Porous silicon trench and capacitor structures
First Claim
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1. A method of forming a semiconductor capacitor structure, said method comprising:
- forming a substrate of monocrystalline silicon, said substrate having an upper portion and a lower portion, said upper portion having a low conductivity and said lower portion having a high conductivity;
anodically etching said substrate of silicon so as to form porous silicon within said lower portion of said substrate;
forming a conformal layer of a dielectric material overlying said porous silicon; and
forming a conformal layer of silicon overlying said layer of dielectric material;
wherein said porous silicon forms a first plate of a capacitor structure and said conformal layer of silicon forms a second plate of said capacitor structure, said first plate separated from said second plate by said dielectric material.
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Abstract
The invention provides a capacitor structure utilizing porous silicon as a first plate of the capacitor structure, thereby greatly increasing the surface area available for the capacitor and thereby the capacitance attainable. The invention also provides a trench structure having a porous silicon region surrounding the sidewalls thereof. Such a trench can then be utilized to form a capacitor according to the subject invention. Methods of producing the capacitor and trench structures according to the subject invention are also provided. Porous silicon is produced utilizing electrolytic anodic etching.
37 Citations
34 Claims
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1. A method of forming a semiconductor capacitor structure, said method comprising:
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forming a substrate of monocrystalline silicon, said substrate having an upper portion and a lower portion, said upper portion having a low conductivity and said lower portion having a high conductivity; anodically etching said substrate of silicon so as to form porous silicon within said lower portion of said substrate; forming a conformal layer of a dielectric material overlying said porous silicon; and forming a conformal layer of silicon overlying said layer of dielectric material; wherein said porous silicon forms a first plate of a capacitor structure and said conformal layer of silicon forms a second plate of said capacitor structure, said first plate separated from said second plate by said dielectric material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 31, 32, 33)
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10. A method of forming a trench capacitor structure, said method comprising:
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forming a trench in a monocrystalline silicon substrate, said substrate comprising an upper portion and a lower portion, said upper portion having a low conductivity and said lower portion having a high conductivity; anodically etching said silicon substrate surrounding said trench so as to form porous silicon within said lower portion of said substrate; forming a conformal layer of a dielectric material overlying said porous silicon; and forming a conformal layer of silicon overlying said layer of dielectric material; wherein said porous silicon forms a first plate of a capacitor structure and said conformal layer of silicon forms a second plate of said capacitor structure, said first plate separated from said second plate by said layer of dielectric material. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 34)
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19. A self-limiting method of forming isolated adjacent trenches in a substrate, said method comprising:
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forming a pair of adjacent trenches in a monocrystalline silicon substrate; anodically etching said silicon substrate surrounding each of said adjacent trenches so as to form a pair of porous silicon regions; wherein said anodic etching is performed contemporaneously within each of said pair of trenches by a self-limiting process and leaves an area of non-porous silicon between said pair of porous silicon regions, thereby isolating said pair of adjacent trenches. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28)
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- 29. The self-limiting method of claim 29 wherein said forming of said conformal layer of silicon comprises deposition of said conformal layer of silicon.
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