Semiconductor device manufacturing: process – Making passive device – Resistor
Reexamination Certificate
1998-10-15
2001-04-03
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making passive device
Resistor
C438S381000, C438S608000, C438S475000
Reexamination Certificate
active
06211030
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 87110877, filed Jul. 6, 1998, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor fabrication method, and more particularly, to a method of fabricating resistors in integrated circuits.
2. Description of Related Art
Resistors are the most often used components in all kinds of electrical and electronic circuits, including integrated circuits such as memory and logic devices. Conventionally, resistors in integrated circuits are made from lightly-doped polysilicon layers that are shaped into specific lengths and cross-sectional areas to provide the desired resistance values. Another conventional method of forming resistors in integrated circuits is to perform a thermal annealing process on a joined structure of a high-resistance conductive layer and a low-resistance conductive layer, such as an undoped polysilicon layer and a highly-doped polysilicon layer. This method also requires the conductive layers to be shaped into specific lengths and cross-sectional areas to provide the desired resistance values.
Patents that disclose methods of fabricating resistors in integrated circuits include the U.S. Pat. No. 5,316,978 entitled “Fabricating Resistors for Integrated Circuits”, the U.S. Pat. No. 5,465,005 entitled “Polysilicon Resistor Structure Including Polysilicon Contact”, and the U.S. Pat. No. 5,677,228 entitled “Method of Fabricating a Resistor in an Integrated Circuit”, to name just a few.
One drawback to the above-mentioned methods, however, is that, since polysilicon is used to form the resistors, the method requires the use of an etching process to shape the polysilicon layers into specific lengths and cross-sectional areas to provide the desired resistance values. This makes the overall process quite complex and thus laborious to carry out. Still another drawback is that the use of polysilicon allows only a limited range of resistance values for the resultant resistors. This is because the resistance of a polysilicon-based resistor is largely dependent on the length and crosssectional area of the resistor. A high resistance therefore requires that the polysilicon layer be very long. Since a wafer is very small in size, the feasible range of resistance values for the resultant resistors is limited.
SUMMARY OF THE INVENTION
It is therefore an objective of the invention to provide a method of fabricating resistors in an integrated circuit without using polysilicon.
It is another objective of the invention to provide a method of fabricating resistors in an integrated circuit, whose fabrication process does not require etching, thus allowing the overall process to be simpler and thus easier than the prior art to carry out.
It is still another objective of the invention to provide a method of fabricating resistors in an integrated circuit which can form resistors with large resistance values but without extensive lengths. This will allow the required wafer area for the layout of the resistors to be less than that required for the prior art.
In accordance with the foregoing and other objectives of the invention, a new method of fabricating resistors in integrated circuits is provided.
In a first preferred embodiment, the method of the invention includes the following process steps: preparing a semiconductor substrate; forming a layer of a refractory metal oxide over the substrate; and performing a hydrogen treatment process on a selected part of the refractory metal oxide layer so as to convert the selected part of the refractory metal oxide layer into a conductive oxide of a specific resistive characteristic to serve as the desired resistor.
In a second preferred embodiment, the method of the invention includes the following process steps: preparing a semiconductor substrate; forming a layer of a refractory metal oxide over the substrate; and performing a number of stages of hydrogen treatment successively on a plurality of selected portions of the refractory metal oxide layer where the resistors to be formed in the integrated circuit are defined. The various stages of hydrogen treatment are performed respectively based on a number of predetermined sets of process parameters so as to convert the selected portions of the refractory metal oxide layer into conductive oxides of various resistive characteristics to serve the desired resistors.
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Lattin Christopher
Niebling John F.
Oppenheimer Wolff & Donnelly LLP
United Microelectronics Corp.
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