Method of chemical mechanical polishing for dielectric layers

A chemical mechanical polishing method for forming a planarized dielectric layer over an array of spaced apart conducting lines on a substrate, comprising the steps of:

• depositing a first dielectric layer on the conducting lines and on the substrate, the first layer having a relatively low polishing rate and a substantially constant thickness across the conducting lines and the substrate, wherein the first layer forms indentations between top surfaces of adjacent conducting lines;
• forming gaps in the indentations of the first layer that extend through the first layer to an underlying surface;
• depositing a second dielectric layer on the first layer so that the second layer fills the gaps and the indentations, and so that the second layer extends above the first layer, the second layer having a higher polishing rate than the first layer and being selectively etchable from the first layer;
• polishing the second layer using a chemical mechanical polishing process;
• and
• endpointing the polishing process at a planar endpoint when the first layer is exposed across the top surfaces of the conducting lines to form a self-aligned pattern between the conducting lines from material of the second layer that extends from the planarized surface to the underlying surface.

A chemical mechanical polishing method for forming a planarized dielectric layer over an array of spaced-apart conducting lines on a substrate, comprising the steps of:

• depositing a silicon nitride layer on the conducting lines and on the substrate, the silicon nitride layer having a substantially constant thickness across the conducting lines and the substrate, wherein the silicon nitride layer forms indentations between top surfaces of adjacent conducting lines;
• depositing a doped silicon dioxide layer on the silicon nitride layer so that the doped silicon oxide layer fills the indentations and extends above the silicon nitride layer, the doped silicon oxide layer having a higher polishing rate than the silicon nitride layer and being selectively etchable from the silicon nitride layer;
• controlling a dopant concentration of the second layer to produce a dopant concentration profile within the second layer that decreases with increasing depth into the second layer and then levels to a substantially uniform concentration;
• controlling a polish rate of the chemical mechanical polishing process using the dopant concentration of the second layer such that the polish rate decreases with increasing depth into the second layer;
• and
• endpointing the polishing process at a planar endpoint.