Wen-Kuan Yeh

Selective tungsten CVD on submicron contact hole

Abstract This work investigates the deposition properties of selective chemically vapor-deposited tungsten for filling the deep sub-half micron contact holes using the process of silane reduction of tungsten hexafluoride. Low-resistivity tungsten with excellent selectivity and conformal coverage can be obtained with a SiH 4 WF 6 flow rate ratios less than 0.6 at deposition temperatures between 280 to 350 °C. Junction leakage and contact resistance of the AlSiCu/W n + P and AlSiCu/W/p + n diodes as well as the electromigration properties of the AlSiCu/W n + p structure were investigated.

Deposition properties of selective tungsten chemical vapor deposition

Abstract This work investigates the basic deposition properties of selective tungsten chemical vapor deposition (W-CVD) using the process of silane reduction of WF6 with the SiH4/WF6 flow rate ratio less than 0.6 over the temperature range 280–350 °C. Selective W-CVD was performed on a contact hole patterned silicon substrate with in situ NF3 plasma etching of the silicon substrate prior to the selective tungsten deposition. The W deposition rate, deposition selectivity and W film resistivity were investigated with respect to the SiH4 partial pressure, WF6 partial pressure, total (SiH4 + WF6) deposition pressure, as well as the flow rate of the hydrogen carrier gas. It was found that the deposition rate is proportional to the SiH4 partial pressure. With a constant SiH4/WF6 flow rate ratio, the deposition rate increases with total pressure. At given flow rates of SiH4 and WF6, the deposition rate and film resistivity are dependent on the flow rate of the carrier gas. The experimental results show that the reverse bias junction leakage for the wet etching pretreated W/p+-n junction diode is smaller than that of the plasma pretreated diode. On the other hand, the contact resistance of the Al/W/n+p diode is smaller than that of the Al/W/p+n diode.

Effect of surface pretreatment of submicron contact hole on selective tungsten chemical vapor deposition

The effects of various predeposition treatments of silicon substrates on selective tungsten chemical vapor deposition were investigated using the silane reduction process. The predeposition treatments include HF or buffered HF wet etch and/or NF3 plasma etch. The experimental results show remarkable differences in the initial nucleation of W and the smoothness of the W surface and the W/Si interface among the various treatments, as revealed by scanning electron microscope inspection and atomic force microscope analysis. Plasma etch leads to a rough W/Si interface while wet treatment with HF dip results in a fairly smooth interface. The experimental results show that better I–V characteristics for the W/n‐Si Schottky contact can be obtained by the wet etch treatment prior to the W deposition. The reverse bias junction leakage for the wet etch pretreated W/p+n junction diode is smaller than that of the plasma pretreated diode. In addition, the substrate surface treatments were found to result in Si consumpt...

Chemical mechanical polishing for selective CVD-W

This work investigates chemical mechanical polishing (CMP) for W-filled contact holes, vias, and trenches by selective chemical vapor deposition. A novel process that combines the CMP technique with selective chemical vapor deposition of tungsten (CVD-W) was employed to remove nail heads due to overgrowth and W-particles on the surface of dielectric due to selectivity loss. The overfilled nail heads and the selectivity loss can be completely removed with very low down-pressure (3 psi) in a very short polishing time (30 s). This indicates that the novel process is very promising for ULSI multilevel interconnection application. The removal rate selectivities of W to thermal oxide. PECVDTEOS, and BPSG were found to be 47:1, 30: 1 and 15:1, respectively, while the selectivities of W to the barrier metals of TiW, Ti and Ta were determined to be 0.6: 1, 6: 1 and 28: 1, respectively. 0 1997 Elsevier Science S.A.

An Efficient Preclean of Aluminized Silicon Substrate for Chemical Vapor Deposition of Submicron Tungsten Plugs

Preclean of aluminum trench and via patterned substrates is vital for successful selective chemical vapor deposition of tungsten (CVD-W). A convenient preclean method uses in situ BCl 3 plasma etching to remove the native metal oxide prior to conducting the CVD-W. During the plasma etching, however, the outsputtered aluminum oxide and aluminum can be redeposited on the sidewall of the trench and via hole and on the surface of the dielectric layer, where W nucleation is induced, resulting in creep-up and selectivity loss during tungsten deposition. By using a solution of hydroxylamine sulfate to pretreat the aluminum trench and via hole patterned substrates, we successfully avoid the creep-up and selectivity loss of W deposition.

Thermal Stability of W‐Contacted Junction Diodes

This work investigates the thermal stability of W-contacted pn junction diodes, in which the tungsten contact was formed by selective chemical vapor deposition (CVD) or sputtering process. Reaction of Al and CVD-W at elevated temperature leads to the formation of WA112, and the barrier capability of CVD-W film was dependent on the consumption of W. The sputter-W film has a colunmar structure and contains a higher content of oxygen. The presence of oxygen

Light emission from the porous boron δ-doped Si superlattice

We report the first study on the porous boron δ-doped Si superlattice. Visible photoluminescence (PL) was observed with multiple peaks from the porous boron δ-doped Si superlattice at room temperature. In the electroluminescence (EL) experiment, a bright yellow light emission was observed from the porous boron δ-doped Si superlattices. However, a weak red light emission was also observed from the conventional porous Si which is anodized at the same etching condition. As a result, the structure of the porous boron δ-doped Si superlattice has the ability of controlling the quantum size in porous Si and enhancing the light intensity from porous Si.

Uniformity of epilayer grown by ultrahigh-vacuum chemical vapor deposition

Abstract In this work, we explored the Ge fraction, layer thickness and dopant concentration uniformity of epilayers grown by an ultrahigh-vacuum chemical vapor deposition system (UHV/CVD). Three epilayers were grown for this study: a single epilayer of SiGe, a heavily boron doped Si epilayer and a Si/SiGe superlattice with p + Si cap. The uniformity in a wafer was measured to be less than ±1.5%. In addition, we explored the wafer-to-wafer uniformity of a strained SiGe layer. The variations in thickness and composition between two samples grown in the same run were evaluated to be ±1.3 and ±1.2%, respectively. These results show that uniform layers can be simultaneously obtained on many wafers by the UHV/CVD system.

Thermal stability of AlSiCu/Wn+p diodes with and without TiN barrier layer

Abstract Thermal stability of AlSiCu/W n + p diodes with two different W contact structures prepared by selective W chemical vapour deposition (W-CVD), was first investigated. The diodes with the self-aligned W-contacted structure were able to sustain a 30 min furnace annealing up to 500 °C without degradation of electrical characteristics. The diodes with the contact-hole W-contacted structure were thermally less stable than the diodes with the self-aligned W-contacted structure, presumably because the sidewall of the W-filled contact hole provided a path for diffusion of Al into the Si substrate, leading to junction spiking. The insertion of a 400 A TiN barrier layer between the AlSiCu and W films blocked the Al diffusion path; thus, the AlSiCu/TiN/W n + p diode was able to retain its integrity up to 550 °C furnace annealing.