Wafer division method

Abstract

To reduce the time required for removing a wafer mask.SOLUTION: Provided is a division method for dividing a wafer (10) along a street (14) by irradiating the wafer with a plasma-activated etching gas (EG), in which the wafer has devices (15) formed in regions divided by the street. A liquid resin (34) is applied to the device and dried to form a mask (17) that masks the device surface while exposing the streets. Plasma-activated etching gas is then applied onto the wafer to form a division groove (18) along the streets. Subsequently, an altered portion (D) on the mask surface is removed by alternating continuous and pulsed irradiation with an oxygen-containing plasma (P), after which the entire mask is removed from the wafer.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for dividing a wafer. [Background technology]

[0002] Patent Documents 1 and 2 disclose a dividing method for dividing a wafer using plasma. In this dividing method, a protective film is formed on the surface of the wafer using a water-soluble resin, and then the protective film is irradiated with a laser beam to remove the protective film along the streets. By removing the protective film, a mask for protecting the device is formed, and the wafer with the formed mask is placed in a processing chamber and plasma etched to divide the wafer.

[0003] A water-soluble resin is used for the mask, and after division, the mask is removed from the wafer by pouring cleaning water over it and dissolving it. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-103330 [Patent Document 2] Japanese Patent Application Publication No. 2018-041935 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the plasma etching method described above, the mask is altered by plasma irradiation, making it difficult to dissolve even when washing water is applied to the mask. This is because the edges of the mask along the streets and the surface of the mask are altered by reaction during plasma irradiation. Therefore, to remove the mask from the wafer, a scrubbing step with a scrubbing sponge is required, which lengthens the cleaning time and reduces productivity.

[0006] The present invention has been made in view of the above points, and one of its objects is to provide a wafer dividing method that can shorten the time required to remove the mask. [Means for solving the problem]

[0007] One embodiment of the present invention provides a wafer dividing method that involves irradiating a wafer having devices formed in areas defined by streets with plasmatized etching gas and dividing the wafer along the streets, the method comprising: a supporting step of supporting the wafer by adhering a support member to the surface opposite to the surface on which the streets are formed; a mask forming step of applying a liquid resin to the devices and drying it to mask the surface of the devices and expose the streets; a dividing step of, after the mask forming step, irradiating the wafer with plasmatized etching gas from the mask side to form dividing grooves along the streets; a first removing step of, after the dividing step, removing the surface of the mask by continuous and pulsed irradiation of the mask with oxygen-containing plasma; and a second removing step of, after the first removing step, removing the entire mask from the wafer. [Effects of the Invention]

[0008] According to the present invention, in the first removal step, the surface of the mask is removed by irradiating it with oxygen-containing plasma, so even if the surface of the mask is altered by the plasma irradiation in the dividing step, the entire mask, including the surface, can be easily removed in a short time. Furthermore, since the oxygen-containing plasma is irradiated in pulses, thermal alteration of the mask can be suppressed, and the mask can be reliably removed in the second removal step, thereby improving productivity. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 10 is an explanatory diagram of a supporting step in the embodiment. [Figure 2] 2A and 2B are explanatory diagrams of a mask formation step according to the embodiment. [Figure 3] 1 is an overall schematic view of an etching apparatus according to an embodiment; [Figure 4] FIG. 10 is an explanatory diagram of a dividing step according to the embodiment. [Figure 5] FIG. 4 is an explanatory view of a first removal step in the embodiment. [Figure 6] FIG. 10 is an explanatory view of a second removal step in the embodiment. [Figure 7] FIG. 10 is an explanatory view of a first removal step in a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] The wafer dividing method of this embodiment will be described below with reference to the accompanying drawings. The wafer dividing method of this embodiment is carried out in the following order: supporting step, mask forming step, dividing step, first removing step, and second removing step. Note that the steps shown in each drawing in this embodiment are merely examples, and are not limited to this configuration.

[0011] FIG. 1 is an explanatory diagram of a supporting step in an embodiment. As shown in FIG. 1, first, a supporting step is performed in which a wafer 10 is supported by a support member 20. The wafer 10 is plate-shaped and has a front surface 11 (upper surface in FIG. 1) and a back surface 12 (lower surface in FIG. 1). The shape of the wafer 10 in a plan view may be any shape, such as a circle or a rectangle. On the front surface 11 of the wafer 10, devices 15 are formed in areas partitioned by streets 14 that form a lattice pattern when viewed from above. The back surface 12 of the wafer 10 is the surface opposite to the surface on which the streets 14 are formed.

[0012] In the supporting process, the wafer 10 and a ring frame 22 having a larger diameter than the wafer 10 are placed on a predetermined table (not shown), and a sheet-like supporting member 20 is attached to the back surface 12 of the wafer 10 and the back surface 23 of the ring frame 22.

[0013] The support member 20 can be exemplified by a dicing tape having an adhesive layer, and the area of ​​the support member 20 is larger than the area of ​​the back surface 12 of the wafer 10, and the support member 20 is attached across the wafer 10 and the ring frame 22. As a result, the wafer 10 is supported by the support member 20 and the ring frame 22, and the wafer 10, support member 20, and ring frame 22 become an integrated unit to be processed 25.

[0014] In addition, the support member 20 may be a sheet that has the property of melting when heated to a predetermined temperature or higher and thermally welding to the object, and when such a sheet is used, the support member 20, the wafer 10, and the ring frame 22 are attached by thermal welding.

[0015] 2A and 2B are explanatory diagrams of a mask forming step in the embodiment. After the supporting step is performed, a mask forming step is performed in which the surface of the devices 15 on the wafer 10 is masked to expose the streets 14.

[0016] 2A, in the mask formation process, first, the processing target unit 25 is transported and held on a holding table 30 of the film forming and cleaning device. A resin supply nozzle 32 connected to a liquid resin supply source 31 is positioned above the holding table 30, and liquid resin 34 is applied (supplied) from the resin supply nozzle 32 to the center of the front surface 11 of the wafer 10.

[0017] After applying a predetermined amount of liquid resin 34, holding table 30 is rotated around a central axis parallel to the vertical direction, whereupon centrifugal force causes liquid resin 34 to spread toward the periphery of wafer 10, and liquid resin 34 is applied to the entire surface 11 of wafer 10, including the surfaces of devices 15.

[0018] An air nozzle 37 connected to an air source 36 is positioned above the holding table 30. After the liquid resin 34 has been applied, air is blown from the air nozzle 37 toward the liquid resin 34 applied to the wafer 10 while the holding table 30 is rotated, and the liquid resin 34 is dried to form a protective film 16 (see FIG. 2B).

[0019] Here, the liquid resin 34 may be either a water-soluble resin or a water-insoluble resin, but from the viewpoint of ease of removal in the second removal step, it is preferable to use a water-soluble resin such as polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), etc. Furthermore, an example of a water-insoluble resin is an acrylic resin.

[0020] After the protective film 16 is formed, as shown in Fig. 2B, for example, the workpiece unit 25 is transported to a chuck table 40 of a laser processing device and held by the chuck table 40. A laser irradiation unit 41 is disposed above the chuck table 40. The chuck table 40 and the laser irradiation unit 41 are provided so as to be movable relative to each other in the horizontal direction, and in this embodiment, the chuck table 40 is movable by an X-axis movement mechanism 42, and the laser irradiation unit 41 is movable by a Y-axis movement mechanism 43.

[0021] The laser irradiation unit 41 irradiates and focuses a laser beam LB onto the street 14 of the wafer 10 while driving the movement mechanisms 42 and 43. By driving the movement mechanisms 42 and 43, the laser irradiation unit 41 is positioned at the street 14 of the wafer 10, and the laser beam LB is irradiated onto the wafer 10 from the protective film 16 side of the wafer 10.

[0022] The laser beam LB has a wavelength that is absorbed by the wafer 10 and is adjusted to be focused near the surface 11 of the wafer 10. When the laser beam LB is irradiated onto the wafer 10, ablation occurs in the protective film 16 and the surface 11 of the wafer 10, causing partial etching. As a result, the protective film 16 is removed in the portions along the streets 14 of the wafer 10, exposing the streets 14. In other words, the protective film 16 that remains unremoved forms a mask 17 that masks (covers) the surface of the device 15.

[0023] 3 is a schematic diagram of an entire etching apparatus used in the dividing step and the first removing step of the embodiment. After the mask forming step is performed, the dividing step and the first removing step are performed using the etching apparatus 50 shown in FIG.

[0024] A sidewall 52 of a chamber 51 of an etching apparatus 50 is formed with a loading / unloading port 53 for loading and unloading the processing target unit 25. A shutter mechanism 55 is attached to the outer wall surface of the sidewall 52 so as to open and close the loading / unloading port 53. The shutter mechanism 55 has a shutter 57 connected to the upper end of a cylinder 56, and the loading / unloading port 53 is opened and closed by the shutter 57 being raised and lowered along the sidewall 52 by the cylinder 56. When the loading / unloading port 53 is closed by the shutter 57, an airtight space is formed within the chamber 51.

[0025] In the chamber 51, a lower electrode unit 60 and an upper electrode unit 70 that form an electric field are disposed facing each other in the vertical direction.

[0026] The lower electrode unit 60 includes a conductive support column 62 that penetrates the bottom wall 54 that forms the chamber 51, and a dielectric holding table 63 that is provided at the upper end of the support column 62. A plurality of suction ports 64 are formed on the upper surface of the holding table 63. The suction ports 64 are connected to a suction source 66 via suction paths 65 in the holding table 63 and the support column 62, and the wafer 10 is held by suction due to the negative pressure generated in the suction ports 64.

[0027] Furthermore, a cooling path 68 is formed within the lower electrode unit 60, through which cooling water sent from a cooling section 67 passes. During etching, heat generated in the holding table 63 is transferred to the cooling water, thereby suppressing an abnormal temperature rise.

[0028] Furthermore, the lower electrode unit 60 also employs a structure in which the upper surface of the holding table 63 serves as an electrostatic chuck-type holding surface, and an internal electrode 69 is embedded in the holding table 63. When a voltage is applied to the internal electrode 69, static electricity is generated on the upper surface of the holding table 63, and the wafer 10 is electrostatically attracted.

[0029] The upper electrode unit 70 is provided at the lower end of a conductive support portion 72 that penetrates the top wall 58 of the chamber 51. The upper electrode unit 70 is equipped with a conductive jet table 73 that introduces gas into the chamber 51. A plurality of gas jet ports 74 that introduce gas into the chamber 51 are formed on the lower surface of the jet table 73. The gas jet ports 74 communicate with a flow path 75 that is provided throughout the jet table 73 and the inside of the support portion 72.

[0030] Gas outlet 74 is connected to a reactive gas supply source 81, an inert gas supply source 82, and an oxygen gas supply source 83 through a flow path 75. Supply valves 84 to 86 are provided in the pipelines of reactive gas supply source 81, inert gas supply source 82, and oxygen gas supply source 83, and the gas supply sources are switched by supply valves 84 to 86. Note that each gas supply source 81 to 83 may supply gas into chamber 51 through a different pipeline.

[0031] The reactive gas from the reactive gas supply source 81 may be a stable fluorine-based gas containing fluorine, such as sulfur hexafluoride (SF), tetrafluoromethane (CF), or nitrogen trifluoride (NF). The inert gas from the inert gas supply source 82 may be, for example, nitrogen (N), helium (He), or argon (Ar).

[0032] The upper end side of the support column 72 protrudes upward from the chamber 51 and is connected to a ball screw type lifting drive mechanism 59 provided on the upper wall 58 of the chamber 51. By driving the lifting drive mechanism 59, the upper electrode unit 70 is moved closer or farther away from the lower electrode unit 60, and the height of the ejection table 73 is adjusted to an appropriate position relative to the wafer 10 on the holding table 63.

[0033] An exhaust port 541 is formed in the bottom wall 54 of the chamber 51 below the holding table 63, and a vacuum pump 542 is connected to the exhaust port 541 via piping. The vacuum pump 542 sucks out the air and plasma gas inside the chamber 51, thereby reducing the pressure inside the chamber 51 to a negative pressure. A pressure gauge 543 is provided between the exhaust port 541 and the vacuum pump 542 to detect the pressure inside the chamber 51.

[0034] The lower electrode unit 60 is electrically connected to a power supply control unit 87, and the upper electrode unit 70 is grounded. The power supply control unit 87 has a high-frequency power supply 88 and a frequency switching unit 89. The frequency switching unit 89 will be described later. The high-frequency power supply 88 applies a high-frequency voltage between the lower electrode unit 60 and the upper electrode unit 70.

[0035] In the division step using the etching apparatus 50, before the wafer 10 is loaded into the chamber 51, the chamber 51 is sealed and the supply valve 85 of the inert gas supply source 82 is opened to supply the inert gas from the upper electrode unit 70 into the chamber 51. Next, the shutter 57 is opened and the processed unit 25 (wafer 10) after the mask formation step is carried into the chamber 51 and held on the holding table 63 of the lower electrode unit 60. Thereafter, the shutter 57 closes the loading / unloading port 53 to seal the chamber 51, and the supply valve 85 is closed to stop the supply of the inert gas.

[0036] In this state, the upper electrode unit 70 is moved closer to the lower electrode unit 60 by driving the lifting mechanism 59, thereby adjusting the inter-electrode distance. Furthermore, the chamber 51 is evacuated by driving the vacuum pump 542 until the pressure inside the chamber 51 reaches the source pressure state (negative pressure state). In this reduced pressure state, the supply valve 84 of the reactive gas supply source 81 is opened, and the reactive gas is irradiated from the upper electrode unit 70. During the irradiation of the reactive gas, a high-frequency voltage is applied between the upper electrode unit 70 and the lower electrode unit 60 by the high-frequency power supply 88, and the reactive gas is converted into plasma (radicals).

[0037] 4 is an explanatory diagram of the dividing step in the embodiment. As shown in FIG. 4, plasmatized etching gas EG is irradiated from the mask 17 side of the wafer 10, whereby the etching gas EG is irradiated onto the streets 14 exposed as areas of the wafer 10 where the mask 17 is not formed. By irradiating the etching gas EG in this manner, the upper surfaces of the exposed streets 14 are dry-etched by a radical chain reaction, and dividing grooves 18 are formed along the streets 14. In other words, in the dividing step, plasma dicing is performed to divide the wafer 10 along the streets 14.

[0038] Here, the plasma dicing in the dividing step may cause the edge portions of the mask 17 along the streets 14 to change due to a reaction, forming changed portions D (see FIG. 4). Although not shown, changed portions due to plasma dicing may also occur on the top surface of the mask 17. In order to remove changed portions D on the surface such as the edge portions and top surface of the mask 17, a first removal step is carried out after the dividing step.

[0039] 3, the supply valve 86 of the oxygen gas supply source 83 is opened, and oxygen gas is irradiated from the upper electrode unit 70 toward the processing target unit 25 (wafer 10) held on the holding table 63. During the irradiation of the oxygen gas, a high-frequency voltage is applied between the upper electrode unit 70 and the lower electrode unit 60 by the high-frequency power supply 88, and the oxygen gas is turned into plasma.

[0040] As a result, as shown in FIG. 5, oxygen-containing plasma P is irradiated onto the mask 17 of the wafer 10, and the altered portion D is removed by oxide plasma ashing. In the first removal step, the oxygen-containing plasma P is irradiated in both continuous and pulsed modes. Continuous irradiation is plasma irradiation that maintains a constant electric field, while pulse irradiation is plasma irradiation that uses a time-modulated pulsed electric field. The frequency of the pulsed irradiation is set to 0.5 Hz or more and 5000 Hz or less (1 Hz to 2 Hz in this embodiment). The frequency of the pulsed irradiation is switched via the frequency switching unit 89 (see FIG. 3) of the power supply control unit 87, and is adjusted, for example, by controlling the supply and stop of high-frequency power. The frequency of the high frequency power that generates the plasma is 13.56 MHz.

[0041] In the first removal step, continuous irradiation and pulse irradiation may be alternately performed, and the irradiation time of pulse irradiation may be longer than that of continuous irradiation, and the ratio may be, for example, "9" for the irradiation time of continuous irradiation (1).

[0042] 6 is an explanatory diagram of the second removal step in the embodiment. After the first removal step is performed, the second removal step is performed to remove the entire mask 17 from the wafer 10.

[0043] 6, in the second removal step, the processed unit 25 is transported and held on a holding table 30 of the film forming and cleaning apparatus, and the holding table 30 is rotated by rotating about the vertical direction as the center of rotation. A cleaning nozzle 39 connected to a cleaning liquid supply source 38 is positioned above the rotating holding table 30, and cleaning liquid L is supplied from the cleaning nozzle 39 to the front surface 11 of the wafer 10. As a result, the mask 17 on the wafer 10 is dissolved by the cleaning liquid L and is removed from the device 15 on the wafer 10 by the centrifugal force of the rotating holding table 30. In addition, air is blown toward the wafer 10 from an air nozzle 37, drying the front surface 11 of the wafer 10.

[0044] Examples of the cleaning liquid L used in the second removal step include pure water and chemical liquids such as acetone.

[0045] According to the above embodiment, even if altered portions D are formed in the mask 17 during the dividing step, the altered portions D can be removed by irradiating them with oxygen-containing plasma P in the first removal step. Therefore, even if the altered portions D become difficult to dissolve in the cleaning liquid L, the step of scrubbing the altered portions D with a scrub sponge can be omitted. As a result, the altered portions D can be removed from the mask 17 by oxide plasma ashing in the first removal step, and then the mask 17 can be removed with the cleaning liquid L in the second removal step, thereby shortening and facilitating the cleaning time.

[0046] Furthermore, since the oxygen-containing plasma P is irradiated continuously and in pulses in the first removal step, thermal alteration of the mask 17 due to oxide plasma ashing can be suppressed compared to when only continuous irradiation is performed.More specifically, while the plasma P irradiated by pulse irradiation is stopped or reduced, the thermal energy on the surface of the mask 17 is dispersed to suppress a temperature rise of the mask 17, thereby suppressing thermal alteration of the mask 17.This ensures the removal of the mask 17 in the second removal step, and eliminates the need for the above-mentioned scraping step, improving productivity.

[0047] Furthermore, since the irradiation time of the pulse irradiation is longer (greater) than the irradiation time of the continuous irradiation of the plasma P in the first removal step, thermal alteration of the mask 17 can be suppressed more effectively.

[0048] The present invention is not limited to the above-described embodiments, and various modifications can be made. In the above-described embodiments, the size and shape shown in the accompanying drawings are not limited to these, and can be modified as appropriate within the scope of the effects of the present invention. In addition, the present invention can be modified as appropriate within the scope of the object of the present invention.

[0049] In the above embodiment, the first removal step is performed using the etching apparatus 50 shown in FIG. 3. However, various modifications are possible, such as using an apparatus shown in FIG. 7. The etching apparatus 50 shown in FIG. 3 is a capacitively coupled plasma etching apparatus (CCP). However, it may be an inductively coupled plasma etching apparatus (ICP) or an electron cyclotron resonance plasma etching apparatus (ECR). FIG. 7 is an explanatory diagram of the first removal step in a modified example. In the first removal step of the modified example, as shown in FIG. 7, the processed unit 25 (wafer 10) after the dividing step is transferred to and held on a holding table 90 of an oxygen plasma irradiation apparatus. A plasma nozzle 92 connected to an oxygen plasma supply source 91 is positioned above the holding table 90. The holding table 90 and the plasma nozzle 92 are arranged so that they can move relative to each other in the horizontal direction. In this embodiment, the holding table 90 is movable by an X-axis moving mechanism 93, and the plasma nozzle 92 is movable by a Y-axis moving mechanism 94.

[0050] For example, when a deteriorated portion D is formed at the edge of the mask 17, the moving mechanisms 93 and 94 are driven to position the plasma nozzle 92 above the dividing groove 18 (streets 14), and the holding table 90 and the plasma nozzle 92 are moved relative to each other along the dividing groove 18. As a result, plasma P containing oxygen is irradiated from the plasma nozzle 92 onto the deteriorated portion D of the mask 17, and the deteriorated portion D is removed by oxidation plasma ashing.

[0051] In the above embodiment, the dividing grooves 18 are formed over the entire thickness of the wafer 10, but the present invention is not limited to this. For example, after etching is performed so that the bottoms of the dividing grooves 18 are formed within the thickness of the wafer 10, the wafer 10 may be divided into individual devices 15 by performing a step of expanding the support member 20 or grinding the back surface 12 of the wafer 10.

[0052] In the above embodiment, a fluorine-based gas is used as the reactive gas for the etching gas EG, but the present invention is not limited to this configuration. The reactive gas can be selected appropriately depending on the material of the wafer 10. [Industrial Applicability]

[0053] As described above, the wafer dividing method of the present invention has the effect of shortening the time required to remove the mask formed for plasma dicing. [Explanation of symbols]

[0054] 10: Wafer 14: Street 15: Device 17: Mask 18:Dividing groove 20: Support member 34: Liquid resin EG: Etching gas L: cleaning solution P: Plasma

Claims

1. A wafer dividing method comprising: irradiating an etching gas in plasma form onto a wafer having devices formed in areas partitioned by streets, and dividing the wafer along the streets, the method comprising: a supporting step of supporting the wafer by attaching a support member to the surface opposite to the surface on which the streets are formed; a mask forming step of applying a liquid resin to the device and drying it to mask the surface of the device and expose the street; a dividing step of irradiating plasmatized etching gas from the mask side of the wafer after the mask forming step to form dividing grooves along the streets; a first removal step of removing the surface of the mask by continuous and pulse irradiation of oxygen-containing plasma onto the mask after the dividing step; a second removing step of removing the entire mask from the wafer after the first removing step.

2. 2. The wafer dividing method according to claim 1, wherein the first removing step increases the pulse irradiation time relative to the continuous irradiation time.

3. 3. The wafer dividing method according to claim 1, wherein the second removing step removes the residue by supplying a cleaning liquid.

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