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WAFER-LEVEL EXTREME ULTRAVIOLET LIGHT DETECTOR
by
Joshua Gubler
A senior thesis submitted to the faculty of
Brigham Young University - Idaho
in partial fulfillment of the requirements for the degree of
Bachelor of Science
Department of Physics
Brigham Young University - Idaho
December 2017
Copyright c© 2017 Joshua Gubler
All Rights Reserved
BRIGHAM YOUNG UNIVERSITY - IDAHO
DEPARTMENT APPROVAL
of a senior thesis submitted by
Joshua Gubler
This thesis has been reviewed by the research committee, senior thesis coor-dinator, and department chair and has been found to be satisfactory.
Date Evan Hansen, Advisor, Senior Thesis Coordinator
Date Lance Nelson, Committee Member
Date Jon Johnson, Committee Member
Date Stephen McNeil, Department Chair
ABSTRACT
WAFER-LEVEL EXTREME ULTRAVIOLET LIGHT DETECTOR
Joshua Gubler
Department of Physics
Bachelor of Science
Integrated circuits are being used in almost every electronic device from smart
phones to supercomputers. These electronic chips are manufactured using pho-
tolithography, which uses electromagnetic radiation to transfer circuit patterns
to silicon wafers. Next generation lithography uses extreme ultraviolet light
to shrink lithography features to the 5 nanometer scale. For this project, a
prototype detector was constructed to measure the intensity of light from a
lithography source. A firmware code was written that controls the data col-
lection process of the detector and collects data samples for every integration
period. The code can switch between a fixed integration period or a variable
integration period. The detector was built and tested and is able to success-
fully integrate voltage from a photodiode. The detector is able to determine
the photodiode current which is proportional to the intensity of light.
ACKNOWLEDGMENTS
I would like to express my gratitude to KLA-Tencor for providing me with
this opportunity and research experience. A special thank you Earl Jensen
would be appropriate for all of the mentorship he provided to me over the
Summer. Thank you for your patience with me and for making me feel com-
fortable while working with you.
I would also like to thank Mei Sun for allowing me the opportunity to work
under her direction in the SensArray Division and providing me a project to
work on.
Next I would like to thank all the professors in the physics department at
Brigham Young University-Idaho. Their preparations for lessons are thorough
and they have been very generous with their time in helping me understand
the material. All of their work has allowed me plenty of opportunities to learn
and grow.
Contents
Table of Contents xi
List of Figures xiii
1 Introduction 11.1 Semiconductor Manufacturing . . . . . . . . . . . . . . . . . . . . . . 11.2 Lithography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.3 Tool Matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.4 EUV Detection Project . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Materials and Methods 72.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3 Results-Discussion 113.1 Analysis of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.2 Converted Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.3 Optocoupler Prototype . . . . . . . . . . . . . . . . . . . . . . . . . . 123.4 Photodiode Circuit Prototype . . . . . . . . . . . . . . . . . . . . . . 143.5 Optocoupler Prototype Resulting Code . . . . . . . . . . . . . . . . . 163.6 Photodiode Prototype Resulting Code . . . . . . . . . . . . . . . . . 183.7 Stability of Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4 Conclusion 214.1 Detector Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . 214.2 Code Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214.3 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.3.1 EUV Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 224.3.2 Potential Code Improvements . . . . . . . . . . . . . . . . . . 22
Bibliography 23
xi
List of Figures
2.1 Diagram of Project Steps . . . . . . . . . . . . . . . . . . . . . . . . . 92.2 Detection Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.3 Final Detector Testing Diagram . . . . . . . . . . . . . . . . . . . . . 102.4 Testing Detector Connections . . . . . . . . . . . . . . . . . . . . . . 10
3.1 Optocoupler Prototype Circuit Diagram . . . . . . . . . . . . . . . . 123.2 Voltage versus Time Small Resistance . . . . . . . . . . . . . . . . . . 133.3 Current versus Sample Small Resistance . . . . . . . . . . . . . . . . 143.4 Voltage versus Time Big Resistance . . . . . . . . . . . . . . . . . . . 153.5 Current versus Sample Big Resistance . . . . . . . . . . . . . . . . . . 153.6 Final Detector Prototype Circuit Diagram . . . . . . . . . . . . . . . 163.7 Voltage versus Time Al 1mm Hole . . . . . . . . . . . . . . . . . . . . 173.8 Current versus Sample Al 1mm Hole . . . . . . . . . . . . . . . . . . 173.9 Stability Testing of Al 1mm Hole with Fixed ADC . . . . . . . . . . . 193.10 Stability Testing of Al 1mm Hole with Variable ADC . . . . . . . . . 20
xiii
Chapter 1
Introduction
1.1 Semiconductor Manufacturing
A semiconductor is a material that will conduct electricity under certain conditions
and under other conditions it will not conduct. Donors are elements that when added
to Silicon they give one or more free electrons. Acceptors are elements that when are
added to silicon they have an empty bond or hole. Silicon is the most widely used
material to make semiconductor devices because its low material cost and relative
abundance. Semiconductor devices are made from adding donors or acceptors to
change the molecular structure of the material in various regions. One kind of device
is made by adding donors on one side (p-side) and acceptors on the other (n-side).
This device is called a diode and when you apply a voltage to the p-side a large
amount of current will flow [1]. Meanwhile if you apply voltage to the n-side very
little current will flow. Another kind of device is made by adding three layers of
alternating donors and acceptors. This device is called a transistor and if its made
of a n-p-n then the middle layer is called the base and the outer layers are called the
emitter and collector. Applying a voltage to the p-side (base) will allow current to
1
2 Chapter 1 Introduction
flow through the collector and emitter (n to n). This amplifies the current through
the device. Another kind of transistor is a field-effect transistor (FET) and it is made
by adding a layer of metal on top of layer of an insulator and placing it directly on top
of the base of a transistor. They call this addition a gate. With no voltage applied
to the gate, the barrier for the electrons to cross the base is too large and no current
flows through. The gate is in the off position. Applying a voltage to the gate reduces
the barrier in the base allowing electrons to cross through, thus creating a current.
The gate is now turned on. Thus, the gate serves as an on/off switch for current to
flow from source to drain.
Transistors and diodes are key components in logic gates. A logic gate is a col-
lection of transistors or diodes that can be arranged in a way to create electronic
switches. An integrated circuit (IC) is an electronic circuit that is created by con-
necting millions of logic gates to build processors to process information. These
integrated circuits are in every modern electronic device and revolutionized the world
when they were invented in 1958 [2].
The semiconductor manufacturing process for building ICs has many steps and
they all fall into four distinct categories: deposition, removal, patterning, and modi-
fications of electrical properties. The deposition category contains any process where
material is grown or transferred onto a wafer. Deposition types: physical vapor depo-
sition (PVD), chemical vapor deposition (CVD), electrochemical deposition (ECD),
and molecular beam epitaxy (MBE). The removal category contains any process that
is used to remove material off of a wafer. The patterning category contains any pro-
cess that is used to shape or alter material on a wafer. The electrical properties of
wafers can be modified by adding in other elements to change their molecular struc-
ture; a process called doping. These four processes can be performed in any order to
create various types of integrated circuits depending on the type of function that is
1.2 Lithography 3
required.
1.2 Lithography
Photolithography is a process used to manufacture electronic chips from silicon wafers.
Photolithography can be categorized as either optical or ultraviolet (UV) lithography.
It is a process being used in micro-fabrication to pattern a thin film by using light
to transfer a pattern from a partially transparent material onto a material that has a
layer of light sensitive material. Photolithography is used to manufacture many inte-
grated circuits in one run by using a pattern that contains hundreds of circuits. The
limit to how small ICs can be produced through lithography can given approximately
by
lm = k1 ·λ
NA(1.1)
where lm is the resolution of the projection system, k1 is the coefficient that contains
various process-related factors, λ is the wavelength of light used, and NA is the
numerical aperture of the lens as seen from the wafer [3]. This equation tells us
the resolution can be improved by increasing the numerical aperture and decreasing
the wavelength of light. Using any kind of light this process also has a competing
restraint since the depth of focus is also a concern with the lens. Depth of focus can
be calculated approximately by
DOF = k2 ·λ
NA2(1.2)
where DOF is the depth of focus, k2 is another coefficient that contains various
process-related factors, λ is the wavelength of light used, and NA is the numerical
aperture of the lens as seen from the wafer [3]. The depth of focus restricts the
thickness of the photoresist that will be affected by the process.
4 Chapter 1 Introduction
Moore’s Law [4] is a projection that the number of transistors in an integrated
circuit doubles approximately every two years. Moore’s Law is used for long-term
planning and to set targets for research and development. Extreme ultraviolet (EUV)
lithography is an upcoming technology to be used to shrink integrated circuits sizes
even smaller than current semiconductor mass produced manufacturing process. EUV
lithography is very desirable because following Eqn. 1.1 it reduces the wavelength
of the light making the feature size of the chips smaller. Since the reduction of the
feature size is happening by decreasing the wavelength of light it allows for a greater
working area in the numerical aperture. Keeping the numerical aperture lower in
Eqn. 1.2 produces a greater depth of focus which allows more of the photoresist to be
affected. EUV lithography would help in keeping up with Moore’s law and improving
technology.
EUV was originally hoped to be used by 2007, but has been delayed due to it
being an incredibly difficult and complex process. EUV lithography machines must
be under vacuum since light radiation at EUV wavelengths is absorbed by almost
anything because of its small wavelength range [5]. Since EUV radiation has such a
small wavelength it causes another complication where all the optics in a EUV light
source need to be made from reflective materials to prevent the radiation from being
absorbed into the optics.
1.3 Tool Matching
Tool matching is important in chip manufacturing because factories can and will have
more than one lithography tool to be used to increase production rates. Companies
can also have multiple factories that have lithography tools making it critical to have
a method of matching various tools against each other, so that you can run the same
1.4 EUV Detection Project 5
process on all the tools. This requires that the tools work the same way, so that
they will have the same results. Adjustments can be made to lithography tools to
calibrate and adjust certain parameters. One parameter that is extremely important
is the light intensity of the source because it directly affects how the patterning is
applied onto the wafers.
If machines do not match each other when running the same process it can cause
many complications because integrated circuits have complex designs and altering
those designs affect what the circuit will do. Any variation in the circuit, even some-
thing as seemingly insignificant as width of the lines and depth of exposure can affect
how the chips run, or if they do at all. Machines that are not matched can also
cause variations in patterns. One variation that can occur is when an originally small
length turn out to be longer than expected. Unmatched machines can also even cause
undesired shorts in circuits, or not shorting when supposed to. All of these variations
can drastically change how an integrated circuit is supposed to run.
1.4 EUV Detection Project
The project involved constructing a detector for EUV light sources to be used for
tool matching. The main task in this project was implementing a detection method
into a working prototype for measuring light intensity. The difficulty in this project
dealt with the fact that this detector is a wafer-level metrology tool which requires
this detector to be the size of a silicon wafer. Wafer-level metrology deals with engi-
neering sensors and tools to monitor machines that process or inspect wafers for chip
manufacturing. This means that the tool was designed to be inserted into a lithog-
raphy tool to measure the intensity of light the source gives off as it is running any
process. That provided serious limitations in the technology we could use to measure
6 Chapter 1 Introduction
light radiation. Since size was an issue there were limitations in the electronics that
were used to build this detector. For this project, the current of the photodiode was
of most interest. However, due to the size, it was necessary to create a way to easily
detect that current. The proposed detection method took care of that limitation by
integrating the voltage of the photodiode by using an operational amplifier as an elec-
tronic integration circuit. The integration of that voltage will let us view the current
of the photodiode since the slope of that integration is the current.
The final task of this project is testing the detector to see how it would perform
under conditions that would match and simulate exposure to an EUV light source.
The EUV light source we are trying to simulate has a pulse of 50 kHz and has a 0.5
Wcm2 light intensity at the wafer level.
Chapter 2
Materials and Methods
2.1 Materials
The materials used to create an integrating circuit were an operational amplifier and
two ceramic capacitors (10 nF). The integrating circuit was tested to verify it could
generate an integrating voltage by using a function generator and an oscilloscope.
This experiment required building an electronic prototype that would be used to
test the intensity of light. The main component of the prototype is a microcontroller
(TI Launchpad MSP430G2553 processor) that is used to control the prototype and
is powered by a USB cable that needs to be connected to a computer. The prototype
was built on a grounded plane prototype board and insulated wire was used with
solder to connect electronic components together. The circuitry consisted of the orig-
inal parts to make the integrating circuit along with one packaged LED-photodiode
array (Optocoupler, HCRN201), one variable resistor (potentiometer, 10kΩ), two 3-
pin jumpers with two jumper caps, and a photodiode (SXUV100). Testing of the
prototype required the following lab equipment: function generator, oscilloscope, os-
cilloscope probes, and microscopes. Code Composer Studio (v4) software was used
7
8 Chapter 2 Materials and Methods
to write and test the code for the microprocessor. The MSP430x2xx Family User’s
Guide [6] was used to look up what bits in the code needed to be added to use com-
ponents of the processor. Texas Instruments TINA was used to write and develop
electronic circuitry.
2.2 Methods
The overall methods of this project can be generalized into three main steps. Figure
2.1 shows a visualization of how those three main steps combine together. The first
step is getting a circuit that will integrate a voltage while a current is being applied,
then it requires setting up a microcontroller to get a light to flash on and off at
the same rate of an EUV source. The final part is getting data collection of the
integration.
The electronic requirement for this design is getting an integrating voltage to
view the current. The main requirement for the code is controlling when electronic
components would be turned on or off. The main requirement for this design is using
a microcontroller to program a microprocessor to handle the data collection. The
detection method required starting the integrator and the analog to digital converter
(ADC) to collect data. The final parts of the detection method are getting the
integrator to stop, transmitting the ADC data buffer, and restarting the whole process
over again.
The first step was setting up the testing apparatus to verify if the detection method
was even possible with some basic lab instruments (function generator, oscilloscope,
power supplies) and the integrating circuit.
After that was building a prototype that would use an optocoupler to provide
the light source and photodiode. This required putting the optocoupler, integrating
2.2 Methods 9
Figure 2.1 A diagram visualizing the three main steps of the project.
Figure 2.2 The detection method for viewing the current of a photodiode byintegrating the voltage shows how the slope of the integration period relatesto the current.
circuit, and potentiometer onto a prototype board. The next step was writing a code
for the microcontroller to control the packaged LED in the optocoupler to flash at
50kHz to simulate the EUV light source.
The first step of the third part of the project was adding to the prototype and the
code to allow for an external light source to be tested with an exposed photodiode.
Writing of the code required a lot of reading to understand what bits of the micro-
controller needed to be stated to use components of the microprocessor. The main
components of the microprocessor that were needed are the comparator, ADC10, and
interrupt routines.
10 Chapter 2 Materials and Methods
Figure 2.3 Photodiode detector prototype testing setup where a LED arraycontrolled by a function generator is used as a light source to test the exposedphotodiode on the detector to collect data that gets sent to the computer.
Figure 2.4 Testing setup for the wiring and connections onto the detectorto view the integration and the ADC sampling times on the oscilloscope.
Chapter 3
Results-Discussion
3.1 Analysis of Results
The first prototype proved that the detection method was possible and controllable
using an optocoupler to simulate the light to keep it known and constant.
The converted data was then used to do calculations of what the current was
from the photodiode when various amounts of light was shone on it. The current was
calculated from I = V ∗Ct
where V is the converted data of the voltage in the circuit,
C is the capacitance in the circuit which was 10nF, and t is the time period.
3.2 Converted Data
Once the detector was running it was sending data via UART through the USB cable
and a program called Tera Term was collecting the data into a log file. That log file
was then exported onto an excel file for better viewing and analysis of the data. Now
that the data was on excel it needed to be converted into useful numbers. The ADC
data was converted into voltage values by multiplying the values by 10242.5
, where 1024
11
12 Chapter 3 Results-Discussion
Figure 3.1 Circuit Schematic for the design of the Optocoupler DetectorPrototype.
is the bit for memory storage and 2.5 is the reference voltage that the ADC uses in
the processor to compare the voltage values. The next step was adding in the time
component for the data which depended on the integration period taken from viewing
the oscilloscope. The time factor is helpful in doing analysis of the data, specifically
looking at the current.
3.3 Optocoupler Prototype
Figure 3.1 is the circuit schematic that was used to build the optocoupler prototype.
This prototype was used to verify that the detector is able to integrate voltage from
a photodiode being exposed to light radiation. The optocoupler prototype was tested
by varying the resistance from the potentiometer which changed how much current
was flowing to the LED inside the optocoupler. Increasing the resistance decreased
the amount of light the LED was giving off which in turn decreased the amount of
current the photodiode in the Optocoupler generated.
Testing was done doing small resistance changes while the detector was collecting
data. Those data were collected following steps as mentioned in the Converted Data
3.3 Optocoupler Prototype 13
Figure 3.2 Graph of the voltage versus time for three samples out of thedata collection for small changes in the resistance of the potentiometer.
section where 93 samples were collected. Each sample had a 358ms integration period
where 32 samples where taken 11.2ms apart from each other. Figure 3.2 shows how
the resistance affects the voltage. The graph has three separate lines where they
vary in when the sample was taken in the data collection. The first line is where
the initial resistance was 1.0kΩ, while the second one was taken in the middle of the
data collection process. The final line was taken when the data collection process was
on the last data sample where the resistance was around 3.0kΩ. This graph shows
how the voltage peak of each line is decreasing as the resistance increases, which
makes sense since there are fewer photons interacting with the photodiodes to create
current. The data were then used to calculate the current of each data sample by
I = V tC
. Figure 3.3 shows the current from each data sample. The graph shows that
the current decreases as the the resistance increases.
Additional testing was done with doing greater resistance changes to see how
well the detector could handle the change to view its limits. This time only 40 data
samples were collected at the same integration period of 358ms. Figure 3.4 shows how
14 Chapter 3 Results-Discussion
Figure 3.3 Graph of the current versus sample number for the data collec-tion of small changes in the resistance of the potentiometer.
greater resistance changes affected the voltage over the data collection. The square
line has a greater slope because the initial resistance was at 0kΩ. Since there was no
resistance the intensity of the LED was too bright and made the integration period go
to fast that the last few ADC conversions were taken after the integration period was
over. This showed the lower limit of the current detector setup where we could not
have the resistance at zero which allowed too much light hitting the detector. The
final line was taken at a resistance of 6.0kΩ. The graph does follow the same trend as
Figure 3.2 did where the voltage peaks decrease as the resistance is increased. Figure
3.5 is the slope of Figure 3.4 data for each data sample. The graph of the current
versus sample number does follow the same general trend where as the resistance is
increased the current decreases. The first quarter of the data points do not match
this trend because the overall slope of their voltage points are lower since some of
them finished the integration period earlier.
3.4 Photodiode Circuit Prototype
The photodiode circuit was the final prototype and was used to record data from an
LED array to view the current from the integrating voltage. The electronic compo-
3.4 Photodiode Circuit Prototype 15
Figure 3.4 Graph of the voltage versus time for three samples out of thedata collection for big changes in the resistance of the potentiometer.
Figure 3.5 Graph of the current versus sample number for the data collec-tion of big changes in the resistance of the potentiometer.
16 Chapter 3 Results-Discussion
Figure 3.6 Circuit Schematic for the design of the Photodiode DetectorPrototype.
nents of the photodiode prototype were connected as shown in Figure 3.6.
Figure 3.7 shows how the voltage increased during time for three separate sample
numbers during the whole collection process for a 1mm hole exposure. Figure 3.8
shows how the current of each sample number for the data collection the LED shining
through a 1mm hole exposure to the detector.
It was also used to test how the light intensity varied by adding filters or changing
the area affected by the light.
3.5 Optocoupler Prototype Resulting Code
This code uses two timers (timer0 and timer1 of timer A) to send a 50kHz pulse to
port 2.6 to control the LED and a 1Hz pulse to port 1.0 to reset the integrator. A
timer interrupt is used to set up the port 1.0 as input to give power to the opamp,
initialize the comparator, and enable the conversions of the ADC. The comparator
interrupt routine is used to reset the P1.0 as output which resets the comparator once
it gets to 1.7V (0.5Vcc) at port 1.5 which is the output of the opamp. The ADC is
3.5 Optocoupler Prototype Resulting Code 17
Figure 3.7 Graph of the voltage versus time for three samples out of thedata collection for a 1mm hole in aluminum foil.
Figure 3.8 Graph of the current versus sample number for the data collec-tion for a 1mm hole in aluminum foil.
18 Chapter 3 Results-Discussion
setup to take 32 data samples during the integration referenced against 2.5V. The
ADC starts conversions after a 5ms interrupt goes off after the integrat. The ADC
conversions are taken from the output of the opamp and stored into an array. After the
comparator interrupt goes off the array of data is sent by the Universal Asynchronous
Receiver/Transmitter (UART) through the USB cable which is initialized in main.
3.6 Photodiode Prototype Resulting Code
The code for the optocoupler prototype was used to create the photodiode prototype
code and some additional improvements were added to it. One of the improvements
that was added was whenever the ADC converts data it turns on power to port 2.3
and turns it right off to send out a pulse that an ADC conversion took place. This
was done to view the ADC conversions by attaching an oscilloscope probe to the port
on the microcontroller. The other improvements to the code dealt with improving
the transmission and the data collection of the data.
When the code is installed in the micro controller and is running it turns on
the integration process. The process starts by allowing the current to flow to the
opamp which then starts integrating the voltage from the photodiode. During the
integration the 32 data samples would be collected that varied in time depending on
the integration period. Once the integration hit 1.7V the integration would stop and
the ADC data buffer would be sent out through the UART. The transmission can
then be collected through the serial port when having the microcontroller connected
with a laptop via a USB cable. After the data was sent the whole process would start
over again to collect more data until the code is terminated.
3.7 Stability of Device 19
Figure 3.9 Graph of the current versus sample number for the data collec-tion for a 1mm hole in aluminum foil where 82 samples were taken using thefixed ADC.
3.7 Stability of Device
The code could switch between either a fixed integration period or a variable inte-
gration period that gets calculated after each integration period while the code is
running. Testing of the stability of the device was done to compare the fixed integra-
tion period code against the variable integration period code. Figure 3.9 shows the
current versus sample number for 82 samples where the fixed integration period code
was used to run the detector. The data had a standard deviation of 0.0007387µA with
regards to the measured current. Figure 3.10 also shows the current versus sample
number for 82 samples, but the variable integration code was running on the detector.
This data had a standard deviation of 0.00324µA.
When the code was running with the variable integration period the stability of
the device was lower because the integration period was changing, which alters when
the data points are collected. The stability of the detector was greater when the
code was running with a fixed integration period because the data was collected at a
constant rate each integration period.
20 Chapter 3 Results-Discussion
Figure 3.10 Graph of the current versus sample number for the data col-lection for a 1mm hole in aluminum foil where 82 samples were taken usingthe variable ADC.
Chapter 4
Conclusion
4.1 Detector Performance
This work has shown the implementation of detection method for a light intensity
detector. The detector is able to integrate voltage from a photodiode that is exposed
to light to tell the current of the photodiode which is proportional to the intensity of
light.
4.2 Code Performance
The code has demonstrated that it can be used to control the detector and collect
the data while the detector is being exposed to a light source. The code controls the
whole data collection process and always collects thirty-two data samples for every
integration period. The integration period depends on the intensity of the light source
where a higher intensity results in a shorter integration period. The code takes the
integration period and calculates an optimal time period to take data samples to
make sure there are always thirty-two data samples.
21
22 Chapter 4 Conclusion
4.3 Future Work
The work that can be continued in this project includes testing the detector with an
EUV light source and improving the code.
4.3.1 EUV Testing
EUV Testing should be done to provide data on how the detector works while being
exposed to an EUV light source.
4.3.2 Potential Code Improvements
The code could be improved to calculate the current and tell the intensity of light
falling on the detector. It would also be beneficial to improve the efficiency of the
code.
Bibliography
[1] H. Stokes, Solid State Physics, 4th ed. Utah: Brigham Young University, 2007.
Print.
[2] J.S.Kilby. Miniaturized electronic circuits. U.S. Patent 3,138,743 filed February
6, 1959 and issued June 23, 1964.
[3] S.M.Sze, M.K.Lee. Semiconductor Devices Physics and Technology, 3rd ed. New
York: John Wiley and Sons, 2012. Print.
[4] G. Moore, ”Cramming More Components onto Integrated Circuits”, Electronics,
Volume 38, Number 8 (1965)
[5] S. Landis. Lithography New York: John Wiley and Son, 2013. Print.
[6] Texas Instruments, MSP430x2xx Family User’s Guide, Rev. J, (2013)
[7] P. Horowitz, W. Hill. The Art of Electronics, 2nd ed. New York: Cambridge
University Press, 1989. Print.
23
24 BIBLIOGRAPHY
