WO2003095698A2

WO2003095698A2 - Device and method for the electron beam attenuation of reactively formed layers on substrates

Info

Publication number: WO2003095698A2
Application number: PCT/DE2003/001524
Authority: WO
Inventors: Otmar Zimmer; Peter Siemroth; Bernd Schultrich; Steffen Schenk; Ulf Seyfert; Christian Hecht; Ekkehart Reinhold; Bernd Schuhmacher
Original assignee: Fraunhofer-Gesellschaft Zur Förderung Der Angewan Dten Forschung E.V.
Priority date: 2002-05-10
Filing date: 2003-05-07
Publication date: 2003-11-20
Also published as: AU2003239759A1; AU2003239759A8; WO2003095698A3

Abstract

The invention relates to a device and method for the electron beam attenuation of reactively formed layers on substrates in a vacuum. The aim of the invention is to increase the efficiency compared to conventional solutions and to improve the quality of the reactively formed layers. To these ends, the invention provides that both a crucible containing a chemical element as well as a substrate to be coated are provided inside a vacuum chamber, and an electron beam source is provided on said vacuum chamber. A shield with an aperture opening, through which the produced vapor can reach the substrate, is placed between the crucible containing the chemical element and the substrate. The shield protects at least one element for exciting, dissociating and/or ionizing a reactive gas, which is introduced via at least one gas inlet protectively arranged between the substrate and the shield.

Description

Device and method for electron beam vapor deposition of reactively formed layers on substrates

The invention relates to a device and a method for electron beam vapor deposition of reactively formed layers on substrates in a vacuum, coatings on the surfaces of substrates as e.g. Oxides, nitrides, carbides but also carbonitrides etc. can be trained.

In addition to various other options, evaporation is e.g. of a metal within a vacuum chamber using electron beams, with which the respective metal can be heated, melted and subsequently evaporated, is known per se.

Such an evaporation process can usually be carried out at internal pressures in vacuum chambers of approximately 0.01 to 0.1 Pa. When using electron beam sources with a relatively high power, layer application rates of several μm / s can be achieved, the particle energy of the metal vapor generated with the electron beam being below 1 eV.

The interaction between metal vapor and electron beam is negligible. The layers thus formed from the pure metal on substrates have a porous and stem-like structure.

Approaches are also known with which, using electron beams from a metal vapor formed with the electron beams and an additionally supplied reactive gas, are applied to substrates. Layers that consist of reactively formed metal compounds can be produced.

Due to the relatively low reactivity of the reactive gases commonly used, e.g. Nitrogen, oxygen or hydrocarbon compounds to the respective metals, a supply of the reaction gas is required, which causes a correspondingly high partial pressure within the vacuum chamber.

As a result of this increased partial pressure of the reactive gas, the electron beam used for the evaporation is scattered to an increased extent and, accordingly, a large proportion of the energy of the electron beam cannot be used for the pure evaporation, so that an increased power loss can be recorded.

The increased partial pressure also has the effect that the particle energies of the atoms contained in the steam are additionally reduced by impacts, and the porosity (increase) and adhesive strength (reduction) of the coating formed on the substrate surface are also adversely affected.

These problems can also not be solved satisfactorily with the solution described in DE 36 27 151 AI.

A crucible containing metal is arranged within a separate inner chamber in a vacuum chamber and an electron beam is directed through an opening to form a metal vapor on the metal surface. There is an additional reactive gas supply inside the inner chamber and it is used at partial pressures of up to 10 Pa worked. As a result of the increased scattering of the electron beam already mentioned, an increased beam power, in particular a high acceleration voltage, is accordingly required. Such an electron beam source must be operated with acceleration voltages that are above 30 kV.

These disadvantages can also not be eliminated with an additional electrode connected as an anode, which is arranged outside the inner chamber, around an opening which is formed in the inner chamber and the electrode between the inner chamber and the substrate.

It is therefore an object of the invention to propose ways in which layers of reactively formed chemical compounds on substrates can be obtained by electron beam evaporation of the respective chemical element with increased efficiency and improved layer properties.

According to the invention, this object is achieved with a device having the features of claim 1 and a method with the features of claim 13. Advantageous embodiments and developments of the invention can be achieved with the features mentioned in the subordinate claims.

The device according to the invention for electron beam vapor deposition of reactively formed layers on substrates uses a crucible containing the respective chemical element within a vacuum chamber. With an electron beam source present on the vacuum chamber, an electron beam can vaporize the chemical element onto the surface be directed within the crucible.

A shield is provided between the crucible containing the chemical element and the substrate in which an aperture for the steam directed onto the substrate is formed. Between this shield and the substrate on which the reactively formed coating is to be formed, there is at least one additional element which is suitable for the excitation, dissociation and / or ionization of a reactive gas used in each case. Both the at least one gas inlet for the reactive gas and the at least one element for activating, dissociating and / or ionizing the reactive gas are arranged within areas protected from vapor deposition, by appropriate design of the shield and the design and arrangement of the aperture. With such an arrangement, the at least one additional element is not directly influenced by the interactions of the reactive gas with the vapor formed.

A gas mixture can also be supplied through the at least one gas inlet for reactive gas, which also contains inert gas in addition to reactive gas. However, inert gas can also be supplied separately, an inert gas supply also being able to be arranged in front of the shielding, that is to say inside the vacuum chamber, and the inert gas can be supplied, for example, into the area of influence of the electron beam and / or into the vapor formed.

As a result, a direct influence on the at least one element and the reactive gas supplied, which is not influenced thereby, by the vapor of the chemical element formed can be avoided. the .

The excitation, dissociation and / or ionization of the respective reactive gas is achieved with the at least one element by appropriate energy supply. This can be achieved by means of electrical discharges, microwave discharges or also by means of electromagnetic fields formed.

Accordingly, the one or more elements can be designed as corresponding electrodes, coils but also as antennas.

The reactive gas can be activated, for example, by arc, glow and / or hollow cathode discharges, and the one or more element (s) can accordingly be designed accordingly.

In a relatively simple embodiment, one or more electrodes can be used, to which a direct voltage positive relative to the electrical potential of the vacuum chamber is connected.

In the simplest case, it can be one or more ring electrodes that are formed around the respective aperture opening.

The diaphragm opening can be designed as a slit diaphragm, preferably with a rectangular or square cross section.

When using arc discharges, the use of at least two electrodes, which act as anode and cathode with appropriate electrical potentials, is len are required.

It is particularly advantageous to arrange the respective anode as an element for increasing the reactivity of the reactive gas in the protected area between the shield and the substrate and to switch the crucible containing the respective chemical element as a cathode. As a result, additional activation of the steam formed can be achieved at the same time.

In the event that the at least one element is a hollow cathode, the reactive gas supplied should be passed through the hollow cathode. In this case, it may be necessary to additionally lead an inert gas to and through the hollow cathode, preferably via a second gas inlet. A suitable inert gas is, for example, argon.

In the solution according to the invention, as already indicated, the diaphragm opening should be designed and the diaphragm opening and the at least one element should be arranged in such a way that steam cannot impinge directly on the one or more correspondingly used element (s), i.e. a linear movement of Steam particles, starting from the crucible to one or more element (s), are not possible. Compared to the known solutions, the supply of the required reactive gas can be significantly reduced with the invention and the reactive layer formation can be carried out at partial pressures which are 0,1 0.15 Pa, preferably also 0,1 0.1 Pa. Furthermore, the electron beam source can be operated with significantly lower power and with acceleration voltages below 20 kv. With the invention, different coatings can be formed from different reactively formed, for example metal, compounds on surfaces of substrates. In addition to metals, other chemical elements such as silicon or boron can also be used.

Accordingly, different reactive gases can be supplied for the respective chemical element and the respectively desired reactively formed compound.

The reactive gas supplied can thus be pure oxygen for the formation of oxide layers, but also pure nitrogen for the formation of nitride layers.

Furthermore, there is the possibility of also supplying hydrogen-containing compounds as reactive gas, it being possible to use the at least one element in addition to excitation or ionization to achieve dissociation in the form of an at least partial splitting of such a hydrogen-containing compound.

As such reactive gases, for example, hydrocarbon compounds can be used, which preferably have a relatively low binding energy, so that a reactive carbide layer or carbonitride layer can be produced after the at least partial splitting.

However, it is also conceivable to use ammonia as a correspondingly suitable reactive gas, which can be split up accordingly, to form nitride layers. When using hydrogen-containing compounds as reactive gas, the released hydrogen can be easily removed from the vacuum chamber by means of the already existing vacuum pump.

With the solution according to the invention there are also possibilities for a regulation or control of the process control which has an advantageous effect on the layer formation.

For example, the volume flow of the reactive gas supplied can be controlled or regulated.

Furthermore, there are possibilities for influencing the effect of the at least one element for excitation, dissociation and / or ionization of the reactive gas by influencing the corresponding electrical voltage, the electrical current and consequently the power that can be supplied. However, the power of a microwave generator can also be regulated or controlled.

In addition and also alone, the respective power of the electron beam source can also be influenced accordingly.

For regulation, it is advantageous to detect plasma-relevant parameters during the process control. This can be done, for example, with a suitable sensor, e.g. optically by means of an emission spectroscope.

But there is also the possibility of the electrical voltage and / or the electrical current, respectively on the one or more elements is flowing, because these parameters are influenced by the conditions and in particular by the state of the plasma.

A further advantageous possibility of exerting influence is that a favorable electrical potential can also be applied to the substrate, on the surface of which the corresponding coating is to be formed. A corresponding positive or negative electrical voltage, which may also take into account the plasma-relevant parameters, can be connected, so that the layer formation rate and the quality of the coating formed can be additionally improved.

In addition to the reduction in partial pressure which can be achieved with the invention and at the same time reduced power, in particular the acceleration voltage of the electron beam source, the invention can also be used to maintain defined and reproducible conditions when carrying out the coating process.

The influence desired according to the invention, with a simultaneous increase in the reactivity of the reactive gas, is limited to a certain range which is favorable for the process. The evaporation process, especially the electron beam, remains largely unaffected by this.

In addition, undesired deposits of reaction products formed on the inner wall of a vacuum chamber and other further internals are largely avoided. There are also options for specifically influencing the chemical reaction between the reactive gas or an elementary component of the reactive gas with the respective vapor of the chemical element. As a result, the layer composition and the layer properties can also be influenced in a targeted manner. The respective substrate temperature can be largely neglected. For example, heating or cooling of a substrate is not necessary, which has an advantageous effect in particular in the case of substrates passed through a vacuum chamber.

The solution according to the invention can be used in the case of substrates moved translationally through a vacuum chamber to form surface layers. However, a corresponding rotation of a substrate within a vacuum chamber is also possible.

The invention will be described in more detail below by way of example.

It shows:

Figure 1 shows an example of a device according to the invention in schematic form.

1 shows an example of a device according to the invention in schematic form. Here, a crucible 7 is arranged within a vacuum chamber; in which a metal is contained as chemical element 8.

With an electron beam source 10, which is present on the vacuum chamber, an electron beam 11 directed to the surface of the chemical element 8, for example a metal, and steam 9 formed by corresponding energy input, which, as indicated by the arrow, is led to the substrate 4 to be coated.

A shield 3 is arranged between the crucible 7 containing the chemical element 8 and the substrate 4, which in this example can be passed through a vacuum chamber as indicated by the horizontally oriented arrow. In this shield 3, an aperture 6 is formed, on which in this example a funnel-shaped inlet for the steam 9 is additionally present.

In this example, the shield 3 forms part of a reaction chamber, the remaining part of the reaction chamber being essentially formed by the substrate 4.

However, there is also the possibility of designing the shield 3 as a whole as a reaction chamber, in which the respective substrate to be coated can then be accommodated.

On the shield 3 shown here there is a gas inlet 5 for a reactive gas, which is arranged as far as possible outside the area that can be directly influenced by the steam 9.

The same also applies to the electrode 1, which in this example is designed as a ring electrode around the aperture.

With this ring electrode 1 as an element, a ne excitation, dissociation and / or ionization of a reactive gas supplied through the gas inlet 5 can be achieved, so that the reactivity between the respective steam 9 and the respective reactive gas or an elementary component of such a reactive gas within zone 2 is increased.

Instead of a ring electrode, two or more electrodes can also be arranged separately in accordance with one another.

An additional ion source is not required in this example.

However, a large-volume excitation of the reactive gas can be achieved and a gas-steam mixture with high reactivity can be achieved in zone 2 to form the respective compound for the layer to be formed.

For the formation of a titanium nitride coating on a substrate 4, titanium is used as the chemical element 8 within the crucible 7.

Before the coating is formed, the vacuum chamber is evacuated to a pressure of 10 ^-3 Pa.

After the titanium has been preheated by means of the electron beam source 10, nitrogen is fed in via the gas inlet 5 until a partial pressure of 0.08 Pa has been reached in the region between the shield 3 and the substrate 4, and is stabilized to this partial pressure by means of an appropriate control system.

The electron beam source 10 is operated with an acceleration voltage of 16 kV. A direct voltage of 60 V is applied to the electrode 1, which is positive with respect to the electrical potential within the vacuum chamber and in particular the electrical potential that is present at the crucible 7.

Following a short start-up time, a discharge current of a few 100 A is established at the electrode 1 and the electrical voltage during this discharge is approximately 40 to 50 V.

With a uniform movement of the substrate 4 through the vacuum chamber, a constant layer thickness of the reactively formed titanium nitride coating can be achieved, stoichiometric titanium nitride layers with a golden yellow color being produced with a modulus of elasticity of 400 GPa.

With otherwise constant process conditions, the respective layer thickness can be influenced by the corresponding speed at which the substrate is moved through the vacuum chamber.

Claims

claims

1. Device for electron beam vapor deposition of reactively formed layers on substrates,

in which a crucible (7) containing a chemical element (8), a substrate (4) to be coated and an electron beam source (10) for evaporating the chemical element (8) are present in a vacuum chamber;

a shield (3) between the crucible (7) containing the chemical element (8) and the substrate (4), in which there is an aperture

(6) for steam directed onto the substrate (4)

(9) as well

protected with the shield (3) at least one element (1) for excitation, dissociation and / or ionization of a reactive gas,

which can be introduced via at least one gas inlet (5) which is arranged between substrate (4) and shield (3) in a protected manner,

are arranged.

2. Device according to claim 1, characterized in that the element (s) (1) is an electrode or an electrical coil.

3. Device according to claim 1 or 2, characterized in that the element (s) (1) is / are designed as a ring electrode (s).

4. The device according to at least one of the preceding claims, characterized in that the element (s) (1) is / are designed as a hollow cathode.

5. The device according to at least one of the preceding claims, characterized in that the element (1) is at least one antenna for microwaves or the formation of electromagnetic fields.

6. The device according to at least one of the preceding claims, characterized in that at least two different elements (1) are present for the excitation, dissociation and / or ionization of reactive gas.

7. The device according to at least one of the preceding claims, characterized in that the aperture (6) is formed and aperture (6) and the at least one element (1) are arranged so that no steam (9) directly on the / the element (e) (1) hits.

8. The device according to at least one of the preceding claims, characterized in that the shield (3) forms a reaction chamber or part of a reaction chamber.

9. The device according to at least one of the preceding claims, characterized in that the crucible containing the chemical element (8)

(7) has an electrically negative potential applied to it and forms a cathode and at least one electrode, as one element (1), is connected to an electrically positive potential and forms an anode.

10. The device according to at least one of the preceding claims, characterized in that at least one additional gas inlet for an inert gas is present.

11. The device according to at least one of the preceding claims, characterized in that at least one sensor for detecting plasma-relevant parameters is present.

12. The device according to claim 11, characterized in that the sensor is an emission spectroscope.

13. Method for electron beam vapor deposition of reactively formed layers on substrates,

in which vapor (9) is formed within a vacuum chamber by means of an electron beam (11) directed at a chemical element (8) contained in a crucible (7),

the steam (9) is directed through an aperture (6) formed in a shield (3) onto the surface of the substrate (4) to be coated,

excitation, dissociation and / or ionization of a reactive gas supplied via at least one gas inlet (5) is carried out within a protected area between the shield (3) and the substrate (4) with at least one element (1),

from the chemical element, the reactive gas or an elementary component of the reactive gas on the substrate surface, the reactively formed layer is formed.

14. The method according to claim 13, characterized in that an elementary gas is supplied as the reactive gas.

15. The method according to claim 14, characterized in that nitrogen or oxygen is supplied.

16. The method according to claim 13, characterized in that a hydrogen-containing compound is supplied as the reactive gas.

17. The method according to claim 16, characterized in that a hydrocarbon compound or ammonia is supplied as the reactive gas.

18. The method according to at least one of claims 13 to 17, characterized in that the reactive gas is supplied with a partial pressure ≤ 0.15 Pa.

19. The method according to at least one of claims 13 to 18, characterized in that the excitation, dissociation and / or ionization is carried out by an electrical and / or microwave discharge.

20. The method according to claim 19, characterized in that the excitation, dissociation and / or ionization is carried out by an arc, glow and / or hollow cathode discharge.

21. The method according to at least one of claims 13 to 19, characterized in that the excitation, dissociation and / or ionization is carried out by means of electromagnetic fields.

22. The method according to at least one of claims 13 to 21, characterized in that an inert gas is additionally supplied.

23. The method according to at least one of claims 13 to 22, characterized in that an additional excitation of the steam with a discharge

(9) is carried out.

24. The method according to claim 23, characterized in that the additional excitation of the steam (9) by means of an arc discharge between an electrode connected as an anode, as an element (1) and that connected as a cathode, the chemical element (8 ) containing crucible (7).

25. The method according to at least one of claims 13 to 24, characterized in that the partial pressure with which the reactive gas is supplied is regulated or controlled.

26. The method according to at least one of claims 13 to 25, characterized in that the electrical parameters of the element (s) (1) and / or the electron beam source (10) are regulated or controlled.

27. The method according to at least one of claims 25 and 26, characterized in that the control is carried out as a function of plasma-relevant and / or electrical parameters.

28. The method according to at least one of claims 13 to 27, characterized in that titanium is used as the metal (8) and nitrogen to form a titanium nitride layer on the substrate (4).

29. The method according to at least one of claims 13 to 28, characterized in that the substrate (4) is moved during the formation of the coating.

30. The method according to at least one of claims 13 to 29, characterized in that a predeterminable electrical potential is applied to the substrate.