Semiconductor device and method of manufacturing thereof

Details Semiconductor device and method of manufacturing thereof Semiconductor device and method of manufacturing thereof

2002-11-06

2004-04-27

Lebentritt, Michael S. (Department: 2824)

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

C438S313000, C438S314000, C438S317000, C438S762000, C438S769000

Reexamination Certificate

active

06727146

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device and a manufacturing technique of the semiconductor device. More particularly, the present invention relates to a technique for optimizing an amount of nitrogen that is contained in an interface between a gate insulation film and a semiconductor substrate of a MISFET (Metal Insulator Semiconductor Field Effect Transistor), thereby improving device reliability such as hot carrier reliability.
BACKGROUND OF THE INVENTION
In recent years, since it becomes evident that a gate oxide film is oxy-nitrided in gas atmosphere such as NO or N
2
O, and nitrogen atoms are piled up on an interface between the gate oxide film and a silicon substrate, thereby making it possible to improve a hot carrier reliability of an n-channel type MISFET, and restrain boron (B) penetration from a p-type polycrystal silicon gate, this oxynitridation has been practically available for use in logic products.
However, there has been a report that, if an amount of nitrogen in the interface between the gate oxide film and the silicon substrate (hereinafter, referred to as a SiO
2
/Si interface) is excessively increased, a p-channel type MISFET is severely degraded (for example, NBTI (negative bias temperature instability) described in 1999 VLSI Symposium Digest of Technical Paper, P. 73). Therefore, control of an amount of nitrogen in the above interface is an important task.
In addition, as a substitutive technique of an oxynitridation, for example, as described in Japanese Patent Application Laid-open No. 10-79506, it is known that a similar advantageous effect is attained by ion implantation when source and drain extensions are formed after nitrogen or a nitrogen-containing ion has been subjected to gate electrode processing.
FIG. 84
shows the test result showing an example, where remarkable improvement of a hot carrier reliability is achieved by almost one hundred times in a nitrogen atom of 1×10
15
cm
−2
in dosage.
SUMMARY OF THE INVENTION
However, according to study of the Inventor, recent logic LSI products employ gate oxide films having dual oxide thickness (hereinafter, these films are referred to as a thin film and a thick film for clarity). Thus, in the same oxynitridation, as a result of shortage of an amount of nitrogen relevant to thick film, there has been a problem that a hot carrier reliability of an n-channel type MISFET using a thick film tends to be in short. On the other hand, in the case where an oxynitridation condition is determined in accordance with a thick film, there has been a problem that an excessive amount of nitrogen is produced, and the NBTI durability of the p-channel type MISFET is impaired, or alternatively, a fixed charge increases, and threshold voltages of the n-channel MISFET and p-channel MISFET are greatly shifted. This problem will be described more specifically with reference to the accompanying drawings.
FIG. 79
to
FIG. 83
each show an outline of CMOS process flow using a gate oxide film having thickness of dual oxide level. A shallow trench isolation region
11
is formed on a silicon (Si) substrate (hereinafter, simply referred to as a substrate)
10
, and a p-well
12
for n-channel type MISFET and an n-well
13
for p-channel type MISFET are formed. Then, the surface of a substrate
10
is fully oxidized, and a thick oxide film
14
is formed (FIG.
79
). Next, the surface
10
of the thick MISFET section is covered with a resist mask
111
, and a thick oxide film
14
at the thin MISFET section is removed by etching (FIG.
80
). Next, after washing the surface of the substrate
10
, the substrate
10
is re-oxidized, thereby forming a thin oxide film
15
on the substrate
10
of the thin MISFET section (FIG.
81
). In this case, the thick oxide film
14
is thus re-oxidized so as to have desired film thickness, although the film thickness slightly decreases due to the above washing step. Thereafter, the full face of the substrate
10
is subjected to oxynitridation by employing an NO gas so that an nitrogen atom in desired amount is contained in an interface between the fate oxide film (
14
,
15
) and the substrate
10
.
Next, a polycrystal silicon film deposited on the substrate
10
is patterned, thereby forming gate electrodes
31
and
32
. Thereafter, an extension region (n
−
type semiconductor region)
113
and a halo region (p-type semiconductor region)
114
for punch-through restraining are formed at the p-well
12
of the thick MISFET section, and an extension region (p-type semiconductor region)
116
and a halo region (n-type semiconductor region)
117
are formed. In addition, an extension region (n-type semiconductor region)
119
and a halo region (p-type semiconductor region)
120
are formed at the p-well
12
of the thin MISFET section, and an extension region (p
−
type semiconductor region)
122
and a halo region (n-type semiconductor region)
123
are formed at the n-well
13
(FIG.
82
).
Next, a sidewall spacer
124
is formed on the side wall of gate electrodes
31
a
,
31
b
,
32
a
, and
32
b
, and then, an As ion and an boron fluoride ion is implanted in the substrate
10
, thereby forming a n
+
type semiconductor region
125
with high impurity concentration that configures the source and drain of an n-channel type MISFET and a p-channel type MISFET
126
with high impurity concentration that configures the source and drain of a p-channel type MISFET. Thereafter, a silicide layer
127
is formed each on the surface of the source and drain of the n-channel type MISFET (n
+
type semiconductor region
125
) and the surface of the source and drain of the p-channel type MISFET (p
+
type semiconductor region
126
) (FIG.
83
).
However, in the above process, gate oxide films
14
and
15
of dual oxide thickness are treated in accordance with one oxynitridation step. Thus, an amount of interfacial nitrogen between the thick gate oxide film
14
and the substrate
10
is smaller than that between an interface between the thin gate oxide film
15
and the substrate
10
, and a hot carrier reliability of the MISFET using a thick film becomes insufficient.
FIG. 85
shows the testing result when oxide under-layer dependency of an amount of nitrogen on the interface is investigated. In the figure, it is found that the current thick film (7 nm) contains nitrogen in amount almost 5 times as much as the current thin film (2.5 nm). Here, this phenomenon is studied by using a simple model.
When an Si substrate surface-oxide in gas such as NO is heat treated, nitridation species such as NO molecules solve and thermally diffuses in the oxide film, whereby the specifies reach an SiO
2
/Si interface. It is considered that this interface has a density of a site that can be coupled with nitrogen, and thus, functions as a sink. In consideration of the nitride species concentration in the oxide film based on this presumption, when the thickness of the oxide film is thin, the film has a linear distribution as shown in
FIG. 86
, and a flux F of the nitride specifies is prosectional to Ns/tox (Ns: oxide film surface concentration such as NO molecules (depending on solid solubility) and tox: Oxide under-layer film thickness). Therefore, the nitrogen amount N of the interface is led to be inversely prosectional to “tox” by dN/dt=F. In actuality, when the oxide film becomes thick, a complimentary error function distribution as shown in
FIG. 87
is obtained, and thus, the flux F decreases more remarkably than linear approximation. Therefore, in the case where an oxide film having two types of thickness is processed in one oxynitridation process, it is found that an amount of nitrogen on the thick interface is inversely prosectional to an amount of nitrogen in thin film×film thickness at most. A policy that a thinner film is produced without changing the film thickness of the thick film is effectual, and thus, a difference in amount of nitrogen is likely to be more remarkable.
In addition, in DRAM (Dynamic Rando

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