Resolving thermoelectric potentials during laser trimming of resistors
First Claim
1. A method for employing laser output to trim resistor material from a resistor to change an initial resistance value of the resistor to a nominal resistance value, wherein the resistor material has a surface area positioned between electrical contacts and is supported on a substrate, wherein laser output applied to the resistor material induces thermoelectric effects in the resistor that cause the resistor to exhibit an errant or transient resistance value that deviates from a true or steady state resistance value of the resistor that is measured during an absence of the laser output such that the applied laser output prevents an accurate measurement of the true or steady state resistance value immediately following the applied laser output, a method for reducing resistance value deviations caused by laser-induced thermoelectric effects, comprising:
- positioning probes of measurement equipment to be in communication with a single resistor or respective resistors from a set of resistors;
setting an applied current value from the measurement equipment to a reference or zero value;
directing respective sets of one or more evaluation pulses of laser output along respective simulation paths to apply heat to different respective locations on the surface areas of the single resistor or the respective resistors, the evaluation pulses causing insignificant change to the true or steady-state resistance value of the initial resistance value;
measuring voltage values across the single resistor or the respective resistors after the respective sets of evaluation laser pulses to obtain voltage deviation information for each of the different respective locations;
using the voltage deviation information to determine a preferred location on the respective surface areas of the respective resistors that exhibits minimal voltage deviation; and
directing trimming pulses of laser output along a trim path at the preferred location on the surface area of the single resistor or the preferred locations on the surface area of some or all of the set of resistors to remove resistor material from them to change their initial resistance value to a nominal resistance value to reduce thermoelectric resistance deviations induced by the laser output.
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Accused Products
Abstract
Thermoelectric effects that occur during laser trimming of resistors (20) are resolved by taking voltage measurements. The voltage attributed to laser heating on a resistor (20) during a low-power simulated trim (10) is used to determine a relatively thermal-neutral location (18) on the resistor (20). A trimming-to-value operation can then be performed on all like resistors (20). Voltage measurements can also be taken before and after every pulse in a trimming operation to establish thermal deviation information that can be used to offset the desired trim value against which resistor measurement values are compared. Spatially distant or nonadjacent resistors (20) in a row or column can also be trimmed sequentially to minimize heating effects that might otherwise distort resistance values on adjacent or nearby resistors (20).
28 Citations
35 Claims
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1. A method for employing laser output to trim resistor material from a resistor to change an initial resistance value of the resistor to a nominal resistance value, wherein the resistor material has a surface area positioned between electrical contacts and is supported on a substrate, wherein laser output applied to the resistor material induces thermoelectric effects in the resistor that cause the resistor to exhibit an errant or transient resistance value that deviates from a true or steady state resistance value of the resistor that is measured during an absence of the laser output such that the applied laser output prevents an accurate measurement of the true or steady state resistance value immediately following the applied laser output, a method for reducing resistance value deviations caused by laser-induced thermoelectric effects, comprising:
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positioning probes of measurement equipment to be in communication with a single resistor or respective resistors from a set of resistors; setting an applied current value from the measurement equipment to a reference or zero value; directing respective sets of one or more evaluation pulses of laser output along respective simulation paths to apply heat to different respective locations on the surface areas of the single resistor or the respective resistors, the evaluation pulses causing insignificant change to the true or steady-state resistance value of the initial resistance value; measuring voltage values across the single resistor or the respective resistors after the respective sets of evaluation laser pulses to obtain voltage deviation information for each of the different respective locations; using the voltage deviation information to determine a preferred location on the respective surface areas of the respective resistors that exhibits minimal voltage deviation; and directing trimming pulses of laser output along a trim path at the preferred location on the surface area of the single resistor or the preferred locations on the surface area of some or all of the set of resistors to remove resistor material from them to change their initial resistance value to a nominal resistance value to reduce thermoelectric resistance deviations induced by the laser output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A method for employing laser output to trim resistor material from a resistor to change an initial resistance value of the resistor to a nominal resistance value, wherein the resistor material has a surface area positioned between electrical contacts and is supported on a substrate, wherein laser output applied to the resistor material induces thermoelectric effects in the resistor that cause the resistor to exhibit an errant or transient resistance value that deviates from a true or steady state resistance value of the resistor that is measured during an absence of the laser output such that the applied laser output prevents an accurate measurement of the true or steady state resistance value immediately following the applied laser output, a method for reducing resistance value deviations caused by laser-induced thermoelectric effects, comprising:
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positioning probes of measurement equipment to be in communication with a resistor; setting an applied current value from the measurement equipment to a reference or zero value; directing low-power pulses of laser output along a simulation path to sequentially apply heat to multiple locations on the surface area of the resistor material; repeatedly measuring voltage values across the resistor after respective sequential sets of laser pulses to obtain voltage deviation information for some or all of the multiple locations; using the voltage deviation information to determine a preferred location on the surface of the resistor that exhibits minimal voltage deviation; and directing high-power pulses of laser output along a trim path at the preferred location on the surface area of the resistor or at the preferred location on any respective resistor on the same substrate or from a same batch of resistors to remove resistor material from the respective resistor to change its initial resistance value to a nominal resistance value to reduce thermoelectric resistance deviations induced by the laser output, the high-power laser pulses having higher power than the low-power laser pulses.
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35. A method for employing laser output to trim resistor material from a resistor to change an initial resistance value of the resistor to a nominal resistance value, wherein the resistor material has a surface area positioned between electrical contacts and is supported on a substrate, wherein laser output applied to the resistor material induces thermoelectric effects in the resistor that cause the resistor to exhibit an errant or transient resistance value that deviates from a true or steady state resistance value of the resistor that is measured during an absence of the laser output such that the applied laser output prevents an accurate measurement of the true or steady state resistance value immediately following the applied laser output, a method for reducing resistance value deviations caused by laser-induced thermoelectric effects, comprising:
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positioning probes of measurement equipment to be in communication with a single resistor or respective resistors from a set of resistors; setting an applied current value from the measurement equipment to a reference or zero value; directing respective sets of one or more evaluation pulses of laser output along respective simulation paths to apply heat to different respective locations on the surface areas of the single resistor or the respective resistors, the evaluation pulses having parameters that are insufficient to cause significant removal of resistor material; measuring voltage values across the single resistor or the respective resistors after the respective sets of evaluation laser pulses to obtain voltage deviation information for each of the different respective locations; using the voltage deviation information to determine a preferred location on the respective surface areas of the respective resistors that exhibits minimal voltage deviation; and directing trimming pulses of laser output along a trim path at the preferred location on the surface area of the single resistor or the preferred locations on the surface area of some or all of the set of resistors to remove resistor material from them to change their initial resistance value to a nominal resistance value to reduce thermoelectric resistance deviations induced by the laser output.
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Specification