JPS6095975A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve appearance of a silver electrode plated layer, by adhering an oxide film on the surface of a semiconductor substrate, providing thereon a nitride film having a shape corresponding to a Schottky pattern to be provided later, producing a thick oxide film around the nitride film used as a mask; removing thereafter the nitride film and the oxide film under it to expose the surface of the substrate, adhering metals for Schottky contact on the surface of the substrate thus exposed, and providing a silver electrode plated layer thereon. CONSTITUTION:A semiconductor substrate 10 is subjected to heat oxidation to produce thin oxidate films 11 on both the upper and lower faces of the substrate, and another nitride film 11 having a shape corresponding to the Schottky pattern to be provided later is formed on the upper film 11. The film is heat treated with the use of the film 11 as a mask such that the film surrounding the mask swells in volume to become a thick oxide film 12, and the film 11 and the film 10 under the same are etched away. After that, a W layer 5, a W silicide layer 6 and a Ti.Ag layer 7 are layered and adhered on the surface of the substrate thus exposed such that each layer covers the edges of the film 10, and an Ag electrode plated layer 8 is adhered on the layer 7.

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing a D 11 D-type diode.In recent years, with the demand for miniaturization and weight reduction of ultra-high frequency devices,
HD type Schittky diodes are now being widely used in place of conventional mini Schittky diodes, as they are advantageous in reducing the size of mounted circuits.
The HD type 7-point key diode is a type in which a pellet is sandwiched between two symmetrical heaton/reed leads, and the entire body is sealed with a glass sleeve, which is directly sealed. It is simple and inexpensive, the container can be made relatively small, and it has excellent heat dissipation. However, on the other hand, in this DHD type shutt key diode, it is necessary to avoid high temperatures during the assembly process. (450°C to 650°C) As a result, pellets with better heat resistance than the mini-type are required. The general manufacturing method for obtaining this DHD type shutter key diode is shown in Figures 2 to 5. After thermally oxidizing the semiconductor substrate l to form an oxide film layer 2, A part of the oxide film layer is etched away by an etching method, and a Schottky pattern shape 4 and a scribe line window portion 3 are opened (FIG. 2). Next, 5t of tungsten is vapor-deposited using a Schottky metal sheet, and then the tungsten other than on the Schottky window is removed, followed by high-temperature heat treatment to form a tungsten silicide contact 6 (FIG. 3). Next, after sequentially depositing titanium and silver 7, the titanium and silver layers except those on the ungsten layer are removed by etching. Approximately 30-7
(about 0μ) 8 (Figure 5) 0 In this manufacturing method example, the formation of the silver electrode plating layer 8 utilizes the forward characteristic of the Schittky diode (i.e., the active layer of the diode is used as the conductive path) f. Therefore, if there are pinholes or step breaks in the photoresist in the exposed portion of the semiconductor substrate 1, such as the scribe line window portion 3 (particularly likely to occur in the step portion 9 of the oxide film layer), the A silver electrode plating layer was also formed at the position, resulting in a problem of a decrease in wafer yield and good product P/W. or,
On the other hand, when the thickness of the photoresist layer is increased due to the fear of pinholes and step breaks in the photoresist, the problem arises that the photoresist residue P is generated and no silver electrode plating layer is formed at all. Furthermore, if the scribe line window section 3 is not opened when the Schottky pattern window section 4 is opened due to concerns about the above-mentioned problems, it is difficult to confirm the end point during etching of the oxide film layer 4. As a result, the oxide film layer 4 is over-etched and under-etched, resulting in frequent characteristic defects. The present invention provides a novel method for manufacturing a semiconductor device that eliminates the above-mentioned drawbacks in the scribe area. Hereinafter, embodiments of the present invention will be explained in detail with reference to all the drawings. A plan view showing an embodiment, and FIGS. 7 to 1θ are cross-sectional views at each step according to an embodiment of the present invention. The same parts as before are given the same numbers. First, a semiconductor substrate 1t is thermally oxidized to form a thin oxide film layer (approximately 500 Å) 10 on the front and back surfaces, and then a nitride film layer 1 is formed thereon. Next, the nitride film layer 11 is processed into a Schottky pattern shape using a conventional photolithography method (FIG. 7), and then thermally oxidized to form a thick oxide film layer 2 around the Schottky pattern. . At this time, since the Schottky pattern portion is covered with the quantized film layer, no thick oxide film layer is formed (FIG. 8). Next, the nitride film layer 11 is removed by etching using hot phosphoric acid, and then about 500A of the oxide film layer other than the scribe line area 13 is removed by etching using a normal photolithography method. - Drill a hole in the pattern window.At this time, there is a concern that the thick oxide film layer 12 will also be corroded at the same time, but since it is a small amount, there is no problem at all.On the contrary, this is used as alignment for the scribe area. 6 Next, a tungsten layer 5, a tungsten silicide layer 6, and a titanium silver layer 7 were sequentially formed in the same manner as in the conventional manufacturing method, and then a silver electrode plating layer with a height of 50 μm was formed using an ordinary photolithography method. 8
(Figure 1O).

As can be seen from the above examples, since the #JVi-applied diode of the present invention does not have a scribe line window, there is a concern that a silver electrode plating layer may be formed in the scribe line window as in the conventional manufacturing method. It is possible to significantly reduce the appearance defects of the silver electrode plating layer due to photoresist residue, photoresist pinholes, and step breaks that often occur in the past, and improve wafer yield and good product P/W.
could be significantly improved. Furthermore, since the opening in the Schottky window area is made possible by removing the thin oxide film layer 10e by etching, it becomes easy to confirm the end point during etching, and as a result, characteristic defects may occur due to over-etching or under-etching. It has become possible to completely eliminate concerns.

In this embodiment, tungsten was used as the metal for contacting the shutter key, but it goes without saying that similar effects can be obtained with other metals such as tantalum, titanium, platinum, etc. Furthermore, in this embodiment, a shutt key diode? It goes without saying that similar effects can be obtained using other diodes such as varactor diodes and PIN diodes.

[Brief explanation of drawings]

Figure 1 is a plan view of a conventional DHD type Schottky diode, and Figures 2-II! Fig. 5 is a cross-sectional view of each process in nine cases when the conventional manufacturing method is applied, Fig. 6 is a plan view when the present invention is applied to a FiDHD type shield key diode, and Figs. FIG. 3 is a cross-sectional view of each process when the present invention is applied to a toky diode. l... Semiconductor substrate, 2... Oxide film layer,
3...Scripe line window section, 4...Schottky window section, 5...Striped key metal layer (
tungsten), 6... Schottky metal silicide layer (tungsten silicide), 7...
・Titanium/silver layer, 8... Silver electrode plating layer, 9.
... Oxide film step part, ]0 ... Thin oxide film layer, 11 ... Nitride film layer, 12 ... Thick oxide film layer, 13 ... ...Scripe line area. Pa-in

Claims (1)

[Claims] A step of forming a nitride film in a Schottky pattern shape on an oxide film layer on a semiconductor surface exhibiting one conductivity type, and using the nitride film layer as a mask. By forming a thick oxide film layer and removing the oxide film layer below the nitride film layer, the semiconductor surface exhibiting the - conductivity type is exposed. A method for manufacturing a semiconductor device, comprising the steps of: opening a button key window; and providing metal for contacting a button key on the semiconductor surface through the button key window.