Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Reexamination Certificate
2001-12-03
2002-11-05
Hiteshew, Felisa (Department: 1765)
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
C117S094000, C117S095000, C117S105000
Reexamination Certificate
active
06475456
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a single crystal silicon carbide film as an electronic material, particularly to silicon carbide which is preferable in preparing a semiconductor device and which has a low defect density and to a method for manufacturing the silicon carbide.
(ii) Description of the Related Art
The growth of silicon carbide (SiC) has heretofore been classified to a bulk growth by a sublimation process, and a thin film formation by epitaxial growth onto a substrate.
In the bulk growth by the sublimation process the growth of 6H-SiC or 4H-SiC which is a polytypism with a high temperature phase is possible, and the preparation of SiC itself as the substrate has been realized. However, there are a large number of defects (micro pipes) introduced into a crystal, and it has been difficult to enlarge a substrate area.
On the other hand, when the epitaxial growth process onto a single crystal substrate is used, the enhancement of controllability of impurity addition or the enlargement of substrate area, and the reduction of micro pipes having caused problems in the sublimation process are realized. In the epitaxial growth process, however, the increase of a plane defect density by a difference in lattice constant between a substrate material and a silicon carbide film often raises a problem. Particularly, since Si usually used as the substrate to grow has a large lattice mismatching from SiC, twins and anti phase boundaries (APB) are remarkably generated in an SiC growth layer, and these deteriorate the properties of SiC as an electronic element.
As a method of reducing surface defects in the SiC film, for example, a technique of reducing the surface defects having inherent or more thickness is proposed in Japanese Patent Publication No. 41400/1994, which includes a process of disposing a growth area on a substrate to grow, and a process of allowing a silicon carbide single crystal to grow in this growth area so that its thickness becomes the same as or more than the thickness inherent to the growth surface orientation of the substrate. However, since two orientations of anti phase boundaries contained in SiC have properties to be enlarged in directions orthogonal to each other with respect to the increase of SiC film thickness, the anti phase boundaries cannot effectively be reduced. Furthermore, the direction of a super structure formed on the grown SiC surface cannot arbitrarily be controlled. Therefore, for example, when the separated growth areas are combined with each other according to the growth, the anti phase boundary is newly formed on this combined part, which deteriorates electric properties.
As a method of effectively reducing the anti phase boundaries, K. Shibahara et al. have proposed a growth process onto an Si (100) surface substrate in which a surface normal axis is slightly inclined to [110] from [001] direction (an off angle is introduced) (Upright Physics Letter, vol. 50, 1987, page 1888). In this method, since an atomic level step is introduced at equal intervals in one direction by applying the slight inclination to the substrate, the surface defect having a direction parallel to the introduced step is propagated. On-the other hand, the propagation of the surface defect to the direction vertical to the introduced step (a direction across the step) is effectively suppressed. Therefore, since the anti phase boundary enlarged in the direction parallel to the introduced step is enlarged in preference to the anti phase boundary enlarged in the orthogonal direction in the two orientations of anti phase boundaries included in the film with respect to the film thickness increase of silicon carbide, the anti phase boundaries can effectively be reduced. However, as shown in
FIG. 1
, in this method, the increase of step density of an SiC/Si interface causes the generation of an undesired anti phase boundary
1
, and there is a problem that the anti phase boundary cannot completely be eliminated. Additionally, in
FIG. 1
, numeral
1
denotes an anti phase boundary generated in the single atom step of Si substrate,
2
denotes an anti phase boundary association point,
3
denotes an anti phase boundary generated in an Si substrate surface terrace, &thgr; denotes an off angle, and &phgr; denotes an angle (54.7°) formed between the Si (001) surface and the anti phase boundary. The anti phase boundary
3
generated in the Si substrate surface terrace disappears in the anti phase boundary association point
2
, but the anti phase boundary
1
generated in the single atom step of the Si substrate has no other boundary to associate, and does not disappear.
SUMMARY OF THE INVENTION
The present invention has been developed under the above-described background, and an object thereof is to provide a silicon carbide film in which anti phase boundaries are effectively reduced or eliminated.
To attain the above-described object, the present invention provides the following constitutions.
(Constitution 1) A method for manufacturing a silicon carbide film in which a crystal orientation is inherited on a single crystal substrate surface and silicon carbide is allowed to epitaxially grow, the method for manufacturing the silicon carbide film comprising the steps of: entirely or partially providing the substrate surface with a plurality of undulations extended parallel in one direction; and allowing silicon carbide to grow on the substrate surface.
(Constitution 2) The method for manufacturing the silicon carbide film in the constitution 1 in which during the growth of the silicon carbide film, an epitaxial growth mechanism is used so that a propagation orientation of a surface defect generated in the film can be limited in a specified crystal surface.
(Constitution 3) The method for manufacturing the silicon carbide film described in the constitution 1 or 2 in which when an average value of an interval between undulation tops of the substrate surface is set to W, the silicon carbide film has a thickness of W/2(=2
½
) or more.
(Constitution 4) The method for manufacturing the silicon carbide film described in the constitutions 1 to 3 in which the interval between the undulation tops of the substrate surface is in a range of 0.01 &mgr;m to 10 &mgr;m, an undulation height difference is in a range of 0.01 &mgr;m to 20 &mgr;m, and the inclination degree of an inclined surface in the undulation is in a range of 1° to 55°.
(Constitution 5) The method for manufacturing the silicon carbide film described in the constitutions 1 to 4 in which the substrate comprises a single crystal Si, the substrate surface comprises a (001) surface, and the surface is provided with the undulation extended in parallel with a [110] orientation.
(Constitution 6) The method for manufacturing the silicon carbide film described in the constitutions 1 to 4 in which the substrate comprises a single crystal 3C-SiC, the substrate surface comprises a (001) surface, and the surface is provided with the undulation extended in parallel with a [110] orientation.
(Constitution 7) The method for manufacturing the silicon carbide film described in the constitutions 1 to 4 in which the substrate comprises a hexagonal single crystal SiC, the substrate surface comprises a (1, 1, −2, 0) surface, and the surface is provided with the undulation extended in parallel with a [1, −1, 0, 0] orientation or a [0, 0, 0, 1] orientation.
(Constitution 8) A silicon carbide film manufactured using the method described in the constitutions 1 to 7.
(Constitution 9) The silicon carbide film which comprises a step of a plurality of undulations entirely or partially formed on a single crystal substrate surface and extended parallel in one direction, and which has a structure subjected to epitaxial growth in a method so that a propagation orientation of a film inner surface defect can be limited in a specified crystal surface.
According to the constitution 1, by providing the surface of the substrate
Kawahara Takamitsu
Nagasawa Hiroyuki
Nakano Yukitaka
Yagi Kuniaki
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Hiteshew Felisa
Hoya Corporation
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