Oxide film quality evaluation method

Abstract

To provide an oxide film quality evaluation method that evaluates and measures oxygen vacancies in an oxide film deposited under the same condition as that used in an actual device.SOLUTION: A method includes preparing a sample 101 in which a conductive layer 16, a semiconductor layer 12, an oxide film to be measured 14, and a conductive film 15 made of a hydrogen catalyst metal or a hydrogen catalyst alloy are sequentially laminated, and measuring the quality of the oxide film 14 to be measured, especially the oxygen vacancies in the film by measuring the C-V between the conductive layer 16 and a conductive film 15 in a hydrogen atmosphere or measuring the capacitance at a bias of 0 V, etc.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for evaluating the quality of an oxide film. Here, the evaluation of the quality of an oxide film in the present invention means measuring the amount of oxygen vacancies in the oxide film and evaluating the amount of oxygen vacancies as the film quality. [Background technology]

[0002] In semiconductor elements such as MOSFETs, the quality of oxide films, including gate insulating films, is extremely important because it directly affects device performance and reliability. For example, various methods for evaluating the quality of oxide films have been disclosed in Patent Documents 1 and 2. However, it is difficult to evaluate oxygen vacancies in oxide films. As disclosed in Non-Patent Document 1, there are reports on evaluating the quality of oxide films by depositing a thick oxide film and using optical techniques such as photoluminescence, but in order to obtain the required measurement sensitivity, the oxide film must be deposited very thick. This results in evaluations under conditions different from those of actual devices, which causes problems with the reliability of the measurements. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-303264 [Patent Document 2] JP 2006-332690 A [Non-patent literature]

[0004] [Non-Patent Document 1] Jie Ni,Qin Zhou,Zhengcao Li,and Zhengjun Zhang,Appl.Phys.Lett.,93,011905(2008) Summary of the Invention [Problem to be solved by the invention]

[0005] The problem that the present invention is to solve is to provide a method capable of evaluating and measuring oxygen vacancies in an oxide film deposited under the same conditions as those applied to an actual device. [Means for solving the problem]

[0006] The configuration of the present invention is shown below. (Configuration 1) preparing a sample in which a conductive layer, a semiconductor layer, a measurement target oxide film, and a conductive film made of a hydrogen catalyst metal or a hydrogen catalyst alloy are sequentially laminated; A method for evaluating film quality of an oxide film, comprising: measuring an electric capacitance between the conductive layer and the conductive film in a hydrogen atmosphere. (Configuration 2) 2. The method for evaluating the quality of an oxide film according to claim 1, wherein the volume concentration of the hydrogen atmosphere is 100 ppm or more and 100% or less. (Configuration 3) 3. The method for evaluating the quality of an oxide film according to claim 1 or 2, wherein the hydrogen partial pressure of the hydrogen atmosphere is 1 kPa or more and 10 atm or less. (Configuration 4) 4. The method for evaluating film quality of an oxide film according to any one of claims 1 to 3, wherein the conductive film contains one or more metals selected from the group consisting of platinum, palladium, iridium, ruthenium, and nickel. (Configuration 5) 5. The method for evaluating film quality of an oxide film according to any one of claims 1 to 4, wherein the conductive film has a thickness of 5 nm or more and 1 μm or less. (Configuration 6) 6. The method for evaluating film quality of an oxide film according to any one of claims 1 to 5, wherein the semiconductor layer is made of one or more selected from the group consisting of GaN, Si, GaAlN, GaAs, ZnO, SiC, and Ga2O3. (Configuration 7) 7. The method for evaluating film quality of an oxide film according to any one of claims 1 to 6, wherein the semiconductor layer has a thickness of 100 nm or more and 1 mm or less. (Configuration 8) 8. The method for evaluating the quality of an oxide film according to any one of claims 1 to 7, wherein the thickness of the oxide film to be measured is 0.1 nm or more and 1 μm or less. (Configuration 9) 9. The method for evaluating the quality of an oxide film according to any one of claims 1 to 8, further comprising applying an electric field to the oxide film to be measured. (Configuration 10) 9. The method for evaluating film quality of an oxide film according to any one of claims 1 to 8, further comprising applying a bias voltage between the conductive layer and the conductive film. (Configuration 11) 11. The method for evaluating the quality of an oxide film according to claim 10, wherein the bias is −20 V or more and 10 V or less. (Configuration 12) 12. The method for evaluating the quality of an oxide film according to any one of claims 1 to 11, wherein the capacitance measurement is performed in a temperature environment of 23°C or higher and 200°C or lower. Effect of the Invention

[0007] According to the present invention, there is provided a method for evaluating and measuring oxygen vacancies in an oxide film deposited under the same conditions as those applied to an actual device. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view showing the configuration of a sample 101. [Diagram 2] FIG. 13 is a characteristic diagram showing the bias start voltage dependence of the CV characteristics of the HfO2-δ film. [Diagram 3] FIG. 1 is a characteristic diagram showing the CV characteristics of Sample 101. [Figure 4] FIG. 2 is a characteristic diagram showing the response characteristics of the sample 101. [Diagram 5] FIG. 13 is a characteristic diagram showing the dependency of capacitance on an oxide film to be measured at a bias of 0 V. [Figure 6] FIG. 13 is a characteristic diagram showing the dependency of the relative charge density in the film on the oxide film to be measured. [Figure 7] FIG. 1 is a characteristic diagram showing the recovery characteristic (initialization characteristic) of the sample 101. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] <Embodiment 1> In the first embodiment, the configuration and measurement principle of the present invention will be described.

[0011] <Sample structure and measurement method> In embodiment 1, a sample 101 having a structure in which a conductive layer 16 shown in FIG. 1, a semiconductor layer 13 consisting of a semiconductor substrate 11 and a semiconductor layer 12, a measured oxide film 14, and a conductive film 15 are sequentially stacked is used, and sample 101 is subjected to CV measurement in a hydrogen gas environment or capacitance measurement at a bias of 0 V or the like to evaluate the film quality of the measured oxide film 14, particularly the oxygen vacancies in that film. Here, the conductive layer 16 is not essential, and when the semiconductor substrate 11 has low electrical resistance due to a high concentration of dopant or the like, the semiconductor substrate 11 can be used in place of the conductive layer 16. Moreover, the semiconductor layer 13 does not necessarily have to be made up of the semiconductor substrate 11 and the semiconductor layer 12, and can be made up of only the semiconductor layer 12.

[0012] There is no particular limitation on the thickness of the oxide film 14 to be measured, and the thickness is allowed to be 0.1 nm or more and 1 μm or less. The oxide film 14 to be measured may be an oxide film deposited under the same conditions as those applied to an actual device. Furthermore, when the thickness of the oxide film 14 to be measured is within this range, hydrogen atoms generated by catalytic action of hydrogen gas by the conductive film 15 described later are sufficiently trapped in the oxygen-vacant portions of the oxide film 14 to be measured, making it possible to evaluate the film quality with sufficient speed and sensitivity, and also making the recovery time when resetting to the initial state acceptable.

[0013] It is preferable that the oxide film 14 to be measured is formed in contact with the semiconductor layer 13. This is because a virtual image of charges due to atomic hydrogen trapped in oxygen vacancies in the oxide film 14 to be measured, which will be described later, can be sufficiently formed in the semiconductor layer 13.

[0014] The conductive film 15 is a conductive film made of a hydrogen catalytic metal or a hydrogen catalytic alloy, and has the function of converting environmental hydrogen gas into atomic hydrogen through catalytic action, and the function of temporarily storing the generated atomic hydrogen in the conductive film 15 and then supplying the atomic hydrogen to the oxide film 14 to be measured by diffusion.

[0015] Specific examples of metals for the conductive film 15 include platinum (Pt), palladium (Pd), iridium (Ir), ruthenium (Ru) and nickel (Ni), and these metals may be used alone or in combination. Here, the term "composite" refers to one or more selected from the group consisting of composite use in separate locations, laminated use, and use as an alloy. Specific examples of alloys for the conductive film 15 include LaNi5, ReNi5, MgNi, Mg2Ni, and Ce2Ni7. In order to efficiently supply the generated atomic hydrogen to the oxide film 14 to be measured, the conductive film 15 is preferably in direct contact with the oxide film 14 to be measured. The thickness of the conductive film 15 is preferably 5 nm or more and 1 μm or less from the viewpoint of ensuring the functions of efficient generation, occlusion, and diffusive supply of atomic hydrogen to the oxide film 14 to be measured. Methods for forming the conductive film 15 include thermal and electron beam evaporation, sputtering, and resistance heating evaporation.

[0016] As shown in FIG. 1, the semiconductor layer 13 may be made up of multiple layers such as a semiconductor substrate 11 and a semiconductor layer 12, or may be made up of a single layer. The role of the semiconductor layer 13 is to detect hydrogen with high sensitivity by generating charges in the semiconductor layer that correspond to the hydrogen-induced charges generated in the oxide film 14 to be measured. Therefore, the hydrogen gas detection sensitivity is significantly improved compared to when the semiconductor layer is replaced with a conductive layer such as a metal, and as a result, the measurement sensitivity for film quality evaluation is improved. The thickness of the semiconductor layer 13 is preferably from 100 nm to 1 mm, which makes it easy to increase the measurement sensitivity. Specific examples of the semiconductor layer 13 include one or more selected from the group consisting of GaN, Si, GaAlN, GaAs, ZnO, SiC, and Ga2O3.

[0017] The conductive layer 16 is not particularly limited as long as it functions as an electrode that can make ohmic contact with the semiconductor layer 13, and for example, Pt (platinum), Au (gold), Ag (silver), W (tungsten), Pd (palladium), Cu (copper), polysilicon, etc. can be used. Here, when Pt or the like is used, it is preferable to form a thin film of Ti between the conductive layer 16 and the semiconductor layer 13 for the purpose of improving adhesion. In order to make ohmic contact with the semiconductor layer 13, when the substrate is n-type, it is preferable that the metal in contact with the semiconductor layer 13 is a metal with a small work function such as Ti or Al. However, even if the substrate is n-type, most metals are acceptable if the concentration is high.

[0018] During CV measurement to evaluate the film quality of the oxide film 14 to be measured, a hydrogen gas environment is used as described above, with the volume concentration of the hydrogen atmosphere being preferably 100 ppm to 100%, and the hydrogen partial pressure being preferably 1 kPa to 10 atm. If the hydrogen gas environment is within this range, a necessary and sufficient amount of atomic hydrogen is generated by the catalytic action of the conductive film 15, and this is observed filling most of the oxygen-deficient portions of the oxide film 14 to be measured, making it possible to evaluate the film quality with high accuracy.

[0019] <Sample preparation method> The sample 101 can be prepared by the following steps. First, a semiconductor layer 13 is prepared, and the interface of the semiconductor layer is cleaned by washing or the like, and then a measurement target oxide film 14 is formed. At this time, it is preferable to form it under the same conditions as the actual device. Thereafter, a conductive film 15 is formed on the oxide film 14 to be measured by thermal or electron beam deposition, sputtering, or the like, and a conductive layer 16 is formed on the lower surface side of the semiconductor layer 13, thereby completing the sample 101.

[0020] <Measurement principle> The measurement principle of the first embodiment is as follows. Hydrogen gas in the measurement environment is converted to atomic hydrogen by the catalytic action of the conductive film 15, and the generated atomic hydrogen is absorbed by the conductive film 15. The absorbed atomic hydrogen diffuses into the measured oxide film 14 and is trapped in the oxygen-deficient portions of the measured oxide film 14. Here, since the atomic hydrogen is trapped in most of the oxygen-deficient portions, the amount of trapped atomic hydrogen is strongly correlated with the amount of oxygen deficiency. Atomic hydrogen trapped in the oxygen vacancy portion becomes positively charged as a result of interacting with the oxygen vacancy portion. The positively charged atomic hydrogen generates a negative image charge in the semiconductor layer, which shifts the CV characteristic to the negative voltage side. By utilizing this characteristic, the hydrogen gas trapped in the oxygen vacancy portion can be detected and quantified from the voltage shift between the CV characteristic curve obtained by CV measurement in an inert gas environment such as N2 and the CV characteristic curve measured in a hydrogen gas environment, and the oxygen vacancy in the oxide film 14 to be measured can be detected and quantified. A calibration curve can be used for this quantification.

[0021] As a result of detailed investigation of the CV characteristics, it was found that application of an electric field to the oxide film 14 to be measured accelerates the recovery of the sample 101 to its initial state. Since hydrogen present in the oxide film 14 to be measured is positively charged, application of an appropriate electric field can accelerate the desorption process from the oxide film 14 to be measured. The electric field may be applied from outside the sample 101, or may be applied by applying a bias between the conductive film 15 and the conductive layer 16.

[0022] It has become clear from numerous experiments that the bias should preferably be between -20V and 10V. This is because the positively charged hydrogen present in the oxide film 14 to be measured is in a relatively stable state, and there is a threshold value for moving it in an electric field applied from the outside. It is preferable to apply a large electric field within the range in which the oxide film 14 to be measured is not destroyed.

[0023] It is preferable to carry out CV measurements in an environment between 23° C. and 200° C. The higher the temperature, the higher the catalytic efficiency, improving the efficiency of atomic oxygen generation and improving the measurement sensitivity. However, on the other hand, the higher the temperature, the higher the reaction with components other than hydrogen gas, such as water and hydrocarbons, increasing noise, so it is preferable to set the upper limit at 200° C.

[0024] Here, by monitoring the change in the capacitance value before and after the introduction of hydrogen gas under a bias of 0V, the atomic hydrogen trapped in the oxygen vacancy portion can be detected in the form of a positive charge generated in the film. As described above, the positive charge generated in the oxide film 14 to be measured has a strong correlation with the amount of oxygen vacancy. Therefore, by measuring the capacitance between the conductive film 15 and the conductive layer 16 at a bias of 0V before and after the introduction of hydrogen gas, it is possible to detect and measure the amount of oxygen vacancy in the oxide film 14 to be measured, and this method can also be used to evaluate the film quality of the oxide film 14 to be measured. However, this method is suitable when the change portion (slope portion of the curve) of the CV curve under a hydrogen gas environment is near the bias of 0V. When the change portion is far from the bias of 0V, the change in the measurement amount is small, and the measurement sensitivity and accuracy are reduced.

[0025] As described above, this method is based on a new principle of atomic hydrogenation of hydrogen gas, trapping of this atomic hydrogen in oxygen vacancy parts of the oxide film to be measured, and quantifying the effect of the charge generated by the trapping by CV measurement or capacitance measurement with the bias voltage fixed at 0 V or the like, and is a method for evaluating the film quality of oxide films, in particular oxygen vacancies in oxide films, that can be evaluated and measured under the same conditions as those applied to actual devices. EXAMPLES

[0026] Example 1 In Example 1, Sample 101 was produced and its characteristics were evaluated. Hereinafter, an explanation will be given with reference to the drawings.

[0027] <Sample> As shown in FIG. 1, the sample 101 prepared in Example 1 has a structure in which a conductor layer 16 made of Pt (platinum) / Ti (titanium), a semiconductor layer 13 made of a semiconductor substrate 11 and an n-GaN semiconductor layer 12, an oxide film 14 to be measured, and a conductor film 15 made of Pt are laminated in this order.

[0028] Here, the conductive layer 16 is formed by electron beam deposition, and the thicknesses of Pt and Ti are 100 nm and 20 nm, respectively. Ti is a film formed for the purpose of strengthening the adhesion of the conductive layer 16 to the semiconductor substrate 11, and is formed so as to be in contact with the semiconductor substrate 11, and the conductive layer 16 and the semiconductor substrate 11 are in ohmic contact.

[0029] The semiconductor substrate 11 is a free-standing n + -GaN(0001) wafer, thickness 300μm, dislocation density and carrier concentration 10 6 cm -2 and 1×10 18 cm -3 It is. The semiconductor layer 12 is a Si (silicon)-doped GaN homoepitaxial layer formed by metalorganic vapor phase epitaxy, and has a thickness of 5 μm and a Si concentration of 2×10 16 cm -3 It is.

[0030] The oxide film 14 to be measured is Al2O3, HfO 2-δ , and Hf 0.57 S 0.43 O 2-δ Here, δ indicates oxygen vacancy. 2-δ , and Hf 0.57 S 0.43 O 2-δ From an evaluation of the characteristics of a device in which the above is implemented, δ in Example 1 is estimated to be approximately 0.02. Al2O3 was formed by the ALD method using trimethylaluminum (TMA) as a precursor and H2O as an oxidizer gas, and is estimated to have few oxygen vacancies for the following reasons.

[0031] HfO 2-δ As shown in Figure 2, when the voltage on the storage side is gradually increased during CV measurement, the CV curve shifts to the positive voltage side as the voltage increases. 2-δ It is believed that the oxygen vacancies in Al2O3 act as electron traps, and it is expected that there will be a very large number of oxygen vacancies. On the other hand, although oxygen vacancies also exist in Al2O3, no significant difference was observed between HfO and Al2O3 even when the sweep voltage range was changed during CV measurements. 2-δ As shown in Fig. 1, no shift in the CV curve is observed, and the CV curves obtained by changing the range of the sweep voltage all overlap perfectly. 2-δ It is considered that the film has less oxygen vacancies compared to the above.

[0032] HfO 2-δ Hf 0.57 S 0.43 O 2-δ The ALD (Atomic Layer Deposition) method was also used to form the films. The formation temperature was 300°C, and the thickness of both films was 15 nm. When forming these films by the ALD method, the samples were pre-treated by cleaning them with a mixture of sulfuric acid and hydrogen peroxide (H2SO4:H2O2=1:1) to remove organic residues, and then treated with buffered hydrofluoric acid (BHF; HF:NH4F=1:6). These films were then immediately deposited. HfO 2-δ The deposition of Hf was performed using tetrakis(dimethylamino)hafnium as a precursor and O2 plasma. 0.57 S 0.43 O 2-δ HfO 2-δ The layer is a laminate of a SiO2 layer and a SiC layer, with thicknesses of 0.164 nm and 0.134 nm, respectively. The SiO2 layer was formed by the ALD method using tris(dimethylamino)silane and O2 plasma.

[0033] In addition, samples with and without post-deposition annealing (PDA) were prepared for the oxide film 14 to be measured, and the characteristics were evaluated to examine the effect of PDA. The PDA conditions were 800°C for 5 minutes in a N2 atmosphere at 1 atm pressure. 2-δ is monoclinic phase, Hf 0.57 S 0.43 O 2-δ It has been confirmed that the material is amorphous.

[0034] The conductive film 15 is a circular electrode with a thickness of 100 nm formed by electron beam deposition through a shadow mask. -4 cm 2 It is.

[0035] <Sample preparation> Sample 101 was prepared by the following steps. First, a semiconductor substrate 11 having the above specifications was prepared, and an n-GaN semiconductor layer 12 was formed thereon by metalorganic vapor phase epitaxy. After the above cleaning, an oxide film 14 to be measured was formed by the ALD method. Here, as described above, the oxide film 14 to be measured was made of Al2O3, HfO 2-δ , and Hf 0.57 S 0.43 O 2-δ The following three types were evaluated: Thereafter, a 100 nm thick Pt conductive film 15 was formed on the oxide film 14 to be measured, and a Pt (100 nm) / Ti (20 nm) conductive layer 16 was formed on the lower surface of the semiconductor substrate 11 by electron beam evaporation. As a final step, some of the samples were subjected to PMA (Post Meatllization Annealing) at 300° C. for 5 minutes under N2 flow. The size of the finished water sample 101 was about 150 μm in diameter and about 300 μm in height, making it very compact.

[0036] <Electrical characteristic evaluation method> The sample 101 was placed in a measurement chamber made of stainless steel, and its electrical properties were evaluated using a tungsten probe. The measurement chamber in which the sample was placed was evacuated by a dry scroll vacuum pump, and then the sample was passed through the measurement chamber at room temperature (25 °C) and a total pressure of 10.0 kPa (100 mL min -1 ) N2 was introduced to evaluate the CV electrical characteristics in an inert gas environment. After that, instead of N2, a hydrogen-containing gas consisting of 1 vol% H2 and 99 vol% N2 was flowed at a total pressure of 10.0 kPa for 30 minutes, and then CV measurements were performed in a hydrogen-containing gas (1 vol% H2 + 99 vol% N2) environment. Here, the flow rate of the hydrogen-containing gas was 100 mL min -1 It is. The capacitance was determined from CV measurements at 100 kHz. In the bias dependence measurements of CV measurements, the bias voltage was set to 0.1 V in steps, and each step was held for 1 second to perform sweep measurements. In measurements of capacitance at a bias of 0 V, an AC voltage of 100 kHz was applied without applying or sweeping a bias voltage to determine the capacitance.

[0037] <Measurement and Evaluation> The conditions of the samples evaluated are summarized in Table 1.

[0038] [Table 1]

[0039] The results of CV measurements performed on samples A2, B1 and C2 are shown in FIG. The measurement results in an environment where 1 vol% hydrogen gas was added were shifted in the negative ΔV direction compared to the measurement results in the nitrogen gas environment. This is based on the above-mentioned mechanism in which atomic hydrogen is generated by the catalytic action of the conductive film 15 in the presence of hydrogen gas, and the generated atomic hydrogen is trapped in the oxide film 14 to be measured, causing the oxide film 14 to have an electric charge. In addition, even without performing CV measurement with a sweep of the voltage, for example, by not applying a bias and keeping the voltage at 0 V, atomic hydrogen can be detected by monitoring the change in capacitance before and after hydrogen introduction, and therefore the amount of oxygen vacancy can be evaluated.

[0040] Next, the responsiveness of this method was examined for samples A2, B1, and C2, and the results are shown in FIG. 4. In this measurement, the bias voltage was fixed at 0 V. The oxide film 14 to be measured was Al2O3 (A2) and HfO 2-δ (B1) for about 3 minutes, Hf 0.57 S 0.43 O 2-δ In the case of (C2), the capacitance was saturated in about 1 minute, which shows that the measurement method of the present invention has excellent responsiveness.

[0041] FIG. 5 is a graph comparing the capacitance of each sample in a nitrogen gas environment and a 1 vol% hydrogen gas environment when the bias voltage is fixed at 0 V. The larger the measured value in the hydrogen gas environment compared to the nitrogen gas environment, the more atomic hydrogen is detected, and therefore the greater the amount of oxygen vacancies. As a result, it is found that the capacitance is larger in the hydrogen gas environment for all samples, and that each measured oxide film 14 has oxygen vacancies. In particular, the capacitance of the Hf 0.57 S 0.43 O 2-δ Sample (C2) was shown to have a very high oxygen vacancy.

[0042] According to FIG. 5, the samples A1 and A2 in which Al2O3 was used as the metal oxide film 14 were better than the samples B1 and B2 in which HfO 2-δ The change in capacitance from the nitrogen gas environment to the hydrogen gas environment is larger than that of the HfO 2-δ has a larger amount of oxygen vacancy than Al2O3.

[0043] This is for the following reasons. FIG. 5 is a graph showing the change in capacity at 0 V in FIG. 3 (from a nitrogen environment to a hydrogen-added environment). As is clear from FIG. 3(a), when Al2O3 is used, 0 V happens to be in the region where the capacitance change is large. On the other hand, as is clear from FIG. 3(b), when HfO 2-δRegarding , 0V is in the region where the capacitance change is small. This is HfO 2-δ In the case of HfO, the CV curve is shifted to the positive voltage direction compared to Al2O3, not because of a large amount of oxygen vacancy. In fact, when the capacity change is converted to a voltage change (ΔV), as is clear from Table 2, the value is 1-δ is larger than Al2O3. From the above, Al2O3 is superior to HfO in Fig. 5. 2-δ The larger change is merely apparent. The actual voltage change (ΔV) and the amount of charge in the membrane calculated from that value are HfO 2-δ Therefore, the amount of oxygen vacancy is larger in HfO 2-δ is more abundant than Al2O3.

[0044] The results of the CV measurement and the dielectric constant of the oxide film 14 to be measured are summarized in Table 2. Table 2 also lists the relative charge density in the oxide film calculated from these results. FIG. 6 shows the relative charge density. Samples B1, B2, C1, and C2, which are hafnium-containing oxide films, have a high relative charge density, and the Hf 0.57 S 0.43 O 2-δ It can be seen that sample (C2) has a particularly high relative charge density.

[0045] [Table 2]

[0046] As the initialization characteristic of sample 101, that is, the recovery characteristic to the initial state, the sample was placed in a hydrogen gas environment, then switched to a dry air environment, and the change in capacitance over time was measured. The results are shown in Figure 7. Here, the bias voltage was fixed at 0 V, and the measurement was performed at room temperature (25°C). The samples measured were B1, B2, C1, and C2.

[0047] HfO without PDA treatment 2-δThe sample B1, which has the oxide film 14 of HfO as the measurement target, recovered its capacitance after 10 minutes to the same as the initial state measured in a nitrogen environment, and it is understood that the sample B1 has excellent recovery characteristics. 2-δ Sample B2, in which the film was subjected to a PDA treatment at 800° C., also has good recovery characteristics, although not as good as those of sample B1. In addition, Hf without PDA treatment 0.57 S 0.43 O 2-δ In the case of the sample C1 having the oxide film 14 to be measured, the capacitance recovered after 10 minutes to the same level as the initial state measured in the nitrogen environment, and it is found that the sample C1 has excellent recovery characteristics. On the other hand, Hf 0.57 S 0.43 O 2-δ Sample C2, which was subjected to a PDA treatment at 800°C, did not have sufficient recovery properties.

[0048] [Table 3] [Industrial Applicability]

[0049] Evaluation of oxide film quality is essential for improving device performance, reliability, and quality control of semiconductor elements such as MOSFETs. The quality of oxide films is highly dependent on the formation method, formation conditions, and formation environment. For this reason, it is desirable to evaluate the film quality of oxide films deposited under the same conditions as those used in devices. The method for evaluating the quality of an oxide film of the present invention is a method for evaluating oxygen vacancies, which are difficult to measure, and is a method that makes it possible to evaluate a film deposited under the same conditions as those applied to a device. Therefore, it is believed that the method for evaluating the quality of an oxide film of the present invention will greatly contribute to improving the device performance and reliability of semiconductor elements and to quality control. [Explanation of symbols]

[0050] 11: Semiconductor substrate (n + -GaN) 12: Semiconductor layer (n-GaN) 13: Semiconductor layer 14: Oxide film to be measured 15: Conductor film (Pt) 16: Conductor layer (Pt / Ti) 101: Sample

Claims

1. Preparing a sample in which a conductive layer, a semiconductor layer, a oxide film to be measured, and a conductive film made of a hydrogen catalyst metal or a hydrogen catalyst alloy are sequentially laminated; A method for evaluating the film quality of an oxide film, comprising measuring the capacitance between the conductive layer and the conductive film in a hydrogen atmosphere.

2. The method for evaluating the film quality of an oxide film according to Claim 1, wherein the volume concentration of the hydrogen atmosphere is 100 ppm or more and 100% or less.

3. The method for evaluating the film quality of an oxide film according to Claim 1 or 2, wherein the hydrogen partial pressure of the hydrogen atmosphere is 1 kPa or more and 10 atmospheres or less.

4. The method for evaluating the film quality of an oxide film according to Claim 1, wherein the conductive film contains one or more metals selected from the group consisting of platinum, palladium, iridium, ruthenium, and nickel.

5. The method for evaluating the film quality of an oxide film according to Claim 1, wherein the thickness of the conductive film is 5 nm or more and 1 μm or less.

6. The semiconductor layer is composed of one or more selected from the group consisting of GaN, Si, GaAlN, GaAs, ZnO, SiC, and Ga ２ O ３ The method for evaluating the film quality of the oxide film according to claim 1, which consists of one or more selected from the group consisting of

7. The method for evaluating the film quality of an oxide film according to Claim 1, wherein the thickness of the semiconductor layer is 100 nm or more and 1 mm or less.

8. The method for evaluating the film quality of an oxide film according to Claim 1, wherein the thickness of the oxide film to be measured is 0.1 nm or more and 1 μm or less.

9. The method for evaluating the film quality of an oxide film according to Claim 1, wherein an electric field is applied to the oxide film to be measured.

10. The method for evaluating the film quality of an oxide film according to Claim 1, wherein a bias voltage is applied between the conductive layer and the conductive film.

11. The method for evaluating the film quality of an oxide film according to Claim 10, wherein the bias is -20 V or more and 10 V or less.

12. The method for evaluating the film quality of an oxide film according to Claim 1, wherein the capacitance measurement is performed in a temperature environment of 23°C or more and 200°C or less.

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