Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – By reaction with substrate
Reexamination Certificate
2003-02-28
2004-08-31
Chaudhari, Chandra (Department: 2813)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
By reaction with substrate
C438S910000, C438S958000
Reexamination Certificate
active
06784114
ABSTRACT:
BACKGROUND OF THE INVENTION
Dangling bonds are an inherent nature of semiconductor surfaces. Such dangling bonds cause a variety of problems in the fabrication of solid-state devices on semiconductor substrates. They act as reaction sites for chemical reactions and create surface states that cause the observed properties of electronic devices to vary from their design specifications. On a semiconductor surface, dangling bonds adsorb oxygen, water, or carbon dioxide, and a layer of silicon dioxide (the so-called “native oxide”) is formed as soon as the surface is exposed to air.
When a clean silicon(001) surface is kept in ultrahigh vacuum, it has little chance for adsorption or reaction with external species. Under such conditions, the surface undergoes reconstruction to reduce its energy. Each atom on a reconstructed Si(001):2×1 surface has one dangling bond and shares a dimer bond with a neighboring surface atom, as shown in FIG.
1
(
a
). Electronically, surface states originate from dangling bonds and strained surface bonds (i.e. dimer bonds and back bonds) and often pin the surface Fermi level, causing surface band bending. When a metal is deposited on the Si(001) surface, surface states (now more appropriately, interface states) pin the interface Fermi level, making the Schottky barrier height less dependent on metal work function and semiconductor electron affinity and instead, the barrier height is controlled by surface states.
The concept of “valence-mending” was proposed to eliminate dangling bonds on semiconductor surfaces. For the Si(001) surface, valence-mending atoms include Group VI atoms sulfur (S), selenium (Se) and tellurium (Te). They can bridge between two surface atoms and nicely terminate dangling bonds and relax strained bonds on Si(001), as shown in FIG.
1
(
b
). This structure is often noted as a 1×1 reconstruction. The difficulty with valence mending is controlling the amount of passivating agent that is incorporated so that a new layer of material that significantly interferes with the intrinsic properties of the semiconductor substrate is not built up. Therefore, there exists a need for an effective method of passivating a semiconductor while concomitantly minimizing any carry over effects from the passivation itself.
SUMMARY OF THE INVENTION
The present invention provides an improved method for passivating a semiconductor surface.
In one form, the present invention is a method for passivating a semiconductor surface with a monolayer of passivating agent including the steps of placing a semiconductor substrate, having at least one surface, in a chamber and heating the semiconductor substrate to a temperature. The semiconductor substrate is then exposed to a passivating agent for a period of time sufficient to react with substantially all of the surface, and the partial pressure of the passivating agent is such that the passivating agent will not condense at the temperature of the substrate. As a result of this treatment the presence of surface states is greatly reduced.
In another form, the present invention is a method for manufacture of a semiconductor device with a low Schottky barrier including the steps of placing an n-type semiconductor substrate having at least one surface in a chamber and heating the semiconductor substrate to a temperature. The semiconductor substrate is then exposed to a passivating agent for a period of time sufficient to react with substantially all of the surface, and the partial pressure of the passivating agent is such that the passivating agent will not condense at the temperature of the substrate. As a result of this treatment the presence of surface states is greatly reduced. A portion of the semiconductor surface is then metallized with a metal having a work function whose magnitude is greater than the magnitude of the electron affinity of the semiconductor substrate.
In another form, the present invention is a method for manufacture of a semiconductor device with a low Schottky barrier including the steps of placing a p-type semiconductor substrate having at least one surface in a chamber and heating the semiconductor substrate to a temperature. The semiconductor substrate is then exposed to a passivating agent for a period of time sufficient to react with substantially all of the surface, and the partial pressure of the passivating agent is such that the passivating agent will not condense at the temperature of the substrate. As a result of this treatment the presence of surface states is greatly reduced. A portion of the semiconductor surface is then metallized with a metal having a work function whose magnitude is less than the sum of the magnitude of the electron affinity and the band gap of the semiconductor substrate.
Yet another form of the present invention is a method for manufacture of a semiconductor device with improved ohmic contacts comprising the steps of placing an n-type semiconductor substrate having at least one surface in a chamber and heating the semiconductor substrate to a temperature. The semiconductor substrate is then exposed to a passivating agent for a period of time sufficient to react with substantially all of the surface, and the partial pressure of the passivating agent is such that the passivating agent will not condense at the temperature of the substrate. As a result of this treatment the presence of surface states is greatly reduced. A portion of the semiconductor surface is then metallized with a metal having a work function whose magnitude is less than the magnitude of the electron affinity of the n-type semiconductor substrate.
Still another form of the present invention is a method for manufacture of a semiconductor device with improved ohmic contacts including the steps of placing an p-type semiconductor substrate having at least one surface in a chamber and heating the semiconductor substrate to a temperature. The semiconductor substrate is exposed to a passivating agent for a period of time sufficient to react with substantially all of the surface, and the partial pressure of the passivating agent is such that the passivating agent will not condense at the temperature of the substrate. As a result of this treatment the presence of surface states is greatly reduced. A portion of the semiconductor surface is then metallized with a metal having a work function whose magnitude is greater than the sum of the magnitude of the electron affinity and the band gap of the p-type semiconductor substrate.
Those skilled in the art will further appreciate the advantages and superior features of the passivation methods of the present invention upon reading the detailed description that follows in conjunction with the drawings.
REFERENCES:
patent: 5760462 (1998-06-01), Barron et al.
patent: 5943568 (1999-08-01), Fujii et al.
patent: 6483172 (2002-11-01), Cote et al.
R.M. Tromp, R.J. Hamers, and J.E. Demuth, Si(001) dimer structure observed with scanning tunneling microscopy, Phys. Rev. Lett., 1985, 1303, 55.
E. Kaxiras, Semiconductor-surface restoration by valence-mending absorbates: Application to Si(100):S and Si(100):Se, Physical Review B, 1991, 6324, 43.
H. Metzner, TH. Haln, and J.-H. Bremer, Structure of sulfur-terminated silicon surfaces, Surf. Sci., 1997, 377-379, pp. 71-74.
J.J. Boland, Structure of the H-saturated Si(100) surface, Phys. Rev. Lett., 1990, 3325, 65.
M. Tao and L.P. Hunt, The thermodynamic behavior of the Si-H system and its role in Si-CVD from SiH4, J. Electrochem. Soc., 1992, 806, 139.
J.E. Northrup, Structure of Si(100)H: Dependence on the H chemical potential, Phys. Rev. B, 1991, 1419, 44.
B.S. Meyerson, F.J. Himpsel, and K.J. Uram, Bistable conditions for low-temperature silicon epitaxy, Appl. Phys. Lett., 1990, 1034, 57.
J.W. Lyding, T.-C. Shen, J.S. Hubacek, J.R. Tucker, and G.C. Abeln, Nanoscale patterning and oxidation of H-passivated Si(100)-2×1 surfaces with an ultrahigh vacuum scanning tunneling microscope, Appl. Phys. Lett., 1994, 2010, 64.
T.-C. Shen, C. Wang, G.C. Abeln, J.R. Tucker, J.W. Lyding, PH. Avouris, and R.E. Walkup, A
Kirk Wiley P.
Tao Meng
Board of Regents , The University of Texas System
Chaudhari Chandra
LandOfFree
Monatomic layer passivation of semiconductor surfaces does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Monatomic layer passivation of semiconductor surfaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Monatomic layer passivation of semiconductor surfaces will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3343667