| 摘要 |
A new and improved method of forming a thin film resistor is provided herein that overcomes many of the drawbacks of prior art methods. More specifically, the new method of forming a thin film provides for a well-controlled dielectric thickness under the thin film resistor which is useful for laser trimming purpose. The preferred thickness of the dielectric layer is an integer of a quarter wavelength of the optical energy used to laser trim the resistor. The new method also provides contacts to the thin film resistor that do not directly contact the thin film resistor so as to prevent any adverse process effects to the thin film resistor. More specifically, the method of forming a thin film resistor includes the steps of forming a pair of spaced-apart polysilicon islands over a semiconductor substrate, forming a dielectric layer over and between the polysilicon islands, forming contact holes through the dielectric layer to expose respective first regions of the polysilicon islands, forming a layer of thin film resistive material that extends between respective first regions of the polysilicon islands, forming another dielectric layer over the polysilicon islands and over the thin film resistive material layer, and forming metal contacts through the second dielectric layer in a manner that they make contact to respective second regions of the polysilicon islands, wherein the first and second regions of the polysilicon islands are different.
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