Process flow for thick isolation collar with reduced length
AssigneesInternational Business Machines Corporation, Infineon Technologies North America Corp.
InventorsJack A. Mandelman, Rama Divakaruni, Gerd Fehlauer, Stephan Kudelka, Uwe Schroeder, Helmut H. Tews
Life of this patent
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Abstract
A trench capacitor memory cell structure is provided with includes a vertical collar region that suppresses current leakage of an adjacent vertical parasitic transistor that exists between the vertical MOSFET and the underlying trench capacitor. The vertical collar isolation, which has a vertical length of about 0.50 μm or less, includes a first portion that is present partially outside the trench and a second portion that is present inside the trench. The first portion of the collar oxide is thicker than said second portion oxide thereby reducing parasitic current leakage.
Claims20
A trench capacitor memory cell structure comprising:
- a plurality of trenches present in a semiconductor substrate, each of said plurality of trenches including a vertical transistor isolated from an underlying trench capacitor, and
- a vertical collar isolation region having a vertical length of about 0.50 μm or less present on sidewalls of each trench between said vertical transistor and said trench capacitor, said collar isolation region having a first portion that is present partially outside the trench and a second portion that is present inside the trench, said first portion is thicker than said second portion thereby reducing current leakage of an adjacent vertical parasitic transistor.
A method of forming a trench capacitor memory cell structure, said method comprising the steps of:
- providing a plurality of trenches in a surface of a semiconductor substrate, each of said plurality of trenches having an upper region and a lower region, said lower region containing a trench capacitor formed therein;
- forming a vertical collar isolation region in each of said trenches, said vertical collar isolation region having a vertical length of about 0.50 μm or less and a first portion that is present partially outside the trench and a second portion that is present inside the trench, said first portion is thicker than said second portion;
- forming a vertical transistor above said vertical collar isolation region.
Dependencies are inferred from the claim text.