Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
2000-06-23
2004-05-18
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C257S416000, C257S734000, C257S771000, C428S001100, C204S298120, C420S528000, C420S529000, C420S537000, C420S538000, C420S548000, C420S549000, C420S550000, C420S551000, C420S552000, C420S580000, C420S581000, C420S587000, C420S588000, C148S421000, C148S422000, C148S423000, C148S424000, C148S426000, C148S432000, C148S437000, C148S438000, C148S442000
Reexamination Certificate
active
06736947
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a sputtering target suitable for formation of wiring of low resistance, an Al wiring film using the same, and electronic components comprising the Al wiring film such as semiconductor elements, liquid crystal display devices, surface acoustic wave devices or the like.
BACKGROUND ART
Recently, semiconductor industry typical in LSI is rapidly advancing. In semiconductor elements such as DRAMs, as higher integration and reliability advance, accuracy required for fine machining is also getting higher and higher. Further, for also sputtering targets being employed in forming wiring or the like, a more homogeneous metallic layer is demanded to form.
Among various kinds of metals for formation of the wiring, aluminum (Al) is attracting attention as formation material of low resistance wiring. Al is also expected as a wiring film being used as gate lines and signal lines of a TFT drive type liquid crystal display device (LCD). This is because as the size of LCD screen becomes larger, the wiring film of lower resistance is in demand. For instance, a large LCD of such as more than 10 inches necessitates the wiring of lower resistance of 10 &mgr;&OHgr; cm or less.
Due to the Al wiring, the low resistance wiring can be realized. However, the Al film, due to heating at approximately 673K during heat treatment after CVD processing or wiring formation, generates protrusions called as hillock. This is because in the course of stress release of the Al film due to heating, Al atoms diffuse to generate the protrusions accompanying the diffusion of the Al atoms. Such protrusions, when generated in the Al wiring, adversely affect on the later process to cause problems.
Thereupon, it is tried to add a slight amount of metallic elements such as Cu, Si, Pd, Ti, Zr, Hf, Nd and Y to the Al wiring (Japanese Patent Laid-Open Publication No. HEI 5-335271). Specifically, these metallic elements are added to an Al target itself. Such metallic elements as mentioned above, forming an intermetallic compound with Al, function as trapping material of Al. Thereby, the aforementioned hillocks are suppressed from forming. In forming Al wiring for highly integrated semiconductor elements and large size LCDs, the Al alloy target that contains a slight amount of such a metallic element is in use.
Now, as higher integration, higher reliability and higher functionality of electronic devices such as semiconductor elements proceed, the structure thereof has become more complicated. As a result of this, a multi level interconnection structure has come to be adopted. Accordingly, further technological innovation is required in fine machining technology. In addition to the wiring, further improvement of reliability and longevity are in demand. For such purposes, sputtering films of high denseness and high orientation are in demand. Since such sputtering films are difficult to obtain by use of the existing general sputtering methods, new sputtering methods such as long throw sputtering or reflow sputtering are being adopted.
In sputtering by the general sputtering method, when segregation or internal defect exists in a target, dust or splash may occur due to an extraordinary electric discharge or the like. These cause defects during formation of DRAMs or TFT elements. There, investigation and elucidation of mechanism causing the dust or splash is in advance, and at the same time, development of preventive measure is also in progress. Some results are being obtained.
However, in the new sputtering methods such as the aforementioned long throw sputtering or reflow sputtering, higher power or higher temperature than ever is being advanced. Accordingly, thermal influence upon a target is becoming more than ever. In the long throw sputtering or reflow sputtering, the thermal influence on the target reaches up to for instance approximately 500° C.
When forming, due to the long throw sputtering or reflow sputtering exposing the target to such severe conditions as mentioned above, an Al wiring film with an Al alloy target including a slight amount of metallic elements such as Cu, Si, Nd, Y or the like, lots of defect modes that have never been ascertained are found to occur. That is, there occurs lots of giant dust particles having a size such large as from 100 to 5000 &mgr;m in the sputtered film to remarkably deteriorate yield of electronic devices such as DRAMs or TFT elements.
Further, in the long throw sputtering or reflow sputtering, there occur a problem that concavities or holes of relatively larger size occur in the sputtering films. These concavities or holes cause to deteriorate electromigration resistance or stress migration resistance. Accordingly, the yield of electronic devices such as DRAMs or TFT elements is deteriorated.
The existing dust preventive measure can not prevent the aforementioned giant dust particles or relatively large size concavities from occurring. Accordingly, sounder fine wiring networks are in demand to be formed by use of the long throw sputtering or reflow sputtering.
Further, in the Al wiring (Al alloy wiring) including a slight amount of the aforementioned metallic elements, due to the intermetallic compound formed between Al and an added element, Al can be suppressed from diffusing. However, there is a problem that a generated intermetallic compound can adversely affect on etching property of the Al wiring. That is, when dry etching such as CDE (Chemical Dry Etching) or RIE (Reactive Ion Etching), or wet etching is applied to the Al wiring film that contains an intermetallic compound, the intermetallic compound cause insoluble remains called as residue. This is largely detrimental in forming the fine wiring network.
From the above, in the Al target and Al wiring that are employed for forming the low resistance wiring, it is demanded to suppress the diffusion of Al due to the heating after film formation to prevent the hillock or the like from occurring. In addition to this, it is demanded for the residue also to be suppressed during etching.
An object of the present invention is to provide a sputtering target that enables to suppress new defect modes (giant dust particles or large concavities) from occurring. The new defect modes occur in particular, when the new sputtering methods such as long throw sputtering or reflow sputtering are employed. Further, the object includes, due to the use of such sputtering target, to provide Al wiring films that are excellent in hillock resistance and formation property of fine wiring network, and electronic components using such Al wiring films.
Further, another object of the present invention is to provide a sputtering target that can form with reproducibility Al wiring films of low resistance that are capable of preventing etching residue as well as hillock from occurring. Further, the object includes, by employing such sputtering target, to provide Al wiring films excellent in hillock resistance and formation property of fine wiring network, and electronic components employing such Al wiring films.
DISCLOSURE OF THE INVENTION
A first invention of the present application enables, through elucidation of reasons why to cause giant dust particles in the new sputtering method such as long throw sputtering or reflow sputtering, to suppress giant dust particles or the like from occurring. The first invention, by stipulating the degree of dispersion of added elements in a sputtering target with the mapping of EPMA (Electron Probe X-ray Microanalyzer) analysis, suppresses the giant dust particles from occurring.
A sputtering target of the first invention consists essentially of 0.1 to 50% by weight of at least one kind of element that forms an intermetallic compound with Al, and the balance of Al. Here, the element that forms the intermetallic compound is uniformly dispersed in the target texture, and, in a mapping of EPMA analysis, a portion of which count number of detection sensitivity of the element is 22 or more is less than 60% by area ratio in a measurement area of 20×20 &mgr;m.
The other sputtering
Ishigami Takashi
Watanabe Koichi
Foley & Lardner
Kabushiki Kaisha Toshiba
McDonald Rodney G.
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