CVD apparatus

Details CVD apparatus CVD apparatus

2001-05-17

2003-12-16

Mills, Gregory (Department: 1763)

Coating apparatus

Gas or vapor deposition

Multizone chamber

C118S715000, C118S725000, C118S728000, C156S915000

Reexamination Certificate

active

06663714

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CVD apparatus, and more particularly, to a CVD apparatus intended for forming a Cu thin film, used as a wiring material or the like in semiconductor integrated circuits.
2. Prior Art
In recent years, as there is a tendency for semiconductor devices to be highly integrated, dimensions such as wiring width, wiring spacing and the like in metallic wiring for formation of integrated circuits tend to decrease. Such reduction in wiring dimensions leads to an increase in wiring resistance and also narrowing of wiring spacing leads to an increase in parasitic capacitance between wirings, which causes a problem that time delay of electric signals in integrated circuits increases. In this case, a measure to increase a wiring height to increase a cross sectional area of wiring is taken in order to suppress an increase in wiring resistance but a wiring height cannot be increased excessively because the increase in areas of facing surfaces of wirings leads to the increase in parasitic capacitance. Such problem in time delay of signals has become serious to the extent that the normal operations of integrated circuits are impeded in wiring dimensions of around 0.1 micron.
Also, an increase in resistance and electric current density, due to a reduced wiring width, will cause wiring temperature rise due to Joule heat and electromigration to degrade reliability in integrated circuits.
Hereupon, in order to solve the problems in time delay of signals and degradation of reliability, Cu having a lower resistance and a higher fusing point than those of Al has recently been used as a material for metallic wiring.
Meanwhile, while a three-dimensional wiring construction using a multi-layered wiring is made in semiconductor integrated circuits, the reduction in wiring dimensions involves a tendency for via holes, by which the connection of three-dimensional wiring is made, to become minute. Embedding of Cu by means of electrolytic plating has been made as a method of embedding a metallic material in such minute via holes.
Plating requires a Cu thin film (seed Cu layer), which is formed by means of the sputtering method.
However, there is a problem that when wiring dimensions come to a level of 0.1 micron to lead to an increase in aspect ratio (ratio of hole depth to opening diameter), the seed layer with adequate thickness is not formed on hole walls due to the poor step covering performance of the sputtering method, thus resulting in failure in plating.
With a further increase in the aspect ratio, the failure is caused in embedding in the holes even with the electrolytic plating. The Cu embedding technique by the CVD method (chemical vapor deposition method) has been given attention and investigated in order to solve the problem of embedding of metallic wiring in such minute holes and to afford the formation of even seed layer and complete embedding in interiors of minute holes having an opening diameter of 0.1 micron or less.
With respect to Cu embedding by the CVD method, a study report has been presented to indicate the possibility of complete embedding in minute holes with an aspect ratio of 7 at adequate deposition rate, as described, for example, in Jpn. J. Appl. Phys. Vol. 37 (1998) pp. 6358-6363, and thus the CVD method has been recognized as a promising Cu embedding technique.
As has been described above, techniques with respect to the Cu wiring and embedding are exceedingly important in semiconductor integrated circuits, which will be further promoted in high integration and high performance in the future, and the importance of the CVD method and apparatus intended for formation of Cu thin films is increasingly enhanced in the semiconductor mass-production process.
It is believed that such development of Cu-CVD apparatus in the semiconductor mass-production process is attainable by application of conventional metal CVD apparatuses. Hereupon, examinations have been tried, in which a gas introduction mechanism of the tungsten CVD apparatus currently involving a most established technique as a metal CVD apparatus is modified to suit for a raw material used in the Cu-CVD apparatus.
The gas introduction mechanism in the tungsten CVD method is one, in which vapor of tungsten hexafluoride being a liquid material is introduced into a deposition chamber while being controlled in flow rate by an ordinary gas mass flow controller. Meanwhile, with the Cu-CVD method, organic liquid materials, for example, Cu (hfac) (tmvs) are used as a raw material, but vapor pressure thereof is as low as at most 100 Pa at room temperature, so that ordinary gas mass flow controllers cannot be used. Hereupon, as described, for example, in Jpn. J. Appl. Phys. Vol. 37 (1998) pp. 6358-6363, an introduction method is used, in which a liquid material is fed to an evaporator at a predetermined flow rate with the aid of a liquid mass flow controller and is vaporized in the evaporator, and then is fed to a deposition chamber. Such a raw material gas introduction mechanism composed of the liquid mass flow controller and the evaporator is different from the gas introduction mechanism in the tungsten CVD method.
Besides this, the introduction method uses a gas introduction section for introducing a vaporized gas directly into the deposition chamber, a substrate heating mechanism and an exhaust mechanism similar to one used in the conventional tungsten CVD method.
Here, in the semiconductor manufacturing process, when a metallic thin film such as tungsten is to be formed with the CVD method, the generation of particles must be suppressed as much as possible in order to stably produce high performance integrated circuits, and so it is necessary in this point of view to prevent the deposition on the back surface of a substrate. Also, in particular, in the case of Cu thin films, the prevention of deposition on the back surface of a substrate becomes further important as compared with tungsten or the like for the following reason. That is, since Cu diffuses in Si at a high rate and greatly affects the performance of Si semiconductors, and the diffusion rate is increased as a substrate temperature rises, the prevention of film adhesion and of spreading of a raw material to the back surface of a substrate during deposition becomes particularly important in the case where the deposition is made at high temperatures (J. Electrochem. Soc., 2258-2260 (1999)).
Several measures, which have been established for preventing the deposition on and adhesion of a raw material gas to the back surface of a substrate in the tungsten CVD method, maybe applied to the Cu-CVD method. Here, mechanisms for preventing a raw material gas from spreading to the back surface of a substrate in conventional tungsten CVD apparatuses will be summarized.
FIG. 5
shows, as a first example, a CVD apparatus disclosed in Japanese Patent Laid-Open No. 7-221024. A raw material gas introduction section
35
and a substrate holder
33
opposed to the section for placing thereon a substrate are arranged in a reduced pressure vessel
31
, and a gas emitted from the raw material gas introduction section
35
is decomposed to form a thin film on the substrate
32
. Here, the holder
33
is moved up and down by a lift
41
, and rises at the time of deposition to lift a ring chuck
34
to bring a surface of the substrate
32
into entirely circumferential contact with a lower, horizontal surface of a tip end
40
of the ring chuck
34
, thereby preventing a raw material gas from spreading to the back surface of the substrate. Also, at the time of substrate exchange, the holder
33
descends and the ring chuck
34
is supported by a support member
36
.
An unreacted raw material gas and a secondary product gas flow into a chamber
71
from a chamber
70
through an opening
39
formed in the support member
36
, and are exhausted outside a vessel via an exhaust port
38
. Also, a purge gas introduction pipe
42
is provided in a chamber
72
for preventing the raw material gas and the secondary p

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