Deep into CPU

During PhD... I have tried to disassemble a CPU step by step and explored what's inside the chips.

The model I worked on is:

AMD Sempron 2600+

Palermo (90 nm SOI)

Part I: Preparation

This is the AMD CPU I grab from a old desktop computer

Use a blade to remove the top metal cap which is used for heat dissipation.

Then we can see the silicon chip beneath the cap

Now, the issue is how to remove the chip from the dark green PCB board. I have tried to use organic solution/H2SO4/HF/HCl, but all of the approaches failed. Then I use some violent way to separate the chip. As you can see, under stress, the Silicon chip broke into pieces. But this would not affect the further works.

Part II: Optical Microscope

I took some small pieces out and take a look under the microscope. After tearing down the chip from the PCB board, we can see these black holes. They are used to connect to the pins we usually see beneath the CPU.

Then remove the “black hole” layers. We can see a clear layered structure and the top metal layers with small holes might be related with packaging.

After removing the top metal covering layer, we final could figure out how a CPU looks like. There are different layers with different functions. Majority of them are interconnections.

Zoom in view, the circuits could be clearly observed.

Keep zooming in, so many lines. Because of these lines, the thousands of transistors in the bottom are connected.

Another region on the chip, different layers can be observed.

Part III: Top-Down Scanning Electron Microscope(SEM)

Because the zoom-ion magnification of microscope is limited too X100. Here I used the SEM to further explore this micro-world. Interconnection again.

Keep zooming in, we can find the interconnection layer are wider for upper layer. This is related with the speed.

Another one of interconnection layers

Something looks like the streets in future world.

We can see the number 16 here. This might indicate certain region of function on the chip

Part IV: Tilted Scanning Electron Microscope

For the SEM top-down view, we could not see these transistors because of the interconnection layers above. Here I used a titled view to see the CPUs. The layers can be very clearly told and the bottom ones are the MOSFETs.

Zoom it in, again, the upper ones are the interconnection lines and the bottom one is the transistor

The tiny little thing on the bottom is the transistor. Read the scale bar.

Let’s look at the bottom transistor layer image. Now we can see the transistors! Each heave indcate a MOSFET.(It’s the gate of the MOSFET). The thick layer between transistor layer and the bulk is the SiO2 as the BOX (This is a SOI (Silicon on Insulator) wafer from AMD, quite different from bulk Si wafer in intel)

Now it's X70000, we can see more details here, there are two transistors in this picture

There is another work done by a student from Lund university. You can take a look here:

http://www.sciencystuff.com/?p=24