Substitute beer and pizza?
Basic Silicon Solar Cell
as fabricated
in Cameron
With
Schematic
A detailed traveler is used to
define the process steps
The process begins with a silicon wafer,
100mm in diameter, (100) orientation,
PRIME grade, p-type boron doped, 1-10
ohm-cm resistivity
The process begins with a silicon wafer,
100mm diameter, (100) orientation, PRIME
grade, p-type boron doped, 1-10 ohm-cm
resistivity
Shown in cross section of wafer
The wafer is cleaned using the
sulfuric acid/hydrogen peroxide
clean
Using PECVD (plasma enhanced chemical
vapor deposition) the back side is coated
with SiO2 to prevent doping of the backside
Using POCl3 as the source for phosphorus
doping an n-region will be created in the ptype silicon wafer
POCl3 bubbler – nitrogen
is bubbled through the
liquid POCl3 and carries
phosphorus into the tube
With the POCl3 running into the tube,
phophorus is diffused into the silicon wafer
at 950C
A n-region is now diffused into the silicon
wafer at 950C
A metal film (aluminum) is sputtered on the
top surface and a photolithographic mask
creates a conductive grid in the metal
A metal film (Aluminum) is sputtered on the
top surface and a photolithographic mask
creates a conductive grid in the metal
Positive photoresist is spun on the metal
coated wafer
A transparency mask of the top side grid is
placed on top of the photoresist coated
wafer and exposed to UV
The image is developed which leaves the
metal conductor pattern
With photoresist protecting the metal,
the unprotected metal is etched away
leaving the top side grid pattern in
metal
A metal film is evaporated on the top surface
and a photolithographic mask creates a
conductive grid in the metal
A second metal film (aluminum) is deposited
on the back for backside contact
A second metal film is deposited on the back
for backside contact
Using PECVD (plasma enhanced chemical
vapor deposition) an anti-reflective coating
of SiO2 is deposited on the top surface
Using PECVD (plasma enhanced chemical
vapor deposition) a anti-relective coating of
SiO2 is deposited on the top surface
Individual cells are diamond saw cut from
the wafer
Individual cells are diamond saw cut from
the wafer
Electrical testing (I-V trace) of the cell is
performed under a solar light simulator
Calibration cell determines the
intensity of sunlight
Electrical testing (I-V trace) of the cell is
performed under a solar light simulator
Electrical testing (I-V trace) of the cell is
performed under a solar light simulator
Blue trace is without sun light, red trace is with sunlight at 1.0 sun
Completed Solar Cell
Assignment
• Lecture 4 assignment from web site