KR20100096948A - Fabrication method of thin film device - Google Patents

Abstract

PURPOSE: A method of manufacturing a thin film device is provided to efficiently transfer a thin film device while simplifying whole process. CONSTITUTION: A sacrificial layer(30) is formed on a reserved board(10). A thin film laminated article(40) is formed on the sacrificial layer to install the desired thin film element(40a). The thin film element connect the desired thin film to a non-device region partly by using a selective etching trough which the sacrificial layer is exposed to the outside. The sacrificial layer is removed through an exposed area of the sacrificial layer.

Description

Manufacturing method of thin film device {FABRICATION METHOD OF THIN FILM DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film device, and more particularly, to a method for manufacturing a thin film device using a thin film transfer process that can be utilized as a manufacturing technology of a flexible device.

In general, thin film transfer technology is widely used in thin film devices such as electronic devices such as thin film transistors (TFTs) and optical devices such as organic EL devices.

The thin film transfer technology is a general technique for forming a desired thin film on a preliminary substrate and then transferring the permanent thin film to produce a desired thin film element. This thin film transfer technique can be very useful when the conditions of the substrate used for film formation and the conditions of the substrate used for the thin film element are different.

For example, when a relatively high temperature process is required, such as a semiconductor film formation technique, when the substrate used for the element has low heat resistance, or a softening point and a melting point are low, the thin film transfer technique can be very advantageously utilized. In particular, even in the case of a flexible thin film element, the benefits of utilization are very large.

Conventionally, in the case of a flexible device, since flexibility is required, an organic substrate such as a polymer has been used, and a thin film constituting a functional part on its upper surface has been adopted as an organic thin film, but it is difficult to guarantee high performance with a functional part implemented with an organic thin film. Therefore, it is necessary to implement a functional part of the flexible element as an inorganic material such as poly-Si or an oxide thin film. In this case, since a high temperature semiconductor film formation technique is hardly applied directly to a flexible substrate which is an organic material, a thin film transfer technique for transferring a thin film formed of an inorganic material such as a semiconductor onto another preliminary substrate is used.

However, in the thin film transfer technology, a surface separated from the preliminary substrate is provided as an upper surface of the thin film transferred onto the permanent substrate, and the residue of the sacrificial layer exists on the upper surface, so that the sacrificial layer is prevented in order to prevent an adverse effect on the thin film device. Further steps are required to remove the residues.

On the other hand, thin film transfer technology generally requires a cut-and-paste process. More specifically, in order to separate a thin film element, which is a transfer object, from a preliminary substrate (also referred to as a "donor substrate"), an acceptor substrate is laminated and a donor is formed using a laser lift off (LLO) process. Separate from the substrate. However, this process is not only complicated, but also has a problem in that defects such as stiction and damage to the thin film element are liable to occur in the process of peeling or the like.

Therefore, in order to secure a mass-produced thin film device manufacturing technology, it is necessary to simplify the complicated cut-and-paste process and to develop a method easy for mass production.

The present invention is to solve the problems of the prior art, and to provide a method of manufacturing a thin film device that can effectively transfer the thin film device while simplifying the overall process.

The present invention as a means for solving the above problems, forming a sacrificial layer on the preliminary substrate; Forming a thin film stack for a desired thin film device on the sacrificial layer; Forming the thin film device such that the desired thin film device and the non-device region are partially connected to the desired thin film device from the thin film stack using a selective etching process performed to expose the sacrificial layer; Removing the sacrificial layer through the exposed area of the sacrificial layer so that the thin film device floats on the preliminary substrate; Separating the thin film device from the thin film stack by temporarily bonding a support on the thin film stack on which the thin film device is formed; And it provides a method for manufacturing a thin film device comprising the step of transferring the thin film device temporarily bonded to the support on a permanent substrate.

Partial connection of the thin film element and the non-element region is preferably made by connecting the connecting portion of the thin film element and the non-element region to face each other.

Partial connection between the thin film device and the non-device region may be performed by an etching process using a photoresist.

Removing the sacrificial layer may be performed by a dry etching process, the sacrificial layer is preferably amorphous silicon, the dry etching process may be performed using Xe ₂ F gas as an etchant.

Before forming the sacrificial layer, the method may further include forming a protective film protecting the preliminary substrate on an upper surface of the preliminary substrate, wherein the protective film is an oxide film or a nitride film.

The step of temporarily bonding the support may be a step of pressing the support so that the upper surface of the thin film laminate and the surface of the support are welded, and the support is preferably a poly dimethyl siloxane-based or silicone rubber-based polymer.

Separating the thin film device may include cutting a portion where the thin film device and the non-device region are connected by applying a physical force to the support to which the thin film device is temporarily bonded.

The permanent substrate may be a flexible substrate, and the thin film device may be any one of a thin film transistor, a solar cell, and a biosensor.

According to the present invention, it is possible to easily transfer only the thin film element from the thin film stack in the form of an independent chip. In addition, by providing a surface separated from the preliminary substrate as a surface bonded to the permanent substrate, the step of removing the residue of the sacrificial layer can be omitted, and the problem due to the residue can be solved.

In addition, after fabricating a thin film device from a thin film laminate, the sacrificial layer is removed and transferred to a desired substrate (eg, a flexible substrate), thereby minimizing adhesion problems between the thin film device and the substrate and changes in overall device characteristics due to laser irradiation. can do.

Hereinafter, with reference to the accompanying drawings will be described a specific embodiment of the present invention.

1A to 1C are cross-sectional views illustrating a process of forming a thin film laminate in a method of manufacturing a thin film device according to an exemplary embodiment of the present invention.

As shown in FIG. 1A, a preliminary substrate 10 is prepared. As in this process, a protective film 20 for protecting the preliminary substrate 10 may be additionally formed on the preliminary sacrificial layer removing process on the preliminary substrate 10. The protective film 20 may be an oxide film such as WO _x or SiO ₂ or a nitride film such as SiN _x .

The preliminary substrate 10 may be a substrate suitable for forming a thin film for forming a specific functional element. For example, when the desired thin film is a semiconductor or a metal, since a high temperature film formation process is generally required to grow it, the material is made of a material having heat resistance and satisfying a desired growth surface condition. For example, in addition to silicon wafers used in conventional semiconductor processes, gallium arsenide (GaAs), sapphire, quartz, glass, magnesium oxide (MgO), lanthanum aluminate (LaAlO ₃ ) and The substrate may be one selected from zirconia.

Next, as shown in FIG. 1B, the sacrificial layer 30 is formed on the preliminary substrate 10 on which the passivation layer 20 is formed.

The sacrificial layer 30 employed in the present invention may be useful as long as it is a material that can be removed while satisfying high selectivity with surrounding materials such as a constituent material of the thin film device by an etching process.

The etching process is preferably performed by dry etching, and the material of the sacrificial layer 30 formed in the present process is preferably amorphous silicon (? -Si). Amorphous silicon can be easily etched by XeF ₂ gas with high selectivity with conventional semiconductor materials and electrode materials. This will be described later in more detail.

Next, as shown in FIG. 1C, a thin film stack 40 is formed on the sacrificial layer 30 to form a desired thin film device.

The thin film stack 40 may be an inorganic material such as a semiconductor or polysilicon, or may be a metal, and may be formed by sputtering, evaporation, and CVD of a plurality of necessary layers 40a, 40b, and 40c constituting a desired thin film device. It can implement by forming using film-forming technique. The thin film device that can be implemented using the present invention may be a flexible device of various forms, but is not limited thereto. The thin film device may be any one of a thin film transistor (TFT), a solar cell, and a biosensor.

In the present embodiment, the thin film stack 40 has a structure in which the lower electrode 40a, the piezoelectric layer 40b, and the upper electrode 40c are sequentially formed. The lower electrode 40a may be deposited using a sputtered Ti / PT layer, and the piezoelectric layer 40b may be formed by coating with a sol-gel method. Subsequently, the upper electrode 40c may be formed using sputtered Pt.

Although not shown, a material film may be formed on the sacrificial layer before the sacrificial layer is formed and the thin film stack 40 is formed. The material film may be an oxide film such as polyethylene oxide (PEO _x ) or SiO ₂ or a nitride film such as SiN _x . Since the XeF ₂ gas used as an etchant in the subsequent sacrificial layer removal process has a low etching rate, the thin film laminate may be protected.

Next, a process of forming a desired thin film device from the thin film laminate is performed. In this process, a selective etching process using lithography may be used to form the device region. In the selective etching process, the sacrificial layer is partially exposed so that the sacrificial layer can be removed by the groove for dividing the device region, and the device region and the non-device region are partially connected. An example of such a process will be described with reference to FIGS. 2 and 3.

First, as shown in FIG. 2A, the first photoresist PR1 is disposed on the thin film stack 40 according to a desired thin film device. The region to be removed of the upper electrode 40c and the piezoelectric layer 40b is exposed by the first photoresist pattern PR1 formed in the present process. As shown in FIG. 2B, the upper electrode 40c and the piezoelectric layer 40b are selectively removed using the first photoresist pattern PR1, and the lower electrode 40a is exposed. This removal process may be performed by a dry etching process using an etchant gas having a low etching rate for the material of the lower electrode 40a.

Next, as shown in FIG. 2C, the second photoresist PR2 is disposed so that the region e1 to be removed of the lower electrode 40a is exposed. Through this process, portions other than the lower electrode 40a of the thin film stack 40 corresponding to the device region may be exposed.

Subsequently, as shown in FIG. 2D, a dry etching process for the lower electrode 40a is applied to selectively remove the lower electrode 40a. The desired thin film device may be formed through the removal process of the lower electrode 40a. In this process, the exposed sacrificial layer 30 region may be provided by removing the lower electrode 40a, and through this, an etching process for removing the sacrificial layer 30 may be applied.

Next, as shown in FIG. 2E, the sacrificial layer 30 is partially removed so that the thin film device 40A floats on the preliminary substrate 10 using an etching process. Preferably, the sacrificial layer 30 positioned below the thin film element 40A is removed, and the sacrificial layer 30 positioned below the non-device region 40B is not removed.

As described above, the present etching process may preferably use dry etching. When the sacrificial layer 30 is amorphous silicon (α-Si), the sacrificial layer 30 can be easily etched by XeF ₂ gas with high selectivity with respect to conventional semiconductor materials and electrode materials. In this case, the high selectivity can not only stably protect the thin film device 40A, but also solve the problem that the thin film device 40A adheres to the preliminary substrate 10 as in the conventional wet etching process. have.

In the etching process using the photoresist PR described above with reference to FIGS. 2A to 2D, the pattern of the photoresist is partially connected such that the thin film device 40A is partially connected to the non-device region 40B of the thin film stack 40 ′. To adjust the selective etching process. This will be described in more detail with reference to FIG. 3.

3A is a top plan view of the thin film laminate in which the thin film device shown in FIG. 2E is formed. FIG. 2E is a cross sectional view taken along a line A-A 'of the thin film laminate shown in FIG. 3A, and FIG. 3B is a cross sectional view taken along a line B-B' of the thin film laminate shown in FIG. 3A.

2E and 3, the thin film element 40A is partially connected to the non-device region 40B. That is, the portion P in which the thin film element and the non-element region are connected to each other may be minimized in a range in which the thin film element 40A may be maintained on the preliminary substrate. Except for the region connected with the non-element region, the thin film element is suspended on the preliminary substrate.

Accordingly, in the subsequent thin film device separation process (FIG. 5), when the thin film device 40A applies a physical force to the temporarily bonded support, the thin film device 40A has a ratio of the thin film stack 40 '. It is easily cut out of the element region 40B.

In the present embodiment, one thin film element 40A is partially connected to the non-element region 40B at two points P1 and P2, P3 and P4. As in the present embodiment, it is preferable that the connection portion between the thin film element 40A and the non-element region 40B is located oppositely. Thereby, the thin film element can be floated on the preliminary substrate by the minimum connection portion.

In addition, in the etching process using the photoresist PR described above with reference to FIGS. 2A through 2D, the upper electrode 40c, the piezoelectric layer 40b, and the lower electrode 40a may be etched to control the thin film device 40A. The thickness of the partially connected region P of the non-device region 40B may be adjusted.

The pattern of the region P in which the thin film element 40A and the non-element region 40B are partially connected is not particularly limited. 4A and 4B are top plan views illustrating regions in which a thin film element and a non-element region are partially connected in a method of manufacturing a thin film element according to another exemplary embodiment of the present invention. Referring to FIG. 4A, one thin film element 41A is partially connected at two points facing the non-element region 41B. Referring to FIG. 4B, one thin film element 42A is a non-element region ( 42B) and four points are partially connected, and each point is located opposite each other.

5A through 5D are cross-sectional views illustrating a process of transferring a transfer object in a method of manufacturing a thin film device according to an exemplary embodiment of the present invention.

As shown in FIG. 5A, the support 50 is temporarily bonded on the thin film device 40A.

The support 50 is a temporary support structure used until the thin film device 40A is transferred to the permanent substrate. The support 50 may be brought into close contact with the upper surface of the thin film element 40A.

As used herein, the term “adhesion” may be understood to mean a bonding state that is weaker than the bonding force with the permanent substrate to be transferred while maintaining the bonding force enough to support / handle the thin film element 40A until at least the transfer process.

In other words, a “weld” process means a bond that does not utilize fusion by additional means such as an adhesive or by a high temperature heat treatment process. In a preferred example, the temporary welding process may be in a state in which the smooth surfaces of the thin film device 40A and the supporter 50 are brought into close contact with each other to be temporarily bonded to each other by the force of Van der Waals. This temporary welding process can be carried out sufficiently even under low pressure conditions at room temperature.

Therefore, after the thin film device 40A is transferred to the permanent substrate, the support 50 can be easily separated from the thin film device 40A, and even after separation from the support 50, the separated surface of the thin film device 40A Cleanliness can be guaranteed.

In order to more easily realize the welding by the van der Waals force, the support 50 is preferably made of a material such as poly dimethyl siloxane (PDMS), a silicone rubber-based polymer material. Of course, it is not limited to this material, and if the above-mentioned easily accessible material through a similar interfacial action, it can be preferably employed.

The present invention is not limited to the above-mentioned temporary welding, but may additionally use other means such as an adhesive which can provide only the weak bonding force of the level required for transfer.

Next, as shown in FIG. 5B, the thin film element 40A bonded to the support 50 is separated from the preliminary substrate 10.

In the foregoing process, since the sacrificial layer disposed below the thin film element 40A is almost removed, and the portion where the thin film element 40A is connected to the non-element region 40B is minimized, the thin film element 40A can be easily removed. have. Using a physical force to separate the thin film device 40A from the preliminary substrate 10 without adding a separate removal process for the portion (not shown) connected to the thin film device 40A and the non-device region 40B. Thus, the thin film element 40A can be separated from the non-element region 40B by mechanically breaking the connecting portion.

Subsequently, as shown in FIGS. 5C and 5D, the thin film element 40A bonded to the support 50 is bonded onto the permanent substrate 60 and the support 50 is separated from the thin film element 40A. do.

 The term "permanent substrate" as used herein corresponds to a substrate constituting a thin film element as a substrate provided as a transfer body. In this process, the thin film element 40A and the permanent substrate 60 are bonded to have a bonding force higher than the strength of the temporary bonding of the support 50 and the thin film element 40A. To this end, as in the present embodiment, a separate bonding material layer 61 may be used to bond the thin film device 40A to the permanent substrate 60.

In this process, the thin film device 40A is applied to the permanent substrate 60 after applying a bonding material 61 including a precursor having a bonding strength stronger than that of the thin film device 40A and the support 50 to the permanent substrate 60. Can be bonded.

On the other hand, even if the sacrificial layer 30 is not completely removed or the material film remains on the separated surface of the thin film device 40A, the separation surface of the thin film device 40A is transferred to the permanent substrate 60. It is not provided on the upper surface, but is bonded to the permanent substrate 60. Therefore, the problem caused by the surface contaminated with the residues of the material film and the sacrificial layer can be solved.

As described above, since the thin film element 40A and the permanent substrate 60 are bonded with a high bonding force by the bonding material layer 61, the thin film element 40A and the permanent substrate 60 may be easily separated from the support 50 having a relatively low bonding force. In particular, if the state is welded to each other by the force of van der Waals, unlike the separation surface of the thin film element 40A obtained by separation from the support 50, the upper surface of the thin film element can be kept very clean.

The thin film transfer technology can be used in various thin film devices. More specifically, although a relatively high temperature process is required, such as a semiconductor film forming technique, the thin film transfer technique can be very advantageously used when the substrate used in the device has low heat resistance or low softening point and melting point. In particular, even in the case of a flexible thin film element, the benefits of utilization are very large.

In this case, the permanent substrate 60 may be a flexible substrate made of a polymer material, and the thin film may be an inorganic material or a metal thin film such as polysilicon, and may be, for example, any one of a thin film transistor, a solar cell, and a biosensor. .

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is defined by the appended claims. Accordingly, it will be apparent to one of ordinary skill in the art that various forms of substitution, modification, and alteration are possible without departing from the spirit of the present invention as set forth in the claims, and also appended claims It belongs to the technical idea described in the range.

1A to 1C are cross-sectional views illustrating a process of forming a thin film laminate in a method of manufacturing a thin film device according to an exemplary embodiment of the present invention.

2A through 2E and 3 are cross-sectional views illustrating a process of forming a thin film device in a method of manufacturing a thin film device according to an exemplary embodiment of the present invention.

4 is a top plan view illustrating a region in which a thin film element and a non-element region are partially connected in a method of manufacturing a thin film element according to another exemplary embodiment of the present disclosure.

5A to 5D are cross-sectional views illustrating a transfer object transfer process in a method of manufacturing a thin film device according to an exemplary embodiment of the present invention.

Claims (13)

Forming a sacrificial layer on the preliminary substrate; Forming a thin film stack for a desired thin film device on the sacrificial layer; Forming the thin film device such that the desired thin film device and the non-device region are partially connected to the desired thin film device from the thin film stack using a selective etching process performed to expose the sacrificial layer; Removing the sacrificial layer through the exposed area of the sacrificial layer so that the thin film device floats on the preliminary substrate; Separating the thin film device from the thin film stack by temporarily bonding a support on the thin film stack on which the thin film device is formed; And A method of manufacturing a thin film device comprising the step of transferring the thin film device temporarily bonded to the support on a permanent substrate. The method of claim 1, Partial connection of the thin film element and the non-element region is made by the connecting portion of the thin film element and the non-element region are located opposite. The method of claim 1, Partial connection between the thin film device and the non-device region is performed by an etching process using a photoresist. The method of claim 1, Removing the sacrificial layer is a method of manufacturing a thin film device, characterized in that performed by a dry etching process. The method of claim 4, wherein The sacrificial layer is a method of manufacturing a thin film device, characterized in that the amorphous silicon. The method of claim 4, wherein The dry etching process is a method of manufacturing a thin film device, characterized in that performed using Xe ₂ F gas as an etchant. The method of claim 1, And forming a protective film protecting the preliminary substrate on an upper surface of the preliminary substrate before forming the sacrificial layer. The method of claim 7, wherein The protective film is a method of manufacturing a thin film device, characterized in that the oxide film or nitride film. The method of claim 1, And temporarily bonding the support to press the support such that the upper surface of the thin film stack and the surface of the support are welded. 10. The method of claim 9, The support is a method for manufacturing a thin film device, characterized in that the poly dimethyl siloxane or silicon rubber polymer. The method of claim 1, The separating of the thin film device may include cutting the portion where the thin film device and the non-device region are connected by applying a physical force to the support on which the thin film device is temporarily bonded. The method of claim 1, The permanent substrate is a method of manufacturing a thin film device, characterized in that the flexible substrate. The method of claim 1, The thin film device is a method of manufacturing a thin film device, characterized in that any one of a thin film transistor, a solar cell and a biosensor.

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