Semiconductor devices including bulb-shaped trenches

Abstract

A method of creating a trench having a portion of a bulb-shaped cross-section in silicon is disclosed. The method comprises forming at least one trench in silicon and forming a liner in the at least one trench. The liner is removed from a bottom surface of the at least one trench to expose the underlying silicon. A portion of the underlying exposed silicon is removed to form a cavity in the silicon. At least one removal cycle is conducted to remove exposed silicon in the cavity to form a bulb-shaped cross-sectional profile, with each removal cycle comprising subjecting the silicon in the cavity to ozonated water to oxidize the silicon and subjecting the oxidized silicon to a hydrogen fluoride solution to remove the oxidized silicon. A semiconductor device structure comprising the at least one trench comprising a cavity with a bulb-shaped cross-sectional profile is also disclosed.

1 . A semiconductor device structure, comprising:
 trenches in silicon, wherein each trench of the trenches has an average width of from about  20  nm to about  60  nm;   a liner on sidewalls of the trenches; and   a cavity having a bulb-shaped cross-sectional profile at proximal portions of each trench of the trenches.   
     
     
         2 . The semiconductor device structure of  claim 1 , wherein the silicon comprises monocrystalline silicon or polycrystalline silicon. 
     
     
         3 . The semiconductor device structure of  claim 1 , wherein the cavity is below the liner. 
     
     
         4 . The semiconductor device structure of  claim 1 , wherein the liner comprises a silicon oxide material or a silicon nitride material. 
     
     
         5 . The semiconductor device structure of  claim 1 , wherein a bottom surface of the cavity is approximately 230 nm from a top surface of the silicon. 
     
     
         6 . The semiconductor device structure of  claim 1 , wherein a distance between adjacent trenches of the trenches is between about 40 nm and about 100 nm. 
     
     
         7 . The semiconductor device structure of  claim 1 , wherein each trench of the trenches has an average width of about 40 nm. 
     
     
         8 . The semiconductor device structure of  claim 1 , wherein the cavity extends about 50 nm below a bottom portion of the liner. 
     
     
         9 . The semiconductor device structure of  claim 1 , further comprising a bit line in the cavity of each trench of the trenches. 
     
     
         10 . A semiconductor device, comprising:
 trenches in silicon, each trench including a first portion having vertical sidewalls and a second portion including a bulb-shaped cavity;   a liner on the vertical sidewalls of the trenches; and   a bit line in the bulb-shaped cavity of each of the trenches.   
     
     
         11 . The semicondcutor device of  claim 10 , wherein:
 the liner on the vertical sidewalls of the trenches terminates at about 180 nm from a surface of the silicon;   and the bulb-shaped cavity extends about 50 nm below the liner.   
     
     
         12 . The semiconductor device of  claim 10 , wherein the bulb-shaped cavity extends between about 30 nm and about 60 nm below the liner. 
     
     
         13 . The semiconductor device of  claim 10 , wherein the liner comprises silicon nitride. 
     
     
         14 . The semiconductor device of  claim 10 , wherein the liner has a thickness between about 50 Angstroms and about 100 Angstroms. 
     
     
         15 . The semiconductor device of  claim 10 , wherein the trenches are less than about 40 nm apart. 
     
     
         16 . The semiconductor device of  claim 10 , further comprising a word line proximate a surface of the silicon. 
     
     
         17 . The semiconductor device of  claim 10 , wherein the liner extends further from a surface of the substrate than the the bulb-shaped cavity extends from the liner. 
     
     
         18 . A semiconductor device, comprising:
 at least one trench having vertical sidewalls;   a bulb-shaped cavity below the vertical sidewalls; and   a bit line in the bulb-shaped cavity.   
     
     
         19 . The semiconductor device of  claim 18 , wherein the at least one trench has a width of between about 20 nm and about 60 nm. 
     
     
         20 . The semiconductor device of  claim 18 , further comprising a liner on the vertical sidewalls, the bulb-shaped cavity extending between about 30 nm and about 60 nm below the liner.