Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2002-03-14
2004-07-06
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C716S030000, C700S097000
Reexamination Certificate
active
06760640
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an automated manufacturing system and method for manufacturing photomasks wherein information provided by a customer at a remote location is interfaced, via a network, to a photomask manufacturer's computer system and automatically processes data for manufacturing a photomask and automatically formats and routes data to processing equipment. The present invention reduces the need for manual intervention, thereby avoiding costly delays and transcription errors associated therewith.
BACKGROUND OF THE INVENTION
Photomasks are high precision plates containing microscopic images of electronic circuits. Photomasks are typically made from very flat pieces of quartz or glass with a layer of chrome on one side. Etched in the chrome is a portion of an electronic circuit design. This circuit design on the mask is also called geometry.
A typical photomask used in the production of semiconductor devices is formed from a “blank” or “undeveloped” photomask. As shown in
FIG. 1
, a typical blank photomask
10
is comprised of three or four layers. The first layer
11
is a layer of quartz or other substantially transparent material, commonly referred to as the substrate. The next layer is typically a layer of opaque material
12
, such as Cr, which often includes a third layer of antireflective material
13
, such as CrO. The antireflective layer, may or may not be included in any given photomask. The top layer is typically a layer of photosensitive resist material
14
. Other types of photomasks are also known and used including, but not limited to, phase shift masks, embedded attenuated or alternating aperature phase shift masks.
The desired pattern of opaque material
12
to be created on the photomask
10
may be defined by an electronic data file loaded into an exposure system which typically scans an electron beam (E-beam) or laser beam in a raster or vector fashion across the blank photomask. One such example of a raster scan exposure system is described in U.S. Pat. No. 3,900,737 to Collier. Each unique exposure system has its own software and format for processing data to instruct the equipment in exposing the blank photomask. As the E-beam or laser beam is scanned across the blank photomask
10
, the exposure system directs the E-beam or laser beam at addressable locations on the photomask as defined by the electronic data file. The areas of the photosensitive resist material that are exposed to the E-beam or laser beam become soluble while the unexposed portions remain insoluble.
In order to determine where the e-beam or laser should expose the photoresist
14
on the blank photomask
10
, and where it should not, appropriate instructions to the processing equipment need to be provided, in the form of a jobdeck. In order to create the jobdeck the images of the desired pattern are broken up (or fractured) into smaller standardized shapes, e.g., rectangles and trapezoids. The fracturing process can be very time consuming. After being fractured, the image may need to be further modified by, for example, sizing the data if needed, rotating the data if needed, adding fiducial and internal reference marks, etc. Typically a dedicated computer system is used to perform the fracturing and/or create the jobdecks. The jobdeck data must then be transferred to the processing tools, to provide such tools with the necessary instructions to expose the photomask.
As shown in
FIG. 2
, after the exposure system has scanned the desired image onto the photosensitive resist material
14
, the soluble photosensitive resist material is removed by means well known in the art, and the unexposed, insoluble photosensitive resist material
14
′ remains adhered to the opaque material
13
and
12
. Thus, the pattern to be formed on the photomask
10
is formed by the remaining photosensitive resist material
14
′.
The pattern is then transferred from the remaining photoresist material
14
′ to the photomask
10
via known etch processes to remove the antireflective material
13
and opaque materials
12
in regions which are not covered by the remaining photoresist
14
′. There are a wide variety of etching processes known in the art, including dry etching as well as wet etching, and thus a wide variety of equipment used to perform such etching. After etching is complete, the remaining photoresist material
14
′ is stripped or removed and the photomask is completed, as shown in FIG.
3
. In the completed photomask, the pattern as previously reflected by the remaining antireflective material
13
′ and opaque materials
12
′ are located in regions where the remaining photoresist
14
′ remain after the soluble materials were removed in prior steps.
In order to determine if there are any unacceptable defects in a particular photomask, it is necessary to inspect the photomasks. A defect is any flaw affecting the geometry. This includes chrome where it should not be (chrome spots, chrome extensions, chrome bridging between geometry) or unwanted clear areas (pin holes, clear extensions, clear breaks). A defect can cause the customer's circuit not to function. The customer will indicate in its defect specification the size of defects that will affect their process. All defects that size and larger must be repaired, or if they can not be repaired the mask must be rejected and rewritten.
Typically, automated mask inspection systems, such as those manufactured by KLA Instruments Corporation or ETEC, an Applied Materials company, are used to detect defects. Such automated systems direct an illumination beam at the photomask and detect the intensity of the portion of the light beam transmitted through and reflected back from the photomask. The detected light intensity is then compared with expected light intensity, and any deviation is noted as a defect. The details of one system, can be found in U.S. Pat. No. 5,563,702 assigned to KLA Instruments Corporation.
After passing inspection, a completed photomask is cleaned of contaminants. Next, a pellicle may be applied to the completed photomask to protect its critical pattern region from airborne contamination. Subsequent through pellicle defect inspection may be performed. Sometimes either before or after a pellicle is applied, the photomask may be cut. After these steps are completed, the completed photomask is sent to a customer for use to manufacture semiconductor and other products. In particular, photomasks are commonly used in the semiconductor industry to transfer micro-scale images defining a semiconductor circuit onto a silicon or gallium arsenide substrate or wafer. The process for transferring an image from a photomask to a silicon substrate or wafer is commonly referred to as lithography or microlithography.
Typically, as shown in
FIG. 4
, the semiconductor manufacturing process comprises the steps of deposition, photolithography, and etching. During deposition, a layer of either electrically insulating or electrically conductive material (like a metal, polysilicon or oxide) is deposited on the surface of a silicon wafer. This material is then coated with a photosensitive resist. The photomask is then used much the same way a photographic negative is used to make a photograph. Photolithography involves projecting the image on the photomask onto the wafer. If the image on the photomask is projected several times side by side onto the wafer, this is known as stepping and the photomask is called a reticle.
As shown in
FIG. 5
, to create an image
21
on a semiconductor wafer
20
, a photomask
10
is interposed between the semiconductor wafer
20
, which includes a layer of photosensitive material, and an optical system
22
. Energy generated by an energy source
23
, commonly referred to as a Stepper, is inhibited from passing through the areas of the photomask
10
where the opaque material are present. Energy from the Stepper
23
passes through the transparent portions of the quartz substrate
11
not covered by the opaque material
12
Croke Charles
Jones Peter F.
Mills Edward Arthur
Morrison James P.
Spano Mary R.
Amster Rothstein & Ebenstein LLP
Kosowski Alexander
Photronics, Inc.
Picard Leo
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