JP2013021211A - Method for processing wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for processing a wafer capable of suppressing excessive use of a protective film agent and forming a protective film in a short time.SOLUTION: A method for processing a wafer in which a device is formed in each of the regions partitioned by a plurality of intersecting division schedule lines formed on a surface of the wafer comprises: a protective film formation step of relatively moving the wafer and protective film agent discharging means and covering a surface of the wafer using surface tension of a liquid protective film agent composed of a water-soluble resin while supplying the liquid protective film agent to the surface of the wafer from the protective film agent discharging means; a laser processing step of forming a laser processing groove on the wafer by irradiating the wafer with a laser beam of a wavelength having absorbability with respect to the wafer along a division schedule line via the protective film after performing the protective film formation step; and a protective film removal step of removing the protective film from the wafer by supplying washing water to the wafer after performing the laser processing step.

Description

  The present invention relates to a wafer processing method in which a water-soluble protective film is coated on the surface of a wafer such as a semiconductor wafer or an optical device wafer, and then ablation is performed with a laser beam.

  A wafer such as a silicon wafer or a sapphire wafer formed on the surface by dividing a plurality of devices such as IC, LSI, LED, etc. by dividing lines is divided into individual devices by a processing apparatus, and the divided devices are mobile phones, Widely used in various electrical equipment such as personal computers.

  A dicing method using a cutting device called a dicer is widely used for dividing the wafer. In the dicing method, a wafer is cut by cutting a wafer into a wafer while rotating a cutting blade having a thickness of about 30 μm by solidifying abrasive grains such as diamond with a metal or a resin at a high speed of about 30000 rpm. Divide into

  On the other hand, in recent years, a laser processing groove is formed by irradiating a wafer with a pulsed laser beam having a wavelength that absorbs the wafer, and the wafer is cut along the laser processing groove by a breaking device. A method of dividing into devices has been proposed.

  The formation of the laser processing groove by the laser processing apparatus can increase the processing speed as compared with the dicing method using the dicer, and relatively easily processes even a wafer made of a material having high hardness such as sapphire or SiC. be able to. In addition, since the processing groove can be made to have a narrow width of, for example, 10 μm or less, the amount of devices taken per wafer can be increased as compared with the case of processing by the dicing method.

  However, when the wafer is irradiated with a pulse laser beam, debris is generated due to concentration of thermal energy in the region irradiated with the pulse laser beam. When this debris adheres to the device surface, there arises a problem that the quality of the device is lowered.

  Therefore, for example, in JP 2006-140311 A, a water-soluble resin such as PVA (polyvinyl alcohol) or PEG (polyethylene glycol) is applied to the processed surface of the wafer in order to solve the problem caused by debris. There has been proposed a laser processing apparatus in which a protective film is coated and a wafer is irradiated with a pulsed laser beam through the protective film.

  In recent years, as a technology for realizing lighter, thinner, and smaller semiconductor devices, flip chips have been formed by forming a plurality of metal protrusions called bumps on the device surface, and directly bonding these bumps against the electrodes formed on the wiring board. A mounting technique called bonding has been put into practical use.

JP 2006-140311 A JP 2004-322168 A

  However, in a wafer in which a bump having a height of, for example, several hundred μm is formed on a device, it is necessary to use a very large amount of protective film agent in order to form a protective film covering the bump. There is a problem that it takes a long time to form.

  In particular, when a water-soluble protective film is formed by the spin coating method disclosed in Patent Document 2, 90% or more of the supplied water-soluble resin is scattered and discarded, which is very uneconomical. .

  The present invention has been made in view of these points, and an object of the present invention is to provide a wafer processing method capable of suppressing overuse of a protective film agent and forming a protective film in a short time. That is.

  According to the present invention, there is provided a wafer processing method in which a device is formed in each region partitioned by a plurality of intersecting division lines formed on the surface, and the liquid protective film made of a water-soluble resin on the surface of the wafer A protective film forming step for covering the surface of the wafer by using the surface tension of the liquid protective film agent by relatively moving the wafer and the protective film agent discharge means while supplying the agent from the protective film agent discharging means; After performing the film forming step, laser processing is performed to form a laser processing groove on the wafer by irradiating the wafer with a laser beam having a wavelength that is absorptive with respect to the wafer along the division line through the protective film. And a protective film removing step of supplying cleaning water to the wafer and removing the protective film from the wafer after performing the laser processing step. The wafer processing method is provided that the symptoms.

  Preferably, in the protective film forming step, the wafer is held by a rotatable holding table, the holding table rotates at a speed at which the liquid protective film agent supplied onto the wafer does not scatter and the protective film agent discharging means The liquid protective film agent is discharged while scanning on the wafer.

  According to the present invention, the protective film agent discharge means for discharging the liquid protective film agent and the wafer move relative to each other while the liquid protective film agent is supplied onto the wafer, and the protective film is formed using the surface tension of the liquid protective film agent. It is formed. Therefore, since the protective film agent is not scattered and discarded, the excessive use of the protective film agent can be suppressed. Furthermore, since the protective film is formed using the surface tension of the liquid protective film agent, the protective film can be formed in a short time.

It is a perspective view of the laser processing apparatus suitable for implementing the processing method of the wafer of this invention. 1 is a perspective view of a semiconductor wafer to be processed by the wafer processing method of the present invention. It is a perspective view of the state which supported the semiconductor wafer with the annular frame via the adhesive tape. It is a partial cross section side view which shows a protective film formation step. It is a top view which shows a protective film formation step. It is sectional drawing of the wafer after a protective film formation step. It is a perspective view which shows a laser processing step. It is a block diagram of a laser beam irradiation unit. It is a partial cross section side view which shows a protective film removal step. It is sectional drawing of the wafer after a protective film removal step.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a perspective view of a laser processing apparatus 2 that includes a protective film forming apparatus and can divide a wafer into individual chips (devices) by laser processing.

  On the front side of the laser processing apparatus 2, an operation panel 4 is provided for an operator to input instructions to the apparatus such as processing conditions. In the upper part of the apparatus, a display monitor 6 such as a CRT on which a guidance screen for an operator and an image captured by an imaging unit described later are displayed is provided.

  As shown in FIG. 2, on the surface of the semiconductor wafer W to be processed, the first street S1 and the second street S2 are formed to be orthogonal to each other, and the first street S1 and the second street S2 are formed. A number of devices D are formed in a region partitioned by. As shown in the enlarged view of FIG. 2, a plurality of protruding bumps 5 are formed on the four sides of each device D.

  As shown in FIG. 3, the wafer W is attached to a dicing tape T that is an adhesive tape, and the outer peripheral edge of the dicing tape T is attached to an annular frame F. As a result, the wafer W is supported by the annular frame F via the dicing tape T, and a plurality of wafers (for example, 25 sheets) are accommodated in the wafer cassette 8 shown in FIG. The wafer cassette 8 is placed on a cassette elevator 9 that can move up and down.

  Behind the wafer cassette 8, loading / unloading means 10 is provided for unloading the wafer W before laser processing from the wafer cassette 8 and loading the processed wafer into the wafer cassette 8.

  Between the wafer cassette 8 and the loading / unloading means 10, a temporary placement area 12, which is an area on which a wafer to be loaded / unloaded is temporarily placed, is provided. A wafer W is fixed in the temporary placement area 12. Positioning means 14 for positioning to the position of is arranged.

  Reference numeral 30 denotes a protective film forming apparatus. The protective film forming apparatus 30 also serves as a cleaning apparatus for cleaning the processed wafer. In the vicinity of the temporary placement region 12, a transport unit 16 having a turning arm that sucks and transports the frame F integrated with the wafer W is disposed.

  The wafer W carried out to the temporary placement area 12 is adsorbed by the conveying means 16 and conveyed to the protective film forming apparatus 30. The protective film forming apparatus 30 coats the protective film by applying a liquid resin to the processed surface of the wafer W, as will be described in detail later.

  The wafer W whose processing surface is coated with a protective film is attracted by the conveying means 16 and conveyed onto the chuck table 18 and is sucked by the chuck table 18, and the frame F is fixed by a plurality of fixing means (clamps) 19. As a result, the chuck table 18 is held.

  The chuck table 18 is configured to be rotatable and reciprocally movable in the X-axis direction. Above the movement path of the chuck table 18 in the X-axis direction, an alignment unit 20 that detects a street of the wafer W to be laser processed. Is arranged.

  The alignment unit 20 includes an imaging unit 22 that images the surface of the wafer W, and can detect a street to be laser processed by image processing such as pattern matching based on an image acquired by imaging. The image acquired by the imaging unit 22 is displayed on the display unit 6.

  On the left side of the alignment unit 20, a laser beam irradiation unit 24 that irradiates the wafer W held on the chuck table 18 with a laser beam is disposed. The laser beam irradiation unit 24 is movable in the Y axis direction.

  Referring to FIG. 4, a partial sectional side view of the protective film forming apparatus 30 is shown. The protective film forming apparatus 30 includes a spinner table mechanism 34 and a liquid receiving mechanism 36 disposed so as to surround the spinner table mechanism 34.

  The spinner table mechanism 34 includes a spinner table (holding table) 38, a support member 40 that supports the spinner table 38, and an electric motor 42 that rotationally drives the spinner table 38 via the support member 40. When the electric motor 42 is rotationally driven, the spinner table 38 is rotated in the arrow A direction.

  The spinner table 38 has a suction holding portion made of a porous material, and the suction holding portion is communicated with negative pressure suction means (not shown). Therefore, the spinner table 38 sucks and holds the wafer on the suction holding portion by placing the wafer on the suction holding portion and applying a negative pressure by a negative pressure suction means (not shown).

  The spinner table 38 is provided with four pendulum type clamps 44. When the spinner table 38 is rotated, the clamps 44 are swung by centrifugal force to clamp the annular frame F shown in FIG.

  The liquid receiving mechanism 36 includes a liquid receiving container 46 and a cover member 48 attached to the support member 40. The liquid receiving container 46 includes a cylindrical outer wall 46a, a bottom wall 46b, and an inner wall 46c.

  A hole 47 into which the support member 40 is inserted is provided at the center of the bottom wall 46 b, and the inner wall 46 c is formed so as to protrude upward from the periphery of the hole 47. The cover member 48 is formed in a disc shape, and includes a cover portion 48a that protrudes downward from the outer peripheral edge thereof.

  When the spinner table 38 is positioned at the work position shown in FIG. 4, the cover member 48 configured in this manner is overlapped with the cover portion 48 a overlapping the outer side of the inner side wall 46 c constituting the liquid receiving container 46. Positioned on.

  The protective film forming apparatus 30 includes a protective film agent discharge means 50 that discharges a liquid protective film agent made of a water-soluble resin onto the unprocessed wafer W held on the spinner table 38. The protective film agent discharging means 50 is a liquid that discharges the liquid protective film agent toward the processed surface of the wafer W before processing, which is formed at the tip of the arm 52 and the arm 52 having a substantially L shape, and held by the spinner table 38. It comprises a protective film agent supply nozzle 54 and an electric motor 56 capable of normal / reverse rotation that swings the arm 52. The protective film agent supply nozzle 54 is connected to a protective film agent supply source 58 via the arm 52.

  The protective film forming apparatus 30 also serves as a cleaning apparatus for cleaning the wafer W after laser processing. Therefore, the protective film forming apparatus 30 includes cleaning water supply means 60 for cleaning the processed wafer W held on the spinner table 38.

  As best shown in FIG. 9, the cleaning water supply means 60 is formed on an approximately L-shaped arm 62 and a processed surface of the processed wafer W formed on the tip of the arm 62 and held on the spinner table 38. The cleaning water nozzle 64 supplies cleaning water, and an electric motor 66 that swings the arm 62 and can be rotated forward and backward. The cleaning water nozzle 64 is connected to the cleaning water supply source 68 via the arm 62.

  Next, the wafer processing method of the embodiment of the present invention by the laser processing apparatus 2 including the protective film forming apparatus 30 configured as described above will be described in detail. The wafer W before processing is transported to the spinner table 38 of the protective film forming apparatus 30 by the turning motion of the wafer transport means 16 and is sucked and held by the spinner table 38. At this time, as shown in FIG. 4, the washing water nozzle 64 is positioned at a standby position isolated from above the spinner table 38.

  While rotating the spinner table 38 in the arrow A direction at a low speed, for example, 30 to 50 rpm, the liquid protective film agent is dropped on the wafer W while the liquid protective film agent supply nozzle 54 is swung in the arrow B direction in FIG. .

  Since the spinner table 38 is rotated, the dropped liquid protective film agent spreads on the processed surface of the wafer W, and the protective film 7 is formed on the processed surface of the wafer W by utilizing the surface tension of the liquid protective film agent. The

  As shown in FIG. 6, it is preferable that the protective film 7 formed on the wafer W has a thickness for completely embedding the bumps 5. As an alternative embodiment, the spinner table 38 may be configured to scan the wafer W evenly without rotating the spinner table 38.

  If the protective film 7 is coated on the surface of the wafer W, the suction and holding of the spinner table 38 is released, and then the wafer W is transported to the chuck table 18 by the wafer transport means 16, and as shown in FIG. The table 18 is sucked and held.

  7, the laser beam irradiation unit 24 of the laser processing apparatus includes a laser beam generation unit 25 shown in FIG. 8 housed in a casing 26, a condenser (laser head) 28 attached to the tip of the casing 26, and the like. Consists of

  As shown in FIG. 8, the laser beam generating unit 25 includes a laser oscillator 27 such as a YAG laser oscillator, a repetition frequency setting means 29, a pulse width adjusting means 31, and the power of the laser beam oscillated from the laser oscillator 27. Power adjusting means 33 for adjusting the power.

  Before performing the laser processing step, the processing area of the wafer W sucked and held by the chuck table 18 is moved directly below the imaging unit 22, and the imaging area of the wafer W is imaged by the imaging unit 22.

  Then, image processing such as pattern matching is performed to align the condenser 28 of the laser beam irradiation unit 24 that irradiates the laser beam and the first scheduled division line S1, and alignment of the laser beam irradiation position is performed. Carry out.

  When the alignment of the first scheduled line S1 is completed, the chuck table 18 is rotated 90 degrees, and then the same alignment is performed on the second scheduled line S2 orthogonal to the first scheduled line S1.

  After the alignment, the chuck table 18 is moved so that the processing start position of the first scheduled division line S1 is positioned directly below the condenser 28, and the pulse adjusted to a predetermined power by the power adjustment means 33 of the laser beam generation unit 25. The laser beam is reflected by the mirror 35 of the condenser 28 shown in FIG. 8 and then condensed on the surface of the wafer W through the protective film 7 by the condenser objective lens 37.

  In this way, while the pulse laser beam is condensed on the surface of the wafer W via the protective film 7 by the condenser 28, the chuck table 18 is moved in the X-axis direction at a predetermined feed rate (for example, 100 mm / second). Then, a laser processing groove 41 (see FIG. 10) is formed by ablation processing along the first scheduled dividing line S1.

  While the laser beam irradiation unit 24 is indexed in the Y-axis direction, similar laser processing grooves 41 are formed along all the first division planned lines S1. After the laser processing step along the first scheduled division line S1, the chuck table 18 is rotated 90 degrees, and a similar laser processed groove 41 is formed on the second scheduled division line S2 by ablation.

  In addition, the laser processing conditions in the laser processing step of this embodiment are as follows, for example.

Light source: YAG pulse laser Wavelength: 355 nm (third harmonic of YAG laser)
Output: 3.0W
Repetition frequency: 20 kHz
Condensing spot diameter: 1.0 μm
Feeding speed: 100 mm / second

  By performing the laser processing step, a laser processing groove 41 is formed in the wafer W along the first and second scheduled division lines S1 and S2 as shown in FIG. Even when debris is generated by laser beam irradiation during the laser processing step, the debris is blocked by the protective film 7 and does not adhere to the electronic circuit and bumps of the device D.

  When the laser processing groove 41 is formed in the wafer W in this way, the chuck table 18 is returned to the position where the first wafer W is sucked and held, and here, the suction holding of the wafer W is released. The wafer W is transported to the spinner table 38 of the protective film forming apparatus 30 by the transport means 32 and sucked and held by the spinner table 38. At this time, as shown in FIG. 9, the liquid protective film agent supply nozzle 54 is positioned at a standby position where the liquid protective film agent supply nozzle 54 is peeled from above the spinner table 38.

  The wafer W is rotated in the direction of arrow A at a low speed (for example, 800 rpm) while supplying cleaning water from the cleaning water nozzle 64 connected to the cleaning water supply source 68 to the protective film 7 of the wafer W held on the chuck table 38. As a result, the protective film 7 is removed from the wafer W by dissolving it in water. For example, pure water is used as the washing water.

  In the protective film removing step, the wafer W on which the protective film 7 is formed is sucked and held by the spinner table 38 of the protective film forming apparatus 30, and the cleaning nozzle 64 is connected to the cleaning water supply source 60 and an air source (not shown) for cleaning. The protective film 7 may be removed by spin cleaning the wafer W while spraying cleaning water composed of pure water and air from the water nozzle 64. FIG. 10 shows a cross-sectional view of the wafer W after the protective film removal step.

  After the laser processing step and the protective film removal step are completed, the wafer W in which the laser processing groove 41 is formed along the first and second division lines S1 and S2 is mounted on the braking device and applied to the wafer W with an external force. Is divided into individual devices D along the laser processing grooves 41.

  In the wafer processing method of the present embodiment described above, the liquid protective film agent is supplied while the protective film agent supply nozzle 54 is swung with respect to the wafer W to form the protective film 7 on the processed surface of the wafer W. The excessive use of the protective film agent is suppressed, and the protective film 7 is formed by utilizing the surface tension of the protective film agent, so that the protective film 7 can be formed in a short time.

W Semiconductor wafer S1 First division planned line S2 Second division planned line D Device 2 Laser processing apparatus 5 Bump 7 Protective film 18 Chuck table 24 Laser beam irradiation unit 28 Condenser 30 Protective film forming apparatus 38 Spinner table 50 Protection Film agent discharge means 54 Protective film agent supply nozzle 60 Wash water supply means 64 Wash water nozzle

Claims (2)

A wafer processing method in which a device is formed in each region defined by a plurality of intersecting division lines formed on a surface,
While supplying a liquid protective film agent comprising a water-soluble resin from the protective film agent discharge means to the surface of the wafer, the wafer and the protective film agent discharge means are relatively moved, and the surface tension of the liquid protective film agent is utilized to A protective film forming step for covering the surface;
After carrying out the protective film forming step, a laser beam having a wavelength that is absorptive with respect to the wafer is irradiated to the wafer along the planned dividing line through the protective film to form a laser processing groove on the wafer. A laser processing step;
After performing the laser processing step, supplying a cleaning water to the wafer to remove the protective film from the wafer;
A wafer processing method characterized by comprising:   In the protective film forming step, the wafer is held by a rotatable holding table, and the holding table rotates at a speed at which the liquid protective film agent supplied onto the wafer does not scatter, and the protective film agent discharging means is on the wafer. 2. The wafer processing method according to claim 1, wherein the liquid protective film agent is discharged while scanning.

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