Wafer processing method

Abstract

To provide a wafer processing method capable of solving a problem which becomes a pollution source in a subsequent process without leaving a fluorine element in a dicing table even if a wafer is divided into device chips by plasma etching.SOLUTION: A wafer processing method comprises a frame unit forming step, a resin film covering step, a partial resin film removing step, an etching step, and an all resin film removing step. The frame unit forming step forms a frame unit 18 by positioning a wafer 10 on an opening Fa of a frame F and sticking a dicing tape T to a lower surface 10a of the wafer and the frame F. The resin film covering step forms a resin film P' by covering an upper surface 10a of the wafer 10 and the dicing tape T exposed between the wafer 10 and the frame F with a water-soluble resin P for solidification. The partial resin film removing step partly exposes the upper surface 10a of the wafer 10 by removing the resin film P' from a region to be divided in the wafer 10. The etching step divides the wafer 10 into individual chips 12' by subjecting the region to be divided in the wafer 10 to plasma etching. The all resin film removing step removes all the resin films P' by cleaning the frame unit 18.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a wafer processing method for dividing a wafer into individual device chips by plasma etching using fluorine gas. [Background technology]

[0002] A wafer having a plurality of devices such as ICs and LSIs formed on its surface along division lines is separated into individual device chips by a dicing machine and used in electrical equipment such as mobile phones and personal computers.

[0003] Furthermore, in order to improve the flexural strength of the device chips, the present applicant has proposed a technology in which the top surface of the wafer is covered with a mask that exposes the intended dividing lines, and the intended dividing lines are plasma etched using a fluorine-based gas to divide the wafer into individual device chips (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-108428 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology described in the above-mentioned Patent Document 1, a wafer is positioned in a frame having an opening in the center for accommodating the wafer, and a dicing tape is attached to the bottom surface of the wafer and the frame to form a frame unit, after which the top surface of the wafer is covered with a mask and plasma etched to separate the wafer into device chips, thereby enabling efficient transport of the wafer divided into individual device chips.

[0006] When the wafer is divided by the above-mentioned technique, the fluorine element generated during the plasma etching adheres to the dicing tape having an adhesive layer, and cannot be completely removed even by cleaning, remaining on the dicing tape. Therefore, when the frame unit holding the wafer via the dicing tape is transported to a subsequent process, the dicing tape becomes a source of contamination containing fluorine element.

[0007] The present invention has been made in view of the above-mentioned circumstances, and its main technical object is to provide a wafer processing method which can eliminate the problem of elemental fluorine becoming a contamination source in subsequent processes, even when plasma etching is performed to divide the wafer into device chips, without leaving any fluorine element on the dicing tape. [Means for solving the problem]

[0008] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a wafer processing method for dividing a wafer into individual device chips by plasma etching using fluorine gas, the method comprising the steps of: positioning the wafer in an opening of a frame having an opening in the center for accommodating the wafer, and adhering a dicing tape to the underside of the wafer and the frame to form a frame unit; and coating the upper surface of the wafer with a water-soluble resin and adhering the dicing tape exposed between the wafer and the frame to form a frame unit. All over The method includes a resin film coating step of coating the wafer with a water-soluble resin and solidifying the resin film to form a resin film, a partial resin film removal step of removing the resin film from the region of the wafer to be divided to partially expose the upper surface of the wafer, an etching step of subjecting the region of the wafer to plasma etching to divide the wafer into individual chips, and a total resin film removal step of cleaning the frame unit to completely remove the resin film. The resin film of the water-soluble resin coated on the dicing tape exposed between the wafer and the frame remains without being removed by the plasma etching performed in the etching step, thereby preventing the fluorine element generated by the plasma etching from adhering to the dicing tape. A method for processing a wafer is provided.

[0009] The fluorine gas is preferably selected from the group consisting of SF6, CF4, C2F6 and C2F4, and the wafer is preferably partitioned by dividing lines and has a plurality of devices formed on the upper surface. Effect of the Invention

[0010] The wafer processing method of the present invention is a wafer processing method for dividing a wafer into individual device chips by plasma etching using fluorine gas, and includes a frame unit forming step of forming a frame unit by positioning the wafer in an opening of a frame having an opening in the center for accommodating the wafer and attaching a dicing tape to the lower surface of the wafer and the frame; and a frame unit forming step of coating the upper surface of the wafer with a water-soluble resin and attaching the dicing tape exposed between the wafer and the frame. All over The method includes a resin film coating step of coating the wafer with a water-soluble resin and solidifying the resin film to form a resin film, a partial resin film removal step of removing the resin film from the region of the wafer to be divided to partially expose the upper surface of the wafer, an etching step of subjecting the region of the wafer to plasma etching to divide the wafer into individual chips, and a total resin film removal step of cleaning the frame unit to completely remove the resin film. The resin film of the water-soluble resin coated on the dicing tape exposed between the wafer and the frame remains without being removed by the plasma etching performed in the etching step, thereby preventing the fluorine element generated by the plasma etching from adhering to the dicing tape. Therefore, the fluorine element is captured by the resin film and is removed together with the resin by washing, and does not adhere to the dicing tape, which solves the problem of the frame unit becoming a source of contamination. [Brief description of the drawings]

[0011] [Figure 1] FIG. 11 is a perspective view showing an embodiment of a frame unit forming step. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a perspective view showing an embodiment of a resin film coating step. [Figure 4] FIG. 2A is a perspective view showing an embodiment of a partial resin film removal step, and FIG. 2B is a partially enlarged cross-sectional view of a wafer in a state where the partial resin film removal step shown in FIG. [Diagram 5] FIG. 2A is a perspective view showing an embodiment of an etching step, and FIG. 2B is a partially enlarged cross-sectional view of a wafer in a state where the etching step shown in FIG. [Figure 6]FIG. 11 is a perspective view showing an embodiment of a complete resin film removal step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a wafer processing method according to the present invention will be described in detail with reference to the accompanying drawings.

[0013] 1 shows a wafer 10 which is a workpiece in this embodiment. The wafer 10 is, for example, a silicon wafer on which a plurality of devices 12, such as ICs and LSIs, are formed on a surface 10a, partitioned by planned division lines 14. When carrying out the wafer processing method of this embodiment, a frame F having an opening Fa in the center for accommodating the wafer 10 is prepared, the wafer 10 is positioned in the opening Fa of the frame F, and a dicing tape T is attached to the lower surface 10b of the wafer 10 and the frame F to integrate them, thereby forming a frame unit 18 (frame unit formation process).

[0014] Next, a water-soluble resin is coated on the upper surface of the wafer 10 (in this embodiment, the surface 10a), and the water-soluble resin is also coated on the dicing tape T exposed between the wafer 10 and the frame F, and the water-soluble resin is solidified to form a resin film (resin film coating process).

[0015] The above-mentioned resin film coating step will be described more specifically with reference to Figures 2 and 3. When carrying out the resin film coating step, the above-mentioned frame unit 18 is transported to a spin coater 20 shown in Figure 2.

[0016] As shown in FIG. 2, the spin coater 20 includes a table mechanism 21 and a cover unit 30 surrounding the table mechanism 21. FIG. 2 is a perspective view of the spin coater 20, and for convenience of explanation, a part of the front side of the liquid cover 31 constituting the cover unit 30 is cut away. As can be seen from FIG. 2, the table mechanism 21 includes a table 22 that holds the frame unit 18. The table 22 includes an adsorption chuck 221 formed of a porous member having air permeability and a frame unit 222 that surrounds the adsorption chuck 221, and the adsorption chuck 221 is connected to a suction source (not shown) to be supplied with a negative suction pressure. Furthermore, the table mechanism 21 includes a shaft unit 24 and is connected to a drive source 25 via a rotating shaft (not shown) housed inside the shaft unit 24. The rotating shaft is driven by an electric motor (not shown) housed in the drive source 25 to rotate the table 22. A plurality of air pistons 26 are disposed on the outer periphery of the driving source 25, and the table 22, the shaft portion 24, and the driving source 25 are raised and lowered integrally by moving the rod 26a back and forth in the up and down directions indicated by the arrows in the figure. The shaft portion 24 and the driving source 25 described above function as a base that supports the table 22.

[0017] A drain hole 32 for discharging the liquid sprayed onto the inside of the liquid cover 31 is provided on the inner bottom surface 31a of the liquid cover 31, and a drain hose 33 for discharging the liquid to a waste tank (not shown) provided outside the liquid cover 31 is connected to the drain hole 32. Furthermore, on the bottom surface 31a of the liquid cover 31, there are provided, surrounding the table 22, a water-soluble resin supply nozzle 34 for supplying a water-soluble resin (e.g., polyvinyl alcohol (PVA)) in liquid form onto the upper surface of the wafer 10 held on the table 22, an air spray nozzle 35 for spraying air onto the upper surface of the wafer 10, and a cleaning liquid supply nozzle 36 for spraying a cleaning liquid onto the upper surface of the wafer 10. The water-soluble resin supply nozzle 34, the air injection nozzle 35, and the cleaning liquid supply nozzle 36 can move the tip of each nozzle in the horizontal direction above the table 22 by operating a driving means (not shown) arranged on the rear side of the bottom surface 31a of the liquid cover 31. As shown in Fig. 2, when the table 22 is positioned at a position (upper position) for loading and unloading the wafer 10, the water-soluble resin supply nozzle 34, the air injection nozzle 35, and the cleaning liquid supply nozzle 36 are positioned at a storage position toward the outer periphery.

[0018] The frame unit 18 transported to the spin coater 20 is placed on a table 22 as shown in Fig. 3, and is held by suction by operating a suction source (not shown). After the frame unit 18 is held by suction, an air piston 26 is operated to lower the frame unit 18 to a processing position as shown in Fig. 3. Next, an electric motor arranged inside the drive source 25 is driven to rotate the frame unit 18 in the direction indicated by the arrow R1 at a predetermined rotation speed (e.g., 300 rpm), and the water-soluble resin supply nozzle 34 is swung in the direction indicated by the arrow R2 in the figure (horizontal direction) to spray the water-soluble resin P, thereby supplying a predetermined amount of liquid water-soluble resin P (e.g., PVA) onto the upper surface (surface 10a) of the wafer 10 and onto the dicing tape T exposed between the wafer 10 and the frame F. Although not shown in the figure, a lid member is provided above the spin coater 20, and when liquid, air, etc. are sprayed from the water-soluble resin supply nozzle 34, the air spray nozzle 35, and the cleaning liquid supply nozzle 36, the upper part of the cover part 30 is closed by the lid.

[0019] As described above, the water-soluble resin P is applied onto the upper surface of the wafer 10 and the dicing tape T, and is uniformly distributed over the entire upper surface of the wafer 10 by centrifugal force, and then the liquid water-soluble resin P solidifies after a predetermined time has passed, forming a resin film P' that covers the upper surface of the wafer 10 and the dicing tape T exposed between the wafer 10 and the frame F, as shown in the lower part of Fig. 3. This completes the resin film coating process.

[0020] Next, a partial resin film removal step is performed in which the resin film P' is removed from the region to be divided of the wafer 10 (the division lines 14 in this embodiment) to partially expose the upper surface (front surface 10a) of the wafer 10. The partial resin film removal step will be described with reference to FIG. 4.

[0021] The frame unit 18 in which a resin film P' is formed on the upper surface of the wafer 10 and on the dicing tape T as a result of the resin film coating process is transported to a laser processing device 40 (only a part of which is shown) shown in Fig. 4(a). The laser processing device 40 at least includes a chuck table (not shown) that holds the frame unit 18, a moving means (not shown) that rotates and drives the chuck table and moves it in the X-axis and Y-axis directions, an alignment means (not shown), and a laser beam application means 41. The laser beam application means 41 includes an optical system (not shown) that oscillates a laser beam LB, adjusts the output of the laser beam LB, and guides it to a condenser 42.

[0022] The frame unit 18 transported to the laser processing device 40 is placed on the chuck table and held by suction. Next, the moving means is operated to move the wafer 10 on the frame unit 18 directly under the alignment means, and the alignment means captures an image of the wafer 10 to detect a predetermined laser processing position (planned dividing line 14). Next, the moving means is operated to move the frame unit 18 directly under the condenser 42 of the laser beam application means 41, and the focal point is positioned on the resin film P' coated on the planned dividing line 14 on the surface 10a of the wafer 10. While moving the wafer 10 in the X-axis direction in the figure, the laser beam LB is applied along the planned dividing line 14. The laser beam LB applied at this time has a wavelength that is absorbed by the resin film P' and is set to have an output that does not ablate the surface 10a of the wafer 10.

[0023] 4(b), the resin film P' is removed from the region to be divided in the wafer 10, i.e., from the dividing lines 14, and an exposed groove 100 is formed in which the surface 10a of the wafer 10 is exposed along the dividing lines 14. After the exposed groove 100 is formed along the dividing lines 14 formed in a predetermined direction, the moving means is operated to index and feed the wafer 10 in the Y-axis direction, and the above-mentioned laser beam LB is irradiated to form the exposed groove 100 along all the dividing lines 14 formed in the predetermined direction. Next, the chuck table is rotated 90 degrees to align the dividing lines 14 along a direction perpendicular to the dividing lines 14 along which the exposed groove 100 was formed in the previous step with the X-axis direction, and the laser beam LB is irradiated along all the dividing lines 14 along the X-axis direction in the same manner as described above to form the exposed groove 100. As a result of the above, exposed grooves 100 are formed along all of the dividing lines 14 formed on the front surface 10a of the wafer 10, and the partial resin film removal process is completed.

[0024] After the partial resin film removal step described above has been performed, an etching step is then performed in which plasma etching is performed along the regions to be divided on the wafer 10, i.e., along the division lines 14, to divide the wafer 10 into individual chips. The etching step will be described in more detail with reference to FIG. 5.

[0025] After the partial resin film removal step is performed as described above, as shown in FIG. 5(a), the frame unit 18 is transferred to a plasma device 50, the details of which are omitted. The plasma device 50 may be a known plasma device. For example, the plasma device 50 includes an etching chamber forming a sealed space, an upper electrode and a lower electrode disposed in the etching chamber, and a gas supply unit that ejects an etching gas from the upper electrode toward the lower electrode in the etching chamber (all of which are omitted from the drawings). Here, the front surface 10a side of the wafer 10 of the frame unit 18 that has been subjected to the partial resin film removal step is placed and held between the upper electrode and the lower electrode with the front surface 10a facing upward, and a fluorine-based gas is supplied as an etching gas into the etching chamber, and high-frequency power that generates plasma is applied to the upper electrode. The fluorine-based gas is selected from, for example, SF6, CF4, C2F6, and C2F4 and supplied.

[0026] Then, an etching gas in the form of plasma is generated in the space between the upper electrode and the lower electrode, and the etching gas in the form of plasma is supplied to the wafer 10. Here, the frame unit 18 transported to the plasma device 50 after the partial resin film removal process is protected by the resin film P' in the region other than the exposed groove 100. As a result, in the plasma device 50, as shown in FIG. 5(b), plasma etching is performed along the exposed groove 100, i.e., along the division lines 14, to form division grooves 110 reaching the dicing tape T, and the wafer 10 is divided into individual device chips 12', completing the etching process.

[0027] After the etching step described above is performed, a complete resin film removal step is performed in which the frame unit 18 is cleaned to completely remove the resin film P'. The complete resin film removal step will be described in more detail with reference to FIG.

[0028] The frame unit 18 that has been subjected to the etching process shown in the upper right of FIG. 6 is transported to the spin coater 20 described above, and the front surface 10a of the wafer 10 is placed on the table mechanism 21 with the front surface 10a facing upward and held by suction. Next, the electric motor arranged in the drive source 25 is driven to rotate the table mechanism 21 in the direction indicated by the arrow R3 at a predetermined rotation speed (e.g., 300 rpm), and the cleaning liquid supply nozzle 36 is swung in the direction indicated by the arrow R4 in the figure (horizontal direction) to spray the cleaning liquid L (e.g., pure water) onto the upper surface (front surface 10a) of the wafer 10 and the dicing tape T for a predetermined time. As a result, the resin film P' that was coated on the wafer 10 and the dicing tape T is melted and discharged into the liquid cover 31. The melted and discharged resin film P' flows over the bottom surface 31a of the liquefying cover 31 and is stored in a predetermined waste tank via the drain hole 32 and the drain hose 33. Next, the cleaning liquid supply nozzle 36 is retreated to the storage position, the air injection nozzle 35 is operated, the tip of the air injection nozzle 35 is moved to the central region on the wafer 10, and air is injected toward the front surface 10a of the wafer 10 while swinging the wafer 10 in the horizontal direction (not shown), and the table mechanism 21 is rotated at high speed (e.g., 3000 rpm) to dry the frame unit 18 including the front surface 10a of the wafer 10, completing the entire resin film removal process. By carrying out this entire resin film removal process, the fluorine element remaining on the frame unit 18 is captured by the molten resin film P' and discharged together with it, and is stored in the waste tank via the drain hose 33 without adhering to the dicing tape T.

[0029] 6, the frame unit 18 is removed from the spin coater 20 and transported to the next process, for example, a pickup device that picks up the device chips 12' separated from the frame unit 18. At this time, no fluorine element remains on the wafer 10 or on the dicing tape T, which solves the problem of fluorine becoming a contamination source for areas where subsequent processes are performed. [Explanation of symbols]

[0030] 10: Wafer 10a: surface 10b: Back side 12: Device 14: Planned division line 18: Frame unit 20: Spin coater 21: Table mechanism 22: Table 221: Suction chuck 222: Frame 24: Shaft 25: Power source 26: Air piston 26a: Rod 30: Cover part 31: Liquid cover 31a: Bottom 32:Drain hole 33: Drain hose 34: Water-soluble resin supply nozzle 35: Air injection nozzle 36: Cleaning liquid supply nozzle 100:Exposed groove 110: Dividing groove F: Frame Fa: Opening T: Dicing tape P0: Water-soluble resin P: Resin film

Claims

1. A wafer processing method for dividing a wafer into individual device chips by plasma etching using fluorine gas, comprising the steps of: a frame unit forming step of positioning the wafer in an opening of a frame having an opening at the center thereof for accommodating the wafer, and attaching a dicing tape to the lower surface of the wafer and the frame to form a frame unit; a resin film coating step of coating the upper surface of the wafer with a water-soluble resin and coating the entire surface of the dicing tape exposed between the wafer and the frame with the water-soluble resin and solidifying the resin film; a partial resin film removal step of removing the resin film from a region of the wafer to be divided to partially expose the upper surface of the wafer; an etching step of subjecting the wafer to plasma etching in a region to be divided to divide the wafer into individual chips; a complete resin film removal process for cleaning the frame unit to completely remove the resin film; The present invention includes: A wafer processing method in which a water-soluble resin film covering the dicing tape exposed between the wafer and the frame remains without being removed by the plasma etching performed in the etching step, thereby preventing elemental fluorine generated by the plasma etching from adhering to the dicing tape.

2. The fluorine gas is SF ６ , C.F. ４ , C ２ F ６ , C ２ F ４ 2. The method for processing a wafer according to claim 1, wherein the wafer is divided by predetermined dividing lines and a plurality of devices are formed on the upper surface of the wafer.

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