DE10208911A1 - Process for depositing material from supply vessel comprises positioning the substrate and supply material in stack, introducing inert gas and reaction gas, expanding the gas flows, stopping the deposition, and cooling the substrate - Google Patents

Abstract

Process for depositing material from a supply vessel comprises positioning substrate and supply material in a stack at short distance from each other before heating reaction chamber, feeding inert gas and reaction gas directly into reaction volume between supply material and substrate at elevated speed, expanding gas flows before reaching supply material to reduce gas flow speed, stopping deposition by switching inert gas and/or adjusting temperature gradient, and cooling substrate and supply material. An Independent claim is also included for a device for carrying out the deposition process, comprising: a unit for positioning the substrate (2) and the supply material (1) in a stack; a reactor (R) having an opening for the gas inlet (4) in the reactor chamber; units for expanding the gas stream; regulating units for separately regulating the supply material and substrate; heating units; and cooling units. Preferred Features: The supply material is chalcopyrites, II-VI or III-V compounds, transition chalcogenides, silicon or germanium, preferably in solid or liquid form. The substrate is made from glass, quartz, ceramic, silicon or other semiconductor material.

Description

The invention relates to a method for separating material from a supply, which is converted into gaseous intermediate products via the reaction with a halogen-containing reaction gas and is deposited on a substrate in the reaction space (chemical gas phase transport), the reaction space with stock material and substrate arranged therein under one The inert gas stream is heated and a temperature gradient between the stock material and the substrate is set such that T _substrate <T _stock , the inert gas stream through a gas stream of carrier gas and halogen-containing gas or halogen-containing gas mixture (reaction gas) for converting the stock material into gaseous compounds and transporting them to the substrate replaced, the deposition ended and the coated substrate is cooled, and an arrangement for performing the method.

Such a method is known from DE 198 55 021 C1, in which the Deposition of semiconductor material from a supply via gaseous ones Halogen compounds are described as intermediates on a substrate. The method mentioned is carried out in an open system in which The stock and substrate can be shifted against each other vertically and horizontally have to. During the deposition, the stock and substrate are in short distance from each other, what is called Close-Spaced Vapor Transport (CVST) is called. The disadvantage of this method is that which is necessary Moving stock and substrate against each other, which is mechanical is difficult to solve because all materials used in the reaction space must be resistant to halogen-containing transport gas and not too may lead to contamination of the semiconductor material. Furthermore must the reactor in the arrangement described completely with halogen Filling transport gas, that means filling one essential larger volume than the reaction volume between the stock and the substrate, in which the transport of the semiconductor material takes place. Therefore, one much larger amount of transport gas is required than for the actual one Transport of the materials to be deposited would be necessary. The disadvantage is likewise the use of two separate heating devices for stock and Substrate with no possibility of cooling one or both sides, thereby insufficient temperature control necessary for process control of is of great relevance. The separation of Compound semiconductors are made in the manner specified in DE 198 55 021 C1 Process - as already mentioned - from a single stock. A congruent one Volatilization in the reaction with the halogen-containing transport agent can however, not set for all compound semiconductors, which is adversely affects the material efficiency of the process.

The CSVT process described in DE 198 55 021 C1 in the open system is based on a process in the closed system for producing chalcopyrite compounds, which is described in Thin Solid Films 226 ( 1993 ) pp. 254-258 "Close-spaced vapor transport of CuInSe ₂ , CuGaSe ₂ and Cu (Ga, In) Se ₂ ", G. Masse and K. Djessas. The process described here takes place in a closed reaction space, the coating of a substrate with a semiconductor material from a supply of the compound semiconductors likewise taking place via gaseous intermediate products. The process is used at low pressures (10 ^-5 mbar) using iodine as a means of transport. Due to the arrangement in the closed volume, the possibilities for process control are limited because a reaction equilibrium is established. It can therefore not be guaranteed that all required chemical reactions will proceed in the desired direction. To make matters worse, in the arrangement described, only the supply is heated and the temperature difference between supply and substrate can only be regulated to a limited extent by the distance between the two, which is particularly disadvantageous since the distance between supply and substrate is used to transport the gaseous Intermediate products decisively influenced. With the help of the one-step process described for the production of chalcopyrite compounds, congruent volatilization of the starting materials used cannot be achieved here either.

A CSVT process in the open system is from J. Electrochem. Soc .: Solid State Science 116 ( 6 ) ( 1969 ), pp. 843-847 "The Epitaxy of ZnSe on Ge, GaAs and ZnSe by an HCl Close-Spaced Transport Process" HJ Hovel and AG Milnes. In contrast to the one-step process mentioned above, the process here takes place at pressures in the range of atmospheric pressure. Both the supply and the substrate are heated by separate IR lamps in the arrangement used by Hovel and Milnes. An H ₂ / HCl mixture is used as the means of transport, the HCl content being at most 0.2%. Temperatures above 600 ° C are therefore required to achieve high growth rates. Similar to the arrangement described in DE 198 55 021 C1, the reactor volume is a multiple of the reaction volume, so that a large part of the transport gas is flushed into the gas outlet of the reactor unused. In addition, the possibilities for temperature control are limited because no cooling device is provided. The congruent volatilization of compound semiconductors is not dealt with in the publication by Hovel and Milnes. For this reason, the method described is not suitable for the rapid deposition of chalcopyrites with the greatest possible material efficiency.

In US 5 769 942 a method and described several devices for the deposition of semiconductor material. The method involves heating the reaction space Positioning of the substrate and the stock material, the initiation of a halogen-containing gas mixture for transporting the semiconductor material, the Deposition of the material, the termination of the deposition, and that Cooling the coated substrate. With epitaxial coating silicon is applied to silicon. The device comprises one Positioning device, heaters for both substrate holder and for the stock material and a gas mixing system. The one mentioned in the Devices described using iodine as halogen, also contain a heatable halogen source. The procedure describes an epitaxial process in which the source material and the substrate material consist of the same semiconductor material. The structure of the devices is described in general terms in US Pat. No. 5,769,942, without concrete Descriptions for realizing such devices are given. The reactor volume is also in the arrangements shown Multiple of the reaction volume, so that the transport gas only very is used inefficiently, which is particularly important for you large-scale industrial process is disadvantageous. Even at this stand the technology, no cooling device is provided, which the possibilities for Temperature control in turn restricted. Likewise, there are no measures provided that the source material is deposited on the cold Prevent walls of the reaction space. By back diffusing the halogen Supply connections can also lead to deposits in the gas supply line come to the reactor, which leads to a blockage of the line. By the direct flow of the supply with the carrier gas is the use of powdered stock material not possible, and the removal of the Stock material is inhomogeneous. There is also a control of the expiring chemical reactions only possible to a limited extent and a desired one congruent volatilization of the supply material is not guaranteed.

Knowing the state of the art, it is therefore the task the invention, an easy to use and industrial use Specify the process by which materials are placed using CSVT (a close-spaced Vapor Transport's - chemical gas phase transport) from a solid or liquid stock through the reaction with a halogen-containing Reaction gas converted into gaseous intermediates and then about the back reaction on a substrate of any shape and size be deposited, the high growth rates with minimal consumption and congruent volatilization of the stock material and - compared to the State of the art - with a reduced amount of halogen Means of transport enables, as well as a simple, robust and highly scalable Order to carry out the method. The litigation must to be precisely controllable to ensure high reproducibility.

The object is achieved according to the invention by a method of the type mentioned at the outset in that, before the reaction space is heated up, the substrate and the supply material are first positioned in a stack at a short distance from one another, inert gas and reaction gas are passed directly into the reaction volume between the supply material and the substrate at an increased speed and before When the supply material is reached, these gas flows are expanded to reduce the gas flow rate, the deposition is ended by switching to inert gas and / or setting a reversed temperature gradient with T _substrate > T _supply , and finally the substrate and supply material are cooled, the temperature gradient between substrate and supply being precise is regulated.

A mixture is also used as the reaction gas in the solution according to the invention understood from carrier gas and halogen-containing gas.

Chalcopyrites, II-VI or III-V compounds, transition chalcogenides (e.g. WS ₂ ) or silicon or germanium in the solid state, as powder, pressed powder or polycrystalline blocks, or in the liquid state are used as stock materials to be applied.

Glass, quartz, ceramic or silicon or others are used as substrates Semiconductor materials (e.g. GaAs), coated or uncoated, are used.

The small fixed distance between substrate and stock material is between 0.1 mm and 100 mm set.

Nitrogen (N ₂ ) or noble gases (e.g. Ar, He) are used as inert gases.

The possible temperature range for the deposition of semiconductor material is between room temperature and 1200 ° C with pressure values in the range between 5 mbar and low atmospheric pressures.

A mixture of hydrogen, nitrogen or forming gas (N ₂ + H ₂ or Ar + H ₂ each with Ar) with the halogens chlorine or bromine or iodine or their gaseous compounds, in particular their hydrogen compounds, is used as the reaction gas.

Several different ones are used to manufacture heterostructures Semiconductor materials are sequentially deposited one after the other. Here, however, a suitable choice of process parameters (e.g. Temperature, pressure) a reaction between the individual To prevent semiconductor layers.

For the deposition of compound semiconductors on the substrate are used as Stock material sub-components of the to be separated Compound semiconductor used, which are deposited and successively the compound semiconductor are implemented, with all sub-components in the sum contain the components of the compound semiconductor. The Implementation of the deposited from subcomponents on the substrate Materials for the compound semiconductor can be suitable Process conditions during or in a targeted tempering step its deposition will be implemented.

The deposition of subcomponents of a compound semiconductor can be done in this way Repeated often until, for example, the desired thickness is reached.

To end the deposition of the semiconductor materials can additionally from Reaction gas can be switched to inert gas.

As already mentioned, in the method according to the invention, inert or reaction gas directly into the reaction volume between the stock and Substrate initiated, first at increased speed and before reaching of the stock material with a reduced gas flow rate, resulting in a homogeneous removal of the stock material is guaranteed and Turbulence when using powdery sources can be avoided.

To improve the homogeneity of the coating of the substrate is in In one embodiment, the substrate or supply material rotates become.

The method according to the invention also enables use different materials for substrate and stock, is not up Epitaxial processes are restricted and work even at lower temperatures compared to epitaxial processes. In addition, the invention The method is not limited to wafers, but with substrates as desired Size and shape applicable. This is the prerequisite for Use of inexpensive substrate materials, such as glass, for the large-scale industrial mass production.

The arrangement for performing the method, one from the outside heatable reactor with substrate and stock material therein, a halogen source located outside the reactor, a controllable one Gas mixing system for the optional flow of inert gas or Reaction gas and separate temperature controls for that Inventory material and the substrate has, according to the invention means for fixed stacked positioning of substrate and stock material in close to each other, the gas inlet to the reaction volume has a narrowed opening in comparison to the supplying gas line in the Reaction volume on, in the direction of the gas flow are before Storage material means for expanding the gas flow and the separate temperature controls for the stock material and the substrate have both heating and cooling means.

The quasi-closed reaction volume is in the invention Solution formed by the volume between the substrate and the stock material, which are "stacked" one above the other. The reaction gas is also in The following is a mixture of carrier gas and halogen-containing gas.

The pressure in the reactor is via a vacuum pump with butterfly valve continuously adjustable. The gases discharged from the reactor are a downstream gas cleaning supplied.

For the optional flow of inert gas or halogen-containing Reaction gas through the reactor is a gas mixing system outside of the Reactor provided. The required gas quantities are set in Gas mixing system via mass flow controller. The different gases can can be switched with pneumatic valves.

To avoid back diffusion and thus deposits in the As already mentioned, gas is supplied through a gas supply narrowed opening to the quasi-closed reaction volume between Supply and substrate, which increases the gas flow rate. In front When the supply is reached, the gas flow is expanded and over a stage passed, which is a decrease in gas flow rate as well as a Swirling of the gas flow. To be parasitic here too Preventing deposition of semiconductor material is the stage in direct thermal contact with the storage material container.

The temperature is controlled via two separately controllable IR Lamp systems for the stock material and the substrate and two also separately controllable convection cooling for the supply and that Substrate, which are implemented by an external gas flow.

The invention provides a solution for efficient, fast and large-scale Deposition of semiconductor material from a stock material, which about the reaction with a halogen-containing reaction gas in gaseous Intermediates is transferred. With low material consumption high growth rates realized. The arrangement can be simple, robust and can be scaled up.

In comparison to the prior art is in the solution according to the invention no mechanical shifting in the reaction space is necessary anymore to realize a stable temperature gradient, because by means of two separate cooling and two separate IR heaters are precise Regulation of the temperature gradient. With the help of these temperature controls and the setting of a defined gas flow in the reaction volume there is a homogeneous natural gas flow from the stock material to the substrate a, which ensures a large-scale homogeneity of the deposited materials is achieved.

The regulation of the gas flow rate, initially an increase the same through a narrowed opening, whereby a back diffusion of Prevented stock material molecules at the gas inlet to the reaction volume and then a decrease in gas velocity between Gas inlet and reaction volume by expanding the gas flow, can - as described - be realized with simple means.

Due to the stacked arrangement of stock material and substrate, the in one embodiment of thermally insulating spacers in short distance are firmly positioned, a minimum quasi-closed volume (reaction volume) in the open system (reactor) generated. An additional valve at the reactor inlet enables the change from an open to a closed system. In the minimal quasi-closed reaction volume is also only a small amount of halogen-containing reaction gas directly into this reaction volume is needed.

The reactor space can be cheap and can be manufactured in any form Graphite and quartz parts to be made. The storage container is for the Recording of solid or liquid stock material is formed and has Means for the quick and reproducible exchange of stock materials on. The solid or liquid starting materials for the stock material can into a graphite boat that can be enlarged as required. The Substrates used are not limited to specific shapes and sizes limited.

As a means for heating the substrate and the stock material is one Lamp heater used. The means of cooling is as convection cooling formed by means of gaseous or liquid media.

In one embodiment of the invention, means for rotating the Substrate or the stock material provided for a better To ensure homogeneity of the coating of the substrate.

The solution according to the invention enables rapid separation and a congruent volatilization of the stock material because Compound semiconductors in sequential steps from sub-components can be separated because this gives better control of the chemical reactions is possible.

The invention is illustrated in the following embodiment with reference to Drawings explained in more detail.

Show

Fig. 1 shows schematically an arrangement according to the invention in cross-section,

Fig. 2 shows schematically the gas flow at the inlet of the arrangement and its expansion in the arrangement.

The solution according to the invention is explained using the example of coating a glass substrate with a polycrystalline CuGaSe ₂ film.

The deposition of the ternary compound CuGaSe ₂ is divided into two steps. In the first step, the subcomponent Cu _x Se _y is first deposited. Powdery Cu _x Se _{y is} used as stock material 1 . In a second step, powdery Ga _x Se _{y is used} as a further component of the compound semiconductor CuGaSe ₂ as a stock material 1 . For this purpose, a graphite storage container 7 can be replaced . The partial component Cu _x Se _y , which is deposited on the substrate 1 in the first step, converts to CuGaSe ₂ during or after the second step, in which Ga _x Se _{y is used} as stock material 1 . The basic procedure for separating the sub-components is explained below.

Storage material 1 and substrate 2 are introduced into the reactor R and firmly positioned at a small distance (for example 5 mm) from one another by means of spacers 13 , 14 made of quartz. The poor thermal conductivity of the quartz ensures the necessary thermal decoupling of supply material 1 and substrate 2 . Now supply material 1 and substrate 2 are initially _regulated to the desired temperature of T _supply = 550 ° C. and T _substrate = 500 ° C. at a reactor pressure of 100 mbar in order to carry out the first step. The heating process takes place under an inert gas stream (N ₂ ), which is passed via a gas mixing system (not shown) via the gas inlet 4 into the reaction volume 3 , which is formed by the two spacers 13 , 14 , semiconductor material 1 and substrate 3 . Between the gas inlet 4 , which has a narrowed opening, and the reaction volume 3 in the reactor R, the gas stream is passed through a columnar volume between a holder 6 made of quartz for the graphite storage container 7 , thereby expanding the gas stream and thus reducing the gas flow rate is effected. The guidance of the gas flow is shown schematically in FIG. 2.

To generate a closed volume in the meantime, there is the possibility of interrupting the gas supply directly at the inlet of the reactor R by means of a pneumatic valve 5 positioned there.

For the heating of powdery Cu _x Se _y as storage material 1 , which is introduced into a graphite storage container 7 , IR lamps 9 , which are arranged outside the reactor R, for example in a ring, are used. In order to regulate the desired temperature difference to the substrate, a second IR lamp system 10 is used, which is in thermal contact with the substrate 2 via a graphite block 8 . Furthermore, two continuously controllable cooling gas flows 11 , 12 are available for the temperature control, which can dissipate radiant heat separately in the area of the substrate 2 and / or in the area of the storage container 1 . As a result, stable and far larger temperature gradients can be set even with the smallest distance between substrate 2 and stock material 1 than in the case of a device without a cooling option. This is particularly important for achieving high growth rates, as these are strongly influenced by distance and temperature gradient.

The pressure in the quartz reactor R can be regulated continuously by means of a vacuum pump (not shown) and a pressure regulator consisting of a control unit, pressure sensor and butterfly valve. The reaction gases led out of the gas outlet 15 are fed to a gas cleaning device (not shown).

After reaching a stable temperature difference between stock material 1 and substrate 2 , the _{stock material is converted} into gaseous compounds by replacing the inert gas stream with a gas stream of halogen-containing reaction gas by reacting the _{stock material} at T _supply with the halogen-containing reaction gas.

The back reaction of the gaseous intermediate products to solid subcomponents of the semiconductor to be grown takes place on the substrate at a temperature T _substrate which is less than T _supply .

The gas flow is switched off to abruptly end the deposition halogenated transport gas switched back to inert gas flow and if necessary, the temperature gradient reversed.

The cooling of stock material 1 and substrate 2 takes place under an inert gas stream, the temperature difference between substrate 2 and stock material 1 being able to be precisely regulated via the IR lamp systems 9 , 10 and the cooling gas streams 11 , 12 .

Claims (20)

1. A method for separating material from a supply, which is converted into gaseous intermediate products via the reaction with a halogen-containing reaction gas and is deposited on a substrate in the reaction space, the reaction space with the stock material and substrate arranged therein being heated under an inert gas stream and a temperature gradient between The stock material and substrate is set such that T _substrate <T _stock , the inert gas stream is replaced by a gas stream of carrier gas and halogen-containing gas or halogen-containing gas mixture for converting the stock material into gaseous compounds and transporting them to the substrate, and the deposition is ended and the coating is finished Substrate is cooled, characterized in that
Before the reaction space is heated up, the substrate and the stock material are first firmly positioned in a stack at a short distance from one another,
Inert gas and reaction gas are passed directly into the reaction volume between the stock material and substrate at an increased rate and these gas streams are expanded to reduce the gas flow rate before the stock material is reached,
the deposition is ended by switching to inert gas and / or setting a reverse temperature gradient with T _substrate > T _device and
finally, the substrate and the stock material are cooled, the temperature gradient between the substrate and the stock material being precisely regulated. 2. The method according to claim 1, characterized in that Chalcopyrites, II-VI- or III-V- as deposit materials to be deposited Compounds, transition chalcogenides or silicon or germanium be used. 3. The method according to claim 2, characterized in that the stock materials are used in solid or liquid state. 4. The method according to claim 3, characterized in that the stock materials in the solid state as powder, pressed powder or polycrystalline blocks can be used. 5. The method according to claim 1, characterized in that as substrate glass, quartz, ceramic or silicon or others Semiconductor materials, coated or uncoated, are used. 6. The method according to claim 1, characterized in that the small fixed distance between substrate and stock material between 0.1 mm and 100 mm is set. 7. The method according to claim 1, characterized in that the reaction gas is a mixture of hydrogen, nitrogen or forming gas (N ₂ + H ₂ or Ar + H ₂ each with Ar) with the halogens chlorine or bromine or iodine or their gaseous compounds , in particular their hydrogen compounds, is used. 8. The method according to claim 1 and 2, characterized in that for the production of heterostructures several different ones Semiconductor materials are sequentially deposited one after the other become. 9. The method according to claim 1 and 2, characterized in that for the deposition of compound semiconductors on the substrate as Stock material sub-components of the to be separated Compound semiconductors are used, which are deposited one after the other and implemented to the compound semiconductor. 10. The method according to claim 9, characterized in that the material deposited from subcomponents on the substrate during its deposition to the compound semiconductor is implemented. 11. The method according to claim 10, characterized in that the material deposited from subcomponents on the substrate its deposition in a tempering step to the compound semiconductor is implemented. 12. The method according to any one of claims 9 to 11, characterized in that the deposition of subcomponents of a compound semiconductor is repeated. 13. The method according to claim 1, characterized in that to end the separation additionally from reaction gas to inert gas is switched. 14. The method according to claim 1, characterized in that the substrate or the stock material rotates during the deposition become. 15. Arrangement for performing the method according to claim 1 to 14, which has an externally heated reactor with a substrate and stock material therein, a halogen source arranged outside the reactor, a controllable gas mixing system for the optional inlet of inert gas or reaction gas into the reactor space and each separate Has temperature controls for the stock material and the substrate, characterized in that
Means for the fixed stack-like positioning of substrate ( 2 ) and storage material ( 1 ) are provided at a short distance from one another,
the reactor (R) has an opening for the gas inlet ( 4 ) into the reactor space which is narrowed in comparison to the gas feed line,
means for expanding the gas flow are provided in the gas flow direction upstream of the stock material ( 1 ),
the separate temperature controls for the stock material ( 1 ) and the substrate ( 2 ) have both heating and cooling means. 16. The arrangement according to claim 15, characterized in that the storage container ( 7 ) is designed to hold liquid and solid storage materials ( 1 ). 17. The arrangement according to claim 15, characterized in that the means for the fixed stack-shaped positioning of the substrate ( 2 ) and the stock material ( 1 ) at a short distance from each other are thermally insulating spacers ( 13 , 14 ). 18. The arrangement according to claim 15, characterized in that the stock material ( 1 ) is arranged in the reactor (R) in a container ( 7 ) which has means for the rapid and reproducible exchange of the stock materials. 19. The arrangement according to claim 15, characterized in that the means for heating the substrate ( 2 ) and the stock material ( 1 ) is a lamp heater ( 9 , 10 ) or a resistance heater. 20. Arrangement according to claim 15, characterized in that the means for cooling as convection cooling by means of gaseous or liquid media is formed.