Abstract
There is provided a high dielectric film including amorphous hydrocarbon of which a dielectric constant is 10 or more. A leakage current of the high dielectric film is 1 A/cm.sup.2 or less, and an insulation level is 1 MV/cm or more. Rms surface roughness of the high dielectric film is 20 nm or less.
Claims
1. A high dielectric film, comprising: amorphous hydrocarbon of which a dielectric constant is 10 or more.
2. The high dielectric film of claim 1, wherein a leakage current of the high dielectric film is 1 A/cm.sup.2 or less, and an insulation level is 1 MV/cm or more.
3. The high dielectric film of claim 1, wherein rms surface roughness of the high dielectric film is 20 nm or less.
4. A high dielectric film manufactured by comprising steps of: (A) positioning a substrate within a plasma reactor; (B) injecting a first gas including a hydrocarbon gas and a second gas including a hydrogen gas into the reactor; and (C) generating plasma within the reactor, thereby growing a hydrocarbon thin film, wherein any one of a temperature, a pressure, a flow rate of the first gas, a flow rate of the second gas, and plasma intensity of the reactor is controlled in order that the hydrocarbon thin film is the hydrocarbon thin film having a dielectric constant of 10 or more.
5. The high dielectric film of claim 4, wherein the reactor is the reactor for plasma-assisted chemical vapor deposition, inductively coupled plasma chemical vapor deposition, or electron cyclotron resonance chemical vapor deposition.
6. The high dielectric film of claim 4, wherein a temperature of the reactor is controlled in a range of 20° C.˜700° C.
7. The high dielectric film of claim 4, wherein flow rates of the first gas and the second gas are controlled in order that a volume ratio of the hydrocarbon gas of the first gas and the hydrogen gas of the second gas is 100:1˜1:50.
8. The high dielectric film of claim 4, wherein a pressure of the reactor is controlled in a range of 0.1 Torr˜10 Torr.
9. The high dielectric film of claim 4, wherein the plasma intensity is controlled in a range of 100 W˜1,000 W.
10. The high dielectric film of claim 4, wherein the substrate is a semiconductor substrate or a metal substrate.
11. The high dielectric film of claim 10, wherein it is grown and is transferred on the metal substrate.
12. A semiconductor device comprising the high dielectric film of claim 1.
13. A capacitor comprising the high dielectric film of claim 1.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is schematic diagrams and TEM images of carbon-based thin films synthesized at various deposition temperatures.
[0035] FIG. 2 is Raman spectra of carbon-based thin films synthesized at various deposition temperatures.
[0036] FIG. 3 is EELS spectra of carbon-based thin films synthesized at various deposition temperatures.
[0037] FIG. 4 is XPS spectra and EXAFS spectra of amorphous hydrocarbon thin films synthesized according to an example of the present disclosure.
[0038] FIG. 5 is FTIR spectra of an amorphous hydrocarbon thin films synthesized according to an example of the present disclosure.
[0039] FIG. 6 is secondary ion mass spectrometry results of amorphous hydrocarbon thin films synthesized according to an example of the present disclosure.
[0040] FIG. 7 is a schematic diagram of a MIS device including a high dielectric film according to an example of the present disclosure.
[0041] FIG. 8 is a graph illustrating an electrical properties of high dielectric films synthesized at various deposition temperatures.
[0042] FIG. 9 is of high dielectric films synthesized at various hydrocarbon gas flow rates.
[0043] FIG. 10 is AFM images of a high dielectric film according to an example of the present disclosure.
[0044] FIG. 11 is a C-V curve of a MIS device including a high dielectric film according to an example of the present disclosure.
DETAILED DESCRIPTION
[0045] Hereinafter, referring to accompanied examples, the present disclosure is more specifically described. However, these examples are only examples for easily explaining a content and range of the technical spirit of the present disclosure and the technical range of the present disclosure is not limited or changed by the examples. Based on these examples, it is natural that various variations and changes are possible for those skilled in the art within a range of the technical spirit of the present disclosure.
EXAMPLES
Example 1: Manufacture of a Hydrocarbon Thin Film According to a Deposition Temperature
[0046] Under conditions below, a hydrocarbon thin film was deposited on a Si wafer or a Si/SiO.sub.2/Ag (200 nm) substrate using a CH.sub.4 gas and a hydrogen gas by Inductively-Coupled Plasma Chemical Vapor Deposition (ICP CVD). Specifically, 1 sccm of a CH.sub.4 gas and 100 sccm of a mixture gas(10% of hydrogen) of hydrogen and Ar were injected into a reactor, wherein a pressure was fixed at 1 Torr, and plasma power was fixed at 600 W.
[0047] At deposition temperatures of 50° C., 400° C., 700° C., or 950° C., a thin film was grown for 5 minutes to manufacture a hydrocarbon thin film. A thin film deposited at 950° C. was deposited on a copper substrate to grow graphene.
[0048] For comparison, graphite was oxidized on chemical solution using a Hummer method and was peeled off to manufacture a graphene oxide thin film.
Example 2: Evaluation of Properties of a Hydrocarbon Thin Film
[0049] 1) Analysis of a Transmission Electron Microscope Image and a Raman Spectrum
[0050] In Example 1, the hydrocarbon thin films grown according to the deposition temperatures were confirmed by an Aberration-corrected Transmission Electron Microscope (TEM) (Titan G2 Cube 60-300 kV, FEI), and results thereof were shown in FIG. 1.
[0051] b of FIG. 1 is a TEM image of the hydrocarbon thin film deposited at 950° C. and shows that carbon atoms have a highly aligned hexagonal arrangement. An internal drawing illustrates a fast Fourier transformed (FFT) digital diffractogram and shows a hexagonal pattern, which is a typical property of high-quality graphene. Also, in a Raman spectrum of FIG. 2, I.sub.2D/I.sub.G exhibits a high value of about 3, and maximum half breadth of a 2D peak is small as 32 cm.sup.−1, so that it could be confirmed that a high-quality graphene thin film was formed in comparative Example 1.
[0052] A thin film of which a deposition temperature was 700° C. showed Nanographite morphology where nanocrystals of hexagonal lattices were partially present within an amorphous matrix(c of FIG. 1). FFT shows a diffused ring shape having dark dots (shown as a circle). An interval of dots is 0.246 nm and it corresponds to carbon allotrope hexagonite.
[0053] When a deposition temperature was more lowered to 400° C. or 50° C., a thin film lost a nano crystallinity and exhibited an amorphous structure, and showed a halo FFT pattern(d and e of FIG. 1).
[0054] All of hydrocarbon thin films of which a deposition temperature is 700° C. or less do not exhibit a meaningful peak at a region of 2000 cm.sup.−1 or more in a Raman spectrum shown in FIG. 2.
[0055] 2) Analysis of an EELS Spectrum
[0056] Using an Electron Energy-Loss Spectroscopy (EELS) device(Gatan Quantum 965 dual), an EELS spectrum was measured with respect to each of thin films manufactured in Example 1. For comparison, an EELS spectrum was also measured with respect to the graphene oxide thin film manufactured by oxidizing graphite in chemical solution using a Hummer method and peeling off it. a and b of FIG. 3 are EELS spectra of a low-loss region and a carbon K-edge region, respectively, wherein bonding aspects of hydrocarbon thin films according to deposition temperatures may be confirmed.
[0057] In a of FIG. 3, a graphene thin film showed two characteristic peaks, wherein a strong peak of 5 eV is a π plasmon peak related to a π.fwdarw.π* transition due to a sp.sup.2 bond of carbon, and a broad peak around 15.5 eV is a (π+σ) plasmon peak. A position of the (π+σ) plasmon peak is in proportion to density of a valence electron, i.e., mass density of a carbon thin film. Compared to graphene thin film grown at 950° C., intensity of the n plasmon peak was significantly reduced on a thin film of which a deposition temperature was lowered to 700° C. Its result matched with that of a TEM image showing that Nanocrystalline hexagonite having a sp.sup.2 bond was present within an amorphous matrix. As a deposition temperature is more lowered, only a (π+σ) plasmon peak is observed on thin films grown at 400° C. and 50° C. respectively. On thin films grown at a temperature of 700° C. or less, energy of a (π+σ) plasmon peak was 25.0 eV, 24.5 eV, and 25.8 eV, respectively, so that it was about 5 eV lower than that of a carbon thin film containing many sp.sup.3 bonds. Accordingly, it was implied that a ratio of sp.sup.3 bonds was very low. It assumes that the reason that energy on a thin film manufactured at 700° C. exhibits a relatively large value is that a crystalline state having high density is contained.
[0058] Presence of a n bond within a thin film may be also confirmed in an EELS spectrum of a carbon K-edge region shown in b of FIG. 3. On a thin film manufactured at 50° C. and 400° C., a first peak is observed at 281 eV, and it corresponds to a transition(1s.fwdarw.π*) from a is state to a π* state over a Fermi level. Based on the fact that a strong peak is observed on a relevant region, it may be confirmed that many sp.sup.2 bonds are present within an amorphous thin film. A second peak is very broadly observed in a region of 290˜305 eV, and it corresponds to a 1s.fwdarw.σ* transition. When a deposition temperature increased to 700° C., a first peak was observed at ˜289.5 eV, so that it could be known that an energy band was narrowed due to nanocrystallization. This peak was more definitely observed in graphene manufactured at 950° C. According to an EELS spectrum, thin films manufactured at 50° C. and 400° C. were very similar with an amorphous hydrocarbon conventionally reported by J. Fink et. al. (Physical Review B, 30, 4713-4718 (1984)). On the contrary, an EELS spectrum of graphene oxides showed a very different aspect compared to hydrocarbon.
[0059] 3) Analysis of XPS and EXAFS Spectra
[0060] A chemical bond characteristic of a hydrocarbon thin film manufactured at 400° C. was confirmed by X-ray Photoelectron Spectroscopy(XPS) and an Extended X-ray Absorption Fine Structure(EXAFS). a of FIG. 4 is a XPS spectrum measured by using MultiLab 2000(Thermo Fisher Scientific) equipment with respect to a thin film manufactured at 400° C. and a thin film formed by etching it with argon plasma of 1 keV intensity for 5˜20 seconds. As confirmed in a of FIG. 4, 285.3 eV corresponding to aliphatic hydrocarbon C.sub.xH.sub.y was observed on the XPS spectrum of the hydrocarbon thin film. Despite etching by using Ar.sup.+ plasma, a position of the relevant peak was not changed, and thus it could be confirmed that a composition of the hydrocarbon thin film was uniform. Despite not additionally illustrating, a position of a peak shifts from 285.0 eV to 284.4 eV according to etching of a surface on a XPS spectrum of a graphene thin film. Various types of hydrocarbon may be absorbed on a graphene surface exposed in the air. As a result, high bonding energy of 285.0 eV is shown. According to etching, if hydrocarbon of the surface is removed, 284.4 eV, which is bonding energy of graphene itself is shown.
[0061] b of FIG. 4 is an EXAFS spectrum of a 1s core level, and c is an EXAFS spectrum around a fermi level. In b of FIG. 4, a strong peak of 285.1 eV corresponds to a peak of 285.3 eV of an XPS spectrum. To confirm that much hydrogen was contained in a hydrocarbon thin film, after manufacturing a thin film, it was heat-treated at 700° C. in-situ. After heat treatment, it was shown that a position of a peak was red-shifted to 284.7 eV and hydrogen was desorbed from aliphatic hydrocarbon C.sub.xH.sub.y. As a result, density of a diffused state of a desorbed specimen increased. As confirmed in c of FIG. 4, it was shown that intensity of a region around a fermi level increased.
[0062] 4) Secondary Ion Mass Spectroscopy
[0063] A spectrum of etching time of 0 second to 8 seconds was obtained while etching a hydrocarbon thin film grown at a deposition temperature of 200° C. to 400° C. according to a method of Example 1, using secondary-ion mass spectrometry(SIMS) equipment (TOF.SIMS M6, IONTOF GmbH) under a high-degree vacuum at room temperature. Its result was illustrated in FIG. 5.
[0064] In FIG. 5, it could be confirmed that a ratio(H/C) of relative intensity of hydrogen versus carbon within a hydrocarbon thin film corresponded to 2˜30. On a SIMS spectrum of a thin film, intensity of H/C was affected by a deposition temperature of the thin film, wherein tendency was shown such that when a deposition temperature increased from 200° C., H/C intensity increased and thus the highest value was exhibited at about 250˜300° C., and when a temperature increased more, it was lowered again. This implies a concentration of hydrogen contained within a thin film is determined by a deposition temperature.
[0065] There was no great difference in H/C intensity of a thin film according to etching time. Therefore, it could be confirmed that a composition of a hydrocarbon thin film was uniform identically to the XPS result.
[0066] 5) Spectroscopic Analysis
[0067] Via spectroscopic analysis of a graphene thin film and a hydrocarbon thin film grown at 400° C., a C—H bond was confirmed. FIG. 6 shows a FRIR spectrum of a thin film grown at a deposition temperature of 400° C. of Example 1. A peak corresponding to C—H stretching of a 2500˜3000 cm.sup.−1 region which was not observed in graphene and a peak corresponding to C—H banding of a 500˜1200 cm.sup.−1 region were observed. Thus, it could be confirmed again that a C—H bond was formed.
Example 3: Evaluation of Electrical Properties of a Hydrocarbon Thin Film
[0068] 1) Electrical Properties According to a Deposition Temperature of a Hydrocarbon Thin Film
[0069] A MIS device having a structure of FIG. 5 using a hydrocarbon thin film as a dielectric layer according to the present disclosure was manufactured, and an electrical property of the hydrocarbon thin film was evaluated. The hydrocarbon thin film was directly grown on a substrate or it was deposited on catalyst metal, and then it was transferred to manufacture a MIS device.
[0070] More specifically, in order to be directly grown on Si 100 wafer, the Si 100 wafer was immersed in 10% of hydrofluoric acid solution. After removing a SiO.sub.2 natural oxide film, it was washed. After inserting the washed substrate into a ICP CVD reactor, the thin film of hydrocarbon was deposited for 30 minutes according to the conditions described in Example 1 except additionally noted conditions. For transfer of the hydrocarbon thin film, after inserting a Si/SiO.sub.2/Ag(200 nm) substrate into an ICV CVD reactor, the hydrocarbon thin film was deposited for 5 minutes in the same condition as that of the direct growth. After the deposited hydrocarbon thin film was spin-coated with PMMA, it was soaked in FeCl.sub.3 aqueous solution to etch an Ag catalyst layer. Accordingly, a hydrocarbon/PMMA film was separated. The separated hydrocarbon/PMMA film was transferred on a Si 100 wafer, and then it was soaked in acetone to remove PMMA. An AFM image of hydrocarbon grown on an Ag catalyst layer or a Si wafer itself where the Ag catalyst layer was not present showed to have a surface which was uniform, did not have a pin hole, and was smooth.
[0071] As described above, an Au electrode having a diameter of 100 μm was formed on the hydrocarbon thin film which was directly grown or transferred on the Si 100 wafer to manufacture a MIS device having a structure of FIG. 7. In Table 1, a thickness and rms roughness of the hydrocarbon thin film, and a dielectric constant in the MIS device measured from the sectional TEM and AFM(Asylum Research, MFP-3D) of the hydrocarbon thin film used in the MIS device were exhibited.
TABLE-US-00001 TABLE 1 Deposition Thin Film rms Dielectric Temperature Thickness Roughness Constant Substrate (° C.) (nm) (nm) (k) Si 400 6.5 1.61 nm 13 Si 350 5.0 90 Si 300 3.1 82 Si 250 2.4 66 Si 200 2.6 19 Si/SiO.sub.2/Ag 600 51.0 30 Si/SiO.sub.2/Ag 500 63.0 61 Si/SiO.sub.2/Ag 400 46.0 3.06 nm 42 Si/SiO.sub.2/Ag 300 9.0 11 Si/SiO.sub.2/Ag 200 3.3 6 Si/SiO.sub.2/Ag 100 1.2 0.4
[0072] FIG. 8 are graphs showing electrical properties measured with respect to the manufactured MIS device. a of FIG. 8 is a C-V curve of the hydrocarbon thin film directly grown on a silicon wafer, wherein .circle-solid. is a value measured from −4 V to 4 V, and o is a value measured from +4 V to −4 V. The most important characteristic in the C-V curve is that hysteresis is less than 5 mV nearly close to 0 in a C-V loop with respect to all specimens. This satisfies a standard (<30 mV) of a high-k gate dielectric. The fact that a transition from accumulation and depletion is fast and hysteresis is very small means that charge density of a thin film and charge density trapped in a thin film and a Si interference is very small. Compared to the above, the MIS device manufactured with the hydrocarbon thin film, which was grown on catalyst metal and then was transferred on a Si substrate exhibited significant hysteresis, wherein transfer from accumulation and depletion was relatively slow (not shown). It is assumed that this is due to deterioration of interfacial properties in a transfer process, and contamination in an etching process of an Ag catalyst thin film during transfer. As confirmed in the internal drawing of a of FIG. 8, compared to the fact that the C-V curve exhibited an ideal shape, flat band voltage of the hydrocarbon thin film slightly shifted to − voltage due to a fixed positive charge. Differences of the flat band voltage among specimen were not great and all of them belonged to a range of −0.3˜0.4 V.
[0073] A dielectric constant(k) of the hydrocarbon thin film may be calculated from the following equation.
C.sub.max=ε.sub.(HC)/t.sub.(HC)
[0074] Here, C.sub.max is an integrated capacitance, ε.sub.(HC) is permittivity of the hydrocarbon thin film, and t.sub.(HC) is a thickness of the hydrocarbon thin film.
[0075] B of FIG. 8 is a graph showing dielectric constants of thin films manufactured at each temperature. Permittivity of the hydrocarbon thin film directly grown on a silicon wafer was maximum 90 and was very excellent compared to 20-30 of a dielectric constant of Hf- and Zr-based oxides known as high dielectric gate oxides. As a growth temperature of a thin film increased, a dielectric constant gradually increased and a maximum value of 90 was exhibited at 350° C. When a temperature more increased and arrived at 400° C., permittivity was lowered to 13. Tendency about a thin film growth temperature of the hydrocarbon thin film transferred on a Si wafer was similar with that of the hydrocarbon thin film directly grown. As a deposition temperature increased, a dielectric constant also gradually increased and a maximum value of 61 is arrived at 500° C. Thereafter, when a temperature more increased and arrived at 600° C., it reduced again. It seems that in a hydrocarbon thin film deposited at a low temperature, dipole moments chaotically arranged offset one another, and thus a relatively low k value is exhibited, and as a temperature increases, structuralization of carbon skeleton construction increases and dipole moments also increase, and thus a dielectric constant increases. If arriving at a critical temperature or more, it is difficult to capture hydrogen and hydrocarbon in a dangling bond, and thus a hydrocarbon structure is broken and a characteristic as a high-k dielectric is lost.
[0076] One of important characteristics as a high-k dielectric is that density of a leakage current is to be low and an insulation level is to be high. c of FIG. 8 is a I-V curve, wherein thin films manufactured at 300° C. and 350° C. of which dielectric constants are 82 and 90, respectively had a leakage current of 0.15 A/cm.sup.2 at 1V with respect to equivalent oxide film thicknesses of 0.15 and 0.2 nm. A leakage current exhibits the lowest value on a thin film deposited at 400° C., wherein its thickness is about 6.5 nm and the relevant thin film is the thickest among thin films. All specimens did not exhibit a breakdown phenomenon up to 5V, so that it could be known that an insulation level had high values as at least 5 MV/Cm or more, and generally 10 MV/Cm or more. These leakage currents and insulation levels are at least identical to or more excellent than high-k oxides recently reported.
Example 4: Evaluation of Properties of a Hydrocarbon Thin Film According to a Composition of a Reaction Gas
[0077] Except that a deposition temperature was fixed at 350° C. and an injecting speed of a CH.sub.4 gas was changed to 1˜20 sccm, a hydrocarbon thin film was manufactured by the same process as that of manufacturing the hydrocarbon thin film of Example 1. Using the thin film, the same MIS as that of Example 3 was manufactured, wherein an electric property of the thin film was evaluated together with a physical property thereof.
[0078] FIG. 9 is a graph showing its result, wherein it may be confirmed that a ratio of a hydrocarbon gas and hydrogen affects an electric property and a physical property of the manufactured hydrocarbon thin film. In particular, as predictable, as supply of a hydrocarbon gas increased, a growth speed of the thin film increased, and thus when a ratio of a generated CH.sub.4 gas was the highest, a thickness of the thin film was the thickest. Roughness of the thin film is one of important factors which determine an interfacial property upon manufacturing a device. As a ratio of the CH.sub.4 gas increased, roughness gradually increased but when it increased more than 10 sccm, a surface roughness was significantly reduced. In the case of 20 sccm, the smoothest thin film was formed. A dielectric constant of the thin film also exhibited tendency of gradually increasing as a ratio of a CH.sub.4 gas increases.
[0079] FIG. 10 is an AFM image of a dielectric film deposited with a reaction gas of 100 sccm of an Ar gas including 20 sccm of a CH.sub.4 gas and 10% of a H.sub.2 gas under conditions of 350° C., 600 W, and 1 torr. It was confirmed that a film on which a pin hole was not present and which was very uniform was grown. A rms surface roughness is very low as 0.059 nm, so that it may excellently applies to a device such as MIS or MIM. A dielectric constant of the thin film gradually increased as plasma power increased.
[0080] FIG. 11 is a C-V curve of an MIS device manufactured by using the high dielectric film. On the C-V curve, there were nearly no C-V hysteresis and flat-band voltage shift. Accordingly, it could be confirmed that an excellent MIS structure where there was nearly no defect on an interface of a hydrocarbon thin film was formed.
