Chemistry: electrical current producing apparatus – product – and – Fuel cell – subcombination thereof – or method of making or... – Means for joining components together
Reexamination Certificate
2000-10-27
2002-12-17
Tsai, Jey (Department: 2812)
Chemistry: electrical current producing apparatus, product, and
Fuel cell, subcombination thereof, or method of making or...
Means for joining components together
C438S413000, C438S388000
Reexamination Certificate
active
06495294
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of Japanese Patent Applications No. 11-307656 filed on Oct. 28, 1999, and No. 2000-268960 filed on Sep. 5, 2000, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate processing technique for formation of a semiconductor element.
2. Description of the Related Art
As shown in
FIG. 18
, to form a doping layer
101
uniform in a depth direction at a desired position in a silicon substrate
100
not only attracts attention as a substrate structure effective in lowering an on resistance of a high withstand voltage MOS device disclosed in U.S. Pat. No. 5,438,215, but also is effective to enable high integration in the depth direction by effectively using the depth direction of the substrate.
As a method of forming the doping layer
101
, it is conceivable to use dopant diffusion from the surface, or a method of dopant ion implantation and heat treatment, which is conventionally generally used in a silicon semiconductor process. However, the depth B of the doping layer
101
is controlled by the diffusion rate of the dopant impurity. Thus, in a generally used heat treatment time, it is possible to merely form the doping layer
101
of a depth of several &mgr;m from the surface. Besides, since the diffusion of the dopant advances isotropically, the diffusion advances not only in the depth direction but also in the lateral direction, and the doping layer
101
having a lateral extension A comparable to the depth is eventually obtained. Thus, in the doping layer formation by the conventional heat diffusion, an aspect ratio (=B/A) does not exceed “1” in principle, and the structure in formation of a device is restricted.
On the other hand, “A new generation of high power MOSFETs breaks the limit line of silicon” IEDM98 Proc. (1998) by G. Deboy et al., proposes the following method. That is, first, as shown in
FIGS. 19A and 19B
, an epitaxial film
111
a
is formed on a substrate
110
by epitaxial growth, and as shown in
FIG. 19C
, a doping layer
112
a
is formed by partial dopant ion implantation with photolithography and heat diffusion treatment. Next, as shown in
FIGS. 20A and 20B
, the epitaxial growth, partial ion implantation, and heat diffusion treatment are repeated. As a result, as shown in
FIG. 20C
, a doping layer
112
extending in the depth direction is formed. According to this method, since the depth of the formed doping layer (doping layer extending in the depth direction)
112
is determined by epitaxial growth thickness, it is not controlled by the diffusion length of the dopant.
However, since the extension in the lateral direction is controlled through the diffusion length of one diffusion treatment, the lateral extension equivalent to the film thickness of one epitaxial growth becomes a processing limit. Thus, in the case where a deeper profile is desired to be formed, it is sufficient if the epitaxial film thickness is increased. However, in order to suppress the extension in the lateral direction, it is necessary to thin the thickness of one epitaxial growth. As a result, the number of times of the epitaxial growth and diffusion treatment of the dopant is increased, and the manufacturing cost of a substrate is increased.
Besides, a processing method proposed in EP-A-53854 is shown in
FIGS. 21A-21C
. First, as shown in
FIGS. 21A and 21B
, trenches
121
are formed in a substrate
120
, and as shown in
FIG. 21C
, an epitaxial layer
122
of a desired dopant concentration is filled in the inside of each of the trenches
121
. Accordingly, a profile in the depth direction is formed. In this processing method, substrate formation can be made by a trench forming step and an epitaxial growth step, and the number of steps is small and it is expected that throughput is improved. Further, since the shape of the doping layer is almost coincident with a trench shape, it is conceivable that an arbitrary shape with high aspect ratio can be formed as compared with the foregoing method of repeating the epitaxial growth and the dopant diffusion plural times.
However, as expected important problems in the case of trench filling epitaxial growth, void-less trench filling, defect-less epitaxial growth, and high controllability of doping concentration can be pointed out. On the other hand, in the present circumstances, a study of the trench filling epitaxial growth has not been sufficiently carried out, and proper measures against the problems and a manufacturing method are not clear.
Besides, there is a selective epitaxial method as an epitaxial growth technique similar to the trench filling epitaxial growth. The selective epitaxial method is a method in which as shown in
FIGS. 22A and 22B
, an oxide film
131
having opening portions
132
is disposed on a substrate
130
, and as shown in
FIG. 22C
, epitaxial films
133
are grown only on portions where the surface of the silicon substrate
130
is exposed.
Thus, the structure in which the epitaxial films
133
are filled in the oxide film opening portions
132
is eventually obtained. The selective epitaxial technique has an object to form such a structure that the epitaxial films
133
are made device formation regions of CMOS and the oxide film
131
which is a mask is made element separation regions. Also in the selective epitaxial growth, void-less trench filling and defect-less epitaxial growth have been studied as the main technical problems.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems. An object of the present invention is to provide a noble structure for a semiconductor substrate that has a semiconductor layer extending in a depth direction of the semiconductor substrate with a uniform concentration profile, and a method for manufacturing the same.
According to a first aspect of the present invention, a semiconductor substrate has a trench having a first width at a bottom thereof and a second width at an opening portion thereof larger than the first width. The trench is filled with a semiconductor layer having a dimension in a normal line direction with respect to a surface of the semiconductor substrate larger than a lateral dimension thereof that is a dimension in a lateral direction on an arbitrary plane parallel to the surface of the semiconductor substrate intersecting the trench.
According to a second aspect of the present invention, a semiconductor substrate has a semiconductor layer filled in a trench and having a dimension in a normal line direction with respect to a surface of the semiconductor substrate larger than a lateral dimension thereof that is a dimension in a lateral direction on an arbitrary plane parallel to the surface of the semiconductor substrate intersecting the trench. Further a conductive material is filled in the semiconductor layer in the trench for taking a potential of the semiconductor layer.
According to a third aspect of the present invention, a semiconductor substrate is manufactured by forming a trench in a semiconductor substrate; forming a first epitaxial layer on a surface of the semiconductor substrate and in the trench; etching a part of the first epitaxial film; and forming a second epitaxial film in the trench so that the trench is filled with the first and second epitaxial films.
According to a forth aspect of the present invention, a semiconductor substrate is manufactured by forming a trench; filling an amorphous semiconductor film in the trench; single-crystallizing the amorphous semiconductor film through a solid phase reaction; and flattening the surface of the semiconductor substrate.
According to a fifth aspect of the present invention, a semiconductor substrate is manufactured by forming a trench; forming an epitaxial film on a surface of the semiconductor substrate and in the trench; forming a conductive material film on the epitaxial film so that the conductive material film is filled in the epitaxial film in t
Onoda Kunihiro
Otsuka Yoshinori
Sakakibara Toshio
Urakami Yasushi
Yamauchi Shoichi
Denso Corporation
Law Offices of David G. Posz
Tsai Jey
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