KR101137292B1 - Method of forming a thin film - Google Patents

Abstract

In the method for forming a thin film according to the present invention, after loading a ZnO target doped with Cr at 0.1 mol% to 30 mol% into a sputtering deposition chamber, loading the substrate and applying power to the target to deposit 0.1 mol of Cr on the substrate Forming a ZnO thin film doped with% to 30 mol%.

Therefore, according to the present invention, a ZnCrO-doped magnetic semiconductor thin film may be formed by forming a ZnO target having 0.1 mol% to 30 mol% of Cr on a substrate by a sputtering method using a ZnO target doped with Cr. In addition, by applying the ZnCrO magnetic semiconductor thin film as described above to the semiconductor device, the efficiency and lifespan of the semiconductor device can be improved.

Magnetic Semiconductor, Cr, Doped, ZnO, Si Substrates

Description

Method of forming a thin film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film formation method, and to a thin film formation method of forming a ZnCrO-diluted Magnetic Semicoducotr (DMS) thin film by forming a Cr-doped ZnO thin film using a sputtering method.

Ferromagnetic semiconductor (FS) refers to a material that electrically has characteristics of a semiconductor and magnetically has ferromagnetic properties. Among the magnetic semiconductors, the most attracting attention recently is a diluted magnetic semiconductor (Diluted Magnetic Semicoducotr: DMS). Dilute magnetic semiconductors are manufactured by injecting magnetic materials into well-known semiconductors so that the semiconductor and ferromagnetic properties appear simultaneously. Accordingly, the thin magnetic semiconductor may use two different magnetic states, as well as electrical positive (+) and negative (-), as well as spin up and spin down. The thin magnetic semiconductor may be applied to various semiconductor devices such as transistors, light emitting devices, and resonance tunneling diodes.

In order to manufacture such thin magnetic semiconductors, in recent years, attempts have been actively made to form ferromagnetic semiconductor thin films by doping transition metals to ZnO. In this case, in the case of the thin magnetic semiconductor, the larger the residual magnetic value, the easier it is to use the spin of the electron. However, a ferromagnetic semiconductor thin film manufactured by the same method as the conventional method has a poor ferromagnetic property or a small residual magnetic value, making it difficult to use in devices.

In order to solve the above problems, an embodiment of the present invention uses a Cr-doped ZnO target to form a thin film for forming a ferromagnetic ZnO thin film that is doped with Cr on a substrate by a sputtering method, that is, a magnetic semiconductor thin film made of ZnCrO. Provide a method.

In the method of forming a thin film according to the present invention, after loading a ZnO target doped with Cr at 0.1 mol% to 30 mol% into a sputtering deposition chamber, loading the substrate and applying power to the target, the Cr is 0.1 on the substrate. forming a ZnO thin film doped with mol% to 30 mol%.

It is effective to form a ZnO thin film doped with Cr at 0.1 mol% to 5 mol% using a ZnO target doped with Cr at 0.1 mol% to 5 mol%.

The ZnCrO thin film doped with Cr in the ZnO is characterized in that the ferromagnetic material.

The target is prepared by mixing Cr powder with 0.1 mol% to 30 mol% of ZnO powder and then molding the mixed powder.

The target is sintered for 5 to 7 hours in a furnace at 800 ° C to 1000 ° C.

The chamber preferably maintains a pressure of 0.005 mbar to 0.025 mbar and an oxygen atmosphere and a substrate temperature of 300 ° C. to 600 ° C.

AC power is applied to the target.

As described above, the present invention can form a magnetic semiconductor thin film made of ZnCrO by forming a ZnO target having 0.1 mol% to 30 mol% of Cr on a substrate by a sputtering method using a ZnO target doped with Cr. In addition, by applying the ZnCrO magnetic semiconductor thin film as described above to the semiconductor device, the efficiency and lifespan of the semiconductor device can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention and to those skilled in the art. It is provided for complete information.

1 is a schematic cross-sectional view of a deposition apparatus used for thin film deposition according to an embodiment of the present invention.

Referring to FIG. 1, a deposition apparatus used for thin film deposition according to an embodiment includes a chamber 100 having an internal space, a substrate support part 200 provided in the chamber 100 to support a substrate s, and a substrate support part 200. A power supply unit for supplying power to the target 300, a target supporter 310 for supporting the target 300, and a target 300 for providing a raw material on the substrate s by a sputtering method disposed opposite to the lower side 400.

The chamber 100 is manufactured to have a rectangular cylindrical shape with an empty inside, and a predetermined reaction space for processing the substrate s is provided therein. In the present embodiment, the chamber 100 is manufactured in a rectangular cylindrical shape, but is not limited thereto, and is preferably manufactured to correspond to the shape of the substrate s. On the other hand, although not shown on one side of the chamber 100, a gas inlet through which a sputtering gas, such as argon (Ar) and oxygen (O ₂ ), is provided, and the other side of the chamber 100, the sputtering gas to the outside A discharged gas outlet is provided.

The substrate support 200 is mounted on the upper wall in the chamber 100 to support the substrate s drawn into the chamber 100. In the present exemplary embodiment, the substrate support part 200 is mounted on the upper wall of the chamber 100. However, if the substrate support part 200 faces the target 300 according to the position of the target 300 that supplies the raw material, It can also be mounted. The substrate support part 200 includes a substrate mounting means 210 on which the substrate s is seated, and a driver 220 for moving the substrate mounting means 210. Here, the substrate placing means 210 may be additionally configured with a variety of chuck means for holding the substrate (s) using a mechanical force, vacuum suction force, electrostatic force, and the like. In the embodiment, a silicon substrate is used as the substrate s.

The target 300 is composed of a material to be deposited on the substrate s to provide a raw material to the substrate s. As the target 300, a ZnO target 300 doped with impurities is used. In an embodiment, Cr is used as an impurity of the target 300, and the target 300 is manufactured by doping Cr with 5 mol%, 10 mol%, and 30 mol% of ZnO. This is to prepare a ZnCrO thin film doped with 5 mol%, 10 mol% and 30 mol% of ZnO by using the target 300 doped with 5 mol%, 10 mol% and 30 mol% of Cr. At this time, the ZnCrO thin film doped with 5 mol%, 10 mol% and 30 mol% of Cr in Zn is a dilluted magnetic semicoductors (DMS) thin film. A lean magnetic semiconductor is a semiconductor that becomes magnetic when a semiconductor having no magnetic at all is partially displaced by atoms of another material. In the embodiment, as described above, ZnO is doped with Cr to prepare a magnetic semiconductor thin film. In order to manufacture the target 300, a high purity ZnO powder (99.99%) and Cr powder (99.99%) are mixed and manufactured. That is, a high purity ZnO powder (99.99%) and Cr powder (99.99%) are mixed for 10 hours using a container having balls. Then, the target 300 is manufactured by molding a mixed powder in which ZnO powder and Cr powder are mixed by using a pelleter press (cylindrical pallets presser). At this time, in the embodiment, the target 300 is manufactured in a disk shape. In addition, the denser the target 300 is, the higher quality plasma can be obtained. Therefore, in order to manufacture the dense target 300, the disk-shaped target 300 is sintered for 5 to 7 hours in the furnace of 800 ℃ to 1000 ℃. Preferably, the target 300 is sintered in a furnace at 950 ° C. for 6 hours. At this time, in the embodiment to produce a target 300 to have a diameter of 20mm to 70mm. The target 300 manufactured as described above is attached to the target support 310 of the deposition apparatus and then uploaded to the chamber 100. At this time, the target 300 is preferably arranged to maintain a distance of 5cm with the substrate (s).

The chamber 100 should be maintained at a predetermined atmosphere, pressure and temperature while the thin film is deposited, while maintaining an oxygen atmosphere of 0.005 mbar to 0.025 mbar, preferably 0.2 mbar and a substrate s temperature of 300 ° C. to 600 ° C. do. Then, 100W AC power (RF power) is supplied to the target 300 using the power supply 400, and a deposition process is performed for 30 minutes to form a thin film on the substrate s. At this time, as described above, in the embodiment, since the target 300 prepared by mixing the Cr powder with 5 mol%, 10 mol% and 30 mol% in the ZnO powder, Cr is 5mol%, 10mol% and 30mol% A doped ZnCrO thin film is formed on the substrate s. After deposition, the thin film is naturally cooled at room temperature for various measurements.

The following describes the characteristics of the ZnO thin film doped with Cr at 0 mol%, 5 mol%, 15 mol% and 30 mol%, respectively.

Figure 2 shows the X-ray diffraction pattern of the ZnO thin film according to the doping concentration of Cr using the method according to an embodiment of the present invention. FIG. 3 shows the result of analyzing the ZnO thin film doped with 5 mol% of Cr by EDS. An impurity doped ZnO thin film has a hexagonal wurtzite structure, and the (002) plane perpendicular to the substrate (s) surface has the lowest surface energy due to the high atomic filling rate. . Because of this, ZnO first grows in the c-axis direction when the thin film is deposited. Referring to FIG. 2, the ZnO thin film (pure of FIG. 2) without Cr doping and the ZnO thin film doped with 5 mol% of Cr show preferential crystal growth in the (002) direction. In addition, in the case of a ZnO thin film doped with 5 mol% of Cr, a peak related to Cr does not appear in addition to the Si peak 200 and the ZnO peak 002. This is because even though 5 mol% of Cr is doped into ZnO, Cr atoms are substituted into the ZnO lattice structure. Thus, ZnO thin films doped with 5 mol% of Cr are hexagonal urethane such as ZnO thin films which are not doped with Cr. Has a structure. In addition, the ZnO thin film doped with 15 mol% of Cr seems to preferentially grow in the (103) direction compared to the (002) direction. The suppression of the (002) directional growth means that the crystalline is reduced, it can be seen that the amount of Cr in the ZnO thin film increased. In addition, the ZnO thin film doped with 30 mol% of Cr (002) peak disappeared, and the ZnCr ₂ O ₄ peak was generated. Thus, the ZnO thin film doped with 30 mol% of Cr has a hexagonal urtzite structure. It is not known. 3, an oxygen (O) peak at 0.52 KeV, a Zn peak at 1.02 KeV and 8.67 KeV, and a Cr peak at 5.4 KeV appear. Through this, it can be seen that the ZnO thin film is doped with 5mol% Cr, ZnO thin film doped with 5mol% it can be seen that other impurities are not doped in addition to ZnO and Cr.

4 is an AFM measurement result showing the surface roughness of the ZnO thin film according to the doping concentration of Cr. Referring to FIG. 4, in the case of the ZnO thin film not doped with Cr, the overall roughness is broad, and as the doping concentration of Cr increases from 0 mol% to 30 mol%, surface roughness increases. At this time, the RMS value of the Cr-doped ZnO thin film is 1.14 nm, and the RMS value of the Cr-doped ZnO thin film is 4.808 nm. This is because sub-grains are produced as the doping concentration of Cr increases. At this time, when Cr is doped to exceed 30 mol%, the roughness of the ZnO thin film is increased to reduce the electrical characteristics of the magnetic semiconductor thin film made of ZnCrO.

5 is a graph showing magnetization characteristics of a ZnO thin film according to Cr doping concentration. In this example, the degree of magnetization was increased while increasing the magnetic field at 300 K (RT) using a vibrating sample magnetometer (VSM). 6 is a graph showing the residual magnetization of the ZnO thin film according to the doping concentration of Cr. Referring to FIG. 5, it can be seen that ZnO thin films doped with 5 mol%, 15 mol%, and 30 mol%, respectively, are ferromagnetic. In addition, referring to FIG. 6, as the doping concentration increases, the residual magnetization (Msat) value increases. At this time, when the doping concentration of Cr is 5%, 15% and 30%, the residual magnetization values are 1.684 × 10 ⁻⁴ , 1.7244 × 10 ^−4, and 2.0553 × 10 ^−4, respectively.

Therefore, in the embodiment, to form a ferromagnetic ZnO thin film based on the above-described results, the ZnO thin film is formed by doping Cr at 0.1 mol% to 30 mol%, preferably 0.1 mol% to 5 mol%. For example, when Cr is doped at less than 0.1 mol%, less than 0.1 mol of Cr does not have sufficient doping concentration to impart ferromagnetic properties to the ZnO thin film. Therefore, the magnetic semiconductor thin film cannot be formed. In addition, when the Cr is doped to exceed 30 mol%, the surface roughness of the ZnO thin film can be increased to reduce the electrical characteristics of the magnetic semiconductor thin film. Thus, in the embodiment, by doping Cr at 0.1 mol% to 30 mol%, a magnetic semiconductor thin film made of ZnCrO is formed.

7 is a cross-sectional view of an organic light emitting diode (OLED) fabricated using a Cr-doped ZnO thin film according to an embodiment of the present invention.

Referring to FIG. 7, the light emitting device according to the embodiment may include a substrate s, a first electrode 510 formed on the substrate s, a light emitting layer 520 and a light emitting layer 520 formed on the first electrode 510. And a second electrode 530 formed thereon. Here, the substrate s according to the embodiment uses a glass substrate, and the first electrode 510 is formed on the glass substrate. The first electrode 510 is an electrode for hole injection, using a ZnO thin film doped with Cr according to an embodiment of the present invention, that is, a ZnCrO thin film having ferromagnetic properties. As described above, the ZnO thin film doped with Cr is formed using AC power sputtering using the target 300 doped with Cr. At this time, in the embodiment, using the ZnO target 300 doped with Cr 0.1 mol% to 30mol%, preferably 0.1mol% to 5mol%, to form a ZnO thin film doped with Cr 0.1mol% to 5mol%. . The Cr-doped ZnO thin film is formed by maintaining a temperature of the substrate s between 300 ° C. and 600 ° C. in an oxygen atmosphere of 0.2 mbar. In this manner, a ZnO thin film doped with Cr, that is, a ZnCrO thin film, becomes a lean magnetic semiconductor.

The light emitting layer 520 includes a hole injection layer 521, a hole transport layer 522, an organic emission layer 523, and an electron transport layer 524. do. In this case, the hole injection layer 521, the hole transport layer 522, the organic light emitting layer 523, and the electron transport layer 524 are sequentially stacked to form the light emitting layer 520. The organic material constituting the light emitting layer 520 may be added or omitted as necessary. For example, the hole injection layer 521 is formed on the first electrode 510 using a material that efficiently injects holes, such as CuPc, 2T-NATA, and MTDATA. The hole transport layer 522 is formed on the hole injection layer 521 using a material capable of efficiently transferring holes such as NPB and TPD. Next, an organic emission layer 523 is formed on the hole transport layer 522. The organic light emitting layer 523 may be formed of a green light emitting layer made of Alq ₃ : C545T, a blue light emitting layer made of DPVBi, a red light emitting layer made of CBP: Ir (acac), and a group consisting of these materials. Subsequently, the electron transport layer 524 is formed on the organic emission layer 523 using a material capable of efficiently transferring electrons such as Alq ₃ . The organic material is deposited using thermal evaporation to form the emission layer 520.

The second electrode 530 is used as an electron injection electrode, and it is preferable to use a metal having a low work function to smoothly inject electrons into the light emitting layer 520. In an embodiment, the second electrode 530 is formed using any one of Al, Ag, Au, Pt, and Cu.

As described above, the ZnO thin film doped with Cr as the first electrode 510, that is, a magnetic semiconductor thin film made of ZnCrO, can be used to control the spin state of charge, thereby improving efficiency of the organic light emitting diode.

In the embodiment, the ZnCrO thin film is used as the first electrode 510, but the ZnCrO thin film may be used as the second electrode 530.

8 is a cross-sectional view of a light emitting diode (LED) fabricated using a Cr-doped ZnO thin film according to an embodiment of the present invention.

Referring to FIG. 8, the light emitting device according to the embodiment may be formed on the substrate s, the buffer layer 610 formed on the substrate s, the n-type layer 620 formed on the buffer layer 610, and the n-type layer 620. The active layer 630 formed, the p-type layer 640 formed on the active layer, the ZnCrO layer 650 formed on the p-type layer 640, the first electrode 661 and the ZnCrO layer formed in some regions on the n-type layer 620 ( And a second electrode 662 formed on the 650. In the embodiment, the substrate s uses a silicon si substrate. Of course, the present invention is not limited thereto, and various substrates may be used.

The n-type layer 620, the active layer 630, and the p-type layer 640 may be formed of a semiconductor thin film including at least one of GaN, InGaN, AlGaN, and AlInGaN. For example, the n-type layer 620 and the p-type layer 640 are formed of a GaN film, and the active layer 630 is formed of an InGaN film. The n-type layer 620 is a layer providing electrons, and may be formed by implanting an n-type dopant, for example, Si, Ge, Se, Te, C, or the like into a semiconductor thin film. The p-type layer 640 is a layer for providing holes, and may be formed by implanting a p-type dopant, for example, Mg, Zn, Be, Ca, Sr, or Ba into a semiconductor thin film. The active layer 630 is a layer that outputs light of a predetermined wavelength while electrons provided from the n-type layer 620 and holes provided from the p-type layer 640 are recombined, and alternates a well layer and a barrier layer. The semiconductor layer may be stacked to form a multilayer semiconductor thin film having a single quantum well structure or a multiple quantum well structure. Since the wavelength of light to be output varies according to the semiconductor material constituting the active layer 630, it is preferable to select an appropriate semiconductor material according to the target output wavelength.

The ZnCrO layer 650 is formed on the p-type layer 640 manufactured as described above. As described above, the ZnCrO layer 650 uses a ZnO thin film doped with Cr of 0.1 mol% to 30 mol%. As described above, the ZnO thin film doped with Cr is formed using alternating current (RF) power sputtering using the target 300 doped with Cr. At this time, in the embodiment, using the ZnO target 300 doped with Cr 0.1 mol% to 30mol%, preferably 0.1mol% to 5mol%, to form a ZnO thin film doped with Cr 0.1mol% to 5mol%. .

 As described above, the ZnO thin film doped with Cr at 0.1 mol% to 30 mol%, that is, ferromagnetic ZnCrO is formed on the p-type layer 640, thereby controlling the spin state of the charge to improve the efficiency of the light emitting diode.

Although the organic light emitting diode (OLED) and the light emitting diode (LED) have been described above, the present invention is not limited thereto, and may be applied to various semiconductor devices such as a span transistor and a resonance tunneling diode.

1 is a schematic cross-sectional view of a deposition apparatus used for thin film deposition according to an embodiment of the present invention.

2 shows an X-ray diffraction pattern of a ZnO thin film according to the doping concentration of Cr using a method according to an embodiment of the present invention.

FIG. 3 shows the result of analyzing the ZnO thin film doped with 5 mol% Cr by EDS.

4 is an AFM measurement result showing the surface roughness of the ZnO thin film according to the doping concentration of Cr

5 is a graph showing the magnetization characteristics of ZnO thin film according to the doping concentration of Cr

6 is a graph showing the residual magnetization of the ZnO thin film according to the doping concentration of Cr

7 is a cross-sectional view of a light emitting device manufactured using a Cr-doped ZnO thin film according to an embodiment of the present invention.

8 is a cross-sectional view of a light emitting diode (LED) fabricated using a Cr-doped ZnO thin film according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: chamber 200: substrate support

300: target 310: target support

400: power supply

Claims (7)

Preparing a ZnO powder and Cr powder, and mixing the ZnO powder and Cr powder using a container having balls; Forming a ZnO target in which Cr is doped with 0.1 mol% to 30 mol% by molding a mixed powder in which the ZnO powder and the Cr powder are mixed using a pellet presser; Sintering the target in a furnace at 800 ° C. to 1000 ° C. for 5 hours to 7 hours; Loading the ZnO target into a sputter deposition chamber and loading a substrate; Applying a power to the ZnO target to form a ZnO thin film doped with 0.1 mol% to 30 mol% Cr on a substrate disposed opposite the target. The method according to claim 1, And forming a ZnO thin film doped with Cr at 0.1 mol% to 5 mol% using a ZnO target doped with Cr at 0.1 mol% to 5 mol%. In claim 1, The ZnCrO thin film doped with Cr on the ZnO is a ferromagnetic material. The method according to claim 1, And a thin film forming method for forming the target into a disk shape. delete The method according to claim 1, Wherein the chamber maintains a pressure of 0.005 mbar to 0.025 mbar and an oxygen atmosphere and a substrate temperature of 300 ° C. to 600 ° C. The method according to claim 1, Thin film formation method for applying an alternating current (RF power) to the target.

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