SEM photos - SDRAM cross sections

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An aluminum line.


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Two aluminum lines.


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The edge of an aluminum bonding pad. The package leads are connected here.


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A close-up of the bonding pad cross-section.


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DRAM capacitors. Each capacitor is one bit.

The difference between DRAM and SRAM is that DRAM uses capacitors, which must be refreshed, while SRAM uses flip-flops that are much faster and do not need to be refreshed, but take up much more space.


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The photo mask for the contact step was misaligned, and the etch has gone down too far.


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Overetch into the silicon substrate.

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An aluminum contact.

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A small contact, currently with tungsten only. Aluminum will be deposited on top.

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Another misaligned contact.

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Aluminum lines.

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Closeup of a capacitor(turned 90 degrees to the right). The bumps are made to increase the surface area and thus the capacitance.

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Contact, again with tungsten only.


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Memory cells. The word line is running left to right just under the surface of the break.

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A problem with the photo-resist. It was apparently too hot and the pattern melted.

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Same problem.

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