JP2018182115A - Processing method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily perform a plasma etching onto a side surface of a divided chip.SOLUTION: A processing method of a wafer comprises: a division step of dividing a wafer W into individual chips 3 along a division schedule line S from a front surface Wa side of the wafer W while adhering a tape 2 to a back surface Wb of the wafer W; a protection layer formation step of forming a protection layer 24 onto an upper surface of each chip 3 by spraying a resin 23 from an upper direction of each divided chip 3; a plasma etching step of performing a plasma etching of a side surface 3a of each chip 3; and a protection layer removing step of removing the protection layer 24 after the plasma etching step. Therefore, the protection layer 24 is formed on the upper surface of each chip 3, and only the side surface 3a of each chip 3 can be exposed while preventing the resin 23 from entering into a gap 4 of the adjacent chips 3. Thus, only a vertical surface of each chip 3 can be masked, and the plasma etching can be easily performed to the side surface 3a of each chip 3.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a wafer processing method for dividing a wafer into individual chips and performing plasma processing on the side surfaces of the chips.

  In a workpiece such as a wafer, devices are formed in regions respectively divided by grid-like planned dividing lines on the surface. In order to divide the wafer into individual chips, for example, there is a method of dividing the wafer by ablation processing by laser beam irradiation or cutting processing by a cutting blade. A modified layer is formed inside the wafer by irradiating a laser beam from the upper surface side of the wafer along the planned dividing line, and an external force is applied along the planned dividing line with reduced strength to start the modified layer. There is also a method of dividing the wafer into individual chips.

When performing ablation processing, thermal energy is concentrated in the area irradiated with the laser beam to generate debris, so a protective layer is formed on the upper surface of the wafer to prevent debris from adhering to the wafer, After the ablation process is completed, the protective layer is removed.
In addition, after the wafer is divided by ablation processing, plasma etching is performed to make the side surface of the chip a mirror surface. Even in the case where the wafer is divided by cutting, or in the case where the laser beam is positioned inside the wafer to form the modified layer and then external force is applied to the wafer to divide the modified layer as a starting point, the side surface of the chip as described above. Plasma etching is performed to make the mirror surface a mirror surface.

  When plasma etching the wafer divided into individual chips, it is necessary to attach the lower surface of the chip to a tape and form a protective layer on the upper surface of the chip as a mask, for example, by spin coating the wafer A liquid resin is applied to the upper surface of the to form a protective layer. Moreover, in the following patent documents, the method of forming a protective layer on liquid resin on the upper surface of a wafer using a roller is proposed, and the application amount of liquid resin is suppressed rather than the case where a protective layer is formed by spin coating. It has become possible.

JP, 2014-155883, A

  However, in order to plasma etch the side surfaces of the divided chips, it is necessary to form a protective layer on a chip basis. When the protective layer is formed by spin coating, the liquid resin intrudes into the gap between the adjacent chips, and the protective layer is also formed on the side surfaces of the chips. Further, in the method of forming the protective layer by the roller, the liquid resin is applied while the roller rolls over the entire surface of the upper surface of the wafer, so there is a possibility that the liquid resin may enter the gap between adjacent chips. is there. When the protective layer is formed on the side surface of the chip, there is a problem that the side surface of the chip is not finished to a desired mirror surface even if plasma etching is performed.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to enable plasma etching to be easily performed on the side surface of a divided chip.

  The present invention is a method of processing a wafer in which the side surface of a chip formed by dividing a wafer partitioned by a planned dividing line along a planned dividing line is subjected to plasma processing to enhance the chip bending strength. Dividing the wafer into individual chips along the planned dividing line from the upper surface side of the wafer by sticking a tape to the lower surface of the wafer, and spraying resin from above the chips divided in the dividing process. Forming a protective layer on the upper surface of the chip, a plasma etching process of plasma etching the side surface of the chip on which the protective layer is formed, and removing the protective layer after performing the plasma etching process And removing the protective layer.

  In the method of processing a wafer according to the present invention, the side surface of a chip formed by dividing a wafer partitioned by a planned dividing line and formed with a device along a planned dividing line is plasma processed to enhance the chip bending strength. A method of processing a wafer, comprising: a dividing step of sticking a tape on the lower surface of the wafer and dividing the wafer into individual chips along a planned dividing line from the upper surface side of the wafer; and from above the chips divided in the dividing step. A protective layer forming step of forming a protective layer on the upper surface of the chip by spraying a resin, a plasma etching step of plasma etching a side of the chip on which the protective layer is formed, and a protective layer removing step after performing the plasma etching step And forming a protective layer on the top surface of each chip by the surface tension of the resin sprayed toward the chips. , It is possible to expose only the side surface of the chip prevents the resin from entering between the chip and the chip. Therefore, only the upper and lower surfaces of each chip can be masked, and plasma etching can be easily performed on the side surface of the chip.

It is a perspective view showing the composition of an example of a wafer. It is sectional drawing which shows a division | segmentation process. It is sectional drawing which shows a protective layer formation process. It is a partially expanded sectional view which shows a protective layer formation process. It is sectional drawing which shows a plasma etching process. It is sectional drawing which shows a protective layer removal process.

  The wafer W shown in FIG. 1 is an example of a workpiece, and has a circular plate-like substrate, and devices D such as IC and LSI are respectively provided in a plurality of areas divided by grid division scheduled lines S. It is formed. The upper surface of the wafer W on which the device D is formed is the front surface Wa, and the lower surface opposite to the front surface Wa is the back surface Wb. Hereinafter, a wafer processing method will be described in which the side surface of the chip formed by dividing the wafer W along the dividing line S is subjected to plasma processing to increase the bending strength of the chip.

(1) Division Process First, as shown in FIG. 2A, the expandable tape 2 is attached to the lower surface of the annular ring frame 1 having the central portion opened, and the tape exposed from the central portion of the ring frame 1 The back surface Wb side of the wafer W is adhered to the surface 2 to expose the front surface Wa upward. In this manner, a work set WS in which the ring frame 1 and the wafer W are integrated via the tape 2 is formed.

  After the work set WS is formed, for example, cutting is performed from the upper surface side (surface Wa side) of the wafer W along the planned dividing line S shown in FIG. 1 using the cutting means 10 for cutting the wafer W. The cutting means 10 includes a rotatable spindle 11 and a cutting blade 12 attached to the tip of the spindle 11. The cutting blade 12 is also rotated by rotation of the spindle 11.

  For example, while moving the work set WS in the X direction, the cutting means 10 is a cutting blade from the surface Wa of the wafer W to the tape 2 along the planned dividing line S shown in FIG. 1 while rotating the cutting blade 12 Make 12 cuts and cut. That is, the wafer W is fully cut (completely cut) in the thickness direction by the cutting blade 12. The wafer W is divided into individual chips 3 as shown in FIG. 2B by cutting with the cutting blade 12 along all the planned dividing lines S.

  Since the tape 2 is attached to the back surface Wb of the wafer W, the chips 3 are not separated after the wafer W is completely cut, and the shape of the wafer W is maintained. After dividing the wafer W along all planned dividing lines S, after cleaning the chips attached to each chip 3, the tape 2 is expanded by using, for example, an expand device or the like, and the distance between adjacent chips 3 is determined. Expand to form a gap 4.

(2) Protective Layer Forming Step After performing the dividing step, for example, as shown in FIG. 3, the work set WS is disposed under the resin supply nozzle 20 for spraying the resin 23 from above the chip 3 divided in the dividing step. Move it. The resin supply nozzle 20 is a spray nozzle, and the tip thereof is provided with a jet port 21 for spraying the liquid resin 23. A resin supply source 22 is connected to the resin supply nozzle 20. The resin supply nozzle 20 is rotatable, and can move to the upper side of the work set WS or retract from the upper side of the work set WS. Further, the resin supply nozzle 20 can be moved up and down in the vertical direction, and the height position of the injection port 21 can be adjusted. In addition, the resin supply nozzle 20 should just be a structure which can inject resin 23 in a mist form from the injection port 21, and the structure in particular is not restricted.

  The work set WS is rotated, for example, at a rotational speed of 500 rpm to 800 rpm in the direction of arrow B around the center of the work set WS in the vertical direction. Subsequently, the resin supply nozzle 20 sprays the resin 23 from the injection port 21 toward the chip 3 while turning on the upper side of the work set WS. The resin supply nozzle 20 pivots parallel to the upper surface of the holding table holding the work set WS, but straight from the outside of the holding table holding the work set WS through the center to the opposite outside. The resin supply nozzle 20 may be moved in the shape of a circle. The resin 23 uses, for example, a water-soluble resin whose main component is polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP) or the like. The resin 23 preferably has a viscosity to some extent.

  Here, as shown in FIG. 4, the resin 23 sprayed downward from the injection port 21 of the resin supply nozzle 20 is a microdroplet including small particles 23a and large particles 23b. When such microdroplets are dropped on the upper surface of the chip 3, the surface tension of the microdroplets attached to the upper surface of the chip 3 attracts the plurality of small particles 23 a and the large particles 23 b to each other. It is formed as a layer 24. The protective layer 24 is formed to cover the upper surface of the chip 3 by supplying the resin 23 in such an amount that the resin 23 does not flow down into the gap 4 from the edge of the chip while staying at the edge of the chip 3. It becomes a mask when performing etching. In addition, the resin 23 dropped onto the upper surface of the chip 3 in the form of minute droplets including the small particles 23 a and the large particles 23 b may be jetted from the injection port 21 of the resin supply nozzle 20 downward with a small force. Preferably, in the illustrated example, microdroplets including small particles 23a and large particles 23b are dropped onto the tip 3.

In the protective layer forming step, since the resin 23 is sprayed toward the upper surface of the chip 3 by the resin supply nozzle 20, there is no possibility that the resin 23 enters the gap 4 between adjacent chips 3 and the entire width direction of the gap 4 is exposed. The protective layer 24 can be formed only on the top surface of the chip 3 while maintaining the state. That is, there is no possibility that the protective layer 24 is formed on the side surface 3 a of each chip 3. However, in practice, as shown in FIG. 4, for example, small particles 23a may enter the gap 4 between adjacent chips 3, but since only a very small amount can enter the gap 4, it hinders plasma etching and It must not be. When the protective layer 24 is formed on the top surfaces of all the chips 3, the protective layer forming process is finished.

  An air supply source (not shown) may be connected to the resin supply nozzle 20 to spray two fluids obtained by mixing the resin 23 and air from the injection port 21. In this case, it is preferable to move the injection port 21 of the resin supply nozzle 20 to a position close to the upper surface of the chip 3 to carry out the protective layer forming step. As a result, even when the resin 23 enters the gap 4 when spraying the resin 23 toward the chip 3, the resin 23 can be blown away from the gap 4 by air, so the protective layer 24 is formed on the side surface 3 a of the chip 3. It can be reliably prevented from being formed.

(3) Plasma Etching Step After carrying out the protective layer forming step, for example, the work set WS is transported to the plasma etching apparatus 30 shown in FIG. The plasma etching apparatus 30 includes a chamber 300 having a processing space 301 in which plasma etching is performed. In the chamber 300, the lower electrode unit 31 and the upper electrode unit 34 are disposed to face each other in the vertical direction.

  The lower electrode unit 31 includes an electrostatic chuck table 310 for holding the wafer W, and an electrode 311 disposed inside the electrostatic chuck table 310. A direct current power supply 32 is connected to the electrode 311, and by applying a direct current voltage to the electrode 311, the wafer W can be adsorbed on the electrostatic chuck table 310 by electrostatic force such as coulomb.

The upper electrode unit 34 includes a support portion 340 disposed through the upper portion of the chamber 300 and a gas supply portion 341 connected to the lower portion of the support portion 340. In the lower surface of the gas supply unit 341, an injection port 342 for injecting a reaction gas (etching gas 36) into the processing space 301 is formed. A lift mechanism (not shown) is connected to the support portion 340 and can raise and lower the gas supply portion 341 together with the support portion 340 in the vertical direction. The injection port 342 is connected to the reactive gas supply source 35 through a flow path 343 formed inside the support portion 340 and the gas supply portion 341. The reactive gas supply source 35 is filled with an etching gas 36 containing fluorine, such as SF ₆ series, for example.

  The lower electrode unit 31 is connected to a high frequency power supply 33. Further, the upper electrode unit 34 is grounded. By applying a high frequency voltage to the lower electrode unit 31 and the upper electrode unit 34, the etching gas 36 is turned into plasma in the processing space 301. The high frequency voltage may be adjusted to a frequency and power at which the etching species can be drawn into the wafer W. An exhaust port 302 communicating with an exhaust source 37 such as a vacuum pump is formed at a lower portion of the chamber 300, and the used etching gas 36 can be exhausted from the exhaust port 302.

  When plasma etching is performed on the wafer W using the plasma etching apparatus 30, the work set WS is carried into the chamber 300, and the electrostatic chuck table 310 holds the wafer W by suction via the tape 2. The top surface of the chip 3 is directed upward. Subsequently, the gas supply unit 341 is lowered, and in this state, the etching gas 36 is supplied from the reaction gas supply source 35 to the flow path 343, and the etching gas 36 is injected from the injection port 342 of the gas supply unit 341. A high frequency voltage is applied between the gas supply unit 341 and the electrostatic chuck table 310 to plasmatize the etching gas 36.

  The plasma acts in contact with each chip 3 in the processing space 301. That is, the side surface 3 a of the chip 3 is plasma-etched through the gap 4 between the divided chips 3. At this time, since the tape 2 is attached to the lower surface of the chip 3 and the protective layer 24 is formed on the upper surface of the chip 3 as a mask, damage to the device D can be reduced. Further, even if the small particles 23a shown in FIG. 4 enter the gaps 4 between the adjacent chips 3, they are removed by plasma etching. During plasma etching, the inside of the processing space 301 is maintained at a predetermined pressure, and the exhaust source 37 exhausts the used etching gas 36 from the exhaust port 302. And if processing time set up beforehand passes, side 3a of tip 3 will be finished to a mirror surface, and the bending strength of tip 3 can be raised.

(4) Protective Layer Removal Step After performing the plasma etching step, as shown in FIG. 6, for example, the work set WS is transported to the cleaning device 40 to remove the protective layer 24 from the top surface of the chip 3. The cleaning device 40 includes at least a spinner table 41 that holds and rotates the work set WS, and a cleaning water supply nozzle 44 disposed on the upper side of the spinner table 41.

  The upper surface of the spinner table 41 is a holding surface 42 for holding the wafer W by suction via the tape 2, and a suction source (not shown) is connected to the holding surface 42. A rotating shaft 43 having an axis in the vertical direction is connected to the lower portion of the spinner table 41, and a motor (not shown) is connected to the rotating shaft 43. When the motor is driven to rotate the rotation shaft 43, the spinner table 41 can be rotated at a predetermined rotation speed. The lower surface of the cleaning water supply nozzle 44 is provided with a supply port 45 for supplying the cleaning water 47 downward, and a cleaning water supply source 46 is connected to the supply port 45.

  When the work set WS is held by the spinner table 41, the motor rotates the rotating shaft 43, and the spinner table 41 is rotated, for example, in the arrow B direction. At this time, the cleaning water 47 is supplied from the supply port 45 of the cleaning water supply nozzle 44 toward the center of the wafer W. The cleaning water 47 flows radially outward due to the centrifugal force generated in the rotating wafer W, and the protective layer 24 on the upper surface of the chip 3 is washed away and removed. For example, pure water can be used as the cleaning water 47.

  Thus, in the method for processing a wafer according to the present invention, the tape 2 is attached to the back surface Wb of the wafer W and the wafer W is divided into individual chips 3 along the planned dividing line S from the front surface Wa side of the wafer W In the dividing step, the protective layer forming step of forming the protective layer 24 on the upper surface of the chip 3 by spraying the resin 23 from above the divided chip 3 and plasma etching the side 3 a of the chip 3 on which the protective layer 24 is formed Since the plasma etching process and the protective layer removing process for removing the protective layer 24 are provided, the protective layer 24 is formed on the upper surface of each chip 3 by the surface tension of the resin 23 sprayed toward the chips 3. It is possible to prevent the resin 23 from entering the gap 4 of the chip 3 and to expose only the side surface 3 a of the chip 3. Thus, according to the present invention, only the upper and lower surfaces of each chip 3 can be masked, and plasma etching can be easily performed on the side surface 3 a of the chip 3.

  In the dividing step shown in the above embodiment, the wafer W is divided into the individual chips 3 by dicing with the cutting blade 12, but the present invention is not limited to this case. In the dividing step, a laser beam having a transmissive wavelength may be positioned inside the wafer W to form a modified layer, and then an external force may be applied to the wafer W to divide the modified layer from the starting point.

  In the dividing step, the wafer W may be fully cut by ablation processing to be divided into individual chips 3. In this case, it is preferable to divide the wafer W after forming a protective layer on the surface Wa of the wafer W in advance. Thereafter, the protective layer is removed by washing, and a new protective layer is formed on the upper surface of each chip 3, and then the plasma etching step and the protective layer removing step are sequentially performed.

1: Ring frame 2: Tape 3: Chip 3a: Side 4: Gap 10: Cutting means 11: Spindle 12: Cutting blade 20: Resin supply nozzle 21: Injection port 22: Resin supply source 23: Resin 23a: Small particles 23b: Large particles 24: Protective layer 30: Plasma etching apparatus 300: Chamber 301: Processing space 302: Exhaust port 31: Lower electrode unit 310: Electrostatic chuck table 311: Electrode 32: DC power supply 33: High frequency power supply 34: Upper electrode unit 340 : Support part 341: Gas supply part 342: Injection port 35: Reaction gas supply source 36: Etch gas 37: Exhaust source 40: Cleaning device 41: Spinner table 42: Holding surface 43: Rotating shaft 44: Cleaning water supply nozzle 45: Supply port 46: Wash water supply source 47: Wash water

Claims (1)

A method of processing a wafer by plasma processing a side surface of a chip formed by dividing a wafer partitioned by a planned dividing line along a planned dividing line, thereby enhancing the bending strength of the chip,
A dividing step of sticking a tape to the lower surface of the wafer and dividing the wafer into individual chips along the planned dividing line from the upper surface side of the wafer;
A protective layer forming step of spraying a resin from above the chip divided in the dividing step to form a protective layer on the upper surface of the chip;
A plasma etching step of plasma etching the side surface of the chip on which the protective layer is formed;
And D. a protective layer removing step of removing the protective layer after the plasma etching step is carried out.

Images