Semiconductor device and production method thereof

Details Semiconductor device and production method thereof Semiconductor device and production method thereof

2000-02-25

2001-11-13

Lee, Eddie (Department: 2815)

Semiconductor device manufacturing: process

Formation of semiconductive active region on any substrate

Polycrystalline semiconductor

C438S239000, C438S251000, C438S486000, C438S488000, C438S491000

Reexamination Certificate

active

06316339

ABSTRACT:

This application is based on Patent Application No. 07-139,633 filed Jun. 6, 1995 in Japan, the content of which is incorporated fereinto by reference. In addition, this application is a continuation application of International Application No. PCT/JP96/01541 filed Jun. 6, 1996.
FIELD OF THE INVENTION
The present invention relates to a semiconductor device having a dielectric film formed by thermal oxidation of polycrystalline silicon and to a production method thereof. More specifically, the present invention relates to a semiconductor device having a dielectric film formed by providing polycrystalline silicon of improved film quality, followed by thermal oxidation and to a production method thereof.
DESCRIPTION OF RELATED ART
A capacitor as a component of IC and LSI is an indispensable part for IC and LSI of a specific field. In general a capacitor of IC and LSI has a structure as shown in
FIG. 1
in which a dielectric film
5
is sandwiched between polycrystalline silicon films
3
and
4
on a silicon oxide film
2
on a silicon substrate
1
. The polycrystalline silicon films
3
and
4
are individually a lower electrode and an upper electrode, which are individually connected with lead wires
7
.
In the production method of such a prior art capacitor, first the polycrystalline silicon film
3
is formed on the silicon oxide film
2
formed on the substrate
1
by way of low pressure CVD (chemical vapor deposition) at a pressure of 28 Pa (monosilane partial pressure: 14 Pa). The polycrystalline silicon film
3
, to enhance the electroconductivity as a capacitor electrode, is doped with an impurity of a doping concentration of about 1×10
19
atoms/cm
3
. In this case, the crystal orientation of the polycrystalline silicon film includes (220), (311), and the like in addition to (111). Next, the dielectric film
4
as an active part of the capacitor is formed by thermal oxidation of the polycrystalline film so as to have a film thickness and an area according to the required capacitance. Then, the polycrystalline silicon film
4
is formed as in the polycrystalline silicon film
3
.
A capacitor is normally required to have a dielectric strength of about 8 MV/cm for the dielectric film in order to maintain the reliability. However, there may be a rare case that an abnormal overvoltage is momentarily applied in addition to the rated voltage, or the dielectric film is contaminated with, for example, a metal, or defects of the film occur in the production process of the dielectric film of the capacitor, resulting in degradation of the dielectric strength of the dielectric film.
Further, as a capacitor, there is a problem in that leak current is high between the upper and lower electrodes.
Then, the thickness of the dielectric film has heretofore been increased to enhance the dielectric strength of the dielectric film itself and to reduce the leak current.
However, a high capacitance cannot be obtained by the method of increasing the dielectric film thickness as used in the prior art. Therefore, in order to obtain a high capacitance, it is necessary to increase the surface area, which results in an increased size of the semiconductor device. Further, with increasing down-sizing requirements for semiconductor devices, if a thin film structure of the dielectric film is used to reduce the capacitor size, it is difficult to maintain the dielectric strength and suppress an increase in leak current.
OBJECT OF THE INVENTION
An object of the present invention is to provide a semiconductor device and production method thereof which solve the above described prior art problems.
Another object of the present invention is to provide a semiconductor device having a capacitive component that can maintain the dielectric strength without increasing the thickness of the dielectric film and suppress an increase in leak current and a production method thereof.
DISCLOSURE OF THE INVENTION
In accordance with a first aspect of the present invention, which attains the above object, there is provided a semiconductor device comprising a polycrystalline silicon layer whose main crystal orientation is oriented in (111), an SiO
2
layer contacting the polycrystalline silicon layer obtained from the polycrystalline silicon layer, and an electrode contacting the SiO
2
, wherein a height difference of surface irregularities of the polycrystalline silicon or the dielectric film is no greater than 30 nm.
Here, the dielectric film preferably has a dielectric strength of no less than 8 MV/cm.
According to a second aspect of the present invention, there is provided a capacitor having a dielectric film between an upper electrode and a lower electrode, wherein the lower electrode is a polycrystalline silicon layer having a high conductivity whose main crystal orientation is oriented in (111), and the dielectric film is an SiO
2
layer obtained from the polycrystalline silicon layer.
The polycrystalline silicon layer preferably contains an impurity in a concentration of 1×10
20
atoms/cm
3
to 1×10
21
atoms/cm
3
.
Further, the polycrystalline silicon layer or the dielectric film preferably has a height difference of surface irregularities of less than 30 nm.
Still further, the dielectric film preferably has a dielectric strength of no less than 8 MV/cm.
According to a third aspect of the present invention, there is provided a production method of a semiconductor device having a polycrystalline silicon layer and an SiO
2
layer obtained from the polycrystalline silicon layer, comprising the steps of: forming the polycrystalline silicon layer by a low pressure CVD method at a monosilane partial pressure of no more than 10 Pa and a film formation temperature of no lower than 600° C.; heat treating the thus formed polycrystalline silicon layer for doping it with an impurity and orienting its main crystal orientation in (111); and thermally oxidizing the surface of the oriented polycrystalline silicon layer to form an SiO
2
film.
In this case, prior to thermally oxidizing the surface of the oriented polycrystalline silicon layer, it is preferable to remove the high-concentration oxide film formed on the surface of the polycrystalline silicon layer.
According to a fourth aspect of the present invention, there is provided a production method of a capacitor having a dielectric film between a lower electrode and an upper electrode, comprising the steps of: forming a polycrystalline silicon layer as the lower electrode by a low pressure CVD method at a monosilane partial pressure of no more than 10 Pa and a film formation temperature of no lower than 600° C.; heat treating the formed polycrystalline silicon layer for doping with an impurity and orienting its main crystal orientation in (111); and thermally oxidizing the surface of the oriented polycrystalline silicon layer to form an SiO
2
film.
In this case, the polycrystalline silicon layer may be formed on the dielectric film by the low pressure CVD method at a monosilane partial pressure of no more than 10 Pa and a film formation temperature of no lower than 600° C., and then heat treatment may be made for doping with an impurity and orienting its main crystal orientation in (111).
Further, it is preferable to make doping with the impurity to a concentration of 1×10
20
atoms/cm
3
to 1×10
21
atoms/cm
3
.
Still further, prior to thermally oxidizing the surface of the oriented polycrystalline silicon layer, it is preferable to remove the high-concentration oxide film formed on the surface of the polycrystalline silicon layer.


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