Voltage contrast inspection of deep trench isolation
A method including forming a first test structure and a second test structure in electrical contact with an inner buried plate and an outer buried plate, respectively, where the first and second test structures each comprise a deep trench filled with a conductive material, and measuring the voltage of the inner buried plate and the outer buried plate immediately after the formation of a deep trench isolation structure, where the inner buried plate and the outer buried plate are positioned on opposite sides of the deep trench isolation structure.
1. A method comprising:
providing a semiconductor-on-insulator (SOI) substrate having a buried dielectric layer located above a buried plate;
forming a deep trench isolation structure in the SOI substrate having a first node dielectric and a first inner electrode, wherein the deep trench isolation structure electrically isolates an inner buried plate located on one side of the deep trench isolation structure from an outer buried plate located on an opposite side of the deep trench isolation structure;
forming a deep trench capacitor in the SOI substrate having a second node dielectric and a second inner electrode;
forming a first test structure and a second test structure in the SOI substrate and on opposite sides of the deep trench isolation structure, the first and second test structures having a third node dielectric and a third inner electrode, wherein the first test structure and the second test structure are similar in size and shape, and have a different width than the deep trench capacitor;
etching the third node dielectric and the third inner electrode of the first and second test structures to a first depth below the buried dielectric layer;
etching the second node dielectric and the second inner electrode of the deep trench capacitor to a second depth above the buried plate and within the buried dielectric layer; and
etching the first node dielectric and the first inner electrode to a third depth above the buried plate and within the buried dielectric layer, wherein the first depth is deeper than the second depth.
2. The method of claim 1 , wherein the first and second test structures have a smaller width than the deep trench capacitor.
3. The method of claim 1 , wherein the first and second test structures have a larger width than the deep trench capacitor.
4. The method of claim 1 , further comprising:
filling the first and second test structures, the deep trench capacitor, and the deep trench isolation structure with an electrically conductive material, wherein the electrically conductive material associated with the first and second test structures is in electrical contact with the inner buried plate and the outer buried plate, respectively, and wherein the electrically conductive material of the deep trench capacitor and the deep trench isolation structure remains isolated from the buried plate.
5. The method of claim 1 , wherein the deep trench isolation structure completely surrounds the inner buried plate and electrically isolates the inner buried plate from the outer buried plate.