DE102022112132A1 - PROCESS AND DEVICE FOR PLASMA ASSISTED ATOMIC LAYER DEPOSITION - Google Patents

Abstract

The present invention relates to a device for coating by plasma-enhanced atomic layer deposition and a corresponding method, the device having a coating chamber (1) which is delimited by a chamber wall (2), the device having at least one gas inlet (3,10) for introducing process gas In the coating chamber (1), with a plasma generating device (4) being arranged outside the coating chamber in such a way that a plasma (16) can be generated inside the coating chamber (1), with at least one component holder (14 ) for receiving the component (15) to be coated, and wherein the device comprises a magnetic field generating device (18) with which a magnetic field can be generated in the region of the component receptacle (14), and/or at least one shielding element within the coating chamber (1). (11, 11', 11'') is arranged, which ge the component holder (14). mechanically and/or electrically shields from the at least one gas inlet (3,10) and/or the plasma generating device (4).

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to a device for coating by plasma-enhanced atomic layer deposition and a corresponding method for this.

STATE OF THE ART

For the deposition of extremely thin layers, up to and including atomic monolayers, atomic layer deposition (ALD) is known from the prior art. This process is a chemical vapor deposition process with one or more cyclically performed self-limiting surface reactions. For this purpose, a process gas containing the material to be deposited is first admitted into a coating chamber. A reactant is then added, e.g. via a process gas or plasma. This can be repeated cyclically. Between the gas inlets of the process gases, the coating chamber is normally purged with a purge gas, e.g., an inert gas such as argon. In this way, the partial reactions are clearly separated from one another and limited to the surface. An essential feature of atomic layer deposition is the self-limiting character of the first partial reactions, i.e. the starting material of this partial reaction does not react with itself, which ideally limits the layer growth of this partial reaction to a maximum of one monolayer for any length of time and amount of gas, or in the real case at least very strongly restricts

A plasma treatment can be carried out during and/or after and/or before a treatment of the component to be coated with a reactant in order to support the chemical reaction.

Such methods for plasma-assisted atomic layer deposition are also used in particular for coating optical elements, such as mirrors or optical lenses, for example for optical systems for microlithography.

It has been shown that with these extremely thin and precisely deposited layers, problems with adhesion can sometimes occur. In addition, the formation of bubbles, holes or similar defects has also been observed in plasma-enhanced atomic layer deposition. However, this is unacceptable for corresponding components that are to be used, for example, in microlithography.

DISCLOSURE OF THE INVENTION

OBJECT OF THE INVENTION

It is therefore the object of the present invention to provide a method and a device for plasma-assisted atomic layer deposition which eliminate or at least reduce the problems occurring in the prior art with regard to layer adhesion and the formation of defects in the coating. At the same time, the method should be reliable and easy to carry out and a corresponding device should be able to be operated efficiently in order to achieve reproducible coating results.

TECHNICAL SOLUTION

This object is achieved by a device having the features of claim 1 and a method having the features of claim 11. Advantageous configurations are the subject matter of the dependent claims.

To achieve the object, the invention proposes a device for coating by plasma-enhanced atomic layer deposition and a corresponding method, the device having a coating chamber which is delimited by a chamber wall and in which the coating of a component to be coated takes place. For the successive provision of the process gases and/or flushing gases between the individual coating steps, the device has at least one gas inlet for introducing process and/or flushing gases into the coating chamber. In addition, the device comprises a plasma generating device inside or outside the coating chamber, for example in a room adjacent to the coating chamber or in the coating chamber separated by a partition wall, which is arranged in such a way that a plasma can be generated inside the coating chamber to support the atomic layer deposition. At least one component holder, which can accommodate one or more components to be coated, is arranged inside the coating chamber to accommodate the component to be coated.

In addition, in a first alternative, the device comprises a magnetic field generating device with which a magnetic field can be generated in the area of the component holder, so that charged particles, such as electrons and/or ions, can be prevented by the magnetic field from entering the component or components to be coated to achieve recording. It has been shown that adhesion problems in the coating or defects in the coating can be avoided or at least reduced if the component to be coated and the coating are prevented from being impacted or bombarded with charged particles such as electrons or ions can be caused by a potential difference between the component and the plasma or the plasma generating device.

Alternatively or additionally, at least one shielding element can be arranged within the coating chamber, which mechanically and/or electrically shields the component holder and the component from the plasma generating device in order to also prevent unwanted particles from being moved or accelerated in the direction of the component to be coated. Correspondingly, an electrical potential can be applied to the shielding element in order to enable electrical shielding.

Any suitable plasma generating device can be used to generate a plasma. For example, the plasma generating device can have electrodes or electrode plates for electrostatic or electromagnetic excitation of a plasma or at least one excitation coil for inductive excitation. It is also conceivable to provide a magnetron for exciting a plasma using microwaves. The arrangement of the plasma generating device outside of the coating chamber is advantageous, since this means that coating of the plasma generating device or parts thereof can be avoided.

In order to keep the electric field strength as small as possible due to a potential difference between the component and the plasma generating device, which can cause charged particles to accelerate in the direction of the component to be coated, the electrode surface of electrodes or electrode plates of the plasma generating device should be kept as large as possible. Correspondingly, the electrode surface of electrodes or electrode plates of the plasma generation device, which are aligned in the direction of the component or on a partition wall that separates the plasma generation device from the coating chamber, can be in the range of at least 2% of the area of the partition wall or chamber wall, in particular more than 5 % or preferably more than 10% of the area of the partition wall or the chamber wall.

The shielding element can be arranged between the at least one component holder and the plasma generating device, in particular an electrode thereof, in order to prevent charged particles from moving in a straight line to the component to be coated.

Alternatively or additionally, the shielding element can be arranged on the side of the component holder that faces away from the plasma generating device and/or the at least one gas inlet if the shielding is effected, for example, by an electrical potential applied to the shielding element.

Since the shielding element is intended to prevent the component to be coated from being bombarded with charged particles or a movement of charged particles to the component to be coated, the shape and/or position of the shielding element can be adapted to the component or components to be coated. Correspondingly, the at least one shielding element can be arranged in only a partial area of the partition wall or the chamber wall, preferably in a variably adjustable or displaceable manner. In this case, the line of sight between the electrode/electrodes and the component/components is preferably interrupted.

The shielding element can be designed as a plate or disc, preferably with passages, in particular holes or slits, for the process gas or flushing gas, or as a lattice structure.

The shielding element can be formed from an insulating material, in particular glass or ceramic, or from a conductive material, in particular a metal.

Accordingly, in a method for coating by plasma-enhanced atomic layer deposition, in particular using a device as described above, during or after a coating step in which process gas is introduced into the coating chamber, a plasma is generated in the area of the component to be coated in order to support coating.

At least partially during the plasma treatment, a magnetic field generating device generates a magnetic field in the area of the component holder in order to deflect charged particles and prevent them from reaching the component or components to be coated.

Alternatively or additionally, a component holder with the component or components to be coated is mechanically and/or electrically shielded by a shielding element within the coating chamber, in particular from a plasma generating device, in order to also protect the component to be coated.

Accordingly, an electric potential can be applied to the shielding element, so that charged particles, in particular negatively charged particles, cannot get into the coating chamber and/or cannot reach the component to be coated.

The plasma can in turn be generated by any suitable method, e.g. by an electrostatic field using electrical DC voltage between electrodes or by capacitive electrical excitation using electrical AC voltage at electrode plates and by high-frequency alternating current through an excitation coil.

Electrodes or electrode plates operated with AC voltage or an excitation coil of the plasma generating device through which alternating current flows can be set to a positive electrical basic voltage, a so-called bias voltage, so that negatively charged particles are moved in the direction of the electrodes or the excitation coil instead of in the direction of the plasma and the component(s) to be coated.

The bombardment of the component to be coated with charged particles can also be reduced or avoided if the pressure of the process gas is adjusted in such a way that the potential difference between the component/components and the electrode/electrodes is minimized. For this purpose, the plasma is first adjusted at any desired process pressure in such a way that the layer shows the desired properties but possibly still has defects. The process pressure is then varied in the range from 0.01 to 100 Pa, preferably between 0.1 and 10 Pa, and the potential difference is measured at the same time. The pressure at which the potential difference is minimal but the plasma still exists in a stable manner is then selected as the process pressure. A different pressure can also be set to ignite the plasma.

Another possibility is to reduce the plasma power and instead provide a longer duration of the plasma treatment. Accordingly, the supply of energy required to produce a coating can be recorded in order to generate a plasma that leads to the desired layer properties, but in which defects are still generated in the layer. The duration of the energy supply can be determined from this total of the energy required to produce the coating or the plasma treatment, if the energy supply per unit of time is minimized so that the energy supplied can be kept constant overall.

The combination of setting the process pressure and plasma power or duration of the plasma treatment should then result in the potential difference between the electrodes and the component or components to be coated being less than 100 V, preferably less than 50 V, particularly preferably less than 30 V. If the component to be coated is not electrically conductive and floats in the plasma, the potential difference between the electrodes and the system ground or the ground of the coating device, e.g. the chamber wall, can be measured instead.

Furthermore, the plasma generation can be shifted to a location outside of the actual coating chamber or be decoupled via a partition. The excited atoms/ions can then be let in via flanges or gaps in the partition.

character list

• 1 eine Darstellung einer ersten Ausführungsform einer erfindungsgenäßen Vorrichtung zur Beschichtung durch plasmagestützte Atomlagenabscheidung,
• 2 eine Darstellung einer zweiten Ausführungsform einer erfindungsgemäßen Vorrichtung zur Beschichtung durch plasmagestützte Atomlagenabscheidung,
• 3 eine Darstellung einer dritten Ausführungsform einer erfindungsgemäßen Vorrichtung zur Beschichtung durch plasmagestützte Atomlagenabscheidung und in
• 4 eine Darstellung einer vierten Ausführungsform einer erfindungsgemäßen Vorrichtung zur Beschichtung durch plasmagestützte Atomlagenabscheidung.

The accompanying drawings show, purely diagrammatically,

• 1 a representation of a first embodiment of a device according to the invention for coating by plasma-enhanced atomic layer deposition,
• 2 a representation of a second embodiment of a device according to the invention for coating by plasma-enhanced atomic layer deposition,
• 3 a representation of a third embodiment of a device according to the invention for coating by plasma-enhanced atomic layer deposition and in
• 4 a representation of a fourth embodiment of a device according to the invention for coating by plasma-enhanced atomic layer deposition.

EXEMPLARY EMBODIMENTS

Further advantages, characteristics and features of the present invention become apparent in the following detailed description of the exemplary embodiments. However, the invention is not limited to these exemplary embodiments.

the 1 shows a first exemplary embodiment of a device according to the invention for coating by plasma-enhanced atomic layer deposition with a coating chamber 1 which is delimited by a surrounding chamber wall 2 becomes. A component holder 14 is arranged in the coating chamber 1, to which one or more components 15 to be coated can be attached in order to be coated by plasma-enhanced atomic layer deposition. For this purpose, the device according to the invention has a gas supply 3, with which different process and/or rinsing gases can be introduced into the coating chamber 1 in alternation, so that the process gases in the coating chamber react with the component 15 to be coated and/or with each other and move towards the coating component 15 can deposit. In the embodiment shown 1 the process and/or flushing gases are introduced into the coating chamber 1 from the gas supply 3 via a separate space 8, which is separated from the actual coating space of the coating chamber 1 via a partition 9, and gas inlet nozzles 10 arranged in the partition 9. The partition 9 can also, like 2 12 can also be omitted so that, for example, the electrodes, the component, the component holder and the gas nozzles are all located within one coating chamber

For example, a first process gas with a first reactant can first be introduced into the coating chamber 1 so that the first reactant can react with the surface of the component 15 to be coated. Thereafter, the coating chamber 1 may be evacuated and/or a purge gas introduced to remove unreacted first reactant gas and possible unreacted reaction products. A second process gas with a second reactant can then be introduced into the coating chamber 1 so that the second reactant can react with the first reactant or reaction product already adhering to the surface of the component 15 to be coated.

During and/or after the introduction of a process gas, a plasma 16 can be generated in the coating chamber 1, in particular in the area of the component holder 14 and the components 15 to be coated, in order to support the reaction of the reactants and the deposition of the coating.

A plasma generating device 4 is provided for generating the plasma 16 , at least parts of which are arranged in the coating chamber 1 or in a space 8 separated by a partition wall 9 . At the in 1 In the exemplary embodiment shown, the plasma generating device 4 comprises a plurality of electrodes 5, with the aid of which an alternating electric field can be generated, so that charged particles oscillate with the frequency of the alternating field in the case of a high-frequency alternating field (high-frequency excitation). To avoid charging the chamber wall, it is connected to ground 17 .

In order to prevent charged particles, such as electrons or negatively charged ions, from being accelerated in the direction of the component 15 to be coated due to a voltage difference between the component 15 and the electrodes 5 of the plasma generating device 4 and the formation of the layer or the deposited coating there impair or damage, various measures have been taken in the inventive device for plasma-enhanced atomic layer deposition.

On the one hand, a shielding plate 11 is arranged between the electrodes 5 and the component holder 14 or the component 15 to be coated, with which the acceleration of undesired particles in the direction of the plasma 16 can be at least partially prevented mechanically. The shielding plate 11 has a multiplicity of passages 12 or is formed in a lattice structure in order not to impair the flow of gas into the coating chamber 1 . Nevertheless, the arrangement of the shielding plate 11 prevents the unimpeded, direct acceleration of undesired particles in the direction of the component 15, in particular if the shielding plate 11 with the openings 12 is arranged in such a way that there is no line of sight between the electrodes 5 and the component 15.

The shielding effect can be further enhanced by setting the shielding plate 11 to a specific electrical potential, for which purpose the shielding plate 11 is connected to a potential source 13 . For example, setting a positive electrical potential on the shielding plate 11 can prevent negatively charged particles from being able to pass through the openings 12 .

Another measure to reduce the acceleration or movement of unwanted charged particles in the direction of the plasma 16 or the components to be coated 15 is realized in that the electrodes 5 of the plasma generating device 4 are connected to a potential source 7 to the electrodes 5 a certain basic potential, a so-called bias voltage, to set. It can thus be achieved that charged particles, such as electrons or negatively charged ions, are not accelerated in the direction of the plasma 16 when the basic voltage of the electrodes 5 is positive, but in the direction of the electrodes 5 of the plasma generating device 4.

Furthermore, the electrode surface 6 of the electrodes 5 is chosen so that the largest possible Electrode surface 6 of all electrodes 5 is given in the direction of the plasma 16 to be generated, so that the potential difference between the plasma 16 and the electrode surfaces 6 of the electrodes 5 is distributed over a large electrode surface 6, which in turn accelerates charged particles in the direction of the component to be coated 15 decreased.

Furthermore, to reduce negative influences on the coating due to unwanted bombardment with charged particles, the procedure can be such that the pressure of the gas in the coating chamber 1 is optimized for the process gases used such that the potential difference between component 15 and electrodes 5 is minimized.

The energy of the charged particles is linked to the momentarily injected plasma power. This means that the energy of the particles - and thus their potential to damage the layer - increases with the injected plasma power. Therefore, another measure to reduce negative effects of charged particles accelerated onto the coating is that the energy supplied for plasma generation per unit of time is minimized, but in return the plasma treatment and thus the duration of the energy supply for plasma generation is extended, so that the plasma power is minimized and the duration of the plasma treatment is extended accordingly, preferably in such a way that the energy supply is kept constant overall. For this purpose, the energy requirement, ie the total energy supply, can first be determined, which is necessary to generate a plasma with which the desired coating can be produced. The energy supply per unit of time can then be reduced to such an extent that a plasma can just about be ignited, but this is then maintained until the previously determined energy requirement over time is reached.

the 2 shows a further embodiment of a device according to the invention for coating by means of plasma-enhanced atomic layer deposition, the device of FIG 2 largely with the device of 1 agrees, so that a repeated description of identical components is dispensed with to avoid repetition. The embodiment of 2 differs from the embodiment of the 1 that a partition wall 9 between the space with the component holder 14 and the space with the components of the plasma generating device or the electrodes 5 is dispensed with.

the 3 shows a further embodiment of a device according to the invention for coating by means of plasma-enhanced atomic layer deposition, the device of FIG 3 largely with the devices of 1 and 2 agrees, so that a repeated description of identical components is dispensed with to avoid repetition. The embodiment of 3 differs from the embodiment of the 1 that a different shielding plate 11' is used. Although the shielding plate 11' also has openings 12, the shielding plate 11' is only provided in a partial area which is matched to the coated component. Accordingly, a corresponding shielding plate 11′ is not provided over the entire area of the gas inlet nozzles 10 or the electrodes 5, but the area of the arrangement of the shielding plate 11′ is matched to the area of the component 15 to be protected.

Correspondingly, it can also be provided that the shielding plate 11′ is movably mounted and can be arranged in different areas of the coating chamber 1 as required, wherein the arrangement of the shielding plate 11′ can be geared in particular to the arrangement of the component 15 to be coated.

In addition, the shielding plate 11' differs from the shielding plate 11 of FIG 1 and 2 characterized in that the shielding plate 11 'no electric potential can be applied, but the shielding plate 11' is made of a non-conductive material such as glass or ceramics, whereas the shielding plate 11 of 1 and 2 can be made of a metallic material, for example. Also in the embodiment of 3 an arrangement of the partition wall 9 can be dispensed with, without this being explicitly shown.

the 4 FIG. 12 shows a further embodiment of a device according to the invention for plasma-enhanced atomic layer deposition, which in turn has identical components to the previous embodiments, which are not described again. Also in this embodiment 4 the partition wall 9 can be dispensed with.

The embodiment of 4 is characterized in that, on the one hand, the component holder 14 is designed in such a way that the component 15 to be coated is not arranged centrally in the component holder 14 and/or centrally in the coating chamber 1, but offset thereto. In addition, the embodiment differs 3 by another variant of a shield plate 11'', which is not arranged between the plasma 16 or the component holder 14 or the component 15 to be coated on the one hand and the partition 9 with the gas inlet nozzle 10 or the plasma generating device 4 on the other hand, but on the side of the component holder 14 that faces away to the gas inlet side or the plasma generation device 4 is. The shielding plate 11'' is designed as a metallic plate, which in turn is connected to a potential source 13, the shielding plate 11'' in this case being set to a negative electrical potential in order to create an opposing field for negatively charged particles, such as electrons or negatively charged To form ions and keep them accordingly from the component 15 to be coated.

In addition, the device of 4 a magnetic field generating device 18 for generating a magnetic field in the area of the component holder 14 or the component 15 to be coated, so that the magnetic field can also prevent or at least restrict charged particles from reaching the component 15 to be coated and being able to damage or destroy the coating.

Although the present invention has been described in detail on the basis of the exemplary embodiments, it is self-evident for the person skilled in the art that the invention is not limited to these exemplary embodiments, but rather that modifications are possible in such a way that individual features are omitted or other types of combinations of features can be implemented without departing from the scope of the appended claims. In particular, the present disclosure includes all combinations of the individual features shown in the various exemplary embodiments, so that individual features that are only described in connection with one exemplary embodiment can also be used in other exemplary embodiments or combinations of individual features that are not explicitly shown.

Reference List

1

coating chamber

2

chamber wall

3

gas supply

4

plasma generating device

5

electrodes

6

electrode surface

7

source of potential

8th

separated room

9

partition wall

10

gas inlet nozzle

11, 11', 11''

shielding plate

12

passage

13

source of potential

14

component recording

15

component to be coated

16

plasma

17

grounding

18

magnetic field generating device

Claims (18)

Device for coating by plasma-enhanced atomic layer deposition, having a coating chamber (1) which is delimited by a chamber wall (2), the device having at least one gas inlet (3,10) for introducing process gas into the coating chamber (1), a plasma generating device ( 4) is arranged in such a way that a plasma (16) can be generated inside the coating chamber (1), and wherein at least one component holder (14) for receiving the component (15) to be coated is arranged inside the coating chamber (1), characterized in that that the device comprises a magnetic field generating device (18) with which a magnetic field can be generated in the area of the component holder (14), and/or that at least one shielding element (11, 11', 11'') is arranged inside the coating chamber (1). , which the component holder (14) against the at least one gas inlet (3.10) and / or the plasma generating device (4) mechanically and / or electrically shields. device after claim 1 , characterized in that the plasma generating device (4) has electrodes (5) or electrode plates for electrostatic or electromagnetic excitation of a plasma (16) or at least one excitation coil for inductive excitation or a magnetron for excitation of a plasma by microwaves. device after claim 2 , characterized in that the electrodes (5) or electrode plates of the plasma generating device (4) have electrode surfaces (6) facing the component holder (14) which have an area in the range of at least 2% of the area of the chamber inner surface, in particular more than 5% or preferably more than 10% of the chamber inner surface. Device according to one of the preceding claims, characterized in that the shielding element (11, 11', 11'') is arranged between the at least one gas inlet (3, 10) and the at least one component holder (14) in the gas flow path. Device according to one of the preceding claims, characterized in that the shielding element (11, 11') is arranged between the plasma generating device (4), in particular an electrode (5) thereof, and the component holder (14). Device according to one of the preceding claims, characterized in that the shielding element (11'') is arranged on the side of the component holder (14) which faces away from the plasma generating device (4) and/or the at least one gas inlet (3, 10). . Device according to one of the preceding claims, characterized in that the shielding element (11') is arranged in the coating chamber (1) in a preferably variably adjustable or displaceable manner. Device according to one of the preceding claims, characterized in that an electrical potential can be applied to the shielding element (11, 11', 11''). Device according to one of the preceding claims, characterized in that the shielding element (11, 11', 11'') is designed as a plate or disc, preferably with passages (12), in particular holes or slots, for the process gas or as a lattice structure. Device according to one of the preceding claims, characterized in that the shielding element (11, 11', 11'') is made of an insulating material, in particular glass or ceramic, or is made of a conductive material, in particular a metal. Device according to one of the preceding claims, characterized in that the plasma generating device (4) is arranged completely or partially outside the coating chamber (1) or separated from the component holder (14) by a partition wall (9). Method for coating by plasma-enhanced atomic layer deposition, in particular using a device according to one of the preceding claims, in which a coating chamber (1) is provided which is delimited by a chamber wall (2), wherein in the coating chamber (1) at least one component (15 ) that is to be coated is arranged in a component holder (14), different process gases being successively introduced into the coating chamber (1) through the chamber wall (2) through at least one gas inlet (3,10) in order to start the coating of the component (15 ), a plasma generating device (4) being arranged in such a way that a plasma (16) is generated at least partially during the coating process within the coating chamber (1) in the region of the component (15), characterized in that a magnetic field generating device (18) at least partially during the coating in the region of the component holder (14), a magnetic field ores and/or that a shielding element (11, 11', 11'') is arranged inside the coating chamber (1), which shields the component holder (14) from the at least one gas inlet (3,10) and/or the plasma generating device (4 ) shields mechanically and/or electrically and/or that the process parameters of the system pressure and/or plasma power are optimized in such a way that the potential difference between the component (15) to be coated and the plasma generating device (4) is minimized when the plasma is stable. procedure after claim 12 , characterized in that the plasma (16) is generated by an electrostatic field using electrical DC voltage between electrodes or by capacitive electrical excitation using electrical AC voltage at electrode plates (5) or by a high-frequency alternating current through an excitation coil. procedure after claim 12 or 13 , characterized in that the shielding element (11, 11'') is subjected to an electrical potential, so that charged particles, in particular negatively charged particles, do not get into the coating chamber (1) and/or do not reach the component (15) to be coated be able. Procedure according to one of Claims 12 until 14 , characterized in that the electrodes (5) or electrode plates operated with alternating voltage or an excitation coil of the plasma generating device through which alternating current flows are set to a positive electrical basic voltage. Procedure according to one of Claims 12 until 15 , characterized in that the pressure of the process gas is kept in the range from 0.01 to 100 Pa, preferably between 0.1 and 10 Pa. Procedure according to one of Claims 12 until 16 , characterized in that the energy supply required to produce a coating for generating a plasma (16) is detected, the energy supply per unit of time being minimized and the duration of the energy supply being adjusted accordingly, so that the energy supplied is kept constant. Procedure according to one of Claims 12 until 17 , characterized in that the potential difference between component and electrodes or system ground and electrodes is less than 100 V, preferably less than 50 V, particularly preferably less than 30 V.

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