KR100826633B1 - Method and system for high-speed, precise micromachining an array of devices - Google Patents

Abstract

Methods and systems for high speed and precise micromachining of device arrays have been described, thereby providing accuracy and improved processing efficiency, such as the accuracy of register trimming. Many resistance measurements are defined by the use of unmeasured cuts, the use of non-sequential collinear cuts, the use of spot pan-out parallel cuts, and the use of retrospective scanning techniques to speed up the straight cuts. Out-of-order cutting is also used for the thermal effect and the measured cuts are used for improving accuracy. The test voltage is controlled to prevent resistor damage.

Micromachining

Description

METHOD AND SYSTEM FOR HIGH-SPEED, PRECISE MICROMACHINING AN ARRAY OF DEVICES

This application claims the benefit of US Provisional Application No. 60 / 368,421, filed Mar. 28, 2002, entitled "Laser-Based Micromachining Methods and Systems and Application to High Speed Laser Trimming of Chip Components and Similar Configurations." Claiming. This application is also a partial continuing application of US application Ser. No. 10 / 108,101, filed Mar. 27, 2002 entitled "Their Processes and Devices for Modeling Devices, Methods and Systems," and claims priority to these. do. The application is currently published in US 2002/0162973. It is assigned to the assignee of the present invention, co-inventor of US Pat. No. 6,341,029, entitled "Method and Device for Shaping Laser Beam Intensity Profile by Dithering," the entire contents of which are incorporated herein by reference. This application also relates to US Pat. No. 6,339,604, "Pulse Control in Laser Systems," assigned to the inventor. This application is also pending and filed on March 27, 2002, issued 10 / 107,027, published in US 2002/1070898, and also treated by one or more target materials within the “area assigned to the inventor. High-speed, laser-based methods and devices ".

The present invention relates to a method and system for high speed, precise micromachining of device arrays. The present invention also relates to the field of register trimming, and more particularly to the trimming of surpentine registers on thin film block bodies. Laser resistor trimming includes laser-processing cuts in the region of resistive material between conductors.

Resistor trimming (also trimming and micromachining of other electronic components and circuits) has evolved in the laser sector for over 20 years and is now being used to tune circuits in thick film, thin film and other electronic technologies. LIA HAND BOOK OF LASER MATERIALS PROCESSING's 2001 “Trimming” book contains articles that describe some aspects of laser trimming in Chapter 17, pages 583-588. 1A-1C of this application are taken from their publication. FIG. 1A shows the current flow line of an untrimmed resistor, and FIG. 1B shows the laser trimming effect on the current flow line. FIG. 1C summarizes some results (stability, speed, tolerance) for various register geometries and truncation types.

The following examples of US patents 6,510,605, 6,322,711, 5,796,392, 4,901,052, 4,853,671, 4,647,899, 4,511,607, and 4,429,298 are those relating to laser trimming.                 

U.S. Patent 4,429,298 relates to many aspects of meander trimming. Basically, the meander register is formed by a sequential plunge cut and the final trim cut is made horizontally from the final plunge to the register edge. The expression "gradually" refers to making plunge cuts on the register surface alternately from one end, determining the maximum or minimum plunge cut length, determining the threshold of resistance of the plunge cut for trim cutting, Faster cutting speeds are determined for lunge cutting, and the process flow is determined through various resistance and cutting length tests.

There is a continuing need for improved high speed micromachining such as precision trimming in all ranges from thick films to wafer trimming.

It is an object of the present invention to provide an improved method and system for high speed, precise micromachining of device arrays.

In carrying out the above and other objects of the present invention, a method for high speed, precise micromachining of device arrays is provided. Each of the devices has at least one measurable characteristic. The method comprises the steps of: a) selectively micromachining a device in an array to change a measurable characteristic value; b) optionally deferring the step of micromachining; c) selectively micromachining at least one or more other elements in the array to change the measurable characteristic value while the selectively micromachining step is postponed; d) resuming the delayed step of selective micromachining to change the measurable characteristic of the device until the measured value is within the desired range.

The device may be a resistor.

The register may be a film register.

Optionally micromachining may be performed with at least one laser beam that cuts the device.

The method may further comprise measuring at least one measurable characteristic of the at least one device to obtain a measurement.

The method may further comprise comparing the measured threshold value with the measured value to obtain a comparison value, and micromachining at least one other device based on the comparison value.

The method may further comprise selectively micromachining at least one or more other devices based on the measured values.

The method may further comprise determining not to measure the measurable characteristic of the at least one other device based on the measured value.

The method may be laser trimming the array of resistors at high speed with precision, and one of the measurable characteristics may be a resistor.

Each step of selectively micromachining may optionally include removing material.                 

An array may contain at least one row and at least one column.

Optionally, at least one of the micromachining steps may be performed with multiple focused laser pulses to irradiate multiple devices substantially simultaneously.

Optionally, at least one of the micromachining steps may be performed with multiple focused laser pulses. The method may further comprise distributing the focused laser pulse.

Distributing may include creating a distribution pattern with a plurality of laser beams and focusing the laser beams.

Laser trimming can make a series of interdigited cuts in the region of resistive material between the resistor conductors.

Optionally, at least one of the micromachining steps may include positioning a laser beam at each location of the devices to be micromachined, and selectively irradiating at least a portion of each device to be micromachined with at least one or more laser pulses. .

At least one of the selectively micromachining steps generates a laser beam and relatively positions the laser beam to move in a first direction within a field of the array, and at least one or more devices in the field with at least one laser pulse. And optionally examining the portion of.

The method generates a laser beam and positions the laser beam relative to move in a second direction substantially opposite to the first direction in the field, the second portion of the at least one device in the field with at least one laser pulse. May optionally include examining.

At least one of selectively micromachining may include relatively positioning the laser beam to generate a laser beam and to move the first scanning pattern across the device, superimposing a second scanning pattern on the first scanning pattern, and And irradiating one or more devices with one or more laser pulses.

The second scanning pattern may be a retrograde scan, wherein the at least one laser pulse scan rate irradiating at least one device is lower than the corresponding scan rate of the first scan. Laser energy may be concentrated on at least one or more devices for a time period longer than the period of time associated with only the first scanning pattern, thereby improving throughput.

The second scanning pattern may include a jump from the first element to the second element.

The step of selective microscanning can be performed with a number of laser pulses, and at least one or more pulses can have an energy in the range of 0.1 micro Joules-25 pre Joules.

The measured value may be a measured temperature value.

The devices can be substantially the same.

Moreover, in carrying out the objects of the present invention and still other objects, a system for high speed, laser based, precise micromachining of device arrangements is provided. Each device has one or more measurable properties. The system has a pulsed laser subsystem. The optical subsystem is coupled to a pulsed laser system to selectively irradiate a portion of the device with a laser pulse. The controller is connected to the subsystem to control the subsystem: a) selectively micromachins the elements in the array to change the measurable characteristic values, b) defers optional micromachining, and c) While micromachining is postponed, selectively micromachine one or more other devices in the array to change the measurable characteristic values, and d) measure the measurable characteristics of the device until the characteristic values are within the desired range. Resume optional micromachining to make changes.

The optical system can include a beam refractor and a beam refraction controller for controlling the beam refractor to scan the laser beam along a first scanning pattern that includes each element to be micromachined.

The system can further include a measurement subsystem for measuring one of the measurable characteristics of the at least one device.

Micromachining can be laser trimming, the arrangement is an array of registers, and the measurement subsystem can be a probe array.

The optical system may include a second beam refractor to superimpose a high speed, second scan pattern over the first scan pattern, thereby improving throughput of the system.

The controller may be coupled to the subsystem to generate a trimming order for at least one device that reduces the temperature of the device while the subsystem is micromachining.

The above and other objects, features and advantages of the present invention will become apparent from the following description as the best mode for carrying out the invention in connection with the accompanying drawings.

1A-1B are schematic diagrams showing current flow lines before and after laser trimming, respectively;

1C is a chart showing the effect of various cuts on some trim parameters;

2A is a schematic diagram of a chip register arrangement arranged in rows and columns, illustrating the results of using a laser trimming step in accordance with an embodiment of the present invention.

FIG. 2B is a block diagram flowchart showing a trimming step corresponding to FIG. 2A.

3 is a block diagram flowchart illustrating the trimming operation of FIGS. 2A and 2B in the system of the present invention.

4A is a schematic of a chip register arrangement arranged in rows and columns, illustrating the results of using laser trimming according to another embodiment of the present invention.

FIG. 4B is a block diagram flowchart showing a trimming step corresponding to FIG. 4A.

5 is a block diagram flow chart illustrating the trimming operation of FIGS. 4A and 4B in the system of the present invention.

6A is a schematic diagram of a laser trimming system that may be used in at least one embodiment of the present invention.

FIG. 6B is a schematic diagram of a register having morphological characteristics, in particular edges, to be measured, using data obtained with the system of FIG. 6A.

FIG. 7 is a graph showing the position of a laser beam versus time during scanning of a register array in one embodiment, where a rapid scan by a solid state refractor selectively forms a cut in either FIG. 2 or FIG. 4 at an increased speed. Superimposed on the electromechanical linear scan.

8 is a schematic diagram of a system for sending multiple focusing beams to at least one or more registers to increase the trimming speed.

9 is a schematic diagram of a system for providing multiple beams to at least one register in a laser trimming system.

Fast meander trimming process

In resistor trimming, the cuts cause a current to flow along the resistive path through the resistive material. Precise control and adjustment of the cut size and shape changes the resistance to the desired value as shown in FIGS. 1A-1C. Typically, chip resistors are arranged in rows and columns on a substrate. 2A shows the arrangement in which the columns of registers R1, R2, ..... RN are to be processed. The probe array with the probe 200 and indicated by the arrow in FIG. 2A is in contact with the conductor of the resistor row. Matrix switching allows addressing the contacts 202 (e.g., contacts of R1) to the first pair of conductors, and a series of cuts and measurements are performed to change the resistance between the conductors to a desired value. When the trimming of the register is completed, the matrix is switched to the second set of contacts of the next element of the column (e.g. R2), and the trimming process is repeated. When the trimming of the entire row of registers R1... RN is completed, the contact between the contacts and the probe array is stopped. The substrate is then positioned relative to other rows, the probe array is contacted, and the second row is processed in the same way as the previous row.

Trimming of the meandering thin film resistor will include laser processing to make cuts in the region of resistive material between the conductors, for example as shown in FIG. 1C. Interposed cuts cause current to flow through the resistive material along a meandering path that wraps around the cut. This geometric shape allows for the creation of a wide range of resistors with a single area film / conductor layout. The method described above proceeds with the order of meandering cuts, such as measuring one register and moving to the next register.

Referring to FIG. 2A, the initial laser position of any cut is indicated by reference numeral 205, and the beam positioner allows the direction of the beam to follow a linear path through the resistor material. According to the present invention, the new paradigm measures the resistance by trimming the leg of the first resistor (e.g. trimming 204 of R1). If the resistance is below the preset limit, a similar collinear trim is made along the other resistors R2 ... RN in the column. The entire trim along the row is indicated by reference numeral 210 in FIG. 2A and the corresponding block 220 is in FIG. 2B. In at least one embodiment of the present invention, a subset of the registers can be measured to determine the density of the thin film along the substrate, but if the density of the thin film is known, one The measurement may be sufficient.

A collinear truncation group along the next row of registers is made in the same manner as shown by reference numeral 211 of FIG. 2A and block 221 of FIG. 2B, and register RN will be trimmed initially. The process is repeated as indicated by reference numerals 212-213 of FIG. 2A to correspond to blocks 222-223 of FIG. 2B. If a measurement appears to exceed the limit, trimming the R1..RN row is switched to the next register (block 214 and reference 214).
Continue measuring each register to trim to the desired value before doing so.

Both the limit of the number of measurements and the maintenance of the trim trace in the same line increase the trim speed.

 The flowchart of FIG. 3 shows the steps corresponding to FIGS. 2A-2B and additional processing steps used in the trimming system (eg indexing and loading).

In at least one embodiment, the truncation step may be performed based on predetermined information. By way of example, in some types of resistors, a series of first elements may be truncated before the resistance is measured, and the order may be determined by a predetermined parameter of the resistor (e.g., geometry) or known film properties (e.g. sheet resistance). Based on. Similarly, multiple unmeasured truncations may be determined in a learn mode in the first register (including, for example, one or more measurements or repeated measurements). The number of non-trim cuts is determined based on measurements and material properties. In at least one embodiment multiple unmeasured truncations may be calculated.

For example, four cuts can be made without measurement. Referring to FIG. 4A, an initial condition 410 is shown and the probe is in contact with the contact 202 of the column as in FIG. 2A. Referring to FIG. 4B, an initial condition is defined in block 420. By way of example, FIGS. 4A-4B show an embodiment of a trimming process wherein the initial four cuts 411 are made without any measurement. As shown in FIG. 4B, block 421 defines a number of predetermined truncations (eg, four) without measurement based on at least one or more pre-trimmed values or conditions. The scan path to complete the four cuts is indicated by reference numeral 405. The first register R1 in the column is trimmed at reference numeral 406 and measured to determine whether a target value has been reached. If the target value has not been reached, the remaining registers R2 ... RNs are truncated (e.g. without measurement) as defined by reference 412 and block 422.

The processing is repeated so that trimming 407 of the RN begins, as defined by block 423 and indicated by reference numeral 413, and the cutting of R [N-1] up to R1. Thus, the direction in which R1 or RN is trimmed is reversed, and each remaining register R2, ... RN or R [N-1] ... R1 is truncated if the target value has not been reached. After R1 or RN reaches the target value, the final step is executed. As indicated by reference numeral 414 and defined in block 424, each register is concatenated and trimmed sequentially.

The flowchart of Fig. 5 defines the steps corresponding to Figs. 4A-4B and further processing steps (e.g. including the steps of indexing and loading) within the trimming system.

In one embodiment, the predetermined information is obtained by use of repetitive measurements, and pre-trim values are provided. The values may be specified by the operator, the process, or obtained in other ways. The software can use or specify pre-trim target values so that the applied test voltage or current is controlled. This property is useful to prevent high voltages sufficient to cause component damage due to extensive resistance changes associated with meander trimming. When using a high speed resistor measurement system in one embodiment of the present invention, the voltage applied to the resistor for the measurement is reduced for an initial low resistance cut, thereby reducing the potential for damage to the current and through resistors. Subsequent cuts are made and the measured voltage rises as the resistance increases.

2A and 2B The typical trimming and cutting sequence of FIGS. 4A and 4B can be modified to account for variations in material properties, process parameters and tolerances.

For example, in at least one embodiment of the present invention, an additional step may be used when the measured trim cut reaches a target value and the length is within a predetermined limit of the maximum allowable cut length. Within limits, variations in material properties require additional cuts, leaving some trim cuts below target values.

In the first mode, the trim cuts are made sequentially in the row of elements and the position of the element that does not reach the target value is stored. By the next trim cut, the elements left in the memorized position are trimmed to the target value.

In the second mode, based on the length of the trimmed first element, the cut length is reduced to prevent reaching the target value, and unmeasured cuts are made to complete the row. Subsequent trim cuts bring all elements of the row to the target value.

In the third mode, the previous at least one cut length for one element is modified to prevent the next cut from falling within the limit conditions.

In at least one embodiment, additional steps may be used when the value of the measured trim cut is within a preset limit of the target value. Within the limits, variations in material properties can all use unmeasured cuts and leave some elements exceeding target values.

In the first mode, the trim cuts are made sequentially in the rows of elements and the positions of the elements that fall short of the target value are stored. The remaining elements in the stored position by the next trim cut are trimmed to the target value.

In the second mode, based on the value measured in the first element, the cut length is reduced to prevent reaching the target value, and a non-measured cut proceeds to complete the heat. Subsequent trim cuts bring all elements of the row to the target value.

In the third mode, the previous at least one cut length for one element is modified to prevent the next cut from falling within the limit conditions.

Experimental data show that the throughput is improved over the conventional single register trim technique, as shown in Figures 2-4 for all registers in a column. By way of example, the approximate results are shown in the table below.

            32 register rows, 20 cuts per register   Laser Q-Speed (KHZ)  Single Resistor Trim (sec)  Trim in seconds          5          39      28         10          27      16         20          20      10

As the number of rows of resistors increases, the measurement decreases, and the time for final (i.e., precision) trimming increases, the overall trim rate increases.

Moreover, each resistor has additional time to recover from the energy generated by the laser. The order of the cuts may be determined to manage temperature changes within the element (eg, reduction of the maximum urea temperature during cutting). For example, referring to FIG. 4A, the sequence 405 can be reversed, where a set of cuts are made starting near the center of the element and proceeding to the element ends proximate the conductor and the probe. In other order, an appropriate order may be used (for example, any order of non-contiguous cutting with advantages for temperature control). Preferably, the second element can be cut before further measuring steps.

The range of resistance changes to meandering cuts varies from about 10 powers of magnitude (eg, X10), typically 10 powers of power (100X), and about 500X for current materials.

Laser trimming system

In at least one embodiment of the present invention, the laser trimming system may first be calibrated using a method as described in US Patent No. 4,818,284, "Method of Calibrating a Laser Trimming Element." The '284 patent controls the laser beam positioning element to move the laser beam to the desired nominal laser position over the substrate area, and imprints a mark (e.g. cutting a line) on the medium to establish the actual laser position. It describes the calibration of a laser trimming element by scanning the imprinted mark to detect the actual laser position and comparing the desired nominal position with the actual laser position. Preferably the laser beam operates at one wavelength and the mark is scanned with a detection element operating at another wavelength. The detection element detects a field covering a part of the entire substrate region portion and determines the position of the mark in the field. The '284 patent also describes determining where the beam position is in relation to the camera field of view.

Other measurement techniques can be used alone or in combination with the '284 patent. For example, "Laser Correction Device and Method" in US Pat. No. 6,501,061 describes a method of determining scanner coordinates for accurately positioning a focused laser beam. The focused laser beam scans a region of interest (eg a gap) on the work surface by a laser scanner. The position of the focused ray beam is detected by the photodetector when the focused laser beam appears through a predetermined interval of time or space or a gap in the working surface. The detected position of the focused laser beam is used to generate the scanner position relative to the beam position data based on the position of the laser scanner when the focused laser beam is detected. Beam position data for the scanner position can be used to determine the center of the gap or scanner position coordinates corresponding to the desired position of the focused laser beam.

Preferably, following system calibration, including calibration of a number of other system components, at least one or more substrates having elements to be trimmed are loaded into the trimming station.

Referring to FIG. 6A, partially cited from the '284 patent, the improved laser trimming system may be an infrared laser 602, typically having a wavelength range of approximately 1.047-1.32 microns and positioning the laser beam along the optical path 604. The laser beam 603 is output to and through the device 605 and to the substrate region 606. For application to the trimming of thin film arrays, the desired wavelength of about 0.532 microns can be obtained by doubling the output frequency of the IR laser using a variety of known and commercially available techniques.

The laser beam positioning element 605 includes a pair of mirrors and galvanometers 607 and 608, each of which is available from the assignee of the present invention. The beam positioning element 605 passes through the lens 609 (which may be telecentric or non-telecentric, preferably achromatic at two wavelengths) to the substrate region 606 throughout the field. 603). The X-Y galvanometer mirror system provides angular coverage for the entire substrate, provided sufficient precision is maintained. In other words, various positioning elements may be used to provide relative motion between the substrate and the laser beam. For example, biaxial precision steps and translators, outlined at 617, can be used to position the substrate in the field of galvanometer 607 (608) (eg, in the X-Y plane). The laser beam positioning element 605 moves the laser beam along two vertical axes, thereby providing that the laser beam 603 is positioned two-dimensionally across the substrate region 606. Galvanometers 607 and 608 associated with each mirror cause the beam to move along the x or y axis, respectively, under the control of the computer 610. An illumination element 611, such as a halogen light or LED, generates visible light to illuminate the substrate region 606.

A beam splitter 612 (partially reflected mirror) is positioned within the optical path 604 to direct light energy reflected back from the substrate region 606 along the path 604 to the detection element 614. The detection element 614 includes a digital camera 615, which may be a digital CCD camera (e.g., color or monochrome), and a frame grabber 616 (or a digital frame buffer installed in the camera), the frame grabber being a substrate area. (606) Digitize the image input from the television camera 615 to obtain pixel data representing some two-dimensional image. The pixel data is stored in the memory of the frame grabber 616 or transmitted directly to the computer 610 for processing, for example on a high-speed link.

The beam positioning system may include other optical elements such as a computer controlled optical system that adjusts the laser spot and / or automatically focuses the laser spot at a location on the substrate.

In applying the invention to thin film trimming of a resistor array, at least one thin film array is supported by a circuit board. The calibration data obtained as mentioned above is an automated machine vision algorithm for locating the elements of the array (e.g., register R1) and measuring one position of at least one geometrical characteristic of the element 620 in FIG. 6B. It is preferably used in combination with. For example, the property may be a horizontal edge or a vertical edge 622 (eg, edge parallel to the Y direction) found by pixel data analysis in memory using one of a number of edge detection algorithms available. 621 (eg, edges parallel to the X direction). The edges may include multiple edge measuring elements along the entire perimeter of one register, edges from multiple registers of a sample or array of edges. The width of the register is then determined, which is generally a predetermined percentage of the width, which can be used to define the cut length. Preferably, the edge information is obtained automatically and used together with the calibration data to control the respective cut lengths in the rows R1 ... RN, for example. Other measurement algorithms, for example image correlation algorithms or blob detection methods, may be used if appropriate.

Calibration can be applied at one or more points along the cut. In at least one embodiment at least one cut start point will be corrected with calibration data.

Preferably, the starting point and length of the multiple cuts in Figures 2 and 4 will be corrected.

Most preferably, the starting point length of all cuts in FIGS. 2A and 4A will be corrected.

 In one embodiment, the first register (eg R1 or RN) will be calibrated and the corresponding correction will be applied to all registers in the column (eg R1... RN).

Fully automated is preferred. However, a semi-automatic algorithm with operator intervention may also be used, for example a galvanometer is positioned such that the array element 620 is in the field, and then sequentially positioned so that the beams interact along the element, and the intensity profile intensity profile (or derivative of intensity) is observed on the display 630 by the operator.

The use of calibration information for coordinate adjustment within the alignment area is very important for improving the precision of laser beam positioning without deteriorating yield. The measurement of register width and alignment data are useful both for adjusting the length of the cut and for correcting deviations from the linearity and non-orthogonality of the array with respect to the scanner's X, Y coordinate system. Using calibration data for geometry correction is particularly suitable for use in laser trimming systems having one or more linear translation stages.

Geometric shape correction does not necessarily replace other useful system design features, including f-theta lens linearity, fan beam compensation, and the like. The tolerance stack-up of the system can be used to determine trade offs between cutting calibration positions based on predicted position errors. Only one is calibrated and aligned when fanning out the beam, especially at large intervals across many registers. For example, when the spacing between registers is relatively large, a single cut may be corrected or aligned. The error in the position obtained is expected for each element and will be partially mitigated by system design, f-theta linearity, and fan spread compensation. Dense cutting of transverse sectors is expected to produce less error than longitudinal sectors.

Better throughput-optical technology

In at least one embodiment of the present invention, throughput can be further improved by an effective scan rate improvement utilizing one or more of the following techniques.

Another increase in the processing speed by collinear trim can be obtained by a faster jump of the trim gap between the register rows. One such gap 216 is shown in FIG. 2A. Referring to FIG. 7, in at least one embodiment of the present invention, the Acousto-Optic Beam Deflector (AOBD) is a galvanometer that can scan across rows at a constant speed 702. When the sawtooth scan pattern 701 is superimposed. During trimming the AOBD scans with retrograde motion 703 and provides a quick jump 704 to the next cut between trims. This allows the galvanometer to scan at a constant speed and minimizes the contribution of the jump in the overall processing time.

The use of acoustic-optical refractors in combination with galvanometers for speed improvement is known in the art. For example, US Pat. No. 5,837,962 shows an improved device for heating, melting, evaporating, and cutting a workpiece. Two-dimensional acoustic-optical refractors provide an approximately five-fold improvement in manufacturing speed.

US Pat. No. 6,341,029, which is hereby incorporated by reference in its entirety, discloses an embodiment having several components that can be used in a complete system when implementing the invention in retrograde mode for speed increase. Is showing in five. In the '029 patent, acoustic-optical refractors and galvanometers with associated controllers are shown to dither the CW beam for laser patterning. Also see lines 47 and 4 of the third column of the '029 patent for further details on the system configuration.

The configuration of the '029 patent can be applied immediately using useful techniques for providing modification of the optical component and scan control profile to effect retrograde scanning in the present invention, preferably involving additional hardware calibration.

In another embodiment of the present invention, trimming in parallel on a meander register can be completed in parallel with multiple spots along the row. Fan-out grating or other multi-beams. A generator is used to make the spot array so that two or more spots are formed and aligned corresponding to the register pitch along the row. For example, US Pat. No. 5,521,628 describes the use of diffractive optical elements to mark multiple portions simultaneously. The multiple beams may be lower power beams from more powerful laser sources or beams combined from multiple laser sources. The scan system scans multiple beams and forms spots across a plurality of registers simultaneously through a common scan lens. The trim process is similar to the single spot method where two or more cuts proceed in parallel while performing a non-measured cut step. When the limit is reached, the system switches to single spot mode, trimming each register in series.

Similarly, a trim in tandem on a meander register can be completed in parallel with multiple spots formed on the target to make parallel cuts. A generator that creates a scalloped unfolding grating or other multi-beam is used to make the spot arrangement and two or more spots are formed, with the spots aligned with respect to the element at predetermined intervals between the cuts. If a predetermined number of cuts (eg as shown in Fig. 4A) has been performed, in one embodiment, the number of passes can be reduced by 50% (e.g. one pass in each direction d). . This embodiment may be most useful when register process variations and tolerances are well established. The grating can optionally form multiple spots or a single spot within the optically switched path.

Published US Patent Application 2002/0162973 describes a method and system for generating multiple spots for processing semiconductor links for memory recovery. Various modifications to the lens system and the refractor system may be used to generate multiple spots for use in the present invention.

In one embodiment, a single laser pulse is used to trim up to two registers at the same time (eg, one or two truncations). Referring to FIG. 8, two focused spots 801, 802 are formed on two cuts by spatially dividing a single parallel laser beam 803 into two diverging parallel laser beams 804, 805. Fine tuning of the differential frequency controls the separation of the spots. It is known in the art to use acoustic-optical devices to spatially divide a beam for material processing purposes. For example, the abstract of Japanese Patent No. 53152662 shows one device for drilling fine holes using a multi-frequency refractor having multi-frequency with a selectable frequency f1 ... fN.

The laser 806 in FIG. 8 is pulsed at a predetermined repetition rate. The laser beam travels to the acousto-optic modulator (AOM) opening through a relay optical element 807 that forms an intermediate image of the laser beam wiast. The AOM, according to Bragg's diffraction equation, preferably controllably generates two slightly divergent parallel first order diffraction laser beams and controls the energy of each laser. AOM is driven by two frequencies f1 and f2, where f1 = f0 + df, f2 = f0-df, and df is a small percentage of the original RF signal frequency f0. The angle between the two beams is roughly equivalent to the Bragg angle for f0 multiplied by 2 (df / f0). The AOM modulates the signal amplitudes of the two frequency components f1 and f2 in the RF signal 812 and controls the energy of each laser beam by adjusting beam cross-coupling.

After exiting the AOM 808, the beam goes through an optional beam rotation control module 809, which rotates the beam 90 degrees toward either the X or Y axis. In one embodiment, a prism is used for this rotation, but many rotation techniques, well known by the associated US Patent Publication No. 2002/0170898, can be used.

The beam then passes through a set of optical elements to position the beam waist and sets the size of the beam to be appropriate for the zoom optical element and the objective lens 810. The zoom optics also change the angle between the two beams so that the angle between the two beams exiting the AOM 808 must be adjusted by setting the zoom to achieve the desired spot separation in the focal plane. Next, the laser beam enters the objective lens 810 providing a pair of focusing spots 801 and 802 on two registers. The two spots are separated by approximately the same distance as the angle between the two beams times the focal length of the lens 810. The retrograde and parallel methods can be combined for trimming in parallel on the meander register. For example, the beam is scanned by the AOBD and then split into pairs to scan the field. Two adjacent registers are trimmed at the same time and the jump is from register N to the next pair of registers, N + 2.

Alternatively, or in conjunction with a two-dimensional refractor, a pair of spots can be made in a direction orthogonal to the meandering scan direction. For example, with relatively simple control and programming of one-dimensional AOBD, the refractor can be used to make at least two of the four beams used to make four cuts simultaneously, as shown in FIG. 4A (using output power control). . Thus, the scan time for cutting can be reduced by 50%. As a result of programmable deflection, AOBD may be preferable to scaffold developing gratings. Multiple spots can also be made during rough or precise trimming as needed.

FIG. 9 schematically illustrates an exemplary embodiment of an improved trimming system with the module 901 of FIG. 8 added for either retrograde scanning, parallel processing, or a combination thereof. For example, the signal 902 from the computer 610 can be used to control the AOBD or other solid state refractor 808 in one or more axes and, if installed, to control the beam rotation module 809. Module 901 may include relay optics 87 and other beam shaping components. Preferably, at least one AOBD may be used with an RF generator that provides control signals 812 from the computer 610, for example, for greater flexibility and ease of use.

Techniques for forming elongated or elliptical spots may be used in the present invention to further increase throughput and quality. Improvements in trimming speeds associated with the shaping of spots are described together in ongoing US Patent Publication No. 2002/0170898.

Various alternatives may be used in at least one or more embodiments of the present invention to enhance system performance and ease of use. For example, alternatives include, but are not limited to the following.

1. The system may provide adjustment of the size and / or focus of a computer controlled spot. U.S. Patent No. 6,438,071, assigned to the assignee of the present invention, shows an optical subsystem that provides both spot size control and dynamic focusing for laser-based memory recovery on both sides.

2. Another alternative is to control the beam energy with a variable beam attenuator. The attenuator may be an acoustic-optical refractor (or modulator). Neutral density filters or polarization-based attenuators can be used and can be adjusted manually or automatically. In US Pat. No. 6,518,540, a suitable variable attenuator is shown by way of example, with a rotating half waveplate and polarity sensitive beam splitting elements.

3. It will be appreciated that the width of the pulse can be varied using methods known to those skilled in the art and can be varied at the energy repetition rate of the q-switched laser, especially at high repetition rates. For dynamic trimming where measurements are made between pulses, it is desirable to maintain a substantially constant pulse energy. A method for controlling pulse energy is described in the 6,339,604 patent, which corresponds to a precise specific time period when the resistance value reaches a preset target value, when the trimming speed is decreased (e.g. Large time intervals) to reduce energy changes at target values.

4. In at least one embodiment, a diode-activated, frequency-doubled YAG laser is used to trim the resistor array. The output wavelength of 532 nm results in low drift, absence of microcracks and negligible heat affected zones when compared to other wavelengths. Pulse widths of about 25-45 ns are preferred, typically less than 30 ns. The preferred maximum laser repetition rate is at least 10 KHz. Much smaller pulse widths than usual for thick film systems provide thin film material removal at relatively high repetition rates. Preferably, the maximum available pulse energy and the high repetition rate at the reduced pulse width will be taken into account the losses associated with the diffractive optics (eg grating or AOBD) such that a plurality of spots are provided.

5. The laser can be focused to an approximate, diffraction limited spot size. Spot sizes are typically no greater than 30 microns, preferred spot sizes are no greater than 20 microns, most preferred spot sizes are in the range of 6-15 microns, for example in the range of 10-15 microns.

6. In the illustrated embodiment of the present invention, the meandering cut is illustrated as a series of parallel cuts. However, it should be understood that the application of the present invention is not limited to parallel cutting. It is contemplated that trimming or micromachining to make a plurality of non-cross cuts with reduced number of measurements is within the scope of the invention.

7. Moreover, embodiments of the present invention are not limited to thin film resistor measurements, but are applicable to other micromachining applications where physical properties are measurable. The measurement is not limited to electrical measuring elements, but may be temperature sensing (eg using an infrared sensor), stress, vibration or other characteristics.

Although the embodiments of the present invention have been shown and described in the drawings, they are not intended to describe all possible forms shown and described in the present invention. It is to be understood that the words used in the specification are not to be limited, and various changes may be made without departing from the spirit and scope of the invention.

Claims (30)

A system in which at least one device is supported on a substrate and at least one of the above-described electrical devices having at least one measurable characteristic is trimmed on a laser basis for high speed and precision. A laser system having one or more laser pulses, each laser pulse generating a pulsed laser output with a pulse energy, visible laser wavelength and pulse duration at a constant repetition rate, A beam delivery subsystem that receives pulsed laser output and The one or more laser output pulses having a selected visible laser wavelength, pulse duration, pulse energy and spot radius are connected by controlling the beam delivery and laser subsystem to selectively irradiate one or more of the devices in connection with the beam delivery and laser subsystem. A controller for laser trimming one or more of the devices by selectively removing material from the one or more devices while preventing microcracking of one or more of the devices, The beam delivery subsystem One or more beam deflectors for positioning one or more laser pulses relative to one or more of the devices to be trimmed; An optical subsystem for focusing one or more laser pulses having a visible laser wavelength into one or more spots with a non-uniform intensity profile along a small spot diameter and direction of 6 microns to 15 microns into the field of the optical subsystem. System. The method of claim 1, Spot is a system characterized by limited diffraction. The method of claim 1, The laser subsystem includes a q-switch, frequency doubling solid-state laser having a fundamental wavelength in the range of 1.047 microns to 1.32 microns, the visible output wavelength being a frequency doubling wavelength in the visible wavelength range of 0.5 microns to 0.7 microns. System characterized. The method of claim 1, The spot diameter is from 6 microns to 10 microns. The method of claim 1, An optical subsystem is a system that is achromatic aberration at two or more wavelengths wherein at least one wavelength is a visible wavelength. The method of claim 5, An illuminator illuminating the substrate region with radiant energy at one or more illumination wavelengths; And a detection element sensitive to radiant energy at one of the illumination wavelengths, wherein one of the at least two wavelengths is a visible laser wavelength and the other is an illumination wavelength. The method of claim 1, The optical subsystem is a telecentric optical subsystem comprising a telecentric lens. The method of claim 1, Positioners for positioning one or more elements supported on the substrate relative to and within the field of the optical subsystem, focusing one or more laser pulses and irradiating the one or more such devices into spots having a small diameter of 6 microns to 15 microns. System comprising a. The method of claim 8, The focused spot diameter is from 6 microns to 10 microns at any location within the field of the optical subsystem. The method of claim 1, And a calibration algorithm for precisely controlling the dimensions of the extent of material removal by adjusting the coordinates of the material to be irradiated in one or more of the devices. The method of claim 1, Further comprising a machine vision subsystem comprising a vision algorithm for locating and measuring one or more geometrical features of one or more of said devices, said vision algorithm including edge detection and said one or more geometrical features are edges of one or more devices, wherein The edge is used to determine the width of one or more devices to form a size for material removal. The method of claim 1, An array of electrical elements of thin film is trimmed into the system, The controller Means for selectively micromachining the array element to change the value of the measurable characteristic; Means for deferring selective micromachining to defer selective micromachining; Means for selectively micromachining one or more other array elements to change the value of the measurable characteristic; And means for resuming selective micromachining to change the measurable characteristic of the array element until the value of the measurable characteristic is within the desired range. The method of claim 1, And further comprising a user program and a software program coupled to the interface and the controller, the software program accepts preliminary trim target values for one or more of the devices to limit the electrical output applied to the one or more devices based on these values. System. In the method of laser-based high-speed, precise laser trimming of one or more electrical elements supported on a substrate, and having one or more measurable characteristics, Having at least one laser pulse, each laser pulse generating a pulse laser output having a pulse energy, a visible laser pulse, and a pulse duration at a constant repetition rate; One having a wavelength, energy and spot diameter by selectively irradiating one or more of said electrical elements with one or more laser pulses focused at one or more spots having a non-uniform intensity profile along a small spot diameter and direction of 6 microns to 15 microns Laser trimming one or more of the devices while causing the at least one laser pulse to selectively remove material from the one or more of the devices, thereby preventing microcracking in the one or more of the devices. The method of claim 14, The microcracking obtained by removing material from at least the first portion of one or more of the devices is comparable to the microcracking obtained when removing material from one or more devices or portions of the second device using one or more other wavelengths beyond that range. Characterized by negligible levels. A method of laser trimming one or more devices having measurable characteristics, Providing a laser trimmer comprising a pulsed laser system, a beam delivery system, and a controller; Providing a control program that, when executed, causes the controller to control the system to prevent microcracking of one or more of the devices while causing the one or more laser output pulses of the pulsed laser output to laser trim the one or more of the devices. , The pulsed laser output has a repetition rate of more than 10Khz and a visible laser wavelength, and the beam delivery system generates a focused spot having a diameter of 6 microns to 15 microns from the one or more laser output pulses and a non-uniform intensity profile along the direction. And an optical subsystem. A method of high speed, precision micromachining of an array of devices having one or more measurable properties, Selectively micromachining the elements of the array to change the value of the measurable characteristic; Optionally deferring the step of micromachining; Selectively micromachining one or more other elements of the array to alter the value of the measurable characteristic while deflecting the selectively micromachining; And resuming optionally deferring micromachining to change the measurable characteristic of the device until the characteristic value is within the desired range. The method of claim 17, Measuring one measurable characteristic of at least one of said devices to obtain a measured value and comparing said measured value with a predetermined threshold to obtain a comparison value and micromachining at least one other device based on said comparison It further comprises a method. The method of claim 17, Optionally micromachining is performed with one or more multiple focused laser pulses to irradiate multiple devices simultaneously. The method of claim 17, Optionally one or more of the micromachining steps generates and positions a laser beam to move in a first direction in the field of the array and selectively irradiates at least a portion of one or more of the devices in the field with one or more laser pulses. Including steps The mitromachining method generates a laser beam and positions it to move in a second direction opposite the first direction in the field and selectively irradiates at least a second portion of the one or more of the devices in the field with one or more laser pulses. The method further comprises the step of. The method of claim 17, Optionally at least one of the micromachining steps generates a laser beam and positions it to move across the device in a first scan pattern, superimposing a second scan pattern on the first scan pattern, and at least one laser Illuminating the one or more devices with a pulse, The second scan pattern is a retrograde scan, wherein the scan rate of one or more pulses irradiating the one or more of the devices is lower than the corresponding scan rate of the first scan pattern such that the energy is longer than the period associated only with the first scan pattern. The throughput is improved by concentrating on the device.  A system for fast and precise micromachining of an array of devices having at least one measurable characteristic based on a laser, A pulsed laser subsystem; An optical subsystem coupled to the pulse laser system for selectively irradiating a portion of the device with a laser pulse; A controller connected to the subsystem and controlling them, The controller selectively micromachines the elements of the array to change the value of the measurable characteristic, defers selective micromachining, and changes the measurable characteristic value while the selected micromachining is deferred. Selectively micromachining another device and restarting selective micromachining to change the measurable characteristic until this value is within a predetermined range. The method of claim 22, The optical subsystem includes a beam deflector and a beam deflector controller that controls the beam deflector to scan the laser beam along a first scan pattern that includes a respective element to be micromachined. The method of claim 22, And a measurement subsystem for measuring one of the measurable characteristics of at least one of said devices. The method of claim 24, Micromachining is laser trimming, the array is an array of resistors, and the measurement subsystem is a probe array. The method of claim 23, wherein And the optical subsystem includes a second beam deflector to improve the throughput of the system by superimposing a high speed second scan pattern on the first scan pattern. The method of claim 22, A controller coupled to the subsystems, the subsystems being controlled to generate a trimming order for at least one of the devices that reduces device temperature during micromachining. delete delete delete

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