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Inspections Processes of Microchip Manufacturing

By John S. Watson

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Contents Introduction .................................................................................................................................................. 3

Manufacturing Process ................................................................................................................................. 4

Example Material Faults in Chip Manufacturing........................................................................................... 5

Solid Materials Inspection by Electron Microscope ...................................................................................... 6

Solid and Gaseous Materials Inspection by IR Spectroscopy ............................................................. 7

Yield ............................................................................................................................................................... 8

Glossary ....................................................................................................................................................... 10

Bibliography ................................................................................................................................................ 12

About The Author ....................................................................................................................................... 14

List of illustrations

1. Bulk Machining process

2. Material defect examples

3. Image of Particle enlarged through use of an electron microscope

4. Electron microscope used for semiconductor inspection

5. Parts of an IR Inspection unit

6. Flow plan for passing product

7. Flow path plan for failing product

8. Infrared Led

9. Electro Magnetic Spectrum 9

10. Wavelength

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Introduction Microchips are silicon wafers onto which microscopic versions of electronic components are etched to

make up complex interconnected circuitry. These are manufactured of semiconductor material. The

manufacturing process often involves multiple points where inspection is strategically checked to collect

information that contributes to a yield forecast.

A material is judged as a conductor or insulator by how easily electrons are shared or travel among its

atoms. Electrons shared among atoms are called free electrons. An atom is a delicately balanced system

of the forces that act upon electrons, neutrons, and protons. Neutrons and protons only exist in the

nucleus. Electrons orbit the nucleus on the valance shells. Conductors such as copper have a small

amount of electrons on the outer valance shell and therefore release electrons easily to travel among

atoms. Insulators such as glass have too many electrons in the outer valance shell for electrons to be

released easily. Semiconductors are a middle ground in these categories. I agree with the definition that

they are neither good nor bad conductors, but this definition is vague. Actually, other than microchips,

these materials are normally used to make components such as diodes, and thyristors. Such components

can be placed in a conditioned environment that causes them to act as conductors or semiconductors.

(Stutz Quantum Physics )

Manufactures judge the efficiency of a chip manufacturing process upon three factors (Spanos 7):

High volume which allows production of the needed volume per day.

Process design which is the engineering of how manufacturing processes act together.

Circuit design which is the function and the layout of the micro-components inside of the chips.

Electronic function tests and materials inspection make sure the standards of the circuit design

process are met.

In this report I intend to mention information about:

A chip manufacturing process known as bulk micromachining

The inspection of microchip material using Electron Microscopy

The inspection of microchip material using Infrared Microscopy

The yield from a manufacturing process.

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Manufacturing Process Bulk micromachining is a fabrication technique to

build elements of interconnected electronic circuitry

by etching away unwanted parts of a silicon wafer

leaving useful patterns of circuitry in the material.

After this process is complete photo patterning

coats the left over material with a protective layer.

The final product is then submerged into a liquid

etchant such as potassium hydroxide to remove

exposed silicon. Figure 1 is an example of a chip

manufacturing process that could use bulk

micromachining. This process can also be used to

make Micro-Electro-Mechanical-System (MEMS) chips. These are microscopic machine systems used

mostly in motion sensing applications. To make these products with bulk machining, mechanical sensors

are manufactured in place of the interconnected circuitry (Mcwhorter). This motion sensing device can be

connected to electronic circuitry forming a system that functions in reaction to sensed motion. The quality

output from a manufacturing process is the reason many chip manufacturing companies are continually

chosen for new contracts.

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Example Material Faults in Chip Manufacturing The two material faults that occur in microchip manufacturing are material defects and contaminate

particles (Spanos 29). Material defects are deformations in material structure such as interconnected

pattering and mask misalignment (see figure 2 for examples of these defaults).

Contaminate particles are any foreign substance on or embedded in semiconductor material averaging

less than 0.50 a micron or 0.000020 of an inch in size. 50,000 units of this measurement is the length of

an inch. They are normally deposited on the surface of oxygen inside of semiconductor material during

manufacturing by contact with people, material handling and process chambers. Clean rooms have air

filtrations systems to limit particle contamination but it does not prevent it 100%. Figure 3 is an example of

a particle magnified using an electron microscope.

Examples of faults such as these and others can also be detected by means of Infrared spectroscopy.

Infrared spectroscopy can also detect particles in the air prior to polluting material.

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Solid Materials Inspection by Electron Microscope Scanning Electron Microscopy Scanning electron microscopy (SEM) is used for high resolution imaging of surfaces. It is often combined

with an energy dispersive x-ray spectrum (EDS) examination to measure chemical quantities. Electron

microscopy forms a three dimensional image of a surface viewed on a monitor. This image is a magnified

reflection scanned by use of an electron beam onto the inside surface of the monitor. The resolution of

this image is measured in nanometers or one thousandth of a micron. This measurement is 0.000000040

of an inch which can also be written as of an inch. units of this measurement is the

length of 1 inch (Materials Evaluation and Engineering (MEE), Inc. 37-40). An example electronic

microscope produced by Joules USA is pictured in figure 2.

Materials Inspection Applications for SEM (Materials Evaluation and Engineering (MEE), Inc. 37-40)

Thin coating evaluations (Examples of this can be verified by IR spectroscopy)

Surface contamination examination (Examples of this can be verified by IR spectroscopy)

Examination of microchip damage after electronics function test failure (Examples of this can be

verified by use IR Spectroscopy)

Materials Inspection for Applications for EDS

Foreign material analysis

(Examples of this can be verified by IR spectroscopy)

Coating composition analysis

Rapid material alloy identification

Small component material analysis

Phase identification and distribution

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Solid and Gaseous Materials Inspection by IR Spectroscopy Fourier Transform Infrared Spectroscopy

Fourier Transform Infrared (FTIR) spectroscopy is an analytical technique used to identify organic and

inorganic substances such as Lipid, Amide Carbohydrate, Glycogen, Protein Phosphorylation, and silicon.

This technique measures the absorption of infrared radiation by the sample material versus wavelength to

identify molecular compounds and structures. Material is exposed to IR radiation from a broadband

source to excite molecules causing molecular vibration. Variables of this radiation are measured by use of

a spectrometer and interferometer. Figure 3 is the depiction for the optical diagram of a spectrometer.

This vibration is unique to the structure of the material and results in absorbing wavelengths of light from

the radiation. A detector measures variables of the radiation not absorbed. The difference in these

measurements can be used to identify characteristics of a material’s molecular structure. Information

collected from this analysis is viewed on a monitor. This technique can examine a specimen in solid liquid

or gaseous form and detects contaminants near 10um microns in size or 0.00040 inches. 2500 units of

this measurement make the length of an inch (Materials Evaluation and Engineering (MEE), Inc. 17-18).

For more information on FTIR spectroscopy see these definitions in the glossary spectrometer,

interferometer, wavelength, Infrared radiation, Infrared detector, molecular structure, molecule, chemical

compound, and molecular vibration.

Typical Methods Material Inspection for FTIR Spectroscopy

(Materials Evaluation and Engineering (MEE), Inc. 17-18)

Identification of foreign materials such as particles, fibers, residue.

(Verification of foreign materials analysis by EDS)

Identification of bulk material compounds

Identification of constituent materials (Shimadzu France )

The amount of material contaminates such as silicone, and esters.

(Verification of surface contamination identification by SEM)

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Yield Microchip manufacturing is a very complicated process that often involves samples to be inspected

several times throughout the manufacturing process. This multiple inspections process comes at a great

cost because it slows manufacturing and the equipment is expensive. This cost of inspection is validated

by the fact that it collects information about variability that determines the yield forecast for a

manufacturing batch. Variability is the range over which a tolerance varies. Yield is the final product from

the given material a process is started with (May and Spanos 16-19). When applied specifically to

manufacturing it is called the manufacturing yield and measured as the percentage of fabricated product

that results from raw material.

Many factors are considered to determine the amount of product to be inspected and what amount must

pass for a batch to be considered good.

Some of the main factors that decide this are:

The function of manufacturing machinery (ability to hold tolerance and quantity per time output)

Manufacturing processes used for a product output to occur

The amount of product in a batch

The tolerance of the quality control standards

The yield forecast consists of information about chip functionality, and the amount of product yield. It can

predict expectations for product yield and cost for a batch process. The yield is measured in stages as it

passes each inspection. The final test yield is the manufacturing product that has passed all inspections

prior to the final test. The functional yield is the portion of the manufacturing product that has passed the

final inspection. The parametric yield is the overall performance achieved by the functional chips. This is

determined by the results of the electric test. Wafer yield is the percentage of wafers that have passed all

prior inspection methods and are currently being examined in a final inspection process. Wafer yield loss

is the amount of imperfect wafers that are disposed of during chip manufacturing (May and Spanos 16-

17, 150). Figure 4 and 5 are the depiction of chip manufacturing flow path plans with inspections taken at

strategic points to determine yield information. (May and Spanos 148)

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Glossary Batch process: The collection of processes that produces a set amount of yield per a set amount of time

(May and Spanos 17).

Chemical compound: “A substance formed by chemical union of two or more elements or ingredients in

definite proportion by weight.” (The Free Dictionary Chemical Compound)

Infrared Detector: A transducer that utilizes an illumination to current process to transform infrared

energy to current energy. Example components of this type include phototransistors, IR Light Emitting

Diodes (LED) (Bhattacharya 347-357).

Infrared Radiation: An invisible range of energy or light wavelengths that measure from about 750

nanometers, just after the red spectrum of visible light, to 1 millimeter, just before the microwave region

(The Free Dictionary Infrared).

Interferometer: “An optical or radio frequency instrument that uses interference phenomena between a

reference wave and an experimental wave or between two parts of an experimental wave to determine

wavelengths, wave velocities, measure very small distances and thicknesses, and calculate indices of

Molecule: A single particle composed of chemical compound of atoms (Capri Matter ).

Molecular structure: The arrangement of a bonded configuration of molecules (Capri Chemical Bonding).

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Molecular Vibration: The molecular motion unique to the molecular structure of a material (World of

Chemistry).

This motion exists in three forms:

Movement of the entire molecule in a random path in space.

Rotation of a molecule around an axis of the molecule.

Movement between the atoms of a molecule.

Spectrometer: “Any instrument for producing a spectrum, especially one in which variables such as

wavelength, energy, and intensity can be measured.” (The Free Dictionary Spectrometer)

Spectrum: “The distribution of energy emitted by a radiant source, as by an incandescent body, arranged,

in order of wavelength.” (The Free Dictionary Spectrum)

Wavelength: “The distance between one peak or crest and the next corresponding peak or crest of a

wave of light, heat, or energy.” (The Free Dictionary Wavelength) Wavelength can be used to determine

characteristics of a wave such as the: light source, radiation source, color, temperature, frequency,

amount of energy (University of Wisconsin-Madison Electro Magnetic Spectrum), (Graphics & Web

Programming Team of the National High Magnetic Feild Labratory Sources of Visible light )

.

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Bibliography Bhattacharya, Pallab. Semiconductor Opto-electronic Devices. Prentice Hall, 1997.

Capri, Anthony PHD. The Visionlearning Encyclopedia. 2000-2011. 20 10 2011

<http://www.visionlearning.com/>.

Carr, G.L., et al. "Semiconductor Characterization." 1996. Infared Micro-spectroscopy of Semiconductors

as the Diffraction-limit. 19 10 2011 <https://pubweb.bnl.gov/~carr/pdf/nist_man.pdf>.

Graphics & Web Programming Team of the National High Magnetic Feild Labratory . Molecular

Expressions Images from the Microscope . 2004. 20 10 2011

<http://micro.magnet.fsu.edu/micro/about.html>.

Hsu Sherman, C.P., PHD. "Handbook of Instrumental Techniques for Analytical Chemistry." 1997.

Chapter 15 Infrared Spectroscopy. 20 10 2011

<http://www.prenhall.com/settle/chapters/ch15.pdf>.

Joel. "Joel Semiconductor Manufacturing and Inspection Equipment ." 2006-2011. JFAD-7000BT Beam

Tracer . 20 10 2011

<http://www.jeol.com/PRODUCTS/SemiconductorEquipment/WaferInspection/JFAS7000BTBea

mTracer/tabid/431/Default.aspx>.

Lucky Light . "Luck LED Electronics Company Ltd. ." n.d. LL-503IRC2E-2AEIRLED. 20 10 2011

<http://www.leds-manufacturer.com/503IRC2E-2AE.htm>.

Materials Evaluation and Engineering (MEE), Inc. . "Materials Evaluation and Engineering (MEE), Inc. ."

2010. Handbook of Analytical Methods for Materials . 20 10 2011 <http://mee-

inc.com/hamm.html>.

May, S. Gary, PHD and J Costas PHD Spanos. "Fundamentals of Semiconductor Manufacturing and

Process Control." 2006. 20 10 2011.

<http://bib.tiera.ru/ShiZ/Great%20Science%20TextBooks/Great%20Science%20Textbooks%20DVD%20

Library%202007%20-

%20Supplement%20Four/Electronics/Fundamentals%20of%20Semiconductor%20Manufacturing%20and

%20Process%20Control%20-%20G.%20May,%20C.%20Spanos%20(Wiley,%202006)%20WW.pdf>

Mcwhorter, Paul. MEMS Technology . 2003-2008. 20 10 2011

<http://www.memx.com/technology.htm>.

Michel, Hackerott. "Semiconductor Manufacturing and Engineering Data Analysis ." 2006. 20 10 2011

<http://inst.eecs.berkley.edu/~ee290h/fa05/Lecture/PDF/lecture%201%20intro%20IC%20Yeild.

pdf>.

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New Hampshire Materials labratory, INC. . "New Hampshire Materials Labratory INC. ." 1 4 2000. Fouier

Transform Infrared (FTIR) Spectroscopy in the Materials Lab. 20 10 2011

<http://www.nhml.com/resources/2000/4/1/fourier-transform-infrared-ftir-spectroscopy-in-

the-materials-lab>.

Shimadzu France . "Shimadzu Solutions for Science ." 2010. IR Prestige-21. 20 10 2011

<http://www.shimadzu.fr/en/products/spectro/ftir/irprestige21/default.aspx>.

Spanos, J. Costas. "EE290H Semiconductor Mnaufacturing ." 1999. Special Issues in Semiconductor,

Lecture 011999.pdf. 20 10 2011

<http://inst.eecs.berkley.edu/~ee290h/fa05/Lectures/PDF/lectrue%201%20intro%20IC%20Yeild

.pdf>.

Stutz, Micheal. All About Circuits . 2000. 10 20 2011 <http://www.allaboutcircuits.com/>.

The Free Dictionary . The Free Dictionary . 2011. 20 10 2011 <http://www.thefreedictionary.com/>.

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2011 <http://cimss.ssec.wisc.edu/satmet/modules/spectrum/wavelength.html>.

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About The Author John S. Watson

Mattapan, MA 02126 e-mail: careerjsw@yahoo.com

LinkedIn: http://www.linkedin.com/pub/john-watson/13/132/925

This report is rewrite of information included in a final report I wrote for a required class of the MS degree

in Technical Communications for Computer industry at Northeastern University. I scored an 80% on the

paper I turned in to the professor.

I’ve been fascinated about engineering since entering the field over 10 years ago. Through my endeavors

as technician and engineering student I’ve developed skills in electronic circuit testing; printed circuit

board design and repair; programming; machining; manufacturing machinery setup and repair, and

technical report writing.

My earned degrees in engineering are an AS in Electrical Engineering Technology specializing in robotics from Springfield Technical Community College (STCC) 1999, and a BS in Electronics Engineering Technology from Wentworth Institute of Technology 2011. In these programs I’ve learned much about engineering principles involved in electronics engineering. Most of my programming experience which consists of C++, C, Allen and Bradley PLC, robotics, Field Programmable Gate Arrays, and microcontrollers was acquired through my education at these colleges. Most of my electronics design experience was acquired through education at these colleges. It consists of:

semiconductor components circuit design

electro-magnetic principles used in circuit board design, and micro wave transmission

motion detection

control circuitry used in battery charging, filter circuits, digital circuit design, and sensor technology.

In regards to this I have over 5 years work experience in the areas of laser technology, electronics assembly, and electronics test among experience in various other industries. I admit every position I will apply to has a learning curve. In this case I have much ability that shall greatly reflect in my ability to learn skills that could eventually lend to excelling in a promotional opportunity. I also desire to learn from any challenge an engineering position shall present. Currently I'm seeking to acquire a position where I can further practice my engineering skills while

enrolled as a student at Northeastern University. There I’m currently taking classes for a Master’s of

Science in Technical Communications for Computer Industry. I’m interested in how Technical

Communications and Usability are changing the comprehension of product function; procedures involved

in the manufacturing, testing, and designing of products; and information collaboration systems. In my

prior experience I have utilized skills in this area as an engineering student and working as an assembler,

electronics test technician, and technical writer. In these positions I used and wrote instructions, reports,

and presentations that improved: the quality of understanding by clearly stating quality control standards;

explaining complicated procedures using well written sequenced tasks; provide lists of parts and

equipment need for an assembly; and explain the function of electronic equipment and involved test

procedures.

You can send any comments, questions, or writing requests to the contact information mentioned above.

Also for more information on my past experience please see my linkedin profile.

Sincerely, John S. Watson