Machining process for a workpiece

Abstract

A method for machining a plate-shaped workpiece (11) comprising layered bodies (17) containing metal, which are arranged in a superimposed relationship with projected parting lines (13), comprising the following steps: holding the workpiece (11) on a first holding table so that the layered bodies (17) are exposed; then cutting the workpiece (11) along the projected parting lines (17) with a cutting blade (10) to form cut grooves (19a) which divide the layered bodies (17); then holding the workpiece (11) on a second holding table so that a mask (25) formed in areas which omit the projected parting lines (13) is exposed, the mask (25) being formed after or at the same time as the cutting of the workpiece (11); and then performing a dry etching on the workpiece (11) through the mask (25) to divide the workpiece (11) along the projected division lines (13);wherein the step of cutting the workpiece (11) includes the step of cutting the workpiece (11) while a cutting fluid containing an organic acid and an oxidizing agent is supplied to the workpiece (11).

Description

BACKGROUND OF THE INVENTIONField of the InventionThe present invention relates to a processing method for a plate-shaped workpiece including layered bodies containing metal formed in an overlapping relationship with projected division lines.Description of the Prior ArtElectronic equipment, typically mobile phones and personal computers, use, as essential components, device chips having devices such as electronic circuits, etc. formed thereon. A device chip is manufactured by dividing the face side of a wafer made of a semiconductor material such as silicon or the like into a plurality of regions having a plurality of projected dicing lines, also known as streets, forming the devices in the respective regions, and then dividing the wafer into individual device chips corresponding to the devices along the projected dicing lines.In recent years, evaluation elements called TEG (test element group) for evaluating electrical characteristics of devices on projected dicing lines on wafers are often formed as described above (see, for example, Japanese Patent Application Laid-Open JP H06-349 926 A and Japanese Patent Application Laid-Open JP 2005-21 940 A). The TEGs at the projected dicing line on a wafer make it possible to maximize the number of device chips that can be manufactured from the wafer. After the TEG has performed evaluations and become unnecessary, it can be removed when the wafer is divided into device chips.JP 2016 040 795 A discloses processing of a workpiece in which a resist layer is exposed and developed before cutting so that the resist layer exposes the surface of the wafer.JP 2016 054 182 A discloses, in processing a workpiece, using a cutting fluid to prevent detachment of a low-k film.SUMMARY OF THE INVENTIONWhen layered bodies containing metal such as TEG are cut and removed by a cutting blade formed of a binder having abrasive grains fixed therein, the metal contained in the layered bodies is elongated to form protrusions called "burrs" due to contact with the cutting blade. If the cutting blade processes the wafer at an increased speed, more heat is generated, resulting in larger burrs being formed. Therefore, according to the processing method using the cutting blade, it is necessary to reduce the processing speed so as not to lower the quality of processing of the wafer.It is therefore an object of the present invention to provide a method for processing a plate-shaped workpiece including layered bodies containing metal formed in an overlapping relationship with projected division lines at an increased speed while maintaining the quality of processing of the workpiece.In accordance with an aspect of the present invention, a method of processing a plate-shaped workpiece including layered bodies containing metal formed in an overlying relationship with projected division lines is that the steps of holding the workpiece on a first holding table so that the layered bodies are exposed, thereafter cutting the workpiece along projected division lines with a cutting blade to form cut grooves that divide the layered bodies so that a mask disposed in regions omitting the projected division lines is exposed, the mask being formed after or with the cutting, and thereafter performing dry etching on the workpiece through the mask to divide the workpiece along the projected division line, wherein the step of cutting the workpiece includes the step of cutting the workpiece, while supplying a cutting fluid including an organic acid and an oxidizing agent to the workpiece.According to the method in accordance with an aspect of the present invention, the cutting fluid containing the organic acid and the oxidizing agent is supplied to the workpiece while the cut grooves sharing the laminated bodies containing metal are formed in the workpiece. The organic acid and the oxidizing agent are effective to modify the metal contained in the laminated bodies, thereby lowering the ductility of the metal while the cutting blade divides the laminated bodies. The metal is thus prevented from forming burrs even when the workpiece is machined at a higher speed. In other words, the speed at which the workpiece is machined can be increased while the quality of the machining of the workpiece is maintained.Further, according to the method in accordance with the aspect of the present invention, after the cut grooves sharing the laminated bodies are formed in the workpiece, dry etching is performed on the workpiece to simultaneously divide the workpiece along all the projected dividing lines. Therefore, the time required to machine the workpiece per projected division line is shortened while maintaining the quality of machining of the workpiece, particularly when the number of the projected division line in the workpiece is large. Consequently, the speed at which the workpiece is machined can be increased while the quality of the machining of the workpiece is maintained.The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood by studying the following description of the appended claims with reference to the appended figures which show a preferred embodiment of the invention.BRIEF DESCRIPTION OF THE FIGURESFIG. 1A is a perspective view schematically illustrating a workpiece by way of example; FIG. 1B is an enlarged plan view of a surface side of the workpiece; FIG. 2A is a perspective view schematically showing the workpiece to which a division tape, etc., is attached; FIG. 2B is a side elevational view, partially in cross section, showing a first holding step of a machining method for a workpiece according to an embodiment of the present invention; FIG. 3A is a partial side elevational view, partially in cross section, showing a cutting step of a machining method for a workpiece; FIG. 3B is a partial side plan view, partially in cross section, showing a mask forming step of the machining method for a workpiece; FIG. 4A is a cross-sectional plan view schematically showing an apparatus for dry etching; FIG. 4B is a partial side elevational view, partially in cross section, schematically showing the workpiece that has been cut in a step of dry etching the processing method for a workpiece; and FIG. 5 is a side elevational view of a nozzle for supplying a cutting fluid according to another embodiment of the present invention.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTA method for machining a workpiece according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The method for machining a workpiece according to the present invention is also referred to as a "workpiece machining method", and is a method for machining a plate-shaped workpiece including layered bodies containing metal formed in an overlapping relationship with projected division lines, and includes a first holding step (see FIG. 2B ), a cutting step (see FIG. 3A ), a mask forming step (see FIG. 3B ), a second holding step (see FIG. 4A ), and a dry etching step (see FIG. 4B ).In the first holding step, the workpiece is held on a chuck table (first holding table) of a cutting apparatus so that the laminated bodies formed in an overlapping relationship with the projected division lines are exposed. In the cutting step, the workpiece is cut along the projected division lines to form cut grooves in the workpiece that divide the laminated bodies while supplying a cutting fluid containing an organic acid and an oxidizing agent to the workpiece. In the mask forming step, a mask is formed in regions of the workpiece with the projected division lines omitted. In the second holding step, the workpiece is held at an electrostatic chuck (second holding table) of a dry etching apparatus so that the mask is exposed. In the dry etching step, a dry etching process is performed on the workpiece through the mask, thereby cutting the workpiece along the projected division lines. The machining method for a workpiece according to the present embodiment will be described in detail below.FIG. 1A is a perspective view schematically showing a workpiece 11 as an example to be processed by the processing method for a workpiece according to the present embodiment, and FIG. 1B is an enlarged partial plan view of a surface 11 aof the workpiece 11.The central device area is further divided into plural areas by a grid of projected division lines or streets 13, where devices 15 such as ICs (integrated circuits) or the like are formed in the respective areas. As shown in FIG. 1B, the plurality of layered bodies 17 containing metal are arranged on the projected division lines 13. The laminated bodies 17 are provided as evaluation elements referred to as TEG (test element group), for example.According to the present embodiment, the workpiece 11 is illustrated that includes a disk-shaped wafer formed of a semiconductor such as silicon or the like. However, the workpiece 11 is not limited to specific materials, shapes, structures, sizes, etc. Similarly, the devices 15 and the layered bodies 17 are not limited to particular grades, quantities, shapes, structures, sizes, arrangements, etc. For example, a packaged substrate on which the laminated bodies 17 serving as electrodes are formed along the projected division lines 13 may be used as the workpiece 11.FIG. 2A is a perspective view schematically illustrating the workpiece 11 to which the division band 21 is attached. As shown in FIG. 2A, before the machining method for a workpiece according to the present embodiment is performed, the division band 21 larger in diameter than the workpiece 11 is attached to a rear side 11 bof the workpiece 11. The annular frame 23 is fixed to an outer circumferential portion of the division band 21.The workpiece 11 is thus supported on the annular frame 23 by the division band 21. Although an example in which the workpiece 11 is supported on the annular frame 23 by the division band 21 will be described below in the present embodiment, the workpiece 11 may be machined without using the division band 21 and the frame 23.In the workpiece processing method according to the present embodiment, the first holding step is performed to hold the workpiece 11 on a chuck table (first holding table) of a cutting apparatus 2. FIG. 2B is a side elevational view, partially in cross section, illustrating the first holding step. The first stopping step is performed using a cutting device 2 shown in FIG. 2B, for example. The cutting apparatus 2 includes a chuck table (first holding table) 4 for holding the workpiece 11 under suction.The chuck table 4 is connected to a rotary actuator, not illustrated, such as a motor or the like, so that it can be rotated about an axis substantially parallel to a vertical direction. The chuck table 4 is disposed above the machining feed mechanism, not illustrated, which moves the chuck table 4 in a machining feed direction.The chuck table 4 has an upper surface, a part of which serves as a holding surface 4 afor holding the workpiece 11, i.e., the division belt 21, under suction. The holding surface 4 ais connected to a suction source, which is not illustrated, through a suction channel, which is not illustrated, formed in the chuck table 4. When negative pressure from the suction source is caused to act on the holding surface 4 a, the workpiece 11 is held on the chuck table 4 under suction. A plurality of clamps 6 for securing the annular frame 23 are provided on an outer circumferential portion of the chuck table 4.In the first holding step, the division tape 21 adhered to the rear side 11 bof the workpiece 11 is held in contact with the holding surface 4 aof the chuck table 4, and negative pressure from the suction source is caused to act on the division tape 21. At the same time, the frame 23 is secured by the clamps 6. The workpiece 11 is thus securely held by the chuck table 4 and the clamps 6 are held with the laminated bodies 17 exposed upward on the surface 11 aside.After the first holding step, the cutting step is performed to form grooves in the workpiece 11 to divide the laminated bodies 17. FIG. 3A is a partial side elevational view, partially in cross section, illustrating the cutting step. The cutting step is also performed using the cutting device 2. As shown in FIG. 3A, the cutting apparatus 2 further includes a cutting unit 8 disposed above the chuck table 4.The cutting unit 8 includes a spindle, not illustrated, that serves as a shaft substantially perpendicular to the machining feed direction. An annular cutting blade 10 formed of a binder with abrasive grains dispersed therein is mounted on one end of the spindle. The other end of the spindle is coupled to a rotary actuator, not illustrated, such as a motor or the like. The cutting blade 10 at the one end of the spindle is supported about its own axis by forces transmitted from the rotary actuator.The spindle is supported on a moving mechanism, not illustrated, that can move the cutting blade 10 in the index feeding direction perpendicular to the machining feed direction and a vertical direction perpendicular to the machining feed direction and the index feeding direction. A pair of nozzles 12 are disposed on both sides of the cutting blade 10, which is thus disposed between the nozzles 12. The nozzles 12 are arranged to supply cutting fluid 14 to the cutting blade 10 and the workpiece 11.In the cutting step, the chuck table 4 is rotated about its own axis to bring a target projected dicing line 13) into alignment with the machining feed direction of the cutting apparatus 2. The chuck table 4 and the cutting unit 8 are moved relative to each other to position the plane of the cutting blade 10 in alignment with an extension of the target projected dicing line 13. Thereafter, the lower end of the cutting blade 10 is moved to position it lower than lower surfaces of the laminated bodies 17.Thereafter, while the cutting blade 10 is rotated about its own axis, the chuck table 4 is moved in the machining feed direction. At the same time, the nozzles 12 supply the cutting fluid 14 containing an organic acid and an oxidizing agent to the cutting blade 10 and the workpiece 11. the cutting blade 10 cuts into the workpiece 11 along the target projected dicing line 13, thereby forming a cut groove 19 athat completely divides the laminated bodies 17 at the target projected dicing line in the surface side 11 aof the workpiece 11.In the above-described embodiment, the organic acid contained in the cutting fluid 14 modifies the metal in the laminated bodies 17 to reduce its ductility. The oxidizing agent contained in the cutting fluid 14 makes it easier to oxidize the metal in the laminated bodies 17 on its surface. As a result, the ductility of the metal in the laminated body 17 is sufficiently lowered to increase the workability of the workpiece 11.As the organic acid contained in the cutting fluid 14, for example, a compound having at least one carboxy group and at least one amino group in its molecule can be used. In this case, it is preferred that at least one of the amino groups is a secondary or tertiary amino group. In addition, the compound used in the organic acid may have a substituent group.As the organic acid, amino acids may be used. Examples of the amino acids usable herein include glycine, dihydroxyethyl glycine, glycyl glycine, hydroxyethyl glycine, N-methyl glycine, β-alanine, L-alanine, L-2-aminobutyric acid, L-norvaline, L-valine, L-leucine, L-norleucine, L-alloisoleucine, L-isoleucine, L-phenylalanine, L-proline, sarcosine, L-ornithine, L-lysine, taurine, L-serine, L-threonine, L-allothrin, L-homoserine, L-thyroxine, L-tyrosine, 3,5-diiodo-L-tyrosine, β-(3,4-dihydroxyphenyl)-L-alanine, 4-hydroxy-L-proline, L-cysteine, L-methionine, L-ethyne, L-lanthionine, L-cystathionine, L-cystine, L-cystic acid, L-glutamic acid, L-aspartic acid, S-(carboxymethyl)-L-cysteine, 4-aminobutyric acid, L-asparagine, L-glutamine, azaserine, L-canavanine, L-citrulline, L-arginine, 5-hydroxy-L-lysine, creatine, L-kynurenine, L-histidine, 1-methyl-L-histidine, 3-methyl-L-histidine, L-tryptophan, actinomycin C1, ergothionein, apamine, angiotensin I, angiotensin II, antipain, etc. Among others, glycine, L-alanine, L-proline, L-histidine, L-lysine, and dihydroxyethyl glycine are particularly preferred.Also, amino polyacids may be used as the organic acid. Examples of the aminopolyacids usable herein include iminodiacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, hydroxyethyliminodiacetic acid, nitrilotrismethylenephosphonic acid, ethylenediamine-N,N,N',N'-tetramethylenesulfonic acid, 1,2-diaminopropanetetraacetic acid, glycoletherdiaminetetraacetic acid, transcyclohexanediaminetetraacetic acid, ethylenediamineorthohydroxyphenylacetic acid, ethylenediaminedisuccinic acid (SS isomer), β-alaninediacetic acid, N-(2-carboxyethyl)-L-aspartic acid, N-N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, etc.Further, carboxylic acids may be used as the organic acid. Examples of the carboxylic acids usable herein include saturated carboxylic acids such as formic acid, glycolic acid, propionic acid, acetic acid, butyric acid, valeric acid, caproic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, malic acid, succinic acid, pimelic acid, mercaptoacetic acid, glyoxylic acid, chloroacetic acid, pyruvic acid, acetoacetic acid, etc., unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, mesaconic acid, citraconic acid, aconitic acid, etc., and cyclic unsaturated carboxylic acids such as benzoic acid, toluylic acid, phthalic acid, naphthoic acids, pyromellitic acid, naphthalic acid, etc.Oxidizing agents which may be present in the cutting fluid which can be used there are, for example, hydrogen peroxide, peroxides, nitrates, iodates, periodates, hypochlorites, chlorites, chlorates, perchlorates, persulfates, dichromates, permanganates, cerates, vanadates, ozonized water, silver(II) salts, iron(III) salts, and their organic complex salts.Moreover, corrosion protection can be mixed in the cutting fluid 14. Mixing the corrosion protector makes it possible to prevent corrosion (elution) of the metal included in the workpiece 11. As the anticorrosive, there is preferably used a heterocyclic ring compound having at least three nitrogen atoms in its molecule and having a fused ring structure or a heterocyclic aromatic ring compound having at least four nitrogen atoms in its molecule. Further, the aromatic ring compound preferably comprises a carboxy group, sulfo group, hydroxy group, or alkoxy group. Specifically preferred examples of the aromatic ring compound include tetrazole derivatives, 1,2,3-triazole derivatives, and 1,2,4-triazole derivatives.Examples of the tetrazole derivatives usable as corrosion protection include those having no substituent group on the nitrogen atoms constituting the tetrazole ring and having, inserted at the 5-position of the tetrazole, a substituent group selected from the group consisting of a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group, and a sulfonamide group or an alkyl group substituted with at least one substituent group selected from the group consisting of a hydroxy group, a carboxy group, a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group, and a sulfonamide group.Examples of the 1,2,3-triazole derivatives usable as corrosion protection include those having no substituent group on the nitrogen atoms constituting the 1,2,3-triazole ring and having, inserted at the 4-position and / or the 5-position of the 1,2,3-triazole, a substituent group selected from the group consisting of a hydroxy group, a carboxy group, a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group, or an alkyl or aryl group substituted with at least one substituent group selected from the group consisting of a hydroxy group, a carboxy group, a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group.Moreover, examples of the 1,2,4-triazole derivatives usable as corrosion protection include those having no substituent group on the nitrogen atoms constituting the 1,2,4-triazole ring and which, inserted at the 2-position and / or the 5-position of the 1,2,4-triazole, have a substituent group selected from the group consisting of a sulfo group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group, or an alkyl or aryl group substituted with at least one substituent group selected from the group consisting of a hydroxy group, a carboxy group, a sulfo group, an amino group, a carbamoyl group, a carbonamide group, a sulfamoyl group and a sulfonamide group.The above process is repeated to cut to form cut grooves 19a along all the projected division lines 13, whereupon the cutting step is completed. According to the present embodiment, as described above, the cutting fluid 14 containing an organic acid and an oxidizing agent is supplied to the workpiece 11 so that the laminated bodies 17 containing the metal are divided with the cutting blade 10. The organic acid and the oxidizing agent are effective to modify the metal formed in the laminated bodies 17, thereby lowering the ductility of the metal while the cutting blade 10 divides the laminated bodies 17. The metal is thus prevented from forming burrs even when the workpiece 11 is machined at an increased speed.The cutting step is followed by a mask forming step to form a mask for dry etching in a covered relationship on the surface side 11 aof the workpiece 11. FIG. 3B is a partial side plan view, partially in cross section, illustrating the mask forming step and schematically a mask 25 formed on the surface side 11 aof the workpiece 11.The mask 25 is formed by a process such as photolithography or the like and has at least a certain degree of resistance to subsequent dry etching. As shown in FIG. 3B, the mask 25 is formed to expose the projected division lines 13, i.e., the cut grooves 19 a. In other words, the mask 25 is formed in regions that omit the projected division lines 13, i.e., the cut grooves 19 a.The mask forming step is followed by the second holding step for holding the workpiece 11 in electrostatic relaxation (second holding table) of a dry etching apparatus (plasma etching apparatus) FIG. 4A is a cross-sectional plan view schematically showing a dry etching apparatus (plasma etching apparatus) 22. The dry etching apparatus 22 includes a vacuum chamber 24 having a processing space formed therein. The vacuum chamber 24 includes a side wall having an opening 24 aformed therein through which the workpiece 11 can be loaded into and removed from the processing space in the vacuum chamber 24.A flap 26 is provided outside the opening 24 ato selectively open and close the opening 24 a. The door 26 is connected to an opening / closing mechanism, not shown, which selectively opens and closes the door 26. When the door 26 is opened to expose the opening 24 a, the workpiece 11 may be loaded into the processing space in the vacuum chamber 24 through the opening 24 aor may be taken out of the processing space of the vacuum chamber 24.The vacuum chamber 24 includes a bottom wall having an evacuation opening 24 bformed therein, which is connected to an evacuation unit 28 such as a vacuum pump or the like. A lower electrode 30 is disposed in the processing space in the vacuum chamber 24. The lower electrode 30 has a plate shape and is formed of an electrically conductive material and is electrically connected to a high-frequency power source 32 disposed outside the vacuum chamber 24.An electrostatic chuck 34 is disposed on an upper surface of the lower electrode 30. The electrostatic chuck 34 has a plurality of electrodes 36 aand 36 bwhich are insulated from each other, for example. The electrostatic chuck 34 attracts and holds the workpiece 11 under electric forces generated between electrodes 36 aand 36 band the workpiece 11. The electrostatic bias voltage 34 according to the present embodiment is arranged such that the electrode 36 acan be connected to the positive terminal of the direct current (DC) power source 38 a, whereas the electrode 36 bcan be connected to the negative terminal of the DC power source 38 b.An upper electrode 40, which has a disc shape and is formed of an electrically conductive material, is mounted on a ceiling wall of the vacuum chamber 24 with an insulator interposed therebetween. The upper electrode 40 has a plurality of gas injection holes 40 aformed in a lower surface thereof, which are connected to a gas supply source 42 through a gas supply hole 40 bformed on an upper surface of the upper electrode 40. Therefore, the gas supply source 42 can supply a material gas for dry etching into the vacuum chamber 24 through the gas supply hole 40 band the gas injection holes 40 ain the processing space. The upper electrode 40 is electrically connected to a high frequency power source 44 disposed outside the vacuum chamber 24.In the second holding step, the opening / closing mechanism lowers the door 26, thereby exposing the opening 24 a. Thereafter, the workpiece 11 is charged through the exposed opening 24 ainto the processing space in the vacuum chamber 24 and placed on the electrostatic chuck 34. Specifically, the division tape 21 adhered to the rear side 11 bof the workpiece 11 is held in contact with the upper surface of the electrostatic chuck 34. Thereafter, the electrostatic chuck 34 is energized to attract and hold the workpiece 11 while the mask 25 is exposed upward from the surface 11a thereof.After the second holding step, the dry etching step is performed to perform dry etching (plasma etching) on the workpiece 11 through the mask 25 to cut the workpiece along the projected division lines 13. The dry etching step is also performed using the dry etching apparatus 22.Specifically, the opening / closing mechanism lifts the lid 26, thereby closing the processing space in the vacuum chamber 24. Thereafter, the evacuation unit 28 is operated to evacuate the processing space. While the material gas for dry etching is supplied from the gas supply source 42 at a predetermined flow rate, the high-frequency power sources 32 and 34 suitably supply high-frequency electric power to the lower electrode 30 and the upper electrode 40, respectively, thereby forming a plasma containing radicals, ions, etc. between the lower electrode 30 in the upper electrode 40.The portions of the surface side 11 aof the day of the workpiece 11 not covered with the mask 25, i.e., the projected division lines 13 or the cut grooves 19 bare exposed to the plasma that processes the workpiece 11. The material gas for dry etching supplied from the gas supply source 42 may be a suitable gas depending on the material, etc., of the workpiece 11. The dry etching step is continued until the workpiece 11 is completely divided along the projected division lines 13.FIG. 4B is a partial side plan view, partially in cross section, schematically showing the workpiece 11 cut in the dry etching step. According to the present embodiment, since the laminated bodies 17 formed on the face side 11a in an overlapping relationship with the projected dicing lines 13 have been cut off, the workpiece can be completely divided into a plurality of device chips in the step of dry etching as shown in FIG. 4B. In the step of dry etching, since the workpiece 11 is divided along all the projected division lines 13 simultaneously, the machining time required to machine the workpiece 11 per projected division line 13 is shortened while the machining quality of the workpiece 11 is maintained, particularly if the number of the projected division lines 13 in the workpiece 11 is large. Surfaces newly generated in the workpiece 11 in the dry etching step serve as side surfaces 19 bof the device chips. After the dry etching step, the mask 25 is removed by ashing or the like.In the processing method for a workpiece according to the present embodiment, as described above, the cutting fluid 14 containing an organic acid and an oxidizing agent is supplied to the cutting blade 10 and the workpiece 11 in forming the cut grooves 19 athat divide the laminated bodies 17 containing metal. The organic acid and the oxidizing agent are effective to modify the metal contained in the laminated bodies 17, thereby lowering the ductility of the metal while the cutting blade 10 divides the laminated bodies 17. The metal is thus prevented from forming burrs even when the workpiece 11 is machined at an increased speed. In other words, the speed at which the workpiece 11 is machined can be increased while the quality of the machining of the workpiece 11 is maintained.The present invention is not limited to the above embodiment, but various changes and modifications may be made therein. For example, when the workpiece 11 in which the layered bodies 17 containing metal are processed on the surface side 11 bthereof in the above embodiment, a workpiece in which a layered body containing metal is formed on the rear side thereof can be processed. According to such a modification, the workpiece is cut from the rear side thereof. The workpiece may include a wafer or the like in which layered bodies, e.g., multilayer metal films of titanium (Ti), nickel (Ni), gold (Au), etc., serving as electrodes and having a thickness of about several micrometers are provided on the rear side thereof.In the above embodiment, a step of dry etching is performed from the surface 11 aside thereof. However, the step of dry etching may be performed on the workpiece 11 from the rear side 11 bthereof. According to such a modification, a mask may be provided at those portions of the rear side 11 bof the workpiece 11 that omit, i.e., are not aligned with, the projected division lines.In the above embodiment, the mask forming step is performed after the cutting step. However, in an unclaimed embodiment, the cutting step may be performed after the step of forming a mask is performed. According to such a modification, since the mask and the laminated bodies can be processed using the cutting blade, according to an alternative of the invention, the formation of the mask is possible with the cutting step, and it is not necessary to use a process such as photolithography or the like for forming the mask pattern.In the above cutting step, the cutting fluid is supplied from the nozzles 12 disposed on both sides of the cutting blade 10. However, the present invention is not limited to a particular nozzle configuration for supplying the cutting fluid 14. FIG. 5 is a side elevational view of a nozzle for supplying the cutting fluid 14 according to another embodiment of the present invention. As shown in FIG. 5, a cutting unit 8 as a modification includes, in addition to the cutting blade 10 and the pair of nozzles 12, a shower nozzle 16 disposed in front of or behind the cutting blade 10.The nozzle 16 makes it easier to supply the cutting fluid 14 into the cut groove 19 ato more efficiently modify the metal contained in the laminated bodies 17. Specifically, the nozzle 16 has an ejection opening oriented inclined downward to a region where the cutting blade 10 processes the workpiece 11 as shown in FIG. 5, so that the cut groove 19 ais supplied and filled with an increased amount of the cutting fluid 14 to more efficiently modify the metal contained in the laminated bodies 17. Although both the nozzle 12 and the nozzle 16 are used in FIG. 5, the nozzles 12 may be discharged, and only the nozzle 16 may be used alone.

Claims

A method of processing a plate-shaped workpiece (11) including layered bodies (17) containing metal formed in an overlying relationship with projected division lines (13), comprising the steps of: holding the workpiece (11) on a first holding table so that the layered bodies (17) are exposed; thereafter cutting the workpiece (11) along the projected division lines (17) with a cutting blade (10) to form cut grooves (19a) that divide the layered bodies (17); thereafter holding the workpiece (11) on a second holding table so that a mask (25) formed in regions that omit the projected division lines (13) is exposed, wherein the mask (25) is formed after or with the cutting of the workpiece (11); and thereafter, performing dry etching on the workpiece (11) through the mask (25) to divide the workpiece (11) along the projected dividing lines (13); wherein the step of cutting the workpiece (11) includes the step of cutting the workpiece (11) while supplying a cutting fluid containing an organic acid and an oxidizing agent to the workpiece (11).

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