JP5441629B2 - Wafer processing method - Google Patents

Description

  The present invention relates to a wafer processing method in which a wafer having a die attach film (DAF) attached to the back surface is divided into individual devices.

  A semiconductor wafer formed in a region partitioned by a plurality of division lines (streets) formed by a plurality of devices such as ICs and LSIs in a grid pattern is cut by a cutting device called a dicing saw. The devices are divided into individual devices, and the divided devices are widely used in electric devices such as mobile phones and personal computers.

  In recent years, ablation processing using a laser processing apparatus instead of cutting using a cutting apparatus has attracted attention because it can increase the amount of devices that can be taken from a single wafer by narrowing the width of the line to be divided.

  In the ablation processing by the laser processing apparatus, the wafer can be divided into individual devices with high accuracy by irradiating the wafer with a laser beam having a wavelength having absorptivity and performing the ablation processing along the planned division line.

  Recently, in order to improve device mounting efficiency, a die attach film (DAF), which is an adhesive film for die bonding, is attached to the back surface of the wafer, and the DAF is processed together with the wafer by a cutting device or a laser processing device. Thus, a processing method for dividing the back surface into devices with DAF has attracted attention.

JP 2008-235398 A

  However, when a laser beam is irradiated on the wafer division line where the DAF supported by the dicing tape is disposed on the back surface of the wafer, and the wafer is divided into individual devices together with the DAF, it is formed in a lattice shape. There is a problem in that the DAF is welded to the dicing tape at the intersection of the scheduled division lines and the device with DAF cannot be picked up from the dicing tape.

  The present invention has been made in view of these points, and an object thereof is to provide a wafer processing method using a laser beam in which DAF is not welded to a dicing tape.

  According to the first aspect of the present invention, the dicing tape is used on the back surface of the wafer in which each device is formed in each region partitioned by the plurality of first division planned lines and the second division planned lines formed in a lattice shape. A wafer processing method in which a supported die attach film is disposed, the chuck table holding and rotating the wafer, and a laser beam irradiation means for irradiating the wafer held on the chuck table with a laser beam, A wafer holding step of sucking and holding the wafer via the dicing tape in the chuck table of a laser processing apparatus provided with a processing feed means for relatively processing and feeding the chuck table and the laser beam irradiation means; The energy of the laser beam is reduced at the intersection of the first division line and the second division line. After performing the energy reduction region forming step for forming the energy reduction region, and the energy reduction region forming step, the first division planned line is irradiated with a laser beam having a wavelength having an absorptivity with respect to the wafer, A first dividing step of dividing the wafer and the die attach film along the first division line by relatively processing and feeding the chuck table and the laser beam irradiation means; and the energy reduction region forming step After performing the above, the laser beam is positioned on the second scheduled division line and irradiated, and the chuck table and the laser beam irradiation means are relatively processed and fed to the wafer along the second scheduled division line. And a second dividing step of dividing the die attach film into a wafer. The law is provided.

  Preferably, in the energy reduction region forming step, a laser beam having a wavelength that is transmissive to the wafer is used as a condensing point of the laser beam inside an intersection of the first scheduled division line and the second scheduled division line. It is comprised from the process of irradiating and forming a deteriorated layer inside a wafer.

  According to the third aspect of the present invention, the dicing tape is used on the back surface of the wafer in which each device is formed in each region defined by the plurality of first division planned lines and the second division planned lines formed in a lattice shape. A method of processing a wafer in which a supported die attach film is disposed, the step of covering a transmission energy suppressing film at the intersection of the first scheduled dividing line and the second scheduled dividing line, and holding the wafer A rotatable chuck table, a laser beam irradiation means for irradiating a wafer held on the chuck table with a laser beam, and a processing feed means for relatively processing and feeding the chuck table and the laser beam irradiation means. Wafer holding step of sucking and holding the wafer through the dicing tape with the chuck table of the laser processing apparatus The first division line is irradiated with a laser beam having a wavelength that is absorptive with respect to the wafer, and the chuck table and the laser beam irradiation means are relatively processed and fed to the first division line. A first dividing step of dividing the wafer and the die attach film along a line; and irradiating the laser beam on the second scheduled division line while positioning the chuck table and the laser beam irradiation means relative to each other. And a second dividing step of dividing the wafer and the die attach film along the second division planned line, and a wafer processing method characterized by comprising:

  According to the present invention, an energy reduction region for reducing the energy of the laser beam is formed at the intersection of the planned division lines, or the transmission energy suppression film is coated at the intersection, and then the first division step and the second division step are performed. Since this is implemented, the DAF is prevented from being welded to the dicing tape at the intersection of the scheduled division lines, and the device with DAF can be easily picked up from the dicing tape.

It is a perspective view of the laser processing apparatus suitable for implementing the processing method of this invention. It is a block diagram of a laser beam irradiation unit. It is a perspective view which shows a mode that a wafer is mounted in dicing tape integrated DAF. It is a perspective view which shows an energy reduction area | region formation process. It is sectional drawing which shows an energy reduction area | region formation process. It is a perspective view which shows a 1st division | segmentation process. It is a perspective view which shows a 2nd division | segmentation process. It is a perspective view of the wafer with DAF of the state supported by the annular frame via the dicing tape after the end of the 1st and 2nd division process. It is sectional drawing which shows a tape expansion process and a pick-up process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a laser processing apparatus 2 suitable for carrying out the processing method of the present invention is shown. The laser processing apparatus 2 includes a first slide block 6 mounted on a stationary base 4 so as to be movable in the X-axis direction.

  The first slide block 6 is moved along the pair of guide rails 14 in the machining feed direction, that is, the X-axis direction, by the machining feed means 12 including the ball screw 8 and the pulse motor 10.

  A second slide block 16 is mounted on the first slide block 6 so as to be movable in the Y-axis direction. That is, the second slide block 16 is moved in the indexing direction, that is, the Y-axis direction along the pair of guide rails 24 by the indexing feeding means 22 constituted by the ball screw 18 and the pulse motor 20.

  A chuck table 28 is mounted on the second slide block 16 via a cylindrical support member 26, and the chuck table 28 can be moved in the X-axis direction and the Y-axis direction by the processing feed means 12 and the index feed means 22. . The chuck table 28 is provided with a clamper 30 for clamping the semiconductor wafer sucked and held by the chuck table 28.

  A column 32 is erected on the stationary base 4, and a casing 35 for accommodating the laser beam irradiation unit 34 is attached to the column 32. As shown in FIG. 2, the laser beam irradiation unit 34 includes a laser oscillator 62 that oscillates a YAG laser or a YVO4 laser, a repetition frequency setting unit 64, a pulse width adjustment unit 66, and a power adjustment unit 68. .

  The pulse laser beam adjusted to a predetermined power by the power adjusting means 68 of the laser beam irradiation unit 34 is reflected by the mirror 70 of the condenser 36 attached to the tip of the casing 35 and further collected by the condenser objective lens 72. The semiconductor wafer W is irradiated with light and irradiated onto the chuck table 28.

  At the tip of the casing 35, an image pickup means 38 for detecting a processing region to be laser processed aligned with the condenser 36 in the X-axis direction is disposed. The image pickup means 38 includes an image pickup element such as a normal CCD that picks up an image of a processing region of a semiconductor wafer with visible light.

  The imaging unit 38 further includes an infrared irradiation unit that irradiates the semiconductor wafer with infrared rays, an optical system that captures the infrared rays irradiated by the infrared irradiation unit, and an infrared CCD that outputs an electrical signal corresponding to the infrared rays captured by the optical system. Infrared imaging means composed of an infrared imaging element such as the above is included, and the captured image signal is transmitted to a controller (control means) 40.

  The controller 40 includes a central processing unit (CPU) 42 that performs arithmetic processing according to a control program, a read-only memory (ROM) 44 that stores a control program, and a random read / write that stores arithmetic results. An access memory (RAM) 46, a counter 48, an input interface 50, and an output interface 52 are provided.

  Reference numeral 56 denotes a processing feed amount detection means comprising a linear scale 54 disposed along the guide rail 14 and a read head (not shown) disposed on the first slide block 6. Is input to the input interface 50 of the controller 40.

  Reference numeral 60 denotes index feed amount detection means comprising a linear scale 58 disposed along the guide rail 24 and a read head (not shown) disposed on the second slide block 16. The detection signal is input to the input interface 50 of the controller 40.

  An image signal picked up by the image pickup means 38 is also input to the input interface 50 of the controller 40. On the other hand, a control signal is output from the output interface 52 of the controller 40 to the pulse motor 10, the pulse motor 20, the laser beam irradiation unit 34, and the like.

  Referring to FIG. 3, a perspective view showing a state where a die attach film (DAF) 53, which is an adhesive film for die bonding, supported on a dicing tape T on the back surface of the semiconductor wafer W is shown.

  The semiconductor wafer W is made of, for example, a silicon wafer having a thickness of about 80 μm, and has a plurality of first division planned lines (first streets) S1 extending in parallel on the surface thereof and orthogonal to the first division planned lines S1. A device D such as an IC or an LSI is formed in each of a plurality of regions partitioned by a plurality of second division planned lines (second streets) S2 extending in the direction of the direction.

  The DAF 53 is formed of an epoxy resin having a thickness of about 80 μm, for example, and is an integrated DAF integrated with the dicing tape T. The dicing tape T is formed, for example, by applying an acrylic resin adhesive layer to a thickness of about 5 μm on the surface of a sheet base material made of polyvinyl chloride (PVC) having a thickness of about 80 μm. The outer peripheral portion of the dicing tape T is attached to the annular frame F.

  In order to attach the DAF 53 to the back surface of the wafer W, the DAF 53 is attached to the back surface of the wafer W by pressing the back surface of the wafer W against the DAF 53 while heating the DAF 53 at a temperature of 80 to 200 ° C.

  Instead of adhering the dicing tape-integrated DAF 53 to the back side of the wafer W, the single DAF 53 is attached to the back side of the wafer W, and then the DAF 53 side of the wafer W is attached to the dicing tape T. Also good.

  In the wafer processing method according to the first embodiment of the present invention, the wafer W with DAF supported by the annular frame F through the dicing tape T in this way is mounted on the chuck table 28, and the wafer W with DAF is mounted on the chuck table 28. Hold the suction.

  Next, as shown in FIG. 4 and FIG. 5, the wavelength having transparency with respect to the wafer W by the condenser 36 while processing and feeding the chuck table 28 and the laser beam irradiation unit 34 in the direction of the arrow X1 relatively. The laser beam condensing point is positioned inside the intersection 55 between the first scheduled division line S1 and the second scheduled division line S2, and the laser beam is intermittently irradiated to form the altered layer 51 inside the intersection 55. .

  The altered layer 51 is preferably formed in a plurality of layers in the thickness direction of the wafer W as shown in FIG. When the deteriorated layer 51 is irradiated with a laser beam having a wavelength that is absorptive with respect to the wafer W, the deteriorated layer 51 disperses and reduces the energy of the laser beam, so that the deteriorated layer 51 becomes an energy reduction region.

  This energy reduction region forming step is performed, for example, under the following processing conditions.

Light source: LD excitation Q switch Nd: YAG pulse laser Wavelength: 1064 nm
Output: 1.0W
Repetition frequency: 10 kHz
Spot shape: φ20μm

  When the energy reduction region forming step is completed, as shown in FIG. 6, the first splitting line S1 is irradiated with a laser beam having a wavelength that is absorptive with respect to the wafer W via the condenser 36, and is irradiated. The chuck table 28 and the laser beam irradiation unit 34 are relatively processed and fed in the direction of the arrow X1, and the first division planned line S1 and the DAF 53 of the wafer W are ablated and divided. In FIG. 6, reference numeral 57a denotes a first dividing groove.

  Actually, since the laser beam irradiation unit 34 is fixed to the stationary base 4, the first division groove 57 a is formed while the chuck table 28 is processed and fed in the direction of the arrow X 1 by the processing feeding means 12. Perform the process.

  Next, as shown in FIG. 7, the laser beam is irradiated by the condenser 36 while being positioned at the second scheduled division line S2, and the chuck table 28 and the laser beam irradiation unit 34 are relatively processed and fed in the direction of the arrow X2. Then, a second division step is performed in which the second division groove 57b is formed by performing ablation processing on the second division planned line S2 and the DAF 53 of the wafer W.

  Actually, the chuck table 28 is rotated by 90 degrees, and then the wafer W and the DAF 53 are ablated by the laser beam while being fed in the direction of the arrow X2 by the machining feed means 12 to form the second divided groove 57b. . FIG. 8 shows a perspective view of the wafer W with DAF in a state where the first dividing groove 57a and the second dividing groove 57b are formed.

  The first dividing step and the second dividing step described above are performed, for example, under the following processing conditions.

Light source: LD excitation Q switch Nd: YAG pulse laser Wavelength: 355 nm (third harmonic of YAG laser)
Output: 3 to 3.75W
Repetition frequency: 10 kHz
Spot shape: Ellipse shape with short axis of 10 μm and major axis of 300 μm Processing feed rate: 100 to 200 mm / sec

  After the second dividing step, the dicing tape T is expanded in the radial direction using a tape expansion device 74 as shown in FIG. 9, and then the DAF 53 is attached to the back surface by the picker 92 of the pickup means 90. Pick up D.

  In FIG. 9, the tape expansion device 74 includes a fixed expansion drum 76, a frame holding unit 78, and a driving unit 84. The frame holding means 78 includes an annular frame holding member 80 and a plurality of clamps 82 as fixing means disposed on the outer periphery of the frame holding member 80.

  An upper surface of the frame holding member 80 forms a placement surface 80a on which the annular frame F is placed, and the annular frame F is placed on the placement surface 80a. The driving means 84 is composed of a plurality of air cylinders 86.

  The annular frame F placed on the placement surface 80 a is fixed to the frame holding member 80 by the clamp 82. The frame holding means 78 configured as described above is connected to the piston rod 88 of the air cylinder 86 and is moved in the vertical direction when the air cylinder 86 is driven.

  A tape expansion process and a pickup process using the tape expansion device 74 configured as described above will be described below. As shown in FIG. 8, an annular frame F in which a DAF wafer W formed with first and second dividing grooves 57 a and 57 b is supported via a dicing tape T is placed on a holding surface 80 a of a frame holding member 80. The frame holding member 80 is fixed by the clamp 82. At this time, the mounting surface 80 a of the frame holding member 80 is positioned at substantially the same height as the upper end of the expansion drum 70.

  Next, the air cylinder 86 is driven to move the frame holding member 80 downward by about 15 mm to lower it to the extended position shown in FIG. As a result, the annular frame F fixed on the mounting surface 80a of the frame holding member 80 is also lowered, so that the dicing tape T attached to the annular frame F abuts on the upper edge of the expansion drum 76 and mainly has a radius. Expanded in the direction.

  As a result, a tensile force acts radially on the DAF 53 and the wafer W attached to the dicing tape T, and the interval between the adjacent devices D with DAF is widened. Therefore, the device D with DAF can be easily picked up by the picker 92 of the pickup means 90.

  According to the wafer processing method of the above-described embodiment, an energy reduction region composed of the altered layer 51 that reduces the energy of the laser beam is formed at the intersection 55 of the planned division lines S1 and S2, and then the divisional lines S1 and S2 are formed. Since the wafer is divided by ablation processing by irradiating the wafer with a laser beam having an absorptive wavelength, the DAF 53 may be adhered to the dicing tape T at the intersection 55 between the division lines S1 and S2. The device D with DAF can be easily picked up from the dicing tape T.

  In the first embodiment described above, a deteriorated layer 51 is formed by irradiating a laser beam having a wavelength that is transmissive to the wafer W to the intersections of the division lines S1 and S2, and the deteriorated layer 51 is used as an energy reduction region. Although the present invention is implemented by using the present invention, the present invention is not limited to the first embodiment, and includes the second embodiment described below.

  That is, in the second embodiment of the present invention, a transmission energy suppression film that suppresses the transmission energy of the laser beam is covered at the intersection of the first division planned line S1 and the second division planned line S2 of the wafer W.

  This suppression film | membrane is formed from resin films, such as metal films, such as aluminum foil, or a polyimide, for example. The transmission energy suppressing film can be formed by a semiconductor device manufacturing process using a mask and a photoresist, for example.

  A DAF 53 supported by a dicing tape T as shown in FIG. 3 is attached to the back surface of the wafer W on which a transmission energy suppression film is formed at each intersection, and the wafer is passed through the dicing tape on the chuck table of the laser processing apparatus. A wafer holding step for sucking and holding is performed.

  After the wafer is sucked and held in this way by the chuck table, the first division step and the second division step are performed using a laser beam having a wavelength that is absorptive to the wafer, as in the first embodiment. The

  According to this embodiment, when the irradiated laser beam hits the transmission energy suppressing film, the energy of the laser beam passing through the film is suppressed by scattering or the like, so that the DAF 53 is dicing tape at the intersection 55 of the division lines S1 and S2. Sticking to T is prevented, and the device D with DAF can be easily picked up from the dicing tape T.

W Semiconductor wafer D Device T Dicing tape F Annular frame 2 Laser processing device 28 Chuck table 34 Laser beam irradiation unit 36 Condenser 51 Denatured layer 53 Die attach film (DAF)
55 Intersection 74 Tape expansion device 90 Pickup means

Claims (3)

A die attach film supported by a dicing tape is disposed on the back surface of the wafer in which each device is formed in each region defined by a plurality of first division planned lines and second division planned lines formed in a lattice shape. A method of processing the wafer,
A chuck table that holds and rotates a wafer, a laser beam irradiation unit that irradiates a wafer held on the chuck table with a laser beam, and a processing feed that relatively processes and feeds the chuck table and the laser beam irradiation unit. A wafer holding step of sucking and holding the wafer through the dicing tape with the chuck table of a laser processing apparatus comprising:
An energy reduction region forming step of forming an energy reduction region for reducing the energy of the laser beam at the intersection of the first division line and the second division line;
After the energy reduction region forming step is performed, the first division line is irradiated with a laser beam having a wavelength that is absorptive with respect to the wafer, and the chuck table and the laser beam irradiation unit are relatively moved. A first dividing step of dividing the wafer and the die attach film along the first division schedule line
After performing the energy reduction region forming step, the laser beam is positioned on the second division planned line and irradiated, and the chuck table and the laser beam irradiation means are relatively processed and fed to the second division. A second dividing step of dividing the wafer and the die attach film along a predetermined line;
A wafer processing method characterized by comprising:   In the energy reduction region forming step, a laser beam having a wavelength that is transmissive to the wafer is positioned at the intersection of the first planned split line and the second planned split line. 2. A wafer processing method according to claim 1, comprising a step of irradiating and forming a deteriorated layer inside the wafer. A die attach film supported by a dicing tape is disposed on the back surface of the wafer in which each device is formed in each region defined by a plurality of first division planned lines and second division planned lines formed in a lattice shape. A method of processing the wafer,
Covering a transmission energy suppressing film at an intersection between the first division planned line and the second division planned line;
A chuck table that holds and rotates a wafer, a laser beam irradiation unit that irradiates a wafer held on the chuck table with a laser beam, and a processing feed that relatively processes and feeds the chuck table and the laser beam irradiation unit. A wafer holding step of sucking and holding the wafer through the dicing tape with the chuck table of a laser processing apparatus comprising:
A laser beam having a wavelength that absorbs the wafer is positioned and irradiated on the first division planned line, and the chuck table and the laser beam irradiation means are relatively processed and fed to the first division planned line. A first dividing step of dividing the wafer and the die attach film along
Positioning and irradiating the laser beam on the second scheduled division line and relatively processing and feeding the chuck table and the laser beam irradiating means to the wafer and the die attach film along the second scheduled division line A second dividing step of dividing
A wafer processing method characterized by comprising:

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