Coating processes – Direct application of electrical – magnetic – wave – or... – Electromagnetic or particulate radiation utilized
Reexamination Certificate
2003-03-20
2004-12-28
Padgett, Marianne (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Electromagnetic or particulate radiation utilized
C427S561000, C219S121620, C219S121810, C219S121820, C219S121850
Reexamination Certificate
active
06835426
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for the manufacture of miniature structures. In particular, this invention directs itself to pulse-position synchronization for use in Direct Write processes.
Still further, the present invention relates to a method for pulse-position synchronization in which a target is initially exposed to a first pulse of energy. Subsequently a pause in the target exposure exists during which time the relative position between the target and the energy source is adjusted which permits a pause time for positioning the next area of the target which is to be exposed. Once positioning of the target has been achieved, the target is exposed to a second pulse of energy.
Additionally, the present invention relates to a technique for pulse-position synchronization in a fabrication tool which includes a target, a source of energy, a substrate, and control unit operatively coupled to the source of energy as well as the target and the substrate. The fabrication tool is operated in patterned “additive” and patterned “subtractive” modes of operation. In the “additive” mode of operation, the target is a material carrier element which has a deposition layer where predetermined areas are ablated in a patterned manner by pulses of energy generated by the source of energy (laser) under the control of a control unit. The depositable material from the deposition layer of the material carrier element is then deposited on a substrate within predetermined deposition regions corresponding to the ablated areas of the deposition layer. The control unit synchronizes the relative motion of the target, substrate and the source of energy in order to (1) expose fresh areas of the target to the laser pulse, (2) provide uniformity of the material deposition on the substrate, and (3) optimize the motion patterns. Thus, miniature structures in the nature of semiconductor chips, electrical and mechanical-electrical elements may be manufactured.
With respect to the “subtractive” mode of operation, the material carrier element is removed from the laser path, whereby the substrate is exposed to pulses of energy ablating the surface of the substrate in patterned manner for cleaning or trimming the substrate as well as for creating vias, channels, guides, through holes, etc.
BACKGROUND OF THE INVENTION
Miniature structures are becoming more widely used as technology advances and a plethora of electrical systems are used in miniaturization of common industrial and domestic appliances. Such structures may be found in TV sets, radios, vehicles, kitchen appliances, computers, etc. Due to the advantage of the use of miniature structures in such electrical systems, a large emphasis has been placed on the development of a wide variety of different manufacturing technologies for fabrication of miniaturized components.
Among others, a Direct Write technology has been developed and successfully applied which uses a laser beam for ablating a source of depositable material. The ablated depositable material from the source is then transferred and deposited at predetermined areas of a workpiece to create miniature structures thereon.
Additionally, a laser micromachining process has been developed which uses a laser beam to ablate predetermined areas of a workpiece to a predetermined depth in order to form vias, through holes, or miniature recesses. This type of process is also applicable to etching, trimming, or cleaning of the workpiece.
In both the Direct Write processes and the laser micromachining processes, coordination of motion between all elements of the system is important. Thus, coordination and control of substrate motion, laser beam scanning, or combinatorial relative motion thereof is of vital importance in the manufacturing process. Specifically, if laser power is maintained in a constant “on” mode during acceleration or deceleration of the relative motion of the substrate and the laser beam, a non-constant dose of a depositable material is delivered to the substrate. This interferes with deposition processes, resulting in locally varying thickness of the fabricated miniature structures.
Still further, the relative motion between the laser and the substrate must be conducted at a speed of relative motion, since excessive laser dwell may overheat and damage sensitive components already existing on the substrate. In the case of laser micromachining processes, variation of the depth of ablation may result which is unsatisfactory for applications where smooth structures with constant thickness or depth are required for optimum performance.
Commercial systems exist which address the problem of variations in laser exposure due to acceleration or deceleration of relative motion between the substrate and the laser beam. For example, the control unit (Aerotech PC-PSO Personal Computer Add-On board) monitors multi-axis motion and produces position synchronized electrical pulses capable of firing a laser at precise increments of travel. The interval can be software selectable for dynamic control of the deposition process or micromachining process. This control unit typically produces one pulse every time the relative position of the substrate changes by m microns, where m is a number that can be set in the software program that is used in conjunction with the control unit to control the substrate motion. When motion occurs in 2 or 3 dimensions, the control unit is normally capable of carrying out the necessary vector algebra to compute the linear change in position.
If the pulse produced by the control unit every n microns is used to trigger the pulsed laser, the separation between successive laser pulses on the substrate will be constant and variations in exposure of illuminated areas will be eliminated. This approach to control the laser firing is normally called pulse-position synchronization. Since all of the processes in the controller and laser needed to fire the laser pulse occur in microseconds, there is no need to slow or stop the relative motion to achieve position-synchronized pulsing of the laser.
As an example, the system may provide generation of laser pulses each 0.25 micrometer of travel in any direction. Such commercially available systems permit bit mapping laser pulses by clocking-out trigger pulses in accordance with a predetermined pattern while scanning the laser or changing a substrate position where an analogous technique is used in laser printer technology.
Although pulse-position synchronization is routinely used in laser micromachining to remove material, it has not previously been applied to the forward transfer technique for material deposition. Without pulse-position synchronization the number of forward transfer events per unit of displacement varies as the substrate accelerates and decelerates, resulting in thickness variations of the deposited material.
Further, failure to provide precise coordination of the relative motion of the target and the laser beam with activation-deactivation of the laser radiation in conventional systems may cause the ablation of unintended areas of a target, or alternatively deposition of a depositable material on unaimed or unwanted regions. In these cases, the laser pulse may impinge not only onto an area of interest but also onto neighboring regions, thus deteriorating the quality and performance of manufactured miniature structures.
Still further in such conventional systems during the Direct Write processes, successive laser pulses impinge at the source of the depositable material (target ribbon) at areas which may be not close enough to each other which results in inefficient use of the depositable material. If the laser pulses impinge onto already ablated area of the source of the depositable material, the depositable material is not delivered to a required area on the substrate which reduces the yield of high quality miniature structures.
Another disadvantage results from impingement of the laser beam on previously ablated areas of the source of a depositable material which causes unwanted direct
Christensen C. Paul
Duignan Michael T.
Gordon Susan
Gordon Susan
Padgett Marianne
Potomac Photonics, Inc.
Rosenberg , Klein & Lee
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