TWI534280B - Preparation of Bismuth Oxide Bismuth Film - Google Patents

Description

β phase yttrium oxide film manufacturing method

The present invention relates to a method for producing a metal oxide film, and more particularly to a method for producing a β-phase yttrium oxide film having a preferred orientation.

Bismuth oxide (Bi ₂ O ₃ ) is an ion semiconductor having ion conduction characteristics, and therefore, oxygen ions and oxygen vacancies of ruthenium oxide are easily moved inside. That is to say, the conductivity of cerium oxide has a great relationship with oxygen ions and oxygen vacancies inside. Because of the aforementioned physical properties, cerium oxide can be widely used in gas sensors, solid fuel cells, and resistance switching.

In general, cerium oxide has five crystal phases of α phase, β phase, γ phase, δ phase, and ω phase; among them, yttrium oxide of β phase has been found to have resistance switching effect and can be applied to resistive memory. (resistive random access memory, RRAM). In addition, the β-phase yttrium oxide film also exhibits semi-transparent goose-yellow color, and the doping through impurities can have n-type or p-type semiconductor characteristics, and thus has great potential for application in the field of optoelectronics.

Many research literatures currently focus on the fabrication of nanostructures of yttrium oxide, such as Yongfu Qiu et al. (Adv. Mater. 2006, 18, 2604-2608) or L.Kumari et al. (Nanotechnology 18 (2007) 295605) to vaporize rhodium metal and mix nitrogen and oxygen molecules to form a niobium oxide nanowire. However, the niobium oxide produced in this way The nanowire is a mixed structure of the α phase and the β phase, and is not a simple β phase oxidized nanowire.

On the other hand, NATulina et al. (solid state comm. 150 (2010) 2089-2092) proposed a multilayer film method to prepare a ruthenium oxide film. It is mainly prepared by oxidizing a metal tantalum film at a high temperature (400 ° C) for 30 minutes under the atmosphere. The cerium oxide film prepared by this process has a molecular formula of Bi ₂ O _2.5 instead of Bi ₂ O ₃ , and the film structure exhibits a polycrystalline structure.

In the case of the pre-opening case and the current relevant research literature, it is still difficult to prepare a β-phase oxide film having a molecular formula of Bi ₂ O ₃ . Therefore, it is a technique to provide a high-quality β-phase yttrium oxide film for resistance switching application. The subject to be solved by relevant technical personnel in the field.

Accordingly, it is an object of the present invention to provide a method for producing a beta phase yttrium oxide film.

Thus, the method for fabricating the β-phase yttrium oxide film of the present invention comprises: a metal layer forming step, an oxide layer forming step, and an annealing step.

The metal layer forming step is to evaporate a metal ruthenium plating in an evaporation system to deposit a continuous layer of metal ruthenium on a substrate on a carrier in the evaporation system.

The oxide layer forming step is: after forming the metal germanium layer, introducing an oxygen gas into the vapor deposition system, and simultaneously evaporating the metal germanium plating material, so that the evaporated germanium atoms are oxidized by the oxygen gas, and the metal germanium layer is deposited on the metal germanium layer. Form one on Yttrium oxide film.

The annealing step continuously introduces the oxygen, and the metal tantalum layer is annealed to the tantalum oxide film to change the tantalum oxide film phase into a first hafnium oxide film having a β phase.

The effect of the present invention is that after the metal ruthenium layer having a preferred orientation is first deposited as a seed layer, the ruthenium oxide film is formed on the ruthenium layer; since the ruthenium oxide film is grown to an amorphous structure at room temperature. Therefore, after the annealing step, a small kinetic energy is obtained between the atoms and ions in the yttrium oxide film, and the metal ruthenium layer having a preferred orientation is applied to the yttrium oxide film to stress the oxidation field. The ruthenium film phase is changed into a ruthenium oxide film having a preferred orientation.

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is an X-ray diffraction (XRD) spectrogram illustrating a specific example of the present invention. A metal ruthenium layer of 1 is formed on a different substrate; FIG. 2 is an XRD spectrum illustrating the crystal phase of the ruthenium oxide layer of the specific example 1; FIG. 3 is a Raman spectrum diagram illustrating The yttrium oxide layer of the specific example 1 is a Bi ₂ O ₃ structure; and FIG. 4 is an atomic force microscope (AFM) diagram illustrating the surface roughness of the yttrium oxide layer of the specific example 1 formed on the glass substrate; It is an XRD spectrum diagram illustrating the crystal phase of the niobium oxide layer of a specific example 2 of the present invention; FIG. 6 is an AFM diagram illustrating the surface roughness of the hafnium oxide layer of the specific example 2; and FIG. 7 is an XRD spectrum diagram. The crystal phase of the niobium oxide layer of a comparative example 1 of the present invention is illustrated; FIG. 8 is an AFM diagram illustrating the surface roughness of the hafnium oxide layer of Comparative Example 1, and FIG. 9 is an XRD spectrum diagram illustrating the present invention. The crystal phase of the niobium oxide layer of Comparative Example 2; FIG. 10 is an AFM diagram illustrating the hafnium oxide layer of Comparative Example 2. FIG. 11 is an AFM diagram illustrating the surface roughness of the niobium oxide layer of a comparative example 3 of the present invention; and FIG. 12 is an XRD spectrum diagram illustrating the formation of a hafnium oxide layer of a comparative example 4 of the present invention. FIG. 13 is an AFM diagram illustrating the surface roughness of the yttrium oxide layer of Comparative Example 4 formed on a glass substrate; FIG. 14 is an XRD spectrum diagram illustrating one of Comparative Example 5 of the present invention. The yttrium oxide layer is formed on a different substrate; FIG. 15 is an AFM diagram illustrating the surface roughness of the yttrium oxide layer of Comparative Example 5 formed on the glass substrate; and FIG. 16 is an XRD spectrum diagram illustrating the present invention. The crystal phases of the niobium oxide layer of Comparative Examples 6 to 8 were compared.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

<Detailed Description of the Invention>

An embodiment of the method for producing a β-phase yttrium oxide film of the present invention comprises the following three steps: a metal forming step, an oxide layer forming step, and an annealing step.

The metal forming step is to first evaporate a metal ruthenium plating in an evaporation system to deposit a metal ruthenium layer having a preferred orientation and an uninterrupted layer on a substrate on a carrier in the evaporation system.

Preferably, the evaporation system is a thermal evaporation coater. The substrate may be selected from Si (100), Si (111), or a glass substrate, but is not limited thereto. In order to form an uninterrupted and complete film morphology, the thickness of the metal ruthenium layer to be vapor-deposited needs to be greater than 10 nm to ensure that the metal ruthenium layer forms a complete ruthenium film with a preferred orientation (001). It should be noted here that since the thickness of the metal germanium layer is less than 10 nm, a complete metal tantalum film cannot be formed, which may cause subsequent processes to be unachievable. However, when the thickness is greater than 30 nm, the metal tantalum film may have a size. The larger metal ruthenium grains cause partial bulging of the subsequent vapor-deposited ruthenium oxide film, thereby affecting the subsequent thin film process. Therefore, preferably, the metal ruthenium layer has a thickness greater than 10 nm and less than 30 nm.

The oxide layer forming step is: after forming the metal germanium layer, introducing an oxygen gas into the vapor deposition system, and simultaneously evaporating the metal germanium plating material, so that the evaporated germanium atoms are oxidized by the oxygen gas, and the metal germanium layer is deposited on the metal germanium layer. A tantalum oxide film is formed thereon. Preferably, in the present embodiment, the oxygen is introduced into the vapor deposition system to maintain a working pressure of the coating chamber of the vapor deposition system at 1 × 10 ^-1 to 5 × 10 ^-3 Torr. It is worth mentioning that in the metal forming step and the oxide layer forming step, the substrate is not heated, and therefore, the metal tantalum layer and the tantalum oxide film are all prepared at room temperature.

After the preparation of the metal ruthenium layer and the ruthenium oxide film is completed, the annealing step is subsequently performed. The annealing step is: after the yttria film is formed, continuously introducing oxygen and heating the substrate to a temperature of not less than 200 ° C, annealing the metal ruthenium layer and the ruthenium oxide film to change the yttrium oxide film phase into one A preferred orientation of the first hafnium oxide film. Preferably, the ruthenium oxide film is phase-changed after the annealing step to form a β phase and has a first yttrium oxide film of preferred orientation (201). However, when the annealing temperature is too high, the internal atoms of the yttrium oxide film will have excessive kinetic energy, and the stress field applied by the underlying metal ruthenium layer will not limit the formation of the β phase of the yttria film with a preferred orientation. (201), therefore, the annealing step is carried out under the conditions of an annealing temperature of 200 ° C to 350 ° C. More preferably, the root mean square roughness of a surface of the first hafnium oxide film is not more than 12 nm.

It is to be noted that, after the first ruthenium oxide film is formed in the annealing step, if the oxygen is continuously introduced for annealing, the metal ruthenium layer can be further oxidized to have a β phase and a preferred orientation (201). The second hafnium oxide film. That is, macroscopically, the first hafnium oxide film and the second hafnium oxide film have the same preferred orientation and substantially form a layer of a β-phase hafnium oxide layer having a preferred orientation of (201).

In order to more clearly explain the production method of the β-phase ruthenium oxide film of the present invention, two specific examples and eight comparative examples will be described below. In the specific examples and the comparative examples, the metal ruthenium layer is continuously oxidized to form the second ruthenium oxide film. Therefore, for convenience of description, the first ruthenium oxide film and the first The film formed by the ruthenium dioxide film is collectively referred to as a ruthenium oxide layer.

It should be noted that the substrates for coating in the specific examples and comparative examples of the present invention need to be pre-cleaned first. The pretreatment process of the substrate is as follows: First, prepare a glass substrate (Corning, Corning 1737) and 矽The substrate ((111) and (100)), the organic substance on the substrate is removed by a conventional acetone, and the remaining acetone is washed away with alcohol, and finally, the remaining water is removed by deionized water (DIwater). Alcohol. It should be noted that before the organic material on the substrate is removed by copper, the germanium substrate is first etched with hydrofluoric acid (HF) to etch the native oxide layer on the surface. In order to avoid the temperature and outgassing in the vacuum chamber in the vapor deposition system, and the water vapor in the surface of the crucible substrate is combined and oxidized, the step of deionized water shaking is omitted.

<Specific example 1>

And pre-cleaning the finished substrate on the carrier in the thermal resistance vapor deposition system, and preparing the metal ruthenium plating onto a tungsten boat of the thermal resistance vapor deposition system, and then performing the mechanical pump The rough drawing and fine drawing are performed to maintain the vacuum of the cavity of the thermal resistance vapor deposition system in an environment of less than 2 × 10 ^-5 Torr. At this point, the cavity is still maintained at room temperature and is at 0.1 The metal plating material was evaporated at a plating rate of /s, and the substrates were not heated to form a metal tantalum layer having a thickness of 10 nm on the substrates.

After the metal ruthenium layer is prepared, oxygen is continuously introduced and the metal ruthenium plating is continuously evaporated and the substrates are not heated, so that the evaporated ruthenium atoms are oxidized by the oxygen to form a thickness of 40 nm on the metal ruthenium layer. A ruthenium oxide film; wherein the flow rate of oxygen is maintained at 0.02 L/min and the working pressure of the chamber is maintained at 2 x 10 ^-3 Torr.

Finally, an annealing step is performed, the substrates are heated to 300 ° C for 3 hours, and the oxygen is continuously introduced to simultaneously oxidize the yttrium oxide film and the metal ruthenium layer, and then phase change to form a β phase with a preferred orientation (201). a layer of ruthenium oxide.

<Specific example 2>

The specific condition of the specific example 2 of the method for producing the β-phase yttrium oxide film of the present invention is substantially the same as that of the specific example 1, except that the specific working pressure of the cavity after the oxygen is introduced into the specific example 2 is Maintain at 1 × 10 ^-1 Torr.

<Comparative Examples 1 to 2>

The implementation conditions of a comparative example 1 to 2 of the method for producing a β-phase yttrium oxide film of the present invention are substantially the same as those of the specific example 1, except that the comparative examples 1 and 2 are opened after the oxygen is introduced into the chamber. The working pressure of the body was maintained at 1 × 10 ^-4 Torr and 4 × 10 ^-4 Torr, respectively.

<Comparative Example 3>

The implementation condition of a comparative example 3 of the method for producing a β-phase yttrium oxide film of the present invention is substantially the same as that of the specific example 1, except that the comparative example 3 is formed by forming a metal having a thickness of 50 nm on the substrate. bismuth After the layer, oxygen was directly introduced and the substrate was simultaneously heated to 300 ° C to directly oxidize the metal ruthenium layer having a thickness of 50 nm to a ruthenium oxide layer at a growth temperature of 300 ° C.

<Comparative Example 4>

A comparative example 4 of the method for fabricating the β-phase yttrium oxide film of the present invention is to place the pre-cleaned substrate in the thermal resistance vapor deposition system, directly introducing oxygen into the high vacuum chamber and simultaneously vapor-depositing the metal ruthenium. The coating was applied to form a cerium oxide layer having a thickness of 50 nm on the substrate, wherein the flow rate of oxygen was maintained at 0.02 L/min and the working pressure of the chamber was maintained at 2 × 10 ^-3 Torr.

<Comparative Example 5>

The comparative example 5 of the method for producing the β-phase yttrium oxide film of the present invention is substantially the same as the comparative example 4 except that the comparative example 5 is formed on the substrate by a ruthenium oxide layer having a thickness of 50 nm. Further, oxygen gas was continuously supplied, and annealing of the cerium oxide layer was performed at 300 °C.

<Comparative Examples 6 to 8>

The conditions for carrying out Comparative Examples 6 to 8 of the method for producing a β-phase yttrium oxide film of the present invention are substantially the same as those of Comparative Example 4, except that the comparative examples 6 to 8 are respectively heating the glass substrate to 200. After °C, 250 ° C, and 300 ° C, oxygen is introduced and the metal ruthenium plating is evaporated, and a ruthenium oxide layer having a thickness of 50 nm is directly formed on the substrate.

<Data Analysis>

Referring to Fig. 1, the metal ruthenium layer deposited on the glass substrate and the ruthenium substrate (111, 100) of the specific example 1 was analyzed by an X-ray diffractometer. Figure 1 It can be seen that no matter what kind of substrate is used to prepare the metal ruthenium layer, a crystal plane of a preferred orientation (001) of the metal ruthenium is shown. Here, it is to be noted that when the metal tantalum layer is vapor-deposited on various substrates at room temperature (that is, the substrate is not heated during the vapor deposition), the metal tantalum layer automatically forms a preferred crystal plane of the metal tantalum (001).

Referring to FIG. 2 to FIG. 4, the metal ruthenium layer is prepared at room temperature, and the metal ruthenium layer having a preferred orientation (001) is automatically formed, and then the ruthenium oxide layer is formed on the metal ruthenium layer. The film is finally subjected to the annealing step to form a beta phase and has a preferred orientation (201) of the first hafnium oxide film. It is to be noted here that the lattice mismatch between the ruthenium oxide film and the metal ruthenium layer is only about 9.09%. Therefore, the crystal face of the metal ruthenium layer having a preferred orientation (001) and the ruthenium oxide film have an epitaxial relationship, so that the ruthenium oxide film can be crystallized by the underlying metal ruthenium layer during the annealing step. The face is caused to form a first hafnium oxide film having a preferred orientation (201). It should be noted that, in the specific example 1, the annealing step is continued for 3 hours, and therefore, the metal ruthenium layer is also oxidized to a second yttrium oxide film having the same preferred orientation as the first ruthenium oxide film. Thus, the first hafnium oxide film and the second hafnium oxide film are treated as a layer of hafnium oxide as shown above (as shown in FIG. 2). Figure 3 shows a view of the Raman spectrum has a bismuth oxide layer, wherein the peak of bismuth oxide layer thus Raman spectra shown in the figure can be seen, at 71.9cm ^-1 and at 89.6cm ^-1, representative of bismuth and A E _{g 1g} Raman vibration mode, and at 122.8cm ^-1 , 310.3cm ^-1 and 469.7cm ^-1 , the Raman vibration mode (A _g , formed by the expansion and contraction of a helium atom and an oxygen atom (Bi-O) bond; B _g ), it can be seen that the molecular formula of the ruthenium oxide layer is indeed a structure of Bi ₂ O ₃ . Further, when the surface roughness of the cerium oxide layer was observed by an atomic force microscope (AFM), it was found from the measurement results of FIG. 4 that the cerium oxide layer of the specific example 1 had a root mean square roughness (R _q ) of 8.851 nm. Therefore, the ruthenium oxide layer obtained by the process of the specific example 1 has a flat surface in addition to the β phase and the excellent preferred orientation (201).

Referring to Fig. 5 and Fig. 6, there are shown XRD patterns and AFM patterns of the yttrium oxide layer prepared on the glass substrate in the specific example 2 at a working pressure of 1 × 10 ^-1 Torr. As can be seen from the XRD pattern of FIG. 5, the cerium oxide layer of this specific example 2 has a crystal structure of a preferred orientation (201), and has, for example, (002), (220), (203), and (421). The peak of the heterophase is shown; and the AFM diagram of Fig. 6 shows that the square root roughness of the yttria layer is 2.101 nm. From this, it can be seen that when the yttrium oxide layer is prepared at a working pressure of 1 × 10 ^-1 Torr, although a small hetero-phase peak is exhibited, the host is mainly in a crystal structure of a preferred orientation (201).

Referring to Figures 7 to 10, when the operating pressure of the down-regulation process is 1 × 10 ^-4 Torr (Comparative Example 1) and 4 × 10 ^-4 Torr (Comparative Example 2), the XRD presented by Figures 7 and 9 As can be seen, the signal intensity of the preferred orientation (201) of the yttrium oxide layer exhibited by Comparative Example 1 and Comparative Example 2 is significantly weaker than that of the specific examples 1-2, and even exhibits an unoxidized metal ruthenium. Crystal structure of crystalline phases (003), (012), and (104). That is to say, when the working pressure is lower than 10 ^{- 3 of the} specific examples 1 to 2, the metal ruthenium cannot be completely oxidized to cerium oxide due to insufficient working pressure of oxygen. It can be seen from Fig. 8 that when the working pressure is too low (1×10 ^-4 Torr), the surface morphology of the cerium oxide layer will have a large block crystallization condition, and the surface roughness will increase to 34.311 nm. The grain gap becomes large, causing discontinuity of the film surface.

Referring to FIG. 11, the surface of the yttrium oxide layer prepared in this Comparative Example 3 was shown to have ridged yttrium oxide crystal grains, and the crystal grains had a height difference of 150 nm and a square root roughness of 50.321 nm. It can be seen that the yttrium oxide layer prepared by directly oxidizing the metal ruthenium layer having a thickness of 50 nm and simultaneously heating to 300 ° C has a sharp ridge formation, resulting in a rough surface or even a discontinuous state of the film.

Referring to Fig. 12 and Fig. 13, this comparative example 4 is an annealing step, and while vaporizing the metal ruthenium plating, oxygen is passed through to directly oxidize the metal ruthenium into the ruthenium oxide layer. As can be seen from the AFM chart, the comparative example 4 without the annealing step has a relatively flat surface (square root roughness is 9.133 nm), but the XRD pattern of the glass substrate or the germanium substrate is amorphous. Produced to be amorphous.

Referring to FIG. 14 and FIG. 15, this Comparative Example 5 differs from the Comparative Example 4 only in that the comparative example 5 has an annealing step. Compared with the comparative example 4, the AFM pattern (Fig. 15) of the yttrium oxide layer prepared in the comparative example 5 shows that although the single crystal grain of the yttrium oxide layer after annealing has not increased, the density is increased. Lifted and still has a flat film surface (square root roughness of 11.045 nm). Furthermore, it is apparent from the XRD pattern (Fig. 14) that although the direct oxidation of the yttrium oxide layer in this manner still exhibits a polycrystalline state, the X-ray diffraction peak position coincides with the standard data of the β-phase yttrium oxide (JCPDS 27). -0050), that is, the annealed yttrium oxide layer does induce a β-phase yttrium oxide layer.

Referring to Fig. 16, the difference between the annealing step prepared by the preparation of the yttrium oxide layer by the comparative example 4 and the comparative example 5 is that the oxygen which induces the β phase is obtained. For the bismuth layer, the high temperature process is an indispensable process condition. Therefore, the comparative examples 6 to 8 are processes for further heating the substrate first when the ruthenium oxide layer is grown. In Comparative Examples 6, 7, and 8, the substrates were individually heated to a high temperature of 200 ° C, 250 ° C, and 300 ° C, and the metal tantalum plating material was simultaneously vapor-deposited while oxygen gas was introduced, so that the tantalum oxide layer was directly formed on the high temperature substrate. on. As can be seen from the XRD pattern of Fig. 16, in this way, the change in the tendency of the ruthenium oxide layer on the crystal phase was not observed. The reason is that during the growth of the ruthenium oxide layer, the temperature of the substrate is increased, and bismuth-oxygen (Bi-O) which is not favorable for the ruthenium oxide layer is deposited on the substrate.

In summary, the method for preparing the β-phase yttrium oxide film of the present invention is to first vapor-deposit the metal ruthenium layer at room temperature, so that the metal ruthenium layer is automatically formed to have a preferred orientation of (001), and then the metal ruthenium layer is further formed. Forming the ruthenium oxide film thereon, and finally, through the epitaxial relationship between the yttrium oxide film and the metal ruthenium layer, annealing the substrate on which the metal ruthenium layer and the ruthenium oxide film are formed, thereby enabling annealing The yttria thin film phase changes into a β phase, and the yttria thin film is pulled by the crystal plane of the metal ruthenium layer, so that after annealing, it may have a preferred orientation of (201), and obtain a β phase at the same time and preferably have a orientation ( The ruthenium oxide film of 201) can indeed achieve the object of the present invention.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

Claims (9)

A method for fabricating a β-phase yttrium oxide film, comprising the steps of: a metal layer forming step of evaporating a metal ruthenium plating material in an evaporation system for depositing on a substrate on a carrier in the evaporation system a continuous metal ruthenium layer; an oxide layer forming step, introducing an oxygen gas into the vapor deposition system, and evaporating the metal ruthenium plating material, so that the evaporated ruthenium atoms are oxidized by the oxygen and on the metal ruthenium layer Forming a niobium monoxide film; and an annealing step, continuously introducing the oxygen, and annealing the metal tantalum layer to the tantalum oxide film to change the tantalum oxide film phase into a first hafnium oxide film having a β phase. The method for fabricating a β-phase yttrium oxide film according to claim 1, wherein the metal ruthenium layer of the metal layer forming step has a (001) preferred orientation, and the first ruthenium oxide film in the annealing step has (201) Preferred orientation. The method for producing a β-phase yttrium oxide film according to claim 2, wherein the annealing step further oxidizes the metal tantalum layer into a second hafnium oxide film having a (201) preferred orientation. The method for producing a β-phase yttrium oxide film according to claim 1, wherein the thickness of the metal ruthenium layer in the metal layer forming step is greater than 10 nm. The method for producing a β-phase yttrium oxide film according to claim 1, wherein a surface of the first yttria film having a preferred orientation of the annealing step has a root mean square roughness of not more than 12 nm. The method for fabricating a β-phase yttrium oxide film according to claim 1, wherein the annealing step is performed at an annealing temperature of 200 ° C to 350 ° C or more. Row. The method for producing a β-phase yttrium oxide film according to claim 1, wherein the oxide layer forming step and the working pressure in the annealing step are not less than 10 ^-3 Torr. The method for producing a β-phase yttrium oxide film according to claim 1, wherein the vapor deposition system is a thermal resistance vapor deposition system. The method for producing a β-phase yttrium oxide film according to claim 1, wherein the metal tantalum layer and the tantalum oxide film are formed without heating the substrate.