commit 0619ffc732941b02588a3f639c04b5dcf76d15ed
Author: Danila Fedorin <danila.fedorin@gmail.com>
Date:   Tue Jan 12 15:34:38 2021 -0800

    Add initial homework solution.

diff --git a/HW1.tex b/HW1.tex
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+\documentclass{article}
+\usepackage[margin=1in]{geometry}
+\title{Homework 1}
+\begin{document}
+\maketitle
+\section*{Q1}
+The three version of Moore's Law are as follows:
+\begin{itemize}
+    \item \textbf{Scaling Up}. We were able to shrink the size
+        of a transistor, thereby roughly doubling the number of transistors
+        on a single chip every 1-2 years.
+    \item \textbf{Scaling Down}. The costs of a single
+        transistor decreased by about 30\% every year.
+        This made it cost-effective to use microprocessors
+        for various applications.
+    \item \textbf{Scaling Out}. We are able to combine
+        microprocessors with other technologies, even
+        entirely in our silicon processing. For instance,
+        we can make tiny accelerometers, or use a saphire
+        substrate instead of silicon to work with
+        light.
+\end{itemize}
+
+\section*{Q2}
+According to Denard scaling, power density remains constant.
+If this holds, we can scale down our designs and things
+will continue to just work.
+
+\section*{Q3}
+We were not able to scale voltage at the desired factor. Eventually,
+thermally-induced voltages are comparable in magnitude with the voltages
+we use to drive our transistors, which makes them work unreliably or leak
+charge. Because we can no longer scale voltage down, our power density
+keeps growing. This means that our processors get increasingly hot,
+which, in turn, limits the clock speeds of our designs.
+
+\section*{Q4}
+A wafer is first covered in Photoresist, a chemical that is
+either soluble until or before it comes into contact with UV light.
+UV light is shined onto the photoresist past a mask, which creates
+regions that are exposed to UV (where not blocked by the mask) and regions
+that are in ``shadow'' (blocked by the mask). Depending on the type of
+photoresist, one of the regions (but not the other) becomes soluble,
+and can be removed using a solvent (developer). This leaves a pattern
+of photoresist on top of the wafer. Different approaches can then
+be used that affect only the areas not covered by photoresist (for instance,
+if gold is below the photoresist layer, a chemical can be used to
+dissolve the gold; the chemical will not touch the gold covered by
+photoresist, thus leaving it in place).
+
+\pagebreak
+\section*{Q5}
+Not quite sure what this question means, but I have a few thoughts:
+
+\begin{itemize}
+    \item Instead of trying to reduce the wavelength of light further
+        down (which didn't actually work out), we use the same old
+        193nm light, and focused on refining the technique.
+    \item We started to perform multiple lithography (and maybe etch)
+        steps for a single layer, which made it possible to
+        halve (or further reduce) the minimum pitch.
+    \item Self-aligned mutli-patterning techniques cannot really lay down
+        ``holes'' in lines; these holes have to be added later.
+        As a result, layouts of modern CPUs are very regular,
+        since many components ``share'' a single line. This
+        allows for far less freedom in where to place the
+        various components of a chip.
+\end{itemize}
+
+\section*{Q6}
+From the ``Rosetta Stone of Lithography'' it looks like with true double patterning,
+the smallest we can get is the 10nm node (50nm pitch).
+
+\section*{Q7}
+We use tin plasma! Apparently, tin is ``fairly efficient'' at converting laser
+light into EUV.
+\end{document}