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How do you make memory?

S

Smartazz

Diamond Member
I am absolutly clueless how memory like ram is made, can anyone please explain to me how companies manufacture it?
 
i'm not very sure about ram like DDR (dram) dimm chips, i think those are just tons of capacitors (circuits which hold an electirc charge). i didn't study those in my computer architecture class. however we did study cache (sram). cache uses either s-r latches or flip flops (these circuits either hold a 1 or a 0 and can be changed).

this will get you started:
http://en.wikipedia.org/wiki/Random_access_memory

also lookup:
integrated circuits
capacitor
s-r latch
flip flop
 
DRAM functions differently than SRAM. For the most basic type of DRAM, it is pretty much just a capacitor with an analog sense/recharge circuit attached to it. When a write strobe comes in, the capacitor is drained. The analog sense circuit interprets this as either a logical high or logical low (based on the threshold voltage) and then determines whether to recharge the capacitor or not. This is one of the reasons why DRAM is slower than SRAM, there is a time required for a recharge.

Those capacitors also need to be periodically recharged (refresh latency) to maintain their charge. The total circuitry is still smaller in terms of area than SRAM (which, in the basic form, requires 6 transistors IIRC) but you pay a penalty in performance and complexity.
 
in terms of manufacturing, DRAM is different because it requires deep trench transistors which so far cannot scale as far as regular processes because they will lose their charge to leakage so fast.
 
DRAM = cheap to make, requires far less transistors to implement, slower
SRAM = expensive, requires far more transistors to implement, but significantly faster

That's why SRAM is used for highspeed caches and things of that nature and DRAM is used for main memory.
 
DRAM also has to be refreshed. The data is stored as a charge on a capacitor - and a rather leaky capacitor at that. So, you can think of data on a DRAM like being a drawing on an etch-a-sketch that is strapped to a paint shaker.

So, for DRAM, you have to , every so often, read back every memory cell and re-write the data to make it stronger. The data is organized in a row/column format. Every so often a row will be refreshed. After a little while, the next row if refreshed. Later still, the next row is refreshed. You get the idea. This way, all of the data stays fresh.
 
Yes, to date, RAM is made like other ICs, through a photo-chemical etching and deposition process that includes conducting, non-conducting, and semi-conducting materials. This GROSSLY oversimplifies the actual process, but I don't know much more than that.
 
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