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WO2016012405A1 - Procédé et dispositif pour structurer les faces supérieure et inférieure d'un substrat semi-conducteur - Google Patents

Procédé et dispositif pour structurer les faces supérieure et inférieure d'un substrat semi-conducteur Download PDF

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Publication number
WO2016012405A1
WO2016012405A1 PCT/EP2015/066560 EP2015066560W WO2016012405A1 WO 2016012405 A1 WO2016012405 A1 WO 2016012405A1 EP 2015066560 W EP2015066560 W EP 2015066560W WO 2016012405 A1 WO2016012405 A1 WO 2016012405A1
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WIPO (PCT)
Prior art keywords
substrate
etching
etching medium
medium
structuring
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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PCT/EP2015/066560
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German (de)
English (en)
Inventor
Anne-Kristin Volk
Maxi Richter
Zimmer MARTIN
Tobias Dannenberg
Ümit Seyhan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
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Publication of WO2016012405A1 publication Critical patent/WO2016012405A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/70—Surface textures, e.g. pyramid structures
    • H10F77/703—Surface textures, e.g. pyramid structures of the semiconductor bodies, e.g. textured active layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F99/00—Subject matter not provided for in other groups of this subclass
    • H10P72/0424—
    • H10P72/0426—
    • H10P72/3314—
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • the present invention relates to a method for structuring the top and bottom of a semiconductor substrate and to an apparatus for carrying out the method.
  • the top of the semiconductor substrate is polished and the bottom is textured. It is therefore an asymmetric process.
  • wafers which can be used for the production of optoelectronic components, in particular of solar cells are particularly suitable as the semiconductor substrate.
  • the present invention is particularly intended for in-line etching processes in which the two sides of a silicon wafer are to be treated differently in one step.
  • PERC cells Passivated Emitter and Rear Cells
  • PERC cells should have a smooth backside to allow for the best possible passivation of the backside.
  • both the front and the back of the substrate are textured.
  • the texture of the backside is removed by removal of material, so that a back surface with the desired low roughness is obtained.
  • the two-sided texturing carried out in the first step is necessary since, in the case of one-sided texturing, the substrate is due to the one-sided mechanical stress would bend. The associated increased susceptibility to breakage would result in a significant impediment of all subsequent processes in the production of the solar cell. Therefore, attempts to mask the back before texturing have not been successful. Furthermore, a two-sided treatment is anyway necessary to remove on both sides of the substrate caused by the wafering shege cooked.
  • Multicrystalline semiconductor substrates are typically textured in moderately concentrated HF / HN0 3 solutions, with both the front and back of the substrate being texturized.
  • DE 103 20 212 A1 discloses such a method for texturing surfaces of silicon wafers. Texturing is accomplished by fully submerging the substrates in an etching solution and then incubating the substrates in the etching solution for several minutes. The texturing of multicrystalline substrates usually takes place in the inline process. In-line process, the substrates are moved horizontally through the device, which is intended to carry out the method.
  • the subsequent removal of the texture from the rear side of the substrate which is also known as a polish, is likewise usually carried out by means of an HF / HNO 3 etching solution in an inline process, although the concentrations of the two acids in the polishing solutions in comparison with the etching solutions used for texturing Polishing process.
  • the etching solution may only come into contact with the back side of the substrate because the texture of the front side is to be preserved.
  • two alternative methods are known, which are in principle suitable for such a one-sided treatment of semiconductor substrates.
  • DE 103 13 1 27 B4 discloses a method for single-sided surface treatment of semiconductor substrates. However, the method does not concern the polishing of the substrate back, but the so-called chemical edge insulation, which also as
  • Emitter residues is known.
  • this step which takes place later in the process in the production of solar cells compared to texturing and polishing, is removed by a small material removal of about 1 ⁇ by means of an etching solution of the previously applied by diffusion on both sides emitter selectively from the substrate back.
  • the substrate is horizontally passed over the liquid etching solution in a bath, the liquid level being adjusted so that the top surface of the substrate does not come into contact with the etching solution.
  • a method for single-sided surface treatment of semiconductor sub strates is known from WO 2007/073887 A1.
  • a method is disclosed in which a process medium is selectively applied to the underside of a silicon substrate.
  • the substrate is transported by means of transport rollers through a tank with process medium, although there is no direct contact between the substrate and the process medium. Rather, the transport rollers fulfill a dual function, on the one hand as a means of transport for the substrate and on the other as a conveyor for the process medium.
  • the function as a conveyor is made possible by the fact that the transport rollers partially submerge in the process medium and that they have a wettable surface. Therefore, the rollers can convey the process medium in low layer thickness against gravity upwards and transferred to the substrate.
  • the production of solar cells by the conventional methods requires three separate etching steps, namely first the two-sided texturing, then the one-sided polishing of the back and finally, the two-sided
  • Emitter diffusion does not provide complete protection of the edges of the substrate, so emitters can diffuse there despite the diffusion barrier. This in turn has a negative effect on the low-light behavior of the solar cells. Furthermore, the masking of the back side before the texturing as well as the application of a diffusion sion barrier before emitter diffusion with additional process steps and thus associated with an increase in costs.
  • Document DE 10 2007 063 202 A1 discloses a method in which a semiconductor substrate is moved along a horizontal transport path and sprayed from above with an etching medium. The top of the substrate should be textured. The bottom is contacted only with a relatively smaller amount of the same etching solution. Only in a second, later process step is the underside moistened with an etching solution for polishing etching. Thus, in this document, the upper surface is textured and the lower surface is polished in successive process steps. The texture of the bottom is expressly undesirable. Insofar as there is an etch, this is not even enough to remove the sawing damage. In contrast to the method according to the invention, in DE 10 2007 063 202 A1 the upper side is therefore textured and not polished. The underside is not textured, but at best slightly etched. The slight etching of the underside is apparently not a deliberate process step, but a side effect that is accepted.
  • WO 2012/020274 A1 describes a method and an apparatus for texturing semiconductor substrates. It should be etched less from the top of the substrate than from the bottom. Thus, an asymmetric texturing is also sought, that is to say texturing in which the top and bottom of the substrate are etched to different extents.
  • the top is just about to be polished and the underside to be textured. It is according to the invention thus removed more from the top than from the bottom.
  • the reason why the upper side is also etched in WO 2012/020274 A1 while the underside texturing is carried out is the avoidance of the bending of the wafers. Therefore, a lower etching effect on the upper side is sufficient in the prior art. However, further process steps must be followed in order to carry out a polishing of the non-textured surface.
  • the etching rate of the gas phase depends on the concentrations of NO 2 and HF contained therein, which in turn depend on the concentrations of the corresponding acids in the etching solutions used and on the strength of the reaction between the etching solution and the substrate.
  • a method is provided that solves the problems of the prior art in providing a simplified method in a totally unexpected manner. Surprisingly, it has been found that the two steps of texturing the front side and the polishing of the rear side of the substrate can be carried out simultaneously in a common method step.
  • the etching medium used for polishing the substrate top may preferably be used to control the consumption of etching components in the process of texturing Substrate substrate used to compensate for etching medium, so this less often must be renewed by fresh chemicals. According to a preferred embodiment of the present invention also described in detail below, even the provision of a separate etching medium for the texturing of the underside of the substrate can be completely dispensed with. As a result, the removal of material on the substrate is reduced, since the back of the substrate does not have to be subjected to the unnecessary further material removal of the two-sided texturing as before before polishing.
  • the object is achieved by a method for structuring the top and bottom of a semiconductor substrate, wherein the top and bottom of the substrate are structured differently with respect to their roughness, namely the top is polished and the bottom textured.
  • the method comprises the following steps: a) providing a semiconductor substrate and b) contacting the top and bottom of the semiconductor substrate with liquid etching media, wherein the structuring effect of the etching media differs at the top and bottom of the substrate, and wherein the top and bottom of the Substrate are structured simultaneously.
  • the etching medium on the upper side has a polishing structuring effect and the etching medium on the underside has a texturing structuring effect.
  • the etching medium having a polishing patterning effect is applied from the top to the top of the substrate so that a reaction of the between the etching medium and the top of the substrate takes place (etching reaction).
  • concentration of etching components in the etching medium decreases so that it can be used for texturing the underside.
  • the etching medium on the underside is preferably the etching medium of the upper side which has been reduced to etching components.
  • the etching medium of the top side reduced to etching components compensates for a loss of etching components in the etching medium of the bottom side.
  • a semiconductor substrate is provided.
  • the semiconductor substrate is preferably a silicon substrate, particularly preferably a silicon wafer.
  • the semiconductor substrate is preferably selected from the group comprising monocrystalline semiconductor substrates and polycrystalline semiconductor substrates.
  • the semiconductor substrate is a polycrystalline semiconductor substrate.
  • the semiconductor substrate has a top and a bottom. The top and bottom are preferably the two major sides of the substrate. Under main pages are according to the invention to understand the two sides of the substrate, which have the largest areas in comparison with the other sides of the substrate.
  • the terms “top” and “bottom” refer to the orientation of the substrate in the device according to the invention during the process.
  • the upper side of the substrate preferably corresponds to the back side of a solar cell produced from the substrate. In this context, the term “backside” refers to the side of a solar cell that faces away from the sun.
  • the top and bottom of the semiconductor substrate are patterned simultaneously.
  • “simultaneously” is to be understood as meaning that the structuring of the top and bottom of the substrate does not take place in two separate method steps, as known from the prior art, but in a single method step. more preferably during a period of time, a majority of both the top and the bottom of the substrate at the same time in contact with the etching medium.
  • "Bulk” in this context means that preferably at least 50%, more preferably at least 80%, even more preferably at least 90%, more preferably at least 95%, most preferably at least 99% of
  • the period of simultaneous contact of upper and lower surfaces of the substrate with etching medium is preferably at least 10 seconds, more preferably at least 30 seconds, more preferably at least 45 seconds. In order to keep the removal of material within an optimal range, it has proved to be favorable to reduce this period to a maximum of 5
  • the top and bottom of the substrate are structured differently with regard to their roughness and reflection properties.
  • Roughness is to be understood as the quantity S q measured according to EN ISO 25178, which represents the mean of the magnitude of the height values of an image detail. This parameter correlates with reflection of the surface of silicon surfaces treated with HF / HN0 3 solutions. surface, which is generally easier to determine and thus used as a direct means of process control. The determination of the reflection takes place either at a single wavelength or as a wavelength-resolved spectrum. To determine the direct reflection, the reflection is measured such that the angle between the light source and the solder above the surface is equal to the angle between detector and solder above the surface. The diffuse reflection is measured using an Ulbricht sphere. The total reflection corresponds to the sum of the direct and the diffuse reflection.
  • the method according to the invention serves to combine front side texturing and back side polishing of a semiconductor substrate in a single method step. Consequently, the inventive method allows a different structuring of the top and bottom of the substrate.
  • top and bottom are structured in accordance with the method according to the invention such that the upper side is polished and the underside is textured.
  • the upper and lower sides are preferably structured in accordance with the method according to the invention in such a way that the structured upper side has a lower roughness and thus a higher reflection than the structured lower side of the substrate.
  • Particularly preferred is the roughness of the structured substrate top by at least 0.5 ⁇ , preferably at least 0.55 ⁇ less than the roughness of the structured substrate underside.
  • the structured upper side of the substrate preferably has a roughness of at most 0.5 ⁇ m, which corresponds to a direct reflection of approximately 1% at 600 nm and a total reflection of more than 35%. If the roughness of the structured substrate top is too high, the passivation of the later solar cell back is made more difficult.
  • the structured underside of the substrate preferably has a roughness of at least 0.6 ⁇ m, more preferably at least 0.75 ⁇ m and particularly preferably at least 1 ⁇ m, which corresponds to a total reflection of ⁇ 30% at 600 nm. If the roughness of the patterned substrate bottom is too low, reflections are not sufficiently reduced, so that solar cells with lower efficiency are obtained.
  • the upper and lower sides of the semiconductor substrate are brought into contact with liquid etching medium.
  • the viscosity of the liquid etching medium should not increase be high so it can wet the substrate and pump.
  • the liquid etching medium has a viscosity of at most 10 3 mPas, more preferably at most 10 2 mPas, even more preferably at most 10 mPas, most preferably at most 7 mPas.
  • the viscosity of the liquid etching medium should also not be too low in order to prevent too rapid outflow of the etching medium from the substrate.
  • the liquid etching medium preferably has a viscosity of at least 1.75 mPas, more preferably at least 2 mPas, even more preferably at least 2.5 mPas.
  • the viscosity of the etching medium is preferably determined using a rotational viscometer in accordance with DIN 53019. Unless stated otherwise, all tests are carried out under standard conditions in accordance with DIN 1343.
  • the liquid etching medium preferably has at least one, more preferably at least two etching components. Particularly preferably, the etching medium has exactly two etching components. Alternatively, the liquid etching medium has at least three etching components. Preferably, the liquid etching medium is an aqueous solution.
  • the liquid etching medium preferably comprises either acids or bases as etching components. For polycrystalline semiconductor substrates, acids are particularly preferred etchants.
  • Particularly preferred etching components are selected from the group comprising HF, HN0 3 , H 2 S0 4 , CH 3 COOH, H 3 P0 4 and mixtures thereof.
  • the etching components are particularly preferably selected from the group comprising HF and HNO 3 .
  • the liquid etching medium comprises HF and HNO 3 as etching components.
  • the etching medium may comprise bases as etching components. Bases are preferred etching components for monocrystalline semiconductor substrates. Preferred bases are selected from the group comprising NaOH and KOH. Most preferably, the base is KOH. Furthermore, the effect of
  • Asymmetry of structuring by addition of organic additives can be further improved.
  • the structuring effect of the etching medium differs at the top and bottom of the substrate. This ensures that the top and bottom of the substrate are structured differently with regard to their roughness.
  • the etching medium has a polishing structuring effect on the upper side of the substrate. Under a polishing structuring effect is to be understood as such a structuring effect which results in a roughness of the structured surface of at most 1 ⁇ m.
  • the etching medium has a texturing structuring effect on the underside of the substrate.
  • a texturizing structuring effect is to be understood as meaning a structuring effect which results in a roughness of the structured surface of more than 1 ⁇ m.
  • the different structuring effect at the top and bottom of the substrate can be caused by various measures according to the invention.
  • the etching medium having a polishing structuring effect is preferably the same etching medium as in the etching medium having a texturizing structuring effect.
  • the different structuring effect can preferably be achieved alternatively or cumulatively in that a. the etching medium having a polishing structuring effect on the upper side of the substrate is modified in such a way as to be suitable for texturing by the reaction with the substrate with regard to the etching components, b. the etching medium with a polishing structuring effect is applied to the underside of the substrate in a (preferably thin) film, so that a texturing structuring effect results, and / or c. the temperature distribution between top and bottom is chosen so that the structuring effects are polishing or texturizing.
  • the different structuring effects on the top and bottom of the semiconductor substrate are caused by bringing the top and bottom of the substrate into contact with etching media having different concentrations of etching components.
  • a polishing structuring effect can be achieved in comparison to a texturing structuring effect by using an etching medium with an adapted, in particular increased, concentration of etching components. Therefore, the upper surface of the substrate is contacted with an etching medium having a higher concentration of at least one etching component than the etching medium brought into contact with the lower surface of the substrate.
  • the top of the substrate is filled with a liquid Etching medium brought into contact with polishing structuring effect.
  • the top surface of the substrate is contacted with a liquid etching medium containing at least 30 g / L, more preferably at least 40 g / L, even more preferably at least 50 g / L, and most preferably at least 60 g / L HF.
  • the top of the substrate is contacted with a liquid etching medium containing at least 500 g / L, more preferably at least 600 g / L, even more preferably at least 700 g / L HNO 3 .
  • the concentration of the etching component HN0 3 is preferably higher in the etching medium having a polishing structuring effect than in the etching medium having a texturing structuring effect.
  • the concentration of the component HF can be higher, but also lower or just as high as in the etching medium having a texturizing structuring effect.
  • the underside of the substrate is brought into contact with a liquid etching medium having a texturizing structuring effect.
  • the underside of the substrate is preferably brought into contact with a liquid etching medium which contains at most 160 g / l, more preferably at most 140 g / l, even more preferably at most 130 g / l HF.
  • the concentration of HF should not be too low.
  • the underside of the substrate is therefore contacted with a liquid etching medium containing at least 30 g / L, more preferably at least 40 g / L, even more preferably at least 50 g / L HF.
  • the underside of the substrate is preferably brought into contact with a liquid etching medium which contains at most 600 g / l, more preferably at most 550 g / l, even more preferably at most 500 g / l of HNO 3 .
  • a liquid etching medium which contains at most 600 g / l, more preferably at most 550 g / l, even more preferably at most 500 g / l of HNO 3 .
  • the concentration of HN0 3 should also not be too low.
  • the underside of the substrate is therefore contacted with a liquid etching medium containing at least 250 g / l, more preferably at least 300 g / l, even more preferably at least 350 g / l HN0 3 .
  • Texturing can be achieved, the said mass ratio in the ⁇ tzme- medium with textur istspatentedier strictly but at least 2, more preferably at least 3 and more preferably at least 3.8.
  • the contacting of the semiconductor substrate with the liquid etching medium is preferably carried out in a modified inline process.
  • the semiconductor substrate for carrying out the method is moved by a device. Further preferably, the substrate is moved horizontally through the device.
  • the etching medium with a polishing structuring effect is preferably applied to the top side of the substrate from above. Particularly preferred is the etching medium with polishing
  • the polishing of the top of the substrate is associated with a removal of material from the top of the substrate.
  • the removal of material from the top of the substrate is at most 20 ⁇ , more preferably at most 15 ⁇ , even more preferably at most 10 ⁇ , most preferably at most 8 ⁇ .
  • the material removal should not be too low, so on the one hand the polishing structuring effect is ensured, on the other hand, the saw damage is completely removed from the surface.
  • the removal of material from the substrate top is therefore at least 3 ⁇ , more preferably at least 4 ⁇ , even more preferably at least 5 ⁇ .
  • the concentration of etching components in the corresponding etching medium is reduced by the reaction of the etching medium with the substrate top side.
  • the etching medium applied from above onto the top side of the substrate flows off the substrate top side after contact with the substrate top side.
  • the etching medium draining from the top of the substrate, as such or after mixing with one or more mixing media, which may be in a process tank may be used to texturize the substrate bottom.
  • the texturing of the underside of the substrate is preferably associated with a material removal from the underside of the substrate.
  • the material removal from the bottom of the substrate is at most 1 ⁇ , more preferably at most 7 ⁇ , even more preferably at most 5 ⁇ .
  • the material removal should not be too low, so that the texturierende structuring effect can be achieved sufficiently and is also completely removed from the bottom of the sawing damage.
  • the removal of material on the underside substrate therefore at least 2 ⁇ , more preferably at least 3 ⁇ , even more preferably at least 4 ⁇ .
  • the removal of material from the top during the polishing is preferably at most three times as great as that from the bottom during the texturing.
  • the material removal on the upper side is at most twice as large, more preferably at most one and a half times as large, and particularly preferably about the same size as the removal of material from the underside.
  • the structuring is therefore different only in terms of roughness, but not with regard to the removal of material. This is achieved with the method according to the invention. Nevertheless, the removal on the underside should be at least so large that the sawing damage is removed.
  • the substrate is transported horizontally via a process tank and brought into contact with the etching medium located therein.
  • the transport of the substrate via the process tank is preferably carried out by means of transport.
  • Particularly preferred are the means of transport selected from transport rollers and retaining pins.
  • the transport means are transport rollers.
  • an etching medium having a texturizing structuring effect is located in the process tank.
  • the level of the etching medium in the process tank is preferably adjusted so that the etching medium contained in the process tank comes into contact only with the underside of the substrate to be textured (meniscus sets).
  • the upper side of the substrate is brought into contact with an etching medium which has changed compared to the etching medium contained in the process tank, in particular at least with regard to an etching component has a higher concentration of etching components.
  • This can be a polishing of the top of the substrate can be achieved.
  • the contacting of the upper side of the substrate with the higher-concentration etching medium takes place according to the method described above instead, preferably while the substrate underside is in contact with the etching medium located in the process tank.
  • the etching medium applied to the upper side of the substrate preferably reaches the process basin located below the substrate, in particular into the etching medium having a texturizing action located therein. Consequently, the amount of etching medium applied to the top should be sufficient to allow drainage.
  • the reaction with the substrate reduces the concentrations of the etching components in the etching media.
  • the etching medium entering the process tank from the upper side of the substrate preferably has a concentration of etching components such that the reduction in the concentration of etching components in the etching medium located inside the process tank is compensated by the etching medium entering from the upper side of the substrate into the process tank. This can be set by the skilled person by suitable composition of the etching media in the context of this invention.
  • no process tank located below the substrate with etching medium of texturizing structuring effect is required and / or the process tank is not used for providing etching medium for texturing the underside, but merely as a catch basin for effluent or dripping etching medium.
  • the underside of the substrate is preferably contacted in this embodiment with liquid etching medium by the from the top of the
  • the transporting means therefore preferably have structures which make it possible to pick up the etching medium flowing off from the substrate top side, to convey it to the underside of the substrate and to bring the etching medium into contact with the underside of the substrate.
  • These structures of the transport means are preferably pores.
  • Particularly preferred means of transport are sponge rollers.
  • a film of etching medium preferably forms on the underside of the substrate, in particular between the transport means and the substrate surface.
  • the film preferably has a thickness of at least 10 ⁇ , more preferably at least 20 ⁇ , even further preferably at least 50 ⁇ . If the film is too thin, the existing etching medium in the film is insufficient to achieve the preferred ablation on the underside of the substrate.
  • the film preferably has a thickness of at most 500 ⁇ , more preferably at most 200 ⁇ , even more preferably at most 100 ⁇ . If the film is too thick, the amount of etching medium therein remains so large that the desired decrease in concentration during the etching does not take place sufficiently and no or insufficient texturing structuring effect occurs.
  • the structuring effect on the underside is preferably produced by bringing the underside into contact only with a thin film of etching solution, in which the concentration of the latter drops significantly in situ due to consumption of the etching components.
  • the concentration of etching components in the substrate underside contacting etching medium is changed due to the previous reaction of the etching medium with the substrate top compared to the freshly applied to the top of the etching medium.
  • the transport of etching medium to the underside of the substrate is not sufficient to prevent a further change in the concentration of etching components in the etching medium due to the reaction of the etching medium with the underside of the substrate.
  • the thus modified concentration of etching components in the etching substrate contacting the substrate underside has, in particular, the consequence that the etching medium contacting the underside of the substrate has a texturing structuring effect.
  • etching reactions are predominantly associated with a polishing structuring effect, while etching reactions whose reaction rate is controlled by the activation energy to be overcome are associated with a texturing structuring effect. It can therefore be assumed that the texturing structuring effect of the etching medium contacting the substrate underside is due to a reaction mechanism controlled by the activation energy to be overcome.
  • the different structuring effect at the top and bottom of the substrate can also be achieved or influenced by a separate temperature control of the etching reactions taking place at the top and bottom of the substrate.
  • the etching rate of an etching medium usually increases with increasing temperature.
  • the same etching media lead to a polishing of the surface at a higher temperature and to a texturing of the surface at a lower temperature. It is therefore preferred according to the invention that the temperature at the top of the substrate is higher than the temperature at the bottom of the substrate. Preferably, the higher temperature at the top side of the substrate is at least partially due to the resulting heat of reaction in the reaction of the etching medium with the substrate top side.
  • the etch media at the top and bottom of the substrate are not significantly different in the concentration of the etch components.
  • the adjustment of the structuring effect over the temperature is preferably used in addition to the setting of the structuring effect via the concentration of etching components in the etching medium.
  • the temperature at the substrate top in the case of acidic etching baths in all embodiments of this invention is at least 15 ° C., more preferably at least 25 ° C.
  • the temperature at the substrate top should not be too high, so that the etching medium does not evaporate on the substrate top.
  • the temperature on the upper side of the substrate is therefore preferably at most 50 ° C., more preferably at most 40 ° C., for acid etching baths.
  • the temperature at the top is preferably at least 40 ° C, more preferably at least 50 ° C and most preferably at least 60 ° C.
  • the temperature of the top preferably at most 1 10 ° C, more preferably at most 100 ° C.
  • the temperature at the substrate top is at least 5 ° C, more preferably at least 10 ° C, even more preferably at least 20 ° C higher than at the substrate bottom.
  • an apparatus for performing the method according to the invention comprising, i. at least one application unit and ii. at least one transport unit.
  • the device comprises at least one application unit.
  • the application unit preferably serves to apply the etching medium with polishing
  • the device preferably has sufficient application units in order to prevent drying of the etching medium applied to the top side of the substrate during the transport of the substrate through the device.
  • the device preferably has at least two, more preferably at least three application units.
  • the application unit preferably comprises at least one inflow and at least one outflow. Due to the inflow preferably passes etching medium with polishing
  • the application unit is preferably connected via the inflow to a master tank containing the etching medium.
  • the starting chemicals of the etching medium are supplied separately to the application unit and are mixed into the etching medium only within the application unit.
  • the etching medium preferably reaches the upper side of the semiconductor substrate.
  • the drain is closable.
  • the drain can be controllably opened and closed. It can thereby be achieved that a precisely defined quantity of etching medium is applied to the substrate becomes.
  • etching medium preferably only leaves the application unit when a substrate to be wetted with etching medium is located below the application unit. This in turn saves etching medium.
  • the transport means are arranged in the device so that the application unit or application units are located above the intermediate spaces between the transport means. Thus, the etching medium is not delivered to the means of transport, when there is no substrate underneath.
  • the application unit is a spray device.
  • the application unit preferably has a plurality of drains.
  • the device according to the invention comprises at least one transport unit.
  • the transport unit is located below the application unit in the device. With the transport unit, the semiconductor substrate is preferably transported horizontally below the application unit. During the implementation of the method according to the invention, the substrate is preferably located in the device above the transport unit and below the application unit.
  • the transport unit preferably comprises at least one, more preferably at least two, more preferably at least five, even more preferably at least ten transport means.
  • the transport means are selected from transport rollers and retaining pins.
  • the transport means are particularly preferably transport rollers.
  • the transport means have structures. Preferably, the structures are pores.
  • the surface of the transport means preferably consists of polyolefins.
  • the device according to the invention may additionally comprise at least one process basin.
  • the bottom of the process tank is below the transport unit.
  • the process tank contains etching medium.
  • the etching medium contained in the process tank has a texturizing
  • the means of transport are in contact with the im
  • Process tank contained etching medium. It can also be provided according to the invention be that the application unit is supplied in addition to fresh etching medium from the reservoir tank or corresponding output chemicals and etching medium from the process tank. As a result, a dilution of the etching medium to be applied to the upper side of the substrate can preferably be achieved, if necessary.
  • all embodiments are also equipped with a dosing unit, which makes it possible to compensate for the inevitable by the etching reaction loss of concentration of etchant by the addition of new etchant (eg concentrated HF and HN0 3 ) in the processing of larger amounts again and thus uninterrupted processing of large To allow quantities.
  • new etchant eg concentrated HF and HN0 3
  • an etching solution consisting of 4 parts by volume of 69% nitric acid and one part by volume of 40% hydrofluoric acid is added.
  • This etching solution is heated to 15 ° C and continuously sprayed on the sponge rollers from above spray bars.
  • Multicrystalline silicon substrates (as-cut) are driven horizontally through the plant at a transport speed corresponding to a total etching time of 1.7 minutes, so that the substrates are sprayed from the top with the etching solution.
  • the laterally running etching solution wets the transport rollers, which in turn form a film of etching solution having a texturing structuring effect contacting the underside of the substrates.
  • the total erosion measured over the weight difference amounts to 12 ⁇ m
  • the underside of the substrates has a total reflection at 600 nm of 28.9%
  • the top side of the substrates has a total reflection at 600 nm of 36.4%
  • the direct Reflection of the top at 600 nm is 2.7%.
  • Figure 1 shows a device according to the invention with a plurality of transport means 1, on which a substrate 2 moves in the horizontal direction.
  • the process medium 3 is located in a process tank. From above, fresh process medium is sprayed onto the substrate from a master tank 5 by means of an application unit 4. The underside of the substrate is in contact with the process medium.
  • the medium sprayed onto the substrate from above serves, on the one hand, to polish the upper side of the substrate and, on the other hand, keeps the concentration of acid in the process basin within the intended range.
  • Figure 2 shows a likewise inventive device with a plurality of transport means 1, on which a substrate 2 moves in the horizontal direction.
  • the process medium 3 is located in a process tank. From above, process medium is sprayed onto the substrate 2 by means of an application unit 4. The underside of the substrate is not in direct contact with the process medium. The medium sprayed from above leads to the polish of the substrate top. Medium draining from the substrate top passes from the substrate to the transport means, which may be sponge rollers, and is conveyed by them to the underside of the substrate.

Landscapes

  • Weting (AREA)
  • Mechanical Treatment Of Semiconductor (AREA)

Abstract

L'invention concerne un procédé et un dispositif permettant la mise en oeuvre du procédé. Le procédé permet de simultanément vernir et structurer les faces avant et arrière de substrats semi-conducteurs aptes à la fabrication de modules solaires. On utilise à cet effet des agents caustiques qui se différencient quant à leur effet structurant sur le substrat semi-conducteur.
PCT/EP2015/066560 2014-07-21 2015-07-20 Procédé et dispositif pour structurer les faces supérieure et inférieure d'un substrat semi-conducteur Ceased WO2016012405A1 (fr)

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DE102014110222.3 2014-07-21
DE102014110222.3A DE102014110222B4 (de) 2014-07-21 2014-07-21 Verfahren und Vorrichtung zur Strukturierung von Ober- und Unterseite eines Halbleitersubstrats

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DE102017206455A1 (de) 2017-04-13 2018-10-18 Rct Solutions Gmbh Verfahren und Vorrichtung zur chemischen Bearbeitung eines Halbleiter-Substrats
CN114496766A (zh) * 2020-10-26 2022-05-13 苏州易益新能源科技有限公司 一种水平连续腐蚀晶体硅片上表面的方法和设备
CN114496767A (zh) * 2020-10-26 2022-05-13 苏州易益新能源科技有限公司 一种碱溶液水平连续腐蚀晶体硅片的方法和设备

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WO2018189130A2 (fr) 2017-04-13 2018-10-18 Rct Solutions Gmbh Procédé et dispositif pour le traitement chimique d'un substrat de semi-conducteur
DE102017206455A1 (de) 2017-04-13 2018-10-18 Rct Solutions Gmbh Verfahren und Vorrichtung zur chemischen Bearbeitung eines Halbleiter-Substrats
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CN114496766A (zh) * 2020-10-26 2022-05-13 苏州易益新能源科技有限公司 一种水平连续腐蚀晶体硅片上表面的方法和设备
CN114496767A (zh) * 2020-10-26 2022-05-13 苏州易益新能源科技有限公司 一种碱溶液水平连续腐蚀晶体硅片的方法和设备

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TW201613114A (en) 2016-04-01

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