JP7300953B2 - Wafer processing method - Google Patents

Description

The present invention relates to a wafer processing method.

In the conventional processing method, in which a wafer on which semiconductor devices are formed is divided into individual device chips by a cutting blade or a laser beam, processing is performed one line at a time. there were. Therefore, a so-called plasma dicing technique has been devised for dicing a wafer by plasma etching.

In addition, a device wafer in which devices are formed of a material such as a Low-k film that peels off when cut with a cutting blade is removed with a laser beam without removing the Low-k film, and then the Low-k film is removed. A technique is known in which a device wafer is divided into regions by processing with a cutting blade or laser beam. However, this technique has a problem that the periphery of the laser-processed groove formed by removing the Low-k film is deteriorated due to the influence of heat, and the bending strength of the device chip obtained by dividing is reduced. . Therefore, a technique for removing the heat-affected layer of the laser-processed groove by plasma etching has been devised.

JP 2016-207737 A

The mask used for the above plasma etching is effective because the water-soluble resin applied to the wafer before laser processing can be easily removed. However, due to the heat of the laser beam and the generated debris, the water-soluble resin layer at the edge of the laser-processed groove becomes thin, and the water-soluble resin layer is etched before the laser-processed groove is etched. It may be removed. As a result, since the water-soluble resin layer cannot function as a mask, there is a risk that areas or devices that do not require etching may be etched.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and its object is to provide a wafer processing method that allows the mask during plasma etching to function up to the edges of laser-processed grooves.

In order to solve the above-described problems and achieve the object, a wafer processing method of the present invention is a method of processing a wafer having devices formed in regions of the surface partitioned by streets, wherein the surface of the wafer is treated with water. a water-soluble resin coating step of coating the surface of the wafer covered with the water-soluble resin with a laser beam having a wavelength that is absorptive to the wafer along the streets; a mask forming step of removing the soluble resin, forming laser-processed grooves, and forming a mask with the water-soluble resin on the surface of the wafer; and applying moisture to the mask of the water-soluble resin, which has become thin due to the decrease in moisture at the edge of the laser-processed groove due to the irradiation of the laser beam, and adjusting the thickness of the mask; After performing the applying step, a plasma etching step of supplying a gas in a plasma state from the surface side of the wafer through the mask to plasma-etch the laser-processed grooves exposed from the mask, and after performing the plasma etching step, the mask and a mask cleaning step of cleaning and removing with a liquid, and in the water applying step, water is applied in an amount such that the water-soluble resin does not protrude from the edge of the laser-processed groove due to surface tension. and

In the moisture application step, the wafer adjusted to a lower temperature than the moisture-containing atmosphere may be placed in the atmosphere, and moisture may be imparted to the water-soluble resin by condensation.

The moisture imparting step may impart moisture to the water-soluble resin by placing the wafer in an atmosphere containing mist.

The present invention allows the mask during plasma etching to function up to the edge of the laser-processed groove.

FIG. 1 is a perspective view showing an example of a frame unit including a processing object of a wafer processing method according to an embodiment. FIG. 2 is a flow chart showing the flow of the wafer processing method according to the embodiment. FIG. 3 is a side view showing an example of the water-soluble resin coating step shown in FIG. 2 in a partial cross section. FIG. 4 is a cross-sectional view of the essential part of the wafer showing one state after the water-soluble resin coating step of FIG. FIG. 5 is a side view showing, in partial cross section, one example of the mask forming steps shown in FIG. FIG. 6 is a cross-sectional view of the main part of the wafer showing one state after the mask forming step of FIG. FIG. 7 is a side view showing a partial cross-section of an example of the water application step shown in FIG. FIG. 8 is a cross-sectional view of the principal part of the wafer showing one state after the moisture imparting step of FIG. FIG. 9 is a cross-sectional view of the main part of the wafer schematically showing one example of the plasma etching step shown in FIG. FIG. 10 is a cross-sectional view of a portion of the wafer showing one state after the plasma etching step of FIG. 11 is a cross-sectional view of a portion of the wafer showing another state after the plasma etching step of FIG. 9. FIG. FIG. 12 is a side view, partially in section, showing an example of the mask cleaning step shown in FIG.

A form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions, or changes in configuration can be made without departing from the gist of the present invention.

[Embodiment]
A method for processing a wafer 10 according to an embodiment of the present invention will be described with reference to the drawings. First, the configuration of the frame unit 1 including the processing target of the embodiment will be described. FIG. 1 is a perspective view showing an example of a frame unit 1 including an object to be processed by a method of processing a wafer 10 according to an embodiment.

As shown in FIG. 1, the frame unit 1 includes a wafer 10 to be processed, an annular frame 20, and an adhesive tape 21 according to the embodiment. The wafer 10 is a disk-shaped semiconductor wafer, an optical device wafer, or the like having a substrate 11 made of silicon (Si), sapphire (Al ₂ O ₃ ), gallium arsenide (GaAs), silicon carbide (SiC), or the like. The wafer 10 has a plurality of streets 13 (dividing lines) formed on the surface 12 of the substrate 11, and devices 14 formed in each area partitioned by the plurality of streets 13 intersecting in a grid pattern.

The device 14 is, for example, an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), or a MEMS (Micro Electro Mechanical Systems), etc.

Also, the wafer 10 has a functional layer 16 laminated on the surface 12 of the substrate 11 . The functional layer 16 is a low dielectric constant insulating film (hereinafter referred to as a Low-k film) made of an inorganic film such as SiOF or BSG (SiOB) or an organic film such as a polyimide or parylene polymer film. ) and a conductor film made of a conductive metal. The low-k film is laminated with a conductive film to form device 14 . The conductive film constitutes the circuitry of device 14 . For this purpose, the device 14 is composed of Low-k films stacked together and conductor films stacked between the Low-k films. The functional layer 16 of the street 13 is composed of a Low-k film and has no conductor film except for TEG (Test Element Group). The TEG is an evaluation element for finding design and manufacturing problems that occur in the device 14 .

Wafer 10 is supported by annular frame 20 and adhesive tape 21 . The annular frame 20 has an opening larger than the outer diameter of the wafer 10 . The annular frame 20 is made of a material such as metal or resin that is resistant to plasma etching. The adhesive tape 21 includes a substrate layer made of an insulating synthetic resin and an adhesive glue layer laminated on at least one of the front surface and the back surface of the substrate layer. The adhesive tape 21 is adhered to the back side of the annular frame 20 at its outer periphery. The wafer 10 is fixed to the annular frame 20 and the adhesive tape 21 by positioning the wafer 10 at a predetermined position in the opening of the annular frame 20 and adhering the back surface 15 to the adhesive tape 21 .

Next, a method for processing the wafer 10 according to the embodiment will be described. FIG. 2 is a flow chart showing the flow of the method for processing the wafer 10 according to the embodiment. The method of processing the wafer 10 includes a water-soluble resin coating step ST1, a mask forming step ST2, a water application step ST3, a plasma etching step ST4, and a mask cleaning step ST5.

(Water-soluble resin coating step ST1)
FIG. 3 is a side view showing a partial cross section of an example of the water-soluble resin coating step ST1 shown in FIG. FIG. 4 is a cross-sectional view of a main part of the wafer 10 showing one state after the water-soluble resin coating step ST1 in FIG. The water-soluble resin coating step ST1 is a step of coating the surface 12 of the wafer 10 with a water-soluble resin 35, as shown in FIGS.

In the water-soluble resin coating step ST1 of the embodiment, the spin coater 30 coats the surface 12 of the wafer 10 with the water-soluble resin 35 . The spin coater 30 includes a holding table 31 , a rotary shaft member 32 , a clamp member 33 and a water-soluble resin supply nozzle 34 .

In the water-soluble resin coating step ST1, first, the back surface 15 side of the wafer 10 is held by suction on the holding table 31 through the adhesive tape 21, and the outer peripheral portion of the annular frame 20 is fixed by the clamp member 33. As shown in FIG. In the water-soluble resin coating step ST1, the water-soluble resin 35 is dripped onto the surface 12 of the wafer 10 from the water-soluble resin supply nozzle 34 while the holding table 31 is being rotated around the axis by the rotating shaft member 32 . . At this time, the water-soluble resin supply nozzle 34 reciprocates in the radial direction of the wafer 10 . The dripped water-soluble resin 35 flows over the surface 12 of the wafer 10 from the center side toward the outer circumference side due to the centrifugal force generated by the rotation of the holding table 31 , and is applied to the entire surface 12 of the wafer 10 . be.

The water-soluble resin 35 is, for example, a water-soluble resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) that is resistant to plasma etching when cured. In the water-soluble resin coating step ST1, the water-soluble resin 35 applied over the entire surface 12 of the wafer 10 is dried and cured to form a layer of the water-soluble resin 35 covering the entire surface 12 of the wafer 10 .

(Mask formation step ST2)
FIG. 5 is a side view showing a partial cross section of an example of the mask forming step ST2 shown in FIG. FIG. 6 is a cross-sectional view of a main part of the wafer 10 showing a state after the mask formation step ST2 of FIG. In the mask forming step ST2, as shown in FIGS. 5 and 6, a laser beam 45 is irradiated along the streets 13 on the surface 12 of the wafer 10 to remove the water-soluble resin 35 and form laser processing grooves 18 to form water-soluble resin. This is the step of forming the mask 17 with the resin 35 .

In the mask forming step ST2 of the embodiment, laser processing grooves 18 are formed along the streets 13 formed on the surface 12 of the wafer 10 by the laser processing device 40 . The laser processing device 40 includes a holding table 41 , a rotating shaft member 42 , a clamp member 43 , a laser beam irradiation unit 44 , and a moving unit that relatively moves the holding table 41 and the laser beam irradiation unit 44 .

In the mask forming step ST2, first, the back surface 15 side of the wafer 10 is held by suction on the holding table 41 through the adhesive tape 21, and the outer peripheral portion of the annular frame 20 is fixed by the clamp member 43. FIG. In the mask forming step ST2, next, while the holding table 41 and the laser beam irradiation unit 44 are relatively moved along the streets 13, the laser beam 45 is irradiated from the laser beam irradiation unit 44 onto the streets 13 on the surface 12 of the wafer 10. . The laser beam 45 is a laser beam with a wavelength that is absorptive to the wafer 10 .

The laser beam 45 removes the water-soluble resin 35 from the areas corresponding to the streets 13 in the layer of the water-soluble resin 35 covering the entire surface 12 of the wafer 10 to form the laser-processed grooves 18 . As shown in FIG. 6, the laser-processed groove 18 exposes the substrate 11 by removing the water-soluble resin 35, the functional layer 16 and part of the substrate 11 in the region corresponding to the street 13. FIG. Thereby, a mask 17 is formed on the surface 12 of the wafer 10 to cover the devices 14 and expose the streets 13 . At this time, the peripheral portion 171 of the edge 181 of the laser-processed groove 18 of the mask 17 is thinned due to the heat of the laser beam 45 and the reduction of moisture in the water-soluble resin 35 due to debris.

(Moisture application step ST3)
FIG. 7 is a side view showing a partial cross-section of an example of the water application step ST3 shown in FIG. FIG. 8 is a cross-sectional view of the main part of the wafer 10 showing one state after the moisture imparting step ST3 of FIG. As shown in FIGS. 7 and 8, the water application step ST3 causes surface dew condensation to occur on the wafer 10, and a peripheral portion 171 of the edge 181 of the laser-processed groove 18, which has become thin due to the reduction in water content due to the irradiation of the laser beam 45, is formed. is a step of applying moisture to the mask 17 of .

In the moisture applying step ST3 of the embodiment, the cooling device 50 causes surface condensation on the wafer 10 to apply moisture to the mask 17 . The cooling device 50 includes a cooling table 51, a cooling source 52 for cooling the cooling table 51 to a predetermined temperature, and a chamber 54 in which the cooling table 51 is provided. The cooling source 52 is, for example, a Peltier element or the like provided along the mounting surface of the cooling table 51 . The inside of the chamber 54 is maintained in an atmosphere 55 containing moisture, which is water vapor.

In the water application step ST3, first, the back surface 15 side of the wafer 10 is placed on the cooling table 51 via the adhesive tape 21, and the outer peripheral portion of the annular frame 20 is fixed by the clamp member 53. FIG. Next, in the moisture supply step ST3, the cooling table 51 is cooled to a predetermined temperature by applying a voltage to the cooling source 52 or the like while the atmosphere 55 containing moisture is maintained in the chamber 54. The mounted wafer 10 is cooled. The wafer 10 cooled by the cooling table 51 in the atmosphere 55 containing moisture causes surface condensation. The cooling device 50 causes dew condensation on the surface 12 of the wafer 10 by, for example, repeating cooling for a predetermined time and natural drying for a predetermined time a predetermined number of times. The cooling temperature, the predetermined time for cooling, the predetermined time for natural drying, and the predetermined number of times for repeating cooling and drying are set in advance based on atmospheric conditions and the like.

Moisture is applied to the mask 17 made of the water-soluble resin 35, which has become thin due to the reduction in water content, due to the surface dew condensation generated on the wafer 10. As shown in FIG. That is, in the mask 17 of the water-soluble resin 35 covering the surface 12 of the wafer 10, the water content of the water-soluble resin 35 is reduced by the heat of the laser beam 45 and debris, and the peripheral portion 171 of the edge 181 of the laser-processed groove 18 is thinned. Moisture is applied to the mask 17 of . By adding moisture to the water-soluble resin 35 with reduced moisture, the thickness of the mask 17 of the water-soluble resin 35 is adjusted to be thick. At this time, by adjusting the humidity in the chamber 54, the cooling temperature, the prescribed time for cooling, the prescribed time for natural drying, the prescribed number of repetitions of cooling and drying, and the like, the amount of moisture imparted to the mask 17 of the water-soluble resin 35 can be adjusted. Adjustable. In the water application step ST3, water is applied in such an amount that the water-soluble resin 35 does not protrude from the edge 181 of the laser-processed groove 18 due to surface tension.

(Plasma etching step ST4)
FIG. 9 is a cross-sectional view of the main part of the wafer 10 schematically showing an example of the plasma etching step ST4 shown in FIG. FIG. 10 is a cross-sectional view of the main part of the wafer 10 showing one state after the plasma etching step ST4 of FIG. FIG. 11 is a cross-sectional view of the main part of wafer 10 showing another state after plasma etching step ST4 in FIG. In the plasma etching step ST4, as shown in FIGS. 9, 10 and 11, a plasma gas 60 is supplied from the surface 12 side of the wafer 10 through the mask 17, and the laser-processed grooves 18 exposed from the mask 17 are etched. This is the step of plasma etching.

In the plasma etching step ST4 of the embodiment, laser-processed grooves 18 are formed along the streets 13 formed on the surface 12 of the wafer 10 by a plasma device that supplies gas 60 in a plasma state. Gas 60 is, for example, sulfur hexafluoride (SF ₆ ), carbon tetrafluoride (CF ₄ ), etc. when substrate 11 is composed of silicon, but the present invention is not limited thereto. The plasma device includes, for example, an electrostatic chuck (ESC), a chamber in which the electrostatic chuck is installed, an exhaust device for decompressing the chamber, and a gas supply device for supplying gas 60 in a plasma state to the chamber. And prepare. The chamber includes a gas supply unit above the electrostatic chuck for injecting plasma gas 60 supplied from a gas supply device into the chamber.

In the plasma etching step ST4, first, the back surface 15 side of the wafer 10 is electrostatically held on the electrostatic chuck via the adhesive tape 21. As shown in FIG. In the plasma etching step ST4, the pressure in the chamber is reduced and the plasma gas 60 is supplied into the chamber. At this time, the plasma gas 60 is supplied from the surface 12 side of the wafer 10 through the mask 17 . A plasma gas 60 is supplied to the substrate 11 of the wafer 10 through the laser-processed groove 18 to etch the groove bottom of the laser-processed groove 18 exposed from the mask 17 of the wafer 10 . The plasma state gas 60 etches the laser-machined grooves 18 to form etched grooves 19 .

The etching groove 19 is a concave groove etched to a predetermined depth in the example shown in FIG. The etching grooves 19 are dividing grooves etched to the back surface 15 side of the substrate 11 in another example shown in FIG.

(Mask cleaning step ST5)
FIG. 12 is a side view showing a partial cross section of an example of the mask cleaning step ST5 shown in FIG. The mask cleaning step ST5 is a step of cleaning and removing the mask 17 with a liquid 75, as shown in FIG.

In the mask cleaning step ST5 of the embodiment, the mask 17 of the water-soluble resin 35 covering the surface 12 of the wafer 10 is cleaned with the liquid 75 and removed by the cleaning device 70 . The cleaning device 70 includes a holding table 71 , a rotary shaft member 72 , a clamp member 73 and a liquid supply nozzle 74 .

In the mask cleaning step ST5, first, the back surface 15 side of the wafer 10 is held by suction on the holding table 71 via the adhesive tape 21, and the outer peripheral portion of the annular frame 20 is fixed by the clamp member 73. FIG. In the mask cleaning step ST5, the liquid 75 is supplied from the liquid supply nozzle 74 toward the surface 12 of the wafer 10 while the holding table 71 is rotated around the axis by the rotating shaft member 72 . The liquid 75 is pressurized water whose water pressure is adjusted to about 10 to 12 MPa in the water channel upstream of the liquid supply nozzle 74 . The liquid supply nozzle 74 reciprocates in the radial direction of the wafer 10 while supplying the liquid 75 which is pressurized water. The supplied liquid 75 flows over the surface 12 of each device 14 of the wafer 10 from the center toward the outer circumference by the centrifugal force generated by the rotation of the holding table 31, and covers the surface 12 of each device 14. The mask 17 of the water-soluble resin 35 is dissolved. Although the surface 12 of the device 14 is washed with the liquid 75 in the mask washing step ST5 in the embodiment, it may be washed with a fluid in which air is mixed in the liquid in the present invention.

Liquid 75 is, for example, pure water. In the mask cleaning step ST5, by dissolving the mask 17 of the water-soluble resin 35 covering the surface 12 of each device 14 of the wafer 10, the surface 12 of the device 14 is exposed.

As described above, in the method of processing the wafer 10 according to the embodiment, before the plasma etching step ST4, the peripheral portion 171 of the edge 181 of the laser-processed groove 18, which has become thin due to the reduction in water content due to the irradiation of the laser beam 45, is removed. A water applying step ST3 for applying water to the mask 17 is performed. As a result, the thickness of the mask 17 in the peripheral portion 171 of the edge 181 of the laser-processed groove 18 can be adjusted thicker, so that the edge 181 of the laser-processed groove 18 can function as the mask 17 for the device 14 during plasma etching. It has the effect of being able to Furthermore, by utilizing surface condensation, a small amount of moisture can be supplied to the streets 13 so that the mask 17 does not protrude.

In addition, this invention is not limited to the said embodiment. That is, various modifications can be made without departing from the gist of the present invention.

For example, in the moisture imparting step ST3, instead of arranging the wafer 10 in the atmosphere 55 containing moisture, which is water vapor, moisture may be imparted to the mask 17 of the water-soluble resin 35 by arranging the wafer 10 in an atmosphere containing mist. good. In the embodiment, the wafer 10 is cooled by the cooling table 51 having the cooling source 52 such as a Peltier element in the water application step ST3. Cooling is not necessary.

In addition, in the water application step ST3, water vapor or mist is applied to the mask 17 on the surface 12 of the wafer 10, so that the peripheral portion 171 of the edge 181 of the laser-processed groove 18, which has been thinned by the irradiation of the laser beam 45, is reduced. Moisture may be applied to the mask 17 . As a method of applying water vapor or mist to the mask 17 , water vapor or mist may be supplied toward the mask 17 to impart moisture to the mask 17 of the water-soluble resin 35 .

Reference Signs List 1 frame unit 10 wafer 11 substrate 12 front surface 13 street 14 device 15 back surface 16 functional layer 17 mask 18 laser processing groove 19 etching groove 30 spin coater 35 water-soluble resin 40 laser processing device 45 laser beam 50 cooling device 55 atmosphere containing moisture 60 gas 70 cleaning device 75 liquid

Claims (3)

A method of processing a wafer having devices formed on surface regions partitioned by streets, comprising:
a water-soluble resin coating step of coating the surface of the wafer with a water-soluble resin;
The surface of the wafer covered with the water-soluble resin is irradiated along the streets with a laser beam having a wavelength that is absorptive to the wafer, thereby removing the water-soluble resin along the streets and forming laser-processed grooves. a mask forming step of forming a mask with the water-soluble resin on the surface of the wafer;
After performing the mask forming step, the wafer is subjected to surface condensation, or water vapor is applied to the wafer, and moisture is removed from the water-soluble resin mask that has become thin due to moisture reduction at the edge of the laser-processed groove due to the irradiation of the laser beam. and adjusting the thickness of the mask;
a plasma etching step of supplying a gas in a plasma state from the surface side of the wafer through the mask to plasma-etch the laser-processed grooves exposed from the mask after the moisture imparting step;
a mask cleaning step of cleaning and removing the mask with a liquid after performing the plasma etching step;
with
2. A method of processing a wafer, wherein, in said water applying step, water is applied in such an amount that said water-soluble resin does not protrude from the edges of said laser-processed grooves due to surface tension. 2. The method of processing a wafer according to claim 1, wherein said moisture imparting step places said wafer adjusted to a lower temperature than an atmosphere containing moisture in said atmosphere, and imparts moisture to said water-soluble resin by means of dew condensation. 2. The method of processing a wafer according to claim 1, wherein said water applying step places said wafer in an atmosphere containing mist to apply water to said water-soluble resin.

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