Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-06-06
2003-02-18
Tran, Minh Loan (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S043000, C257S310000
Reexamination Certificate
active
06521930
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and its manufacturing method, and in particular, to a semiconductor device which has a capacitative element in which tantalum oxide (Ta
2
O
5
) is employed for a capacitative insulating film and its manufacturing method.
Description of the Related Art
In a manufacturing method of a semiconductor device of this kind, high permittivity Ta
2
O
5
has been employed for a semiconductor device having a capacitative element (DRAM, for example) for the purpose of high integration. Just after a Ta
2
O
5
thin film is produced, the characteristics are poor. Therefore methods for improving the characteristics such as heat treatment have been proposed. The following examples have been proposed:
a process for producing a Ta
2
O
5
film of high quality by thermal oxidation to a laminated film of Ta
2
N and Ta (Japanese Patent Application Laid-Open No.SHO62-136035);
a process for executing heat treatment in order to densify a Ta
2
O
5
film by ion implantation of titanium after the film is produced (Japanese Patent Application Laid-Open No.HEI 4-359557);
a process for executing heat treatment in order to densify a Ta
2
O
5
film by ion implantation of fluorine after the film is produced (Japanese Patent Application Laid-Open No.SHO64-82557); and
a process for producing a Ta
2
O
5
film by thermal oxidation after a Ta film is converted into amorphous (Japanese Patent Application Laid-Open No.SHO60-5531).
However, in any case described above, a physical property of the film in an atomic bonding level and its changes according to the post processes have not been comprehended exactly, and therefore these methods are just experiential ones. That is because the Ta
2
O
5
in an atomic bonding state (crystal structure) is extremely complex, so that there is no means to evaluate the quality of the film easily, and that there is no character to control it.
The first problem is that although high permittivity and low leak current are required even in a thin film of under 10 nm thickness; it is impossible to control and produce a stable film having high quality. This is because a physical property which is, different from a bulk material is shown when Ta
2
O
5
is thinned down and is used as a capacitative insulating film.
The second problem is that although some improvements in the characteristics are made by heat treatment and so forth, in order to solve the problem, these methods are just experiential ones because a physical property of the film and its changes have not been comprehended exactly. This is because Ta
2
O
5
in an atomic bonding state (crystal structure) is extremely complex, so that there is no means to evaluate the quality of the film easily, and that there is no character to control it.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a manufacturing method of a semiconductor device, in which a Ta
2
O
5
thin film, which has high permittivity and low leak current, is employed for a capacitative insulating film.
Another object of the present invention is to provide a method for monitoring an atomic bonding state in a film, which is for the purpose of controlling quality of a Ta
2
O
5
film.
First, for achieving the objects mentioned above, a Ta
2
O
5
thin film that has double bond (Ta═O) of Ta and O (oxygen) is employed for a capacitative insulating film. By measuring a transmission infrared absorption spectrum of a Ta
2
O
5
thin film using Fourier Transform Infrared Spectroscopy (FTIR), it is monitored whether absorption peak that appears in 2340 cm
−1
exists or not and it is large or small. This technique is realized because a new fact has been brought to light that the existence of the peak described above is discovered and the peak is the absorption peak which appears by stretching vibration of Ta═O. As a concrete process, there are Rapid Thermal Anneal (RTA) in oxygen and UV/O
3
(Ultra Violet-Ozone) treatment at a suitable temperature and in suitable time, for example.
Second, a Ta
2
O
5
thin film, wherein an abundance ratio of oxygen in a three coordinate bonding (triple bonding) state is large, is employed for a capacitative insulating film. By using FTIR, an intensity ratio of each double peak which appears around 510 cm
−1
and 570 cm
−1
is measured, so that the Ta
2
O
5
film whose ratio (510/570) is larger than another one is used as a character in order to improve the quality of a film. This technique is realized because a new fact has been brought to light that all of the peak appears by an asymmetric stretching vibration mode of three coordinate oxygen (O≡3Ta).
By using a Ta
2
O
5
film which has Ta═O bond or that of which an abundance ratio of oxygen in a three coordinate bonding state is large as a capacitative insulating film, the capacitance characteristics of leak electric current and reduced coating thickness etc. are improved. First, this is because Ta═O double bond whose bonding strength is very strong is produced by dissociation of organic impurities in CVD raw gas over 500° C. and atomic oxygen bonding to the vacant site. Second, this is because the quality of the film becomes strong by producing more stable three coordinate bond than unstable two coordinate bond (Ta—O—Ta) in the complex crystalline structure of Ta
2
O
5
.
After measuring Ta═O peak or an intensity ratio of the 510/570 peak in a Ta
2
O
5
thin film which has been processed by a variety of heat treatment, in comparison with these capacitance characteristics, there is an evident relevance. Therefore, the present invention is as follows:
(1) a semiconductor device wherein an Amorphous Ta
2
O
5
thin film having double bond (Ta═O) of Ta with O (oxygen) which is formed on a semiconductor substrate is a capacitative insulating film;
(2) a semiconductor device wherein a polycrystal or single crystal Ta
2
O
5
thin film having double bond (Ta═O) of Ta with O (oxygen) which is formed on a semiconductor substrate is a capacitative insulating film;
(3) a semiconductor device wherein a Ta
2
O
5
thin film in which an abundance ratio of oxygen in a three coordinate bonding state is large, which is formed on a semiconductor substrate, is a capacitative insulating film;
(4) a manufacturing method of a semiconductor device comprising steps of:
adhering a Ta
2
O
5
thin film on an N-type silicon substrate by chemical vapor deposition; and
forming an amorphous Ta
2
O
5
thin film having double bond (Ta═O) of Ta with O (oxygen) by executing Rapid Thermal Anneal at 300-600° C. to the Ta
2
O
5
thin film under an oxidized atmosphere;
(5) the manufacturing method of a semiconductor device as described in (4), wherein the Rapid Thermal anneal is executed while infrared absorption peak of 2340 cm
−1
in the Ta
2
O
5
thin film is measured;
(6) the manufacturing method of a semiconductor device as described in (5), wherein a state of distribution of Ta═O bond in the Ta
2
O
5
thin film is monitored by the measurement;
(7) the manufacturing method of a semiconductor device as described in (4), wherein the Rapid Thermal Anneal is executed within 1 second-4 hours;
(8) a manufacturing method of a semiconductor device comprising steps of:
adhering a Ta
2
O
5
thin film on an N-type silicon substrate by chemical vapor deposition; and
forming a polycrystal or single crystal Ta
2
O
5
thin film having double bond (Ta═O) of Ta with O (oxygen) by executing Rapid Thermal Anneal at 700-1000° C. to the Ta
2
O
5
thin film under an oxidized atmosphere;
(9) the manufacturing method of a semiconductor device as described in (8), wherein the Rapid Thermal Anneal is executed while infrared absorption peak of 2340 cm
−1
in the Ta
2
O
5
thin film is measured;
(10) the manufacturing method of a semiconductor device as described in (9), wherein a state of distribution of Ta═O bond in the Ta
2
O
5
thin film is monitored by the measurement;
(11) the manufacturing method of a semiconductor device as described in (8), wherein
Hayes & Soloway PC
NEC Corporation
Tran Minh Loan
LandOfFree
Semiconductor device having Ta2O5 thin film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor device having Ta2O5 thin film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor device having Ta2O5 thin film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3180475