JPH0748562B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device having a MOS semiconductor element using a high melting point gate electrode by an ion implantation method. .

(B) Conventional Technology Conventionally, for example, in manufacturing a highly integrated semiconductor device,
An ion implantation method, which enables highly accurate selective doping according to a mask pattern, is effectively used when doping impurities or controlling the physical properties of a solid surface. On the other hand, as the degree of integration is improved, high-temperature heat treatment is widely used for the purpose of annealing and surface flattening, and therefore various restrictions are imposed on the material used.

For example, as the gate electrode of the FET, silicon having a high melting point has been conventionally used because at least a material that can withstand the annealing treatment (for example, about 1000 ° C.) after the ion implantation treatment is required. However, with the recent miniaturization of semiconductor devices, an electrode material having a high melting point and a low specific resistance has been required, and the application of metal gate electrodes such as tungsten (W), molybdenum (Mo), titanium (Ti), etc. Is being considered. As a low resistance gate, a tungsten / polycrystalline silicon (n ⁺ -PolySi) structure is promising, but if heat treatment at 500 to 600 ° C or higher is performed, a silicidation reaction occurs at the W / n ⁺ -PolySi interface and it cannot be put to practical use.

Therefore, in order to prevent the silicidation reaction, a titanium nitride (TiN) film that serves as a diffusion barrier is used to form W / TiN / n ⁺ -PolyS
A gate structure having an i structure has been proposed.

(C) Problems to be Solved by the Invention However, in the manufacture of a semiconductor device in which the tungsten gate electrode is applied to form a MOS semiconductor element by an ion implantation method, since the crystal structure of tungsten is columnar, When ions for source and drain formation are irradiated from the gate structure surface after forming the tungsten gate electrode, so-called channeling in which the ions penetrate into the crystal without causing a large collision in the gap of the tungsten crystal structure easily occurs Ions may pass through the gate electrode and be injected into the channel portion under the gate, possibly disturbing the threshold voltage.

After the gate electrode is formed, an interlayer insulating film (NSG, NSG / BPSG, etc.) is usually formed on the gate electrode by the atmospheric pressure CVD method. At this time, the surface of the gate electrode is oxidized and tungsten oxide (WO
₂ ) is generated. After that, when a high temperature heat treatment (for example, an annealing treatment) of about 900 to 1000 ° C. is performed, tungsten oxide itself, sublimation occurs with respect to the high temperature heat treatment, and since it is very unstable without strength, For example, the NSG / W interface becomes unstable, which hinders the subsequent contact formation process.

Further, it is difficult to etch with the above-mentioned three-layer film, W / TiN / n ⁺ -PolySi.

The present invention has been made to solve the above problems, the gate electrode is relatively easy to etch,
A semiconductor device in which contact formation is facilitated by improving the maskability of the tungsten gate electrode during the ion implantation process and preventing the formation of unstable tungsten oxide on the surface of the tungsten gate electrode during the interlayer insulating film formation or the annealing process. It is intended to provide a method.

(D) Means for Solving the Problems According to the present invention, a step of sequentially forming polysilicon and tungsten on a semiconductor substrate via an insulating film, and providing a gate electrode by patterning, and heat treatment in an ammonia atmosphere By this, the surface of the tungsten,
A method of manufacturing a semiconductor device, comprising: a step of nitriding a side surface and an interface with the polysilicon; and a step of performing an ion implantation process from the electrode surface side to form a source and a drain.

In the present invention, first, n ⁺ − is formed on an insulating film on a semiconductor substrate such as Si or GaAs doped with a predetermined conductivity type impurity.
A polysilicon film is formed, a tungsten film is directly formed on the polysilicon film, and a gate electrode is provided.

The insulating film can be produced, for example, by exposing the semiconductor substrate to a high temperature oxidizing atmosphere to grow the oxide film, or by depositing the oxide film by a CVD method.

The nitriding treatment of the gate electrode in this invention is performed by heating in NH ₃ gas from which oxygen has been removed. A heating temperature of 600 to 900 ° C is suitable at this time, and an electric furnace, a graphite heater furnace, and a lamp heating furnace are used as the heating furnace. Among them, the lamp heating furnace is instantaneously heated and effective for preventing entrapment of oxygen. And high quality tungsten nitride (nitride film)
Are preferably formed on the surface of the tungsten gate electrode.

In the present invention, after that, ion implantation is performed from the gate electrode surface side to form the source and drain. Ion implantation is usually carried out by introducing a gas such as PH ₃ , BF ₃ or AsH ₃ into the ion source at about 10 ^-3 torr, extracting ions from the plasma generated by DC or RF discharge, and irradiating the semiconductor substrate at a predetermined position. Is done. When ions are irradiated from the side of the gate electrode surface, the ions pass through the insulating film, the lower portion of the tungsten gate electrode is blocked by the nitride film, and the ions are accurately injected into the positions corresponding to the drain and the source. Almost no implantation is performed to form a channel region under the drain, the source and the gate electrode between them.

The MOS type semiconductor device obtained as described above is usually subjected to deposition of an interlayer insulating film and annealing treatment. Here, the interlayer insulating film is formed by depositing SiO ₂ around the upper portion of the nitride film of the gate electrode by, for example, the CVD method. The annealing process is performed for the purpose of removing the irradiation damage induced by the ion implantation process after the deposition of the interlayer insulating film and introducing the implanted impurity atoms into the lattice position to electrically activate them.

However, this annealing treatment may be performed after the ion implantation treatment, and may be performed before the formation of the interlayer insulating film. Suitable annealing temperature is 900-1000 ℃.

(E) Function The tungsten nitride film on the surface of the tungsten gate electrode formed in the present invention blocks the ions irradiated during the ion implantation process and prevents the ion implantation into the channel region.

Further, since this tungsten nitride film has excellent heat resistance and oxidation resistance, surface oxidation deterioration of the tungsten gate electrode is prevented during formation of the interlayer insulating film on the gate electrode and annealing treatment.

(F) Example Hereinafter, an example of a method of manufacturing a semiconductor device in which a gate electrode has a two-layer structure of a tungsten (W) film and polycrystalline polysilicon (n ⁺ -PolySi) is shown in the process explanatory diagram of FIG. It will be explained based on.

First, a P-type semiconductor substrate 1 in which silicon is doped with boron is exposed to a high-temperature oxidizing atmosphere to form an insulating film (SiO ₂ ) 2, and then a polycrystalline polysilicon (n ⁺ -PolySi) film 3 is formed.
Then, a tungsten (W) film 4 is deposited (FIG. 1 (a)), and by a reactive ion etching (RIE) method,
An electrode composed of a two-layer film (W / n ⁺ -PolySi) is formed. (Same (b)).

Then, an annealing treatment is performed at a temperature of 800 to 900 ° C. in an ammonia atmosphere to form a nitride film (WN) 5 (the same (c)). At this time, if a normal electric furnace is used, WO ₂ is formed by entrainment of oxygen and the like, so it is better to use a lamp heating furnace. Further, As ⁺ (n ⁺ ) or BF ₂ ⁺ (p ⁺ ) is injected from the gate electrode surface side to form the source 6 and the drain 7 (FIG. 3D), and interlayer insulation is performed by atmospheric pressure CVD method or the like. A membrane (NSG) 8 was formed (Fig. (E))
After that, in order to activate the implanted impurities (As ⁺ , BF ₂ ⁺ ), annealing treatment was performed in a nitrogen gas atmosphere at 950 to 1000 ° C. for about 30 minutes (FIG. 6 (f)) to form a contact. To manufacture a semiconductor device.

The semiconductor device manufactured as described above has the following characteristics.

Etching of W / n ⁺ -PolySi layer structure, W / TiN / n ⁺ -Poly
It is relatively easy compared to the three-layer structure of Si.

When the W / n ⁺ -PolySi film is subjected to an annealing treatment in an ammonia gas atmosphere, the W surface is nitrided (formation of WN), and at the same time, N atoms diffuse in the film and the W / n ⁺ -PolySi interface is formed. Thus, a nitride film of WN, SiN, etc. is formed. Therefore, even if a high temperature annealing treatment of about 1000 ° C is performed, the W
The mutual diffusion of Si and Si is suppressed and the silicide layer is not formed.

By forming the W / N film on the W film, the normal columnar crystal structure of W is changed and the masking property at the time of ion implantation is improved, so that penetration of impurities into the Si substrate is prevented and channeling is performed. Is prevented.

By forming the W / N film on the W film, the oxidation reaction of the W film is prevented even by the oxidizing atmosphere when the NSG film (around 400 ° C.) is formed on the W film by the atmospheric pressure CVD method or the like. , W / NSG interface characteristics become stable.

(G) Effect of the Invention According to the present invention, it is possible to provide a method for manufacturing a semiconductor device in which contact formation with a tungsten gate electrode is easy.

According to the present invention, it is possible to provide a method for manufacturing a semiconductor device having stable current characteristics between a source and a drain with respect to a gate voltage.

According to the present invention, the nitride film formed on the tungsten (W) layer has heat resistance such that a silicide layer is not formed even when subjected to a high temperature treatment of about 1000 ° C., and the reaction between Al and W is prevented. As a result, the barrier property against the Al / Si film is improved,
Furthermore, the oxidation reaction of W can be prevented even in an oxidizing atmosphere during the formation of an interlayer insulating film such as NSG / BPSG, and a semiconductor device having stable current characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a process explanatory view for explaining an example of the manufacturing method of the present invention with a schematic sectional view. 1 ... semiconductor substrate, 2 ... insulating film, 3 ... n ⁺ -polysilicon film, 4 ... tungsten film, 5 ... nitride film, 6 ...
Source, 7 ... Drain, 8 ... Interlayer insulating film.

Claims (1)

[Claims] 1. A step of sequentially forming polysilicon and tungsten on a semiconductor substrate via an insulating film and providing a gate electrode by patterning, and a heat treatment in an ammonia atmosphere to form a surface, a side surface and a surface of the tungsten. A method of manufacturing a semiconductor device, comprising: a step of nitriding an interface with polysilicon, and a step of performing ion implantation from the electrode surface side to form a source and a drain.