WO2018109970A1 - 半導体デバイスおよびその製造方法 - Google Patents
半導体デバイスおよびその製造方法 Download PDFInfo
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- WO2018109970A1 WO2018109970A1 PCT/JP2017/025245 JP2017025245W WO2018109970A1 WO 2018109970 A1 WO2018109970 A1 WO 2018109970A1 JP 2017025245 W JP2017025245 W JP 2017025245W WO 2018109970 A1 WO2018109970 A1 WO 2018109970A1
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- layer
- insulating layer
- oxide semiconductor
- semiconductor device
- electrode
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02612—Formation types
- H01L21/02617—Deposition types
- H01L21/02631—Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/01—Chemical elements
- H01L2924/0103—Zinc [Zn]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/01—Chemical elements
- H01L2924/0104—Zirconium [Zr]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/01—Chemical elements
- H01L2924/01049—Indium [In]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/01—Chemical elements
- H01L2924/01074—Tungsten [W]
Definitions
- the present invention relates to a semiconductor device including an oxide semiconductor layer containing indium (In), tungsten (W), and zinc (Zn), and a manufacturing method thereof.
- the present application claims priority based on Japanese Patent Application No. 2016-240229, which is a Japanese patent application filed on December 12, 2016. All the descriptions described in the Japanese patent application are incorporated herein by reference.
- a thin film EL (electroluminescence) display device an organic EL display device, etc.
- amorphous silicon (a-Si) film has been mainly used as a semiconductor film functioning as a channel layer of a TFT (thin film transistor) as a semiconductor device.
- a-Si amorphous silicon
- Patent Document 1 Japanese Patent Laying-Open No. 2010-219538 describes that an oxide semiconductor film containing IGZO as a main component is formed by a sputtering method using an oxide sintered body as a target. .
- the IGZO-based oxide semiconductor According to the IGZO-based oxide semiconductor, higher carrier mobility can be expected as compared with a-Si.
- the field-effect mobility of an IGZO-based oxide semiconductor is generally 10 cm 2 / Vs, and further increase in mobility is demanded with the increase in size and definition of a display device.
- JP 2010-219538 A Japanese Patent Laid-Open No. 2015-056566
- a semiconductor device includes a gate electrode, a channel layer disposed in a region immediately below or directly above the gate electrode, a source electrode and a drain electrode disposed in contact with the channel layer, a gate electrode, and a channel And a first insulating layer disposed between the layers.
- the channel layer includes a first oxide semiconductor
- at least one of the source electrode and the drain electrode includes a second oxide semiconductor.
- the first oxide semiconductor and the second oxide semiconductor contain indium, tungsten, and zinc. The content of tungsten with respect to the total of indium, tungsten, and zinc in the first oxide semiconductor and the second oxide semiconductor is greater than 0.001 atomic% and equal to or less than 8.0 atomic%.
- the content of zinc with respect to the total of indium, tungsten, and zinc in the first oxide semiconductor and the second oxide semiconductor is 1.2 atomic percent or more and 40 atomic percent or less.
- the atomic ratio of zinc to tungsten in the first oxide semiconductor and the second oxide semiconductor is greater than 1.0 and less than 20000.
- the first insulating layer may be a gate insulating layer.
- the manufacturing method of the semiconductor device which concerns on another aspect of this invention is a manufacturing method of the semiconductor device which concerns on the said aspect,
- the process of forming the layer containing an oxide semiconductor, the process of forming a gate electrode, and an oxide semiconductor A step of forming a partially covering insulating layer that covers a part of the main surface of the layer that includes, and a step of performing a heat treatment that is performed after the step of forming the partially covering insulating layer.
- FIG. 1 is a schematic view of a semiconductor device as viewed from above.
- FIG. 2 is a schematic cross-sectional view illustrating an example of a semiconductor device according to one embodiment of the present invention.
- FIG. 3 is a schematic cross-sectional view illustrating another example of a semiconductor device according to an aspect of the present invention.
- FIG. 4 is a schematic cross-sectional view showing an example of a method for manufacturing the semiconductor device shown in FIG.
- FIG. 5 is a schematic cross-sectional view showing an example of a manufacturing method of the semiconductor device shown in FIG.
- the source electrode and the drain electrode are designed so that part of them overlaps the gate electrode through the gate insulating layer. ⁇ It is formed. This is because when the width of the gate electrode is shorter than the distance between the source electrode and the drain electrode, the channel layer where there is no gate electrode does not generate carriers even when a voltage is applied to the gate electrode, and the TFT operates. It is because it does not.
- Such an overlapping structure of electrodes causes parasitic capacitance between the gate electrode and the source electrode, and between the gate electrode and the drain electrode, thereby degrading the characteristics of the TFT.
- Patent Document 2 describes a top-gate TFT including an oxide semiconductor layer (TAOS layer 12) made of IGZO.
- This TFT is manufactured by using a self-alignment technique that exposes a part of the TAOS layer 12 immediately below the gate insulating film 14 by patterning the gate insulating film 14 using the gate electrode 15 as a photomask.
- the part of the TAOS layer 12 (the region not covered with the gate insulating film 14) is reduced in resistance by reduction treatment with a reducing gas (TAOS reduction layer 13), and is connected to connect the source electrode and the drain electrode. Used as an electrode.
- a semiconductor device includes a gate electrode, a channel layer disposed in a region immediately below or directly above the gate electrode, a source electrode and a drain electrode disposed in contact with the channel layer, a gate A first insulating layer disposed between the electrode and the channel layer, the channel layer including a first oxide semiconductor, at least one of the source electrode and the drain electrode including a second oxide semiconductor,
- the physical semiconductor and the second oxide semiconductor contain indium (In), tungsten (W), and zinc (Zn).
- the W content (hereinafter also referred to as “W content”) with respect to the total of In, W, and Zn in the first oxide semiconductor and the second oxide semiconductor is greater than 0.001 atomic% and 8.0 atoms. % Or less.
- the Zn content relative to the total of In, W, and Zn in the first oxide semiconductor and the second oxide semiconductor (hereinafter also referred to as “Zn content”) is 1.2 atomic percent or more and 40 atomic percent or less. is there.
- the atomic ratio of Zn to W in the first oxide semiconductor and the second oxide semiconductor (hereinafter also referred to as “Zn / W ratio”) is larger than 1.0 and smaller than 20000.
- the first insulating layer may be a gate insulating layer.
- the semiconductor device of this embodiment can reduce the parasitic capacitance and can exhibit high field-effect mobility.
- the semiconductor device of this embodiment is further advantageous in improving the reliability under light irradiation.
- the semiconductor device is specifically a TFT (Thin Film Transistor).
- the contents of In, W, and Zn in the first oxide semiconductor are the same as the contents of In, W, and Zn in the second oxide semiconductor, respectively.
- the electrical resistivity of the channel layer is preferably 10 ⁇ 1 ⁇ cm or more, and the electrical resistivity of the source electrode and the drain electrode is preferably 10 ⁇ 2 ⁇ cm or less. This is advantageous in increasing the field effect mobility of the semiconductor device.
- the first oxide semiconductor and the second oxide semiconductor can be composed of nanocrystalline oxide or amorphous oxide. This is advantageous in increasing the field effect mobility of the semiconductor device, and is also advantageous in increasing the reliability of the semiconductor device under light irradiation.
- the first insulating layer may be a layer that covers the main surface of the channel layer and does not cover the main surfaces of the source electrode and the drain electrode.
- An example of such a semiconductor device is a top gate type TFT.
- the first insulating layer covering the main surface of the channel layer and not covering the main surface of the source electrode and the drain electrode reduces the parasitic capacitance of the semiconductor device, reduces the field effect mobility and the light irradiation. It is advantageous for improving reliability.
- the semiconductor device includes an insulating layer that covers the main surface of the source electrode and the drain electrode May not be included.
- the first insulating layer covers the main surface of the channel layer and does not cover the main surface of the source electrode and the drain electrode
- It may further include a low oxygen insulating layer that covers the main surfaces of the source electrode and the drain electrode and has a lower oxygen atom content than the first insulating layer. This is also advantageous in increasing the field effect mobility of the semiconductor device and the reliability under light irradiation.
- the semiconductor device of the present embodiment further includes a second insulating layer that covers the main surface of the channel layer and does not cover the main surfaces of the source electrode and the drain electrode. Also good.
- An example of such a semiconductor device is a bottom gate type TFT. Further including a second insulating layer that covers the main surface of the channel layer and does not cover the main surfaces of the source electrode and the drain electrode reduces the parasitic capacitance of the semiconductor device, improves the field effect mobility and the reliability under light irradiation. It is advantageous for improving the performance.
- the semiconductor device further includes a second insulating layer that covers the main surface of the channel layer and does not cover the main surface of the source electrode and the drain electrode
- the semiconductor device covers the main surface of the source electrode and the drain electrode.
- the insulating layer may not be provided.
- the semiconductor device of this embodiment further includes a second insulating layer that covers the main surface of the channel layer and does not cover the main surface of the source electrode and the drain electrode
- the insulating layer that covers the main surfaces of the source electrode and the drain electrode and may further include a low oxygen insulating layer having a lower oxygen atom content than the second insulating layer. This is also advantageous in increasing the field effect mobility of the semiconductor device and the reliability under light irradiation.
- the first oxide semiconductor preferably contains hexavalent tungsten. This is advantageous in increasing the field effect mobility of the semiconductor device.
- the channel layer may further contain zirconium.
- the content of zirconium is preferably 1 ⁇ 10 17 atoms / cm 3 or more and 1 ⁇ 10 20 atoms / cm 3 or less. Inclusion of zirconium at this content is advantageous for enhancing the reliability of the semiconductor device under light irradiation.
- a method for manufacturing a semiconductor device is a method for manufacturing a semiconductor device according to the above embodiment, and includes a step of forming a gate electrode and a step of forming a layer including an oxide semiconductor. And a step of forming a partially covering insulating layer that covers a part of the main surface of the layer containing the oxide semiconductor, and a step of performing a heat treatment that is performed after the step of forming the partially covering insulating layer.
- a semiconductor device having a small parasitic capacitance, high field effect mobility, and high field effect mobility and high reliability under light irradiation is comparatively obtained. It can be easily manufactured.
- the oxide semiconductor corresponds to a first oxide semiconductor and a second oxide semiconductor included in the semiconductor device according to the embodiment.
- the manufacturing method of the semiconductor device of the present embodiment is the above-described one on the main surface of the layer including the oxide semiconductor after the step of forming the layer including the oxide semiconductor and before the step of performing the heat treatment.
- the method may further include a step of forming a low oxygen insulating layer covering a region adjacent to the portion.
- the low oxygen insulating layer is a layer having a lower oxygen atom content than the partially covering insulating layer. Further including the step of forming the low oxygen insulating layer is advantageous in realizing a semiconductor device having high field effect mobility and high reliability under light irradiation.
- the partially covering insulating layer may be the first insulating layer or a second insulating layer different from the first insulating layer.
- An example of a semiconductor device in the case where the partially covering insulating layer is the first insulating layer is a top gate type TFT.
- An example of a semiconductor device in the case where the partially covering insulating layer is the second insulating layer is a bottom gate type TFT.
- the manufacturing method of the semiconductor device of the present embodiment including the step of forming the partially covering insulating layer that is the first insulating layer or the second insulating layer different from the first insulating layer, the parasitic capacitance is small, A semiconductor device having high field effect mobility and high reliability under light irradiation can be manufactured relatively easily.
- the partially covering insulating layer is preferably patterned by self-alignment using a gate electrode. This eliminates the need to use a photomask separately, so that a semiconductor device can be easily manufactured at low cost, and the parasitic capacitance of the resulting semiconductor device can be reduced.
- the step of performing the heat treatment included in the method for manufacturing a semiconductor device of the present embodiment preferably includes a step of performing a heat treatment at a temperature of 100 ° C. or higher and 500 ° C. or lower.
- the inclusion of this step is advantageous in realizing a semiconductor device that can reduce the parasitic capacitance of the obtained semiconductor device, has high field-effect mobility, and high reliability under light irradiation.
- the semiconductor device of this embodiment includes a gate electrode, a channel layer disposed in a region immediately below or directly above the gate electrode, a source electrode and a drain electrode disposed in contact with the channel layer, and a gate electrode and a channel layer.
- a physical semiconductor contains indium (In), tungsten (W), and zinc (Zn).
- the semiconductor device is specifically a TFT (Thin Film Transistor).
- the electrical resistivity of the channel layer is preferably higher than the electrical resistivity of the source and drain electrodes.
- the channel layer is arranged in the region immediately below or directly above the gate electrode, it is possible to eliminate the above-described electrode overlapping structure that the conventional semiconductor device has, and thereby parasitic capacitance can be eliminated. Can be reduced.
- the channel layer is disposed in the region immediately below or directly above the gate electrode, as shown in FIG. 1, when the semiconductor device is viewed from above, the length 15 of the channel layer 7 is equal to the width 12 of the gate electrode 2. Means you are doing it. Therefore, at this time, the interface position between the channel layer 7 and the source electrode 5 and the interface position between the channel layer 7 and the drain electrode 6 coincide with the position of the end face of the gate electrode 2.
- the distance 13 of the gate electrode 2 and the width 14 of the channel layer 7 do not have to coincide with each other.
- the structure in which the channel layer 7 is disposed in the region immediately below or directly above the gate electrode 2 can be formed by a self-alignment technique using the patterned gate electrode 2 as described later.
- the semiconductor device of this embodiment can be, for example, a bottom gate type or a top gate type.
- the case where the channel layer is arranged in the region immediately above the gate electrode is, for example, a case where the semiconductor device is a bottom gate type.
- the case where the channel layer is arranged in the region immediately below the gate electrode is, for example, a case where the semiconductor device is a top gate type.
- FIG. 2 is a schematic cross-sectional view illustrating an example of a semiconductor device according to one embodiment of the present invention, and illustrates an example of a bottom-gate semiconductor device (TFT).
- 2 includes a substrate 1; a gate electrode 2 disposed on the substrate 1; a channel layer 7 disposed in a region immediately above the gate electrode 2; a source electrode 5 disposed in contact with the channel layer 7;
- the drain electrode 6 includes a first insulating layer (gate insulating layer) 3 disposed between the gate electrode 2 and the channel layer 7.
- the source electrode 5 and the drain electrode 6 are disposed on the first insulating layer 3 without being in contact with each other.
- the electrical resistivity of the channel layer 7 is higher than the electrical resistivity of the source electrode 5 and the drain electrode 6.
- a second insulating layer (insulating protective layer) 8 also called an etch stopper layer, a passivation layer or the like, is laminated.
- the second insulating layer (insulating protective layer) 8 is not laminated on the source electrode 5 and the drain electrode 6.
- the semiconductor device shown in FIG. 2 includes a third insulating layer (insulating protective layer) 9 disposed on the second insulating layer 8 and on the source electrode 5 and the drain electrode 6. May be omitted.
- the gate electrode 2 may be stacked on the substrate 1 via another layer.
- the source electrode 5 and the drain electrode 6 can also be used as pixel electrodes.
- the length of the channel layer 7 matches the width of the gate electrode 2 when viewed from above. More specifically, the channel layer 7 is disposed in a region immediately above the gate electrode 2 when the semiconductor device is viewed from above. Therefore, the interface position between the channel layer 7 and the source electrode 5 and the interface position between the channel layer 7 and the drain electrode 6 coincide with the position of the end face of the gate electrode 2. Thereby, the semiconductor device shown in FIG. 2 can exhibit a reduced parasitic capacitance.
- FIG. 3 is a schematic cross-sectional view showing another example of the semiconductor device according to one embodiment of the present invention, and shows an example of a top gate type semiconductor device (TFT).
- TFT top gate type semiconductor device
- 3 includes a substrate 1; a channel layer 7 disposed on the substrate 1, a gate electrode 2 disposed in a region immediately above the channel layer 7, a source electrode 5 disposed in contact with the channel layer 7, and
- the drain electrode 6 includes a first insulating layer (gate insulating layer) 3 disposed between the gate electrode 2 and the channel layer 7.
- the source electrode 5 and the drain electrode 6 are disposed on the substrate 1 without being in contact with each other.
- the electrical resistivity of the channel layer 7 is higher than the electrical resistivity of the source electrode 5 and the drain electrode 6.
- the third insulating layer (insulating protective layer) 9 disposed on the gate electrode 2 and on the source electrode 5 and the drain electrode 6, but the third insulating layer 9 is omitted. May be.
- the channel layer 7, the source electrode 5, and the drain electrode 6 may be stacked on the substrate 1 via other layers.
- the source electrode 5 and the drain electrode 6 can also be used as pixel electrodes.
- the length of the channel layer 7 matches the width of the gate electrode 2 when viewed from above. More specifically, when the semiconductor device is viewed from above, the channel layer 7 is disposed in a region immediately below the gate electrode 2. Therefore, the interface position between the channel layer 7 and the source electrode 5 and the interface position between the channel layer 7 and the drain electrode 6 coincide with the position of the end face of the gate electrode 2. Thus, the semiconductor device shown in FIG. 3 can exhibit a reduced parasitic capacitance.
- the channel layer 7 includes a first oxide semiconductor, and at least one (preferably both) of the source electrode 5 and the drain electrode 6 includes a second oxide semiconductor.
- the two oxide semiconductor contains In, W, and Zn.
- the W content (W content) with respect to the total of In, W, and Zn in the first oxide semiconductor and the second oxide semiconductor is greater than 0.001 atomic% and 8.0 atoms.
- the Zn content (Zn content) with respect to the total of In, W, and Zn in the first oxide semiconductor and the second oxide semiconductor is 1.2 atomic percent or more and 40 atomic percent or less.
- the atomic ratio of Zn to W (Zn / W ratio) in the first oxide semiconductor and the second oxide semiconductor is larger than 1.0 and smaller than 20000.
- the semiconductor device of this embodiment can reduce parasitic capacitance and can exhibit high field effect mobility.
- the semiconductor device of this embodiment is further advantageous in improving the reliability under light irradiation.
- the channel layer 7 is preferably a layer made of a first oxide semiconductor, and the source electrode 5 and the drain electrode 6 are preferably layers made of a second oxide semiconductor.
- the contents of In, W and Zn in the first oxide semiconductor included in the channel layer 7 are the contents of In, W and Zn in the second oxide semiconductor included in the source electrode 5 and / or the drain electrode 6, respectively.
- the rate is preferably the same.
- the contents of In, W and Zn are measured by TEM-EDX (transmission electron microscope with an energy dispersive fluorescent X-ray analyzer) or RBS (Rutherford backscattering analysis).
- a part of the channel layer 7 (first oxide semiconductor) and a part of the source electrode 5 and / or the drain electrode 6 (second oxide semiconductor) are quantitatively analyzed by the above method, and the first oxide semiconductor
- the contents of In, W, and Zn and the contents of In, W, and Zn in the second oxide semiconductor are measured.
- the number of W atoms per 1 cm 3 is measured by SIMS (secondary ion mass spectrometer). For example, when the number of W atoms per 1 cm 3 is 1.5 ⁇ 10 20 / cm 3 , the W content is set to 0.5 atomic%. For example, when the number of W atoms per cm 3 is 1.5 ⁇ 10 19 atoms / cm 3 , the W content is set to 0.05 atomic%.
- the difference between the content in the source electrode 5 and / or the drain electrode 6 (second oxide semiconductor) and the content in the channel layer 7 (first oxide semiconductor) is the channel layer 7 (first oxide semiconductor).
- 1 oxide semiconductor) ⁇ (first oxide semiconductor layer ⁇ second oxide semiconductor layer) / first oxide semiconductor layer ⁇ 100%) ⁇ within the range of ⁇ 20%, both are the same It is judged that.
- the W content in the channel layer 7 is preferably greater than 0.001 atomic% and equal to or less than 8.0 atomic%
- the Zn content is preferably Is 1.2 atomic% or more and 40 atomic% or less
- the atomic ratio of Zn to W that is, the ratio of Zn content to W content (Zn content / W content.
- Zn / W ratio Is also preferably greater than 1.0 and less than 20000.
- the W content in the source electrode 5 and the drain electrode 6 is preferably more than 0.001 atomic% and not more than 8.0 atomic%, and contains Zn.
- the rate is preferably 1.2 atomic percent or more and 40 atomic percent or less, and the Zn / W ratio is preferably larger than 1.0 and smaller than 20000.
- Use of such a source electrode 5 and drain electrode 6 is advantageous in realizing a semiconductor device exhibiting high field effect mobility and high reliability under light irradiation, and the source electrode 5 and drain electrode. 6 is also advantageous in reducing the electrical resistivity.
- the W content in the channel layer 7 (first oxide semiconductor) and the source electrode 5 and drain electrode 6 (second oxide semiconductor) is: More preferably, it is 0.01 atomic% or more, More preferably, it is 0.08 atomic% or more, More preferably, it is 5 atomic% or less, More preferably, it is 3 atomic% or less.
- the threshold voltage V th characteristic which is one of the important characteristics of a semiconductor device, tends not to be good, and the reliability of the semiconductor device under light irradiation decreases. Can do.
- the threshold voltage V th is 0 V or more and 5 V or less because of the ease of device control. If the W content exceeds 8 atomic%, good field effect mobility tends to be difficult to obtain. Further, when the source electrode 5 and / or the drain electrode 6 having a W content exceeding 8 atomic% are used, it is difficult to reduce the electrical resistivity of these electrodes.
- the W content in the channel layer 7 (first oxide semiconductor), the source electrode 5 and the drain electrode 6 (second oxide semiconductor) is 0.5 atomic% or less, the reliability under light irradiation. It is desirable from the point of raising.
- Zn content in channel layer 7 (first oxide semiconductor), source electrode 5 and drain electrode 6 (second oxide semiconductor) is 1.2 atomic% or more and 40 atomic% or less, and a Zn / W ratio Is larger than 1.0 and smaller than 20000 is advantageous in realizing a semiconductor device exhibiting high field-effect mobility and high reliability under light irradiation.
- the Zn content in the channel layer 7 (first oxide semiconductor) and the source electrode 5 and drain electrode 6 (second oxide semiconductor) is: More preferably, it is 3 atomic% or more, More preferably, it is 10 atomic% or more, More preferably, it is 25 atomic% or less, More preferably, it is 18 atomic% or less.
- the Zn content is less than 1.2 atomic%, the reliability of the semiconductor device under light irradiation can be lowered.
- the Zn content exceeds 40 atomic% good field effect mobility tends to be difficult to obtain.
- the Zn / W ratio in the channel layer 7 (first oxide semiconductor) and the source electrode 5 and drain electrode 6 (second oxide semiconductor) is 1.0 or less, the reliability of the semiconductor device under light irradiation Can be reduced.
- the Zn / W ratio is more preferably 3.0 or more, and further preferably 5.0 or more.
- the Zn / W ratio in the channel layer 7 (first oxide semiconductor) and the source electrode 5 and drain electrode 6 (second oxide semiconductor) is 20000 or more, good field-effect mobility tends to be difficult to obtain. is there.
- the Zn / W ratio is more preferably 500 or less, and even more preferably 300 or less.
- the Zn / W ratio may be 80 or more.
- the In / (In + Zn) atomic ratio in the channel layer 7 (first oxide semiconductor) and the source electrode 5 and the drain electrode 6 (second oxide semiconductor) is from 0.8. Larger is preferred.
- a semiconductor device including an oxide semiconductor can change reliability under light irradiation depending on a temperature of heat treatment in manufacturing the semiconductor device. Reliability can be improved by increasing the temperature of the heat treatment. However, generally, when the heat treatment temperature is increased, the field effect mobility is lowered. For this reason, it has been desired that the field effect mobility does not decrease even at a high heat treatment temperature.
- “the field effect mobility is high and the reliability under light irradiation is high” means that the field effect mobility does not decrease even at a high heat treatment temperature, and the light treatment is performed at a high heat treatment temperature. This means that high reliability can be obtained.
- the channel layer 7 preferably has an electrical resistivity of 10 ⁇ 1 ⁇ cm or more, and the source electrode 5 and the drain electrode 6 preferably have an electrical resistivity of 10 ⁇ 2 ⁇ cm or less.
- a transparent conductive film As described in, for example, Japanese Patent Application Laid-Open No. 2002-256424, a film used for a transparent conductive film has an electrical resistivity of 10 ⁇ 1 ⁇ cm. The lower one is common, and the electric resistivity is preferably low similarly in the source electrode 5 and the drain electrode 6 in the semiconductor device of the present embodiment, and more preferably 10 ⁇ 2 ⁇ cm or less.
- the electrical resistivity of the channel layer 7 of the semiconductor device of this embodiment is desirably 10 ⁇ 1 ⁇ cm or more. In order to realize the electrical resistivity, it is preferable to comprehensively study the W content, the Zn content, and the Zn / W ratio of the channel layer 7.
- the first oxide semiconductor constituting the channel layer 7 is preferably composed of nanocrystalline oxide or amorphous oxide.
- the second oxide semiconductor constituting the source electrode 5 and the drain electrode 6 is preferably composed of nanocrystalline oxide or amorphous oxide.
- the “nanocrystalline oxide” means that only a broad peak appearing on a low angle side called a halo is observed without observing a peak due to a crystal even by X-ray diffraction measurement according to the following conditions.
- region is implemented according to the following conditions using a transmission electron microscope, the ring-shaped pattern is observed.
- the ring-shaped pattern includes a case where spots are gathered to form a ring-shaped pattern.
- amorphous oxide means that only a broad peak appearing on the low angle side called a halo is observed without a peak due to a crystal being observed even by X-ray diffraction measurement under the following conditions.
- it means an oxide in which an unclear pattern called a halo is observed even when transmission electron beam diffraction measurement of a fine region is performed according to the following conditions using a transmission electron microscope.
- Measuring method Micro electron diffraction method, Acceleration voltage: 200 kV, Beam diameter: The same as or equivalent to the film thickness of the oxide semiconductor layer to be measured.
- an oxide semiconductor layer as disclosed in, for example, Japanese Patent No. 5172918 includes c-axis-oriented crystals along a direction perpendicular to the surface of the layer. When the nanocrystals in the region are oriented in a certain direction, a spot-like pattern is observed.
- the nanocrystal is observed when the surface perpendicular to the layer plane (layer cross section) is observed.
- the crystal is not oriented with respect to the surface of the film, and it is non-oriented and has a random orientation. That is, the crystal axis is not oriented with respect to the film thickness direction.
- the first oxide semiconductor that constitutes the channel layer 7 and the second oxide semiconductor that constitutes the source electrode 5 and the drain electrode 6 in addition to this are composed of nanocrystalline oxide or amorphous oxide. This is advantageous in increasing the field effect mobility. From the viewpoint of increasing the field effect mobility, the first oxide semiconductor and the second oxide semiconductor are more preferably made of an amorphous oxide. In the case where the Zn content is 10 atomic% or more and / or the W content is 0.4 atomic% or more, the first oxide semiconductor and the second oxide semiconductor are likely to be amorphous oxides, and higher heat treatment is possible. Amorphous oxide is stable up to temperature.
- the first oxide semiconductor constituting the channel layer 7 has a binding energy peak position measured by X-ray photoelectron spectroscopy (XPS) of 32. It is preferable to contain W which is 9 eV or more and 36.5 eV or less.
- the peak position of the binding energy is more preferably 34 eV or more and 36.5 eV or less, and further preferably 35 eV or more and 36.5 eV or less.
- the first oxide semiconductor preferably contains hexavalent W from the viewpoint of increasing the field effect mobility.
- the second oxide semiconductor constituting the source electrode 5 and the drain electrode 6 also has a binding energy peak position measured by X-ray photoelectron spectroscopy (XPS) of 32. It is preferable to contain W which is 9 eV or more and 36.5 eV or less, more preferably W which is 34 eV or more and 36.5 eV or less, further preferably W which is 35 eV or more and 36.5 eV or less, Further, it preferably contains hexavalent W.
- the channel layer 7 preferably further contains zirconium (Zr), and the content thereof is 1 ⁇ 10 17 atms / cm 3 or more and 1 ⁇ 10 20 atms / cm 3 or less. It is preferable. Thereby, the reliability of the semiconductor device under light irradiation can be enhanced.
- Zr is often applied to an oxide semiconductor for the purpose of improving thermal stability, heat resistance, chemical resistance, or reducing the S value or off-current, but in the present invention, It has been newly found that the reliability under light irradiation can be improved by using together with W and Zn.
- the Zr content in the channel layer 7 is determined as a number of atoms per 1 cm 3 of the channel layer 7 by analyzing a given point of the channel layer 7 in the depth direction using secondary ion mass spectrometry (SIMS). .
- SIMS secondary ion mass spectrometry
- the content of Zr is more preferably 1 ⁇ 10 18 atoms / cm 3 or more, and more preferably 1 ⁇ 10 19 atoms / cm 3 or less.
- the source electrode 5 and the drain electrode 6 also preferably further contain Zr, and the content thereof is 1 ⁇ 10 17 atoms / cm 3 or more and 1 ⁇ 10 20 atoms. / Cm 3 or less is preferable.
- the content of inevitable metals other than In, W, and Zn with respect to the total of In, W, and zinc Zn in the channel layer 7 and the source electrode 5 and the drain electrode 6 is preferably 1 atomic% or less. .
- the channel layer 7 and the film thickness of the source electrode 5 and the drain electrode 6 are preferably 2 nm or more and 100 nm or less, and more preferably 5 nm or more and 80 nm or less.
- the source electrode 5 and the drain electrode 6, for example, a layer including an oxide semiconductor constituting them is integrally formed on the substrate 1, and the channel layer 7 and the source electrode 5 are formed from the oxide semiconductor layer. And the drain electrode 6 can be formed by self-alignment.
- the layer including an oxide semiconductor is also referred to as an oxide semiconductor layer.
- the oxide semiconductor layer is preferably a layer made of an oxide semiconductor.
- the oxide semiconductor layer may be formed directly on the substrate 1 or may be formed on the substrate 1 via another layer (for example, the first insulating layer 3).
- the first oxide semiconductor and the second oxide semiconductor have the same composition.
- the oxide semiconductor layer can be obtained by a manufacturing method including a step of forming a film by a sputtering method. This is advantageous in obtaining a semiconductor device having high field effect mobility and high reliability under light irradiation.
- the oxide layer constituting the channel layer 7 and the source electrode 5 and the drain electrode 6 is a transparent layer that can transmit ultraviolet rays applied to the resist layer used in the semiconductor device manufacturing process.
- the source electrode 5 and the drain electrode 6 are transparent, when a semiconductor device is applied to, for example, an image display device, a portion that is shielded from light in each pixel is reduced, so that the aperture ratio can be increased.
- a target and a substrate are placed facing each other in a film formation chamber, a voltage is applied to the target, and the surface of the target is sputtered with a rare gas ion, so that atoms constituting the target are converted from the target.
- a pulse laser deposition (PLD) method As a method for forming the oxide semiconductor layer, in addition to the sputtering method, a pulse laser deposition (PLD) method, a heating deposition method, and the like have been proposed. However, it is preferable to use the sputtering method for the above reason.
- PLD pulse laser deposition
- sputtering method a magnetron sputtering method, an opposed target sputtering method, or the like can be used.
- Ar gas, Kr gas, and Xe gas can be used as the atmospheric gas at the time of sputtering, and oxygen gas can be mixed and used with these gases.
- heat treatment may be performed after film formation by sputtering, or heat treatment may be performed while film formation is performed by sputtering.
- an oxide semiconductor layer composed of nanocrystalline oxide or amorphous oxide is easily obtained.
- the heat treatment is also advantageous in realizing a semiconductor device with high field effect mobility and high reliability under light irradiation.
- a heat treatment method performed while performing film formation by a sputtering method is not particularly limited, and heat treatment using lamp irradiation, an electric resistor, a laser, or the like can be given.
- the substrate temperature is preferably 100 ° C. or higher and 250 ° C. or lower.
- the heat treatment time corresponds to the film formation time, and the film formation time depends on the thickness of the oxide semiconductor layer to be formed, but can be, for example, about 1 second to 10 minutes.
- the heat treatment performed after the film formation by the sputtering method is not particularly limited, and may be heat treatment by lamp irradiation, an electric resistor, a laser, or the like.
- the method for manufacturing a semiconductor device of this embodiment preferably includes a step of performing a heat treatment after forming the oxide semiconductor layer.
- the oxide semiconductor layer is integrally formed, and the oxide semiconductor layer is formed from the oxide semiconductor layer.
- the gate electrode 2 can be, for example, an electrode having a single layer structure made of a metal such as Ti, Al, Mo, W, or Cu, or an electrode having a multilayer structure using two or more of these metals.
- the gate electrode 2 Is preferably made of a material capable of shielding ultraviolet rays applied to the resist layer used in the semiconductor device manufacturing process.
- the semiconductor device is disposed as a gate insulating layer disposed at least between the gate electrode 2 and the channel layer 7.
- the first insulating layer 3 is provided.
- the semiconductor device in the bottom gate type semiconductor device, it is also called an etch stopper layer, a passivation layer, or the like that covers the main surface of the channel layer 7 (the main surface opposite to the first insulating layer 3).
- a second insulating layer (insulating protective layer) 8 can be further included.
- the semiconductor device can further include a third insulating layer (insulating protective layer) 9 that covers the surface of the semiconductor device, as shown in FIGS.
- the third insulating layer (insulating protective layer) 9 is an arbitrary insulating layer provided as necessary.
- the semiconductor device in which the oxide semiconductor layer is integrally formed and the channel layer 7, the source electrode 5 and the drain electrode 6 are formed by making the oxide semiconductor layer separately is viewed from the viewpoint of the arrangement position of the insulating layer. For example, it can be classified into the following modes.
- (X) A high oxygen insulating layer that covers the main surface of the channel layer 7 and does not cover the main surfaces of the source electrode 5 and the drain electrode 6 in the heat treatment step that is performed after the oxide semiconductor layer is formed.
- (Y) A high-oxygen insulating layer that covers the main surface of the channel layer 7 and does not cover the main surfaces of the source electrode 5 and the drain electrode 6 in the heat treatment step that is performed after the oxide semiconductor layer is formed. And a low oxygen insulating layer that covers the main surfaces of the source electrode 5 and the drain electrode 6.
- the high oxygen insulating layer in Embodiments (X) and (Y) is an insulating layer that can suppress the release of oxygen from the oxide semiconductor layer that occurs during heat treatment or can diffuse oxygen into the oxide semiconductor layer.
- the oxide semiconductor layer covered with the high oxygen insulating layer becomes a layer which functions as a channel layer by suppressing desorption of oxygen during heat treatment or by supplying oxygen from the high oxygen insulating layer.
- the high oxygen insulating layer there is an insulating layer in which the number of oxygen atoms per unit volume is larger than that of the oxide semiconductor layer. The number of oxygen atoms per unit volume in the oxide semiconductor layer is determined as follows.
- Atomic content ratio target atomic content / total atomic content present in the oxide semiconductor layer, the ratio of each atom constituting the oxide semiconductor layer (atomic content ratio) is determined. The sum of the atomic content ratios for all atoms is 1.
- Number of oxygen atoms per unit volume oxygen atom content ratio (value when the whole is 1) ⁇
- the number of atoms contained in the film per unit volume can be measured by RBS.
- the film density is calculated using 6.8 g / cm 3 for convenience.
- the content ratio of In is A In
- the content ratio of W is A W
- the content ratio of Zn is A Zn
- the content ratio of O is Assuming A 2 O
- a In , A W , A Zn , and A 2 O can be obtained by TEM-EDX measurement.
- the number of oxygen atoms per unit volume in the high oxygen insulating layer can be calculated from the composition formula of the insulating material constituting the same as the method for calculating the number of oxygen atoms per unit volume in the oxide semiconductor layer. If the number of oxygen atoms per unit volume of the oxide semiconductor layer is less than the number of oxygen atoms per unit volume of the insulating layer, the insulating layer can be said to be a high oxygen insulating layer.
- a layer made of a material having an insulating property and a dielectric constant and having a relatively high oxygen atom content can be a high oxygen insulating layer.
- the insulating layers such as the SiO x layer (x ⁇ 1.5), the SiO x N y layer (x ⁇ 1.5), and the AlO x layer (x ⁇ 1.5) have the number of oxygen atoms per unit volume. Regardless of the judgment by contrast, it can be a high oxygen insulating layer.
- the high oxygen insulating layer is preferably a SiO x layer (x ⁇ 1.5) from the viewpoint of reliability under light irradiation of the semiconductor device. In the case of the bottom gate type, if a SiN x layer is laminated on the SiO x layer, the reliability under light irradiation can be further improved.
- the low oxygen insulating layer in the embodiment (Y) is a layer that cannot suppress the release of oxygen from the oxide semiconductor layer that occurs during heat treatment. When oxygen is released, the oxide semiconductor layer covered with the low oxygen insulating layer has a low electric resistance and becomes a conductive film.
- the low oxygen insulating layer may be defined as an insulating layer having a lower oxygen atom content than the high oxygen insulating layer.
- the low oxygen insulating layer there is an insulating layer in which the number of oxygen atoms per unit volume is smaller than that of an oxide semiconductor layer. The number of oxygen atoms per unit volume in the low oxygen insulating layer can be calculated by the method as described above.
- the low oxygen insulating layer has fewer oxygen atoms per unit volume than the high oxygen insulating layer.
- a layer made of a material having an insulating property and a dielectric constant and having a relatively low oxygen atom content can be a low oxygen insulating layer.
- Insulating layers such as SiO x N y layer (x ⁇ 1.5), Al 2 O x N y layer (x ⁇ 3, y> 0), SiN x layer, etc. are compared with the number of oxygen atoms per unit volume described above. It can be a low oxygen insulating layer regardless of the judgment by From the viewpoint of reliability of the semiconductor device under light irradiation, the low oxygen insulating layer is preferably a SiN x layer.
- the high oxygen insulating layer can be the second insulating layer 8.
- the second insulating layer 8 may be a layer that is present in the heat treatment step but is removed thereafter and does not exist in the obtained semiconductor device.
- the high oxygen insulating layer can be the first insulating layer (gate insulating layer) 3.
- a plurality of types of insulating layers may serve as the high oxygen insulating layer.
- the first insulating layer (gate insulating layer) 3 in the top gate type semiconductor device and the second insulating layer 8 in the bottom gate type semiconductor device are, for example, an SiO x layer (x ⁇ 1.5), an SiO x N y layer, for example.
- (X ⁇ 1.5, y ⁇ 0.5) which can be an Al 2 O 3 layer, preferably a SiO x layer (x ⁇ 1.5), more preferably a SiO 2 layer.
- the low oxygen insulating layer in the aspect (Y) can be, for example, the third insulating layer 9 formed before the heat treatment step.
- the third insulating layer 9 is, for example, a SiO x N y layer (x ⁇ 1.5, y> 0.5), a SiN x layer, or an Al 2 O x N y layer (x ⁇ 3, y> 0).
- it is a SiN x layer.
- the third insulating layer 9 is a layer that does not exist during the heat treatment step.
- the finally obtained semiconductor device may have the third insulating layer 9.
- the third insulating layer 9 can be a low oxygen insulating layer.
- the third insulating layer 9 is the second insulating layer 8 (bottom gate type) or the first insulating layer 3 (top). It can be a layer having a lower oxygen atom content than the gate type).
- the oxide semiconductor layer formed on the substrate 1 is heat-treated, a portion of the oxide semiconductor layer whose main surface is covered with the high oxygen insulating layer (partial covering insulating layer) has an electrical resistance.
- the ratio can be increased to show semiconductor characteristics, and that portion can be used as the channel layer 7.
- the oxide semiconductor layer formed on the substrate 1 is heat-treated in the heat treatment step, a portion of the oxide semiconductor layer whose main surface is not covered with the high oxygen insulating layer (partial covering insulating layer), Alternatively, the portion of the oxide semiconductor layer whose main surface is covered with the low oxygen insulating layer has low electric resistivity, and thus can be used as the source electrode 5 or the drain electrode 6.
- the method of separately forming the channel layer 7, the source electrode 5, and the drain electrode 6 from the oxide semiconductor layer by the heat treatment step is advantageous in obtaining a semiconductor device having high field effect mobility and high reliability under light irradiation. is there.
- an insulating layer may be laminated on the uncovered main surface of the source electrode 5 and the drain electrode 6 after the heat treatment step.
- the insulating layer include a SiO x layer, a SiO x N y layer, a SiN x layer, an AlO x layer, an Al 2 O x N y layer, and the like. From the viewpoint of maintaining the resistivity, the SiN x layer is preferable. As described above, the insulating layer may be the third insulating layer 9.
- the method of heat treatment performed after the oxide semiconductor layer is formed is not particularly limited, and may be heat treatment using lamp irradiation, an electric resistor, a laser, or the like.
- the heating temperature is preferably 100 ° C. or higher and 500 ° C. or lower. In order to realize high field effect mobility, the heating temperature is more preferably 450 ° C. or lower, and further preferably 400 ° C. or lower. In order to realize high reliability under light irradiation, the heating temperature is more preferably 200 ° C. or higher, and further preferably 300 ° C. or higher. From the viewpoint of achieving both high field effect mobility and high reliability under light irradiation, the heating temperature is particularly preferably from 300 ° C to 500 ° C.
- the atmosphere of the heat treatment may be various atmospheres such as air, nitrogen gas, nitrogen gas-oxygen gas, Ar gas, Ar-oxygen gas, water vapor-containing air, water vapor-containing nitrogen, etc.
- nitrogen gas can be atmospheric pressure, reduced pressure conditions (for example, less than 0.1 Pa), and pressurized conditions (for example, 0.1 Pa to 9 MPa), but is preferably atmospheric pressure.
- the heat treatment time can be, for example, about 0.01 second to 2 hours, and preferably about 1 second to 10 minutes.
- the semiconductor device manufacturing method according to the present embodiment is a method for manufacturing the semiconductor device according to the first embodiment, and is not particularly limited.
- the semiconductor device manufacturing method can exhibit high field effect mobility, and further has high field effect.
- the following steps are included from the viewpoint of efficiently and relatively easily manufacturing the semiconductor device according to the first embodiment that can exhibit high mobility and high reliability under light irradiation.
- the manufacturing method of the semiconductor device according to the present embodiment is a low oxygen covering the region adjacent to the part of the main surface of the oxide semiconductor layer after the step (3) and before the step (4). It may further include a step (5) of forming an insulating layer.
- an oxide semiconductor is formed using a partially covered insulating layer formed at a predetermined position.
- a semiconductor device is obtained by separately forming a channel layer, a source electrode, and a drain electrode from the layers.
- the partially covering insulating layer formed at a predetermined position can be formed by a self-alignment technique using a gate electrode that has been formed in advance, and by this self-alignment technique, the channel layer, the source electrode, and the oxide semiconductor layer are formed.
- a drain electrode can be made separately.
- both bottom gate type and top gate type semiconductor devices are manufactured. Can do.
- the obtained semiconductor device is specifically a TFT (Thin Film Transistor).
- TFT Thin Film Transistor
- FIG. 4 is a schematic cross-sectional view showing an example of a manufacturing method of the bottom gate type semiconductor device shown in FIG.
- a bottom gate semiconductor device manufacturing method will be described below by taking the bottom gate semiconductor device shown in FIG. 2 as an example.
- the bottom gate type semiconductor device manufacturing method shown in FIG. 2 includes, for example, the following steps in this order.
- [A] a step of forming the gate electrode 2 on the substrate 1 [corresponding to the above step (1)], [B] forming a first insulating layer (gate insulating layer) 3 on the gate electrode 2; [C] A step of forming the oxide semiconductor layer 4 on the first insulating layer 3 [corresponding to the above step (2)], [D] forming a second insulating layer (insulating protective layer) 8 on the oxide semiconductor layer 4; [E] A step of patterning the second insulating layer 8 to form a partially covering insulating layer that covers a part of the main surface of the oxide semiconductor layer 4 [corresponding to the above step (3)], [F] A step of performing heat treatment [corresponding to the above step (4)].
- This step is a step of forming the gate electrode 2 on the substrate 1.
- the substrate 1 is not particularly limited, but is preferably a quartz glass substrate, an alkali-free glass substrate, an alkali glass substrate, or the like from the viewpoints of transparency, price stability, and surface smoothness.
- the gate electrode 2 is not particularly limited, it is a material that has high oxidation resistance, low electrical resistance, and is capable of shielding ultraviolet rays applied to a resist layer used in a later process. An electrode, an Al electrode, a Cu electrode or the like is preferable.
- the formation method of the gate electrode 2 is not particularly limited, but is preferably a vacuum deposition method, a sputtering method, or the like because it can be uniformly formed in a large area on the main surface of the substrate 1.
- the gate electrode 2 may be formed directly on the main surface of the substrate 1 or may be formed on the substrate 1 via another layer (such as an insulating layer made of an organic material or an inorganic material).
- the gate electrode 2 is preferably formed with a uniform film thickness.
- a resist pattern corresponding to the designed wiring pattern of the gate electrode 2 is formed by applying a resist agent, irradiating with ultraviolet rays using a photomask, and developing. Subsequently, after etching the portion of the gate electrode 2 not covered with the resist layer by an acid solution or plasma treatment, the wiring of the gate electrode 2 (patterned gate electrode 2) is formed by removing the resist layer. .
- This step is a step of forming a first insulating layer (gate insulating layer) 3 on the patterned gate electrode 2.
- the first insulating layer 3 is formed on the entire main surface of the laminate including the substrate 1 and the gate electrode 2 including the main surface of the patterned gate electrode 2.
- the method for forming the first insulating layer 3 is not particularly limited, but is preferably a plasma CVD (Chemical Vapor Deposition) method or the like from the viewpoint of ensuring uniform formation in a large area and ensuring insulation.
- the first insulating layer 3 is preferably formed with a uniform film thickness.
- the first insulating layer (gate insulating layer) 3 can be, for example, a SiO x layer, a SiO x N y layer, a SiN x layer, an AlO x layer, or an Al 2 O x N y layer.
- a SiO x layer is preferable.
- This step is a step of forming the oxide semiconductor layer 4 on the first insulating layer 3.
- the oxide semiconductor layer 4 is preferably formed including a step of forming a film by a sputtering method, and can also be formed by heat treatment while forming a film by a sputtering method.
- the oxide semiconductor layer 4 is preferably formed with a uniform film thickness.
- a resist pattern corresponding to the designed wiring pattern of the channel layer 7, the source electrode 5 and the drain electrode 6 is formed by applying a resist agent, irradiating with ultraviolet rays using a photomask, and developing. Subsequently, after etching the portion of the oxide semiconductor layer 4 not covered with the resist layer by an acid solution or plasma treatment, the resist layer is removed, whereby the wiring pattern of the oxide semiconductor layer 4 (patterned oxide) A semiconductor layer 4) is formed.
- This step is a step of forming a second insulating layer (insulating protective layer) 8 on the patterned oxide semiconductor layer 4.
- the second insulating layer 8 is formed on the entire main surface of the stacked body including the substrate 1, the gate electrode 2, the first insulating layer 3, and the oxide semiconductor layer 4 including the main surface of the patterned oxide semiconductor layer 4.
- the method of forming the second insulating layer 8 is not particularly limited, but is preferably a plasma CVD (Chemical Vapor Deposition) method or the like from the viewpoint of being able to be uniformly formed in a large area and ensuring insulation.
- the second insulating layer 8 is preferably formed with a uniform film thickness.
- the second insulating layer 8 corresponds to the above-described high oxygen insulating layer, and is a layer that becomes a partially covering insulating layer.
- the second insulating layer 8 can be, for example, a SiO x layer (x ⁇ 1.5), a SiO x N y layer (x ⁇ 1.5), an AlO x layer (x ⁇ 1.5),
- the SiO x layer (x ⁇ 1.5) is preferable. More preferred is a SiO 2 layer.
- the oxygen atom content of the second insulating layer 8 is preferably larger than that of the oxide semiconductor layer 4.
- the oxygen atom content of the second insulating layer 8 is preferably larger than that of the third insulating layer 9.
- This step is a step of patterning the second insulating layer 8 to form a partially covering insulating layer that covers a part of the main surface of the oxide semiconductor layer 4.
- a resist agent is applied to form a resist layer 10 on the second insulating layer 8.
- a laminate having the structure shown in FIG. Next, ultraviolet rays are irradiated from the substrate 1 side. At this time, ultraviolet rays are shielded by the gate electrode 2, whereby a region A that is not exposed to ultraviolet rays and a region B that is exposed without being shielded by ultraviolet rays are formed in the resist layer 10.
- development is performed to dissolve the resist layer 10 in the region B exposed to ultraviolet rays. As a result, a laminate having the structure shown in FIG. 4B is obtained.
- the patterned second insulating layer 8 is a partially covering insulating layer. As described above, the partially covering insulating layer is formed by patterning by self-alignment using the gate electrode 2 previously formed. Thereafter, the resist layer 10 on the patterned second insulating layer 8 is removed.
- This step is a step of performing heat treatment.
- a part of the oxide semiconductor layer 4 covered with the second insulating layer 8 becomes the channel layer 7, while the other part of the oxide semiconductor layer 4
- the region where the main surface is exposed without being covered with the second insulating layer 8 becomes the source electrode 5 or the drain electrode 6 as the electric resistivity decreases.
- the source electrode 5 and the drain electrode 6 can also be used as pixel electrodes.
- the length of the channel layer 7 which is a part of the oxide semiconductor layer 4 matches the width of the gate electrode 2. More specifically, the channel layer 7 is disposed in a region immediately above the gate electrode 2 when the stacked body is viewed from above. Therefore, the interface position between the channel layer 7 and the source electrode 5 and the interface position between the channel layer 7 and the drain electrode 6 coincide with the position of the end face of the gate electrode 2.
- Such a positional relationship between the channel layer 7 and the gate electrode 2 may be only in the TFT region which is a semiconductor device, and the wiring pattern of the gate electrode other than the TFT region is not necessarily patterned in the oxide semiconductor layer.
- the method of heat treatment is not particularly limited, and may be heat treatment with lamp irradiation, electric resistor, laser or the like.
- the heating temperature is preferably 100 ° C. or higher and 500 ° C. or lower. In order to realize high field effect mobility, the heating temperature is more preferably 450 ° C. or lower, and further preferably 400 ° C. or lower. In order to realize high reliability under light irradiation, the heating temperature is more preferably 150 ° C. or higher, and further preferably 300 ° C. or higher. From the viewpoint of achieving both high field effect mobility and high reliability under light irradiation, the heating temperature is particularly preferably from 300 ° C to 500 ° C.
- the atmosphere of the heat treatment may be various atmospheres such as air, nitrogen gas, nitrogen gas-oxygen gas, Ar gas, Ar-oxygen gas, water vapor-containing air, water vapor-containing nitrogen. More preferably, it is in nitrogen gas.
- the atmospheric pressure can be atmospheric pressure, reduced pressure conditions (for example, less than 0.1 Pa), and pressurized conditions (for example, 0.1 Pa to 9 MPa), but is preferably atmospheric pressure.
- the heat treatment time can be, for example, about 0.01 second to 2 hours, and preferably about 1 second to 10 minutes.
- the signal wiring not only a part of the oxide semiconductor layer 4 but also a separate metal layer that can be formed by the same method as the gate electrode 2 can be used together as the signal wiring.
- a step [g] of forming the third insulating layer 9 on the surface of the stacked body may be provided.
- the 3rd insulating layer 9 is formed in the whole main surface of a laminated body.
- the method for forming the third insulating layer 9 is not particularly limited, but is preferably a plasma CVD (Chemical Vapor Deposition) method or the like from the viewpoint of being able to be formed uniformly in a large area and ensuring insulation.
- the step [g] of forming the third insulating layer 9 may be performed before the step [f] of performing the heat treatment or after the step [f].
- the third insulating layer 9 can be the above-described low oxygen insulating layer.
- the third insulating layer 9 is, for example, a SiO x N y layer (x ⁇ 1.5, y> 0.5), a SiN x layer, an Al 2 O x N y layer (x ⁇ 3, y> 0). From the viewpoint of lowering the electric resistivity of the source electrode 5 and the drain electrode 6, it is preferably a SiN x layer.
- the third insulating layer 9 The oxygen atom content is preferably smaller than that of the oxide semiconductor layer 4 and / or the oxygen atom content of the third insulating layer 9 is preferably smaller than that of the second insulating layer 8.
- the third insulating layer 9 includes, for example, a SiO x layer, a SiO x N y layer, a SiN x layer, an AlO x layer, an Al 2 O x N y. From the viewpoint of maintaining the low electrical resistivity of the source electrode 5 and the drain electrode 6, the SiN x layer is preferable.
- FIG. 5 is a schematic cross-sectional view showing an example of a manufacturing method of the top gate type semiconductor device shown in FIG.
- a method for manufacturing a top gate type semiconductor device will be described below by taking the top gate type semiconductor device shown in FIG. 3 as an example.
- the top gate semiconductor device manufacturing method shown in FIG. 3 includes, for example, the following steps in this order.
- [A] A step of forming the oxide semiconductor layer 4 on the substrate 1 [corresponding to the above step (2)], [B] forming the first insulating layer 3 on the oxide semiconductor layer 4; [C] a step of forming the gate electrode 2 on the first insulating layer 3 [corresponding to the above step (1)], [D] A step of patterning the gate electrode 2 to form a partially covering insulating layer that covers a part of the main surface of the oxide semiconductor layer 4 [corresponding to the above step (3)], [E] A step of performing heat treatment [corresponding to the above step (4)].
- This step is a step of forming the oxide semiconductor layer 4 on the substrate 1.
- the oxide semiconductor layer 4 may be formed directly on the main surface of the substrate 1 or may be formed on the substrate 1 via another layer (such as an insulating layer made of an organic material or an inorganic material).
- the oxide semiconductor layer 4 is preferably formed with a uniform film thickness. Subsequently, patterning of the oxide semiconductor layer 4 is performed, and the description of the manufacturing method of the bottom gate type semiconductor device is cited here as well.
- This step is a step of forming the first insulating layer (gate insulating layer) 3 on the patterned oxide semiconductor layer 4.
- the first insulating layer 3 is formed on the entire main surface of the stacked body including the substrate 1 and the oxide semiconductor layer 4 including the main surface of the patterned oxide semiconductor layer 4.
- the first insulating layer 3 is preferably formed with a uniform film thickness.
- This step is a step of forming the gate electrode 2 on the first insulating layer 3.
- the gate electrode 2 is formed on the entire main surface of the laminate.
- a laminated body having the structure shown in FIG. With regard to the material and forming method of the gate electrode 2, the description of the manufacturing method of the bottom gate type semiconductor device is cited.
- This step is a step of patterning the gate electrode 2 and using this to form a partially covering insulating layer that covers a part of the main surface of the oxide semiconductor layer 4.
- a resist agent is applied to form a resist layer 10 on the gate electrode 2.
- a resist pattern corresponding to the designed wiring pattern of the gate electrode 2 is formed by performing ultraviolet irradiation and development using a photomask. As a result, a laminate having the structure shown in FIG. 5B is obtained.
- the gate electrode 2 is etched by etching the portion of the gate electrode 2 not covered with the resist layer 10 by an acid solution or plasma treatment.
- the first insulating layer 3 is exposed.
- the exposed first insulating layer 3 is etched by an acid solution or plasma treatment until the oxide semiconductor layer 4 is exposed. 3 patterning is performed.
- the patterned first insulating layer 3 is a partially covering insulating layer. As described above, the partially covering insulating layer is formed by patterning by self-alignment using the gate electrode 2 previously formed. Thereafter, the resist layer 10 on the patterned gate electrode 2 is removed.
- This step is a step of performing heat treatment.
- a part of the oxide semiconductor layer 4 that is covered with the first insulating layer 3 (partial covering insulating layer) becomes the channel layer 7, while the other part of the oxide semiconductor layer 4.
- the region where the main surface is exposed without being covered with the first insulating layer 3 (partial covering insulating layer) becomes the source electrode 5 or the drain electrode 6 as the electric resistivity decreases.
- the source electrode 5 and the drain electrode 6 can also be used as pixel electrodes.
- the description of the method for manufacturing the bottom gate type semiconductor device is cited.
- the length of the channel layer 7 which is a part of the oxide semiconductor layer 4 matches the width of the gate electrode 2. More specifically, the channel layer 7 is disposed in a region immediately below the gate electrode 2 when the stacked body is viewed from above. Therefore, the interface position between the channel layer 7 and the source electrode 5 and the interface position between the channel layer 7 and the drain electrode 6 coincide with the position of the end face of the gate electrode 2.
- the signal wiring not only a part of the oxide semiconductor layer 4 but also a separate metal layer that can be formed by the same method as the gate electrode 2 can be used together as the signal wiring.
- a step [F] of forming the third insulating layer 9 on the surface of the laminate may be provided.
- the 3rd insulating layer 9 is formed in the whole main surface of a laminated body.
- the step [F] of forming the third insulating layer 9 may be performed before the step [E] of performing the heat treatment, or may be performed after the step [E].
- the third insulating layer 9 can be the above-described low oxygen insulating layer.
- the third insulating layer 9 is, for example, a SiO x N y layer (x ⁇ 1.5, y> 0.5), a SiN x layer, an Al 2 O x N y layer (x ⁇ 3, y> 0). From the viewpoint of lowering the electric resistivity of the source electrode 5 and the drain electrode 6, it is preferably a SiN x layer.
- the third insulating layer 9 The oxygen atom content is preferably smaller than that of the oxide semiconductor layer 4 and / or the oxygen atom content of the third insulating layer 9 is preferably smaller than that of the first insulating layer 3.
- the third insulating layer 9 includes, for example, a SiO x layer, a SiO x N y layer, a SiN x layer, an AlO x layer, an Al 2 O x N y. From the viewpoint of maintaining the low electrical resistivity of the source electrode 5 and the drain electrode 6, the SiN x layer is preferable.
- Examples 1 to 18 Production of bottom gate TFT> A TFT having a configuration similar to that of the bottom gate TFT shown in FIG. 2 was manufactured by the following procedure. First, a non-alkali glass substrate having a length of 50 mm, a width of 50 mm, and a thickness of 0.6 mm was prepared as the substrate 1, and a Mo electrode having a thickness of 100 nm was formed as the gate electrode 2 on the substrate 1 by a sputtering method.
- a positive resist agent was applied to the surface of the gate electrode 2 to form a resist layer, and prebaked at 90 ° C. for 60 seconds.
- the substrate 1 having a resist layer was irradiated with ultraviolet rays (wavelength: 310 to 440 nm) through a photomask in which a metal film was arranged in accordance with a predetermined wiring pattern of the gate electrode 2.
- the substrate 1 having a resist layer was immersed in the developer.
- the resist layer in the region where the ultraviolet ray was shielded by the metal film of the photomask and was not irradiated with the ultraviolet ray remained at the time of development.
- the resist layer corresponding to the portion of the photomask without the metal film was exposed to ultraviolet rays through the glass of the photomask and was dissolved in the developer during development. After development, the substrate 1 was washed with water.
- aqueous solution kept at 30 ° C. in a water bath
- the gate electrode 2 was patterned by immersing the substrate 1 in a portion of the gate electrode 2 where the surface was exposed by development until the substrate 1 was exposed. After etching, the substrate 1 was washed with water, and the resist layer on the gate electrode 2 was peeled and removed with a resist stripping solution.
- a first insulating layer (gate insulating layer) 3 by a plasma CVD method to form a SiO x layer having a thickness of 200nm which is an amorphous oxide layer.
- a mixed gas of SiH 4 and N 2 O was used as the source gas.
- the oxide semiconductor layer 4 was formed on the first insulating layer (gate insulating layer) 3 by DC (direct current) magnetron sputtering.
- a plane having a target diameter of 3 inches (76.2 mm) was a sputter surface.
- the target is an oxide sintered body containing In, W, and Zn, mainly composed of In 2 O 3 crystal, ZnO crystal, ZnWO 4 crystal, In 2 O 3 (ZnO) m (m is a natural number).
- An oxide sintered body in which at least one of crystal and In 6 WO 12 crystal was mixed was used.
- Zr zirconium
- ZrO 2 was added during preparation of the oxide sintered body to prepare an oxide sintered body.
- Table 1 shows the thickness of the formed oxide semiconductor layer 4.
- the film thickness of the oxide semiconductor layer 4 was calculated by observing the layer cross section with a transmission electron microscope, measuring the distance from the lowermost surface to the uppermost surface of the layer, and dividing by the observation magnification. The distance was measured at 5 points, and the film thickness was calculated from the average value.
- the target was disposed at a distance of 60 mm so as to face the first insulating layer 3.
- the target was sputtered as follows with the vacuum in the film formation chamber being about 6 ⁇ 10 ⁇ 5 Pa.
- a mixed gas of Ar (argon) gas and O 2 (oxygen) gas was introduced into the film formation chamber up to a pressure of 0.5 Pa while a shutter was put between the first insulating layer 3 and the target.
- the O 2 gas content in the mixed gas was 10% by volume.
- Sputtering discharge was caused by applying DC power of 120 W to the target, thereby cleaning the target surface (pre-sputtering) for 5 minutes.
- the oxide semiconductor layer 4 was deposited on the first insulating layer 3 by removing the shutter while maintaining the atmosphere in the deposition chamber. Note that no bias voltage was applied to the substrate holder. Further, the substrate holder was water-cooled or heated to adjust the temperature of the substrate 1 during film formation and after film formation.
- the substrate temperature is set by heating the substrate holder during film formation. The heat treatment was performed simultaneously with the film formation by adjusting to the temperature described in the column of “Processing temperature” in Table 3.
- the heating time is a total of 30 minutes from before the film formation of the oxide semiconductor layer 4 to after the film formation.
- the heat treatment was not performed during film formation.
- the substrate temperature during film formation was about 20 ° C.
- the film formation time was adjusted so that the thickness of the oxide semiconductor layer 4 was as shown in Tables 1 to 3.
- the oxide semiconductor layer 4 was formed by DC (direct current) magnetron sputtering using an oxide sintered compact target.
- a positive resist agent was applied on the oxide semiconductor layer 4 to form a resist layer, and prebaked at 90 ° C. for 60 seconds.
- the substrate 1 having a resist layer was irradiated with ultraviolet rays (wavelength: 310 to 440 nm) through a photomask in which a metal film was arranged in accordance with a predetermined wiring pattern of the oxide semiconductor layer 4.
- the substrate 1 having a resist layer was immersed in the developer.
- the resist layer in the region where the ultraviolet ray was shielded by the metal film of the photomask and was not irradiated with the ultraviolet ray remained at the time of development.
- the resist layer corresponding to the portion of the photomask without the metal film was exposed to ultraviolet rays through the glass of the photomask and was dissolved in the developer during development. After development, the substrate 1 was washed with water.
- the portion of the oxide semiconductor layer 4 whose surface is exposed by development is formed as a first layer.
- the oxide semiconductor layer 4 was patterned by etching until the insulating layer (gate insulating layer) 3 was exposed. After the etching, the substrate 1 was washed with water, and the resist layer on the oxide semiconductor layer 4 was peeled and removed with a resist stripping solution.
- a second insulating layer (insulating protective layer) 8 (a layer that becomes a partially covering insulating layer) on the patterned oxide semiconductor layer 4 by plasma CVD, an amorphous oxide layer having a thickness of 200 nm is formed.
- a SiO x layer was formed over the entire exposed surface. That is, in the region where the first insulating layer (gate insulating layer) 3 was exposed by the previous etching, the first insulating layer (gate insulating layer) 3 and the second insulating layer 8 were in contact with each other.
- a mixed gas of SiH 4 and N 2 O was used as the source gas.
- a positive resist agent was applied on the second insulating layer 8 to form a resist layer 10 and prebaked at 90 ° C. for 60 seconds.
- the laminated body which has a structure similar to the structure shown by Fig.4 (a) was obtained.
- ultraviolet light (wavelength: 310 to 440 nm) was irradiated from the upper surface with the substrate 1 surface of the laminate as the upper surface and the resist layer 10 surface as the lower surface.
- the substrate 1 having the resist layer 10 was immersed in the developer. Only the gate electrode 2 shields ultraviolet rays in the laminate.
- the resist layer 10 in the region where the ultraviolet rays were shielded by the gate electrode 2 and not irradiated with the ultraviolet rays remained at the time of development.
- the resist layer 10 corresponding to the portion without the gate electrode 2 was exposed and dissolved in the developer during development. After development, the substrate 1 was washed with water. Thereby, the laminated body which has a structure similar to the structure shown by FIG.4 (b) was obtained.
- the substrate 1 was immersing the substrate 1 in a buffered hydrofluoric acid aqueous solution maintained at 30 ° C. in a water bath, the portion of the second insulating layer 8 whose surface is exposed by development is changed from the oxide semiconductor layer 4 and the first semiconductor layer 8.
- the second insulating layer 8 was patterned by etching until the insulating layer (gate insulating layer) 3 was exposed. Thereby, the laminated body which has a structure similar to the structure shown by FIG.4 (c) was obtained.
- the substrate 1 was washed with water, and the resist layer on the gate electrode 2 was peeled and removed with a resist stripping solution.
- the stacked body has a second insulating layer 8 (partial covering insulating layer) that covers a part of the upper surface (main surface) of the oxide semiconductor layer 4 when the surface of the substrate 1 is the lower surface.
- the upper surface (main surface) of the oxide semiconductor layer 4 that is not covered with the second insulating layer 8 is exposed.
- the length of the channel layer 7 which is a part of the oxide semiconductor layer 4 matches the width of the gate electrode 2. More specifically, the channel layer 7 is disposed in a region immediately above the gate electrode 2 when the stacked body is viewed from above. Therefore, the interface position between the channel layer 7 and the source electrode 5 and the interface position between the channel layer 7 and the drain electrode 6 coincide with the position of the end face of the gate electrode 2.
- a first insulating layer (gate insulating layer) 3 is interposed between the gate electrode 2 and the oxide semiconductor layer 4.
- the entire exposed surface of the stacked body (including the exposed surface of the oxide semiconductor layer 4, the exposed surface of the first insulating layer (gate insulating layer) 3 and the exposed surface of the second insulating layer 8) is formed by plasma CVD.
- the third insulating layer (insulating protective layer) 9 an SiN x layer having a thickness of 200 nm, which is an amorphous nitride, was formed to obtain a bottom gate type TFT having a configuration similar to FIG.
- the first insulating layer (gate insulating layer) 3 and the third insulating layer 9 were in contact with each other.
- a mixed gas of SiH 4 and NH 3 was used as the source gas.
- Example 1 the third insulating layer 9 is formed after the heat treatment, but there is an example in which the third insulating layer 9 is formed before the heat treatment.
- the third insulating layer 9 was formed before the heat treatment, and “After” In the example described, the third insulating layer 9 was formed after the heat treatment. In the example described as “none”, the third insulating layer 9 was not formed.
- the third insulating layer 9 can be a low oxygen insulating layer.
- the tungsten contained in the oxide semiconductor was measured using X-ray photoelectron spectroscopy (XPS). When the binding energy was measured, it was confirmed that the peak position was 35 eV or more and 36.5 eV or less. This confirmed that the oxide semiconductor contained hexavalent tungsten.
- XPS X-ray photoelectron spectroscopy
- Example 19 to Example 36 Production of top gate type TFT>
- a TFT having a configuration similar to that of the top gate TFT shown in FIG. 3 was manufactured by the following procedure. First, an alkali-free glass substrate having a length of 50 mm, a width of 50 mm, and a thickness of 0.6 mm was prepared as the substrate 1, and the oxide semiconductor layer 4 was formed on the substrate 1 by a DC (direct current) magnetron sputtering method. A plane having a target diameter of 3 inches (76.2 mm) was a sputter surface.
- the target is an oxide sintered body containing In, W, and Zn, mainly composed of In 2 O 3 crystal, ZnO crystal, ZnWO 4 crystal, In 2 O 3 (ZnO) m (m is a natural number).
- An oxide sintered body in which at least one of crystal and In 6 WO 12 crystal was mixed was used.
- ZrO 2 was added during preparation of the oxide sintered body to prepare an oxide sintered body.
- the film thickness of the formed oxide semiconductor layer 4 is shown in Table 2 (the measurement method is as described above).
- the substrate 1 is placed on a water-cooled substrate holder in a film formation chamber of a sputtering apparatus.
- the target was disposed at a distance of 60 mm so as to face the substrate 1.
- the target was sputtered as follows with the vacuum in the film formation chamber being about 6 ⁇ 10 ⁇ 5 Pa.
- a mixed gas of Ar (argon) gas and O 2 (oxygen) gas was introduced into the film forming chamber to a pressure of 0.5 Pa with a shutter placed between the substrate 1 and the target.
- the O 2 gas content in the mixed gas was 10% by volume.
- Sputtering discharge was caused by applying DC power of 120 W to the target, thereby cleaning the target surface (pre-sputtering) for 5 minutes.
- the oxide semiconductor layer 4 was deposited on the substrate 1 by removing the shutter while maintaining the atmosphere in the deposition chamber. Note that no bias voltage was applied to the substrate holder. Further, the substrate holder was water-cooled or heated to adjust the temperature of the substrate 1 during film formation and after film formation.
- the oxide semiconductor layer 4 was formed by DC (direct current) magnetron sputtering using an oxide sintered compact target.
- a positive resist agent was applied on the oxide semiconductor layer 4 to form a resist layer, and prebaked at 90 ° C. for 60 seconds.
- the substrate 1 having a resist layer was irradiated with ultraviolet rays (wavelength: 310 to 440 nm) through a photomask in which a metal film was arranged in accordance with a predetermined wiring pattern of the oxide semiconductor layer 4.
- the substrate 1 having a resist layer was immersed in the developer.
- the resist layer in the region where the ultraviolet ray was shielded by the metal film of the photomask and was not irradiated with the ultraviolet ray remained at the time of development.
- the resist layer corresponding to the portion of the photomask without the metal film was exposed to ultraviolet rays through the glass of the photomask and was dissolved in the developer during development. After development, the substrate 1 was washed with water.
- the substrate 1 is dipped in an “ITO-07A” solution manufactured by Kanto Chemical Co., Ltd., which is kept at 30 ° C. in a water bath, so that the oxide semiconductor layer 4 whose surface is exposed by development becomes the underlying substrate 1.
- the oxide semiconductor layer 4 was patterned by etching until exposed. After the etching, the substrate 1 was washed with water, and the resist layer on the oxide semiconductor layer 4 was peeled and removed with a resist stripping solution.
- a Mo electrode having a thickness of 100 nm was formed as the gate electrode 2 on the first insulating layer (gate insulating layer) 3 by a sputtering method. Thereby, the laminated body which has a structure similar to the structure shown by Fig.5 (a) was obtained.
- a positive resist agent was applied to the surface of the gate electrode 2 to form a resist layer 10 and prebaked at 90 ° C. for 60 seconds.
- the substrate 1 having the resist layer 10 was irradiated with ultraviolet rays (wavelength: 310 to 440 nm) through a photomask in which a metal film was arranged in accordance with a predetermined wiring pattern of the gate electrode 2.
- the substrate 1 having the resist layer 10 was immersed in the developer.
- the resist layer 10 in the region where the ultraviolet ray was shielded by the metal film of the photomask and the ultraviolet ray was not irradiated remained during development.
- the resist layer 10 corresponding to the portion without the metal film of the photomask was exposed to ultraviolet rays through the glass of the photomask, and was dissolved in the developer during development. After development, the substrate 1 was washed with water. Thereby, the laminated body which has a structure similar to the structure shown by FIG.5 (b) was obtained.
- aqueous solution kept at 30 ° C. in a water bath
- the gate electrode 2 was patterned by immersing the substrate 1 in a portion of the gate electrode 2 where the surface was exposed by development until the first insulating layer (gate insulating layer) 3 was exposed. After the etching, the substrate 1 was washed with water.
- the first portion of the surface exposed by the previous etching is used.
- the first insulating layer 3 was patterned by etching the one insulating layer (gate insulating layer) 3 until the oxide semiconductor layer 4 and the substrate 1 were exposed. Thereby, the laminated body which has a structure similar to the structure shown by FIG.5 (c) was obtained.
- the substrate 1 was washed with water, and the resist layer 10 on the gate electrode 2 was peeled and removed with a resist stripping solution.
- the laminated body has a first insulating layer (gate insulating layer) 3 (partial covering insulating layer) covering a part of the upper surface (main surface) of the oxide semiconductor layer 4 when the surface of the substrate 1 is the lower surface.
- a first insulating layer (gate insulating layer) 3 partial covering insulating layer covering a part of the upper surface (main surface) of the oxide semiconductor layer 4 when the surface of the substrate 1 is the lower surface.
- the channel layer 7 is disposed in a region immediately below the gate electrode 2 when the stacked body is viewed from above. Therefore, the interface position between the channel layer 7 and the source electrode 5 and the interface position between the channel layer 7 and the drain electrode 6 coincide with the position of the end face of the gate electrode 2.
- a first insulating layer (gate insulating layer) 3 is interposed between the gate electrode 2 and the oxide semiconductor layer 4.
- a third insulating layer (insulating protective layer) is formed on the entire exposed surface of the stack (including the exposed surface of the oxide semiconductor layer 4, the exposed surface of the gate electrode 2, and the exposed surface of the substrate 1) by plasma CVD.
- the substrate 1 and the third insulating layer 9 were in contact with each other.
- a mixed gas of SiH 4 and NH 3 was used as the source gas.
- Example 19 the third insulating layer 9 is formed after the heat treatment. However, as described above, there is an example in which the third insulating layer 9 is formed before the heat treatment. When the third insulating layer 9 is formed before the heat treatment, the third insulating layer 9 can be a low oxygen insulating layer.
- the tungsten contained in the oxide semiconductor was measured using X-ray photoelectron spectroscopy (XPS). When the binding energy was measured, it was confirmed that the peak position was 35 eV or more and 36.5 eV or less. This confirmed that the oxide semiconductor contained hexavalent tungsten.
- XPS X-ray photoelectron spectroscopy
- ⁇ Comparative Example 1> Except that an oxide sintered body having an atomic ratio of In: Ga: Zn 1: 1: 1 was used as a target for forming the oxide semiconductor layer 4, the same as in Examples 19 to 36 was used. A top gate type TFT was produced. Even when heat treatment was performed at 350 ° C. for 10 minutes in an atmospheric pressure nitrogen atmosphere, the electrical resistivity of the source electrode 5 and the drain electrode 6 did not decrease, and the TFT could not be driven.
- a top gate type TFT was produced in the same manner as in Examples 19 to 36 except that the production conditions shown in Table 3 were adopted.
- a top gate type TFT was produced in the same manner as in Examples 19 to 36 except that the production conditions shown in Table 3 were adopted.
- 0.05: 0.00 (atomic ratio)] was used as a target for forming the oxide semiconductor layer 4. The same measurement as above was performed, and it was confirmed that the oxide semiconductor included in the oxide semiconductor layer 4 contained hexavalent tungsten.
- a top gate type TFT was produced in the same manner as in Examples 19 to 36 except that the production conditions shown in Table 3 were adopted.
- the target for forming the oxide semiconductor layer 4 is an oxide sintered body (Zr content 6 ⁇ 10 18 atms / cm 3 ) mainly composed of In 2 O 3 crystals and mixed with ZrO 2 crystals. It was used.
- a top gate type TFT was produced in the same manner as in Examples 19 to 36 except that the production conditions shown in Table 3 were adopted.
- a top gate type TFT was produced in the same manner as in Examples 19 to 36 except that the production conditions shown in Table 3 were adopted.
- a top gate type TFT was produced in the same manner as in Examples 19 to 36 except that the production conditions shown in Table 3 were adopted.
- a top gate type TFT was produced in the same manner as in Examples 19 to 36 except that the production conditions shown in Table 3 were adopted.
- a top gate type TFT was produced in the same manner as in Examples 19 to 36 except that the production conditions shown in Table 2 were adopted.
- As a target for forming the oxide semiconductor layer 4, an oxide sintered body [In: W: Zn containing an In 2 O 3 crystal as a main component and a mixture of ZnWO 4 crystal, ZnO crystal, and ZrO 2 crystal. 1: 0.008: 0.012 (atomic ratio)] was used. The same measurement as above was performed, and it was confirmed that the oxide semiconductor included in the oxide semiconductor layer 4 contained hexavalent tungsten.
- the contents of In, W, and Zn in the oxide semiconductor layer 4 were measured by RBS (Rutherford backscattering analysis). Based on these contents, the W content of the oxide semiconductor layer 4 (atomic%, expressed as “W content” in Tables 1 to 3), Zn content (atomic%, in Tables 1 to 3) And the Zn / W ratio (number ratio, expressed as “Zn / W ratio” in Tables 1 to 3). The results are shown in Tables 1 to 3.
- the W content is 0.5 atomic% or less
- the content of Zr in the oxide semiconductor layer 4 was determined by secondary ion mass spectrometry ( SIMS). The results are shown in Tables 1 to 3.
- the oxide semiconductor layer 4 (first oxide semiconductor) constituting the channel layer 7 and the oxide semiconductor layer 4 (second oxide semiconductor) constituting the source electrode 5 and the drain electrode 6 have an In content, W It was the same in content, Zn content, Zn / W ratio, and Zr content.
- the electrical resistivity of the channel layer 7 was determined by the following method. A measuring needle was brought into contact with the source electrode 5 and the drain electrode 6. Next, the source-drain current I ds was measured while changing the voltage from 1 V to 20 V between the source and drain electrodes. The slope when the graph of I ds -V ds is drawn is the resistance R. From the resistance R, the channel length C L (30 ⁇ m), the channel width C W (40 ⁇ m), and the film thickness t, the electrical resistivity of the channel layer 7 can be obtained as R ⁇ C W ⁇ t / C L. . In all Examples and Comparative Examples, the electrical resistivity of the channel layer 7 was 10 ⁇ 1 ⁇ cm or more.
- the electrical resistivity of the source electrode 5 and the drain electrode 6 was determined by the following method.
- the oxide semiconductor layer 4 having a size of length M L (150 ⁇ m) and width M W (30 ⁇ m) was manufactured by the same method as the source electrode 5 and the drain electrode 6 in the TFT manufacturing method described above.
- Two measuring needles were brought into contact with two end portions in the length direction, which is the center position in the width direction of the obtained oxide semiconductor layer 4. Then, while applying to the voltage V t is changed from 1V to 20V to the two measuring needle was measured I flowing between the measurement needle.
- the slope when the IV- t graph is drawn is the resistance R.
- the resistance R, the length M L (150 [mu] m), a width M W (30 [mu] m), film thickness t, the electrical resistivity of the source electrode 5 and drain electrode 6, be obtained as R ⁇ M W ⁇ t / M L Can do.
- the measurement results are shown in Tables 1 to 3.
- the electrical resistivity of the source electrode 5 and the drain electrode 6 is expressed as “S / D electrical resistivity” in Tables 1 to 3.
- TFT Characteristic evaluation of TFT
- a measuring needle was brought into contact with the gate electrode 2, the source electrode 5 and the drain electrode 6.
- a source-drain voltage V ds of 0.2 V is applied between the source electrode 5 and the drain electrode 6, and a source-gate voltage V gs applied between the source electrode 5 and the gate electrode 2 is changed from ⁇ 30V.
- the voltage was changed to 20 V, and the source-drain current I ds at that time was measured.
- V gs ⁇ (I ds ) 1 The threshold voltage V th was measured for the TFT when the above heat treatment was performed at 250 ° C. in a nitrogen atmosphere and when the above heat treatment was performed at 350 ° C. in a nitrogen atmosphere. The results are shown in Tables 1 to 3.
- the capacitance C i of the first insulating layer (gate insulating layer) 3 was 3.4 ⁇ 10 ⁇ 8 F / cm 2 , and the source-drain voltage V ds was 0.2V.
- the field effect mobility ⁇ fe was measured for the TFT when the above heat treatment was performed at 250 ° C. in a nitrogen atmosphere and when the above heat treatment was performed at 350 ° C. in a nitrogen atmosphere. The results are shown in Tables 1 to 3.
Abstract
Description
TFTの製造においては、レジストを紫外線露光により感光させるフォトリソグラフィーを用いることが一般的である。紫外線露光においては、必要な領域のレジスト(フォトレジスト)のみに光を照射するために、フォトマスクと呼ばれる、紫外線を遮断する必要がある領域に金属膜を形成したガラス板が用いられている。しかし、このようなフォトマスクを用いた紫外線露光は、TFTの製造コスト増加につながる。
上記によれば、寄生容量を小さくすることが可能であり、電界効果移動度が高く、好ましくはさらに光照射下での信頼性が高い半導体デバイスを提供することができる。また、上記半導体デバイスを比較的簡便に製造することのできる半導体デバイスの製造方法を提供することができる。
まず、本発明の実施形態を列記して説明する。
[実施形態1:半導体デバイス]
本実施形態の半導体デバイスは、ゲート電極と、ゲート電極の直下領域または直上領域に配置されるチャネル層と、チャネル層に接して配置されるソース電極およびドレイン電極と、ゲート電極とチャネル層との間に配置される第1絶縁層とを含み、チャネル層は第1酸化物半導体を含み、ソース電極およびドレイン電極の少なくとも一方は第2酸化物半導体を含み、第1酸化物半導体および第2酸化物半導体は、インジウム(In)、タングステン(W)および亜鉛(Zn)を含有する。半導体デバイスは、具体的にはTFT(薄膜トランジスタ)である。チャネル層の電気抵抗率は、好ましくはソース電極およびドレイン電極の電気抵抗率より高い。
In含有率(原子%)={In含有量/(In含有量+W含有量+Zn含有量)}×100
で定義される。
W含有率(原子%)={W含有量/(In含有量+W含有量+Zn含有量)}×100で定義される。
Zn含有率(原子%)={Zn含有量/(In含有量+W含有量+Zn含有量)}×100
で定義される。
W含有率=SIMSでの1cm3あたりのWの原子数/(3×1022)×100%
のとおりである。
測定方法:In-plane法(スリットコリメーション法)、
X線発生部:対陰極Cu、出力50kV 300mA、
検出部:シンチレーションカウンタ、
入射部:スリットコリメーション、
ソーラースリット:入射側 縦発散角0.48°
受光側 縦発散角0.41°、
スリット:入射側 S1=1mm*10mm
受光側 S2=0.2mm*10mm、
走査条件:走査軸 2θχ/φ、
走査モード:ステップ測定、走査範囲 10~80°、ステップ幅0.1°、
ステップ時間 8sec.。
測定方法:極微電子線回折法、
加速電圧:200kV、
ビーム径:測定対象である酸化物半導体を含む層の膜厚と同じか、または同等。
(X)上述の酸化物半導体層を成膜した後に実施する熱処理の工程時において、チャネル層7の主面を被覆し、ソース電極5およびドレイン電極6の主面を被覆しない高酸素絶縁層(部分被覆絶縁層)を備え、ソース電極5およびドレイン電極6の主面を被覆する絶縁層を備えない半導体デバイス。
(Y)上述の酸化物半導体層を成膜した後に実施する熱処理の工程時において、チャネル層7の主面を被覆し、ソース電極5およびドレイン電極6の主面を被覆しない高酸素絶縁層(部分被覆絶縁層)を備え、かつ、ソース電極5およびドレイン電極6の主面を被覆する低酸素絶縁層を備える半導体デバイス。
原子含有比=対象原子含有量/酸化物半導体層中に存在する全原子含有量
により、酸化物半導体層を構成する各原子の比率(原子含有比)を求める。すべての原子についての原子含有比の合計は1である。次に、酸化物半導体層の膜密度と、構成する全原子の各々の含有比から、下記式:
単位体積あたりの酸素原子数=酸素原子含有比(全体を1とした場合の値)×アボガドロ数×膜密度/{(酸化物半導体層を構成する対象原子の原子量×対象原子の含有比(全体を1とした場合の値)を全ての構成原子に関して合計した値}
または、下記式:
単位体積あたりの酸素原子数=酸素原子含有比(全体を1とした場合の値)×単位体積あたりの膜に含まれる原子数
より、単位体積あたりの酸素原子数を求めることができる。
単位体積あたりの酸素原子数=AO×アボガドロ数×6.8/{AIn×In原子量(114.82)+AW×W原子量(188.84)+AZn×Zn原子量(65.39)+AO×酸素原子量(16.0)}
より求めることができる。AIn、AW、AZn、およびAOは、TEM-EDX測定によって得ることができる。
本実施形態に係る半導体デバイスの製造方法は、上記実施形態1に係る半導体デバイスを製造するための方法であり、特に制限はないが、高い電界効果移動度を示し得る、さらには、高い電界効果移動度および光照射下での高い信頼性を示し得る上記実施形態1に係る半導体デバイスを効率良く比較的簡便に製造する観点から、たとえば、以下の工程を含む。
(2)酸化物半導体を含む層(酸化物半導体層)を形成する工程、
(3)酸化物半導体層の主面の一部を被覆する部分被覆絶縁層を形成する工程、
(4)部分被覆絶縁層を形成する工程の後に実施される、熱処理を行う工程。
図4は、図2に示されるボトムゲート型の半導体デバイスの製造方法の一例を示す概略断面図である。ボトムゲート型の半導体デバイスとして図2に示されるものを例に挙げて、ボトムゲート型の半導体デバイスの製造方法について以下説明する。図2に示されるボトムゲート型の半導体デバイスの製造方法は、たとえば、下記の工程をこの順で含む。
〔b〕ゲート電極2上に第1絶縁層(ゲート絶縁層)3を形成する工程、
〔c〕第1絶縁層3上に酸化物半導体層4を形成する工程[上記工程(2)に相当]、
〔d〕酸化物半導体層4上に第2絶縁層(絶縁保護層)8を形成する工程、
〔e〕第2絶縁層8をパターニングして、酸化物半導体層4の主面の一部を被覆する部分被覆絶縁層を形成する工程[上記工程(3)に相当]、
〔f〕熱処理を行う工程[上記工程(4)に相当]。
本工程は、基板1上にゲート電極2を形成する工程である。基板1は、特に制限されないが、透明性、価格安定性の観点、および表面平滑性を高くする観点から、石英ガラス基板、無アルカリガラス基板、アルカリガラス基板等であることが好ましい。ゲート電極2は、特に制限されないが、耐酸化性が高く、電気抵抗が低く、さらには後の工程で用いるレジスト層に照射する紫外線を遮光できる材質であることから、Mo電極、Ti電極、W電極、Al電極、Cu電極等であることが好ましい。ゲート電極2の形成方法は、特に制限されないが、基板1の主面上に大面積で均一に形成できる点から、真空蒸着法、スパッタリング法等であることが好ましい。ゲート電極2は基板1の主面に直接形成されてもよいし、他の層(有機物または無機物からなる絶縁層など)を介して基板1上に形成されてもよい。ゲート電極2は、好ましくは均一な膜厚で形成される。
本工程は、パターニングされたゲート電極2上に第1絶縁層(ゲート絶縁層)3を形成する工程である。通常は、パターニングされたゲート電極2の主面を含めた、基板1およびゲート電極2を有する積層体の主面全体に第1絶縁層3を形成する。第1絶縁層3の形成方法は、特に制限はないが、大面積で均一に形成できる点および絶縁性を確保する観点から、プラズマCVD(化学気相堆積)法等であることが好ましい。第1絶縁層3は、好ましくは均一な膜厚で形成される。
本工程は、第1絶縁層3上に酸化物半導体層4を形成する工程である。上述のように、酸化物半導体層4は、スパッタリング法により成膜する工程を含んで形成されることが好ましく、スパッタリング法により成膜を行いながら熱処理することによって形成されることもできる。酸化物半導体層4は、好ましくは均一な膜厚で形成される。
本工程は、パターニングされた酸化物半導体層4上に第2絶縁層(絶縁保護層)8を形成する工程である。通常は、パターニングされた酸化物半導体層4の主面を含めた、基板1、ゲート電極2、第1絶縁層3および酸化物半導体層4を有する積層体の主面全体に第2絶縁層8を形成する。第2絶縁層8の形成方法は、特に制限はないが、大面積で均一に形成できる点および絶縁性を確保する観点から、プラズマCVD(化学気相堆積)法等であることが好ましい。第2絶縁層8は、好ましくは均一な膜厚で形成される。
本工程は、第2絶縁層8をパターニングして、酸化物半導体層4の主面の一部を被覆する部分被覆絶縁層を形成する工程である。この工程ではまず、レジスト剤の塗布を行って、第2絶縁層8上にレジスト層10を形成する。これにより、図4(a)に示される構造の積層体を得る。次いで、基板1側から紫外線を照射する。この際、ゲート電極2によって紫外線が遮蔽されることにより、レジスト層10には、紫外線によって感光されない領域Aと、紫外線が遮蔽されずに感光される領域Bとが形成される。次いで、現像を行うことで、紫外線によって感光された領域Bのレジスト層10を溶解させる。これにより、図4(b)に示される構造の積層体を得る。
本工程は、熱処理を行う工程である。この熱処理により、酸化物半導体層4の一部であって第2絶縁層8(部分被覆絶縁層)で被覆されている領域はチャネル層7となり、一方で、酸化物半導体層4の他の部分であって第2絶縁層8(部分被覆絶縁層)で被覆されることなく主面が露出している領域は、電気抵抗率が下がることでソース電極5またはドレイン電極6となる。ソース電極5およびドレイン電極6は画素電極として用いることも可能である。
図2に示されるように、積層体の表面に第3絶縁層9を形成する工程〔g〕を設けてもよい。通常は、積層体の主面全体に第3絶縁層9を形成する。第3絶縁層9の形成方法は、特に制限はないが、大面積で均一に形成できる点および絶縁性を確保する観点から、プラズマCVD(化学気相堆積)法等であることが好ましい。
図5は、図3に示されるトップゲート型の半導体デバイスの製造方法の一例を示す概略断面図である。トップゲート型の半導体デバイスとして図3に示されるものを例に挙げて、トップゲート型の半導体デバイスの製造方法について以下説明する。図3に示されるトップゲート型の半導体デバイスの製造方法は、たとえば、下記の工程をこの順で含む。
〔B〕酸化物半導体層4上に第1絶縁層3を形成する工程、
〔C〕第1絶縁層3上にゲート電極2を形成する工程[上記工程(1)に相当]、
〔D〕ゲート電極2をパターニングし、これを用いて酸化物半導体層4の主面の一部を被覆する部分被覆絶縁層を形成する工程[上記工程(3)に相当]、
〔E〕熱処理を行う工程[上記工程(4)に相当]。
本工程は、基板1上に酸化物半導体層4を形成する工程である。基板1、および酸化物半導体層4の形成方法については、ボトムゲート型半導体デバイスの製造方法についての記述が引用される。酸化物半導体層4は基板1の主面に直接形成されてもよいし、他の層(有機物または無機物からなる絶縁層など)を介して基板1上に形成されてもよい。酸化物半導体層4は、好ましくは均一な膜厚で形成される。続いて、酸化物半導体層4のパターニングを行うが、これについても、ボトムゲート型半導体デバイスの製造方法についての記述が引用される。
本工程は、パターニングされた酸化物半導体層4上に第1絶縁層(ゲート絶縁層)3を形成する工程である。通常は、パターニングされた酸化物半導体層4の主面を含めた、基板1および酸化物半導体層4を有する積層体の主面全体に第1絶縁層3を形成する。第1絶縁層3の形成方法および材質については、ボトムゲート型半導体デバイスの製造方法についての記述が引用される。第1絶縁層3は、好ましくは均一な膜厚で形成される。
本工程は、第1絶縁層3上にゲート電極2を形成する工程である。通常は、積層体の主面全体にゲート電極2を形成する。これにより、図5(a)に示される構造の積層体を得る。ゲート電極2の材質および形成方法については、ボトムゲート型半導体デバイスの製造方法についての記述が引用される。
本工程は、ゲート電極2をパターニングし、これを用いて酸化物半導体層4の主面の一部を被覆する部分被覆絶縁層を形成する工程である。この工程ではまず、レジスト剤の塗布を行って、ゲート電極2上にレジスト層10を形成する。続いて、フォトマスクを用いた紫外線照射、現像を行うことで、設計されたゲート電極2の配線パターンに応じたレジストパターンを形成する。これにより、図5(b)に示される構造の積層体を得る。
本工程は、熱処理を行う工程である。この熱処理により、酸化物半導体層4の一部であって第1絶縁層3(部分被覆絶縁層)で被覆されている領域はチャネル層7となり、一方で、酸化物半導体層4の他の部分であって第1絶縁層3(部分被覆絶縁層)で被覆されることなく主面が露出している領域は、電気抵抗率が下がることでソース電極5またはドレイン電極6となる。ソース電極5およびドレイン電極6は画素電極として用いることも可能である。熱処理の方法については、ボトムゲート型半導体デバイスの製造方法についての記述が引用される。
図3に示されるように、積層体の表面に第3絶縁層9を形成する工程〔F〕を設けてもよい。通常は、積層体の主面全体に第3絶縁層9を形成する。第3絶縁層9の形成方法ついては、ボトムゲート型半導体デバイスの製造方法についての記述が引用される。
次の手順で、図2に示されるボトムゲート型TFTと類似の構成を有するTFTを作製した。まず、基板1として縦50mm×横50mm×厚み0.6mmの無アルカリガラス基板を準備し、その基板1上にスパッタリング法によりゲート電極2として厚み100nmのMo電極を形成した。
次の手順で、図3に示されるトップゲート型TFTと類似の構成を有するTFTを作製した。まず、基板1として縦50mm×横50mm×厚み0.6mmの無アルカリガラス基板を準備し、その基板1上にDC(直流)マグネトロンスパッタリング法により酸化物半導体層4を形成した。ターゲットの直径3インチ(76.2mm)の平面がスパッタ面であった。ターゲットには、In、WおよびZnを含む酸化物焼結体であって、In2O3結晶を主成分とし、ZnO結晶、ZnWO4結晶、In2O3(ZnO)m(mは自然数)結晶、In6WO12結晶の少なくともいずれか1つ以上が混在している酸化物焼結体を使用した。酸化物半導体層4がジルコニウム(Zr)を含有する場合、上記酸化物焼結体の調製時にZrO2を添加して酸化物焼結体を調製した。形成した酸化物半導体層4の膜厚を表2に示す(測定方法は上述のとおり)。
酸化物半導体層4を形成するためのターゲットとして、原子数比がIn:Ga:Zn=1:1:1である酸化物焼結体を使用したこと以外は実施例19から36と同様にしてトップゲート型TFTを作製した。大気圧窒素雰囲気中、350℃10分の条件での熱処理を行ってもソース電極5およびドレイン電極6の電気抵抗率が低くならず、TFTとして駆動できなかった。
表3に示される製造条件を採用したこと以外は実施例19から36と同様にしてトップゲート型TFTを作製した。酸化物半導体層4を形成するためのターゲットには、In2O3結晶を主成分とし、ZnO結晶およびZrO2結晶が混在している酸化物焼結体〔In:W:Zn=1:0.0:0.30(原子数比)〕を使用した。
表3に示される製造条件を採用したこと以外は実施例19から36と同様にしてトップゲート型TFTを作製した。酸化物半導体層4を形成するためのターゲットには、In2O3結晶を主成分とし、WO3結晶およびZrO2結晶が混在している酸化物焼結体〔In:W:Zn=1:0.05:0.00(原子数比)〕を使用した。上と同様の測定を行い、酸化物半導体層4を構成する酸化物半導体が6価のタングステンを含有することを確認した。
表3に示される製造条件を採用したこと以外は実施例19から36と同様にしてトップゲート型TFTを作製した。酸化物半導体層4を形成するためのターゲットには、In2O3結晶を主成分とし、ZrO2結晶が混在している酸化物焼結体(Zr含有量6×1018atms/cm3)を使用した。
表3に示される製造条件を採用したこと以外は実施例19から36と同様にしてトップゲート型TFTを作製した。酸化物半導体層4を形成するためのターゲットには、In2O3結晶を主成分とし、ZnWO4結晶、ZnO結晶およびZrO2結晶が混在している酸化物焼結体〔In:W:Zn=1:0.000005:0.20(原子数比)〕を使用した。上と同様の測定を行い、酸化物半導体層4を構成する酸化物半導体が6価のタングステンを含有することを確認した。
表3に示される製造条件を採用したこと以外は実施例19から36と同様にしてトップゲート型TFTを作製した。酸化物半導体層4を形成するためのターゲットには、In2O3結晶を主成分とし、ZnWO4結晶、ZnO結晶およびZrO2結晶が混在している酸化物焼結体〔In:W:Zn=1:0.000005:0.30(原子数比)〕を使用した。上と同様の測定を行い、酸化物半導体層4を構成する酸化物半導体が6価のタングステンを含有することを確認した。
表3に示される製造条件を採用したこと以外は実施例19から36と同様にしてトップゲート型TFTを作製した。酸化物半導体層4を形成するためのターゲットには、In2O3結晶を主成分とし、ZnWO4結晶、ZnO結晶およびZrO2結晶が混在している酸化物焼結体〔In:W:Zn=1:0.1:0.20(原子数比)〕を使用した。上と同様の測定を行い、酸化物半導体層4を構成する酸化物半導体が6価のタングステンを含有することを確認した。
表3に示される製造条件を採用したこと以外は実施例19から36と同様にしてトップゲート型TFTを作製した。酸化物半導体層4を形成するためのターゲットには、In2O3結晶を主成分とし、ZnWO4結晶、ZnO結晶およびZrO2結晶が混在している酸化物焼結体〔In:W:Zn=1:0.008:0.48(原子数比)〕を使用した。上と同様の測定を行い、酸化物半導体層4を構成する酸化物半導体が6価のタングステンを含有することを確認した。
表2に示される製造条件を採用したこと以外は実施例19から36と同様にしてトップゲート型TFTを作製した。酸化物半導体層4を形成するためのターゲットには、In2O3結晶を主成分とし、ZnWO4結晶、ZnO結晶およびZrO2結晶が混在している酸化物焼結体〔In:W:Zn=1:0.008:0.012(原子数比)〕を使用した。上と同様の測定を行い、酸化物半導体層4を構成する酸化物半導体が6価のタングステンを含有することを確認した。
(1)チャネル層、ソース電極およびドレイン電極を構成する酸化物半導体層の結晶性、W含有率、Zn含有率、Zn/W比、およびZr含有量
作製したTFTが備える酸化物半導体層4(すなわち、チャネル層7、ソース電極5およびドレイン電極6)の結晶性を上述の測定方法および定義に従って評価した。結果を表1~表3に示す。表1~表3において「N」は、酸化物半導体層4(すなわち、チャネル層7、ソース電極5およびドレイン電極6)がナノ結晶酸化物で構成されていることを、「A」は、アモルファス酸化物で構成されていることを意味する。
W含有率=SIMSでの1cm3あたりのWの原子数/(3×1022)×100%
にてW含有率を算出した。
チャネル層7の電気抵抗率は以下の方法により求めた。ソース電極5とドレイン電極6に測定針を接触させた。次に、ソース-ドレイン電極間に電圧を1Vから20Vに変化させて印加しながら、ソース-ドレイン間電流Idsを測定した。Ids-Vdsのグラフを描いたときの傾きが抵抗Rである。この抵抗Rと、チャネル長さCL(30μm)、チャネル幅CW(40μm)、膜厚tから、チャネル層7の電気抵抗率は、R×CW×t/CLとして求めることができる。すべての実施例および比較例においてチャネル層7の電気抵抗率は、10-1Ωcm以上であった。
作製したTFTの特性を次のようにして評価した。まず、ゲート電極2、ソース電極5およびドレイン電極6に測定針を接触させた。ソース電極5とドレイン電極6との間に0.2Vのソース-ドレイン間電圧Vdsを印加し、ソース電極5とゲート電極2との間に印加するソース-ゲート間電圧Vgsを-30Vから20Vに変化させて、そのときのソース-ドレイン間電流Idsを測定した。そして、ソース-ゲート間電圧Vgsとソース-ドレイン間電流Idsの平方根〔(Ids)1/2〕との関係をグラフ化した(以下、このグラフを「Vgs-(Ids)1/2曲線」ともいう。)。Vgs-(Ids)1/2曲線に接線を引き、その接線の傾きが最大となる点を接点とする接線がx軸(Vgs)と交わる点(x切片)を閾値電圧Vthとした。閾値電圧Vthは、窒素雰囲気中250℃の上述の熱処理を実施したときと、窒素雰囲気中350℃の上述の熱処理を実施したときのTFTについて測定した。結果を表1~表3に示す。
gm=dIds/dVgs 〔a〕
に従って、ソース-ドレイン間電流Idsをソース-ゲート間電圧Vgsについて微分することによりgmを導出した。そしてVgs=15.0Vにおけるgmの値を用いて、下記式〔b〕:
μfe=gm・CL/(CW・Ci・Vds) 〔b〕
に基づいて、電界効果移動度μfeを算出した。上記式〔b〕におけるチャネル長さCLは30μmであり、チャネル幅CWは40μmである。また、第1絶縁層(ゲート絶縁層)3のキャパシタンスCiは3.4×10-8F/cm2とし、ソース-ドレイン間電圧Vdsは0.2Vとした。電界効果移動度μfeは、窒素雰囲気中250℃の上述の熱処理を実施したときと、窒素雰囲気中350℃の上述の熱処理を実施したときのTFTについて測定した。結果を表1~表3に示す。
Claims (15)
- ゲート電極と、
前記ゲート電極の直下領域または直上領域に配置されるチャネル層と、
前記チャネル層に接して配置されるソース電極およびドレイン電極と、
前記ゲート電極と前記チャネル層との間に配置される第1絶縁層と、
を含み、
前記チャネル層は第1酸化物半導体を含み、前記ソース電極および前記ドレイン電極の少なくとも一方は第2酸化物半導体を含み、
前記第1酸化物半導体および前記第2酸化物半導体は、インジウム、タングステンおよび亜鉛を含有し、
前記第1酸化物半導体および前記第2酸化物半導体中のインジウム、タングステンおよび亜鉛の合計に対するタングステンの含有率が0.001原子%より大きく8.0原子%以下であり、
前記第1酸化物半導体および前記第2酸化物半導体中のインジウム、タングステンおよび亜鉛の合計に対する亜鉛の含有率が1.2原子%以上40原子%以下であり、
前記第1酸化物半導体および前記第2酸化物半導体中のタングステンに対する亜鉛の原子比が1.0より大きく20000より小さい、半導体デバイス。 - 前記第1酸化物半導体のインジウム、タングステンおよび亜鉛の含有率はそれぞれ、前記第2酸化物半導体のインジウム、タングステンおよび亜鉛の含有率と同じである、請求項1に記載の半導体デバイス。
- 前記チャネル層の電気抵抗率が10-1Ωcm以上であり、
前記ソース電極および前記ドレイン電極の電気抵抗率が10-2Ωcm以下である、請求項1または請求項2に記載の半導体デバイス。 - 前記第1酸化物半導体および前記第2酸化物半導体は、ナノ結晶酸化物またはアモルファス酸化物で構成される、請求項1から請求項3のいずれか1項に記載の半導体デバイス。
- 前記第1絶縁層は、前記チャネル層の主面を被覆し、前記ソース電極および前記ドレイン電極の主面を被覆しない層である、請求項1から請求項4のいずれか1項に記載の半導体デバイス。
- 前記ソース電極および前記ドレイン電極の主面を被覆する絶縁層であって、前記第1絶縁層よりも酸素原子含有率の小さい低酸素絶縁層をさらに含む、請求項5に記載の半導体デバイス。
- 前記チャネル層の主面を被覆し、前記ソース電極および前記ドレイン電極の主面を被覆しない第2絶縁層をさらに含む、請求項1から請求項4のいずれか1項に記載の半導体デバイス。
- 前記ソース電極および前記ドレイン電極の主面を被覆する絶縁層であって、前記第2絶縁層よりも酸素原子含有率の小さい低酸素絶縁層をさらに含む、請求項7に記載の半導体デバイス。
- 前記第1酸化物半導体は、6価のタングステンを含有する、請求項1から請求項8のいずれか1項に記載の半導体デバイス。
- 前記チャネル層は、ジルコニウムをさらに含有し、
前記ジルコニウムの含有量が1×1017atms/cm3以上1×1020atms/c
m3以下である、請求項1から請求項9のいずれか1項に記載の半導体デバイス。 - 請求項1から請求項10のいずれか1項に記載の半導体デバイスの製造方法であって、
前記ゲート電極を形成する工程と、
酸化物半導体を含む層を形成する工程と、
前記酸化物半導体を含む層の主面の一部を被覆する部分被覆絶縁層を形成する工程と、
前記部分被覆絶縁層を形成する工程の後に実施される、熱処理を行う工程と、
を含む、製造方法。 - 前記酸化物半導体を含む層を形成する工程の後であって、前記熱処理を行う工程の前に、前記酸化物半導体を含む層の主面における前記一部に隣接する領域を被覆する低酸素絶縁層を形成する工程をさらに含み、
前記低酸素絶縁層は、前記部分被覆絶縁層よりも酸素原子含有率が小さい、請求項11に記載の製造方法。 - 前記部分被覆絶縁層は、前記第1絶縁層であるか、または前記第1絶縁層とは異なる第2絶縁層である、請求項11または請求項12に記載の製造方法。
- 前記部分被覆絶縁層を形成する工程において、前記部分被覆絶縁層は、前記ゲート電極を利用した自己整合によりパターニングされる、請求項11から請求項13のいずれか1項に記載の製造方法。
- 前記熱処理を行う工程は、100℃以上500℃以下の温度で熱処理する工程を含む、請求項11から請求項14のいずれか1項に記載の製造方法。
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