Method for separating a carbon structure from a seed structure

Abstract

A method is employed to separate a carbon structure, which is disposed on a seed structure, from the seed structure. In the method, a carbon structure is deposited on the seed structure in a process chamber of a CVD reactor. The substrate comprising the seed structure (2) and the carbon structure (1) is heated to a process temperature. At least one etching gas is injected into the process chamber, the etching gas having the chemical formula AO.sub.mX.sub.n, AO.sub.mX.sub.nY.sub.p or A.sub.mX.sub.n, wherein A is selected from a group of elements that includes S, C and N, wherein O is oxygen, wherein X and Y are different halogens, and wherein m, n and p are natural numbers greater than zero. Through a chemical reaction with the etching gas, the seed structure is converted into a gaseous reaction product. A carrier gas flow is used to remove the gaseous reaction product from the process chamber.

Claims

1. A method, comprising: within a single process chamber (7) of a chemical vapor deposition (CVD) reactor (4), (i) depositing a carbon structure (1) on a seed structure (2) by providing a carbon containing process gas; and (ii) afterwards separating the seed structure (2) from the carbon structure (1) by: heating, in the process chamber (7) of the CVD reactor (4), a substrate (3) to a process temperature, wherein the substrate (3), during the heating step, comprises the seed structure (2) and the carbon structure (1) formed on the seed structure (2); with the carbon structure (1) formed on the seed structure (2), injecting, into the process chamber (7), at least one etching gas with the molecular formula AO.sub.mX.sub.n, AO.sub.mX.sub.nY.sub.p or A.sub.mX.sub.n, wherein A is selected from a group of elements comprising S, C, and N, wherein O is oxygen, wherein X and Y are different halogens, and wherein m, n, and p are natural numbers greater than zero; converting the seed structure (2) through a chemical reaction with the at least one etching gas into a gaseous reaction product; and removing the gaseous reaction product from the process chamber (7) by means of a carrier gas flow.

2. The method of claim 1, wherein the seed structure is a metal structure.

3. The method of claim 1, wherein the seed structure includes at least one element from the following group of elements: Cu, Ni, Co, Fe, Ru, Ir, Ga, Gd, Mo, Mn, Ag, Au, B, Si, and Ge.

4. The method of claim 1, wherein the seed structure (2) is disposed between the substrate (3) and the carbon structure (1), is disposed above the carbon structure, is formed by particles, is a layer on a substrate (3) or is formed by the substrate itself.

5. The method of claim 1, wherein the at least one etching gas is activated by heat, by ultraviolet light or by a plasma.

6. The method of claim 5, wherein the etching gas is activated by heating the etching gas within the CVD reactor (4).

7. The method of claim 6, wherein the etching gas is heated within a gas inlet body (8) of the CVD reactor (4) or within the process chamber (7) of the CVD reactor (4).

8. The method of claim 1, wherein the at least one etching gas is SOCl.sub.2.

9. The method of claim 1, wherein the at least one etching gas is a gas mixture consisting of a plurality of gases that differ from one another.

10. The method of claim 1, wherein the at least one etching gas is provided in an etching gas source (11), within which a liquid is evaporated.

11. The method of claim 1, further comprising injecting an additive gas with the molecular formula RX into the process chamber together with the at least one etching gas, wherein R is hydrogen or a metal and X is a halogen.

12. The method of claim 1, wherein a progress of the conversion of the seed structure (2) into the gaseous reaction product is determined by determining a reflectivity of a surface (2) of the seed structure, wherein a light source (18), which generates an incident light beam (19) that is reflected on the surface (2) of the seed structure, and a detector (21), which measures an intensity of the reflected light beam (20), are used to determine the reflectivity of the surface (2), wherein the incident light beam (19) is oriented vertically or at an angle to the surface (2) and/or the light beam is generated continuously or in a pulsed manner.

13. The method of claim 12, wherein the injection of the etching gas into the process chamber terminates when the intensity of the reflected light beam (20), as determined by the detector (21), reaches a maximum after passing through a minimum.

14. The method of claim 1, wherein the carbon structure (1) comprises graphene, carbon nanotubes or semiconductor nanowires.

15. The method of claim 1, wherein the at least one etching gas is activated by ultraviolet light.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention will be explained below by means of enclosed drawings.

(2) FIG. 1 shows a CVD reactor arrangement of a first exemplary embodiment in a schematic view;

(3) FIG. 2 shows a CVD reactor arrangement of a second exemplary embodiment in a schematic view;

(4) FIG. 3 shows a first exemplary embodiment of the separating method in a schematic view;

(5) FIG. 4 shows a second exemplary embodiment of the separating method;

(6) FIG. 5 shows a third exemplary embodiment of the separating method,

(7) FIG. 6 shows a fourth exemplary embodiment of the separating method;

(8) FIG. 7 shows an illustration according to FIG. 6 prior to the introduction of the etching gas at the time t.sub.0;

(9) FIG. 8 shows a follow-up illustration for FIG. 7 during the etching process at the time t.sub.1;

(10) FIG. 9 shows a follow-up illustration for FIG. 8 at the time t.sub.2 and

(11) FIG. 10 shows the chronological sequence of the reflectivity of the boundary surface 2 of the seed structure 2 to the carbon structure 1 during the etching process, only qualitatively.

DETAILED DESCRIPTION

(12) The CVD reactor 4 illustrated in FIGS. 1 and 2 consists of a housing, which is gas-tight to the outside. A susceptor 5 of graphite, quartz or a metal for accommodating objects 2, 3, on which a carbon structure 1 is deposited, is located inside the housing. A heater 6 is located underneath the susceptor 5. It can be a resistance heater, an IR heater or an RF heater. The circular disk-shaped susceptor 5 is surrounded by a gas outlet body, which is connected to a pump 15 by means by gas drain 16. A process chamber 7 is located above the susceptor 5. The ceiling of the process chamber 7 is formed by a gas exit surface of a gas inlet body 8. The gas inlet body 8 can be a shower head-shaped hollow body, which has a plurality of gas exit openings 9 on its underside. A process gas can be injected into the gas inlet body 8 by means of a supply line 10.

(13) To carry out the method for depositing the carbon structures 1, thus for example a graphene layer, a graphene layer consisting of a plurality of layers, of carbon nanotubes or of semiconductor nanowires, a suitable process gas, which includes carbon, for example methane, is injected into the process chamber 7 through the supply line 10. The objects, which bear on the susceptor 5 therein, have a seed structure, for example a seed layer or a structured seed layer 2, which consists of copper. The mentioned carbon nanostructures 1 form on this seed structure 2. The objects can have substrates 3, which are coated with a seed structure 2. The seed structure 2 can have a smooth surface. It is also possible, however, that catalytically acting particles, which form the seed structure 2, bear on the substrates 3. The particles have a diameter, which lies in the nanometer range. In response to the deposition of the nanostructures, nanotubes or nanowires form between substrate and particle. The particles can be spaced apart from one another.

(14) An etching gas is used to separate the carbon nanostructures 1 from the seed structures 2. This etching gas is generated in an etching gas source 11. The etching gas is guided through the supply line 10 into the gas inlet body 8 by means of a carrier gas, which is an inert gas from Ar, N.sub.2 or H.sub.2, which is injected into a supply line 12. In the supply line 10, a further inert gas, for example Ar, N.sub.2 or H.sub.2, is additionally injected into the supply line 10 by means of the supply line 13.

(15) In the case of the exemplary embodiment illustrated in FIG. 1, the etching gas 11 is activated by heating within the process chamber 7 or within the gas inlet body 8, respectively. The etching gas source 11 can be a bubbler as it is illustrated in FIG. 2.

(16) The bubbler illustrated in FIG. 2 is a container in which a liquid starting material is stored. The starting material can be SOCl.sub.2, SOBr.sub.2, COCl.sub.2, NOCl.sub.2, NOBr.sub.2 or SOBr. Preferably, the liquid is thionyl chloride. An etching gas is generated by guiding an inert gas through the liquid.

(17) In the exemplary embodiment illustrated in FIG. 2, provision is made for an external activator 14, in which the etching gas is activated. This can take place by adding heat to the etching gas, by UV or by a plasma. A heat source, a UV source or a plasma generator can thus be arranged in the activator 14.

(18) A pre-decomposition of the etching gas can take place in response to the activation of the etching gas.

(19) To carry out the etching process, the susceptor 5 is heated to a temperature of approximately 800 C. The etching gas or the pre-decomposed etching gas reacts with the seed structure 2 and converts the latter into a volatile starting material, which is removed from the drain 16 from the process chamber 7 together with the carrier gas.

(20) The exemplary embodiment illustrated in FIG. 3 shows an object consisting of a substrate 3, which can be a dielectric body and which consists of a seed structure 2 applied thereto. The seed structure 2 can consist of copper and can be a layer comprising a smooth surface. A graphene layer 1 is deposited on the seed structure 2. It can be a mono-layer of graphene. A few graphene layers can also be deposited on top of one another. In response to the above-described etching process, the etching gas or first reaction products of the etching gas penetrates the graphene layer 1 and converts the seed structure 2 into a gaseous second reaction product, so that the result illustrated on the right in FIG. 3 is created, in the case of which the graphene layer 1 bears directly on the substrate 3.

(21) On the left, FIG. 4 shows a graphene layer 1, which was deposited on a seed structure 2, which is a copper plate. The copper plate 2 is removed by means of the etching process, so thatas is illustrated on the right in FIG. 4only graphene 1 remains.

(22) In the case of the exemplary embodiment illustrated in FIG. 5, the carbon structure 1, for example in the form of nanowires or nanotubes, grows underneath a seed structure 2 of copper, which consists of particles bearing on the surface of the substrate 3. To deposit such carbon structures 1, copper particles or particles of another suitable catalytically acting material, are applied to a substrate 3. The carbon structures 1 then grow between substrate 3 and the particles. A corresponding structure is illustrated schematically on the left in FIG. 5. After the etching process, the seed structure 2 is removed, so thatas is illustrated on the right in FIG. 5the nanotubes 1 or nanowires, respectively, bear directly on the substrate 3.

(23) In the case of the exemplary embodiment illustrated in FIG. 6, an object, in the case of which a substrate 3 has a laterally structured seed structure 2, is illustrated on the left. Nanotubes 1 are deposited on this seed structure 2. The state illustrated on the right in FIG. 6, in the case of which the nanotubes 1 bear directly on the substrate 3, is attained by means of the above-described etching process, in the case of which the seed structure 2 is removed by means of a dry etching method.

(24) The deposition process as well as the separating process, which takes place by introducing an etching gas, can be carried out in the device illustrated in FIGS. 1 and 2.

(25) FIGS. 7 to 9 show a cross section through an object consisting of a substrate 3, to which a metallic seed structure 2 comprising a smooth surface 2 is applied, in a schematic view. A carbon structure 1 was deposited on the surface 2 either as graphene layer or as graphene layer sequence or as nanotubes or nanowires. The surface 2 thus forms a boundary surface between the carbon structure 1 and the seed structure 2. An incident light beam 19 is generated by means of a light source 18, which can be a semiconductor laser. The incident light beam is reflected on the boundary surface 2. The outgoing light beam 20 falls into a detector 21. The light source 18 and the detector 21 can be arranged in a process chamber, so that the change of the intensity of the light beam 19, 20, which is reflected on the boundary surface 2, can be measured continuously during the etching process. In the case of an exemplary embodiment, the incident light beam 19 hits the boundary surface 2 at an acute angle >20. It is also possible, however, that the incident light beam 19 hits the boundary surface 2 vertically to the boundary surface 2.

(26) FIG. 7 shows the object at the time t.sub.0 at the beginning of the etching process.

(27) FIG. 10 shows the course of the change of the reflectivity on the boundary surface 2 during the etching process in a qualitative manner. At the time t.sub.0, the incident light beam 19 is reflected on the smooth surface of the seed structure 2, which has a high reflection capacity, so that the reflectivity R, which can be determined via the intensity of the reflected light beam, has a maximum.

(28) Material of the seed structure 2 is removed at the boundary surface 2 during the etching process, so that the boundary surface 2 becomes rougher as the etching process continues. The reflection capacity decreases, so that the detector 21 detects a decreasing intensity/reflectivity. This is illustrated in FIG. 8 at the time t.sub.1. The intensity/reflectivity passes a minimum and subsequently increases again, if only partial sections of the substrate surface 3 are still coated with the material of the seed structure 2. The substrate surface 3 has a high reflection capacity, because it is smooth. At the time t.sub.2, the intensity/reflectivity reaches a maximum. It does not increase any further. This is a sign that the light beam 19 is only still reflected on the substrate surface 3, which now forms the boundary surface between carbon structure 1 and substrate 3.

(29) If the intensity/reflectivity R reaches the maximum, which follows the minimum, or if it is determined, respectively, that the reflectivity does not increase further, the etching process is ended.

(30) The above statements serve to explain the inventions, which are captured as a whole by the application and which in each case independently further develop the prior art at least by means of the following feature combinations, namely:

(31) A method for separating a carbon structure 1, for example graphene, carbon nanotubes or semiconductor nanowires, deposited on a seed structure 2, from the seed structure 2, consisting of the steps: providing a carbon structure deposited on a seed structure 2 in a process chamber 7 of a CVD reactors 4; heating the substrate comprising the seed structure 2 and the carbon structure 1 to a process temperature; injecting at least one etching gas with the molecular formula AO.sub.mX.sub.n, AO.sub.mX.sub.nY.sub.p or A.sub.m,X.sub.n, wherein A is selected from a group of elements, which includes S, C, N, wherein O is oxygen, wherein X, Y are different halogens and m, n, p are natural numbers greater than zero; converting the seed structure 2 through a chemical reaction with the etching gas into a gaseous reaction product; removing the gaseous reaction product from the process chamber 7 by means of a carrier gas flow.

(32) A method, which is characterized in that the seed structure is a metal structure.

(33) A method, which is characterized in that the seed structure includes at least one element from the following group of elements: Cu, Ni, Co, Fe, Ru, Ir, Ga, Gd, Mo, Mn, Ag, Au, B, Si, Ge.

(34) A method, which is characterized in that the seed structure 2 is arranged between a substrate 3 and the carbon structure 1 or above the carbon structure and in the substrate, and is formed by particles, a layer on a substrate 3 or that the seed structure is formed by the substrate itself.

(35) A method, which is characterized in that the etching gas is activated in particular by the supply of heat, by ultraviolet light or by a plasma, wherein provision is in particular made for the activation of the etching gas to take place by heating within the CVD reactor 4, in particular within a gas inlet body 8 therein or within the process chamber 7.

(36) A method, which is characterized in that the etching gas includes the element chlorine and is in particular SoCl2.

(37) A method, which is characterized in that the etching gas is a gas mixture consisting of a plurality of gases, which differ from one another.

(38) A method, which is characterized in that the etching gas is provided in an etching gas source 11, in which in particular a liquid is evaporated.

(39) A method, which is characterized in that an additive gas with the molecular formula RX is injected into the process chamber together with the etching gas, wherein R is hydrogen or a metal and X is a halogen.

(40) A method, which is characterized in that the progress of the conversion of the seed structure 2 into a gaseous reaction product is determined by determining the reflectivity of the surface 2 of the seed structure, wherein a light source 18, which generates an incident light beam 19, which is reflected on the surface 2, and a detector 21, which measures the intensity of the reflected light beam 20, is in particular used to determine the reflectivity, wherein the incident light beam 19 is oriented vertically or at an angle to the surface extension of the surface 2 and/or the light beam is generated continuously or in a pulsed manner.

(41) A method, which is characterized in that the introduction of the etching gas into the process chamber is ended, when the intensity of the outgoing light beam 20 determined by the detector 21 has reached a maximum after passing through a minimum.

(42) A method, which is characterized in that the carbon structure 1 is deposited on the seed structure 2 in the same process chamber 7 prior to separating the carbon structure 1 from the seed structure 2.

(43) A device, which is characterized by a source for providing the etching gas, which in particular has a container 11, in which a liquid is stored, from which the etching gas can be generated by evaporation.

(44) A device, which is characterized by a light source 18 and a detector 21, wherein the light source 18 generates a light beam, which is reflected on a boundary layer between carbon structure 1 and seed structure 2, and which has a detector 21, which determines the intensity of the light beam reflected on the boundary layer.

(45) A device, which is characterized by a control device, which cooperates with the detector 21, and which turns off the admission of the etching gas into the process chamber 7, when the intensity of the reflected light beam 20, which is determined by the detector 21, does not increase further after passing through a minimum.

(46) All disclosed features are significant for the invention (alone, but also in combination with one another). The disclosure content of the corresponding/enclosed priority documents (copy of the prior application) is hereby also included in its entirety into the disclosure of the application, also for the purpose of adding features of these documents into claims of the application at hand. With its features, the subclaims characterize independent inventive further developments of the prior art, in particular to file divisional applications on the basis of these claims.

REFERENCE LIST

(47) 1 carbon structure

(48) 2 seed structure

(49) 2 boundary surface

(50) 3 substrate

(51) 3 boundary surface

(52) 4 CVD reactor

(53) 5 susceptor

(54) 6 heater

(55) 7 process chamber

(56) 8 gas inlet body

(57) 9 gas exit opening

(58) 10 supply line

(59) 11 etching gas source

(60) 12 supply line

(61) 13 inert gas line

(62) 14 activation annihilator

(63) 15 pump

(64) 16 drain

(65) 18 light source

(66) 19 incident light beam

(67) 20 outgoing light beam

(68) 21 detector

(69) R reflectivity

(70) t.sub.0 time

(71) t.sub.1 time

(72) t.sub.2 time