Method of trimming a component and a component trimmed by such a method
A method of trimming a component is provided in which the component is protected from oxidation or changes in stress after trimming. As part of the method, a protective glass cover is bonded to the surface of a semiconductor substrate prior to trimming (e.g., laser trimming) of a component. This can protect the component from oxidation after trimming, which may change its value or a parameter of the component. It can also protect the component from changes in stress acting on it or on the die adjacent it during packaging, which may also change a value or parameter of the component.
1. A method of trimming a component formed on a substrate, the method comprising:
securing a transparent cover to the substrate so as to provide a protected volume around the component prior to dicing a wafer that includes the component, the transparent cover having a surface patterned with regularly spaced depressions; and
trimming the component to adjust a parameter of the component, wherein the trimming comprises applying light through the surface of the transparent cover to the component.
2. A method as claimed in claim 1 , in which the trimming comprises adjusting at least one of a mass of the component or a mass distribution of the component.
3. A method as claimed in claim 1 , in which the trimming comprises laser trimming.
4. A method as claimed in claim 1 , in which the trimming comprises laser trimming, and the laser trimming is performed prior to the dicing the wafer.
5. A method as claimed in claim 1 , in which the component is a microelectrical mechanical systems (MEMS) resonator.
6. A method as claimed in claim 1 , in which the component is an accelerometer or a gyroscope, and the trimming modifies a mass or a mass distribution of the component.
7. A method as claimed in claim 1 , in which the component is a filter and the trimming adjusts a center frequency of the filter.
8. A method as claimed in claim 1 , in which the component is a microelectrical mechanical systems component.
9. A method as claimed in claim 1 , where the securing comprises bonding the transparent cover to the substrate or to structures extending from a surface of the substrate.
10. A microelectronic circuit comprising at least a first component formed on a substrate, wherein the first component has a parameter that varies as a function of a fabrication process changes used in the formation of the microelectronic circuit, wherein the microelectronic circuit comprises a laser-transparent cover secured to the substrate so as to form a hermetically sealed enclosure around the first component, the laser-transparent cover having a surface patterned with regularly spaced depressions, wherein the first component comprises a microelectrical mechanical systems (MEMS) component that includes piezoelectric layer, and wherein a trim site of the first component lacks oxidation.
11. A microelectronic circuit formed by a process that comprises laser trimming a microelectrical mechanical systems (MEMS) component formed on a substrate while the MEMS component is within a sealed enclosure formed at least partly by a laser-transparent material coupled to the substrate prior to dicing a wafer that includes the MEMS component, the laser-transparent material having a surface patterned with regularly spaced depressions, wherein the MEMS component has a parameter that varies as a function of a fabrication process changes used in the formation of the microelectronic circuit.
12. A microelectronic circuit as claimed in claim 11 , wherein the MEMS component comprises a lamb wave resonator.
13. A microelectronic circuit as claimed in claim 11 , wherein the component comprises an aluminum nitride layer.
14. A microelectronic circuit as claimed in claim 11 , wherein the laser-transparent material is glass.
15. A method as claimed in claim 5 , wherein laser trimming comprises varying at least one of a mass of a platform of the MEMS resonator or a mass of a piezoelectric layer of the MEMS resonator.
16. A method as claimed in claim 5 , wherein the MEMS resonator comprises a piezo-on-silicon lamb wave resonator.
17. A microelectronic circuit in claim 10 , wherein the laser-transparent cover comprises a recess.
18. A microelectronic circuit in claim 10 , wherein the MEMS component comprises a lamb wave resonator.
19. A method as claimed in claim 1 , further comprising interrupting a standing wave pattern with the regularly spaced depressions during the trimming.
20. A method as claimed in claim 1 , wherein the regularly spaced depressions have a depth corresponding to approximately one quarter of a wavelength of the light.
21. A microelectronic circuit as claimed in claim 11 , wherein the regularly spaced depressions are configured to interrupt a standing wave pattern within laser light for the laser trimming.