KR101198409B1 - Flexible electronic circuits including mesa-hybride structire and preparation method thereof - Google Patents

Abstract

The present invention seeks to provide a flexible electronic circuit comprising a mesa hybrid structure capable of reducing damage of an island in which semiconductor devices are installed and a method of manufacturing the same. In the flexible electronic circuit of the present application, a buffer layer is stacked on a flexible substrate, an island including a hard thin film is stacked on the buffer layer, a semiconductor device is provided on the island, and the buffer layer and the island are mesas. mesa) to form a hybrid structure. The method of manufacturing the flexible electronic circuit may include stacking a buffer layer on a flexible substrate, stacking an island including a hard thin film on the buffer layer, installing a semiconductor device on the island, and mesa-etching the buffer layer. Forming a mesa hybrid structure comprising the islands.

Description

FLEXIBLE ELECTRONIC CIRCUITS INCLUDING MESA-HYBRIDE STRUCTIRE AND PREPARATION METHOD THEREOF

The present invention relates to a flexible electronic circuit and a method of manufacturing the same that can be used in a flexible display panel, a solar roll panel, a biosensor, and the like.

Flexible electronic circuits are electronic circuits that can accommodate large external deformations, and have a wide range of applications, such as flexible display fields, solar roll panels, and biosensors, and are easier to install and carry than electronic products made through conventional semiconductor processes. It is easy to express smooth curves, and can improve the performance of the device. Generally, however, substrates such as organic polymers and stainless steel foils can be easily deformed into any shape, while inorganic semiconductor materials such as amorphous silicon and silicon nitride are susceptible to deformation and can easily crack when subjected to external stresses. Can be broken. Therefore, in order to implement a deformable electronic circuit, a method of installing semiconductor devices susceptible to deformation in hard islands and depositing the islands on a deformable flexible substrate has been performed, and thus in hundreds of micrometers The island pattern of size serves to reduce the deformation of semiconductor devices from the outside to maintain the performance of the circuit. However, in spite of using this method, since the layer which realizes the performance of the electronic circuit is basically brittle, it is damaged even by a very small deformation of 1-2% and loses the functionality.

Meanwhile, the island may be formed by patterning a hard thin film, such as SiN, by a photolithography process. The independent islands and the semiconductor devices installed thereon can be protected through deformation of the inter island zone existing between the islands. However, if sufficient inter island area is not secured or the difference in elastic modulus between the hard film and the flexible substrate is not sufficient, the island itself may be damaged by various destruction mechanisms, thereby preventing the function of the electric circuit.

There are many forms of Ireland's destruction mechanism. For example, FIGS. 1A and 1B are schematic diagrams of destruction by delamination and electron scanning microscopy (SEM) photographs of island structures destroyed by delamination, respectively. Circuits on a Spherical Dome ", Journal of The Electrochemical Society , 153 3 G259-G265 (2006), FIG. 2A and FIG. 2B are conceptual diagrams of fracture by channel cracks and optical electron micrographs of island structures destroyed by channel cracks, respectively. Concept diagram of destruction by substrate penetration and SEM image of island structure destroyed by substrate failure [RABIN BHATTACHARYA, SIGURD WAGNER, YEH-JIUN TUNG, JAMES R. ESLER, AND MIKE HACK, " Organic LED Pixel Array on a Dome ", PROCEEDINGS OF THE IEEE, VOL. 93, NO. 7, JULY 2005.], and FIG. 4 is an SEM image of an island structure destroyed by Island slip [Rabin Bhattachary, Ashley Salomon, and Sigurd Wagner, "Fabricating Metal Interconnects for Circuits on a" Spherical Dome ", Journal of The Electrochemical Society , 153 3 G259-G265 (2006).

Accordingly, there is a need for development of an electronic circuit structure capable of reducing breakage or damage of an island despite deformation of the substrate.

Accordingly, the present application is to provide a flexible electronic circuit including a mesa hybrid structure that can reduce the damage of the island in which the semiconductor devices are installed despite the deformation of the substrate and a method of manufacturing the same.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, in one aspect of the present invention, a buffer layer is stacked on a flexible substrate, an island including a hard thin film is stacked on the buffer layer, and the island is provided with a semiconductor device, The buffer layer and the island provide a flexible electronic circuit that forms a mesa hybrid structure.

Another aspect of the present disclosure is directed to stacking a buffer layer on a flexible substrate; Stacking an island including a hard thin film on the buffer layer; Installing a semiconductor device in the island; And mesa etching the buffer layer to form a mesa hybrid structure including the buffer layer and the island.

Another aspect of the present application is to provide a flexible electronic circuit to a flexible display panel, solar roll panel, biosensor, camera lens, TFT transistors (TFTs), OLED, electronic paper, skin sensor or electrotextiles Provide a method of use.

According to the present disclosure, a flexible electronic circuit having a buffer layer formed between the flexible substrate and the island may reduce the damage to the island by buffering the buffer layer when the flexible substrate is deformed. In addition, since the buffer layer and the island form a mesa hybrid structure, when the deformation is applied to the flexible substrate, the external force transmitted to the buffer layer itself may be reduced, thereby reducing the external force applied to the island.

In addition, the electronic products including the flexible electronic circuits are easier to install and carry than the electronic products made through the conventional semiconductor process, and can be easily applied as high value-added products because they can express smooth curves.

1A and 1B are schematic diagrams of destruction by delamination and electron scanning microscope (SEM) photographs of island structures destroyed by delamination, respectively.
2A and 2B are optical electron micrographs of an island structure broken by a channel crack and a conceptual diagram of breaking by a channel crack, respectively.
3A and 3B are schematic diagrams of fracture due to substrate penetration and electron scanning microscope (SEM) images of island structures destroyed by substrate failure, respectively.
4 is an electron scanning microscope (SEM) photograph of an island structure destroyed by an island slip.
5 illustrates a flexible electronic circuit according to an embodiment of the present disclosure.
FIG. 6 is a diagram where the flexible electronic circuit is deformed by external stress in one embodiment of the present disclosure. FIG.
FIG. 7 is a flowchart illustrating forming a flexible electronic circuit according to an embodiment of the present disclosure. FIG.
8A to 8F are process diagrams illustrating a method of forming a flexible electronic circuit according to an exemplary embodiment of the present disclosure.
9 illustrates an electronic circuit (Comparative Example 1) including an island without a buffer layer.
FIG. 10 is a diagram showing an electronic circuit (Comparative Example 2) in which the buffer layer includes islands having no mesa structure. FIG.
11A, 11B and 11C show a flexible electronic circuit (Example 1) and an electronic circuit without a buffer layer according to an embodiment of the present application measured using the ABAQUS6.9 standard, which is an analysis program, respectively (Comparative Example 1). And a simulation result of the stress (σ _x ) state applied to the inside of the electronic circuit of the electronic circuit (Comparative Example 2) including the island where the buffer layer does not form a mesa structure.
12 illustrates a flexible electronic circuit (Example 1), an electronic circuit not including a buffer layer (Comparative Example 1), and a buffer layer according to an embodiment of the present application measured using an analysis program ABAQUS6.9 standard to form a mesa structure. Shows the simulation results of normalized stress ( σ _x ) applied to the ends of normalized islands of electronic circuits (Comparative Example 2) containing islands not being used.
FIG. 13 shows normalization between a substrate and an island of a flexible electronic circuit (Example 1) and an electronic circuit (Comparative Example 1) not including a buffer layer according to an embodiment of the present invention measured using an analysis program ABAQUS6.9 standard. This graph shows the simulation results of the normalized stress intensity factor ( K) according to the initial crack size.

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains.

It should be understood, however, that the present invention may be embodied in many different forms and is not limited to the embodiments and examples described herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

As used herein, the terms "about", "substantially", and the like, are used at, or in close proximity to, numerical values when manufacturing and material tolerances inherent in the meanings indicated are provided to aid the understanding herein. In order to prevent the unfair use of unscrupulous infringers. In addition, throughout this specification, "step to" or "step of" does not mean "step for."

In one aspect of the present invention, a buffer layer is stacked on a flexible substrate, an island including a hard thin film is stacked on the buffer layer, a semiconductor device is provided on the island, and the buffer layer and the island are mesas. ) Provides a flexible electronic circuit, forming a hybrid structure.

In one embodiment of the present application, the buffer layer may be smaller than the Young's modulus than the soft thin film, but is not limited thereto.

In another embodiment of the present application, the flexible substrate may be one having a lower Young's modulus than the hard thin film, but is not limited thereto.

In another embodiment of the present disclosure, the flexible substrate may include, but is not limited to, polyimide, polyethylene, terephthalate, polydimethylsiloxane, polyethylene naphthalate, or a combination thereof.

In another embodiment of the present disclosure, the hard thin film may include silicon, silicon nitride (SiN _x ), silicon oxide (SiO _x ), indium tin oxide (ITO), or a combination thereof, but is not limited thereto. It doesn't happen.

In another embodiment of the present disclosure, the buffer layer may include polydimethylsiloxane (PDMS), modified polydimethylsiloxane, polyurethane, or a combination thereof, but is not limited thereto.

Another aspect of the present disclosure is directed to stacking a buffer layer on a flexible substrate; Stacking an island including a hard thin film on the buffer layer; Installing a semiconductor device in the island; And mesa etching the buffer layer to form a mesa hybrid structure including the buffer layer and the island.

In one embodiment of the present application, the mesa etching may be to use a method including a dry etching, wet etching, or a combination thereof, but is not limited thereto.

In another embodiment of the present disclosure, the flexible substrate may include, but is not limited to, polyimide, polyethylene, terephthalate, polydimethylsiloxane, polyethylene naphthalate, or a combination thereof.

In another embodiment of the present disclosure, the hard thin film may include silicon, silicon nitride (SiN _x ), silicon oxide (SiO _x ), indium tin oxide (ITO), or a combination thereof, but is not limited thereto. It doesn't happen.

In another embodiment of the present disclosure, the buffer layer may include polydimethylsiloxane (PDMS), modified polydimethylsiloxane, polyurethane, or a combination thereof, but is not limited thereto.

Another aspect of the present application uses flexible electronic circuits in flexible display panels, solar roll panels, biosensors, camera lenses, TFT transistors (TFTs), OLEDs, electronic paper, skin sensors or electrotextiles. Provide a way to.

Hereinafter, a flexible electronic circuit according to an exemplary embodiment of the present disclosure will be described with reference to FIG. 5, but is not limited thereto.

The flexible electronic circuit according to the present invention includes an island including a hard thin film 2, a flexible substrate 1 and a buffer layer 3.

In the present application, the island refers to an independent unit formed on a substrate of an electronic circuit and electrically separated from the substrate. The island may include a hard thin film 2, and the hard thin film 2 may be patterned by a photolithography process. The hard thin film 2 is an electrical insulator, and a semiconductor device or the like that is easily damaged by an external force is installed on the patterned hard thin film 2. give. The semiconductor devices may be, for example, a silicon thin-film-transister (TFT), a flexible tactile sensor array, an organic light-emitting diode (OLED), or the like.

The flexible substrate 1, the hard thin film 2, and the buffer layer 3 may be selected in consideration of Young's modulus, and the flexible substrate 1 has a Young's modulus smaller than that of the buffer layer 3, The soft substrate has a Young's modulus smaller than that of the hard thin film 2. That is, Young's modulus Y has the following relationship.

Y _{hard thin film} 〉 Y _{flexible substrate} 〉 Y _{buffer layer}

In the present application, the Young's modulus refers to an elastic modulus indicating the degree of stretching and the degree of deformation of the object when the object is stretched from both sides. Specifically, when an object is forced from both sides, the length of the object increases from L ₀ to L _n and the cross-sectional area A decreases. The stretched object also returns to its original form when the force is removed. In this case, the length of the length of the object is called the strain (S), S = (L _n -L ₀ ) / L ₀ , and when the length of the object is divided by the cross-sectional area A to increase the strain (T) This is referred to as T = F / A. Young's modulus means a proportional relationship between strain and strain and can be expressed as "Young's modulus = T / S". For example, the Young's modulus of the flexible substrate 1 may be 0.1 GPa to 10 GPa, and the Young's modulus of the hard thin film 2 may be 1/10 to 1/1000 of the Young's modulus of the flexible substrate 1. The Young's modulus of the buffer layer 3 may be 10 to 1000 times the Young's modulus of the flexible substrate 1, but is not limited thereto. The flexible substrate 1 may be, for example, polyimide, polyethylene, terephthalate, polydimethylsiloxane, or polyethylene naphthalate, and may be, for example, polyimide in consideration of Young's modulus and compatibility with an island.

The hard thin film 2 may be, for example, silicon nitride (SiN _x ), silicon oxide (SiO _x ), or indium-tin-oxide (ITO), and for example SiN _x work in consideration of Young's modulus and electrical conductivity. Can be.

The buffer layer 3 serves to disperse the external force applied to the hard thin film 3 from the flexible substrate 1 into the buffer layer 3. As the Young's modulus of the buffer layer 3 is lower, external force transmitted between the flexible substrate 1 and the hard thin film 3 is dispersed and absorbed in the buffer layer 3 itself. Therefore, the buffer layer 3 preferably uses a material having a low Young's modulus, and may be, for example, polydimethylsiloxane (PDMS), modified polydimethylsiloxane, or polyurethane. For example, it may be polydimethylsiloxane in consideration of Young's modulus, cost, and the like.

In the flexible electronic circuit according to the present invention, islands including the flexible substrate 1, the buffer layer 3, and the hard thin film 2 are sequentially stacked. Since the external force generated when the flexible substrate 3 is deformed is dispersed in the buffer layer 3, the external force applied to the island can be reduced as compared with the electronic circuit (see FIG. 8) not including the buffer layer.

In the flexible electronic circuit according to the present application, the buffer layer 3 and the hard thin film 2 form a mesa hybrid structure. In other words, the buffer layer 3 is islanded. Since the buffer layer 3 is included in the mesa structure, the external force applied to the buffer layer itself when the flexible substrate 3 is deformed is reduced, and thus the electronic circuit including the buffer layer that does not form the mesa structure (see FIG. 9). This can reduce the external force on the island.

A method of manufacturing a flexible electronic circuit according to an embodiment of the present disclosure will be described with reference to FIGS. 7 and 8A to 8F.

First, the flexible substrate 1 and the metal plate 4 are attached by using the double-sided tape 5, and are bonded by pressing them (S10). Next, the buffer layer 3 is coated on the flexible substrate 1 (S20). The coating method is not limited, and for example, spin-coating, spray-coating, knife-over-edge coating, gravure coating method and the like can be used. A positive photoresist 6 is coated on the buffer layer 3. The coating method is not limited, and for example, spin-coating, spray-coating, knife-over-edge coating, gravure coating method and the like can be used. Following the coating, the photoresist 6 is developed on the buffer layer 3 in a desired shape (S30). Subsequently, the hard thin film 2 is deposited on the buffer layer 3 on which the photoresist 6 is developed (S40). The deposition method is not limited, and may be deposited by, for example, chemical vapor deposition (CVD) such as high density plasma chemical vapor deposition (HDPCVD), reduced pressure chemical vapor deposition (SACVD) or plasma chemical vapor deposition (PECVD). Subsequently, the hard thin film 2 is patterned by stripping and removing the remaining photoresist 6 (S50). Subsequently, the buffer layer 3 is mesa-etched to the stretched substrate 1, and the aluminum plate 4 is separated (S60). The mesa etching may be by a method including, for example, dry etching, wet etching, or a combination thereof.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present application is not limited thereto.

[ Example ]

[ Example  1] Mesa hybrid  Containing structure Flexible  Manufacture of electronic circuits

A 70 μm thick polyimide (PI) foil substrate was prepared using Kapton-E (DuPont, Wilmington, DE). It was washed with methanol and acetone and attached to a 3 mm thick aluminum (Al) plate using double sided tape to prepare a PI substrate sample. The sample was pressurized under vacuum for 24 hours to remove bubbles between the PI foil and the Al plate.

Separately, a polydimethylsiloxane (PDMS) (Sylgard 184, Dow Corning, Midland, MI) was prepared by mixing a silocon gel and a crosslinking agent in a weight ratio of 10: 1. Subsequently, the PDMS was spin-coated to the PI substrate with a thickness of 10 μm, left for 20 minutes in a vacuum to remove the gas, and cured at 80 ° C. for 1 hour to prepare a PI substrate sample on which PDMS was laminated. The PDMS surface was hydrophilized by O ₂ plasma treatment in a 20 W power micro stripper (Series 220, Technics, Danville, Calif.) For 20 seconds.

A positive photoresist (S1818, Microl. Shipley, Marlborough, Mass.) Was then spin-coated on the PDMS to 3.2 μm thickness. The coated sample was baked at 115 ° C. for 2 minutes and then exposed to a chrome mask using an MJB4 mask aligner (SUSS MicroTec, Garching, Germany). The sample was then developed in a MF-319 photoresist developer (Microposit), rinsed in deionized water for 1 minute, and dried with N ₂ gas.

The PI substrate on the sample was then cut into a rectangular shape of 7 mm x 60 mm, and 500 nm thick SiN _X on the sample. The film was deposited using chemical vapor deposition (CVD) in a NEXX system (base pressure: 5 × 10 ⁻⁶ Torr, working pressure: 10 mTorr). At this time, the electromagnetic wave power was 265 W, the substrate temperature was maintained at 22 ℃, the gas flow rate is 3% SiH ₄ (Adjusted with Ar), N ₂ and Ar were maintained at 40, 5.8 and 20 sccm, respectively.

Then, the stripping of the photoresist together with the remaining SiN _X stacked on the photoresist in acetone to pattern the SiN _X. Then, the PDMS layer is mesa-etched using Reactive Ion Eching (RIE), and the Al plate is removed to form a mesa hybrid structure of a buffer layer (PDMS layer) and an island (patterned SiN _X ) on a soft substrate (PI substrate). A flexible electronic circuit including a mesa hybrid structure in which the was formed was manufactured.

[ Comparative example  One] SiN _X Of PI  Manufacture of electronic circuits

A 25 μm thick polyimide (PI) foil substrate was prepared using Upilex-S (UBE Industries, Inc., Tokyo, Japan). This was processed in the same manner as in Example 1 except for the PDMS coating and the mesa etching process, to prepare an electronic circuit in which SiN _X was stacked on a PI substrate. 9 is a cross-sectional view of the manufactured electronic circuit.

[ Comparative example  2] SiN _X Of PDMS Of PI  Manufacture of electronic circuits

Using the same method as in Example 1 except for mesa etching of the PDMS layer, PDMS was deposited on a PI substrate, and an electronic circuit in which only SiN _X had a mesa structure was manufactured. The manufactured electronic circuit is shown in FIG.

[ Experimental Example  1] the stress applied to the inside of the electronic circuit (σ _x State measurement

Stress applied to each substrate and island when strain (ε _x ) 1% was applied to the electronic circuits prepared in Example 1, Comparative Example 1 and Comparative Example 2 using the analysis program ABAQUS6.9 standard. The simulation result of the _x ) state was shown to FIG. 11A, FIG. 11B, and FIG. 11C, respectively. As can be seen in FIGS. 11A, 11B, and 11C, when the same strain (1%) is applied, the stress concentration applied to the island of Example 1 including the mesa hybrid structure is the smallest. This means that the mesa hybrid structure herein is the safest.

[ Experimental Example  2] normalized Normalized Stress (σ) _x )of  Measure

Using the analysis program ABAQUS6.9 standard, the simulation results of the normalized stress ( σ _x ) applied to the ends of the normalized islands of Example 1, Comparative Example 1 and Comparative Example 2 prepared above are shown. It is shown in 12. In the graph, x on the X axis means the distance from the edge portion where the substrate and the island are in contact, and h means the thickness of the island. In other words, x / h means the ratio of the island thickness and the distance from the edge portion where the substrate and the island are in contact. In the graph, the Y axis represents the normalized stress state, σ is the stress applied to the substrate, E _sun is the Young's modulus of the substrate, ν is the Poison ratio of the substrate, and ε _appl is the strain applied to the electronic circuit (1 %). As can be seen in FIG. 12, the magnitude of the stress applied near the edge where the substrate and the island are in contact is the smallest in the case of the electronic circuit of Example 1 of the present application, and the magnitude of the stress applied to the electronic circuit of Comparative Example 1 of the present application. Is the largest. This means that the mesa hybrid structure herein is the safest.

[ Experimental Example  3] normalized stress intensity factor ( stress intensity factor , K)

Using the ABAQUS6.9 standard, an analysis program, simulation results of the normalized stress intensity factor ( K) according to the normalized initial crack size between the substrate and the island of Example 1 and Comparative Example 1 prepared above were obtained. It is shown in FIG. In the graph, a on the X axis means the size of the crack occurring between the substrate and the island, and h means the thickness of the island. That is, a / h means the ratio of crack size and island thickness. In the graph, Y axis means normalized stress intensity factor, K is stress intensity factor at crack tip between island and substrate, E is Young's modulus of substrate, ν is Poison ratio of substrate, ε Is the strain (1%) applied to the electronic circuit, and a is the size of the crack occurring between the substrate and the island. As can be seen in FIG. 13, as the size of the crack between the substrate and the island increases, the normalized stress intensity factor of each electronic circuit also increases, and the size of the normalized stress intensity factor is the electron of Example 1 of the present application. The circuit is relatively small compared to the electronic circuit of Comparative Example 1. This means that the mesa hybrid structure of the present application is safer than the general island structure.

Although described above with reference to preferred embodiments and examples of the present application, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the invention as set forth in the claims below. It will be understood that various modifications and changes can be made.

1: flexible substrate
2: rigid thin film
3: buffer layer
4: aluminum plate
5: double sided tape
6: photoresist

Claims (12)

A buffer layer is stacked on the flexible substrate, an island including a hard thin film is stacked on the buffer layer, a semiconductor device is provided on the island, and the buffer layer and the island form a mesa structure. Flexible electronic circuitry.
The method of claim 1,
Wherein the buffer layer has a Young's modulus smaller than the soft thin film.
The method of claim 1,
The flexible substrate has a lower Young's modulus than the hard thin film.
The method of claim 1,
Wherein the flexible substrate comprises polyimide, polyethylene, terephthalate, polydimethylsiloxane, polyethylenenaphthalate, or a combination thereof.
The method of claim 1,
Wherein the hard thin film comprises silicon, silicon nitride (SiN _x ), silicon oxide (SiO _x ), indium-tin-oxide (ITO), or a combination thereof.
The method of claim 1,
Wherein said buffer layer comprises polydimethylsiloxane (PDMS), modified polydimethylsiloxane, polyurethane, or a combination thereof.
Depositing a buffer layer on the flexible substrate;
Stacking an island including a hard thin film on the buffer layer;
Installing a semiconductor device in the island; And
Mesa etching the buffer layer to form a mesa structure including the buffer layer and the islands:
Including, a manufacturing method of a flexible electronic circuit.
The method of claim 7, wherein
The mesa etching is a method of manufacturing a flexible electronic circuit using a method comprising a dry etching, wet etching, or a combination thereof.
The method of claim 7, wherein
Wherein the flexible substrate comprises polyimide, polyethylene, terephthalate, polydimethylsiloxane, polyethylenenaphthalate, or a combination thereof.
The method of claim 7, wherein
Wherein the hard thin film comprises silicon, silicon nitride (SiN _x ), silicon oxide (SiO _x ), indium-tin-oxide (ITO), or a combination thereof.
The method of claim 7, wherein
The buffer layer is a polydimethylsiloxane (PDMS), modified polydimethylsiloxane, polyurethane or a combination thereof, the method of manufacturing a flexible electronic circuit.
The flexible electronic circuit according to any one of claims 1 to 6, comprising a flexible display panel, a solar roll panel, a biosensor, a camera lens, TFT transistors, OLEDs, an electronic paper, a skin sensor or an electronic Method for use in electrotextiles.

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