Semiconductor Technology Alternative Assignment

Note: This is the alternative assignment for EGA211 due to early closure
of the EEE labs because of the Coronavirus. Students who completed the
Silvaco assignment before the labs closed are welcome to submit that
assignment instead. Both versions of the assignment now have the above
This alternative assignment is worth 30% of the marks in the module, the
remaining 70% will be another alternative assessment released later near
the usual exam window. The College of Engineering will provide detailed
instructions in due course.
This assignment has three compulsory questions, each worth ten marks.
You should submit this assignment using Turn-it-in in the Alternative
Assessment folder in the EGA211 mystudies (Blackboard) module.
Please do not cut and paste from other sources. Answer questions in your
own words and prepare your own diagrams/figures as required.
Silvaco Athena/Atlas software is used to model semiconductor technology
process flows and devices. The software is described as a ‘sophisticated
physical finite-element simulator’. Explain the meaning of this description
in 400 words (+/- 100 words) using semiconductor technology or devicebased examples where appropriate.
[10 marks]
Shallow Trench Isolation (STI) has become the preferred method for
isolation in modern CMOS technologies.
a) Draw a process flow (electronically or by hand) to achieve a shallow
trench isolation structure; there is no need to draw the whole CMOS
process. Very briefly describe each main process step.
[5 marks]
b) Briefly discuss the reasons for the semiconductor industry moving
to the STI process and its advantages over older isolation
technologies (maximum of 300 words).
[5 marks]
Figure Q3 shows the current-voltage characteristics of an NMOSFET
device. Using cross-sectional sketches of the NMOSFET, give a physical
explanation of the form of the current-voltage characteristics. Pay special
attention to the effects of the gate voltage and the reasons for the linear
and saturation regions. Your answer should be no longer than 400 words.
[10 marks]
Figure Q3 Typical Current-Voltage Characteristics for NMOSFET