Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – Insulated gate formation
Reexamination Certificate
1999-05-17
2001-02-27
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
Insulated gate formation
C438S618000, C438S660000, C438S675000
Reexamination Certificate
active
06194295
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for producing a refractory metal by chemical phase deposition of a bilayer-stacked tungsten metal, and in particular, to a process for producing a refractory metal by chemical vapor deposition of a bilayer-stacked tungsten metal through using a combination of amorphouslike tungsten nitride and a conventional tungsten metal layers to promote the reliability and stability of adjacent metal layers as well as to reduce the problem of fluorine contamination.
2. Description of the Prior Art
On view of the current technical level, in the latter stages of the manufacture of integrated circuit, it is better for the metal connector line to have a quicker propagation velocity, as well as in various process steps of the subsequent procession process, especially after heat treating, characteristics thereof shall not be caused to change. However, in the present rend, in order to search and study metal silicide having low resistance and high thermal stability, as well as to meet the requirement of ultra large integrated circuit, an device must be made from such metal silicide through a way of chemical vapor deposition. Unfortunately, typical chemical vapor deposition involves fluorine and infiltration of fluorine atom into the device will invariably impair the characteristics of the device.
In addition, according to the recent report, as the size of the device becomes smaller in the future, resistance of the interconnection line will increase in associated with the reduction of the width of the interconnection line. Therefore, it is the present trend to find a conducting material having low resistivity. While use of refractory metal silicide as the gate electrode of metal-oxide-semiconductor field effect transistor (MOSFET) or metal-oxide-semiconductor (MOS) capacitor has been studied for many years, the current topic focuses on the silicides of titanium and cobalt, whereas pure metal has been never employed due to problem of thermal stability. Further, the inward diffusion of fluorine atom during chemical vapor deposition of refractory metal and the outward diffusion of dopants from the polycrystalline silicon has been studied also.
At present, thermal stability has been considered mostly in the study and mass production of refractory metal material having low resistivity. The refractory metal silicide having lowest resistivity is titanium disilicide, but it does not exhibit sufficient thermal stability to meet the requirement of many heating steps in the subsequent procession process. Consequently, most of recent studies are directed to silicide of cobalt. However, there are problems in the silicidification of cobalt, such as, consumption of excess silicon, and lump aggregation.
In view of the foregoing, prior art materials do not how perfect designs and still have many disadvantages to be improved.
In view of various disadvantages derived from the conventional chemical vapor deposition process, the present inventors had tried to improve these and finally found, after persistently and extensively studying for many years, a process for producing a refractory metal by chemical vapor deposition of a bilayer-stacked tungsten metal, thus accomplished the present invention.
SUMMARY OF THE INVENTION
Accordingly, one of the object of the invention is to provide a process for producing a refractory metal by chemical vapor deposition of a bilayer-stacked tungsten metal, wherein pure refractory metal is used to replace refractory metal silicide for obtaining less resistivity, which is based on the fact that the resistivity of the conventional single-layer silicide is up to 70 &mgr;&OHgr;-cm, while that of stacked tungsten is 10 &mgr;&OHgr;-cm which is relatively close to that of pure metal.
The further object of the invention is to provide a process for producing a refractory metal by chemical vapor deposition of a bilayer-stacked tungsten metal, characterized in that amorphous-like tungsten used does not essentially contain grain boundaries such that fluorine atom will not diffuse into the underlayer material during the chemical vapor deposition and hence will not impair the characteristics of the device.
The another object of the invention is to provide a process for producing a refractory metal by chemical vapor deposition of a bilayer-stacked tungsten metal, characterized in that the nitridizing treatment after deposition of the amorphous-like tungsten can be carried out without breaking the vacuum such that the thermal stability and reliability can be improved.
Still another object of the invention is to provide a process for producing a refractory metal by chemical vapor deposition of bilayer-stacked tungsten metal, characterized in that the amorphous-like tungsten nucleates during deposition in the gas phase which does not cause the consumption of silicon on the surface of the silicon substrate during the deposition, and atoms such as phosphorus, boron, and arsenic in the polycrystalline silicon are confined such that they can not diffuse outwardly.
The present process for producing a refractory metal by chemical vapor deposition of a bilayer-stacked tungsten metal, which exhibits various advantages described above, comprises depositing a bilayer tungsten metal in a manner of not breaking the vacuum, by, firstly, depositing one layer of amorphous-like tungsten so as to increase thermal stability thereof and to prevent the diffusion of fluorine atom; then, performing a nitridizing treatment to further promote the fluorine barrier capacity and thermal stability of the amorphous-like tungsten; and finally, deposing a conventional selective chemical vapor deposited tungsten having low resistance on said amorphous-like tungsten to form a bilayer-stacked tungsten MOS capacitor or MOSFET structures that do not influence the propagation resistance thereof.
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Chang Kow-Ming
Deng I-Chung
Yeh Ta-Hsun
Bacon & Thomas
Elms Richard
Lebentritt Michael S.
National Science Council of Republic of China
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