Leveling system for cantilever calibration
In a micro-electromechanical system (MEMS) structure, leveling of a cantilever is performed using a dual-capacitor leveling system. One capacitor is used to determine the amount or degree of deformation. The other capacitor is used in conjunction with a diode to determine the direction of the deformation. This information can be used to calibrate the position of the cantilever for consistent positioning during operation. Methods for forming the dual-capacitor leveling system are also disclosed.
1 . A method for making a dual-capacitor leveling system for a cantilever, comprising:
forming a bottom electrode layer, a piezoelectric layer upon the bottom electrode layer, and a top electrode layer upon the piezoelectric layer;
forming a first capacitor that comprises the bottom electrode layer, a first insulator film upon the bottom electrode layer, and a primary metal layer upon the first insulator film that is electrically connected to the top electrode layer;
forming a diode that is electrically connected to the bottom electrode layer; and
forming a second capacitor upon the diode, the second capacitor comprising a secondary metal layer electrically connected to the diode, a second insulator film over the secondary metal layer, and a tertiary metal layer upon the second insulator film that is electrically connected to the top electrode layer.
2 . The method of claim 1 , wherein the primary metal layer of the first capacitor and the secondary metal layer of the second capacitor are concurrently formed.
3 . The method of claim 1 , wherein the first capacitor is formed by:
applying a first intermetal dielectric (IMD) sublayer over the bottom electrode layer;
patterning the first IMD sublayer to expose the bottom electrode layer in a first capacitor region;
forming the first insulator film in the first capacitor region upon the bottom electrode layer, the first insulator film including a first end, a central region, and a second end;
applying a second IMD sublayer to cover the first insulator film in the first capacitor region;
patterning the IMD sublayer to expose the first insulator film in the first capacitor region; and
applying the primary metal layer over the first insulator film to form the first capacitor.
4 . The method of claim 1 , wherein the second capacitor is formed by:
applying a first intermetal dielectric (IMD) sublayer over the bottom electrode layer;
patterning the first IMD sublayer to expose the bottom electrode layer in a second capacitor region;
forming a diode in the second capacitor region;
applying a third IMD sublayer over the second capacitor region;
patterning the third IMD sublayer to expose the diode;
forming a first metal layer over the exposed diode;
forming a second insulator film over the first metal layer; and
applying the tertiary metal layer over the second insulator film to form the second capacitor.
5 . The method of claim 1 , further comprising:
forming a first metal pad electrically connected to the primary metal layer of the first capacitor;
forming a second metal pad electrically connected to the bottom electrode layer of the first capacitor;
forming a third metal pad electrically connected to the tertiary metal layer of the second capacitor; and
forming a fourth metal pad electrically connected to the bottom electrode layer below the diode.
6 . The method of claim 1 , wherein the first capacitor and the second capacitor are formed over a substrate; and wherein the piezoelectric layer and the top electrode layer are present beyond an edge of the substrate.
7 . The method of claim 1 , further comprising forming the bottom electrode layer over a first dielectric layer.
8 . The method of claim 1 , further comprising applying a passivation layer over the first capacitor and the second capacitor.
9 . The method of claim 1 , wherein the diode is formed from an n-type semiconductor and a p-type semiconductor.
10 . The method of claim 1 , wherein the piezoelectric layer comprises a piezoelectric ceramic.
11 . The method of claim 1 , wherein planarization is not used in forming the first capacitor or the second capacitor.
12 . The method of claim 1 , further comprising forming electrical interconnections from the top electrode layer and the bottom electrode layer to a piezoelectric capacitor on the cantilever.
13 . A dual-capacitor leveling system for a cantilever, comprising:
a piezoelectric region comprising a bottom electrode layer, a piezoelectric layer upon the bottom electrode layer, and a top electrode layer upon the piezoelectric layer;
a first capacitor comprising the bottom electrode layer, a first insulator film upon the bottom electrode layer, and a primary metal layer upon the first insulator film that is electrically connected to the top electrode layer;
a diode that is electrically connected to the bottom electrode layer; and
a second capacitor upon the diode that comprises a secondary metal layer electrically connected to the diode, a second insulator film over the secondary metal layer, and a tertiary metal layer upon the second insulator film that is electrically connected to the top electrode layer.
14 . The system of claim 13 , further comprising:
a first metal pad electrically connected to the primary metal layer of the first capacitor;
a second metal pad electrically connected to the bottom electrode layer of the first capacitor;
a third metal pad electrically connected to the tertiary metal layer of the second capacitor; and
a fourth metal pad electrically connected to the bottom electrode layer below the diode.
15 . The system of claim 13 , further comprising an intermetal dielectric (IMD) region separating the piezoelectric layer from the first insulator film and the second insulator film.
16 . The system of claim 13 , wherein the first capacitor and the second capacitor are located over a substrate; and wherein the piezoelectric region is not located over the substrate.
17 . The system of claim 13 , further comprising a piezoelectric capacitor upon the cantilever which is electrically connected to the piezoelectric region.
18 . A method for making a dual-capacitor leveling system, comprising:
forming a first dielectric layer upon a substrate;
forming an adhesion layer upon the first dielectric layer;
forming a bottom electrode layer upon the adhesion layer;
forming a piezoelectric layer upon the bottom electrode layer;
forming a top electrode layer upon the piezoelectric layer;
patterning the top electrode layer and the piezoelectric layer to expose the bottom electrode layer;
applying a first intermetal dielectric (IMD) sublayer upon the substrate;
patterning the first IMD sublayer to expose the bottom electrode layer in a first capacitor region of the substrate;
forming a first insulator film in the first capacitor region, the first insulator film including a first end, a central region, and a second end;
applying a second IMD sublayer upon the substrate to cover the first insulator film in the first capacitor region and form an IMD layer;
patterning the IMD layer to expose the bottom electrode layer in a second capacitor region of the substrate;
forming a diode in the second capacitor region, the diode including a first end, a central region, and a second end;
applying a third IMD sublayer upon the substrate that covers the diode in the second capacitor region and adds to the IMD layer;
patterning the third IMD sublayer to expose the diode;
forming a secondary metal layer over the diode;
forming a second insulator film over the secondary metal layer;
applying a fourth IMD sublayer upon the substrate that covers the second insulator film in the second capacitor region and adds to the IMD layer;
patterning the IMD layer to expose the top electrode layer;
patterning the IMD layer to expose the first end and the second end of the first insulator film in the first capacitor region, with a portion of the IMD layer remaining above the central region of the first insulator film;
patterning the IMD layer to expose the first end and the second end of the second insulator film in the second capacitor region, with a portion of the IMD layer remaining above the central region of the second insulator film;
depositing a second metal layer upon the substrate, the second metal layer covering the first end and the second end of the first insulator film and the first end and the second end of the second insulator film, wherein a first capacitor is formed in the first capacitor region and a second capacitor is formed in the second capacitor region; and
removing the substrate below the piezoelectric layer to form a backside cavity.
19 . The method of claim 18 , further comprising:
forming a first metal pad electrically connected to the second metal layer in the first capacitor region;
forming a second metal pad electrically connected to the bottom electrode layer in the first capacitor region;
forming a third metal pad electrically connected to the second metal layer in the second capacitor region; and
forming a fourth metal pad electrically connected to the bottom electrode layer in the second capacitor region.
20 . The method of claim 18 , further comprising depositing a passivation layer over the substrate.