Rainer Giedigkeit

Impact of dual beam laser spike annealing parameters on nickel silicide formation characteristics

Nickel silicide is a common contact material for current generation microelectronic devices. As the technology nodes become smaller, forming the NiSi phase with milli-second or below annealing is an attractive alternative to conventional RTA annealing because of the potential for increased device performance and yield. This paper will discuss the use of a dual beam laser spike annealing (LSA) to form nickel silicide on silicon wafers in the microsecond regime. A detailed evaluation of anneal times (400µs and 800µs) and anneal exposure (100% and 50% stitching, or single and double anneals) was done on 300mm wafers with NiPtSix film (post-RTA1 anneal/100Å). Analytical testing by sheet resistance, CGS, XRD, AES depth profile, AFM, SEM, and ellipsometry was performed on the wafers to examine the effects of anneal times and exposure on phase transition and/or film morphology. A study of the nickel silicide transition curve by sheet resistance vs. temperature shows that there is a higher NiSi damage threshold temperature for single anneal as compared to double anneal. For uniformly annealed full wafers processed at temperatures slightly below the damage threshold, the results confirm: 1) NiSi was formed with negligible or small differences in film structure and, 2) the 100% stitching single annealed wafers show similar process performance in terms of sheet resistance and within wafer uniformity to the 50% stitching double annealed wafers at both 400 and 800µs.

Characterization of nickel silicide transition behavior using non-contact CGS metrology

Advanced millisecond annealing technologies are being implemented to enable scaling of silicidation of Ni for contacts. There are several aspects of the millisecond annealing process that must be optimized in order to minimize defects and improve yield. One critical aspect is that NiSi agglomeration must be suppressed at higher annealing temperatures. Typically, the onset of agglomeration can be detected by microscopic observation, phase analysis or electrical measurement. This paper describes an alternate approach using the Coherent Gradient Sensing (CGS) interferometer to provide a fast, non-contact method for quickly identifying the nickel silicide agglomeration threshold. Wafers with blanket Ni films were annealing using laser spike annealing (LSA) at various temperatures. The CGS technique is demonstrated to be sensitive to changes in surface morphology associated with the nickel silicide phase transitions and agglomeration and the results correlate to more conventional metrology approaches.