Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of...
Reexamination Certificate
2001-03-13
2002-08-13
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
C438S623000, C438S789000, C438S790000, C438S760000
Reexamination Certificate
active
06432839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming a flattened interlayer insulating film to cover the wiring layer or the like of a semiconductor integrated circuit device, and a method for manufacturing a semiconductor device.
2. Description of the Prior Art
In recent years, within the field of semiconductor integrated circuit devices (hereinafter, referred to as a semiconductor IC device), progress has been made toward achieving a much higher density, and an increasing number of such devices have multilayer wiring, i.e., wiring extended over several layers. In such a case, because of the frequent use of, especially, an aluminum material for the wiring, a need has developed for a method for forming a flattened interlayer insulating film at a low temperature of 500° C. or lower.
Conventionally, flattening methods include: that shown in
FIG. 1
, which performs flattening by forming a film by a thermal chemical vapor deposition method (hereinafter, referred to as a TH-CVD method); a plasma enhanced chemical vapor deposition method (hereinafter, referred to as a PE-CVD method) or the like, heating the formed film, and then fluidizing the film; the etch back method shown in
FIG. 2
; and the chemical mechanical polishing method (hereinafter, referred to as a CMP method) shown in
FIG. 3
, which removes unevenness on the surface of the insulating film by etching or polishing.
In the case of the former method, as shown in
FIG. 1A
, a boro-phospho silicate glass film (hereinafter, referred to as a BPSG film)
4
is formed by a TH-CVD method, which uses any one of the following deposition gases:
(1) SiH
4
+PH
3
+B
2
H
6
+O
2
(PH
3
: phosphine)
(2) TEOS+TMOP+TMB or TEB+O
2
or O
3
(TEOS: tetraethylorthosilicate (Si-(OC
2
H
5
)
4
), TMOP: trimethylphosphate (PO(OCH
3
)
3
)).
Alternatively, as shown in
FIG. 1A
, a BPSG film
4
is formed by a PE-CVD method, which uses any one of the following deposition gases:
(1) SiH
4
+PH
3
+B
2
H
6
+O
2
(2) TEOS+TMOP+TMB or TEB+O
2
.
For reference, see: J. Electrochem. Soc., 134.3,: 657, 1987, by Williams, D. S. and Dein, E. A; J. Vac.Sci. Technol., B1, 1:54, 1983, by Levin, R. M. and Evans-Lutterodt, K; Extended Abstract of Electrochem. Soc. Spring Meeting: 31, 1971, by Sato, J. and Maeda, K.
Then, as shown in
FIG. 1B
, the formed BPSG film
4
is heated to a temperature of about 850° C., and thereby fluidized and flattened. In the case of a phospho-silicate glass film (hereinafter, referred to as a PSG film), a film is formed by a TH-CVD method, a PE-CVD method or the like, which uses the foregoing deposition gas minus the boron containing gas (B
2
H
6
, TMB or TEB), which film is then heated to a temperature of 1000° C. or lower, and thereby fluidized and flattened.
In the case of the latter method, as shown in FIG.
2
A and
FIG. 3A
, firstly, a non-doped silicate glass (hereinafter, referred to as a NSG film)
5
is formed by a TH-CVD method, a PE-CVD method or the like, which uses one of the following deposition gases, and then flattened:
(1) SiH
4
+O
2
(TH-CVD method or PE-CVD method)
(2) TEOS+O
2
or O
3
(TH-CVD method)
(3) TEOS+O
2
(PE-CVD method)
In the etch back method, as shown in
FIG. 2B
, a resist film
6
is formed on the NSG film
5
by a coating method, and then, as shown in
FIG. 2C
, the film
6
is subjected to etching to form a flattened NSG film
5
a
. In the CMP method, as shown in
FIG. 3B
, the NSG film
5
is formed, and then polished to flatten the surface and form a flattened NSG film
5
b.
In
FIGS. 1
to
3
, reference numeral
1
denotes a semiconductor substrate;
2
a base insulating film; and
3
a
and
3
b
wiring layers formed on the base insulating film
2
.
Incidentally, the above-described flattening methods based on the etch back method or the CMP method are effective, especially when a low temperature is required, because these methods can be executed without heating, unlike the case of flattening by heating to fluidize. However, as shown in
FIGS. 2A-2C
,
3
A and
3
B, if any voids or recesses are formed between the wires
3
a
in the insulating film
5
, the voids and recesses are left unchanged even after flattening. Currently available methods for forming insulating films having good gap-filling capabilities include a high-density PE-CVD method, a PE-CVD method, an atmospheric pressure TH-CVD method, an spin-on-glass (hereinafter, referred to as SOG) coating method, and the like. However, since these flattening methods do not use thermal fluidity, particularly when a high densification is attained by narrowing the spaces between the wiring, recesses cannot be completely filled.
On the other hand, in the flattening method based on fluidizing by heating, since thermal fluidity is utilized, as shown in
FIG. 1
, complete filling can be expected. At present, the BPSG film
4
is frequently used for such a purpose. However, heating to at least a temperature of 850° C. must be carried out for fluidization. Thus, such a film cannot be applied to the base film
2
of the wiring
3
a
and
3
b
or the interlayer insulating film
4
, where a low temperature is needed for formation. In particular, the film cannot be applied to an insulating film to cover the aluminum wiring layer. In this case, the temperature of fluidization can be somewhat lowered by increasing the concentration of boron or phosphorus. Even so, the temperature is not sufficiently low. Rather, new problems may occur, such as a reduction in the stability or humidity resistance of the insulating films
2
and
4
. Similar problems may occur in the case of a PSG film, because a temperature of fluidization substantially equal to that for the BPSG film is necessary.
As an insulating film having a low fluidization temperature, a GeBPSG film formed by adding GeO
2
to the BPSG film has been developed. However, the temperature cannot be lowered below about 750° C. Thus, it is difficult to apply this film to a base film or an interlayer insulating film, for which a much lower temperature is required.
SUMMARY OF THE INVENTION
The fluidization temperature is preferably as low as possible, not only when aluminum, copper or the like is used for wiring in a semiconductor large scale integrated circuit (hereinafter, referred to as LSI) or the like, but also to prevent re-distribution of impurities from an impurity introduction region which is generally caused by heat.
An object of the present invention is to provide a method for forming an insulating film, capable of greatly reducing the fluidization temperature for flattening a surface, and a manufacturing method for a semiconductor device.
The inventors focused on the following points:
(1) the BPSG film or the phospho-silicate glass film (hereinafter, referred to as PSG film) is conventionally formed from a mixture of SiO
2
+P
2
O
5
+B
2
O
3
, or of SiO
2
+P
2
O
5
(the PH
3
of the deposition gas SiH
4
+PH
3
+B
2
H
6
+O
2
is III valance phosphorus, and bonds with externally supplied oxygen to generate, not P
2
O
3
, but P
2
O
5
. This may be attributed to the fact that since PH
3
itself contains no oxygen, when it is bonded with externally supplied oxygen, stable P
2
O
5
is easily generated.);
(2) in the BPSG film of P
2
O
5
—SiO
2
, a eutectic point for the composition of 20 to 80% of P
2
O
5
is theoretically 850° C., and its fluidization temperature is dependent on the melting point of the P
2
O
5
itself; and
(3) P
2
O
3
has a melting point much lower than that of P
2
O
5
as shown in Table 1.
TABLE 1
Melting point
Boiling point
P
2
O
3
(III valance)
23.8° C.
175.4° C.
P
2
O
5
(V valance)
580 to 585° C.
300° C.
(sublimation)
(CRC Handbook of Chemistry: 1978/88 edition, by CRC press)
Accordingly, the inventors theorized that the fluidization temperature would be lowered if the BPSG film or the PSG film contains mainly P
2
O
3
, instead of P
2
O
5
.
Accordingly, the present invention oxidizes a phosphorus containing compound in a
Ishii Yuki
Maeda Kazuo
Nishiyama Toshiro
Tokumasu Noboru
Canon Sales Co., Inc.
Lorusso & Loud
Luk Olivia T
Niebling John F.
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