KR20030079981A - Resistor trimming with small uniform spot from solid-state UV laser - Google Patents

Abstract

Uniform laser spots, such as from imaged Gaussian output 118 or clipped Gaussian spots of less than 20 @ m in diameter, can be used for thin film or thick film resistor trimming to substantially reduce microcracking. Such spots can be created at a removable, non-thermal UV laser wavelength to reduce the shift in HAZ and / or TCR.

Description

Resistor trimming with small uniform spot from solid-state UV laser}

Background of the Invention

Conventional laser systems are typically used to process targets, such as electrically resistive or conductive films of passive electrical device structures, such as film resistors, inductors, or capacitors of circuits formed on ceramic or other substrates. Used. Laser processing to trim the resistance values of the film resistors may include passive, functional or activated laser trimming techniques, as described in detail in US Pat. No. 5,685,995 to Sun et al.

The following background is presented here by way of example only for thick film resistors. 1 is an isometric view of a workpiece 10, such as a conventional thick film resistor 10a, forming part of a hybrid integrated circuit device, and FIG. 2 shows a conventional laser output pulse 12 It is an elevation view of the cross section side which shows the thick film resistor 10a to receive. 1 and 2, a conventional thick film resistor 10a is typically deposited on portions of the top surfaces of metallic contacts 16 and thick film layers of ruthenium or ruthenium oxide material extending therebetween. (14). Layer 14 and metal contacts 16 are supported on a ceramic substrate 18 such as alumina. Modern ruthenium based thick film pastes have been optimized to stabilize after laser trimming with a 1.047 micron (μm) Nd: YLF laser or a 1.064 μm Nd: YAG laser.

With particular reference to FIG. 1, the resistance value of resistor 10a is mostly a function of the intrinsic resistance of the resistor material and its geometry, including length 22, width 24, and height 26. Since they are difficult to screen with exact tolerances, thick film resistors are intentionally screened with a resistance lower than the nominal values and trimmed up to the desired values. Multiple resistors 10a having approximately the same resistance values are made in relatively large batches and then perform trimming operations to remove the increases in resistor material until the resistance is increased to the desired value.

With particular reference to FIG. 2, one or more laser pulses 12 substantially eliminate the total height 26 of the resistor material in the spot dimensions 28 of the laser output pulses 12, and the overlapping spots. The dimensions 28 form a kerf 30. A simple or complex pattern can be trimmed through the resistor material of resistor 10a to better adjust its resistance value. Laser pulses 12 are typically applied until resistor 10a meets a predetermined resistance value.

3 is an equally sized view of a portion of a prior art resistor 10 showing two convenient common pattern trim paths 32 and 34 (separated by dashed lines) between metal contacts 16. The "L-incision" path 32 represents a typical laser induction change. In the L-cut path 32, the first removal strip 36 of resistor material is removed in a direction perpendicular to the line between the contacts that adjust the course to the resistance value. A second removal strip 38 perpendicular to the first removal strip 36 can then be connected to remove it to better adjust the resistance value. The "surpentine cut" pathway 34 represents another common type or laser control. In the serpentine incision 34, the resistor material is removed along the removal strips 40 to increase the length of the membrane path 42. Removal strips 40 are added until the desired resistance value is reached. Removal strips 36, 38 and 40 are typically the width of a single cuff 30 and weighted " nibbling " of the train of overlapped laser pulses 12 removing almost all resistive material in the described patterns. ". Thus, when the trimming operation is complete, the cuffs 30 are "clean" so that their bottoms are substantially free of resistor material, and thus the substrate 18 is fully exposed. Unfortunately, the creation of conventional clean cuffs 30 requires some laser collision of the substrate 18 surface.

As in the newer 0402 and 0201 chip resistors, the smaller the film resistors, the smaller the spot sizes are required. Use conventional optics and see at 1.047 μm and 1.064 μm laser wavelengths while maintaining a standard working distance (required to avoid removal debris and clean probes) and a sufficient depth of field (eg, uneven ceramic) Getting small spot sizes is an ever increasing challenge. The need for more accurate resistance values also leads to searching for tighter trim tolerances.

IEEE Transactions on Parts, Hybrids, and Packaging, June 1972, by Albin and Swenson; Vol. A paper entitled "Laser Resistance Trimming from the Measurement Point of View" in PHP-8, No. 2, describes measurement devices and advantages using a solid state laser for trimming thin film resistors.

Chapter 7 of the NEC Education Manual describes the challenges encountered when using an infrared (IR) Gaussian beam to trim resistors, especially thick film resistors. Thermal affected areas (HAZ), cracks, and drift are some of the problems that are solved.

A paper by Swenson et al., IEEE Transactions on Components, Hybrids, and Manufacturing Technology, December 1978, entitled "Reducing Post Trim Drift of Thin Film Resistors by Optimizing YAG Laser Output Characteristics," reduces HAZ and post-trim drift. The use of a green (532 nm) solid state laser Gaussian output to trim thin film resistors is described.

U.S. Patent Nos. 5,569,398, 5,685,995 and 5,808,272 to Sun and Swenson are not conventional, such as 1.3 μm for trimming films or devices to avoid damage to the silicon substrate and / or reduce calibration time during functional trimming. Describe the use of laser wavelengths.

International Publication No. WO 99/40591 to Sun and Swenson, published August 12, 1999, describes the concept of resistor trimming with an ultraviolet (UV) Gaussian laser output. Referring to FIG. 4, they use a UV Gaussian laser output to remove the area 44 of the surface of the film resistors to maintain their surface area and protect their high frequency response characteristics. By maintaining the depth 46 of the resistor film in the intentionally trimmed regions 44, they avoid having to clean the cuff bottoms 48 and substantially eliminate the interaction between the laser output and the substrate 18. Thus eliminating any problems that could have been caused by this interaction. Unfortunately, surface removal trimming is a relatively slow process because the laser parameters must be carefully reduced and controlled to avoid complete removal of the resistor film.

Microcracking is another challenge associated with the use of a solid state Gaussian laser beam to trim resistors. Microcracks, which often occur in the center of the cuff 30 on the substrate, may extend into the resistor film causing potential drift problems. Microcracks may also cause a shift associated with the temperature coefficient of resistance (TCR). This microcracking is better delivered in newer 0402 and 0201 chip resistors fabricated on thinner substrates 18, having a typical height or thickness of about 100-200 [mu] m compared to that of conventional resistors. Microcracking of these thinner substrate resistors may propagate and may result in catastrophic failure or physical breakdown of the resistor, particularly along the trim cuff 30, during subsequent adjustments.

Thus, improved resistor trimming techniques are desirable.

Related Applications

This patent application is obtained on priority from US Provisional Application No. 60 / 266,172, filed February 1, 2001 and US Provisional Application No. 60 / 301,706, filed June 28, 2001.

Technical field

FIELD OF THE INVENTION The present invention relates to laser trimming, and more particularly to laser trimming thick film or thin film resistors with a uniform spot from a solid state laser.

1 is a fragmentary equal sized drawing of a thick film resistor.

2 is a cross-sectional view of a thick film resistor receiving a laser output that removes the entire thickness of the resistor material.

3 is a fragmentary equally sized diagram of a resistor showing two common prior art trim paths.

4 is an equally sized view of a thick film resistor having a surface removal trim profile.

5 is an elevational and partial schematic view of a simplified side view of an embodiment of a laser system used to trim films in accordance with the present invention.

6A-6C illustrate a sequence of simplified radiation profiles of a laser beam as it changes through various system components of the laser system of FIG. 5.

7A-7D illustrate typical substantially uniform square or circular emissivity profiles.

FIG. 8 shows a graphical comparison of ideal influence distributions in the aperture plane for clipped Gaussian output and output formed with images at some typical transmission levels under typical laser process parameters.

9 is a graph of tapper ratio as a function of working surface position relative to the nominal image plane.

10 is a graph of diameter as a function of working surface position with respect to the nominal image plane.

11 is an electron micrograph of a cuff showing microcracks formed on a substrate of a resistor trimmed by a Gaussian beam.

12 is an electron micrograph of the cuff showing the absence of significant microcracks formed in the substrate of the resistor trimmed by uniform spots.

Summary of the Invention

It is therefore an object of the present invention to provide an improved system and / or method for solid state laser trimming.

Another object of the present invention is to provide spot sizes smaller than 20 μm for trimming smaller chip resistors, such as resistors of 0402 and 0210 chips.

Part of the microcracking may be caused by the high intensity center of the Gaussian beam spot in the same way that the Gaussian beam may be responsible for damaging the center of the blind via in laser drilling operations (even if the targets and substrates are other materials). Can be. International Publication No. WO 00/73013, published December 7, 2000 by Dunsky et al. Describes a method of generating and using an image-shaped Gaussian beam to provide a uniform laser spot, which is particularly useful for via drilling operations. .

Swenson, Sun and by Dunsky, in July 2000, on the 30th August SPIE's four-day ^{45 th Annual Meeting, The international Symposium} on Optical Science and Technology of the title: thesis of "Laser Machining in Electronics Manufacturing A HistoricalOverview " Describes an improved surface scanning method using a 40 μm uniform spot formed by a lens described by Dickey et al. US Pat. No. 5,864,430.

The present invention preferably employs uniform spots, such as imaged Gaussian spots or clipped Gaussian spots, having a diameter of less than 20 μm and transmitting a constant energy across the bottom of the cuff 30, and thus of microcracking Volume and difficulty are minimized. Where appropriate, such spots may be created at a removable, non-thermal UV laser wavelength to reduce HAZ and / or shift in the TCR. These techniques can be used for both thin and thick film resistor processes.

Additional objects and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments, which proceeds with reference to the accompanying drawings.

Detailed description of the preferred embodiments

Referring to FIG. 5, a preferred embodiment of the laser system 50 of the present invention preferably comprises a Q-switch diode comprising a solid state latent such as Nd: YAG, Nd: YLF, or Nd: YVO ₄ A pump (DP) solid state (SS) UV laser 52. The laser 52 is preferably 355 nm (triple Nd: YAG frequency), 266 nm (quadruple Nd: YAG frequency), or 213 nm (quintuple) with harmonic generating UV laser pulses or preferentially a TEM ₀₀ spatial mode profile. Output 54 at a wavelength such as Nd: TAG frequency). Those skilled in the art will appreciate that other wavelengths and their harmonics are available from the other listed accents. For example, preferred YLF wavelengths include 349 nm and 262 nm. Those skilled in the art will also understand that although most lasers 52 do not send a perfect Gaussian output 54, for convenience, Gaussian is generally used herein to describe the radiation profile of the laser output 54. Laser cavity arrangements, harmonic generation, and Q switch operation are all well known to those skilled in the art. Details of typical lasers 52 are described in International Publication No. WO99 / 40591 to Sun and Swenson.

Other solid state laser wavelengths may be used, such as green (eg 532 nm) or IR (eg 1.06 μm or 1.32 μm), but are removable and relatively thermal, which reduces post trim drift. UV laser wavelengths are preferred for trimming because they do not. The UV laser wavelength also uniquely provides a smaller spot size at the surface of the workpiece 10 than provided by IR or green laser wavelengths using the same depth of field.

UV laser pulses 54 may be passed through various known lenses, including beam extender and / or ascending lens components 56 and 58 located along beam path 64. UV laser pulses 54 are then directed to produce uniform pulses or output 72, preferably through a forming and / or imaging system, which is then preferably scanned beam 80 by beam position system 74. ) Is directed to the target uniform output 72 (the scan lens is also commonly referred to as a "second imaging", focusing, incision, or objective lens), such as thick film resistors 10a or thin film resistors. The laser target position 82 is desired in the image plane on the workpiece 10. The uniform output 72 is preferably cut (clipped), focused and clipped, formed or formed and clipped.

Imaging system 70 preferably uses an aperture mask 98 positioned between the optical element 90 and the aggregation or collimating lens 112 and at or near the focus of the beam waist generated by the optical element 90. do. The opening mask 98 preferably blocks any side lobes that are undesirable with the beam to represent a circular or other shaped spot profile that is continuously imaged on the working surface. In addition, varying the size of the opening can control the edge sharpness of the spot profile to create a smaller, sharper edge strength profile that should enhance alignment precision. In addition, the shape of the opening can be precisely circular or can be changed to rectangular, ellipse, or other non-circular shapes that can be advantageously used for resistor trimming.

Mask 98 may comprise a material suitable for use at the wavelength of laser output 54. If the laser output 54 is UV, then the mask 98 may comprise, for example, a UV reflective or UV absorbing material, but preferably a high UV in multiple layers of fused silica or other UV resistant coating in a UV step. The reflective coating can be formed from a dielectric material such as sapphire coated. The opening of the mask 98 may optionally protrude outward at its light emitting surface.

The optical element 90 may include beam forming components such as a focusing lens or an aspheric lens, a refractive double-sided lens, a biased double-sided lens, or a diffractive lens. Some or all of these may be used with or without the aperture mask 98. In one preferred embodiment, the beam forming component comprises a diffractive optic element (DOE) capable of performing complex beam forming with high efficiency and accuracy. The beam forming component not only transmits the Gaussian emissivity profile of FIG. 6A to the nearly uniform emissivity profile of FIG. 6BB, but also focuses on an output 94 formed of a determinable or specific spot size. The formed radiation profile 94b and the previously described spot sizes are designed such that downstream of the optical element 90 occurs at the design distance Z ₀ . Although a single element DOE is preferred, the DOE may include a number of discrete elements such as the phase substrate and transmission elements described in Dickey et al. US Pat. No. 5,864,430, which also describes techniques for designing DOEs for beam forming purposes. Those skilled in the art will understand that it can.

6A-6C (collectively FIG. 6) show a sequence of simplified radiation profiles 92, 96, and 102 of a laser beam that is varied through various system elements of laser system 50. 6B-6BC show simplified radiance profiles 96a-96c of output 94 (94a, 94b, and 94c, respectively) formed as a function of distance Z to Z ₀ ′. Z ₀ ′ is the distance at which the formed output 94 has its flatst emissivity profile shown in the emissivity profile 96b. In a preferred embodiment, Z ₀ ′ is close to or equal to the distance Z ₀ .

Referring back to FIGS. 5 and 6, a preferred embodiment of the formed imaging system 70 prior to the opening mask 98 downstream of the beam forming component, low Gaussian radiation into the formed (and focused) pulses. One or more beam forming components that transform the output 94b with the profile 92 or the nearly uniform “best hat” profile 96b, or in particular the collimated pulses 60 with the super Gaussian emissivity profile. Include. 6B shows a typical emissivity profile 94a with Z <Z ₀ 'and FIG. 6BC shows a typical emissivity profile 94c with Z> Z ₀ '. In this embodiment, lens 112 includes an imaging lens useful for suppressing diffraction rings. Those skilled in the art will appreciate that a single imaging lens component or multiple lens components may be used.

The forming and imaging techniques described above are described in detail in International Application No. WO 00/73013, published December 7, 2000. The relevant portions of the specification of Dunsky's corresponding US Patent Application No. 09 / 580,396 on May 26, 2000, are incorporated herein by reference.

7A-7D (collectively FIG. 7) illustrate typical substantially uniform emissivity profiles generated by Gaussian beam propagation through DOE as described in US Pat. No. 5,864,430. 7A-7C show square radiation profiles and FIG. 7D shows a cylindrical radiation profile. The emissivity profile of FIG. 7C is “transformed” and shows higher emissivity at those edges towards its center. One skilled in the art can design the beam forming components 90 to provide a change in other emissivity profiles that may be useful for certain applications, and these emissivity profiles are typically a function of their distance from Z ₀ '. Will be appreciated. Those skilled in the art will preferably use a cylindrical radiation profile as shown in FIG. 7D for the circular opening 98; Cubic radiance profiles would be desirable for square openings; It will be appreciated that the properties of the other beam forming components 90 will be tailored to the shapes of the other openings. For example, many straight lines pointing towards it through trimming applications may use a modified cubic emissivity profile with square openings in the mask 98.

Beam position system 74 preferably uses a conventional locator used in laser trimming systems. This positioning system 74 typically has one or more stages that move the workpiece 10. Positioning system 74 may be used to move laser spots of output 118 formed in an overlapping manner to form cuffs 30 along trim paths 32 or 34. Preferred beam positioning systems include Electro Scientific Industries, Inc. It can be found on ESI's Model 2300, Model 4370, or the soon to be released Model 2370 Laser Trimming Systems, commercially available from of Portland, Oregon. Other location systems may be substituted and are well known to those skilled in the laser art.

Examples of preferred laser systems 50 that include many of the system components described above are Model 5200 laser systems or Electro Scientific Industries, Inc. UV laser (355 nm or 266 nm) is used in a series of other devices manufactured by of Portland, Oregon. Those skilled in the art, however, will understand that any other laser type with a Gaussian beam intensity profile (prior to imaging or formation as described herein), other wavelengths such as IR, or other beam extension factors may be used.

The laser system 50 preferably comprises: an ultraviolet wavelength between about 180-400 nm; Average power densities greater than about 100 mW, preferably greater than 300 mW; Spot size diameters or spatial major axes greater than about 5 μm to about 50 μm; Repetition rate greater than about 1 kHz, preferably greater than about 5 kHz or higher than 50 kHz; Temporal pulse widths shorter than about 100 ns, preferably about 40-90 ns or less; A scan speed of about 1-200 mm / sec or faster, preferably about 10-100 mm / sec, and most preferably about 10-50 mm / sec; And a laser system output 114 having the desired parameters of typical resistor trimming windows, which may include a byte size of about 0.1-20 μm, preferably 0.1-10 μm and most preferably 0.1-5 μm. have. Preferred parameters of the laser system output 114 are selected in an attempt to thermal environment or other unwanted damage to the substrates 18. Those skilled in the art will appreciate that these output pulse parameters are independent and indicated by the required performance.

Those skilled in the art will also appreciate that although the spot area of the laser system output 114 is preferably circular or rectangular, other simple shapes, such as ellipses and rectangles, can be used and even optically complex shapes form the desired aperture shape of the mask 98. It will be appreciated that an appropriate selection of elements 90 is possible. Preferred spot areas for laser trimming, in particular UV laser trimming, are preferably smaller than about 40 micrometers in diameter, more preferably smaller than about 20 micrometers in diameter, and most preferably smaller than about 15 micrometers in diameter. Those skilled in the art will appreciate that since the spot size of the UV laser output is smaller than the spot size of a conventional laser trimming output, and because the uniform output 72 allows the cuffs 30 to have straight uniform walls or edges, therefore, a smaller HAZ, It will be appreciated that the resistors 10a may be trimmed to tighter tolerances than possible tolerances for conventional cuff trimming techniques.

One difference between the Gaussian output 54 and the imaged output 118 is that the Gaussian output 54 has a higher energy density at its center, which may increase microcracking and other undesirable damage to the ceramic substrate 18. Or “hot spot,” whereas pulse 94 illuminates the opening of mask 98 uniformly at all points. The imaged output 118 thus facilitates the formation of cuffs 30 having or on the ceramic substrate 18 having a very flat and uniform bottom 48, which flatness and uniformity are undeformed Gaussian. Not possible with output 54. In addition, since the uniform shape of the pulse 94 substantially eliminates the possibility of creating a hot spot in the bottom center of the cuff 30, the imaged output 118 also has unwanted damage to the underlying substrate 18. It is also possible to clean the resistor material from the bottom edges of the cuffs 30 more completely without the risk of the damage, thus minimizing the amount and damage of the microcracks. The trimming speed can also be increased with the output 118 formed into an image that can be obtained with an unaltered Gaussian output 54. Since the potential "hot spot" damage can be eliminated, the imaged output 118 can be applied to a larger laser output than it can be a Gaussian, thus trimming faster at byte size, repetition rate, and beam movement speed. Can be adjusted appropriately.

Although clipped Gaussian spots may advantageously be used alternatively via Gaussian output 54, substantially more energy will have to be sacrificed to achieve more desired uniformity with output 118 formed into an image. The imaged output 118 also provides cleaner bottom edges and faster trimming speeds than performing clipped Gaussian output. 8 shows a comparison of ideal influence profiles in the aperture plane for the formed output 94b with clipped Gaussian output at some typical transmission levels under typical laser processing parameters. The influence levels on the workpiece 10 are the same as the aperture influence levels multiplied by the squared imaging de-expansion factor. In one example, the effects at the opening edge are about 1.05 J / cm ² and 0.60 J / cm ² or less for the formed output 94b and clipped Gaussian output, respectively. Thus, in the workpiece 10, the effects at the edges (cuff edges) of the imaged spot are about 7.4 and 4.3 J / cm ² for the imaged output 118 and clipped Gaussian output, respectively. The speed in typical resistor materials can be eliminated and typically varies between center and edge influence levels. As a result, the processing of each cuff 30 can be completed at fewer pulses with a faster scanning speed, or with larger byte sizes (or smaller pulse overlaps) with an imaged output 118, To increase.

An example of a method for trimming to an imaged output 118 according to these considerations of the present invention is described below. The impact across all imaged spots can be maintained at 90% of the value in unacceptable ceramic penetration or damage occurrences, F _damage , for example. For example, acceptable ceramic transmission to thick film resistors is typically less than 10 μm, preferably less than 5 μm. The resistor material is then removed under conditions that will not cause damage such as severe microcracking. In contrast, with a clipped Gaussian beam at T = 50%, the center of the spot can be maintained at this influence, and for the edges it will only be at 45% of F _damage . Alternatively, the spot edge can be maintained at 90% of the F _damage , and in the center will be at 180% of the damage threshold effect causing sufficient damage. Since each pulse removes a lot of material, maintaining the edges of the imaged spot at high impact may be the resistor material to be cleaned from the cuff edges with smaller laser pulses. Thus, the trimming throughput of the output 118 formed into the image can be much larger than that of the clipped Gaussian output.

Additionally, if it is possible to clean the resistor material from the bottom edges of the faster cuffs 30 as described above, the imaged output 118 may also be substantially cuffed with a uniform shape of the pulse 94. By eliminating the possibility of creating a hot spot at the bottom center of 30, it is possible to more thoroughly wash the resistor material from the bottom edges of the cuffs 30 without risk of damage to the underlying ceramic substrate 18.

For cuff quality, the imaged output 118 of the present invention also provides for very precise laser spot geometry and a better tapper that minimizes efficiency at Gaussian or clipped Gaussian output and throughput rates higher than those available. This allows for sharper edges than can be used with Gaussian output 54. The formation of more precise edges and uniform energy across the bottom of the cuffs 30 provides better predictable trimming results, including enhanced repeatability and positional precision for smaller target areas.

9 shows the ratio of cuff bottom width to cuff top width as the functional working surface position for the nominal image plane, z = 0. With reference to FIG. 9, the nominal image plane is in a position where the cuffs 30 are most tapper free, with the sharpest defined top edges. The position values of z indicate having the workpiece 10 positioned farther from the system lens than planes below the nominal image plane, ie the distance of separation with z = 0. The 3σ error bar is shown for reference because the floor width measurements are different from what was actually measured. The largest bottom / best ratio is at the image plane with z = 0. In the throughput range of ± 400 μm, the bottom / best ratio is always greater than 75% at the highest throughput.

10 shows the cuff width as a function of work surface position with respect to the nominal image plane, z = 0. As the workpiece 10 is moved back onto the nominal image plane, the average cuff top width steadily increases. For locations below z = 0, the top width is fairly maintained at 400 μm below the image plane. 3σ widths are generally within ± 3 μm of the mean value except z = + 300 μm and z = -300 μm. In comparison, the mean value for the bottom width decreases steadily below the nominal image plane from above positions. Since the width of the cuff bottom is significantly different than the cuff best size to adjust, the bottom width is shown for reference only. Statistical processing controls techniques that can be applied to the laser system 50 and thus applied as a feature of cuff bests.

The data in FIGS. 9 and 10 suggest some approaches for managing the depth of issues of focus for processing intensity. If one wishes to maintain a constant cuff top width through varying material thickness and machine conditions, it would be advantageous to set the process to a working surface located just below the nominal image plane at z = + 200 μm. This will produce an area of ± 200 μm of z-variable that can be adapted with very little impact on the highest diameter. If, on the other hand, it is more desirable to maintain a constant cuff bottom / best diameter ratio, it may be better to set the treatment with the workpiece 10 positioned exactly in the nominal image plane. This ensures that the bottom / best ratio will be reduced no more than 5% through the z range of at least ± 200 μm. The viability of these approaches depends on whether other cuff characteristics are within acceptable limits as the workpiece 10 is removed from the nominal image plane.

Further, the beam forming components 90 generate pulses with the modulated emissivity profile shown in FIG. 7C, which is the outer dashed lines 130 clipped to facilitate removal of the resistor material along the outer edges of the cuff 30. Can be selected, thus improving the tapper. The present invention allows tapper ratios greater than 80% at maximum throughput without unwanted damage to the ceramic substrate 18, with tapper ratios greater than 95% (for low aspect ratio cuffs 30) being greater than 95%. It is possible without unwanted damage to 18. Tapper ratios better than 75% may be possible for the smallest cuff widths from about 5-18 μm wide at the top of the cuff of the deepest cuffs 30 with a conventional lens. Higher tapper ratios are another evidence of cuff bottom uniformity, although the tapper ratio is typically extended to affect the cuff widths on the small resistors 10a and is not seriously considered in many other trimming operations.

The trimming techniques described herein can be used for both thick and thin film resistor processing applications as described in any references located in the background of the present invention, including spatial depth trimming. For thick film resistors, especially ruthenium oxide on ceramics, including 0402 and 0201 chip resistors having a ruthenium layer height or thickness less than about 200 μm, cuffs with the preferred trimming standard having a minimum amount of penetration into the ceramic substrate 18. It is to remove all ruthenium in (30). These preferred cuffs 30 are washed so that the ceramic material is evenly exposed and the bottom of the cuffs 30 is “cleaned”. Such cleaning often results in internal penetration into the ceramic to a thickness of about 0.1-5 μm and often at least 1 μm. The imaged output 118 may provide such clean or clean cuffs 30 without creating severe microcracking. UV is particularly desirable for treating resistor materials on ceramics, and other wavelengths may be used.

Although UV wavelengths can be used, IR wavelengths, in particular about 1.32 μm, can be used for active or optoelectronic devices in applications that include functional trimming, especially for trimming materials such as NiCr, SiCr, or TaN from silicon substrates. It may be a preferred wavelength to use a uniform spot for trimming.

Those skilled in the art will appreciate that the uniform spot trimming techniques described herein may be applied to single resistors, resistor arrays (including those on snapshots), voltage regulators, capacitors, inductors, or other apparatus requiring any trimming operation. It will be appreciated that it can be used. Additionally, uniform spot trimming techniques may be used for applications where surface removal trimming or substrate penetration is desired, as well as other applications where the imaged output 118 does not penetrate the substrate 18.

11 and 12 illustrate the differences in microtracking between resistor 10a (FIG. 11) trimmed with a UV Gaussian beam and resistor 10a (FIG. 12) trimmed with a UV uniform (imaged) beam. Electron microscopes. Referring to FIG. 11, resistor 10a was trimmed to UV Gaussian output 54 with an average power of 0.6 W at a repetition rate of 14.29 kHz at a trimming rate of 30 mm / sec with a byte size of 2.10 μm. 30a shows various microcracks corresponding to microcracks 140, a substantially wide cuff edge 150a, and deep penetration into the ceramic substrate 18 at the center of the cuff 30a. Referring to FIG. 12, resistor 10a was trimmed to an output 118 formed of a UV image with an average power of 2.86 W at a repetition rate of 8 kHz at a trimming rate of 32 mm / sec with a byte size of 4 μm. The resulting cuff 30b shows that there is no undesirable damage in the presence of any microcracks. Cuff edges 150b are relatively narrow and substrate transmission is shallow and substantially uniform.

It will be apparent to those skilled in the art that many changes can be made in the details of the above-described embodiments of the invention without departing from the underlying principles of the invention. The scope of the invention should therefore only be determined by the following claims.

Claims (50)

A method of laser trimming a film resistor to change a parameter of a film resistor comprising a film resistor material supported on a substrate from an initial value to a nominal value, wherein the film resistor material contributes to the determination of the initial value of the parameter, The method is: Generating a Gaussian beam of at least one laser pulse of UV radiation having a general Gaussian shape energy density spatial profile; Propagating the Gaussian beam along a light path through a beam forming element to convert the Gaussian beam into a modified beam having a more substantially uniform energy density spatial profile; Propagating the major portion through the aperture to convert the major portion of the modified beam into a target beam forming a target spot having a substantially uniform energy density spatial profile; Direct the target beam to the target region of the film resistor material to remove the film resistor material in the target area of the resistor to change the initial value to the nominal value, and a kef through the film resistor material. Penetrating the substrate to form and uniformly expose a major portion of the substrate in the target area, wherein the substantially uniform energy density spatial profile of the target spot is effective to minimize formation of microcracks of the substrate. And having said energy density value. The method of claim 1, wherein the substrate is penetrated to a depth of less than 10 μm. The method of claim 1, wherein the substrate is penetrated to a depth of at least 0.1 μm. The method of claim 3, wherein the substrate is penetrated to a depth of less than 5 μm. The method of claim 1, wherein the film resistor material comprises a thick film resistor material comprising ruthenium oxide. 6. The method of claim 5, wherein the substrate comprises a ceramic material. The method of claim 1, wherein the resistor comprises a 0402 or 0201 chip resistor. 4. The method of claim 3, wherein the resistor comprises a 0402 or 0201 chip resistor. The method of claim 1, wherein the substrate comprises a ceramic material and the film resistor material comprises a thin film resistor material. 10. The method of claim 9, wherein the thin film resistor material comprises a nickel chromium compound or a tantalum nitrogen compound. The resistor film material of claim 1, wherein the resistor film material is arranged spaced apart from each other and supported on the substrate and separated by the plurality of similar scribe lines formed by preformed scribe lines formed on the substrate to separate the plurality of similar areas. Constitute one of the regions; Each of the plurality of similar regions of the membrane material has opposing ends located between metallic conductors; The substantially uniform energy density spatial profile of the target spot produces an effective energy density value that minimizes the formation of microcracks of sizes and depths causing the substrate to have dotted lines distinct from the preformed scribe lines. Having, laser trimming method. The laser of claim 1, wherein the cuffs have a bottom center and the substantially uniform energy density spatial profile of the target spot has an effective energy density value that minimizes the formation of microcracks in the substrate at the bottom center of the cuffs. How to trim. The method of claim 1, wherein the substantially uniform energy density spatial profile of the target spot minimizes the formation of microcracks of sizes and depths that cause parameter value drift from the nominal value in the substrate or in the film material. And an effective energy density value. The method of claim 1, wherein the cuff has sidewalls that exhibit a depth of at least 100 μm and a taper ratio of at least 75% at maximum throughput. The method of claim 1, wherein the target spot having a substantially uniform energy density profile has a major axis shorter or equal to 20 μm. The method of claim 1 wherein: Generating the Gaussian beam from a Q switch diode pump solid state laser. The method of claim 1, wherein the Gaussian beamforming element comprises a diffractive optical element. The method of claim 1, wherein the Gaussian beam comprises a wavelength of about 355 nm, 349 nm, 266 nm, or 262 nm. The method of claim 1, wherein the Gaussian beam has energy and the target beam has an aperture shape energy greater than 50% of the energy of the Gaussian beam. The laser trimming method according to claim 1, wherein the opening is rectangular. A method of changing a parameter of a microelectronic circuit element comprising a region of film material supported on a substrate from an initial value to a nominal value with long term stability, the region defining a volumetric measurement space contributing to the determination of the initial value of the parameter. To prescribe, said change method is: Generating a laser beam having a general Gaussian shape energy density spatial profile; Converting the laser beam having a Gaussian energy density spatial profile into a target beam forming a target spot having a substantially uniform energy density spatial profile; Directing the target beam to a region of the film material to remove the amount of film material to change an initial value to the nominal value, wherein a substantially uniform energy density spatial profile of the target spot is formed on the substrate or And having an effective energy density value that minimizes the formation of microcracks of sizes and depths that cause dot line formations in the substrate in the film material. 22. The method of claim 21, wherein said substrate comprises a ceramic material and said film material comprises a thick film resistor material. 23. The method of claim 22, wherein the thick film resistor material comprises ruthenium oxide. The method of claim 21, wherein the substrate comprises a ceramic material and the film material comprises a thin film resistor material. 25. The method of claim 24, wherein the thin film resistor material comprises a nickel chromium compound or a tantalum nitrogen compound. 22. The method of claim 21, wherein the regions of the membrane material are spaced from each other and constitute one of a plurality of similar regions of the membrane material supported on the substrate, each of the plurality of similar regions of the membrane material being metallic conductive. And with opposing ends located between the sieves. 27. The method of claim 26, wherein the plurality of similar regions of film material are separated by preformed scribe lines formed in the substrate. 27. The method of claim 26, wherein the substrate comprises a ceramic material and the film material comprises a thick film resistor material. 22. The device of claim 21, wherein said region of film material constitutes an element of an array of electrically interconnected elements, and also comprises a plurality of arrays of electrically interconnected elements, said arrays being spaced apart from each other and said substrate Supported on the phase. 30. The method of claim 29, wherein the arrays of electrically interconnected elements are separated by preformed scribe lines formed on the substrate. 22. The method of claim 21, wherein the microelectronic element is a resistor, the parameter is a resistor, and the substrate comprises a ceramic material. The method of claim 21, wherein the target spot with the substantially uniform energy density profile has a major axis shorter or equal to 20 μm. The method of claim 21 wherein: Generating a Gaussian beam from a Q switch diode pump solid state laser. 22. The method of claim 21, wherein converting the Gaussian beam to the target beam includes passing the beam through an aperture mask to clip a peripheral portion of the Gaussian beam. 35. The method of claim 34, wherein converting the laser beam to a target beam includes passing the laser beam through a beamforming element located upstream of the aperture mask to form the laser beam. Way. 36. The method of claim 35, wherein said beam forming element comprises a diffractive optical element. 37. The method of claim 36, wherein converting the laser beam into a target beam includes passing the beam through a focusing element located upstream of the aperture mask to form the laser beam. 22. The method of claim 21 wherein the substantially uniform energy density spatial profile of the target spot minimizes the formation of microcracks of sizes and depths that cause parameter value drift from the nominal value in the substrate or in the film material. A change method having an effective energy density value. 22. The method of claim 21, wherein said microelectronic device comprises a 0402 or 0201 chip resistor. The method of claim 21, wherein the substrate is penetrated to a depth of less than 10 μm. The method of claim 40 wherein: And forming a cuff having a substrate that is uniformly exposed at the bottom of the cuff. The method of claim 21, wherein the substrate is penetrated to a depth of at least 0.1 μm. The method of claim 21, wherein the substrate is penetrated to a depth of less than 5 μm. 22. The method of claim 21, wherein converting the laser beam into a target beam comprises passing the laser beam through a beam forming element. The method of claim 21, wherein the laser beam comprises a UV wavelength. 36. The method of claim 35, wherein the laser beam comprises an IR wavelength. The method of claim 46, wherein the target spot comprises a wavelength of about 1.32 μm and the substrate comprises silicon. 22. The method of claim 21, wherein only the top amount of the volumetric space of the film material is removed so that the substrate remains unexposed. 36. The method of claim 35, wherein the laser beam comprises a visible wavelength. The method of claim 21, wherein the microelectronic device comprises a capacitor or an inductor.