DE102022114717A1 - Method and device for depositing a layer containing an element of main group V in a process chamber and subsequent cleaning of the process chamber - Google Patents

Abstract

The invention relates to a method for depositing layers containing an element of main group V on a substrate (6) in a CVD reactor, in which the process gas is fed into the process chamber (2) through a central gas inlet element (11) and flows through the process chamber (2) in the radial direction. After the layer has been deposited, the process chamber (2) is cleaned, the process chamber (2) being heated to a first cleaning temperature (T ₁ ); wherein after the first cleaning temperature (T ₂ ) has been reached, a halogen or a halogen compound is fed into the process chamber (2) in a first cleaning step (21); wherein after the first cleaning step (21), the process chamber (2) is brought to a second cleaning temperature (T ₂ ); wherein after reaching the second cleaning temperature (T ₂ ) in a second cleaning step (22) O ₂ is fed into the process chamber (2); wherein after the second cleaning step (22), the process chamber (2) is brought to a third cleaning temperature (T ₃ ); wherein after the third cleaning temperature (T ₂ ) has been reached, essentially only H ₂ is fed into the process chamber (2) in a third cleaning step (23); and wherein after the third cleaning step (23) the process chamber (2) is cooled (24).

Description

field of technology

The invention relates to a method for depositing a layer containing an element of main group V on a substrate in a CVD reactor. The CVD reactor has a reactor housing in which a graphite part is arranged. The graphite part can be coated with SiC. It can be coated to be resistant to Cl ₂ . The graphite part is arranged in the process chamber in such a way that, when a coating process is carried out, it is coated with parasitic coatings that consist of decomposition products of the process gas. The method also relates to a cleaning method which follows the method step of depositing the layer on the substrate and consists of a plurality of cleaning steps which are carried out in succession in order to remove the parasitic coatings from the at least one graphite part.

The device according to the invention has a control device that contains a control program that executes control commands with which valves and mass flow controllers of a gas supply device are switched or controlled, so that the method is carried out in the device.

State of the art

The U.S. 2020/385861A1 describes a method performed after depositing a layer in a CVD reactor, using Cl ₂ to remove parasitic coatings from walls of components within the process chamber.

The DE 10 2017100 725 A1 describes a CVD reactor and a method carried out therein to remove coatings from the walls with the injection of chlorine.

In a method according to the invention, a carbon-containing gas can also be a component of the process gas. For example, the process gas can be an organometallic compound of an element of III. main group included. This is particularly the case when a III-V layer is deposited on the substrate. When this component of the process gas is broken down, carbon can form, which is deposited on a surface of the graphite part in the form of pure carbon or as a component of a carbon compound. Carbon residues can form in particular when the process gas contains NH ₃ . The DE 10 2013 104 105 A1 describes a method in which such carbon residues can be removed with an etching gas.

The U.S. 4,816,113 describes a method in which carbon residues are removed from a process chamber using a plasma and chlorine.

A cleaning process that uses chlorine is also shown in the US2013/005118A1 .

Summary of the Invention

The object of the invention is to improve a method for depositing a layer containing an element of main group V, which is followed by a cleaning process of the process chamber consisting of several steps, and in particular to improve the cleaning process in a deposition process in which the process gas and/or or the cleaning gas is fed into the center of a process chamber, flows through the process chamber in a radial direction, wherein a rotating substrate holder supporting susceptor is rotated around the center of the process chamber.

The object is achieved by the invention specified in the claims, with the subclaims not only representing advantageous developments of the main claim, but also independent solutions to the object.

The method according to the invention requires the use of a CVD reactor which has a reactor housing in which a graphite part is located. Several graphite parts can also be located in the reactor housing. At least one of the preferably several graphite parts is coated. It can be coated with silicon carbide. However, it can also be coated with another coating that makes the graphite part resistant to exposure to Cl ₂ , O ₂ or HCl. The graphite parts can be parts of the process chamber or parts that delimit the process chamber. In particular, it is provided that a susceptor, which forms the bottom of the process chamber, consists of graphite and is coated with silicon carbide. The susceptor may have a back facing away from the process chamber and adjoining a heating zone. A heating device can be arranged in the heating zone. The heater can be an IR heater or an RF heater. However, the graphite part can also be a process chamber cover, which delimits the process chamber at the top. The process chamber can be brought to an elevated temperature as a result of thermal radiation emanating from the susceptor. The susceptor can be heated to temperatures of up to 1000°C or more during the deposition of the layer. In the center of A gas inlet element can be arranged in the process chamber. This can basically be made of quartz
or metal. However, it is also possible to manufacture the gas inlet element or parts of the gas inlet element from graphite. These parts can also be coated with silicon carbide. Pockets can be arranged in the susceptor. The pockets can be arranged in a uniform angular distribution around the center of the process chamber. They are therefore at the same distance from the gas inlet element, so that process gas emerging from the gas inlet element flows in the radial direction through the process chamber and over the pockets. At least one substrate holder that supports the substrate is located in each pocket, so that the process gas stream flows over the substrate. Gas supply lines, through which an inert gas can be fed into the pockets, can open into the bottoms of the pockets. A gas cushion forms. A directed gas flow can force the substrate holder to rotate about its axis via the gas cushion. The process chamber is surrounded by a gas outlet element, which can consist of a ceramic material or metal. However, it is also possible to manufacture parts of the gas outlet element or the entire gas outlet element from graphite and in particular from SiC-coated graphite. The gas inlet element can have a large number of gas outlet zones arranged one above the other, through which different components of the process gas can be fed into the process chamber. The graphite can also be only partially coated with SiC.

In a first step of the method, a layer is deposited on one or more substrates that have previously been brought into the process chamber and that are arranged in particular on the substrate carriers. This is preferably done in that a component of the process gas is fed into the process chamber that has an element of the V main group. The process gas preferably contains another component which is an element of III. has main group. The process gas can thus be a mixture of a hydride of an element of main group V and an organometallic compound of an element of III. be main group. For example, the process gas can contain AsH ₃ , PH ₃ (or also NH ₃ ). The process gas can also contain an organometallic gas which, in particular, contains an element from main group III, for example TMGa, TMIn or TMA1 or TEGa. The reactive gases last mentioned are fed into the process chamber together with an inert gas, for example H ₂ . The reactive gases of the process gas decompose due to the increased temperature within the process chamber and in particular the increased temperature of the substrate, so that a layer is deposited on the substrate surface, which consists of the elements of III. and V. main group. As a result, the reaction products of the reactive gases or parasitic compounds of the reaction products of the reactive gases that form condense on surfaces of the process chamber and in particular on the surfaces of the at least partially coated graphite parts, in particular coated with a CL ₂ /O ₂ resistant coating, such as SiC. After the end of the first step, for example after depositing one or more layers on the substrate, the at least one substrate is removed from the process chamber. In this intermediate step of removing the substrates from the process chamber, no reactive gases or at most the reactive gas of main group V are fed into the process chamber. Otherwise only an inert gas, for example hydrogen, is fed into the process chamber. During the intermediate step of removing the at least one substrate, the process chamber can be cooled to a lower temperature.

In a further method following the first step, the process chamber is cleaned. The parasitic coatings on the walls of the process chamber and in particular on the walls of the graphite parts are removed. This is done by feeding in cleaning gases, which successively form various volatile compounds with the molecules of the coating, which are then transported away through the gas outlet element. It is provided according to the invention that after the removal of the at least one substrate, the process chamber is heated to a first cleaning temperature. The first cleaning temperature can be in a range from 500°C to 1000°C or in a range between 800°C and 900°C. At the first cleaning temperature, a first cleaning step is performed in which a halogen or a halogen compound is fed into the process chamber. HCl or Cl ₂ is preferably fed into the process chamber. The halogen or Cl ₂ is fed into the process chamber together with nitrogen. The total pressure in the process chamber can be in the range between 50 mbar and 200 mbar. It is also provided that approximately 11 slm N ₂ is fed into the process chamber during the first cleaning step. The first cleaning gas used for cleaning and further cleaning gases mentioned further below are each kept ready in the form of gas sources. The halogen, for example Cl ₂ can be kept ready in any mixing ratio with nitrogen. A 5% mixture is preferred. This cleaning gas is fed into the process chamber with a mass flow of 2 to 40 slm when the temperature of the process chamber is the first cleaning temperature has been reached. In the first cleaning step, essentially metallic components of the parasitic coating and components belonging to main group V are converted into volatile compounds, which are then removed from the process chamber together with the inert gas. Etching rates of 80±20 μm/h are achieved, particularly with Cl ₂ .

The intermediate step of heating the process chamber from, for example, 300° C. to a first cleaning temperature of, for example, 900° C. takes about 10 minutes. During this intermediate step, the inert gas can be switched from hydrogen to nitrogen. During the intermediate step, the total pressure within the process chamber can also be changed to the above-mentioned pressure and, in particular, lowered.

The first cleaning step is carried out at a constant temperature of, for example, 900 °C for around 20 - 30 minutes. Thereafter, the inflow of the first cleaning gas is shut off. In a subsequent intermediate step, the temperature of the process chamber is changed and in particular increased to a second cleaning temperature. In addition, the total pressure within the process chamber can also be changed during this intermediate step.

The intermediate step ends when the second cleaning temperature is reached. The second cleaning temperature can be between 500°C and 1100°C. It can be between 950°C and 1000°C, for example. As soon as the second cleaning temperature is reached, a second cleaning gas is fed into the process chamber. This cleaning gas can be dry air, O ₃ , O ₂ , or NH ₃ . The cleaning gas can be provided as a mixture in nitrogen. 9 slm of this mixture are preferably fed into the process chamber. Together with this second cleaning gas, N ₂ is fed into the process chamber. Preferably with a mass flow of 11 slm. The total pressure during the second cleaning step is 100 mbar to 800 mbar, but in particular also 600 mbar to 800 mbar. During the second cleaning step, essentially carbonaceous components of the parasitic coating are removed. For this purpose, the carbon reacts or carbon-containing compounds react with the oxygen fed in to form oxides of the carbon. The second cleaning step can be carried out for a period of 7 - 15 minutes. It is preferable that the duration of the second cleaning step is shorter than the duration of the first cleaning step. However, the duration can also depend on the layer thickness to be removed. Removing a thicker layer takes longer than removing a thinner layer.

In a further intermediate step after the second cleaning step, in which no cleaning gas but only an inert gas is fed into the process chamber, the temperature of the process chamber is changed and in particular lowered to a third cleaning temperature, which can be between 500 °C and 1100 °C. However, it can also be between 800°C and 1000°C. Along with this, the total pressure in the process chamber can also be changed. The total pressure is preferably lowered to a pressure of between 50 mbar and 200 mbar. A third cleaning step is then carried out at this total pressure. The inert gas can also be changed during the intermediate step, so that hydrogen is fed into the process chamber after the intermediate step.

The third cleaning step is an "H2-bake" or an "N ₂ -bake", in which the process chamber is essentially only heated in the presence of H _2. This occurs at the third cleaning temperature mentioned above for a time between 15 minutes and 30 minutes The third cleaning step can be longer than the first cleaning step During the third cleaning step, only hydrogen is fed into the process chamber, preferably with a mass flow of 26 slm.

The third cleaning step can be followed by further optional steps in which the process chamber is alternately flooded with an inert gas, which can be hydrogen or nitrogen, and evacuated. This is done with a vacuum pump that is connected to the gas outlet element.

character list

• 1 schematisch im Querschnitt einen CVD-Reaktor, eine Gasversorgungseinrichtung mit Gasquellen 25 und schematisch eine elektronische Steuereinrichtung;
• 2 einen Schnitt gemäß der Linie II-II in 1;
• 3 ein Ablaufdiagramm der Reinigungsschritte, die sich an einen Prozessschritt anschließen, indem eine Schicht auf einem Substrat abgeschieden wird;
• 4 eine Tabelle der wesentlichen Prozessparameter und
• 5 ein Zeit-Temperaturdiagramm des in der 3 dargestellten Reinigungsverfahrens.

An embodiment of the invention is explained below with reference to the accompanying drawings. Show it:

• 1 schematically in cross section a CVD reactor, a gas supply device with gas sources 25 and schematically an electronic control device;
• 2 a cut according to the line II-II in 1 ;
• 3 a flowchart of the cleaning steps that follow a process step in which a layer is deposited on a substrate;
• 4 a table of the essential process parameters and
• 5 a time-temperature diagram of in the 3 illustrated cleaning process.

Description of the embodiments

The inventive method is carried out in a device as in the 1 is shown. A CVD reactor has a gas-tight housing 1, for example made of stainless steel, in which a process chamber 2 is located. The bottom of the process chamber 2 is formed by a susceptor 3, which can be made of graphite and is coated with SiC. The susceptor 3 has a circular disc shape and a rear side facing downwards, which faces a heating device 31 . The heating device 31 can be a coil that generates an RF field that induces eddy currents in the susceptor 3 that heat the susceptor 3 to a process temperature.

The susceptor 3 can be driven in rotation about an axis of rotation 8 with a shaft 9 and a rotary drive (not shown). Also not shown are feed lines that run through the shaft 9 in order to feed an inert gas into gas channels (not shown) of the susceptor 3 . These gas channels open into the bottoms of pockets 4 which are arranged in the broad side surface of the susceptor 3 which faces upwards. A substrate holder 5 made of graphite is located in each of these pockets 3 . The substrate holder 5 can also be coated with SiC. A substrate 6 can be placed on the substrate holder 5 . It can be a substrate made of Si, GaAs, or a substrate made of sapphire or another suitable material.

In the central area of the susceptor 3 there is a recess 18 into which a lower section of a gas inlet element 11 can dip. The gas inlet element 11 is fixed in place on the housing 1 and has three gas outlet zones 13, 15, 17 arranged vertically one above the other reactive gases and inert gases are fed into the process chamber 2, which extends between a process chamber ceiling 10 and the susceptor 3. The process gas, which enters the process chamber 2 through the gas outlet zones 13, 15, 17, flows through the process chamber 2 in a radial direction and flows over the substrates 6.

The process chamber cover 2 can be made of graphite and coated with SiC.

The process chamber 2 is surrounded by an annular gas outlet element 19 that has a gas outlet opening, not shown, to which a suction line of a vacuum pump, not shown, is connected in order to evacuate the process chamber 2 or to be able to set a predetermined total pressure in the process chamber 2.

The 1 also shows a gas supply device with a plurality of gas sources 25. The gas supply device can provide the following gases, for example: AsH ₃ , PH ₃ as a component of a reactive gas of a process gas, TMGa, TMIn also as a component of the reactive gas of the process gas for separating a III -V layer on the according 2 substrates 6 arranged annularly around the gas inlet element 11. The gas supply device can also provide inert gases, for example H ₂ and N ₂ . Furthermore, the gas supply device can provide cleaning gases Cl ₂ and O ₂ . The two cleaning gases are preferably provided as a 5% mixture in N ₂ .

A programmable electronic controller 32 can control valves 27 and mass flow controllers 26 in order to feed predetermined mass flows of the aforementioned gases through the supply lines 12, 14, 16 into the process chamber 2.

The device described above is used to deposit 6 layers of elements of the III. and V. main group to separate. These can be GaInAsP layers or layers that have at least two of the elements mentioned above. For this purpose, the substrates are first brought into the process chamber 2 and subsequently, after the process chamber 2 has been heated to a process temperature, the reactive gases described above are fed into the process chamber 2 . After the one or more layers have been deposited, the process chamber 2 is cooled to, for example, 300° C. and the substrates are removed. During the deposition process described above, coatings are formed on some SiC surfaces from the solid chemical compounds formed during the reactions of the reactive gases.

After the substrates have been removed, the temperature inside the process chamber 2 is heated to a first cleaning temperature T ₁ , which can be 900° C., in a heating step 20 from a time t ₁ to a time t ₂ . A total pressure of between 50 mbar and 100 mbar is set in the process chamber.

After reaching the first cleaning temperature T ₁ , in a first cleaning step 21 from time t ₂ to time t ₃ , Cl ₂ together with N ₂ fed into the process chamber. A reaction of the chemical compounds deposited on the SiC surfaces with Cl ₂ takes place in the process chamber 2 . Volatile reaction products form, which are removed from the process chamber 2 with the N ₂ .

In an intermediate step following the first cleaning step 21 from a time t ₃ to a time t ₄ , the temperature of the process chamber 2 is heated to a second cleaning temperature T ₂ of 1000° C. in an N ₂ atmosphere. The total pressure inside the process chamber is changed to 600 mbar to 800 mbar. After the second cleaning temperature T ₂ has been reached, O ₂ is fed into the process chamber together with N ₂ during the time from t ₄ to t ₅ . During this second cleaning step 22, carbon compounds are removed from the SiC surfaces by a chemical reaction of the carbon compounds with oxygen. Volatile oxides form, which are removed from the process chamber 2 with the N ₂ .

After the time t ₅ has been reached, the temperature of the process chamber is lowered to a third cleaning temperature T ₃ , which can be 900°. Along with this, the total pressure can be set to a value between 50 mbar and 100 mbar. After the third cleaning temperature T ₃ has been reached, only H ₂ is fed into the process chamber during the time t ₆ -t ₇ . During this third cleaning step 23, remaining oxides are removed from the surfaces. In addition, the CVD reactor can be conditioned.

After time t ₇ has been reached, the temperature of the process chamber 2 is lowered to 300° C., for example, in a cooling phase 24 . At time t8, at which the process temperature 2 has reached the value 300° C., approximately 70 minutes have elapsed compared to the start of the cleaning process at time _t1 .

The 3 shows an exemplary embodiment in which a heating step 20 is followed by a Cl ₂ etching step 21 and a rinsing step 21′ is carried out between a subsequent O ₂ etching step 22. The O ₂ etching step 22 is followed by a heating step 23, which in turn is followed by a cooling step 24.

During the rinsing step 21', the etching gases used in the Cl ₂ etching step 21 and in particular Cl ₂ can be completely removed from the reactor housing, so that in a subsequent O ₂ etching step 22 there is no longer any Cl ₂ in the process chamber. Flushing can be done with nitrogen.

The above statements serve to explain the inventions covered by the application as a whole, which also independently develop the state of the art at least through the following combinations of features, whereby two, several or all of these combinations of features can also be combined, namely:

A method for depositing a layer containing an element of main group V on a substrate (6) in a CVD reactor, the CVD reactor having a reactor housing (1) in which at least one SiC-coated graphite part (3, 5, 10,11,19) which during deposition comes into contact with the process gas fed into a process chamber (2) of the CVD reactor in such a way that a decomposition product of the process gas is deposited on the surface of the graphite part (3, 5, 10, 11, 19) depositing a parasitic coating to form, providing a process gas comprising molecules containing an element of Group V; wherein at least one substrate (6) is brought into the process chamber (2); wherein the process gas is fed into the process chamber (2), the process gas decomposes in the process chamber (2) heated to a process temperature and the element of main group V is deposited as a component of the layer on the substrate; wherein the substrate (6) is removed from the process chamber (2); wherein the process chamber (2) is heated to a first cleaning temperature (T ₁ ); wherein after the first cleaning temperature (T ₂ ) has been reached, a halogen or a halogen compound is fed into the process chamber (2) in a first cleaning step (21); wherein after the first cleaning step (21), the process chamber (2) is brought to a second cleaning temperature (T ₂ ); wherein after reaching the second cleaning temperature (T ₂ ) in a second cleaning step (22) O ₂ is fed into the process chamber (2); wherein after the second cleaning step (22), the process chamber (2) is brought to a third cleaning temperature (T ₃ ); wherein after the third cleaning temperature (T ₂ ) has been reached, essentially only H ₂ is fed into the process chamber (2) in a third cleaning step (23); and wherein after the third cleaning step (23) the process chamber (2) is cooled (24).

A process which is characterized in that the process gas contains AsH ₃ , PH ₃ or NH ₃ and/or that the process gas additionally contains a gas whose molecules contain an element of III. Have main group and / or that the process gas also contains TMGa, TMIn or TMA1.

A method, which is characterized in that during the heating (20) an inert gas and / or a noble gas and / or N ₂ or H ₂ in the Pro process chamber (2) is fed and/or only an inert gas is fed into the process chamber (2).

A method characterized in that during the first purification step (21) only the halogen or halogen compound and N ₂ is fed into the process chamber (2) and/or only Cl ₂ together with N ₂ is fed into the process chamber (2). becomes.

A method characterized in that during the second cleaning step (22) only O ₂ is fed into the process chamber (2) together with N ₂ .

A method which is characterized in that only H ₂ is fed into the process chamber (2) during the cooling (23).

A method characterized in that the graphite part is a susceptor (3) delimiting the process chamber (2) and/or that the graphite part is a process chamber cover (10) delimiting the process chamber (2) and/or that the graphite part is a gas inlet element ( 11) and/or that the graphite part is a gas outlet element (19) and/or that the graphite part is a substrate holder (5) which is mounted in a pocket (4) of the susceptor (3), with an inert gas being introduced through a gas supply line in such a can be fed into the pocket (4) so that a gas cushion is formed there which causes the substrate holder (5) to rotate about an axis (7).

A method which is characterized in that the susceptor (3) is driven in rotation about an axis of rotation (8) at least during the deposition of the layer and/or that the susceptor (3) during the deposition of the layer and during the heating (20), and/or is heated by a heating device (31) during the three cleaning steps (21, 22, 23).

A device for carrying out the method with a CVD reactor which has a reactor housing (1) in which at least one graphite part (3, 5, 10, 11, 19) is arranged, with a gas supply device which has gas sources (25). which a process gas whose molecules contain an element of III. Has main group, a halogen or a halogen compound, O2, H2 and N2 is provided, and with a control device (32) for controlling valves (27) and mass flow controllers (26) such that in a process chamber (2) of the reactor housing ( 1) a method according to any one of claims 1-8 is carried out.

All disclosed features are essential to the invention (by themselves, but also in combination with one another). The disclosure of the application also includes the disclosure content of the associated/attached priority documents (copy of the previous application) in full, also for the purpose of including features of these documents in claims of the present application. The subclaims, even without the features of a referenced claim, characterize with their features independent inventive developments of the prior art, in particular for making divisional applications on the basis of these claims. The invention specified in each claim can additionally have one or more of the features specified in the above description, in particular with reference numbers and/or specified in the list of reference numbers. The invention also relates to designs in which some of the features mentioned in the above description are not implemented, in particular if they are clearly superfluous for the respective application or can be replaced by other technically equivalent means.

Reference List

1

reactor housing

2

process chamber

3

susceptor

4

Bag

5

substrate holder

6

substrate

7

Axis of rotation substrate holder

8th

Axis of rotation susceptor

9

shaft

10

process chamber ceiling

11

gas inlet element

12

supply line

13

gas exit zone

14

supply line

15

gas exit zone

16

supply line

17

gas exit zone

18

deepening

19

gas outlet organ

20

Warm up

21

Cleaning with chlorine

21'

Wash

22

Cleaning with oxygen

23

Bake out with hydrogen

24

cooling down

25

gas source

26

Mass Flow Controller

27

Valve

28

supply line

29

supply line

30

supply line

31

heating device

32

control device

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US2020385861A1 [0003]
• DE 102017100725 A1 [0004]
• DE 102013104105 A1 [0005]
• US4816113 [0006]
• US2013005118A1 [0007]

Claims (10)

Process for depositing a layer containing an element of main group V on a substrate (6) in a CVD reactor, the CVD reactor having a reactor housing (1) in which at least one SiC-coated graphite part (3, 5, 10 ,11,19) which during deposition comes into contact with the process gas fed into a process chamber (2) of the CVD reactor in such a way that a decomposition product of the process gas is deposited on the surface of the graphite part (3, 5, 10, 11, 19 ) deposits a parasitic coating to form, wherein a process gas is provided which has molecules containing an element of main group V; wherein at least one substrate (6) is brought into the process chamber (2); wherein the process gas is fed into the process chamber (2), the process gas decomposes in the process chamber (2) heated to a process temperature and the element of main group V is deposited as a component of the layer on the substrate; wherein the substrate (6) is removed from the process chamber (2); wherein the process chamber (2) is heated to a first cleaning temperature (T ₁ ); wherein after the first cleaning temperature (T ₂ ) has been reached, a halogen or a halogen compound is fed into the process chamber (2) in a first cleaning step (21); wherein after the first cleaning step (21), the process chamber (2) is brought to a second cleaning temperature (T ₂ ); wherein after reaching the second cleaning temperature (T ₂ ) in a second cleaning step (22) O ₂ is fed into the process chamber (2); wherein after the second cleaning step (22), the process chamber (2) is brought to a third cleaning temperature (T ₃ ); wherein after the third cleaning temperature (T ₂ ) has been reached, essentially only H ₂ is fed into the process chamber (2) in a third cleaning step (23); and wherein after the third cleaning step (23) the process chamber (2) is cooled (24). procedure after claim 1 , characterized in that the process gas contains AsH3, PH ₃ or NH ₃ and/or that the process gas additionally contains a gas whose molecules contain an element of III. Have main group and / or that the process gas also contains TMGa, TMIn or TMA1. Method according to one of the preceding claims, characterized in that during the heating (20) an inert gas and/or a noble gas and/or N ₂ or H ₂ is fed into the process chamber (2) and/or only an inert gas is fed into the process chamber ( 2) is fed. Method according to one of the preceding claims, characterized in that during the first cleaning step (21) only the halogen or the halogen compound and N ₂ is fed into the process chamber (2) and/or only Cl ₂ together with N ₂ is fed into the process chamber (2 ) is fed. Method according to one of the preceding claims, characterized in that during the second cleaning step (22) only O ₂ is fed into the process chamber (2) together with N ₂ . Method according to one of the preceding claims, characterized in that only H ₂ is fed into the process chamber (2) during the cooling (23). Method according to one of the preceding claims, characterized in that the graphite part is a susceptor (3) delimiting the process chamber (2) and/or that the graphite part is a process chamber cover (10) delimiting the process chamber (2) and/or that the graphite part is a gas inlet element (11) and/or that the graphite part is a gas outlet element (19) and/or that the graphite part is a substrate holder (5) which is stored in a pocket (4) of the susceptor (3), with a gas supply line Inert gas can be fed into the pocket (4) in such a way that a gas cushion is formed there which causes the substrate holder (5) to rotate about an axis (7). Method according to one of the preceding claims, characterized in that the susceptor (3) is driven in rotation about an axis of rotation (8) at least during the deposition of the layer and/or that the susceptor (3) during the deposition of the layer and during the heating (20 ), and/or is heated by a heating device (31) during the three cleaning steps (21, 22, 23). Device for carrying out the method with a CVD reactor which has a reactor housing (1) in which at least one graphite part (3, 5, 10, 11, 19) is arranged, with a gas supply device which has the gas sources (25) with which a process gas whose molecules contain an element of III. Has main group, a halogen or a halogen compound, O ₂ , H ₂ and N ₂ is provided, and with a control device (32) for controlling valves (27) and mass flow controllers (26) such that in a process chamber (2) of the reaction gate housing (1) a method according to any one of Claims 1 - 8th is carried out. Method or device, characterized by one or more of the characterizing features of one of the preceding claims.

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