Method of making self-aligned lightly-doped-drain structure for MOS transistors

Patent · Mon Jan 01 00:00:00 EST 2001

OSTI ID:874057

Weiner, Kurt H ^[1]; Carey, Paul G ^[2]

---

1. San Jose, CA
2. Mountain View, CA

A process for fabricating lightly-doped-drains (LDD) for short-channel metal oxide semiconductor (MOS) transistors. The process utilizes a pulsed laser process to incorporate the dopants, thus eliminating the prior oxide deposition and etching steps. During the process, the silicon in the source/drain region is melted by the laser energy. Impurities from the gas phase diffuse into the molten silicon to appropriately dope the source/drain regions. By controlling the energy of the laser, a lightly-doped-drain can be formed in one processing step. This is accomplished by first using a single high energy laser pulse to melt the silicon to a significant depth and thus the amount of dopants incorporated into the silicon is small. Furthermore, the dopants incorporated during this step diffuse to the edge of the MOS transistor gate structure. Next, many low energy laser pulses are used to heavily dope the source/drain silicon only in a very shallow region. Because of two-dimensional heat transfer at the MOS transistor gate edge, the low energy pulses are inset from the region initially doped by the high energy pulse. By computer control of the laser energy, the single high energy laser pulse and the subsequent low energy laser pulses are carried out in a single operational step to produce a self-aligned lightly-doped-drain-structure.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• DOE Contract Number: W-7405-ENG-48
• Assignee: The Regents of the University of California (Oakland, CA)
• Patent Number(s): US 6303446
• OSTI ID: 874057
• Country of Publication: United States
• Language: English

Related Subjects

method
self-aligned
lightly-doped-drain
structure
transistors
process
fabricating
lightly-doped-drains
ldd
short-channel
metal
oxide
semiconductor
utilizes
pulsed
laser
incorporate
dopants
eliminating
prior
deposition
etching
steps
silicon
sourcedrain
region
melted
energy
impurities
gas
phase
diffuse
molten
appropriately
dope
regions
controlling
formed
processing
step
accomplished
single
pulse
melt
significant
depth
amount
incorporated
furthermore
edge
transistor
gate
pulses
heavily
shallow
two-dimensional
heat
transfer
inset
initially
doped
computer
control
subsequent
carried
operational
produce
lightly-doped-drain-structure
metal oxide
heat transfer
laser pulse
pulsed laser
energy laser
oxide semiconductor
/438/