Method for processing a wafer

Abstract

Method for dividing a wafer (11) into component chips and for removing machining-induced strains from machined grooves of the wafer (11) on which components (15) are formed in a plurality of areas which are divided on its end face (11a) by a plurality of projected parting lines (13) arranged in a lattice structure, the method comprising: a cutting groove formation step in which a cutting blade (80) is caused to cut into the wafer (11) from its back side (11b) along the projected parting lines (13) in order to form cutting grooves (41) in the wafer (11) to a depth just before the end face (11a) of the wafer (11); a separation step involving the application of a laser beam (45) to the bottoms of the cutting grooves (41) from the back (11b) of the wafer (11) to divide the wafer (11) into the component chips corresponding to the respective components (15); and after the separation step a plasma etching step with a supply of an etching gas (47) in a plasma state to the wafer (11) from its back side (11b) in order to remove the processing-related strains that remained on the component chips, including the plasma etching step: Converting the etching gas (43) into the plasma state outside a low-pressure chamber (24) which contains the wafer (11), wherein the etching gas contains ions and radicals, and Reducing the number of ions by supplying the etching gas (43) from outside the vacuum chamber (24) in the plasma state through a supply nozzle (52) connected to the vacuum chamber (24) into the vacuum chamber (24).

Description

BACKGROUND OF THE INVENTION AREA OF THE INVENTION

[0001] The present invention relates to a method for processing a wafer using a gas in a plasma state. DESCRIPTION OF THE RELATED STATE OF THE ART

[0002] Electronic components, such as mobile phones and personal computers, contain essential components called component chips, which themselves contain electronic circuits. A component chip is created by dividing the end face of a wafer into numerous regions using a variety of projected dividing lines, also known as roads. Components are formed in these regions, and then corresponding component chips are produced along the projected dividing lines. The wafer is made of a semiconductor material, such as silicon or similar materials.

[0003] In recent years, wafers with integrated devices have frequently been thinned by grinding or similar processes to reduce the size and weight of the resulting device chips. However, thinning a wafer by grinding reduces the flexural stiffness of the resulting device chips, incurring deformations referred to as "machining strains" caused by the cutting process that remain on the ground surface of the wafer. One solution is to remove these machining strains from the wafer using a plasma etching process after grinding, employing a gas in a plasma state (see, for example, German Patent Application JP 2000 - 353 676 A).

[0004] A plasma etching device used to remove machining-induced strains from ground wafers typically features a vacuum chamber containing a pair of electrodes in the form of flat plates positioned parallel to each other. With a ground wafer placed between the electrodes, the vacuum chamber is evacuated and its pressure reduced. While the vacuum chamber is supplied with an etching gas, a high-frequency voltage is applied between the electrodes to bring the gas into a plasma state. The gas in this plasma state is then directed onto the ground surface of the wafer to remove machining-induced strains.

[0005] For example, US 9,196,498 B1 discloses a plasma processing device with a processing chamber. The plasma processing device includes a plasma source in an upper section of the processing chamber and is used to cut a semiconductor wafer. Further plasma etching devices, methods, and applications are disclosed in DE 10 2009 004 567 A1, US 2003 / 0 127 428 A1, US 2017 / 0 062 278 A1, US 2016 / 0 148 842 A1, and US 2013 / 0 059 428 A1. SUMMARY OF THE INVENTION

[0006] The plasma etching process referenced above is also considered effective for removing machining-induced strains in wafers created by processes other than grinding. The removal of machining-induced strains or residues, also referred to as machining wafer-fabricated chips when processed using a cutting blade with abrasive grains or an absorptive laser beam, and the removal of modified layers created in wafers by focusing a transmission laser beam within them, can be considered applications of the plasma etching process.

[0007] In accordance with the usual procedure of etching a wafer in a gas that is converted into a plasma state using a pair of electrodes in the form of parallel flat plates, the etching occurs mainly on one area of ​​the wafer that tends to be more exposed to the gas. With this method, it is difficult to remove machining-induced strains, residues, modified layers, or similar features from deep locations within the wafer that are spaced away from one of its faces without excessive etching progress on that one face. In other words, this method is not capable of adequately removing machining-induced strains, residues, modified layers, or similar features that are located inside grooves formed in the wafer by machining.

[0008] The subject matter of the present invention is defined in the independent claims. The dependent claims describe preferred embodiments of the invention.

[0009] It is therefore an object of the present invention to provide a method involving the processing of a wafer to remove processing-induced strains, residues, modified layers or the like from deep positions in the wafer that are spaced apart from a surface of the wafer, without excessive etching progress on that one surface of the wafer.

[0010] In accordance with one aspect of the present invention, a method is provided for dividing a wafer into component chips and for removing machining-induced strains from machined grooves of the wafer, on which components are formed in a plurality of areas, the components being divided at its end face by a plurality of projected parting lines arranged in a lattice structure, the method comprising a groove formation step in which a cutting blade is caused to cut into the wafer from its back side along the projected lines to form grooves in the wafer to a depth just short of the end face of the wafer; a separation step comprising applying a laser beam to the bottoms of the grooves from the back side of the wafer to divide the wafer into the component chips corresponding to the respective components;and after the separation step includes a plasma etching step with the supply of an etching gas in a plasma state to the wafer from its back side to remove the processing-related strains or residues that have remained on the device chips, wherein the plasma etching step includes converting an etching gas into the plasma state outside a vacuum chamber which contains the wafer, wherein the etching gas has ions and radicals, and reducing the number of ions by supplying the etching gas from outside the vacuum chamber in the plasma state through a feed nozzle connected to the vacuum chamber.

[0011] In accordance with a further aspect of the present invention, a method is provided for dividing a wafer into device chips and for removing modified layers remaining on side faces of the device chips, wherein devices are formed on the wafer in a plurality of regions which are divided at its front face by a plurality of projected separation lines arranged in a lattice structure, wherein the method includes a separation step involving the application of a laser beam having a wavelength transmissible through the wafer from its rear side onto the wafer along the projected separation lines, focusing the laser beam on positions in the wafer to form modified layers in the wafer and to develop cracks extending from the modified layers to the front and rear faces of the wafer, thereby dividing the wafer into the device chips.which correspond to the respective components; and after the separation step includes a plasma etching step with the introduction of an etching gas into a plasma state onto the wafer from its back side in order to remove the modified layers that remained on the side faces of the component chips, wherein the plasma etching step includes converting an etching gas into a plasma state outside a vacuum chamber which contains the wafer, wherein the etching gas has ions and radicals, and reducing the number of ions by introducing the etching gas in the plasma state from outside the vacuum chamber through a feed nozzle connected to the vacuum chamber.

[0012] In accordance with yet another aspect of the present invention, a method is provided for dividing a wafer into component chips and for removing processing-related strains remaining on the component chips, wherein components are formed on the wafer in a plurality of regions which are divided at its end face by a plurality of projected parting lines arranged in a lattice structure, wherein the method includes a parting step in which a cutting blade is caused to cut into the wafer from its back side along the projected parting lines in order to divide the wafer into component chips corresponding to the respective components;and after the separation step includes a plasma etching step with the supply of an etching gas in a plasma state to the wafer from its back side to remove processing-related strains remaining on the device chips, wherein the plasma etching step includes converting an etching gas into a plasma state outside a vacuum chamber which contains the wafer, wherein the etching gas has ions and radicals, and reducing the number of ions by supplying the etching gas from outside the vacuum chamber in the plasma state through a feed nozzle connected to the vacuum chamber.

[0013] In wafer manufacturing processes in accordance with the present invention, processing-related strains, residues, modified layers or the like, which have remained at positions spaced apart from one face of the wafer, can be removed without excessive etching progress on that one face of the wafer, since an etching gas that has been converted into a plasma state outside the vacuum chamber containing the wafer is introduced into the vacuum chamber during the plasma etching step by introducing the etching gas into the plasma state.

[0014] If ions are more abundant than radicals in the plasma state of the etching gas, then etching progresses primarily due to the ions on the one surface of the wafer that tends to be more exposed to the etching gas. In this case, it is therefore difficult to remove processing-related strains, residues, modified layers, or similar features present at positions further away from that one surface of the wafer—that is, at deeper positions in the wafer—without excessive etching progress on that one surface.

[0015] Since the etching gas, which has been converted to the plasma state outside the vacuum chamber, is introduced into the vacuum chamber, it is assumed that, in the present invention, radicals are more abundant than ions in the vacuum chamber. Therefore, the progress of etching on the one area of ​​the wafer, which tends to be more exposed to the etching gas, is inhibited by ions, and the processing-related strains, residues, modified layers, or the like that remain at positions spaced away from that one area of ​​the wafer can be removed without excessive etching progress on that one area of ​​the wafer.

[0016] The above and other tasks, features and advantages of the present invention and the manner of its implementation will become clearer by studying the following description and attached claims with reference to the accompanying drawings, which show preferred embodiments of the invention, and the invention itself will be best understood by this. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view showing a wafer and other elements in an exemplary manner; The Fig. 2A and Fig. 2B are lateral partial sectional views illustrating a protective film application step in accordance with embodiment 1; Fig. Figure 3 is a lateral partial sectional view illustrating a forming step of a machined groove in accordance with embodiment 1; Fig. 4 is a sectional view, which schematically shows a plasma etching device, partly in block form; Fig. Figure 5 is a partial lateral sectional view illustrating a plasma etching step in accordance with embodiment 1; Fig. Figure 6 is a lateral partial section view illustrating a training step of a machined groove in accordance with a modification; Fig. Figure 7 is a perspective view showing a wafer and other elements by way of example; Fig. Figure 8 is a lateral partial sectional view illustrating a cutting groove formation step in accordance with embodiment 2; Fig. 9 is a lateral partial sectional view illustrating a separation step in accordance with embodiment 2; Fig. 10 is a lateral partial sectional view illustrating a plasma etching step in accordance with embodiment 2; Fig. 11A is a lateral partial sectional view of a separation step in accordance with embodiment 3; Fig. 11B is a sectional view illustrating the separation step in accordance with embodiment 3; Fig. 12 is a lateral partial sectional view illustrating a plasma etching step in accordance with embodiment 3; Fig. Figure 13 is a partial lateral sectional view illustrating a separation step in accordance with embodiment 4; and Fig. Figure 14 is a lateral partial sectional view illustrating a plasma etching step in accordance with embodiment 4. DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0017] Embodiments of the present invention are described below with reference to the accompanying drawings. Identical or corresponding parts are identified by the same or corresponding reference numerals in the views. Embodiment 1 (not according to the invention):

[0018] A method for processing a wafer in accordance with the present embodiment is described below to form grooves (machined grooves) in the end face of a wafer after it has been coated with a protective film. Fig. Figure 1 is a perspective view showing a wafer 11 and other elements by way of example, wherein the wafer 11 is machined by the machining process in accordance with the present embodiment. As in Fig. As shown in Figure 1, the wafer has a disk shape and is made of silicon (Si), silicon carbide (SiC), sapphire (Al2O3), or similar materials. The wafer 11 has an end face 11a that is divided into a multitude of regions by projected cutting lines or roads 13 arranged in a lattice structure. Devices 15, such as integrated circuits (ICs), light-emitting diodes (LEDs), etc., are formed in these regions on the wafer 11.

[0019] In accordance with the present embodiment, the wafer 11 is illustrated as having a disk shape and is made of silicon, silicon carbide, sapphire, or the like. However, the wafer 11 is not limited to specific materials, shapes, structures, sizes, etc. The wafer 11 can be made of other materials, including semiconductors, ceramics, resins, metals, etc. Likewise, the components 15 are not limited to specific types, quantities, shapes, structures, sizes, layouts, etc.

[0020] The wafer 11 has a back surface 11b to which a separating strip 17 is glued, the separating strip having a larger diameter than the wafer 11. The separating strip 17 has an outer circumferential section that is attached to the annular frame 19. In other words, the wafer 11 is supported on the frame 19 via the separating strip 17.

[0021] In the wafer processing method according to the present embodiment, a protective film application step is carried out to coat the end face 11a of the wafer 11 with a protective film. Fig. 2A and Fig. Figure 2B shows partial sectional views of the side, illustrating the protective film application step. The protective film application step, in accordance with the present embodiment, is carried out, for example, using a [missing information - likely a specific tool or component]. Fig. 2A shows spincoater 2 executed. As in Fig. As shown in Figure 2A, the spincoater 2 includes a rotary table or holding table 4 for holding the wafer 11. The rotary table 4 is coupled to a rotary actuator (not shown), such as a motor, which rotates the rotary table 4 about its axis, which is substantially parallel to a vertical direction. The rotary table 4 has an upper surface that serves as a holding surface for gripping the wafer 11. The holding surface is connected to a suction source (not shown) via a suction channel (not shown) defined in the rotary table 4. The spincoater 2 also includes a nozzle 6 located above the rotary table 4 for dripping a liquid resin 21 as the material of the protective film. A plurality of clamps (not shown) for securing the annular frame 19 to the rotary table 4 are provided at an outer circumferential region of the rotary table 4.

[0022] During the protective film application step, the release tape 17, which adheres to the back 11b of the wafer 11, is held in contact with the holding surface of the rotary table 4, and a vacuum from the suction source is applied to the release tape 17. Simultaneously, the frame 19 is secured to the rotary table 4 by the clamps. The wafer 11 is thus held securely to the rotary table 4 with its end face 11a exposed. Then the nozzle 6 drips, as shown in Fig. As shown in Figure 2A, the liquid resin 21 is applied to the end face 11a of the wafer 11, and the rotary table 4 is rotated about its own axis, coating the end face 11a of the wafer 11 with the liquid resin 21. The liquid resin 21 applied to the end face 11a is then dried and cured to form a protective film covering the components 15 (see Figure 2A). Fig. 2B).

[0023] The protective film application step is followed by a forming step of a machined groove, which forms machined grooves in the end face 11a of the wafer 11 along the projected cutting lines 13. Fig. Figure 3 is a partial lateral sectional view illustrating the forming step of a machined groove in accordance with the present embodiment. The forming step of a machined groove in accordance with the present embodiment is, for example, achieved by using a Fig. 3 laser processing device 12 is carried out as shown. Fig. As shown in Figure 3, the laser processing device 12 includes a clamping table or holding table 14 for holding the wafer 11. The clamping table 14 is coupled to a rotary actuator (not shown), such as a motor, which rotates the clamping table 14 about its axis, which is substantially parallel to a vertical direction. The clamping table 14 is arranged above a table movement mechanism (not shown) that moves the clamping table 14 in a processing feed direction (i.e., a first horizontal direction) and a division feed direction (i.e., a second horizontal direction).

[0024] The clamping table 14 has an upper surface that serves as a holding surface for gripping the wafer 11 under suction force. The holding surface is connected to a suction source (not shown) via a suction channel (not shown) defined in the clamping table 14. A plurality of clamps (not shown) for securing the annular frame 19 to the clamping table 14 are provided on an outer circumferential region of the clamping table 14. The laser processing device 12 also includes a laser irradiation unit 16 arranged above the clamping table 14. The laser irradiation unit 16 applies a pulsed laser beam 25, generated and emitted by a laser oscillator (not shown), and focuses the pulsed laser beam 25 onto predetermined positions.In particular, the laser oscillator is configured to generate and emit a pulsed laser beam 25 having a wavelength that can be absorbed by the wafer 11, for example a wavelength that is absorbable by the wafer 11 or a wavelength that can be easily absorbed by the wafer 11.

[0025] During the machining step of a groove, the separating strip 17, which adheres to the back 11b of the wafer 11, is held in contact with the clamping surface of the clamping table 14, and a vacuum from the suction source is applied to the separating strip 17. Simultaneously, the frame 19 is secured to the clamping table 14 by the clamps. The wafer 11 is thus securely held to the clamping table 14 with the protective film 23, which is exposed upwards at its end face 11a, in place. The clamping table 14 is then rotated about its own axis to align one of the projected cutting lines 13 to be machined, i.e., a projected target cutting line 13, with the machining feed direction of the laser processing device 12. Furthermore, the clamping table 14 is moved to align the laser irradiation unit 16, for example, with a direction of extension of the projected target cutting line 13.

[0026] While the pulsed laser beam 25 is applied from the laser irradiation unit 16 to the end face 11a of the wafer 11, the clamping table 14 is then, as in Fig. As shown in Figure 3, the laser beam 25 is moved in the processing feed direction. For example, the pulsed laser beam 25 is focused on the end face 11a of the wafer 11. The conditions under which the pulsed laser beam 25 is applied—that is, the power level, spot diameter, repetition rate, etc.—are set within a range such that the pulsed laser beam 25 does not cut through the wafer 11. In this way, a machined groove 27 with a depth insufficient to cut through the wafer 11 is formed along the projected target cutting line 13 by the pulsed laser beam 25 irradiating the wafer 11 along this line. The above process is repeated to form machined grooves 27 in the wafer 11 along all projected cutting lines 13, thus completing the machining groove formation step.During the machining step of a machined groove, residues or machining chips 29 not shown and machining-related expansions are generated in the machined grooves 27 and adjacent areas.

[0027] The machining step of a machined groove is followed by a plasma etching step, which is carried out to remove the residues 29 and the machining-related elongations that remain in the machined grooves 27 and adjacent areas. Fig. 4 is a sectional view showing a schematic, partially block-shaped plasma etching device 22, which is used in the plasma etching step in accordance with the present embodiment. As in Fig. As shown in Figure 4, the plasma etching device 22 encloses a vacuum chamber 24, which has a defined processing area. The vacuum chamber 24 encloses a side wall 24a with a defined opening 24b through which the wafer 11 can be loaded into and removed from the processing area in the vacuum chamber 24. A locking mechanism 26 is mounted on an outer surface of the side wall 24a for controlled closing of the opening 24b. The locking mechanism 26 is connected to an opening / closing unit 28, such as an air cylinder or similar device, which is located below the locking mechanism 26. The locking mechanism 26 is movable in the vertical direction by the opening / closing unit 28. When the lock 26 is lowered by the opening / closing unit 28, the opening 24b is exposed to allow the wafer 11 to be loaded into or removed from the processing space through it.

[0028] The vacuum chamber 24 encloses a bottom wall 24c, which is connected via a pipe 30 to an evacuation pump 32. To process the wafer in the processing chamber, the opening / closing unit 28 moves the lock 26 upwards to close the opening 24b. The evacuation pump 32 then evacuates the processing chamber to create a pressure drop within it. The processing chamber contains a table base 34 to support the wafer 11. The table base 34 includes a disc-shaped plate 36 and a column-shaped post 38 that extends downwards from the center point of a lower surface of the disc-shaped plate 36.

[0029] A disc-shaped electrostatic clamping table 40, which has a smaller diameter than the disc-shaped plate 36, is arranged on an upper surface of the disc-shaped plate 36. The electrostatic clamping table 40 includes a table body 42, which is made of an insulating material, and a plurality of electrodes 44 embedded in the table body 42. The electrostatic clamping table 40 attracts the wafer 11 and holds it against it under electrostatic forces generated between the electrodes 44. Each of the electrodes 44 is electrically connected to a direct current source (DC power source) 46, which generates a DC high voltage of, for example, approximately 5 kV. The table body 42 of the electrostatic clamping table 40 has defined suction openings 42a for transmitting suction forces through them to attract the wafer 11 to the table body 42 under suction force.The suction passages 42a are connected to a suction pump 48 via a suction channel 34a, which is defined in the table base 34.

[0030] To hold the wafer 11 against the electrostatic clamping table 40, the wafer 11 is placed on the upper surface of the electrostatic clamping table 40 and the suction pump 48 is activated. The wafer 11 is held in close contact with the upper surface of the electrostatic clamping table 40 by suction forces generated by the suction pump 48. Then, the DC power supply 46 applies the DC voltage to the electrodes 44, which develops a potential difference between the electrodes 44 to attract and hold the wafer 11 against the upper surface of the electrostatic clamping table 40 under electrostatic forces.

[0031] The table base 34 has a coolant channel 34b, which is defined therein. The coolant channel 34b has opposite ends that are connected to a circulation unit 50, which circulates a coolant through the coolant channel 34b. When the circulation unit 50 is actuated, the coolant flows through the coolant channel 34b from one end to its other end, thus cooling the table base 34 and adjacent parts.

[0032] The vacuum chamber 24 has an upper wall 24d connected to a downstream end of a gas supply nozzle 52, which supplies an etching gas in a plasma state to the wafer 11, which is held in position on the electrostatic clamping table 40. The supply nozzle 52 has an upstream end connected to a parallel array of gas supply sources for supplying different gases to the gas supply nozzle 52. In particular, a first gas supply source 60a for supplying SF6 is connected to the upstream end of the supply nozzle 52 via a valve 54a, a flow control 56a, and a valve 58a. A second gas supply source 60b for supplying O2 is connected to the upstream end of the supply nozzle 52 via a valve 54b, a flow control 56b, and a valve 58b.A third gas supply source 60c for supplying an inactive or inert gas is connected to the upstream end of the supply nozzle 52 by a valve 54c, a flow control 56c, and a valve 58c. In this way, an etching gas, comprising a mixture of these different gases mixed in a desired ratio, is supplied to the supply nozzle 52.

[0033] An electrode 62 for applying a high-frequency voltage to the etching gas flowing through the feed nozzle 52 is mounted on a central section of the feed nozzle 52 between its upstream and downstream ends. The electrode 62 is electrically connected to a high-frequency power supply 64. The electrode 62 and the high-frequency power supply 64 together form a high-frequency voltage application unit. The high-frequency power supply 64 applies a high-frequency voltage in the range of 0.5 to 5 kV with a frequency in the range of 450 kHz to 2.45 GHz to the electrode 62. By applying the high-frequency voltage to the etching gas flowing through the feed nozzle 52 with the electrode 62 and the high-frequency power supply 64, the etching gas is converted into a plasma state in which ions and radicals are present.The etching gas in the plasma state is supplied to the processing chamber via a feed opening 52a, which is defined at the downstream end of the feed nozzle 52 and opens into the processing chamber. The number of gas supply sources and the types of gases supplied by the gas supply sources can be changed depending on the type of wafer 11 being processed. The flow rates at which the respective gases flow to the feed nozzle 52 are adjusted to suitable values ​​to ensure that the etching gas can be converted into a plasma state.

[0034] A diffuser 66 is mounted on an inner surface of the upper wall 24d around the feed opening 52a, where the feed nozzle 52 is connected to the vacuum chamber 24. The diffuser 66 distributes the etching gas in the plasma state, which flows from the feed nozzle 52 into the processing chamber in the vacuum chamber 24, over the electrostatic clamping table 40. A tube 68 is mounted in the side wall 24a opposite the opening 24b and opens into the processing chamber. The tube 68 is connected to the third gas supply source 60c, for example, by a valve and flow control (not shown). The inert gas supplied from the third gas supply source 60c via the tube 68 acts as an internal gas that fills the processing chamber in the vacuum chamber 24.

[0035] In the plasma etching step, the barrier 26 is initially lowered by the opening / closing unit 28, exposing the opening 24b. The wafer 11 is then loaded through the exposed opening 24b into the processing chamber in the vacuum chamber 24 and positioned on the upper surface of the electrostatic clamping table 40 such that the protective film 23 covering the end face 11a of the wafer 11 is exposed upwards. In other words, the release tape 17, which adheres to the back 11b of the wafer 11, is held in contact with the upper surface of the electrostatic clamping table 40. At this point, the annular frame 19 can remain attached to the outer circumferential section of the release tape 17. Alternatively, the annular frame 19 can be removed if necessary.

[0036] The suction pump 48 is then activated to keep the wafer 11, i.e., the separating strip 17 attached to it, in close contact with the electrostatic clamping table 40. The DC power supply 46 applies the DC voltage to the electrodes 44, creating a potential difference between them to attract and hold the wafer 11 against the upper surface of the electrostatic clamping table 40 under electrostatic forces. The opening / closing unit 28 is activated to lift the lock 26 and close the opening 24b, and the evacuation pump 32 is activated to evacuate the processing chamber and reduce its pressure. Once the pressure in the processing chamber has been reduced to, for example, 200 Pa, the chamber is filled with the internal gas, which is supplied as an inert gas from the third gas supply source 60c through the tube 68.The internal gas filling the processing chamber can be a rare gas, such as Ar, He or similar, or a gas mixture including a rare gas mixed with N2, H2 or similar.

[0037] After the processing chamber has been filled with the inactive gas, the first gas supply source 60a, the second gas supply source 60b, and the third gas supply source 60c, respectively, feed SF6, O2, and the inactive gas to the gas supply nozzle 52 at their respective flow rates. The high-frequency power supply 64 applies the high-frequency voltage to the electrode 62, which, as it flows through the gas supply nozzle 52, converts the mixture of SF6, O2, and the inactive gas into a plasma state containing ions and radicals. The gas supply nozzle 52 then feeds the gas mixture in its plasma state through the supply opening 52a into the processing chamber in the vacuum chamber 24. When the gas mixture in the plasma state flows through the diffuser 66, which is arranged below the feed opening 52a, the gas mixture in the plasma state is distributed through the diffuser 66 and directed to the end face 11a of the wafer 11, which is attracted and held on the electrostatic clamping table 40.

[0038] Fig. Figure 5 is a partial lateral sectional view illustrating how the gas mixture, also referred to as "etching gas" and designated 31, is supplied in the plasma state to the end face 11a of the wafer 11 during the plasma etching step. Since the gas mixture 31, which has been converted to the plasma state outside the vacuum chamber 24, is supplied to the vacuum chamber 24 through the feed nozzle 52 in accordance with the present embodiment, it is assumed that a large proportion of the highly reactive ions in the gas mixture 31 are lost before it is introduced into the vacuum chamber 24, and that radicals are more abundant than ions in the processing space within the vacuum chamber 24.This moderates the progress of the etching of the end face 11a (a surface) of the wafer 11 by ions, and the residue 29 and the machining-related strains that remain in the machined grooves 27 and adjacent areas can be, as in . Fig. 5 shown, without excessive etching progress being removed from the end face 11a of wafer 11.

[0039] Following the plasma etching step, a protective film removal step is performed to remove the protective film 23 from the end face 11a of the wafer 11. In this step, the protective film 23 is removed from the end face 11a of the wafer 11, for example, by an aqueous solution, peeling, incineration, or similar methods. These removal processes are for illustrative purposes only, and the protective film 23 can be removed by other suitable methods.

[0040] In the wafer manufacturing process in accordance with the present embodiment, the residues 29 and the processing-related strains that remain at positions spaced apart from the end face 11 (a surface) of the wafer 11 can be removed without excessive etching progress at the end face 11a of the wafer, since, as described above, the gas mixture 31, which has been converted into the plasma state outside the vacuum chamber 24, which receives the wafer 11 therein, is introduced into the vacuum chamber 24 through the feed nozzle 52 during the plasma etching step.

[0041] In the forming step of a machined groove in accordance with the present embodiment, the machined grooves 27 are formed in the wafer 11 by applying the pulsed laser beam 25 to the end face 11a of the wafer 11. However, machined grooves in the wafer 11 can be formed by other processes. Fig. Figure 6 is a partial lateral section view illustrating a machining step of a groove according to a modification. The machining step of a groove according to the modification is shown, for example, as in Fig. 6 shown, carried out by using a cutting device 72. As shown in Fig. As shown in Figure 6, the cutting device 72 includes a clamping table or holding table 74 for holding the wafer 11. The clamping table 74 is coupled to a rotary actuator (not shown), such as a motor, which rotates the clamping table 74 about its axis, which is substantially parallel to a vertical direction. The clamping table 74 is arranged above a table movement mechanism (not shown) that moves the clamping table 74 in a processing feed direction, i.e., a first horizontal direction. The clamping table 74 has an upper surface that serves as a holding surface for holding the wafer 11 against it under suction force. The holding surface is connected to a suction source (not shown) via a suction channel (not shown) defined in the clamping table 74. A plurality of clamps (not shown) for securing the annular frame 19 to the clamping table 74 are provided on an outer circumferential region of the clamping table 74.

[0042] The cutting device 72 includes a cutting unit 76, which is arranged above the clamping table 74. The cutting unit 76 has a spindle 78 that is rotatable about its own axis, which extends substantially perpendicular to the machining feed direction. At one end, the spindle 78 supports an annular cutting blade 80, which is made with a bonding agent containing abrasive grains. A nozzle (not shown) for supplying a cutting fluid to the wafer 11 and the cutting blade 80 are arranged in the vicinity of the cutting blade 80. The other end of the spindle 78 is coupled to a rotary actuator (not shown), such as a motor. The cutting blade 80, mounted at one end of the spindle 78, is rotatable about its own axis by rotational forces transmitted by the rotary actuator.The cutting unit 76 is supported by a cutting unit movement mechanism (not shown) which moves the cutting unit 76 in a division feed direction, i.e. a second horizontal direction, and a vertical direction.

[0043] In the machining step of a groove according to the modification, the separating strip 17, which adheres to the back 11b of the wafer 11, is held in contact with the clamping surface of the clamping table 74, and a vacuum from the suction source is applied to the separating strip 17. Simultaneously, the frame 19 is secured to the clamping table 74 by the clamps. The wafer 11 is thus securely held to the clamping table 74 with the protective film 23 on its end face 11a facing upwards. The clamping table 74 is then rotated about its own axis to align a projected target separation line 13 with the machining feed direction of the cutting device 72. The clamping table 74 and the cutting unit 76 are moved relative to each other to align the plane of the cutting blade 80 with the extension of the projected target separation line 13.The lower end of the cutting blade 80 is moved to a vertical position that is lower than the front face 11a of the wafer 11, but higher than its back face 11b.

[0044] While the cutting blade 80 is rotated, the clamping table 74 is moved in the machining feed direction. Simultaneously, the nozzle delivers a cutting fluid to the wafer 11 and the cutting blade 80. The cutting blade 80 cuts along the projected target parting line 13 into the wafer 11, forming a machined groove 33 in the wafer 11 to a depth insufficient to completely sever the wafer 11. The above process is repeated to form machined grooves 33 along all projected parting lines 13 in the wafer 11, whereupon the machining groove formation step is completed in accordance with the modification. During the machining groove formation step, residues or machining chips 35 (not shown) and machining-related strains are generated in the machined grooves 33 and adjacent areas. Design 2:

[0045] A method for processing a wafer is now described in order to separate the wafer with a laser beam applied to the bottoms of cut grooves formed in a back side of the wafer in accordance with the present embodiment. Fig. Figure 7 is a perspective view schematically illustrating a wafer 11 and other elements in accordance with the present embodiment by way of example. The wafer 11 to be processed by the wafer processing method in accordance with the present embodiment is identical to the wafer 11 in accordance with embodiment 1 described above. In accordance with the present embodiment, the wafer 11 has, as shown in Fig. Figure 7 shows an end face 11a to which a separating strip 37 is attached, the separating strip having a larger diameter than the wafer 11. The separating strip 37 has an outer circumferential section attached to an annular frame 39. In other words, the wafer 11 is supported on the frame 39 by the separating strip 37.

[0046] The wafer processing method in accordance with the present embodiment begins with a slot forming step to form slot forming along the projected parting lines 13 in a back side 11b of the wafer 11. Fig. Figure 8 is a partial lateral sectional view illustrating the groove formation step. This groove formation step is performed, for example, using the cutting device 72 described above. During this step, the separating strip 37, which adheres to the end face 11a of the wafer 11, is held in contact with the clamping surface of the clamping table 74, and a vacuum from the suction source is applied to the separating strip 37. Simultaneously, the frame 39 is secured to the clamping table 74 by clamps. The wafer 11 is thus securely held on the clamping table 74 with its back side 11b facing upwards. The clamping table 74 is then rotated about its own axis to align a projected target separation line 13 with the processing feed direction of the cutting device 72.The clamping table 74 and the cutting unit 76 are moved relative to each other to align the plane of the cutting blade 80 with an extension of the projected target dividing line 13. The lower end of the cutting blade 80 is moved to a vertical position that is lower than the back side 11b of the wafer 11, but higher than its front side 11a.

[0047] While the cutting blade 80 is rotated, the clamping table 74 is moved in the machining feed direction. Simultaneously, the nozzle supplies a cutting fluid to the wafer 11 and the cutting blade 80. The cutting blade 80 cuts along the projected target parting line 13 into the wafer 11, forming a groove 41 in the wafer 11 to a depth that does not extend to the end face 11a, i.e., a depth that is not sufficient to completely pierce the wafer 11. The above process is repeated to form grooves 41 in the wafer 11 along all projected parting lines 13, whereupon the groove formation step is completed. During the groove formation step, residues or machining chips 43 (not shown) and machining-related strains are generated in the grooves 41 and adjacent areas.

[0048] The cutting groove formation step is followed by a separation step to divide the wafer 11 into individual components 15 by applying a laser beam to the bottoms of the cutting grooves 41. Fig. Figure 9 is a partial lateral sectional view illustrating the separation step. The separation step is performed, for example, using the laser processing device 12 described above. During the separation step, the separation strip 37, which adheres to the end face 11a of the wafer 11, is held in contact with the clamping surface of the clamping table 14, and a vacuum from the suction source is applied to the separation strip 37. Simultaneously, the frame 39 is secured to the clamping table 14 by the clamps. The wafer 11 is thus securely held against the clamping table 14 with its back side 11b facing upwards. The clamping table 14 is then rotated about its own axis to align a target cutting groove 41 with the processing feed direction of the laser processing device 12. Furthermore, the clamping table 14 is moved to align the laser irradiation unit 16, for example, with an extension of the target cutting groove 41.

[0049] While a pulsed laser beam 45 is applied from the laser irradiation unit 16 to the back side 11b of the wafer 11, the clamping table 14 is then, as in Fig. As shown in Figure 9, the process is carried out in the feed direction. The pulsed laser beam 45 is focused, for example, on the bottom of the target cutting groove 41. The conditions under which the pulsed laser beam 45 is applied—that is, the power level, the spot diameter, the repetition rate, etc.—are set within such a range that the pulsed laser beam 45 cuts through the wafer 11 at the bottom of the cutting groove 41. In this way, the laser beam 45 is applied to the wafer 11 along the cutting groove 41, i.e., the projected separation line 13, thereby cutting through the wafer 11. The above process is repeated to cut through the wafer 11 along all projected separation lines 13, forming component chips corresponding to the respective components 15, and thus completing the separation step.During the separation step, residues 43 (not shown) and machining-related strains are generated in the cut grooves 41 and adjacent areas. In other words, residues 43 and machining-related strains generated during the cut groove formation step or the separation step remain on each of the component chips.

[0050] The separation step is followed by a plasma etching step to remove the residues 43 and processing-related strains that remain on each of the component chips. Fig. Figure 10 is a partial sectional side view illustrating the plasma etching step. The plasma etching step according to the present embodiment is performed using the plasma etching device 22 described above. Specific details of the plasma etching procedure are the same as those of the plasma etching step according to embodiment 1.

[0051] In the plasma etching step according to the present embodiment, the barrier 26 is initially lowered by the opening / closing unit 28, exposing the opening 24b. The wafer 11 is then loaded through the exposed opening 24b into the processing chamber in the vacuum chamber 24 and placed on the upper surface of the electrostatic clamping table 40, so that the back side 11b of the wafer 11 is exposed upwards. In other words, the separating strip 37, which adheres to the end face 11a of the wafer 11, is held in contact with the upper surface of the electrostatic clamping table 40. At this point, the annular frame 39 can remain attached to the outer circumferential section of the separating strip 37. Alternatively, the annular frame 39 can be removed if necessary.

[0052] The suction pump 48 is then activated to keep the wafer 11, i.e., the separating strip 37 attached to it, in close contact with the electrostatic clamping table 40. The DC power supply 46 applies the DC voltage to the electrodes 44, creating a potential difference between the electrodes 44 to attract and hold the wafer 11 against the upper surface of the electrostatic clamping table 40 under electrostatic forces. The opening / closing unit 28 is activated to lift the lock 26 and close the opening 24b, and the evacuation pump 32 is activated to evacuate the processing chamber and reduce the pressure within it. After the pressure of the processing chamber has been reduced to approximately 200 Pa, for example, the processing chamber is filled with the internal gas, which is supplied as the inactive gas, supplied through the tube 68 from the third gas supply source 60c.The internal gas filling the processing chamber can be a rare gas, such as Ar, He or similar, or a gas mixture containing a rare gas mixed with N2, H2 or similar.

[0053] After the processing chamber has been filled with the inactive gas, the first gas supply source 60a, the second gas supply source 60b, and the third gas supply source 60c, respectively, supply SF6, O2, and the inactive gas to the gas supply nozzle 52 at their respective flow rates. The high-frequency power supply 64 applies the high-frequency voltage to the electrode 62, whereby the mixture of SF6, O2, and the inactive gas is converted into a plasma state containing ions and radicals as it flows through the gas supply nozzle 52. The gas supply nozzle 52 then delivers the gas mixture, i.e., an etching gas 47, in this plasma state through the supply opening 52a to the processing chamber in the vacuum chamber 24.When the gas mixture 47 in the plasma state flows through the diffuser 66, which is arranged below the feed opening 52a, the gas mixture 47 in the plasma state is distributed through the diffuser 66 and is fed to the back side 11b of the wafer 11, which is attracted and held on the electrostatic clamping table 40.

[0054] Insofar as the gas mixture 47, which has been converted to the plasma state outside the vacuum chamber 24, is supplied to the vacuum chamber 24 through the feed nozzle 52 in accordance with the present embodiment, it is assumed that the majority of the highly reactive ions in the gas mixture 47 are lost before being introduced into the vacuum chamber 24, and radicals are more abundant than ions in the processing space within the vacuum chamber 24. Therefore, the progress of the etching of the back side 11b of the wafer 11 is inhibited by ions, and the residues and processing-related strains remaining on the device chips can be removed without excessive etching progress on the back side 11b (a surface) of the wafer 11, as shown in Fig. 10 shown, be appropriately removed. Design 3:

[0055] A method for processing a wafer in accordance with the present embodiment is now described in order to divide or separate the wafer by forming modified layers and cracks therein along projected parting lines. In the present embodiment, a wafer 11 is used which is identical to the wafer 11 in accordance with embodiment 2. In other words, the parting strip 37 adheres to the end face 11a of the wafer 11.

[0056] The wafer processing method in accordance with the present embodiment begins with a separation step to divide the wafer 11 by forming modified layers and cracks therein along the projected separation lines 13. Fig. Figure 11A is a side sectional view illustrating the separation step, and Fig. Figure 11B is a side sectional view illustrating the separation step. The separation step is performed, for example, using the laser processing device 12 described above. However, the laser oscillator of the laser irradiation unit 16 (not shown) is configured to generate and emit a pulsed laser beam 49 with a wavelength that can be transmitted through the wafer 11, that is, a wavelength that is readily absorbed by the wafer 11. The laser irradiation unit 16 applies and focuses the pulsed laser beam 49, which is to be transmitted through the wafer 11, at predetermined positions.

[0057] During the separation step, the separation strip 37, which adheres to the end face 11a of the wafer, is held in contact with the clamping surface of the clamping table 14, and a vacuum from the suction source is applied to the separation strip 37. Simultaneously, the frame 39 is secured to the clamping table 14 by the clamps. The wafer 11 is thus securely held on the clamping table 14 with its back side 11b facing upwards. The clamping table 14 is then rotated about its own axis to align the projected target separation line 13 with the processing feed direction of the laser processing device 12. The clamping table 14 is moved, for example, to align the laser irradiation unit 16 with the extent of the projected target separation line 13.

[0058] While a pulsed laser beam 49 is applied from the laser irradiation unit 16 to the back side 11b of the wafer 11, the clamping table 14 is then, as in Fig. 11A, shown, moved in the processing feed direction. The pulsed laser beam 49 is focused, for example, in the wafer 11. Conditions under which the pulsed laser beam 49 is applied, i.e., the power level, spot diameter, repetition rate, etc., of the pulsed laser beam 49 are set within such a range that the pulsed laser beam 49 can modify the interior of the wafer 11 by means of multiphoton absorption to form a modified layer 51 and a crack 53 in the wafer 11. In this way, the laser beam 49, which is applied along the projected target separation line 13, forms a modified layer 51 in the wafer 11, with a crack 53 developing from the modified layer 51 to the end face 11a or the back face 11b, as shown in Fig. As shown in Figure 11B, the wafer 11 is extended, thereby dividing it along the projected target dividing line 13. The above process is repeated to divide the wafer 11 along all projected dividing lines 13, for example, into component chips corresponding to the respective components 15, whereupon the dividing step is completed. The modified layers 51, which served as points where the wafer 11 begins to be divided, remain on the side faces of the component chips.

[0059] The separation step is followed by a plasma etching step to remove the modified layers 51 that remain on the component chips. Fig. Figure 12 is a partial lateral sectional view illustrating the plasma etching step. The plasma etching step according to the present embodiment is performed using the plasma etching device 22 described above. Specific details of the plasma etching procedure are the same as those of the plasma etching step according to embodiment 2. In the plasma etching step according to the present embodiment, a gas mixture or etching gas 55, which has been converted into a plasma state outside the vacuum chamber 24, is used as described in Figure 12. Fig. Figure 12 shows the gas mixture 55 being supplied through the feed nozzle 52 into the vacuum chamber 24. Consequently, it is assumed that a large proportion of the highly reactive ions in the gas mixture 55 are lost before it is introduced into the vacuum chamber 24, and radicals are more abundant than ions within the processing space in the vacuum chamber 24. Therefore, the etching progress of the back surface 11b of the wafer 11 is inhibited by ions, and the modified layers 51 remaining on the device chips can be adequately removed without excessive etching progress on the back surface 11b (a face) of the wafer 11. Design 4:

[0060] A method for processing a wafer to divide it is now described below, by causing a cutting blade to cut along the projected parting lines. In the present embodiment, a wafer 11 is used that is identical to the wafer 11 in accordance with embodiment 2. In other words, the parting strip 37 adheres to the end face 11a of the wafer 11.

[0061] The wafer processing method in accordance with the present embodiment begins with a separation step to divide the wafer 11 by causing a cutting blade to cut into the wafer along the projected separation lines 13, thereby dividing the wafer 11 along the projected separation lines 13. Fig. Figure 13 is a partial sectional view illustrating the separation step. The separation step is performed using the cutting device 72 described above. During the separation step, the separation strip 37, which adheres to the end face 11a of the wafer 11, is held in contact with the clamping surface of the clamping table 74, and a vacuum from the suction source is applied to the separation strip 37. Simultaneously, the frame 39 is secured to the clamping table 74 by the clamps. The wafer 11 is thus securely held on the clamping table 74 with its back side 11b facing upwards. The clamping table 74 is then rotated about its own axis to align a projected target separation line 13 with the processing feed direction of the cutting device 72. The clamping table 74 and the cutting unit 76 are moved relative to each other in order to align the plane of the cutting blade 80 with an extension of the projected target cutting line 13.The lower end of the cutting blade 80 is moved to a vertical position that is lower than the end face 11a of the wafer 11.

[0062] While the cutting blade 80 is rotated, the clamping table 74 is moved in the machining feed direction. Simultaneously, the nozzle supplies a cutting fluid to the wafer 11 and the cutting blade 80. The cutting blade 80 cuts along the projected target parting line 13 into the wafer 11, forming a kerf or slot 57 along which the wafer 11 is cut. The above process is repeated to form kerfs 57 along all projected parting lines 13 in the wafer 11, forming device chips that correspond to the respective devices 15, whereupon the parting step is completed. During the parting step, residues or machining chips 59 (not shown) and machining-related strains are generated in the kerfs 57 and adjacent areas. In other words, the residues 59 and the machining-related strains remain on the device chips.

[0063] The separation step is followed by a plasma etching step to remove the residues 59 and the processing-related strains that remained on each of the component chips. Fig. Figure 14 is a partial lateral sectional view illustrating the plasma etching step. The plasma etching step according to the present embodiment is performed using the plasma etching device 22 described above. Specific details of the plasma etching procedure are the same as those of the plasma etching step according to embodiment 2. In the plasma etching step according to the present embodiment, a gas mixture or etching gas 61, which has been converted into a plasma state outside the vacuum chamber 24, is used as described in Figure 14. Fig.As shown in Figure 14, the gas mixture 61 is supplied through the feed nozzle 52 into the vacuum chamber 24. Consequently, it is assumed that a large proportion of the highly reactive ions in the gas mixture 61 are lost before it is introduced into the vacuum chamber 24, and radicals are more abundant than ions within the processing space in the vacuum chamber 24. Therefore, the progress of the etching of the back side 11b of the wafer 11 is inhibited by ions, and the residues 59 and processing-related strains remaining on the device chips can be adequately removed without excessive etching progress on the back side 11b (one face) of the wafer 11.

Claims

[1] Method for dividing a wafer (11) into component chips and for removing processing-induced strains from machined grooves of the wafer (11) on which components (15) are formed in a plurality of areas which are divided on its end face (11a) by a plurality of projected parting lines (13) arranged in a lattice structure, the method comprising: a cutting groove formation step in which a cutting blade (80) is caused to cut into the wafer (11) from its back side (11b) along the projected parting lines (13) in order to form cutting grooves (41) in the wafer (11) to a depth just before the end face (11a) of the wafer (11); a separation step involving the application of a laser beam (45) to the bottoms of the cutting grooves (41) from the back (11b) of the wafer (11) to divide the wafer (11) into the component chips corresponding to the respective components (15); and after the separation step a plasma etching step with a supply of an etching gas (47) in a plasma state to the wafer (11) from its back side (11b) in order to remove the processing-related strains that remained on the component chips, including the plasma etching step: Converting the etching gas (43) into the plasma state outside a low-pressure chamber (24) which contains the wafer (11), wherein the etching gas contains ions and radicals, and Reducing the number of ions by supplying the etching gas (43) from outside the vacuum chamber (24) in the plasma state through a supply nozzle (52) connected to the vacuum chamber (24) into the vacuum chamber (24). [2] Method for dividing a wafer (11) into component chips and for removing modified layers that remain on side faces of the component chips, wherein components (15) are formed on the wafer (11) in a plurality of regions which are divided at its end face (11a) by a plurality of projected separation lines (13) arranged in a lattice structure, the method comprising: a separation step involving the application of a laser beam (49) having a wavelength that can be transmitted through the wafer (11), from its rear side (11b) along the projected separation lines (13) onto the wafer (11), focusing the laser beam (49) on positions in the wafer (11) to form modified layers (51) in the wafer (11) and to develop cracks (53) extending from the modified layers (51) to the front face (11a) and the rear side of the wafer (11), thereby dividing the wafer (11) into the component chips corresponding to the respective components (15); and After the separation step, a plasma etching step is performed by supplying an etching gas (43) in a plasma state to the wafer (11) from its back side to remove the modified layers that remained on the side faces of the component chips. including the plasma etching step: Converting the etching gas (43) into the plasma state outside a low-pressure chamber (24) which contains the wafer (11), wherein the etching gas contains ions and radicals, and Reducing the number of ions by supplying the etching gas (43) in the plasma state from outside the vacuum chamber (24) through a supply nozzle (52) connected to the vacuum chamber (24) into the vacuum chamber (24). [3] Method for dividing a wafer (11) into component chips and for removing processing-related strains remaining on the component chips, wherein components (15) are formed on the wafer in a plurality of areas which are divided at its end face (11a) by a plurality of projected separation lines (13) arranged in a lattice structure, the method comprising: a separation step in which a cutting blade (80) is caused to cut into the wafer (11) from its rear side (11b) along the projected separation lines (13) in order to divide the wafer (11) into component chips corresponding to the respective components (15); and after the separation step a plasma etching step with a supply of an etching gas (61) in a plasma state to the wafer (11) from its back side (11b) in order to remove processing distortions that remained on the component chips, including the plasma etching step: Converting the etching gas (61) into a plasma state outside a low-pressure chamber (24) which contains the wafer (11), wherein the etching gas contains ions and radicals, and Reducing the number of ions by supplying the etching gas (61) from outside the vacuum chamber (24) in the plasma state through a supply nozzle (52) connected to the vacuum chamber (24) into the vacuum chamber (24).

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