RU2242534C1 - Method of production of a current-conducting alloyed diamond-like nano-composite film - Google Patents

Abstract

FIELD: production of materials for microelectronics.

SUBSTANCE: the invention presents a method of production of a current-conducting alloyed diamond-like nano-composite film and is pertinent to the field of production of materials for microelectronics. The methods provides for production of a film containing C, Si, O, H as the basic elements and alloyed by molybdenum, pass through the film of an alternating current as a pulse train, expos the film to an electrothermal action using different outside power supplies at different parts of the N-shaped voltage-current characteristic measured during a test- training and with a current periodic switching-off after each measured value of an amplitude of the current, ensuring cooling of the film up to the temperature below 400°С. The produced film has a thermostable microscopic structure, high mechanical strength, and the method ensures its low percent of rejects.

EFFECT: the invention allows to produce a film with a thermostable microscopic structure, high mechanical strength and lower percentage of rejects.

5 cl, 5 dwg

Description

The present invention relates to microelectronics, and more specifically to a method for manufacturing a conductive doped diamond-like nanocomposite film.

These films can be used in microelectronics in resistors emitting when heated by current, in spectroscopic devices, gas indicators, thermal printers.

A known method of manufacturing a conductive diamond-like metal-containing nanocomposite film with a thickness of 0.2-2 microns (see, for example, patent RU No. 2111206, 1998), having in its composition as the main elements carbon, silicon, metal, oxygen and hydrogen and located on a dielectric membrane with a thickness of 1 to 10 microns. A gas-discharge plasma is created in a vacuum chamber into which organosiloxane is evaporated. A holder with a substrate of dielectric material is placed in a vacuum chamber. Carry out the deposition on the substrate of atoms or ions of carbon, silicon, oxygen and hydrogen, as well as atoms or ions of the alloying material from a source containing metal. Get a lot of conductive doped carbon nanocomposite films.

Films having an atomic concentration (A.K.) of carbon ranging from about 25% A.K. are selected. up to about 39% A.K. from the general A.K. elements, the atomic concentration of the metal from about 20% A.K. up to about 35% of the total A.K. elements and total A.K. carbon, silicon and metal from about 85% A.K. up to about 90% of the total A.K. elements. They cover the surface of each selected film with a layer of silicon dioxide, connect it to an alternating current source, and subject the film to electrothermal action (ETV) for restructuring.

To do this, an alternating current is passed through the film in the form of a series of pulses with a duration of 5 to 100 ms, depending on the thickness of the film and the substrate in the current generator mode. A step-wise increase in the current amplitude is carried out by a value causing hysteresis on the current-voltage characteristic (CVC) with an exposure of each newly set value until the current-voltage characteristic of the film is stabilized.

In the mode of temperature fluctuations and fluctuations in mechanical stresses, the temperature of the film is brought to about 800-1050 ° C. At the same time, the I – V characteristic characteristic of the ETV process shows a decrease in resistance at each of its next points in the direction of increasing current and during the holding of each current newly established during the ETV.

As a result of the described actions, a conductive doped diamond-like nanocomposite film is obtained. In this case, the film has a layered structure in which A.K. metal in the direction from silicon dioxide to the substrate varies periodically and smoothly relative to the average film thickness A.K. metal, and this change is antiphase to a change in the same direction from silicon dioxide to the substrate and with the same period of atomic concentrations of C and Si, and at the interface between the silicon dioxide layer and the film, a metallide nanolayer of Me and Si atoms is formed.

The resulting film has a nanostructure that is thermally stable to a temperature of 1200 ° C, which determines the high mechanical strength of the film during thermal cycling (i.e., raising and lowering the temperature), and thermally stable electrical properties of the film up to the temperature indicated above.

The specified method of manufacturing a doped conductive diamond-like nanocomposite film has significant disadvantages.

Since the description does not indicate any specific metal with which the film is alloyed, it is understood that the list of metals should be wide.

However, additional studies have determined that films doped with chromium, when subjected to ETH, do not show the ability to restructure the nanostructure. The atomic chemical bonds after ETV remain the same as before ETV, for example, carbon bonds remain typical for bonds in soot, i.e. the films remain carbon, do not transform into diamond-like ones, the films do not acquire the claimed layered structure, high mechanical strength during thermal cycling, and thermally stable electrical properties. These films are destroyed when heated to about 800 ° C.

It was also determined that the prototype did not explicitly identify a relationship between the internal processes occurring in the film and the behavior of the I – V characteristic during ETV. As a result, the use of a current generator as a power source during the entire ETV process is unreasonable and leads to a high probability of film destruction during the ETV process or shortly after its completion due to the formation of microcracks.

In addition, in the known method, the ETV is completed when the temperature of the film reaches a temperature of (800-1050) ° C. Since no relationship was found between the internal processes in the film and the behavior of the I – V characteristic during ETF, the determination of temperature requires its direct measurement in the process of ETF. However, this process is laborious and unreliable, because with tangible film sizes, for example, an area of several mm ² , heat dissipation in its various places is different and it is difficult to fix that the entire film is heated to the indicated temperature. At the same time, if some sections of the film are heated to less than 800 ° C, the same structural changes will not occur in the entire film volume. This will lead to a lack of temperature and temporal stability of the electrical resistance of the film even after the completion of the ETV, which means a deterioration in its working qualities.

In the known method, the ETV is carried out in a continuous pulsed current mode with a stepwise increase in the current amplitude and the exposure of each newly set amplitude value until the I – V characteristic of the film is stabilized. Thus, the mode of temperature fluctuations and fluctuations of mechanical stresses is set. It has been experimentally determined that the indicated regime of temperature and mechanical vibrations is insufficient and does not exclude the destruction of the film during the ETF at temperatures lower than that required to complete the ETF.

The basis of the present invention is the task of creating a method of manufacturing a doped diamond-like nanocomposite film having a thermally stable nanostructure, high electrical conductivity simultaneously with thermal strength, mechanical strength during thermal cycling and having stable electrical properties.

The problem is solved in that in a method for manufacturing a conductive doped diamond-like nanocomposite film, comprising creating a gas discharge plasma in a vacuum chamber into which organosiloxane is vaporized, deposition of carbon atoms, carbon atoms, silicon Si, oxygen O, hydrogen on substrates placed in a vacuum chamber N and alloying metal (Me), the choice of films characterized by the following composition of elements in atomic concentrations, A.K.%:

S 25-39

Me 20-35

Σ (C + Si + Me) 85-90

coating the surface of the selected films with a SiO ₂ layer, connecting them to an alternating current source and electrothermal action (ETV) on the film by passing through the alternating current film in the form of a series of pulses from 5 to 100 ms in duration with a stepwise increase in the current amplitude and holding the newly set value until the current-voltage stabilizes characteristics (CVC) of the film with the regime of temperature and mechanical stress fluctuations in the film for restructuring the nanostructure of the film to obtain a layered nanostructure in oroy A.K. Me in the direction from silicon dioxide to the substrate periodically and smoothly changes relative to the average film thickness A.K. Me, and this change is antiphase to a change in the same direction from silicon dioxide to the substrate and with the same period of atomic concentrations of C and Si, and at the interface between the silicon dioxide layer and the film, a transition metal layer of me and Si atoms is formed according to the invention Mo is used as an alloying Me, electrothermal action is carried out using a current generator in the I – V characteristic at ETH with an negative increase in resistance and a voltage generator in the I – V characteristic as an external power source a positive increase in resistance or constant resistance, in this case, the current is switched off after each set value of the current amplitude is held for a period of time necessary to cool the film to a temperature below 400 ° C, and the electrothermal action is completed at the I – V characteristic corresponding to a decrease in the film resistance by 10–25 % of the resistance value, the maximum achieved with its growth.

It is advisable that the I – V characteristic for ETH in an area corresponding to a temperature from 750 to 1100 ° C be N-shaped — alternating sections with a negative and positive increase in resistance with increasing temperature.

It is useful that the coating of the film surface with a layer of silicon dioxide is carried out by deposition.

Preferably, the surface of the film is coated with a layer of silicon dioxide by pyrolytic growth or magnetron sputtering of silicon dioxide.

It is advantageous that when passing alternating current through the film in the current generator mode and in the voltage generator mode in the form of a series of continuous pulses, the pulse duration is set depending on the thickness of the film and the substrate.

The use of Mo as a metal is proposed in connection with the following. It was determined by additional studies that, unlike other metals, the use of molybdenum as the metal ligature in the carbon nanocomposite films initial for ETV leads to the production of a layered film with the qualities necessary to achieve this goal during the ETV. It was determined that it is the presence of molybdenum in the initial carbon film that leads (when the temperature reaches 800 ° C during the ETH process, the film nanostructure is restructured (the film becomes layered), which is accompanied by a change in the chemical bond between the atoms — carbon bonds identified in the initial carbon films as bonds in soot, bonds are identified that are identified as bonds in silicon carbide (withstanding high temperatures) .Thus, it is determined that molybdenum is specific in this application.

It was determined that the onset and further dynamics of the process of restructuring the film nanostructure — the transition from a metastable nanostructure to a stable one with a change in chemical bonds — is associated with a specific behavior of the I – V characteristics during ETV of molybdenum-doped films. In a certain section of the CVC, its qualitative character sharply changes, i.e. a negative increase in film resistance with an increase in the amplitude of the current and when holding a certain value of the amplitude changes to a positive increase, or the resistance remains almost constant.

It was found that the beginning of the CVC section with a positive increase in resistance corresponds to heating of the local film section (in the region of the lowest heat removal) to a temperature of about (800-850) ° C, and it is at this point in the ETW and at the indicated local place that the film nanostructure is restructured. Thus, a relationship was revealed between the behavior of the I – V characteristics at ETH and internal processes in the film. When the entire film volume in the ETV process is heated to a temperature of at least (800-850) ° C, the portion of the I – V characteristic with a positive increase in resistance with a further increase in the current amplitude is again replaced by a section with a negative increase in resistance.

Thus, in the process of restructuring in a limited section of the I – V characteristic corresponding to a temperature of 750-1100 ° C, it acquires an N-shape. If a current generator is used as a source of electric power in the CVC section with a positive increase in resistance (the beginning corresponds to reaching a local temperature of 800-850 ° C and the beginning of the restructuring of the film nanostructure), the nature of the CVC (Fig. 1, ACB section) leads to a sharp uncontrolled transition from point A to point B (indicated by an arrow), the rapid course of the restructuring process, accompanied by uncontrolled growth of the power released on the film. This is followed by uncontrolled overheating of the film and its possible destruction during the ETV process or the formation of latent microcracks leading to destruction some time after the ETV.

Considering the relationship between the nature of the I – V characteristic during the ETH process and the internal processes of restructuring the film nanostructure, it is advisable to use a current generator in the I – V section with a negative increase in resistance (OEA section, Fig. 1), and in a section with a positive increase in resistance or practically stable resistance (AC section, Fig. .1) use a voltage generator as an external source. In the latter case, the indicated portion of the I – V characteristic during the ETV process is controlled by a stepwise increase in voltage, which will be accompanied by a stepwise decrease in current due to an increase in resistance, and an uncontrolled jump-like increase in electric power, and therefore, overheating of the film and the associated explosive nature of internal restructuring processes, will be excluded.

At point C, almost the entire film is restructured. The conductive doped diamond-like nanocomposite film (Fig.2b) has a layered structure in which A.K. Mo in the direction from silicon dioxide to the substrate periodically and smoothly changes relative to the average value of the film thickness A.K. Mo, and this change is antiphase to a change in the same direction from silicon dioxide to the substrate and with the same period of atomic concentrations of C and Si, and at the interface between the silicon dioxide layer and the film, a transition metal nanolayer 14 (Fig. 4) of atoms Mo and Si.

It is advisable for the guaranteed completion of structural changes in the entire film volume to focus not on reaching a certain temperature over the entire film area, but on changes in the qualitative nature of the I – V characteristic during the ETV process. The ETV process should be completed no earlier than at point D (Fig. 1) of the I – V characteristic, in which the film resistance decreases by 10–25% of the resistance value maximally achieved with its growth, since this decrease means that all sections of the film went through an increase in resistance, and therefore through the restructuring of the nanostructure. Guaranteed stable CVC of the film after ETV is shown in Fig. 1, section OD.

The invention is further explained in the description of the preferred embodiments with reference to the accompanying drawings, in which:

figure 1 depicts the current-voltage characteristic (CVC) of a doped carbon nanocomposite film - section OEACD in the ETV process - and the current-voltage characteristic of a doped diamond-like nanocomposite film - sections OC, OD, according to the invention;

figa depicts A.K. (atomic concentration) in% of the elements included in the composition of the conductive doped carbon nanocomposite film before ETV, according to the invention;

figv depicts A.K. a conductive doped carbon nanocomposite film with a modified nanostructure after ETV, according to the invention;

figa depicts current pulses in the process of ETV, according to the invention;

figv depicts a temperature change in the process of ETV, according to the invention;

4 depicts a conductive molybdenum-doped diamond-like nanocomposite film according to the invention.

A method of manufacturing a conductive alloyed diamond-like nanocomposite film is as follows.

Example

The dielectric substrates 1 of alternating layers 2, 3 (FIG. 1) of SiO ₂ and Si ₃ N ₄ with a total thickness of 2 μm are placed in the vacuum chamber on the holder, and the substrates 1 are placed on silicon membranes 4 with an area of 1 mm × 1.5 mm located on silicon frames 5 with a thickness of 1 μm.

A gas discharge plasma with an energy density of more than 5 kWh / gram atom of carbon particles is created in a vacuum chamber. Organosiloxane heated to a temperature of 500-800 ° C is evaporated into the created gas-discharge plasma, which, when decomposed in the plasma, serves as a source of carbon, silicon, oxygen and hydrogen. The temperature of the substrates is maintained at about 300 ° C.

Deposition from a gas-discharge plasma onto dielectric substrates placed in a vacuum chamber of carbon or silicon, oxygen, oxygen and hydrogen atoms with simultaneous deposition of silicon and molybdenum atoms by magnetron sputtering of a target from molybdenum silicide and producing a conductive doped carbon nanocomposite film 6 with a thickness on a dielectric substrate 0.4 μm with a uniform distribution of atoms throughout the volume (figa), part of the area which is located on the dielectric membrane is equal to 0.8 mm · 1.5 mm

According to the invention, Mo molybdenum is used as a source of alloying material.

The resulting films are tested and films are selected (Fig. 2a) having an atomic concentration (A.K.) of carbon of about 30% A.K. from the general A.K. elements, the atomic concentration of the alloying material of molybdenum is about 30% A.K. from the general A.K. elements and total A.K. silicon about 35% A.K. from the general A.K. elements.

Coat the surface of the films with a layer 7 (Fig. 4) of silicon dioxide with a thickness of 0.5 μm by pyrolytic buildup or by magnetron sputtering of silicon dioxide.

In the holes 8 of the layers of silicon dioxide place aluminum electrodes 9 by thermal spraying of aluminum. Carbon films 6 are connected through aluminum electrodes 9 to an alternating current source (not shown) to carry out the process of electrothermal action (ETV). The data below correspond to the embodiment described above with the indicated geometric dimensions of the structure and film.

The initial film resistance is measured at room temperature at a current of I = 1 mA, R = 300 Ohm. Set the current generator mode. A load resistance of 3 kΩ is set in the power source.

An alternating current is passed through the film in the form of a series of pulses having, for example, the shape of a rectified sinusoid, and the duration of a single pulse is set to 10 ms (Fig. 3a) in accordance with the above geometric dimensions of the film and the substrate, whereby the film is subjected to electrothermal action (ETV) while carrying out a stepwise increase in the amplitude of the current each time by 5 mA with a shutter speed of each newly set value. This allows, at the above geometric dimensions of the film and the substrate, after each subsequent increase in the current, to achieve the appearance of a small hysteresis in the region of the maximum current amplitude on the irreversible current-voltage characteristic (CVC) of the ETV process.

They carry out the exposure of each newly set current value for two minutes, which at the indicated geometric dimensions of the film and the substrate allows stabilization of the I – V characteristic (minimization of hysteresis).

Before each subsequent increase in the amplitude value, the current is turned off for two minutes, which, with the indicated geometric dimensions of the film and the substrate, allows the film to be cooled to a temperature below 400 ° C, and thus enhance the mode of temperature fluctuations and internal mechanical vibrations in the film.

The specified duration of the current transmission and the duration of the pause support throughout the process of ETV.

In this case, a stepwise increase in the current amplitude from 0 to 90 mA with shutter speeds and intercoolers of the aforementioned duration and in the current generator mode for the given example corresponded to a section with a negative increase in the OEA resistance (Fig. 1) on the I – V characteristic of the ETV process. In the indicated range of current variation, the resistance changed from 300 to 175 Ohms.

In the ETH process, up to a film temperature of 1100 ° С in the temperature range of 750-1100 ° С, an irreversible CVC of an N-shaped film is obtained in the EACD section, including an AC section corresponding to the process of restructuring the film nanostructure with increasing resistances. In this particular example, when the current was increased from 90 to 95 mA during the ETV process, an increase in resistance was recorded from 175 to 180 Ohms (the voltage on the film increased from 15.8 V to 17 V). Thus, on this basis, at the power of P = 1.62 W, the beginning of the restructuring of the film nanostructure was recorded, and due to a change in the sign of the differential resistance, the power supply mode at this point of the I – V characteristic was switched to voltage generator mode - the load resistance R = 20 Ohms was established.

Then, in the ETV process, the voltage amplitude value was changed stepwise (and not the current amplitude value), and the value of each step was 0.2 V, which, in accordance with the above geometric dimensions of the film and the substrate, provides a smooth change in the power released on the film during its internal restructuring in the AC area, preventing the destruction of the film in this section of the CVC (Fig 1).

At a voltage value of V = 18.2 V and a current of I = 88 mA, the maximum film resistance at ETV is R = 207 Ohm — corresponds to point C in FIG. 1. At this point C, the nanostructure of almost the entire film is restructured, i.e. a layered structure is obtained and chemical bonds are changed. With a further increase in voltage, a negative increase in resistance is observed. In this regard, the power supply mode is returned to the current generator mode - the load resistance R is set to at least 2 kΩ.

A further increase in the amplitude of the current will correspond to the plot of CB (figure 1). The ETV process is terminated at a current of I = 100 mA and a voltage of V = 19 V. R = 190 Ohms, which differs by ~ 10% from the value of the resistance achieved during its growth (corresponds to point D in Fig. 1). This decrease means that all The sites went through an increase in resistance, and therefore through the restructuring of the nanostructure.

The ETV process is carried out at the stand according to a computer-controlled program.

The result is a conductive doped diamond-like nanocomposite film (fig.2b) having a layered structure, in which A.K. molybdenum in the direction from silicon dioxide to the substrate varies periodically and smoothly relative to the average value of the film thickness A.K. molybdenum, and this change is out of phase with a change in the same direction from silicon dioxide to the substrate and with the same period of atomic concentrations of C and Si, and at the interface between the layer of silicon dioxide and the film, a transition metal layer of molybdenum and silicon atoms is formed.

The resulting film has a thermally stable (up to a temperature of 1200 ° C) microstructure, which determines the high mechanical strength of the film during thermal cycling, thermally stable electrical properties of the film up to the temperature indicated above, characterized by a stable and reversible current-voltage characteristic of the OD line in FIG. 1.

The inventive method allows to provide a small percentage of destruction of the films during the ETV process - in the control batch of 20 films with the same geometric and initial electrical parameters indicated above, one film was destroyed during the ETV process, which amounted to 5% of the total number.

Claims (5)

1. A method of manufacturing a conductive alloyed diamond-like nanocomposite film, comprising creating a gas-discharge plasma in a vacuum chamber into which organosiloxane is vaporized, deposition on a substrate placed in a vacuum chamber of carbon or carbon atoms (C), silicon (Si), oxygen (O), hydrogen (H) and alloying metal (Me), the choice of films, characterized by the following composition of elements in atomic concentrations, A.K.%: S 25-39 Me 20-35 Σ (C + Si + Me) 85-90 coating the surface of the selected films with a SiO ₂ layer, connecting them to an alternating current source and electrothermal action (ETV) on the film by passing through the alternating current film in the form of a series of pulses from 5 to 100 ms in duration with a stepwise increase in the current amplitude and holding the newly set value until the current-voltage stabilizes characteristics (CVC) of the film with the regime of temperature and mechanical stress fluctuations in the film for restructuring the nanostructure of the film to obtain a layered nanostructure in oroy A.K. Me in the direction from silicon dioxide to the substrate varies periodically and smoothly relative to the average value over the film thickness A.K. Me and this change are antiphase to a change in the same direction from silicon dioxide to the substrate and with the same period of atomic concentrations of C and Si, and at the interface between the silicon dioxide layer and the film, a transition metallide nanolayer of Me and Si atoms is formed, characterized in that that Mo is used as an alloying Me, the electrothermal action is carried out using a current generator in the I – V characteristic section at EHV as an external power source with a negative increase in resistance and a voltage generator in the VA section with a positive increase in resistance or constant resistance, in this case, the current is switched off after each set value of the current amplitude is held for a period of time necessary to cool the film to a temperature below 400 ° C, and the electrothermal action is completed at the I – V characteristic corresponding to a decrease in the film resistance by 10- 25% of the maximum resistance value achieved with its growth. 2. The method according to claim 1, characterized in that the I – V characteristic at ETH in the area corresponding to a temperature from 750 to 1100 ° C has an N-shape — alternating sections with a negative and positive increase in resistance with increasing temperature. 3. The method according to claim 1, characterized in that the coating of the film surface with a layer of silicon dioxide is carried out by deposition. 4. The method according to claim 1, characterized in that the coating of the film surface with a layer of silicon dioxide is carried out by pyrolytic build-up or magnetron sputtering of silicon dioxide. 5. The method according to claim 1, characterized in that when passing through the film an alternating current in the current generator mode and in the voltage generator mode as a series of continuous pulses, and the pulse duration is set depending on the thickness of the film and the substrate.

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