Patent ID: 8895339

Claim:
A method for manufacturing a microelectromechanical systems (MEMS) device, the method comprising: forming a first polysilicon layer over a substrate; forming a sacrificial layer over the first polysilicon layer, wherein the sacrificial layer comprises silicon oxide deposited using tetraethyl orthosilicate (TEOS) gas; forming a second polysilicon layer over the sacrificial layer; annealing the second polysilicon layer wherein said annealing comprises heating the first and second polysilicon layers and the sacrificial layer to a temperature sufficient to relieve stress in the second polysilicon layer; and forming a carbon barrier layer between the sacrificial layer and one or more of the first and second polysilicon layers, wherein the carbon barrier layer prevents diffusion of carbon into an adjacent polysilicon layer from the sacrificial layer during said annealing, and said forming the carbon barrier layer further comprises forming a first carbon barrier layer over and in contact with at least a portion of the first polysilicon layer, wherein the first carbon barrier layer is formed prior to said forming the sacrificial layer; and forming a second carbon barrier layer over and in contact with the sacrificial layer, wherein the second carbon barrier layer is formed prior to said forming the second polysilicon layer, and at least a portion of the second polysilicon layer is formed in contact with the second carbon barrier layer.