Active solid-state devices (e.g. – transistors – solid-state diode – With means to control surface effects – Insulating coating
Reexamination Certificate
1997-09-24
2001-05-22
Chaudhuri, Olik (Department: 2823)
Active solid-state devices (e.g., transistors, solid-state diode
With means to control surface effects
Insulating coating
C257S635000, C257S760000, C438S790000
Reexamination Certificate
active
06236105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a semiconductor device and a method of fabricating the same, and more particularly to an improvement in an interlayer insulating film suitable for a semiconductor device having multi-layered wirings.
2. Description of the Related Art
Recently, integration in a semiconductor device has been significantly enhanced. With such enhancement in integration, a semiconductor device is designed to have a multi-layered wiring structure including a growing number of wiring layers. A semiconductor device is designed to have an insulating film around or between wiring layers for prevention of current leakage. In particular, an insulating film formed between wiring layers is called an interlayer insulating film. As mentioned above, under the circumstance that steps on a surface of a semiconductor substrate on which a wiring layer(s) is(are) formed are increased with a wiring layer in a semiconductor device being designed to have a multi-layered wiring structure having the growing number of layers, it is indispensable that such surface steps are planarized by means of an interlayer insulating film.
In order to planarize steps formed on a surface of a semiconductor substrate, the following method is presently and widely used in the field of semiconductor fabrication.
First, a wiring pattern made of aluminum is formed on a semiconductor substrate such as a silicon substrate, and then, a film made of ozone (O
3
) tetra etyl ortho silicate (TEOS) boron phospho silicate glass (BPSG) is formed all over the semiconductor substrate by normal pressure chemical vapor deposition (CVD). Then, the semiconductor substrate is annealed, for instance, at 800° C. to 900° C. in nitrogen (N
2
) atmosphere to thereby reflow the O
3
TEOS BPSG film.
One conventional method of forming a O
3
TEOS BPSG film is illustrated in
FIGS. 1A
to
1
C.
First, as illustrated in
FIG. 1A
, a polysilicon film
11
is formed on a silicon substrate
10
and patterned. Then, a film
12
made of O
3
TEOS BPSG containing boron (B) and phosphorus (P) at a relatively low concentration is formed over the patterned polysilicon film
11
and the silicon substrate
10
by normal pressure CVD.
Then, as illustrated in
FIG. 1B
, a film
13
made of O
3
TEOS BPSG containing boron (B) and phosphorus (P) at a relatively high concentration is formed over the O
3
TEOS BPSG film
12
.
Then, as illustrated in
FIG. 1C
, the silicon substrate
10
is subject to heat treatment by exposing to nitrogen (N
2
) atmosphere at 800° C. to 900° C., to thereby reflow the O
3
TEOS BPSG films
12
and
13
.
Japanese Unexamined Patent Publication No. 4-94539 has suggested another method of planarizing surface steps of a semiconductor substrate. In the suggested method, a surface of a substrate is first reformed by irradiating high frequency plasma thereto. Then, there are formed PSG film, BSG film and BPSG film on the substrate under normal or lowered pressure by employing a mixture gas containing an organic silane (SiH
4
), a gas containing impurities such as phosphorus and boron, and ozone.
Japanese Unexamined Patent Publication No. 5-259297 has suggested still another method of planarizing surface steps of a semiconductor substrate. In this method, prior to formation of an interlayer insulating film, there is formed a nitrogen containing layer which is to be disposed just below the interlayer insulating film.
However, the above-mentioned prior methods have a problem as follows.
It is well known that a O
3
TEOS BPSG film, formed by normal pressure CVD, containing boron (B) and phosphorus (P) at higher concentration would provide more excellent planarization of surface steps on a substrate. On the other hand, if a O
3
TEOS BPSG film contains boron (B) and phosphorus (P) at high concentration, there takes place a phenomenon that boron and phosphorus particles are precipitated at a surface of the O
3
TEOS BPSG film. Such precipitation of boron and phosphorus particles on a surface of a O
3
TEOS BPSG film exerts a harmful influence on subsequent steps, resulting in reduction in a yield. That is, the above-mentioned prior methods have a problem of a narrow margin with respect to boron and phosphorus concentrations.
In other words, the prior methods have a problem that it is not allowed to let a O
3
TEOS BPSG film contain boron and phosphorus at high concentration because of low limit thereof about precipitation of boron and phosphorus, resulting in that the O
3
TEOS BPSG film cannot be sufficiently planarized after being reflowed.
To the contrary, if a O
3
TEOS BPSG film were designed to contain boron and phosphorus at higher concentration in order to sufficiently planarize the O
3
TEOS BPSG film by reflow process, it would be accompanied with a problem that boron and phosphorus particles precipitate at a surface of the O
3
TEOS BPSG film.
SUMMARY OF THE INVENTION
In view of the foregoing problems of the prior methods, it is an object of the present invention to provide a semiconductor device and a method of fabricating the same both of which are capable of sufficiently planarizing an interlayer insulating film by reflow process and preventing precipitation of impurities at a surface of the interlayer insulating film.
In one aspect, there is provided a semiconductor device including an interlayer insulating film disposed between upper and lower wiring layers, the interlayer insulating film having a two-layered structure including an upper insulating film and a lower insulating film, the lower insulating film being formed by an ozone (O
3
)-TEOS reaction in an atmosphere containing a first concentration of ozone and the upper insulating film being formed by an O
3
-TEOS reaction in an atmosphere containing a second concentration of ozone (O
3
) concentration different from that of the lower insulating film.
There is further provided a semiconductor device including an interlayer insulating film disposed between upper and lower wiring layers, the interlayer insulating film having a two-layered structure including an upper insulating film and a lower insulating film, the upper insulating film being formed in an atmosphere of ozone (O
3
) having a concentration higher than that of the concentration of ozone in the atmosphere in which the lower insulating film was formed.
For instance, the upper insulating film may have been formed in an ozone concentration ranging from 120 to 140 mg/litter both inclusive, and the lower insulating film may have been formed in an ozone concentration ranging from 70 to 100 mg/litter both inclusive.
There is still further provided a semiconductor device including an interlayer insulating film disposed between upper and lower wiring layers, the interlayer insulating film having a multi-layered structure including a plurality of insulating films, the insulating films having been formed in an ozone (O
3
) concentration different from that of one another.
It is preferable an insulating film in the multi-layered structure, disposed on another insulating film formed using a higher ozone concentration than that of the another insulating film. It is also preferable that a top insulating film has the highest ozone concentration among all of the insulating films.
The interlayer insulating film may be composed of any electrically insulating material. It is preferable that the interlayer insulating film is composed of O
3
tetra etyl ortho silicate (TEOS) boron phospho silicate glass (BPSG).
In another aspect, there is provided a method of fabricating a semiconductor device, including the step of forming an interlayer insulating film between upper and lower wiring layers so that the interlayer insulating film has a two-layered structure including an upper insulating film and a lower insulating film, in which the lower insulating film is formed in accordance with an ozone (O
3
)-TEOS reaction in an atmosphere containing a first concentration of ozone and the upper insulating film is formed by an O
3
-TEOS reaction in an atmosphere containing a second concentr
Chaudhuri Olik
Eaton Kurt
McGuireWoods LLP
NEC Corporation
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