Reliable thin film resistors for integrated circuit applications
First Claim
1. A thin film resistor for an integrated circuit comprising:
- substrate means having a top surface;
insulating layer means formed on the top surface of said substrate means, said insulating layer means having a top surface;
resistor layer means formed on and in contact with the top surface of said insulating layer means opposite to the substrate means; and
contact means for making electrical contact with said resistor layer means, whereby said insulating layer means between said substrate means and said resistor layer means prevents diffusion of said resistor layer means into said substrate means.
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Accused Products
Abstract
A thin film resistor with an insulating layer disposed between a substrate material and a resistor material is disclosed. Also, disclosed is a technique for fabricating this thin film resistor. In accordance with the preferred embodiment, the thin film resistor employs an insulating layer of silicon nitride with a thickness of 2000 Å. The insulating layer prevents the resistor layer from diffusing into the substrate material which, in turn, significantly reduces variations in the resistor value during accelerated life testing. Compared to thin film resistors with a resistor layer evaporated directly upon a substrate material, reliability is increased from a few hundred hours up to thousands of hours. Also, the maximum current handling capability is increased by greater than one order of magnitude, which results in a thin film resistor which requires less surface area of a wafer.
29 Citations
20 Claims
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1. A thin film resistor for an integrated circuit comprising:
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substrate means having a top surface; insulating layer means formed on the top surface of said substrate means, said insulating layer means having a top surface; resistor layer means formed on and in contact with the top surface of said insulating layer means opposite to the substrate means; and contact means for making electrical contact with said resistor layer means, whereby said insulating layer means between said substrate means and said resistor layer means prevents diffusion of said resistor layer means into said substrate means. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An integrated circuit comprising:
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integrated circuit substrate means having a top surface; insulating layer means formed on the top surface of said integrated circuit substrate means, said insulating layer means having a top surface; resistor layer means formed on and in contact with the top surface of said insulating layer means opposite to the substrate means; and contact means for making electrical contact with said resistor layer means, whereby said insulating layer means between said integrated circuit substrate means and said resistor layer means prevents diffusion of said resistor layer means into said integrated circuit substrate means. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. An integrated circuit comprising:
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gallium arsenide integrated circuit substrate means having a top surface; insulating layer means composed of silicon nitride and formed on said integrated circuit substrate means top surface, said insulating means having a top surface; resistor layer means composed of nichrome and formed on top of said insulating layer opposite to the substrate means and in contact with the top surface of the insulating means; passivation layer means composed of silicon nitride and formed on top of said resistor layers means, whereby said passivation layer means passivates said resistor layer means; and contact means for making electrical contact with said resistor layer means, whereby said insulating layer means between said integrated circuit substrate means and said resistor layer means prevents diffusion of said resistor layer means into said integrated circuit substrate means.
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16. A method of producing a thin film resistor comprising the steps of:
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providing a substrate wafer having a substantially flat top surface; forming an insulating layer means on top of said flat top surface of said substrate wafer, said insulating layer means having a top surface; forming a resistor layer means on top of said insulating layer means opposite to the substrate means an in contact with the top surface of the insulating means, whereby said insulating layer means prevents said resistor layer means from diffusing into said substrate wafer; and forming a contact means for making electrical contact with said resistor layer means. - View Dependent Claims (17, 18, 19, 20)
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Specification