Browsing by Author "Chang, JJ"

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Direct COSi2 thin-film formation with homogeneous nanograin-size distribution by oxide-mediated silicidation
(2004-09-01)
Chang, JJ
;
Liu, CP
;
Chen, SW
;
Chang, CC
;
Hsieh, TE
By annealing at 460 degreesC for 120 s followed by 600 degreesC 120 s, nanocrystalline CoSi2 thin film with an average grain size of 5 nm can be directly formed from a Co/SiOx/Si multilayer with the SiOx, as a mediated layer. It is found that annealing at 460 degreesC for enough time is crucial for generating enough diffusion channels within the SiOx, layer. After these channels are created, subsequent annealing at 600 degreesC keeps these channels open and is responsible for rapid grain growth. In other words, by using two-step annealing, nucleation and growth processes can be effectively controlled and, hence, the resulting microstructure. The homogeneous nanograin-size distribution is important for ultralarge-scale integration technology below 90 nm to prevent resistance degradation induced by CoSi2, agglomeration. (C) 2004 American Vacuum Society.
Formation of pyramid-like nanostructures during cobalt film growth by magnetron sputtering
(2005-04-01)
Liu, CP
;
Chang, JJ
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Chen, SW
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Chung, HC
;
Wang, YL
Cobalt pyramid-like nanostructures with sharp tips were formed on the surfaces of cobalt thin films grown by magnetron sputtering only when a negative bias was applied. There are two types of pyramids, which grew on top of a columnar grain structure directly from Si(001) substrates. The formation of pyramid-like nanostructures is only selective to a epsilon-Co (hcp) thin film but not a alpha-Co (fcc) thin film, where the basal plane is 10 (1) over bar0 with several well-defined low-energy faceted planes. When grown on Si(111) substrates, the shape of the basal plane changes to a pentagon or other polygon. The island nucleation seems to depend on adatom energy, sputtering rate and the interface stress between the Co thin film and the substrate, but growth is significantly determined by the minimum surface configuration of the structure.
Investigation of the gate dielectric oxidation treatment in trench gate power devices
(2001)
Lin, MJ
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Liaw, CE
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Chang, JJ
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Chang, FL
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Hsu, CCH
In respect of trench gate power devices, it is difficult to achieve satisfactory gate oxide leakage current, breakdown voltage and reliability characteristics. Trench etching process induced silicon surface damage, convex corner and contamination, which will degrade the silicon dioxide quality. It is convinced that post etching treatment including sacrificial oxidation and chemical dry ashing can improve the gate oxide quality significantly. In this article, we study the treatment of a trench capacitor with sacrificial oxidation and classify the effect of each parameter in the oxidation process. The benefit of N2O annealing after gate oxidation will also be discussed. The evaluations of I-V and CV characteristics are the main considerations of the gate oxide quality in this research.
Modified polycrystalline silicon chemical-vapor deposition process for improving roughness at oxide/polycrystalline silicon interface
(2005-01-24)
Chang, JJ
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Hsieh, TE
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Wang, YL
;
Tseng, WT
;
Liu, CP
A new modified low pressure chemical-vapor deposition process for stacked polysilicon (poly-Si) films is developed in this study. The proposed stacked film process combines polysilicon with amorphous silicon films. In this process, polysilicon film was deposited first at 630degreesC, followed by a continuous temperature decrease down to 560degreesC for the deposition of amorphous silicon film. It was found that the doped stacked polysilicon films deposited by this process result in lowering of surface roughness, together with reduction of the (311) phase of the doped amorphous silicon and (110) phase of the doped polysilicon. As a consequence, device performance based on the stacked films also improves. Results of surface roughness analysis indicated that the doped stacked polysilicon film has a root-mean square surface roughness (Rrms) of 78 A, which is smaller than those of doped conventional (630degreesC) polysilicon film (Rrms=97 A), and doped amorphous silicon film (Rrms=123 A, deposited at 560degreesC). Transmission electron microscopic (TEM) observation performed at oxide/polysilicon interface showed that the conventional (630degreesC) oxide/polysilicon interface has high angle grain boundaries on the polysilicon side, which may induce leakage current around the interfacial area. (C) 2004 Elsevier B.V. All rights reserved.
Study of diffusion and quality control for CoSi2 formation by oxide-mediated cobalt silicidation with Ti capping
(2005-09-01)
Chang, JJ
;
Liu, CP
;
Hsieh, TE
;
Wang, YL
;
材料科學與工程學系
The mechanism for the enhancement Of COSi2 thin film formation and film quality control by oxide-mediated cobalt silicidation with a Ti-capping layer is discussed. It is found that Ti absorbs oxygen from the SiOx layer, which induces weak points in the SiOx layer and then enhances Co diffusion as well as COSi2 formation. The control of the reactions between Ti and SiOx is significant because a low reaction rate cannot form a suitable thickness Of CoSi2 film, whereas a high reaction rate tends to form the highly resistive CoSi phase. In addition, to maintain the SiOx layer still existing after annealing is also important because if no SiOx layer remains, unreacted Co would react with Si directly to form the highly resistive phase of CoSi, leading to the smooth interface between CoSi2 and Si and dense bulk CoSi2 thin film being destroyed. (c) 2005 American Vacuum Society.
The study of diffusion and nucleation for COSi2 formation by oxide-mediated cobalt silicidation
(2006-02-24)
Chang, JJ
;
Liu, CP
;
Hsieh, TE
;
Wang, YL
;
材料科學與工程學系
The role of cobalt in oxide-mediated silicidation is studied in terms of diffusion and nucleation by varying annealing conditions, oxide thickness and implantation in Si substrate. Electroscopic imaging in transmission electron microscopy shows that SiOx act as a one-way diffusion barrier reducing the Co effective concentration at the cobalt silicide growth interface leading to CoSi2 as the first formation phase during silicidation. X-ray photoelectron spectroscopy analysis shows that unreacted Co coexists with CoSi2 at the interface between the SiOx layer and Si substrate, implying that Co diffusion rate is faster than CoSi, nucleation rate. An Si-implanted substrate can increase the CoSi2 nucleation rate and reduce the Co accumulation. (c) 2005 Elsevier B.V. All rights reserved.
Uniform COSi2 nano-nucleus formation by oxide mediated silicidation with a Ti capping layer
(2006-03-01)
Chang, JJ
;
Hsieh, TE
;
Liu, CP
;
Wang, YL
;
材料科學與工程學系
The nucleation stage toward CoSi2 with average island size of about 4 nm and uniform island size distribution is obtained from a TiN/Co/ Ti/Co/SiOx/Si multilayer with the SiOx as a mediated layer by annealing at 460 degrees C for 240 s followed by 600 degrees C 240 s. It is found that Ti capping layer can enhance Co diffusion into the Si substrate at higher temperature (600 degrees C 240 s) annealing, which results in larger nucleus size (average grain size about 12 nm) but nonuniform nucleus size distribution. However, two-step annealing for 460 degrees C 240 s followed by 600 degrees C 240 s results in a smaller average nucleus size with better nucleus size distribution. The mechanism responsible for the discrepancy is discussed in the paper. (c) 2005 Elsevier B.V. All rights reserved.