Photocopying – Projection printing and copying cameras – With temperature or foreign particle control
Reexamination Certificate
2000-12-29
2004-03-23
Nguyen, Henry Hung (Department: 2851)
Photocopying
Projection printing and copying cameras
With temperature or foreign particle control
C355S053000
Reexamination Certificate
active
06710845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a method and apparatus for making semiconductor devices using lithography. More particularly, the invention relates to a gas-filled enclosure between a mask protective device and a patterned mask, and a method and apparatus for removing a gas from the enclosure and adding a different gas.
2. Background Information
Photolithography is a process frequently used in processes to manufacture semiconductor devices. During photolithography, a light-sensitive layer on a semiconductor device is selectively exposed to light through the use of a reticle or mask. Light is transmitted toward the light-sensitive layer, through the reticle, which contains transparent regions that transmit light to the light-sensitive layer and opaque regions that prevent exposure of certain areas of the light-sensitive layer to the light. Typically, the reticle is a transparent quartz plate with a pattern defined by opaque chrome included on one side of the quartz plate. The transparent and opaque regions are associated with circuitry to be created on the semiconductor device. The exposed portions of the light-sensitive layer are transformed, allowing them to be removed by solvents, to create the circuitry of the semiconductor device.
FIG. 1
shows a prior art pellicle-reticle system
100
. The pellicle-reticle system
100
includes a reticle
110
protected from ambient particles, by a pellicle
120
. The pellicle
120
is typically a light-transparent polymeric film attached to a rigid frame. Particles, such as airborne particles, settle on the pellicle
120
, rather than on the reticle
110
. The pellicle
120
is typically separated from the reticle
110
by a short distance sufficient to eliminate or dissipate effects of particles on the surface of the pellicle
120
from creating a shadow on the reticle
110
or on a semiconductor device. Without the pellicle
120
, such particles could create unintended images on the semiconductor device and alter the circuitry. Accordingly, the pellicle
120
allows particles to be collected a short distance away from the reticle
110
, where they will be out of focus on the wafer surface, and will not generate circuitry defects.
The pellicle
120
is typically connected to the reticle
110
by a wall
130
. The pellicle
120
, the reticle
110
, and the wall
130
create an enclosed volume
140
, typically of air. A single, small pressure equalization orifice
150
is typically provided to equalize the pressure across the pellicle
120
. This orifice
150
prevents changes in the pressure of the enclosed volume, or ambient air from damaging or altering optical properties of the pellicle
120
. The orifice
150
is made small to discourage external particles from entering the enclosed volume
140
and surfacing directly on the reticle
110
. For example, considering an enclosed volume approximately 115 mm in length and 90 mm in width, the single, small orifice
150
is typically less than approximately 3 mm in length by 1 mm in height. For the same reason, the orifice
150
is sometimes a convoluted passageway in order to trap particles in the passageway before entering the enclosed volume. Multiple orifices are not used, since multiple orifices promote convective flow into and out of the enclosure, which is not desired. The primary purpose of the pellicle
120
is to keep particles off of the surface of the reticle
110
. Thus, only a single small orifice
150
has been used in prior art pellicle-reticle systems.
The wavelength of the light affects the size of the circuitry that can be produced by photolithography. Shorter light wavelengths allow circuits with smaller features to be produced. Likewise, single-frequency light allows smaller circuitry to be produced than multi-frequency light. Ultraviolet light has traditionally been used. Common wavelengths are 436 nm (called G-Line), 405 nm (H-line), 365 nm (I-line) and 248 nm (called Deep UV), and 193 nm. Prior art photolithography methods and apparatus based on these frequencies have been conducted in ambient temperature, humid air, since nitrogen (N
2
), oxygen (O
2
), water (H
2
O), and carbon dioxide (CO
2
) do not appreciably absorb ultraviolet light at these frequencies.
Shorter-wavelength ultraviolet light, such as 157 nm, may be used to produce even smaller circuitry features. However, oxygen and carbon containing species present in normal atmospheric air, such as oxygen (O
2
), water vapor (H
2
O), and carbon dioxide (CO
2
), absorb 157 nm ultraviolet light. This may cause irregularities and imperfections in the circuits produced. Unfortunately, due to the single, small orifice
150
and the prior art motivation to minimize airflow into and out of the enclosure, prior art photolithography methods and apparatus are not satisfactory for removal of these species.
REFERENCES:
patent: 5422704 (1995-06-01), Sego
patent: 5453816 (1995-09-01), Wang
patent: 5529819 (1996-06-01), Campi, Jr.
patent: 5559584 (1996-09-01), Miyaji et al.
patent: 5793836 (1998-08-01), Maldonado et al.
patent: 5814381 (1998-09-01), Kuo
patent: 6153044 (2000-11-01), Klebanoff et al.
patent: 6317479 (2001-11-01), Chiba et al.
patent: 6542220 (2003-04-01), Schrijver et al.
Kuse Ronald J.
Wu Han-Ming
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