Methods for fabricating memory devices using sacrificial layers
A protection layer is formed on a semiconductor substrate having a cell array region and an alignment key region. A plurality of data storage elements are formed on the protection layer in the cell array region. An insulating layer is formed on the data storage elements, a barrier layer is formed on the insulating layer, and a sacrificial layer is formed on the barrier layer. The sacrificial layer, the barrier layer and the insulating layer are patterned to form contact holes that expose the data storage elements, and conductive plugs are formed in the contact holes. The sacrificial layer is etched to leave portions of the conductive plugs protruding from the barrier layer. The protruding portions of the conductive plugs are removed by polishing.
1. A method of fabricating an integrated circuit memory device, the method comprising:
forming a protection layer on a semiconductor substrate having a cell array region and an alignment key region;
forming a plurality of data storage elements on the protection layer in the cell array region;
forming an insulating layer on the data storage elements;
forming a barrier layer on the insulating layer;
forming a sacrificial layer on the barrier layer;
patterning the sacrificial layer, the barrier layer and the insulating layer to form contact holes that expose the data storage elements;
forming conductive plugs in the contact holes;
etching the sacrificial layer to leave portions of the conductive plugs protruding from the barrier layer; and
polishing to remove the protruding portions of the conductive plugs.
2. The method of claim 1 :
wherein forming a plurality of data storage elements comprises:
forming a plurality of phase change material regions on the protection layer; and
forming respective upper electrodes on respective ones of the phase change material regions; and
wherein patterning the sacrificial layer, the barrier layer and the insulating layer to form contact holes that expose the data storage elements comprises patterning the sacrificial layer, the barrier layer and the insulating layer to form contact holes that expose the upper electrodes.
3. The method of claim 2 , wherein forming a plurality of data storage elements further comprises forming a plurality of lower electrodes in the protection layer, and wherein forming a plurality of phase change material regions comprises forming respective ones of the phase change material regions on respective ones of the lower electrodes.
4. The method of claim 3 , wherein the contact holes are wider than the lower electrodes.
5. The method of claim 1 , wherein the barrier layer comprises an impurity blocking layer and/or a stress buffer layer.
6. The method of claim 1 , wherein the barrier layer comprises a silicon nitride layer and/or a silicon oxynitride layer, and wherein the sacrificial layer comprises a silicon oxide layer.
7. The method of claim 1 , wherein the barrier layer comprises a silicon nitride layer, an aluminum oxide layer and/or a titanium oxide layer.
8. The method of claim 1 , wherein the barrier layer provides a stress opposite to a stress provided by the insulating layer and the sacrificial layer.
9. The method of claim 1 , wherein the barrier layer provides a compressive stress and wherein the insulating layer and the sacrificial layer glass (USG) layer provide a tensile stress.
10. The method of claim 1 , wherein the conductive plugs comprise tungsten, titanium nitride, titanium aluminum nitride (TiAlN), tantalum nitride and/or a titanium tungsten (TiW).
11. The method of claim 1 , wherein forming conductive plugs in the contact holes comprises:
forming a conductive layer on the sacrificial layer and filling the contact holes; and
etching the conductive layer to form the conductive plugs.
12. The method of claim 11 , wherein etching the conductive layer comprises dry and/or wet etching.
13. The method of claim 1 , wherein patterning the sacrificial layer, the barrier layer and the insulating layer to form contact holes that expose the data storage elements comprises patterning the sacrificial layer, the barrier layer and the insulating layer to form the contact holes in the cell array region and a trench in the alignment key region, and wherein the method further comprises forming an alignment key in the alignment key trench.
14. The method of claim 13 , wherein the alignment key trench is deeper than the contact holes.
15. The method of claim 13 , wherein forming conductive plugs in the contact holes and forming an alignment key comprise:
forming a conductive layer on the sacrificial layer, filling the contact holes and conforming to the alignment key trench;
etching the conductive layer to form the conductive plugs and a conductive region disposed in the alignment key trench and on the sacrificial layer adjacent to the alignment key trench; and
wherein polishing to remove the protruding portions of the conductive plugs comprises polishing to remove the protruding portions of the conductive plugs and to remove a portion of the conductive region on the sacrificial layer adjacent the alignment key trench and thereby form the alignment key in the alignment key trench.
16. The method of claim 13 , further comprising:
forming a conductive plate layer on the contact plugs; and
patterning the conductive plate layer using the alignment key to form plate lines on the contact plugs.
17. The method of claim 1 , wherein etching the sacrificial layer to leave portions of the conductive plugs protruding from the barrier layer comprises etching the sacrificial layer without polishing to leave portions of the conductive plugs protruding from the barrier layer.