Semiconductor device manufacturing: process – Making passive device – Resistor
Reexamination Certificate
1994-05-23
2001-07-17
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Making passive device
Resistor
Reexamination Certificate
active
06261915
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to the fabrication of semiconductor devices and specifically to a resistor structure and process.
BACKGROUND OF THE INVENTION
Electronic digital and analog integrated circuits often require resistors to perform the desired functions. One type of resistor is the diffused resistor wherein a region of a semiconductor layer is doped to the opposite polarity as the remainder of the layer. There are several disadvantages to using diffused resistors. In the diffused resistor there inherently is a capacitance at the interface of the resistor and the underlying semiconductor layer. This capacitance can lead to current leakage and slower device operation.
Another type of resistor which may be formed on an integrated circuit is a polysilicon resistor. Although some of the capacitance problems may be minimized with certain poly resistor structures, the devices are typically more difficult to build. Typically, two masking levels and possibly two layers of polysilicon are required to implement a poly resistor. This complex process adds additional cost and potential yield problems.
Accordingly, improvements which overcome any or all of the problems are presently desirable.
SUMMARY OF THE INVENTION
Other objects and advantages will be obvious, and will in part appear hereinafter and will be accomplished by the present invention which provides a method and structure for a resistor.
A method of forming an integrated circuit device including at least one polysilicon resistor is disclosed herein. A polysilicon layer is formed, possibly over a field oxide. The polysilicon layer is then doped to achieve a selected sheet resistance. An insulating layer (e.g., an oxide, a nitride or a combination thereof) is then formed over the polysilicon layer. The insulating layer is patterned and etched to define a resistor body in the underlying polysilicon layer. The polysilicon layer is then patterned and etched to define first and second resistor heads abutting the resistor body while simultaneously at least one polysilicon element of a second electronic device is formed.
An advantage of the invention is its simplicity since the poly resistor is formed using basically the same process steps as the remainder of the fabrication flow. The minimization of additional process steps will reduce production costs.
In addition, the process of the invention is simplified since the polysilicon resistor is isolated by the insulating layer on top and on the sidewalls if the resistor heads are to be silicided.
A further advantage is obtained if the resistor is formed over a field insulating region such as an oxide. With the oxide formed between the resistor and the substrate, the capacitance from the resistor to the substrate will be minimized.
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Eklund Robert H.
Havemann Robert H.
Stroth Leo
Brady III Wade James
Fourson George
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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