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The main topic of this thesis is to discuss the Si dioxide related
technologies. The thesis consists of two main parts. The first part is
high temperature rapid thermal related oxide. The second part is the
fabrication of Si opto-electronic devices utilizing room temperature
process. For the first part, we discuss the temperature compensation
techniques for high temperature rapid thermal processor in chapter 2.
We put monitor wafers on different susceptors, such as quartz susceptor,
Si susceptor or Si rings on Si susceptor. The monitor wafers'' oxide
thickness distribution behave different for different susceptors. The
role of Si rings is different for different susceptors. In a
transparent susceptor with poor thermal conductivity such as planar
quartz, Si rings work as radiation barrier to prevent heat radiation
loss through quartz susceptor. In a susceptor with good thermal
conductivity such as Si, Si rings work as heat conductive media to
transfer heat from monitor wafer to susceptor. In chapter 2, we also
do numerical simulations to analyze the monitor wafers'' temperature
distributions with different designed patterned susceptors. When using
Si rings as patterned susceptor, although the monitor wafers'' front
surface temperature distributions can be improved, their back surface
temperature distributions show very large temperature gradients. In
order to improve the monitor wafers'' back surface temperature
distribution, we designed back patterned Si susceptor as temperature
compensator. We found that when using back patterned Si susceptor as
temperature compensator, except the monitor wafers'' front surface
temperature distributions can be improved, their back surfaces sustain
much smaller temperature gradients.
In chapter 3, we use irradiation-then-nitridation (ITN) method to
improve the radiation hardness of MOS gate dielectrics. The ITN
process will introduce more nitrogen at the SiO2/Si interface. Since
the existence of strong Si-N bonds at the SiO2/Si interface,
oxynitrides exhibit better performance and are more reliable than
conventional oxides. It appears that more nitrogen atoms can be
incorporated into oxides by ITN method. The ITN treated samples are
more radiation hard than those nitrided in N2O directly.
For the second part, we fabricate Si opto-electronic devices
utilizing room temperature process. We use saturated H2SiF6 to deposit
SiO2 (liquid phase deposited SiO2) to fabricate opto-electronic
devices, or adding HCl into the non-saturated H2SiF6 to etch the Si
into porous structure to fabricate opto-electronic devices. In
chapter 4, we study the electrical properties of the liquid phase
deposited (LPD) SiO2. The electrical properties of LPD SiO2 grown on
native or on bare Si are much different. The larger tunneling current
for LPD SiO2 grown on bare Si may be due to the surface roughness and
the boundaries between oxide seeds'' domains. The existed negative
charges will also affect the MOS diodes'' reverse biased dark current.
In chapter 5, we use the LPD SiO2 to fabricate the MOS solar cells.
First, we fabricate the edge-illuminated LPD MOS solar cells. With a
series combination of 120 pieces edge-illuminated LPD MOS solar cells,
high open circuit voltages of 25~33 V can be obtained in a small area.
Second, we fabricate the planar LPD MOS solar cells. For the LPD SiO2
grown on native oxide, the MOS solar cells perform worse. For the LPD
SiO2 grown on bare Si, the MOS solar cells perform well. For the best
performed LPD MOS solar cells, the LPD SiO2 thickness ranges from
4.5 nm to 5.0 nm. With additional thin transparent Al film on the
exposure area, the solar cells'' parameters are all improved. The
optimal thin transparent Al thickness is about in the range between
4.0 nm to 5.0 nm. Trap-assisted tunneling and photoconductivity
properties of LPD SiO2 are found. The thicker oxide thickness makes
the LPD SiO2 MOS solar cells to be more reliable than conventional
MIS ones.
In chapter 6, we add HCl into the non-saturated H2SiF6 to etch the
Si into porous structure. This kind of porous Si called stain etched
porous Si. Photo-luminescence and electro-luminescence properties of
this stain etched porous Si can be found. We also oxidize the stain
etched porous Si in the rapid thermal processor or in the furnace.
For the rapid thermal oxidized porous oxide, the thicker the initial
porous Si is, the smaller the porous oxide dielectric breakdown field
behaves. However for the furnace oxidized porous oxide, the dielectric
breakdown field is much larger than the conventional oxide. This is
due to the electron traps exist in the furnace oxidized porous oxide.
In addition, the trapped electrons in the furnace oxidized porous oxide
can be "erase out" or "re-write" into the oxide by the biased voltage.
This property of furnace oxidized porous oxide has the potential to be
used as the material of gate dielectrics for nonvolatile memory''s
applications.
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