Building Transistors Today is done with Lithography

Reading Passage Question

Building transistors today is done with lithography, which is a “top-down” process that uses patterning to create the complex layers that make up the transistor structure. It’s a bit like exposing a negative on photographic paper to get the pattern you want and then using this pattern as a template to place each material – metal, insulator or semiconductor – in exactly the right location. This process has worked successfully since the 1950s. But as we get to ever-smaller dimensions, new approaches to building nano-scale devices will be required. At IBM’s T.J. Watson Research Center, we use a technique called self-assembly to grow and directly control nanostructures that could one-day form parts of integrated circuits. Self-assembly looks at a “bottom-up” approach that builds nanostructures in a way that is dictated by physics rather than by an imposed pattern. In some ways it’s like farming, in that you plant seeds to grow a crop, and then support the growth with the right conditions to get the result you want.

Exploring self-assembly doesn’t mean we are ready to throw away today’s approach; instead, we want to use top-down strategies that we have already learned over many years, and combine them with new tricks that use self-assembly. Think of it as water splashing onto a pane of glass. It spontaneously forms little hemispheres because of surface tension. But the positions and sizes of the droplets are random. Now imagine there is a scratch on the glass. Water droplets form on the scratch, because it is a good, low-energy place for the water molecules to stick. We have now combined self-assembly (make a hemispherical droplet on this surface) with an imposed pattern (make a droplet on this part of the surface by using carefully placed scratches.) The result is that we can build more complicated patterns. Flexible, customized patterns—like this water example, but on the nano-scale —help us build integrated circuits. The more precisely we can direct this self-assembly, the more versatility we can achieve.

‘Building transistors today is done with lithography’ is a GMAT reading comprehension passage with answers. Candidates need a strong knowledge of English GMAT reading comprehension.This GMAT Reading Comprehension consists of 4 comprehension questions.

The GMAT Reading Comprehension questions are designed for the purpose of testing candidates’ abilities in understanding, analyzing, and applying information or concepts. Candidates can actively prepare with the help of GMAT Reading Comprehension Practice Questions.

Solution and Explanation

1. What does the passage do as a whole

1. Explains why self-assembly is the best approach to make integrated circuits
2. Explains how the “top-bottom” approach is better than the “bottom-up approach”
3. Shows how the “bottom-up” and the “top-bottom approach” can both complement and hinder development of nano- scaling techniques
4. discusses how “top-bottom approach” has been discarded because of the new approach
5. Reasons that the future necessitates an innovative approach

2. According to the author the primary difficulty in using the top- bottom approach is that

1. The new approach is easier to work with
2. The task of working on ever-smaller dimensions is way too complicated for the approach
3. This process has worked since the 1950s till now only
4. It is not future-ready
5. It is as tedious a task as exposing a negative on photographic paper

3. Why does the author use the example of water splashing on a pane of glass

1. Explain how integrated circuits can be made only by self-assembly
2. To provide an analogy for the combined method
3. To illustrate bottom-up approach
4. To raise questions about the bottom-up approach
5. To evaluate the combined method

4. Which of the following best expresses the function of the first paragraph in relation to the passage as a whole

1. To establish the parameters of an ensuing debate
2. To identify problems in one of the processes, which are then explored in greater details
3. To provide a backdrop for a discussion of a modern day approach
4. To discuss an existing prototype that the author admires
5. To introduce opposing viewpoints, which are then evaluated

5. Which of the following titles best summarizes the passage as a whole

1. A look at the history of nanostructures
2. Pointing out limited usefulness of the “top-down” process
3. Detailed study of transistors
4. At the threshold of a new approach
5. How the top-bottom approach works

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