TWI536627B - Method of forming top contact organic thin film transistor with passivation layer - Google Patents

Description

Upper contact type organic thin film transistor and method for manufacturing protective layer

The present invention relates to a method of fabricating a semiconductor structure, and more particularly to a method of fabricating an organic thin film transistor.

In general, the upper contact structure is formed by depositing an organic active layer before depositing the source/drain. While the organic semiconductor material as the active layer is quite sensitive to solvents such as developer solutions, it is generally not possible to pattern the organic active layer and subsequently deposited source/drain electrodes using general lithography. The more commonly used method is a metal shadow mask to achieve local deposition, and the fabricated component is better than the lower contact structure. However, in general, metal masks are manufactured by laser processing, so that the mask gaps are about tens of micrometers, and the size of the components thus produced is also in the same size range, which is disadvantageous for the integration of components. Not suitable for large-scale mass production.

In view of the above, the present invention provides a method for fabricating an organic thin film transistor, which defines an active layer and a source/drain in a lithography process, thereby facilitating the miniaturization and integration of the device.

The present invention provides a method of producing an organic thin film transistor. Forming a gate, an insulating layer, a composite buffer layer, and a first photoresist layer on the substrate, and the first photoresist layer has at least one first opening. The first opening is deepened until a portion of the insulating layer is exposed. An active layer is formed at the bottom of the first opening. The first protective layer fills the first opening and covers the active layer. The first photoresist layer is removed. Forming a second protective layer and a second photoresist layer on the first protective layer, and the second photoresist layer has at least two second openings. The second opening is deepened until each of the second openings exposes a portion of the active layer. A contact is formed in the second opening.

In an embodiment of the invention, the composite buffer layer includes a first buffer layer and a second buffer layer sequentially disposed on the insulating layer, the first buffer layer is a water-soluble material layer, and the second buffer layer is non-water soluble. Layer of material.

In an embodiment of the invention, the first protective layer is a water-soluble material layer, and the second protective layer is a water-insoluble material layer.

In an embodiment of the invention, the material of the first protective layer comprises polyvinyl alcohol (PVA), and the material of the second protective layer comprises polyvinylphenol (PVP).

In an embodiment of the invention, the materials of the first photoresist layer and the second photoresist layer each include an image inversion photoresist.

In an embodiment of the invention, the first photoresist layer and the second photoresist layer The materials each include a positive photoresist.

In an embodiment of the invention, the step of deepening the first opening includes performing an oxygen plasma etching process and then using deionized water.

In an embodiment of the invention, the step of deepening the second opening includes first performing an oxygen plasma etching process and then using deionized water.

In an embodiment of the invention, after the step of forming the contact, the method further includes removing the second photoresist layer, leaving the second protective layer on the active layer and the first protective layer.

In an embodiment of the invention, the material of the active layer comprises a unipolar semiconductor layer or a bipolar semiconductor layer.

Based on the above, by the method proposed by the present invention, the upper contact organic thin film transistor can be fabricated without damaging the organic active layer. In the present invention, since the organic active layer and the source/drain are defined by a lithography process, the upper contact structure can also be applied to the component size miniaturization, and the high component is still maintained while maintaining good component characteristics. Density, the aperture ratio of a large flat panel display.

The above described features and advantages of the invention will be apparent from the following description.

100‧‧‧Substrate

102‧‧‧ gate

104‧‧‧Insulation

106, 106a, 106b‧‧‧ first buffer layer

108, 108a, 108b‧‧‧ second buffer layer

110‧‧‧Composite buffer layer

112‧‧‧First photoresist layer

113‧‧‧ first opening

114‧‧‧Semiconductor layer

114a‧‧‧Active layer

114b‧‧‧Excessive

116, 116a‧‧‧ first protective layer

118, 118a‧‧‧ second protective layer

120‧‧‧second photoresist layer

121‧‧‧second opening

122‧‧‧Conductor layer

122a‧‧‧Contacts

122b‧‧‧Excess

1A through 1I are schematic cross-sectional views showing a method of fabricating an organic thin film transistor in accordance with an embodiment of the present invention.

1A through 1I are schematic cross-sectional views showing a method of fabricating an organic thin film transistor in accordance with an embodiment of the present invention.

Referring to FIG. 1A, a gate 102, an insulating layer 104, a composite buffer layer 110, and a first photoresist layer 112 are sequentially formed on the substrate 100. As the substrate 100, a semiconductor substrate or a glass substrate can be used. The material of gate 102 can include a transparent conductive oxide or metal. The transparent conductive oxide includes indium tin oxide (ITO) or indium zinc oxide (IZO). The metal includes gold (Au), silver (Ag), aluminum (Al), copper (Cu), titanium (Ti), chromium (Cr) or tantalum (Ta). In one embodiment, when the substrate 100 is heavily doped with a germanium substrate, the step of forming the gate 102 may be omitted, and the substrate 100 may be used as a gate. In another embodiment, a glass substrate coated with an ITO film may be employed. Methods of forming gate 102 include performing a physical vapor deposition process (such as evaporation), conductive ink jet printing, or other transfer techniques.

The material of the insulating layer 104 includes an inorganic insulating material or an organic insulating material. The inorganic insulating material includes cerium oxide, cerium nitride or hafnium oxide (HfO ₂ ). The organic insulating material includes polyvinylphenol (PVP). The method of forming the insulating layer 104 includes performing a physical vapor deposition process (such as evaporation) or a solution process. In one embodiment, a polymer solution including PVP may be formed first, and then the polymer solution is coated on the gate 102 and baked to crosslink the PVP. In one embodiment, the polymer solution includes PVP as a solute, propylene glycol monomethylether acetate (PGMEA) as a solvent, and a polymer of melamine and co-formaldehyde as a crosslinking agent (poly(melamine) -co-formaldehyde), PMCF).

The composite buffer layer 110 is composed of a plurality of layers of material. In an embodiment, the composite buffer layer 110 includes a first buffer layer 106 and a second buffer layer 108 sequentially disposed on the insulating layer 104, as shown in FIG. 1A. The characteristics of the first buffer layer 106 and the second buffer layer 108 are opposite. For example, the first buffer layer 106 is a layer of water soluble material and the second buffer layer 108 is a layer of water insoluble material.

In an embodiment, the material of the first buffer layer 106 comprises polyvinyl alcohol (PVA). The method of forming the first buffer layer 106 includes performing a solution process. In one embodiment, an aqueous solution comprising PVA may be formed first, and then the aqueous solution is applied to the insulating layer 104 and baked to dry the PVA.

In an embodiment, the material of the second buffer layer 108 is the same as that of the insulating layer 104, for example, all of polyvinylphenol (PVP), and the forming method thereof is similar to the method for forming the insulating layer 104, and details are not described herein again. In another embodiment, the material of the second buffer layer 108 is different from the material of the insulating layer 104.

The first photoresist layer 112 is a photoresist layer using an aqueous solution developer, and the material thereof includes a positive photoresist or an image reversal photoresist. In one embodiment, the first photoresist layer 112 is, for example, an AZ5214E photoresist (trade name, available from Jingming Chemical Company). The AZ5214E photoresist is an image reversal photoresist, which means it can be used as a positive or negative photoresist.

In one embodiment, when the AZ5214E photoresist is used as a positive photoresist, the portion of the light that is exposed to it (forming a bond) is soluble in the developer. Coating AZ5214E photoresist Thereafter, exposure, post-exposure bake (PEB), development, and hard bake (HB) are performed to form a first photoresist layer 112 having at least one first opening 113, wherein the developer used is water-soluble. A developer such as RD6 (trade name, purchased from Yajun Enterprise Co., Ltd.). Here, although FIG. 1A illustrates the photoresist pattern as an ideal long square shape, since the first photoresist layer 112 is a positive photoresist layer, the remaining photoresist pattern is formed. Will be slightly laddered.

In another embodiment, when the AZ5214E photoresist is used as an image reversal photoresist, it is generally used to turn positive and negative, and the flow is described as follows. First, the image reversal photoresist is exposed to the first part of the light after image reversal bake, and then exhibits insoluble characteristics. This first part is also the part to be left. Then, after the flood exposure, the second portion which is not exposed to light at the beginning may form a bond, and the second portion may be developed by the water-soluble developer to form at least one first The first photoresist layer 112 of the opening 113. Here, although FIG. 1A illustrates the photoresist pattern as an ideal long square shape, since the first photoresist layer 112 is an image inversion photoresist layer, the remaining photoresist is formed. The pattern will be slightly inverted.

Referring to FIG. 1B and FIG. 1C, the first opening 113 is deepened until a portion of the insulating layer 104 is exposed.

First, as shown in FIG. 1B, a portion of the second buffer layer 108 is removed by using the first photoresist layer 112 having the first opening 113 as a mask to form a second buffer layer 108a. The method of removing a portion of the second buffer layer 108 includes performing an oxygen plasma etching process. In an embodiment, the oxygen plasma etching process further removes a surface portion of the first buffer layer 106. The first opening 113 is extended into the first buffer layer 106, but the insulating layer 104 is not exposed.

Next, as shown in FIG. 1C, a portion of the first buffer layer 106 is removed by using the first photoresist layer 112 having the first opening 113 as a mask to form a first buffer layer 106a. The removal liquid that removes part of the first buffer layer 106 is a water-soluble removal liquid such as deionized water. In one embodiment, the time of use of deionized water is controlled using a time mode.

Next, referring to FIG. 1D, a semiconductor layer 114 is formed on the substrate 100. In an embodiment, the semiconductor layer 114 includes a main layer 114a at the bottom of the first opening 113 and an excess portion 114b on the top surface of the first photoresist layer 112. The material of the semiconductor layer 114 includes a unipolar semiconductor layer or a bipolar semiconductor layer. In an embodiment, the material of the semiconductor layer 114 comprises a pentacene or a derivative thereof. The step of forming the semiconductor layer 114 includes performing an evaporation method, a sputtering method, or a solution process. In the present embodiment, the semiconductor layer 114 is a semiconductor layer having a high hole mobility (such as a pentacene ring) or a semiconductor layer having a high electron mobility, and thus can be regarded as a unipolar semiconductor layer. In another embodiment, the N-type organic semiconductor material and the P-type organic semiconductor material, the vapor-deposited or sputtered N-type inorganic semiconductor material and the P-type inorganic semiconductor material, and the co-evaporation of the N-type organic semiconductor material may be separately vapor-deposited. A P-type organic semiconductor material or an organic semiconductor material having bipolar characteristics is vapor-deposited to form a bipolar semiconductor layer.

Thereafter, referring to FIG. 1D, a first protective layer 116 is formed on the active layer 114a, and the first protective layer 116 is filled in the first opening 113 and covers the active layer 114a. The first protective layer 116 is a layer of water soluble material. In an embodiment, the first protective layer 116 The material of the first buffer layer 106 is the same as that of the first buffer layer 106, and the formation method thereof is similar to the method of forming the first buffer layer 106, and details are not described herein again. In another embodiment, the first protective layer 116 is different in material from the first buffer layer 106.

Referring to FIG. 1E, the first photoresist layer 112 is removed. In an embodiment, during removal of the first photoresist layer 112, the excess portion 114b of the semiconductor layer 114 overlying the first photoresist layer 112 is simultaneously removed, leaving the active layer 114a. The method of removing the first photoresist layer 112 includes performing oxygen plasma or using an acetone lift off.

Referring to FIG. 1F , a second protective layer 118 and a second photoresist layer 120 are sequentially formed on the first protective layer 116 , and the second photoresist layer 120 has at least two second openings 121 .

The second protective layer 118 is a layer of water insoluble material. In an embodiment, the second protective layer 118 is the same material as the second buffer layer 108a, such as polyvinylphenol (PVP), and is formed in a similar manner to the second buffer layer 108a. Narration. In another embodiment, the second protective layer 118 is different in material from the second buffer layer 108a.

The second photoresist layer 120 is a photoresist layer of an aqueous solution developer, and the material thereof includes a positive photoresist or an image inversion photoresist. In an embodiment, the first photoresist layer 112 is, for example, an AZ5214E photoresist. The method of forming the second photoresist layer 120 is similar to the method of forming the first photoresist layer 112, and details are not described herein again. In this embodiment, the second photoresist layer 120 is the same material as the first photoresist layer 112. In another embodiment, the second photoresist layer 120 is different from the material of the first photoresist layer 112. Here, although FIG. 1F is an example in which the photoresist pattern is illustrated as an ideal long square shape, when the second photoresist layer 120 is a positive type. When the photoresist layer is formed, the photoresist pattern formed by the photoresist layer may be slightly ladder-shaped; and when the second photoresist layer 120 is an image inversion photoresist layer, the photoresist pattern formed by the photoresist layer may be slightly inverted. Ladder type.

Referring to FIG. 1G, the second opening 121 is deepened until each of the second openings 121 exposes a portion of the active layer 114a. First, a portion of the second protective layer 118 and a portion of the second buffer layer 108a are removed by using the second photoresist layer 120 having the second opening 121 as a mask to form a second protective layer 118a and a portion of the second buffer layer 108b. The removing step includes performing an oxygen plasma etching process. In one embodiment, the oxygen plasma etching process further removes the surface portion of the first protective layer 116 such that the second opening 121 extends into the first protective layer 116, but the active layer 114a is not exposed.

Next, a portion of the first buffer layer 106a and a portion of the first protective layer 116 are removed by using the second photoresist layer 120 having the second opening 121 as a mask to form the first buffer layer 106b and the first protective layer 116a. Here, the removal liquid that removes part of the first buffer layer 106a and part of the first protection layer 116 is deionized water, and the deionized water does not affect the performance of the active layer 114a. In one embodiment, the time mode is used to control the time of use of the deionized water.

Next, referring to FIG. 1H, a conductor layer 122 is formed on the substrate 100. In an embodiment, the conductor layer 122 includes a contact 122a at the bottom of the second opening 121 and an excess portion 122b on the top surface of the second photoresist layer 120. The material of the conductor layer 122 includes a metal such as copper (Cu), gold (Au), platinum (Pt) or an alloy thereof. In an embodiment, the material of the conductor layer 122 comprises gold. The step of forming the conductor layer 122 includes performing physical vapor deposition such as evaporation or sputtering.

Thereafter, referring to FIG. 1I, the second photoresist layer 120 is removed. In one embodiment, the second photoresist layer 120 and the excess portion 122b of the conductor layer 122 thereon are removed by lift off, leaving the second protective layer 118a on the active layer 114a and the first protection. Layer 116a, and leaving a contact 122a (ie, source/drain) in the second opening 121. The removal liquid from which the second photoresist layer 120 is removed is acetone. Thus far, the fabrication of the contact organic thin film transistor of the present invention was completed.

In the present invention, the active layer and the source/drain are defined by a positive photoresist or an image inversion photoresist, which is advantageous for the miniaturization and integration of the components. In addition, the use of image reversal photoresist has more unpredictable effects. Since the positive photoresist generally has a trapezoidal shape after development, it is difficult to conform to the size exposed by the reticle; in addition, since the positive photoresist forms a bond for the exposed portion of the light (soluble in the developer) Therefore, the unexposed portion is not bonded (the portion left after development), and the softening point temperature is about 110 to 130 degrees, which is unfavorable for subsequent deposition processes such as helium/source. Will make the photoresist soften and deform, affecting the component production yield and accuracy. Generally, the deposition enthalpy/source temperature is higher than this temperature. However, in the present invention, we use an image inversion photoresist which can form an inverted angle and the exposed portion is bonded, thereby preventing subsequent high temperature deposition and conforming to the size of the mask.

In summary, the present invention provides a method for fabricating an organic thin film transistor, wherein the active layer and the source/drain are defined by a lithography process, which facilitates the miniaturization and integration of the device. By the method of the invention, in addition to the contact organic thin film transistor having better electrical properties, and simultaneously leaving a protective layer with high water barrier/gas barrier properties above the active layer (ie, in the middle of FIG. 1I) Second protective layer 118a and First protective layer 116a). Therefore, the method of the invention has the characteristics of simplifying the process, widening the area, compatible with the general yellow light lithography process, and having the characteristics of relatively accurate fabrication and small component size, and is quite competitive.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Substrate

102‧‧‧ gate

104‧‧‧Insulation

106a‧‧‧First buffer layer

108a‧‧‧Second buffer layer

112‧‧‧First photoresist layer

113‧‧‧ first opening

114‧‧‧Semiconductor layer

114a‧‧‧Active layer

114b‧‧‧Excessive

116‧‧‧First protective layer

Claims (10)

A method for manufacturing an organic thin film transistor, comprising: sequentially forming a gate, an insulating layer, a composite buffer layer, and a first photoresist layer on a substrate, the first photoresist layer having at least one first opening Deepening the first opening until a portion of the insulating layer is exposed; forming an active layer at the bottom of the first opening; forming a first protective layer on the active layer, the first protective layer filling the first Opening and covering the active layer; removing the first photoresist layer; sequentially forming a second protective layer and a second photoresist layer on the first protective layer, the second photoresist layer having at least two second Openings; the second openings are deepened until the second openings expose portions of the active layer; and two contacts are formed in the second openings, respectively. The method for fabricating an organic thin film transistor according to claim 1, wherein the composite buffer layer comprises a first buffer layer and a second buffer layer sequentially disposed on the insulating layer, the first buffer layer It is a layer of water soluble material, and the second buffer layer is a layer of water insoluble material. The method for producing an organic thin film transistor according to claim 1, wherein the first protective layer is a water-soluble material layer, and the second protective layer is a water-insoluble material layer. The method for producing an organic thin film transistor according to claim 1, wherein the material of the first protective layer comprises polyvinyl alcohol (PVA), and the material of the second protective layer comprises polyvinylphenol (PVP). The method for fabricating an organic thin film transistor according to claim 1, wherein the materials of the first photoresist layer and the second photoresist layer each comprise an image inversion photoresist. The method for producing an organic thin film transistor according to claim 1, wherein the materials of the first photoresist layer and the second photoresist layer each comprise a positive photoresist. The method for producing an organic thin film transistor according to claim 1, wherein the step of deepening the first opening comprises performing an oxygen plasma etching process and then using deionized water. The method for producing an organic thin film transistor according to claim 1, wherein the step of deepening the second openings comprises performing an oxygen plasma etching process and then using deionized water. The method for manufacturing an organic thin film transistor according to claim 1, after the step of forming the contacts, further comprising removing the second photoresist layer, leaving the second protection on the active layer a layer and the first protective layer. The method for producing an organic thin film transistor according to claim 1, wherein the material of the active layer comprises a unipolar semiconductor layer or a bipolar semiconductor layer.