JP2013021210A - 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 comprises: a liquid supply step of forming a liquid layer 15 on the wafer by supplying a liquid to a surface side of a wafer W; a water-soluble protective sheet sticking step of disposing a water-soluble protective sheet 16 on the liquid layer 15 on a surface of the wafer W, removing the liquid from between the surface of the wafer W and the water-soluble protective sheet 16, and sticking the water-soluble protective sheet to the surface of the wafer; a laser processing step of forming a laser processing groove on the wafer W by irradiating the wafer W with a laser beam of a wavelength having absorbability with respect to the wafer W along a division schedule line via the water-soluble protective sheet 16; and a water-soluble protective sheet removal step of removing the water-soluble protective sheet 16 from the wafer W by supplying washing water to the wafer W.

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 defined by a plurality of intersecting division lines formed on a surface, the liquid being supplied to the surface side of the wafer, A liquid supply step for forming a liquid layer on the substrate, and after the liquid supply step is performed, a water-soluble protective sheet is disposed on the liquid layer on the surface of the wafer, and the liquid is disposed on the surface of the wafer and the water-soluble layer. After performing the water-soluble protective sheet attaching step for removing the protective sheet from between the protective sheets and attaching the water-soluble protective sheet to the surface of the wafer, and the water-soluble protective sheet attaching step, the wafer is made absorbent. A laser processing step of forming a laser processing groove on the wafer by irradiating the wafer with a laser beam having a wavelength having the wavelength along the division line through the water-soluble protective sheet; There is provided a wafer processing method comprising: a water-soluble protective sheet removing step of supplying cleaning water to a wafer after removing the laser processing step and removing the water-soluble protective sheet from the wafer. The

  According to the present invention, after forming a liquid layer on the wafer, a water-soluble protective sheet is disposed on the liquid layer, and the water layer is removed from between the surface of the wafer and the water-soluble protective sheet. Since the sheet is attached to the surface of the wafer to form a protective film, excessive use of the protective film agent can be suppressed and a protective film can be formed in a short time.

1 is a perspective view of a semiconductor wafer to be processed by the wafer processing method of the present invention. It is a partial cross section side view which shows a liquid supply step. It is a partial cross section side view which shows a water-soluble protective sheet sticking 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 water-soluble protective sheet removal step. It is sectional drawing of the wafer after a water-soluble protective sheet removal step.

  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 semiconductor wafer W to which the processing method of the present invention is applied is shown. On the surface of the semiconductor wafer W, the first planned division line (street) S1 and the second planned division line (street) S2 are formed orthogonally, and the first division planned line S1 and the second division planned line S1 A device D is formed in each region partitioned by the planned division line S2. As shown in the enlarged view of FIG. 1, a plurality of protruding bumps 5 are formed on the four sides of each device D.

  In the wafer processing method of the present invention, first, the liquid supply step shown in FIG. 2 is performed. In this liquid supply step, the liquid 14 is supplied from the liquid supply nozzle 13 connected to the liquid supply source 12 to the wafer W held on the holding table 10 to form the liquid layer 15 on the surface of the wafer W. Preferably, pure water is used as the liquid 14.

  After performing a liquid supply step, the water-soluble protective sheet sticking step shown in FIG. 3 is performed. In this water-soluble protective sheet attaching step, a water-soluble protective sheet 16 is disposed on the liquid layer 15 formed on the surface of the wafer W, as shown in FIG.

  Then, when the water-soluble protective sheet 16 is pressed against the wafer W and the liquid is removed from between the surface of the wafer W and the water-soluble protective sheet 16, the water-soluble protective sheet 16 is moved to the wafer as shown in FIG. Attached to W in close contact. The water-soluble protective sheet 16 that protrudes from the outer periphery of the wafer W may be cut along the outer periphery of the wafer.

  The water-soluble protective sheet 16 is made of, for example, PVA (polyvinyl alcohol), PEG (polyethylene glycol), or the like. When the thickness of the water-soluble protective sheet 16 is thicker than the height of the bump 5, it is preferable because the bump 5 can be completely embedded in the protective sheet 16 and the laser beam incident surface can be flattened.

  After performing the water-soluble protective sheet attaching step, the wafer W to which the water-soluble protective sheet 16 is attached is placed on the chuck table 40 of the laser processing apparatus as shown in FIG. W is sucked and held.

  In FIG. 4, the laser beam irradiation unit 20 of the laser processing apparatus includes a laser beam generating unit 24 shown in FIG. 5 housed in a casing 22, a condenser (laser head) 26 attached to the tip of the casing 22. Consists of

  As shown in FIG. 5, the laser beam generating unit 24 includes a laser oscillator 28 such as a YAG laser oscillator, a repetition frequency setting means 30, a pulse width adjusting means 32, and the power of the laser beam oscillated from the laser oscillator 28. Power adjusting means 34 for adjusting the power.

  Before performing the laser processing step, the processing area of the wafer W sucked and held on the chuck table 40 is moved directly below the imaging unit 42, and the processing area of the wafer W is imaged by the imaging unit 42.

  Then, image processing such as pattern matching for performing alignment between the condenser 26 of the laser beam irradiation unit 20 that irradiates the laser beam and the first scheduled division line S1 is executed, 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 40 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 40 is moved so that the processing start position of the first scheduled division line S1 is positioned directly below the condenser 26, and the pulse adjusted to a predetermined power by the power adjusting means 34 of the laser beam generating unit 24. The laser beam is reflected by the mirror 36 of the condenser 26 shown in FIG. 5 and then condensed on the surface of the wafer W through the water-soluble protective sheet 16 by the condenser objective lens 38.

  In this way, the chuck table 40 is moved in the X-axis direction at a predetermined feed speed (for example, 100 mm / second) while condensing the pulse laser beam on the surface of the wafer W via the water-soluble protective sheet 16 by the condenser 26. However, the laser processing groove 41 (see FIGS. 6 and 7) is formed by ablation processing along the first scheduled division line S1.

  While indexing the laser beam irradiation unit 20 in the Y-axis direction, similar laser processing grooves 41 are formed along all the first scheduled division lines S1. After the laser processing step along the first division line S1, the chuck table 40 is rotated by 90 degrees, and the same laser processing groove 41 is formed by ablation on the second division line S2.

  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 FIGS. Even when debris is generated by laser beam irradiation during the laser processing step, the debris is blocked by the water-soluble protective sheet 16 and does not adhere to the electronic circuit and bumps of the device D.

  After performing the laser processing step, as shown in FIG. 6, the cleaning water 48 is supplied from the cleaning water nozzle 46 connected to the cleaning water supply source 44 to the water-soluble protective sheet 16, and the water-soluble protective sheet 16 is applied from above the wafer W. Is dissolved in water and removed. For example, pure water is used as the cleaning water 48. A sectional view of the wafer W after the water-soluble protective sheet removing step is shown in FIG.

  In the water-soluble protective sheet removing step, for example, the wafer W to which the water-soluble protective sheet 16 is adhered is sucked and held by a spinner table of a spinner cleaning device, and purified from a cleaning water nozzle connected to the cleaning water supply source 44 and the air source. The water-soluble protective sheet 16 may be removed by cleaning the wafer W by rotating the wafer W at a low speed (for example, 300 rpm) while spraying cleaning water composed of water and air.

  After the laser processing step is completed, the wafer W in which the laser processing groove 41 is formed along the first and second divisional lines S1 and S2 is mounted on the braking device to apply an external force to the wafer W. And divided into individual devices D along the laser processing grooves 41.

  In the wafer processing method of the present embodiment described above, since the water-soluble protective sheet 16 is attached to the surface of the wafer W to form a protective film, excessive use of the protective film agent is suppressed, and protection in a short time. Film formation is possible.

  In the embodiment described above, the wafer W is directly held by the holding table 12 in the water-soluble protective sheet attaching step, but before the water-soluble protective sheet 16 is attached, the back surface of the wafer W is attached to the adhesive tape. And after sticking the outer peripheral part of an adhesive tape to a cyclic | annular flame | frame, you may make it implement each step after a water-soluble protective sheet sticking step. Thereby, the handling property of the wafer W is improved.

W Semiconductor wafer S1 First division planned line S2 Second division planned line D Device 5 Bump 10 Holding table 15 Liquid layer 16 Water-soluble protective sheet 20 Laser beam irradiation unit 24 Laser beam generation unit 26 Condenser (laser head)
30 Condensing objective lens 40 Chuck table 41 Laser processing groove

Claims (1)

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,
A liquid supply step of supplying a liquid to the surface side of the wafer to form a liquid layer on the wafer;
After performing the liquid supply step, a water-soluble protective sheet is disposed on the liquid layer on the surface of the wafer, and the water is removed from between the surface of the wafer and the water-soluble protective sheet. A water-soluble protective sheet attaching step for attaching the protective sheet to the surface of the wafer;
After performing the water-soluble protective sheet adhering step, the wafer is irradiated with a laser beam having a wavelength that is absorptive with respect to the wafer along the planned division line through the water-soluble protective sheet, and the wafer is laser-treated. A laser processing step for forming a processing groove;
A water-soluble protective sheet removing step of supplying cleaning water to the wafer and removing the water-soluble protective sheet from the wafer after performing the laser processing step;
A wafer processing method characterized by comprising:

Images