DE102011104132B3 - Plasma assisted atomic layer deposition useful for forming thin layer on substrate, in reaction zone, comprises carrying out coating cycles, rinsing reaction area and converting adsorbed fraction of layer-forming process gas into thin layer - Google Patents

Abstract

Plasma assisted atomic layer deposition (ALD) for forming thin layer on substrate in reaction zone at process pressure reduced by vacuum system, comprises coating cycles, within which layer-forming process gas is supplied in cycle steps, rinsing reaction area and subsequently converting adsorbed fraction of layer-forming process gas by the supply or generation of reactive process gas, into thin layer. The process gas with rinsing properties is supplied over first process area with limited flow cross-section to second process area with respect to first process area larger flow cross-section. Plasma assisted atomic layer deposition (ALD) for forming a thin layer on a substrate in a reaction zone at a process pressure reduced by a vacuum system, comprises coating cycles, within which a layer-forming process gas is supplied in cycle steps, rinsing the reaction area and subsequently converting the adsorbed fraction of the layer-forming process gas by the supply or generation of a reactive process gas, into a thin layer. The process gas with rinsing properties is supplied over a first process area with a limited flow cross-section to a second process area with respect to the first process area larger flow cross-section and is pumped out, where the ratio and size of the flow cross sections, the pumping capacity of the vacuum system and the supply time and the mass flow of the process gas is adjusted at least during a cycle step such that a transition flow is formed between molecular and viscous flow with local process pressure different in both the process areas and different ratios between flow and diffusion, such that the first process area is rinsed due to predominant flow, the supplied process gas remains in the second process area due to the predominant diffusion, such that two different process steps are performed at least partially at the same time during a cycle step. An independent claim is also included for a device comprising (i) a processing chamber having device for the supply of process gases, device for generating plasma coupled in a capacitive manner, and a vacuum system for evacuating the process gases, preferably for plasma assisted ALD, and (ii) at least one electrode arranged in the reaction chamber and is configured in such a hollow manner that it forms the first flow region and a substrate can be introduced into the electrode, the process gases can be fed through the electrode, and openings in the electrode are provided between the substrate and a counter electrode and are in fluid contact with the second process area, which corresponds to the process chamber, and the vacuum system, such that the plasma is generated in the process chamber, which ensures an uniform film formation reaction in response to a substrate contained in the electrode, by diffusion of the process gas radicals in the first flow region and by a suitable arrangement and design of the electrode openings.

Description

The invention relates to a method for forming a thin layer by means of atomic layer deposition (ALD) using plasma and devices suitable for this purpose. Such methods are also referred to as plasma enhanced atomic layer deposition (PEALD).

PEALD methods are used in particular in semiconductor technology and are suitable for a wide variety of coating applications. More particularly, the present invention relates to a PEALD method with varying mass flow within a coating cycle and with two process areas, wherein plasma is generated in one process area, while no plasma generation occurs in the other process area.

A process with varying mass flows of process gases within a coating cycle is over US 2005/0016956 A1 known. The coating takes place essentially in the viscous flow region. It is envisaged to supply layer-forming process gases with low gas flow and to purge the reaction area with a high gas flow. In order to obtain a long residence time in the reaction area and a concomitant reduction in consumption of the layer-forming process gas, the pressure in the reaction area is preferably kept constant by changing the pumping capacity. A change in the pumping power is complicated and costly while pressure fluctuations in the mentioned pressure range between 0.133 and 1.33 mbar can lead to dust contamination of the layers.

Another method with varying mass flows of the process gases is in US 2011/0070141 A1 described. Again, the pump power is changed, with a special Gaede pumping stage reduces the mechanical complexity. In a preferred embodiment of the invention, it is provided that the process pressure when supplying a layer-forming process gas with low mass flow to achieve a high residence time is regulated higher than the process pressure when supplying a high-flow purging process gas.

Furthermore, PEALD processes with two process areas are known.

US 2003/0075273 A1 relates to a method with a process area is generated in the plasma and another process area without plasma generation, in which a substrate is arranged. The flow direction of the process gases runs at least partially over the process area with plasma generation in the process area without plasma generation. Another procedure is over US 2011/0003087 A1 known. Again, part of the process gas flows through the process area with plasma generation in the process area without plasma generation but with improved flow control.

Classic ALD processes require four process steps (supplying a layer-forming process gas, purging, supplying a reactive process gas, purging) while for PEALD processes even only three process steps ( EP 1092233 B1 ) required are.

The object of the invention is an in particular plasma-assisted ALD method with extended functionality compared to known ALD methods. In this case, for example, excess layer-forming process gas is to be decomposed by an additional plasma reaction before it enters the pump system or in a batch system, the coating of multiple substrates are made possible with changing process pressure, without causing over conventional ALD process, an extension of the cycle time. With preferably constant pumping power, the advantages of different process pressures for an ALD process with fast coating cycles, simple process technology and extremely low process gas consumption should be utilized, wherein a use of layer-forming process gases with low vapor pressure is preferably provided without carrier gas.

This object is achieved by a method according to claim 1 wherein one or more substrates are arranged depending on the embodiment of the invention in a first or a second process area, the flow cross-section (Strömungsleitwert) of the first process area smaller the flow area (Strömungsleitwert) of the second process area (plasma area) a process gas with purging properties is supplied to the second process area via the first process area and pumped out of it, the process chamber and process parameters being designed such that, during the residence time of a layer-forming or a reactive process gas in the second process area, the first process area is purged and thereby is prepared for a subsequent cycle step, so that two process steps are performed simultaneously in one cycle step. The ALD method according to the invention thereby makes possible a functional extension of ALD processes without additional lengthening of the cycle time. It is according to the invention that the diffusion of a process gas against the flow direction defined by pressure gradient and mass flow is used in at least one process step in at least one of the process areas. mass flow refers to the mass flow or the mass flow in relation to time (eg grams per second). The choice of process pressure in the range of Knudsen flow is particularly advantageous for processes with changing process pressure, because due to relatively low continuum flow, the usual disadvantages of pressure fluctuations (dust turbulence and the like) are substantially avoided, while the residence time of process gases without changing the flow rate through Process pressure change with a corresponding change in the diffusion coefficient on the mass flow of the process gases can be controlled. Knudsen flow prevails in the fine vacuum range between 0.001 and 1 mbar. For the process according to the invention, a process pressure range between 0.005 and 0.5 mbar is preferred, with a preferred pressure of between 0.008 and 0.03 mbar being selected for plasma generation.

In accordance with claim 1, two different process steps are carried out simultaneously in two process areas which are in fluid communication with one another while the process gas is supplied together. In this case, a process area can be purged while a second process area arranged in the same flow path continues to be exposed to a layer-forming process gas. This is particularly advantageous for preparing a subsequent rinsing step with a higher process pressure during continued adsorption in the second process area, or for reacting excess process gas in the second process area without significant influence on the first process area. The method according to the invention can be used for PEALD processes with different number of cycle steps and any number of process gases as well as to a limited extent for ALD processes without plasma generation.

In the claims 2 to 9 particularly preferred embodiments of a plasma-assisted ALD method and a device suitable for this purpose are mentioned.

Before flow principles of the invention are explained:
Viscous flow or continuum flow refers to the flow of a plurality of gas particles that predominantly collide against each other and only occasionally on process chamber walls by thermal motion (Brownian motion) and flow together as a continuum. Molecular flow refers to the flow of gas particles that, due to lower particle density relative to a flow cross-section, predominantly abut against process chamber walls and only occasionally against each other. Knudsen flow is a transitional flow between molecular and viscous flow. Flow is a directed movement of particles or a continuum, especially in the direction of lower process pressure (or in the direction of mass flow), while diffusion describes a direction-independent particle movement, which also includes particle movements against the flow direction with superimposed flow.

In this case, the so-called inherent diffusion of a process gas or process gas mixture is fundamentally comparable to molecular flow, since it involves particle movements that are only conditionally dependent on the flow movement of a gas continuum. In molecular flow, however, only the gas movement in Abpumprichtung (mass flow) or in the direction of a higher to a lower pressure is considered, while diffusion basically refers to the movement of a gas particle from its origin in any direction. Diffusion is definable as the mean distance from which a particle (process gas molecule) in a quiescent medium leaves its place of origin in a given time. In additionally agitated medium, the flow movement is superimposed (gas particles obtained by other gas particles movement pulses in the flow direction), so that a diffusion opposite to the flow direction decreases with increasing velocity of the flow and accounts for about the speed of sound. In order to purge all diffusing particles from a process area below the speed of sound, a suitable purge time is required, as explained in the following example in an approximation. In the present application, "diffusion" refers both to diffusion of individual process gases or uniform process gas mixtures with one another and to diffusion of different process gases having different local concentrations, since the same propagation principle is present and only basic comparison between diffusion and flow motions is required to illustrate the invention. In the example calculation, the term "diffusion" is used to denote the mean distance (or the mean distance) of a particle traveled within a selected time from the place of origin when the medium is at rest.

Diffusion can generally be described by the diffusion coefficient D [m ² / s]. By the Einstein-Smoluchowsky equation d ² = 2Ds (with d = average distance of a particle from the place of origin, D = diffusion coefficient, s = seconds), the distance d traveled by the gas particles in a spatial direction with the gas continuum at rest can then be calculated time-dependent. From the Einstein-Smoluchowsky equation it can be seen that the diffusion (distance per time) is not linear. For example, to penetrate a double track takes four times the time. The diffusion coefficient increases with pressure reduction.

The present invention makes use of this law for a very advantageous ALD process. By choosing the process pressure range (Knudsen flow / transition flow), different diffusion parameters can be set without changing the pumping power of a vacuum system. When using a relatively linear vacuum system (eg. B. turbomolecular pump having a backing pump) in both the process gas supply at a low flow rate (z. B. 10 cm ³ / min under standard conditions) (as well as process gas supply with a higher flow z. B. 100 cm ³ / min at standard conditions) achieved about the same average flow velocities. This means that the process pressure is lower at lower mass flow than at higher gas flow. However, the gas diffusion increases significantly with pressure decrease, so that increases the residence time of already supplied process gas particles at the same average flow velocity by diffusion movement against the flow direction. At the same time, the number of surface contacts increases by diffusion radially to the flow direction, so that a higher proportion of the supplied gas particles can be adsorbed. Of course, it should be taken into consideration that an amount of gas particles sufficient for the process is supplied within a designated supply period and the process pressure can not be reduced in any desired manner while the feed time remains the same.

The process conditions should be selected in the example such that a cubic process area with 220 mm edge length is traversed over the entire flow cross-section with 4.6 m / s process gas velocity. Upon supply of 10 cm ³ / min at standard conditions of a layer-forming process gas, while the process pressure in the process area is about 0.001 mbar and with supply of 100 cm ³ / min at standard conditions of a purging process gas, the process pressure is about 0.01 mbar. The example calculations were carried out approximately with argon as process gas at 70 ° C and self-diffusion and serve only to illustrate the invention. In principle, of course, more detailed calculations can be performed. However, the method according to the invention can already be implemented by a person skilled in the art with appropriate selection of the process pressure range and choice of high and low mass flows, so that rough calculations and estimates (without consideration of all process gas portions, etc.) are completely sufficient.

When the layer-forming process gas is supplied at 10 cm ³ / min under standard conditions of gas flow and 0.001 mbar process pressure in the process area, the diffusion coefficient is about 19 m ² / s. This results in a diffusion of 3.4 m at 0.3 seconds supply while the average flow rate is 4.6 m / s and the gas (considered as a continuum) in the same time only 1.4 m (0.3 s × 4.6 m / s) in the direction of the vacuum system. It is assumed in simplified terms that the starting point of the diffusion also moves with a flow velocity of 4.6 m / s in the direction of the vacuum system and thus a diffusion of 2.0 m remains opposite to the flow direction of the gas continuum. Due to these considerations, the supply time of the process gas would have to be more than 2 seconds to replace all gas particles in the process area at the start of the feed. However, when a layer-forming process gas is supplied, rapid distribution and adsorption of the gas particles and no gas exchange are desired, so that a low gas flow rate of 10 cm ³ / min at standard conditions (equivalent to a mass flow of about 0.0003 g per second for example in argon) is advantageous ,

A detailed description of the calculation channels has been omitted since these are easily accessible to the person skilled in the art. In this case, the determination of the diffusion coefficient over the mean free path and the average thermal velocity of the corresponding gas particles. The calculation bases required in addition to the Einstein-Smolucholsky equation can, for example, be taken from Wutz, Handbook of Vacuum Technology (pages 37-40 and 53-54).

For flushing the process area 100 cm ³ / min are provided under standard conditions gas flow at 0.01 mbar process pressure according to Example, wherein the diffusion coefficient is 1.9 m ² / s.

This results in a diffusion of 1.1 m at a delivery time of 0.3 seconds, while the gas continuum in the same time again moves 1.4 m in the direction of the vacuum system. According to the above assumption, a remaining diffusion of -0.3 m is now obtained so that, given a mass flow of about 0.003 g / s (100 cm ³ / min at standard conditions), in principle a complete gas exchange within 0.3 seconds of supply time is possible. It should be noted that an average diffusion is calculated under simplified assumptions and, if necessary, a larger reserve (higher flow velocity or longer flow time) must be planned.

However, it is shown that by suitable choice of the process pressure range with appropriate gas flows (mass flow) and suitable flow control, the pumping capacity of a vacuum system can be maintained and the resulting process pressure fluctuation fast Coating cycles with good residence time of the layer-forming process gas and effective flushing of the purging process gas allows. By choosing a vacuum pump with less linear pump characteristic, such. B. a Roots pump, the pump power at higher pressure can be much larger than at lower pressure. As a result, a relatively larger flushing performance (higher flow velocity) compared to reduced flow velocity at low pressure is achieved. This can be advantageous for the method according to the invention, provided that the mass flow at low process pressure is sufficient. Compared to turbomolecular pumps usually much larger pumping stations are needed for this purpose.

As a layer-forming process gas are any process gases according to the invention, which are vaporous at given process conditions and can be converted or decomposed by reaction with a reactive or an activated process gas in a layer or decomposed. In the case of oxidative layer formation, for example, elements of the reactive or of the activated process gas can be incorporated into the layer, while in the case of reductive layer formation, the reactive or activatable process gas is generally not incorporated into the layer. Process gases which can be activated are those which are essentially unreactive at given process conditions without the production of plasma and, similar to inert gases, have purging properties, but become reactive in the area of influence of the plasma when plasma is generated. Representative examples of such gases are oxygen, hydrogen and nitrogen. Representative examples of reactive gases are water vapor and ammonia, although these also do not necessarily have to be reactive with any layer-forming process gas without plasma generation, but react directly with many layer-forming process gases.

As process steps, both the classical process steps such. As "supplying a layer-forming process gas" or "rinsing the reaction area" and additional steps such. B. "decomposition or conversion of excess layer-forming process gas" by plasma-assisted surface reaction or vapor deposition outside the reaction area or "rinsing the first process area (supply area)" for preparing a pressure increase in the supply area referred to. The timing of the process steps takes place in cycle steps. It is according to the invention that due to the use of different ratios of flow and diffusion in the region of the so-called Knudsen flow, different process steps are combined to form a common cycle step or at least partially performed simultaneously. This allows extended functionality ALD processes with no cycle time extension, with cycle times between 0.5 and 1.5 seconds (per coating cycle) being preferred.

Claim 2 relates to a preferred embodiment of the invention, wherein the pumping power of a vacuum system is kept constant and the generation of plasma takes place in the second process area. The plasma generation is carried out in particular during the supply of an activatable or reactive process gas. The term "in the presence" additionally includes the generation of plasma after supply of an activatable or reactive process gas during its residence time in the second process area.

The claims 3 to 5 relate to preferred embodiments, in particular for a "remote plasma method" with capacitive plasma coupling, wherein the decomposition or conversion of excess layer-forming process gases forms a significant extension of the range of functions. Due to the relatively larger and preferably substantially larger second process area relative to the first process area (reaction area) and the choice of process pressure in the transition region between viscous flow (flow of multiple process gas particles as continuum (continuum flow)) and molecular flow (flow due to thermal movement of the individual process gas particles) good process control contamination of the vacuum system by layer-forming process gases are avoided. In this case, the duration of a coating cycle is essentially not prolonged compared with conventional coating processes, since the decomposition of excess process gas takes place at least partially during the rinsing of the first process region (reaction region).

The embodiment according to the invention can also be formulated in such a way that process gas flow is provided from a first process area without plasma generation via a second process area with plasma generation into a vacuum system with a pressure drop running in the direction of flow, whereby at least one substrate is arranged in the first process area and process pressure and flow rate are selected in that in the case of plasma generation in the second process area a radical is supplied by diffusion of the radicals counter to the flow direction or laterally to the flow direction.

The claims 6 and 7 relate to a preferred embodiment of the method according to the invention, in particular for a direct plasma process with inductive plasma coupling preferably for batch coating of multiple substrates. The first process area is not the same as in Previous embodiments, the reaction area, but a preparation area for pressure increases (supply area).

In the supply of purge gas with relative to other process gases high mass flow layer-forming or reactive process gases can be pushed back by pressure increase in the first process area (supply area) in the supply lines, optionally also condense and slowly released together with the purge gas, so that no optimal flushing effect is achieved , According to the invention, an optimum rinsing effect is achieved such that the first process area (with low flow cross-section) is first rinsed with low mass flow without significant pressure increase, while the process gas to be rinsed (layer-forming or reactive) is still available in the second process area by diffusion, and then a purging process gas is supplied with a correspondingly higher mass flow over the first process area for purging the second process area. Thus, the first process area, which corresponds to the supply area of the process gases, is already purged before an increase in pressure so that there are no layer-forming or reactive process gases in the supply area that could be forced back into the supply lines, while the process pressure in the second process area is also at Supply of the purging process gas usually does not exceed the supply pressure of the layer-forming process gas. It is called a two-fold mass flow of the purging process gas relative to the mass flow of the activatable process gas to achieve a noticeable rinsing effect by the purging process gas. Preferably, however, the purging process gas is supplied with more than five times and more preferably more than ten times the mass flow.

In PEALD processes with layer-forming and reactive process gases, which are already reactive with each other without plasma generation at given process conditions, it is particularly volteilhaft that the supply of process gases in the first process area (supply area) via at least two supply lines, wherein one of the supply line for layer-forming process gases and the other feed line for reactive process gases is used, and that during the supply of a film-forming or a reactive process gas through one of the supply lines, the other supply line is protected by a low-flow line purging gas from penetrating the respective process gas. It is also advantageous that a pipeline purging gas, which essentially fulfills no function as a process gas in the reaction region, is conducted through all supply lines with low mass flow over the entire duration of a coating cycle, the process gases being coupled into the supply lines in such a way that the pipeline purging gas additionally acts as Carrier gas is used and before process pressure increase process gas supply pauses are provided, within which the supply area (first process area) and the supply lines are flushed with the line purging gas. Such a process gas supply is also applicable to ALD processes without plasma generation and suitable as a feed method for ALD process with changing process pressure.

When activatable process gases are used which become reactive only during the generation of plasma under given process conditions and are not directly reactive in the first process region (feed region) but have purging properties, the above-mentioned supply of a line purging gas to individual supply lines is not required. It is preferred that the first process area is purged with a mass flow which forms a local process gas pressure which substantially corresponds to the local process gas pressure when supplying a layer-forming process gas, and preferably less than or equal to it, but optionally also selected to be larger at very low process gas pressure of the layer-forming process gas becomes. It is advantageous that the process pressure in the first process area and particularly preferably in the supply line for layer-forming process gases is monitored cycle step-dependent, so that the lack of a layer-forming process gas can be detected directly in a simple manner and the corresponding process gas in a coating break, without interrupting the coating process can be exchanged. It is likewise advantageous that the process pressure in the second process area or preferably in the pumpdown area is monitored in a cycle-step-dependent manner and an excessive supply of layer-forming process gas detectable by pressure increase is avoided. Corresponding pressure controls are not only applicable in relation to this embodiment but on the invention in general.

Claim 8 relates to a specification of the invention by means of calculation, wherein means for the inventive design of process gas flows with predominant diffusion or prevailing flow are mentioned.

According to claim 8 and the above example are obtained:
For 10 cm ³ / min at standard conditions of gas flow rate and a process pressure of 0.001 mbar, the square of the flow speed is multiplied by half the feed period ((4.6 m / s) ² × 0.5 × 0.3 s = 3,173 m ² / s ) is smaller than the diffusion coefficient of 19 m ² / s and diffusion with high residence time of supplied process gases is predominant.

For 100 cm ³ / min at standard conditions of gas flow at a process pressure of 0.01 mbar, the square of the flow speed is multiplied by half the feed period ((4.6 m / s) ² × 0.5 × 0.3 = 3.173 m ² s / s) greater than the diffusion coefficient of 1.9 m ² / s and flow with purging properties is predominant.

This relationship can also be formulated such that diffusion prevails in a process area when the process conditions are chosen such that the average flow velocity determined from mass flow and particle density (pressure) of a process gas multiplied by the supply time of the process gas results in a distance that is smaller than the mean The distance is that a process gas particle at a stationary process gas and the same particle density (pressure) in a time corresponding to the supply time by thermal movement (diffusion) away from its place of origin. And that flow with purging properties predominates when the process conditions are selected such that the average flow velocity determined from mass flow and particle density (pressure) of a process gas multiplied by the supply time of the process gas results in a distance greater than the mean travel that a process gas particle with stationary process gas and same particle density (pressure) in a time corresponding to the supply time by thermal movement (diffusion) from its place of origin.

Due to the selected flow regime (Knudsen flow), "prevailing flow" could also be referred to as "prevailing viscous flow" because the viscous flow fraction is attributed the better purging properties and the viscous flow fraction increases over the molecular flow fraction with increasing process pressure. However, since the mean flow velocity is determined from the mass flow and the flow cross section or the particle density, both molecular and viscous flow fraction are included in the calculation, so that should be spoken of "prevailing flow". Prevailing flow means that for a given supply time, the flow prevails over the diffusion and outweighs the purging properties.

Claim 9 relates to a device, in particular for a preferred embodiment of the method according to one of claims 3 to 5.

In the following, embodiments of the invention will be explained in more detail with reference to the drawing. Show it:

1 a schematic representation of a coating cycle according to the invention in the arrangement of a substrate in the first process area

2 a schematic representation of an apparatus for a method according to 1

3 a schematic representation of another device for a method according to 1 .

4 a schematic representation of a coating cycle according to the invention in the arrangement of substrates in the second process area,

5 a schematic representation of a method accordingly 4 when supplying a layer-forming and a non-plasma reactive process gas,

6 a schematic representation of an apparatus for a coating method according to 4 or 5 .

7 an element with a first process area for process gas supply and subsequent symmetrical flow cross-sectional widening,

8th a schematic representation of the flow path within a device accordingly 6 and 7 and

9 Reflection and transmission curves of two silver layers generated by direct plasma exposure

In 1 the process steps within a first process area are shown in a first line and the process steps within a second process area are shown in the second line. Furthermore, the letters "S" and "D" show whether flow (S) or diffusion (D) prevails in the respective process step according to the invention. The simultaneous process steps of both process areas together form successive cycle steps corresponding to the numbering 1), 2) and 3).

In the following lines, process gas flows and temporal placement of the plasma generation are represented by rectangles. In the process gas flows, the rectangular height indicates low and high mass flows of the process gases.

• 1) Zuführen eines schichtbildenden Prozessgases A über den ersten Prozessbereich zur Adsorption auf einem im ersten Prozessbereich angeordnetem Substrat und Beenden der Zufuhr,
• 2) Zuführen eines aktivierbaren Prozessgases B über den ersten Prozessbereich bei vorherrschender Strömung im ersten Prozessbereich und Spülen des Substrates bei zumindest teilweise gleichzeitiger Erzeugung von Plasma im zweiten Prozessbereich zur Zersetzung überschüssigen schichtbildenden Prozessgases A, wobei eine Diffusion von Radikalen in den ersten Prozessbereich durch die im ersten Prozessbereich vorherrschende Strömung reduziert oder im Wesentlichen gesperrt wird, und
• 3) Zuführen eines aktivierbaren Prozessgases B bei derart reduziertem Massefluss durch den ersten Prozessbereich, dass Diffusion im ersten Prozessbereich vorherrscht und Erzeugen von Plasma im zweiten Prozessbereich mit vorherrschender Diffusion von Radikalen in den ersten Prozessbereich, so dass auf dem Substrat adsorbiertes schichtbildendes Prozessgas A in eine Schicht umgewandelt wird, wobei bevorzugt der reduzierte Anteil des Massenflusses von Prozessgas B umgelenkt und dem zweiten Prozessbereich direkt zugeführt wird.

When arranging at least one substrate in a first process area, a coating cycle is formed from the following cycle steps, wherein the coating cycle is repeated until a desired layer thickness is reached:

• 1) supplying a layer-forming process gas A via the first process area for adsorption on a substrate arranged in the first process area and terminating the feed,
• 2) supplying an activatable process gas B over the first process area at prevailing flow in the first process area and rinsing the substrate at least partially simultaneous generation of plasma in the second process area to decompose excess layer-forming process gas A, wherein a diffusion of radicals in the first process area by the in first process area prevailing flow is reduced or substantially blocked, and
• 3) supplying an activatable process gas B at such reduced mass flow through the first process area that diffusion prevails in the first process area and generating plasma in the second process area with prevailing diffusion of radicals into the first process area, so that adsorbed on the substrate layer-forming process gas A in a Layer is converted, wherein preferably the reduced portion of the mass flow of process gas B is deflected and fed directly to the second process area.

The generation of plasma in the second cycle step 2) preferably begins by an initiation period 7 delayed to the start of supply of the activatable process gas B, so that in the first process area at the beginning of the plasma already prevails flow.

2 and 3 Embodiments of the invention substantially according to claim 9.

2 shows one as a hollow electrode 50 designed first process area 100 , which with RF power 70 can be acted upon while the process chamber 300 represents a grounded counter electrode and simultaneously the second process area 200 forms. The hollow electrode 50 is with gas-permeable openings 55 for the flow of process gases 10 . 20 fitted. A substrate 40 is inside the hollow electrode 50 arranged. The supply of process gases 10 . 20 takes place in particular via the hollow electrode 50 , In a preferred embodiment, means for flow diversion 25 a portion of the activatable process gas 20 directly into the second process area (plasma area) 200 provided during the supply of the layer-forming process gas 10 exclusively via the first process area (reaction area) 100 is provided. The diverted portion of the activatable process gas 20 can be adjusted by the skilled person by suitable choice of the flow cross sections or use of throttle elements.

By adjusting the size and number of openings 55 is in addition to the influence of the flow cross sections of the process areas 100 . 200 the pressure difference between the two process areas 100 and 200 adjustable. With respect to the Strömungsleitwert (flow cross-section) of the first process area 100 reduced Strömungsleitwert the sum of the openings 55 For example, diffusion in the direction of the substrate can be essentially blocked even with a relatively small mass flow, whereas with larger conductance the ratio between diffusion and purging flow is predominantly regulated so that flow or diffusion predominates. The pumping out of the process gases 10 . 20 takes place via the second process area 200 by means of a vacuum system, not shown, through a pump-down opening 31 , It is an electrically insulating connection element 90 between grounded process chamber 300 and hollow electrode 50 provided, wherein the heating of the hollow electrode 50 preferably takes place via the generation of plasma. It is advantageous that the plasma generation within the same coating cycles during prevailing diffusion in the first reaction region 100 kept constant and only at prevailing flow in the first process area 100 is changed for temperature control, so that supply length and type of radicals supplied in the coating process for the same coating cycles remains substantially the same.

The flow direction between the first process area 100 and second process area 200 through openings 55 is represented by flow arrows, wherein process-dependent in at least one cycle step, a diffusion opposite to the flow direction is provided.

3 essentially corresponds 2 , with the difference that the hollow electrode 50 is grounded and one with high frequency power 70 act on counter electrode 60 in the second process area 200 is arranged. In this way, the properties of the plasma can be changed and it can be applied to an electrically insulating connecting element ( 90 ) corresponding 2 be dispensed with, so that heating of the substrate 40 also directly via a grounded heating element 95 is feasible. Also in this embodiment of the invention, it may be advantageous that the first process area 100 with the exception of the process gas supply is thermally separated from the process chamber, so that not the entire process chamber must be heated to process temperature.

In 4 a coating cycle with 4 cycle steps according to a further embodiment of the invention is shown schematically. In a first line, the process steps within a first process area (feed area) and in the second line the process steps within a second process area (reaction area) are shown. Furthermore, the letters "S" and "D" show whether in the respective process step flow (S) or diffusion (D) prevails according to the invention. The simultaneous process steps of both process areas together form successive cycle steps corresponding to the numbering 1), 2), 3) and 4).

The following line shows the process gas flows, with the rectangular height indicating low and high mass flows of the process gases. The illustrated embodiment essentially corresponds to claim 7. In contrast to known methods, the reaction area (second process area) is not rinsed by supplying the activatable process gas B, but only with additional supply of the purging process gas S. This is preferably selected as the inert gas, since this makes it possible to use it for any desired process gases, and thus the purging step for the second process region can be set fixed independently of process for any desired processes. In this case, a simultaneous supply of the activatable process gas B with the purging process gas S is not absolutely necessary, but reduces the switching frequency of the corresponding valve by two circuits per coating cycle and the flow of activatable process gas B is already initiated and uniform in plasma generation. Argon is preferably used as the purging process gas.

• 1) Zuführen eines schichtbildenden Prozessgases A mit relativ zu einem spülenden Prozessgas S niedrigem Massenfluss bevorzugt über den ersten Prozessbereich in den zweiten Prozessbereich zur Adsorption auf einem oder mehreren Substraten im zweiten Prozessbereich und Beenden der Zufuhr des schichtbildenden Prozessgases A,
• 2) Zuführen eines aktivierbaren Prozessgases B mit relativ zum spülenden Prozessgas S niedrigem Massenfluss über den ersten Prozessbereich zum Spülen des ersten Prozessbereiches bei zumindest teilweise fortgesetzter Verweildauer des zugeführten schichtbildenden Prozessgas A im zweiten Prozessbereich durch vorherrschende Diffusion,
• 3) Zuführen eines spülenden Prozessgases S mit relativ zu den anderen Prozessgasen A, B hohem Massenfluss über den ersten Prozessbereich zum Spülen der Substrate im zweiten Prozessbereich, wobei bevorzugt die Zufuhr des aktivierbaren Prozessgases B mit relativ zum spülenden Prozessgas S niedrigem Massenfluss beibehalten wird, und Beenden der Zufuhr des spülenden Prozessgases S, und
• 4) Zuführen eines aktivierbaren Prozessgases B mit relativ zum spülenden Prozessgas S niedrigem Massenfluss über den ersten Prozessbereich und Erzeugung von Plasma im zweiten Prozessbereich, so dass auf dem Substrat adsorbiertes schichtbildendes Prozessgas in eine Schicht umgewandelt wird und Beenden von Plasmaerzeugung und Zufuhr des aktivierbaren Prozessgases B,

wobei als spülendes Prozessgas mit hohem Massenfluss bevorzugt ein Inertgas (Edelgas) verwendet wird.When arranging at least one substrate in a second process area, a coating cycle is formed from the following cycle steps, wherein the coating cycle is repeated until a desired layer thickness has been reached:

• 1) supplying a layer-forming process gas A with a low mass flow relative to a purging process gas S preferably via the first process area into the second process area for adsorption on one or more substrates in the second process area and terminating the supply of the layer-forming process gas A,
• 2) supplying an activatable process gas B with a low mass flow relative to the purging process gas S via the first process area for purging the first process area with at least partially continued dwell time of the supplied layer-forming process gas A in the second process area due to prevailing diffusion,
• 3) feeding a purging process gas S relative to the other process gases A, B high mass flow over the first process area for purging the substrates in the second process area, wherein preferably the supply of the activatable process gas B is maintained relative to the purging process gas S low mass flow, and Terminating the supply of the purging process gas S, and
• 4) supplying an activatable process gas B with low mass flow relative to the purging process gas S over the first process area and generating plasma in the second process area, so that layer-forming process gas adsorbed on the substrate is converted into a layer and terminating plasma generation and supplying the activatable process gas B .

wherein an inert gas (noble gas) is preferably used as the high-mass-flow purging process gas.

In 5 is a coating cycle accordingly 4 but shown with a total of 6 cycle steps. This coating cycle is particularly suitable for use of a reactive process gas instead of an activatable process gas and basically also allows ALD coating processes without plasma generation at variable process pressure. The representation corresponds 4 , However, it was waived to specify the respective process gas flow, since this is analogous to 4 result.

• 1) Zuführen eines schichtbildenden Prozessgases A mit relativ zu einem spülenden Prozessgas S niedrigem Massenfluss bevorzugt über den ersten Prozessbereich in den zweiten Prozessbereich zur Adsorption auf einem oder mehreren Substraten im zweiten Prozessbereich sowie Zuführen eines Leitungsspülgases S* zumindest über die Zufuhrleitung eines reaktiven Prozessgases C mit relativ zu einem spülenden Prozessgas S niedrigem Massenfluss und Beenden der Zufuhr des schichtbildenden Prozessgases,
• 2) Zuführen des Leitungsspülgases S* mit relativ zum spülenden Prozessgas S niedrigem Massenfluss über beide Zufuhrleitungen in den ersten Prozessbereich zum Spülen des ersten Prozessbereiches bei zumindest teilweise fortgesetzter Verweildauer des zugeführten schichtbildenden Prozessgas A im zweiten Prozessbereich durch vorherrschende Diffusion,
• 3) Zuführen eines spülenden Prozessgases S mit relativ zu den anderen Prozessgasen A, C und dem Leitungsspülgas S* hohem Massenfluss zum Spülen der Substrate im zweiten Prozessbereich, wobei bevorzugt die Zufuhr des Leitungsspülgases S* mit relativ zum spülenden Prozessgas S niedrigem Massenfluss über zumindest eine Zufuhrleitung beibehalten wird, und Beenden der Zufuhr des spülenden Prozessgases S
• 4) Zuführen eines reaktiven Prozessgases C mit relativ zum spülenden Prozessgas S niedrigem Massenfluss über den ersten Prozessbereich und Erzeugung von Plasma im zweiten Prozessbereich, so dass auf dem Substrat adsorbiertes schichtbildendes Prozessgas A in eine Schicht umgewandelt wird, sowie Zuführen eines Leitungsspülgases S* zumindest über die Zufuhrleitung des schichtbildenden Prozessgases A mit relativ zu dem spülenden Prozessgas S niedrigem Massenfluss und Beenden von Plasmaerzeugung und der Zufuhr des reaktiven Prozessgases C,
• 5) Zuführen des Leitungsspülgases S* mit relativ zum spülenden Prozessgas S niedrigem Massenfluss über beide Zufuhrleitungen in den ersten Prozessbereich zum Spülen des ersten Prozessbereiches bei zumindest teilweise fortgesetzter Verweildauer des zugeführten reaktiven Prozessgas C im zweiten Prozessbereich durch Diffusion,
• 6) Zuführen eines spülenden Prozessgases S mit relativ zu den anderen Prozessgasen A, C und dem Leitungsspülgas S* hohem Massenfluss zum Spülen der Substrate im zweiten Prozessbereich, wobei bevorzugt die Zufuhr des Leitungsspülgases S* mit relativ zum spülenden Prozessgas S niedrigem Massenfluss über zumindest eine Zufuhrleitung beibehalten wird, und Beenden der Zufuhr des spülenden Prozessgases S,

wobei bevorzugt das spülende Prozessgas S sowie das Leitungsspülgas S* als Inertgas gewählt werden und besonders bevorzugt als Leitungsspülgas S* Helium und als spülendes Prozessgas S Argon verwendet wird.When arranging at least one substrate in a second process area, a coating cycle is formed from the following cycle steps:

• 1) supplying a layer-forming process gas A with relative to a purging process gas S low mass flow preferably over the first process area in the second process area for adsorption on one or more substrates in the second process area and supplying a Leitungsspülgases S * at least via the supply line of a reactive process gas C with relative to a purging process gas S low mass flow and terminating the supply of the layer-forming process gas,
• 2) supplying the pipeline flushing gas S * with low mass flow via both supply lines into the first process area for purging the first process area with at least partially continued dwell time of the supplied layer-forming process gas A in the second process area due to prevailing diffusion,
• 3) feeding a purging process gas S with relative to the other process gases A, C and the line purging gas S * high mass flow for purging the substrates in the second process area, wherein preferably the supply of the line purging gas S * relative to the purging process gas S low mass flow over at least one Maintaining supply line is maintained, and stopping the supply of the purging process gas S
• 4) supplying a reactive process gas C with low mass flow relative to the purging process gas S over the first process area and generation of plasma in the second process area, so that on the substrate adsorbed layer-forming process gas A is converted into a layer, as well as supplying a Leitungsspülgases S * over the supply line of the layer-forming process gas A with relative to the purging process gas S low mass flow and termination of plasma generation and the supply of the reactive process gas C,
• 5) supplying the pipeline flushing gas S * with low mass flow via both supply lines into the first process area for purging the first process area with at least partially continued dwell time of the supplied reactive process gas C in the second process area by diffusion,
• 6) feeding a purging process gas S with relative to the other process gases A, C and the line purging gas S * high mass flow for purging the substrates in the second process area, wherein preferably the supply of Leitungsspülgases S * relative to the purging process gas S low mass flow over at least one Supply line is maintained, and stopping the supply of the purging process gas S,

wherein preferably the purging process gas S and the line purging gas S * are selected as the inert gas and is particularly preferably used as a line purging gas S * helium and as a purging process gas S argon.

Inert gases can be used for any process, since they are unreactive with the choice of a reactive or a layer-forming process gas.

In this case, helium is very well suited as a carrier gas and has a very small influence on the formation of layers during plasma generation, while argon has very good rinsing properties owing to its high molecular weight.

As reactive process gas C are all process gases according to the invention, which form a layer with a respective layer-forming process gas A with or without plasma generation. Particularly preferred are reactive process gases C, which are formed by evaporation of water, formic acid, oxalic acid or ammonium formate.

6 shows a process chamber for coating a plurality of substrates according to a method in particular according to claim 6. Through outlet openings 43 of an element for flow cross-sectional widening process gases are a second process area 201 (Reaction area) fed through a tubular antenna element 501 is limited to the coupling of high frequency power and in a reaction chamber 301 located. This is the second process area 201 due to the arrangement of the outlet openings 43 and the boundary by the antenna element 501 Of process gases can be flowed through evenly and in particular suitable for simultaneous recording and coating of multiple substrates. Substrates and substrate holders (preferably of dielectric material) are not shown and preferably to be arranged such that furthermore a uniform flow through the second process area 201 is guaranteed. To improve the flow guidance are insulation elements 91 and 92 intended. The antenna element 501 corresponds to a coil with one turn and is transformed into a high-frequency resonant circuit via the two coil ends through two feedthroughs 51 and 52 involved. Optional is a grounding point 53 provided in the middle of the coil. Here is the temperature of the antenna element 501 preferably either via the two feedthroughs 51 . 52 or the grounding point 53 adjustable.

The reaction chamber 301 is about as symmetrical as possible to the reaction area 501 arranged Abpumpöffnung 31 be evacuated, with several Abpumpöffnungen can be provided. There is a chamber door provided, which looks into the reaction chamber 301 would block and therefore was not shown. To increase the plasma density is a stationary magnetic field 71 provided, which preferably symmetrically to the flow direction through the second process area (reaction area) 201 runs and is preferably carried out by suitable arrangement of Helmholz coils for generating electron cyclotron resonance (or ion cyclotron resonance) in its field strength controllable. The first process area 101 is in 6 not shown and from the associated 7 seen. 7 shows an element for flow cross-sectional widening 401 with outlet openings 43 , Process gas supply openings (supply lines) 41 and 42 and a first process area (feed area) 101 , The flow path of the process gases is represented schematically by flow arrows, wherein points correspond to the arrowheads of a flow perpendicular to the representation plane. Process gas flow through the centrally arranged supply line 41 passes through the first process area 101 (Feed area) and is symmetrical to the outlet openings 43 divided, and flows from these into one 6 illustrated second process area 201 , Process gas flow through the other supply line 42 is also symmetrical over the first process area on the outlet openings 43 split, being in the feed area 101 However, a flow control means a flow steering element 81 in the direction of the outlet openings 43 is provided and flow in the direction of the centrally disposed supply line 41 is reduced.

Preferably, according to the embodiment according to 5 a layer-forming process gas A through the centrally arranged supply line 41 fed while the other supply line 42 is purged with a line purge S *. The supply of a reactive process gas C is via the other supply line 42 made while the centrally located supply line 41 is purged with a line purge S *. At least during the cycle steps for purging the first process area 101 but preferably throughout the coating cycle, line purge S * is through both supply lines 41 . 42 fed. The second process area 201 is preferred over the supply line 42 with flow path over the flow deflecting element 81 flushed with a purging process gas S. In a method according to an embodiment according to 4 is the centrally located supply line 41 sufficient and it can be on the other supply line 42 and the flow path with flow-directing element 81 be omitted because the layer-forming process gas A and the activatable process gas B under suitable process conditions only in the second process area 201 when plasma generation react with each other and the feed into the first process area 101 Can be done without separation of the flow paths. It is provided that the coupling of the layer-forming process gases A in the supply line 41 so between the first process area 101 and coupling region of the process gases with purging properties B, S, that at least when supplying the activatable process gas B, the entire supply line 41 is rinsed.

The temperature of the substrates is preferably controlled by the supplied plasma power. This preferably takes place in that a temperature-regulating process gas is supplied between a layer-forming reaction by plasma generation and renewed supply of a layer-forming process gas and plasma is generated during the feed in the plasma reaction region, the plasma energy input of the non-coating plasma being changed in the course of the coating to control the substrate surface temperature, and either the Reduces plasma energy input as the coating progresses, and the substrate surface temperature is kept substantially constant or by temperature measurement of a substrate or a representative region in the reaction region, the substrate temperature is controlled by a closed loop, while plasma power and plasma duration of the layering plasma are not changed depending on the coating process. In this case, helium is preferably chosen as the temperature-regulating process gas, since this has a very small influence on the layer formation. However, the temperature-regulating process gas can also be selected as an activatable or reactive process gas, wherein the plasma length is changed after the layer formation reaction has taken place and a minimum time for layer formation is maintained.

8th shows according to the flow simulation of a device accordingly 6 and 7 that the entire second process area 201 , which corresponds to the reaction region and is provided for receiving substrates, is flowed through substantially uniformly over the entire flow cross-section, so that the entire reaction region 201 In particular, homogeneous plasma generation and prevalent diffusion of the process alley a uniform coating of substrates can be achieved.

In 9 are two silver layers based on the reflection curves 16 . 18 and the transmission curves 17 . 19 shown. There is a widespread belief that only thin layers of moderate quality can be produced by direct plasma exposure.

Based on the example 9 for a PEALD method accordingly 4 respectively. 5 It is shown that direct plasma generation with suitable process gas selection enables the formation of thin layers with excellent properties.

It is on the one hand a silver layer by reflection curve 18 and transmission curve 19 which also corresponds to conventional PEALD layers and both reduced reflection in the reflection curve 18 as well as absorption in the short-wave range (380-480 nm) of the transmission curve 19 shows. This layer was formed by direct plasma generation in the presence of argon with silver pivalate as a layer-forming process gas and oxygen and hydrogen as activatable process gases. In coating cycles, first an oxygen plasma (formation of silver oxide) and then a hydrogen plasma (reduction of the silver oxide layer in a silver layer) were generated. With the same coating cycle with reduced argon supply, the reflection behavior could be significantly improved, but absorption in the short-wave range could not be completely avoided.

On the other hand, a silver layer becomes a reflection curve 16 and transmission curve 17 which shows a high reflection and no perceptible absorption and is approximately comparable to vapor deposited or sputtered silver layers of very good quality. This silver layer ( 16 . 17 ) was with no significant presence of argon with silver pivalate as a layer-forming process gas and water vapor as a reactive process gas with a 5 formed similar method.

For a method according to the invention, in particular with direct plasma generation in the reaction region, it is necessary that substantially no carrier gas with undesirable influence is supplied to the layer formation during plasma generation or is present during plasma generation. It is preferred that when using a carrier gas, an inert carrier gas is selected with a molecular weight which is less than the molecular weight of the reactive or activatable gas.

Furthermore, it is preferred that the reactive or activatable process gas is selected such that the generated plasma has both oxidizing and reducing radicals which are in a neutral equilibrium such that reaction products formed during the layer formation reaction essentially do not continue with the plasma generation react formed layer, wherein preferably used as the reactive process gas steam. In principle, instead of water, a gas mixture composed accordingly of oxygen and hydrogen would also be possible, and this is prohibited for safety reasons. However, it is advantageous that (especially with a process gas formed from water), the neutral balance of the plasma is improved by the addition of oxygen or hydrogen.

Likewise, the reactive or activatable process gas can be formed from formic acid, oxalic acid or ammonium formate optionally with additional oxygen or hydrogen content. The use of water to form a reactive process gas with the simultaneous generation of plasma according to the present invention allows in particular the formation of high quality metallic layers. In this case, the layer-forming process gas particularly preferably contains silver or is likewise preferably formed with copper, nickel, gold, platinum, palladium, iridium or ruthenium. In this case, layer-forming process gases are preferably selected, which are composed of the layer-forming portion and one or more of the elements carbon, oxygen, hydrogen, and / or nitrogen and thus are preferably free of phosphorus, fluorine and sulfur.

Claims (9)

Plasma assisted ALD method of forming a thin film on a substrate in a reduced vacuum process pressure reaction zone with coating cycles within which a process gas is applied in cycle steps, the reaction region is purged, and subsequently the adsorbed portion of the process gas forming the film by supplying or generating a reactive process gas a thin layer is converted, characterized in that a process gas with purging properties over a first process area with limited flow cross section a second process area with relative to the first process area larger flow cross-section supplied and pumped out of this, wherein the ratio and size of the flow cross-sections, the pumping power of the vacuum system , And as the supply duration and the mass flow of the process gas at least during a cycle step are coordinated such that a Transitional flow is formed between molecular and viscous flow with different local process pressure and such different ratio between flow and diffusion in the two process areas that the first process area is purged due to prevailing flow, while the second process area is exposed to the supplied process gases due to prevailing diffusion, so that two different process steps are performed at least partially simultaneously during a cycle step. Plasma-assisted ALD method according to claim 1, characterized in that the adjustment of different process pressures and flow conditions between diffusion and flow within a coating cycle by supply duration and mass flow of the process gases without changing the pumping power of the vacuum system or the flow cross-sections is controlled and that when supplied or in the presence of an activatable or reactive process gas in the second process area plasma is generated. Plasma-assisted ALD method according to claim 1 or 2, characterized in that a substrate arranged in the first process area and in the second process area during the supply of an activatable process gas high frequency plasma is generated, wherein the activatable process gas is supplied within a cycle step such that in the first process area with flow when the process gas is activated by plasma generation in the second flow region, a propagation of radicals against the flow direction into the first process region is reduced or blocked and wherein in a subsequent cycle step the mass flow of the process gas through the first process region is reduced such that in the first process region Diffusion prevails and a high spread of radicals against the Flow direction is such that adsorbed on the substrate layer-forming process gas is converted into a thin layer. Plasma-assisted ALD method according to claim 3, characterized in that the reduction of the mass flow through the first process area by deflection of the reduced process gas content and direct supply is effected in the second process area, so that the process pressure in the second process area is kept constant during the plasma generation. Plasma-assisted ALD method according to one of the preceding claims, characterized in that a coating cycle is formed by the following cycle steps: Supplying a layer-forming process gas via the first process area for adsorption on a substrate arranged in the first process area, Supplying an activatable process gas over the first process area at prevailing flow in the first process area and purging the substrate at least partially simultaneously generating plasma in the second process area for decomposing excess layer-forming process gas, wherein a diffusion of radicals into the first process area by the prevailing flow in the first process area is reduced or blocked, and Supplying an activatable process gas at such reduced mass flow through the first process area that diffusion prevails in the first process area and generating plasma in the second process area with prevailing diffusion of radicals into the first process area so that layer-forming process gas adsorbed on the substrate is converted into a layer Preferably, the reduced portion of the mass flow is deflected and fed directly to the second process area. Plasma-assisted ALD method according to claim 1 or 2, characterized in that the flow cross section of the first process area is brought by uniform flow distribution to the flow cross section of the second process area and one or more substrates are arranged in the second process area, wherein after rinsing the first process area in prevailing diffusion in second process area, a purging process gas is supplied in such a high mass flow and suitable supply duration that prevails in the second process area flow with purging properties and the substrates are purged before by suitable means in the second process area, which corresponds to the reaction area, preferably an inductively coupled high-frequency plasma is produced. Plasma-assisted ALD method according to one of the preceding claims for forming a thin layer on a substrate in a reaction region, wherein the supply of process gases via a feed region with respect to the reaction region smaller flow cross-section, characterized in that a coating cycle is formed by the following cycle steps: Supplying a layer-forming process gas for adsorption on the substrate, Supplying an activatable process gas, wherein mass flow and cycle step duration are chosen such that the feed region is purged by prevailing flow, while in the reaction region by prevailing diffusion no rinsing effect is achieved, Supplying a purging process gas with high mass flow relative to the other process gases for purging the reaction area with continued supply of the activatable process gas and Generating plasma with continued supply of the activatable process gas for process gas activation and formation of a thin layer, wherein an inert gas is selected as the purging process gas and supplied with more than twice the mass flow relative to the mass flow of the activatable process gas. Method according to one of the preceding claims, characterized in that selected for process gas flow with prevailing diffusion of the mass flow in relation to the pumping power of the vacuum system and the respective flow cross-section such that the square of the average flow velocity multiplied by the half supply time at the same unit selection is smaller than the diffusion coefficient which is determinable from local process pressure, type of process gas and process temperature, while for predominantly flowed process gas flow the mass flow is chosen in relation to the pump power and flow cross section such that at a resulting process pressure the square of the mean flow velocity multiplied by half the feed duration is greater than the diffusion coefficient is. Device having a process chamber with means for supplying process gases, means for generating a capacitively coupled plasma and a vacuum system for pumping out the process gases, in particular for a plasma-assisted ALD method according to one of claims 1, 2, 3, 4, 5 or 8, characterized in that at least one electrode is arranged within the reaction chamber and is hollow so that it forms the first flow region and a substrate can be introduced into the electrode, that process gases can be supplied through the electrode and that openings in the electrode between substrate and one Counter electrode are provided, which are in flow contact with the second process area, which corresponds to the process chamber, and the vacuum system, so that plasma can be generated in the process chamber, which by suitable arrangement and configuration of the electrode openings a uniform film forming reaction on a substrate located in the electrode Diffusion of process gas radicals in the first flow range allows.

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