Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2000-04-28
2001-11-06
Powell, William A. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C216S058000, C438S704000, C438S715000, C134S030000
Reexamination Certificate
active
06313041
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method of enhancing the rate of removal of a layer of light-sensitive material in the fabrication of electronic devices on wafers of semiconductor material for which at least one etching step through a layer at least partially protected by said light-sensitive material is provided.
More particularly, the invention relates to a novel processing method whereby the process of removing a layer of photoresist can be made quicker and more effective, and in the ensuing description reference will be made to this application field for convenience of explanation only.
BACKGROUND OF THE INVENTION
Photoresist is an organic material which is employed to define by photolithography predetermined patterns in layers of materials commonly used in the processes for fabricating semiconductor electronic devices from monocrystalline silicon wafers, for example.
In this field, the semiconductor silicon wafers are required to undergo a plurality of chemical-physical treatments directed to define complex layouts of monolithically integrated electronic circuits thereon.
Particularly where submicron patterns are to be defined, a processing technique known as plasma etching is extensively used whereby thin films of conductive and dielectric materials can be etched.
As an example,
FIG. 1
of the accompanying drawings shows schematically a portion
1
of a semiconductor substrate
2
on top of which a layer or film
3
of a plasma etch-susceptible material, e.g., a dielectric layer, a layer of polycrystalline silicon, or a metallization layer, has been deposited. A protective mask
4
, e.g., of a photoresist, is provided on top of this layer
3
to be etched.
In order to define patterns in the film
3
protected by the mask
4
, the semiconductor must be subjected to a plasma etching step that will remove some of the film
3
material, through openings made in the mask
4
.
After the end of the plasma etching step, as shown in
FIG. 2
, the photoresist mask
4
must be removed. Removing the photoresist mask
4
uncovers the patterns of the finished product as shown in FIG.
3
.
The mask
4
removal is usually effected by subjecting the wafer to a second plasma or wet treatment which is selective enough to remove the mask of organic material without affecting the layers underneath.
Removing the protective mask
4
is often a fairly lengthy procedure.
As the technology progresses, the number of films or layers wherein patterns are to be defined tends to increase with the complexity of the microelectronic device. Consequently, the removal of the photoresist mask is a reiterative process that is carried out several times for each etched layer in the course of the device fabrication.
There is, therefore, a growing demand for techniques which allow the protective mask to be removed as effectively and rapidly as possible.
The prior art techniques have been directed to fill this demand by developing more aggressive removal processes and at the same time optimizing the parameters involved in the process, such as pressure, temperature, the type of reactant employed, etc.
SUMMARY OF THE INVENTION
Embodiments of the invention provide a method of effecting a removal of a light-sensitive material layer in the process of fabricating electronic devices on wafers of semiconductor material, which can make the removal both quicker and more effective. More particularly, removing the layer of light-sensitive material is made quicker and more effective. Even though embodiments according to the invention add additional steps, which thereby takes additional time, the benefit for using this extra step is outweighed by its reduction in overall processing time.
Presented is a method that subjects the semiconductor material wafer, while still covered with the mask to be removed, to a steam medium. Preferably, the steam interaction can be effected as a thermal treatment, using low-pressure steam for a predetermined time period.
Advantageously and preferably, the treatment is applied at a relatively high temperature in the 200° to 300° C. range, using steam in amounts between 500 and 2,000 sccm (standard cubic centimeters/per minute) and under a pressure from 5,000 to 15,000 mTorr for a few seconds, e.g., 10-30 seconds. Subsequent to this treatment, the protective mask is removed by conventional techniques, but within a much shorter time.
The features and advantages of a method according to this invention will become apparent from the following description of an embodiment thereof, given by way of non-limitative example with reference to the accompanying drawings.
REFERENCES:
patent: 3890176 (1975-06-01), Bolon
patent: 4863561 (1989-09-01), Freeman et al.
patent: 5112437 (1992-05-01), Watanabe et al.
Galanthay Theodore E.
Iannucci Robert
Powell William A.
Seed IP Law Group PLLC
STMicroelectronics S.r.l.
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