WO2024068143A1 - Deposition of material layers by evaporation and dual activation - Google Patents

Abstract

Deposition of a material such as indium in the form of nitrided thin layers, by evaporation and dual activation using a nitrogen plasma (41) and an electron beam (42).

Description

Deposition of layers of material by evaporation and double activation

The invention relates to the field of deposition of material in the form of thin layers.

The invention has particular applications in the optoelectronics and electronics sectors.

State of the prior art

A conventional technique consists of carrying out vapor deposition of material under vacuum. The material is evaporated from a crucible towards a substrate passing through a medium which can be passive or active.

It is particularly known to use a plasma as the active medium, typically making it possible to improve the adhesion of the material to the substrate and to obtain uniform and non-porous layers.

Among other disadvantages, known plasma processes do not allow the production of layers with low thermal dissociation energy, in particular of indium nitride whose dissociation temperature is approximately 500°C.

Alternative techniques have been proposed to develop layers of indium nitride, in particular epitaxy, reactive sputtering, as well as pulsed laser deposition.

However, these techniques are not satisfactory because they require high temperatures and high radiofrequency plasma powers which degrade the quality of the layers deposited.

The invention aims to remedy the drawbacks of the deposition techniques known in the prior art and, in particular, to provide a solution making it possible to deposit layers with low dissociation energy, in particular layers of indium nitride.

The invention is however not limited to this type of material and also aims to provide a deposition technique making it possible to obtain layers of different materials, having satisfactory physicochemical, electrical, optical and/or mechanical properties. .

To this end, the subject of the invention is a material deposition device comprising:
– a surface for receiving a sample of material,
– a substrate intended for depositing the material,
– an enclosure defining between the receiving surface and the substrate a first region capable of receiving plasma and a second region capable of receiving electrons,
– a plasma generation member for a gas such as nitrogen configured to generate the plasma in the first region of the enclosure,
– an electron emitting member configured to emit electrons in the second region of the enclosure,
– an evaporation member configured to evaporate the material from the sample so as to move the material thus evaporated successively in the first region and in the second region of the enclosure towards the substrate.

The invention thus makes it possible to carry out a double activation of the evaporated material, on the one hand with the plasma and on the other hand with the electrons generated in the enclosure, making it possible to deposit nitrided layers on the substrate by evaporation.

Generally speaking, the invention makes it possible to obtain thin nitrided layers on a large scale, at lower cost, at a high deposition rate and of good quality.

The invention makes it possible in particular to carry out deposition at low temperature, in particular at a temperature lower than 300°C, with a plasma generated at low power, in particular a power lower than 100 W.

Thus, unlike epitaxy, sputtering or pulsed laser techniques, the low power of plasma allows, among other things, the deposition of layers of indium nitride to form a material presenting the required physicochemical and structural properties.

More generally, the sample of material used may include an inorganic element from the periodic table, such as aluminum, indium or even titanium, which are likely to acquire electrical and optical properties following their nitriding.

Many applications can be envisaged, including the manufacture of optoelectronic or power electronic components, particularly in the form of layers of indium or aluminum nitride, the manufacture of materials with high or low thermal conductivity, particularly in the form of layers of aluminum nitride, or even the manufacture of surface coatings, in particular in the form of layers of titanium nitride.

In one embodiment, the device comprises a member for generating a magnetic field. This member is preferably configured to generate a magnetic field in said second region of the enclosure in order to modify the trajectory of the electrons emitted in this second region.

This organ can be a magnet or an electromagnet.

The presence of such a magnetic field makes it possible to lengthen the trajectory of the electrons emitted in the enclosure, leading to an increase in the rate of ionization of nitrogen and, consequently, in the rate of nitriding of the evaporated material.

This results in an increase in the nitriding rate of the deposited layers.

In one embodiment, the device comprises a pumping member configured to lower the pressure of the enclosure.

The pumping device allows the enclosure to be placed under vacuum.

This pumping member may include a vacuum pump of the cryogenic or turbomolecular type.

In one embodiment, the device comprises a member configured to generate a pressure difference between a first chamber of the enclosure forming the first region and the second region and a second chamber receiving the sample.

This organ can be a partition type diaphragm with an opening sized to produce such a pressure difference.

In other words, differential pumping can be implemented in the enclosure, for example to promote the evaporation of the material.

In one embodiment, the electron emitting member comprises a filament and means for heating the filament.

In one embodiment, the plasma generating member comprises means for injecting said gas into the enclosure and a mechanism configured to create an electrical potential difference so as to generate the plasma in said first region of the enclosure .

The invention also relates to a method of depositing material on a substrate using a device as described above.

More generally, a method of the invention comprises:
– generation of plasma from a gas such as nitrogen in a first region of an enclosure,
– an emission of electrons in a second region of the enclosure,
– an evaporation of material so as to move the material thus evaporated towards the substrate, successively in the first region in which the plasma is generated and in the second region in which the electrons are emitted.

In one mode of implementation, the method comprises generating a magnetic field, using a magnet or electromagnet, in said second region of the enclosure so as to modify the trajectory of the electrons emitted in this second region.

In one embodiment, the method includes lowering the pressure of the enclosure using a pumping member.

It is preferred that the material comprises an inorganic element from the periodic table, such as aluminum or indium, or an alloy comprising such an inorganic element.

Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows.

Brief description of the figure

The following detailed description refers to:

schematically showing a device according to the invention.

Detailed description of embodiments

He is represented at the a device 1 provided for evaporating a sample 2 of material, for activating the evaporated material then depositing it on a substrate 3 in the form of thin layers, that is to say layers typically having a thickness which can range from a few nanometers to a few microns.

The device 1 comprises a frame 4 forming an enclosure 5 and comprising a structure 6 for supporting the substrate 3 as well as a partition 7 intended to separate the enclosure 5 into two chambers 5A and 5B.

Device 1 further comprises a crucible 11, an evaporation member 12, a plasma generation member 13, an electron emitting member 14, a pumping member 15 and a magnet 16.

There indicates a frame of reference defining mutually orthogonal directions D1, D2 and D3.

Substrate 3 and crucible 11 are away from each other along direction D2, called “longitudinal direction”.

More precisely, the crucible 11 comprises a surface 21 for receiving the sample 2 arranged opposite a surface 22 of the substrate 3 intended for depositing the material, these surfaces 21 and 22 being spaced apart from each other according to D2 by distance X1.

As an indication, the distance X1 is in this example equal to 400 mm.

The enclosure 5 presents, longitudinally between the surface 21 of the crucible 11 and the surface 22 of the substrate 3, a space provided to allow movement of the material of the sample 2 evaporated from the crucible 11 to the substrate 3 along a trajectory having at least one longitudinal component, that is to say oriented along the direction D2 in a direction going from the bottom to the top of the .

The member 12 is in this example a thermal evaporation member, configured to heat the sample 2 placed on the surface 21 of the crucible 11 by the Joule effect.

Of course, crucible 12 is made of a material having a melting temperature higher than the evaporation temperature of sample 2. In this example, crucible 12 is made of tungsten.

Concerning the generation of plasma, organ 13 of the comprises on the one hand a means 31 making it possible to inject a gas into the enclosure 5, in particular into the chamber 5A. In this example, the gas injected by the injection means 31 comprises nitrogen.

The member 13 also comprises a mechanism 32 configured to create an electrical potential difference in order to produce the plasma with the nitrogen injected into the enclosure 5 under the action of this potential difference. To the , the reference 32 designates a polarization rod of this mechanism, the other elements of this mechanism not being shown.

In a manner known per se, the mechanism 32 may comprise a voltage or radio frequency generator making it possible to create said potential difference between a cathode, which may be formed by a part of the polarization rod 32, and an anode.

As an indication, the potential difference can be of the order of 500 V and the plasma power less than 100 W.

Concerning the emission of electrons, the member 14 comprises in this example a filament (not shown) configured to be crossed by an electric current so as to heat the filament and thus emit electrons.

In the example of the , the device 1 is configured so that the member 13 can generate the plasma in a first region 41 of the enclosure 5 and so that the member 14 can concomitantly generate an electron beam in a second region 42 of the enclosure 5. enclosure 5, adjacent to the first region 41.

In this example, regions 41 and 42 are both constituted by parts of the space formed by chamber 5A and extend longitudinally between crucible 11 and substrate 3.

Concerning also the pumping member 15, this comprises in the present embodiment a vacuum pump. In other embodiments, the organ 15 may comprise another type of pump, for example a turbomolecular pump.

Pumping member 15 is configured to lower the pressure of chamber 5B.

Taking into account the geometry of partition 7, pumping member 15 also makes it possible to lower the pressure of chamber 5A during deposition (see further below).

In other words, the pumping member 15 is in this non-limiting example designed to lower the pressure of the entire volume of enclosure 5.

Furthermore, structure 6 supporting substrate 3 is in this example mounted movable relative to frame 4, in this case rotating around an axis parallel to direction D2. Device 1 comprises means (not shown) making it possible to move structure 6 in rotation around this axis, so as to be able to move substrate 3 relative to frame 4 during deposition (see further below).

Partition 7 includes an opening 51 allowing evaporated material to move from chamber 5B to chamber 5A through this opening 51. In this example, opening 51 is dimensioned so that the pressure is substantially identical in chamber 5A and in room 5B.

In this example, the magnet 16 is a permanent magnet mounted on the frame 4, near said second region 42. In particular, the device 1 is arranged so that the substrate 3 is arranged longitudinally between the magnet 16 and the second region 42 of enclosure 5.

Magnet 16 is more specifically configured to generate a magnetic field in the second region 42 of enclosure 5.

A non-limiting example of the implementation of this device 1 will now be described.

In the example described here, sample 2 includes indium.

The pressure of enclosure 5, initially at atmospheric pressure, is lowered using pumping member 15.

The nitrogen plasma is generated in the first region 41 of enclosure 5 using organ 13.

An electron beam is emitted in the second region 42 of enclosure 5 using organ 14.

The material from sample 2 is heated using member 12 so as to cause this material to pass into the vapor state.

The evaporated material 60 is thus moved towards the substrate 3, along a trajectory comprising at least one component parallel to the direction D2. In doing so, the evaporated material 60 passes from chamber 5B receiving crucible 11 to chamber 5A via opening 51 of partition 7, then successively passes through the first region 41 and the second region 42.

Particles of the evaporated material from sample 2 are thus ejected towards substrate 3, being subjected to double activation by the nitrogen plasma on the one hand and the electron beam on the other hand.

This double activation leads to an increase in the nitriding rate of the material before deposition on substrate 3.

The magnetic field generated in the second region 42 increases the length of the electron trajectory, which increases the rate of ionization of nitrogen and consequently the rate of nitriding of the deposited material.

Upon arriving at substrate 3, the particles of material thus activated condense so as to form thin layers adhering to substrate 3.

During deposition, structure 6 supporting substrate 3 is rotated in order to improve the homogeneity of the deposited layers.

The invention thus makes it possible to form thin layers rich in nitrogen, with a high deposition speed, typically of the order of a few nm/s, a low deposition temperature, a low plasma generation power and a production cost. reduced.

Of course, numerous variations can be made to device 1 and to the deposition process which have just been described, in particular by modifying the means making it possible to fulfill the functions described above and/or the arrangement of these different means, provided that they make it possible to carry out a double activation of evaporated material before deposition on a substrate.

Thus, in an alternative embodiment, the evaporation member 12 comprises a means other than a Joule effect heating means, for example an induction heating means, or a means configured to carry out the evaporation of material using another technique, for example by electronic bombardment.

For another example, the device 1 can be devoid of the permanent magnet 16 illustrated on the . The device may not include a magnet or may include another type of magnet, for example an electromagnet or another means of generating a magnetic field in the second region 42 and/or in other regions of the enclosure 5 .

In one embodiment, not shown, the device 1 is distinguished from that of the in that it does not have partition 7.

In another embodiment, opening 51 of partition 7 is dimensioned so as to generate a pressure differential between chambers 5A and 5B under the action of pumping, in order to promote the evaporation of an element such as aluminum, for example.

The invention can also implement additional means, not described above. For example, device 1 may include a quartz balance placed near substrate 3 in order to control the thickness of the layers deposited.

Furthermore, the invention can be implemented to produce layers from a material comprising elements other than indium. In particular, sample 2 may comprise an inorganic element from the periodic table, for example a metallic element such as aluminum or titanium, or an alloy comprising such an inorganic element.

Claims (5)

Process for depositing material on a substrate (3) comprising:
– generation of plasma from a gas such as nitrogen in a first region (41) of an enclosure (5),
– an emission of electrons in a second region (42) of the enclosure (5),
– an evaporation of material so as to move the material thus evaporated towards the substrate (3), successively in the first region (41) in which the plasma is generated and in the second region (42) in which the electrons of so as to increase the nitriding rate of the material before deposition on the substrate (3). Method according to claim 1, comprising generating a magnetic field, using a magnet (16) or electromagnet, in said second region (42) of the enclosure (5) so as to modify the trajectory of the electrons emitted in this second region (42). Method according to claim 1 or 2, comprising lowering the pressure of the enclosure (5) using a pumping member (15). Method according to claim 3, in which the first region (41) and the second region (42) of the enclosure (5) are formed by a first chamber (5A) of the enclosure (5), the material to be evaporated being arranged on a surface (21) of a crucible (11) placed in a second chamber (5B) of the enclosure (5), the second chamber (5B) being separated from the first chamber (5A) by a partition (7 ) having an opening (51) which allows movement of the evaporated material from the second chamber (5B) towards the first chamber (5A) through this opening (51) and which is dimensioned to produce a pressure difference between the first chamber (5A) and the second chamber (5B) when the pressure of the enclosure (5) is lowered under the action of said pumping member (15). A method according to any one of claims 1 to 4, wherein the material comprises an inorganic element of the periodic table, such as aluminum or indium, or an alloy comprising such an inorganic element.