METHOD OF FORMING ASYMMETRIC SPACERS AND METHODS OF FABRICATING SEMICONDUCTOR DEVICE USING ASYMMETRIC SPACERS
A method of fabricating asymmetrical spacers, structures fabricated using asymmetrical spacers and an apparatus for fabricating asymmetrical spacers. The method includes: forming on a substrate, a structure having a top surface and opposite first and second sidewalls and having a longitudinal axis parallel to the sidewalls; forming a conformal layer on the top surface of the substrate, the top surface of the structure and the sidewalls of the structure; tilting the substrate about a longitudinal axis relative to a flux of reactive ions, the flux of reactive ions striking the conformal layer at acute angle; and exposing the conformal layer to the flux of reactive ions until the conformal layer is removed from the top surface of the structure and the top surface of the substrate leaving a first spacer on the first sidewall and a second spacer on the second sidewall, the first spacer thinner than the second spacer.
1 . An apparatus, comprising:
a chamber having a gas inlet and an exhaust port connected to a vacuum pump;
a magnetic filter positioned between means for generating an electron/reactive ion plasma from a gas supplied through said gas inlet and means for holding a surface of a substrate at a pre-selected angle between 0° and 90° relative to a plane defined by said magnetic filter; and
means for applying a bias voltage to said means for holding said substrate.
2 . The apparatus of claim 1 , wherein said means for holding said substrate is a tiltable stage.
3 . The apparatus of claim 1 , wherein said means for holding said substrate is a stage fixed at said pre-selected angle.
4 . The apparatus of claim 1 , wherein said magnetic filter includes a row of magnetic cores spaced apart less than half a gyroradius of an electron at the magnetic field strength generated by said magnetic filter cores.
5 . The apparatus of claim 1 , wherein said means for generating an electron/reactive gas ion plasma is inductively coupled to a plasma power supply.
6 . The apparatus of claim 1 , wherein said means for generating an electron/reactive gas ion plasma is capacitively coupled to a plasma power supply.
7 . The apparatus of claim 1 , wherein said means for generating an electron/reactive gas generates a plasmas density of between about 10 12 and 10 13 ions per cm 3 .
8 . The apparatus of claim 1 , said magnetic filter has a field strength between about 5 G and about 500 G.
9 . The apparatus of claim 1 , wherein said magnetic filter has a field strength between about 5 G and about 500 G and includes cores spaced apart less than half a gyroradius of an electron at said field strength.
10 . The apparatus of claim 1 , wherein said magnetic filter is positioned between said means for holding a substrate and said high density plasma.
11 . The apparatus of claim 1 , wherein said magnetic filter includes a row of magnetic filter cores spaced apart a distance that is less than half a gyroradius of an electron at the magnetic field strength generated by said magnetic filter cores, said distance allowing a flux of charged ions to pass from said electron/reactive ion plasma through said magnetic filter to said substrate and not allowing electrons from said electron/reactive ion plasma to pass through said magnetic filter to said substrate.
12 . The apparatus of claim 1 , wherein said magnetic filter prevents formation of a sheath around a plasma generated between said magnetic filter and said substrate.
13 . The apparatus of claim 1 , wherein said magnetic filter allows formation of an ion-ion plasma between said magnetic filter and said substrate.
14 . The apparatus of claim 1 , wherein only reactive ions and neutral species strike said surface of said substrate.
15 . The apparatus of claim 1 , wherein said magnetic filter includes a row of magnetic cores spaced apart less than 1 cm.
16 . The apparatus of claim 1 , wherein said electron/reactive ion plasma is a non-equilibrium plasma.
17 . The apparatus of claim 1 , wherein said gas comprises CH x F 4-x where x is 1, 2 or 3.
18 . The apparatus of claim 1 , wherein said substrate comprise a semiconductor material having a dielectric layer thereupon.
19 . The apparatus of claim 1 , wherein said substrate is a silicon-on-insulator substrate comprising a single-crystal silicon layer separated from a semiconductor substrate by a buried insulating layer.
20 . The apparatus of claim 1 , wherein said substrate is a circular disk of silicon having a dielectric layer thereupon.