Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
1998-11-12
2001-01-30
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S003000, C438S005000
Reexamination Certificate
active
06180541
ABSTRACT:
This application claims the benefit of Korean patent application No. 12338/1998, filed Apr. 8, 1998, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor manufacturing process, and more particularly, to an MOCVD (metal-organic chemical vapor deposition) method and a metal-organic chemical vapor deposition reactor for forming a semiconductor film by flowing a carrier gas and a reactant gas heated to a predetermined temperature into the MOCVD reactor.
2. Discussion of the Related Art
Generally, various methods are used to form a layer (thin film) in a semiconductor manufacturing process. Particularly, a CVD process is widely used, since a thin film obtained by the CVD process has excellent step coverage, fast deposition rate and uniform thickness.
In the CVD process, a thin film (or an epi-layer) is formed on a semiconductor substrate from a gaseous compound. The formation of the thin film is mainly accomplished by flowing a gas to a reaction chamber without consuming a material of a silicon wafer. An effective CVD reaction occurs within a certain temperature range, and in order to assist the reaction, a gas plasma created by RF or optical energy, such as laser or ultraviolet rays, is used. Thus, the reaction of atoms or molecules, which are resolved by heating the substrate, may be accelerated, and physical characteristics of the thin film may be controlled for a more effective CVD reaction.
The CVD process typically grows a thin film by using a gaseous source. However, when depositing ferroelectric materials, such as Ta, PZT (lead zirconium titanium oxide) or BST (Ba, Sr)TiO
3
, and wiring materials such as Al or Cu, it is difficult to form a gaseous source with these materials. Thus, the CVD process deposits a thin film using a solid or liquid source of a metal-organic type. Such a process is called an MOCVD process.
FIG. 1
illustrates equipment used in the MOCVD process. The MOCVD equipment
1
includes a source supply unit
2
, a vaporization unit
3
and a reaction unit
4
. The vaporization unit
3
is described in more detail in
FIGS. 2A and 2B
, where
FIG. 2A
illustrates a structure of the vaporization unit
3
, and
FIG. 2B
illustrates part ‘A’ of
FIG. 2A
in greater detail.
As shown in
FIG. 2B
, when a non-gaseous source is introduced into the vaporization unit
3
, the source is converted to a gas, and the gaseous source and a flowed carrier gas are mixed with each other while passing through a metal frit
5
. The metal frit
5
, which is heated to a predetermined temperature, vaporizes the liquid. The vaporized liquid produced by the frit
5
flows into the reaction unit
4
after being carried by the carrier gas and mixed therewith.
The reaction unit
4
includes a heater
41
for heating the substrate to a higher temperature than a deposition temperature, a quartz cover
42
and a shower head
43
. In the MOCVD equipment
1
, the shower head
43
uses a type of a metal plate having a number of holes for uniformly depositing ejected gas.
The source used in the MOCVD process exists in either a solid or a liquid condition. However, it is preferable to use the liquid source to control the amount of gas which flows into the vaporization unit
3
or to control the composition ratio of the source. Thus, a solid source is typically dissolved in a solvent.
In the MOCVD process, the source is in a liquid or solid state as described above, and the vaporization unit
3
is used to convert the source into a gas for the CVD process.
The source from the source supply unit
2
flows into the vaporization unit
3
, as shown in
FIG. 2A
, which maintains a temperature higher than the vaporization temperature of the source but lower than the deposition or reaction temperature. Due to flash evaporation, the introduced liquid source becomes a gas in the vaporization unit
3
at high temperature. The gaseous source is carried into the reaction unit
4
by the carrier gas, and then the gaseous source reacts with the reactant gas in the reaction unit
4
, and the thin film is deposited on the substrate.
However, the temperature of the reaction unit
4
before the gaseous source reaches the substrate should be high enough so that the gaseous source does not condense or react before reaching the substrate. Therefore, the temperature of the shower head
43
of the conventional reaction unit
4
, through which the gaseous source passes, is maintained at a uniform temperature using various methods. Although the shower head
43
functions to eject the gaseous source for uniform deposition, this function may be affected by radiation from elements such as the heater
41
in the reaction chamber
4
. Accordingly, the reaction chamber
4
should be kept at a uniform temperature. If a proper change in temperature and uniform ejection of the gas are not maintained, the formation and uniformity of the thin film are adversely affected. Accordingly, the uniformity and deposition rate of the thin film depend considerably on the temperature of the shower head
43
as well as the material making up the shower head
43
.
However, it is difficult to manufacture and control the shower head
43
to maintain the uniform temperature. Furthermore, the deposition rate of the thin film at low temperatures is low, and the thin film formed at a low temperature may not have uniform thickness, affecting the performance of the semiconductor device.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an improved MOCVD equipment and an MOCVD method that substantially obviates the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an MOCVD equipment and an MOCVD method that deposits a thin film with less dependence on a temperature of a shower head in the MOCVD equipment.
Another object of the present invention is to provide an MOCVD equipment and an MOCVD method that improves the step coverage of the thin film by lowering a deposition temperature.
Another object of the present invention is to provide an MOCVD equipment and an MOCVD method that improves the deposition rate of the thin film and obtains a uniform thickness of the thin film.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, in one aspect of the present invention there is provided a method for forming a thin film on a semiconductor substrate including the steps of vaporizing a metal-organic source, preheating a carrier gas, carrying the vaporized metal-organic source to a reaction unit using the carrier gas, and reacting the metal-organic source with a reactant gas to form the thin film on the semiconductor substrate in the reaction unit by a chemical vapor deposition process.
In another aspect of the present invention there is provided a method for forming a thin film for a capacitor for a dynamic random access memory DRAM including the steps of vaporizing a metal-organic source, preheating a carrier gas, carrying the vaporized metal-organic source to a chemical vapor deposition reactor using the carrier gas, and reacting the metal-organic source with a reactant gas in the chemical vapor deposition reactor to form the thin film on a semiconductor substrate in the chemical vapor deposition reactor.
In another aspect of the present invention there is provided a metal-organic chemical vapor deposition reactor including a vaporization unit for vaporizing a metal-organic source, a reaction unit for forming a semiconductor film, and first preheating means connected to the vaporization unit for preh
Hyundai Electronics Industries Co,. Ltd.
Le Dung A
Morgan & Lewis & Bockius, LLP
Nelms David
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