JPH01310539A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent tungsten from biting a silicon substrate, etc., by a method wherein, in the selective depositing process of the tungsten by CVD process, polycrystalline silicon film formed in contact holes is used as a reducing agent. CONSTITUTION:Contact holes 10 are formed in an insulating film 6 to deposit a polycrystalline silicon film 11 on the surface while the polycrystalline silicon film 11 is coated with a photoresist 12 by spin-coating process to flatten the surface thereof and after setting the photoresist 12 by baking process, the polycrystalline silicon film 11 and the photoresist 12 are dryetched away until the polycrystalline silicon film 11 on the insulating film 6 is completely removed at the equal etching rates of the two 11, 12. Next, any residual photoresist 12 on a wafer is removed and cleaned up and then tungsten 13 is selectively deposited in the contact holes 10 using the residual polycrystalline silicon films 11 in the contact holes 10 as reducing agent to form electrodes 8 on the tungsten 13. Through these procedures, the tungsten 13 can be prevented from biting a silicon substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a semiconductor device using selective growth of tungsten to form electrodes.

2. Description of the Related Art In recent years, a method of selectively embedding tungsten into an opening (contact hole) provided in an insulating film using a CVD method has been developed to form an electrode.

The formation of electrodes of an MO3 field effect transistor using this selective growth method of tungsten will be explained with reference to the cross-sectional view shown in FIG.

First, a source region 2 and a drain region 3 are formed in a silicon substrate 1, a gate oxide film 4 is formed between the source region 2 and the drain region 3, and a gate electrode made of polysilicon is formed on the gate oxide film 4. A silicon oxide film 6 is formed on the surface of the silicon substrate 1. Next, source area 2. Silicon oxide film 6 on drain region 3 and gate electrode
to form a contact hole. Next, CV
Tungsten is selectively grown using method D to form a tungsten film 7 in the contact hole. On this tungsten film 7, aluminum (A[> and silicon (
An electrode 8 containing a small amount of Si) and steel (Cu) is formed.

Through the above steps, an MO3 field effect transistor is formed.

Problems to be Solved by the Invention In conventional manufacturing methods, when growing tungsten into contact holes using selective CVD, silicon, which is a reducing agent for tungsten hexafluoride, which is a reactive gas, is supplied from a silicon substrate. Therefore, the tungsten 7 digs into the lower side of the silicon oxide film 6 around the contact hole (encroachment), causing the source region 2. A tungsten encroachment region 9 is created in the drain region 3 and the polysilicon gate electrode. Therefore, tungsten penetrates through the shallow junction, causing a short circuit failure or an increase in leakage current even if no short circuit occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device that eliminates the encroachment of tungsten when forming tungsten in a contact hole using a selective CVD method.

Means for Solving the Problem The method for manufacturing a semiconductor device of the present invention to solve this problem is to form a contact hole in an insulating film, grow a polycrystalline silicon film on the surface, and grow a polycrystalline silicon film on the polycrystalline silicon film. After applying a photoresist using a spin coating method so that the surface is flat and hardening the photoresist by baking, the polycrystalline silicon film and this photoresist are etched on the insulating film under conditions that the etching rate of both is equal. Dry etching is performed until the polycrystalline silicon film is removed. After this, the photoresist remaining on the wafer is removed, and the wafer is cleaned.
Using the polycrystalline silicon film remaining in the contact hole as a reducing agent, tungsten is selectively grown in the contact hole by CVD, and an electrode is formed on the tungsten.

According to the method for manufacturing a semiconductor device of the present invention, CVD is performed with a polycrystalline silicon film formed in the contact hole.
In order to selectively grow tungsten using this method, silicon, which is a reducing agent for tungsten hexafluoride, which is a raw material gas for the selective growth of tungsten, is present in the contact hole, so silicon, which is a reducing agent, is supplied, and the growth of tungsten is It is possible to prevent the insulating film from moving downwards and from digging into the silicon substrate.

Embodiment 1 Regarding an embodiment of the method for manufacturing a semiconductor device of the present invention
This will be explained with reference to the process cross-sectional diagram of the MO3 field effect transistor shown in the figure.

First, a source region 2 and a drain region 3 are formed in a silicon substrate 1, a gate oxide film 4 is formed on the silicon substrate 1 between the source region 2 and the drain region 3, and a gate oxide film 4 is formed on the gate oxide film 4. The thickness of polycrystalline silicon is 300 nm.
A gate electrode 5 is formed on the surface of the silicon substrate 1, and a CV
A silicon oxide film 6 having a thickness of 400 nm is formed by method D.

After this, source area 2. A contact hole 10 is formed in the silicon oxide layer above the drain region 3 and gate electrode 6 (FIG. 1A).

Next, on the surface of the silicon substrate 1, by low pressure CVD method,
A polycrystalline silicon film 11 is grown to a thickness of 80 to 300 nm, and a positive photoresist 12 is applied onto the polycrystalline silicon film 11 using a spin coating method so that the surface becomes flat.
Coat to a thickness of 1.2 μm. Thereafter, the photoresist 12 is cured in a constant drying oven at a temperature of 130° C. for 30 minutes (FIG. 1B).

Next, the photoresist 12 and the polycrystalline silicon film 11 are
Reactive ion etching is performed under conditions where both etching rates are equal, and etching is continued until the polycrystalline silicon film 11 on the silicon oxide film 6 is completely removed. The etching conditions at this time are as follows.

Gas pressure: 140 mTorr RF power: 200 W Etching gas: CF4+5F6 (6%) After completion of this dry etching, the remaining photoresist 12 is completely removed by oxygen plasma ashing and cleaning, and the wafer is cleaned. After this cleaning, the polycrystalline silicon film 11 is 80 to 30% thick in the contact hole.
It is formed with a thickness of 00 nm (FIG. 1C).

Note that this polycrystalline silicon film 11 serves as a reducing agent during the subsequent formation of tungsten by the CVD method.

Next, by CVD method using tungsten hexafluoride,
Tungsten 13 is selectively grown to a thickness of about 350 nm and is buried in the contact hole. At this time, since the polycrystalline silicon film 11 serves as a reducing agent for tungsten hexafluoride, no region is formed in the silicon substrate 1 or the gate electrode 5 where tungsten bites. Subsequently, Ae containing Si and Cu and having a thickness of 500 nm is formed on the tungsten 13 to form the electrode 8 (FIG. 1D).

Through the above steps, a MOS field effect transistor is completed.

In addition, although the example of a MOS field effect transistor was shown in the Example, it goes without saying that this invention can be utilized also for the contact of a bipolar transistor, other semiconductor elements, and multilayer wiring.

Effects of the Invention According to the method of manufacturing a semiconductor device of the present invention, since the polycrystalline silicon film formed in the contact hole is used as a reducing agent in the selective growth process of tungsten by the CVD method, the process can be performed in a self-aligned manner. It is possible to suppress tungsten from digging into a silicon substrate or the like.

In addition, since a polycrystalline silicon film is formed in the contact hole and is used as a silicon supply source when forming tungsten using the CVD method, even if the contact region of the electrode is lined with a high-melting point metal or high-melting point metal silicide. , stable tungsten reduction is possible, and tungsten can be easily formed in contact holes.

[Brief explanation of the drawing]

FIG. 1 is a process cross-sectional view of a MOS field effect transistor showing an embodiment of the semiconductor device manufacturing method of the present invention, and FIG. 2 is a cross-sectional view of a MOS field effect transistor showing a conventional semiconductor device manufacturing method. DESCRIPTION OF SYMBOLS 1... Silicon substrate, 2... Source region, 3... Drain region, 4... Gate oxide film, 5... Gate electrode , 6...
Silicon oxide film, 8...electrode, 10...
・Contact hole, 11... Polycrystalline silicon film, 12... Photoresist, 13...
·tungsten.

Claims (1)

[Claims] A process of forming an opening in an insulating film, a process of growing a polycrystalline silicon film over the entire surface of the wafer, forming a photoresist film on the polycrystalline silicon film by a spin coating method, and then baking the photoresist film. a step of dry etching the photoresist film and the polycrystalline silicon film under conditions where both etching rates are equal until the polycrystalline silicon film on the insulating film disappears; The remaining photoresist film is removed and cleaned, and tungsten is selectively grown by CVD using the polycrystalline silicon film remaining in the opening as a source of silicon, which is a reducing agent, to form the opening. a step of forming tungsten only on the portion;
A method for manufacturing a semiconductor device, comprising the step of forming an electrode on the tungsten.