JPH0530055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to the formation of a high melting point metal silicide layer used for wiring layers of semiconductor devices and the like.

(b) Background of the Technology As integrated circuits become more highly integrated, aluminum is often used as the wiring material for the top layer, and doped polycrystalline silicon layers with a two to three layer structure are used as the wiring material for the intermediate layer. In particular, since a polycrystalline silicon layer is used for the gate of the MIS element, the word line polycrystalline silicon layer of the memory element connected to the gate is extremely widely used.

However, as integrated circuits become faster, the resistance of polycrystalline silicon layers is greater than that of metals, so delays due to the product of wiring resistance and capacitance become a problem. For this reason, high-melting point metals were considered as wiring materials, but they cannot be used as masks for ion implantation.

Easy to oxidize.

Poor chemical resistance.

Contact resistance is large.

It has the following disadvantages.

Therefore, high melting point metal silicides have come to be used. For example, tungsten silicide,
Molybdenum silicide, titanium silicide,
Tantalum silicide etc. are used. The specific resistance of these silicides is 10 to 100 .mu..OMEGA.cm, which is one to two digits smaller than the lowest value of polycrystalline silicon, 1000 .mu..OMEGA.cm, and furthermore, ohmic junctions with silicon are easily formed. For example, the specific resistance is 30 ~ tungsten silicide
100μΩcm, molybdenum silicide 40 to 100μΩ
cm, tantalum silicide is 30 to 60 μΩcm, and titanium silicide is 13 to 30 μΩcm.

When silicide is used in an element, it may be used as a single layer of silicide, or it may have a so-called polycide structure in which polycrystalline silicon is laid under a silicide layer.
Since the polycide structure is a composite layer, it is difficult to set etching conditions for forming fine patterns. However, the polycide structure tends to form ohmic junctions with silicon.
Since the part in contact with the silicon substrate or silicon dioxide film is polycrystalline silicon, it is a proven process, and device characteristics such as threshold voltage and rise voltage remain the same as before. There is little concern that new problems will occur with respect to interfaces with many .

(c) Prior Art and Problems A conventional technique for forming a high melting point metal silicide layer using tungsten as the high melting point metal and a silicon substrate or a silicon dioxide layer deposited thereon as the base will be described below.

i Svatuta method A metal is deposited directly on silicon or polycrystalline silicon and reacted with high temperature treatment to form a silicide layer. A method of simultaneously depositing silicon and metal is also often used. In this case, methods for depositing metal and silicon include sputtering, vapor deposition, plating, etc., but sputtering is used here as a representative example.

Spatter adhesion is directional, so step coverage is poor. In addition, the high melting point metal used as a sputtering target contains trace amounts of radioactive elements such as uranium and thorium, and these impurities are included in wiring materials, resulting in loss of stored information due to α-ray damage in semiconductor devices, especially memory elements. A so-called soft error may occur.

Low pressure vapor phase growth method using tungsten hexafluoride and monosilane Tungsten hexafluoride and monosilane were introduced separately into the chamber, mixed in the chamber,
React at ~450°C to form a silicide layer.
In this case, the silicide layer is formed only in the vicinity of the gas mixture, and it is difficult to form the silicide layer on a large number of semiconductor wafers, so mass production is not possible.

(d) Purpose of the Invention The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a high melting point material that is difficult to peel off, provides good step coverage, is free from α-ray damage, and has a large mass production effect that allows the simultaneous formation of a large number of substrates. An object of the present invention is to provide a method for forming a metal silicide layer.

(e) Structure of the Invention According to the present invention, the above object is to sequentially deposit a polycrystalline silicon layer and a hydrogenated amorphous silicon layer on a base, and replace the hydrogenated amorphous silicon layer with a high melting point metal containing fluorine. This is achieved by forming a high melting point metal silicide layer by reacting with a compound gas, and forming a composite film of the polycrystalline silicon layer and the high melting point metal silicide layer deposited thereon.

The present invention utilizes the fact that amorphous silicon contains a large amount of hydrogen, and therefore silicide formation is easily carried out.

For example, in the case of tungsten, tungsten silicide (Si _x W _y ) can be easily produced using the following reaction formula.

SiH+WF ₆ →Si _x W _y +HF Si+WF ₆ →W+SiF ₆ (f) Embodiment of the Invention FIG. 1 is a cross section showing an embodiment of the invention. In the figure, 1 is a base, 2 is a polycrystalline silicon layer, and 3 is an amorphous silicon layer.

In FIG. 1a, a silicon dioxide layer deposited on a silicon substrate is used as the base 1, and a thickness of
A 2000 Å doped polycrystalline silicon layer 2 is deposited at 620° C. by conventional vapor deposition. This layer is formed to improve adhesion to the base and to provide various advantages for the reasons mentioned above.

Next, by plasma vapor deposition method, a thickness of 2000~
A 3000 Å amorphous silicon layer 3 is deposited.

In FIG. 2, plasma vapor phase growth is performed in a container 2
The silicon substrate 22 placed in 1 is grounded, and 450
Monosilane heated to 0.degree. C. and diluted to 1 to 5% with argon is introduced into the container 21, a 13.56 MHz or several 100 KHz power source 23 is connected to the counter electrode 24, and a power of several 10 to several 100 W is applied.

Cleaning the amorphous silicon layer 3 after growth
Cleaning is performed by flowing carbon tetrafluoride or nitrogen trifluoride containing 5 to 20% oxygen as a gas.

In FIG. 1b, the amorphous silicon layer 3 is reacted with tungsten hexafluoride and converted into a tungsten silicide layer 3A.

The apparatus used for this reaction is an ordinary vapor phase growth apparatus, as shown in FIG. In the figure, 31 is a container, 3
2 is a substrate, and 33 is a heater.

A large number of substrates 32 are arranged in a container 31, and the inside of the container is
The mixture is evacuated to 0.2 to 0.3 Torr, heated to 300 to 500° C. by a heater 32, and a mixture of tungsten hexafluoride and hydrogen at a flow rate of 30 c.c./min and 200 c.c./min is introduced. From another inlet, 800 c.c./min of nitrogen is flowed as a carrier gas, which serves to dilute the tungsten hexafluoride and distribute it evenly within the container.

Hydrogen may be omitted when the base is a silicon dioxide layer as in the embodiment, but when the base is silicon, it is necessary to prevent erosion of the base.

In the embodiment, a silicon dioxide layer is used as the base, but silicon, both silicon dioxide and silicon, or other materials may be used.

Furthermore, although tungsten was used as the high melting point metal in the embodiment, the gist of the invention would not change even if other metals such as molybdenum were used instead.

(g) Effects of the Invention As explained in detail above, according to the present invention, a high melting point metal silicide is difficult to peel off, has good step coverage, is free from α-ray damage, and has a great productivity effect, allowing the simultaneous formation of a large number of substrates. A method of forming a layer can be provided.

[Brief explanation of drawings]

FIG. 1 is a cross section of a substrate showing an embodiment of the present invention, and FIG.
The figure shows an amorphous silicon layer forming apparatus, and FIG. 3 shows a silicide layer forming apparatus. In the figure, 1 is a base layer, 2 is a polycrystalline silicon layer, 3 is an amorphous silicon layer, 3A is a silicide layer, 21
2 is a container, 22 is a silicon substrate, 23 is a power source, 24 is an electrode, 31 is a container, 32 is a substrate, and 33 is a heater.

Claims (1)

[Claims] 1. A polycrystalline silicon layer and a hydrogenated amorphous silicon layer are sequentially deposited on the base, and the hydrogenated amorphous silicon layer is reacted with a high melting point metal compound gas containing fluorine to form a high melting point metal silicide layer. and forming a composite film of the polycrystalline silicon layer and the refractory metal silicide layer deposited thereon.