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
2002-08-27
2004-09-14
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C148S415000
Reexamination Certificate
active
06791188
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film aluminum alloy used as a conductive thin film material for flat type display circuits, such as a liquid crystal display and for semiconductor integrated circuits, and to a sputtering target to form the thin film aluminum alloy.
2. Description of the Related Art
Either aluminum type alloys or copper type alloys are currently used as thin film electrodes and wire materials for semiconductor elements and liquid crystal displays. Among them, copper type alloys have insufficient adhesion to an oxide film and unsatisfactory corrosion resistance and involve difficulties in plasma etching and are therefore used solely for devices in specific use. Aluminum alloys are therefore usually used. Such aluminum materials are required to be decreased in specific resistance and to have hillock resistance. The request for the decrease in specific resistance among these characteristics is intended to prevent signal delay along with accelerated trends to up-sizing and high refinement of wiring width in the fields of recent liquid crystal displays as well as semiconductor elements. On the other hand, the hillock resistance is needed to prevent fine projections (hillocks) from being formed on the film surface due to internal stress caused by Al which inherently has low heat resistance in heating treatment (annealing treatment) after forming electrodes and wiring material films when using an aluminum alloy as electrode and wiring materials having a low specific resistance.
As aluminum type alloys having this type of hillock resistance, aluminum alloys which are made to contain, as an alloy component, based on Al at least one type selected from Nd, Gd and Dy in an amount exceeding 1.0 atom % and up to 15 atom %, are known as shown in Japanese Patent No. 2733006. Eventually, aluminum type electrode materials formed on a substrate for a liquid crystal display suffer from the occurrence of hillocks through heating treatment (annealing treatment) which is inevitable in the production step of the device. For these electrode materials, aluminum alloys are formed by adding Nd and the like to Al for the purpose of improving heat resistance due to a solid solution effect.
Also, for example, Japanese Patent Application Laid-Open Specification No. 2000-235961 discloses a conductive thin film formed using an aluminum alloy comprising Al as its major component, at least one element selected from Zr, Hf, Cu, Ti, Mo, W, Fe, Cr and Mn in a content of 0.5 to 1.5 atom % as a metallic element being sub-component and at least one element selected from Si and Ge in a content of 0.5 to 1.5 atom % as a semiconductor element forming an alloy in combination with Al. This alloy is made to contain a metallic element for the purpose of preventing the occurrence of hillocks by segregating the metallic element at the grain boundary and to contain a semiconductor element for the purpose of preventing the occurrence of hillocks by allowing the element to form an alloy in combination with Al.
SUMMARY OF THE INVENTION
All of the foregoing current aluminum alloys improve heat resistance by reinforcement due to a solid solution effect and segregation effect obtained by adding other elements to Al. In this case, the raw materials of the aluminum alloys are anneal-treated, because the above solid solution effect and segregation effect bring about an increase in specific resistance at the same time. This process ensures that the elements existing as solid solution in Al precipitate, so that the total amount of the solid solution of the elements put in a solid solution, which is a cause of an increase in specific resistance, decreases and the specific resistance therefore falls.
However, the reduction in specific resistance caused by annealing treatment as mentioned above depends upon the temperature under annealing treatment. Therefore, there is a possibility that no aluminum alloy having a desired low resistance is obtained in relatively low temperature (about 350° C. or less) among annealing treatment conditions. Further, it is difficult to converge the specific resistance to a specified range irrespective of ambient temperature conditions, because the specific resistance varies depending on the heat treatment temperature.
Also, if the content of elements to be added to obtain solid solution and segregation effects is high, the hardness of the film formed using an electrode film-forming sputtering target comprising such an aluminum alloy tends to be high. Such an increase in hardness can be suppressed by the precipitation of the added elements through annealing treatment. However, the hardness varies depending upon the temperature under annealing treatment in the same manner as in the case of the above specific resistance and it is therefore difficult to converge the hardness to a specified range.
In view of the above problems, it is an object of the present invention to provide a thin film aluminum alloy which is limited in the occurrence of hillocks, in which stable low specific resistance is consistently maintained irrespective of annealing treatment temperature, and also to provide a sputtering target used to form the thin film aluminum alloy.
In order to solve the above problems, a thin film aluminum alloy according to the present invention is designed to have a Vickers hardness of 30 Hv or less and a film stress (absolute value indication) of 30 kg/mm
2
or less when performing annealing treatment at 25° C. to 500° C. and such physical properties that the above hardness and film stress are distributed in a predetermined hardness range and in a predetermined film stress range respectively within the temperature range of the above-mentioned annealing treatment. The aluminum alloy has the characteristics that the above-mentioned hardness and film stress which inherently vary depending on annealing temperature are distributed in a small variation range within the temperature range of the above-mentioned annealing treatment, so that the dependencies of the hardness and stress on annealing temperature may be neglected approximately and both may be therefore almost regarded as constant against the annealing temperature. In addition, the occurrence of hillocks can be restrained and a low specific resistance, which Al inherently has, can be maintained, because a thin film having a small residual stress (film stress) and a low hardness is formed.
Incidentally, the film stress is expressed as compressive stress when it is minus and as tensile stress when it is plus.
In this case, the thin film aluminum alloy of the present invention preferably comprises, as alloy components, 0.5 to 15 atom % of one or more types selected from Ag, Cu, Mg and Zn, 0.01 to 5 atom % of one or more types selected from Co, Cr, Gd, Hf, Li, Mn, Mo, Nb, Nd, Ni, Pd, Pt, Ru, Sc, Sr, Ta, Ti, W, Y and Zr, and, as remnant, Al and unavoidable impurities. An elemental group consisting of Ag, Cu, Mg and Zn is added as a crystalline nucleus in the above alloy to increase the density of nucleic generation. On the other hand, another elemental group consisting of Co, Cr, Gd, Hf, Li, Mn, Mo, Nb, Nd, Ni, Pd, Pt, Ru, Sc, Sr, Ta, Ti, W, Y and Zr segregates at the grain boundary of the above alloy to prevent crystalline particles from being coarsened. The addition of each of the above elements brings about the result that a fine structure in the aluminum alloy is maintained under annealing and the residual stress is limited to such a small level as mentioned above that the generation of hillocks is restrained, in which a low hardness and a low specific resistance are maintained.
When the content (composition ratio) of at least one or more elements among an elemental group consisting of Ag, Cu, Mg and Zn is less than 0.5 atom % or the content (composition ratio) of at least one or more elements among an elemental group consisting of Co, Cr, Gd, Hf, Li, Mn, Mo, Nb, Nd, Ni, Pd, Pt, Ru, Sc, Sr, Ta, Ti, W, Y and Zr is less than 0.01 atom %, too many hillods are generated to be practical. On
Hagihara Junichiro
Tokuda Ichiro
Andújar Leonardo
Arent & Fox PLLC
Flynn Nathan J.
Vacuum Metallurgical Co., Ltd.
LandOfFree
Thin film aluminum alloy and sputtering target to form the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thin film aluminum alloy and sputtering target to form the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thin film aluminum alloy and sputtering target to form the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3205587