BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
a illustrates the operation and results obtained with various conventional functional trimming systems that utilize IR laser outputs; FIG. 1a is a top plan view, partially broken away, of a portion of an integrated circuit depicting resistors having a resistive film path between metal contacts; FIG. 1b is a block diagram of a prior art automated dynamic-trim system and device under test; FIG. 1c is a simplified schematic diagram of a multiplier cell the +Y input is switched between a specified +voltage pair while a trimming laser increases the resistance of either R1 or R2, wherein FIGS. 1b and 1c correspond to FIGS. 3 and 4, respectively, of chapter 3 of the handbook entitled “Nonlinear Circuits Handbook” published by Analog Devices Inc. in 1976; FIG. 1d is a top schematic view, partially broken away, of a die of a semiconductor wafer; there are thin film resistance elements as well as metal links (i.e., copper, gold or Al etc.) on the die; another possible combination of devices to be processed would include thick film-based devices;
FIG. 2 is a graph which illustrates the relation between the minimum relative energy required for trimming as a function of pulse width;
FIGS. 3
a-3d are graphs which illustrate a relationship of absorption and photoelectric response for certain semiconductor materials, and also the absorption of certain materials over a wide wavelength range; the graph of FIG. 3a is taken from FIG. 9.7 of Moss, “Optical Properties of Semiconductors” and illustrates spectral response of silicon containing boron and indium; FIG. 3b is taken from U.S. Pat. No. 4,399,345 to Lapham, et al. and illustrates absorption of silicon as a function of wavelength; the graphs of FIG. 3c show typical responsivity curves of silicon and indium gallium arsenide-based detectors versus wavelength as illustrated in the '995 and '272 patents; FIG. 3d is taken from the publication of Liu, et al. (hereinbelow) and illustrates the effect of wavelength and doping concentration on the damage threshold of Si, with 150 fs pulses;
FIG. 4
a is a top plan schematic view of a conventional laser trim with a relatively large HAZ; FIG. 4b is a top plan schematic view of an exemplary ultra-fast laser trim with little or no HAZ; FIG. 4c is a combined graph and side view of a resistor which illustrates a kerf size and profile to be obtained with an embodiment of the present invention; a focused laser spot and a pulse width sub-diffraction limited kerf size are shown;
FIG. 5
a is an example of a sequence of laser material processing pulses;
FIG. 5
b is an enlarged graph of power (y-axis) versus time (x-axis) for one of the laser material processing pulses of FIG. 5a generated in accordance with one embodiment of the present invention;
FIG. 6 is a schematic block diagram illustrating a system corresponding to an one embodiment of the invention;
FIG. 7 schematically illustrates a system corresponding to another embodiment of the present invention; (the system may include a short wavelength mode-locked or fiber laser having a pulse width of a one picosecond or less);
FIGS. 8
a-8b are oscilloscope traces; the trace of FIG. 8a shows an output voltage of a typical voltage regulator device undergoing laser functional processing in accordance with one embodiment of the present invention; laser output pulses with ultrashort pulse width may be directed at a resistor of an activated voltage regulator; the straight line of the oscilloscope trace of FIG. 8b depicts the output voltage of the voltage regulator and shows no momentary dips in output voltage; therefore, measurements can be made immediately after laser impingement, or at any time before or after laser impingement to obtain a true measurement value of the output voltage;
FIG. 9
a is a schematic diagram illustrating an exemplary photodetection/amplifier device which may be both trimmed and measured in accordance with the present invention; and
FIGS. 9
b and 9c illustrate systems for trimming and testing the device of FIG. 9a.
Patent Application
20070215575
