Silicon pillars for vertical transistors
AssigneeMicron Technology, Inc.
InventorPatrick Thomas
Life of this patent
Estimating the term…
Abstract
In order to form a more stable silicon pillar which can be used for the formation of vertical transistors in DRAM cells, a multi-step masking process is used. In a preferred embodiment, an oxide layer and a nitride layer are used as masks to define trenches, pillars, and active areas in a substrate. Preferably, two substrate etch processes use the masks to form three levels of bulk silicon.
Claims38
A method of forming pillars in a substrate for integrated circuits comprising:
- forming a lower hard mask on a substrate;
- forming an upper hard mask over the lower hard mask;
- forming a first resist mask over the upper hard mask to form first exposed portions of the upper hard mask and the lower hard mask;
- removing the first exposed portions of the upper hard mask and the lower hard mask;
- forming a second resist mask over the upper hard mask to form second exposed portions of the upper hard mask after removing the first resist mask;
- removing the second exposed portions of the upper hard mask to form a third exposed portion of the lower hard mask;
- etching the substrate selectively to the upper hard mask and the third exposed portions of the lower hard mask after removing the second exposed portions of the upper hard mask;
- removing the third exposed portions of the lower hard mask after etching the substrate;
- and
- etching the substrate using the upper hard mask to form a plurality of active areas and trenches after removing the third exposed portion of the lower hard mask.
A method of forming silicon pillars for vertical transistors for integrated circuits comprising:
- forming a first mask layer over a silicon substrate;
- forming a second mask layer over the first mask layer;
- patterning the first mask layer to expose a first portion of the silicon substrate;
- patterning the second mask layer to form an unmasked portion of the first mask layer after patterning the first mask layer;
- etching the first exposed portion of the silicon substrate to a first depth;
- removing the unmasked portion of the first mask layer to expose a second portion of the silicon substrate;
- and
- etching the first exposed portion to a second depth and the second exposed portion to a third depth.
A method of forming a silicon pillar, comprising:
- forming an oxide layer over a silicon substrate;
- depositing a nitride layer over the oxide layer;
- removing a first portion of the nitride layer and the oxide layer to expose a plurality of trench regions in the silicon substrate and to form an oxide hard mask;
- removing a second portion of the nitride layer to form a nitride hard mask and to form unmasked portions of the oxide hard mask after removing the first portion of the oxide layer and the nitride layer;
- etching the trench regions after removing the second portion of the nitride layer;
- removing the unmasked portions of the oxide hard mask to expose a plurality of intermediate substrate regions;
- and
- etching the intermediate substrate regions and the trench regions.
A method of forming a pillar in a substrate, comprising:
- exposing a trench region of a substrate;
- etching the trench region to a first depth;
- exposing an intermediate region of the substrate after etching the trench region;
- and
- etching the intermediate region to a second depth and the trench region to a third depth, wherein the third depth is equal to a sum of the first depth and the second depth.
Dependencies are inferred from the claim text.