Method for production of contacts on a wafer
View Patent ↗The invention relates to a method for production of contacts on a wafer, preferably with the aid of a lithographic process. The preferred embodiment provides a method which overcomes the disadvantages of the complex point/hole lithography process, and which avoids any increase in the process complexity. This method is achieved in that a strip structure extending over two layers is used to structure the contacts. The strip structure in the first layer is rotated at a predetermined angle with respect to the strip structure in the second layer, and the contacts are formed in the mutually overlapping areas of the strip structures in the two layers.
1. A method of forming a semiconductor device, the method comprising:
providing a surface that includes a plurality of contacts laid out in a matrix of rows and columns;
forming a first plurality of strips over the surface, each strip in the first plurality contacting ones of the contacts disposed along a diagonal of the matrix;
forming a second plurality of strips over the surface and over the first plurality of strips, each strip in the second plurality disposed along a row of the matrix; and
removing portions of the first plurality of strips not underlying the second plurality of strips.
2. The method of claim 1 wherein the first plurality of strips is formed by means of a lithographic process using a first exposure mask and wherein the second plurality of strips is formed by means of a lithographic process using a second exposure mask.
3. The method of claim 2 wherein the lithographic process uses a positive resist.
4. The method of claim 1 wherein the first plurality of strips comprises a plurality of parallel strips and wherein the second plurality of strips comprises a plurality of parallel strips.
5. The method of claim 1 wherein the angle between the first plurality of strips and the second plurality of strips is about 45 degrees.
6. The method of claim 1 wherein the strips in the second plurality of strips are corrugated.
7. The method of claim 1 wherein snips in the first plurality of strips have a different pitch than strips in the second plurality of strips.
8. The method of claim 7 wherein strips in the first plurality of strips have a width that is the same as a width of strips in the second plurality of strips and wherein a distance between strips in the first plurality of strips is different than a distance between strips in the second plurality of strips.
9. The method of claim 8 wherein the distance between strips in the first plurality of snips is greater than the distance between strips in the second plurality of strips.
10. The method of claim 1 wherein removing portions comprises over-etching a space region between the strips in the second plurality of strips.
11. The method of claim 1 wherein the semiconductor device comprises a memory array and wherein the contacts comprise memory cell contacts, and wherein the strips in the second plurality of strips line along a row line for memory cells.
12. The method of claim 11 wherein the second plurality of strips is formed in an M0 metallization.