JP4236566B2 - Diamond-like carbon processing method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a diamond-like carbon processing method for finely processing a diamond-like carbon thin film surface on a nanoscale, and in particular, a diamond-like carbon processing method for specifying a position or height of a diamond-like carbon thin film surface for fine processing. About.

  Conventionally, as a processing method of this kind of diamond-like carbon, those disclosed in Japanese Patent Application Laid-Open No. 2003-115258 (hereinafter referred to as a first background technology) and Japanese Patent Application Laid-Open No. 2002-184300 (hereinafter referred to as a second background technology). The first background art is shown in FIG. 5 and FIG. 6, and the second background art is shown in FIG. 7 and FIG.

5 and 6, in the diamond-like carbon processing method according to the first background art, a diamond-like carbon film 112A is formed on a substrate 111 made of a semiconductor, metal, glass or ceramic (see FIG. 6A). Next, the diamond-like carbon film 112A is subjected to oxygen plasma treatment to form an emitter electrode 112 made of a diamond-like carbon film having a rough surface (see FIG. 6B), and the emitter electrode 112 is masked. Thus, an insulating layer is formed to form an insulating spacer 113 (see FIG. 6C), and a gate electrode 114 is formed on the insulating spacer 113 (FIG. 5D).
Here, as the oxygen plasma treatment, the conditions are preferably a pressure of 1 Pa to 5 Pa, a power of 5 W to 20 W, and a treatment time of 10 minutes to 30 minutes. Further, an oxygen plasma treatment of the diamond-like carbon film, that is, oxygen reactive ion etching (RIE) is performed at a pressure of 1 Pa and a power of 20 W.

  Since the emitter electrode 112 can be formed by oxygen plasma treatment in this way, an inexpensive field electron emission source can be realized without requiring an expensive fine processing apparatus. Further, the emitter electrode 112 can be formed at an arbitrary place. Furthermore, since the emitter electrode 112 made of a protrusion-formed product having a rough surface is formed, electric field concentration is likely to occur, the field emission current can be increased, the threshold value can be reduced, and field electron emission can be efficiently performed at a low voltage. Can be done automatically.

  Next, in the method of processing diamond-like carbon according to the second background art in FIGS. 7 and 8, the emitter wiring layer 202 and the resistance layer 203 are formed on the insulating substrate 201 (see FIG. 8A). Then, a silicon nitride film 204 and a gate electrode 205 are sequentially stacked on the resistance layer 203 (see FIG. 8B), and the gate electrode 205 is obliquely deposited on the insulating substrate 201 to form a gate. A release layer 207 is formed only on the electrode 205 (see FIG. 8C), and an emitter material is deposited on the resistance layer 203 and the release layer 207 from a direction perpendicular to the insulating substrate 201 to form an emitter 206. Is formed (see FIG. 8D), and at the same time the release layer 207 is peeled off, the emitter material on the release layer 207 is peeled off to form the gate electrode 205 in the uppermost layer (see FIG. 8E). It is formed.

The resistance layer 203 is formed, for example, by depositing diamond-like carbon. In this way, by forming the resistance layer 203 with a carbon-based material such as diamond-like carbon, the emission current can be easily and highly controlled because the temperature characteristics are more stable than those of amorphous silicon. It becomes possible.
JP 2003-115258 A JP 2002-184300 A

  Since the first technical background is configured as described above, even if an oxygen plasma treatment can be performed on a predetermined region of the diamond-like carbon 112A to produce a projection formation with a rough surface, Each has a problem that it cannot be formed at any specific position by the oxygen plasma treatment.

  In addition, since the second background art is configured as described above, after the mask pattern is transferred by a photolithography technique using a mask and a resist, an emitter serving as a protrusion is formed at a predetermined position by the mask pattern. However, the machining process is complicated, and there is a problem that the diamond-like carbon cannot be processed easily and rapidly.

  In particular, in the first and second background arts, it is impossible to process protrusions and the like with nanoscale accuracy. The first background art has a problem that the processing wavelength becomes shorter than the current deep ultraviolet region in order to process the photolithography on the nanoscale, and the processing wavelength becomes difficult.

Method for processing a diamond-like carbon according to the present invention, impurities are doped into the diamond-like carbon, and disposed opposite the electrode the impurity doped thin film surface of the diamond-like carbon, the electrode as a negative potential The diamond-like carbon is applied by applying an electric field that generates a predetermined tunnel current between the diamond-like carbon thin film surface and having a predetermined potential difference that is less than a potential difference that causes discharge and exceeds the potential difference of the electric field . Protrusions are formed on the surface of the thin film .

The diamond-like carbon processing method according to the present invention applies an electric field with a potential difference of −10 V between the electrode and the diamond-like carbon thin film surface, if necessary, when protrusions are formed on the diamond-like carbon thin film surface. To do .
In the diamond-like carbon processing method according to the present invention, the distance between the electrode and the diamond-like carbon thin film surface is changed as necessary.

The diamond-like carbon processing method according to the present invention changes the applied electric field as required.
In the diamond-like carbon processing method according to the present invention, the electrode moves to a position facing the diamond-like carbon thin film surface as necessary.
In the diamond-like carbon processing method according to the present invention, if necessary, the impurity is nitrogen and the diamond-like carbon is doped with the nitrogen.

  In the present invention, an electrode is separated from a diamond-like carbon thin film surface doped with impurities by a predetermined distance, and an electric field with a potential difference less than the potential difference at which discharge occurs between the electrode and the thin film surface is applied. The composition of the electrode facing position on the surface of the thin film can be changed, and the nanoscale protrusion can be easily and reliably finely processed simply by making the electrode to which an electric field is applied at an arbitrary specific position in close proximity. It can be processed.

  In addition, if necessary, the present invention applies an electric field strength that is greater than or equal to the electric field where the tunnel current is generated and less than the electric field where the discharge current is generated. Therefore, the fine processing of the nanoscale protrusion can be performed accurately.

  In addition, since the present invention changes the distance between the electrode to which an electric field is applied and the diamond-like carbon thin film surface as necessary, the degree of composition change on the diamond-like carbon thin film surface can be adjusted, The height of the nanoscale protrusion can be arbitrarily generated.

  In addition, since the present invention changes the electric field strength applied to the electrode and the diamond-like carbon thin film surface as necessary, the degree of composition change on the diamond-like carbon thin film surface can be adjusted. The height of the protrusion can be arbitrarily generated.

  Moreover, since the present invention moves the position of the electrode facing the diamond-like carbon thin film surface as necessary, the position of the composition change on the diamond-like carbon thin film surface can be changed. The nanoscale protrusions can be finely processed and processed by moving to a specific position. In particular, by moving the electrode while applying an electric field, the linear protrusion can be finely processed / processed.

  In addition, since the present invention uses nitrogen as an impurity to be doped into diamond-like carbon as necessary, diamond-like carbon can be easily produced while doping nitrogen gas plasmified by chemical vapor deposition. The diamond-like carbon can be reliably formed.

(First embodiment of the present invention)
The diamond-like carbon processing method according to the first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an operation flowchart of the diamond-like carbon processing method according to the present embodiment, FIG. 2 is a surface perspective view based on the observation result of the apparatus finely processed and processed according to FIG. 1, and FIG. 3 is a processing time corresponding to FIG. FIG. 4 shows a tunnel current-voltage characteristic diagram of diamond-like carbon finely processed / processed according to FIG. 1.

  In each of the drawings, the diamond-like carbon processing method according to the present embodiment is performed by doping diamond-like carbon (hereinafter referred to as DLC) with an impurity, and the DLC doped with the impurity opposes a metal tip serving as an electrode on the surface of the thin film. The metal tip is used as a negative potential, and a voltage due to a potential difference which is equal to or higher than the electric field at which a tunnel current is generated between the DLC thin film surface and less than the voltage at which a discharge current is generated is applied.

  The metal tip is made of tungsten, and is configured so that positioning control can be performed at any specific position on the plane of the XY axis. The metal tip and the DLC thin film surface are housed in a 2 × 10 −8 Pa ultra-high vacuum container, and the voltage is applied in this ultra-high vacuum state.

  Next, a specific operation of the diamond-like carbon processing method according to this embodiment based on the above configuration will be described. First, DLC to be processed is manufactured by using methane gas and nitrogen gas as source gases, doping nitrogen into DLC composed of silicon and glass substrate by a plasma chemical vapor deposition (CVD) apparatus, and nitriding DLC The thin film is deposited and formed (step 1).

  The DLC thin film was deposited under the conditions of a nitrogen partial pressure of 10 mTorr, a total pressure of 20 mTorr, a cathode self-bias of −1200 V, and a deposition time of 8 minutes. Under this deposition condition, the DLC thin film can be grown to a thickness of 200 nm. By this nitrogen doping treatment, the DLC thin film has conductivity (σ = 0.1 to 10 s / cm).

  The nitrided DLC thin film is stored in a 2 × 10 −8 Pa ultrahigh vacuum container (step 2), and a metal tip is made to face a predetermined position on the surface of the DLC thin film under this ultrahigh vacuum condition (step 3). ), A predetermined weak DC voltage is applied between the metal tip and the DLC thin film surface to allow a 0.1 mA tunnel current to flow (step 4). In this state, the metal tip and the DLC thin film surface A DC voltage of -10 V is applied between them (step 5). The processing position on the surface of the DLC thin film is determined by moving the metal tip on the two-dimensional plane of the XY coordinate by the positioning device. Note that the weak DC voltage varies depending on the characteristics or intervals of the metal tip and DLC, and at least a value of −0.1 to −1 V, for example, smaller than the voltage (−10 V) at the time of the processing is selected. There is.

  A projection of 3 to 5 nm is formed on the DLC thin film facing the positioned metal tip (step 6). The protrusion on the thin film of DLC is not formed by the movement of tungsten atoms forming the metal tip because the voltage is applied as a negative potential to the metal tip. It is thought that the bulge was changed and formed.

  The surface of the protrusion formed on the surface of the DLC thin film was observed with a scanning tunneling microscope (STM). In this surface observation, scanning was performed while maintaining a state in which a tunnel current of 0.1 nA flows between the surface of the DLC thin film with an STM metal probe, and a voltage was applied by the metal tip to position the surface of the DLC thin film. 3 nm to 5 nm protrusions were detected.

  FIG. 2 shows a character “F” drawn in a 200 nm × 300 nm region by moving a metal tip intermittently and applying a voltage at a spot. The size of the character is 200 nm × 250 nm appearing in the character “F” in the form of white dots. FIG. 3 shows a two-dimensional image of the magnitude of the tunnel current flowing through the STM metal probe in the same region as FIG. In the figure, the white part is a region where the current value is high, and the voltage in the figure indicates the voltage applied to the metal tip during processing. Thus, it can be seen that the current started to flow from the portion where the protrusion was formed by applying the voltage to the metal tip. This is an effective technique when used as a DLC electron cathode in a display device such as a PDP.

  FIG. 4 shows tunneling current-voltage characteristics in the portion where the protrusion is formed and the portion where the protrusion is not formed in FIG. Both showed non-linearity characteristic of the tunnel current, but it can be seen that the current value in the portion where the protrusion was formed was high. From this, it can be seen that it is possible to form an electrode with fine protrusions that becomes an efficient electron source by DLC processing only by voltage application.

(Other embodiments of the present invention)
In the above embodiment, the processing is performed with the voltage applied between the surface of the DLC thin film and the metal tip being constant, but the applied voltage is equal to or higher than the voltage at which the tunnel current is generated and the discharge current is The height of the protrusion formed on the surface of the DLC thin film can be adjusted by changing the voltage value below the voltage that does not occur.

  Further, in the above embodiment, the processing is performed with the metal tip distance to the DLC thin film surface being constant (1 nm), but the height of the protrusion formed on the DLC thin film surface is adjusted by changing this distance. can do.

  In the above embodiment, the metal tip is intermittently applied to the surface of the DLC thin film so as to apply the voltage at the spot. However, the voltage is continuously applied as the metal tip moves. It can also be set as the structure to do. In this case, the portion where the voltage is continuously applied can form the protruding portion as a partition having a predetermined height.

  Diamond, carbon nanotubes, diamond-like carbon (hereinafter DLC), etc., which are carbon economic fees, are expected to have various applications in the nanotechnology field. For example, a high emission current has been obtained as a cathode material for field emission displays. When forming the cathode, microfabrication and surface treatment of the surface are required to enhance the emission characteristics. Further, when these carbon materials having conductivity are used as electrodes, processing for forming electrodes is required. Furthermore, microfabrication and deformation in the nanotechnology field are also necessary. In these processes and treatments, a fine projection is formed by forming a resist pattern by a photolithography transfer technique using a mask and a resist and chemically etching the resist pattern. In such microfabrication, the present invention relates to a technique for performing microfabrication and processing on a nanoscale without using the above-described mask, and can be an indispensable technique for industrialization of nanotechnology. In particular, since DLC has transparency, it can be used as a transparent electrode of a display device.

It is an operation | movement flowchart of the processing method of the diamond-like carbon which concerns on the 1st Embodiment of this invention. It is a surface perspective view based on the apparatus observation result microfabricated and processed by FIG. FIG. 3 is an electron emission mapping from a processed part due to differences in applied voltages during processing corresponding to FIG. 2. FIG. FIG. 2 is a tunnel current-voltage characteristic diagram of diamond-like carbon finely processed / processed according to FIG. 1. It is a projection form figure formed by the processing method of diamond like carbon in the 1st technical background. It is operation | movement explanatory drawing which forms the protrusion shown in FIG. It is a projection form figure formed by the processing method of diamond like carbon in the 2nd technical background. It is operation | movement explanatory drawing which forms the protrusion shown in FIG.

Explanation of symbols

111 Substrate 112 Emitter electrode 112A Diamond-like carbon 11
113 Insulating spacers 114 and 205 Gate electrode 201 Insulating substrate 202 Emitter wiring layer 203 Resistance layer 204 Silicon nitride film 207 Release layer

Claims (4)

Impurities are doped into the diamond-like carbon, diamond-like carbon doped with the impurity of the electrode on the thin film surface facing arranged, a predetermined between the diamond-like carbon thin film surface the electrode as a negative potential Protrusions are formed on the surface of the diamond-like carbon thin film by applying an electric field with a predetermined potential difference that is less than the potential difference that causes discharge and exceeds the potential difference of the electric field while applying an electric field that generates a tunnel current. How to process diamond-like carbon. In the diamond-like carbon processing method according to claim 1,
A method for processing diamond-like carbon, wherein the strength of an electric field applied when forming protrusions on the surface of the diamond-like carbon thin film is -10V . In the diamond-like carbon processing method according to claim 1,
A method for processing diamond-like carbon, characterized in that the distance between the electrode and the diamond-like carbon thin film surface is changed. In the diamond-like carbon processing method according to claim 1 or 3 ,
A method for processing diamond-like carbon, wherein the applied electric field is changed.