Method of wafer-level fabrication of MEMS devices
First Claim
1. A method of fabricating a micromachined device, the method comprising:
- (a) providing a wafer comprising (i) a substrate having (A) a front side surface and (B) a back side surface opposing the front side surface, (ii) a composite thin film on the front side surface of the substrate, the composite thin film having an internal structure defining one or more etchable portions and one or more etch-resistant portions and including a circuitry layer stack comprising at least one etch resistant metallic layer and insulating material between an uppermost metallic layer and the front side surface of the substrate, and (iii) an etch mask on the back side surface of the substrate, the etch mask defining one or more isolation portions substantially aligned with the etchable portions of the composite thin film;
(b) anisotropically etching the back side of the substrate via the isolation portions of the etch mask, thereby forming one or more first isolation trenches, wherein the first isolation trenches (i) are substantially aligned with the etchable portions of the composite thin film and (ii) extend partially into the substrate;
(c) removing the etch mask;
(d) anisotropically etching the back side of the substrate via the first isolation trenches, thereby extending the first isolation trenches to form one or more second isolation trenches, wherein the second isolation trenches (i) are substantially aligned with the etchable portions of the composite thin film and (ii) extend through the substrate to the composite thin film; and
(e) anisotropically etching the etchable portions of the composite thin film, thereby defining one or more final isolation trenches.
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Abstract
The present disclosure relates to a method of fabricating a micromachined CMOS-MEMS integrated device as well as the devices/apparatus resulting from the method. In the disclosed method, the anisotropic etching (e.g., DRIE) for isolation trench formation on a MEMS element is performed on the back side of a silicon wafer, thereby avoiding the trench sidewall contamination and the screen effect of the isolation beams in a plasma etching process. In an embodiment, a layered wafer including a substrate and a composite thin film thereon is subjected to at least one (optionally at least two) back side anisotropic etching step to form an isolation trench (and optionally a substrate membrane). The method overcomes drawbacks of other microfabrication processes, including isolation trench sidewall contamination.
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Citations
30 Claims
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1. A method of fabricating a micromachined device, the method comprising:
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(a) providing a wafer comprising (i) a substrate having (A) a front side surface and (B) a back side surface opposing the front side surface, (ii) a composite thin film on the front side surface of the substrate, the composite thin film having an internal structure defining one or more etchable portions and one or more etch-resistant portions and including a circuitry layer stack comprising at least one etch resistant metallic layer and insulating material between an uppermost metallic layer and the front side surface of the substrate, and (iii) an etch mask on the back side surface of the substrate, the etch mask defining one or more isolation portions substantially aligned with the etchable portions of the composite thin film; (b) anisotropically etching the back side of the substrate via the isolation portions of the etch mask, thereby forming one or more first isolation trenches, wherein the first isolation trenches (i) are substantially aligned with the etchable portions of the composite thin film and (ii) extend partially into the substrate; (c) removing the etch mask; (d) anisotropically etching the back side of the substrate via the first isolation trenches, thereby extending the first isolation trenches to form one or more second isolation trenches, wherein the second isolation trenches (i) are substantially aligned with the etchable portions of the composite thin film and (ii) extend through the substrate to the composite thin film; and (e) anisotropically etching the etchable portions of the composite thin film, thereby defining one or more final isolation trenches. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 29)
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14. A method of fabricating a micromachined device, the method comprising:
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(a) providing a wafer comprising (i) a substrate having (A) a front side surface, (B) a back side surface opposing the front side surface, and (C) a substrate thickness between the front side surface and the back side surface, and (ii) a composite thin film having (A) a front side surface and (B) a back side surface on the front side surface of the substrate, the composite thin film having an internal structure defining one or more etchable portions and one or more etch-resistant portions and a circuitry layer stack including at least one metallic layer; (b) depositing an insulating layer over the back side surface of the substrate; (c) patterning the insulating layer, thereby forming one or more isolation portions of the insulating layer, wherein the isolation portions of the insulating layer are substantially aligned with the etchable portions of the composite thin film; (d) depositing a photoresist layer over the back side surface of the substrate and over the isolation portions of the insulating layer; (e) patterning the photoresist layer, thereby defining one or more isolation portions of the photoresist layer, wherein the isolation portions of the photoresist layer are substantially aligned with the etchable portions of the composite thin film; (f) etching the isolation portions of the insulating layer via the isolation portions of the photoresist layer, thereby exposing the back side surface of the substrate; (g) anisotropically etching the back side of the substrate via the isolation portions of the photoresist layer, thereby forming one or more first isolation trenches, wherein the first isolation trenches (i) are substantially aligned with the etchable portions of the composite thin film and (ii) extend partially into the substrate; (h) removing the photoresist layer; (i) anisotropically etching the back side of the substrate via the first isolation trenches, thereby extending the first isolation trenches to form one or more corresponding second isolation trenches, wherein the second isolation trenches (i) are substantially aligned with the etchable portions of the composite thin film and (ii) extend through the substrate to, but not through, the composite thin film on the front side surface of the substrate; and (j) anisotropically etching the etchable portions of the composite thin film from the front side surface of the composite thin film and through the composite thin film to the second isolation trenches, thereby defining one or more final isolation trenches. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30)
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Specification