Method and apparatus for protecting oxygen sensitive target materials in a coating source - Patents.com
Patent Information
- Application Number
- JP2024556040
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-11-03
- Filing Date
- 2023-02-22
- Publication Date
- 2025-04-11
Smart Images
Figure 2025509916000001_ABST
Abstract
Description
[Technical field]
[0001] Sputtering is a coating technique from the group of PVD (physical vapour deposition) methods. Sputtering, also called cathodic scattering, is a physical process in which atoms are ejected from a solid, the so-called target, into the gas phase by bombardment with energetic (noble gas) ions. Depending on the material used and the envisaged film properties and deposition rate, different sputtering techniques are used.
[0002] That is, in the field of coating technology, sputtering is used to scatter material, which then deposits on a substrate to form a solid film. When coating a substrate with various materials, especially when sputtering, a shutter system is used to control the flow rate of material to the substrate to be coated in order to obtain a desired film thickness.
[0003] Sputtering is carried out under vacuum conditions in a coating apparatus. Depending on the sputtering mode used (DC sputtering, radio frequency sputtering, magnetron sputtering, ion beam sputtering, reactive sputtering, etc.), a voltage is applied between the two electrodes and a working gas is introduced into the gas chamber. A plasma is formed in the gas chamber by bombardment ionization of the atoms of the working gas used, for example argon. The target usually forms the negative pole, and the substrate to be coated usually forms the positively charged pole. In the case of magnetron sputtering, an additional magnetic field is arranged behind the cathode. In the case of reactive sputtering, one or more reactive gases are added to the inert working gas (argon). The gas reacts with the scattered film atoms at the target or substrate in the vacuum chamber to form new material. In the case of ion beam sputtering, a beam of noble gas-sputter ions (argon, krypton, xenon) is guided from an ion source towards the target, where scattering is caused by the incident ion beam.
[0004] For a stable sputtering process, the coating device is switched on, i.e., a voltage is applied to the electrodes, the plasma is ignited, and the desired operating power for a stable process is adjusted and started. Only then is the shutter opened, which starts the coating of the substrate. The coating source is first shielded by the shutter. To ensure the ignition of the plasma, a gap of several millimeters must exist between the coating source and the shutter. Generally, a metal sheet as the shutter is laterally pivoted in front of the coating source, so that material cannot reach the substrate to be coated in an inconvenient manner from the coating source.
[0005] When the distance of the metal sheet to the coating source is minimal and the coating source is thus optimally shielded from the substrate, undesirable material flows onto the substrate and into the surroundings of the coating source, so-called cross-contamination, are most effectively prevented.
[0006] In particular, if several coating sources are arranged in a coating or processing chamber, the inability to completely close the coating sources can result in mutual coating of the coating sources (targets) due to cross-contamination, which often requires the contaminated targets to be removed again by sputtering, also called removal sputtering, before the actual coating process of the substrate, in order to maintain and guarantee the quality of the coating material. This reduces the quality of the coating and the utilization rate of the materials as well as the productivity of the coating device.
[0007] Conventionally used shutter plates are slid in front of the coating source with a distance of about 1-4 mm. This distance, however, cannot guarantee a completely closed shielding of the coating source. However, this distance is necessary for the sputtering of the coating source. In practical configurations, smaller, i.e. shorter, distances cannot be realized, since such distances generally cause friction between the shutter plate and the coating source. This friction effect causes a large number of undesirable particles that can lead to additional contamination of the coated substrate, and these particles can also lead to the detachment of the film from the substrate. This effect can significantly impair the quality of the film.
[0008] In the shutter mechanism known from WO 2021 / 091890, the shutter is connected to an actuator via a coupling system, so that the shutter can be moved in a combined motion from an open position to a closed position covering the coating source. In this case, the actuator only performs a linear motion along a translation axis, which is converted into a tilting motion via a grooved cam and then converted into a final linear motion again until the shutter surrounds the sputter source. The shutter first performs a linear motion along the translation axis of the actuator, then a pivoting motion, for example by 90° relative to the translation axis of the actuator, and finally a linear motion again along the translation axis of the actuator. The disadvantage is that these motions cannot be controlled separately and independently of one another, since on the one hand they are set by a grooved cam and on the other hand only a very limited fine adjustment of the shutter by the actuator is possible. Fixing the shutter in an intermediate position, for example for the sputtering process or pre-sputtering process, i.e. a few millimeters above the sputtering source, is not possible without additional technical equipment in the configuration described in WO 2021 / 091890 and can only be reproduced inaccurately, especially when pneumatic actuators are used.
[0009] Due to the fact that in the configuration described in WO 2021 / 091890 the axis of rotation of the shutter is not parallel to the longitudinal axis of the coating source, furthermore, during the opening and closing pivoting of the shutter, undesirable curvature of the gas plasma may occur, since the angle between the target surface and the shutter surface changes, which may additionally result in undesirable coating of the inside of the chamber or of the coating source itself.
[0010] It is also disadvantageous that in WO 2021 / 091890 the actuator is arranged in the vacuum chamber together with the grooved cam. The mechanical load of friction in the coupling system and the associated grooved cam can lead to undesirable wear in coating systems with high purity requirements. Maintenance and / or repair of the shutter control device is therefore also significantly more laborious, since maintenance and / or repair can only be carried out when the vacuum chamber is vented.
[0011] The use of oxygen-sensitive target materials in coating sources (sputter sources) also precludes the use of conventional shutter systems. In particular for cleaning or maintenance operations, it is often necessary to open the vacuum chamber or process chamber inside which the coating source is located. If oxygen-sensitive materials are used, such as lithium, contact with oxygen can cause a chemical reaction with the target material, which makes the target material unusable and requires special safety measures. A gap between the shutter plate and the coating source is desirable to be avoided for maintenance purposes as well, since it encourages the ingress of oxygen.
[0012] It is therefore an object of the present invention to provide a method and an apparatus with which reactive, in particular oxygen-sensitive, target material of a coating source can be protected from contamination.
[0013] This problem is solved by a method according to the independent device claim 1. In a method for protecting a coating source with reactive coating material, in which a coating source with a coating material is shielded from a treatment chamber by a shutter, the shutter first seals the coating source and a protective gas is flowed through a gas inlet into the coating source space formed by the coating source and the shutter, creating an overpressure in the coating source space compared to the vacuum chamber pressure in the treatment chamber and compared to the atmospheric pressure outside the treatment chamber when the treatment chamber is subsequently vented. Then, another gas for cleaning, i.e. for neutralizing the coating in the treatment chamber, is flowed into the treatment chamber. The film is passivated. Air or nitrogen can now be vented into the treatment chamber without undesired reactions taking place. The treatment chamber is then opened to the atmosphere, i.e. the door of the treatment chamber is opened to the surroundings, in which case an overpressure is always maintained in the coating source space.
[0014] This constant overpressure in the coating source chamber prevents gases, especially oxygen, from reaching the coating source, especially the reactive target material, and reacting with it. It is important that the shutter closes the coating source space and is accordingly closed, i.e. pivoted over the coating source. Furthermore, it is desirable that the coating source is switched off.
[0015] In one configuration of the method according to the invention, the reactive coating material is an oxygen-sensitive target material, such as lithium, magnesium, calcium and / or similar highly reactive materials as mentioned above. Lithium is very reactive and reacts with many elements and compounds. It therefore needs to be particularly protected to avoid cross-contamination. This is ensured by the shutter being closed by the pivoting and / or pivoting and / or folding / tilting movements and the additional stroke movement in the direction of the coating source and the overpressure generated in the coating source space.
[0016] In one further embodiment of the method according to the invention, as another protective measure, an inert gas, in particular nitrogen or argon, is used as protective gas. The constant overpressure in the source space closed by the shutter and in the protective gas flowing in has the advantage that oxygen or air cannot flow into the source space behind the shutter.
[0017] In one further embodiment of the method according to the invention, carbon dioxide is flowed into the treatment chamber as a separate gas for cleaning or neutralizing the coating in the treatment chamber, which prevents subsequent reactions in the treatment chamber and further minimizes contamination of the coating source.
[0018] The object of the present invention is also achieved by a sputtering device according to the invention, which comprises a process chamber and at least one coating source space, which is formed from a coating source and a shutter and is arranged in the process chamber. This sputtering or coating device is suitable for carrying out the method according to any one of claims 1 to 5. Particularly advantageously, the shutter can be positioned over the coating source by means of a pivoting and / or swiveling and / or folding / tilting movement, and the shutter is designed to perform an additional relative movement with respect to the coating source and / or the coating source is designed to perform an additional relative movement with respect to the shutter, in which case the shutter covers the coating source in a sealing manner, so that during maintenance procedures of the sputtering device a permanent overpressure can be built up in the coating source space. The relative movement is preferably a stroke movement. This prevents undesirable particles, gas atoms etc. from reaching the target, i.e. in the coating source space. This concept has been found to be particularly advantageous when the coating source space contains targets made of oxygen-sensitive materials, such as lithium, magnesium and / or calcium.
[0019] According to the present invention, the shutter can be positioned to cover the coating source by a rotating movement and / or a pivoting movement and / or a folding / tilting movement, and the shutter is configured to perform an additional relative movement with respect to the coating source in the form of a stroke movement and / or the coating source is configured to perform an additional relative movement with respect to the shutter in the form of a stroke movement, in which case the shutter covers the coating source in a sealing manner.
[0020] Hermetically covering means completely shielding the coating source from the rest of the process chamber, thus preventing any cross-contamination of the coating source and undesired coating of the substrate to be coated, i.e. no oxygen can enter the coating source space and contaminate the target material, causing undesired reactions.
[0021] Advantageously, the shutter of the shutter device according to the invention is not only pivoted or rotated or folded / tilted over the coating source based on the first degree of freedom, but also the shutter or the coating source is moved in a sealing manner with respect to one another based on a second degree of freedom by a relative movement between the shutter and the coating source. The shutter performs a stroke movement in the direction of the coating source or the coating source performs a stroke movement in the direction of the shutter, so that the shutter and the coating source are positioned sealingly overlapping one another, i.e. completely closed. Both movements can be performed independently of one another, so that the shutter can be positioned in any required and desired position. No deflection of the gas plasma is performed by the movement of the shutter. In this case, no particles are generated due to friction between the shutter plate and the coating source, such as in a pure pivoting of the shutter over the coating source. When the shutter is closed, there are no longer any gaps that could cause contamination of the target material due to the operation of another coating source in the same device or the ingress of oxygen during maintenance work.
[0022] The shutter can be positioned to cover the coating source, for example by a rotational movement about an axis, or by a pivoting movement by moving laterally towards the coating source, or by a folding / tilting movement. Only then can a relative movement or stroke movement take place between the shutter and the coating source. The rotational / pivoting / folding / tilting and / or stroke movement is generated by a shutter movement means such as a motor or a lift cylinder. The control of the shutter system is located outside the vacuum chamber, so that wear due to mechanical components in the vacuum chamber is reduced to a minimum.
[0023] The proposed configuration allows for a significantly more compact arrangement of different coating sources in parallel and / or joint coating systems (e.g. sputter systems), since cross-contamination of the coating sources is prevented. Large overhangs of the shutter plate are no longer necessary.
[0024] In one configuration of the shutter device according to the invention, the relative movement between the shutter and the coating source is achieved via a bellows or ring seal and / or a sliding feedthrough, which reduces mechanical wear in the vacuum chamber to a minimum, and no contamination due to wear or mechanical friction occurs.
[0025] The relative movement between the shutter and the coating source can be achieved via a stroke movement performed by the shutter or by the coating source, which is structurally easier to achieve if the shutter is moved while the coating source is not moved at the same time.
[0026] In one further embodiment of the shutter device according to the invention, the distance between the coating source and the shutter is adjustable. This has the advantage that, in particular during maintenance work in the process chamber, the distance between the shutter and the coating source can be adjusted to zero, thereby preventing contamination of the target. Another advantage is that when starting the plasma ignition process in the sputtering process, the required gap between the coating source and the shutter can be adjusted, and in particular in the actual coating process with multiple coating sources, the currently unused coating sources can be shielded so as to be optimally sealed. By controlling the shutter system according to the invention, it is possible to hold the shutter in any required and desired position. This is made possible by the movements of the shutter systems, which can be controlled separately and carried out independently of one another.
[0027] In one further configuration of the shutter device according to the invention, the shielding is further optimized to a greater extent if the shutter has curved edges, which allow the shutter to act as a sort of hood over the coating source, thus completely preventing cross-contamination.
[0028] Furthermore, the shutter and the coating source have a circular or elliptical or rectangular or polygonal shape, which allows the shutter to be adapted to the shape of the coating source to be coated, which allows the coating source to be optimally sealed. Due to the independently operable movement processes of the shutter (rotating and / or pivoting and / or folding or tilting movements, as well as additional relative movements), the shutter system of the shutter device can be adapted very simply to any coating source in the same way.
[0029] The method according to the invention for protecting a coating source, in particular a reactive oxygen-sensitive target material, in a sputtering apparatus and the sputtering apparatus according to the invention for carrying out the method according to the invention can be used for any coating source with a directed particle flow, which makes it possible in a simple and compact way to prevent cross-contamination of the coating source and to prevent reactions with the reactive target material.
[0030] The present invention will be described in more detail below with reference to examples. [Brief description of the drawings]
[0031] [Figure 1] FIG. 2 shows a sputtering apparatus according to the invention with a coating source (sputter target) in a coating source space that can be closed by a shutter with curved edges. [Figure 2a] FIG. 2 is a schematic diagram showing method step a) according to the invention. [Figure 2b] FIG. 2 is a schematic diagram showing method step b) according to the invention. [Figure 2c] FIG. 2 is a schematic diagram showing method step c) according to the invention. [Figure 2d] FIG. 3 is a schematic diagram illustrating method step d) according to the invention. [Figure 2e] FIG. 2 is a schematic diagram showing method step e) according to the invention. [Figure 2f] FIG. 2 is a schematic diagram showing method step f) according to the invention. [Figure 2g] FIG. 2 is a schematic diagram showing method step g) according to the invention. [Figure 2h] FIG. 2 is a schematic diagram showing method step h) according to the invention. [Figure 2i] FIG. 2 is a schematic diagram showing method step i) according to the invention.
[0032] 1 shows a schematic diagram of a sputtering device 1 according to the invention, which comprises a process chamber 2 in which at least one coating source space 3 formed by a coating source 4 and a shutter 5 is arranged. The process chamber 2 further comprises an inlet valve 6 for a cleaning gas, a vent valve 7 for the process chamber 2, a vacuum pump 8 and a glove box 9 for carrying out maintenance work or substrate and / or target 11 exchange without the need to interrupt the vacuum in the process chamber 2. The coating source space 3 additionally comprises an inlet 10 for a protective gas, for example nitrogen and / or argon. The protective gas, which is supplied into the coating source space 3 at an excess pressure compared to the vacuum chamber pressure in the process chamber 2 and later compared to the atmospheric pressure outside the process chamber 2 during venting of the process chamber 2, prevents the possibility of oxygen penetrating into the coating source space 3 through the residual gap.
[0033] FIG. 2 shows a schematic diagram of the method steps according to the invention using a sputtering device according to the invention.
[0034] In a typical coating process, the substrate 13 to be coated is located in the process or vacuum chamber 2 opposite the coating source 4. During the coating process, the coating source space 3 is open, i.e. the shutter 5 is pivoted / rotated / folded to the side, so that material is removed / sputtered from the target 11 and deposited on the substrate surface 13. Once the coating process is over, the shutter 5 is again moved in front of the coating source 4 so that no gap remains between the shutter 5 and the coating source 4. This is mechanically ensured by an additional relative movement between the shutter 5 and the coating source 4. The control of the shutter system is located outside the vacuum chamber 2, so that wear due to mechanical components in the vacuum chamber is reduced to a minimum. The coating source 4 is then switched off. A protective gas, for example nitrogen or argon, is then introduced into the coating source space 3 via the gas inlet 10. The process chamber 2 is then filled with a cleaning gas, for example CO2, so that the components in the vacuum chamber 2 can be cleaned and the interior of the process chamber 2 is neutralized. At the same time, an overpressure is generated in the coating source space 3, which effectively prevents the ingress of particles and gases, for example oxygen. In the next step, gas is discharged from the process chamber 2, and the overpressure in the coating source space 3 is still maintained. In a subsequent method step, nitrogen or another ventilation gas is introduced into the process chamber 2 via the ventilation valve 7, and a low overpressure compared to the atmospheric pressure outside the process chamber 2 is still maintained in the coating source space 3. The process chamber 2 is then opened and any necessary maintenance work etc. can be carried out, in which case contamination of the reactive, in particular oxygen-sensitive, target material 11 is completely prevented by the constantly low overpressure in the coating source space 3. [Explanation of symbols]
[0035] 1. Sputtering equipment 2 Processing chamber / vacuum chamber 3 Coating source space 4. Coating Source 5. Shutter 6 Inlet valve for purification process gas 7 Vent Valve 8. Vacuum Pump 9 Glove Box 10 Protective gas inlet 11. Target 12 Processing Room Door 13 Substrate to be coated 14 Shutter movement means
Claims
1. A method for protecting a coating source (4) containing a reactive coating material (11), wherein the coating source (4) with the coating material (11) is shielded from a process chamber (2) by a shutter (5), comprising: the shutter (5) seals the coating source (4), and a protective gas is allowed to flow through a gas inlet (10) into a coating source space (3) formed by the coating source (4) and the shutter (5), creating an overpressure in the coating source space (3) compared to the vacuum chamber pressure in the treatment chamber (2) and subsequently compared to the atmospheric pressure outside the treatment chamber (2), Another gas for cleaning the coating in the treatment chamber (2) is flowed into the treatment chamber (2), The other gas is discharged from the processing chamber (2); The treatment chamber (2) is vented (7) while nitrogen or another gas is introduced; The treatment chamber (2) is open to the atmosphere, An excess pressure is then always maintained in the coating source space (3). A method comprising:
2. The method of claim 1, wherein the reactive coating material (11) is an oxygen-sensitive target material.
3. The method of claim 2, wherein the target material (11) is formed from lithium, magnesium, calcium and / or similar highly reactive materials.
4. 2. The method according to claim 1, wherein the protective gas is an inert gas, in particular nitrogen or argon.
5. 2. The method according to claim 1, wherein the further gas for purging is, in particular, carbon dioxide.
6. 1. A sputtering apparatus (1), comprising a process chamber (2) and at least one coating source space (3), the coating source space (3) being formed from a coating source (4) and a shutter (5) and arranged in the process chamber (2), and configured in such a way that it is suitable for carrying out the method according to claims 1 to 5, the shutter (5) being positionable to cover the coating source (4) by a rotating and / or pivoting and / or folding / tilting movement, the shutter (5) being configured to perform an additional relative movement with respect to the coating source (4) and / or the coating source (4) being configured to perform an additional relative movement with respect to the shutter (5), the shutter (5) sealingly covering the coating source (4), and wherein a permanent overpressure can be formed in the coating source space (3) during a maintenance process of the sputtering apparatus (1).
7. 7. The sputtering apparatus (1) according to claim 6, wherein the relative movement between the shutter (5) and the coating source (4) is formed via a bellows or ring seal and / or a sliding feedthrough.
8. 8. The sputtering device (1) according to claim 6 or 7, characterized in that the distance between the coating source (4) and the shutter (5) is adjustable.
9. 7. The sputtering device (1) according to claim 6, wherein the shutter (5) has curved edges.
10. 7. The sputtering device (1) according to claim 6, wherein the shutter (5) and the coating source (4) have a circular or elliptical or rectangular or polygonal shape.