METHOD AND DEVICE FOR DEPOSITING A LAYER CONTAINING A GROUP FIVE ELEMENT IN A PROCESS CHAMBER AND SUBSEQUENT CLEANING OF THE PROCESS CHAMBER

Abstract

A method for depositing layers containing a group five element on a substrate, in which process gas is fed into a process chamber. After depositing the layer, the process chamber is cleaned as follows. The process chamber is heated to a first cleaning temperature. After reaching the first cleaning temperature, a halogen or a halogen compound is fed into the process chamber in a first cleaning step. After the first cleaning step, the process chamber is brought to a second cleaning temperature. After reaching the second cleaning temperature, O.sub.2 is fed into the process chamber in a second cleaning step. After the second cleaning step, the process chamber is brought to a third cleaning temperature. After reaching the third cleaning temperature, substantially only H.sub.2 is fed into the process chamber in a third cleaning step. After the third cleaning step, the process chamber is cooled.

Claims

1. A method for depositing a layer on a substrate (6) in a process chamber (2) arranged in a reactor housing (1) of a chemical vapor deposition (CVD) reactor, the method comprising: heating the process chamber (2) to a process temperature; loading the substrate (6) into the process chamber (2); feeding a process gas into the process chamber (2), wherein at the process temperature, the process gas decomposes into decomposition products, and wherein the decomposition products are deposited as a layer on a first surface on the substrate (6) and are deposited as a parasitic coating on a second surface in the reactor housing (1), removing the substrate (6) from the process chamber (2); heating the process chamber (2) to a first cleaning temperature (T.sub.1); after the process chamber (2) has reached the first cleaning temperature (T.sub.1), feeding a halogen or a halogen compound fed into the process chamber (2) in a first cleaning step (21); after the first cleaning step (21), bringing the process chamber (2) to a second cleaning temperature (T.sub.2); after the process chamber (2) has reached the second cleaning temperature (T.sub.2), feeding O.sub.2 into the process chamber (2) in a second cleaning step (22); after the second cleaning step (22), bringing the process chamber (2) to a third cleaning temperature (T.sub.3); after the process chamber (2) has reached the third cleaning temperature (T.sub.3), feeding essentially only H.sub.2 into the process chamber (2) in a third cleaning step (23); and after the third cleaning step (23), cooling down the process chamber (2).

2. The method of claim 1, wherein the process gas contains at least one reactive gas that contains at least one element of main group II-VI, and wherein the layer contains the element of the main group II-VI.

3. The method of claim 2, wherein the at least one reactive gas is comprises one or more of AsH.sub.3, PH.sub.3, NH.sub.3, a silane, a carbon compound, a magnesium compound, an organometallic compound, TMGa, TMIn, TMAl, or an oxide.

4. The method of claim 1, wherein the second surface is located on a graphite part (3, 5, 10, 11, 19) arranged in the reactor housing (1).

5. The method of claim 4, wherein the parasitic coating is deposited on a coating of the second surface of the graphite part (3, 5, 10, 11, 19), wherein the coating is resistant to an etching gas, a carbide coating, a TaC-coating, or an SiC-coating.

6. The method of claim 1, wherein during the heating of the process chamber (2) to the first cleaning temperature (T.sub.1), one or more of an inert gas, a noble gas, N.sub.2 or H.sub.2 is fed into the process chamber (2).

7. The method of claim 1, wherein during the first cleaning step (21), only the halogen, or the halogen compound, and N.sub.2, are fed into the process chamber (2), or only Cl.sub.2, together with N.sub.2, are fed into the process chamber (2).

8. The method of claim 1, wherein during the second cleaning step (22), only O.sub.2, together with N.sub.2, are fed into the process chamber (2).

9. The method of claim 1, wherein during the cooling process (24), only H.sub.2 is fed into the process chamber (2).

10. The method of claim 4, wherein the graphite part is one or more of a susceptor (3) bounding the process chamber (2), a process chamber ceiling (10) bounding the process chamber (2), a gas inlet element (11), a gas outlet element (19), or a substrate holder (5) that rests on a gas cushion formed within a pocket (4) of the susceptor (3).

11. The method of claim 1, wherein at least one of: the susceptor (3) is driven in rotation about an axis of rotation (8) at least during the deposition of the layer, or the susceptor (3) is heated by a heating device (31) during one or more of the deposition of the layer, during the heating of the process chamber (2) to the first cleaning temperature (T.sub.1), during the first cleaning step (21), during the second cleaning step (22) or during the third cleaning step (23).

12. A device for depositing a layer on a substrate (6), the device comprising: a chemical vapor deposition (CVD) reactor with a reactor housing (1), in which at least one graphite part (3, 5, 10, 11, 19) is arranged; a gas supply device with gas sources (25) configured to supply a process gas; valves (27) and mass flow controllers (26); and a control device (32) configured to control the valves (27) and the mass flow controllers (26) according to the method of claim 1 such that said steps of feeding said process gas and said first, second, and third cleaning steps are executed in a process chamber (2) of the reactor housing (1).

13. The device of claim 12, the gas sources (25) are further configured to supply a reactive gas containing at least one element of main group II-VI.

14. The device of claim 12, wherein the process gas contains at least one of AsH.sub.3, PH.sub.3, NH.sub.3, a silane, a carbon compound, a magnesium compound, an organometallic compound, TMGa, TMIn, TMAl, or an oxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In what follows, an example embodiment of the invention is explained with reference to the accompanying drawings. Here:

[0025] FIG. 1 shows a schematic cross-section of a CVD reactor, a gas supply device with gas sources 25, and a schematic of an electronic control device;

[0026] FIG. 2 shows a cross-section along the line II-II in FIG. 1;

[0027] FIG. 3 shows a flow chart of the cleaning steps that follow a process step in which a layer is deposited on a substrate; and

[0028] FIG. 4 shows a time-temperature diagram of the cleaning process illustrated in FIG. 3.

DETAILED DESCRIPTION

[0029] The inventive method is executed in a device as shown in FIG. 1. A CVD reactor has a gas-tight housing 1, made, for example, from stainless steel, in which a process chamber 2 is located. The floor of the process chamber 2 is formed by a susceptor 3, which can be made of graphite, and which is coated with SiC. The susceptor 3 has the shape of a circular disk, and a downward-facing rear face that faces towards a heating device 31. The heating device 31 can take the form of a coil, which generates an RF field that induces eddy currents in the susceptor 3, which heat the susceptor 3 up to a process temperature.

[0030] The susceptor 3 can be rotated about an axis of rotation 8 using a shaft 9 and a rotary drive (not shown). Also not shown are supply lines that run through the shaft 9 in order to feed an inert gas into the gas channels (not shown) of the susceptor 3. These gas channels open into the floors of pockets 4, which are arranged in the upward-facing surface of the susceptor 3. A substrate holder 5 made of graphite is inserted into 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. This can be a substrate made of Si, GaAs, or a substrate made of sapphire or another suitable material.

[0031] In the central region of the susceptor 3, there is a recess 18, into which a lower section of a gas inlet element 11 can be inserted. The gas inlet element 11 is fixedly attached to the housing 1, and has three gas outlet zones 13, 15, 17, arranged vertically one above the other. A gas supply line 12, 14, 16 leads to each of the three gas outlet zones 13, 15, 17. Reactive gases and inert gases can be fed through the gas supply lines 12, 14, 16 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 thereby flows over the substrates 6.

[0032] FIG. 1 just shows one example of a process chamber in a CVD reactor. In further examples of embodiment (not shown), the central gas inlet element 11 can have another configuration. Furthermore, example embodiments are envisaged in which the gas inlet element is formed by a ceiling of the process chamber, and has a large number of essentially evenly distributed gas outlet openings in the form of a showerhead.

[0033] The process chamber ceiling 2 can be made of graphite and coated with SiC.

[0034] The process chamber 2 is surrounded by an annular gas outlet element 19, which has a gas outlet opening (not shown), to which a suction line of a vacuum pump (not shown) is connected, so as to evacuate the process chamber 2, or so as to be able to set a predetermined total pressure in the process chamber 2.

[0035] FIG. 1 also shows schematically a gas supply device with a large number of gas sources 25. The gas supply device can, for example, provide the following gases: AsH.sub.3, PH.sub.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 the deposition of a III.sup.rd-V.sup.th layer on the substrates 6 arranged in an annulus around the gas inlet element 11 in accordance with FIG. 2. The gas supply device can also provide inert gases, for example H.sub.2 and N.sub.2. Furthermore, the gas supply device can provide cleaning gases Cl.sub.2 and O.sub.2. The two cleaning gases are preferably provided as a 5% mixture in N.sub.2.

[0036] A programmable electronic control device 32 can control valves 27 and mass flow controllers 26 to feed predetermined mass flows of the above-cited gases through the supply lines 12, 14, 16, 28, 29, 30 into the process chamber 2.

[0037] One of the devices described above is used to deposit layers of elements from the III.sup.rd and V.sup.th main groups on the substrates 6 described above. These can take the form of GaInAsP layers, or layers containing at least two of the above-cited elements. To this end, the substrates are first brought into the process chamber 2 and then, after the process chamber 2 has been heated to a process temperature, the above-described reactive gases are fed into the process chamber 2. After the one or plurality of layers have been deposited, the process chamber 2 is cooled to, for example, 200-300 C., 300-400 C., or 300 C., and the substrates are removed. During the above-described deposition process, coatings form on some SiC surfaces from the solid chemical compounds that are formed during the reactions of the reactive gases.

[0038] Referring to FIG. 4, after the substrates have been removed, the temperature inside the process chamber 2 is heated in a heating step 20 from a time t.sub.1 to a time t.sub.2 to a first cleaning temperature T.sub.1, which can be between 800 C. and 1,000 C., and which can be 900 C. A total pressure of between 50 mbar and 100 mbar is set in the process chamber.

[0039] After achievement of the first cleaning temperature T.sub.1, Cl.sub.2 is fed into the process chamber, together with N.sub.2, in a first cleaning step 21 from time t.sub.2 to time t.sub.3. In the process chamber 2, a reaction of the chemical compounds deposited on the SiC surfaces with O.sub.2 takes place. Volatile reaction products are formed, which are removed from the process chamber 2 with the N.sub.2.

[0040] In an intermediate step following the first cleaning step 21, the temperature of the process chamber 2 is heated from a time t.sub.3 to a time t.sub.4 in an N.sub.2 atmosphere to a second cleaning temperature T.sub.2, which can be between 900 C. and 1,000 C., or between 1,000 C. and 1,100 C., but which can also be between 1,100 C. and 1,200 C., or which can be 1,050 C. The total pressure inside the process chamber is altered. In particular, it is altered to a pressure between 600 mbar and 800 mbar. After achievement of the second cleaning temperature T.sub.2, O.sub.2 is fed into the process chamber together with N.sub.2 during the time from t.sub.4 to t.sub.5. During this second cleaning step 22, carbon compounds are removed from the SiC surfaces by means of a chemical reaction of the carbon compounds with oxygen. Volatile oxides are formed, which are removed from the process chamber 2 together with the N.sub.2.

[0041] After the time t.sub.5 has been reached, the temperature of the process chamber is altered to a third cleaning temperature T.sub.3. In particular, the temperature is lowered to a temperature that can be between 800 C. and 1,000 C., or to a temperature that can be 900 C. At the same time, the total pressure can be set to a value between 50 mbar and 100 mbar. After achievement of the third cleaning temperature T.sub.3, only H.sub.2 is fed into the process chamber during the time from t.sub.6 to t.sub.7. During this third cleaning step 23, any remaining oxides are removed from the surfaces. A conditioning of the CVD reactor can also be executed.

[0042] When the time t.sub.7 has been reached, the temperature of the process chamber 2 is lowered, for example, to between 200 C. and 400 C., or to 300 C., in a cooling phase 24. At the time t.sub.7, when the process temperature 2 has reached the value of 300 C., for example, approximately 70 minutes have passed since the start of the cleaning process at the time t.sub.1.

[0043] FIG. 3 shows an example of embodiment in which a heating step 20 is followed by a Cl.sub.2 etching step 21, and a rinsing step 21 is executed before a subsequent O.sub.2 etching step 22. The O.sub.2 etching step 22 is followed by a heating step 23, which in turn is followed by a cooling step 24.

[0044] During the rinsing step 21, the etching gases used in the Cl.sub.2 etching step 21, and in particular Cl.sub.2, can be completely removed from the reactor housing so that no more Cl.sub.2 is present in the process chamber in a subsequent O.sub.2 etching step 22.

[0045] An example of embodiment of the method can be executed with the following steps: [0046] Heating of the process chamber to a first cleaning temperature T.sub.2 (800 C. to 900 C.), [0047] Injection of Cl.sub.2 into a nitrogen atmosphere (5% Cl.sub.2 12 slm, N.sub.2 11 slm, total pressure 50 mbar to 100 mbar), [0048] Termination of the injection of Cl.sub.2 and heating up to a second cleaning temperature T.sub.2 (950 C. to 1,000 C.), [0049] Injection of O.sub.2 into a nitrogen atmosphere (5% O.sub.2 9 slm, N.sub.2 11 slm, total pressure 600 mbar to 800 mbar) [0050] Termination of the injection of O.sub.2 and alteration of the temperature to a third cleaning temperature T.sub.3 (800 C. to 1,000 C.), [0051] Baking in a hydrogen atmosphere (26 slm, total pressure 50 mbar to 100 mbar)

[0052] The above statements serve to explain the inventions covered by the application as a whole; these also further develop the prior art, at least by means of the following combinations of features and also independently, wherein two, a plurality of, or all of, these combinations of features can also be combined, namely:

[0053] A method for the deposition of a layer containing an element of the V.sup.th main group on a substrate (6) in a CVD reactor, wherein the CVD reactor has a reactor housing (1), in which is arranged at least one graphite part (3, 5, 10, 11, 19) coated with SiC, which, during deposition, comes into contact with process gas fed into a process chamber (2) of the CVD reactor, such that a decomposition product of the process gas is deposited on the surface of the graphite part (3, 5, 10, 11, 19), forming a parasitic coating, wherein a process gas is provided, which has molecules containing an element of the V.sup.th main group; 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 V.sup.th main group element is deposited on the substrate (6) 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.sub.1); wherein after achievement of the first cleaning temperature (T.sub.1), 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.sub.2); wherein after achievement of the second cleaning temperature (T.sub.2), O.sub.2 is fed into the process chamber (2) in a second cleaning step (22); wherein after the second cleaning step (22), the process chamber (2) is brought to a third cleaning temperature (T.sub.3); wherein after achievement of the third cleaning temperature (T.sub.3) in a third cleaning step (23) essentially only H.sub.2 is fed into the process chamber (2); and wherein after the third cleaning step (23), the process chamber (2) is cooled (24).

[0054] A method, which is characterized in that the process gas contains AsH.sub.3, PH.sub.3, or NH.sub.3, and/or in that the process gas additionally contains a gas, the molecules of which contain an element of the III.sup.rd main group, and/or in that the process gas additionally contains TMGa, TMIn, or TMAl.

[0055] A method, which is characterized in that during heating (20) an inert gas, and/or a noble gas, and/or N.sub.2 or H.sub.2, is fed into the process chamber (2), and/or only an inert gas is fed into the process chamber (2).

[0056] A method, which is characterized in that during the first cleaning step (21) only the halogen. or the halogen compound, and N.sub.2 is fed into the process chamber (2), and/or only Cl.sub.2 is fed into the process chamber (2), together with N.sub.2.

[0057] A method, which is characterized in that during the second cleaning step (22) only O.sub.2, together with N.sub.2, is fed into the process chamber (2).

[0058] A method, which is characterized in that during the cooling process (24) only H.sub.2 is fed into the process chamber (2).

[0059] A method, which is characterized in that the graphite part is a susceptor (3) bounding the process chamber (2), and/or in that the graphite part is a process chamber ceiling (10) bounding the process chamber (2), and/or in that the graphite part is a gas inlet element (11), and/or in that the graphite part is a gas outlet element (19), and/or in that the graphite part is a substrate holder (5), which is mounted in a pocket (4) of the susceptor (3), wherein an inert gas can be fed into the pocket (4) through a gas supply line such that a gas cushion is there formed, which causes the substrate holder (5) to rotate about an axis (7).

[0060] 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 in that the susceptor (3) is heated by a heating device (31) during the deposition of the layer and during the heating process (20), and/or during the three cleaning steps (21, 22, 23).

[0061] A device for the execution of 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 that has gas sources (25) with which a process gas whose molecules have an element of the III.sup.rd main group, a halogen. or a halogen compound, O.sub.2, H.sub.2 and N.sub.2 is provided, and with a control device (32) for the control of valves (27) and mass flow controllers (26), such that a process in accordance with one of the claims 1-8 is executed in a process chamber (2) of the reactor housing (1).

[0062] All disclosed features are essential to the invention (individually, but also in combination with each other). The disclosure of the application hereby also includes the full disclosure content of the associated/attached priority documents (copy of the previous application), also for the purpose of including features of these documents in the claims of the present application. The subsidiary claims, even without the features of a claim referred to, characterise with their features independent inventive developments of the prior art, in particular in order to make divisional applications on the basis of these claims. The invention specified in each claim can additionally have one or a plurality of the features specified in the above description, in particular those provided with reference numerals, and/or in the list of reference numerals. The invention also relates to forms of design, in which individual features cited in the above description are not realized, in particular to the extent that they can recognisably be dispensed with for the respective intended use, or can be replaced by other means having the same technical effect.

LIST OF REFERENCE SYMBOLS

[0063] 1 Reactor housing [0064] 2 Process chamber [0065] 3 Susceptor [0066] 4 Pocket [0067] 5 Substrate holder [0068] 6 Substrate [0069] 7 Substrate holder axis of rotation [0070] 8 Susceptor axis of rotation [0071] 9 Shaft [0072] 10 Process chamber ceiling [0073] 11 Gas inlet element [0074] 12 Supply line [0075] 13 Gas outlet zone [0076] 14 Supply line [0077] 15 Gas outlet zone [0078] 16 Supply line [0079] 17 Gas outlet zone [0080] 18 Recess [0081] 19 Gas outlet element [0082] 20 Heating step [0083] 21 Cleaning with chlorine [0084] 21 Rinsing step [0085] 22 Cleaning with oxygen [0086] 23 Bake with hydrogen [0087] 24 Cooling step [0088] 25 Gas source [0089] 26 Mass flow controller [0090] 27 Valve [0091] 28 Supply line [0092] 29 Supply line [0093] 30 Supply line [0094] 31 Heating device [0095] 32 Control device