Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2001-03-20
2001-11-06
Ghyka, Alexander G. (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S761000, C438S681000, C438S685000
Reexamination Certificate
active
06313047
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an MOCVD (Metal Organic Chemical Vapor Deposition) method of a tantalum oxide film in a semiconductor processing system, and more specifically to a technique of forming, e.g., a gate insulating film, capacitor insulating, or the like of a semiconductor device. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or an LCD (Liquid Crystal Display) substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
In order to manufacture semiconductor devices, film formation and pattern etching are repeatedly applied to a semiconductor wafer. As semiconductor devices are becoming more and more highly miniaturized and integrated, demands on film formation have become stricter. For example, very thin insulating films, such as capacitor insulating films and gate insulating films are still required to be thinner and to be more insulating.
Conventionally, silicon oxide films and silicon nitride films are used as the insulating films. In recent years, however, it has been proposed to form the insulating films from materials having even higher insulating properties, such as a metal oxide, e.g., tantalum oxide (Ta
2
O
5
). The film of this material can be formed by means of MOCVD, i.e., using a vaporized metal organic compound.
To form a tantalum oxide film by means of MOCVD, a metal (tantalum) alkoxide, such as Ta(OC
2
H
5
)
5
(pentoethoxytantalum: PET) is used as a raw material liquid. The raw material liquid is made to bubble by e.g., nitrogen gas, or vaporized by a vaporizer set at a vaporizing temperature, to be in a gaseous state, and is supplied to a process chamber preset to have a vacuum atmosphere. At the same time, an oxidizing gas, such as oxygen, is supplied to the process chamber. The supplied raw material is decomposed to offer a film forming material on the surface of a semiconductor wafer heated to a predetermined process temperature. With this film forming material, a tantalum oxide (Ta
2
O
5
) film is formed on the surface of the semiconductor wafer by means of deposition.
As semiconductor device design rules have become stricter, the required thickness of tantalum oxide films is now about 10 nm at max. Tantalum oxide films grow at a deposition rate of about 150 nm/min when a deposition temperature is about 600° C. Accordingly, where tantalum oxide films having a thickness of about 10 nm have to be formed with high accuracy, a low deposition temperature of about 400° C. is used to reduce the deposition rate. In the case of using such conditions for forming tantalum oxide films, however, the present inventors have found a problem in that the surface of the tantalum oxide films becomes uneven, i.e., the degree of surface roughness is higher and the surface morphology is degraded, thereby deteriorating the electric properties of the film.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an MOCVD method, which allows a thin tantalum oxide film to be formed with high controllability in the film thickness, and to have excellent electric properties.
According to a first aspect of the present invention, there is provided an MOCVD method of forming a tantalum oxide film on a target substrate in an airtight process container of a semiconductor processing system, comprising:
a step of preparing first and second materials consisting essentially of one and the other, respectively, of an oxidizing agent and an organic tantalum, and third and fourth materials consisting essentially of one and the other, respectively, of an oxidizing agent and an organic tantalum;
an adsorption step of forming a state where the first material is adsorbed on a surface of the target substrate placed in the process container;
a first layer formation step of supplying the second material in a gaseous state into the process container, and causing the first material adsorbed on the surface of the target substrate and the second material to react with each other, thereby forming a first layer consisting essentially of tantalum oxide on the target substrate, wherein the target substrate is set at a temperature of from 200 to 350° C. in the first layer formation step; and
a second layer formation step, after the first layer formation step, of supplying the third and fourth materials in gaseous states into the process container, and causing the third and fourth materials to react with each other on the target substrate, thereby forming a second layer consisting essentially of tantalum oxide on the first layer, so that the tantalum oxide film comprises first and second layers.
According to a second aspect of the present invention, there is provided an MOCVD method of forming a tantalum oxide film on a target substrate in an airtight process container of a semiconductor processing system, comprising:
a step of preparing first and second materials consisting essentially of one and the other, respectively, of an oxidizing agent and an organic tantalum, and third and fourth materials consisting essentially of one and the other, respectively, of an oxidizing agent and an organic tantalum;
an adsorption step of supplying the first material in a gaseous state into the process container to cause the first material to be adsorbed on a surface of the target substrate;
a purge step of purging the process container with an inactive gas after the adsorption step to remove the first material from an atmosphere in the process container;
a first layer formation step, after the purge step, of supplying the second material in a gaseous state into the process container, and causing the first material adsorbed on the surface of the target substrate and the second material to react with each other, thereby forming a first layer consisting essentially of tantalum oxide on the target substrate, wherein the target substrate is set at a temperature of from 200 to 350° C. in the first layer formation step; and
a second layer formation step, after the first layer formation step, of supplying the third and fourth materials in gaseous states into the process container, and causing the third and fourth materials to react with each other on the target substrate, thereby forming a second layer consisting essentially of tantalum oxide on the first layer, so that the tantalum oxide film comprises first and second layers, wherein the third and fourth materials are supplied into the process container at substantially the same time from nozzles independent of each other, in the second layer formation step.
In a preferable manner of first and second aspects, the oxidizing agent used as one of the third and fourth materials has an oxidizing power lower than that of the oxidizing agent used as one of the first and second materials, the organic tantalum used as the other of the third and fourth materials is the substantially the same material as the organic tantalum used as the other of the first and second materials, and the target substrate is set at a temperature of from 350 to 500° C. in the second layer formation step.
As the organic tantalum, PET (pentoethoxytantalum), i.e., Ta(OC
2
H
5
)
5
, may be used.
The oxidizing agent used as one of the first and second materials may be selected from the group consisting of H
2
O, H
2
O
2
, O
3
, oxygen radical, a mixture of H
2
and O
2
, a mixture of H
2
and N
2
O, a mixture of H
2
and NO, a mixture of NH
3
and O
2
, and a mixture of O
3
and H
2
.
The oxidizing agent used as one of the third and fourth materials may be selected from the group consisting of O
2
, O
3
, and H
2
O.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantag
Choi Dong-Kyun
Hasebe Kazuhide
Inumiya Seiji
Morozumi Yuichiro
Sugawara Takuya
Ghyka Alexander G.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokyo Electron Limited
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