KR102803860B1 - Apparatus and method for transferring micro device - Google Patents

Abstract

The present invention relates to a micro-element transfer device and transfer method capable of minimizing damage quickly and precisely using an ultrashort pulse laser. The micro-element transfer device includes a laser irradiation unit that irradiates a femtosecond pulse laser, and a carrier on which a micro-element is adhered and which detaches the micro-element when irradiated with an ultrashort pulse laser. With this configuration, an effect of improving transfer precision can be obtained by forming a blister with a high aspect ratio using an ultrashort pulse laser.

Description

{APPARATUS AND METHOD FOR TRANSFERRING MICRO DEVICE}

The present invention relates to a micro-element transfer device and a transfer method, and more specifically, to a micro-element transfer device and a transfer method capable of minimizing damage quickly and precisely using an ultrashort pulse laser.

Recently, in the fields of micro-devices such as micro LED (light emitting diode) and thin wafer packaging, a technology for mass transferring LED chips from a source substrate to a target substrate has been required. For this purpose, various transfer techniques have been proposed, but laser-based transfer, which has high process speed, selective transfer, and area expandability, is attracting attention.

Micro LEDs are generally manufactured with a chip size of 10 to 100 μm and can be applied to all optical applications that require low power consumption, miniaturization, and light weight.

By manufacturing LED chips in this way to be tens of microns in size, we can overcome the disadvantage of inorganic materials that break when bent, and can be widely used in flexible displays, smart fibers that combine fibers and LEDs, medical devices that can be attached to or inserted into the human body, bio-contact lenses, HMDs (Head Mounted Displays), and wireless communications.

However, in order for micro LED light sources to be applied in these various application fields, the development of a process technology for transferring individual or arrayed micro LED chips onto a flexible substrate based on flexible materials/elements is a top priority.

The high-speed laser transfer process is a technology that can transfer thin film chips of 10㎛ or less at high speed with high precision without damage. High-speed transfer is possible based on high-speed pulse laser and high-speed beam control.

Meanwhile, known laser thermal transfer mechanisms include ablation transfer, thermal transfer mechanism, and thermal mechanical transfer.

In the ablation transfer mechanism, a sacrificial layer is vaporized by laser ablation and the chip can be transferred using the vapor pressure generated thereby. However, since it is difficult to control the strength and shape of the vapor pressure, it is difficult to secure transfer alignment and there is also a risk of damage to the chip.

In the thermal transfer mechanism, the adhesive strength of the adhesive layer is reduced by the laser heat, and the chip can be transferred by this reduction in adhesive strength and the gravity of the chip, but it has the disadvantage of being sensitive to the adhesive layer and laser conditions, and thus has a high probability of transfer failure.

On the other hand, in the thermomechanical transfer mechanism, when the laser light is absorbed by the polymer-based absorbing layer of the DRL (Dynamic Release Layer), which consists of two layers of an absorbing layer and an adhesive layer, the generated bubbles push out the chip, and the chip attached to the adhesive layer is transferred to the substrate due to the decrease in the bonding area and gravity. This is a high-speed process, and the laser is not directly transmitted to the chip, so it is non-damaging, and it is transmitted to the substrate, so precise positioning is possible.

However, as the size of the chips and the distance between the chips become smaller due to the demand for high resolution, there is a problem that precise transfer becomes difficult due to interference between neighboring chips due to the size of the bubbles (blisters) generated by absorbing the laser light.

Korean Patent Registration No. 10-2160225 (2020.09.21)

The present invention has been created to solve the above problems, and its purpose is to provide a micro-element transfer device and transfer method capable of improving transfer precision by forming a high aspect ratio blister using an ultrashort pulse laser.

In order to achieve the above-mentioned purpose, a micro-element transfer device according to a preferred embodiment of the present invention comprises: a laser irradiation unit that irradiates an ultrashort pulse laser; and a carrier on which a micro-element is adhered and which detaches the micro-element when the ultrashort pulse laser is irradiated.

For example, the laser irradiation unit may be configured to irradiate an ultrashort pulse laser having a wavelength of 500 to 3,000 nm.

In addition, the laser irradiation unit can be configured to irradiate an ultrashort pulse laser having a pulse width of 10 fs to 100 ps.

As another example, the laser irradiation unit may be configured to irradiate a femtosecond pulse laser having a wavelength of 900 to 3,000 nm.

In addition, the laser irradiation unit can be configured to irradiate a femtosecond pulse laser having a pulse width of 10 to 800 fs.

The carrier may include a base layer through which a laser is transmitted; an adhesive layer formed on the base layer and to which a micro device is adhered; and a blister layer provided between the base layer and the adhesive layer, which expands when irradiated with an ultrashort pulse laser to deform the adhesive layer and cause the micro device to detach.

With this configuration, the ultrashort pulse laser can be nonlinearly absorbed in a specific region inside the blister layer after passing through a portion of the blister layer to form a blister with a high aspect ratio, thereby deforming the adhesive layer and causing the micro device to detach.

Here, the diameter of the blister formed in the blister layer can be formed smaller than the diameter of the femtosecond pulse laser beam irradiated onto the blister layer.

For example, by irradiating the blister layer with a femtosecond pulse laser beam having a diameter of 40 μm at an energy density of 0.4 to 2.0 J/cm ² , a blister having a diameter of 15 to 35 μm can be formed.

At this time, a femtosecond pulse laser can be irradiated onto the blister layer to form a blister having an aspect ratio (height/diameter) of 0.7 to 1.1.

In order to achieve the above purpose, a micro-element transfer method according to a preferred embodiment of the present invention may include a picking step for transferring a micro-element placed on a source substrate to an adhesive portion of a carrier; and a placing step for transferring the micro-element to the target substrate by irradiating the carrier with an ultrashort pulse laser after placing the carrier on a target substrate.

For example, the placing step may be performed by irradiating an ultrashort pulse laser having a wavelength of 500 to 3,000 nm.

Additionally, the above-mentioned placing step can be performed to irradiate an ultrashort pulse laser having a pulse width of 10 fs to 100 ps.

As another example, the placing step may be performed by irradiating a femtosecond pulse laser having a wavelength of 900 to 3,000 nm.

Additionally, the above-mentioned placing step can be performed by irradiating a femtosecond pulse laser having a pulse width of 10 to 800 fs.

In this way, the ultrashort pulse laser irradiated in the placing step can be made to pass through a part of the blister layer formed on the carrier and then be nonlinearly absorbed in a specific area inside the blister layer to form a blister with a high aspect ratio, thereby deforming the adhesive layer and causing the micro device to detach.

Here, the diameter of the blister formed in the blister layer can be formed smaller than the diameter of the ultrashort pulse laser beam irradiated onto the blister layer.

For example, the placing step may be performed by irradiating the blister layer with a femtosecond pulse laser having a diameter of 40 μm at an energy density of 0.4 to 2.0 J/cm ² to form a blister having a diameter of 15 to 35 μm.

At this time, the placing step can be performed by irradiating the blister layer with a femtosecond pulse laser to form a blister having an aspect ratio (height/diameter) of 0.7 to 1.1.

According to the micro-element transfer device and transfer method of the present invention, it is possible to obtain the effect of improving transfer precision by forming a blister with a high aspect ratio using an ultrashort pulse laser.

Figure 1 is a schematic diagram illustrating a thermal mechanical transfer mechanism.
Figure 2 is a schematic diagram showing a state in which a laser is linearly absorbed in a blister layer by a nanosecond laser.
Figure 3 is a drawing schematically illustrating a state in which a micro element is transferred by a conventional thermal mechanical transfer device.
FIG. 4 is a drawing schematically illustrating a state in which a micro device is transferred by a micro device transfer device according to an embodiment of the present invention.
Figure 5 is a schematic diagram showing a state in which a laser is nonlinearly absorbed in a blister layer by a femtosecond pulse laser.
Figure 6 is a graph showing the diameter of blisters formed by nanosecond laser and femtosecond pulse laser according to energy density.
Figure 7 is a graph showing the aspect ratio (height/diameter) of blisters formed by nanosecond lasers and femtosecond pulse lasers according to energy density.
Figure 8 is a photograph showing the shape of a blister formed by a nanosecond laser and a femtosecond pulse laser according to energy density.
Figure 9 is a flow chart schematically showing a micro device transfer method according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

The present invention may have various modifications and embodiments, and specific embodiments are illustrated in the drawings and specifically described in the detailed description. This is not intended to limit the present invention to specific embodiments, but should be interpreted to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

The terminology used in this application is only used to describe specific embodiments and is not intended to limit the invention. Singular expressions may include plural expressions unless the context clearly indicates otherwise.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries, such as those defined in common dictionaries, may be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and may not be interpreted in an idealized or overly formal sense, unless explicitly defined in this application.

FIG. 1 is a drawing schematically illustrating a thermomechanical transfer mechanism, FIG. 2 is a drawing schematically illustrating a state in which a laser is linearly absorbed in a blister layer by a nanosecond laser, and FIG. 3 is a drawing schematically illustrating a state in which a micro element is transferred by a conventional thermomechanical transfer device.

Referring to FIGS. 1 to 3, a thermal mechanical transfer mechanism can attach a micro-element (C) to a source substrate (not shown) through an adhesive layer (13) provided on a carrier (10), and, while positioned on the upper side of a target substrate (TS), irradiate the carrier (10) with a laser (Lns) to detach the micro-element (C) attached to the adhesive layer (13) and transfer it to the target substrate (TS).

Here, the carrier (10) may be composed of a base layer (11) through which the laser is transmitted, an adhesive layer (13) to which the micro element (C) is adhered, and a blister layer (12) provided between the base layer (11) and the adhesive layer (13) and made of polyimide (PI), etc.

With this configuration, when the carrier (10) is irradiated with a laser (Lns), the laser (Lns) passes through the base layer (11), and as shown in FIG. 2, is linearly absorbed from the surface of the blister layer (12) to form a blister, thereby deforming the adhesive layer (13), thereby reducing the adhesive area in the adhesive layer (13) while pushing out the micro-element (C), so that the micro-element (C) can be transferred to the target substrate (TS), as shown in FIG. 1.

And, the laser (Lns) irradiated to the carrier (10) uses a nanosecond pulse laser.

In the case of a nanosecond laser, as shown in Fig. 2, the heat is linearly absorbed in the blister layer (12) and spreads to the surroundings to form a blister, so that the diameter of the blister is formed larger than the diameter of the laser beam.

For example, when a nanosecond laser with an energy density of 1.1 J/cm ² and a laser beam diameter of 26 μm is irradiated, a blister is formed with a diameter of approximately 40 μm.

In this case, if the size of the micro-element is manufactured to be approximately 40 ㎛ or smaller, or if the spacing between the elements becomes small, a problem occurs in which the micro-element placed adjacent to the micro-element being transferred is also affected by the formation of blisters.

For example, as illustrated in FIG. 3, a problem may occur in which a part of a micro-element (C) being transferred is separated from the adhesive layer (13) and the adhesion position of the micro-element is partially changed, thereby causing a slight change in the transfer position.

Accordingly, the present invention proposes a micro-element transfer device and transfer method capable of improving transfer precision by forming a blister having a high aspect ratio.

Hereinafter, specific embodiments of the present invention will be described with reference to the attached drawings.

FIG. 4 is a drawing schematically illustrating a state in which a micro device is transferred by a micro device transfer device according to an embodiment of the present invention, and FIG. 5 is a drawing schematically illustrating a state in which a laser is nonlinearly absorbed in a blister layer by a femtosecond pulse laser. In addition, FIG. 6 is a graph illustrating the diameter of a blister formed by a nanosecond laser and a femtosecond pulse laser according to energy density, and FIG. 7 is a graph illustrating the aspect ratio (height/diameter) of a blister formed by a nanosecond laser and a femtosecond pulse laser according to energy density. In addition, FIG. 8 is a photograph illustrating the shape of a blister formed by a nanosecond laser and a femtosecond pulse laser according to energy density.

Referring to FIGS. 3 to 8, a micro-element transfer device according to an embodiment of the present invention may include a laser irradiation unit (200) that irradiates an ultrashort pulse laser (Lfs), and a carrier (100) that detaches a micro-element (C) when the micro-element (C) is attached and irradiated with the ultrashort pulse laser (Lfs).

Here, the carrier (100) may include a base layer (110) through which laser is transmitted, an adhesive layer (130) formed on the base layer (110) and to which a micro-element (C) is adhered, and a blister layer (120) provided between the base layer (110) and the adhesive layer (130) and which expands when irradiated with an ultrashort pulse laser (Lfs) to deform the adhesive layer (130) and cause the micro-element (C) to detach.

A device for transferring micro-elements onto a target substrate using a conventional thermal mechanical transfer mechanism uses a nanosecond pulse laser, but in the present invention, an ultrashort pulse laser (Lfs) is irradiated to form a blister having a high aspect ratio in the blister layer (120), so that even micro-elements (C) of a smaller size or micro-elements (C) arranged in a micro gap can be transferred more precisely.

To this end, the laser irradiation unit (200) may be configured to irradiate an ultrashort pulse laser having a wavelength of 500 to 3,000 nm and a pulse width of 10 fs to 100 ps. Preferably, the laser irradiation unit (200) may be configured to irradiate a femtosecond pulse laser having a wavelength of 900 to 3,000 nm and a pulse width of 10 to 800 fs.

Such femtosecond pulse laser (Lfs) is not absorbed from the surface of the blister layer (120) when irradiated onto the carrier (100), but is absorbed nonlinearly in a specific region inside the blister layer (120) after passing through a portion of the blister layer (120), as illustrated in FIG. 5. In addition, since the femtosecond pulse laser (Lfs) has an energy transfer time (approximately 10 ^-13 to 10 ^-15 seconds) in the blister layer (120) that is shorter than the heat diffusion time (approximately 10 ^-12 seconds), local heat transfer can be performed without heat diffusion to the surroundings.

Through these features, it is possible to form blisters having a higher aspect ratio than blisters formed via a nanosecond laser, thereby allowing for more precise transfer of micro-elements (C).

Figure 6 shows the results of measuring the diameter (D) of blisters formed by irradiating a nanosecond laser (ns pulse) and a femtosecond pulse laser (fs pulse). Here, the energy density of the irradiated laser was applied in the range of 0.4 to 2.0 J/cm ² , and the beam diameter (Beam D) of the nanosecond laser (ns pulse) was 26 μm, and the beam diameter (Beam D) of the femtosecond pulse laser (fs pulse) was 40 μm.

As illustrated in Fig. 6, a nanosecond laser (ns pulse) was irradiated with a beam diameter of 26 μm. When irradiated with an energy density of 0.6 J/cm ² , the diameter (D) of the blister was approximately 30 μm. When irradiated with an energy density of 1.1 J/cm ² , the diameter (D) of the blister was approximately 35 μm. When irradiated with an energy density of 1.7 J/cm ² , the diameter (D) of the blister was approximately 40 μm. That is, it can be seen that the diameter (D) of the blister formed is larger than the diameter of the irradiated laser beam.

In comparison, the femtosecond pulse laser (fs pulse) was irradiated with a beam diameter of 40 μm, which is larger than the beam diameter of the nanosecond laser (ns pulse). However, when irradiated with an energy density of 0.4 J/cm ² , the diameter of the blister (D) was about 15 μm, when irradiated with an energy density of 0.8 J/cm ² , the diameter of the blister (D) was about 20 μm, when irradiated with an energy density of 1.4 ^J /cm ² , the diameter of the blister (D) was about 25 μm, and when irradiated with an energy density of 2.0 J/cm 2 , the diameter of the blister (D) was about 25 to 30 μm. That is, it can be seen that the diameter (D) of the formed blister is smaller than the diameter of the irradiated laser beam.

Therefore, it was confirmed that the femtosecond pulse laser (fs pulse) forms a blaster with a diameter smaller than the diameter of the laser beam being irradiated, and that the diameter of the blister does not increase significantly even when the energy density is increased.

Fig. 7 shows the results of measuring the aspect ratio (H/D) of blisters formed by irradiating a nanosecond laser (ns pulse) and a femtosecond pulse laser (fs pulse). Here, the energy density of the irradiated laser was applied in the range of 0.4 to 2.0 J/cm ² , and the beam diameter (Beam D) of the nanosecond laser (ns pulse) was 26 μm, and the beam diameter (Beam D) of the femtosecond pulse laser (fs pulse) was 40 μm. In addition, Fig. 8 is a photograph showing the shape of a blister formed by irradiating a nanosecond laser (ns pulse) and a femtosecond pulse laser (fs pulse).

As illustrated in FIGS. 7 and 8, when a nanosecond laser (ns pulse) is irradiated with an energy density of 0.6 J/cm ² , the aspect ratio (H/D) of the blisters is formed to be approximately 0.1 to 0.4, when irradiated with an energy density of 1.1 J/cm ² , the aspect ratio (H/D) of the blisters is approximately 0.2 to 0.8, and when irradiated with an energy density of 1.7 J/cm ² , the aspect ratio (H/D) of the blisters is approximately 0.1 to 0.3. That is, it can be seen that the aspect ratio (H/D) of the formed blisters increases as the energy density increases and then decreases again. That is, it can be seen that when the energy density increases, the diameter (D) of the blister increases greatly, while the height (H) decreases.

In comparison, it can be confirmed that when a femtosecond pulse laser (fs pulse) is irradiated with an energy density of 0.4 J/cm ² , the aspect ratio (H/D) of the blisters is formed as approximately 0.8 to 0.1, when irradiated with an energy density of 0.8 J/cm ² , the aspect ratio (H/D) of the blisters is formed as approximately 0.8 to 0.95, when irradiated with an energy density of 1.4 J/cm ² , the aspect ratio (H/D) of the blisters is formed as approximately 0.8 to 0.9, and when irradiated with an energy density of 2.0 J/cm ² , the aspect ratio (H/D) of the blisters is formed as approximately 0.8 to 0.85. That is, it can be confirmed that the height of the blisters is formed similar to the size of the width, and it can be confirmed that the minimum aspect ratio is maintained at 0.8 even when the energy density increases.

Therefore, it can be confirmed that the femtosecond pulse laser (fs pulse) forms blisters with a high aspect ratio compared to the nanosecond laser (ns pulse). In conclusion, by irradiating a femtosecond pulse laser beam with a diameter of 40 μm at an energy density of 0.4 to 2.0 J/cm ² , blisters with a diameter of 15 to 35 μm can be formed, and blisters with a high aspect ratio of 0.7 to 1.1 can be formed.

In this way, in the present invention, by irradiating a carrier with a femtosecond pulse laser, a blister having a high aspect ratio is formed, so that even micro-elements of smaller size or micro-elements arranged in a micro gap can be transferred more precisely.

Figure 9 is a flow chart schematically showing a micro device transfer method according to an embodiment of the present invention.

Referring to FIG. 9, a micro-element transfer method according to an embodiment of the present invention may include a picking step (S110) for transferring a micro-element placed on a source substrate to an adhesive portion of a carrier, and a placing step (S120) for transferring the micro-element to the target substrate by irradiating the carrier with a femtosecond pulse laser after placing the carrier on a target substrate.

In particular, the placing step (S120) may be performed to irradiate an ultrashort pulse laser having a wavelength of 500 to 3,000 nm and a pulse width of 10 fs to 100 ps. Preferably, the placing step (S120) may be performed to irradiate a femtosecond pulse laser having a wavelength of 900 to 3,000 nm and a pulse width of 10 to 800 fs.

In this placing step (S120), the femtosecond pulse laser irradiated passes through a part of the blister layer formed on the carrier and is nonlinearly absorbed in a specific area inside the blister layer to form a high aspect ratio blister, thereby deforming the adhesive layer to detach the microelement and transfer it to the target substrate.

For example, in the placing step (S120), a femtosecond pulse laser beam having a diameter of 40 μm is irradiated at an energy density of 0.4 to 2.0 J/cm ² to form a blister having a diameter of 15 to 35 μm and a blister having a high aspect ratio of 0.7 to 1.1. That is, the diameter of the blister formed in the blister layer is formed smaller than the diameter of the femtosecond pulse laser beam irradiated to the blister layer.

In this way, in the present invention, by irradiating a carrier with a femtosecond pulse laser, a blister having a high aspect ratio is formed, so that even micro-elements of smaller size or micro-elements arranged in a micro gap can be transferred more precisely.

Although the present invention has been described in detail through specific examples, this is only for the purpose of specifically explaining the present invention, and the present invention is not limited thereto, and it is obvious that the present invention can be modified or improved by a person having ordinary knowledge in the relevant field within the technical spirit of the present invention.

All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific protection scope of the present invention will be made clear by the appended claims.

100 : Carrier
110 : Base layer
120 : Blister layer
130 : Adhesive layer
200 : Laser irradiation unit

Claims (19)

A laser irradiation unit that irradiates an ultrashort pulse laser; and
A carrier comprising a blister layer on which micro-elements are adhered and which expands when irradiated with an ultrashort pulse laser to release the micro-elements;
Including,
The above carrier,
a base layer through which the laser is transparent; and
It comprises an adhesive layer formed on the base layer and to which a micro device is adhered,
A micro device transfer device characterized in that an ultrashort pulse laser passes through a part of the blister layer provided between the base layer and the adhesive layer, is nonlinearly absorbed in a specific area inside the blister layer to form a high aspect ratio blister, and deforms the adhesive layer to detach the micro device.
In the first paragraph,
The above laser irradiation unit,
A micro-element transfer device characterized by irradiating an ultrashort pulse laser having a wavelength of 500 to 3,000 nm.
In the first paragraph,
The above laser irradiation unit,
A micro-element transfer device characterized by irradiating an ultrashort pulse laser having a pulse width of 10 fs to 100 ps.
In the first paragraph,
The above laser irradiation unit,
A micro-element transfer device characterized by irradiating a femtosecond pulse laser having a wavelength of 900 to 3,000 nm.
In the first paragraph,
The above laser irradiation unit,
A micro-device transfer device characterized by irradiating a femtosecond pulse laser having a pulse width of 10 to 800 fs.
delete delete In the first paragraph,
A micro-element transfer device, characterized in that the diameter of the blister formed in the above blister layer is smaller than the diameter of the ultrashort pulse laser beam irradiated onto the blister layer.
In the first paragraph,
A micro device transfer device characterized in that it forms a blister having a diameter of 15 to 35 μm by irradiating the blister layer with a femtosecond pulse laser beam having a diameter of 40 μm at an energy density of 0.4 to 2.0 J/cm ² .
In the first paragraph,
A micro device transfer device characterized in that it forms a blister having an aspect ratio (height/diameter) of 0.7 to 1.1 by irradiating the blister layer with a femtosecond pulse laser.
A picking step for transferring micro-elements placed on a source substrate to an adhesive layer of a carrier; and
A placing step of placing the carrier on a target substrate and then irradiating the carrier with an ultrashort pulse laser to expand a blister layer formed on the carrier to transfer the micro-element to the target substrate;
Including,
The above placing step is,
A micro-element transfer method characterized in that an ultrashort pulse laser passes through a part of a blister layer formed on the carrier and is nonlinearly absorbed in a specific area inside the blister layer to form a high aspect ratio blister, thereby deforming the adhesive layer and detaching the micro-element.
In Article 11,
The above placing step is,
A micro-element transfer method characterized by irradiating an ultrashort pulse laser having a wavelength of 500 to 3,000 nm.
In Article 11,
The above placing step is,
A micro-element transfer method characterized by irradiating an ultrashort pulse laser having a pulse width of 10 fs to 100 ps.
In Article 11,
The above placing step is,
A micro-element transfer method characterized by irradiating a femtosecond pulse laser having a wavelength of 900 to 3,000 nm.
In Article 11,
The above placing step is,
A micro-element transfer method characterized by irradiating a femtosecond pulse laser having a pulse width of 10 to 800 fs.
delete In Article 11,
A micro-element transfer method, characterized in that the diameter of the blister formed in the above blister layer is smaller than the diameter of the ultra-short pulse laser beam irradiated onto the blister layer.
In Article 11,
The above placing step is,
A micro device transfer method characterized by forming a blister having a diameter of 15 to 35 μm by irradiating the blister layer with a femtosecond pulse laser having a diameter of 40 μm at an energy density of 0.4 to 2.0 J/cm ² .
In Article 11,
The above placing step is,
A micro device transfer method characterized by forming a blister having an aspect ratio (height/diameter) of 0.7 to 1.1 by irradiating the blister layer with a femtosecond pulse laser.