Sunday, November 11, 2007

Semiconductor Manufacturing Revisited

Because of the complexity involved in manufacturing semiconductor chips, I thought it would be worth providing some additional reading material in addition to the Applied Materials technical tutorials. Hardware Secrets and Tom's Hardware are both good sites for computer articles, so you may also want to check out their other articles sometime.

I have spent some time inside cleanroom environments, and they are quite an interesting place to be. The machinery is very expensive costing in the millions of dollars for many tools, and the air generally contains less than 10 particles ≥0.5 ┬Ám (microns) in diameter (200 times smaller than the size of a human hair). In layman's terms: If you have a job in which you work inside a cleanroom and you go to work and have allergies that morning, you will feel great inside the cleanroom because there are no particles (dust, pollen, etc.) to affect you! The air is kept clean by a huge air handler system that circulates a large volumne of air through HEPA filters that capture any particulate.

The last bit of information worth adding about semiconductor manufacturing is that it is a very complex environment from a production control perspective. Many products in the world are made by batch processes such as paper, chemicals, Coca-Cola, etc. On the other hand many products are made in discrete units with a lot of 1 (Cars are a good example). Semiconductors wafers are generally run together as a lot, but you sometimes split or merge wafers from that original lot and to a secondary lot. Additionally, in some tools you input a lot of wafers (say a quantity of 25), but the tool processes the wafers individually (these tools are fittlingly called single wafer processors). To make things even more difficult there are sometimes batch tools such as diffusion furnances (as shown on the right) where you place multiple lots into the furnace and wait several hours for the processing to finish. In summary, line balancing is very important and can make a large impact on how smoothly the wafers are processed!

So on to the articles:
How Chips are Manufactured brought to you by Hardware Secrets
Semiconductor Production 101brought to you by Tom's Hardware

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