1. Sohan Purohit, University of Rochester 1 Semiconductor Cooling Techniques -Sohan Purohit Department of Electrical and Computer Engineering, University of Rochester

2. Sohan Purohit, University of Rochester 2 Introduction High Performance-High Power go hand in hand. Cooling and Power Delivery become important issues. In the near future Total Chip power rises by ~ 60 % Heat Flux-Expected to double

3. Sohan Purohit, University of Rochester 3 Projection of Processor Power

4. Sohan Purohit, University of Rochester 4 Nottingham Inversion Cooling Based on Internal Field Emission Uses Composite-Thin-Film Device + Heat Sink Uses Wide Band Gap materials-prevents tunneling of electrons

5. Sohan Purohit, University of Rochester 5 How it Works Injected Electrons are transported Quasi Ballistically. Heat carried by electrons is decoupled from the lattice. Cooling due to removal of hot electrons by tunneling- Also called NOTTINGHAM INVERSION COOLING

6. Sohan Purohit, University of Rochester 6 Cooling by Luminescence up-conversion Interaction of a system with radiation can lead to cooling. Physicists report observation of phonon-mediated up- conversion of luminescence in GaAs. Sample is resonantly pumped with light energy. Temperature drops as much as 10% of initial temperature are reported. Localised lattice cooling takes place-Important for the semiconductor industry.

7. Sohan Purohit, University of Rochester 7 Cooling is due to a strong electron phonon coupling at the localised spot-somehow disconnected from the rest of the lattice sub system. This coupling still remains somewhat a mystery. Results –Qualitative. Possibility of Localized cooling however has been demonstrated.

8. Sohan Purohit, University of Rochester 8 Electronic Cooling by Quasiparticle Tunneling A very much unexplored approach. Replace metal by a heavily doped semiconductor, in the cooling device. From the Practical and Technological side-Best choice. Efficient Integration in today’s Semiconductor industry.

9. Sohan Purohit, University of Rochester 9 How it Works Weak Electron Phonon coupling at low temperatures. Weak EP coupling-Key Issue in the Cooling Process. Silicon films-Strong candidates for low-temperature on-chip cooling applications.

10. Sohan Purohit, University of Rochester 10 Recent Developments Semiconductor Cooling has received much attention in the past few years. Novel Cooling techniques coming up. Promising new Techniques Micro-pump Cooling Ion Pump Cooling.

11. Sohan Purohit, University of Rochester 11 Conclusions As on-chip power increases-Cooling issues become important problems to deal with. Novel cooling techniques discussed here are a direct off shoot of this. “Either we let our fate determine its own course or we proactively attack the power issues”- Christian Belady, Hewlett Packard Company