TWI815002B - Peeling method for temporarily fixed substrates, composite substrates and electronic components - Google Patents

Abstract

[Problem] Improve the peeling yield when temporarily fixing an electronic component to a temporarily fixed substrate and irradiating laser light from the side of the temporarily fixed substrate to peel the temporarily fixed substrate. [Solution] The temporary fixing substrate 2 includes a fixing surface 2a for adhering and temporarily fixing electronic components, and a bottom surface 2b located on the opposite side of the fixing surface 2a. The temporary fixation substrate 2 has an outer peripheral part 9 and an inner peripheral part 10 . The total light transmittance of the inner peripheral portion 9 is lower than the total light transmittance of the outer peripheral portion 10 and is 60% or more.

Description

Peeling method for temporarily fixed substrates, composite substrates and electronic components

The present invention relates to a temporarily fixed substrate including a fixing surface for adhering and temporarily fixing electronic components, and a bottom surface located on the opposite side of the fixing surface.

In recent years, the demand for miniaturization and height reduction of electronic components has been increasing, and silicon wafers used to manufacture electronic components are increasingly used in an extremely thin state. It is known that the thinned silicon wafer has insufficient rigidity and cannot withstand processes such as transportation, grinding, and polishing. Therefore, a method of temporarily fixing the substrate made of glass or ceramic can be used (Patent Documents 1, 2, 3).

In these prior technologies, a silicon wafer is adhered to a supporting substrate using a thermosetting resin and cooled, and then the silicon wafer is thinned by grinding or grinding. Furthermore, a step of forming multilayer wiring and the like on the surface of the silicon wafer is performed, and then the silicon wafer is peeled off from the temporarily fixed substrate and diced into a desired size. Peeling is performed by irradiating the peeling layer previously provided on the adhesive layer with laser light from the side of the temporarily fixed substrate. [Prior art documents] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2011-023438 [Patent Document 2] Japanese Patent Laid-Open No. 2010-058989 [Patent Document 3] Japanese Patent No. 5304112

[Problem to be solved by the invention]

However, when laser light is irradiated from the side of the temporarily fixed substrate to peel the temporarily fixed substrate from the silicon wafer, the degree of peeling may cause unevenness in the plane of the temporarily fixed substrate. In this case, the temporarily fixed substrate is divided into a part that can be peeled off and a part that cannot be peeled off, which may cause the silicon wafer to crack.

The inventor also tried to promote the peeling off of the entire surface of the temporarily fixed substrate by increasing the energy of the laser light. However, when the energy of laser light is increased, electronic components on the silicon wafer may be damaged.

An object of the present invention is to improve the peeling yield when an electronic component is temporarily fixed to a temporarily fixed substrate and a laser light is irradiated from the side of the temporarily fixed substrate to peel the temporarily fixed substrate. [Means used to solve problems]

The present invention relates to a temporarily fixed substrate, which includes a fixed surface for adhering and temporarily fixing electronic components, and an irradiation surface located on the opposite side of the fixed surface, wherein the temporarily fixed substrate has an outer peripheral portion and The total light transmittance of the inner peripheral part is lower than the total light transmittance of the outer peripheral part and is 60% or more.

Furthermore, the present invention relates to a composite substrate including the aforementioned temporarily fixed substrate and an electronic component adhered to the aforementioned fixed surface of the aforementioned temporarily fixed substrate.

Furthermore, the present invention relates to a method for peeling off an electronic component, in which the temporarily fixed substrate is peeled off from the electronic component by irradiating the composite substrate with laser light from the side of the irradiation surface of the temporarily fixed substrate. [Effects of the present invention]

The present inventors have studied the causes of cracks in semiconductor substrates and the like when a semiconductor substrate or the like is adhered to a temporarily fixed substrate and then laser light is irradiated from the side of the temporarily fixed substrate to peel off the temporarily fixed substrate. As a result, it is considered that the position of the crack in the semiconductor substrate or the like is not fixed, and when the laser is irradiated, stress is concentrated on a portion that is difficult to peel off, thereby causing the crack.

Therefore, the inventors tried to set the total light transmittance of the inner peripheral part of the temporarily fixed substrate to be lower than the total light transmittance of the outer peripheral part, so that when laser light is irradiated from the side of the temporarily fixed substrate, the outer peripheral part will be lower than the total light transmittance of the outer peripheral part. The inner peripheral part becomes easier to peel earlier. As a result, peeling was carried out in the radial direction from the outer peripheral part to the inner peripheral part, and it was found that the adhesive portion that temporarily fixed the substrate remained in the inner peripheral part and was eventually peeled off. As a result, experiments confirmed that almost no cracks were generated on the entire surface of the temporarily fixed substrate until the peeling was completed, and the present invention was completed.

Hereinafter, a process of temporarily fixing the electronic component to the temporarily fixed substrate and then peeling it off will be described. First, as shown in FIG. 1( a ), the adhesive layer 3 is provided on the fixing surface 2 a to which the substrate 2 ( 2A) is temporarily fixed. Label 2b refers to the irradiation surface of the laser light.

Next, as shown in FIG. 1( b ), the semiconductor substrate 7 is placed on the temporarily fixed substrate 2 ( 2A), and the adhesive layer 3 is cured to form the adhesive layer 3A, thereby obtaining the composite substrate 12 . This curing step can be carried out according to the properties of the adhesive, for example, it can be carried out by heating or ultraviolet irradiation.

Next, as shown in Fig. 2(a) , the composite substrate 12 is irradiated with laser light as shown by arrow A from the side of the irradiation surface 2b of the temporarily fixed substrate 2 (2A), and the semiconductor substrate is removed as shown in Fig. 2(b) 7 is separated from the temporarily fixed base plate 2 (2A).

Figures 3 and 4 relate to other embodiments. As shown in FIG. 3( a ), an adhesive layer 3 is provided on the fixing surface 2 a to which the substrate 2 ( 2A) is temporarily fixed. Next, as shown in FIG. 3( b ), a plurality of electronic components 4 are fixed on the fixed surface of the temporarily fixed substrate 2 ( 2A), and the adhesive layer 3 is cured to form the adhesive layer 3A. Next, as shown in FIG. 4( a ), the electronic component 4 is covered with the resin mold 6 , and the resin mold 6 also penetrates into the gap 5 between the adjacent electronic components 4 . In this way, the electronic component 4 and the resin mold 6 are fixed on the temporarily fixed substrate 2 (2A), and the composite substrate 12A is obtained. Reference numeral 6a refers to a covering layer for covering the electronic component, and reference numeral 6b refers to a filling portion for filling the gap 5 .

Next, as shown in Fig. 4(a) , the composite substrate 12A is irradiated with laser light as shown by arrow A from the side of the irradiation surface 2b of the temporarily fixed substrate 2 (2A), and the resin mold is molded as shown in Fig. 4(b) The plastic 6 and the electronic component 4 are separated from the temporarily fixed substrate 2 (2A).

Here, in the present invention, the temporarily fixed substrate has an outer peripheral part and an inner peripheral part, and the total light transmittance of the outer peripheral part is higher than the total light transmittance of the inner peripheral part. For example, when temporarily fixing the substrate 2 as shown in FIG. 5 , the fixing surface 2 a is substantially circular and has an annular outer peripheral portion 9 , an inner peripheral portion 10 and an annular middle portion 11 between them. Furthermore, when temporarily fixing the substrate 2A as shown in FIG. 6, the fixing surface 2a has a rectangular shape. Furthermore, the temporarily fixed base plate 2A has a rectangular inner peripheral portion 10, an outer peripheral portion 9 that circles along the edge portion of the temporarily fixed base plate 2A, and an intermediate portion 11 located between the two.

Here, the total light transmittance of the outer peripheral portion 9 is set to be higher than the total light transmittance of the inner peripheral portion 10 . In this way, as shown in FIGS. 2(a) and 4(a) , when the irradiation surface of the temporarily fixed substrate 2 (2A) is irradiated with laser light A, since the total light transmittance of the outer peripheral part is high, it is easy to The step of peeling off the electronic component from the temporarily fixed substrate is performed, but the peeling off of the inner peripheral portion is delayed. As a result, as shown by arrow B, peeling proceeds from the outer peripheral portion 9 toward the inner peripheral portion 10 in a circle along the edge of the fixing surface where the substrate is temporarily fixed (Figs. 5 and 6). As a result, it was found that the peeling state is easy to become uniform when viewed in the circumferential direction of the fixing surface, and there is almost no local concentration of stress, and the electronic components are less likely to be damaged during peeling.

In the present invention, the shape of the fixing surface for temporarily fixing the substrate is not particularly limited, and may be a curved shape such as a circle or an ellipse, or a polygonal shape such as a triangle, a quadrilateral, or a hexagon.

The outer peripheral portion refers to an area surrounding the fixed surface along the outer contour of the fixed surface to which the substrate is temporarily fixed. In addition, the inner peripheral part means the area including the center O of the fixed surface. Furthermore, assuming that the center of the fixing surface to which the substrate is temporarily fixed is O, a vertical line L (L1, L2) extending from the center O to two points of the outer contour of the fixing surface is assumed, and these vertical lines L (L1, L2) are The length of L2) is set to X, Y. At this time, as shown in Figures 5 and 6, a strip-shaped area with a width of 0.05X (5% of X) calculated from the outer contour of the fixed surface is defined as the outer peripheral portion. Furthermore, the distance from the center O of the fixed surface to the outline 10 a of the inner peripheral portion 10 is set to 0.2X (20% of X).

For example, in the example of FIG. 5 , the fixing surface 2 a is circular, the outer peripheral portion 9 is annular, and the inner peripheral portion 10 is circular. When the diameter of the fixing surface is set to X, the width of the outer peripheral portion 9 is set to 0.05X, and the width of the inner peripheral portion 10 is set to 0.20X. Furthermore, in the example of FIG. 6 , the fixing surface 2 a is rectangular, the outer peripheral portion 9 is strip-shaped, and the inner peripheral portion 10 is rectangular. Here, let the lengths of the vertical lines L1 and L2 extending from the center O to the outer contour 20 of the fixed surface be X and Y. At this time, the width of the outer peripheral portion 9 is 0.05Y in the vertical direction and 0.05X in the horizontal direction. Furthermore, the width of the inner peripheral portion 10 is 0.40Y in the vertical direction and 0.40X in the horizontal direction.

The total light transmittance of the temporarily fixed substrate refers to the ratio of the intensity of the emitted light irradiated from the fixed surface of the temporarily fixed substrate to the intensity of the incident light irradiated to the irradiation surface of the temporarily fixed substrate (intensity of emitted light / incident light intensity). The total light transmittance is measured according to JIS standard K7361. In addition, at this time, the wavelength distribution of the incident light is set to be the same as the wavelength distribution of the incident light when it is incident on the composite substrate and peels off the electronic component from the temporarily fixed substrate. For example, when the wavelength of the laser light used to peel off the electronic component is 300 nm, the wavelength of the incident light when measuring the total light transmittance is also 300 nm. Again, a spectrophotometer was used to measure the total light transmittance.

Specifically, when measuring the transmittance of the outer peripheral portion, a vertical line L (L1, L2) extending from the center O of the fixed surface to two points on the outer contour of the fixed surface is assumed, and the length of this vertical line is X (Y), select 12 measuring points of X/30 (Y/30) in the direction from the outer contour of the fixed surface towards the center O. At this time, the 12 measurement points are separated from each other by an angle of 30∘ with respect to the center O. Then, the total light transmittance can be measured individually for each of the 12 points, and its average value is defined as the transmittance of the peripheral portion.

Furthermore, when measuring the transmittance of the inner peripheral part, assume a vertical line L (L1, L2) extending from the center O of the fixed surface to two points on the outer contour of the fixed surface, and let the length of this vertical line be X (Y), select 12 measuring points of X/3 (Y/3) in the direction from the outer contour of the fixed surface towards the center O. At this time, the 12 measurement points are separated from each other by an angle of 30∘ with respect to the center O. Then, the total light transmittance can be measured individually for each of the 12 points, and the average value thereof is defined as the transmittance of the inner peripheral portion.

Here, from the viewpoint of the present invention, the total light transmittance of the inner peripheral part is lower than the total light transmittance of the outer peripheral part, and the difference is preferably 0.1% or more, more preferably 0.3% or more, and is Above 0.5% is particularly good. On the other hand, when the difference between the total light transmittance of the inner peripheral portion and the total light transmittance of the outer peripheral portion increases, the degree of peeling will differ, resulting in a situation where the inner peripheral portion cannot be peeled off at all. From this point of view, the difference between the total light transmittance of the inner peripheral portion and the total light transmittance of the outer peripheral portion is preferably 5.0% or less, more preferably 3.0% or less, and particularly preferably 1.0% or less.

In the present invention, the total light transmittance of the inner peripheral portion is set to 60.0% or more. If this value is low, cracks will easily occur in the inner peripheral portion during peeling. From this point of view, the total light transmittance of the inner peripheral portion is set to 60.0% or more, preferably 65.0% or more, and more preferably 70.0% or more. Furthermore, the total light transmittance of the outer peripheral part exceeds 60.0%, preferably 65.0% or more, and more preferably 70.0% or more. The light transmittance of the inner peripheral part and the light transmittance of the outer peripheral part are preferably 95.0% or less, and more preferably 90.0% or less.

The thickness of the temporarily fixed substrate 2 is preferably set to 0.3~3.0mm. By setting the thickness of the temporary fixing substrate 2 to 0.3 mm or more, mechanical strength suitable for temporary fixing can be easily ensured. Furthermore, by setting the thickness of the temporarily fixed substrate 2 to 3.0 mm or less, a suitable total light transmittance can be easily obtained.

The material for temporarily fixing the substrate is not limited in some cases, but it is preferably durable against irradiation with laser light. In a preferred embodiment, the temporarily fixed substrate is made of aluminum oxide, silicon nitride, aluminum nitride or silicon oxide. These materials are easily densified and highly resistant to chemicals.

In a preferred embodiment, the material constituting the temporarily fixed substrate is translucent alumina. In this case, it is preferable to add 100 ppm or more and 300 ppm or less magnesium oxide powder to high-purity alumina powder with a purity of 99.9% or more (preferably 99.95% or more). As such high-purity alumina powder, high-purity alumina powder manufactured by Daemyung Chemical Industry Co., Ltd. can be cited. Furthermore, the magnesium oxide powder preferably has a purity of 99.9% or more, and an average particle size of 50 μm or less.

Furthermore, in a preferred embodiment, 200 to 800 ppm of zirconium oxide (ZrO ₂ ) and 10 to 30 ppm of yttrium oxide (Y ₂ O ₃ ) are preferably added to the alumina powder as a burning aid.

The method of forming the temporarily fixed substrate is not particularly limited, and may be any method such as a doctor blade method, an extrusion molding method, or a mold casting method. It is particularly preferable to use a molding method to manufacture the base substrate.

In a preferred embodiment, a slurry containing ceramic powder, a dispersion medium and a curing agent is prepared, and the slurry is cast and solidified to obtain a shaped body. Here, in the forming stage, the release agent is applied to the mold, the mold is assembled, and the slurry is cast. Next, the slurry is solidified in the mold to obtain a shaped body, and the shaped body is peeled from the mold. Then clean the mold.

Next, the shaped body is dried, preferably fired in air and then fired in hydrogen. From the viewpoint of densification of the sintered body, the sintering temperature during sintering is preferably 1700 to 1900°C, and more preferably 1750 to 1850°C.

Furthermore, after a sufficiently dense sintered body is generated during firing, additional annealing can be performed to correct warpage. The annealing temperature is preferably 1200°C to 1900°C. Furthermore, the annealing time is preferably 1 to 6 hours.

Here, in order to make the total light transmittance of the inner peripheral portion of the temporarily fixed substrate lower than the total light transmittance of the outer peripheral portion, the firing temperature of the outer peripheral portion can be set to be higher than the firing temperature of the inner peripheral portion. To promote firing and reduce porosity. The temperature difference is preferably 5 to 200°C, and more preferably 10 to 100°C. Furthermore, by setting the sintering temperature of the outer peripheral portion to be higher than the sintering temperature of the inner peripheral portion, annealing of the outer peripheral portion can be accelerated.

Examples of adhesives include double-sided tape and hot-melt adhesives. Furthermore, various methods such as roll coating, spray coating, screen printing, and spin coating can be used to provide the adhesive layer on the temporarily fixed substrate. method.

As a semiconductor substrate, a silicon substrate that complies with JEITA or SEMI standards is preferred.

Furthermore, examples of molds for filling electronic components include epoxy resins, polyimide resins, polyurethane resins, urethane resins, etc. plastic resin.

[Example]

Prepare a slurry mixed with the following ingredients.

(raw material powder)

(dispersion medium)

‧2-ethylhexanol (2-ethylhexanol) 45 parts by weight

(binder)

‧PVB resin 4 parts by weight

(dispersant)

‧Polymer surfactant 3 parts by weight

(Plasticizer)

‧DOP 0.1 parts by weight

This slurry was formed into a strip shape using a doctor blade method and cut so that the thickness after firing became 0.9 mm and the size after firing became Φ300 mm. The obtained powder compact was calcined (preliminarily calcined) in air at 1240° C., and then the substrate was placed on a molybdenum (molybdenum) plate and placed in a gas atmosphere of hydrogen:nitrogen of 3:1. Leave it at 1800°C for 2.5 hours for firing. After that, the grinder was used for grinding, the diamond abrasive grains were used for lap processing, and the CMP liquid was used for grinding in order to obtain a thickness of 0.8 mm. Temporarily secure base plate 2.

By setting a temperature gradient for each firing temperature during firing, the porosity with internal and external differences is adjusted, thereby adjusting the total light transmittance of the inner peripheral portion 10 and the outer peripheral portion 9 of the temporarily fixed substrate 2 .

Evaluation of transmittance was performed using a spectrophotometer.

Specifically, on the straight line (vertical line) L extending in the radial direction from the outer contour 20 of the fixing surface 2a toward the center O, 12 measurement points are set at positions 10 mm (300 mm/30) away from the outer contour. Set 12 measuring points one by one at 30° intervals. Then, the average value of the 12 measured values is defined as the total light transmittance of the peripheral portion 9 . Furthermore, on a straight line extending in the radial direction from the outer contour 20 of the fixing surface 2a toward the center O, 12 measurement points are provided at positions 100 mmm (300 mm/3) away from the outer contour. Set 12 measuring points one by one at 30° intervals. Then, the average value of the 12 measured values is defined as the total light transmittance of the inner peripheral part.

Next, a peeling layer (Light-to-Heat Conversion layer manufactured by 3M Company) is formed on the temporarily fixed substrate by spin coating. Furthermore, the adhesive (LC-5320 F1035 manufactured by 3M Company) is coated on the surface of the silicon wafer (thickness: 0.775mm) by spin coating, and the temporarily fixed substrate is bonded to the silicon wafer. to obtain a composite substrate.

Thereafter, laser light A is irradiated from the side of the irradiation surface 2 b of the temporarily fixed substrate 2 to peel the temporarily fixed substrate 2 from the silicon wafer. The same experiment was repeated 20 times, and the case where the silicon wafer was cracked or the silicon wafer and the supporting substrate could not be separated was recorded as "defective". These results are shown in Tables 1, 2, and 3.

[Table 2] Example 6 7 8 Substrate thickness (mm) 0.8 0.3 3.0 Total transmittance of peripheral part (%) 60.5 70.5 60.5 Total light transmittance of inner peripheral part (%) 60.0 70.0 60.0 The total light transmittance of the outer peripheral part - the total light transmittance of the inner peripheral part (%) +0.5 +0.5 +0.5 Defects occurred (number of times) n=20 0 0 0

[table 3] Comparative example 1 2 3 4 Substrate thickness (mm) 0.8 0.8 0.8 0.8 Total transmittance of peripheral part (%) 70.0 69.9 69.5 50.5 Total light transmittance of inner peripheral part (%) 70.0 70.0 70.0 50.0 The total light transmittance of the outer peripheral part - the total light transmittance of the inner peripheral part (%) +0.0 -0.1 -0.5 +5.0 Defects occurred (number of times) n=20 1 1 2 20

It can be seen from Table 1 and Table 2 that when the outer peripheral part and the inner peripheral part of the temporarily fixed substrate satisfy the concept of the present invention, the occurrence of cracks and peeling defects in the silicon wafer and the temporarily fixed substrate can be suppressed.

It can be judged from Comparative Examples 1, 2, and 3 in Table 3 that when the total light transmittance of the inner peripheral portion of the temporarily fixed substrate is equal to or greater than the total light transmittance of the outer peripheral portion, there is a problem when peeling off the silicon wafer. Problems such as cracks and poor peeling may occur. In Comparative Example 4, although the total light transmittance of the inner peripheral part is lower than the total light transmittance of the outer peripheral part, the total light transmittance of the inner peripheral part is less than 60%, so the problem of peeling failure occurs.

2 (2A): Temporarily fix the substrate 2a: Fixed surface 2b:Irradiated surface 3,3A: Adhesive layer 4: Electronic components 5: Gap 6: Resin molding 6a: Covering layer 6b: Filling part 7:Semiconductor substrate 9: Peripheral part 10: Inner circumference part 10a:Contour 11:Middle part 12,12A: Composite substrate 20:Outside contour A,B:arrow L,L1,L2: vertical lines O:center X: diameter/length Y:length

[Fig. 1] (a) shows a state where the adhesive 3 is provided on the fixing surface 2a of the temporarily fixed substrate 2 (2A), and (b) shows the fixing surface 2a of the temporarily fixed substrate 2 (2A). The semiconductor substrate 7 is adhered to it. [Fig. 2] (a) shows a state in which the composite substrate is irradiated with laser light A from the side of the temporarily fixed substrate 2 (2A), and (b) shows the semiconductor substrate 7 being separated from the temporarily fixed substrate 2 (2A). status. [Fig. 3] (a) shows a state where the adhesive 3 is provided on the fixing surface 2a of the temporarily fixed substrate 2 (2A), and (b) shows the fixing surface 2a of the temporarily fixed substrate 2 (2A). The electronic component 4 is adhered to it. [Fig. 4] (a) shows a state in which the composite substrate 12A is irradiated with laser light A from the side of the temporarily fixed substrate 2 (2A), and (b) shows the electronic component 4 and the resin molding from the temporarily fixed substrate 2 (2A) The state of separation. [Fig. 5] is a plan view showing the temporarily fixed substrate 2. [Fig. 6] is a plan view showing the temporarily fixed substrate 2A.

2(2A): Temporarily fix the substrate

2a: Fixed surface

2b:Irradiated surface

3A: Adhesive layer

7:Semiconductor substrate

9: Peripheral part

10: Inner circumference part

11:Middle part

12: Composite substrate

A:arrow

Claims (7)

A temporarily fixed substrate, which includes a fixed surface for adhering and temporarily fixing electronic components, and an irradiation surface located on the opposite side of the fixed surface, wherein the temporarily fixed substrate has an outer peripheral part and an inner peripheral part, and the aforementioned temporarily fixed substrate The total light transmittance of the inner peripheral part is lower than the total light transmittance of the outer peripheral part and is 60% or more. The temporarily fixed substrate as claimed in claim 1, wherein the temporarily fixed substrate is made of glass, silicon or ceramics. The temporarily fixed substrate according to claim 2, wherein the temporarily fixed substrate is made of translucent alumina. A composite substrate includes the temporarily fixed substrate according to any one of claims 1 to 3, and an electronic component adhered to the fixed surface of the temporarily fixed substrate. The composite substrate according to claim 4 includes a semiconductor substrate adhered to the fixed surface, and the electronic component is formed on the semiconductor substrate. The composite substrate according to claim 4 includes a molded resin adhered to the fixing surface, and the electronic component is fixed in the molded resin. A method for peeling off an electronic component as described in any one of claims 4 to 6, wherein the composite substrate is irradiated from the side of the irradiation surface of the temporarily fixed substrate. Laser light peels off the temporarily fixed substrate from the electronic component.

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