JPS6148262B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method that is effective when applied to manufacturing a semiconductor device having fine electrodes and wiring made of a high melting point metal. In recent years, high melting point metals such as molybdenum (Mo) and tungsten (W) are often used for electrodes and wiring. The reasons for this are that these metal materials have lower resistance than polycrystalline silicon, which contributes to higher speed devices, that they have excellent processability, such as the ability to perform precise patterning, and that after forming electrodes and wiring, The main requirement is that it can sufficiently withstand the heat treatment temperature of . By the way, in general, photolithography technology that uses ultraviolet light is often used to form electrode and wiring patterns, but when using this technology, the range in which patterns can be miniaturized with good reproducibility is said to be up to 2 [μm]. ing. The present invention enables the formation of electrodes and wiring made of high-melting point metals such as Mo, W, titanium (Ti), tantalum (Ta), niobium (Nb), and hafnium (Hf) in fine patterns with good reproducibility. This will be explained in detail below. Figures 1 to 7 show MIS as an embodiment of the present invention.
This represents the process of forming a gate electrode of a field effect semiconductor device, and will be described next with reference to these figures. Refer to FIG. 1 (1) A field insulating film 2 and a gate insulating film 2G are formed on a silicon semiconductor substrate 1 having one conductivity type, for example, an n-type, by applying a conventional technique. (2) Applying a sputtering method, a molybdenum nitride (Mo ₂ N) film 3 is formed to a thickness of, for example, about 3000 to 5000 [Å]. (3) For example, a chemical vapor deposition method (CVD method) is applied to form a silicon nitride (Si ₄ N ₄ ) film 4. Since this silicon nitride film 4 serves as a mask for reducing the molybdenum nitride film 3, its thickness may be sufficient as long as it does not allow hydrogen (H ₂ ) to pass through. Refer to FIG. 2 (4) Pattern the silicon nitride film 4 using a photoresist film (not shown). The length L may be approximately 2 [μm], which is possible using photolithography technology. As the etching technique at this time, it is preferable to apply a dry etching method. Refer to FIG. 3 (5) Furthermore, the molybdenum nitride film 3 is patterned by applying, for example, a dry etching method. Refer to FIG. 4 (6) The molybdenum nitride film 3 is reduced in a hydrogen atmosphere (reducing atmosphere) at a temperature of 500 to 900 [°C]. This proceeds depending on the equation:

[Table] Since the thickness W of the reduced layer 3 _RED is determined by the diffusion of H ₂ , it can be controlled by time. 8th
The figure is a diagram showing the relationship between thickness W and reduction time t. See FIG. 5 (7) After completion of the reduction for a desired time, the silicon nitride film 4 is removed. Refer to FIG. 6 (8) Etch the reduced layer 3 _RED , that is, the molybdenum layer, using a phosphoric acid-based etching solution or a potassium ferricyanide-based etching solution. in this case,
The etching rate of molybdenum nitride is extremely small compared to that of molybdenum, and a sufficient selectivity can be achieved. FIG. 9 is a diagram comparing the etching rates of molybdenum and molybdenum nitride. Refer to FIG. 7 (9) When the reduction is performed again, the molybdenum nitride film 3 becomes a molybdenum gate electrode 3G.
The length L' of the molybdenum gate electrode 3G is 2-
2W [μm], for example, 1 [μm]
This can be easily achieved by controlling the reduction time t in step (6). After the above steps, the molybdenum gate electrode 3G is
Then, using the field insulating film 2 as a mask, donor impurity (phosphorus or arsenic) is ion-implanted or diffused to form an n-type source region and a drain region (not shown). Further, according to a conventional manufacturing method, a source electrode, a drain electrode, etc. are derived, and wiring is formed. As can be seen from the above description, according to the present invention, in manufacturing a semiconductor device having electrodes and wiring made of a high melting point metal, a high melting point metal nitride film is first formed, and then the film is processed using normal photolithography. The patterned nitride film is patterned using technology, and the periphery of the patterned nitride film is partially reduced to become the high-melting point metal itself, which has a significantly higher etching rate than nitride, and then only the high-melting point metal is removed, and the remaining nitride film is removed. By reducing the nitride film, fine patterns of electrodes and wiring made of high melting point metal can be obtained. When carrying out the present invention, further miniaturization is possible by forming a mask for patterning molybdenum nitride using deep UV light, an electron beam, X-rays, or the like. In any case, the present invention is easy to implement because the electrode/wiring pattern can be made finer by controlling only the time for reducing the nitride of the high melting point metal.

[Brief explanation of the drawing]

1 to 7 are side sectional views of main parts of a semiconductor device at key points in the process to explain the case where the present invention is applied to the formation of a gate electrode, and FIG. 8 shows the relationship between reduction and time. FIG. 9 is a diagram showing the relationship between etching rates. In the figure, 1 is a substrate, 2 is a field insulating film, 2G is a gate insulating film, 3 is a molybdenum nitride film, _3RED is a reduction layer, 3G is a gate electrode, and 4 is a silicon nitride film.

Claims (1)

[Claims] 1. A high melting point metal nitride film is formed on a semiconductor substrate, and after patterning the nitride film, a part of its periphery is reduced to form a high melting point metal and then removed, and the remaining fine patterned nitride film is removed. A method for manufacturing a semiconductor device, comprising a step of reducing the metal to form electrodes and wiring of a high melting point metal.