Wafer cleaning method and cleaning apparatus

Abstract

The present invention provides a wafer cleaning method that can effectively remove cutting debris from the wafer surface. [Solution] The wafer cleaning method includes a holding step of holding the back surface of the wafer 56 with a spinner table 4 that can hold and rotate the wafer 56 to expose the front surface 56a of the wafer 56; a first cleaning step of rotating the spinner table 4 to supply cleaning water to the front surface 56a of the wafer 56 to perform a first cleaning; and a second cleaning step of supplying ammonia water to the front surface 56a of the wafer 56 and cleaning the front surface 56a of the wafer 56 with a brush.

Description

Technical Field

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[0001] The present invention relates to a wafer cleaning method and a cleaning apparatus in which device regions partitioned by a planned division line are formed on the surface of a wafer by a plurality of devices.

Background Art

[0002] A wafer having device regions partitioned by a planned division line on its surface by a plurality of devices such as ICs and LSIs is thinned by grinding the back surface, and then divided into individual device chips by a dicing device, a laser processing device, etc. Each of the divided device chips is used in electrical devices such as mobile phones and personal computers.

[0003] Since a chamfer portion surrounding the device region is formed on the outer periphery of the wafer, when the back surface of the wafer is ground and thinned, the chamfer portion becomes a sharp knife edge. Therefore, the operator must pay more attention to handling the wafer. In addition, when the chamfer portion becomes a sharp knife edge, cracks are likely to enter from the outer periphery to the inside of the wafer, increasing the risk of device damage. Therefore, a technique has been proposed to remove a necessary amount of the chamfer portion in advance so that no knife edge is formed on the outer periphery of the wafer even when the wafer is thinned (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document - 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when a cutting blade is positioned on the chamfered portion of a wafer and cutting is performed while supplying cutting fluid, cutting debris adheres to the wafer surface and contaminates the device area. Cutting debris adhering to the wafer surface may not be completely removed even by washing with high-pressure water or a two-fluid mixture of high-pressure water and high-pressure air. Furthermore, if cutting debris remains on the wafer surface, it can become a critical problem, especially in technologies that bond and stack wafers together.

[0006] The object of the present invention is to provide a wafer cleaning method and cleaning apparatus that can sufficiently remove cutting debris from the surface of the wafer. [Means for solving the problem]

[0007] According to the present invention, the following wafer cleaning method is provided that solves the above problems. That is, A method for cleaning a wafer in which multiple devices are divided by planned division lines and a device region is formed on the surface, A holding step in which the back surface of the wafer is held by a spinner table that holds the wafer and rotates, thereby exposing the front surface of the wafer, A first cleaning step involves rotating the spinner table to supply cleaning water to the surface of the wafer and performing a first cleaning, A method for cleaning a wafer is provided, which includes a second cleaning step of supplying ammonia water to the surface of the wafer and cleaning the surface of the wafer with a brush.

[0008] Preferably, the process includes a third cleaning step after the second cleaning step, in which pure water is supplied to the surface of the wafer for final cleaning. A chamfered portion is formed on the outer circumference of the wafer, surrounding the device area, and it is desirable to perform a chamfered portion removal step prior to the first cleaning step, in which a cutting blade is positioned on the chamfered portion and cutting water is supplied to remove the required amount of the chamfered portion.

[0009] Furthermore, the present invention provides the following cleaning apparatus that solves the above problems. That is, A cleaning apparatus that performs the wafer cleaning method described above, A cleaning apparatus is provided, comprising: a spinner table; a cleaning water supply means equipped with a cleaning nozzle for supplying cleaning water to the surface of a wafer held on the spinner table; and an ammonia cleaning means for supplying ammonia water to the surface of a wafer held on the spinner table and cleaning the surface of the wafer with a brush. [Effects of the Invention]

[0010] The wafer cleaning method of the present invention is A method for cleaning a wafer in which multiple devices are formed on the surface in device regions partitioned by division lines, A holding step in which the back surface of the wafer is held by a spinner table that holds the wafer and rotates, thereby exposing the front surface of the wafer, A first cleaning step involves rotating the spinner table to supply cleaning water to the surface of the wafer and performing a first cleaning, The process includes a second cleaning step in which ammonia water is supplied to the wafer surface and the wafer surface is cleaned with a brush, thereby ensuring that cutting debris is sufficiently removed from the wafer surface.

[0011] Furthermore, the cleaning apparatus of the present invention is A cleaning apparatus for performing the wafer cleaning method described above, The system includes a spinner table, a cleaning water supply means equipped with a cleaning nozzle for supplying cleaning water to the surface of a wafer held on the spinner table, and an ammonia cleaning means for supplying ammonia water to the surface of a wafer held on the spinner table and cleaning the wafer surface with a brush, thereby enabling sufficient removal of cutting debris from the wafer surface. [Brief explanation of the drawing]

[0012] [Figure 1] A perspective view of the cleaning apparatus according to the present invention. [Figure 2] A perspective view of a wafer held by suction on the chuck table of a cutting machine. [Figure 3](a) Schematic diagram showing the chamfer removal process, (b) Perspective view of the wafer with the chamfer removed. [Figure 4] Plan view showing the holding process. [Figure 5] Plan view showing the first cleaning process. [Figure 6] Plan view showing the second cleaning process. [Figure 7] Plan view showing the third cleaning process. [Figure 8] Plan view showing the drying process.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the wafer cleaning method and cleaning apparatus according to the present invention will be described with reference to the drawings.

[0014] (Cleaning apparatus 2) First, the cleaning apparatus 2 will be described with reference to FIG. 1. The cleaning apparatus 2 includes a spinner table 4 that holds and rotates a wafer, a cleaning water supply means 6 having a cleaning nozzle that supplies cleaning water to the surface of the wafer held by the spinner table 4, and an ammonia cleaning means 8 that supplies ammonia water to the surface of the wafer and cleans it with a brush.

[0015] (Spinner table 4 of the cleaning apparatus 2) A circular suction chuck 10 is disposed at the upper end portion of the spinner table 4. The suction chuck 10 is formed of a porous member such as porous ceramics. Further, the suction chuck 10 is connected to a suction means (not shown). In the spinner table 4, a suction force is generated on the upper surface of the suction chuck 10 by the suction means, and the wafer placed on the upper surface of the suction chuck 10 is sucked and held.

[0016] The output shaft 12a of a motor 12 that rotates the spinner table 4 is connected to the center of the spinner table 4. The motor 12 rotates the spinner table 4 with its axis in the vertical direction. A lifting mechanism 14, which may consist of an actuator such as an air cylinder, is mounted on the outer surface of the motor 12. The lifting mechanism 14 raises and lowers the spinner table 4 between a raised position where wafers are attached and detached (the position shown in Figure 1) and a lowered position where wafers are cleaned (not shown).

[0017] (Washing water supply means 6 of the washing device 2) The cleaning water supply means 6 includes a cleaning nozzle 16 that supplies cleaning water to the surface of a wafer held on the spinner table 4, and a motor (not shown) that oscillates the cleaning nozzle 16. The cleaning nozzle 16 is connected to a high-pressure pure water source 20 via a conduit 18. An on-off valve 22 is located in the conduit 18. The cleaning water supply means 6 then oscillates the cleaning nozzle 16 and supplies pure water from the high-pressure pure water source 20 as cleaning water to the surface of the wafer on the spinner table 4 from the nozzle 16a of the cleaning nozzle 16.

[0018] Furthermore, the cleaning nozzle 16 in this embodiment is also connected to a high-pressure air source 26 via a pipeline 24. An on-off valve 28 is located in the pipeline 24. The cleaning water supply means 6 can also supply a two-fluid mixture of pure water from the high-pressure pure water source 20 and high-pressure air from the high-pressure air source 26 as cleaning water to the surface of the wafer on the spinner table 4 from the nozzle 16a of the cleaning nozzle 16 while the cleaning nozzle 16 is oscillating.

[0019] (Ammonia cleaning means 8 of the cleaning device 2) The ammonia cleaning means 8 comprises an ammonia water nozzle 30 that supplies ammonia water to the surface of a wafer held on a spinner table 4, and a motor (not shown) that oscillates the ammonia water nozzle 30. As shown in an enlarged view in Figure 1, the tip of the ammonia water nozzle 30 is provided with a nozzle 30a for spraying ammonia water onto the wafer on the spinner table 4, and a brush 30b for cleaning the surface of the wafer. The brush 30b may be made of a suitable synthetic resin material such as polyvinyl alcohol (PVA). The ammonia water nozzle 30 is connected to an ammonia water source 34 via a conduit 32. An on / off valve 36 is located in the conduit 32. The ammonia cleaning means 8 oscillates the ammonia water nozzle 30 and supplies ammonia water from the ammonia water source 34 to the surface of the wafer on the spinner table 4 through the nozzle 30a of the ammonia water nozzle 30, cleaning the surface of the wafer with the brush 30b.

[0020] Furthermore, the ammonia water nozzle 30 in this embodiment is also connected to a high-pressure air source 40 via a pipeline 38. An on-off valve 42 is located in the pipeline 38. The ammonia cleaning means 8 can also clean the wafer surface on the spinner table 4 by supplying a two-fluid ammonia water mixture, which is a mixture of ammonia water from the ammonia water source 34 and high-pressure air from the high-pressure air source 40, from the nozzle 30a of the ammonia water nozzle 30 while oscillating the ammonia water nozzle 30, and using a brush 30b.

[0021] The cleaning apparatus 2 further includes an air nozzle 44 for supplying drying air to the surface of wafers held on the spinner table 4, a motor (not shown) for oscillating the air nozzle 44, a drain pan 46 for receiving cleaning water and ammonia water, and a drain hose 48 for discharging the cleaning water and ammonia water received in the drain pan 46. The air nozzle 44 is connected to a high-pressure air source 52 via a pipeline 50. An on-off valve 54 is located in the pipeline 50.

[0022] (Waha 56) Figure 2 shows a disc-shaped wafer 56 that can be cleaned by the cleaning method of this embodiment. The wafer 56 can be formed from a suitable semiconductor material such as silicon. On the surface 56a of the wafer 56, a device region 62 is formed in which multiple devices 58 such as ICs and LSIs are demarcated by grid-like division lines 60. A chamfered portion 64 is formed on the outer periphery of the wafer 56, surrounding the device region 62. For convenience, the ring-shaped boundary 66 between the device region 62 and the chamfered portion 64 is shown by a dashed line, but in reality, there is no line indicating the boundary 66.

[0023] (Chamfering removal process) In this embodiment, before cleaning the wafer 56 using the cleaning device 2 described above, a chamfering removal step is performed in which a cutting blade is positioned on the chamfered portion 64 of the wafer 56 and cutting fluid is supplied while removing the required amount of the chamfered portion 64.

[0024] (Cutting device 68) The chamfer removal process can be carried out, for example, using a cutting device 68 shown in Figure 3(a). The cutting device 68 comprises a chuck table 70 for suction holding of a wafer 56 and a cutting means 72 for cutting the wafer 56 held by suction on the chuck table 70. The chuck table 70 is configured to suction hold of the wafer 56 on its upper surface and to be rotatable about an axis in the vertical direction. The cutting means 72 includes a spindle housing 74, a spindle 76 rotatably supported by the spindle housing 74, and an annular cutting blade 78 fixed to the tip of the spindle 76. The cutting edge of the cutting blade 78 is formed to a predetermined thickness from abrasive grains such as diamond and a binder such as metal or resin.

[0025] In the chamfer removal process, first, the wafer 56 is held in place by suction on the upper surface of the chuck table 70 with its surface 56a facing upwards. Next, the wafer 56 is imaged from above by the imaging means (not shown) of the cutting device 68, and the cutting blade 78 is positioned on the chamfered portion 64 of the wafer 56 based on the image of the wafer 56 captured by the imaging means. Then, the cutting edge of the cutting blade 78, which is rotated at high speed in the direction indicated by arrow R1, is driven into the chamfered portion 64 of the wafer 56 to a predetermined depth, and cutting fluid is supplied to the part of the cutting edge of the cutting blade 78 that is being driven into the chamfer, while the chuck table 70 is rotated in the direction indicated by arrow R2. This allows the required amount of the chamfered portion 64 to be removed. In Figure 3(b), the portion from which the chamfered portion 64 has been removed is indicated by reference numeral 80.

[0026] (holding process) After the chamfer removal process is performed, as shown in Figure 4, a holding process is performed in which the back surface 56b of the wafer 56 is held by the spinner table 4 of the cleaning apparatus 2, exposing the front surface 56a of the wafer 56. In the holding process, the wafer 56 is placed on the spinner table 4 with the front surface 56a facing upwards. Then, suction force is generated on the upper surface of the suction chuck 10 of the spinner table 4, and the back surface 56b side of the wafer 56 is held by suction. During the holding process, the spinner table 4 is positioned in the raised position (position shown in Figure 1). In addition, the cleaning nozzle 16, ammonia water nozzle 30, and air nozzle 44 are positioned in a standby position (position shown in Figure 1) spaced away from directly above the spinner table 4.

[0027] (First cleaning process) After the holding process is performed, a first cleaning process is carried out in which the spinner table 4 is rotated to supply cleaning water to the surface 56a of the wafer 56 for the first cleaning. In the first cleaning process, first, the spinner table 4 is positioned in the lowered position by the lifting mechanism 14. Next, a lid (not shown) to prevent splashing of cleaning water and ammonia water is placed over the upper end of the drain pan 46. Then, the spinner table 4 is rotated at a predetermined rotational speed (for example, 800 rpm) in the direction indicated by arrow R3 in Figure 5. Then, while the cleaning nozzle 16 is oscillated back and forth above the wafer 56 in the direction indicated by arrow R4, cleaning water is supplied to the surface 56a of the wafer 56 from the nozzle 16a of the cleaning nozzle 16. This roughly cleans the surface 56a of the wafer 56 and removes abrasive particles that have fallen off the cutting blade 78 from the surface 56a of the wafer 56. The cleaning water supplied to the wafer 56 may be pure water from the high-pressure pure water source 20 alone, but a two-fluid mixture of pure water from the high-pressure pure water source 20 and high-pressure air from the high-pressure air source 26 is preferable because it exhibits a higher cleaning effect. The cleaning time in the first cleaning step may be, for example, 30 to 120 seconds.

[0028] (Second cleaning process) After performing the first cleaning step, a second cleaning step is performed in which ammonia water is supplied to the surface 56a of the wafer 56 and the surface 56a of the wafer 56 is cleaned with a brush 30b. In the second cleaning step, the spinner table 4 is rotated at a predetermined rotational speed (for example, 500 rpm) in the direction indicated by arrow R3 in Figure 6. Then, while the ammonia water nozzle 30 is reciprocated above the wafer 56 in the direction indicated by arrow R5, ammonia water is supplied to the surface 56a of the wafer 56 from the nozzle 30a and the surface 56a of the wafer 56 is cleaned with a brush 30b. This removes cutting debris adhering to the surface 56a of the wafer 56. In this embodiment, since the surface 56a of the wafer 56 is cleaned by rubbing it with a brush 30b while supplying ammonia water, even minute cutting debris at the 0.05 μm level can be removed. The ammonia water supplied to the wafer 56 may be only the ammonia water from the ammonia water source 34, but a two-fluid ammonia water mixture, which is a mixture of the ammonia water from the ammonia water source 34 and the high-pressure air from the high-pressure air source 40, is preferable because it exhibits a higher cleaning effect. The cleaning time in the second cleaning step may be, for example, 7 to 21 seconds.

[0029] (Third cleaning step) In this embodiment, after performing the third cleaning step, a third cleaning step is performed in which pure water is supplied to the surface 56a of the wafer 56 for final cleaning. In the third cleaning step, the spinner table 4 is rotated at a predetermined rotational speed (for example, 500 rpm) in the direction indicated by arrow R3 in Figure 7. Then, while the cleaning nozzle 16 is oscillated back and forth above the wafer 56 in the direction indicated by arrow R4, cleaning water is supplied to the surface 56a of the wafer 56 from the nozzle 16a of the cleaning nozzle 16. This suppresses the residue of ammonia water on the surface 56a of the wafer 56. The cleaning water supplied to the wafer 56 may be pure water from the high-pressure pure water source 20 alone, but a two-fluid mixture of pure water from the high-pressure pure water source 20 and high-pressure air from the high-pressure air source 26 is preferable because it exhibits a higher rinsing effect. The cleaning time in the third cleaning step may be, for example, about 30 seconds.

[0030] (drying process) After performing the third cleaning step, it is preferable to perform a drying step in which drying air is supplied to the surface 56a of the wafer 56 to dry the surface 56a of the wafer 56. In the drying step, the spinner table 4 is rotated at a predetermined rotational speed (for example, 2000 rpm) in the direction indicated by arrow R3 in Figure 8. Then, while the air nozzle 44 is oscillating back and forth above the wafer 56 in the direction indicated by arrow R6, drying air is supplied to the surface 56a of the wafer 56 from the nozzle 44a of the air nozzle 44. This dries the surface 56a of the wafer 56. The drying time in the drying step may be, for example, about 20 to 30 seconds.

[0031] As described above, in this embodiment, the spinner table 4 is rotated to supply cleaning water to the surface 56a of the wafer 56 to perform the first cleaning, and ammonia water is supplied to the surface 56a of the wafer 56 to clean the surface 56a of the wafer 56 with the brush 30b, so that cutting debris can be sufficiently removed from the surface 56a of the wafer 56.

[0032] Furthermore, in this embodiment, in the first cleaning step, the abrasive grains that have fallen off the cutting blade 78 are removed from the surface 56a of the wafer 56 with cleaning water before the second cleaning step is performed. Therefore, in the second cleaning step, the abrasive grains that have fallen off the cutting blade 78 are not dragged by the brush 30b, and damage to the device area 62 caused by dragging the abrasive grains can be prevented. [Explanation of symbols]

[0033] 2: Cleaning device 4: Spinner Table 6: Washing water supply means 8: Ammonia cleaning method 16: Cleaning nozzle 16a: Spray nozzle of the cleaning nozzle 30: Ammonia water nozzle 30a: Ammonia water nozzle nozzle 30b: Brush 56: Wafer 56a: Wafer surface 56b: Back side of the wafer 58: Device 60: Planned division line 62: Device Area 64: Chamfered section 78: Cutting blade

Claims

1. A method for cleaning a wafer in which multiple devices are formed on the surface in device regions partitioned by division lines, A holding step in which the back surface of the wafer is held by a spinner table that holds the wafer and rotates, thereby exposing the front surface of the wafer, A first cleaning step involves rotating the spinner table to supply cleaning water to the surface of the wafer and performing a first cleaning, A method for cleaning a wafer, comprising a second cleaning step of supplying ammonia water to the surface of the wafer and cleaning the surface of the wafer with a brush.

2. A method for cleaning a wafer according to claim 1, further comprising a third cleaning step of supplying pure water to the surface of the wafer after the second cleaning step to perform a final cleaning.

3. A method for cleaning a wafer according to claim 1, wherein a chamfered portion is formed on the outer circumference of the wafer surrounding the device region, and a chamfered portion removal step is performed prior to the first cleaning step, in which a cutting blade is positioned on the chamfered portion and cutting fluid is supplied to remove the chamfered portion to the required extent.

4. A cleaning apparatus for carrying out the wafer cleaning method described in claim 1, A cleaning apparatus comprising: a spinner table; a cleaning water supply means equipped with a cleaning nozzle for supplying cleaning water to the surface of a wafer held on the spinner table; and an ammonia cleaning means for supplying ammonia water to the surface of a wafer held on the spinner table and cleaning the surface of the wafer with a brush.

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