JP2015138858A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method that can part a wafer without damage of a device and without occurrence of chipping.SOLUTION: A wafer W can be parted into individual chips without exfoliation of a part of protection film 11a from a surface Wa of the wafer W and without damaging a device D by executing a protection film coating step of covering the surface Wa of the wafer W with the protection film 11a, a cutting step of cutting the protection film 11a along a parting-scheduled line S by a cutting blade 22 to form a cutting groove 12 and form an uncut portion 13 in the protection film 11a after the protection film coating step is executed, and an etching step of executing etching on the wafer W to etch the uncut portion 13 and the wafer W along the parting-scheduled line S, thereby parting the wafer W along the parting-scheduled line S after the cutting step is executed.

Description

  The present invention relates to a processing method for dividing a wafer into individual chips.

  A workpiece such as a semiconductor wafer is formed in each region defined by a plurality of streets that intersect vertically and horizontally on the surface, and each workpiece is divided into individual device chips by dividing the workpiece along the streets. It is divided.

  As a method of dividing the work piece, a resist dry film is attached to the surface of the wafer, and the resist film on the street is cut to form a cutting groove, and then plasma etching is performed, whereby the wafer is divided into individual chips. Has been proposed (for example, see Patent Document 1 below). Moreover, it replaces with sticking of a resist dry film, and the method of coating a resist film on the surface of a wafer is also proposed (for example, refer the following patent document 2).

JP 2003-257896 A JP 2001-127011 A

  However, when the protective film is mechanically removed by cutting the protective film with a cutting blade or the like as described in the above-mentioned patent document, the interface between the protective film layer and the wafer is started at the cut surface. In addition, a part of the protective film may be peeled off. If the wafer is etched with the protective film peeled off, the device may be damaged. Further, since chipping occurs in the wafer during cutting, there is a problem that the bending strength of the chip formed by etching is lowered.

  The present invention has been made in view of the above circumstances, and has a problem to be solved by making it possible to divide a wafer without damaging a device or causing chipping.

The present invention relates to a wafer processing method in which devices are formed in each region of a surface partitioned by intersecting division lines, a protective film coating step for covering the surface of the wafer with a protective film, and the protective film coating After performing the step, a cutting step of cutting the protective film with a cutting blade along the planned dividing line to form a cutting groove and forming an uncut portion in the protective film;
An etching step of etching the uncut portion and the wafer along the planned dividing line and dividing the wafer along the planned dividing line after performing the cutting step.

  The etching step includes an uncut portion etching step for etching the uncut portion, and a wafer etching step for etching the wafer subsequent to the uncut portion etching step, the uncut portion etching step and the wafer etching step, Then, it is desirable to use different etchants or etching gases.

  In the wafer processing method of the present invention, the protective film is mechanically thickened by performing a cutting step to form a cutting groove in the protective film coated on the surface of the wafer by a cutting blade and to form an uncut portion. The wafer is not completely divided in the direction, and then the uncut portion and the wafer are divided by etching, so that the protective film is not peeled off from the surface of the wafer or chipping occurs. Therefore, there is no possibility that the device is damaged or the chipping occurs in the device, and it is possible to prevent the bending strength from being lowered due to the chipping.

  In addition, after the cutting step, the uncut portion etching step for removing only the uncut portion and the wafer etching step for etching the wafer along the planned division line of the portion from which the uncut portion is removed are sequentially performed. By using different etchants or etching gases in the uncut portion etching step and the wafer etching step, optimum processing can be performed according to the material of the uncut portion and the wafer.

It is a perspective view which shows the wafer of the state integrated with the flame | frame via the tape. It is sectional drawing which shows a protective film coating step. It is sectional drawing which shows a cutting step. It is sectional drawing which shows the wafer after a cutting step. It is sectional drawing which shows the wafer after an uncut part etching step. It is sectional drawing which shows the wafer after a wafer etching step. It is sectional drawing which shows a protective film removal step.

  Below, the processing method which divides | segments the wafer W which is a workpiece shown in FIG. 1 into a some chip | tip is demonstrated, referring attached drawing.

(1) Protective film coating step First, a protective film is coated on the surface Wa of the wafer W. The wafer W is configured by, for example, forming a device D on a silicon substrate. On the surface Wa of the wafer W, the device D is formed in each of the regions partitioned by the division lines S that intersect in the vertical and horizontal directions. On the other hand, the device D is not formed on the surface opposite to the surface Wa.

  As shown in FIG. 1, the tape T is stuck to the lower part of the annular frame F whose center is open, and the back surface Wb side of the wafer W is stuck to the tape T exposed from the center. As a result, the wafer W is integrated with the frame F via the tape T.

  Next, a protective film is coated on the surface Wa of the wafer W integrated with the frame F using the spin coat means 1 shown in FIG. The spin coat means 1 has a holding table 2 that holds and rotates the wafer W. On the outer peripheral side of the holding table 2, a frame placement portion 3 on which the frame F is placed, a shaft portion 4 disposed on the frame placement portion 3, and a frame placement by rotating around the shaft portion 4. The clamp part 5 which fixes the flame | frame F mounted in the part 3 is provided. A weight is mounted on the lower portion of the clamp portion 5. A rotating shaft 6 having a vertical axis is connected to the lower side of the holding table 2, and a motor 7 is connected to the rotating shaft 6. Around the upper part of the rotating shaft 6, a cover portion 8 for preventing the material liquid of the protective film from adhering to the rotating shaft 6 and the motor 7 is disposed. Around the holding table 2, an annular case 9 for preventing the material liquid of the protective film from scattering is disposed. From the bottom of the case 9, a nozzle 10 serving as a supplying means for the material liquid for the protective film is erected, and the tip thereof faces downward of the holding table 2. The lower end of the nozzle 10 is connected to a motor 10 a, and the motor 10 a can move the tip of the nozzle 10 between the position above the holding table 2 and the position retracted from above the holding table 2.

  The wafer W integrated with the frame F is transferred to the spin coat means 1 configured as described above. Specifically, the central portion of the tape T attached to the back surface Wb of the wafer W is placed on the upper surface of the holding table 2 and the peripheral portion of the tape T attached to the frame 4 is placed on the frame placement portion 3. Place. Thereafter, the wafer W is sucked and held on the upper surface of the holding table 2 by operating a suction source (not shown).

  Next, the nozzle 10 rotates and the tip thereof moves above the wafer W held on the holding table 2. When the motor 7 rotates the rotary shaft 6 and rotates the holding table 2 at a high speed, for example, in the direction of arrow A, the weight mounted on the clamp unit 5 is swung to the outer peripheral side by centrifugal force. The wafer W is fixed by rotating to the center and pressing the upper part of the frame F. Then, while rotating the holding table 2, the liquid 11 serving as the material liquid for the protective film is appropriately lowered from the nozzle 10 toward the surface Wa of the wafer W. As the liquid 11, for example, a resist solution for forming a resist film is used.

  The dropped liquid 11 flows from the center side to the outer peripheral side of the surface Wa of the wafer W due to the centrifugal force generated by the rotation of the holding table 2, and the liquid 11 spreads over the entire surface Wa of the wafer W. As shown in FIG. 3, the protective film 11a can be coated so as to cover the entire surface Wa of the wafer W.

  In the illustrated protective film coating step, the protective film 11a is coated on the surface Wa of the wafer W using the spin coat means 1, but the method of coating the protective film on the surface Wa of the wafer W is not limited to this. . For example, a dry film made of a resist may be attached to the surface Wa of the wafer W. Since this dry film has adhesiveness, it is easy to adhere to the surface Wa of the wafer W.

(2) Cutting Step After performing the protective film coating step, as shown in FIG. 3, the cutting means 20 performs cutting while leaving an uncut portion on the protective film 11 a coated on the surface Wa of the wafer W. The cutting means 20 includes at least a spindle 21 having an axis in a direction parallel to the surface Wa of the wafer W, and a cutting blade 22 that is detachably mounted at the tip of the spindle 21.

  The wafer W whose surface Wa is coated with the protective film 11a is moved below the cutting means 20, and the cutting blade 20 is rotated in the direction of the arrow B by rotating the spindle 21, for example. Lower in a direction approaching the surface Wa.

  Then, the cutting blade 22 is cut into the protective film 11a coated on the surface Wa of the wafer W along the scheduled dividing line S that intersects the surface Wa of the wafer W shown in FIG. A cutting groove 12 is formed in 11a. Here, the cutting groove 12 shown in FIG. 3 and FIG. 4 is formed in a quadrangular cross section, but is not necessarily formed in this shape, and the cutting groove 12 according to the state of the tip shape of the cutting blade 22 is not necessarily formed. A shape is formed.

  As shown in FIG. 4, when the cutting groove 12 is formed, the lowering operation of the cutting means 20 is controlled so that the cutting edge of the cutting blade 22 shown in FIG. The uncut portion 13 is formed. The thickness H of the uncut portion 13 is not particularly limited and is, for example, 5 μm. In this way, the same cutting as described above is repeated along all the division lines S shown in FIG. 1 to form the uncut portion 13 together with the cutting grooves 12 in the protective film 11a on the division line S.

(3) Uncut portion etching step After performing the cutting step, an uncut portion etching step for removing the uncut portion 13 of the protective film 11a coated on the surface Wa of the wafer W is performed. When the protective film 11a is a resist film, the protective film 11a is etched by oxygen plasma under the following etching condition A, for example. The uncut portion etching step may be performed using a plasma etching apparatus disclosed in Japanese Patent Application Laid-Open No. 2004-247454, or may be performed using a different etching apparatus.

[Etching condition A]
Etching gas: O ₂
Processing pressure: 10 to 150 [Pa]
Gas supply amount: 1000 [cc / min]
Applied high frequency power: 1000 [W]
Stage temperature: 20 [° C]

Specifically, as shown in FIG. 5, the gas supply unit 30 that is disposed above the wafer W and injects an etching gas downward is provided with a protective film 11a using an etching gas composed of O ₂ at a processing pressure (10 to 150 Pa). It sprays toward the cutting groove 12 formed in the above. A fluorine-based gas such as N ₂ , CF ₄ , or CHF ₃ may be added to the etching gas composed of O _{2 according} to the material of the protective film 11 a and the shape of the cutting groove 12. Thereby, the protective film 11a can be etched more effectively.

  When the etching gas flows into the cutting groove 12, the uncut portion 13 shown in FIG. 4 is removed, and the surface Wa of the wafer W is exposed as shown in FIG. Thus, in the uncut portion etching step, it is only necessary to remove the uncut portion 13 formed in the protective film 11a. Therefore, the etching gas is appropriately selected according to the material of the protective film 11a, and only the protective film 11a is selected. Etching is preferably performed.

(4) Wafer Etching Step After performing the uncut portion etching step, a wafer etching step for etching the wafer W itself is performed as shown in FIG. The wafer etching step can be performed using a plasma etching apparatus disclosed in Japanese Patent Application Laid-Open No. 2004-247454. Here, when the wafer W is formed of, for example, a silicon substrate, it is preferable to perform etching based on the following etching conditions B and C.

[Etching condition B]
Etching gas: SF ₆
Processing pressure: 10 [Pa]
Gas supply amount: 1500 [cc / min]
High frequency power applied to the plasma generator: 3000 [W]
High frequency power applied to the substrate side: 300 [W]

[Etching condition C]
Etching gas: C ₄ F ₈
Processing pressure: 10 [Pa]
Gas supply amount: 1000 [cc / min]
High frequency power applied to the plasma generator: 3000 [W]
High frequency power applied to the substrate side: 0 [W]

Specifically, as shown in FIG. 6, the gas supply unit 31 that is arranged above the wafer W and jets the etching gas downward is directed toward the cutting groove 12 shown in FIG. An etching gas composed of SF _{6 is} injected at a processing pressure (10 Pa) for 0.6 seconds, for example. Next, the gas supply unit 31 changes the etching condition B to the etching condition C and injects an etching gas composed of C ₄ F ₈ toward the cutting groove 12 at a processing pressure (10 Pa) for 0.4 seconds, for example. In this way, the 0.6 second etching based on the etching condition B and the 0.4 second etching based on the etching condition C are alternately repeated, and etching is performed along the division line S of the wafer W for 4 minutes. As a result, as shown in FIG. 6, the division grooves 14 are formed along the division line S shown in FIG. By alternately repeating the etching condition B and the etching condition C, silicon is etched at high speed under the condition A, and a protective film is formed on the side wall of the etched portion under the condition B. Etching can be performed at high speed. When the thickness of the silicon substrate is 100 μm, the dividing groove 14 can be formed by continuing this for 4 minutes.

As an etching gas used in the condition B of the wafer etching step, NF ₃ or XeF ₂ may be used in addition to SF ₆ , and it is desirable to appropriately select an etching gas to be used according to the material of the wafer W. In this way, in the uncut portion etching step and the wafer etching step, the uncut portion 13 of the protective film 11a and the wafer W shown in FIG. Can be optimally processed according to the material of the protective film 11a constituting the uncut portion 13 and the wafer.

  The uncut portion etching step and the wafer etching step can also be performed by wet etching. Also in this case, by using different etchants in the uncut portion etching step and the wafer etching step, optimum processing can be performed according to the material of the protective film 11a constituting the uncut portion 13 and the wafer.

(5) Protective film removal step After performing the wafer etching step, since the surface Wa of the wafer W other than the division line S shown in FIG. 1 is still covered with the protective film 11a, the wafer W The protective film 11a is removed from the entire surface Wa. The method for removing the protective film 11a is not particularly limited. For example, when the protective film 11a is a resist film, a dedicated photoresist film remover can be used. Further, the protective film 11a can be removed by oxygen plasma in the same manner as the uncut portion etching step. By removing the protective film 11a from the surface Wa of the wafer W in this way, the entire surface Wa of the wafer W is exposed as shown in FIG. 7, and the wafer W is divided into individual chips with the device D. it can.

  As described above, in the wafer processing method of the present invention, the cutting step is performed to form the cutting groove 12 and the uncut portion 13 in the protective film 11a coated on the surface Wa of the wafer W by the cutting blade 22. Later, since the uncut portion 13 and the wafer are etched by etching, the protective film 11a is not completely divided in the thickness direction mechanically. Thus, a part of the protective film 11a is not peeled off from the surface Wa of the wafer W, and the wafer W can be divided into individual chips without damaging the device D or causing chipping of the device D. It becomes possible.

1: Spin coating means 2: Holding table 3: Frame placing part 4: Shaft part 5: Clamping part 6: Rotating shaft 7: Motor 8: Cover part 9: Case 10: Nozzle 11: Liquid 11a: Protective film 12: Cutting Groove 13: Uncut portion 14: Divided groove 20: Cutting means 21: Spindle 22: Cutting blade 30, 31: Gas supply portion

Claims (2)

A wafer processing method in which a device is formed in each region of a surface defined by intersecting division lines,
A protective film covering step of covering the surface of the wafer with a protective film;
After performing the protective film coating step, a cutting step of cutting the protective film with a cutting blade along the planned division line to form a cutting groove and forming an uncut portion in the protective film;
An etching step of etching the uncut portion and the wafer along the planned division line and dividing the wafer along the planned division line after performing the cutting step. The etching step includes an uncut portion etching step for etching the uncut portion, and
And a wafer etching step for etching the wafer subsequent to the uncut portion etching step,
The wafer processing method according to claim 1, wherein different etchants or etching gases are used in the uncut portion etching step and the wafer etching step.

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