Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
2000-11-21
2003-12-09
Potter, Roy (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S764000
Reexamination Certificate
active
06661096
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
Technical Field of the Invention
The present invention relates to a wiring material of semiconductor devices. Specifically the present invention relates to a semiconductor device having a circuit comprising a thin film transistor (hereinafter referred to as TFT), and a manufacturing method thereof. For example, the present invention relates to an electro-optical device, which is represented by a liquid crystal display panel, and an electronic device with an electro-optical device loaded as a component.
In this specification, a semiconductor device indicates general devices that can function by using semiconductor characteristics, and that electro-optical devices, semiconductor circuits, and electronic devices are all categorized as semiconductor devices.
Prior Art
Recently, techniques for using semiconductor thin films (with a thickness of about several nm to several hundreds of nm) formed over a substrate having an insulating surface to constitute a thin film transistor (TFT) have been in the spotlight. Thin film transistors are widely applied to electronic devices such as ICs and electro-optical devices, and the development thereof as switching elements for image display devices is hastened.
Conventionally, aluminum films formed by sputtering and having low resistivity have been often used as the wiring material for the above stated TFTs. However, when a TFT is manufactured by using aluminum as a wiring material, operation error or deterioration of TFT characteristics were caused by formation of projections such as hillocks or whiskers or by diffusion of aluminum atoms into the channel forming region, in the heat treatment.
Problem to be Solved by the Invention
As stated above, aluminum is not a preferable wiring material in the TFT manufacturing process because of its low heat resistance.
Therefore, materials comprising, for example, tantalum (Ta) or titanium (Ti) as a main component are being tested for use as a wiring material other than aluminum. Tantalum and titanium have a high heat resistance in comparison to aluminum, but on the other hand there arises a problem of high electrical resistivity. Further, if tantalum is performed with heat treatment at a temperature of about 500° C., it becomes a problem that the electrical resistance increases by several times in comparison with that before heat treatment.
Furthermore, in the case that a film formed on a substrate possesses a large stress, substrate warping and film peeling generate, so it is preferable to perform film stress control and to form a film which possesses as low a stress as possible for a film formed by sputtering. As one means of controlling film stress, the use of a mixed gas of argon (Ar), krypton (Kr), xenon (Xe) as a sputtering gas has been proposed. However, since krypton (Kr) and xenon (Xe) are expensive, it is unsuitable for cases of mass production to use the mixed gas.
The present invention is accomplished in view of the above stated problems. The object of the present invention is to provide an electro-optical device having high reliability by using a material which has sufficiently low electrical resistivity, and sufficiently high heat resistance, as a wiring or as an electrode of respective circuits in the electro-optical device, typically an AM-LCD, and method of manufacturing thereof.
Means to Solve the Problems
The structure of the present invention disclosed in this specification relates to a wiring material comprising tungsten or a tungsten compound as a main component, characterized in that argon is contained in an inert element within the wiring material at an amount of 90% or more, and the amount of sodium contained within the wiring material is 0.3 ppm or less.
In the above structure, the tungsten compound is a compound between a kind or a plural kinds of elements selected from the group consisting of Ta, Ti, Mo, Cr, Nb, and Si, and tungsten.
Further, the electrical resistivity of the wiring material in the above structure is 40 &mgr;&OHgr;·cm or less, preferably 20 &mgr;&OHgr;·cm or less.
Further, the structure of another invention relates to a semiconductor device having a wiring made from a metallic film containing a kind or a plural kinds of elements selected from the group consisting of W, Ta, Ti, Mo, Cr, Nb, and Si, a metallic compound film comprising said elements as main components; an alloy film of a combination of said elements; or a lamination film of thin films selected from the group consisting of said metallic film, said metallic compound film and said alloy film, characterized in that the wiring includes argon in an inert element within the wiring at 90% or more, and the amount of sodium contained within the wiring is 0.3 ppm or less.
Furthermore, the structure of another invention relates to a semiconductor device provided with a wiring containing a film comprising tungsten or a tungsten compound as a main component, characterized in that the wiring includes argon in an inert element within the wiring at an amount of 90% or more, and the amount of sodium contained within the wiring is 0.3 ppm or less.
Still further, the structure of another invention relates to a semiconductor device provided with a wiring having a lamination structure containing a film comprising tungsten or a tungsten compound as a main component, and a nitride film of tungsten, characterized in that the wiring includes argon in an inert element within the wiring material at an amount of 90% or more, and the amount of sodium contained within the wiring material is 0.3 ppm or less.
In addition, the structure of another invention relates to a semiconductor device provided with a wiring having a lamination structure including a silicon film having an added impurity element for imparting conductivity, a film comprising tungsten or a tungsten compound as a main component, and a nitride film of tungsten, characterized in that the wiring includes argon in an inert element within the wiring at an amount of 90% or more, and the amount of sodium contained within the wiring is 0.3 ppm or less.
In each of the above structures, the wiring is characterized by being formed by sputtering using argon as a sputtering gas.
In each of the above structures, an inert element other than argon (Xe or Kr) is characterized by being contained within the wiring at an amount of 1 atoms % or less. preferably, 0.1 atoms % or less.
Furthermore, any one of the above respective structures is characterized in that the internal stress of the tungsten film or the film comprising the tungsten compound as its main component is from −2×10
10
dyn/cm
2
to 2×10
10
dyn/cm
2
, preferably, −1×10
10
dyn/cm
2
to 1×10
10
dyn/cm
2
.
In addition, any one of the above respective structures is characterized in that the line width of the wiring is 5 &mgr;m or less.
Further, any one of the above respective structures is characterized in that the film thickness of the wiring is 0.1 &mgr;m or more, and 0.7 &mgr;m or less.
Still further, any one of the above respective structures is characterized in that the wiring is used as a gate wiring of a TFT.
The structure of the present invention for realizing each of the above structures, relates to a method of manufacturing a semiconductor device comprising at least a wiring on an insulating surface, characterized in that the wiring is formed by steps of forming a tungsten film by a sputtering method and patterning the tungsten film.
In the above structure, the sputtering method is characterized in that a tungsten target having a purity of 4N or more is used.
In the above structure, the sputtering method is characterized by using a tungsten alloy target having a purity of 4N or more.
In the above structure, the sputtering method is characterized by using only argon as a sputtering gas.
Further, in each of the above structures, it is possible to obtain the desired value of film stress within the range of −2×10
10
dyn/cm
2
to 2×10
10
dyn/cm
2
, preferably, −1×10
10
dyn/cm
2
to 1×10
10
dyn/cm
2
Sato Keiji
Takayama Toru
Yamazaki Shunpei
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Potter Roy
Semiconductor Energy Laboratory Co,. Ltd.
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