A method for forming a highly activated ultra shallow
ion implanted semiconductive elements for use in sub-tenth micron
MOSFET technology is described. A key feature of the method is the ability to activate the implanted
impurity to a highly
active state without permitting the
dopant to diffuse further to deepen the junction. A selected single
crystalline silicon active region is first amorphized by implanting a
heavy ion such as
silicon or
germanium. A semiconductive
impurity for example
boron is then implanted and activated by
pulsed laser annealing whereby the pulse
fluence, frequency, and duration are chosen to maintain the amorphized region just below it's
melting temperature. It is found that just below the
melting temperature there is sufficient local
ion mobility to secure the
dopant into active positions within the
silicon matrix to achieve a high degree of activation with essentially no change in concentration profile. The selection of the proper
laser annealing parameters is optimized by observation of the reduction of
sheet resistance and concentration profile as measured on a
test site. Application of the method is applied to forming a MOS FET and a
CMOS device. The additional
processing steps required by the invention are applied simultaneously to both n-channel and p-channel devices of the
CMOS device pair.