Browsing by Author "Lain, KD"

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Suppression of fluorine impurity in blanket chemical vapor deposited tungsten film for via fills with a novel two-step deposition technique
(1997-04-01)
Chang, KM
;
Yeh, TH
;
Lain, KD
;
Fu, CM
;
電子工程學系及電子研究所
Blanket chemical vapor deposited tungsten (CVD-W) offers the potential to fabricate reliable contacts for submicron multilevel metallization. In via filling application, various aluminum fluorides were formed by the reduction of WF6 with aluminum underlayer. These compounds will stay at CVD-W/Al interface and act as insulating layers which cause electrical degradation. In addition, impurities like fluorine or oxygen induce the formation of beta-W lattices as well as high film resistivity. In this work, a two-step chemical vapor deposition of tungsten was developed to suppress the fluorine impurities in tungsten films and at CVD-W/Al interface for blanket CVD-W application. The first step involves a gas phase nucleation with high SiH4/WF6 flow ratio (i.e., 2.5) to deposit a thin tungsten film as the glue layer. It was found that the probability of the WF6 reduction with underlying aluminum was suppressed because the WF6 was completely consumed by SiH4 before arriving onto aluminum surface. Meanwhile, this gas phase nucleated tungsten exhibits blanket deposition capability and an amorphous structure. The second step includes typical CVD-W process (i.e., SiH4/WF6 flow ratio <1) to grow thick tungsten film. Secondary Ion Mass Spectroscopy (SIMS) measurements indicate that the fluorine impurities in tungsten aim and at CVD-W/Al interface are drastically reduced. Also, the gas phase nucleated tungsten can be reproducibly deposited without attacking the aluminum underlayer. Moreover, a lower tungsten resistivity, lower via resistance and longer electromigration lifetime are achieved in the Al/W/Al Kelvin structures produced by two-step deposition technique than those of the typical CVD-W films deposited directly on aluminum.
Suppression of fluorine impurity in blanket chemical vapor deposited tungsten film for via fills with a novel two-step deposition technique
(1997-04-01)
Chang, KM
;
Yeh, TH
;
Lain, KD
;
Fu, CM
;
電子工程學系及電子研究所
Blanket chemical vapor deposited tungsten (CVD-W) offers the potential to fabricate reliable contacts for submicron multilevel metallization. In via filling application, various aluminum fluorides were formed by the reduction of WF6 with aluminum underlayer. These compounds will stay at CVD-W/Al interface and act as insulating layers which cause electrical degradation. In addition, impurities like fluorine or oxygen induce the formation of beta-W lattices as well as high film resistivity. In this work, a two-step chemical vapor deposition of tungsten was developed to suppress the fluorine impurities in tungsten films and at CVD-W/Al interface for blanket CVD-W application. The first step involves a gas phase nucleation with high SiH4/WF6 flow ratio (i.e., 2.5) to deposit a thin tungsten film as the glue layer. It was found that the probability of the WF6 reduction with underlying aluminum was suppressed because the WF6 was completely consumed by SiH4 before arriving onto aluminum surface. Meanwhile, this gas phase nucleated tungsten exhibits blanket deposition capability and an amorphous structure. The second step includes typical CVD-W process (i.e., SiH4/WF6 flow ratio <1) to grow thick tungsten film. Secondary Ion Mass Spectroscopy (SIMS) measurements indicate that the fluorine impurities in tungsten aim and at CVD-W/Al interface are drastically reduced. Also, the gas phase nucleated tungsten can be reproducibly deposited without attacking the aluminum underlayer. Moreover, a lower tungsten resistivity, lower via resistance and longer electromigration lifetime are achieved in the Al/W/Al Kelvin structures produced by two-step deposition technique than those of the typical CVD-W films deposited directly on aluminum.
The characteristics of chemical vapor deposited amorphous-like tungsten film as a gate electrode
(1998-09-01)
Chang, KM
;
Deng, IC
;
Shih, CW
;
Lain, KD
;
Fu, CM
Tungsten films are often advantageously formed by the chemical vapor deposition system which using WF6 gas through SiH4 or H-2 reduction. The fluorine species will diffuse into poly-Si/SiO2/[Si] multilayers by a driving force which is the reaction of WF6 and poly-Si gate. When too many fluorine atoms diffused into the gate oxide, the fluorine atoms will cause more strain in the gate oxide and the electrical characteristics of device will shift. An amorphous-like tungsten layer was deposited at a flow rate ratio of 2.5 of SiH4/WF6. The driving force in the amorphous-like tungsten film deposition is far less than that in selective tungsten film deposition; therefore, the concentration of fluorine atoms in the amorphous-like tungsten film is much less than in the selective tungsten film. We proved that only few fluorine atoms were incorporated in amorphous-like tungsten film which has good characteristics in the application of gate electrode.
Thermal stability of amorphous-like WNx/W bilayered diffusion barrier for chemical vapor deposited-tungsten/p(+)-Si contact system
(1999-03-01)
Chang, KM
;
Deng, IC
;
Yeh, TH
;
Lain, KD
;
Fu, CM
The barrier characteristics of tungsten nitride/tungsten (WNx/W) bilayer formed by an in situ nitridation on a thin chemical vapor deposited amorphous-like tungsten (CVD a-W) film in CVD-W/Si contact system have been investigated. The thickness of WNx layer after a 5 min of N-2 plasma exposure at 300 degrees C approximated 50 nm and the atomic ratio of W to N in WNx layer was 2 : 1. In the CVD-W/a-WNx/a-W/Si multilayered sample, no discernible tungsten silicide was detected by X-ray diffractometer (XRD) at W/Si interface after annealing at 750 degrees C. Meanwhile, with the Rutherford backscattering spectroscopy (RBS) analysis and the measurement of p(+)n junction leakage current, the CVD-W/a-WNx/a-W/Si multilayer maintained the integrity of interface and the CVD-W/a-WNx/a-W/p(+)n diode kept the reverse leakage current density less than 9 x 10(-9) A/cm(2) while the post annealing was carried out at 700 degrees C for 30 min. As the experimental results, the effectiveness of amorphous-like WNx/W bilayered diffusion barrier is attributed to stuff grain boundary with N atoms as well as to eliminate the rapid diffusion paths by using CVD a-W material.