DE102009059193A1 - Plant and method for doping semiconductor materials - Google Patents

Abstract

The invention relates to a system and a method for doping substrates with laser, wherein in the method at least one dopant is in contact with the substrate surface and a local heating of the substrate surface by a laser beam. It is the object of the present invention to provide a laser doping process that allows substrates to be doped at high speed, thereby producing a low dislocation density at the substrate surface, achieving good electrical activation of dopants, and moreover providing the option of certain Doping areas targeted higher. This object is achieved by a system for doping substrates with laser, wherein the system has at least one fiber laser with a laser beam with a circular beam cross section and a scanner unit, through which the substrate surface can be latched with a laser beam. The object is further achieved by a method for doping substrates in which at least one dopant is in contact with the substrate surface and a local heating of the substrate surface by a laser beam, wherein a fiber laser with a laser beam with a circular beam cross-section generates, which with a scanner unit is guided over the substrate surface.

Description

The invention relates to a system and a method for doping substrates with laser, wherein in the method at least one dopant is in contact with the substrate surface and a local heating of the substrate surface by a laser beam.

Plants of the type mentioned are usually in industrial practice batch ovens or continuous doping systems in which the solar cell substrates are heated to required for dopant diffusion temperatures of more than 800 ° C. In the doping of the emitter of solar cells, as for example in the document DE 10 2007 035 068 partially contradictory requirements for the doping. In the optically open regions, the doping must not be too high, since very high doping atom concentrations favor the recombination of electron-hole pairs and thus stand in the way of a desired high efficiency of the solar cells. On the other hand, a very high doping is particularly necessary in the contact region of terminal electrodes for the production of a required ohmic contact. The contrary requirements have recently led, especially in laboratory samples, to the realization of more heavily doped areas in the contact areas and the so-called selective emitters. The preparation of these selective emitters often requires an uneconomically high cost when realized with conventional methods.

In recent years, laser systems for doping semiconductors have also been developed. In the publication DE 10 2004 036 220 B4 Laser doping processes are described as a replacement for conventional furnace doping processes, the main advantage of which is that the processing time and process logistics are more favorable than in furnace processes and that the energy efficiency in laser processes is better. However, the methods described in this document generally have the problem that the laser-doped substrates have high dislocation densities and low quality.

The document solves the problem of high dislocation density after surface melting and recrystallization by focusing the laser beam into a line having a width of 10 μm and a length of 100 μm and scanning this line focus on the surface of the substrate. The disadvantages of this method are the low processing speed and the technical complexity for realizing a reliable autofocus system. The desired characteristics for the doping are based on the characteristics of the dopants, which are produced in furnace processes. That is, the depth of the doping is a range up to a micrometer is desired. From the known depth of penetration of light into silicon as a function of the wavelength, it is concluded that laser radiation having a wavelength of 600 nm or less must be used.

Batch systems for doping are currently standard in silicon solar cell production. Disadvantages are a relatively long processing time on these systems and large mechanical dimensions. The controllable temperatures are limited to less than 1000 ° C, and the heating of the entire substrates poses the problem of introducing contaminants across the back of the substrate. Another problem with conventional doping methods is that although the dopants diffuse into the silicon crystal, they are largely not incorporated into lattice sites and are electrically activated.

It is the object of the present invention to provide a laser doping process which allows substrates to be doped at high speed, thereby producing a low dislocation density at the substrate surface, achieving good electrical activation of dopants and, moreover, offering the option of to dope certain areas targeted higher.

This object is achieved by a plant of the abovementioned type, which has at least one fiber laser with a laser beam with a round beam cross section and a scanner unit, by means of which the substrate surface can be latched to the laser beam.

Fiber lasers are a recent development in the field of laser technology. These novel lasers are characterized by a very high performance and very high beam quality at the same time low price. Due to the high performance of this new laser class, it is possible to break new ground in the construction of laser doping systems.

The energy required for processing can now be provided not only locally in a focal point, but it can be used with a laser beam whose round beam cross-section dimensions of 20 to 500 microns and this cross-section is available in a comfortable beam length range of about 1 mm , The performance of these lasers is suitable for processing complete substrate surfaces of photovoltaic substrates.

In comparison of the energy efficiency of the laser doping system according to the invention with a conventional furnace doping system Laserdotieranlage invention is advantageous. In fiber lasers For example, the light beam is generated with high efficiency, and the light energy in the laser doping process is efficiently utilized because only the surface of the substrate and not the entire substrate is heated. The sparing of the substrate from thermal stress in the doping process also opens up new possibilities for the overall technology of the solar cells. Thus, unlike furnace doping, laser doping may occur in a later step in overall technology, where the substrate already has temperature sensitive elements. This advantage is particularly important in more complex technologies and, for example, in bifacial cell concepts. With Laserdotieranlagen more doping processes in sequence and on both surfaces of the substrates can be performed.

In comparison to conventional furnace doping systems not only the energy is used more efficiently but also the dopants are more efficiently fed to their task of semiconductor doping. The dopants are not incorporated undesirably at interstices on the surface, but they are installed by the higher temperatures advantageous and efficient on lattice sites. Because of the more efficient use, a smaller dopant application is sufficient.

For moving the laser beam over the substrate surface, it is also possible according to the invention to use suitable commercially available scanner units, which can move the beam with the necessary precision and speed. The speed of the scanners can be varied so that in addition to uniform processing over the entire surface, locally differentiated processing is also possible.

The laser process is very flexibly controllable, controllable and optimized, since both the scanner unit and the fiber laser itself are very flexible to operate. Due to the properties of the fiber laser and scanner unit system, the depth of the doped region in the substrate can be flexibly controlled. Doping profiles and electrical resistances are precisely adjustable. As a result, the use of laser doping systems according to the invention can lead to improved products, for example improved solar cells.

In addition to the advantages of the actual doping process, the use of laser doping also leads to further advantages on the edge of the processing. Since the substrate surface heats up very quickly by the impinging laser beam, no preheating phase and no cooling phase are necessary for the substrates. This makes a faster overall process possible. Furthermore, the laser doping system according to the invention can be realized with smaller spatial dimensions as a doping furnace. The space savings when using laser doping systems leads to a cost advantage in the construction of manufacturing facilities.

According to an advantageous embodiment of the invention, the laser doping system uses a fiber laser that emits light having a wavelength in the range of 750 to 3000 nm. Sophisticated fiber lasers exist in this wavelength range. For the processing of silicon substrates, however, this wavelength range initially seems to be unsuitable, since silicon is transparent in this area. However, due to the high power density in a fiber laser beam, the surface of the substrate is heated rapidly, with the effect of thermal accumulation of volume excitation. Due to the material heating, the optical properties of the substrate change. Silicon increases the absorption. This reduces the penetration depth. The penetration depth is even by setting suitable parameters such. As the power, the scanner speed, the pulse energy, the pulse duration or the repetition rate to a desired range adjustable. With a laser doping system in this wavelength range, silicon substrates can be doped deeper than with furnace processes. In the production of solar cells and especially the phosphorus doping of the emitter of solar cells, for example, doping depths in the range of 1 to 10 microns can be realized hereby. Due to the higher doping depth and at the same time homogeneous doping over the depth, the contacting and the overall efficiency of the solar cell can be improved.

An alternative laser doping system according to the invention for semiconductor substrates uses a fiber laser which emits light in a wavelength range of 500 to 600 nm. Fiber lasers in this wavelength range have only recently become commercially available. Systems operating in this shorter wavelength range are of particular interest for applications where low doping depth is desired.

In a preferred embodiment of the present invention, the fiber laser employed is a CW laser or a pulsed laser having relatively long pulse lengths in the range of 80 ns to 10 μs. Under these conditions, a doping of substrates is possible without superficially damaging their crystalline structure. Furthermore, the dopants are well incorporated into the substrate crystal and electrically activated. In continuous wave operation, particularly high powers of, for example, 5 kW are available. The use of continuous wave lasers is therefore particularly advantageous for rapid and cost-effective processing. In pulsed operation, only lower powers of, for example, 300 W are available. Advantages in pulse mode are additional available parameters. So For example, the pulse shape, the pulse duration, the repetition rate and the spatial pulse-to-pulse overlap can have a stronger influence on the dopant distribution.

In a favorable development of the invention, the system has a plurality of fiber lasers and / or at least one beam splitter for producing a plurality of laser partial beams while forming a multi-beam arrangement. The use of multiple lasers operating in parallel can be beneficial to increase plant throughput. Thus, a high-power laser beam whose entire power is not required in one beam can be separated into a plurality of laser sub-beams using the beam splitter, thereby enabling simultaneous processing of the substrate with a plurality of laser beams or partial laser beams, thereby enabling a higher processing speed.

In a specific embodiment of the present invention, the laser doping system uses a diffractive element for holographic beam splitting in 50 to 400 laser partial beams. This beam splitter is tuned to the respective task. For example, with such a split beam on solar cell substrates, a plurality of selective emitter fingers can be written. The beam splitter is preferably structurally adapted to the arrangement of the fingers. The contact electrode of a solar cell comprises not only the fingers but also main lines, so-called "bus bars", on which the charges of the individual fingers are collected. The selective emitter of solar cells is formed both in the areas of the individual fingers and in the areas of the "bus bars". The Laserdotierprozess is divided into several steps that serve the writing of the individual fingers and the "bus bars". The doping depth can be changed in the laser doping process, which can be used for example to form a deeper doping in individual steps in the production of a selective emitter.

In a further advantageous variant of the invention, the scanner unit has at least one fast scanner, which may be, for example, a galvo scanner, a polygon scanner and / or a resonance scanner. With such a fast scanner, a sufficiently high processing speed is possible on large-area substrates that meet the requirements of production. The selection of the scanner components depends on the laser used and on the planned laser beam movements. Standard values for currently achievable process speeds are 20 m / s when using pulsed lasers with repetition rates up to 1 MHz and 400 m / s when using continuous lasers.

In a favorable embodiment of the system for doping substrates, the scanner unit has a scanning region which extends over at least two substrates. If smaller substrates, such as wafers, are processed in the system and, for example, 7 × 8 wafers are processed on a substrate carrier, it is particularly favorable if the scanner unit has a scanning area which is as large as the substrate carrier, since in this case only a fiber laser and a scanner unit per system must be installed. However, the processing area can also be divided into two or more laser beams, each laser beam then having a scanning area which is smaller than the substrate carrier.

In a development, the system according to the invention has at least one positioning device for the substrates in the scanning region of the laser and / or at least one control device for the substrates. If the substrates are not only processed over the entire surface, but should undergo special processing locally defined, it is necessary that an exact positioning of the substrates takes place relative to the scanner unit. To ensure this high positioning accuracy in the laser doping system, a positioning device known from the prior art can either be integrated in the laser doping module, or the positioning device can be arranged in the transport direction in front of the laser doping module, in which case a transport system with exact substrate position transmission must be used.

Furthermore, in a favorable development, a control device can be provided for the doping that has taken place. This control device may be a known from the prior art measuring device for optical or electrical surface characterization. For the correct assignment of the measured values in their position, an exact substrate position transmission is necessary again.

The stated object is further achieved by a method for doping substrates in which at least one dopant is in contact with the substrate surface and a local heating of the substrate surface by a laser beam takes place. In this case, a fiber laser is used which generates a round beam cross section and which is guided with a scanner unit over the substrate surface.

A prerequisite for the realization of the method described is that the laser technology has undergone rapid development in recent years, which has led, inter alia, to high-performance and low-cost fiber lasers. Essential features that lead to a realization of a technically functioning and economically meaningful Laser doping process, the low price of the fiber laser, the good beam quality with Gaussian power density distribution in the beam cross section, a round beam cross section and the sophisticated scanner units, which allow the scanning of the substrate surface.

In an advantageous embodiment of the method according to the invention, the fiber laser emits light having a wavelength of 750 nm to 3000 nm. Silicon is transparent to low power light in this wavelength range. However, at high power densities, such as occur in the beam of a fiber laser, the substrate surface is heated rapidly and there is a change in optical properties. As a result, the penetration depth of the light into the silicon is reduced to the order of 1 μm. The exact penetration depth can even be adjusted by the choice of process parameters.

However, the fiber laser doping method of the present invention is not limited to the near infrared spectral range. In an alternative variant of the invention, it is also possible to use fiber lasers which emit light having a wavelength of 500 nm to 600 nm. Such methods are mainly used when a low penetration depth of the laser into the substrate or a low doping depth is desired.

In carrying out the laser doping method according to the invention, it has proven to be advantageous to use continuously operating continuous wave lasers or pulsed lasers with relatively long pulse lengths in the range of 80 ns to 10 μs. The use of these long pulses causes a relatively long temperature reaction time on the substrate surface, which therefore does not have to be melted or only slightly melted and therefore no crystal damage to the substrate surface can be recorded after the doping. Sufficient dopant introduction is achieved despite the relatively low temperature for laser doping processes due to the relatively long temperature action time.

In a favorable embodiment of the method according to the invention, the pulse shape of the pulsed laser is designed so that it appears in a time-power diagram, an approximately rectangular shape with at least a short rise time and pulse lengths in the range of 80 ns to 10 microseconds and without significant power peaks. Unlike other pulsed lasers, where the available power is concentrated on very short power peaks, a fiber laser makes it possible to generate very long pulses with uniform pulse power. These long pulses enable gentle substrate processing, which, even when the substrate is melted, leads to low crystal damage and thus to efficient solar cell products. For rapid processing of the substrates, it is advantageous if the front pulse edge is steep, that is, that the pulse power of the laser is reached quickly. On the other hand, the falling flank can be made flatter to increase the temperature response time and to enable a slower and less stressful recrystallization.

In an advantageous variant of the method according to the invention, work is carried out so that the substrate surface is heated only to the extent that its solid state of aggregation is maintained. In this case, the laser doping according to the invention takes place at a relatively low temperature, that is to say below the melting temperature of the substrate and, in return, with a relatively long doping time; This allows a very gentle processing of the substrates. By avoiding melting and recrystallization, failure mechanisms associated with recrystallization are completely avoided. For the processing of solar cell substrates whose surface is structured to increase the photosensitivity, it is also essential that doping methods are used which completely preserve the surface structures produced and do not melt.

In a favorable embodiment of the method according to the invention, the method is used for a full-area doping of substrates. The gentle substrate processing with the continuous wave laser or the pulsed with long pulses fiber laser allows both technically and economically the doping of large substrate surfaces such as the optically active regions on solar cells.

In an advantageous development of the method according to the invention not all areas of the substrate surface are processed the same, but defined substrate areas are more thermally stressed and more heavily doped. An important process parameter for realizing a stronger doping is a reduced speed of the scanner movement. Alternatively or as a support thereto, however, other parameters of the laser doping method can also be varied.

In a possible variant of the method according to the invention, work is carried out in such a way that the substrate surface is melted locally. If the surface morphology of the substrates need not be obtained, laser doping with reflow and recrystallization of the substrate surface is also possible. Due to the higher temperature and the liquid state of aggregation at the surface, the production of a very high doping is possible. When using very high energy densities, it is also possible to open on the substrate existing insulating layers, if necessary to remove or to diffuse into the substrate melt. For example, when using solar cell substrates with already existing emitter doping and antireflection coating, the method variant according to the invention can be used to open the antireflection coating in the regions of the subsequent contacting and at the same time to carry out high doping in these selective emitter regions. Since only the surface areas intended for the contacts are electrically conductive in this method, a particularly simple, self-aligned galvanic deposition of the contacts is possible.

In a further embodiment of the method according to the invention, the processing speed is increased by several lasers simultaneously irradiating different spatial regions of the substrate surface and multiplying the processing speed by the parallel processing.

In a special variant of the laser doping method according to the invention, the laser beam is split by a beam splitter into laser partial beams. Such a method is especially interesting if not the entire substrate is to be processed, but only local areas. For example, such a method may be used when 50 to 400 finger structures of a selective emitter are to be written on a solar cell substrate. In the doping process, the laser beam may be split by a holographic beam splitting diffractive element into 50 to 400 laser sub-beams, which may then simultaneously write 50 to 400 finger lines of the selective emitter.

In a favorable embodiment of the method according to the invention, the scanner unit moves the laser beam in at least one spatial direction over at least two substrates. When using the Laserdotierverfahrens invention is often the case that multiple substrates are arranged in a row in the scanning direction of a laser. The fact that the laser beam is moved directly over several substrates, the process is particularly simple. Depending on the design of the system, the laser beam movement can take place over several substrates in one or in two spatial directions.

The present invention will be explained in more detail below with reference to figures, wherein

1 shows a possible basic structure of a laser doping system according to the invention on the basis of a schematic diagram;

2 schematically shows a further possible embodiment of the present invention, in which a division of a laser beam by means of a beam splitter takes place in partial beams;

3 schematically shows a possible pulse shape of a fiber laser;

4 outlined a possible embodiment of a system according to the invention as a component of an inline substrate processing system;

5 schematically illustrates that the scanning length of the laser can extend over several substrates; and

6 schematically outlines another possible embodiment of a system according to the invention and a possible procedure for laser doping.

1 schematically shows a possible embodiment of a Laserdotieranlage invention. The individual, in 1 shown elements of Laserdotieranlage only illustrate their operating principle and are therefore not drawn to scale and detail, the arrangement of the elements in the drawing is due only to the representability. It does not reflect the concrete arrangement of the elements in the laser doping system. A fiber laser 1 emits a laser beam 2 out, from a scanner unit 3 on a defined path D over a substrate surface 4 of a substrate 8th to be led. The individual components of the laser doping system will now be described below.

The laser doping system has at least one fiber laser 1 which, in the illustration shown, is a powerful laser whose power is high enough to support the substrate 8th to process in acceptable time. The wavelength of the in the embodiment of 1 used fiber laser 1 lies in the near infrared spectral range, in a wavelength range between 750 nm and 3 μm. The wavelength range and the power of the fiber laser 1 determine the penetration depth of the laser beam 2 in the substrate 8th , In a silicon substrate, the penetration depth of the laser beam 2 preferably adjusted to a favorable depth range between 1 .mu.m and 10 .mu.m.

The actually used fiber laser 1 or its actual wavelength used depends on the nature of the substrate 8th and from the desired depth of penetration. Thus, shallower wavelengths than 750 nm can also be used for flat dopants in silicon or for other substrate materials. The choice of laser wavelength used also depends on the availability of fiber lasers in the market. Currently, in addition to the Fiber lasers operating in the near infrared range provide fiber lasers that produce green light in the spectral range of 500 nm to 600 nm by frequency doubling infrared light. In embodiments where low doping depth is desired, these short wavelength lasers are preferred.

Depending on the laser development and of new substrates or applications other than the doping of silicon solar cell emitters, however, other wavelength ranges between ultraviolet light with wavelengths of 150 nm and infrared light with wavelengths of 11 μm can also be used according to the invention.

For the application of the laser doping of solar cell substrates, it has proved to be beneficial, the thermal budget in the substrate 8th to enter in a relatively long time. The substrate surface 4 should be melted by the laser processing as little as possible in order to avoid dislocations. That is why the in 1 applied fiber laser 1 a continuous laser, ie a cw laser. In another embodiment, not shown, is the fiber laser 1 a pulsed laser with relatively long pulse lengths between 80 ns and 10 μs. When using pulsed lasers, the doping profile can additionally be adjusted via the pulse shape. Be particularly favorable rectangular pulses have proven with steep edges at the beginning of the pulse. However, the pulse shape is only one parameter that must be considered and adjusted together with other parameters. For example, laser power, beam diameter, beam quality, intensity distribution in beam cross section, relative laser beam velocity, pulse-to-pulse overlap, line overlap, substrate material, texture, crystallinity and quality, dopant used, ambient temperature and a number of other parameters.

The laser beam 2 has a simple circular beam cross section with preferably Gaussian intensity distribution over the cross section. Such a beam has the advantages that a simple optics for beam shaping is sufficient and that the beam has a large focal depth of about 1 mm at a focus diameter in a preferred range between 20 .mu.m and 500 .mu.m. This long focus area results in a robust and unproblematic process. On a complex and expensive autofocus system can thus in the laser beam 2 be waived.

A scanner unit 3 Realizes the guidance of the laser beam 2 over the substrate surface 4 , The scanner unit 3 can, as in 1 shown different scanner components 3a . 3b include. As a rule, every scanner component is 3a . 3b for the movement of the laser beam 2 responsible in a spatial direction. However, it is also possible that the scanner unit 3 just a scanner to move the laser beam 2 in a spatial direction. In this case, not shown here, a substrate transport device, not shown here, ensures a relative movement between the substrate 8th and laser beam 2 in a second spatial direction.

In the illustration in 1 is the scanner component 3a a polygon scanner, which is rotatable about its axis of rotation A and thus a laser beam movement in the x-direction on the substrate 8th can cause. As a scanner component 3b is outlined a galvo scanner. This scanner is movable about its axis of rotation B in both directions C from its rest position and can thus cause a laser beam movement in the y-direction on the substrate.

The control of the scanner components 3a . 3b leads to the movement of the laser beam 2 on a defined path D over the substrate surface 4 , The web D can be defined so that a uniform substrate doping occurs, but it can also be defined so that a locally higher doping is achieved. The selection of scanner components 3a . 3b occurs depending on the fiber laser used 1 and from the desired path on the substrate 8th , In addition to the types of scanners mentioned, resonance scanners or other scanners could also be used.

The substrate surface 4 is in the laser doping process in contact with a dopant source, which may be in the solid, liquid or gaseous state. However, the dopants may also be present in the form of aerosols, and especially in connection with laser doping, other special forms may also be used. Thus, a liquid precursor under the influence of the laser beam 2 be transferred into a steam bell, from which then the doping takes place. As dopants, it is possible to use all compounds known in the prior art. For doping of silicon are the compounds of elements from the second, the third, the fifth or the sixth main group, often, for example, compounds of boron and phosphorus are used. Particularly preferred for the doping of silicon are the phosphoric acid for an n-doping and the boric acid for a p-doping. The dopants may be applied in a manner known in the art, for example liquid dopants by spraying, rolling or spin coating.

For the processing of liquid dopants, a dilution with an organic or inorganic solvent may be favorable, and the most common solvent used is water used. For example, when using phosphoric acid, concentrations between 0.001% and 85% are used. In particular, when using gaseous precursors also inert or active diluent or purge gases, such as noble gases, nitrogen, hydrogen or oxygen are used. Depending on the dopant used, it may be favorable, the dopant or the substrate 8th to heat to temperatures up to 200 ° C. This may be necessary for procedural reasons or because of a desired side effect such as an etching activity.

In 2 a further embodiment of the laser doping system according to the invention is shown. There are the same elements as in 1 denoted by the same reference numerals. In the course of the laser beam 2 is a beam splitter 5 arranged, which the laser beam 2 into several partial beams 9 Splits. The fiber laser used here 1 is a very powerful laser whose performance is on multiple sub-beams 9 can be divided, which then form a multi-beam arrangement and allow a simultaneous processing of different substrate areas faster overall processing. A multi-beam arrangement can also be formed by a simultaneous use of multiple lasers.

In a particularly preferred embodiment, which is not shown, however, the multi-beam arrangement comprises a fiber laser 1 and a diffractive element for holographic beam splitting. With such a beam splitter is a split in 50 to 400 laser partial beams 9 possible. Such a fanned beam can be used, for example, on solar cells to produce a selective emitter structure.

A selective emitter consists of higher doped regions of the substrate surface 4 on which contact electrodes are later formed. The selective emitter structure comprises, as in 2 shown schematically, a variety of thin fingers 6 and some main lines perpendicular to it 7 , which are referred to as "bus bars" based on the English term. In a favorable embodiment of the Laserdotieranlage the laser beam 2 of the fiber laser 1 split so that the individual partial beams 9 for writing the individual fingers 6 the selective emitter structure can be used.

According to the invention, the production of a selective emitter structure can be carried out in a general doping system, which performs both the formation of a planar basic doping and a local selective emitter doping. However, it is also possible to construct specialized plants which are specialized either only for the formation of planar basic doping or only for the formation of local or selective doping. A special plant for producing a selective emitter structure could also be combined with a conventional furnace doping process. In this case, as a dopant source, a highly doped surface layer, such as the so-called "dead layer" may be used, which is present as an unwanted layer after a furnace doping.

The selective emitter structures which have been produced by the laser doping method according to the invention are distinguished by particularly favorable properties. The higher doping depth producible with the laser doping method according to the invention has already been mentioned. Another positive characteristic, which results from a deep and homogeneously doped emitter, is a better barrier effect against the diffusion of contact materials, such. For example, copper in the substrate material. A further feature to be emphasized of the selective emitter structure produced in the laser doping method according to the invention is the sharp lateral delineation of the more highly doped regions in relation to adjacent regions. In addition, neighboring areas are not damaged by selective emitter doping. With the laser doping method according to the invention, high dopant concentrations of more than 10 ²⁰ at / cm ³ in the surface region and low film resistances of <20 Ω / sq. will be realized.

3 schematically shows a preferred substantially rectangular pulse shape of the fiber laser according to the invention. The fiber laser beam quickly reaches its high maximum power after a short rise time compared to the pulse length. As a result, a rapid substrate heating is achieved. The high power is then maintained for a relatively long time, which may be between 80 ns and 10 μs. In this case, the laser pulse has no appreciable power peaks, even at the beginning of the laser pulse on. The energy input within a relatively long period of time, a good diffusion of the dopants and a gentle substrate processing is achieved. In principle, it is possible in this case for an at least partial melting of the substrate surface 4 can come. In a preferred embodiment of the invention, however, the substrate surface becomes 4 through the fiber laser 1 only heated to the extent that their solid state of aggregation is maintained. Thus, unwanted melting and recrystallization effects can be avoided and still very good doping results can be achieved.

4 shows a detail of a possible inline system, which as a component of a Laserdotieranlage invention in the form of a Laserdotiermoduls has. The inline system has other components, such as lock chambers, but the other components are not shown. The laser doping system 10 includes the process chamber 11 and components outside the process chamber 11 , A fiber laser 1 generates a laser beam 2 passing through a window 12 in the process chamber 11 irradiates. In the illustrated embodiment, the Laserdotieranlage 10 just a scanner, which specifically the polygon scanner 3a is on. The scanner can use the laser beam 2 move in one spatial direction; for adjusting the position of the laser processing on the planar substrate surface 4 In a second spatial direction, the substrate in the illustrated embodiment with the substrate transport device 15 emotional. In other non-illustrated embodiments of laser doping modules, discontinuous transport devices and two-dimensional scanner units are used. The laser doping system further comprises a media supply 13 , which can provide controlled liquid and gaseous media, and a media disposal unit 14 , which serves the removal of spent liquids, gases and auxiliary gases.

5 in addition to the preceding figures schematically shows that the scanner unit 3 the laser beam 2 on a path E across multiple substrates 8th can move. In the example shown, the laser beam 2 moved in y-direction. For controlling the laser path in a second spatial direction x on the substrates 8th no means of movement is shown. For movement, the beam or wafer may be moved, or both the wafer and the beam may be moved.

6 outlines another possible embodiment of a laser doping system according to the invention and a process sequence for laser doping. One or more substrates 8th be in a first step by a transport system 15 , which may be, for example, a belt transport system, an air cushion transport system or a moving Chuck transport system, moves in a transport direction T in the system. In a first method step E, an application of a dopant, which may be, for example, a liquid, which, for example, by a spraying or rolling technique on the substrates 8th is applied. In a next method step F, a further transport of the substrates takes place 8th up to a position detection system 17 where the substrates 8th from a chuck 16 be recorded, the exact substrate position is detected and the substrates 8th then on the chuck 16 be transported with a high spatial position accuracy in the scanning range of a fiber laser explained in the above embodiments.

In a next method step G, the laser doping of the substrates takes place 8th with the laser beam schematically shown here 2 of the fiber laser, wherein due to the high positioning accuracy also a locally defined doping of the substrates 8th is possible. In a further method step H, a further transport of the substrates takes place 8th also high positioning accuracy to below a control device 18 where the result of laser doping can be controlled. After control, the further transport of the substrates takes place 8th with a normal transport system 15 , In a next step K, the substrates 8th , For example, by applying a rinsing liquid cleaned.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102007035068 [0002]
• DE 102004036220 B4 [0003]

Claims (21)

Plant for doping substrates ( 8th ) with laser, characterized in that the system comprises at least one fiber laser ( 1 ) with a laser beam ( 2 ) with round beam cross section ( 2 ) and a scanner unit ( 3 ), through which the substrate surface ( 4 ) with the laser beam ( 2 ) is latched. Plant according to claim 1, characterized in that the emitted light of the fiber laser ( 1 ) has a wavelength in the range of 750 nm to 3000 nm. Plant according to claim 1, characterized in that the emitted light of the fiber laser ( 1 ) has a wavelength in the range of 500 nm to 600 nm. Installation according to one of claims 1 to 3, characterized in that the fiber laser ( 1 ) is a CW laser or a pulsed laser with pulse lengths in the range of 80 ns to 10 μs. Installation according to one of claims 1 to 4, characterized in that the plant several fiber lasers ( 1 ) and / or at least one beam splitter ( 5 ) for generating a plurality of laser partial beams ( 9 ) to form a multi-beam arrangement. Plant according to claim 5, characterized in that the multi-beam arrangement comprises a diffractive element for holographic beam splitting in 50 to 200 laser partial beams ( 9 ) having. Installation according to one of claims 1 to 6, characterized in that the scanner unit ( 3 ) at least one galvo scanner ( 3b ), a polygon scanner ( 3a ) and / or a resonance scanner. Installation according to one of claims 1 to 7, characterized in that the scanner unit ( 3 ) has a scanning region extending over at least two substrates ( 8th ). Installation according to one of claims 1 to 8, characterized in that the system at least one positioning device for the substrates ( 8th ) in the scanning area of the laser 1 and / or at least one control device for the substrates ( 8th ) having. Method for doping substrates ( 8th ) in which at least one dopant is in contact with the substrate surface ( 4 ) and local heating of the substrate surface ( 4 ) by a laser steel ( 2 ), characterized in that a fiber laser ( 1 ) a laser beam ( 2 ) with a round beam cross-section, which is connected to a scanner unit ( 3 ) over the substrate surface ( 4 ) to be led. Method according to claim 10, characterized in that the fiber laser ( 1 ) Emits light with a wavelength of 750 to 3000 nm. Method according to claim 10, characterized in that the fiber laser ( 1 ) Emits light at a wavelength of 500 to 600 nm. Method according to one of claims 10 to 12, characterized in that the fiber laser ( 1 ) is emitted as a continuous wave laser continuously or as a pulsed laser with pulse lengths in the range of 80 ns to 10 μs. A method according to claim 13, characterized in that the pulsation of the fiber laser ( 1 ) is performed in a time-power diagram with a rectangular pulse shape without power peaks. Method according to one of claims 10 to 14, characterized in that the substrate surface ( 4 ) is heated only so far that their solid state of aggregation is maintained. Method according to one of claims 10 to 12, characterized in that the method for a full-surface doping of substrates ( 8th ) is used. Method according to one of claims 10 to 16, characterized in that in locally limited areas of the substrate surface ( 4 ) the speed of movement of the scanner unit ( 3 ) is reduced. Method according to one of claims 10 to 17, characterized in that the substrate surface ( 4 ) is melted locally. Method according to one of claims 10 to 18, characterized in that a plurality of lasers ( 1 ) simultaneously different spatial regions of the substrate surface ( 4 ). Method according to one of claims 10 to 19, characterized in that at least one laser beam ( 2 ) with a beam splitter ( 5 ) in laser partial beams ( 9 ) and the laser partial beams ( 9 ) simultaneously generate locally defined structures. Method according to one of claims 10 to 20, characterized in that the scanner unit ( 3 ) the laser beam ( 2 ) in at least one spatial direction over at least two substrates ( 8th ) emotional.

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