Patent ID: 8940612
Filing Date: 2015-01-27
Classification: H01L

Abstract:
1. A method of forming an integrated circuit, comprising the steps of: providing a substrate; forming a first layer of polysilicon over said substrate; forming a resistor opening mask over said first layer of polysilicon which exposes an area for a thin polysilicon resistor and covers an area for a metal gate transistor; removing said first layer of polysilicon in areas exposed by said resistor opening mask so that said first layer of polysilicon is removed in said area for said thin polysilicon resistor and is left in said area for said metal gate transistor; subsequently removing said resistor opening mask; forming a second layer of polysilicon over said first layer of polysilicon and over said substrate in said area for said thin polysilicon resistor; forming a gate etch mask over said second layer of polysilicon which covers an area for a gate of said metal gate transistor and said area for said thin polysilicon resistor; removing said second layer of polysilicon and said first layer of polysilicon in areas exposed by said gate etch mask so that said second layer of polysilicon is left in said area for said thin polysilicon resistor to form a thin resistor body of said thin polysilicon resistor and said second layer of polysilicon and said first layer of polysilicon are left in said area for said metal gate transistor to form a sacrificial gate of said metal gate transistor; subsequently removing said gate etch mask; forming a pre-metal dielectric (PMD) layer over said substrate, said thin resistor body and said sacrificial gate; removing a top portion of said PMD layer so as to expose said sacrificial gate and so as to leave said thin resistor body covered by said PMD layer; removing said first layer of polysilicon and said second layer of polysilicon from said sacrificial gate so that said second layer of polysilicon in said thin resistor body is not damaged; forming a metal replacement gate in said metal gate transistor, such that said thin polysilicon resistor is thinner said metal replacement gate; and forming contacts through said PMD layer to said second layer of polysilicon in said thin resistor body.