Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2000-10-27
2002-07-23
VerSteeg, Steven H. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S298060, C204S298080, C204S298110, C204S298170
Reexamination Certificate
active
06423192
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-310298, filed Oct. 29, 1999; and No. 2000-166059, filed Jun. 2, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a sputtering apparatus and film forming method and, more particularly, to a sputtering apparatus effective for forming an interconnection film made of Al or Cu, a barrier metal film made of TaN or TiN, and a liner film made of Ti or Nb, and a film forming method using this apparatus.
In the semiconductor process, a sputtering apparatus is widely used as a film forming apparatus. One of the reasons for this is that the sputtering apparatus requires a low running cost while providing a high productivity.
As semiconductor devices are recently micro-patterned and highly integrated, the aspect ratio (the ratio of depth to opening diameter) of a contact hole tends to increase. For example, when an interlevel insulating film is to be deposited on an Si substrate with a surface having a diffusion layer and a contact hole to be connected to the diffusion layer is to be formed in this interlevel insulating film, this contact hole has a high aspect ratio. Therefore, for example, when a Ti silicide layer is to be formed on the surface of the diffusion layer, it is not easy to form a thick Ti film on the bottom surface of the contact hole by sputtering. When the inner surface (side and bottom surfaces) of the contact hole is to be covered with a barrier metal film such as a TiN film, or a glue layer for W-CVD, the barrier metal or the like cannot be easily formed on the entire inner surface of the contact hole to a uniform thickness by sputtering.
The Al reflow technique is known as a technique of filling a contact hole with an Al film. Of the Al reflow technique, a 2-step reflow scheme of sequentially forming a liner film, a first Al film, and a second Al film by sputtering has become the mainstream. According to the 2-step reflow scheme, the first Al film is formed by cooling, while the second Al film is formed while heating. When forming the second Al film, Al flows in the contact hole through the first Al film as the diffusion path. Therefore, the first Al film must be formed on the entire inner surface of the contact hole.
A film forming method using the conventional sputtering apparatus has poor step coverage. Accordingly, it is not easy to increase the thickness of the film on the bottom surface of the contact hole, to uniform the thickness of the film on the entire inner surface of the contact hole, or to form the film on the entire inner surface of the contact hole.
Conventionally, an Al interconnection is often used as an LSI interconnection. In recent years, an interconnection structure as a combination of an insulating film with a low dielectric constant and a Cu interconnection has been studied. This is sought for in order to decrease the resistance and increase the reliability of the interconnection, i.e., in order to improve RC delay and improve the EM resistance. Since compounds of Cu that have a high vapor pressure are few, Cu is difficult to process by RIE (Reactive Ion Etching). Accordingly, it is difficult to form an RIE interconnection from Cu. Hence, when forming a Cu interconnection, the damascene process that does not use RIE is the mainstream.
In the damascene process, a metal film is formed by deposition on the entire surface to fill an interconnection groove formed in an interlevel insulating film in advance. After that, an excessive portion of the metal film outside the interconnection groove is removed by CMP (Chemical Mechanical Polishing) to form an interconnection (damascene interconnection) formed of the metal film. In particular, a process of forming a groove and contact hole in an interlevel insulating film in advance and filling the groove and contact hole with a metal film at once, thereby forming an interconnection and plug simultaneously is called a dual damascene process (DD process).
When a Cu interconnection is to be formed by the damascene process, a Cu film is naturally used as the metal film. As Cu tends to diffuse in the interlevel insulating film, Cu in the Cu film diffuses to the Si substrate. Cu diffused to reach the Si substrate forms a deep level in Si. This deep level traps carriers to degrade the element characteristics.
For this reason, when a Cu interconnection is to be formed by the damascene process, a barrier metal film diffusion preventive film) for preventing diffusion of Cu is formed by sputtering on the inner surface of the interconnection groove before the Cu film is deposited. With the DD process, a barrier metal film must also be formed on the inner surface of the contact hole. As the barrier metal film, a TIN film, a TaN film, and the like are widely studied. The barrier metal film is desirably formed uniformly on the entire inner surface of the interconnection groove, or the entire inner surfaces of the interconnection groove and contact hole because of its purpose.
In the DD process for Cu, the interconnection groove and the like must be filled with a Cu film. As a Cu film forming method, electroplating is widely studied. Cu electroplating requires a seed layer for supplying electrons to electroplating solution. The barrier metal film, such as the TaN film, described above however does not function well as a seed layer. For this reason, after the barrier metal film is formed, a seed layer is often formed by sputtering Cu itself as the material of the interconnection. Such a seed layer (Cu seed layer) is desirably formed uniformly on the entire inner surface of the interconnection groove, or the entire inner surfaces of interconnection groove and contact hole because of its purpose.
To meet these requirements, a sputtering apparatus, e.g., a long throw sputtering apparatus or ionization sputtering apparatus, which has an improved sputtering particle directivity is used to form a Ti film, TiN film, TaN film, and Cu seed layer.
FIG. 22
is a schematic view showing a conventional long throw sputtering apparatus. In the long throw sputtering apparatus, the distance between a substrate
81
and target
82
is increased, and an Ar pressure is decreased to suppress gas scattering. This suppresses oblique incident components of the sputtering particles into the contact hole, thereby improving the directivity of the sputtering particles.
FIG. 22
shows a process chamber
83
, a magnet
84
, a backing plate
85
, cooling water paths
86
, an insulating member
87
, an earth shield
88
, a first shield plate
89
to prevent deposition on the other portions (to be referred to as a shield plate), a second shield plate
90
, an elevating system
91
of the second deposition preventive plate
90
, an electrostatic chucking plate
92
, a susceptor
93
(worktable), a coolant
94
, a DC voltage source
95
for applying a voltage to the target
82
, and a pair of ring-like magnets
84
a
and
84
b.
A film forming method using the conventional long throw sputtering apparatus has the following problems more specifically, the shape of the formed film becomes asymmetric at the end of the substrate. A metal film is accordingly difficult to form uniformly, and the coverage is poor.
In the ionization sputtering apparatus, an RF (Radio-Frequency) power is introduced to an induction coil attached between the target and substrate, thereby generating a high-density plasma of Ar gas supplied into the process chamber. The sputtering particles are ionized in the high-density plasma, and a negative voltage is applied to the substrate, thereby improving the directivity of the sputtering particles.
The film forming method using the conventional ionization sputtering apparatus has the following problems. During film formation, Ar as the sputter gas is also ionized in addition to the sputtering particles. Hence, ionized sputter particles and Ar are attracted to the substrate. The Ar ions attracted to the subst
Katata Tomio
Matsuyama Hideto
Sakata Atsuko
Wada Jun-ichi
Watanabe Koichi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
VerSteeg Steven H.
LandOfFree
Sputtering apparatus and film forming method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sputtering apparatus and film forming method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sputtering apparatus and film forming method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2889899