Depositor for depositing a dielectric layer with fewer metallic impurities and a method for reducing the content of the metallic impurities in the dielectric layer by using this depositor

The present invention is characterized by setting a filter in the O.sub.3 -pipe of the depositor used to depositing a dielectric layer, wherein the filter is used to adsorb the metallic impurities in the O.sub.3 /O.sub.2 pipe. Therefore, the content of metallic impurities in the deposited dielectric layer can be efficiently reduced.

FIELD OF THE INVENTION 
The invention relates to a depositor for depositing a dielectric layer with 
fewer metallic impurities, and a method for reducing the content of the 
metallic impurities in the dielectric layer by means of the above 
depositor. 
BACKGROUND OF THE INVENTION 
In BPSG or PSG processes, metallic impurities are a serious problem. In the 
64M DRAM process, BPSG and PSG are used as a pre-metal dielectric layer 
(PMD) overlaying the gate, therefore the content of the metallic layer 
therein is important. For example, if the content of the metallic 
impurities in the PMD consisting of BPSG is more than 1.times.10.sup.15 
.about.2.times.10.sup.16 atoms/cm.sup.3, the PMD overlaying the gate will 
make leakage current and reduce the functionality of the products. 
SUMMARY OF THE INVENTION 
Therefore, the feature of the present inventions is to provide a novel 
depositor to efficiently reduce the content of the metallic impurities in 
the PMD. 
The present invention is characterized by setting a filter with metal 
adsorbent thereon in the O.sub.3 pipe to adsorb the metallic impurities in 
the O.sub.3 /O.sub.2 generated by the O.sub.3 -generator, resulting in 
fewer metallic impurities present in the depositing gas reactor. 
Therefore, the content of the metallic impurities of the dielectric layer 
deposited by this modified depositor with an O.sub.3 -filter will be 
efficiently reduced.

DETAILED DESCRIPTION OF THE INVENTION 
One feature of the invention is that a depositor for depositing a 
dielectric layer with fewer metallic impurities is disclosed. This 
depositor comprises an O.sub.3 -generator, a depositing gas reactor, an 
O.sub.3 /O.sub.2 pipe, and an O.sub.3 filter set in the O.sub.3 /O.sub.2 
pipe to filter the metallic impurities from the O.sub.3 -generator and 
subsequently reduce the content of the metallic impurities in the 
depositing gas. Therefore, the metallic impurities in the dielectric layer 
deposited by the depositor can be reduced. The dielectric layer is 
selected from one of the group consisting of USG, BPSG, PSG and BSG. The 
depositor is an Atmospheric Pressure Deposition Technology APT-system. 
Moreover, the filter consists of a gas filter, such as a filter consists 
of carbon fibers upon which metal particles can be adsorbed. 
Another feature of the present invention is that a method for reducing the 
metallic impurities in depositing dielectric layer is disclosed. First, a 
depositor comprising of an O.sub.3 -generator, a depositing gas reactor, 
and an O.sub.3 /O.sub.2 pipe is provided. Then an O.sub.3 -filter is set 
in the O.sub.3 /O.sub.2 pipe to filter the metallic impurities in O.sub.3 
/O.sub.2 generated by the O.sub.3 -generator. As described above, the 
dielectric layer is selected from one of the group consisting of USG, 
BPSG, PSG and BSG. The depositor is an APT-system. Moreover, the filter 
consists of a gas filter, such as a filter consists of carbon fibers upon 
which metal particles can be adsorbed. 
EMBODIMENT OF THE INVENTION 
Referring to FIG. 1, the modified Cannon-APT system according to the 
present invention is illustrated. However, this is not intended to limit 
the present invention; any conventional depositor for depositing a 
dielectric layer can also be applied. 
This system comprises of an O.sub.2 -supplier 10, an O.sub.3 -generator 16, 
a depositing gas generator 26 and a reactant supplier 28, wherein the 
O.sub.2 -supplier 10 is used to supply O.sub.3 -generate 16 with O.sub.2 
through the O.sub.2 pipe 12 to generator desired O.sub.3. Moreover, the 
O.sub.2 flux can be adjusted by means of an O.sub.2 flux controller (AFC) 
14 set in the O.sub.2 pipe 12. 
The O.sub.3 /O.sub.2 generated by the O.sub.3 -generator 16 is introduced 
into the depositing gas generator 26 by the O.sub.3 /O.sub.2 pipe 20 
connected to outlet 18. Moreover, the O.sub.3 /O.sub.2 pipe 20 is 
connected to a pressure-controlling pipe 21 to adjust the pressure of the 
O.sub.3 /O.sub.2 in the pipe 20. When the pressure of pipe 20 is too high, 
the on/off valve 23 in pipe 21 opens to introduce excess O.sub.3 into the 
O.sub.3 output device and transfer the excess O.sub.3 to outlet 29 through 
pipe 27. 
It is a characteristic of the present invention that an extra O.sub.3 
-filter is set in the O.sub.3 /O.sub.2 pipe of this system to remove the 
metal particles of the O.sub.3 /O.sub.2 generated by the O.sub.3 
-generator 16 of this system. In this embodiment, a gas filter 24, such as 
a filter consisting of carbon fiber, is set in the O.sub.3 /O.sub.2 pipe 
25 to adsorb the metallic impurities by means of the metal-adsorbent 
thereon. Then, O.sub.3 /O.sub.2 containing trace metallic impurities is 
obtained and introduced into the depositing gas generator 26 through pipe 
20. Moreover, in order to control the O.sub.3 /O.sub.2 flux in pipe 20, 
controlling valves 22a and 22b are independently set in the pipe 24 
between outlet 18 and filter 24 and the pipe 20 between filter 24 and 
depositing gas generator 26. 
In addition, the reactant for depositing a dielectric layer, such as TEOS 
for TEOS glass film, is supplied by reactant supplier 28. The reactant is 
introduced into the depositing gas generator 26 through pipe 30. 
Similarly, a controlling valve 32 is set in pipe 30 to adjust the reactant 
flux. When the O.sub.3 /O.sub.2 has mixed well with the reactant in the 
depositing gas generator 26, the depositing gas is sprayed out through 
pipe 34 to deposit a desired dielectric layer. 
In order to compare the content of metallic impurities in BPSG layers 
deposited by the Cannon-APT system with or without setting an O.sub.3 
-filter in the O.sub.3 /O.sub.2 pipe to adsorb the metallic impurities, 
the BPSG layers formed by the system of the prior art and by the system of 
the present invention were analyzed by AAS. The results are recorded in 
table 1. 
TABLE 1 
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Metallic impurities (atoms/cm.sup.3) 
Sample Na Cr Fe Ni Al Cu 
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APT 7.1E15 2.2E14 2.6E14 
2.7E15 
1.4E15 
1.5E14 
WPT + filter 
2.9E15 ND ND ND 4.6E14 
1.0E14 
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ND: no detection 
As shown in table 1, the metallic impurities of the BPSG sample deposited 
by the modified APT-system with an O.sub.3 -filter were less than the BPSG 
sample deposited by the ATP system without an O.sub.3 -filter. The result 
indicates that the metallic impurities in O.sub.3 /O.sub.2 can be 
efficiently adsorbed by the O.sub.3 -filter set in the O.sub.3 /O.sub.2 
pipe. A dielectric layer with only trace metallic impurities can be 
obtained by the APT-system with an O.sub.3 -filter as described above, 
therefore the leakage current of this dielectric can be reduced. 
From the above description, one skilled in this art can easily ascertain 
the essential characteristics of the present invention, and, without 
departing from the spirit and scope thereof, can make various changes and 
modifications of the invention to adapt it to various usage and 
conditions. Thus, other embodiments also fall within the scope of the 
following claims.