A study into the formation and characterisation of electroless nickel silicide for laser doped solar cells
In this paper we will study the formation and characteristics of nickel silicide compounds and the subsequent specific contact resistivity (Ω.cm2) during the formation of an ohmic contact in solar cells. Using Transmission Line Method (TLM) we will analyse the electrical characteristics of the formed nickel silicides at different sintering temperatures and durations. In each sintering condition tested, the relationship between the total resistance and the distance between the contact pads on the fabricated test structures is measured and graphed. From these graphs the contact resistance (Ω) and specific contact resistivity (Ω.cm2) of the metallisation stack is calculated and tabulated. We conclude the paper by showing the optimum sintering condition of 350°C for three minutes for laser doped solar cells which yields negligible contact resistance.
Development of a Full Silicidation (FUSI) Process for Nickel Silicide
Suicides have been long used to solve the problem of poly depletion effects in the CMOS circuits. The depletion layer in the poly-gates increases the total effective gate-dielectric thickness causing a poor device performance. Many advantages are promised in replacing the Polysilicon gates with metal gates, which include improved sheet resistance of the gates, decreased equivalent electrical thickness of gate dielectric by eliminating the Polysilicon gate depletion effect, and dual work functions, higher than n+ poly work function for NMOS and lower than p+ poly for PMOS in a single full Silicidation (FUSI) of Polysilicon gates. In the ever reducing gate dimension and junction depths, nickel Suicide has become one of the promising candidates for silicides applications in submicron CMOS devices. Nickel silicides has many advantages over other metal silicides due to its one step low temperature formation, low resistivity (l4~2O /.t≤2cm), low Si consumption, and its nature of not suffering from resistivity degradation on narrow lines or gates. However, nickel suicides have some problems associated with them such as the large junction leakage current and sheet resistance degradation due to oxygen contamination and rough interface between NiSi and Si. Nickel Silicide was formed on doped Polysilicon to simulate the effects on gate CMOS regions. Sheet resistance will be measured on silicided Polysilicon and results will be introduced in this report as well.
Study of nickel silicide contact on Si/Si1-xGex
The properties of nickel silicide formed by depositing nickel on Si/p/sup +/-Si/sub 1-x/Ge/sub x/ layer are compared with that of nickel germanosilicide on p/sup +/-Si/sub 1-x/Ge/sub x/ layer formed by depositing Ni directly on p/sup +/-Si/sub 1-x/Ge/sub x/ layer without silicon consuming layer. After thermal annealing, nickel silicide on Si/p/sup +/-Si/sub 1-x/Ge/sub x/ layer shows lower sheet resistance and specific contact resistivity than that of nickel germanosilicide on p/sup +/-Si/sub 1-x/Ge/sub x/ layer. In addition, small junction leakage current is also observed for nickel silicide on a Si/p/sup +/-Si/sub 1-x/Ge/sub x//n-Si diode. In summary, with a Si consuming layer on top of the Si/sub 1-x/Ge/sub x/, the nickel silicide contact formed demonstrated improved electrical and materials characteristics as compared with the nickel germanosilicide contact which was formed directly on the Si/sub 1-x/Ge/sub x/ layer.