FR2975107A1 - TREATMENT OF A PRECURSOR BY INJECTION OF A REACTIVE ELEMENT IN A STEAM PHASE. - Google Patents

Abstract

The process comprises heating a reactive element to obtain a part of the reactive element in vapor phase, circulating a carrier gas in the reactive element in vapor phase for driving the reactive element in vapor phase of the carrier gas, and injecting the carrier gas comprising the reactive element in vapor phase on a precursor. A heating temperature of the reactive element is controlled for controlling a quantity of the reactive element in the carrier gas. The heating step comprises controlling, via the control of the heating temperature, a saturated vapor pressure of the reactive element. The process comprises heating a reactive element to obtain a part of the reactive element in vapor phase, circulating a carrier gas in the reactive element in vapor phase for driving the reactive element in vapor phase of the carrier gas, and injecting the carrier gas comprising the reactive element in vapor phase on a precursor. A heating temperature of the reactive element is controlled for controlling a quantity of the reactive element in the carrier gas. The heating step comprises controlling, via the control of the heating temperature, a saturated vapor pressure of the reactive element with a thermodynamic equilibrium comprising the vapor phase of the reactive element, and controlling the temperature of a support of the reactive element for controlling the quantity of the reactive element in the carrier gas. The step of controlling the pressure is conducted for controlling the partial pressure of the reactive element in the carrier gas. The support is an electrically conductive crucible. The circulating step comprises mixing the reactive element in vapor phase with the carrier gas. The method further comprises injecting hot gas for promoting a reaction of the reactive element with the precursor, and cooling a quenching effect of the precursor, after the reaction of the reactive element with the precursor, by injecting a cold gas on the precursor. The reactive element is reactive with the precursor in vapor phase. The temperature of the reactive element injected on the precursor is controlled in function including: the temperature of the carrier gas; the flow of the mixture of the reactive element in vapor phase with the carrier gas; and a distance between the precursor and an injection pipe of the mixture on the precursor. The reactive element comprises: an element of column VI for the manufacture of group I-III-VI 2alloy with photovoltaic properties; an element of column V for the manufacture of group II-IV-V alloy with photovoltaic properties; an element of column VI for the manufacture of group I 2-II-IV-VI 4alloy with photovoltaic properties; and an element of column I and III. The carrier gas is heated to a controlled temperature of 100[deg] C. The reactive element comprises a mixture of reactive elements driven by the carrier gas to react together. An independent claim is included for an installation for routing a reactive gas on a precursor.

Description

Treatment of a precursor by injection of a reactive element in the vapor phase

The present invention relates to the field of the treatment of materials, in particular for a supply of reactive material on a precursor.

In particular, especially but not exclusively for the manufacture of type I-III-VI2 alloys of crystallographic structure of the chalcopyrite type and with photovoltaic properties, it is sought to react at controlled pressure with a precursor (in the form of a thin layer) in a reactive atmosphere. The notation "1" (respectively "III" and "VI") designates the elements of column I (respectively III and VI) of the periodic table of elements, such as copper (respectively indium and / or gallium and / or or aluminum, and selenium and / or sulfur).

A problem that arises is how to perform reactive annealing to obtain thin-film materials based on Cu (for copper), In (for indium), Ga (for gallium), Al (for aluminum) , Se (for selenium), S (for sulfur), but also more generally Zn (for zinc), or Sn (for tin) or P (for phosphorus).

In particular, it is sought to introduce a reactive product (often in gaseous form) in an enclosure to react with intermediate thin layers (hereinafter referred to as "precursors"), and this, at high temperature, typically for processes capable of apply up to 700 ° C in one minute, these processes being referred to as rapid thermal processes (or "Rapid Thermal Process").

Two pressure control solutions are known such as: the injection of the reactive gas into a pumping reaction chamber for the control of the pressure ("dynamic vacuum" method); - The injection of the reactive gas into a reaction chamber without pumping but at low pressure maintained (method applying a "static vacuum").

In both cases, the pressure control requires a closed chamber with hot walls to avoid condensation of the reactive product (initially in gaseous form). This chamber must incorporate injectors to inject a reactive gas (such as Se, or S, or H2S, or H2Se) and control valves to control the pressure.

The present invention improves the situation.

To this end, it proposes a process for delivering a reactive gas to a precursor, 10 comprising the steps of: a) heating at least one reactive element until at least a portion of the vapor phase reactive element is obtained, b ) circulating a carrier gas in the vapor phase reactive element to drive the vapor phase reactive element into the carrier gas, and c) injecting the vector gas comprising the vapor phase reactive element onto a precursor. In particular, in step a), a heating temperature of the reactive element is controlled to control in quantity the reactive element in the carrier gas in step b).

Advantageously, by the above-mentioned heating temperature, the saturating vapor pressure of the reactive element in step a) is controlled at a thermodynamic equilibrium comprising the vapor phase of the reactive element (for example by sublimation or evaporation). ). Advantageously, the partial pressure of the reactive element in the carrier gas is thus controlled in step b) to manage the exact amount of reactive gas injected onto the precursor.

Advantageously, step a) comprises a temperature control of a support of the reactive element to control the amount of reactive element in the carrier gas in step b). This support may for example be an electrically conductive crucible, heated by circulation of a current of adjustable intensity to control the temperature of the crucible, and thence the amount of reactive element in the carrier gas in step b) .

Step b) comprises a mixture of the reactive element in the vapor phase with the carrier gas, by disturbance of the flow of the carrier gas and the vapor phase reactive element.

In order to keep the reactive element in the vapor phase during the injection on the precursor, it may advantageously be provided to heat the carrier gas at a temperature of the order of a few hundred degrees Celsius. In an exemplary embodiment of selenization at low pressure, the carrier gas is heated to a temperature of the order or slightly higher than the reaction temperature with the precursor (from 300 to 350 ° C at low pressure). It can be higher (around 500 ° C) under normal pressure conditions.

Of course, the temperature of the carrier gas can be controlled for example by means of a circulation in a hot circuit (for example having a heating resistance by Joule effect whose intensity which passes through it is controlled by a control circuit comprising for example, a dimmer of potentiometer or other type).

In addition or alternatively, the method of the invention may further comprise a step d) of injecting a hot gas to promote a reaction of the reactive element with the precursor. For example, in one possible embodiment, the injected reactive element can condense and form a thin surface layer on the precursor. Thus, the hot gas injected can further promote the passage of the reactive element in the vapor phase and the reaction of the gas thus formed with the precursor.

Alternatively, when the carrier gas is sufficiently hot, the reactive element reacts with the precursor directly in the vapor phase in step c).

According to the tests carried out, a few important parameters emerge to finely control the temperature of the reactive element injected onto the precursor and hence to control the reaction temperature with the precursor. It is typically: - the temperature of the carrier gas, - the flow rate of the mixture of the reactive element in the vapor phase with the carrier gas, and - the distance between the precursor and an injection pipe of the mixture on the precursor.

Advantageously, the process may also comprise a cooling step according to a quenching effect, after the reaction of the reactive element with the precursor, by injection of a cold gas.

It may be advantageous (particularly for example in the processes for adding selenium and sulfur) to provide a reactive element comprising a mixture of a plurality of reactive elements entrained by the carrier gas to react together.

For example, it is possible to deposit the precursor itself by vapor phase entrainment of reactive elements. Thus, these reactive elements may comprise elements of columns I and III and form a thin layer of this precursor, corresponding to an alloy I-III, on a substrate. It is then possible to co-deposit with the precursor the VI element injected in the vapor phase, then directly forming a deposit I-III-VI2 on the substrate. Such an embodiment is hereinafter described by way of example with reference to FIG. 4.

In the case where the precursor is first deposited in the form of alloy I-III, the method may further comprise a preliminary step of reducing annealing of this alloy.

The present invention also relates to an installation for carrying out the process within the meaning of the invention, comprising: - means carrying a precursor, - means for heating at least one reactive element to bring the vapor phase at least one part of the reactive element; means for circulating a carrier gas in the reactive element in the vapor phase and driving the reactive element in the vapor phase into the carrier gas, and for injecting the vector gas comprising the reactive element; in the vapor phase on the precursor.

The installation comprises in particular means for controlling the heating means for controlling in quantity the reactive element in the carrier gas injected into the reaction chamber.

Thus, advantageously, there is provided a method and an installation for a heat treatment with supply of reactive product, by projection of hot gas with controlled reactive gas pressure. In particular, the reactive element partial pressure is controlled by establishing a thermodynamic equilibrium between the reactive element in solid or liquid form and its saturation vapor pressure. The hot gas vector of the thermal energy for annealing the sample is charged with the reactive element at a partial pressure set by the sublimation temperature.

This process then no longer requires pressure control devices (no valves, no conventional injectors, no end-of-mass flow controller, etc.).

Of course, other advantages and characteristics of the invention, and in particular of the installation in the sense of the invention, will appear on examining the detailed description of possible embodiments, presented below, and attached drawings in which: - Figure 1 is a schematic diagram of a reactor according to an exemplary embodiment of the invention, - Figure 2 shows changes, depending on the temperature, the saturated vapor pressure various formulations of selenium (from Set to Se8), - Figure 3 illustrates a mixer 15 in a reaction device comprising an injector of a reactive element, - Figure 4 illustrates an example with three injectors of reactive elements, - FIG. 5 illustrates the evolution of the temperature T (V) as a function of time for three crucibles of FIG. 4, the sublimation temperatures Ts of the reactive elements being marked by dotted lines; - Figure 6 schematically shows a device for a heat treatment with reactive gas injection implemented in the card of a so-called "roll-to-roll" process; FIG. 7 illustrates an example of a succession of heat treatments applied with the device of FIG. 6; - Figure 8 illustrates a variant of the device shown in Figure 6, with in particular a common injector at least for the supply of reactive gas and heat treatment by injection of a hot gas, neutral.

Hereinafter, it is designated by: - precursor: a deposit composed of one or more of the elements: Cu, In, Ga, Zn, Sn, Al, Se, S, O on a Mo / glass substrate or a flexible substrate type Mo / insulating layer / (stainless steel, polymer or other); - Reductive annealing: annealing of the precursor with a gas composed of one or more elements: ethanol, methanol, H 2; reactive element: sulfur (S) or selenium (Se) in the elemental state or in the form of compounds or other compounds containing Cu, In, Ga, Sn, Al, Zn; reactive annealing: the crystallization reaction which consists in reacting the precursor (which has or has not undergone a reducing annealing) with a reactive element; Tr: reaction temperature between the reactive element and the precursor; Ps: sublimation pressure of the reactive element; Ts: sublimation temperature of the reactive element. Reference is first made to FIG. 1, in which an input flow of the carrier gas 1 passes through a reaction chamber 3, comprising a power supply 2 for activating a heating element 4 (electrical resistance for example) for, in the example described here, bring the carrier gas to a temperature Tr (arrow 5 of Figure 1). Reference 6 in FIG. 1 denotes an injector of one or more reactive elements in gaseous form at a pressure Ps (and at a temperature Ts). This reactive gas is injected onto a thin film on SUB substrate, in front of it, as a precursor (for example based on Cu, In, Ga, Zn, Sn, Al), undergo a reaction with the reactive gas (for example Se and / or S, but also possibly Cu, In, Ga, Zn, Sn, Al), and this: - at a reaction temperature Tr, and - at a pressure Ps (associated with the sublimation temperature Ts).

Reference 8 designates a gas recovery outlet (vector and reagents).

Examples of reactive gases that may be used in exemplary embodiments of the present invention, as well as their property of variation of saturation vapor pressure as a function of temperature, are described below.

In a particular embodiment where it is desired to react a selenium or sulfur-type VI element with a precursor I-III, it is sought to sublimate the selenium (Se) and / or the sulfur (S) on a thin film. such a precursor (for example a material of CuInnGai_X type). However, other embodiments could also concern the formation of the precursor itself, or the direct deposition of a layer I-III-VI2 without necessarily precursor. As such, it is given here additional information on elements such as: Cu, In, Ga, Zn, Sn, Na, Al since their use in exemplary embodiments of the process is possible.

Table 1 below summarizes the triple point values Tp, melting temperature Tm, sublimation temperature Tb at atmospheric pressure of the abovementioned elements. These values are taken from Handbook of Chemistry and Physics, W.M Haynes 91 st Edition, 2010-2011. Element Tp (° C) Tm (° C) Tb (° C) Al 660.32 2519 Cu 1084.62 2562 Ga 29.7666 2204 In 156.5936 156.6 2072 Na 97.794 882.940 S (rhombic) 95.3 444.61 S (monoclinic) 115.21 444.61 Se (glassy) 180 685 Se (gray) 220.8 685 Sn (gray) 13.2 2602 Sn (white) 231.93 2602 Zn 419.53 907 Table 1 Reference is now made to FIG. 2 to describe more precisely the particular case of the elements S and Se, and more particularly that of the selenium (the case of sulfur, with similar properties, deducing selenium).

These elements exist in several forms in the vapor state. The evolution of the vapor pressures of the various gaseous species of Se in particular, in equilibrium with the condensed phase, as a function of the temperature, is shown in the diagram of FIG. 2. Thus, for example, when selenium is heated to 690.degree. ° K, its saturated vapor pressure is of the order of 0.004 atm (curve solid line), and begins to form a selenium vapor that can be driven by a carrier gas as discussed below. It will be understood here that the control of the selenium temperature allows control of saturated vapor pressure and thence a control of the partial pressure of the selenium in the mixture it constitutes with the carrier gas.

More particularly, FIG. 2 shows the evolution of the saturating vapor pressures of the various gaseous selenium species (Se2: a; Sei: b; Seo: c; Ses: d; Se6: e; Sel: f; Se8: g; the total pressure being represented by the curves in solid line h), in equilibrium with the condensed phase, as a function of the temperature. This figure is taken from Jean-François Guillemoles' thesis "Contribution to the control of the electrically-deposited CuInSe2 semiconductor properties and to the improvement of its photovoltaic properties" (Pierre and Marie Curie University, 1994).

For the other aforementioned species (copper, indium, gallium, etc.), Table 2 presents the values of constants A, B, C of the relation between the vapor pressure P and the temperature T: log (P / atm) = A + B / T + C logT, (values extracted from Handbook of Chemistry and Physics, WM Haynes 91 st Edition, 2010-2011, pages 4-124 to 4-125). Element ABC Al (solid) 9.459 -17342 -0.7927 Al (liquid) 5.911 -16211 Cu (solid) 9.123 -17748 -0.7317 Cu (liquid) 5.849 -16415 Ga (solid) 6.657 -14208 Ga (liquid) 6.754 -13984 -0.3413 In (solid) 5.991 -12548 In (liquid) 5.374 -12276 Na (solid) 5.298 -5603 Na (liquid) 4.704 -5377 Sn (solid) 6.036 -15710 Sn (liquid) 5.262 -15332 Zn (solid) 6.102 -6776 Zn (Liquid) 5.378 -6286 Table 2 The elements can be introduced in the vapor phase in elemental form but also in the form of compounds (for example, H 2 S), in particular in the case of metals whose vapor pressures at the temperatures considered are low. (Ga, In, in particular). In this case, it is possible to use more volatile precursors such as acetyl acetonates, organometallic compounds (of the tri-methyl-gallium, diethyl-zinc type, etc.), halides, sodium salts (NaCl, NaI, NaF). The reagents can also be introduced by nebulization of solution or injection of solid powders.

It will thus be understood that the process within the meaning of the invention proposes a fine control of the partial pressure in the mixture of the gas reactive with the carrier gas. The partial pressure of the reactive gas is then a first parameter of the reaction with the precursor. A second parameter that is also proposed to control, in a particularly advantageous embodiment of the process within the meaning of the invention, relates to the temperature of the reaction. In particular, the reaction temperature is advantageously controlled through the temperature of the carrier gas. An existing solution for such a control and which fits suitably in an embodiment within the meaning of the invention relates to the integration of a mixer. A mixer solution is shown in FIG. 3, which illustrates the integration of such a reactive steam mixer with the hot carrier gas. In FIG. 3, the arrival of the carrier gas bears the reference 11 and is heated beforehand to a chosen temperature. In particular, provision is made in one exemplary embodiment of a crucible 12 supporting the reactive element (which will be detailed hereinafter with reference to FIG. 4), raised to a high temperature (of the order of 400 to 700 ° C for example) by a heating resistor 13, which is electrically powered (current or voltage V). In particular, means are provided such as a potentiometer 14 for controlling the power supply of the heating resistor, and hence the temperature of the crucible 12 and its contents, which is therefore equivalent to controlling the vapor pressure saturating the reactive element (via the control of its temperature in the crucible), and thus its partial pressure in the mixture. The reactive element is sublimed in the crucible 12. The particles of the reactive element evaporate and are entrained by the carrier gas 11. The particles meet a diffuser 15. In contact with the diffuser 15 (then acting as a mixer) the particles propagate and their distribution becomes homogeneous in the carrier gas. The reaction on the surface of the precursor (illustrated by its substrate SUB in FIG. 3) can thus be carried out at homogeneously controlled temperature and pressure.

A device of the type shown in FIG. 3 (with a single injector) is advantageously suitable for the sublimation of a species and its reaction with a precursor.

Of course, a plurality of injectors may be provided to react respectively several reactive gases, as shown in FIG. 4 (illustrating three injectors in the example shown), in which: a power supply (controlled for example in voltage V1) of a heating resistor 31 for heating a crucible 21, support of a first reactive element, - a power supply (controlled for example by voltage V2) of a heating resistor 32 for heating a crucible 22, support of a second reactive element, and - a power supply (driven for example by voltage V3) of a heating resistor 33 is used to heat a crucible 23, support of a third reactive element, the reference 40 designating, in the example shown , the section of a vector gas supply duct (seen from the front).

The embodiment of Figure 4 thus shows the compatibility of the annealing process with several injectors (three in the example shown). Each crucible is heated independently. The sublimation of the reactive elements is thus controlled independently because the temperature of the crucible T depends on the applied voltage V, denoted hereinafter T (V) .30 It is then possible to define temperatures changing over time and for each crucible. , and thus define reaction sequences. FIG. 5 shows, by way of example, a sublimation sequence of a method with three reactive elements, from a device of the type shown in FIG.

Thus: for a time t such that t <tl, all the crucibles are at ambient temperature; for a time t such that tl <t <t2, the crucible 21 is at the temperature Tl (Vl)> Tsl and the first reactive element is thus sublimed at a pressure P 1 (T 1); for a time t such that t2 <t <t3, the crucible 22 is at the temperature T2 (V2)> Ts2 and the second reagent is sublimated at a pressure P2 (T2), so that the first and second reactive elements are sublimated at the same time at the respective pressures P1 and P2; for a time t such that t3 <t <t4, the crucible 21 is cooled, with Tl (Vl) <Tsl, so that only the second reactive element is sublimed; for a time t such that t4 <t <t5, the crucible 22 is cooled (T2 (V2) <Ts2) and no element n 'is sublimated; finally - for a time t such that t5 <t, the crucible 23 is at the temperature T3 (V3)> Ts3 and only the third reactive element is sublimated at a pressure P3 (T3). It will then be understood that a possible example of deposition obtained by such a sequence may be: copper, for example, for the first element, indium for example, for the second element, and selenium for example for the third element, for a subsequent reaction (t> t5) called "selenization", in which the selenium reacts at high temperature with a precursor I-III. Maintaining the high temperature, for selenization, can be ensured at the precursor by the injection of a carefully chosen coolant vector gas. In this regard, there is shown in Table 3 below carrier gases compatible with the reactive elements to be conveyed. Thus, the flexibility of the process in the sense of the invention vis-à-vis the inlet gas and the reactive element allows to produce a wide range of reactive gases. Vector gas Reactive gas Argon, Nitrogen Cu, In, Ga, Zn, Sn, Se, S Cu, In, Ga, Zn, Sn, Se, S Alcohol, NH3, H2, Hydrazine Se, S H2S, H2Se Table 3

Advantageously, it is possible to control a thermal treatment of a precursor at several levels with, for example: the application of a reducing annealing such as ethanol or hydrogen H 2; depositing the reactive element on the substrate; the application of a reactive annealing with / without propulsion of the reactive element; And finally, the application of a quench. It will then be understood that for the application of the quenching effect, an injection gas (which may for example be of the same nature as the carrier gas itself, or a neutral gas) may undergo cooling in a circuit adapted. The term "neutral gas" is generally to be considered as a neutral gas in the reaction of the reactive element with the precursor.

Such an example of a sequence can advantageously be integrated in a so-called "roll-to-roll" processing line for selenization (and / or sulphidation) of a precursor to obtain a thin layer I-III-VI2. With reference to FIG. 6 illustrating a method of this type, a pair of rollers R1, R2 tend to a flexible substrate SUB (for example metal) on which is deposited a precursor intended to undergo a treatment sequence S1, S2, S3, in running in front of corresponding injectors, with: the treatment S1 corresponding to a reducing heat treatment, the treatment S2 corresponding to a crystallization of the precursor, with an insertion of the reactive element into the crystal, and the treatment S3 corresponding to a tempering at low temperature.

The surface to be treated thus undergoes a reducing annealing S1, then moves for the treatment S2 which can be carried out according to two embodiments which are different from each other: the reactive element can be provided by a carrier gas; it can then condense on the surface of the precursor (in the form of a surface layer); then a hot neutral gas is propelled to crystallize and integrate the reactive element to the precursor, according to a selenization and / or sulfidation reaction above; or the hot gas is propelled and the partial pressure of the reactive element is controlled via control of the sublimation temperature, to remain in the vapor phase and react directly, in this state, with the precursor.

However, the temperature of the reactive element projected by the carrier gas on the precursor depends on: the temperature of the mixture of the reactive element in the carrier gas (and therefore of the temperature of the carrier gas itself); the gaseous mixture injected onto the substrate, and the distance between the injection pipe of the mixture and the surface of the SUB substrate receiving the gaseous mixture.

Thus, it is possible to control the choice of one or the other of the embodiments above, by controlling the following parameters: the temperature of the carrier gas in particular (since the temperature of the reactive element before mixing the carrier gas is fixed by the sublimation temperature), the flow rate of the gaseous mixture injected onto the substrate, and the distance between the injector and the substrate.

If the injection temperature of the reactive element is lower than the selenization reaction or sulfuration reaction temperature, the reactive element condenses in solid phase on the precursor and the injection of a hot gas then initiates the reaction. selenization or sulphidation.

On the other hand, if the injection temperature of the reactive element is greater than or close to the selenization or sulphurization temperature Tr, the reactive element is incorporated directly into the precursor gas phase during the selenization or sulphurization reaction. .

Finally, the quenching treatment S3 can be carried out on the surface of the crystal obtained by passing a gas at ambient temperature (around 20 ° C.) without passing through a hot chamber. Preferably, it is a neutral gas with good heat transfer properties. It may be the same for the carrier gas itself.

The sequences of temperature variations applied to the substrate of FIG. 6 are shown in FIG.

The thermal treatment sequence of the proposed substrate is as follows: the origin of the times corresponds to the moment when the substrate is positioned under the injector for the treatment S1, at a temperature T1; the substrate undergoes a rise in temperature from T1 to T3 for a time t1, followed by a plateau at temperature T3 for a period of time (t2-t1); the heat treatment is done under a reducing carrier gas (hydrogen for example); between times t2 and t3, the substrate passes through the rollers to undergo treatment S2 and cools from temperature T3 to temperature T2; - Next, a reactive heat treatment is applied thereto: a rise in temperature (T2 to T4) is applied for a period (t4-t3), followed by a plateau at the temperature T4 for a period (t5-t4); this heat treatment is accompanied, in the example shown, a supply of reactive element (s) in the vapor phase on the surface of the precursor; between times t5 and t6, the substrate then passes (which causes a cooling of the temperature T4 to the temperature T3), to finally undergo the quenching treatment S3 of the temperature T3 at the temperature Tl for a period of time (t7- t6).

It will thus be understood that the process according to the invention may advantageously comprise a succession of stages of injection of successive reactive elements, thus defining a temporal profile of treatment of the precursor such as that illustrated by way of example in FIG. .

A variant of the device shown in FIG. 6 will now be described with reference to FIG. 8. Another approach consists in bringing the substrate under the gas projection duct and then sequentially applying the different treatments to it from the same duct. The supply of neutral gas carries the reference 51. The inlet of reducing gas is designated 54. There is furthermore a channel 55 for supplying a gas at ambient temperature for quenching, as well as a first valve. 52 three-way, and a second valve 53 three-way.

Thus, the SUB substrate to be treated has only one displacement to undergo to receive the different heat treatments. Indeed, by the action of the rollers R1, R2, the SUB substrate is placed under the main conduit 56. The reducing gas (channel 54) is oriented by the valve 53 to pass through a hot chamber 57 and reduce the precursor. When the reduction is complete, the valve 53 is closed. The neutral gas (channel 51) comprising the reactive element is then directed towards the hot chamber 57 via the valves 52 and 53.

For example, for the selenization of the Cu-In precursor (to obtain the crystalline alloy CulnSe2), it is observed that a temperature of about 450 ° C. is usually required, whereas the selenization of the Cu-Ga precursor (for obtaining the Crystalline alloy CuGaSe2) requires a temperature of the order of 550 ° C.

Thus, to control the temperature of the substrate SUB and to promote the crystallization reaction (generally between 400 and 700 ° C., as a function of the alloy composition), it is of course possible to control the temperature of the neutral gas in the enclosure upstream. heating 57 before its injection, but also two parameters related to its injection: - its flow at the outlet of the conduit 56, and - the distance between the outlet pipe of the conduit 56 and the substrate surface SUB.

The precursor can then crystallize, with the added reactive element, according to the two modes described above: condensation and reaction, or reaction at controlled gas pressure.

When the crystallization is complete, the valve 53 interrupts the arrival of the hot gas. The latter can pass directly through the channels 51 and 55, without being heated to apply quenching to the crystal obtained on the substrate SUB. It should be noted that in the known processes, such cooling is not proposed between the heat treatments because of the heat transfer times, in particular because of the delay between two treatments.

Of course, the displacement of the SUB substrate relative to the main conduit 56 is "relative" in the broad sense. Thus, the conduit 56 may comprise a flared tubing to cover the entire width of the substrate (in a direction parallel to the axes of the rollers R1, R2), the substrate simply moving in translation between the two rollers.

Alternatively, the conduit 56 may comprise a nozzle movable at different points on the surface of the substrate SUB, to apply the heat treatment locally, to cover the entire surface of the substrate.

The present invention finds many applications. The precursor may be deposited on a metal strip or a flexible polymer, as possible substrates, in scrolling driven by the rollers R1, R2, motorized. In this case, the substrate can be wound on one roll and unwind from the other roll. However, in one possible variant, the precursor may be deposited on a molybdenum-coated glass substrate. In this variant, the SUB substrate is deposited flat between the rollers and conveyed by a "rolling" belt driven by the movement of the rollers.

It is possible to use injection tubing as well as hot air guns with propulsion of reactive elements. It is also possible to use pistols of this type to anneal precursors originating from an earlier stage of manufacture (from electrolysis, sputtering or sputtering, or from liquid ink printing techniques comprising the elements of the precursor ), in the presence or absence of reagents.

In addition, crucibles have been described above to heat (typically Joule effect) the reactive elements they contain. Nevertheless, variants are possible. For example, it is possible to provide the reactive elements in the form of targets heated by laser firing or by plasmas. Moreover, the reactive element can be in the solid phase before its heating or in the liquid phase, the thermodynamic equilibrium between one of these phases and the vapor phase being reached by controlled heating of the reactive element.

The invention naturally has applications in the manufacture of solar panels with photovoltaic properties using a rapid annealing process for the synthesis of a photovoltaic light absorber based on Cu, Ag, In, Ga, Zn, Sn, Al, Se, Te, S, P the process in the sense of the invention is particularly well suited for the manufacture of such materials, and low cost of implementation, while increasing their production rate.

Moreover, the present invention is not limited to the embodiments described above by way of example; For example, there has been described above a possible application to the selenization (or sulfidation) of precursors type I-III. In this embodiment, the precursor is therefore a thin layer of alloy of elements of columns I and III of the periodic table, and the reactive element comprises at least one element of column VI for the production of alloys. photovoltaic properties of type I-III-VI2.

However, in a possible variant embodiment, the precursor may be in the form of a thin layer of alloy of elements of columns I, II and IV of the periodic table, for the production of alloys with photovoltaic properties of type I2-II-IV-VI4 (such as for example Cu2ZnSn (SXSei_X) 4), and the reactive element comprises at least one element of column VI (S or Se).

More generally, the invention may be applied in a context other than selenization or sulphurization, for example for the manufacture of alloys with photovoltaic properties of type II-IV-V. In this case, the precursor is a thin layer of alloy of elements of columns II and IV of the periodic table. The reactive element comprises at least one element of column V, for example phosphorus P for obtaining the ZnSnP alloy.

Claims (19)

REVENDICATIONS1. Process for conveying a reactive gas on a precursor, characterized in that it comprises the steps of: a) heating (14, 13, 12) at least one reactive element until at least a part of the element is obtained vapor phase reagent, b) circulating (11) a carrier gas in the vapor phase reactive element to drive the vapor phase reactive element into the carrier gas, and c) injecting the carrier gas comprising the reactive element. in the vapor phase on a precursor (SUB), and in that, in step a), a heating temperature of the reactive element is controlled (14, V) to control in quantity the reactive element in the carrier gas in step b). 2. Method according to claim 1, characterized in that step a) comprises, via a control of the heating temperature, a control of the saturated vapor pressure of the reactive element, a thermodynamic equilibrium comprising the vapor phase. of the reactive element. 3. Method according to claim 2, characterized in that the control of the saturated vapor pressure is conducted to control the partial pressure of the reactive element in the carrier gas in step b). 4. Method according to one of the preceding claims, characterized in that step a) comprises a temperature control of a support (12; 21, 22, 23) of the reactive element to control the amount of element reactant in the carrier gas in step b). 5. Method according to claim 4, characterized in that said support is an electrically conductive crucible (12; 21, 22, 23), heated by circulation in the crucible of a current of adjustable intensity to control the temperature of the crucible, and thence the amount of reactive element in the carrier gas in step b). 20 6. Method according to one of the preceding claims, characterized in that step b) comprises a mixture of the reactive element in the vapor phase with the carrier gas, by disturbance (15) of flow of the carrier gas and the reactive element in the vapor phase. 7. Method according to one of the preceding claims, characterized in that it further comprises a step d) of injection of a hot gas (S2) to promote a reaction of the reactive element with the precursor. 8. Method according to one of claims 1 to 6, characterized in that the reactive element reacts with the precursor vapor phase in step c). 9. Method according to one of the preceding claims, characterized in that the temperature of the reactive element injected on the precursor, to control the reaction temperature with the precursor, is controlled according to: - the temperature of the carrier gas, the flow rate of the mixture of the reactive element in the vapor phase with the carrier gas, and the distance between the precursor and an injection pipe of the mixture on the precursor. 10. Method according to one of the preceding claims, characterized in that it comprises a cooling step according to a quenching effect (S3), after the reaction of the reactive element with the precursor, by injection of a cold gas . 11. Method according to one of the preceding claims, characterized in that the precursor is a thin layer of alloy of elements of columns I and III of the periodic table, and in that the reactive element comprises at least one element. of column VI for the manufacture of alloys with photovoltaic properties of type I-III-VI2. 12. The method of claim 11, characterized in that it comprises a preliminary step (S l) reducing annealing of the alloy I-III. 13. Method according to one of claims 1 to 10, characterized in that the precursor is a thin layer of alloy elements of columns II and IV of the periodic table, and in that the reactive element comprises at least a column V element for the manufacture of alloy with photovoltaic properties of type II-IV-V. 14. Method according to one of claims 1 to 10, characterized in that the precursor is a thin layer of alloy elements of columns I, II and IV of the periodic table, and in that the reactive element comprises at least one element of column 10 VI for the manufacture of alloy with photovoltaic properties of type I2-II-IV-V14. 15. Method according to one of the preceding claims, characterized in that the carrier gas is heated to a controlled temperature of a few hundred degrees Celsius. 15 16. Method according to one of the preceding claims, characterized in that the reactive element comprises a mixture of a plurality of reactive elements (21, 22, 23), driven by the carrier gas to react together. 17. The method as claimed in claim 16, characterized in that it comprises a succession of stages of injection of successive reactive elements defining a temporal profile of treatment of the precursor. 18. Method according to one of claims 16 and 17, taken in combination with claim 11, characterized in that said plurality of reactive elements comprises elements of columns I and III and forms a thin layer of said precursor, corresponding to an I-III alloy, on a substrate. 19. Installation for carrying out the method according to one of the preceding claims, characterized in that it comprises: - means (R1, R2) carrying a precursor (SUB), - heating means (12, 13) at least one reactive element for supplying at least a portion of the vapor phase reactive element; means for circulating (11,15) a carrier gas in the vapor phase reactive element and driving the vapor phase reactive element in the carrier gas, and for injecting the vector gas comprising the vapor phase reactive element onto the precursor (SUB), and in that the installation comprises control means (V, 14) of said heating means for controlling in quantity the reactive element in the carrier gas injected into the reaction vessel.