SEMICONDUCTOR DEVICE AND METHOD OF MANUFACTURING THE SAME

Abstract

An embodiment semiconductor device includes an n type layer disposed on a first surface of a substrate, the n type layer including beta-gallium oxide (-Ga.sub.2O.sub.3), a p type layer disposed on the n type layer and including nickel oxide represented by a formula M.sub.yNi.sub.1-yO.sub.x, wherein M is a doping element, x is 0.8x1.0, and y is 0y<1, a first electrode disposed on the p type layer, and a second electrode disposed on a second surface of the substrate opposite the first surface.

Claims

1. A semiconductor device comprising: an n type layer disposed on a first surface of a substrate, the n type layer comprising beta-gallium oxide (-Ga.sub.2O.sub.3); a p type layer disposed on the n type layer and comprising nickel oxide represented by a formula M.sub.yNi.sub.1-yO.sub.x, wherein M is a doping element, x is 0.8x1.0, and y is 0y<1; a first electrode disposed on the p type layer; and a second electrode disposed on a second surface of the substrate opposite the first surface.

2. The semiconductor device of claim 1, wherein a P-N heterojunction is present at a contact surface of the n type layer and the p type layer.

3. The semiconductor device of claim 1, wherein the substrate comprises n type gallium oxide (Ga.sub.2O.sub.3).

4. The semiconductor device of claim 3, wherein the n type gallium oxide comprises the n type gallium oxide doped with Si or Sn.

5. The semiconductor device of claim 1, wherein the substrate has a doping concentration of 110.sup.16 cm.sup.3 to 110.sup.20 cm.sup.3.

6. The semiconductor device of claim 1, wherein a thickness of the substrate is 100 m to 700 m.

7. The semiconductor device of claim 1, wherein the beta-gallium oxide comprises beta-gallium oxide doped with Si or Sn.

8. The semiconductor device of claim 7, wherein the n type layer has a doping concentration of 110.sup.15 cm.sup.3 to 110.sup.17 cm.sup.3.

9. The semiconductor device of claim 1, wherein a thickness of the n type layer is 1 m to 10 m.

10. The semiconductor device of claim 1, wherein y is 0<y<1.

11. The semiconductor device of claim 1, wherein y is 0.06y0.1.

12. The semiconductor device of claim 1, wherein the doping element comprises a monovalent element, a divalent element, or a combination thereof.

13. The semiconductor device of claim 12, wherein: the monovalent element comprises Li, K, Cu, Ag, Cs, or a combination thereof; and the divalent element comprises Mg, Ca, Sr, Ba, or a combination thereof.

14. The semiconductor device of claim 1, wherein a thickness of the p type layer is 10 nm to 300 nm.

15. The semiconductor device of claim 1, wherein the first electrode comprises an anode and the second electrode comprises a cathode.

16. A method of manufacturing a semiconductor device, the method comprising: forming an n type layer comprising beta-gallium oxide (-Ga.sub.2O.sub.3) on a first surface of a substrate; forming a p type layer comprising nickel oxide represented by a formula M.sub.yNi.sub.1-yO.sub.x on the n type layer, wherein M is a doping element, x is 0.8x1.0, and y is 0y<1; forming a first electrode on the p type layer; and forming a second electrode on a second surface of the substrate opposite the first surface.

17. The method of claim 16, wherein the p type layer is formed by a radio frequency (RF) sputtering process.

18. The method of claim 17, wherein a partial pressure of oxygen injected during the RF sputtering process is 5% to 30%.

19. The method of claim 16, wherein y is 0<y<1.

20. The method of claim 16, wherein the doping element comprises a monovalent element, a divalent element, or a combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a cross-sectional view briefly illustrating the structure of a semiconductor device according to an embodiment.

[0025] FIG. 2A is a graph showing the carrier concentration for an undoped NiO.sub.x thin film according to an embodiment, FIG. 2B is a graph showing the mobility for an undoped NiO.sub.x thin film according to an embodiment, and FIG. 2C is a graph showing the resistivity of an undoped NiO.sub.x thin film according to an embodiment.

[0026] FIG. 3A is a graph showing the carrier concentration for a Li-doped NiO.sub.x thin film according to an embodiment, FIG. 3B is a graph showing the mobility for a Li-doped NiO.sub.x thin film according to an embodiment, and FIG. 3C is a graph showing the resistivity of a Li-doped NiO.sub.x thin film according to an embodiment.

[0027] FIGS. 4A to 4E are graphs showing the bandgap according to oxygen partial pressure for an undoped NiO.sub.x thin film of Example 1, respectively.

[0028] FIGS. 5A to 5E are graphs showing the bandgap according to oxygen partial pressure for a Li-doped NiO.sub.x thin film of Example 2, respectively.

[0029] FIGS. 6A to 6C are graphs showing current characteristics of the semiconductor devices according to Examples 1 and 2 and Comparative Example 1.

[0030] FIG. 7 is a graph showing on-resistance characteristics of the semiconductor devices according to Examples 1 and 2 and Comparative Example 1.

[0031] FIGS. 8A to 8C are graphs showing the electrical characteristics of the semiconductor devices according to Examples 1 and 2 and Comparative Example 1.

[0032] FIG. 9 is a graph showing electrical characteristics according to doping content of a Li-doped NiO.sub.x thin film according to an embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0033] The advantages, features, and aspects to be described hereinafter will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter. However, the embodiments should not be construed as being limited to the embodiments set forth herein. Although not specifically defined, all of the terms including the technical and scientific terms used herein have meanings understood by ordinary persons skilled in the art. The terms defined in a generally used dictionary may not be interpreted ideally or exaggeratedly unless clearly defined. In addition, unless explicitly described to the contrary, the word comprise, and variations such as comprises or comprising, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

[0034] Further, the singular includes the plural unless mentioned otherwise.

[0035] In the drawings, the thickness of layers, films, panels, regions, etc. are exaggerated for clarity. Like reference numerals designate like elements throughout the specification.

[0036] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being on another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being directly on another element, there are no intervening elements present.

[0037] The semiconductor device according to an embodiment is a device based on beta-gallium oxide (-Ga.sub.2O.sub.3), an ultra-wide band gap (UWBG) material, and may have a diode structure, but it is not limited to this structure, and it may achieve high breakdown voltage and low leakage current characteristics through P-N heterojunction.

[0038] FIG. 1 is a cross-sectional view briefly illustrating the structure of a semiconductor device according to an embodiment.

[0039] Referring to FIG. 1, a semiconductor device 10 according to an embodiment includes a substrate 100, an n type layer 200, a p type layer 300, a first electrode 400, and a second electrode 500.

[0040] The substrate 100 may include n type gallium oxide (Ga.sub.2O.sub.3). The n type gallium oxide may be beta-phase of beta-gallium oxide (-Ga.sub.2O.sub.3). The n type gallium oxide may include undoped n type gallium oxide, n type gallium oxide doped with Si or Sn, or a combination thereof, for example, n type gallium oxide doped with Si or Sn may be used.

[0041] The substrate 100 may have a doping concentration of about 110.sup.16 cm.sup.3 to about 110.sup.20 cm.sup.3, for example, about 110.sup.17 cm.sup.3 to about 110.sup.19 cm.sup.3. When the substrate has a doping concentration within the ranges, appropriate values for on-resistance and breakdown voltage characteristics in a trade-off relationship may be secured.

[0042] The substrate 100 may have a thickness of about 100 m to about 700 m, for example, about 200 m to about 700 m.

[0043] The n type layer 200 is disposed as an epitaxial layer on the first surface of the substrate 100.

[0044] The n type layer 200 includes beta-gallium oxide (-Ga.sub.2O.sub.3) as an n type semiconductor material. The beta-gallium oxide may include an undoped beta-gallium oxide, an Si- or Sn-doped beta-gallium oxide, or a combination thereof, for example, the Si- or Sn-doped beta-gallium oxide.

[0045] The n type layer 200 may have a doping concentration of about 110.sup.15 cm 3 to about 110.sup.17 cm.sup.3, for example, about 110.sup.16 cm.sup.3 to about 110.sup.17 cm.sup.3. When the n type layer has a doping concentration within the ranges, appropriate values for on-resistance and breakdown voltage characteristics in a trade-off relationship may be secured.

[0046] The n type layer 200 may have a thickness of about 1 m to about 10 m, for example, about 2 m to about 10 m.

[0047] The p type layer 300 is disposed on the n type layer 200 and includes nickel oxide as a p type semiconductor material. The p type layer 300 is disposed between the n type layer 200 and the first electrode 400 to form an interlayer.

[0048] According to an embodiment, as the p type layer 300 of a p type nickel oxide material is formed to be inserted between the n type layer 200 of an n type beta-gallium oxide material and the first electrode 400 of a metal material, P-N heterojunctions (hetero junctions) are formed on the contacting surface of the n type layer 200 and the p type layer 300, thereby obtaining a semiconductor device having high breakdown voltage and low leakage current characteristics.

[0049] The nickel oxide may be specifically represented by Chemical Formula 1.

M.sub.yNi.sub.1-yO.sub.xChemical Formula 1:

[0050] In Chemical Formula 1, M is a doping element, x is 0.8x1.0, and y is 0y<1.

[0051] The nickel oxide, as shown in Chemical Formula 1, may be undoped NiO.sub.x or NiO.sub.x doped with a doping element.

[0052] Since conductivity of the nickel oxide is caused by a hole state induced by Ni vacancies, in oxygen-rich conditions, energy formation for the Ni vacancies is low, while energy formation for oxygen (O) vacancies is high. Accordingly, the Ni vacancies may be increased by adding impurities such as Li, wherein one hole goes to a balance band, keeping the charge neutral. Accordingly, when the nickel oxide is used to form the p type layer, a carrier concentration may be controlled by adjusting an oxygen content or doping.

[0053] In other words, when NiO.sub.x doped with a doping element is used to form the p type layer 300, the Ni vacancies may be increased to increase the conductivity of the nickel oxide, and the carrier concentration may be controlled, exhibiting more excellent high breakdown voltage and low leakage current characteristics.

[0054] The doping element may include a monovalent element, a divalent element, or a combination thereof. The monovalent element may include Li, K, Cu, Ag, Cs, or a combination thereof, for example, Li may be used. The divalent element may include Mg, Ca, Sr, Ba, or a combination thereof.

[0055] The doping element may have a content indicated by y, which is about 0y<1, for example, about 0<y<1, or for example about 0.06y0.1. When a nickel oxide doped with the content ranges is used to form a p type layer, conductivity and a carrier concentration may be increased, securing more excellent high breakdown voltage and low leakage current characteristics.

[0056] A thickness of the p type layer 300 may be about 10 nm to about 300 nm, for example, about 50 nm to about 300 nm.

[0057] The first electrode 400 is disposed on the p type layer 300 in the top of the substrate 100 and may be an anode.

[0058] The first electrode 400 may include a metal of Ni, Au, Ag, or a combination thereof, and for example, Ni metal may be used.

[0059] The first electrode 400 may have a single-layer or a multi-layer structure.

[0060] The second electrode 500 may be disposed at the bottom of the substrate 100, that is, on the second surface of the substrate 100, and may be a cathode.

[0061] The second electrode 500 may include metals such as Ti, Au, Al, Mo, or a combination thereof, and for example, metals such as Ti and Au may be used.

[0062] The second electrode 500 may have a single-layer or a multi-layer structure, and as for the multi-layer structure, a second electrode may include, for example, a Ti metal layer and an Au metal layer.

[0063] The above semiconductor device may exhibit high breakdown voltage and low leakage current characteristics by inserting the p type layer of a nickel oxide material between the n type layer of a -Ga.sub.2O.sub.3 material and the first electrode of a Ni metal to form P-N heterojunctions on the interface thereof. Accordingly, the beta-gallium oxide (-Ga.sub.2O.sub.3)-based device may realize high performance in a simple process, which may lead to developing a beta-gallium oxide (-Ga.sub.2O.sub.3)-based device with various device structures including a junction FET (field effect transistor) as well as Schottky types and MOS (metal oxide semiconductor) types.

[0064] The semiconductor device can be manufactured in the following manner.

[0065] A substrate 100 is prepared, an n type layer 200, a p type layer 300, and a first electrode 400 are sequentially formed on the first surface of the substrate 100, and the second electrode 500 is formed on the second surface of the substrate 100.

[0066] For example, the second electrode 500, the substrate 100, the n type layer 200, the p type layer 300, and the first electrode 400 are sequentially deposited to form a desired structure through a lift-off process or an etching process.

[0067] The p type layer 300 may be formed by a radio frequency (RF) sputtering process.

[0068] In the RF sputtering process, an injected oxygen partial pressure may be about 5% to about 30% or, for example, about 10% to about 30%. When oxygen is injected within the ranges, the conductivity and carrier concentration of the nickel oxide may be controlled to exhibit more excellent high breakdown voltage and low leakage current characteristics.

[0069] According to the aforementioned method of manufacturing a semiconductor device, a semiconductor device having high performance such as low leakage current and high breakdown voltage characteristics in a simple process may be manufactured.

[0070] Hereinafter, the embodiments are illustrated in more detail with reference to examples. However, these examples are exemplary, and the scope of the claims is not limited thereto.

Example 1

[0071] With the same structure as in FIG. 1, a semiconductor device was manufactured by sequentially forming an n type layer 200, a p type layer 300, and a first electrode 400 on the first surface of a substrate 100, while forming a second electrode 500 on the second surface of the substrate 100.

[0072] Herein, the substrate 100 was prepared by using Sn-doped n type Ga.sub.2O.sub.3 to have a doping concentration of 4.310.sup.18 cm.sup.3 and a thickness of 642 m. The n type layer 200 was prepared by using Si-doped n type -Ga.sub.2O.sub.3 to have a doping concentration of 3.510.sup.16 cm.sup.3 and a thickness of 10 m. The p type layer 300 was prepared by using undoped NiO.sub.x to have a thickness of 300 nm. The first electrode 400 was an anode prepared by using a Ni metal to have a thickness of 100 nm. The second electrode 500 was a cathode prepared by forming a 160 nm-thick Au metal layer and a 20 nm-thick Ti metal layer on the Au metal layer to have a multi-layer structure.

[0073] The p type layer was formed through a RF sputtering process and specifically through deposition by injecting 20% of an oxygen partial pressure into a NiO (Ni:O=1:1) target. As a result of X-ray photoelectron spectroscopy (XPS) analysis, the formed NiO thin film had 49.59 atom % of nickel (Ni) and 50.41 atom % of oxygen (O), which had an atomic ratio of about 1:1 and thus confirmed that the NiO thin film was stable.

Example 2

[0074] A semiconductor device was manufactured in the same manner as in Example 1 except that the p type layer 300 was prepared by using Li-doped NiO.sub.x.

Comparative Example 1

[0075] A semiconductor device was manufactured in the same manner as in Example 1 except that the p type layer 300 was not formed.

Evaluation 1: Electrical Characteristics of Nickel Oxide Thin Films

[0076] (1) In order to evaluate electrical characteristics of an undoped NiO.sub.x thin film used for forming a p type layer in Example 1, an undoped NiO.sub.x thin film was deposited on a slide glass through a RF sputtering process, while increasing the oxygen content, and then measured with respect to electrical characteristics, and the results are shown in FIGS. 2A to 2C.

[0077] FIG. 2A is a graph showing a carrier concentration for the undoped NiO.sub.x thin film according to an embodiment, FIG. 2B is a graph showing mobility for the undoped NiO.sub.x thin film according to an embodiment, and FIG. 2C is a graph showing resistivity of the undoped NiO.sub.x thin film according to an embodiment.

[0078] Referring to FIG. 2A, as the oxygen content was increased, the undoped NiO.sub.x thin film showed a tendency that the carrier concentration was increasing but then, converging. Referring to FIG. 2B, mobility of the undoped NiO.sub.x thin film significantly decreased from an oxygen content of 1 sccm to 2 sccm but increased again from 3 sccm. Referring to FIG. 2C, resistivity of the undoped NiO.sub.x thin film significantly decreased beyond an oxygen content of 1 sccm but from 2 sccm decreased to less than 1 cm.

[0079] (2) In order to evaluate electrical characteristics of the Li-doped NiO.sub.x thin film used for forming a p type layer in Example 2, a Li-doped NiO.sub.x thin film was deposited on a slide glass through a RF sputtering process, while increasing an oxygen content, and then evaluated with respect to electrical characteristics through a hall effect measurement method, and the results are shown in FIGS. 3A to 3C.

[0080] FIG. 3A is a graph showing a carrier concentration for the Li-doped NiO.sub.x thin film according to an embodiment, FIG. 3B is a graph showing mobility for the Li-doped NiO.sub.x thin film according to an embodiment, and FIG. 3C is a graph showing resistivity of the Li-doped NiO.sub.x thin film according to an embodiment.

[0081] Referring to FIG. 3A, as oxygen was increased, the carrier concentration of the Li doped NiO.sub.x thin film increased but was controlled within a range of 110.sup.18 cm.sup.3 to 110.sup.22 cm.sup.3. Referring to FIG. 3B, the mobility of the Li-doped NiO.sub.x thin film tended to decrease, while the oxygen content was increased. Referring to FIG. 3C, the resistivity of the Li-doped NiO.sub.x thin film was reduced to less than 1 cm during the oxygen injection.

Evaluation 2: Optical Properties of Nickel Oxide Thin Films

[0082] (1) In order to evaluate optical characteristics of the undoped NiO.sub.x thin film for forming a p type layer in Example 1, a NiO.sub.x thin film was formed through RF sputtering and then measured with respect to transmittance of through UV-visible spectroscopy, and the results are shown in FIGS. 4A to 4E.

[0083] FIGS. 4A to 4E are graphs showing the bandgap according to oxygen partial pressure for an undoped NiO.sub.x thin film of Example 1, respectively. FIGS. 4A to 4E sequentially show bandgaps when injected under the oxygen partial pressure of 0%, 5%, 10%, 15%, and 20% during the sputtering process.

[0084] Referring to FIGS. 4A to 4E, as a result of calculating the bandgaps through the measured transmittance, the deposited NiO.sub.x thin film turned out to have a bandgap of 3.35 eV to 3.58 eV, wherein as the oxygen content was increased, the bandgap tended to decrease.

[0085] (2) In order to examine optical characteristics of the Li-doped NiO.sub.x thin film for using a p type layer in Example 2, a Li-doped NiO.sub.x thin film was formed through RF sputtering and then measured with respect to transmittance by using a UV-visible spectrometer, and the results are shown in FIGS. 5A to 5E.

[0086] FIGS. 5A to 5E are graphs showing a bandgap for the Li-doped NiO.sub.x thin film according to an embodiment. FIGS. 5A to 5E sequentially show bandgaps when injected under the oxygen partial pressure of 0%, 5%, 10%, 20%, and 30% during the sputtering process.

[0087] Referring to FIGS. 5A to 5E, as a result of calculating the bandgaps through the measured transmittance, the deposited Li-doped NiO.sub.x thin film turned out to have a bandgap of 3.37 eV to 3.54 eV, wherein as the oxygen content was increased, the bandgap tended to decrease.

Evaluation 3: Electrical Characteristics of Semiconductor Devices

[0088] FIGS. 6A to 6C are graphs showing current characteristics of the semiconductor devices according to Examples 1 and 2 and Comparative Example 1. FIGS. 6A and 6B sequentially show a case of forward bias, and FIG. 6C shows a case of reverse bias.

[0089] Referring to FIGS. 6A and 6B, comparing current characteristics of Comparative Example 1 having no p type layer such as a SBD (Schottky barrier diode) type, Example 1 whose p type layer was formed of undoped NiO.sub.x, and Example 2 whose p type layer was formed of Li-doped NiO.sub.x, a current in a forward region moved to the right depending on presence or absence of the p type layer formed of NiO.sub.x. In addition, referring to FIG. 6C, in the reverse region, a breakdown voltage increased in Examples 1 and 2, compared with Comparative Example 1, but a leakage current significantly decreased.

[0090] FIG. 7 is a graph showing on-resistance characteristics of the semiconductor devices according to Examples 1 and 2 and Comparative Example 1.

[0091] Referring to FIG. 7, Comparative Example 1 and Examples 1 and 2 exhibited on-resistance of 0.184 m.Math.cm.sup.2, 52.01 m.Math.cm.sup.2, and 6.71 m.Math.cm.sup.2 at 2 V, and at 3 V, on-resistance of 0.097 m.Math.cm.sup.2, 0.215 m.Math.cm.sup.2, and 0.067 m.Math.cm.sup.2. In other words, Comparative Example 1 exhibited the lowest on-resistance at 2 V, but Example 2 exhibited lower on-resistance at 3 V than Comparative Example 1. The reason is that since Examples 1 and 2, in which P-N heterojunctions were formed by inserting a p type layer, exhibited a decrease in Ni contact resistance, as a voltage was increased, the on-resistance decreased, improving a current and thereby reducing conductivity loss.

[0092] Accordingly, when a p type layer formed of NiO.sub.x was inserted on the interface between the n type layer and the electrode, a breakdown voltage was increased, improving the on-resistance characteristics. Accordingly, conductivity may be inferred to be effectively controlled by doping NiO.sub.x with Li to substitute Ni sites and thus to produce LiNi receptors or supplying reactive oxygen during deposition of the NiO thin film to induce formation of empty spaces in Ni.

[0093] FIGS. 8A to 8C are graphs showing the electrical characteristics of the semiconductor devices according to Examples 1 and 2 and Comparative Example 1. FIG. 8A shows a Schottky barrier height (SBH), FIG. 8B shows an ideality factor, and FIG. 8C shows the on-resistance. Specifically, the electrical characteristics of the semiconductor devices according to Examples 1 and 2 and Comparative Example 1 are shown in Table 1.

TABLE-US-00001 TABLE 1 V.sub.on R.sub.on @ 2V Ideality (V) (m .Math. cm.sup.2) B.V. (V) factor (n) SBH (eV) Comparative 1.52 0.184 552 1.67 1.10 Example 1 Example 1 2.83 52.01 807 2.07 1.39 Example 2 2.57 6.71 974 2.65 1.15

[0094] Referring to FIGS. 8A to 8C and Table 1, Examples 1 and 2, where P-N heterojunctions were formed by inserting a p type layer, exhibited excellent electrical characteristics, compared with Comparative Example 1 having no p type layer.

Evaluation 4: Electrical Characteristics According to Doping Content of Nickel Oxide Thin Film

[0095] FIG. 9 is a graph showing electrical characteristics according to doping content of a Li-doped NiO.sub.x thin film according to an embodiment. Specifically, the electrical characteristics according to a doping content of the Li-doped NiO.sub.x thin films according to an embodiment are shown in Table 2.

[0096] Li-doped NiO.sub.x is expressed by Li.sub.yNi.sub.1-yO.sub.x, wherein y indicates a Li doping content (concentration), d indicates a thickness, indicates conductivity, E.sub.a indicates a bandgap, S indicates conductivity, p indicates a hole carrier concentration, indicates hole effect mobility, and T indicates transmittance in a visible light region in Table 2.

TABLE-US-00002 TABLE 2 d E S p T y (nm) (S .Math. cm.sup.1) (eV) (V .Math. K.sup.1) (cm.sup.3) (cm.sup.2 . V.sup.1 . s.sup.1) (%) 0 31 87.3 0.006 32 0.10 0.224 649 5.90 10.sup.19 0.011 80.9 0.03 31 2.7 0.185 485 3.94 10.sup.20 0.047 66.6 0.06 29 6.6 0.182 297 3.31 10.sup.21 0.023 54.9 0.09 19 11.2 0.166 239 6.13 10.sup.21 0.025 44

[0097] Referring to FIG. 9 and Table 2, as the Li doping content was increased, conductivity and a carrier concentration of a nickel oxide tended to increase, wherein its increase rate became larger from y of 0.06.

[0098] While embodiments of this invention have been described in connection with what is presently considered to be practical example embodiments, it is to be understood that the embodiments of invention are not limited to the disclosed embodiments. On the contrary, they are intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0099] The following reference identifiers may be used in connection with the drawings to describe various features of embodiments. [0100] 10: semiconductor device [0101] 100: substrate [0102] 200: n type layer [0103] 300: p type layer [0104] 400: first electrode [0105] 500: second electrode