Guard ring of a combination wafer or singulated die
A combination wafer is manufactured by (i) forming a plurality of alternating dielectric and metal layers, (ii) forming a guard ring trench in the layers, (iii) forming a guard ring layer in the guard ring trench, and then repeating (i), (ii) with a slightly wider guard ring trench, and (iii). A number of layers are thus simultaneously etched and lined with a guard ring layer, but the number of layers is not so large so as to cause lithographic problems that may occur when a deep, narrow guard ring trench is formed. An upper one of the layers that are patterned is always made of silicon dioxide, which includes less carbon than lower polymer layers and allows for a carbon mask to be formed and be easily removed. The slightly wider guard ring trench each time the process is repeated overcomes lithographic alignment problems that may occur when the guard ring trenches are exactly the same size. Subsequent guard ring layers are partially formed on one another, and provide a moisture seal. The guard ring layers are formed at the same time when vias are formed that are connected to electronic elements.
1. A method of making a combination wafer, comprising:
forming a first ground ring trench having a first width into a first set of alternating dielectric layers and layers of metal lines on a substrate having a plurality of electronic elements formed therein or thereon;
forming a first metal layer including a first guard ring layer on surfaces of the first guard ring trench and a first via connected to one of the electronic elements;
forming a second guard ring trench having a second width which is more than the first width above the first guard ring trench into a second set of alternating dielectric layers and layers of metal lines on the first set; and
forming a second metal layer including a second guard ring layer on surfaces of the second guard ring trench and a second via connected to one of the electronic components.
2. The method of claim 1 , further comprising:
forming the second set of layers after the first guard ring layer is formed.
3. The method of claim 1 , wherein:
(i) the first guard ring layer is partially formed on a top surface of a layer of the first set; and
(ii) the second guard ring layer is partially formed on a top surface of the first guard ring layer where the first guard ring layer is formed on the top surface of the layer of the first set.