JP2019140171A - Pattern forming method and wafer processing method - Google Patents

Abstract

To provide a pattern forming method that is simpler and more economical than photolithography.SOLUTION: A pattern forming method of forming a pattern having irregularities on the front surface side or the back surface side of a wafer includes a coating step of coating the front side or back side of a wafer with a resin cured by external stimulus, and a pattern formation step of aligning the position of a cylindrical drum having the reverse pattern in which the concavity and convexity are reversed with respect to the pattern on the outer peripheral surface and the position of the wafer, rotating and pushing the drum against the resin that coats the wafer, and applying external stimulus to the resin to form a pattern made of resin on the front side or back side of the wafer after the coating step.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a pattern forming method for forming a pattern having irregularities on a wafer and a wafer processing method using this pattern forming method.

  When manufacturing a device chip to be incorporated into various electronic devices, first, a device such as an IC (Integrated Circuit) is formed in each region of the wafer partitioned by a plurality of division lines (streets). A plurality of device chips corresponding to each device can be obtained by cutting the wafer along the scheduled division line using, for example, a cutting device or a laser processing device.

  By the way, in the processing method using the above-described cutting apparatus, since the wafer is cut while being crushed with a rotating cutting blade, the chip is likely to be damaged (chipping) and the bending strength tends to be lowered. is there. Moreover, since it is necessary to cut the cutting blade into each of the plurality of division lines, it takes a long time to complete the processing.

  On the other hand, in the processing method using the laser processing apparatus, the wafer is cut without mechanically scraping, so that the occurrence of chipping is suppressed, the bending strength is increased, and the width (cutting allowance) required for cutting is small. (Narrow) However, in this processing method, since the interval between adjacent device chips is also narrowed, the device chips may come into contact with each other at the time of transportation or the like, causing damage such as chipping.

  In recent years, a processing method for dividing a wafer using plasma etching has also been proposed (see, for example, Patent Document 1). In this processing method, since the entire wafer is processed at once by plasma etching, the processing time does not increase even if the diameter of the wafer increases or the size of the device (device chip) decreases. . Further, since the wafer is not mechanically scraped off, it is possible to suppress the occurrence of chipping and the like and to prevent the bending strength from being lowered.

JP 2006-114825 A

  By the way, in the processing method of dividing the wafer using the above-described plasma etching, it is necessary to form a pattern serving as a mask for protecting the device chip from plasma on the front surface side or the back surface side of the wafer. The pattern serving as the mask is usually formed by photolithography. However, since photolithography requires various facilities and the process is complicated, it tends to be expensive to form a pattern.

  The present invention has been made in view of such problems, and the object thereof is to provide a pattern forming method that is simpler and more economical than photolithography, and a wafer that uses this pattern forming method. Is to provide a method.

  According to one aspect of the present invention, there is provided a pattern forming method for forming a pattern having irregularities on a front surface side or a back surface side of a wafer, wherein the front surface side or the back surface side of the wafer is made of resin cured by an external stimulus. After performing the coating step and the coating step, the position of the cylindrical drum having the reverse pattern with the irregularities reversed with respect to the pattern on the outer peripheral surface is aligned with the position of the wafer, and the wafer is coated A pattern forming step of forming the pattern made of the resin on the front surface side or the back surface side of the wafer by rotating the drum while pressing the drum against the resin and applying the external stimulus to the resin. A pattern forming method is provided.

  In one embodiment of the present invention, the length of the outer periphery of the drum is larger than the diameter of the wafer, and the outer peripheral surface of the drum is provided with a silicon wafer thin enough to be bent with the reverse pattern on the surface. Also good.

  According to another aspect of the present invention, there is provided a wafer processing method for processing a wafer having a device in each region on the surface side defined by a plurality of intersecting division lines, and is cured by an external stimulus. The position of a cylindrical drum having a coating step for coating the front surface side or the back surface side of the wafer with resin, and a pattern in which a convex portion corresponding to the planned division line is formed on the outer peripheral surface after performing the coating step And rotating the wafer while pressing the drum against the resin coating the wafer, and applying the external stimulus to the resin, the surface side of the wafer or the wafer A mask forming step for forming a mask having a recess along the planned dividing line on the back surface side, and after performing the mask forming step, the wafer is passed through the mask. A plasma etching step for performing a plasma etching wafer processing method of a wafer comprising is provided.

  According to the pattern forming method of one aspect of the present invention, the front side or the back side of the wafer is coated with a resin that is cured by an external stimulus, and the external stimulus is rotated by pressing a cylindrical drum against the resin. The pattern which has an unevenness | corrugation can be formed by hardening | curing resin only by providing. Therefore, the pattern formation method according to one embodiment of the present invention is simpler and more economical than photolithography.

It is a perspective view which shows the example of a structure of a wafer typically. FIG. 2A is a partial cross-sectional side view schematically showing the covering step, and FIG. 2B is a cross-sectional view schematically showing the state of the wafer and the like after the covering step. FIG. 3A is a perspective view schematically showing the external appearance of a cylindrical drum, and FIG. 3B is an enlarged plan view of a part of the reverse pattern. 4A is a perspective view schematically showing the pattern forming step, FIG. 4B is a cross-sectional view schematically showing the pattern forming step, and FIG. 4C is a pattern forming step. It is sectional drawing which shows the done wafer typically. FIG. 5A is a schematic view showing the plasma etching step, and FIG. 5B is a cross-sectional view schematically showing the wafer cut by the plasma etching step.

  Embodiments according to one aspect of the present invention will be described with reference to the accompanying drawings. The pattern forming method according to the present embodiment includes a covering step (see FIGS. 2A and 2B) and a pattern forming step (FIGS. 3A, 3B, and 4A). And FIG. 4B).

  In the coating step, the front side of the wafer is coated with a resin that is cured by an external stimulus. In the pattern formation step, an external stimulus is applied to the resin that covers the wafer by rotating the resin while pressing a cylindrical drum having an inverted pattern in which irregularities are inverted with respect to the pattern to be formed on the outer peripheral surface. . Hereinafter, the pattern forming method according to the present embodiment will be described in detail.

  FIG. 1 is a perspective view schematically showing a configuration example of a wafer used in the pattern forming method of the present embodiment. As shown in FIG. 1, the wafer 11 is configured in a disk shape from a semiconductor material such as silicon. The surface 11a side of the wafer 11 is divided into a plurality of regions by a plurality of intersecting scheduled lines (streets) 13, and a device 15 such as an IC (Integrated Circuit) is formed in each region.

  In this embodiment, a disk-shaped wafer 11 made of a semiconductor material such as silicon is used, but the material, shape, structure, size, etc. of the wafer 11 are not limited. For example, the wafer 11 made of other materials such as semiconductors, ceramics, resins, and metals can be used. Further, the type, quantity, shape, structure, size, arrangement, etc. of the device 15 are not limited. The device 15 may not be formed on the wafer 11.

  In the pattern forming method according to the present embodiment, first, a covering step of covering the surface 11a side of the wafer 11 with a resin that is cured by an external stimulus is performed. 2A is a partial cross-sectional side view schematically showing the covering step, and FIG. 2B is a cross-sectional view schematically showing the state of the wafer 11 and the like after the covering step. The covering step according to the present embodiment is performed by, for example, the spin coating apparatus 2 shown in FIG.

  The spin coater 2 includes a chuck table 4 that holds a wafer 11. The chuck table 4 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the vertical direction. The upper surface of the chuck table 4 is a holding surface 4 a that sucks and holds the back surface 11 b side of the wafer 11.

  The holding surface 4 a is connected to a suction source (not shown) via a suction path (not shown) formed in the chuck table 4. The wafer 11 can be held by the chuck table 4 by applying the negative pressure of the suction source to the holding surface 4a. Above the chuck table 4, a nozzle 6 for dropping a liquid resin as a pattern raw material is disposed.

  In the covering step, first, the back surface 11b side of the wafer 11 is brought into contact with the holding surface 4a of the chuck table 4 to apply a negative pressure of the suction source. As a result, the wafer 11 is held on the chuck table 4 with the surface 11a side exposed upward. Next, the chuck table 4 is rotated, and the liquid resin 21 is dropped from the nozzle 6. Thereby, the liquid resin 21 can be applied to the front surface 11 a side of the wafer 11.

  In the present embodiment, a liquid resin 21 that is cured by an external stimulus such as ultraviolet rays is used. However, when a pattern formed using the liquid resin 21 is used as a mask for plasma etching, it is necessary to use the resin 21 having a certain resistance to the plasma etching after being cured. Examples of such a resin 21 include polyimide and epoxy that are cured by ultraviolet rays. When the surface 11a side of the wafer 11 is coated with the liquid resin 21, the coating step ends.

  In the present embodiment, the liquid resin 21 is coated by spin coating using the spin coating device 2, but the resin 21 may be coated by using other methods such as spray coating and dip coating. In this embodiment, the front surface 11 a side of the wafer 11 is coated with the resin 21, but the back surface 11 b side of the wafer 11 may be coated with the resin 21. In this case, a pattern is formed on the back surface 11 b side of the wafer 11.

  After the coating step, a pattern forming step for forming an uneven pattern on the surface 11 a of the wafer 11 is performed by applying an external stimulus while pressing a cylindrical drum against the resin 21 that covers the wafer 11. FIG. 3A is a perspective view schematically showing the appearance of the cylindrical drum 12 used in this pattern forming step.

  As shown in FIG. 3A, the drum 12 includes a cylindrical body 14 configured in a cylindrical shape. The cylindrical body 14 is configured to be rotatable around a rotation shaft 14a corresponding to the central axis. Both the length of the cylindrical body 14 in the direction along the rotation axis 14 a and the length of the outer periphery are longer than the diameter of the wafer 11. Further, the cylindrical body 14 is supported by a support structure (not shown) so as to be movable in a direction perpendicular to the rotation shaft 14a.

  On the outer peripheral surface of the cylindrical body 14, an inverted pattern 16 is provided in which the irregularities are inverted with respect to the pattern formed on the surface 11 a of the wafer 11. FIG. 3B is an enlarged plan view of a partial region A of the reversal pattern 16. In FIG. 3B, the region A of the reversal pattern 16 is shown with the surface side facing upward.

  As shown in FIG. 3B, the reverse pattern 16 includes a convex structure (convex portion) 16b protruding outward (upward in FIG. 3) from the reference surface 16a. For example, the structure 16 b is disposed at a position corresponding to the division line 13 of the wafer 11. That is, in the region corresponding to the device 13 of the wafer 11, there is a space 16c partitioned by the reference surface 16a and the structure 16b.

  There is no particular limitation on the method of forming the drum 12 including the reversal pattern 16. For example, the drum 12 can be formed by a method in which a reversal pattern 16 is provided on the surface and a silicon wafer thin enough to be bent is attached to the outer peripheral surface of the cylindrical body 14. In this case, for example, the reverse pattern 16 may be formed by processing the surface of the silicon wafer by a method such as etching. In this case, the wafer is thinned in advance by a method such as grinding to such an extent that the wafer can be bent in accordance with the outer peripheral surface of the cylindrical body 14.

  FIG. 4A is a perspective view schematically showing a pattern forming step, and FIG. 4B is a cross-sectional view schematically showing the pattern forming step. In the pattern forming step, first, the position of the cylindrical drum 12 is aligned with the wafer 11. Specifically, the position of the drum 12 and the position of the wafer 11 are adjusted so that the structure 16 b of the reverse pattern 16 overlaps the division line 13 of the wafer 11.

  Next, the drum 12 is rotated while being pressed against the resin 21 covering the wafer 11. As described above, the reverse pattern 16 including the structural body 16b is provided on the outer peripheral surface of the drum 12 (cylindrical body 14). Therefore, as shown in FIGS. 4A and 4B, when the drum 12 is rotated while being pressed against the resin 21, a recess 21a corresponding to the structure 16b is formed in the resin 21. .

  For this reason, while pressing the cylindrical drum against the resin 21, an external stimulus such as ultraviolet rays is applied to the region in contact with the drum 12, and the resin 21 in this region is cured, so that the cured resin is uneven. Can be formed. FIG. 4C is a cross-sectional view schematically showing the wafer 11 on which a pattern (mask) 23 having unevenness is formed. As shown in FIG. 4C, when the entire resin 21 is cured and a pattern 23 having a recess 23a is formed in a region corresponding to the planned dividing line 13, the pattern forming step is completed.

  As described above, according to the pattern forming method of the present embodiment, the surface 11 a side of the wafer 11 is coated with the resin 21 that is cured by an external stimulus, and the cylindrical drum 12 is rotated against the resin 21 while rotating. By simply applying an external stimulus, the resin 21 can be cured to form a pattern 23 having irregularities. Therefore, the pattern forming method according to the present embodiment is simpler in process and more economical than photolithography.

  In addition, this invention is not restrict | limited to description of the said embodiment etc., A various change can be implemented. For example, if the wafer processing method using the pattern forming method according to the above embodiment is used, the wafer 11 can be processed easily at low cost. Specifically, first, a pattern (mask) 23 that functions as a mask is formed on the front surface 11a side (or the back surface 11b side) of the wafer 11 by the pattern forming method described above.

  That is, the coating step of covering the front surface 11a side (or the back surface 11b side) of the wafer 11 with the resin 21 that is cured by an external stimulus is performed. Further, by applying external stimulus while pressing the cylindrical drum 12 against the resin 21, a pattern forming step (mask forming step) for forming a pattern 23 that functions as a mask on the surface 11 a of the wafer 11 is performed.

  After the pattern forming step (mask forming step), a plasma etching step for performing plasma etching on the wafer 11 through the formed pattern 23 is performed. FIG. 5A is a schematic diagram showing a plasma etching step. The plasma etching step is performed using, for example, a plasma etching apparatus 22 shown in FIG.

  The plasma etching apparatus 22 includes a vacuum chamber 24 in which a processing space is formed. An opening 24 a for carrying in and out the wafer 11 is formed on the side wall of the vacuum chamber 24. A gate 26 having a size covering the opening 24a is provided outside the opening 24a.

  The gate 26 is connected to an opening / closing mechanism (not shown), and the gate 26 is opened / closed by the opening / closing mechanism. By opening the gate 26 and exposing the opening 24 a, the wafer 11 can be carried into the space inside the vacuum chamber 24 through the opening 24 a, or the wafer 11 can be carried out from the space inside the vacuum chamber 24.

  An exhaust port 24 b is formed in the bottom wall of the vacuum chamber 24. The exhaust port 24b is connected to an exhaust unit 28 such as a vacuum pump. A lower electrode 30 is disposed in the space of the vacuum chamber 24. The lower electrode 30 is formed in a disk shape using a conductive material, and is connected to a high frequency power supply 32 outside the vacuum chamber 24.

  An electrostatic chuck 34 is disposed on the upper surface of the lower electrode 30. For example, the electrostatic chuck 34 includes a plurality of electrodes 36 a and 36 b that are insulated from each other, and attracts and holds the wafer 11 by an electric force generated between the electrodes 36 a and 36 b and the workpiece 11. Note that the electrostatic chuck 34 of the present embodiment is configured such that the positive electrode of the DC power supply 38a can be connected to the electrode 36a, and the negative electrode of the DC power supply 38b can be connected to the electrode 36b.

  An upper electrode 40 formed in a disk shape using a conductive material is attached to the ceiling wall of the vacuum chamber 24 via an insulating material. A plurality of gas ejection holes 40 a are formed on the lower surface side of the upper electrode 40, and the gas ejection holes 40 a are gas supply sources 42 via gas supply holes 40 b provided on the upper surface side of the upper electrode 40. It is connected to the. Thereby, a gas for plasma etching can be supplied into the space of the vacuum chamber 24. The upper electrode 40 is also connected to a high frequency power supply 44 outside the vacuum chamber 24.

  In the plasma etching step, first, the gate 26 is lowered by an opening / closing mechanism. Next, the wafer 11 is carried into the space of the vacuum chamber 24 through the opening 24 a and placed on the electrostatic chuck 34. Specifically, the back surface 11 b side of the wafer 11 is brought into contact with the upper surface of the electrostatic chuck 34. Thereafter, when the electrostatic chuck 34 is operated, the workpiece 11 is attracted and held by the electrostatic chuck 34 with the pattern 23 on the surface 11a side exposed upward.

  After the wafer 11 is attracted and held by the electrostatic chuck 34, the wafer 11 is divided along the scheduled division line 13 by performing plasma etching on the wafer 11 through the pattern 23. Specifically, first, the gate 26 is raised by an opening / closing mechanism to seal the space of the vacuum chamber 24.

  Further, the exhaust unit 28 is operated to depressurize the space. In this state, when a high frequency power is supplied to the lower electrode 30 and the upper electrode 40 by the high frequency power sources 32 and 44 while supplying a gas for plasma etching from the gas supply source 42 at a predetermined flow rate, Plasma containing radicals and ions is generated between the electrodes 40.

  Thus, the wafer 11 can be processed by exposing the surface 11 a side (that is, the division line 13) of the wafer 11 not covered with the pattern 23 to plasma. The plasma etching gas supplied from the gas supply source 42 is appropriately selected according to the material of the wafer 11 and the like. For example, the plasma etching is continued until the workpiece 11 is completely divided along the division line 13.

  FIG. 5B is a cross-sectional view schematically showing the wafer 11 divided in the plasma etching step. As shown in FIG. 5B, when the wafer 11 is completely divided and a plurality of device chips 17 are formed, the plasma etching step is finished. In this plasma etching step, the workpiece 11 can be processed at a time along all the division lines 13, so that when the workpiece 11 having a large number of division lines 13 is divided, the quality of the processing is improved. It is possible to shorten the time required for processing per line to be divided 13 while maintaining.

  Note that the surface 11a of the wafer 11 does not necessarily have to be exposed at the bottom of the recess 23a of the pattern 23 formed by the pattern forming method of the above embodiment. This is because the pattern 23 remaining on the bottom of the recess 23a can be removed and the surface 11a of the wafer 11 can be exposed by exposing the pattern 23 to plasma as in the plasma etching step according to the wafer processing method described above. .

  Further, the pattern 23 formed by the pattern forming method of the above embodiment may be used for patterning or the like when forming the device 15.

  In addition, the structures, methods, and the like according to the above-described embodiments and modifications can be appropriately changed and implemented without departing from the scope of the object of the present invention.

11 Wafer 11a Front surface 11b Back surface 13 Scheduled line (street)
15 Device 17 Device chip 21 Resin 21a Recess 23 Pattern (mask)
23a Concave part 2 Spin coating device 4 Chuck table 4a Holding surface 6 Nozzle 12 Drum 14 Cylindrical body 14a Rotating shaft 16 Reverse pattern 16a Reference surface 16b Structure (convex part)
16c space 22 plasma etching apparatus 24 vacuum chamber 24a opening 24b exhaust port 26 gate 28 exhaust unit 30 lower electrode 32 high frequency power supply 34 electrostatic chuck 36a, 36b electrodes 38a, 38b DC power supply 40 upper electrode 40a gas ejection hole 40b gas supply hole 42 Gas supply source 44 High frequency power source A area

Claims (3)

A pattern forming method for forming a pattern having irregularities on the front side or the back side of a wafer,
A coating step of coating the front side or the back side of the wafer with a resin that is cured by an external stimulus;
After performing the coating step, the position of the cylindrical drum having the inverted pattern with the irregularities reversed with respect to the pattern is aligned with the position of the wafer, and the resin covering the wafer is A pattern forming step of forming the pattern made of resin on the front surface side or the back surface side of the wafer by rotating the drum while pressing it and applying the external stimulus to the resin. A characteristic pattern forming method. The outer circumference of the drum is larger than the diameter of the wafer,
2. The pattern forming method according to claim 1, wherein a thin silicon wafer is provided on the outer peripheral surface of the drum so as to be bent with the reverse pattern on the surface. A wafer processing method for processing a wafer having a device in each region on the surface side defined by a plurality of division lines to intersect,
A coating step of coating the front side or back side of the wafer with a resin that is cured by an external stimulus;
After carrying out the coating step, the position of the cylindrical drum having the pattern formed with the projections corresponding to the planned division lines on the outer peripheral surface is aligned with the position of the wafer, and the resin for coating the wafer The mask is rotated while pressing the drum against the resin, and the external stimulus is applied to the resin, thereby forming a mask having a recess along the planned dividing line on the front surface side or the back surface side of the wafer. A mask forming step;
And a plasma etching step of performing plasma etching on the wafer through the mask after performing the mask forming step.