Patent Application
20220275513
The present invention relates to a new method for producing coatings, especially thin films.
In the context of the present invention the term “thin films” is used for referring to coating films having film thickness in nanometers and/or micrometers range.
Commonly different vapor deposition methods are used for producing thin films for improving surface properties of tools and components.
However, it remains a challenge to produce coatings exhibiting all desired coating properties in one process when high temperatures are required for the synthesis of the coatings.
In other words, since some materials to be synthesized as coatings need to be processed at temperatures above 500° C. or above 600° C. and sometimes even above 1000° C. in order to develop the wished coating properties, it is commonly necessary that at least the surfaces of the substrates at which such materials should be synthesized, be processed to the necessary high process temperature (above 500° C. or above 600° C. or even above 1000° C.).
However, it is not always so that the substrates to be coated (in the context of the present description also called parts to be coated) are made of materials or comprise materials that can withstand such high process temperatures.
Likewise, sometimes even the material of the coating chamber or the material of some parts of the coating chamber cannot withstand such high process temperatures.
In such cases in which temperature sensible materials are present in the substrates to be coated and/or in parts of the coating chamber, the necessary process temperature cannot be attained because heating of the temperature sensible materials till such high temperatures can cause damages to the substrates and/or to parts of the coating chamber, respectively.
One of the objectives of the present invention is to provide an alternative method which allows to overcome the above described problems of the state of the art.
In particular, the present invention should provide a method that allows processing of coatings, which avoid typical heating of the substrates to be coated for attaining the necessary high process temperature that is usually necessary for producing some materials with particular properties.
One further objective of the present invention is to provide a new method for producing coatings, in particular thin films, exhibiting a predefined set of desired coating parameters.
The objective of the present invention is attained by providing a new method for producing coating materials by conducting at least following two steps:
The objective of the present invention is attained by providing a method comprising at least following two process steps:
The process step b) is conducted for inducing one or more changes in one or more physical and/or chemical properties of the coating deposited in the process step a).
The thermal treatment in step b) in the present invention does not refer a standard heating process conducted by ovens or heaters, which are done either by conventional or convection ovens or heaters. The thermal treatment in step b) in the present invention is conducted as explained above by using a radiation source, e.g. a radiant heater, which heats by using photons. It means, in the present invention the thermal treatment should be understood as a heating by photons from the arc lamp (also called flashlamp or flashtube).
More specifically an appropriate radiation source in the present invention is one or more arc lamps, preferably plasma arc lamps and/or electric arc lamps (these kinds of lamps are also commonly called flashlamps or flashtubes). Such lamps produce incoherent full-spectrum white extremely intense light for very short durations. Thus such lamps can deliver very high energies in the form of the short pulses. Therefore such a lamp can also be called a pulsed radiation source. Such lamps are in the use in for instance photographic applications, as well as in entertainment industry, medical, scientific applications. From recently such lamps are also used in the field of printed electronic industry in the process of sintering nanomaterials on the temperature sensitive substrates by exposing it to the flashlamps. Since in this way nanomaterials are exposed to heating by photons from the flashlamps, such process is often called photonic curing as described for example by Schroder et al. in the patent document U.S. Pat. No. 7,820,097B2 or in the article “Mechanisms of Photonic Curing: Processing High Temperature Films on Low Temperature Substrates” published in Nanotechnology, 2011—novacentrix.com.
However, using such a lamp for inducing a transformation of a coating material M1 deposited by using a vapor deposition process into a new material M2 having different physical and/or chemical properties as compared to those of material M1 was unexpected.
Interestingly, photons can carry different energies and when photons hit a surface material, they can penetrate that material depending on their energy and on the properties of that material only very close to that surface in the depth in nanometers or very few micrometers range. Surprisingly, such photons could be placed to interact with coating films having thickness in nanometers and/or micrometers range till attaining the necessary high energies for producing the desired coating properties, in other words, for transforming the material M1 into the material M2.
In this manner the inventor has attained that desired coating properties, which otherwise can only be obtained by heating the substrate till attaining high process temperatures of above 500° C. or preferably above 600° C. or preferably even sometimes above 1000° C.
The above mentioned changes of the coating properties (in other words: transformations of the coating material originally deposited) are attained by choosing the suitable lamp's operating parameters (for instance lamp properties, such as wavelength, intensity, flux, all pulse properties, such as pulse length, intensity, waiting time in-between the pulses etc.) after considering the required properties that need to have the coating deposited in the process step a) (such as coating thickness, refractive index of the coating material, absorbance of the coating material for the wavelength of our choice) in order to obtain the desired transformations.
For conducting the step b) in the inventive examples described afterwards, the inventor decided to use an equipment called PulseForge®1300 comprising a flashlamp, designed for photonic curing, manufactured by the company Novacentrix.
The properties of such type of equipment containing flashlamps will be given on the example of PulseForge®1300 from the company Novacentrix equipped with xenon flash lamps:
By selecting values of the above mentioned parameters, the process step b) can be designed in such a manner that it delivers via photons from flashlamp the energy input to the material M1 which is needed to induce the desired changes of properties of the material M1 in order to transform it into the material M2.
The energy input which is needed for this purpose (the desired transformation) will be calculated depending on a large number of parameters of both the equipment that will be used and the material M1 of the coating layer 1 itself. Thus, calculating the exact energy input which is needed in every single case can be a very complex process.
Therefore, such kind of equipment, typically has a suitable software which can simulate temperature to which the material to be irradiated would be exposed when the material is processed (irradiated) by using the flashlamp. As an example, the equipment PulseForge®1300 from the company Novacentrix is equipped with the software SimPulse Thermal Simulation. This software uses determined properties of the material to be exposed to irradiation (in the context of the present invention: material M1) and the selected process parameters for the operation of the flashlamp to calculate the temperature and the energy to which the material M1 would be exposed during the process of applying irradiation with the flashlamp.
The mentioned properties that need to be known from the material to be treated in the step b) (in this case material M1) depends from the equipment and the respective software but are for example thickness (μm), thermal conductivity (W/mK), density (g/cm3), molar mass (g/mol), melting temperature (° C.), etc.
As explained above, this equipment was used for carrying out some examples of the invention, but the present invention is not limited to the use of this equipment. This equipment is only one example of an equipment with a lamp for carrying out a process step b) for the conduction of a method according to the present invention.
This new inventive method allows producing new desired coating properties in coatings being already deposited on substrates (such as but not limited to cutting tools, forming tools, as well as parts, such as turbine parts, semiconductor industry parts, car industry parts, medical devices parts etc.).
A big advantage of this new inventive method is the possibility of a flexible adjustment or generation of new material properties at the surface of already coated substrates without affecting substrate material and without being limited by the substrate material and/or the materials of VD chamber.
Some of these coating properties that can be changed in the process step 2) of the present inventive method are for example:
In order to attain a better understanding of the present invention, some examples of coatings produced according to the present invention will be described. The changes of coating properties regarding crystallinity during the conduction of an inventive method as described in the Examples 1 and 2 are shown in the
The process parameters used for operating the arc lamp for the conduction of the second step (process step b)) in the inventive methods described in the Examples 1 and 2 are shown in Table 1.
An amorphous aluminium oxide coating either non-doped or doped with other chemical elements (such as metal or metalloids) can be easily deposited by using for instance a physical vapor deposition process. Such an amorphous aluminium oxide coating can be easily deposited on different substrate materials, such as steel. The substrate material can be any material allowing the use of the chosen vapor deposition process. Hence in order to produce a crystalline aluminium oxide coating by using a method according to the present invention, a first process step a) is carried out, in which aluminium oxide is deposited in amorphous state by using a VD process.
The amorphous aluminium oxide coating layer in this example was deposited by PVD (in a known manner) on Si wafer. The total coating layer thickness was 3.7 μm. This coating layer was examined with the step size 0.02° on a laboratory X-ray diffractometer using Cu Kα radiation model Discover D8 from Bruker. The resulting diffractogram (XRD diffractogram) is shown in
After producing the substrate coated with amorphous aluminium oxide in this manner, the coating deposited on the coated substrate was subjected to a thermal treatment in a second process step b) according to the present invention.
The equipment used in this example PulseForge®1300 from the company Novacentrix containing xenon flash lamp. PulseForge®1300 was equipped with software Sim Pulse for thermal simulation. The combination of the process parameters were optimized in such way that with this process we can induce desired change of the physical and/or chemical properties of the material M1 after step (a). For instance the starting material for this Example as after step (a) is amorphous alumina. Amorphous alumina is soft material, which has no benefits in use as protective coating. However, crystalline alumina is well known to be versatile material, which has lot of different crystalline phases, such as alfa, beta, gamma, delta, etc. However for the wear resistance applications like hard coating the most beneficial is corundum phase, alfa alumina. But desired corundum phase require large energy for phase transformation and thus corundum can be obtained only in the specific conditions. If one could have alumina in corundum phase that would be highly desired material for hard coatings because of high oxidation resistance, high wear resistance, temperature stability, etc.
This mentioned energy required for phase transformation of amorphous into crystalline alumina with exactly corundum phase regardless a crystalline orientation of the corundum crystals is typically delivered to the material as thermal energy. Numerous publications indicates that the required high temperature range to obtained corundum is from 900° C. to 1200° C. Therefore, the combination of process parameters for using flashlamps needs to be optimized in such way that material with given thickness and properties can receive energy in the sufficient amount and in the suitable way which can induce transformation of amorphous alumina into crystalline alumina with the exactly desired corundum phase.
Thus, the combination of process parameters was adjusted in such way that the process creates really energy via temperature in the required range in order to transform amorphous alumina into corundum.
The optimized combination of process parameters used for operating the arc lamp for conducting the process step (b) is given in Table 1 (Example 1). The software SimPulse simulated temperature in the coating to be up to 1250° C. with the chosen combination of the process parameters.
Indeed after applied the second process step, the previously amorphous material without any characteristic XRD peak was transformed into crystalline alumina displaying numerous characteristic peaks of aluminium oxide, indicating a partially corundum crystalline structure (grey plotted line with characteristic peaks shown in
In this manner the amorphous aluminium oxide coating deposited in process step a) was transformed into crystalline aluminium oxide in process step b) according to the present invention.
The big advantage of the inventive method in this example is that the previously amorphous coating could be transformed in partially crystalline aluminium oxide, in particular in partially corundum crystalline structure without producing any substrate damages by conducting the second process step (b)) according to the present invention.
After conducting the second process step (process step b)) by applying energy with an arc lamp to the amorphous aluminium oxide coating (by using the arc lamp parameters indicated in Table 1 for Example 1), the coating material deposited in the process step a) was transformed and shows clearly characteristic peaks of highly crystalline aluminium oxide with marked detected peaks (110), (113), (214), (119).
In this example we proved that the inventive method can be used to transform the material M1 obtained in the step (a) into material M2 by applying step (b). In this way we had information which energy is necessary to transform exactly our material with the given nature (amorphous alumina) and given properties, such as thickness of 3.7 μm. That energy delivered by flash lamps of PulseForge®1300 in the inventive Example 1 was about 1 kJ/cm2 (as given in the Table 1) or more precisely 1020 J/cm2, what is a value obtained as product of pulse energy per count (which was in this Example optimized to be 10.2 J/cm2) and total number of courts (which was in this Example chosen to be 100). This discovery was the base for the work in the following inventive Example 2.
An amorphous aluminium oxide coating can be easily deposited by using for instance a physical vapor deposition process. Such amorphous aluminium oxide coating can be easily deposited on different substrate materials, such as steel (substrate material can be any material allowing the use of the chosen vapor deposition process) according to the first process step (a)) of a method according to the present invention.
The amorphous aluminium oxide coating in this example was deposited on Si wafer. XRD given in
After producing the coated substrate in this manner, the coating deposited on the coated substrate was subjected to a thermal treatment according to the second process step (b)) of a method according to the present invention. The detailed process parameters of the process step (b) are given in the Table 1.
As describe above, in the previous inventive Example 1 we already proved that the total energy needed for transformation of amorphous alumina of 3.7 μm into crystalline alumina in the highly desired corundum phase is about 1 kJ/cm2. This discovery was used as the base for the process optimization in this inventive Example 2. Namely, the combination of the process parameters was optimized and changed in such way that the total energy is also about 1 kJ/cm2. That energy delivered by flash lamps of PulseForge®1300 in the inventive Example 2 was about 1 kJ/cm2 (as given in the Table 1) or more precisely 995 J/cm2, what is a value obtained as product of pulse energy per count (which was in this Example optimized to be 19.9 J/cm2) and total number of courts (which was in this Example chosen to be 50). Thus, the energy per count is double higher than in the Example 1, but the number of repeated counts is double lower than in the Example 1 (here is 50 while in the Example 1 is 100). In this way, total deliver energy is roughly the same in both examples, but delivered to the material in different way via double more energetic counts and with lower number of counts. Moreover, this energy was delivered with lower frequency as comparing to the frequency used in the Example 1. More precisely, in the Example 2 frequency is 0.1 Hz, while in the Example 1 it is 3.1 Hz. Chosen lower frequency allows to material to “relax” after receiving the higher energy counts in this Example, meaning that this energy delivered in the pulse can dissipate into material while waiting for the next pulse allowing that material receive almost the same total energy without reaching the temperature as high as in example 1. Thus here in the Example 2 temperature is lower (max around 580C) but total delivered energy is the same giving the possibility that material M1, amorphous alumina, transform into material M2, crystalline corundum.
After such processing step previously amorphous material without any characteristic XRD peak, indeed display numerous characteristic peaks of aluminium oxide with the partially corundum crystalline structure (characteristic peaks are indicated in the
Surprisingly, crystalline structure of aluminium oxide obtained in the Example 1 and 2 by the use of the different process parameters as given in the Table 1 is different. More precisely, those two crystalline structure differ in the one characteristic peak (as it can be seen by comparing the peaks in
This demonstrate that here proposed inventive method allows not only for transformation of the properties of “as deposited” material, but surprisingly also allows for very selective transformation and for tuning of the final properties of the material after the process step (b).
In this manner the amorphous aluminium oxide coating deposited in process step a) was transformed into crystalline aluminium oxide in process step b) according to the present invention.
The big advantage of the inventive method in this example is that the previously amorphous coating could be transformed in crystalline aluminium oxide without producing any substrate damages by conducting the second process step (b)) according to the present invention.
Apart from alumina, there are also other materials that can be useful as coating materials but which exhibit some desired coating properties only if they are produced during exposition of the substrate surface to high energies that are typically attained by using process temperatures (also called substrate temperatures, in particular when PVD or CVD processes are used) of above 500° C. or preferably above 600° C. or preferably sometimes even above 1000° C., for example: SiO2, SiN and SiC. This list is not exhaustive. The mentioned materials as well as other materials that can be produced with a method according to the present invention can be produced as non-doped as well as doped materials. In the context of the present invention the term “doped materials” means materials which comprise one or more dopant chemical elements in a total dopant concentration in atomic percentage of 0.1% to 30%. In the context of the present invention dopants are preferably metals such as titanium and/or metalloids such as boron.
It means that a coating produced by using a method according to the present invention, can be for example a SiO2 coating doped with tungsten, so that the concentration of tungsten in the SiO2 coating is between 0. 1 at. % to 30 at. %.
For example, according to the present invention an amorphous silicon oxide coating can be deposited on different substrate materials, such as steel (substrate material can be any material allowing the use of the chosen vapor deposition process) according to the first process step (a)) of a method according to the present invention.
For conducting the process step a), this coating can be deposited by using a vapor deposition process. Usually processes that can be used are PVD processes, such as Arc PVD or Sputtering PVD processes, and CVD processes such as plasma assisted (or enhanced) CVD processes (also called PA-CVD or PE-CVD).
After producing the coated substrate in this manner, the coating deposited on the coated substrate must be subjected to a thermal treatment according to the second process step (b) of a method according to the present invention.
In this manner the amorphous silicon coating deposited in process step a) is transformed into crystalline silicon dioxide in process step b) according to the present invention.
The big advantage of the inventive method in this example is that crystalline silicon dioxide cannot be deposited on the substrate by a physical deposition process in an easy manner due to various reasons, such as limited temperature to which this substrate and/or materials of a VD chamber can be exposed. However, advantageously the previously amorphous coating could be transformed in crystalline silicon dioxide without producing any substrate damages by conducting the second process step (b)) according to the present invention.
According to a further example an amorphous carbon coating (doped or non-doped, for example doped with Si or W) can be deposited in a process step a) by using a known VD process, such as PVD and/or CVD known processes, so that the amorphous carbon coating contains only or mainly carbon bound by sp2 hybridized bonds.
Subsequently the above mentioned amorphous carbon coating deposited in the process step a) is transformed in a process step b) in an amorphous carbon coating containing more sp3 hybridized bonds. It is possible because during the process step b) at least some of the sp2 hybridized bonds available in the coating deposited in the step a) are transformed into sp3 hybridized bonds, i.e. the amorphous carbon coating produced in step a) is at least partially transformed in the process step b) into carbon, which is bound by sp3 hybridized bonds.
According to one more further example, an amorphous aluminium oxide coating doped with one or more chemical elements, e.g. doped with titanium in a concentration between 0. 1 to 30 atomic percent, is deposited in a known manner in a process step a).
Subsequently the above mentioned Ti-doped amorphous aluminium oxide coating is transformed in process step b) into a non-amorphous or non-completely amorphous material consisting in a Ti-doped aluminium oxide exhibiting at least partially corundum crystalline structure.
Moreover, the above mentioned process step b) such treatment could be used for an heating of large coating parts, such as forming tool parts or components (such as turbine blades), which would occur outside a coating chamber (externally) prior to the coating process, to reduce heating time of such large parts.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/070375 | 7/17/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62875077 | Jul 2019 | US |
