JP2008277665A - Electronic element, and method of manufacturing electronic element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic element using a semiconductor film comprising a wurtzite type crystal having excellent carrier mobility and having excellent electric property, and to provide a method of manufacturing the electronic element. <P>SOLUTION: An electronic element 10 comprises a projection 13, a semiconductor film 14 comprising ZnO, which is a wurtzite type crystal, a gate insulating film 18, a gate electrode 31, and a protective film 20. The force of pulling to the outside of the film is applied to the ZnO film 14 by the projection 13. This allows the c axis length of the ZnO crystal of the ZnO film 14 to extend and the an axis length to be shortened, and therefore improves the carrier mobility of the ZnO film 14. Further, the ZnO film 14 has a compressive residual stress. The gate insulating film 18, the gate electrode 31, and the protective film 20 have a compressive stress, respectively. Therefore, the force of pulling to the outside of the film is further applied to the ZnO film 14, and the carrier mobility of the ZnO film 14 can be improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic device using zinc oxide and a method for manufacturing the electronic device.

  Conventionally, zinc oxide (ZnO) crystals including polycrystals are known to have piezoelectric properties because the crystal structure does not have central symmetry. Therefore, using this piezoelectric effect, ZnO crystals are used in various actuators. On the other hand, ZnO has attracted attention as a wide gap semiconductor in recent years, and development for using ZnO as a semiconductor material such as a thin film transistor (TFT), an LED (Light Emitting Diode), and a transparent conductive film is being promoted. . Patent Document 1 discloses a method of forming a p-type semiconductor crystal using ZnO.

TFTs and LEDs using ZnO are at the stage where research has begun, and their use as transparent conductive films is also the same. Therefore, there are many unclear parts regarding the application of ZnO to electronic devices. In particular, the problems when the ZnO film that exhibits the piezoelectric effect described above is applied to TFTs, transparent conductive films, and LEDs are almost discussed. Not. For this reason, it can be said that it is the stage which is searching the directionality of what kind of factor should be controlled to improve performance.
JP 2002-289918 A

  By the way, in electronic devices such as TFT and LED, characteristics such as carrier movement in the film influence the performance. Therefore, when ZnO is used in an electronic device such as a TFT, it is necessary to improve the carrier mobility in the ZnO film.

  Such a request is a problem common to films having a wurtzite crystal structure.

  The present invention has been made in view of the above-described circumstances, and provides an electronic device having good electrical characteristics and a method of manufacturing the electronic device using a semiconductor film made of a wurtzite crystal having good carrier mobility. The purpose is to do.

In order to achieve the above object, an electronic device according to the first aspect of the present invention includes:
A semiconductor film made of wurtzite crystal,
And an external force application film that is formed on one surface of the semiconductor film and applies an external force in a direction to pull the semiconductor film out of the semiconductor film.

  The semiconductor film may have internal stress.

  In the semiconductor film, the c-axis of the wurtzite crystal may be oriented in a direction along the external force.

  The semiconductor film may have a larger c-axis length and a shorter a-axis length than when the external force application film is not formed.

  The semiconductor film may have a unit cell volume smaller than that in the case where the external force application film is not formed.

  The semiconductor film may have a higher film density than the case where the external force application film is not formed.

  In the semiconductor film, c / a may be increased as compared with the case where the external force application film is not formed.

  The external force application film is formed in a convex shape, and an external force in a direction of pulling the semiconductor film out of the semiconductor film may be applied by placing the semiconductor film along the external force application film.

An insulating layer formed on the semiconductor film;
The insulating layer may apply an external force in a direction that pulls the semiconductor film out of the semiconductor film.

An electrode formed on the insulating layer;
The electrode may have a stress that applies an external force in a direction to pull the semiconductor film out of the semiconductor film.

  The external force application film may be formed of an insulating material and may be formed in a planar shape.

Further comprising an electrode formed on the external force application film,
The electrode may have a stress that applies an external force in a direction to pull the semiconductor film out of the semiconductor film.

  The external force application film has a concave portion formed in a concave shape, and applying an external force in a direction to pull the semiconductor film out of the semiconductor film by causing the semiconductor film to follow the external force application film. Good.

An insulating layer formed between the external force application film and the semiconductor film;
The insulating layer may have a stress so as to apply an external force in a direction to pull the semiconductor film out of the semiconductor film.

Further provided with a protective film made of an insulating material,
The protective film may have a stress so as to apply an external force in a direction to pull the semiconductor film out of the semiconductor film.

  The semiconductor film may be a ZnO film.

In order to achieve the above object, a method of manufacturing an electronic device according to the second aspect of the present invention includes:
A semiconductor film forming step of forming a semiconductor film made of wurtzite crystal;
An external force application film forming step of forming an external force application film that is formed on one side of the semiconductor film and applies an external force in a direction of pulling the semiconductor film out of the semiconductor film.

  In the semiconductor film forming step, the semiconductor film may have an internal stress.

  In the semiconductor film, the c-axis of the wurtzite crystal may be oriented in a direction along the external force.

  The external force application film may be formed in a convex shape so as to apply an external force in a direction of pulling the semiconductor film out of the semiconductor film by placing the semiconductor film along the external force application film.

The external force application film is made of an insulating material and is formed in a planar shape.
In the external force application film forming step, the external force application film may be formed such that a stress that applies an external force in a direction of pulling the semiconductor film out of the semiconductor film remains.

  The external force application film may be formed in a concave shape so as to apply an external force in a direction of pulling the semiconductor film out of the semiconductor film by bringing the semiconductor film along the external force application film.

  The semiconductor film may be a ZnO film.

  ADVANTAGE OF THE INVENTION According to this invention, by applying the external force of the direction pulled | pulled out of a semiconductor film, it can provide the electronic device provided with the favorable carrier mobility and the favorable electrical property, and the manufacturing method of an electronic device. .

  Hereinafter, an electronic device and a method for manufacturing the electronic device according to Embodiment 1 of the present invention will be described with reference to the drawings.

(Embodiment 1)
An electronic device 10 according to Embodiment 1 of the present invention is shown in FIG. FIG. 1 is a cross-sectional view showing the electronic element 10. In the present embodiment, a TFT will be described as an example of an electronic element. The electronic element 10 is used for supplying a signal to a pixel electrode of a liquid crystal display device, for example.

  As shown in FIG. 1, the electronic element 10 according to the present embodiment includes a substrate 11, an undercoat layer 12, a protrusion 13, a semiconductor film (ZnO film) 14, a channel region 15, a source region 16, and a drain. The region 17, the gate insulating film 18, the interlayer insulating film 19, the protective film 20, the gate electrode 31, the source electrode 32, and the drain electrode 33 are provided. The electronic element 10 is formed with a transparent electrode (not shown) for supplying a predetermined signal to a liquid crystal display device (not shown) on which the electronic element 10 is installed.

  The substrate 11 is made of, for example, an alkali-free glass substrate, a resin substrate, or the like. An undercoat layer 12 is formed on the substrate 11. As the substrate 11, a sapphire substrate, a silicon single crystal substrate, other insulating, semi-insulating or semiconductor substrates, a resin film such as a plastic, and a composite thereof can also be used.

  The undercoat layer 12 is formed on the main surface of the substrate 11. The undercoat layer 12 includes a silicon nitride film 12a formed with a thickness of 100 nm, for example, and a silicon oxide film 12b formed with a thickness of 100 nm on the silicon nitride film 12a, for example. By forming the undercoat layer 12, it is possible to prevent impurities contained in the substrate from diffusing into the semiconductor film or the like in a process such as when high-temperature heat treatment such as laser heat treatment is applied, and stable characteristics And good reliability can be obtained.

  The protrusion 13 is made of an insulating material such as a silicon oxide film, and is formed on the upper surface of the undercoat layer 12. A semiconductor film (ZnO film) 14 is formed on the upper surface of the protrusion 13. The projecting portion 13 has a planar shape, for example, a substantially square shape, and a thickness of, for example, 100 nm. As will be described in detail later, in the present embodiment, the protrusion 13 is formed under the ZnO film 14, and the ZnO film 14 is deformed into a convex shape so as to be substantially parallel to the normal line of the ZnO film. By applying an external force in the pulling direction to the ZnO film, the carrier mobility of the ZnO film 14 can be improved. Note that the shape and thickness of the protrusion 13 are not limited to those described above as long as a predetermined external force can be applied to the ZnO film 14.

  The semiconductor film (ZnO film) 14 is a film made of ZnO crystals. The semiconductor film 14 is formed so as to cover the undercoat layer 12 and the protrusions 13, and a channel region 15, a source region 16, and a drain region 17 are formed in the surface region of the semiconductor film 14. The ZnO film 14 is formed on the substrate by, for example, sputtering. At this time, in this embodiment, the residual stress in the ZnO film 14 is formed to be a compressive stress. The ZnO crystal has a wurtzite crystal structure as shown in FIG. 2, and the unit cell is defined by the c axis and the a axis. At this time, the ZnO film tends to have the c-axis oriented in the direction perpendicular to the substrate surface and the a-axis oriented in the horizontal direction. In this embodiment, the carrier mobility in the semiconductor film 14 can be increased by forming the ZnO film 14 so as to generate a compressive residual stress with respect to the ZnO film 14 as described later. Further, the protrusion 13 is formed on the ZnO film whose c-axis is oriented in the direction perpendicular to the substrate surface so that the ZnO film is deformed in a convex shape in the direction perpendicular to the substrate surface and compressive stress is generated in the film. As a result, the carrier mobility in the semiconductor film 14 can be increased as will be described in detail later.

The channel region 15 is formed on the upper surface of the semiconductor film 14. The channel region 15 is a region where the conductivity type is inverted when a predetermined voltage is applied to the gate electrode, and a channel is formed, and impurities such as phosphorus and boron are diffused. In order to realize a predetermined threshold voltage, doping of the order of 10 ¹³ atoms / cm ² to 10 ¹⁴ atoms / cm ² is performed by an ion implantation method or the like.

  The source region 16 is formed in the surface region of the semiconductor film 14. In the source region 16, n-type or p-type impurities such as phosphorus and boron are diffused. A source electrode 32 is formed on the upper surface of the source region 16.

  The drain region 17 is formed in the surface region of the semiconductor film 14. In the drain region 17, n-type or p-type impurities such as phosphorus and boron are diffused. A drain electrode 33 is formed on the upper surface of the drain region 17.

  The gate insulating film 18 is made of an insulating material such as a silicon oxide film or a silicon nitride film, and is formed on the semiconductor film 14. A gate electrode 31 (gate electrode wiring) is formed on the gate insulating film 18. The gate insulating film 18 is formed with a thickness of 100 nm, for example. The gate insulating film 18 is formed by, for example, a sputtering method, a CVD method, or the like, and is formed so that the residual stress becomes a compressive stress. By forming the gate insulating film 18 in this way, it is possible to apply an external force in a direction of pulling the ZnO film 14 so as to be substantially parallel to the normal line of the ZnO film 14. The gate insulating film 18 has contact holes 18 s and 18 d formed in a shape corresponding to the contact hole of the interlayer insulating film 19, and a source electrode 32 and a drain electrode 33 are formed in the contact holes 18 s and 18 d. It is formed.

  The interlayer insulating film 19 is made of an insulating material such as a silicon oxide film or a silicon nitride film, and is formed so as to cover the gate insulating film 18 and the gate electrode 31. In the interlayer insulating film 19, a contact hole 19s for forming the source electrode 32, a contact hole 19d for forming the drain electrode 33, and a contact hole 19g for forming the gate lead electrode 34 are formed. The The interlayer insulating film 19 is formed with a thickness of, for example, 500 nm.

  The protective film 20 is made of an insulating material and is formed so as to cover the interlayer insulating film 19, the source electrode 32, the drain electrode 33, and the gate extraction electrode 34. The thickness of the protective film 20 is formed to 500 nm, for example. In the present embodiment, it is possible to further increase the stress generated in the ZnO film 14 by forming the protective film 20 to have a compressive stress.

The gate electrode 31 is made of a conductive material such as Al, Ta, W, Mo, etc., and is formed on the gate insulating film 18. In the present embodiment, the gate electrode is formed by sputtering, for example. At this time, a metal film having a strong compressive stress can be formed by controlling the argon gas pressure to 10 ⁻¹ level. This is preferable because an external force in a direction of pulling out of the film can be applied to the ZnO film so as to be substantially parallel to the normal line of the ZnO film 14. The gate electrode 31 is formed with a thickness of 150 nm, for example. A predetermined voltage is applied to the gate electrode 31 from a gate extraction electrode 34 formed in a contact hole 19 g provided in the interlayer insulating film 19.

  The source electrode 32 is made of a conductive material, such as aluminum, and is formed so as to fill the contact hole 19 s provided in the interlayer insulating film 19. The source electrode 32 is formed with a thickness of, for example, 0.9 μm. A titanium nitride film is formed as a barrier layer on the side wall of the contact hole 19s.

  The drain electrode 33 is made of a conductive material, such as aluminum, and is formed so as to fill the contact hole 19 d provided in the interlayer insulating film 19. The drain electrode 33 is formed with a thickness of, for example, 0.9 μm. A titanium nitride film is formed as a barrier layer on the side wall of the contact hole 19d.

  The gate extraction electrode 34 is formed of a conductive material, such as aluminum, and is formed so as to fill the contact hole 19 g provided in the interlayer insulating film 19.

  In the present embodiment, on the semiconductor film (ZnO film) 14, an insulating film that generates an external force in a direction of pulling out of the film is formed so as to be substantially parallel to the normal line to the semiconductor film 14. Thereby, the carrier mobility in the semiconductor film 14 can be increased as described below.

  First, the ZnO crystal has a wurtzite crystal structure as shown in FIG. 2, as is conventionally known. In the wurtzite crystal structure, the crystal structure is defined by defining the lattice constants c and a of the crystal unit cell. The ideal structure of the wurtzite crystal structure is c / a = 1.633. Here, the wurtzite crystal structure has a hexagonal crystal structure, and the unit cell, that is, the bottom surface is an equilateral triangle with one side a, and six columnar structures extending in the c-axis direction are gathered to form one unit cell. Forms a unit cell. Further, if the c-axis length and the a-axis length are obtained, the capacity (volume) of the unit cell can be obtained. Further, the film density of a ZnO film having a wurtzite crystal structure is obtained by obtaining the thickness and area of the film, obtaining the volume thereof, and dividing the value by the mass of the film in the same manner as the normal density. Therefore, the film density includes the inside of crystal grains and the grain boundary portion. It also includes crystal defects. Since the volume of the grain boundary is negligible compared to the inside of the grain, the unit cell volume and the film density are almost completely correlated although they do not correspond completely.

  In general, the ZnO film is formed by a method such as sputtering, pulse laser vapor deposition, molecular vapor deposition, or CVD. A ZnO film formed by such a method has a c-axis orientation in a direction perpendicular to the substrate surface, and a film having an a-axis orientation in the in-plane direction tends to grow.

  On the other hand, in the electronic device using the ZnO film described above, desired characteristics are obtained by moving carriers (flowing current) in an in-plane direction (a-axis direction) substantially parallel to the substrate. As described above, the ZnO film tends to have the c-axis oriented in the direction perpendicular to the substrate surface and the a-axis oriented in the horizontal direction. Therefore, in an electronic device using a ZnO film, carriers that are information carriers such as electrons and holes move mainly in a direction perpendicular to the c-axis, in other words, in the Zn plane or the O plane.

  Therefore, in order to facilitate the movement of carriers, the distance between each element in the Zn plane or O plane is reduced to increase the overlap of electron clouds, and the distance from the oppositely polarized element is increased by increasing the distance between Zn-O. The influence on the inner mobile carrier may be reduced. That is, the lattice constant c may be increased and the lattice constant a may be decreased. As described above, the ZnO film has a tendency that the c-axis is easily oriented in the vertical direction (normal direction) to the substrate surface and the a-axis is oriented in the horizontal direction.

Therefore, in the present embodiment, the protruding portion 13 is formed in a convex shape so as to apply an external force in the direction of pulling out of the ZnO film 14, preferably in a direction of pulling in the normal direction of the substrate surface. In other words, the protrusion 13 applies a force in the normal direction of the substrate surface, that is, in a direction substantially parallel to the c-axis. In general, it is considered that when an external force is applied so as to apply a tensile stress to the film, the film expands in volume and the density decreases. However, as in this embodiment, the protrusion 13 is formed so as to apply a force in a direction substantially parallel to the c-axis, and the ZnO film 14 is deformed so as to protrude upward, whereby the tensile stress is applied to the ZnO film 14. As a result, the c-axis length is increased, the a-axis length is decreased, and c / a is increased. At this time, the unit cell volume of the ZnO film is reduced and the film density is reduced. As will be described in detail later, the value of c / a approaches 1.633, which is the ideal value of the wurtzite crystal structure, as compared with the case where the ZnO film is not deformed. As described above, when the c-axis length is extended and the a-axis length is reduced, the overlap of atomic clouds between adjacent atoms of the Zn plane and the O plane is increased, and carriers are more easily moved on the Zn plane and the O plane. That is, the resistance value of the ZnO film can be reduced, and in other words, the carrier mobility can be increased. This is because the resistivity ρ, the carrier density n, the carrier mobility μ, and the electron charge e between the resistivity and the carrier mobility,
(Formula 1)
1 / ρ = n ・ e ・ μ
It is clear from the point that

  Thus, according to this embodiment, by forming the convex protrusion 13 on the undercoat layer 12, the resistance value of the ZnO film 14 can be lowered, in other words, the carrier mobility is increased. It becomes possible. In this embodiment, the carrier mobility can be further increased by forming the ZnO film so that the residual compressive stress is generated in the ZnO film. Furthermore, in this embodiment, the carrier is further formed by forming an external force in a direction in which the gate insulating film, the gate electrode, and the protective film are pulled out of the ZnO film, preferably an external force substantially parallel to the normal line. Mobility can be increased.

  Next, a method for manufacturing an electronic element according to Embodiment 1 of the present invention will be described with reference to FIGS.

  First, for example, as shown in FIG. 3A, a substrate 11 made of an alkali-free glass substrate is prepared. On one main surface of the substrate 11, a silicon nitride film 12a is formed with a thickness of, for example, 100 nm by, for example, a CVD (Chemical Vapor Deposition) method. Further, a silicon oxide film 12b is formed on the silicon nitride film 12a with a thickness of, for example, 100 nm by, eg, CVD. Thereby, the undercoat layer 12 is formed as shown in FIG.

  Next, a silicon oxide film having a thickness of, for example, 150 nm is formed on the upper surface of the undercoat layer 12 by, eg, CVD. Subsequently, the protrusion 13 is formed by photolithography, wet etching or the like as shown in FIG.

Subsequently, a ZnO film 14 is formed to a thickness of, for example, 100 nm on the undercoat layer 12 and the protruding portion 13 by, for example, sputtering as shown in FIG. 4D. At this time, compressive residual stress is generated in the ZnO film 14 by setting the gas pressure of the argon gas used in the sputtering method to a level of 10 ⁻¹ Pa. The gas pressure is not limited to this as long as a desired compressive residual stress can be generated.

  Next, an impurity is introduced into a predetermined region of the ZnO film 14 by using an ion implantation method or the like to form a channel region 15, a source region 16, and a drain region 17.

  Next, a gate insulating film 18 made of an insulating material such as a silicon oxide film, a silicon nitride film, or a composite thereof is formed on the ZnO film 14 by CVD or the like as shown in FIG. . The gate insulating film 18 is formed with a thickness of 100 nm, for example.

Subsequently, a metal film made of a conductive material such as Al, Ta, W, or Mo is formed on the gate insulating film 18 by sputtering or the like. At this time, it is possible to generate a compressive stress in the metal film by setting the gas pressure of argon gas used in the sputtering method to a level of 10 ⁻¹ Pa. Subsequently, the metal film is processed into a predetermined pattern by photolithography, dry etching, wet etching, or the like to form the gate electrode 31 as shown in FIG.

  Next, as shown in FIG. 5G, an insulating material such as a silicon oxide film, a silicon nitride film, or a composite thereof is formed on the gate insulating film 18 and the gate electrode 31 by a CVD method or the like. An insulating film 19 is formed. The interlayer insulating film 19 is formed with a thickness of 150 nm, for example.

  Next, contact holes 19s, 19d, and 19g are formed at predetermined positions of the interlayer insulating film 19 by photolithography, etching, or the like. At the same time, contact holes 18 s and 18 d are formed at predetermined locations on the gate insulating film 18. Subsequently, a metal film made of a conductive material such as aluminum is formed by sputtering or the like so as to fill the contact holes 19s, 19d, 19g, 18s, and 18d. Next, the metal film is removed so that a predetermined pattern remains, and a source electrode 32, a drain electrode 33, and a gate lead electrode 34 are formed.

Subsequently, a protective film 20 made of an insulating material and having a compressive stress is formed so as to cover the interlayer insulating film 19, the source electrode 32, the drain electrode 33, and the gate extraction electrode 34.
From the above steps, the electronic device 10 is manufactured as shown in FIG.

  As described above, in the present embodiment, by forming the protrusions 13, an external force that pulls the ZnO film 14 out of the film, more preferably in a direction that pulls out of the film substantially horizontally in the normal direction of the ZnO film 14. A force can be applied. Thereby, the c-axis of the ZnO crystal of the ZnO film 14 extends and the a-axis contracts, whereby the carrier mobility in the ZnO film 14 can be improved.

  Further, in this embodiment, when the ZnO film 14 is formed, the stress remaining in the ZnO film 14 can be made a compressive stress by controlling the gas pressure and the like, and the carrier mobility of the ZnO film 14 is further improved. be able to. Further, when forming the gate insulating film 18, the gate electrode 31, and the protective film 20, the deposition conditions are controlled, and an external force that pulls the ZnO film 14 out of the film, more preferably the normal direction of the ZnO film 14. The carrier mobility of the ZnO film 14 can be further improved by allowing the stress to remain so that a force can be applied in the direction of being pulled out of the film substantially horizontally.

(Embodiment 2)
An electronic device 40 according to Embodiment 2 of the present invention is shown in FIG. The electronic device 40 of the present embodiment is different from the above-described first embodiment in that the electronic device 10 of the first embodiment includes a protrusion 13 on the ZnO film 14 that generates compressive stress on the ZnO film 14. However, in the second embodiment, the protrusion 13 is omitted. Detailed description of portions common to the first embodiment will be omitted.

  As shown in FIG. 6, the electronic device 40 of the present embodiment includes a substrate 11, an undercoat layer 12, a semiconductor film (ZnO film) 14, a channel region 15, a source region 16, a drain region 17, A gate insulating film 18, an interlayer insulating film 19, a protective film 20, a gate electrode 31, a source electrode 32, and a drain electrode 33 are provided.

  In the electronic device 40 of this embodiment, the ZnO film 14 is formed flat, but the compressive residual stress generated in the ZnO film 14 itself and the compressive stress of the gate insulating film 18 formed on the upper surface of the ZnO film 14 The external force that pulls the ZnO film 14 out of the film by combining at least one of the compressive stress of the gate electrode 31 and the compressive stress of the protective film 20 or a combination thereof, more preferably the ZnO film 14. A force pulling out of the film substantially horizontally in the normal direction can be applied, and the carrier mobility in the ZnO film 14 can be increased.

(Embodiment 3)
An electronic element 50 according to Embodiment 3 is shown in FIG. The electronic device of this embodiment is different from the first and second embodiments in the method for manufacturing the electronic device. Portions common to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 7, the electronic element 50 includes a substrate 11, an undercoat layer 12, a protrusion 13, a semiconductor film (ZnO film) 14, a channel region 15, a source region 16, a drain region 17, A gate insulating film 51, an interlayer insulating film 19, a protective film 20, a gate electrode 31, a source electrode 52, a drain electrode 53, a gate lead electrode 34, a source wiring 56, and a drain wiring 57 are provided. .

  In this embodiment, as will be described in detail later, the order of formation of the gate electrode, the source electrode, and the drain electrode is different. For this reason, in the electronic device 50 of this embodiment, the source electrode 52 is formed under the gate insulating film 51, and the source electrode 52 is formed so as to fill the contact hole 51 s provided in the gate insulating film 51. A voltage is applied through the source wiring 56 formed. Similarly, the drain electrode 53 is also formed under the gate insulating film 51, and the drain electrode 53 is connected via a drain wiring 57 formed so as to fill a contact hole 51 d provided in the gate insulating film 51. A voltage is applied.

  The gate insulating film 51 is formed so as to cover the ZnO film 14, the source electrode 52, and the drain electrode 53.

  Next, the manufacturing method of the electronic device concerning Embodiment 3 of this invention is demonstrated using FIG.

  First, for example, a substrate 11 made of an alkali-free glass substrate is prepared. On one main surface of the substrate 11, a silicon nitride film 12a and a silicon oxide film 12b are formed to form an undercoat layer 12. Next, a silicon oxide film having a thickness of, for example, 150 nm is formed on the upper surface of the undercoat layer 12 by, eg, CVD. Subsequently, as shown in FIG. 8A, the protrusion 13 is formed by photolithography, wet etching, or the like.

Subsequently, a ZnO film 14 is formed to a thickness of, for example, 100 nm on the undercoat layer 12 and the protruding portion 13 by, for example, sputtering, as shown in FIG. 8B. At this time, compressive residual stress is generated in the ZnO film 14 by setting the gas pressure of the argon gas used in the sputtering method to a level of 10 ⁻¹ Pa. The gas pressure is not limited to this as long as a desired compressive residual stress can be generated.

  Next, an impurity is introduced into a predetermined region of the ZnO film 14 by using an ion implantation method or the like to form a channel region 15, a source region 16, and a drain region 17.

Next, a metal film made of a conductive material such as Al, Ta, W, or Mo is formed on the ZnO film 14 by sputtering or the like. At this time, it is possible to generate a compressive stress in the metal film by setting the gas pressure of argon gas used in the sputtering method to a level of 10 ⁻¹ Pa. Subsequently, the metal film is processed into a predetermined pattern by photolithography, dry etching, wet etching, or the like, and the source electrode 52 and the drain electrode 53 are formed as shown in FIG.

  Subsequently, a gate insulating film 51 made of an insulating material such as a silicon oxide film, a silicon nitride film, or a composite of these is formed by sputtering or CVD, as shown in FIG. The drain electrode 53 and the ZnO film 14 are formed so as to cover them.

Subsequently, a metal film made of a conductive material such as Al, Ta, W, or Mo is formed on the gate insulating film 18 by sputtering or the like. At this time, it is possible to generate a compressive stress in the metal film by setting the gas pressure of argon gas used in the sputtering method to a level of 10 ⁻¹ Pa. Subsequently, the metal film is processed into a predetermined pattern by photolithography, dry etching, wet etching, or the like, and a gate electrode 31 is formed as shown in FIG.

  Next, an interlayer insulating film 19 made of an insulating material such as a silicon oxide film, a silicon nitride film, or a composite thereof is formed on the gate insulating film 51 and the gate electrode 31 by a CVD method or the like.

  Next, contact holes 51 s, 51 d, and 19 g are formed at predetermined locations on the gate insulating film 51 and predetermined locations on the interlayer insulating film 19 by photolithography, etching, or the like. Subsequently, a metal film made of a conductive material such as aluminum is formed by sputtering or the like so as to fill the contact holes 51s, 51d, and 19g. Next, the metal film is removed so that a predetermined pattern remains, and a source wiring 56, a drain wiring 57, and a gate extraction electrode 34 are formed.

Subsequently, a protective film 20 made of an insulating material and having compressive stress is formed so as to cover the interlayer insulating film 19, the source electrode 52, the drain electrode 53, and the gate extraction electrode 34.
From the above steps, the electronic device 50 is manufactured as shown in FIG.

(Embodiment 4)
An electronic element 60 according to Embodiment 4 of the present invention will be described with reference to FIG. The electronic device of the present embodiment is different from the above-described first to third embodiments. In the first to third embodiments, the top gate type TFT has been described as an example of the electronic device, but in this embodiment, the bottom gate type TFT is used. It is a TFT. Portions common to the above-described embodiments are assigned the same reference numerals, and detailed descriptions thereof are omitted.

  As shown in FIG. 10, the electronic device 60 according to the present embodiment includes a substrate 11, an undercoat layer 12, a recessed portion 63, a ZnO film 64, a channel region 65, a source region 66, and a drain region 67. A gate insulating film 68, a protective film 70, a gate electrode 71, a source electrode 72, and a drain electrode 73.

  The substrate 11 is made of an alkali-free glass substrate, a resin substrate, or the like, for example. On the substrate 11, an undercoat layer 12 having a silicon oxide film 12a and a silicon nitride film 12b is formed.

  The concave portion 63 is formed on the undercoat layer 12 and is made of an insulating material such as a silicon oxide film. The concave portion 63 is formed with a thickness of 150 nm, for example. Further, the concave portion 63 has an opening 63a having a square shape in a plan view and a trapezoidal shape in cross section. Further, a metal film of Al, Ta, W, Mo or the like is deposited by 150 nm, for example, by sputtering in the opening 63a and the upper surface of the concave portion 63, and then the gate electrode 71 is formed by photolithography, wet etching, or the like. Is done.

  Next, a gate insulating film 68 made of an insulating material such as a silicon oxide film, a silicon nitride film, or a composite thereof is formed on the gate electrode 71 and the concave portion 63 by CVD or the like as shown in FIG. Form. The gate insulating film 68 is formed with a thickness of 100 nm, for example. The gate insulating film 68 is formed so that the residual stress becomes a tensile stress. Thereby, a tensile stress can be further generated in the ZnO film 64 together with a concave portion 63 described later.

  Since this embodiment is a bottom-gate TFT, a semiconductor film (ZnO film) 64 made of ZnO crystal is next formed to cover the gate insulating film 68 by, for example, sputtering. A channel region 65, a source region 66, and a drain region 67 are formed in the surface region of the semiconductor film 64. At this time, in this embodiment, unlike the first embodiment, the residual stress in the ZnO film 64 is formed to be a tensile stress. The ZnO crystal of the ZnO film 64 is the same as in the first embodiment in that the c-axis is oriented in the direction perpendicular to the substrate surface and the a-axis is oriented in the horizontal direction.

  The concave portion 63 described above corresponds to the protruding portion 13 of the first embodiment, and the gate electrode 71 and the gate insulating film 68 formed on the concave portion 63 are concave, and the gate insulation formed into the concave shape. The ZnO film 64 formed on the film 68 has a function of generating a tensile stress. In this way, tensile stress can be generated in the ZnO film 64 by the concave portion 63, and carrier mobility in the ZnO film 64 can be improved. The shape and thickness of the concave portion 63 are not limited to those described above as long as a predetermined tensile stress can be generated in the ZnO film 64.

The channel region 65 is formed in the surface region of the semiconductor film 64. The channel region 65 is a region where the conductivity type is inverted when a predetermined voltage is applied to the gate electrode 71 and a channel is formed, and impurities such as phosphorus and boron are diffused. In order to realize a predetermined threshold voltage, doping of the order of 10 ¹³ atoms / cm ² to 10 ¹⁴ atoms / cm ² is performed by an ion implantation method or the like.

  The source region 66 is formed in the surface region of the semiconductor film 64. In the source region 66, n-type or p-type impurities such as phosphorus and boron are diffused. A source electrode 72 is formed on the upper surface of the source region 66.

  The drain region 67 is formed in the surface region of the semiconductor film 64. In the drain region 67, n-type or p-type impurities such as phosphorus and boron are diffused. A drain electrode 73 is formed on the upper surface of the drain region 67.

  The protective film 70 is made of an insulating material and is formed so as to cover the ZnO film 64, the source electrode 72, and the drain electrode 73. The thickness of the protective film 70 is formed to 500 nm, for example. In the present embodiment, the protective film 70 is formed to have a tensile stress, whereby the stress generated in the ZnO film 64 can be further increased.

The gate electrode 71 is made of a conductive material such as Al, Ta, W, Mo, etc., and is formed on the undercoat layer 12 and the concave portion 63. In the present embodiment, the gate electrode 71 is formed by sputtering, for example. At this time, for example, a metal film having a strong tensile stress can be formed by controlling the argon gas pressure to 10 ⁻¹ level. Thereby, the stress generated in the ZnO film 64 is further increased. The gate electrode 71 is formed with a thickness of 150 nm, for example. In the structure of this embodiment, the residual stress of the gate electrode 71 need not be concerned.

  The source electrode 72 is made of a conductive material such as aluminum and is formed on the source region 66. The source electrode 72 is formed with a thickness of, for example, 0.9 μm.

  The drain electrode 73 is made of a conductive material, such as aluminum, and is formed on the drain region 67. The drain electrode 73 is formed with a thickness of, for example, 0.9 μm.

  In the present embodiment, by forming the concave portion 63 having the opening 63a on the undercoat layer 12, the ZnO film 64 formed thereon can be deformed downward and the ZnO film 64 is formed as a film. An external force that pulls outward, more preferably a force that pulls substantially horizontally in the normal direction of the ZnO film 14 can be applied. As a result, the carrier mobility in the ZnO film 64 can be increased as in the first embodiment.

  In the present embodiment, the carrier mobility in the ZnO film 64 can be further increased by forming the ZnO film 64 so that the tensile stress remains. By forming the gate insulating film 68 and the protective film 70 so as to have a tensile stress, an external force that pulls the ZnO film 64 out of the film, more preferably a force that pulls substantially horizontally in the normal direction of the ZnO film 14 is applied. The carrier mobility in the ZnO film 64 can be further increased.

  Next, a method for manufacturing an electronic element according to Embodiment 4 of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 11A, a substrate 11 made of, for example, an alkali-free glass substrate is prepared. On one main surface of the substrate 11, a silicon nitride film 12a is formed with a thickness of, for example, 100 nm by, for example, a CVD (Chemical Vapor Deposition) method. Further, a silicon oxide film 12b is formed on the silicon nitride film 12a with a thickness of, for example, 100 nm by, eg, CVD. As a result, the undercoat layer 12 is formed as shown in FIG.

  Next, a silicon oxide film having a thickness of, for example, 150 nm is formed on the upper surface of the undercoat layer 12 by, for example, sputtering or CVD. Subsequently, as shown in FIG. 11C, a concave portion 63 having an opening 63a is formed by photolithography, wet etching, or the like.

Subsequently, a metal film made of a conductive material such as Al, Ta, W, Mo, or the like is formed on the undercoat layer 12 and the concave portion 63 by a sputtering method or the like. At this time, a tensile stress may be generated in the metal film by setting the gas pressure of the argon gas used in the sputtering method to a level of 10 ⁻⁰ Pa. Subsequently, the metal film is processed into a predetermined pattern by photolithography, dry etching, wet etching, or the like, and a gate electrode 71 is formed as shown in FIG.

  Next, a gate insulating film 68 made of an insulating material such as a silicon oxide film, a silicon nitride film, or a composite thereof is formed by CVD or the like so as to cover the undercoat layer 12 and the gate electrode 71. The gate insulating film 68 is formed with a thickness of 100 nm, for example. At this time, the gate insulating film 68 is preferably formed to have a tensile stress.

Next, as shown in FIG. 12E, a ZnO film 64 is formed to a thickness of, for example, 100 nm so as to cover the gate insulating film 68. At this time, a tensile residual stress is generated in the ZnO film 64 by setting the gas pressure of the argon gas used in the sputtering method to a level of 10 ⁻⁰ Pa. The gas pressure is not limited to this as long as a desired compressive residual stress can be generated.

  Next, an impurity is introduced into a predetermined region of the ZnO film 64 to form a channel region 65, a source region 66, and a drain region 67 using an ion implantation method or the like.

  Next, a metal film is formed on the ZnO film 64 and patterned to form a source electrode 72 and a drain electrode 73 as shown in FIG.

Subsequently, a protective film 70 made of an insulating material is formed by a CVD method or the like so as to cover the ZnO film 64, the source electrode 72, and the drain electrode 73. When the protective film 70 is formed, the protective film 70 is preferably formed so as to have a tensile stress.
From the above steps, the electronic device 60 is manufactured as shown in FIG.

  As described above, in this embodiment, by forming the concave portion 63 having the opening 63a on the undercoat layer 12, the ZnO film 64 formed thereon can be deformed downward and convex. An external force that pulls the ZnO film 64 out of the film, more preferably, a force that pulls the ZnO film 64 substantially horizontally in the normal direction of the ZnO film 14 can be applied. As a result, the carrier mobility in the ZnO film 64 can be increased as in the first embodiment.

  Further, in this embodiment, when the ZnO film 64 is formed by sputtering or the like, the stress remaining in the ZnO film 64 can be set as a tensile stress by controlling the gas pressure or the like, and carrier movement of the ZnO film 64 can be performed. The degree can be improved. Furthermore, when forming the gate insulating film 68, the gate electrode 71, and the protective film 70, the film forming conditions are controlled so that the tensile stress remains, and an external force that pulls the ZnO film 64 out of the film. More preferably, the carrier mobility of the ZnO film 64 can be further improved by allowing the stress to remain so that a force can be applied in the direction of being pulled substantially horizontally in the direction normal to the ZnO film 14.

(Example)
Hereinafter, the result of verifying the ZnO film when a film for applying an external force to the ZnO film is formed will be described. As a means for applying an external force to the ZnO film, a case where an SiN film (insulating film) is formed is taken as an example.

First, a ZnO film is formed on a glass substrate. The ZnO film is formed by an RF magnetron sputtering apparatus. The substrate temperature during film formation is 175 ° C., and the film is formed in an Ar, O ₂ atmosphere. The ZnO film is formed to a thickness of 100 nm. In this example, additive-free ZnO is used, but almost the same result can be obtained even when Ga ₂ O ₃ is added. Next, a silicon nitride film having a strong compressive stress of 500 to 700 MPa was formed on the ZnO film to a thickness of 10 nm, 30 nm, and 50 nm using a plasma CVD method at a low temperature of about 250 ° C.

The c / a of the ZnO film at this time was evaluated by an X-ray diffraction method. The c-axis and a-axis of the ZnO film were measured using a multi-functional X-ray diffractometer model ATX-G for surface structure evaluation manufactured by Rigaku. Specifically, the a-axis length was measured by an in-plane diffraction measurement method. In this method, X-rays were incident from 0.35 degrees near the total reflection angle, and the measurement was performed with a so-called 2qc-f optical arrangement in which the sample and detector were rotated in the vicinity of the sample surface. In this measurement, the a-axis was obtained from the (300) diffraction peak of ZnO observed when 2qc was around 110 degrees. The c-axis was obtained from a (002) diffraction peak in which 2q appears in the vicinity of 34 degrees in a wurtzite crystal structure ZnO in ordinary X-ray diffraction measurement, so-called 2q-q optical configuration measurement. X-rays use copper kα rays, that is, the wavelength is 0.154184 nm.

  FIG. 14 shows the c-axis length and the a-axis length thus obtained. As is apparent from FIG. 14, when the SiN film is not formed, the c-axis length is 0.5216 nm and the a-axis length is 0.3260 nm. On the other hand, when the SiN film is formed with a thickness of 10 nm, the c-axis length can be 0.5216 nm and the a-axis length can be 0.3257 nm. When the SiN film is formed with a thickness of 30 nm, the c-axis length is 0. 5222 nm, the a-axis length can be 0.3254 nm, and when the SiN film is formed to a thickness of 50 nm, the c-axis length can be 0.5232 nm and the a-axis length can be 0.3244 nm. It can be seen that the c-axis length increases and the a-axis length decreases as the SiN film thickness increases.

  Further, when c / a is obtained, c / a is 1.600 when the SiN film is not formed. However, when the SiN film is formed with a thickness of 10 nm, c / a becomes 1.6015 and a thickness of 30 nm. When formed, the thickness is 1.6014, and when the thickness is 50 nm, 1.613 and c / a can be brought close to the ideal state of 1.633.

  Similarly, FIG. 15 shows the relationship between the film density and the cell volume (unit cell volume) when SiN films having a thickness of 10 nm, 30 nm, and 50 nm are formed on a 100 nm ZnO film. The film density is the same as the one used to obtain the c-axis and a-axis, and the X-ray reflected from the film top surface and the X-ray reflected from the film substrate side by the normal X-ray reflectivity measurement method The interference spectrum was measured, and the waveform was subjected to fitting analysis by computer simulation to obtain the density. A Cu target (rotor type 50 kV-300 mA) was used as the X-ray source.

  As is clear from FIG. 15, comparing the case where the SiN film is formed and the case where the SiN film is not formed, it can be seen that the cell volume is reduced and the film density is increased by forming the SiN film. Further, it can be said that as the SiN film thickness increases, the cell volume gradually decreases and the film density increases. When comparing the case where the SiN film was formed with a thickness of 150 nm and the case where the SiN film was not formed, it was confirmed that the film density was increased by about 11% reflecting the unit cell contraction. It was also confirmed that the unit cell capacity (cell volume) was reduced by 0.7%.

The present invention is not limited to the above-described embodiments, and various modifications and applications are possible.
For example, Embodiment 2 described above can be applied to Embodiment 3.

  In the above-described embodiment, an external force that pulls the ZnO film out of the film, such as a gate insulating film, a gate electrode, and a protective film formed on the ZnO film, more preferably in the normal direction of the ZnO film 14. Although a stress that pulls substantially horizontally is generated and an external force is applied to the ZnO film, it is possible to appropriately change which external force is applied by which film.

In the above-described embodiment, the point that the residual stress is controlled by setting the argon gas pressure to 10 ⁻¹ Pa or 10 ⁻⁰ Pa in the sputtering method when forming a film such as a ZnO film or a SiN film is described. However, the gas pressure is not limited to this. In particular, in the sputtering method, not only the gas pressure but also the stress generated in the film can be controlled by the substrate temperature, input power, etc., it is possible to change other than the gas pressure.

  In each of the above-described embodiments, the top gate type and the bottom gate type TFT are described as examples of the electronic element, but the present invention is not limited to this. For example, a ZnO film may be used as an electrode of an LED, a liquid crystal display device, an organic EL element, etc., and a compressive stress or a tensile stress may be generated in the ZnO film, and the ZnO film is pulled out of the film. A film having a compressive stress or a tensile stress may be formed so as to apply a force.

  In Embodiment 4 described above, the concave portion 63 has been described by taking as an example the case where the opening 63a is formed so that the undercoat layer 12 is exposed, but the present invention is not limited thereto. For example, if the depression is formed to such an extent that a predetermined tensile stress can be generated in the ZnO film 64 formed on the concave portion 63, the opening 62a need not be formed.

  In each of the above-described embodiments, the configuration using a ZnO film as a semiconductor film has been described as an example. However, the present invention is not limited to this, and any compound having a wurtzite crystal structure can be applied. .

It is sectional drawing which shows the structural example of the electronic element which concerns on Embodiment 1 of this invention. It is a figure which shows a wurtzite type crystal structure typically. It is a figure which shows the manufacturing method of the electronic device which concerns on Embodiment 1 of this invention. It is a figure which shows the manufacturing method of the electronic device which concerns on Embodiment 1 of this invention. It is a figure which shows the manufacturing method of the electronic device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the structural example of the electronic element which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the structural example of the electronic element which concerns on Embodiment 3 of this invention. It is a figure which shows the manufacturing method of the electronic device which concerns on Embodiment 3 of this invention. It is a figure which shows the manufacturing method of the electronic device which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the structural example of the electronic element which concerns on Embodiment 4 of this invention. It is a figure which shows the manufacturing method of the electronic device which concerns on Embodiment 4 of this invention. It is a figure which shows the manufacturing method of the electronic device which concerns on Embodiment 4 of this invention. It is a figure which shows the manufacturing method of the electronic device which concerns on Embodiment 4 of this invention. It is a figure which shows the change of c axis | shaft and a axis | shaft at the time of forming a SiN film | membrane on a ZnO film | membrane. It is a figure which shows the change of the film density at the time of forming a SiN film | membrane on a ZnO film | membrane, and a unit cell volume.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 10 ... Electronic device, 11 ... Substrate, 12 ... Undercoat layer, 13 ... Projection part, 14 ... Semiconductor film Semiconductor film (ZnO film), 15 ... Channel region, 16. .. Source region, 17... Drain region, 18... Gate insulating film, 19... Interlayer insulating film, 20. ... Drain electrode, 34 ... Gate extraction electrode

Claims (23)

A semiconductor film made of wurtzite crystal,
An electronic device comprising: an external force application film that is formed on one surface of the semiconductor film and applies an external force in a direction to pull the semiconductor film out of the semiconductor film.   The electronic device according to claim 1, wherein the semiconductor film has an internal stress.   3. The electronic device according to claim 1, wherein the semiconductor film has a c-axis of the wurtzite crystal oriented in a direction along the external force.   4. The semiconductor device according to claim 1, wherein the semiconductor film has a larger c-axis length and a shorter a-axis length than the case where the external force application film is not formed. 5. Electronic elements.   4. The electronic device according to claim 1, wherein the semiconductor film has a unit cell volume smaller than that in a case where the external force application film is not formed. 5.   4. The electronic device according to claim 1, wherein the semiconductor film has a higher film density than a case where the external force application film is not formed. 5.   4. The electronic device according to claim 1, wherein c / a of the semiconductor film is increased as compared with a case where the external force application film is not formed. 5.   The external force application film is formed in a convex shape, and an external force in a direction to pull the semiconductor film out of the semiconductor film is applied by placing the semiconductor film along the external force application film. Item 8. The electronic device according to any one of Items 1 to 7. An insulating layer formed on the semiconductor film;
9. The electronic device according to claim 8, wherein the insulating layer has a stress that applies an external force in a direction of pulling the semiconductor film out of the semiconductor film. An electrode formed on the insulating layer;
The electronic device according to claim 8, wherein the electrode has a stress that applies an external force in a direction of pulling the semiconductor film out of the semiconductor film.   The electronic device according to claim 1, wherein the external force application film is formed of an insulating material and is formed in a planar shape. Further comprising an electrode formed on the external force application film,
The electronic device according to claim 11, wherein the electrode has a stress that applies an external force in a direction of pulling the semiconductor film out of the semiconductor film.   The external force application film has a concave portion formed in a concave shape, and applying an external force in a direction to pull the semiconductor film out of the semiconductor film by aligning the semiconductor film along the external force application film. The electronic device according to claim 1, wherein the electronic device is characterized in that: An insulating layer formed between the external force application film and the semiconductor film;
14. The electronic device according to claim 13, wherein the insulating layer has a stress so as to apply an external force in a direction of pulling the semiconductor film out of the semiconductor film. Further provided with a protective film made of an insulating material,
The electronic device according to claim 1, wherein the protective film has a stress so as to apply an external force in a direction of pulling the semiconductor film out of the semiconductor film.   The electronic device according to claim 1, wherein the semiconductor film is a ZnO film. A semiconductor film forming step of forming a semiconductor film made of wurtzite crystal;
An external force application film forming step of forming an external force application film that is formed on one surface side of the semiconductor film and applies an external force in a direction of pulling the semiconductor film to the outside of the semiconductor film. Production method.   18. The method of manufacturing an electronic device according to claim 17, wherein in the semiconductor film formation step, the semiconductor film is formed so as to have an internal stress.   19. The method of manufacturing an electronic device according to claim 17, wherein the semiconductor film has a c-axis of the wurtzite crystal oriented in a direction along the external force.   The external force application film is formed in a convex shape so as to apply an external force in a direction of pulling the semiconductor film out of the semiconductor film by bringing the semiconductor film along the external force application film. The method for manufacturing an electronic device according to any one of claims 17 to 19. The external force application film is made of an insulating material and is formed in a planar shape.
18. The external force application film is formed such that in the external force application film formation step, a stress that applies an external force in a direction of pulling the semiconductor film out of the semiconductor film remains. 20. The method for manufacturing an electronic device according to any one of 19 above.   The external force application film is formed in a concave shape so as to apply an external force in a direction of pulling the semiconductor film out of the semiconductor film by aligning the semiconductor film with the external force application film. The method for manufacturing an electronic device according to claim 17.   The method for manufacturing an electronic device according to claim 17, wherein the semiconductor film is a ZnO film.

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