JP2016076547A - Fabrication method of field effect transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fabrication method of a field effect transistor, facilitating the wiring formation and the formation of a semiconductor layer by inkjet printing.SOLUTION: A fabrication method of a bottom-contact type field effect transistor includes the steps of: forming a lyophilic/lyophobic pattern having a lyophilic portion and a lyophobic portion on a gate insulation film or a base material; printing a conductive ink to the lyophilic portion by inkjet printing to form a source/drain electrode; and forming a semiconductor layer by inkjet printing on the source/drain electrode. In the source/drain electrode, the width of a channel portion is 20 μm or less, the channel portion has a comb shape, and the width of the source/drain electrode is 20-50 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a field effect transistor, particularly using ink jet printing.

  Field effect transistors (hereinafter also referred to as FETs) are widely used as drive elements such as displays and sensors. A typical FET structure can be divided into a bottom gate type in which a gate electrode is disposed in a lower layer of a gate insulating film and a top gate type in which a gate electrode is disposed in an upper layer of the gate insulating film. Further, it can be divided into a bottom contact type FET in which a semiconductor layer is disposed above the source / drain electrodes and a top contact type FET in which a semiconductor layer is disposed below the source / drain electrodes. The FET is conventionally produced using a vacuum device such as wiring formation using photolithography, vapor deposition / sputtering, or the like.

  However, in circuit formation by photolithography, an increase in waste liquid becomes a problem due to etching and development, and the equipment of a vacuum apparatus increases with the size of the processing area, resulting in high costs.

  Therefore, in recent years, a method for manufacturing an FET using a printing method has attracted attention. In the printing method, each component such as an electrode and a semiconductor layer can be additionally manufactured only in a necessary region, so that cost can be reduced. Moreover, it is excellent also in continuous productivity, and it is easy to make a base material flexible like a film.

  Printing methods that allow patterning such as wiring formation include gravure printing, gravure offset printing, flexographic printing, reverse offset printing, ink jet printing, and screen printing. Of these, ink jet printing requires and does not require a printing plate. It is possible to print ink only at a certain point, and attention is paid to the fact that the amount of ink used can be greatly reduced.

  However, ink jet printing is not suitable for forming high-definition wiring because ink drops with relatively low viscosity are liable to flow and formability of fine wiring is inferior to plate printing. .

  However, as one of the methods for forming high-definition wiring, there is a lyophobic treatment in which a lyophilic portion and a lyophobic portion are formed in advance on the printed material using the lyophilicity and lyophobic property for ink. Can be mentioned. For example, in Patent Document 1, a first region having surface characteristics (lyophilicity) on which a material for forming a pattern is preferentially deposited on the surface of a substrate is compared with the first region. And forming a second region having surface characteristics (liquid repellency) on which the material for forming the pattern is difficult to be deposited, and applying the material for forming the pattern to the substrate. A pattern forming method comprising: selectively depositing the material in the first region; and depositing a second material having low compatibility with the material for forming the pattern. Have been described. In this way, fine wiring can be produced by applying an affinity treatment to the substrate surface before printing.

  However, the lyophobic treatment is an effective method for producing a fine FET. However, when producing a bottom contact type FET, if the semiconductor ink is printed after the source / drain electrodes are produced, the ink is ejected from the liquid-repellent part. As a result, the channel portion cannot be formed stably. Further, when a top contact type FET is to be manufactured, there is a problem in that the semiconductor layer has to be repellent and the semiconductor is damaged.

JP 2006-303199 A

  An object of the present invention is to provide a method for manufacturing a field effect transistor (FET) that facilitates the formation of wiring by inkjet printing and the formation of a semiconductor layer.

That is, the present invention includes a step of producing a lyophobic pattern having a lyophilic portion and a lyophobic portion on a gate insulating film or a substrate, and printing a conductive ink by inkjet printing on the lyophilic portion. A step of forming a source / drain electrode and a step of forming a semiconductor layer on the source / drain electrode by ink jet printing, wherein the channel width of the source / drain electrode is 20 μm or less; The present invention relates to a method of manufacturing a bottom contact type field effect transistor having a comb shape and a width of the source / drain electrodes of 20 to 50 μm.
The present invention also relates to the above-described method for producing a field effect transistor, wherein the difference between the contact angle of the lyophilic portion and the contact angle of the liquid repellent portion with respect to the conductive ink is 20 ° or more.

  According to the present invention, it is possible to form a wiring by ink jet printing without landing near the channel portion by utilizing the flow of ink, and the semiconductor layer can be formed by ink jet printing by forming the shape of the channel portion into a comb shape. In the formation, a method for manufacturing a transistor can be provided in which a semiconductor layer can be easily formed without the semiconductor ink being repelled from the liquid-repellent channel portion.

  According to the present invention, when forming a bottom contact type FET using ink jet printing, by controlling the shape of the lyophilic part and the liquid repellent part produced by the lyophobic treatment, wiring formation by ink jet printing is facilitated, and It is possible to provide a method for manufacturing a field effect transistor (FET) that facilitates formation of a semiconductor layer by inkjet printing.

It is a schematic diagram which shows the source / drain electrode which concerns on embodiment of this invention. It is a photograph of the source / drain electrode after conductive ink printing in Example 1 of the present invention. It is a photograph of the source / drain electrode and semiconductor layer after semiconductor ink printing in Example 1 of the present invention.

  A method for manufacturing a bottom contact type field effect transistor (FET) according to this embodiment includes a step of forming a lyophobic pattern having a lyophilic portion and a lyophobic portion on a gate insulating film or a substrate, and A step of forming a source / drain electrode by printing a conductive ink by ink jet printing on a liquid portion; and a step of forming a semiconductor layer by ink jet printing on the source / drain electrode, The channel portion has a width of 20 μm or less, the channel portion has a comb shape, and the source / drain electrodes have a width of 20 to 50 μm.

  The affinity pattern produced in this embodiment is formed on the gate insulating film when the FET has a bottom gate structure, and on the substrate when the FET has a top gate structure. The lyophobic pattern is formed by forming an extremely thin lyophobic part (also referred to as a lyophobic layer) on the lyophilic part (also referred to as a lyophilic layer) and ablating (decomposing) the lyophobic part at a site to be a circuit However, the method is not limited to these.

  In the case where the FET has a bottom gate structure, the gate insulating film for forming the hydrophobic / repellent pattern is formed above the gate electrode. When the FET has a top gate structure, any substrate can be used for producing the repellent pattern, as long as the repellent pattern can be produced. A gate insulating film is formed on the source / drain electrodes and the semiconductor layer. A gate electrode is formed on the upper portion. In addition, as a base material, substrates, such as a single crystal silicon, a glass substrate, and a plastic, are mentioned.

  The gate insulating film includes an inorganic insulating film and an organic insulating film, and a manufacturing method thereof is not particularly limited. For example, it can be produced by applying an insulating film ink by spin coating or slit die coating, and then drying, baking or curing the ink solvent.

  The thickness of the gate insulating film is preferably 50 to 3000 nm, and more preferably 100 to 2000 nm. If the thickness of the gate insulating film is less than 50 nm, the possibility of a short circuit is increased, which is not preferable. If the thickness exceeds 3000 nm, the gate electrode cannot play the role of a switching gate.

  The dielectric breakdown voltage of the gate insulating film is preferably 2 MV / cm or more, and more preferably 3 MV / cm or more. The dielectric constant is preferably 3-4.

In this embodiment, a source / drain electrode is formed by printing conductive ink on the lyophilic portion of the lyophilic portion having a lyophilic portion and a lyophobic portion by inkjet printing.
The surface states of the lyophilic part and the liquid repellent part can be usually grasped using a contact angle meter. For the contact angle measurement, water, an organic solvent, or the like is used, and a conductive ink for electrode preparation used for inkjet printing is preferable.
As the lyophobic pattern, the difference between the contact angle of the lyophilic portion and the contact angle of the lyophobic portion with respect to the conductive ink is preferably 20 ° or more, more preferably 30 ° or more, and 40 ° or more. Further preferred. By being 20 ° or more, the conductive ink is printed on the lyophilic portion without bleeding or the like, and a highly accurate source / drain electrode is formed.
Further, the contact angle is preferably an advancing contact angle, and a dynamic contact angle is obtained by using a method in which a droplet is slid down by tilting the substrate or an expansion / contraction method in which the droplet amount is increased / decreased. Can be measured as
The dynamic contact angle includes an advancing contact angle and a receding contact angle. For example, when a droplet is slid down (moved) with the substrate inclined, the front (sliding direction or advancing direction) of the droplet. Is the advancing contact angle and the back of the droplet is the receding contact angle.
The surface tension of the conductive ink used is usually 20 to 50 mN / m, preferably 25 to 40 mN / m at room temperature (25 ° C.).

  As the conductive ink for electrode preparation, an ink in which metal particles or metal compound particles are dispersed can be used. The metal is preferably a noble metal, and examples thereof include, but are not limited to, gold, silver, copper, platinum, aluminum, nickel, chromium, palladium, iridium, rhodium, and ruthenium.

  The source / drain electrodes produced by ink jet printing are comb-shaped as shown in FIG. By making the shape of the channel portion into a comb shape, it becomes difficult for semiconductor ink printed by ink jet to be repelled from the channel portion. The electrode width of the source / drain electrodes is characterized by being in the range of 20-50 μm. If the electrode width is less than 20 μm, the circuit forming ink (conductive ink) does not flow, and the source electrode or the drain electrode may not be produced. Further, if the electrode width exceeds 50 μm, when the semiconductor ink is printed after the electrode is formed, the semiconductor ink may flow on the electrode, and the semiconductor ink may be repelled from the channel portion, so that the semiconductor layer cannot be stably formed. . The semiconductor ink is ink for forming a semiconductor layer on the source / drain electrodes.

  The width of the channel part of the source / drain electrode produced by inkjet printing is 20 μm or less, preferably 3 to 20 μm, more preferably 3 to 10 μm. If the width of the channel portion exceeds 20 μm, the ink-jet printed semiconductor ink is likely to be repelled from the channel portion, and the semiconductor layer may not be stably formed. Further, if the width of the channel portion is less than 3 μm, the possibility that the source electrode and the drain electrode come into contact with each other and short-circuit increases, which is not preferable.

  The thickness of the source / drain electrode produced by inkjet printing is preferably 20 nm or more, and more preferably 50 nm or more. If it is less than 20 nm, it is not preferable because a current for switching cannot be supplied.

  In the inkjet printing for producing the source / drain electrodes, it is preferable that the droplets be deposited at a site separated by 20 μm or more from the channel portion in consideration of the accuracy of the droplet deposition position of the inkjet printer, and at a site separated by 30 μm or more. More preferably, the droplets are deposited. If the droplets are deposited to a thickness of less than 20 μm, the conductive ink may protrude from the lyophilic portion and the channel portion may not be formed.

The ink for ink jet printing (semiconductor ink) for producing the semiconductor layer is not particularly limited as long as it can be printed by ink jet. What can form is preferable.
For example, semiconductor inks include low molecular organic semiconductors such as TIPS pentacene and benzothiophene derivatives, poly (3-alkylthiophene) (P3HT) and poly [(9,9-dioctylfluorenyl-2,7-diyl)- Polymer organic semiconductors such as co-bithiophene] (F8T2), polysilicon, carbon nanotubes, oxide semiconductors and the like can be mentioned, but there is no particular limitation.

  The thickness of the semiconductor layer produced by inkjet printing is preferably 10 nm or more, and more preferably 30 nm or more. If the thickness is less than 10 nm, it is not preferable because a current for switching cannot be supplied.

  The gate electrode of the FET only needs to act as a switching gate. There is no particular limitation on a method for manufacturing the gate electrode, but a printing method is preferable in accordance with a method for manufacturing another layer.

  Moreover, in order to perform switching of FET stably, it is preferable to cover a semiconductor layer with an organic or inorganic insulating layer.

Examples using the present invention will be described below, but the present invention is not limited thereto.
Example 1
A gate electrode was produced on a 10 × 10 cm glass substrate using a reversal offset printing machine (PE TESTER manufactured by MHI Solution Technologies). Subsequently, an organic insulator ink (SC-GI01 manufactured by Sumitomo Chemical Co., Ltd.) was applied onto the gate electrode using a spin coater (MS-A150 manufactured by Mikasa Co., Ltd.) and cured in an oven at 180 ° C. for 1 hour. Thus, a gate insulating film was produced.

  The gate insulating film is subjected to UV ozone treatment using a UV ozone cleaning and reforming apparatus (manufactured by Takeden Co., Ltd.) for 3 minutes, and then a fluorine-based ink (Cytop manufactured by Asahi Glass Co., Ltd.) is formed using a spin coater. The plate was dried at 80 ° C. for 3 minutes to prepare a liquid repellent layer (liquid repellent portion).

Ablating the liquid repellent layer (liquid repellent part) using an excimer stepper exposure machine (ELP-300 manufactured by SUS MicroTec, exposure amount: 100 mJ / cm ² ) to remove the liquid repellent part and expose the lyophilic part A repellent pattern was prepared. Here, the length of the channel portion of the repellent pattern is 10 μm, the width of the channel portion is 20 μm, and the electrode width is 30 μm.

The produced repellent pattern was subjected to UV ozone treatment for 3 minutes, and then a conductive silver ink (L-Ag1TeH manufactured by ULVAC, Inc.) was inkjet printed. A material printer (DMP-3000) manufactured by FUJIFILM Dimatix was used for the ink jet apparatus. The discharge position was printed at a position 30 μm away from the channel portion at the shortest. After printing, baking was performed in an oven at 150 ° C. for 1 hour.
As shown in FIG. 2, source / drain electrodes were produced along the repellent pattern. When the thickness of the source / drain electrode was measured with a contact-type step gauge (P-15 manufactured by KLA Tencor), the thickness of the source electrode was 204 nm and the thickness of the drain electrode was 186 nm (both average values).
The channel length of the fabricated source / drain electrodes was 10 μm, the width of the channel portion was 20 μm, the shape was a comb, and the electrode width was 30 μm.

A bottom-gate / bottom-contact type FET was manufactured by ink-jet printing a semiconductor ink (FS0085 manufactured by Flexink) on the prepared source / drain electrodes. The same ink-jet apparatus as that used for producing the source / drain electrodes was used. The discharge amount of the semiconductor ink was 120 pL. As shown in FIG. 3, the ink was not repelled from the liquid repellent part of the channel part, and the semiconductor layer could be formed. It was 560 nm (average value) when the thickness of the semiconductor layer was measured with the contact-type level difference meter. Further, when the FET characteristics were measured using a semiconductor device analyzer (B1500A manufactured by Agilent Technologies), the mobility was 7 × 10 ⁻² cm ² / Vs, and the on / off ratio was 2 × 10 ⁴ .

The contact angle of ink on the produced repellent pattern was measured. For the contact angle measurement, a solid-liquid interface analysis system (DropMaster 500) manufactured by Kyowa Interface Science Co., Ltd. was used. As the measurement method, the advancing contact angle and the receding contact angle were measured using an expansion / contraction method for increasing / decreasing the droplet amount. The ink used was the conductive ink used when the source / drain electrodes were made.
First, a 0.5 μL droplet is made at the tip of the syringe and brought into contact with the substrate, and then the forward contact angle is measured by pushing the ink from the syringe at 6 μL / sec and increasing (expanding) the droplet volume to 22 μL. did. Then, the receding contact angle was measured by sucking ink into the syringe at 6 μL / sec and reducing (shrinking) an appropriate amount of the liquid. The lyophilic part of the produced lyophobic pattern had an advancing contact angle of 6 ° and a receding contact angle of 0 °. On the other hand, the advancing contact angle of the liquid repellent part was 52 °, and the receding contact angle was 7 °.

(Comparative Example 1)
An FET was fabricated under the same conditions as in Example 1 except that the length of the channel portion of the hydrophobic / repellent pattern was 30 μm, the width of the channel portion was 110 μm, and the width of the source / drain electrodes was 30 μm. Although the source / drain electrodes could be produced along the liquid repellent part of the channel part, the semiconductor ink was repelled from the channel part and the semiconductor layer could not be formed.

(Comparative Example 2)
An FET was fabricated under the same conditions as in Example 1 except that the length of the channel portion of the hydrophobic / repellent pattern was 10 μm, the width of the channel portion was 110 μm, and the width of the source / drain electrodes was 30 μm. Although the source / drain electrodes could be produced along the repellent pattern, when the semiconductor ink was inkjet printed, the semiconductor ink was repelled from the channel portion, and the semiconductor layer could not be formed.

(Comparative Example 3)
An FET was manufactured under the same conditions as in Example 1 except that the length of the channel portion of the hydrophobic / repellent pattern was 10 μm, the width of the channel portion was 110 μm, and the width of the source / drain electrodes was 10 μm. Source / drain electrodes could not be produced along the repellent pattern.

(Comparative Example 4)
An FET was fabricated under the same conditions as in Example 1 except that the length of the channel portion of the hydrophobic / repellent pattern was 10 μm, the width of the channel portion was 110 μm, and the width of the source / drain electrodes was 60 μm. Although the source / drain electrodes could be produced along the repellent pattern, when the semiconductor ink was ink-jet printed, the semiconductor ink was wet spread on the electrodes, the semiconductor ink was repelled from the channel portion, and the semiconductor layer could not be formed.

  As shown in the examples, when fabricating a bottom contact type FET using ink jet printing, by controlling the shape and dimensions of the lyophobic pattern (lyophilic part and lyophobic part) produced by the lyophilic process. Therefore, it is possible to easily form a wiring by ink jet printing and to easily form a semiconductor layer by ink jet printing.

1: source electrode, 2: drain electrode, 3: channel part.

Claims (2)

Producing a lyophobic pattern having a lyophilic part and a lyophobic part on the gate insulating film or the substrate;
Forming a source / drain electrode by printing conductive ink on the lyophilic part by inkjet printing; and
Forming a semiconductor layer by inkjet printing on the source / drain electrodes,
A method of manufacturing a bottom contact type field effect transistor, wherein in the source / drain electrode, the channel portion has a width of 20 μm or less, the channel portion has a comb shape, and the source / drain electrode has a width of 20 to 50 μm.   The method for producing a field effect transistor according to claim 1, wherein a difference between a contact angle of the lyophilic portion and a contact angle of the lyophobic portion with respect to the conductive ink is 20 ° or more.

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