TWI510142B - Micro plasma device - Google Patents

Description

Micro-plasma device

The present invention relates to a plasma device, and more particularly to a microplasma device.

Plasma has been widely used in various fields such as neon, plasma display, arc welding material processing, and even in recent years, it has been widely applied to plasma in the manufacture of semiconductor integrated circuits. Thin film deposition and dry etching of various materials are generally achieved by plasma technology.

Now with the advancement of technology, the application of plasma has gradually expanded to the fields of energy and medical treatment. For example, the active reactants such as charged ions and ozone in plasma can be used to achieve sterilization. Since it is to be used for medical sterilization, the plasma equipment originally used in the industry is not only large, but also requires expensive vacuum systems because of the high vacuum requirements. Therefore, in order to make the application surface of the plasma more competitive in the market, the development of the micro-plasma device has gradually begun to develop toward the trend of small component size, low energy consumption, and operating pressure close to atmospheric pressure.

Referring to Figure 1, U.S. Patent No. 6,687,048, the invention patent (hereinafter referred to as 548) discloses a microdischarge device 1 comprising a high-doped single crystal germanium (Si). Yin The pole 11, an insulating layer 12 formed on the cathode 11, an anode metal layer 13 formed on the insulating layer 12, and a voltage source 14 electrically connected to the cathode 11 and the anode metal layer 13. The microdischarge device 1 further includes a hole 10 penetrating through the cathode 11, the insulating layer 12 and the anode metal layer 13 to serve as a discharge space for plasma lighting, and is coupled to an optical fiber. The micro-discharge device 1 shown in FIG. 1 is the main structure of a generally common micro-plasma device. Among them, the case of the 548 case also mentions that the cathode 11 can also be selected from copper (Cu), aluminum (Al), gold (Au), A material such as silver (Ag), nickel (Ni), zinc (Zn), an alloy of the above metals, a polymer containing carbon black, or a conducting polymer.

However, in order to reduce the plasma disintegration voltage of the microplasma device as a whole, those skilled in the art have also begun to study the electrode structure. Referring to Figure 2, the Republic of China No. I313476 certificate number invention patent case (hereinafter referred to as 476 case) discloses a tip-enhanced microplasma element 2 comprising a cathode 21, an anode 22, and a cathode 21 and an anode 22 spaced apart from each other. A support frame 23 is provided, and a microtip electrode 24 is provided. The cathode 21 has a glass substrate 211, and a cathode conductive layer 212 formed of the chromium substrate (Cr) formed on the glass substrate 211. The anode 22 has an indium tin oxide (ITO) substrate 221 and an anode electrode layer 222 formed on the indium tin oxide substrate 221. The microtip electrode 24 is attached to the cathode conductive layer 212 through a silver paste, and the cathode 21 and the anode 22 and the support frame 23 together form a discharge space 20 (ie, a plasma generating region) in a vacuum state. The microtip electrode 24 is placed in the discharge space 20 and directed to the anode 22. The case of the 476 is mainly to use the microtip electrode 24 to exert an electric field concentration effect to reduce the electricity. The effect of the slurry disintegration voltage.

However, existing electrode materials are still dominated by metals or alloys such as copper or even tungsten. The conductivity of copper is high, and the electron field emission (EFE) characteristics such as turn-on electrical field (E ₀ ) are low, and the hardness is low and easy to damage. It is slightly worse, and the electron field emission characteristics are poor, but its hardness is much higher than copper, so the service life is longer. Therefore, how to further improve the plasma plasma resistance field (E _th ) of the micro-plasma device to save power and improve the stability of the plasma is the object of the research object of the present inventor.

Accordingly, it is an object of the present invention to provide a microplasma apparatus having a small initial electric field, a high plasma generation rate, and excellent plasma stability.

Thus, the microplasma device of the present invention comprises: an anode plate unit, a cathode plate unit and a power unit. The cathode plate unit is disposed facing the anode plate unit and cooperates with the anode plate unit to define a closed discharge space. The cathode plate unit has a diamond film facing the anode plate unit, and the electron field emission starting electric field (E ₀ ) of the diamond film is 5 V/μm or less. The power unit is electrically connected to the anode plate unit and the cathode plate unit, respectively, and generates plasma in the discharge space when power is supplied to the anode plate unit and the cathode plate unit.

Preferably, the diamond film of the cathode plate unit has an electron field emission current density (J _e ) greater than 1.10 mA/cm ² at an applied electric field of 10 V/μm and a vacuum of 10 ^-6 Torr, and the micro-plasma The plasma current density (J _p ) of the device at an applied electric field of 0.4 V/μm and a vacuum of 12 Torr or more is greater than 6.0 mA/cm ² .

Preferably, the cathode plate unit further has a wire layer and a frame layer facing away from the anode plate unit to be disposed on the diamond film and located outside the discharge space, the frame layer facing the anode unit to be disposed In the diamond film, the frame layer has a plurality of through holes exposing a surface of the diamond film, the frame layer of the cathode plate unit cooperates with the anode plate unit to jointly define the discharge space, and the through holes of the frame layer The discharge space is divided into a plurality of lighting intervals.

Preferably, the diamond film of the cathode plate unit comprises a base portion and a plurality of tapered portions which are spaced apart from each other and protrude from the base portion toward the anode plate unit; the wire layer faces away from the anode plate unit The frame layer is disposed on the base of the diamond film, and the frame layer is disposed on the base of the diamond film, and the through holes of the frame layer are the tapered portions for exposing the diamond film.

Preferably, the diamond film of the cathode plate unit is an ultra-nano crystalline diamond (UNCD) film or a mixture of micro crystalline diamond (MCD) and super nanocrystalline diamond. (UNCD) composite diamond (HiD) film.

Preferably, the discharge space contains an inert gas and has a background pressure of 12 Torr or more.

The invention has the effect of utilizing the excellent electron field emission characteristics of the diamond film itself to reduce the initial electric field (E ₀ ) of the cathode plate unit in generating the electron field emission, thereby effectively reducing the time when the microplasma device is illuminated. The critical electric field strength (E _th ) of the plasma, on the other hand, can also enhance the overall service life of the micro-plasma device by virtue of the excellent mechanical properties of the diamond film.

3‧‧‧Anode plate unit

4‧‧‧ cathode plate unit

40‧‧‧discharge space

400‧‧‧Lighting interval

41‧‧‧Diamond film

411‧‧‧ base

412‧‧‧Cone

42‧‧‧Wire layer

43‧‧‧Box

430‧‧‧through holes

5‧‧‧Power unit

61‧‧‧n type wafer

611‧‧‧back

612‧‧‧ Groove

613‧‧‧ top surface

614‧‧‧ cylindrical through hole

62‧‧‧Oxide mask

620‧‧‧ square opening

63‧‧‧Comprehensive diamond (HiD) film

631‧‧‧The Pyramid Department

64‧‧‧ nitride film

640‧‧‧round opening

65‧‧‧Bronze tape

66‧‧‧ITO glass plate

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is a schematic diagram illustrating a microdischarge device disclosed in US Pat. No. 6,687,548, the disclosure of FIG. A tip-enhanced micro-plasma component disclosed in the invention patent No. I313476 of the Republic of China; FIG. 3 is a partial front elevational view showing a first preferred embodiment of the micro-plasma device of the present invention; A partial front view showing a second preferred embodiment of the micro-plasma device of the present invention; and FIG. 5 is a partial front elevational view showing a specific example 1 (E1) of the micro-plasma device of the present invention in a manufacturing process. A back surface of the n-type germanium wafer is subjected to a first wet etching; FIG. 6 is a partial front elevational view showing the specific example 1 (E1) of the present invention after the first wet etching step Applying a diamond film deposition on the back side of the n-type germanium wafer; FIG. 7 is a partial front elevational view showing the top of the n-type germanium wafer after the diamond film deposition step of the specific example 1 (E1) of the present invention Forming a tantalum nitride mask film; 8 is a partial front elevational view showing the specific example 1 (E1) of the present invention, after the step of forming the tantalum nitride mask film, applying the top surface of the n-type germanium wafer a reactive ion etching (RIE); FIG. 9 is a partial front elevational view showing the specific example 1 (E1) of the present invention, after the RIE step, continuing to apply the n-type germanium wafer a second wet etching and attaching a copper conduction tape under the diamond film; FIG. 10 is a partial front elevational view showing the final flow of the specific example 1 (E1) of the present invention, in the n-type germanium wafer An indium tin oxide (ITO) glass is disposed on the top surface as an anode plate unit of the specific example 1 (E1); and FIG. 11 is a Raman spectrogram to illustrate the specific example 1 (E1) of the present invention. The macroscopic structure of the diamond film; FIG. 12 is an optical microscope (OM) image and a scanning electron microscope (SEM) image, illustrating the macroscopic and microscopic appearance of the specific example 1 (E1) of the present invention. FIG. 13 is a cross-sectional SEM image and a tilt SEM image illustrating the specific example 1 (E1) of the present invention before and after the second wet etching. Surface topography; Figure 14 is a transmission electron micro Scope, TEM) image and selected area electron diffraction (SAED) pattern, illustrating a crystal of a nucleation layer formed by the specific example 1 (E1) of the present invention during the diamond film deposition step Figure 15 is a TEM image and SAED pattern illustrating the crystal structure of the diamond film of the specific example 1 (E1) of the present invention; Figure 16 is a high-magnification TEM image and Fourier transform (Fourier-transformed, FT) diffraction diagram, showing the detailed crystal structure at the dotted line 1 in Figure 15 (a); Figure 17 is a high-magnification TEM image and FT diffraction diagram, illustrating Figure 15 (a) The dotted box 2 indicates the detailed crystal structure; Figure 18 is an electron energy loss spectrogram (EELS) and partial amplification EELS, indicating the bonding at the marked boxes 3, 4, and 5 in Figure 17. FIG. 19 is a current density versus electric field strength (JE) curve and a Fowler-Nordheim (FN) graph illustrating the specific example 1 (E1) and a specific example 3 of the present invention ( E3) The electron field emission characteristic of the diamond film; and FIG. 20 is a JE graph illustrating a comparative example (CE) and the micro-plasma device of the specific example 1 (E1) and the specific example 3 (E3) of the present invention. The plasma ignites the test performance.

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.

Referring to Figure 3, a first preferred embodiment of the microplasma apparatus of the present invention comprises: an anode plate unit 3, a cathode plate unit 4 and a power unit 5.

The cathode plate unit 4 is disposed facing the anode plate unit 3 and cooperates with the anode plate unit 3 to define a closed discharge space 40. The cathode plate unit 4 has a diamond film 41, a wire layer 42 and a frame layer 43. The diamond film 41 faces the anode plate unit 3, and the electron field emission starting electric field (E ₀ ) of the diamond film 41 is 5 V/μm or less. The wire layer 42 faces away from the anode plate unit 3 to be disposed on the diamond film 41 and outside the discharge space 40. The frame layer 43 faces the anode unit 3 to be disposed on the diamond film 41, and the frame layer 43 has a plurality of through holes 430 which expose one surface of the diamond film 41. The frame layer 43 of the cathode plate unit 4 cooperates with the anode plate unit 3 to define the discharge space 40, and the through holes 430 of the frame layer 43 divide the discharge space 40 into a plurality of lighting intervals 400.

The power unit 5 is electrically connected to the anode plate unit 3 and the cathode plate unit 4, respectively, and generates electric plasma in the discharge space 40 when power is supplied to the anode plate unit 3 and the cathode plate unit 4. Preferably, the discharge space 40 contains an inert gas and has a base pressure which is 12 Torr or more.

The diamond film 31 suitable for the cathode plate unit 3 of the first preferred embodiment of the present invention is a super nanocrystalline diamond (UNCD) film or a mixture of microcrystalline diamond (MCD) and super nanocrystalline diamond. (UNCD) composite diamond (HiD) film. Preferably, when the background pressure of the discharge space 40 is equal to 10 ^-6 Torr, the electron field emission current density (J _e ) of the diamond film 31 of the cathode plate unit 3 at an applied electric field of 10 V/μm is greater than 1.10 mA. / cm ^2; in addition, when the background pressure in the discharge space 40 is equal to 12 Torr, the microplasma apparatus applied field of 0.4 V / plasma current density (J _p) in μm of greater than 6.0 mA / cm ^2.

It should be additionally noted herein that in the first preferred embodiment of the present invention, the super nanocrystalline diamond (UNCD) film is defined as containing amorphous carbon and graphite phase (graphite). Phase In (matrix), a plurality of super nanocrystalline diamond (UNCD) grains having a grain size of less than 5 nm are dispersed; and the composite diamond (HiD) film is defined as containing amorphous carbon and In the matrix of the graphite phase, most of the microcrystalline diamond (MCD) grains with a grain size larger than 0.15 μm and most of the super nanocrystalline diamond (UNCD) grains are dispersed, and the microcrystalline diamonds (MCD) are in the use of microwaves. In the process of growing the diamond film 41 by the plasma plasma enhanced chemical vapor deposition (MPECVD), a super nanocrystalline diamond (UNCD) is combined and grown.

Further, it should be further explained here that the diamond band has a wide energy band gap and has a negative electron affinity. Therefore, the ion-induced secondary electron emission coefficient (γ) of the diamond structure is high; in contrast, the plasma generation rate of the first preferred embodiment of the present invention is high, and the generated plasma Good stability. In addition, the diamond structure has a high resistance to damage caused by ion bombardment, and therefore, the service life of the micro-plasma device can be effectively extended.

Referring to Figure 4, a second preferred embodiment of the microplasma apparatus of the present invention is substantially identical to the first preferred embodiment in that the cathode of the second preferred embodiment of the present invention is The diamond film 41 of the plate unit 4 includes a base portion 411 and a plurality of tapered portions 412. The tapered portions 412 are spaced apart from each other and protrude from the base portion 411 toward the anode plate unit 3. The wire layer 42 faces away from the anode plate unit 3 to be disposed on the base portion 411 of the diamond film 41. The frame layer 43 faces the anode unit 3 to be disposed on the base portion 411 of the diamond film 41, and each of the frame layers 43 Through hole 430 is for revealing the diamond film The tapered portions 412 of 41.

The following three specific examples of the present invention and a comparative example (CE) and experimental data thereof will be further described in detail later.

<Specific Example 1 (E1)>

The structure of Specific Example 1 (E1) of the micropulp device of the present invention corresponds to the structure of the second preferred embodiment of the present invention, and is implemented according to the following production flow.

Referring to FIG. 5, first, a back surface 611 of an n-type germanium wafer 61 having a square shape of 20 mm × 20 mm and a thickness of 525 μm is formed into a cerium oxide (SiO ₂ ) mask film having a thickness of 1 μm. 62. The yttria mask film 62 has an array of square openings 620 arranged in a two-dimensional array of n x m to expose the back side 611 of the portion of the n-type germanium wafer 61 to the outside. Each square opening 620 of the yttria mask film 62 has a side length of 4 μm and a spacing of 10 μm per two adjacent square openings 620. Then, after the step of forming the yttrium oxide mask film 62, a potassium hydroxide (KOH) etchant is applied to the back surface 611 of the n-type germanium wafer 61 exposed outside the square openings 620, and the temperature is maintained at 80 ° C. The first wet etching is performed to form an array of grooves 612 on the back surface 611 of the n-type germanium wafer 61. The contour of each of the grooves 612 of the array of grooves 612 is an inverted pyramid.

Referring to FIG. 6, after the first wet etching, the n-type germanium wafer 61 is placed in a reaction chamber (not shown) of an MPECVD system to perform a first deposition to be in the n-type. The back surface 611 of the germanium wafer 61 forms a 300 nm thick super nanocrystalline diamond (UNCD) film and serves as a nucleation layer; further, a second deposition of 1 hour is performed to make The nucleation layer is grown into a composite diamond (HiD) film 63, and a pyramid portion 631 is formed corresponding to each of the grooves 612. In this embodiment 1 (E1) of the present invention, the first deposition is carried out at a working pressure of 120 Torr, and the reaction gas is 4:196 methane (CH ₄ ) and argon (Ar). The second deposition was carried out at a working pressure of 60 Torr, and the reaction gas was 1:50:49 CH ₄ , Ar and hydrogen (H ₂ ).

Referring to FIG. 7, after the composite diamond (HiD) film 63 is completed, the whole semi-finished product is turned 180°, and a tantalum nitride (SiN) having a thickness of 100 nm is formed on a top surface 613 of the n-type germanium wafer 61. Mask film 64. The tantalum nitride mask film 64 has an array of circular openings 640 arranged in a two-dimensional array of 10 x 10 to expose the top surface 613 of the portion of the n-type germanium wafer 61. Each of the circular openings 640 of the tantalum nitride mask film 64 has a diameter of 150 μm and a pitch of 200 μm per two adjacent circular openings 640.

Referring to FIG. 8, after the tantalum nitride mask film 64 is completed, the top surface 613 of the n-type germanium wafer 61 is subjected to RIE, and an n-type germanium wafer 61 having a thickness of about 50 μm is reserved.

Referring to FIG. 9, after the RIE is completed, the n-type germanium wafer 61 is continuously subjected to a second wet etching using a KOH etchant to expose the pyramid portions 631 of the composite diamond (HiD) film 63, and A plurality of cylindrical through holes 614 respectively corresponding to the circular openings 640 of the tantalum nitride mask film 64 are formed in the n-type germanium wafer 61; further, the lower surface of the composite diamond (HiD) film 63 is attached A copper guide tape 65.

Referring to FIG. 10, an ITO glass plate 66 is further disposed on the top surface 611 of the n-type germanium wafer 61 as the specific example 1 (E1) of the present invention. An anode plate unit. Finally, a micro-plasma device of the specific example 1 (E1) of the present invention is completed by connecting a copper power supply belt 65 and an ITO glass plate 66 to a power supply (not shown).

<Specific example 2 (E2)>

The production flow of the specific example 2 (E2) of the micropulp device of the present invention is substantially the same as that of the specific example 1 (E1), and the difference is that the specific example 2 (E2) is not implemented in the component manufacturing process. The yttria mask film 62 is formed with the first wet etch and only the first deposition step is performed to form a planar super nanocrystalline diamond (UNCD) film after completion of MPECVD. Therefore, the structure of this specific example 2 (E2) of the present invention corresponds to the structure of the first preferred embodiment of the present invention.

<Specific example 3 (E3)>

The production process of the specific example 3 (E3) of the micro-plasma apparatus of the present invention is substantially the same as that of the specific example 2 (E2), except that the specific example 3 (E3) is in the first deposition step. A second deposition step is to form a planar composite diamond (HiD) film.

<Comparative Example (CE)>

The production flow of the comparative example (CE) used for comparison with the specific examples (E1 to E3) of the present invention is substantially the same as the specific example E2, and the difference is that the comparative example (CE) is fabricated in the element. The first wet etching, the second wet etching, and the diamond film deposition step are not performed in the process, only the n-type germanium wafer having the thickness of the RIE fashion reserve portion is implemented; that is, the n-type germanium wafer is used. Replace the diamond film of these specific examples (E1 to E3).

<Microscopic image and structure identification>

Referring to Fig. 11, the Raman spectrum of the composite diamond (HiD) film of the specific example 1 (E1) of the present invention shows that the Raman spectrum contains a dispersed resonance peak, and the diamond film of the specific example 1 (E1) of the present invention is shown. Has ultra-small grains. In detail, the resonance peaks ν ₁ and ν ₃ at 1140 cm ^-1 and 1480 cm ^-1 shown in Fig. 11 represent the reverse-polyacetylene disposed along the grain boundary of the diamond film. The trans-polyacetylene phase, while the resonance peaks D* and G at 1350 cm ^-1 and 1580 cm ^-1 represent the disordered carbon and graphite phase in the diamond film; The signal D at 1332 cm ^-1 indicates the Γ _2g resonance mode of the large diamond grains. It can be confirmed by the foregoing analysis that there are obvious Raman resonance peaks of D-band and D*-band at the same time, which indicates that the diamond film of the specific example 1(E1) of the present invention has both large diamond grains and Ultra small diamond grain.

Referring to Fig. 12(a) and Fig. 10, it is understood that the top view optical microscopy (OM) image of the specific example 1 (E1) of the present invention is formed in the n-type germanium wafer 61 of the specific example 1 (E1). The cylindrical through holes 614 (with reference to FIG. 10) are arranged in a two-dimensional array; further, the top view SEM and the tilt SEM images respectively shown in FIG. 12(b) and FIG. 12(c) show a cylindrical shape. The bottom of the hole 614 is provided with an array of pyramid portions 631 of a composite diamond (HiD) film 63 spaced apart from each other.

Further, the cross-sectional SEM images (which can be further referred to in FIG. 10) shown in FIGS. 13(a) and 13(b) are respectively the first example (E1) of the present invention before the second wet etching and the second A cross-sectional image after the second wet etching; wherein the composite diamond (HiD) film 63 of the specific example 1 (E1) has a total height of the pyramid portion 631 of about 6 μm, and the height of each pyramid portion 631 is about 3 μm. .

Referring to FIG. 14(a), the TEM image of the nucleation layer obtained by the first deposition of the specific example 1 (E1) of the present invention and the SAED pattern thereof show that the uniformly dispersed grain size approaches 5 nm. The granular structure, and the SAED pattern is composed of a uniform diffraction ring, showing that it contains ultra-small diamond grains in random orientation. Fig. 14 (b) shows a high-magnification TEM image of the nucleation layer of this specific example 1 (E1) of the present invention, confirming that the (111) interplanar spacing of the diamond grains of the nucleation layer is 2.05 Å.

Referring to Fig. 15(a), the TEM image and the SAED pattern of the composite diamond (HiD) film of the specific example 1 (E1) of the present invention show that the diamond grain size is about 150 μm and the ribbon axis of [110] The SAED pattern obtained by the zone axis also shows the annular diffraction pattern of diamond grains and the separated electron diffraction points, confirming that the composite diamond (HiD) film has both super nanocrystalline diamonds (UNCD) and microcrystals. Diamond (MCD). Fig. 15(b) shows a TEM image and its SAED pattern having the same area as Fig. 15(a), and the TEM image obtained by moving away from the [110] ribbon axis shows a large ratio of visible super nanometers. Crystal diamond (UNCD), indicating that the super nanocrystalline diamond (UNCD) does exist simultaneously with the microcrystalline diamond (MCD), and the microcrystalline crystal is invisible when the microcrystalline diamond (MCD) is oriented toward the axis of some of the crystal ribbons. Diamond (UNCD), which stands for Super Nano Crystal Diamond (UNCD), may be located above or below the Microcrystalline Diamond (MCD). In particular, the SAED pattern shown in Fig. 15(b) is composed of a strongly diffused diffraction ring located in the center, which implies that the super nanocrystalline diamond (UNCD) in the composite diamond (HiD) film contains a large amount of graphite. Phase or amorphous carbon; in addition, in addition to the (111) diffraction ring of diamond, the SAED pattern of Figure 15(b) also has a weak diffraction ring, which is equivalent to the allotrope of the diamond. That is, i -carbon, which implies the combination of nano-scale diamond grains, is caused by the second deposition.

Referring to Fig. 16, there is shown a high-magnification TEM image obtained by the dotted line 1 of Fig. 15(a) and its FT diffraction pattern. As can be seen from the FT0 diffraction pattern shown in Fig. 16, the complete structure image of the specific example 1 (E1) of the present invention shows the ordered diffraction points and the stripes connecting the diffraction points. Ordered diffraction points represent hexagonal diamonds, ie, allotropes of Fd3m symmetrical cubic diamond, which correspond to the fixed spacing in the FT1 diffraction pattern of Figure 16. The same direction edge. The fringes passing through the respective diffraction points represent a stacking fault, which corresponds to the irregularly spaced co-directional edges in the FT2 diffraction pattern of FIG. The emergence of hexagonal diamonds and stacking of these planar defects again means that large diamond grains are formed by the combination of ultra-small diamond grains.

Figure 17 shows a high-magnification TEM image taken with the dotted line 2 of 15(a) and its FT diffraction pattern. The FT0 diffraction pattern in Fig. 17 corresponds to the overall structure of the high-magnification TEM image of Fig. 17. Located at the same edge of the diamond grain (shown at the arrow in Figure 17), equivalent to a hexagonal diamond and a stack, which means a sequence of diffraction points and stripes through each diffraction point. presence. Except for the diffraction point, there is a diffusion ring at the center of the FT0 diffraction pattern of Fig. 17, which means that this area (i.e., the dashed box 3, the dashed box 4 indicated in the high-magnification TEM image of Fig. 17 The dotted box 5) has a graphite phase or amorphous carbon. The FT3 diffraction pattern of Fig. 17 corresponds to the dotted line, and the FT4 diffraction pattern and the FT5 diffraction pattern correspond to the dotted line box 4 and the dotted line box 5, respectively. Represents a graphite cluster. To further confirm the dashed box 3 of Figure 17, The structure of the dashed box 4 and the dashed box 5 is confirmed by the inventor through EELS. For the description, please refer to the description of Figure 18 below.

Figure 18 shows the EELS [Fig. 18(a)] and its partial magnification EELS [Fig. 18(b)] taken from the dotted boxes 3, 4, and 5 of Fig. 17. The curve 3 of Figure 18(a) suddenly rises at the 289.5 eV (σ*-bond) and drops to a low point at 302.0 eV, which is a typical signal for the diamond lattice. Curves 4 and 5 of Fig. 18(a) show an enhanced π*-bond signal at 285 eV, which is equivalent to graphite. To illustrate the graphite phase located near the large diamond grains, the spectrum at 18(a) adjacent to the π*-bond (~285 eV) is magnified in Figure 18(b). Curves 4 and 5 in Fig. 18(b) show a significantly enhanced π*-key signal at 285 eV.

<Analysis of electron field emission characteristics of diamond film>

The electron field emission characteristics of the diamond films of the specific examples (E1 to E3) and the comparative example (CE) of the present invention were analyzed by Keithley 237 analytical equipment, and the field emission current of each diamond film was analyzed under an operating pressure of 10 ^-6 torr. Density (J _e ) and electric field strength (E); wherein each diamond film itself is a cathode, and a molybdenum (Mo) rod having a diameter of 3 mm is used as an anode, and the distance between the anode and the cathode is fixed to 1 μm. In addition, the starting electric field (E ₀ ) of each diamond film is obtained according to the FN model. Briefly, the electron field emission characteristics of the material itself are defined in the art as the electric field strength obtained with a pitch of 1 μm between the plates and an operating pressure of 10 ^-6 Torr. The association between the FN model and the starting electric field of the material is not the technical focus of the present invention, and will not be further described herein.

Referring to the JE graph shown in FIG. 19 (or in conjunction with Table 1. below), the starting electric field (E ₀ ) of the specific example 1 (E1) and the specific example 3 (E3) of the present invention is about 2.70 V/μm, respectively. 3.75 V/μm; in addition, the field emission current density (J _e ) of the specific example 1 (E1) and the specific example 3 (E3) at an electric field strength of 10 V/μm is as high as 2.35 mA/cm ² and 1.15 mA/cm ² .

^a field emission current density at an applied electric field of 10 V/μm.

In addition, as can be seen from the data shown in Table 1. above, the starting electric field (E ₀ ) of the super nanocrystalline diamond (UNCD) film of the specific example 2 (E2) of the present invention can also reach 5.00 V/μm, and the field The emission current density (J _e ) can also reach 1.10 mA/cm ² ; in contrast to the comparative example (CE), the starting electric field (E ₀ ) using 矽 (Si) as the cathode is as high as 31.60 V/μm, and contributes The field emission current density (J _e ) is also only about 0.01 mA/cm ² . It is worth mentioning here that when the second deposition is carried out to form the composite diamond (HiD) film, it induces the formation of graphite around the grain of the large diamond (ie, MCD) and induces the bit to be super Formation of graphite at the grain boundaries of small diamonds (ie, UNCD) grains. This graphite phase can transmit electrons more efficiently, and therefore, the electron field emission characteristics of the composite diamond (HiD) film are presumed to be superior to those of the nanocrystalline diamond (UNCD) film.

<Lighting test of micro-plasma device>

The lighting test of the plasma device of each of the specific examples (E1 to E3) and the comparative example (CE) of the present invention was carried out using a Keithley 236 analysis apparatus under a background pressure of 12 Torr in a discharge space containing argon (Ar), respectively. Obtaining the plasma current density (J _p ) and the plasma critical electric field strength (E _th ) of each micro-plasma device; wherein each micro-plasma device takes 1 mm thick Teflon as its The gap between the anode and the cathode of the plasma device is illuminated by a DC pulse having a pulse rate of 2000 times/second to illuminate each microplasma device. In the present invention, the plasma critical electric field strength (E _th ) is defined as the electric field strength at the time of lighting each microplasma device.

Referring to Fig. 20, together with the accessories and Table 2 below, it can be seen that the critical electric field strength (E _th ) of the specific example 1 (E1) and the specific example 3 (E3) of the present invention is about 0.25 V/μm and 0.26 V/, respectively. In addition, the plasma current density (J _p ) of the specific example 1 (E1) and the specific example 3 (E3) at an electric field strength of 0.4 V/μm is as high as 9.5 mA/cm ² and 8.0 mA/ respectively. Cm ² .

^b The plasma current density at an applied electric field of 0.4 V/μm.

In addition, as can be seen from the data shown in Table 2. above, the critical electric field strength of the plasma when the microplasma apparatus of the specific example 2 (E2) of the present invention uses a super nanocrystalline diamond (UNCD) film as a cathode (E _th ), not only can be maintained at 0.26 V / μm, and the plasma current density (J _p ) can also reach 6.7 mA / cm ² ; in contrast, the micro-plasma device of the comparative example (CE) uses bismuth (Si) as a cathode The critical electric field strength (E _th ) of the plasma is increased to 0.3 V/μm, and the corresponding plasma current density (J _p ) is also reduced to 5.2 mA/cm ² .

In summary, the microplasma device of the present invention utilizes the excellent electron field emission characteristics (EFE) of the diamond film itself to reduce the initial electric field (E ₀ ) of the cathode plate unit 4 when generating an electron field emission, thereby being effective. Decreasing the critical electric field strength (E _th ) of the plasma when the micro-plasma device is lit, and the high secondary electron emission coefficient (γ) of the diamond film itself and the high electron field emission current density also make the generated plasma stability On the other hand, by virtue of the excellent mechanical properties of the diamond film to enhance the overall service life of the micro-plasma device, the object of the present invention can be achieved.

The above is only the preferred embodiment and the specific examples of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent change of the patent application scope and the patent specification content of the present invention. And modifications are still within the scope of the invention patent.

3‧‧‧Anode plate unit

4‧‧‧ cathode plate unit

40‧‧‧discharge space

400‧‧‧Lighting interval

41‧‧‧Diamond film

42‧‧‧Wire layer

43‧‧‧Box

430‧‧‧through holes

5‧‧‧Power unit

Claims (5)

A micro-plasma device comprising: an anode plate unit; a cathode plate unit disposed adjacent to the anode plate unit and defining a closed discharge space together with the anode plate unit, the cathode plate unit having a microwave plasma assist a diamond film deposited by a chemical vapor deposition (MPECVD) method, the diamond film facing the anode plate unit, the diamond film being a super nanocrystalline diamond film containing super nanocrystalline diamond grains and a graphite phase, or Is a composite diamond film mixed with microcrystalline diamond grains, super nanocrystalline diamond grains and graphite phase, and the crystallite size of the super nanocrystalline diamond grains is not more than 5 nm, the diamond film has a base and a plurality of tapered portions that are spaced apart from each other and protrude from the base portion toward the anode plate unit, and a surface of each of the tapered portions includes a plurality of super nanocrystalline diamond grains, wherein the diamond film The electron field emission starting electric field (E ₀ ) is less than or equal to 5 V/μm, and the field emission current density (J _e ) at an electric field strength of 10 V/μm is not less than 1 mA/cm ² ; and one power unit is electrically connected The anode plate unit and the cathode plate Element, and electric power is supplied to the anode plate and the cathode plate unit seasonal unit of the discharge space to generate plasma. The micro-plasma device according to claim 1, wherein the diamond film of the cathode plate unit has an electron field emission current density (J _e ) greater than 1.10 mA at an applied electric field of 10 V/μm and a vacuum of 10 ^-6 Torr. /cm ² , and the micropulp device has a plasma current density (J _p ) of more than 6.0 mA/cm ² at an applied electric field of 0.4 V/μm and a vacuum degree of 12 Torr or more. The micro-plasma device of claim 2, wherein the cathode plate unit further has a wire layer and a frame layer, the wire layer facing away from the anode plate unit to be disposed on the diamond film and located outside the discharge space, The frame layer faces the anode plate unit to be disposed on the diamond film, and the frame layer has a plurality of through holes exposing a surface of the diamond film, and the frame layer of the cathode plate unit cooperates with the anode plate unit to jointly define the The discharge space, and the through holes of the frame layer cause the discharge space to be divided into a plurality of lighting intervals. The micro-plasma device of claim 3, wherein the wire layer faces away from the anode plate unit to be disposed at a base of the diamond film, and the frame layer faces the anode plate unit to be disposed at a base of the diamond film. And the through holes of the frame layer are the tapered portions for revealing the diamond film. The micropulp device according to any one of claims 1 to 4, wherein the discharge space contains an inert gas and has a background pressure of 12 Torr or more.