JPS59227120A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the disconnection of a wiring electrode due to a difference in level and the discoloration of a metal on a Schottky metal layer, by using a metal layer or an Schottky metal as a mask when the Schottky metal is etched. CONSTITUTION:A buried region 2, an epitaxial layer 3, an oxide film layer 4, an ohmic diffusion region 11, a Schottky window and a Ti layer 5 formig a Schottky layer are formed on a semiconductor substrate 1, and then an Mo layer 6 is evaporated thereon. Next, the entire surface is covered with a photo resist 7, and thereafter the resist 7 is removed except for the part thereof covering the Schottky window, so as to expose a part of the layer 6. Then, the remaining resist 7 being used as a mask, the layer 6 is removed by etching to expose the layer 5. After the resist 7 is removed, the layer 5 is removed by etching with the layer 6 used as a mask. After a part of the surface of the ohmic diffusion layer is exposed thereafter, a Schottky electrode 8 and an manufacture, a part to which metal sticks again can be reduced sharply, and as the result, a defect of wiring electrodes due to a difference in level, as well as the discoloration of the layer 6, can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device having a Schottky barrier.
In particular, the present invention relates to a method of manufacturing a semiconductor device in which an ohmic electrode is formed on the same plane.

In recent years, UHF, V) Ili'i equipment,
An ohmic electrode and a Schottky electrode are formed on the same plane as a convenient structure for monolithically integrating a plurality of diodes. A so-called horizontal diode structure has been proposed. The series resistance of a diode with this structure is mainly due to the spread resistance from the Schottky effect to the ohmic electrode, and there is a % characteristic that the shorter the electrode interval and the longer the circumference of the Schottky electrode, the smaller the resistance. be.

As shown in the plan view in Figure 1, the technology for creating a 2-layer structure is as follows. There is a rectangular Schottky diode with a Schottky electrode contacting the shape. General kl to obtain a Schottky diode with such structure
The 'llt method is shown in Figures u52 to Figure 5.

First, a buried region 2 having a conductive type 11 (type 1) opposite to that of the semiconductor substrate 1 is formed on a semiconductor substrate 1, and then it is formed into a conductive type opposite to that of the semiconductor substrate 1 by a conventional vapor phase growth method. An epitaxial layer 3 is formed. Next, after forming an oxide M'p)t34, a part of the oxide film layer 4, that is, a part corresponding to the ohmic region, is etched away by ordinary photolithography, and the epitaxial layer 3 is formed. After exposing 3 (FIG. 2), an ohmic region 11 is formed by diffusing an impurity having the same conductivity type as the buried region at a high concentration.

Next, after thermal oxidation and covering the ohmic region with an oxide film 4,
Further, a part of the oxide film layer 4, that is, a part corresponding to the Schottky region, is removed by etching, and the epitaxial layer ff1 is etched away.
3 is exposed and the sirot key window is drilled. then 100
After successive evaporation of a titanium layer 5 of OA and a molybdenum layer 6 of the same (1000λ), the entire surface is covered with 7 photoresists.

Thereafter, the photoresist having non-Schottky characteristics is removed by ordinary photolithography to expose the molybdenum layer 6. Next, the exposed molybdenum layer 6 and titanium layer 5 are removed by a conventional ion milling method using the photoresist 7 as a mask (FIG. 4). Next, after removing the photoresist, the oxide film on the ohmic 'rl electrode extraction part is removed to expose the surface, and a metal that can be used as an electrode is vapor deposited to form the ohmic electrode 9 and the sheet key W, i8. and form (
Figure 5).

In such a manufacturing method, the shape is HL with a thickness of 1.
Since a photoresist is used as a mask when etching away the etched titanium layer 5 and molybdenum 1φ6 by ion milling, the etched side surface is thick and the metal re-deposition layer 10 is formed up to the photoresist part 7. . As a result, this redeposited layer could not be removed satisfactorily, and as a result, step breakage often occurred when forming the aluminum 111 frame, resulting in open noise and poor reliability. Furthermore, in order to remove the photoresist used as a mask for ion milling, oxidation plasma must be irradiated, but at that time the underlying gold IFM
A phenomenon in which the C Moriplan layer) 6 becomes acclimatized and forms a bond often occurs, causing problems such as ①F defects and deterioration of Schottky characteristics.

The present invention provides a novel method for manufacturing a semiconductor device that eliminates step-breaks in electrodes and discoloration of metal on a white-key metal layer.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. 6 to 8 are sectional views of each manufacturing process showing an embodiment of the present invention. The same parts as before are given the same numbers.

A buried region 2. is formed in the semiconductor substrate 1 in the same manner as in the conventional manufacturing method. Epitaxial layer 3. Breeding film layer 4. Ohmic diffusion region 1
1. A Sirotchi window, a titanium layer 5 and a pudane layer 6 are deposited. The thickness of the metal (molybdenum in this example) on the titanium layer serving as the Schottky metal is preferably about twice as thick as the Schottky metal, and has a slow etching rate. Next, after covering the entire surface with photoresist, the seven photoresists other than those on the Sirotchi window are removed by ordinary photolithography to expose a part of the molybdenum layer. Next, the remaining photoresist 7 is used as a gold mask to perform normal dry etching in a chlorine gas atmosphere to remove the molybdenum layer and expose the titanium layer 5.
Figure 6). Next, after removing the photoresist, the titanium layer 5 is etched away by a normal ion milling method using molybdenum M6 as an etching mask. At this time, there is a concern that the molybdenum layer may be etched at the same time. Since it is twice as thick, this problem does not occur. Finally, after exposing a part of the surface of the ohmic diffusion layer, aluminum is deposited to form a Schottky characteristic 8 and an ohmic electrode 9 (FIG. 8).

As can be seen from the above embodiments, in the titanium shipput key diode to which the present invention is applied, the metal layer (molybdenum layer), it has become possible to greatly reduce the amount of metal re-deposition, and as a result, it has become possible to eliminate the disconnection defects of electrodes made of aluminum etc. that often occurred in the past. . Furthermore, since it is no longer necessary to use a photoresist as an etching-resistant mask during ion milling, it is possible to eliminate poor characteristics and lower reliability due to discoloration of the lower medal (molybdenum layer) that often occurred in the past. It has become possible.

. In this embodiment, Mo was used as the metal for preventing intrusion of the aluminum electrode, but it goes without saying that similar effects can be obtained with other dry-etchable metals such as W and Ta. In addition, this manufacturing method uses Sittky F.
It can be similarly applied to other semiconductor devices such as ET.

[Brief explanation of drawings]

Figure 1 is a plan view of a horizontal titanium cut key diode.
2 to 5 are cross-sectional views at each step when the conventional manufacturing method is applied, and FIGS. 6 to 8 are cross-sectional views at each step according to an embodiment when the present invention is applied. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Buried diffusion layer, 3... Epitaxial layer, 4... Oxide film layer, 5... Titanium layer, 6...Molybdenum layer, 7...Photoresist scraps s8...
-...Rebox key electrode, 9...Group ohmitter electrode, 1
0...Metal re-deposition layer, 11...Ohmic diffusion layer. Agent Patent Attorney Susumu Uchihara ] A 7゜ Figure 1, 2, $3, Senma, 4, Figure 5, Figure 6, House, Figure 7, Figure O

Claims (1)

[Claims] In a method for forming a Schottky electrode and an ohmic electrode on a semiconductor substrate, at least a different metal R4t- is formed on the Schottky metal as a Schottky electrode structure.
A method for manufacturing a semiconductor device characterized by etching the underlying Schottky metal using the different metal layer as a mask.