JP5391158B2 - Wafer sticking adhesive sheet and wafer processing method using the same - Google Patents

Description

  The present invention relates to a wafer sticking pressure sensitive adhesive sheet and a wafer processing method using the same, and more specifically, in wafer processing using laser light, a wafer sticking pressure sensitive adhesive capable of irradiating laser light from the wafer sticking pressure sensitive adhesive sheet side. The present invention relates to a sheet and a wafer processing method using the sheet.

  In recent years, the demand for light-emitting diodes (hereinafter referred to as “LEDs”), which are power-saving and have a long life compared with conventional fluorescent lamps, is rapidly increasing as light sources for liquid crystal displays and lighting equipment. Sapphire is mainly used as a substrate for LED formation, and in the LED manufacturing process, after forming a light emitting layer such as gallium nitride on the sapphire substrate, it is thinned from the back side of the substrate, and is then separated into LED chips. A process to implement and implement is adopted.

  The sapphire substrate is generally harder than silicon wafers used for general semiconductor devices, and the LED device is a light-emitting element, so the allowable width of cracks is narrower than general semiconductor wafers. Rather than individualizing with a rotating blade, which is a separate process, a laser processing groove is formed by irradiating a laser beam along the street formed on the wafer, and a method of breaking along the laser processing groove is applied. (For example, refer to Patent Document 1).

However, in devices where a metal film or organic film is formed on the opposite side of the circuit surface, it may not be desired to apply an adhesive sheet to the film forming surface. In such devices, an adhesive sheet is applied to the circuit surface side. It was necessary to divide the wafer into individual pieces.

  In such a process, the circuit side with the adhesive sheet attached is monitored with a CCD or the like to check the streets between the circuits, and the operation of the dicing device is synchronized with the position information read from the CCD, Since it is necessary to perform alignment (alignment) based on this, the adhesive sheet is required to have high visible wavelength region light transmittance.

  On the other hand, it is also proposed to irradiate a laser beam through a dicing sheet affixed to the circuit surface side to dice the wafer, and an adhesive sheet that is permeable to infrared wavelength laser light has also been proposed ( For example, see Patent Document 2).

JP-A-10-305420 JP 2007-123404 A

  However, in general, the base resin film side surface of the semiconductor processing tape is usually roughened from the viewpoint of blocking prevention and handling in the wound state, so when a laser is incident from the film side Scattered by the irregularities, there was not enough permeability.

  Moreover, in patent document 2, since several adhesive sheets were used, there existed the subject of the cost side. In addition, the pressure-sensitive adhesive sheet of Patent Document 2 specifies a substrate film having a total reflection transmittance of 1064 nm of 70% or more and a parallel light transmittance of 30% or more. For monitoring, it is preferable that the permeability is higher.

  The present invention has been made in view of the above-described problems, and the purpose thereof is to align the circuit surface from the pressure-sensitive adhesive sheet side and the pressure-sensitive adhesive sheet even when the circuit surface of the wafer is bonded to the pressure-sensitive adhesive sheet. It is possible to form a modified layer by incidence of infrared wavelength laser light from the side.

That is, the present invention provides the following inventions.
(1) and the base resin film, a pressure-sensitive adhesive sheet where the pressure-sensitive adhesive layer is formed on the base resin film on state, and are more than 80% parallel light transmittance in the wavelength range of 400～1100Nm, the group The arithmetic average roughness Ra of the surface opposite to the surface on which the pressure-sensitive adhesive layer of the material resin film is formed is 0.1 to 0.3 μm, and alignment is performed by irradiating laser light in the visible wavelength region. A pressure-sensitive adhesive sheet for attaching to a wafer, which is used for forming a modified layer by irradiating a laser beam in an infrared wavelength region .
( 2 ) From the circuit surface side which is the side to which the wafer sticking adhesive sheet described in (1) is stuck to the circuit surface of the wafer on which the circuit is formed, and the side to which the wafer sticking adhesive sheet is adhered. Irradiating the wafer with laser light in the visible wavelength region, aligning the wafer, and laser light in the infrared wavelength region from the circuit surface side to which the adhesive sheet for sticking the wafer is adhered A laser processing step of performing laser processing to form a modified layer serving as a starting point for breakage along the street formed on the wafer, and pushing up from the opposite side of the wafer sticking surface of the wafer sticking adhesive sheet A wafer processing method comprising: expanding a member to expand the pressure-sensitive adhesive sheet for wafer sticking and expanding the wafer into individual pieces.
( 3 ) The wafer sticking pressure-sensitive adhesive sheet according to ( 1 ) is stuck to the lower surface of the ring frame by the pressure-sensitive adhesive layer, and the wafer is stuck to the pressure-sensitive adhesive layer. ( 2 ) The wafer processing method according to ( 2 ).

  According to the present invention, even when the circuit surface of the wafer is attached to the adhesive sheet, it is possible to form a modified layer by aligning the circuit surface from the adhesive sheet side and incident infrared wavelength laser light from the adhesive sheet side. Become.

The schematic sectional drawing which shows embodiment of the adhesive sheet for wafer sticking of this invention. The schematic sectional drawing explaining the cleavage process using the adhesive sheet for wafer sticking of this invention. The schematic sectional drawing explaining the expanding process using the adhesive sheet for wafer sticking of this invention. The graph which shows the relationship between the surface roughness and parallel light transmittance of an Example and a comparative example.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of an adhesive sheet 1 for sticking a wafer according to the present invention. The adhesive layer 5 is formed on the base resin film 3 and the base resin film 3, and the wafer 7 is fixed on the adhesive layer 5. The parallel light transmittance of the adhesive sheet for sticking a wafer is 80% or more in the region of 400 to 1100 nm. Moreover, the average surface roughness Ra on the arrow A side of the base resin film 3 is 0.1 to 0.3 μm. Here, the surface roughness Ra means the arithmetic average roughness Ra (JIS B 0601-2001).

  The material of the base resin film 3 is not particularly limited as long as the transmittance is as described above, but is preferably polyolefin, ethylene copolymer, soft polyvinyl chloride, semi-rigid polyvinyl chloride, polyester, polyurethane. Polymers such as polyamide, polyimide, natural rubber and synthetic rubber are applied. These may be a single layer film or a multilayer film. Specific examples of the ethylene copolymer include ethylene-vinyl acetate (VA) copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer, ethylene- ( Examples thereof include (meth) acrylic acid ester copolymer rubber, ethylene- (meth) acrylic acid ester- (meth) acrylic acid copolymer rubber (acrylic rubber), and ethylene / α-olefin copolymer. Further, the base resin film 3 is preferably a thermoplastic resin when it is molded by an extruder.

  The surface roughness Ra of the base resin film for realizing sufficient parallel light transmittance is 0.3 μm or less, more preferably 0.25 μm or less, and if larger than that, incident light is scattered, Sufficient transmittance cannot be obtained.

In devices where a metal film or organic film is formed on the opposite side of the wafer circuit surface, it may not be desired to attach an adhesive sheet to these film formation surfaces. In such devices, an adhesive sheet is applied to the circuit surface side. Thus, it is necessary to divide the wafer. However, in such a process, the circuit surface side to which the adhesive sheet is affixed is monitored with a CCD or the like to check the streets between the circuits, and the operation of the dicing device for cutting is synchronized with the position information read from the CCD. Since it is necessary to perform alignment (alignment) based on the street on the circuit surface side, the adhesive sheet is required to have high visible wavelength region light transmittance.
In order to perform alignment with a CCD or the like, the parallel light transmittance in the visible wavelength region is preferably 80% or more. Below that, accurate alignment is not possible.

FIG. 2 shows a singulation process by cleavage, which is called breaking division after alignment. The wafer 7 has an adhesive sheet 1 attached to the circuit surface side. Laser light in the visible wavelength region is irradiated from the circuit surface side (adhesive sheet 1 side), alignment is performed based on the streets on the circuit surface side, and the streets between the circuits from the opposite side of the circuit surface based on the alignment information A laser beam 9 is incident, half-cut is performed, and a groove 11 serving as a starting point of cleavage is formed. As this laser beam 9, generally, a laser beam in the ultraviolet wavelength region is used. Thereafter, laser light in the visible wavelength region is again irradiated from the circuit surface side (adhesive sheet 1 side), the streets between the circuits are confirmed, alignment is performed, and the pressing blade 13 is applied from the adhesive sheet 1 side according to the streets. Thus, the chip is cleaved and separated into individual pieces.
Since both of these two alignments are performed by reading the street with a CCD or the like on the circuit surface side, the parallel light transmittance in the visible wavelength region needs to be 80% or more.

On the other hand, after alignment, in the case of including an individualization step of irradiating infrared laser light from the pressure-sensitive adhesive sheet side to form a modified layer on the wafer as in Patent Document 2, other than the visible wavelength region (400 to 760 nm) In addition, transparency in the infrared wavelength region (760 to 1100 nm, particularly around 1064 nm) is also required. The wafer may be attached to the pressure-sensitive adhesive sheet on the circuit surface side, or may be attached to the pressure-sensitive adhesive sheet on the opposite side as in Patent Document 2, but the required transmittance is The same.
In order to form a sufficient modified layer, the parallel light transmittance in the wavelength region from the visible wavelength to 1100 nm is required to be 80% or more. Below that, a sufficient modified layer cannot be formed, and individual wafers cannot be formed. It cannot be tidy up.
In addition, when the test element group (TEG) is provided on the circuit surface of the wafer, or in the case of a wafer with aluminum wiring, the infrared laser beam cannot pass through these materials, so the laser is also penetrated into the wafer. The focal point of light does not reach and the modified layer cannot be formed. Therefore, the surface opposite to the circuit surface of the wafer is attached to the adhesive sheet. On the other hand, when a metal film or the like is formed on the surface (wafer back surface) opposite to the circuit surface of the wafer, the modified layer cannot be formed because infrared laser light does not pass through from the wafer back surface side. Therefore, the circuit surface of the wafer is attached to the adhesive sheet. Another reason for bonding the circuit surface side of the wafer to the pressure-sensitive adhesive sheet is to protect the circuit surface from microdust generated when the wafer is divided.

By the way, the surface roughness Ra of the base film is a factor that affects the ease of scattering of the laser beam described above, but also affects the ease of handling of the pressure-sensitive adhesive sheet. It is necessary to appropriately control the roughness during film forming.
The pressure-sensitive adhesive sheet is generally handled in the form of a scroll, but the surface roughness Ra on the arrow A side of the base resin film 3 is preferably 0.1 μm or more. When this Ra is too small, when the pressure-sensitive adhesive sheet is drawn out from the scroll shape, the pressure-sensitive adhesive sheets stick to each other, resulting in poor workability.

Further, the surface roughness Ra of the base film is a factor that affects the ease of scattering of the laser beam described above, but at the same time affects the slipperiness of the expanding ring in the expanding step.
FIG. 3 is a schematic cross-sectional view illustrating an expanding process using the adhesive sheet for adhering a wafer according to the present invention. A wafer sticking adhesive sheet 1 is stuck to the lower surface of the ring frame 21 by an adhesive layer 5. In addition, the wafer 7 (already separated into chips 15 in FIG. 3) is adhered to the adhesive layer 5 and bonded and fixed to the ring frame 21. The wafer 7 may be affixed to the adhesive sheet 1 on the circuit surface side, or may be affixed to the adhesive sheet 1 on the side opposite to the circuit surface.
As shown in FIG. 3, the expanding process here refers to the adhesive sheet 1 on which chips 15 separated by a laser beam and external stress are placed, pulled down by a pressing tool 17 and an expanding ring 19, and picked up. This is a process for opening the chip interval to facilitate the process.
Further, as described above, the pressure-sensitive adhesive sheet 1 on which a wafer having a modified layer formed by irradiation with infrared laser light is drawn and stretched by the pulling pressing tool 17 and the expanding ring 19, and the wafer 7 is made into individual chips 15. It also refers to the process of cutting and separating. At this time, the surface roughness Ra on the arrow A side of the base resin film 3 is preferably 0.1 μm or more. If this Ra is too small, the sliding with the expanding ring 19 is deteriorated, so that only the contact portion expands locally, so that a sufficient chip interval or sufficient cutting and separation cannot be obtained.

  The surface of the base resin film that contacts the pressure-sensitive adhesive layer may be subjected to corona treatment in order to improve adhesion. The thickness of the base resin film 3 is not particularly limited, but is preferably 30 to 200 μm, particularly preferably 50 to 150 μm.

  The pressure-sensitive adhesive layer 5 is preferably an acrylic layer, but is not limited thereto, and can be formed of various pressure-sensitive adhesives. As such an adhesive, for example, an adhesive having a base polymer such as rubber, silicone, or polyvinyl ether may be used.

  In order to add cohesion to these base polymers, a crosslinking agent can be blended. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a metal chelate-based crosslinking agent, an aziridine-based crosslinking agent, and an amine resin corresponding to the base polymer. Further, the pressure-sensitive adhesive can contain various additive components as desired within the range in which the object of the present invention is not impaired.

  As the pressure-sensitive adhesive, a radiation curable or heat-foamed pressure-sensitive adhesive can be used. As the radiation curable adhesive, it is possible to use an adhesive that is cured by ultraviolet rays, electron beams, etc., and easily peels off at the time of peeling. An adhesive that easily peels can be used. As the radiation curable pressure-sensitive adhesive, for example, those described in JP-B-1-56112 and JP-A-7-135189 are preferably used, but are not limited thereto. In the present invention, it is preferable to use an ultraviolet curable adhesive. In that case, it is only necessary to have a property of being cured by radiation to form a three-dimensional network. For example, at least two photopolymerizations in a molecule relative to a normal rubber-based or acrylic pressure-sensitive base resin (polymer). A compound comprising a low molecular weight compound having a reactive carbon-carbon double bond (hereinafter referred to as a photopolymerizable compound) and a photopolymerization initiator is used.

  The above rubber-based or acrylic base resins are natural rubber, rubber polymers such as various synthetic rubbers, or poly (meth) acrylic acid alkyl esters, (meth) acrylic acid alkyl esters, (meth) acrylic acid alkyl esters. And an acrylic polymer such as a copolymer of the above and other unsaturated monomer copolymerizable therewith.

  Moreover, an initial stage adhesive force can be set to arbitrary values by mixing an isocyanate type hardening | curing agent in said adhesive. Specific examples of such a curing agent include polyvalent isocyanate compounds such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane. -4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, Lysine isocyanate and the like are used.

In the case of an ultraviolet curable pressure-sensitive adhesive, by mixing a photopolymerization initiator in the pressure-sensitive adhesive, it is possible to reduce the polymerization curing time and the amount of ultraviolet irradiation by ultraviolet irradiation. Specific examples of such a photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloranthraquinone and the like can be mentioned.
Although the thickness in particular of an adhesive layer is not restrict | limited, Preferably it is 4-30 micrometers, Most preferably, it is 5-25 micrometers.

  According to the pressure-sensitive adhesive sheet of the present invention, since the parallel light transmittance in the visible light region is high, even when the circuit surface of the wafer is bonded to the pressure-sensitive adhesive sheet, the circuit surface side on which the pressure-sensitive adhesive sheet is bonded is monitored with a CCD or the like. Thus, the streets between the circuits can be confirmed, and the operation of the dicing device can be synchronized with the position information read from the CCD, and alignment (alignment) can be performed based on the streets on the circuit surface side.

  Further, according to the present invention, since it has a sufficient parallel light transmittance, the laser beam is not scattered, and a laser beam is irradiated through an adhesive sheet affixed to the circuit surface side. Can be formed.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples. In addition, the adhesive and base material constituent resin used in Examples and Comparative Examples are as follows.

  The pressure-sensitive adhesive sheet shown in Table 1 was prepared, and the parallel light transmittance and the average surface roughness on the side opposite to the pressure-sensitive adhesive layer were measured.

Each material shown in Table 1 was produced as follows.
-Preparation of base film for adhesive sheet (A) Polyethylene resin "NUC-8122" manufactured by Nihon Unicar Company
(B) Sumitomo Chemical's EMMA resin “ACRIFT WD201”
(C) Sumitomo Chemical's ethylene vinyl acetate copolymer resin “Evaate”
(D) Propylene-based thermoplastic elastomer "Zeras" manufactured by Mitsubishi Chemical Corporation
Was used to form a film having a thickness of 100 μm.
During molding, the surface to which the adhesive was not applied was subjected to a rough surface treatment to adjust the surface roughness.

Preparation of pressure-sensitive adhesive sheet The pressure-sensitive adhesive described in the column of the pressure-sensitive adhesive layer in Table 1 was applied to the base resin film obtained by preparing the base film of the pressure-sensitive adhesive sheet so as to have a thickness of 20 μm.
In addition, the composition of each adhesive described in Table 1 is as follows.
・ Non-UV curable adhesive (adhesive E):
Acrylic copolymer 100 parts by weight Curing agent 2 parts by weight UV curable adhesive (adhesive F):
Acrylic copolymer 100 parts by weight Curing agent 2 parts by weight Acrylate oligomer 150 parts by weight Photopolymerization initiator 2 parts by weight In addition, the acrylic copolymer comprises 2-ethylhexyl acrylate, methyl acrylate, and 2-hydroxyethyl acrylate. A copolymer was used. The weight average molecular weight is 200,000.
As the curing agent, Coronate L manufactured by Nippon Polyurethane Co., Ltd. was used.
The product name AD-PMT manufactured by Shin-Nakamura Chemical Co., Ltd. was used as the acrylate oligomer.
As a photopolymerization initiator, Irgacure 184 manufactured by Ciba Geigy Japan was used.

<Parallel light transmittance / total light transmittance>
The parallel light transmittance and total light transmittance of the pressure-sensitive adhesive sheet were measured using a UV-3101 spectrophotometer manufactured by Shimadzu Corporation. The lowest transmittance in the measurement range of 400 to 1100 nm is shown in the table.

<Arithmetic surface roughness Ra>
The arithmetic average roughness Ra on the side of the pressure-sensitive adhesive sheet on which the adhesive is not applied is measured at N = 10 using a surface roughness measuring instrument (Surf Test SJ-301) manufactured by Mitutoyo, and the average value is obtained. It was.

<Alignment>
A ground silicon wafer having a diameter of 8 inches and a thickness of 100 μm was stuck on the pressure-sensitive adhesive sheet surface of the pressure-sensitive adhesive sheet shown in Table 1 so that the ground wafer circuit surface was a sticking surface. An 8-inch frame was used as the ring frame.
This was installed in the laser processing apparatus ML200 manufactured by Tokyo Seimitsu Co., Ltd., and alignment was performed from the adhesive sheet side.

<Chip breakability>
A ground silicon wafer having a diameter of 8 inches and a thickness of 100 μm was stuck on the pressure-sensitive adhesive sheet surface of the pressure-sensitive adhesive sheet shown in Table 1 so that the ground surface of the ground wafer was affixed. An 8-inch frame was used as the ring frame.
This is installed in the laser processing equipment ML200 manufactured by Tokyo Seimitsu Co., Ltd., and laser light is incident from the pressure-sensitive adhesive sheet side so that the focal point matches the inside of the wafer, and along the planned cutting line where the chip size becomes 5 mm × 5 mm Thus, a modified region by multiphoton absorption was formed. Thereafter, using an expanding device attached to the laser processing device ML200, the adhesive sheet was stretched at a withdrawal amount of 20 mm and an expanding speed of 10 mm / s, and a chip cutting / separating step was performed.
Details of the laser processing conditions were as follows.

<Laser>
Light source: Semiconductor laser excitation Nd: YAG laser Wavelength: 1064 nm
Laser light spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ²
Oscillation form: Q switch pulse repetition frequency: 100 kHz
Pulse width: 30ns
Output: 20 μJ / pulse laser light quality: TEM00 40
Polarization characteristics: linearly polarized light

<Condensing lens>
Magnification: 50 times NA: 0.55
Transmittance with respect to laser light wavelength: 60% <Movement speed of mounting table on which substrate is mounted>
Movement speed: 100mm / sec

  As shown in Table 1, the wafer adhesive pressure-sensitive adhesive sheets of Examples 1 to 8 show higher transmittance than the wafer adhesive pressure-sensitive adhesive sheets of Comparative Examples 1 to 8, and the parallel light transmittances of Examples 1 to 8 are as follows. It was 80% or more. Moreover, although the adhesive sheet | seats for wafer sticking of Examples 1-8 were able to perform the expansion parting after the modification layer formation by an infrared laser without a problem, in Comparative Examples 1-4, it was not partly parted. This is because the laser for forming the modified layer did not transmit sufficiently due to the low parallel light transmittance of Comparative Examples 1 to 4. Further, in Comparative Examples 5 to 8 having a low parallel light transmittance, a reformed layer can hardly be formed. Therefore, a large load is applied to the wafer during expansion, and the wafer is cracked. Despite almost no difference in the total light transmittance between Examples 1 to 8 and Comparative Examples 1 to 4, there was a difference in fragmentation and alignment. It turns out that the effect cannot be realized.

  Moreover, Examples 1-8 and Comparative Examples 1-8 were plotted in FIG. As shown in FIG. 4, the numerical value of the surface roughness Ra of the pressure-sensitive adhesive sheet and the parallel light transmittance of the pressure-sensitive adhesive sheet show a close relationship regardless of the material, and the surface roughness Ra is 0.3 μm or less. It can be seen that high parallel light transmittance is exhibited.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

DESCRIPTION OF SYMBOLS 1 ......... Adhesive sheet 3 ......... Base resin film 5 ......... Adhesive layer 7 ......... Wafer 9 ......... Laser light 11 ......... Groove 13 ......... Pressure blade 15 ......... Chip 17 ... ...... Pushing tool 19 ......... Expanding ring 21 ......... Ring frame

Claims (3)

A base resin film, and an adhesive sheet having an adhesive layer formed on the base resin film,
Der 80% or more parallel light transmittance in the wavelength range 400~1100nm is,
The arithmetic average roughness Ra of the surface opposite to the surface on which the pressure-sensitive adhesive layer of the base resin film is formed is 0.1 to 0.3 μm,
An adhesive sheet for sticking to a wafer, which is used for alignment by irradiating a laser beam in a visible wavelength region and forming a modified layer by irradiating a laser beam in an infrared wavelength region . The process of sticking the adhesive sheet for wafer sticking according to claim 1 on the circuit surface of the wafer on which the circuit is formed;
Irradiating the wafer with laser light in the visible wavelength region from the circuit surface side, which is the side to which the wafer sticking adhesive sheet is adhered, and aligning the wafer;
Irradiating the wafer with laser light in the infrared wavelength region from the circuit surface side that is the side to which the adhesive sheet for sticking the wafer is adhered, and a modified layer serving as a fracture starting point along the street formed on the wafer A laser processing step for applying laser processing to be formed;
Expanding the wafer sticking adhesive sheet by raising the push-up member from the opposite side of the wafer sticking surface of the wafer sticking adhesive sheet, and expanding the wafer into individual pieces,
A method for processing a wafer, comprising: Wafer sticking pressure-sensitive adhesive sheet according to claim 1, which is adhered to the lower surface of the ring frame by the adhesive layer, the wafer is claim 2, characterized in that it is adhered to the pressure-sensitive adhesive layer 2. A method for processing a wafer according to 1.

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