JP5105044B2 - Oxide transistor and manufacturing method thereof - Google Patents

Description

  The present invention relates to an oxide transistor in which at least two of three electrodes of a source electrode, a drain electrode, and a gate electrode, a channel layer, and a gate insulating film are formed of an In—Ga—Zn—O film, and a manufacturing method thereof.

  Oxide semiconductors, particularly transparent oxide semiconductors, are indispensable materials for realizing electronic and optical devices having new characteristics. Recently, it has been shown that an In—Ga—Zn—O film has a large field effect mobility even in an amorphous state, and an FET element using an In—Ga—Zn—O film as a channel layer on a PET substrate has been successfully produced. (Non-patent Document 1: Nature 2004, 432, 488).

  However, such an oxide semiconductor is manufactured by forming each electrode, an insulating film, and a channel layer on a substrate by a sputtering method, a vapor deposition method, a CVD method, or the like, but an In—Ga—Zn—O film is formed. When an oxide semiconductor such as a TFT element is used as a channel layer, various other sputtering targets have conventionally been used because the source electrode, the drain electrode, and the gate electrode use three different materials for the insulating film. In addition, a vapor deposition source and an apparatus are required, and it is difficult to manufacture at a low cost.

  Thus, in order for an oxide semiconductor using an In—Ga—Zn—O film to have favorable versatility, reduction in manufacturing cost is a significant issue.

Nature 2004 432 pages 488

  The present invention has been made in view of the above circumstances, and an object thereof is to efficiently manufacture an oxide transistor using an In—Ga—Zn—O film at low cost.

In order to achieve the above object, the present inventor does not need a complicated apparatus in order to manufacture an electronic device such as a TFT transistor on a transparent substrate such as a glass substrate or polyethylene terephthalate at a low cost. As a result of intensive studies in accordance with the guidelines that it is essential to develop processes, combinations of materials, and simple device structures, the resistivity of In-Ga-Zn-O films varies greatly depending on the oxygen content. A plurality of device components formed on the substrate, such as a source electrode, a drain electrode, a gate electrode, a channel layer, and a gate insulating film, and all the components are formed of an In—Ga—Zn—O film. In-Ga by sputtering using a target containing In, Ga and Zn under an atmosphere containing oxygen gas. When forming the Zn—O film, the oxygen content of the In—Ga—Zn—O film is adjusted by changing the oxygen gas flow rate to form In—Ga—Zn—O films having different electrical resistivity. For example, when patterning is performed using a metal mask, two or more of the above-described components can be formed on the substrate only by exchanging the metal mask and adjusting the oxygen gas flow rate. it is also possible to form, it found that an oxide transistors data using an in-Ga-Zn-O oxide can inexpensively manufactured at low cost, and completed the present invention.

Accordingly, the present invention includes a source electrode, the drain electrode and the third electrode of the gate electrode, the oxide transistors each element obtained by forming on a substrate a channel layer and the gate insulating film, the three-electrode electrical resistance of 1 ×, respectively 10 ⁻³ to 1 × 10 ⁻¹ Ωcm of a conductive In—Ga—Zn—O film, and the channel layer is a semiconductive In—Ga—Zn—O film having an electrical resistivity of 1 to 1 × 10 ³ Ωcm. Provided is an oxide transistor characterized in that the gate insulating film is formed of a high-resistance In—Ga—Zn—O film having an electrical resistivity of 1 × 10 ⁶ to 1 × 10 ¹⁰ Ωcm. To do.

Further, according to the present invention, as a method for manufacturing the oxide transistor, an In—Ga—Zn—O film with a predetermined pattern is formed by sputtering using a target containing In, Ga, and Zn in an atmosphere containing oxygen gas. An oxide transistor is formed over a substrate, and the In—Ga—Zn—O film is used to form at least one of each element of a source electrode, a drain electrode, and a gate electrode, a channel layer, and a gate insulating film. In the manufacturing method, an In—Ga—Zn—O film having a predetermined pattern is formed on a substrate using a metal mask, the metal mask is replaced, and the oxygen gas flow rate is changed, whereby the electric resistivity is 1 × 10. ^{-3 ~1} × 10 ^-1 Ωcm conductive in-Ga-Zn-O film source electrode made of, and the electrodes of the drain electrode and the gate electrode, the electrical resistivity of 1 to 1 × 10 ³ [Omega] cm of A channel layer formed of a conductive In-Ga-Zn-O film, a gate insulation film of a high-resistance In-Ga-Zn-O film of the electrical resistivity of ^{1 × 10 6 ~1 × 10 10} Ωcm is formed by sputtering An oxide transistor manufacturing method is provided.

  According to the present invention, an oxide transistor such as a TFT element using an In—Ga—Zn—O film having stable characteristics can be manufactured with high productivity.

Hereinafter, the present invention will be described in more detail.
As described above, the oxide transistor of the present invention is formed by forming each element of the source electrode, the drain electrode and the gate electrode, the channel layer, and the gate insulating film on the substrate, and each element as described above. 2 or more are formed of an In—Ga—Zn—O film. For example, the TFT element having the configuration shown in FIG. 1 can be exemplified.

  In the transistor of FIG. 1, a gate electrode 2 is formed on a substrate 1, the gate electrode 2 is covered with a gate insulating film 3, and the source electrode 4 is sandwiched between the gate insulating film 3 and the gate electrode 2. And the drain electrode 5 are opposed to each other, and a channel layer 6 is further formed between the source electrode 4 and the drain electrode 5. In the present invention, the source electrode 4, the drain electrode 5, the three electrodes of the gate electrode 2, the channel layer 6, and at least two elements of the gate insulating film 3 are formed of an In—Ga—Zn—O film. It is a thing.

  In this case, as the substrate, conventionally known substrates for electronic devices such as transistors can be used. For example, glass substrates such as white plate glass, blue plate glass, quartz glass, and polyethylene terephthalate (PET) are used. If a transparent substrate such as a polymer film substrate or a device where transparency is not required, various metal substrates, Si wafers, plastic substrates, non-transparent polymer substrates such as polyimide, etc. can be used. .

  In the transistor of the present invention, at least two elements of the source electrode 4, the drain electrode 5, the gate electrode 2, the channel layer 6, and the gate insulating film 3 formed on the substrate are formed of an In—Ga—Zn—O film. However, the source electrode 4, the drain electrode 5, and the gate electrode 2 are all formed of a material having good conductivity, and these electrodes are formed of an In—Ga—Zn—O film. In some cases, it is usually preferable to form all three electrodes with an In—Ga—Zn—O film having a low electrical resistivity.

The source electrode 4, the drain electrode 5 and the gate electrode 2 are not particularly limited, but have an electric resistivity of 1 × 10 ⁻³ to 1 × 10 ⁻¹ Ωcm, particularly 1 × 10 ⁻³ to 1 × 10. ⁻² Ωcm is preferable, and in the case of using an In—Ga—Zn—O film, a conductive In—Ga—Zn—O film into which oxygen vacancies are sufficiently introduced is formed. When these electrodes are formed of other materials, such as transparent electrode materials such as ITO and FTO, metal materials such as Au, Pt, Ti, and Al, and various conductive polymer materials if transparency is not required. What is necessary is just to form an electrode by a well-known method using a well-known material.

The gate insulating film 3 is not particularly limited, but usually has an electrical resistivity of 1 × 10 ⁶ to 1 × 10 ¹⁰ Ωcm, preferably 1 × 10 ⁸ to 1 × 10 ¹⁰ Ωcm. In the case of using an In—Ga—Zn—O film, a high-resistance In—Ga—Zn—O film in which oxygen vacancies are reduced as much as possible is formed. When this gate insulating film is formed of other materials, insulating polymer materials such as metal oxides such as SiO ₂ , Y ₂ O ₃ , Ta ₂ O ₅ , and Hf oxide, and polyimide are used. The insulating film may be formed using a known method such as a known method.

Next, the channel layer 6 is not particularly limited, usually electrical resistivity 1~1 × 10 ³ Ωcm, be particularly 10~1 × 10 ³ Ωcm Preferably, an In-Ga-Zn In the case of forming with a —O film, a semiconductive In—Ga—Zn—O film with moderate oxygen vacancies is formed. In this case, although not particularly limited, a composition gradient film (conductivity gradient film) in which the oxygen content is gradually changed may be applied to the interface between the source electrode 4 and the drain electrode 5 and the channel layer 6. Thus, the barrier at the interface between the source electrode 4 and drain electrode 5 and the channel layer 6 can be reduced, and the characteristics can be improved. When this channel layer is formed of another material, the channel layer is formed by a known method using a known material such as an oxide semiconductor material such as ZnO or an organic semiconductor material such as pentacene. do it.

The source electrode 4, the drain electrode 5 and the gate electrode 2, the channel layer 6 and the gate insulating film 3 are formed by using an In—Ga—Zn—O film as a reactive method such as DC reactive sputtering or RF sputtering. A physical vapor deposition method such as a pulsed laser deposition method or the like can be used, but a sputtering method using a target containing In, Ga, and Zn, particularly in an atmosphere containing oxygen gas, is preferably employed. In this case, the amount of oxygen vacancies in the In—Ga—Zn—O film is adjusted by adjusting and changing the flow rate of the oxygen gas, so that the electric resistivity suitable for each element of the In—Ga—Zn—O film is obtained. Each element having different electric resistivity can be formed relatively easily by adjusting the oxygen gas flow rate. In this case, the patterning of each element can adopt a known method such as a method using a photolithograph or a metal mask, and is not particularly limited. From this point, it is possible to form the above-described elements having different electric resistivity very easily by the same apparatus by exchanging the metal mask and adjusting the flow rate of the oxygen gas. As a sputtering target or a vapor deposition source, an In—Ga—Zn alloy target or an InGaZnO ₄ sintered body target can be used.

  In addition, conventional film formation methods such as DC reactive sputtering and RF sputtering may not provide sufficient productivity because the film formation rate is relatively slow, and an In—Ga—Zn—O film may be obtained. The stable composition control is not easy and it may be difficult to maintain the characteristics. Therefore, although not particularly limited, it is possible to improve productivity by applying a dual cathode sputtering method for producing these films at high speed by applying a pulsed voltage to a plurality of cathodes in the future. it can. Furthermore, it is also preferable to use a PEM (Plasma Emission Monitor) control feedback system that controls the amount of oxygen introduced in real time by measuring the ion concentration in the plasma, which makes it possible to stabilize the thin film without depending on the state of the target. Composition control and oxygen content control can be performed. Furthermore, when the source electrode 4, the drain electrode 5 and the gate electrode 2 are formed of In—Ga—Zn—O films, as described above, conductive In—Ga— into which oxygen vacancies are sufficiently introduced. Although a Zn—O film is formed, an In—Ga—Zn—O film formed while adding hydrogen and water to further reduce the resistance can be used.

  Here, in the oxide transistor of the present invention, at least two of the three elements of the source electrode 4, the drain electrode 5 and the gate electrode 2, the channel layer 6 and the gate insulating film 3 have different electric resistivity. Although it is formed of an In—Ga—Zn—O film, it is preferable that all elements formed on the substrate 1 are formed of an In—Ga—Zn—O film, which makes it very efficient. An oxide transistor using an In—Ga—Zn—O film can be manufactured at low cost.

  That is, each element of the source electrode 4, the drain electrode 5, the gate electrode 2, the channel layer 6, and the gate insulating film 3 is formed by sputtering using a target containing In, Ga, and Zn in an atmosphere containing oxygen gas. Each element can be formed of the In—Ga—Zn—O film having the predetermined electrical resistivity by changing the oxygen gas flow rate at that time while forming the film with the —Ga—Zn—O film, By adjusting the oxygen gas flow rate, the above-described elements having different electric resistivity can be easily formed efficiently. Furthermore, if patterning is performed using a metal mask, the metal mask is replaced, and the oxygen gas flow rate is changed, so that only a single device can be replaced and the oxygen gas flow rate adjusted by a single device. All of the above elements can be formed using In—Ga—Zn—O films having different resistivity, and an oxide transistor using the In—Ga—Zn—O film can be manufactured with extremely high productivity. It is.

  The oxide transistor of the present invention is not limited to the bottom gate / bottom contact type shown in FIG. 1, but includes a bottom gate / top contact, a top gate / bottom contact, a top gate / top contact, etc. Other forms are also possible.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not restrict | limited to the following Example.

[Example 1]
First, in order to confirm the oxygen dependency of the electrical resistivity of the In—Ga—Zn—O film, a film forming operation was performed by a DC magnetron sputtering method under the following conditions. FIG. 2 shows the relationship between the electrical resistivity of the obtained In—Ga—Zn—O film and the amount of oxygen introduced. The electrical resistivity was measured using “Loresta-AP MCP-T400” manufactured by Mitsubishi Chemical Corporation.
Film forming conditions Target: InGaZnO ₄ sintered body (size 75 mmφ)
Ultimate vacuum: 5.0 × 10 ⁻⁴ Pa
Deposition pressure: 0.5 Pa
Applied power: 100W
Substrate used: Corning 7059 alkali-free glass film formation atmosphere: The gas flow rate was fixed at 100 sccm, and the flow ratio of Ar and O ₂ was changed.

  As shown in the graph of FIG. 2, the electrical resistivity of the obtained In—Ga—Zn—O film is regularly changed by increasing or decreasing the amount of oxygen introduced during film formation in the range of 1 sccm or more. Confirmed to get.

Further, when the obtained In—Ga—Zn—O film was observed, the obtained film was colored black because the oxygen deficiency was excessive when the introduced oxygen amount was 0.5 sccm or less. On the other hand, all the films having an introduced oxygen amount of 1 sccm or more were transparent in the visible light region. Further, the Hall effect measurement was performed on the films prepared with the introduced oxygen amounts of 1 sccm and 3 sccm, and the carrier concentration was examined. The measurement was performed using a Hall effect measuring device “ResiTest 8300” manufactured by Toyo Technica. As a result, the carrier concentration was about 10 ¹⁹ cm ⁻³ and 10 ¹⁶ cm ⁻³ in each film. The hole mobility was almost the same in both cases, which was about 10 cm ² / Vsec, and there was no significant change in mobility due to the amount of carriers.

From the above results, it was confirmed that the electrical resistivity of the In—Ga—Zn—O film can be changed from 10 ⁻² to 10 ¹⁰ Ωcm by controlling the amount of introduced oxygen.

  Next, using the In—Ga—Zn—O film in which the electrical resistivity was changed by controlling the oxygen gas flow rate during film formation, the TFT element having the configuration shown in FIG. Created. This TFT element is a bottom gate / bottom contact type as shown in FIG. The film forming conditions were the same as in the above oxygen dependence test.

First, the gate electrode 2 was formed of the In—Ga—Zn—O film having the lowest resistance and transparent in the visible light region on the substrate 1 made of Corning 7059 alkali-free glass. The oxygen gas flow rate during film formation was 1 sccm, and the resistance was reduced as much as possible. The electrical resistivity of the obtained gate electrode 2 made of the In—Ga—Zn—O film is estimated to be about 10 ⁻² Ωcm from the result of FIG.

Next, the metal mask was replaced, the oxygen gas flow rate during film formation was controlled to 5.5 sccm, an In—Ga—Zn—O film was formed, and the gate insulating film 3 was formed. The electrical resistivity of the gate insulating film 3 is estimated to be about 10 ⁹ Ωcm or more from the result shown in FIG.

Further, the metal mask was replaced, and an In—Ga—Zn—O film having an electrical resistivity of about 10 ⁻² Ωcm was formed in the same manner as the gate electrode 2, and the source electrode 4 and the drain electrode 5 were formed.

Finally, the metal mask was replaced, the oxygen gas flow rate during film formation was controlled to 3 sccm, an In—Ga—Zn—O film was formed, and the channel layer 6 was formed. The electrical resistivity of the channel layer 6 is estimated to be about 10 ² Ωcm from the result of FIG. The channel length is 50 μm and the channel width is 200 μm.

  The operating characteristics of the obtained TFT device were tested using a semiconductor parameter analyzer manufactured by Agilent. As a result, by changing the source / drain electrode from 0 to 50 V when a gate voltage of 20 V was applied, an On / Off ratio of about 300 could be obtained, and the operating characteristics as a TFT element were confirmed.

[Example 2]
First, an In—Ga—Zn—O film was formed under the same conditions as in Example 1 without patterning a substrate made of Corning 7059 alkali-free glass, and a gate electrode was formed uniformly. The electrical resistivity of this gate insulating film is estimated to be about 10 ⁻² Ωcm as in the first embodiment.

Next, a gate insulating film and a channel layer (channel length 50 μm, channel width 200 μm) were sequentially formed under the same conditions as in Example 1 without patterning. The electrical resistivity of the obtained gate insulating film and channel layer is presumed to be about 10 ⁹ Ωcm or more and about 10 ² Ωcm of the channel insulating film as in Example 1.

Finally, the source electrode and the drain electrode were patterned by a photolithographic process and formed under the same conditions as in Example 1 to produce a TFT element. In this case, the source electrode and the drain electrode were formed so that the channel layer had a channel length of 50 μm and a channel width of 200 μm. The electrical resistivity of the obtained source electrode and drain electrode is presumed to be about 10 ⁻² Ωcm, as in Example 1. It is estimated that

  The operating characteristics of the obtained TFT device were tested using a semiconductor parameter analyzer manufactured by Agilent. As a result, by changing the source / drain electrode from 0 to 10 V when a gate voltage of 6 V was applied, an On / Off ratio of about 130 could be obtained, and the operating characteristics as a TFT element were confirmed.

It is a schematic sectional drawing which shows the TFT element (oxide transistor) concerning one Example of this invention. It is a graph which shows the relationship between the electrical resistivity of the film | membrane obtained when forming an In-Ga-Zn-O film | membrane by sputtering, and the oxygen introduction amount at the time of film-forming.

Explanation of symbols

1 Substrate 2 Gate electrode 3 Gate insulating film 4 Source electrode 5 Drain electrode 6 Channel layer

Claims (4)

In an oxide transistor in which elements of a source electrode, a drain electrode and a gate electrode, a channel layer, and a gate insulating film are formed on a substrate, the three electrodes each have an electrical resistivity of 1 × 10 ⁻³ to 1 ×. 10 ^-1 Ωcm of a conductive In-Ga-Zn-O film, the channel layer is formed of a semiconductive In-Ga-Zn-O film having an electrical resistivity of 1 to 1 x 10 ³ Ωcm, and An oxide transistor, wherein the gate insulating film is formed of a high-resistance In—Ga—Zn—O film having an electrical resistivity of 1 × 10 ⁶ to 1 × 10 ¹⁰ Ωcm . In-Ga-Zn-O film elements formed of the oxide transistor according to claim 1, wherein one formed on the base plate by sputtering.   3. The oxide transistor according to claim 1, wherein the oxide transistor is a transparent oxide semiconductor using a substrate made of a transparent material. By sputtering using a target containing In, Ga, and Zn in an atmosphere containing oxygen gas, an In—Ga—Zn—O film having a predetermined pattern is formed on the substrate, and the In—Ga—Zn—O film is formed. In a method of manufacturing an oxide transistor by forming at least one of each element of a source electrode, a drain electrode and a gate electrode, a channel layer, and a gate insulating film with a film, a predetermined pattern of In is formed using a metal mask. A conductive In— with an electrical resistivity of 1 × 10 ⁻³ to 1 × 10 ⁻¹ Ωcm is obtained by forming a Ga—Zn—O film on the substrate, exchanging the metal mask, and changing the oxygen gas flow rate. Ga-Zn-O film source electrode made of, and the electrodes of the drain electrode and the gate electrode, a channel layer made of a semiconductive in-Ga-Zn-O film of the electrical resistivity of 1 to 1 × 10 ³ [Omega] cm, electrostatic Method of manufacturing an oxide transistor, wherein a gate insulating film made of a high-resistance In-Ga-Zn-O film of resistivity ^{1 × 10 6 ~1 × 10 10} Ωcm is formed by sputtering.

Images