DEPOSITION OF INTEGRATED CIRCUIT FABRICATION MATERIALS USING A PRINT HEAD
BACKGROUND OF THE INVENTION 5
1. Field of the Invention
The present invention relates generally to integrated circuit (IC) fabrication, and more particularly but not exclu- 10 sively to deposition of IC fabrication materials using a print head.
2. Description of the Background Art
The use of ink jet technology to print on paper is well known. A typical ink jet print head has several nozzles that 15 are coupled to an ink reservoir. Ink from the reservoir are dispensed through the nozzles to form a pattern on paper. The ink jet print head may be scanned relative to the paper, or vice versa, to cover a large area.
FIG. 1 schematically illustrates the operation of an exem- 20 plary ink jet print head 20. Print head 20 may be of the type available from Ink Jet Technology Inc. of San Jose, Calif, for example. Print head 20 may have any number of nozzles 22 (i.e., 22-1, 22-2, . . .) but only four are shown for clarity of illustration. A digital firing pattern may be serially loaded 25 into a firing register 23 of print head 20 to enable or disable a nozzle 22. Each nozzle 22 may have a corresponding bit position in firing register 23. A logical "1" enables a nozzle 22 to fire (i.e., dispense ink), while a logical "0" disables a nozzle 22 from firing. For example, assuming a 4-bit firing 30 register 23, a firing pattern of "1000" may be loaded into firing register 23 to enable firing of nozzle 22-1 but not nozzles 22-2, 22-3, and 22-4; a firing pattern of "1001" may be loaded into firing register 23 to enable firing of nozzles 22-1 and 22-4 but not nozzles 22-2 and 22-3; and so on. 35
Each nozzle 22 may be coupled to an ink reservoir via a chamber (not shown). Ink flows from the reservoir into the chambers prior to being dispensed out of nozzles 22. The amount of ink drawn into the chambers, and thus the amount 4Q of ink dispensed by nozzles 22, may be controlled by loading an appropriate timing pattern into a timing circuit 24. Timing circuit 24 converts the timing pattern into timing pulses that are applied to all nozzles 22.
The use of ink jet technology in the fabrication of inte- 45 grated circuits (IC's) is disclosed in commonly-assigned U.S. Pat. No. 6,436,843, which is incorporated herein by reference in its entirety. Unlike paper printing applications where the emphasis is on printing sharply delineated marks, film deposition in an IC fabrication process is concerned 50 with dispensing a uniform amount of material on a substrate. This uniform amount may be in terms of unit volume per unit area. Because of manufacturing tolerances, the nozzles of a print head may dispense varying amounts of material for the same timing pulses. The amount of material dispensed 55 from nozzles, which may be in terms of drop volume, may vary by 10% or more from nozzle to nozzle for a given print head.
One way of compensating for variations in drop volume is to provide a separate timing circuit for each nozzle. This 60 approach, however, requires relatively expensive electronics and bulky cabling as each nozzle may have to be connected to its own drive circuit with independent timing. Using a relatively low-cost, off-the-shelf print head poses its share of problems because such a print head typically employs a 65 serially loaded firing register and a common timing circuit for all nozzles. Conventionally, a common timing circuit
does not allow for the use of a tuned timing pattern for each individual nozzle without adversely affecting print frequency.
In one embodiment, an integrated circuit (IC) fabrication material is dispensed from a print head by dividing its nozzles into several groups, and sequentially allowing each group to fire. The nozzles may be grouped based on the amounts of material they dispense. For example, the nozzles may be grouped by drop volume or drop mass.
In one embodiment, an IC fabrication material is dispensed on a substrate by controlling a firing sequence of a nozzle to promote merging of material on the substrate. The firing sequence may also be altered to take into account the firing sequence of adjacent nozzles.
These and other features of the present invention will be readily apparent to persons of ordinary skill in the art upon reading the entirety of this disclosure, which includes the accompanying drawings and claims.
DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically illustrates the operation of an exemplary ink jet print head.
FIG. 2 schematically shows a an integrated circuit (IC) fabrication system in accordance with an embodiment of the present invention.
FIG. 3(a) shows an example chart of drop volume distribution in accordance with an embodiment of the present invention.
FIG. 3(b) schematically illustrates an example grouping of nozzles in accordance with an embodiment of the present invention.
FIG. 3(c), which is a magnified view of the upper left hand corner of the chart of FIG. 3(A), schematically illustrates the tuning of nozzles for each group in accordance with an embodiment of the present invention.
FIG. 4 shows a flow diagram of a method of dispensing a material from a print head in accordance with an embodiment of the present invention.
FIG. 5 schematically illustrates an example print area in accordance with an embodiment of the present invention.
FIG. 6 shows an example firing table in accordance with an embodiment of the present invention.
FIG. 7 shows an example offset table in accordance with an embodiment of the present invention.
FIG. 8 shows a flow diagram of a method of dispensing a material from a print head in accordance with an embodiment of the present invention.
In the present disclosure, numerous specific details are provided such as examples of systems, components, and methods to provide a thorough understanding of embodiments of the invention. Persons of ordinary skill in the art will recognize, however, that the invention can be practiced without one or more of the specific details. In other instances, well-known details are not shown or described to avoid obscuring aspects of the invention.
FIG. 2 schematically shows a an integrated circuit (IC) fabrication system 200 in accordance with an embodiment of the present invention. System 200 includes a computer 204, a print head 210, a pedestal 202, and a reservoir 205. Pedestal 202 supports a substrate 201, which may be a