JP4019305B2 - Thin film device manufacturing method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for manufacturing a semiconductor device using an inter-substrate transfer technique for thin film elements.
[0002]
[Prior art]
In semiconductor application devices such as liquid crystal display (LCD) panels and electroluminescence (EL) displays, it is sometimes desirable to use a plastic substrate as the base substrate for reasons such as prevention of breakage due to deformation and dropping, and cost reduction. is there.
[0003]
However, high-temperature processes are used in the manufacture of thin film transistors used in panel-type displays, but some circuit elements such as plastic substrates and EL elements cannot withstand high temperatures.
[0004]
Therefore, the applicant manufactured a thin film semiconductor device on a heat-resistant basic substrate by a conventional semiconductor manufacturing technique including a high temperature process, and then peeled off the element formation film (layer) on which the thin film semiconductor device was formed from the substrate, A transfer technique for manufacturing a semiconductor application device by sticking this to a plastic substrate is proposed. For example, it is described in detail in Japanese Patent Application Laid-Open Nos. 10-12529, 10-12530, and 10-12531 as “peeling method”.
[0005]
[Problems to be solved by the invention]
However, in the thin film device manufactured by using the above-described peeling transfer technology, the element forming layer is transferred from the base substrate to the transfer substrate relatively upside down in a single transfer state. The original upper surface is in close contact with the transfer substrate, and external wiring cannot be connected to the element formation layer as it is.
[0006]
For this reason, when the first transfer is performed from the basic substrate to the temporary transfer substrate, and the second transfer is performed from the temporary transfer substrate to the target transfer substrate (such as a plastic substrate), thereby forming the basic substrate. The element formation layer is transferred to the transfer substrate so as to have the same orientation as in FIG. That is, in order to perform wiring connection and formation of other elements on the upper surface of the element formation layer, transfer twice is required.
[0007]
Further, since the process becomes complicated as the thin film devices are multi-layered, it is desirable that the number of times of transfer be one.
[0008]
Therefore, an object of the present invention is to provide a method of manufacturing a thin film device that can reduce the complexity and time of the process due to twice transfer.
[0009]
Another object of the present invention is to reduce the degree of lamination of a thin film device on one side of a substrate.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a thin film device manufacturing method according to a reference example is characterized in that a thin film device formed on a basic substrate is transferred to a transfer substrate, and the thin film device is peeled off by applying necessary energy to the basic substrate. Forming a separation layer having a thin film element on the separation layer, bonding a transfer substrate to one surface of the transfer layer via an adhesive layer, and the separation Applying the energy to the layer to cause peeling, transferring the transfer layer to the transfer substrate, and connecting the thin film element to the other surface of the transfer layer exposed by being transferred to the transfer substrate And a step of forming a new thin film element connected to the thin film element through the exposed hole on the other surface side of the transferred layer.
[0011]
With this configuration, the back surface of the transfer layer including the thin film element can be used for forming the thin film device, and only one transfer is required.
[0012]
Further, the thin film device manufacturing method of the reference example is a thin film device manufacturing method for transferring a thin film element formed on a basic substrate to a transfer substrate. Forming a base layer on the separation layer, forming a transfer layer including a thin film element on one surface of the base layer, and forming a transfer substrate on the transfer layer via an adhesive layer. A step of bonding, a step of transferring the transfer layer to the transfer substrate by applying the energy to the separation layer, and a base substrate of the transfer layer exposed by being transferred to the transfer substrate Forming an exposed hole for connecting to the thin film element on the other surface, and forming a new thin film element connected to the thin film element through the exposed hole on the other surface side of the base substrate And including.
[0013]
By adopting such a configuration, it is possible to form elements, wirings, and the like on both surfaces of the base substrate of the transfer target layer to be peeled and transferred, and only one transfer is required.
[0014]
The method for manufacturing a thin film device of the present invention includes a step of forming a separation layer on a base substrate having a protrusion, a step of forming a foundation layer on which the element is formed on the separation layer, and the foundation layer. Etch back the exposed layer from one side of the underlying layer to expose the separation layer, forming the transferred layer including a thin film element on the underlying layer, and on one side of the transferred layer A step of bonding a transfer substrate through an adhesive layer; peeling of the separation layer; transferring the transfer layer from the base substrate to the transfer substrate; and transferring the transfer layer from the other side of the base layer And a step of forming a new thin film element on the other surface side of the base layer.
Preferably, the transferred layer and the new thin film element are electrically connected at a portion where a part of the transferred layer is exposed from the base layer.
[0015]
By adopting such a configuration, it becomes possible to connect a new thin film element on the other surface side of the transferred layer to the thin film element in the transferred layer without the need for drilling the substrate later.
[0016]
Preferably, the new thin film element includes a wiring layer, an electrode layer, and a thin film transistor. Accordingly, a wiring layer, an electrode layer, a thin film transistor, and the like can be formed on the flat back surface of the base layer of the element formation layer positioned so as to be inverted with respect to the substrate by one-time transfer.
[0017]
Preferably, the material of the separation layer is selected so as to cause ablation in which the bonding force between atoms or molecules disappears or decreases by irradiation with light such as a laser beam.
[0018]
Preferably, the separation layer is formed of a multilayer film including an amorphous silicon film and a metal film formed thereon. This facilitates peeling in the separation layer and peeling at the boundary between the separation layer and the adjacent layer.
[0019]
Preferably, the separation layer includes amorphous silicon or silicon nitride, and the amorphous silicon includes hydrogen. Thereby, when light is irradiated, hydrogen is separated (gasified), and the bonding force between molecules becomes weak. Further, silicon nitride contains nitrogen, and when irradiated with light, nitrogen is separated and the bonding force between molecules is weakened.
[0020]
Preferably, the bonding layer between the transfer substrate and the transferred layer is a permanent adhesive.
[0021]
The thin film device manufactured as described above is, for example, a thin film semiconductor device or an electro-optical device. The electro-optical device includes a liquid crystal display device, an EL device, an electrophoresis device, and the like, and is advantageously applied to an active matrix substrate using those plastic substrates. In the present invention, the transfer substrate is not limited to a plastic substrate, and various substrates such as glass and ceramic can be used.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a method for manufacturing a thin film device of the present invention will be described with reference to the drawings.
[0023]
FIGS. 1A to 1E show a manufacturing process (process) of a thin film device according to a reference example of the present invention.
[0024]
First, as shown in FIG. 1A, for example, a light-transmitting heat-resistant substrate such as quartz glass that can withstand about 1000 ° C. is used as the element formation substrate 1. In addition to quartz glass, heat-resistant glass such as soda glass, Corning 7059, Nippon Electric Glass OA-2, or the like can be used for the element forming substrate 1. The thickness of the element formation substrate 1 does not have a large limiting element, but is preferably about 0.1 mm to 0.5 mm, and more preferably 0.5 mm to 1.5 mm. If the thickness of the element forming substrate 1 is too thin, the strength is lowered. Conversely, if the thickness is too thick, the irradiation light is attenuated when the transmittance of the element forming substrate 1 is low. However, when the transmittance of the irradiation light of the element forming substrate 1 is high, the thickness can be increased beyond the upper limit. A separation layer 2 is formed on the element formation substrate 1.
[0025]
The separation layer 2 is peeled (also referred to as “in-layer peeling” or “interface peeling”) in the layer or at the interface by irradiation light such as laser light. That is, by irradiating light of a certain intensity, the interatomic or intermolecular bonding force of the atoms or molecules of the material constituting the separation layer 2 disappears or decreases, resulting in ablation, etc. It is what happens. Moreover, gas may be emitted from the separation layer 2 by irradiation with irradiation light, leading to separation. There are cases where the component contained in the separation layer 2 is released as a gas and leads to separation, and there are cases where the separation layer 2 absorbs light to become a gas and its vapor is emitted to cause separation.
[0026]
As the composition of the separation layer 2, for example, amorphous silicon (a-Si) can be used. This amorphous silicon may contain hydrogen (H). The hydrogen content is preferably about 2 at% or more, and more preferably 2 to 20 at%. When hydrogen is contained, hydrogen is released by light irradiation, thereby generating an internal pressure in the separation layer 2, which promotes peeling. The content of hydrogen is set appropriately according to film forming conditions, for example, when using the CVD method, such as gas composition, gas pressure, gas atmosphere, gas flow rate, gas temperature, substrate temperature, and light power to be input. To make adjustments. Other separation layer materials include silicon oxide or silicate compounds, nitride ceramics such as silicon nitride, aluminum nitride, and titanium nitride, and organic polymer materials (those whose atomic bonds are broken by light irradiation). , Metals such as Al, Li, Ti, Mn, In, Sn, Y, La, Ce, Nd, Pr, Gd, or Sm, or an alloy containing at least one of them.
[0027]
The thickness of the separation layer 2 is preferably about 1 nm to 20 μm, more preferably about 10 nm to 2 μm, and further preferably about 40 nm to 1 μm. This is because if the thickness of the separation layer 2 is too thin, the uniformity of the formed film thickness is lost and uneven peeling occurs, and if the thickness of the separation layer 2 is too thick, the irradiation light required for the peeling is reduced. It is necessary to increase the power (light quantity), and it takes time to remove the residue of the separation layer 2 remaining after peeling.
[0028]
The formation method of the separation layer 2 may be any method that can form the separation layer 2 with a uniform thickness, and can be appropriately selected according to various conditions such as the composition and thickness of the separation layer 2. For example, various vapor deposition methods such as CVD (including MOCCVD, low pressure CVD, ECR-CVD), vapor deposition, molecular beam vapor deposition (MB), sputtering, ion plating, PVD, electroplating, immersion plating ( Dipping), various plating methods such as electroless plating method, Langmuir-Blodget (LB) method, spin coating, spray coating method, roll coating method and other coating methods, various printing methods, transfer method, inkjet method, powder jet method Applicable to etc. Of these, two or more methods may be combined.
[0029]
In particular, when the composition of the separation layer 2 is amorphous silicon (a-Si), it is preferable to form the film by CVD, particularly low pressure CVD or plasma CVD. In addition, when the separation layer 2 is formed by using a ceramic by a sol-gel method or is made of an organic polymer material, it is preferably formed by a coating method, particularly by spin coating.
[0030]
Preferably, an intermediate layer is formed between the separation layer 2 and an element formation layer 3 to be described later, or the separation layer 3 includes a plurality of layers including the intermediate layer. This intermediate layer prevents migration of components to or from the protective layer, insulating layer, transferred layer, or the like, which physically or chemically protect the transferred layer during manufacture or use, for example. It exhibits at least one of the functions as a barrier layer and a reflective layer.
[0031]
The composition of the intermediate layer can be appropriately selected according to the purpose. For example, in the case of an intermediate layer formed between the separation layer made of amorphous silicon and the transfer layer, silicon oxide such as SiO 2 can be used. Examples of the composition of the other intermediate layer include metals such as Pt, Au, W, Ta, Mo, Al, Cr, Ti, or alloys containing these as main components.
[0032]
The thickness of the intermediate layer is appropriately determined according to the purpose of formation. Usually, the thickness is preferably about 10 nm to 5 μm, and more preferably about 40 nm to 1 μm.
[0033]
As a method for forming the intermediate layer, various methods described in the separation layer 2 can be applied. In addition to forming the intermediate layer as a single layer, two or more layers can be formed using a plurality of materials having the same or different compositions.
[0034]
On the separation layer 2, an element formation layer 3 on which an electric element such as a thin film transistor is formed is formed. The element formation layer 3 includes an insulating layer 31 such as a silicon oxide film serving as a base layer for element formation, a silicon layer including source / drain regions doped with impurities, a gate insulation film 33, a gate wiring film 34, an interlayer insulation. The film 35, the source / drain wiring film 36, and the like.
[0035]
For example, the insulating layer 31 is formed by depositing a silicon oxide film by a CVD method, and the silicon layer 32 is further formed. Next, the silicon layer 32 is patterned to form a transistor region. The gate oxide film 33 is formed by oxidizing the silicon film. Ion implantation for the gate region is performed in the transistor region. Next, polysilicon in which impurities are diffused at a high concentration is deposited by CVD, and patterning is performed to form a gate wiring film 34. High concentration impurity implantation is performed on the source / drain region using the gate wiring to form the source / drain. A heat treatment for impurity activation is performed, and then a silicon oxide film is deposited by a CVD method to form an interlayer insulating film 35. Contact holes are opened in the interlayer insulating film 35 on the source / drain regions. Polysilicon in which impurities are implanted at a high concentration is deposited by a CVD method or a metal film is deposited by a sputtering method, and this is patterned to form a wiring film.
[0036]
In this way, the element forming layer 3 is configured. In addition, as the thin film element included in the element formation layer 3, a pixel electrode, a connection pad, a resistor, a capacitor, or the like can be formed. A method of forming a thin film transistor or the like can be performed, for example, according to the method described in Japanese Patent Publication No. 2-50630.
[0037]
In the above case, the element forming layer 3 is a transferred layer. However, the transferred layer is not limited to a thin film, and may be a thick film such as a coating film or a sheet.
[0038]
Next, as shown in FIG. 1B, an adhesive is applied on the element forming layer 3 by spin coating or the like to form the adhesive film 4. On this, the transfer substrate 5 is placed and bonded.
[0039]
As the adhesive, for example, various curable adhesives such as a reactive curable adhesive, a thermosetting adhesive, a photocurable adhesive, and an anaerobic curable adhesive can be used. The composition is appropriately selected from epoxy, acrylate, silicone and the like.
[0040]
The transfer substrate 5 may be inferior in characteristics such as heat resistance and corrosion resistance, for example, if there is no high-temperature process in the subsequent process. It may be flexible and elastic. Examples of such materials include various synthetic resins and various glass agents. The synthetic resin may be either a thermoplastic resin or a thermal effect resin. For example, other resins such as polyethylene, polypropylene, and ethylene-propylene copolymer are applicable. As the glass material, for example, quartz glass, alkali silicate glass, soda lime glass, and others can be used.
[0041]
As the transfer substrate 5, for example, a liquid crystal cell constituting an independent device itself, for example, a color filter, an electrode layer, a dielectric layer, an insulating layer, a semiconductor element, or the like. It may constitute a part.
[0042]
Next, as shown in FIG. 1C, the entire surface is irradiated with, for example, laser light from the first substrate side 1 to weaken the bonding of atoms and molecules in the separation layer 2. Further, the hydrogen in the separation layer 2 is molecularized and separated from the crystal bonds, and the base substrate side 1 and the element formation layer 3 are separated. As a result, the element forming layer 3 as the transfer layer is transferred to the transfer substrate 5.
[0043]
Next, as shown in FIG. 1D, a very flat base insulating film 31 corresponding to the source / drain regions of the element formation layer 3 is patterned to open contact holes having a diameter of about 20 to 30 μm. For patterning, dropping of an etching solution by photolithography or an inkjet method, laser etching, or the like can be applied.
[0044]
Next, as shown in FIG. 1E, for example, a transparent electrode ITO 38 is laminated on the base layer 31 and patterned to form pixel electrodes, terminal electrodes, and the like. Such a substrate is used as a pixel substrate of a liquid crystal display or an EL display.
[0045]
In the reference example , the transparent electrode is formed as the thin film element, but is not limited thereto. For example, various things such as a pixel electrode, a connection terminal, a wiring, a thin film transistor, a dielectric, and an EL light emitter can be formed.
[0046]
2 (a) to 2 (e) show an embodiment of the present invention. In the figure, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
[0047]
In this embodiment , instead of forming the opening 37 in the subsequent process on the base substrate 31 (see FIG. 1D), a substrate having the protrusion 1a formed on the base substrate 1 corresponding to the opening 37 is formed. I use it. After the separation film 2 is formed on the base substrate 1, a silicon oxide film 31 as a base layer is deposited to a predetermined thickness. The silicon oxide film 31 is etched back to the separation film 2 and flattened. Etch back can use mechanical polishing and etching. Thereafter, the same process as in the first embodiment is performed to form the element formation layer 3 (FIG. 2A). Thereafter, the transfer substrate 5 is bonded (FIG. 2B), and the base substrate 1 is peeled off (FIG. 2C). An opening 37 that can be connected to the element formation layer is formed in the base layer 31 by the protrusion 1a of the base substrate 1 (FIG. 2D). Using this opening 37, the thin film element 38 formed on the back surface side of the base layer 31 and the element of the element formation layer 3 formed on the front surface side are electrically connected (FIG. 2E). Such a panel is used as a pixel substrate of a liquid crystal display or an EL display. Various elements such as a pixel electrode, a connection terminal, a wiring, a thin film transistor, a dielectric, and an EL light emitter can be formed as the thin film element 38.
[0048]
Since the base substrate 1 on which the protrusions 1a are formed can be used repeatedly, it is convenient to use a relatively expensive base substrate efficiently.
[0049]
As described above, according to the above-described embodiment , the element forming layer 3 is transferred and formed on the transfer substrate 5 such as plastic without going through the step of using the temporary transfer substrate. Since the transfer process only needs to be performed once, the manufacturing process is simplified. In addition, a thin film element base substrate back surface that is not normally used is used. Since this surface is a flat surface, it can be easily used in subsequent processes.
[0050]
Moreover, the said process can be used for normal thin-film transistor manufacturing equipment, and its condition is good.
[0051]
【The invention's effect】
As described above, in the present invention, the wiring is drawn out to the back side of the base of the element forming film. Connection can be easily secured.
[Brief description of the drawings]
FIG. 1 is a process diagram illustrating a reference example of the present invention.
FIG. 2 is a process diagram illustrating an embodiment of the present invention.
[Explanation of symbols]
1 Substrate 2 Separation layer 3 Element formation layer 4 Adhesive layer 5 Transfer substrate

Claims (10)

Forming a separation layer on the base substrate having the protrusions;
Forming a base layer on which the element is formed on the separation layer;
Etching back the foundation layer to expose the separation layer on the protrusion from one side of the foundation layer;
Forming a transfer layer including a thin film element on the underlayer;
Bonding a transfer substrate to one surface of the transfer layer via an adhesive layer;
Causing the separation layer to peel off, transferring the transferred layer from the base substrate to the transfer substrate, and exposing a part of the transferred layer from the other side of the base layer;
Forming a new thin film element on the other surface side of the base layer;
A method of manufacturing a thin film device including:   The method for manufacturing a thin film device according to claim 1, wherein the transferred layer and the new thin film element are electrically connected to each other at a portion where the transferred layer is partially exposed from the underlayer.   The method for manufacturing a thin film device according to claim 1, wherein the new thin film element includes a wiring film, an electrode, a terminal, and a thin film transistor.   4. The method for manufacturing a thin film device according to claim 1, wherein the separation layer loses or decreases the bonding force between atoms or molecules by irradiation of light. 5.   The method of manufacturing a thin film device according to claim 1, wherein the separation layer includes a plurality of films.   The method for manufacturing a thin film device according to claim 1, wherein the separation layer includes amorphous silicon or silicon nitride.   6. The method of manufacturing a thin film device according to claim 5, wherein the plurality of films include an amorphous silicon film and a metal film formed thereon.   The method of manufacturing a thin film device according to claim 6, wherein the amorphous silicon contains hydrogen.   The method for manufacturing a thin film device according to claim 1, wherein the adhesive layer is a permanent adhesive.   The method for manufacturing a thin film device according to claim 1, wherein the thin film device is a semiconductor device.

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