in the epitaxial layer, and a step of forming an epitaxial layer or a diffusion layer of conductivity opposite to the epitaxial layer; A step of forming a metal electrode on the epitaxial layer or diffusion layer, and a step of etching the semiconductor substrate on which the epitaxial layer etc. is formed, using the metal electrode as a mask, and forming an overhang portion of the metal electrode. , forming an insulating film on the surface of the mesa-etched semiconductor substrate and using photo-etching technology to leave the insulating film under the overhang of the electrode; and depositing metal on the semiconductor substrate and using photo-etching technology to leave the insulating film on the metal electrode. A method for manufacturing a semiconductor device, comprising the steps of: forming a metal layer on the surface of the semiconductor substrate except for a portion below the overhang portion; and forming an ohmic electrode on the back surface of the semiconductor substrate.