are described above may also be used at 640 some of the silicon on the backside of the silicon wafer may be removed to expose the porous silicon pumping medium 100 the silicon may be removed using standard etching techniques such as plasma reactive ion etching lapping or chemical mechanical polishing finally at 645 a liner material may be deposited on top of the porous silicon substrate and within the pores of the porous silicon in some embodiments the liner material may be sio 2 which may be created by thermally oxidizing the porous silicon alternatively the sio 2 may be deposited within the pores by first depositing at least one layer of nitride through low pressure chemical vapor deposition lpcvd or by adding at least one layer of polycrystalline silicon through lpcvd and then oxidizing the polycrystalline silicon layer through standard techniques the liner material may also be a polymeric material such as parylene fig7 is a logic flow diagram illustrating another method 700 for manufacturing porous silicon in accordance with some embodiments of the present invention whenever porous silicon is made on the order of less than 100 microns the porous silicon wafer may become damaged when the backside of the silicon wafer is ground away to open the pores in the porous silicon another method for fabricating porous silicon may use the technique of bonding.