Film stress management for MEMS through selective relaxation
View Patent ↗An apparatus comprising a microelectromechanical system. The microelectromechanical system includes a crystalline structural element having dislocations therein. For at least about 60 percent of adjacent pairs of the dislocations, direction vectors of the dislocations form acute angles of less than about 45 degrees.
1. A method of manufacturing a device, comprising:
forming a microelectromechanical system having a crystalline structural layer, including:
providing a substrate having a first crystal layer located thereon;
patterning said first crystal layer to form a lattice dislocation blocking feature;
forming one or more nucleation sites in said lattice dislocation blocking feature; and
covering said first crystal layer with a second crystal layer, wherein:
misfit dislocations form at an interface between said first crystal layer and said second crystal layer, and
at least about 60 percent of adjacent pairs of said misfit dislocations have direction vectors of said adjacent pairs form acute angles of less than about 45 degrees.
2. The method of claim 1 , further including removing portions of said first crystal layer that lay outside of said lattice dislocation blocking feature, wherein said removing portions of said first crystal layer includes removing said one or more of said nucleation sites and portions of said second crystal layer lying directly above said nucleation sites.
3. The method of claim 1 , further including removing at least part of an underlying layer of said substrate such that a first part of said lattice dislocation blocking feature is released from said substrate and a second part of said lattice dislocation blocking feature remains fixed to said substrate, wherein said crystalline structural layer has a suspended portion, corresponding to said first part of said lattice dislocation blocking feature, whose major or minor surface is bent.
4. The method of claim 3 , wherein said suspended portion of said crystalline structural layer is bent away from said second crystal layer after said releasing.
5. The method of claim 3 , wherein said suspended portion of said crystalline structural layer is bent towards said second crystal layer after said releasing.
6. The method of claim 1 , wherein a concentration of implanted atoms is substantially the same in all of said nucleation sites.
7. The method of claim 1 , wherein said nucleation sites are located along an edge of said lattice dislocation blocking feature.
8. The method of claim 1 , wherein said nucleation sites progressively increase in said nucleation site density, or in implanted atom concentration, along a dimension of said lattice dislocation blocking feature.
9. The method of claim 1 , further including entirely removing said second crystal layer after forming said misfit dislocations such that edge dislocations remain in said first crystal layer.
10. The method of claim 1 , wherein said patterning of said first crystal layer includes forming a second lattice dislocation blocking feature of said first crystal layer, said second lattice dislocation blocking feature being located adjacent to said nucleation site.
11. The method of claim 1 , wherein said first crystal layer and said second crystal layer have bulk lattice constants that differ by at least about 0.1 percent.