TW202410191A - Wafer processing methods - Google Patents

Abstract

[Problem] Provide a wafer processing method that can improve processing quality in plasma etching. [Solution] A wafer processing method, including the following steps: a first processing groove forming step, irradiating laser light from the front side of the wafer along a planned division line to form a first processing groove in the functional layer; masking In the protective film forming step, after the first processing groove forming step is performed, a protective film covering the front surface of the wafer and filled in the first processing groove is formed; in the second processing groove forming step, the protective film for masking is formed After the forming step is performed, laser light is irradiated along the first processing groove to form a second processing groove with a smaller width than the first processing groove, and the substrate is exposed along the second processing groove; and a plasma etching step, After the second processing groove forming step is performed, plasma etching is performed along the second processing groove using the protective film as a mask.

Description

Wafer processing methods

The present invention relates to a wafer processing method.

When plasma dicing is performed on a wafer with a functional layer laminated on a substrate, a protective film is first formed on the front side of the wafer, laser light is irradiated along the planned division line, and the protective film and functional layer are removed. After exposing the substrate, plasma cutting is performed using the protective film as a mask (see, for example, Patent Document 1). Prior technical literature patent documents

Patent document 1: Japanese Patent Application Publication No. 2022-052821

Invention Problems to be Solved

However, due to the heat effect of the laser beam, the side surface of the functional layer or the exposed front surface of the substrate will melt, forming a degraded layer with unevenness or tiny cracks or becoming more fragile than other areas.

If plasma etching is performed with such an area exposed, the unevenness will be etched to extend in the depth direction, and unevenness will be formed on the side surface of the etched substrate, resulting in poor processing quality.

Accordingly, the purpose of the present invention is to provide a wafer processing method that can improve the processing quality during plasma etching. Means for solving the problem

According to the present invention, a wafer processing method can be provided, wherein a wafer having a plurality of devices formed by laminating a functional layer on the front side of a substrate is processed along a plurality of predetermined dividing lines that cross and divide the plurality of devices. The wafer processing method comprises the following steps: A first processing groove forming step, wherein a laser beam is irradiated from the front side of the wafer along the predetermined dividing line to form a first processing groove in the functional layer; A mask protective film forming step, wherein after the first processing groove forming step is performed, a mask protective film is formed that covers the front side of the wafer and fills the first processing groove; A second processing groove forming step, after the implementation of the mask protective film forming step, irradiating laser light along the first processing groove to form a second processing groove narrower than the first processing groove, and exposing the substrate along the second processing groove; and a plasma etching step, after the implementation of the second processing groove forming step, plasma etching is performed along the second processing groove using the mask protective film as a mask.

Preferably, in the second processing groove forming step, the output of the irradiated laser light is smaller than in the first processing groove forming step.

Preferably, the plasma etching step is to separate the wafer to produce a plurality of device chips.

Preferably, the wafer processing method further includes a first protective film forming step and a first protective film removing step. The first protective film forming step is performed on the wafer before the first processing groove forming step is performed. A first protective film is formed on the front surface, and the first protective film removal step is performed by washing and removing the first protective film after the first processing groove forming step is performed.

Preferably, the first processing grooves are not all of the same width, and the second processing grooves are all of the same width.

Preferably, the first processing groove has a width wider than the metal parts already layered on the front side of the predetermined dividing line. Effect of the invention

The present invention can improve the processing quality in plasma etching.

The form used to implement the invention

The following is a detailed description of the implementation forms of the present invention with reference to the drawings. The present invention is not limited by the contents described in the following implementation forms. Furthermore, the constituent elements described below include constituent elements that can be easily conceived by a person with ordinary knowledge in the relevant technical field and substantially the same constituent elements. In addition, the structures described below can be appropriately combined. Furthermore, various omissions, substitutions or changes in the structure can be made without departing from the gist of the present invention.

[First Embodiment] The wafer processing method according to the first embodiment of the present invention will be described based on the drawings. FIG. 1 is a perspective view schematically showing a wafer to be processed by the wafer processing method according to the first embodiment. FIG. 2 is a cross-sectional view schematically showing the main parts of the wafer shown in FIG. 1 . FIG. 3 is a flowchart showing the flow of the wafer processing method according to the first embodiment.

(wafer) The wafer processing method of the first embodiment is the processing method of wafer 1 shown in FIG. 1 . In the first embodiment, the wafer 1 is a disc-shaped semiconductor wafer or the like having a substrate 2 of silicon, glass, SiC, sapphire, gallium arsenide, or the like. As shown in FIG. 1 , the wafer 1 has devices 5 formed in regions divided into a grid shape by a plurality of planned division lines 4 formed in a grid shape on the front surface 3 .

The device 5 may be an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration), a CCD (Charge Coupled Device), or a memory (semiconductor memory). device) etc.

As shown in FIGS. 1 and 2 , in the first embodiment, the wafer 1 has the functional layer 6 laminated on the front surface of the substrate 2 . The functional layer 6 includes: a low dielectric constant insulator film (hereinafter referred to as a Low-k film), an inorganic film made of SiOF, BSG (SiOB), etc., or a polymer of a polyimide system, a parylene system, etc. The physical film is composed of an organic film or carbon-containing silicon oxide (SiOCH); and the circuit layer is composed of a conductive metal pattern or metal film.

The Low-k film can be laminated with the circuit layer to form the device 5. The circuit layer constitutes the circuit of the device 5. Therefore, the device 5 is constituted by the Low-k film formed by laminating the functional layer 6 laminated on the substrate 2, and the circuit layer laminated between the Low-k films. On the predetermined dividing line 4, the functional layer 6 is constituted by the Low-k film laminated on the substrate 2.

If the wafer 1 is cut from the front 3 sides by a cutting blade, the functional layer 6 such as the Low-k film will be easily peeled off from the substrate 2 . In this manner, in the first embodiment, the wafer 1 has the device 5 formed on the front surface 3 of the functional layer 6 laminated on the substrate 2 .

Furthermore, in the first embodiment, the predetermined dividing lines 4 include a plurality of mutually parallel first predetermined dividing lines 7 and a plurality of mutually parallel second predetermined dividing lines 8 intersecting (intersecting in the first embodiment) the first predetermined dividing lines 7. Thus, the wafer 1 has a plurality of devices 5 and predetermined dividing lines 7 and 8 for partitioning the plurality of devices 5 formed on the front surface 3. Furthermore, in the first embodiment, the width of the first predetermined dividing lines 7 and the width of the second predetermined dividing lines 8 of the wafer 1 are equal.

(wafer processing method) The wafer processing method of the first embodiment is to place the wafer 1 on which a plurality of devices 5 are formed by laminating the functional layer 6 on the front surface of the substrate 2 along the planned division lines 7 and 8 dividing the plurality of devices 5 How to process. Furthermore, in the first embodiment, the wafer processing method is also one of dividing the wafer 1 into individual device wafers 10 (shown in FIG. 1 ) along the planned division lines 7 and 8 (equivalent to processing). method. Furthermore, the device wafer 10 includes a part of the substrate 2 and the device 5 .

As shown in FIG3 , the wafer processing method includes a first protective film forming step 101, a first processing groove forming step 102, a first protective film removing step 103, a mask protective film forming step 104, a second processing groove forming step 105, a plasma etching step 106, and a mask protective film removing step 107. Furthermore, in the first embodiment, the wafer processing method is as shown in FIG1 , a disk-shaped adhesive tape 11 having a larger diameter than the wafer 1 is attached to the back surface 9 of the back side of the front surface 3, and an annular frame 12 is attached to the outer edge of the adhesive tape 11, and the wafer 1 supported by the frame 12 is processed.

(First protective film forming step) FIG. 4 is a cross-sectional view schematically showing the main parts of the wafer after the first protective film forming step of the wafer processing method shown in FIG. 3 . The first protective film forming step 101 is a step of forming the first protective film 13 (shown in FIG. 4 ) on the front surface 3 of the wafer 1 before the first processing groove forming step 102 is performed.

In the first embodiment, in the first protective film forming step 101, the resin coating device (not shown) holds the back side 9 of the wafer 1 on the holding surface of the rotating table by suction through the tape 11, and the frame 12 is clamped by the clamping part, and the rotating table is rotated around the axis, and the liquid water-soluble resin is dripped from the water-soluble resin supply nozzle toward the center of the front side 3 of the wafer 1. The dripped water-soluble resin flows from the center side to the outer peripheral side on the front side 3 of the wafer 1 due to the centrifugal force generated by the rotation of the rotating table, and is coated on the entire surface of the front side 3 of the wafer 1. In addition, for all the embodiments, although the configuration including the frame 12 is described, the frame 12 may not be used.

Furthermore, the water-soluble resin includes water-soluble resins such as polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP). In the first protective film forming step 101, the water-soluble resin applied to the entire surface of the front surface 3 of the wafer 1 is dried, and as shown in FIG. 4, the first protective film 13 including the water-soluble resin covers the entire surface of the front surface 3 of the wafer 1. In this way, in the first embodiment, the first protective film 13 is composed of a water-soluble resin. Furthermore, the water-soluble resin constituting the first protective film 13 is a resin that, after drying, is etched at a lower rate than the substrate 2 and is more resistant to the plasma etching gas 18 (shown in FIG. 9 ) used in the plasma etching step 106 .

(First processing groove forming step) FIG. 5 is a cross-sectional view schematically showing the main part of the wafer after the first processing groove forming step of the processing method of the wafer shown in FIG. 3. The first processing groove forming step 102 is a step of irradiating the front surface 3 of the wafer 1 along the predetermined dividing lines 7 and 8 to form the first processing groove 14 (shown in FIG. 5) in the functional layer 6.

In the first embodiment, in the first processing groove forming step 102, the laser processing device (not shown) attracts and holds the back side 9 of the wafer 1 on the holding surface of the holding table through the tape 11, and clamps the frame 12 with the clamping part. In the first embodiment, in the first processing groove forming step 102, the laser processing device photographs the front side 3 of the wafer 1 with the photographing unit (not shown) to detect the predetermined splitting lines 7 and 8, and completes the calibration of the laser light irradiation unit and the predetermined splitting lines 7 and 8.

In the first embodiment, in the first processing groove forming step 102, the laser processing device moves the wafer 1 and the laser light irradiation unit relatively along the predetermined dividing lines 7 and 8, and irradiates the laser light of a wavelength that is absorbent to the wafer 1 from the laser light irradiation unit toward the wafer 1 along the predetermined dividing lines 7 and 8. Furthermore, in the first embodiment, in the first processing groove forming step 102, the laser processing device sets the focal point of the laser light on the front surface of the first protective film 13 or the front surface of the substrate 2, and irradiates the laser light toward the wafer 1 along each predetermined dividing line 7 and 8.

In the first embodiment, in the first processing groove forming step 102, the laser processing device performs ablation processing on the first protective film 13, the functional layer 6 and the substrate 2 on each predetermined dividing line 7, 8 to remove a portion thereof, and as shown in Figure 5, the first processing groove 14 that separates the functional layer 6 is formed on each predetermined dividing line 7, 8.

Furthermore, in the first embodiment, in the first processing groove forming step 102, laser light is irradiated to both sides of each predetermined dividing line 7, 8 in the width direction, and the first protective film 13, the functional layer 6 and the substrate 2 on both sides of the width direction of each predetermined dividing line 4 are etched to form processing grooves. Then, laser light is irradiated between the processing grooves of each predetermined dividing line 7, 8 to form the first processing groove 14 by etching the first protective film 13, the functional layer 6 and the substrate 2 between the processing grooves of each predetermined dividing line 4. Furthermore, in the first embodiment, in the first processing groove forming step 102, the irradiation wavelength is 355nm (not limited to 355nm, preferably a wavelength in the ultraviolet region) and the repetition frequency is 200kHz to 2000kHz.

Alternatively, in the first embodiment, in the first processing groove forming step 102, the laser beam is divided to form two both-edge processing grooves on both edges in the width direction of the planned dividing lines 7 and 8. During ablation processing, the average output of the laser light is set to 0.5W, and the relative moving speed of the laser light irradiation unit and the wafer (hereinafter referred to as the processing feed speed) is set to 100mm/second to 400mm/ Seconds, the spot of the laser light focusing point is set to a circle with a diameter of 5 μm. In the first embodiment, in the first processing groove forming step 102, when performing ablation processing between the two edge processing grooves of the planned division lines 7 and 8, the average output of the laser light is set to 10.0 W. Set the processing feed speed from 200mm/second to 1000mm/second, and set the laser light spot to a rectangle with a width of 60μm.

In the first embodiment, the widths 14 - 1 of all the first processing grooves 14 are the same.

(1st protective film removal step) FIG. 6 is a cross-sectional view schematically showing the main parts of the wafer after the first protective film removal step of the wafer processing method shown in FIG. 3 . The first protective film removal step 103 is a step of cleaning and removing the first protective film 13 after the first processing groove forming step 102 is performed.

In the first embodiment, in the first protective film removal step 103, a cleaning device (not shown) sucks and holds the back surface 9 of the wafer 1 on the holding surface of the spin table through the tape 11, and The frame 12 is clamped by the chuck portion, and the wash water composed of pure water is supplied from the wash water supply nozzle to the center of the front surface 3 of the wafer 1 while the rotary table is rotated around the axis. The cleaning water supplied to the front surface 3 of the wafer 1 flows from the center side toward the outer peripheral side on the front surface 3 of the wafer 1 due to the centrifugal force generated by the rotation of the rotary table, thereby washing the front surface 3 of the wafer 1 After cleaning, as shown in FIG. 6 , the first protective film 13 containing water-soluble resin and foreign matter such as debris are removed from the front surface 3 of the wafer 1 .

(Process for forming protective film for mask) FIG. 7 is a cross-sectional view schematically showing the main parts of the wafer after the step of forming a mask protective film in the wafer processing method shown in FIG. 3 . The mask protective film forming step 104 is to form the mask protective film 15 covering the front surface 3 of the wafer 1 and filling the first processing groove 14 after the first processing groove forming step 102 is performed. Film formation step.

In the first embodiment, in the mask protective film forming step 104 , a resin coating device (not shown) attracts and holds the back surface 9 of the wafer 1 on the holding surface of the spin table through the tape 11 . The frame 12 is clamped by the clamp part, the rotary table is rotated around the axis, and the liquid water-soluble resin is dropped from the water-soluble resin supply nozzle toward the center of the front surface 3 of the wafer 1 . The dropped water-soluble resin flows from the center side toward the outer peripheral side of the front surface 3 of the wafer 1 due to the centrifugal force generated by the rotation of the rotary table, and is coated on the entire surface of the front surface 3 of the wafer 1. Fill the first processing groove 14.

Furthermore, the water-soluble resin includes water-soluble resins such as polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP). In the mask protective film forming step 104, the water-soluble resin applied to the entire surface of the front surface 3 of the wafer 1 is dried, and as shown in FIG. 7, the mask protective film 15 containing the water-soluble resin is coated on the entire surface of the front surface 3 of the wafer 1, and the mask protective film 15 is filled into the first processing groove 14.

As described above, in the first embodiment, the mask protective film 15 is made of water-soluble resin. In addition, the water-soluble resin constituting the protective film 15 for the mask is a resin that, after drying, is etched at a faster rate than the substrate 2 by the plasmatized etching gas 18 used in the plasma etching step 106 . Lower and more tolerable. Furthermore, in the first embodiment, the water-soluble resin constituting the mask protective film 15 is made of the same material as the water-soluble resin constituting the first protective film 13 formed in the first protective film forming step 101. However, in the present invention, as long as it has resistance to the etching gas 18, the material may be different from the water-soluble resin constituting the first protective film 13 formed in the first protective film forming step 101.

(Second processing groove forming step) FIG. 8 is a cross-sectional view schematically showing the main part of the wafer after the second processing groove forming step of the processing method of the wafer shown in FIG. 3. The second processing groove forming step 105 is a step of irradiating laser light along the first processing groove 14 after the implementation of the mask protective film forming step 104 to form a second processing groove 16 (shown in FIG. 8) with a width 16-1 smaller than the first processing groove 14, and exposing the substrate 2 along the second processing groove 16.

In the first embodiment, in the second processing groove forming step 105, a laser processing device (not shown) attracts and holds the back surface 9 of the wafer 1 on the holding surface of the holding table through the tape 11, and The frame 12 is clamped by the clamp part. In the first embodiment, in the second processing groove forming step 105, the laser processing device uses an imaging unit (not shown) to photograph the front three sides of the wafer 1 to detect the planned division lines 7 and 8, and The alignment of the laser light irradiation unit and the planned segmentation lines 7 and 8 is completed.

In the first embodiment, in the second processing groove forming step 105, the laser processing device moves the wafer 1 and the laser light irradiation unit relatively along the predetermined dividing lines 7 and 8, and irradiates the laser light of a wavelength that is absorbent to the wafer 1 from the laser light irradiation unit along the predetermined dividing lines 7 and 8 toward the wafer 1. Furthermore, in the first embodiment, in the second processing groove forming step 105, the laser processing device sets the focal point of the laser light on the front surface of the mask protective film 15 or the substrate 2, and irradiates the laser light toward the wafer 1 along the first processing grooves 14 formed on each of the predetermined dividing lines 7 and 8.

In the first embodiment, in the second processing groove forming step 105, the laser processing device performs ablation processing on the mask protective film 15 and the substrate 2 on the bottom surface 17 of the first processing groove 14 formed on each predetermined dividing line 7, 8 to remove a portion thereof, and as shown in Figure 8, a second processing groove 16 with a width 16-1 smaller than the first processing groove 14 is formed on the bottom surface 17 of the first processing groove 14 in which the functional layer 6 is severed at each predetermined dividing line 7, 8.

Furthermore, in the first embodiment, in the second processing groove forming step 105, the center of the width direction of the first processing groove 14 formed on each of the predetermined dividing lines 7 and 8 is irradiated with laser light, and the mask protective film 15 and the substrate 2 on the bottom surface 17 of the first processing groove 14 are etched to form the second processing groove 16. Furthermore, in the first embodiment, in the second processing groove forming step 105, the laser light having a wavelength of 355 nm (not limited to 355 nm, preferably a wavelength in the ultraviolet region) and a repetition frequency of 200 kHz to 1000 kHz is irradiated.

Furthermore, in the first embodiment, in the second processing groove forming step 105, the average output of the laser light is set to 1.0 W, the processing feed speed is set to 200 mm/second, and the focus of the laser light is set to 1.0 W. The light spot of the light spot is set to be a circle with a diameter of 25 μm to 40 μm. In the first embodiment, in the second processing groove forming step 105, the average output of the laser light suffices to be lower than the average output of the laser light irradiated between the processing grooves in the first processing groove forming step 102. . Thus, in the first embodiment, the output of the laser beam irradiated in the second processing groove forming step 105 is smaller than that in the first processing groove forming step 102 . Alternatively, in the first embodiment, the energy density of one spot of the laser beam irradiated in the second processing groove forming step 105 is higher than that of the laser beam irradiated in the first processing groove forming step 102 . The energy density of 1 spot is lower. Furthermore, in the first embodiment, the widths 16-1 of all the second processing grooves 16 are all the same.

(Plasma etching step) FIG. 9 is a cross-sectional view schematically showing the main parts of the wafer during the plasma etching step of the wafer processing method shown in FIG. 3. The plasma etching step 106 is a step of performing plasma etching along the second processing groove 16 using the mask protective film 15 as a mask after the second processing groove forming step 105 is performed.

In the first embodiment, in the plasma etching step 106 , a plasma etching apparatus (not shown) holds the back surface 9 side of the wafer 1 on the holding surface of the holding table via the tape 11 . In the first embodiment, in the plasma etching step 106, a high-frequency electric power capable of producing and maintaining plasma is applied to the upper electrode, and a power for pulling in ions is applied to the holding table serving as the lower electrode. The etching gas 18 is supplied to the front 3 sides of the wafer 1 while using high-frequency power.

Thus, in the first embodiment, in the plasma etching step 106, the plasma etching device will plasmatize the etching gas 18 in the space between the workbench and the upper electrode, and pull the plasmatized etching gas 18 into the side of the wafer 1, and perform etching (so-called plasma etching) on the bottom surface of the substrate 2 exposed to the second processing groove 16 of the mask, i.e., the mask protective film 15 formed on the wafer 1, so that the second processing groove 16 moves toward the back side 9 of the wafer 1.

Furthermore, in the first embodiment, in the plasma etching step 106, as shown in FIG9 , the plasma etching device plasma etches the wafer 1 until the second processing groove 16 opens on the back surface 9 to divide the wafer 1 into device chips 10. In this way, in the first embodiment, the wafer 1 is divided in the plasma etching step 106 to manufacture a plurality of device chips 10.

(Process for removing mask protective film) FIG. 10 is a cross-sectional view schematically showing the main parts of the wafer after the mask protective film removal step in the wafer processing method shown in FIG. 3 . The mask protective film removal step 107 is a step of cleaning and removing the mask protective film 15 after the plasma etching step 106 is performed.

In the first embodiment, in the mask protective film removal step 107, a cleaning device (not shown) attracts and holds the back side 9 of the wafer 1 on the holding surface of the rotating table via the tape 11, and clamps the frame 12 with a clamp portion. When the rotating table is rotated around the axis, cleaning water consisting of pure water or pure water containing a surfactant is supplied from a cleaning water supply nozzle to the center of the front side 3 of the wafer 1. The cleaning water supplied to the front side 3 of the wafer 1 flows from the center side toward the peripheral side on the front side 3 of the wafer 1 due to the centrifugal force generated by the rotation of the rotating worktable to clean the front side 3 of the wafer 1. As shown in FIG. 10, the mask protective film 15 containing a water-soluble resin and foreign matters such as debris are removed from the front side 3 of the wafer 1.

In the conventional processing method, when the substrate 2 on the bottom surface of the first processing groove 14 is plasma etched, the first protective film 13 and the functional layer 6 are removed to form the first processing groove 14, so it becomes necessary. The irradiation of a large-output laser light will also cause greater thermal damage to the functional layer 6. In particular, the functional layer 6 will have unevenness on the inner surface of the first processing groove 14. Therefore, when the conventional processing method performs plasma etching on the substrate 2 on the bottom surface of the first processing groove 14 , the substrate 2 will be etched especially along the unevenness of the functional layer 6 on the inner surface of the first processing groove 14 . Etching causes unevenness on the side of the device wafer 10 and reduces the flexural strength of the device wafer 10 .

Compared with such conventional processing methods, the wafer processing method of the first embodiment described above requires filling the first processing trench 14 with the masking protective film 15 and removing the masking film 15 in the first processing trench 14. The protective film 15 for masking is used to form the second processing groove 16. However, since the protective film 15 for masking can be processed with smaller energy than the functional layer 6, the output of the laser light when forming the second processing groove 16 can be reduced. The output of the laser light is suppressed to be smaller than when the first processing groove 14 is formed. Therefore, the wafer processing method of the first embodiment can suppress the thermal damage caused to the mask protective film 15 when the second processing trench 16 is formed compared with the thermal damage to the functional layer 6 when the first processing trench 14 is formed. The thermal damage caused is smaller, and the unevenness of the inner surface of the second processing groove 16 formed by the masking protective film 15 is suppressed compared with the unevenness of the inner surface of the first processing groove 14 formed by the functional layer 6. The bumps are smaller.

In addition, in the wafer processing method of the first embodiment, since the mask protective film 15 can be processed with smaller energy than the functional layer 6, it is possible to reduce the laser beam in the second processing groove forming step 105. The output becomes smaller than the output of the laser light in the first processing groove forming step 102, so that the second processing groove 16 can be formed and the unevenness generated on the inner surface of the second processing groove 16 can be reduced. . Although the side surface of the device wafer 10 formed by plasma etching is formed by transferring the unevenness on the side surface of the processing groove that becomes a mask, the processing method of the wafer in the first embodiment becomes the second process of the mask. The unevenness on the inner side of the trench 16 is smaller, so the unevenness on the side of the device wafer 10 can also be smaller.

As a result, the wafer processing method of the first embodiment etches the substrate 2 at the bottom surface of the second processing groove 16 along the second processing groove 16 in the plasma etching step 106, thereby improving the processing quality during plasma etching, and suppressing the unevenness of the side surface of the device chip 10, thereby suppressing the reduction in the flexural strength of the device chip 10.

[Modification] A wafer processing method according to a modified example of the first embodiment will be described based on the drawings. 11 is a cross-sectional view schematically showing the main parts of the wafer after the first protective film forming step in the wafer processing method according to the modification of the first embodiment. 12 is a cross-sectional view schematically showing the main parts of the wafer after the first processing trench forming step in the wafer processing method according to the modification of the first embodiment. 13 is a cross-sectional view schematically showing the main parts of the wafer after the first protective film removal step in the wafer processing method according to the modification of the first embodiment. 14 is a cross-sectional view schematically showing the main parts of the wafer after the step of forming a protective film for a mask in the wafer processing method according to the modification of the first embodiment. 15 is a cross-sectional view schematically showing the main parts of the wafer after the second processing groove forming step in the wafer processing method according to the modification of the first embodiment. 16 is a cross-sectional view schematically showing a main part of a wafer during a plasma etching step of the wafer processing method according to the modification of the first embodiment. 17 is a cross-sectional view schematically showing the main parts of the wafer after the mask protective film removal step in the wafer processing method according to the modification of the first embodiment. In addition, in FIGS. 11 , 12 , 13 , 14 , 15 , 16 and 17 , the same parts as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

The wafer processing method in the modified example of the first embodiment is the same as the first embodiment, and is a method of dividing the wafer 1 into individual device wafers 10 along the planned dividing lines 7 and 8 . The wafer processing method of the modified example of the first embodiment is the same as the first embodiment and includes a first protective film forming step 101, a first processing groove forming step 102, a first protective film removing step 103, and a mask protective film. The forming step 104 , the second processing groove forming step 105 , the plasma etching step 106 and the mask protective film removal step 107 .

In a modification of the first embodiment, the first protective film forming step 101 is the same as the first embodiment, but as shown in FIG. 11 , the wafer is covered with the first protective film 13 containing a water-soluble resin. The front side of 1 and the entire side of 3.

In a variation of the first embodiment, in the first processing groove forming step 102, as in the first embodiment, the laser processing device moves the wafer 1 and the laser light irradiation unit relative to each other along the predetermined dividing lines 7 and 8, while irradiating the wafer 1 with laser light of a wavelength that is absorptive to the wafer 1 from the laser light irradiation unit along the predetermined dividing lines 7 and 8.

In a variation of the first embodiment, in the first processing groove forming step 102, the laser processing device performs etching processing on the first protective film 13 and the functional layer 6 on each predetermined dividing line 7, 8 to remove a portion thereof, and as shown in Figure 12, a first processing groove 14 is formed on each predetermined dividing line 7, 8, which is recessed from the front side of the functional layer 6 and does not break the functional layer 6.

In a variation of the first embodiment, in the first protective film removal step 103, the front surface 3 of the wafer 1 is cleaned and the first protective film 13 is removed from the front surface 3 of the wafer 1 as shown in FIG. 13, the same as in the first embodiment.

In a variation of the first embodiment, in the mask protective film forming step 104, as in the first embodiment, as shown in FIG. 14, the entire front surface 3 of the wafer 1 is covered with a mask protective film 15 containing a water-soluble resin, and the mask protective film 15 is filled into the first processing groove 14.

In a variation of the first embodiment, in the second processing groove forming step 105, as in the first embodiment, the laser processing device moves the wafer 1 and the laser light irradiation unit relative to each other along the predetermined dividing lines 7 and 8, while irradiating the wafer 1 with laser light of a wavelength that is absorptive to the wafer 1 from the laser light irradiation unit along the predetermined dividing lines 7 and 8.

In a modification of the first embodiment, in the second processing groove forming step 105 , the laser processing device masks the bottom surface 17 of the first processing groove 14 formed on each of the planned dividing lines 7 and 8 . The protective film 15, the functional layer 6 and the substrate 2 are subjected to an ablation process to partially remove them, and as shown in FIG. 16-1 is a second processing groove 16 which is smaller than the first processing groove 14 and separates the functional layer 6.

Furthermore, in a modification of the first embodiment, the output of the laser beam irradiated in the second processing groove forming step 105 is smaller than that in the first processing groove forming step 102. Alternatively, in a modification of the first embodiment, the energy density of one spot of the laser beam irradiated in the second processing groove forming step 105 is lower than that of one spot of the laser beam irradiated in the first processing groove forming step 102. Furthermore, in a modification of the first embodiment, the width 14-1 of all the first processing grooves 14 is the same, and the width 16-1 of all the second processing grooves 16 is the same.

In a variation of the first embodiment, in the plasma etching step 106, as in the first embodiment, as shown in FIG. 16, the substrate 2 exposed at the bottom surface of the second processing groove 16 of the mask, i.e., the mask protective film 15 formed on the wafer 1 is etched (so-called plasma etching) so that the second processing groove 16 moves toward the back side 9 of the wafer 1, and the wafer 1 is plasma etched until the wafer 1 is divided into device chips 10.

In a variation of the first embodiment, in the mask protective film removal step 107, as in the first embodiment, the front side 3 of the wafer 1 is cleaned, and the mask protective film 15 containing a water-soluble resin and foreign objects such as debris are removed from the front side 3 of the wafer 1 as shown in FIG. 17 .

The wafer processing method of the variation of the first embodiment is the same as the first embodiment, in that the mask protective film 15 is filled into the first processing groove 14 and the mask protective film 15 in the first processing groove 14 is removed to form the second processing groove 16. Therefore, the unevenness of the inner side surface of the second processing groove 16 can be suppressed to be smaller than the unevenness of the inner side surface of the first processing groove 14, and the following effects of improving the processing quality are exerted: the unevenness of the side surface of the dividing groove formed in plasma etching becomes smaller, and the flexural strength of the manufactured device chip 10 is improved. Furthermore, compared with the first embodiment in which the first processing groove 14 having a depth for breaking the functional layer 6 is formed at one time in the first processing groove forming step 102, the wafer processing method of the variant example of the first embodiment has the effect of reducing the thermal influence generated on the functional layer 6 and the substrate 2 and improving the flexural strength of the device chip 10 because the first processing groove 14 having a depth for breaking the functional layer 6 is formed in a divided manner of the first processing groove forming step 102 and the second processing groove forming step 105. In addition, in the wafer processing method of the variation of the first embodiment, since the remaining functional layer 6 and the mask protective film 15 are removed to expose the substrate 2 in the second processing groove forming step 105, the output of the laser light becomes larger than that of the second processing groove forming step 105 of the first embodiment. However, compared with the previous technology in which the functional layer 6 is exposed on the entire inner surface of the second processing groove 16 serving as a mask, the side surface of the second processing groove 16 can be less uneven, thereby improving the processing quality during plasma etching.

[Second Embodiment] The wafer processing method of the second embodiment will be described based on the drawings. 18 is a plan view schematically showing the main parts of the wafer to be processed in the wafer processing method according to the second embodiment. Fig. 19 is a cross-sectional view taken along line XIX-XIX in Fig. 18. FIG. 20 is a cross-sectional view taken along line XX-XX in FIG. 18 . 21 is a cross-sectional view schematically showing a cross-section orthogonal to the first planned dividing line of the main portion of the wafer after the first protective film forming step in the wafer processing method according to the second embodiment. 22 is a cross-sectional view schematically showing a cross-section orthogonal to the second planned dividing line of the main portion of the wafer after the first protective film forming step in the wafer processing method according to the second embodiment.

FIG23 is a cross-sectional view schematically showing a cross section orthogonal to the first predetermined dividing line of the main part of the wafer after the first processing groove forming step of the wafer processing method of the second embodiment. FIG24 is a cross-sectional view schematically showing a cross section orthogonal to the second predetermined dividing line of the main part of the wafer after the first processing groove forming step of the wafer processing method of the second embodiment. FIG25 is a cross-sectional view schematically showing a cross section orthogonal to the first predetermined dividing line of the main part of the wafer after the first protective film removal step of the wafer processing method of the second embodiment. FIG26 is a cross-sectional view schematically showing a cross section orthogonal to the second predetermined dividing line of the main part of the wafer after the first protective film removal step of the wafer processing method of the second embodiment.

27 is a cross-sectional view schematically showing a cross-section orthogonal to the first planned division line of the main portion of the wafer after the step of forming a protective film for a mask in the wafer processing method of the second embodiment. 28 is a cross-sectional view schematically showing a cross-section orthogonal to the second planned dividing line of the main portion of the wafer after the step of forming a protective film for a mask in the wafer processing method of the second embodiment. 29 is a cross-sectional view schematically showing a cross-section orthogonal to the first planned division line of the main portion of the wafer after the second processing groove forming step in the wafer processing method according to the second embodiment. 30 is a cross-sectional view schematically showing a cross-section of a main part of the wafer orthogonal to the second planned dividing line after the second processing groove forming step in the wafer processing method according to the second embodiment.

FIG31 is a cross-sectional view schematically showing a cross section orthogonal to the first predetermined division line of a main portion of a wafer during a plasma etching step of a wafer processing method according to the second embodiment. FIG32 is a cross-sectional view schematically showing a cross section orthogonal to the second predetermined division line of a main portion of a wafer during a plasma etching step of a wafer processing method according to the second embodiment. FIG33 is a cross-sectional view schematically showing a cross section orthogonal to the first predetermined division line of a main portion of a wafer after a mask protective film removal step of a wafer processing method according to the second embodiment. FIG34 is a cross-sectional view schematically showing a cross section orthogonal to the second predetermined division line of a main portion of a wafer after a mask protective film removal step of a wafer processing method according to the second embodiment. 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 and 34 , the same symbols are attached to the parts that are the same as those in the first embodiment, and the description is omitted.

The wafer 1 to be processed in the wafer processing method of the second embodiment has a width of the first planned dividing line 7 smaller than the width of the second planned dividing line 8 as shown in FIG. 18 . Furthermore, as shown in FIGS. 18 and 20 , the wafer 1 to be processed in the wafer processing method of the second embodiment has a metal component, namely TEG (Test Element Group, Test), laminated on the front area of the second planned division line 8 Elementary Group)21. Furthermore, in the second embodiment, the wafer 1 has the metal component TEG 22 laminated on the front surface of the first planned division line 7 as shown in FIGS. TEG 22 is not laminated on the front surface of the planned division line 7 .

Furthermore, TEGs 21 and 22 are evaluation elements for finding out design or manufacturing problems that occur in device 5. In the wafer 1 to be processed by the wafer processing method of the second embodiment, the width of TEG 21 is slightly narrower than the width of the second predetermined dividing line 8 and wider than the width of the first predetermined dividing line 7. In the second embodiment, the width of TEG 22 is slightly narrower than the width of the first predetermined dividing line 7.

The wafer processing method of the second embodiment is the same as the first embodiment, and is a method for dividing the wafer 1 along the predetermined dividing lines 7 and 8 into individual device chips 10. The wafer processing method of the second embodiment is the same as the first embodiment, and includes a first protective film forming step 101, a first processing groove forming step 102, a first protective film removing step 103, a mask protective film forming step 104, a second processing groove forming step 105, a plasma etching step 106, and a mask protective film removing step 107.

In the second embodiment, the first protective film forming step 101 is the same as in the first embodiment, but as shown in FIGS. 21 and 22 , the wafer is covered with the first protective film 13 containing a water-soluble resin. The front side of 1 and the entire side of 3.

In the second embodiment, in the first processing groove forming step 102, as in the first embodiment, the laser processing device moves the wafer 1 and the laser light irradiation unit relative to each other along the predetermined dividing lines 7 and 8, while irradiating the wafer 1 with laser light of a wavelength that is absorptive to the wafer 1 from the laser light irradiation unit along the predetermined dividing lines 7 and 8.

Furthermore, in order to suppress the occurrence of burrs on TEGs 21 and 22 and maintain the processing quality of the device wafer 10 , it is necessary to remove the TEGs 21 and 22 already laminated on the front surface of the planned division lines 7 and 8 in the first processing groove forming step 102 overall removal. In addition, in the wafer 1 to be processed in the wafer processing method of the second embodiment, the width of the TEG 21 is slightly narrower than the width of the second planned division line 8 and wider than the width of the first planned division line 7 .

Therefore, in the wafer processing method of the second embodiment, in the first processing groove forming step 102, the first processing groove 14 (shown in FIG. 23, hereinafter referred to as numeral 141) is formed on the first planned dividing line 7. The width 141 - 1 becomes narrower than the width 142 - 1 of the first processing groove 14 (shown in FIG. 24 , hereinafter referred to as symbol 142 ) formed on the second planned dividing line 8 . Furthermore, the wafer processing method of the second embodiment is such that the first processing grooves 141 and 142 formed in the first processing groove forming step 102 have a width 141-1 wider than the width of the metal parts, that is, the TEGs 22 and 21. ,142-1. Thus, in the wafer processing method of the second embodiment, the widths 141-1 and 142-1 of the first processing grooves 141 and 142 formed in the first processing groove forming step 102 are not all the same. Furthermore, in the second embodiment, the width 141-1 of the first processing groove 141 is 60 mm, and the width 142-1 of the first processing groove 142 is 120 mm.

In the second embodiment, in the first processing groove forming step 102, the laser processing device performs ablation processing on the first protective film 13, TEG21, 22, functional layer 6 and substrate 2 on each predetermined dividing line 7, 8 to remove the first protective film 13, the functional layer 6 and a part of the substrate 2 and the entirety of TEG21, 22, and as shown in Figures 23 and 24, the first processing grooves 141, 142 that cut off the functional layer 6 are formed on each predetermined dividing line 7, 8.

In the second embodiment, in the first protective film removal step 103, the front side 3 of the wafer 1 is cleaned and the first protective film 13 is removed from the front side 3 of the wafer 1 as shown in FIG. 25 and FIG. 26, similarly to the first embodiment.

In the second embodiment, the mask protective film forming step 104 is the same as in the first embodiment, but as shown in FIGS. 27 and 28 , it is covered with a mask protective film 15 containing a water-soluble resin. The entire front surface 3 of the wafer 1 is filled with the mask protective film 15 into the first processing trenches 141 and 142 .

In the second embodiment, in the second processing groove forming step 105, as in the first embodiment, the laser processing device moves the wafer 1 and the laser light irradiation unit relative to each other along the predetermined dividing lines 7 and 8, while irradiating the wafer 1 with laser light of a wavelength that is absorptive to the wafer 1 from the laser light irradiation unit along the predetermined dividing lines 7 and 8.

In the second embodiment, in the second processing groove forming step 105, the laser processing device performs etching processing on the mask protective film 15 and the substrate 2 formed on the bottom surface 17 of the first processing grooves 141, 142 of each predetermined dividing line 7, 8 to remove a portion thereof, and as shown in Figures 29 and 30, a second processing groove 16 with a width 16-1 smaller than the first processing grooves 141, 142 is formed on the bottom surface 17 of the first processing grooves 141, 142 of each predetermined dividing line 7, 8.

Furthermore, in the second embodiment, the output of the laser beam irradiated in the second processing groove forming step 105 is smaller than that in the first processing groove forming step 102 . Furthermore, in the second embodiment, the widths 16-1 of all the second processing grooves 16 are all the same.

In the second embodiment, the plasma etching step 106 is the same as in the first embodiment. As shown in FIGS. 31 and 32 , the mask is exposed on the mask already formed on the wafer 1 . The substrate 2 on the bottom surface of the second processing groove 16 of the protective film 15 is etched (so-called plasma etching), and the second processing groove 16 is advanced toward the back surface 9 of the wafer 1 to plasma-etch the wafer 1 to the edge of the wafer 1 . Circle 1 is divided into device wafers 10.

In the second embodiment, in the mask protective film removal step 107, as in the first embodiment, the front side 3 of the wafer 1 is cleaned, and the mask protective film 15 containing a water-soluble resin and foreign objects such as debris are removed from the front side 3 of the wafer 1, as shown in FIG. 33 and FIG. 34.

The processing method of the wafer of the second embodiment is the same as that of the first embodiment, that is, the mask protective film 15 is filled into the first processing grooves 141, 142, and the mask protective film 15 in the first processing grooves 141, 142 is removed to form the second processing groove 16. Therefore, the unevenness of the inner side surface of the second processing groove 16 can be suppressed to be smaller than the unevenness of the inner side surface of the first processing groove 14, thereby exerting the effect of improving the processing quality during plasma etching.

If the entire TEG 21 and 22 are removed in the first processing groove forming step 102 in order to suppress the generation of burrs of the TEG 21 and 22, the widths 141-1 and 142-1 of the first processing grooves 141 and 142 will be different. Therefore, if the wafer 1 is plasma etched using the conventional processing method, the processing during the plasma etching will be uneven and cannot be processed uniformly. However, the processing method of the wafer of the second embodiment can suppress the uneven processing during the plasma etching because the width 16-1 of the second processing groove 16 is the same even if the widths 141-1 and 142-1 of the first processing grooves 141 and 142 are different.

[Modification] A wafer processing method according to a modified example of the second embodiment will be described based on the drawings. 35 is a cross-sectional view schematically showing a cross-section orthogonal to a first planned division line of a main portion of the wafer after the first protective film forming step in the wafer processing method according to the modification of the second embodiment. 36 is a cross-sectional view schematically showing a cross-section orthogonal to a second planned dividing line of a main portion of the wafer after the first protective film forming step in the wafer processing method according to the modification of the second embodiment.

37 is a cross-sectional view schematically showing a cross-section of a main portion of the wafer orthogonal to the first planned dividing line after the first processing groove forming step in the wafer processing method according to the modification of the second embodiment. 38 is a cross-sectional view schematically showing a cross-section orthogonal to the second planned division line of the main portion of the wafer after the first processing groove forming step in the wafer processing method according to the modification of the second embodiment. 39 is a cross-sectional view schematically showing a cross-section orthogonal to the first planned dividing line of the main portion of the wafer after the first protective film removal step in the wafer processing method according to the modification of the second embodiment. 40 is a cross-sectional view schematically showing a cross-section orthogonal to the second planned division line of the main portion of the wafer after the first protective film removal step in the wafer processing method according to the modification of the second embodiment.

FIG41 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined dividing line of a main portion of a wafer after the step of forming a mask protective film in the wafer processing method of a modification of the second embodiment. FIG42 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined dividing line of a main portion of a wafer after the step of forming a mask protective film in the wafer processing method of a modification of the second embodiment. FIG43 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined dividing line of a main portion of a wafer after the step of forming a second processing groove in the wafer processing method of a modification of the second embodiment. FIG44 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined dividing line of a main portion of a wafer after the step of forming a second processing groove in the wafer processing method of a modification of the second embodiment.

45 is a cross-sectional view schematically showing a cross-section of a main portion of a wafer orthogonal to a first planned division line during a plasma etching step of a wafer processing method according to a modification of the second embodiment. 46 is a cross-sectional view schematically showing a cross-section orthogonal to a second planned dividing line of a main portion of a wafer during a plasma etching step in the wafer processing method according to a modification of the second embodiment. 47 is a cross-sectional view schematically showing a cross-section of a main portion of the wafer orthogonal to the first planned division line after the mask protective film removal step in the wafer processing method according to the modification of the second embodiment. 48 is a cross-sectional view schematically showing a cross-section orthogonal to the second planned division line of the main portion of the wafer after the mask protective film removal step in the wafer processing method according to the modification of the second embodiment. Furthermore, Figure 35, Figure 36, Figure 37, Figure 38, Figure 39, Figure 40, Figure 41, Figure 42, Figure 43, Figure 44, Figure 45, Figure 46, Figure 47 and Figure 48 are consistent with the first embodiment The same parts as those in the second embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

The wafer 1 to be processed in the wafer processing method of the modification of the second embodiment is the same as the second embodiment, in that the width of the first predetermined dividing line 7 is smaller than the width of the second predetermined dividing line 8, and the metal part, namely, TEG 21, is stacked on the front side of the second predetermined dividing line 8. In the modification of the second embodiment, the metal part, namely, TEG 22, is stacked on the front side of the first predetermined dividing line 7 of the wafer 1, as in the second embodiment. However, in the present invention, TEG 22 may not be stacked on the front side of the first predetermined dividing line 7. In the wafer 1 to be processed by the wafer processing method according to the modified example of the second embodiment, the width of the TEG 21 is narrower than the width of the second planned dividing line 8 and wider than the width of the first planned dividing line 7.

The wafer processing method of the second embodiment is similar to the first and second embodiments, and is a method for dividing the wafer 1 into individual device chips 10 along the predetermined dividing lines 7 and 8. The wafer processing method of the second embodiment is similar to the first and second embodiments, and includes a first protective film forming step 101, a first processing groove forming step 102, a first protective film removing step 103, a mask protective film forming step 104, a second processing groove forming step 105, a plasma etching step 106, and a mask protective film removing step 107.

In a modification of the second embodiment, the first protective film forming step 101 is the same as in the first embodiment, but as shown in FIGS. 35 and 36 , the first protective film 13 containing a water-soluble resin is used. The entire front surface 3 of the wafer 1 is covered.

In a modification of the second embodiment, in the first processing groove forming step 102, similar to the first embodiment and the second embodiment, the laser processing device moves the wafer 1 along with the laser beam irradiation unit. While moving relatively along the lines to be divided 7 and 8 , the laser beam irradiation unit irradiates the wafer 1 with laser light having a wavelength that is absorptive to the wafer 1 along the lines 7 and 8 to be divided.

The wafer processing method of the modification of the second embodiment is similar to the second embodiment, and in the first processing groove forming step 102, the width 141-1 of the first processing groove 141 formed on the first predetermined dividing line 7 is narrower than the width 142-1 of the first processing groove 142 formed on the second predetermined dividing line 8. Thus, in the wafer processing method of the modification of the second embodiment, the first processing grooves 141 and 142 formed in the first processing groove forming step 102 do not all have the same width 141-1 and 142-1.

In a variation of the second embodiment, in the first processing groove forming step 102, the laser processing device performs etching processing on the first protective film 13, TEG21, 22 and functional layer 6 on each predetermined dividing line 7, 8 to remove the first protective film 13, a portion of the functional layer 6 and the entire TEG21, 22, and as shown in Figures 37 and 38, the first processing grooves 141, 142 are formed on each predetermined dividing line 7, 8, which are recessed from the front side of the functional layer 6 and do not break the functional layer 6.

In a variation of the second embodiment, in the first protective film removal step 103, the front side 3 of the wafer 1 is cleaned and the first protective film 13 is removed from the front side 3 of the wafer 1, as shown in FIGS. 39 and 40, in the same manner as in the first and second embodiments.

In a variation of the second embodiment, in the mask protective film forming step 104, it is the same as the first and second embodiments, and as shown in Figures 41 and 42, the entire surface of the front side 3 of the wafer 1 is covered with a mask protective film 15 containing a water-soluble resin, and the mask protective film 15 is filled into the first processing grooves 141, 142.

In a variation of the second embodiment, in the second processing groove forming step 105, as in the first and second embodiments, the laser processing device moves the wafer 1 and the laser light irradiation unit relative to each other along the predetermined dividing lines 7 and 8, while irradiating the wafer 1 with laser light of a wavelength that is absorptive to the wafer 1 from the laser light irradiation unit along the predetermined dividing lines 7 and 8.

In a variation of the second embodiment, in the second processing groove forming step 105, the laser processing device performs ablation processing on the mask protective film 15, the functional layer 6 and the substrate 2 on the bottom surface 17 of the first processing grooves 141, 142 formed on each predetermined dividing line 7, 8 to remove a portion thereof, and as shown in Figures 43 and 44, a second processing groove 16 having a width 16-1 smaller than the first processing grooves 141, 142 is formed on the bottom surface 17 of the first processing grooves 141, 142 of each predetermined dividing line 7, 8 to cut off the functional layer 6.

Furthermore, in a modification of the second embodiment, the output of the laser beam irradiated in the second processing groove forming step 105 is smaller than that in the first processing groove forming step 102. Alternatively, in a modification of the second embodiment, the energy density of one spot of the laser beam irradiated in the second processing groove forming step 105 is lower than that of one spot of the laser beam irradiated in the first processing groove forming step 102. Furthermore, in a modification of the second embodiment, the width 16-1 of all the second processing grooves 16 is the same.

In a modification of the second embodiment, in the plasma etching step 106, the process is the same as in the first embodiment and the second embodiment. As shown in FIGS. 45 and 46, the plasma etching step 106 is exposed on the wafer formed on the wafer. The mask 1, that is, the substrate 2 on the bottom surface of the second processing groove 16 of the mask protective film 15 is etched (so-called plasma etching), so that the second processing groove 16 moves toward the back surface 9 of the wafer 1, so as to remove the wafer 1. Wafer 1 is plasma etched until wafer 1 is singulated into device wafers 10 .

In a modification of the second embodiment, in the mask protective film removal step 107, it is the same as the first embodiment, but as shown in FIGS. 47 and 48, the front surface 3 of the wafer 1 is cleaned. The mask protective film 15 containing water-soluble resin is removed from the front surface 3 of the wafer 1 together with foreign matter such as debris.

The wafer processing method in the modified example of the second embodiment is the same as that in the first and second embodiments. The method is to fill the first processing grooves 141 and 142 with the masking protective film 15 and remove the first processing method. The protective film 15 is used to cover the grooves 141 and 142 to form the second processed groove 16. Therefore, the unevenness of the inner surface of the second processed groove 16 can be suppressed to be smaller than the unevenness of the inner surface of the first processed groove 14. It has the effect of improving processing quality in plasma etching.

In addition, since the wafer processing method of the modified example of the second embodiment is the same as the second embodiment, even if the widths 141-1 and 142-1 of the first processing grooves 141 and 142 are different, the width of the second processing groove 16 16-1 is still the same, so it is possible to suppress uneven processing during plasma etching.

In addition, this invention is not limited to the invention of the said embodiment. That is, various modifications can be made without departing from the gist of the present invention. For example, in the present invention, the first protective film forming step 101 and the first protective film removing step 103 may not be performed. Furthermore, in the present invention, in the plasma etching step 106, the wafer 1 does not need to be divided into individual device wafers 10.

1:wafer 2:Substrate 3: Front 4: Split the scheduled line 5: Device 6: Functional layer 7: The first planned division line (planned division line) 8: The second planned division line (planned division line) 9: Back 10: Device wafer 11: Tape 12:Frame 13: 1st protective film 14,141,142: 1st processing ditch 14-1,141-1,142-1,16-1:Width 15: Protective film for masking 16: 2nd processing ditch 17: Bottom 18: Etching gas 21,22:TEG 101: The first protective film formation step 102: The first machining groove formation step 103: The first protective film removal step 104: Steps for forming protective film for mask 105: Second processing groove formation step 106: Plasma etching step 107: Steps to remove protective film for mask XIX-XIX: line XX-XX: line

FIG. 1 is a perspective view schematically showing a wafer to be processed by the wafer processing method of the first embodiment. FIG. 2 is a cross-sectional view schematically showing the main parts of the wafer shown in FIG. 1. FIG. 3 is a flow chart showing the process of the wafer processing method of the first embodiment. FIG. 4 is a cross-sectional view schematically showing the main parts of the wafer after the first protective film forming step of the wafer processing method shown in FIG. 3. FIG. 5 is a cross-sectional view schematically showing the main parts of the wafer after the first processing groove forming step of the wafer processing method shown in FIG. 3. FIG. 6 is a cross-sectional view schematically showing the main parts of the wafer after the first protective film removing step of the wafer processing method shown in FIG. 3. FIG. 7 is a cross-sectional view schematically showing the main parts of the wafer after the mask protective film forming step of the wafer processing method shown in FIG. 3. FIG8 is a cross-sectional view schematically showing the main part of the wafer after the second processing groove forming step of the wafer processing method shown in FIG3. FIG9 is a cross-sectional view schematically showing the main part of the wafer during the plasma etching step of the wafer processing method shown in FIG3. FIG10 is a cross-sectional view schematically showing the main part of the wafer after the mask protective film removal step of the wafer processing method shown in FIG3. FIG11 is a cross-sectional view schematically showing the main part of the wafer after the first protective film forming step of the wafer processing method of a modified example of the first embodiment. FIG12 is a cross-sectional view schematically showing the main part of the wafer after the first processing groove forming step of the wafer processing method of a modified example of the first embodiment. FIG. 13 is a cross-sectional view schematically showing the main part of the wafer after the first protective film removal step of the wafer processing method of the modification of the first embodiment. FIG. 14 is a cross-sectional view schematically showing the main part of the wafer after the mask protective film forming step of the wafer processing method of the modification of the first embodiment. FIG. 15 is a cross-sectional view schematically showing the main part of the wafer after the second processing groove forming step of the wafer processing method of the modification of the first embodiment. FIG. 16 is a cross-sectional view schematically showing the main part of the wafer during the plasma etching step of the wafer processing method of the modification of the first embodiment. FIG. 17 is a cross-sectional view schematically showing the main part of the wafer after the mask protective film removal step of the wafer processing method of the modification of the first embodiment. FIG. 18 is a plan view schematically showing a main portion of a wafer to be processed by the wafer processing method of the second embodiment. FIG. 19 is a cross-sectional view taken along line XIX-XIX in FIG. 18. FIG. 20 is a cross-sectional view taken along line XX-XX in FIG. 18. FIG. 21 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined division line of the main portion of the wafer after the first protective film forming step of the wafer processing method of the second embodiment. FIG. 22 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined division line of the main portion of the wafer after the first protective film forming step of the wafer processing method of the second embodiment. FIG. 23 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined division line of the main portion of the wafer after the first processing groove forming step of the wafer processing method of the second embodiment. FIG. 24 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined division line of the main part of the wafer after the first processing groove forming step of the wafer processing method of the second embodiment. FIG. 25 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined division line of the main part of the wafer after the first protective film removal step of the wafer processing method of the second embodiment. FIG. 26 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined division line of the main part of the wafer after the first protective film removal step of the wafer processing method of the second embodiment. FIG. 27 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined division line of the main part of the wafer after the mask protective film forming step of the wafer processing method of the second embodiment. FIG. 28 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined division line of the main part of the wafer after the step of forming a protective film for mask in the wafer processing method of the second embodiment. FIG. 29 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined division line of the main part of the wafer after the step of forming a second processing groove in the wafer processing method of the second embodiment. FIG. 30 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined division line of the main part of the wafer after the step of forming a second processing groove in the wafer processing method of the second embodiment. FIG. 31 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined division line of the main part of the wafer during the plasma etching step of the wafer processing method of the second embodiment. FIG. 32 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined division line of a main portion of a wafer during a plasma etching step of a wafer processing method of the second embodiment. FIG. 33 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined division line of a main portion of a wafer after a mask protective film removal step of a wafer processing method of the second embodiment. FIG. 34 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined division line of a main portion of a wafer after a mask protective film removal step of a wafer processing method of the second embodiment. FIG. 35 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined division line of a main portion of a wafer after a first protective film forming step of a wafer processing method of a variation of the second embodiment. FIG. 36 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined dividing line of the main part of the wafer after the first protective film forming step of the wafer processing method of the second embodiment. FIG. 37 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined dividing line of the main part of the wafer after the first processing groove forming step of the wafer processing method of the second embodiment. FIG. 38 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined dividing line of the main part of the wafer after the first processing groove forming step of the wafer processing method of the second embodiment. FIG. 39 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined dividing line of the main part of the wafer after the first protective film removing step of the wafer processing method of the second embodiment. FIG. 40 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined dividing line of the main part of the wafer after the first protective film removal step of the wafer processing method of the second embodiment. FIG. 41 is a cross-sectional view schematically showing a cross section perpendicular to the first predetermined dividing line of the main part of the wafer after the mask protective film forming step of the wafer processing method of the second embodiment. FIG. 42 is a cross-sectional view schematically showing a cross section perpendicular to the second predetermined dividing line of the main part of the wafer after the mask protective film forming step of the wafer processing method of the second embodiment. FIG. 43 is a cross-sectional view schematically showing a cross section of a main part of a wafer orthogonal to the first predetermined dividing line after the second processing groove forming step of the wafer processing method of the second embodiment. FIG. 44 is a cross-sectional view schematically showing a cross section of a main part of a wafer orthogonal to the second predetermined dividing line after the second processing groove forming step of the wafer processing method of the second embodiment. FIG. 45 is a cross-sectional view schematically showing a cross section of a main part of a wafer orthogonal to the first predetermined dividing line during the plasma etching step of the wafer processing method of the second embodiment. FIG. 46 is a cross-sectional view schematically showing a cross section orthogonal to the second predetermined dividing line of a main portion of a wafer during a plasma etching step of a wafer processing method of a modification of the second embodiment. FIG. 47 is a cross-sectional view schematically showing a cross section orthogonal to the first predetermined dividing line of a main portion of a wafer after a mask protective film removal step of a wafer processing method of a modification of the second embodiment. FIG. 48 is a cross-sectional view schematically showing a cross section orthogonal to the second predetermined dividing line of a main portion of a wafer after a mask protective film removal step of a wafer processing method of a modification of the second embodiment.

101: Step 1 of forming the protective film

102: The first processing groove forming step

103: Step 1 of removing the protective film

104: Step of forming a protective film for masking

105: Second processing groove forming step

106: Plasma etching steps

107: Steps to remove the protective film used for masking

Claims (6)

A method of processing a wafer in which a plurality of devices are formed on a wafer by stacking a functional layer on the front surface of a substrate, and the wafer is processed along a plurality of planned dividing lines that intersect the plurality of devices. The processing method consists of the following steps: The first processing groove forming step is to irradiate laser light from the front surface of the wafer along the planned division line to form the first processing groove in the functional layer; The mask protective film forming step is to form a mask protective film covering the front surface of the wafer and filled in the first processing trench after the first processing groove forming step; In the second processing groove forming step, after the mask protective film forming step is performed, a laser beam is irradiated along the first processing groove to form a second processing groove with a narrower width than the first processing groove, and Exposing the substrate along the second processing groove; and In the plasma etching step, after the second processing groove forming step is performed, plasma etching is performed along the second processing groove using the mask protective film as a mask. The wafer processing method of claim 1, wherein the output of the irradiated laser light is smaller in the second processing groove forming step than in the first processing groove forming step. A wafer processing method as claimed in claim 1, wherein the plasma etching step is to divide the wafer to produce a plurality of device chips. The wafer processing method of claim 1 further includes a first protective film forming step and a first protective film removing step, The first protective film forming step is to form the first protective film on the front surface of the wafer before the first processing groove forming step is performed. In the first protective film removal step, after the first processing groove forming step is performed, the first protective film is washed and removed. A wafer processing method as claimed in claim 1, wherein the first processing grooves are not all of the same width, and the second processing grooves are all of the same width. A wafer processing method as claimed in claim 5, wherein the first processing groove has a width wider than that of the metal parts layered on the front side of the predetermined dividing line.