Micro-Lesson: A Slice Of Knowledge

microchip image

Q:

This object can hold the knowledge of over 100 million books, but it’s made from sand. What is it?

A:

A microchip. The main ingredient of sand is an element called silicon--the second most common element on Earth, next to oxygen. A microchip consists of an ultra-thin wafer (slice) of silicon. A single microchip could store the text of over 100 million books.

Micro-Lesson* Plan

Topic: Innovations in Science and Technology

Some objects occur in nature; others have been designed and made by people to solve human problems and enhance the quality of life.

Download the enlarged image and show it to your class (using a projector or a color printout). Ask the question above.

In the process of the discussion, be sure to ask students whether they think the item in the image is natural or man-made. Help them to observe the features of the object that indicate that it is man-made (the straight lines, smoothness of surface, and shininess).

Once you have elicited or presented the answer, introduce the concepts of science, technology, and innovation, with a question such as “Where do you think microchips came from?” Guide students to understand that innovators take the knowledge gained through rigorous observation and testing (science) and create practical applications for such knowledge (technology). The following brief summary of how microchips get made can be introduced in the process of your discussion:

1. First, you may wish to explain these terms:

Semiconductor: A material that can’t conduct electricity as well as a conductor (a material, like copper, through which electricity can flow easily), and which doesn’t resist the flow of electricity as much as a resistor (a material, like rubber, that acts to impede the flow of electricity). This quality makes semiconductor material ideal for a microchip, because it makes it more possible to change and control the flow of electricity.

Silicon: The main ingredient of sand, and the second most common element on Earth (next to oxygen). Silicon is a semiconductor.

Circuit: A complete path through which electricity can flow.

Transistor: A device that can amplify (increase) an electrical signal, or that can switch the signal on or off.

Wafer: A thin slice of material.

Microchip (also called an “integrated circuit”): A set of interconnected circuits and devices--such as transistors--that have (normally) been imprinted onto a tiny wafer of silicon.

2. Next have students position their hands under a light and above a surface, and have them notice that this generates a shadow pattern on the surface. Why? [Guide them to an understanding that the light strikes every part of the surface except where it’s blocked by the hand, which leaves a shadow pattern in the shape of that hand.]

3. Now you can explain the process by which a complex pattern of circuits is put onto a microchip. A wafer of silicon is covered with a special type of liquid plastic that reacts to light. A pattern (like a stencil) is made for the arrangement of circuits that are needed on the chip. This “stencil” (called a mask) is held in place above the silicon wafer. From above, light is shone down past the mask, then through a series of lenses to focus its pattern down onto the tiny space of the microchip. Not all of the light strikes the chip; some of the light is blocked by the mask. In the places where the light strikes the chip, it hardens the liquid plastic. The rest of the liquid plastic (which is in the exact shape of the desired circuit pattern) remains soft and gummy and is washed away.

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