Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
1999-11-10
2004-03-16
Meeks, Timothy (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C216S067000, C216S069000, C216S076000, C216S079000, C134S001100, C438S707000, C438S715000, C438S723000, C438S726000
Reexamination Certificate
active
06706334
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a processing method and apparatus for removing an oxide film formed on a surface of an object and a contaminant to be treated mainly such as a semiconductor wafer, particularly, to a processing method and apparatus for removing a thin oxide film such as a native oxide film formed on a surface of the object such as a semiconductor wafer, and more particularly, to a processing method and apparatus for removing a native oxide film formed in a bottom portion of a fine hole formed on a surface of the object such as a semiconductor wafer.
The present invention is directed mainly to a technique of removing an oxide film formed on a surface of an object such as a semiconductor wafer, particularly, to a technique for removing a native oxide film. Although, the object to be processed-in-the present invention is not limited to a semiconductor wafer, the related art in relation to a technique for removing a native oxide film formed in a bottom portion of a fine hole formed on a surface region of a semiconductor wafer in order to specifically describing the related art is described.
As widely known to the art, processes to form a film on a semiconductor wafer used as a substrate and etching treatments to selectively etch the resultant film in a predetermined pattern are repeatedly carried out in the manufacture of a semiconductor integrated circuit on the semiconductor wafer. During these processes, the substrate is transferred among various processing devices. During the transfer, the substrate is exposed to the air atmosphere, with the result that the oxygen and water within the air atmosphere unavoidably cause a native oxide film to be formed on a surface of the substrate. Formation of the native oxide film causes the properties such as electrical properties of the film on a surface of the substrate to be deteriorated. Where deterioration of the film properties is undesirable in the process for forming a film on the substrate or in the etching process of the film, it is necessary to remove the native oxide film formed on the substrate.
A wet etching is one of the conventional techniques for removing the native oxide film. In the wet etching, the semiconductor substrate (wafer) having a native oxide film formed thereon is immersed in a washing liquid for removing the native oxide film. It should be noted that the line width of a wiring and the diameter of a contact hole formed in the semiconductor wafer are diminished with increase in the scale of integration and miniaturization of the semiconductor integrated circuit. For example, the diameter of the contact hole is 0.2 to 0.3 &mgr;m or less (e.g., 0.12 &mgr;m). What should be noted is that, since the contact hole has a very small diameter, the washing liquid is unlikely to enter sufficiently the contact hole. Also, the washing liquid once entering the contact hole is not likely to be easily expelled from within the contact hole because of the surface tension of the washing liquid. Under the circumstances, it is difficult for the washing liquid to remove sufficiently a native oxide film formed in a bottom portion of the contact hole.
Where the substrate is subjected to a wet washing, the wall of the contact hole is also etched together with the native oxide film. It should be noted in this connection that the contact hole extends through a plurality of layers formed on the substrate, with the result that the wall of the contact hole consists of a plurality of these layers. What should be noted is that these plural layers differ from each other in the etching rate when subjected to etching with the wet washing liquid. It follows that the surface of the contact hole is rendered irregular after the etching with the wet washing liquid.
FIGS. 6A and 6B
show in detail the situation. Specifically,
FIG. 6A
shows that a contact hole
2
for achieving an electrical contact with a drain or source region is formed in a surface region of a silicon substrate W. The contact hole
2
, which has a diameter of about 0.2 to 0.3 &mgr;m, extends through three layers consisting of a SiO
2
&lgr;
1
layer
4
formed by thermal oxidation, a phosphorus-doped glass (SiO
2
) &lgr;
2
layer
6
formed by a spin-coating method, and a silica glass (SiO
2
) &lgr;
3
layer
8
, as shown in the drawing. A native oxide film
10
is formed at the bottom of the contact hole
2
. These SiO
2
layers
4
,
6
and
8
slightly differ from each other in the etching rate when washed with a washing liquid. It follows that, if the native oxide film
10
is removed by the wet etching, the wall surface of the contact hole
2
is caused to be irregular by the difference in the etching rate noted above, as shown in FIG.
6
B. In addition, the washing liquid tends to enter the boundary regions between the adjacent two layers, leading to an over-etching of the boundary regions.
To overcome the above-noted difficulties, it is proposed to employ a so-called dry etching method in place of the wet etching method for removing the native oxide film at the bottom of the contact hole. Japanese Patent Disclosure (Kokai) No. 2-256235 discloses a method of removing a native oxide film by utilizing a NF
3
gas (halogen gas) or NH
3
gas (basic gas). It is disclosed that the halogen gas or the basic gas noted above is introduced into a process chamber, and the native oxide film is removed by plasma formed within the process chamber. In this technique, however, required is an apparatus for exhausting these two kinds of the special gases (NF
3
, NH
3
) leading to a high operating cost. Japanese Patent Disclosure No. 6-338478 discloses another technique. It is disclosed that an H
2
gas and an H
2
O vapor are supplied into a plasma generating section for activation of these gas and vapor. Then, an NF
3
gas or a gaseous mixture containing NF
3
gas is added to the activated gas and vapor for removing the native oxide film. However, since H
2
O (steam) is used in this technique, a native oxide film tends to be formed in an amount larger than the amount of the removed native oxide film. As a matter of fact, a native oxide film was not sufficiently removed in the experiment conducted by the present inventor.
In order to resolve the above drawback of the conventional wet cleaning, a method of removing a native oxide film from a subject to be treated using etching gas, i.e., a so-called dry cleaning (etching) method is proposed in, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 5-275392, 6-338478, and 9-106977.
FIG. 14
shows a prior art dry etching apparatus for dry-etching an SiO
2
film by the dry cleaning method as disclosed in the above No. 5-275392 Publication. The dry cleaning method for eliminating a native oxide film from a subject to be treated, will now be described with reference to
FIG. 14
showing the dry etching apparatus. In the apparatus shown in
FIG. 14
, an open/close valve
450
is closed to cut off Ar gas from an Ar-gas source
454
. Open/close valves
436
and
438
are opened to supply NF
3
gas and H
2
gas from an NF
3
-gas source
444
and an H
2
-gas source
446
to a pipe
432
by controlling their flow rates by means of flow-rate controllers (MFC)
440
and
442
. In the pipe
432
, both the NF
3
gas and H
2
gas are mixed at a mixing ratio of 1:2 into a mixed gas having a total pressure of 0.2 Torr. A 2.45-GHz-frequency, 50-w-power microwave is supplied from a magnetron into the pipe
432
via a microwave waveguide
448
, and the mixed gas thus becomes plasma therein. A fluorine active species F*, a hydrogen active species H*, and a nitrogen active species N*, which are generated by the plasma, move toward a chamber
410
within the pipe
432
and enter a buffer chamber
430
of the chamber
410
. These species are then supplied downstream onto a wafer W placed on a susceptor
412
through a porous plate
428
. The wafer W is cooled by a chiller which is supplied from a chiller supply unit
418
and cooled to not higher than room temperature. The active species F*, H* and N* supplied to the cooled wafe
Kobayashi Yasuo
Maekawa Kaoru
Miyatani Kotaro
Meeks Timothy
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokyo Electron Limited
LandOfFree
Processing method and apparatus for removing oxide film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Processing method and apparatus for removing oxide film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Processing method and apparatus for removing oxide film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3225610