JP3074754B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a Schottky barrier diode.

[0002]

2. Description of the Related Art A conventional method for manufacturing a Schottky barrier diode (hereinafter referred to as SBD) will be described with reference to FIG. First, after a silicon oxide film 2 is formed on an N-type silicon substrate 1, an opening 3A is provided in a required portion.
Next, a platinum (Rt) film is applied to the exposed portion of the silicon substrate 1 and then subjected to a heat treatment to cause a silicide reaction.
The SBD was realized by forming the platinum silicide film 5A.

[0003] This SBD utilizes characteristics such as a high on / off switching speed and a low on-voltage as compared with a normal PN junction diode, and saturates a transistor / transistor logic circuit (hereinafter referred to as a TTL circuit). It is used as a clamp element for the purpose of prevention, or as a part of a load element of a flip-flop circuit constituting a unit memory cell of an emitter-coupled logic type random access memory (hereinafter, referred to as an ECLRAM) requiring a high-speed operation. Especially SB in ECLRAM
D has two roles: first, it functions as a speed-up capacitor for improving the operation speed, and second, it functions as a capacitor for improving the α-ray soft error resistance. In other words, the larger the capacitor capacity determined by the area of the SBD, the higher the performance of the ECLRAM.

[0004]

In the era of mass information processing in recent years, large-capacity ECLRAMs, which are used as cache memories of large-sized computers, are also required to have a large capacity. Is the SBD. Naturally, with the increase in capacity, the area occupied by the unit memory cells constituting the memory cells must be reduced.
The area occupied by the SBD must also be reduced.

However, in the conventional SBD, since the SBD is formed on the plane of the silicon substrate, the reduction of the occupied area is directly linked to the reduction of the capacitance of the capacitor, which causes a reduction in operation speed and a reduction in α-ray soft error resistance. There was a disadvantage. For this reason, the ECLRAM
It was extremely difficult to increase the capacity. An object of the present invention is to provide a method for manufacturing a semiconductor device having an SBD with a small occupied area.

[0006]

According to a method of manufacturing a semiconductor device of the present invention, a step of forming a first insulating film on a silicon substrate and then patterning the same to form an opening; Forming a groove by etching the silicon substrate using the insulating film as a mask, forming a platinum silicide layer on the inner wall of the groove, and forming only a side wall of the groove on which the platinum silicide layer is formed. Forming a second insulating film; and selectively growing a tungsten film in the trench in which the second insulating film is formed.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1A to 1C are cross-sectional views of a semiconductor chip for explaining an embodiment of the present invention.

First, as shown in FIG. 1A, after a silicon oxide film 2 having a thickness of about 300 nm is formed on a silicon substrate 1, an opening 3 is provided by ordinary photolithography and RIE. The opening 3 is formed, for example, by 10
A gas plasma containing CF ₄ as a main component may be used under the conditions of Pa and 800 W. Next, using the silicon oxide film 2 as a mask, a groove 4 having a depth of 1.0 to 2.0 μm is formed in the silicon substrate 1 using a gas plasma mainly composed of SiCl ₄ under the conditions of 10 Pa and 200 W. Next, as shown in FIG. 1B, a platinum film is deposited on the entire surface to a thickness of about 50 nm by a sputtering method, and is subjected to a heat treatment for about 20 minutes in a nitrogen atmosphere at a temperature of 500 to 600 ° C. . After the silicide reaction is caused by this treatment to convert the entire inner wall surface of the groove 4 into the platinum silicide film 5, the unreacted platinum film on the surface of the silicon oxide film 2 is removed with aqua regia.

Next, as shown in FIG. 1C, a silicon nitride film is deposited on the entire surface to a thickness of about 100 nm by a sputtering method, and then etched back by an RIE method, and only the side wall of the groove 4 is formed. The silicon nitride film 6 is left. For the etching, for example, gas plasma containing CF ₃ as a main component under the conditions of 12 Pa and 800 W is used. Next, the tungsten film 7 is selectively grown from the platinum silicide surface at the bottom of the groove 4 under the condition of, for example, 2 Pa at 250 to 300 ° C. using the SiH ₄ reduction method of WF ₆ , and the groove 4 is buried.

The reason why the silicon nitride film 6 is provided on the side wall of the groove 4 is to bury and flatten the tungsten film. If the silicon nitride film 6 is not provided, the tungsten film is grown from the platinum silicide film on the side wall of the groove 4. Therefore, the tungsten film has a raised shape around the groove, and flattening cannot be performed. Note that a silicon oxide film may be used instead of the silicon nitride film.

Next, the effect of the embodiment will be described using actual dimensions. For example, 4 × 5 in 16Kbit ECLRAM
Although the SBD area of = 20 μm ² was used, the occupation area of the SBD is required to be reduced to 40% or less in the 64-Kbit ECLRAM, that is, 80 μm ² or less is the given occupation area. When a groove having a depth of 1.5 μm is formed by using this embodiment, an occupied area without reducing the capacity is only about 2.4 × 2.4 = 5.76 μm ² .
Therefore, the required value can be sufficiently satisfied.

[0012]

As described above, according to the present invention, it is possible to manufacture a semiconductor device in which the occupied area of the Schottky barrier diode is significantly reduced without reducing the capacitance. Therefore, there is an effect that the capacity of the ECLRAM can be increased without deteriorating the performance.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor chip for explaining one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor chip for describing a conventional method of manufacturing a semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 silicon oxide film 3, 3A opening 4 groove 5, 5A platinum silicide film 6 silicon nitride film 7 tungsten film

Claims (1)

(57) [Claims] A step of forming a first insulating film on a silicon substrate and then patterning the opening to form an opening; and etching the silicon substrate using the first insulating film having the opening formed as a mask. Forming a groove, forming a platinum silicide layer on the inner wall of the groove, forming a second insulating film only on the side wall of the groove where the platinum silicide layer is formed, Selectively growing a tungsten film in the trench in which an insulating film is formed.