Coating apparatus – Program – cyclic – or time control – Having prerecorded program medium
Reexamination Certificate
2000-11-30
2001-08-21
Bueker, Richard (Department: 1763)
Coating apparatus
Program, cyclic, or time control
Having prerecorded program medium
C118S715000
Reexamination Certificate
active
06277200
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the fabrication of integrated circuits. More particularly, the invention provides a technique, including a method and an apparatus, for increasing the deposition rate of dielectric films, at a given temperature, while demonstrating good gap filling properties comparable with existing film deposition techniques.
Deposition of dielectric films, such as silicon dioxide (SiO
2
), silicon nitride (SiN), silicon oxynitride (SiON) and the like, over a semiconductor substrate is a common step in the formation of some integrated circuit (IC) structures. For example, dielectric films may be used to form gates of field effect transistors (FETs), spacers separating adjacent FETs, or sacrificial layers in the formation of dynamic random access memories. These films are typically deposited employing chemical vapor deposition (CVD) techniques.
Particularly suitable as an inter-level dielectric, SiO
2
films may be formed by using silane, SiH
4
, as a silicon source and molecular oxygen, O
2
, as an oxygen source, forming on a substrate according to the following reaction:
SiH
4
+O
2
→SiO
2
(1)
Historically, silane has provided adequate silicon dioxide inter-level dielectric films at varying chamber pressures and substrate temperatures. However, advances in integrated circuit technology have led to a scaling down of device dimensions and an increase in chip size and complexity. This has necessitated improved methods for deposition of dielectric films with enhanced gap filling properties. As a result, tetraethylorthosilicate, Si(OC
2
H
5
)
4
, [hereinafter referred to as TEOS] as a silicon source has gained wide acceptance due to its superior gap-filling properties.
TEOS reacts with molecular oxygen, O
2
, as an oxygen source to form SiO
2
on a substrate according to the following reaction:
Si(OC
2
H
5
)
4
+O
2
→SiO
2
+by products (2)
Originally, TEOS had limited use as an inter-level dielectric film, because of the high substrate temperature required to deposit the same efficiently. Reaction (2) required a temperature of approximately 700° C. in order to achieve an acceptable deposition rate. The aforementioned temperature is incompatible with aluminum metallization. As a result, there has been a constant endeavor to lower the deposition temperature of inter-level dielectric films formed using TEOS as a silicon source.
One employs a plasma in the chamber for plasma enhanced chemical vapor deposition (PECVD) apparatus. Another such effort replaces molecular oxygen with ozone, O
3
, to produce a silicon dioxide film according to the following reaction:
Si(OC
2
H
5
)
4
+O
3
→SiO
2
+by-products (3)
With this reaction, silicon dioxide films may be deposited at temperatures as low as 400° C. while still providing an acceptable deposition rate.
Another composition of dielectric films employs nitrogen sources to form silicon nitride films on a substrate. The silicon nitride films are amorphous insulating materials that are typically used as a final passivation layer for integrated circuits, as a mask for selective oxidation of silicon, and as a gate dielectric material for MNOS devices.
An early composition of a silicon nitride film, Si
3
N
4
is deposited using low pressure chemical vapor deposition (LPCVD) techniques according to the following reaction:
SiH
2
Cl
2
+NH
3
→Si
3
N
4
(4)
Similar to reaction (2), reaction (4) had limited use, because of the high substrate temperature required to deposit the same efficiently. In order to achieve an acceptable deposition rate, reaction (4) requires a temperature of approximately 800° C., which is incompatible with many post deposition processes. To further reduce the deposition temperature of silicon nitride films, the following PECVD reactions has been developed:
SiH
4
+NH
3
+N
2
→SiN(H) (5)
SiH
4
+NH
3
+N
2
O→SiON (6)
Both reactions (5) and (6) may be deposited at a process temperature as low as 200° C. while still providing an acceptable deposition rate.
What is needed, therefore, is a technique for improving the deposition rate of dielectric films without increasing the deposition temperature of the same.
SUMMARY OF THE INVENTION
The present invention provides a method and an apparatus for increasing a deposition rate of dielectric films deposited on a substrate at a given temperature while providing good step coverage and gap-fill properties. The method does so by employing bistertiarybutylaminesilane [hereinafter referred to as BTBAS] as a silicon source to react with a reducing agent to form a dielectric film, which includes silicon, on a substrate. Use of BTBAS allows depositing either a silicon oxide or silicon nitride film at an accelerated rate while demonstrating superior uniformity and step coverage and reducing the presence of gaps. This results from, among other things, the relatively high chamber pressures that may be achieved using BTBAS as a silicon source.
The method of the present invention includes placing a substrate in a deposition zone, flowing, into the deposition zone of a process chamber, a process gas including bistertiarybutylaminesilane (BTBAS) and a nitrogen source. The process chamber is pressurized to a predetermined pressure level and the substrate is heated to a predetermined temperature. Thereafter, the deposition zone is maintained at process conditions suitable for depositing a silicon-containing dielectric film on the substrate. The nitrogen source may be ammonia, NH
3
, molecular nitrogen, N
2
, or both. If both NH
3
and molecular nitrogen, N
2
, are present in the process gas, a silicon nitride, SiN, dielectric film is deposited on the substrate at a rate of 50 angstroms/minute with a uniformity of 14%. In the absence of NH
3
, an oxygen source is included in the process gas that may be ozone, O
3
, but preferably is molecular oxygen, O
2
. In this fashion, a silicon oxide, such as silicon dioxide, SiO
2
, dielectric film is deposited on the substrate at a rate of approximately 1,800 angstroms/minute with a uniformity of 14%. To practice the aforementioned methods, a substrate processing system is provided that includes a housing defining a process chamber; a substrate moving system for moving the substrate into the process chamber and positioning the substrate on the substrate holder; a gas delivery system for introducing a process gas into the process chamber to deposit a layer over the substrate, a temperature control system for maintaining a selected temperature within the process chamber; a pressure control system for maintaining a selected pressure within the vacuum system; a controller for controlling the gas delivery system, the temperature control system; and the pressure control system, and a memory data communication with the controller containing a computer program, to be operated on by the controller, for practicing the aforementioned methods.
These and other embodiments of the present invention, as well as their advantages and features, are described in more detail in conjunction with the text below and attached figures.
REFERENCES:
patent: 4822830 (1989-04-01), Adkins
patent: 5492736 (1996-02-01), Laxman
patent: 5744196 (1998-04-01), Laxman
patent: 5874368 (1999-02-01), Laxman
Laxman et al, Low Temp. LPCVD Silicon Nitride Using Chlorine-Free Organosilicon Precursor, International VLSI Multilevel Interconnection Conf., 1998; 15thp. 568-573.
Xia Li-Qun
Yieh Ellie
Applied Materials Inc.
Bueker Richard
Townsend and Townsend and Crew
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