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  • Final Report Summary - SOLNOWAT (Development of a competitive 0 GWP dry process to reduce the dramatic water consumption in the ever-expanding solar cells manufacturing industry.)
FP7

SOLNOWAT Streszczenie raportu

Project ID: 286658
Źródło dofinansowania: FP7-SME
Kraj: Ireland

Final Report Summary - SOLNOWAT (Development of a competitive 0 GWP dry process to reduce the dramatic water consumption in the ever-expanding solar cells manufacturing industry.)



Executive Summary:

The project SOLNOWAT aims to develop a dry process alternative for the solar Photovoltaic (PV) cell industry. The wet chemical steps are replaced by 0 GWP dry process steps, addressing the current unsustainable water usage in the photovoltaic solar cell manufacturing industry.

The consortium is composed of 4 SMEs including equipment manufacturers, and 2 RTD performers located in 5 different European countries.

Silicon etching is a key technology in various processing steps during the production of PV solar cells. There is currently no suitable alternatives technology to carry out this processing step. The novel dry process will overcome the limitations of the incumbent technology.

The dry etching process has been investigated and developed in order to produce very efficient light absorbing silicon surface textures, with weighed reflectivity values as low as 2%, and uniformity across a whole solar wafer, while removing a minimum amount of silicon (<1um). This single sided etching was also demonstrated using thin wafers with thickness below 100um. Various textures have been created, demonstrating the versatility of the technology. Process monitoring solutions including FT-IR were applied to better understand the process. A great deal of understanding of the thermally activated fluorine etching at atmospheric pressure has been gathered. An LCA analysis has been carried out confirming the lower impact of the dry etching process compared to the standard wet etching process.

A novel etching tool was built specifically for this project by the SME Nines Photovoltaics, and installed in the process development facilities at Fraunhofer ISE. The dry etching process has been integrated in a standard solar cell manufacturing process for two main applications: front side texturing and rear side etching. The downstream manufacturing steps were optimised through several iterations in order to suit the dry texture. Optimization led to effective surface recombination velocities below 100 cm/s.

Novel hardware concepts have been successfully developed and prototypes were tested to provide non-contact handling conveying of the wafers inside a proof of concept reactor. Also, a novel mass spectrometry solution has been devised in order to provide in-line monitoring of Fluorine, and all other species involved in the etch process that will eventually be implemented as a statistical process control (SPC) tool in an industrial environment.

The results of the SOLNOWAT project have been disseminated to the wider PV scientific and industrial community through photovoltaic conferences in Europe and the USA. Several cell manufacturers have been made aware of the results through direct presentations, and have all expressed interests in the technology. Disseminations activities have also led to identifying a new upcoming market for the technology. All the SMEs involved have developed a lasting relationship, increasing their level of European collaboration. They have also been able to access critical R&D services to develop their technology. SOLNOWAT dissemination activities have already raised their profile within the PV community, as they are now well recognised for their work, and IP developed will further add value to each of them.

Project Context and Objectives:

The project SOLNOWAT aims to develop a dry process alternative for the solar Photovoltaic (PV) cell industry. This innovation will deliver the following main benefits:

(A) Reduction in the very high water consumption of PV manufacturing plants
(B) Reduction in Global Warming Potential (GWP) emissions
(C) Improved solar cell production yields
(D) Improve solar cell efficiency

Novel technical solutions will be developed, including:

+ A novel atmospheric pressure, Silicon (Si) wafer texturing process based on thermal activation.
+ A novel mass spectrometric process monitoring solution.
+ An innovative in-process non-contact Si wafer handling solution.
+ A complete PV solar cell manufacturing process incorporating all these developments.

This project will clearly outline the environmental impact, cost and solar cell conversion efficiency improvements associated with the new manufacturing processes and will include dissemination to cell manufacturers. It will add significant value for the SMEs partners involve, by the development of new manufacturing equipment for PV production.

Summary of benefits:

+ Dramatic reduction of water usage*
+ Very low environmental impact processing *
+ Advance process control, real time monitoring* for highest precursor utilization
+ High-throughput, high-yield, integrated industrial processing (inline)*
+ PV solar cell devices with increased conversion efficiency*
+ Enabling thin Si wafer processing* and surface decoupling (single sided).
+ Smaller footprint manufacturing equipment
+ Low manufacturing cost of ownership*
+ Reviewed by a panel of cell manufacturers

Most of these benefits(*) are fundamental criteria outlined by the European Photovoltaic Technology Platform in its Strategic Research Agenda for Photovoltaic Solar Energy Technology, in order to meet the sector’s ambitions for technology implementation and industry competitiveness.

The Problem:

The current water usage in the photovoltaic (PV) solar cell manufacturing industry is not sustainable. The PV solar industry as a whole has been growing dramatically over the last 10 years. PV solar is indeed recognised as the renewable energy alternative that can meet our global energy needs for the foreseeable future. Companies involved in this industry have been growing significantly, answering the demand, and scaling their production capacity accordingly. Equipment and processes developed by cell manufacturers have been for most adopted and scaled up from semiconductor manufacturing.

However, the value-add and cost structures for both sectors are vastly different despite the manufacturing processing technologies being similar. As the industry continues to increase its capacity, very large footprint factories that have heavy consumption of chemicals, water and emissions of high Global Warming Potential (GWP) gases become unsustainable. New regulations, including the Kyoto agreement, will enforce strict control on water management and emissions. The availability of environmentally friendly production technologies that can cope with emission regulations in Europe will be crucial for the continuity of cell manufacturing in the EU. At the same time EU regulations are expected to further restrict the use of production technologies with high GWP. There is therefore a need to rethink and develop new process solutions that meet these requirements in order to strengthen the economic and ecological innovation ability of European SMEs and cell producers.

In order to access this market dominated by very large companies, SMEs across Europe are introducing innovations. A step change delivering significant improvement can only be achieved by collaborations between SMEs and RTDs. The SMEs involved believe that by cooperating together through this SOLNOWAT R&D program, they will be able to achieve significant results. The consortium is composed of 4 SMEs and 2 RTD performers located in 5 different European countries.

Explanation of Existing Processes for Solar Cell Manufacturing:

Silicon etching is a key technology in various processing steps during the production of PV solar cells:

- Removal of sawing damage that has occurred during the “wafering” process,
- Texturing of the Si wafer to reduce its reflection prior to the formation of the emitter layer.
- The removal of the residual phosphorus silicate glass (PSG) that grows during the high temperature emitter formation step.

Currently most of the etching steps are carried out using wet chemistry equipment; the wafers are moved across large baths containing chemical liquid mixtures. A large volume of water is also required for rinsing after etch step, typical 5 litres/Watt. It takes about 1.5L of “tap water” to produce one litre of DI water.

A 1 Giga Watt (GW) factory uses up to 15 000 litres/min of de‐ionised (DI) water. These staggering numbers outline how unsustainable wet processes are, if the PV solar industry is to grow as predicted.

Technical limitations of existing wet process:

• Unsustainable due to water consumption
• Poor process control
• Limited throughput (due to large footprint)
• Very large tool footprint on factory floor (up to 17m long)
• Not adapted to advanced cell concept or thin wafers
• Not truly single sided process
• Process recipe highly dependent on substrate used
• Relatively poor texturing efficiency for mono‐crystalline wafers for inline wet chemistry or long time process for batch alkaline (anisotropic) texturing
• Surface contamination issues after a wet clean and subsequent drying

Technical limitations of existing DRY process alternatives:

Dry processing is a generic term that indicates all technologies that make little or no use of water.

Such plasma and vacuum based technologies are so far only established in the semiconductor industry. It has been seen as a potential alternative to the wet benches. However, despite being demonstrated in the lab, there has been no uptake of this dry vacuum based technology. This is mainly due to:

• Large price tag and CoO of the vacuum and plasma equipment
• Limited throughput
• High GWP gases required by the plasma etching chemistry (NF3, SF6).

The R&D work proposes to develop a novel process where the wet chemical steps are replaced by 0 GWP dry process steps. The successful development will lead to a cleaner, highly controllable, and potentially cheaper process that will deliver more efficient solar cell products with far less environmental impact. The process will meet the high throughput demand from the industry and show its potential to meet the PV market growth demand (potential for >2000 wafers/hour).

Each SME involved in the consortium has technology and process that need to be developed in order to achieve significant added value and applicability to the PV Solar cell manufacturing market. The combined development of the SMEs product will allow them to provide this novel processing solution for this market. This development cannot be achieved as a single step; it has to be carried out within the context of a complete PV solar cell manufacturing process development involving all of the manufacturing steps required for a solar cell. Specific solutions adapted to the dry technology will be developed. For the SMEs, this can only be achieved through an R&D collaboration that will address the following technological needs:

- Develop a novel texturing process using thermally activated Fluorine
- Develop novel mass spectrometry instrumentation for accurate texturing process control
- Develop novel wafer handling solutions to be integrated inside the etching reactor
- Develop a novel, viable solar cell manufacturing process that includes this dry texturing technology by using most adapted subsequent process steps solutions.

This cell process will eliminate the water usage and wafer contamination issues of the incumbent wet process and increase the overall solar cell product efficiency.

Project Results:

A first proof of concept for a non-contact wafer handling system was designed and tested, providing a means to move a floating wafer on the bottom face of an aluminium reactor wall. This set up incorporated ultrasound-air-bearing technology from ZS-Handling. Data gathered were used for further refinement, combined with acoustic and CFD modelling, in order to meet all the requirements of wafer processing in an in-line atmospheric reactor. The integration remained quite challenging but some very good new concepts had been developed during the first phase of the project. A second proof of concept for conveying solar wafers through a section of the atmospheric reactor was designed, built and tested. It incorporated an innovative concept of coupled ultra-sound bearing plates. The tests were very positive; the prototype provided accurate wafer positioning through the high purge gas flows and inside the very small entry slit of the reactor, frictionless motion and highly efficient pre-heating. The wafer pre-heating adds extra functionality to this section an atmospheric chemical reactor. The overall solution could be readily used for any atmospheric reactor. It provides perfect isolation of the chemical reacting zone, avoiding any sort of contamination, as only the wafer is travelling in and out of the reactor. In an industrial environment, where continuous 24/7 operation, this would lead to less disruptions of the production process due to maintenance and cleaning of the tool but also would increase the process stability as contamination can also lead to process drifts. The application of such technology would translate into cost saving for the production line.

A dry etching process using etching chemistries that do not generate global warming potential gases was developed, using a thermally activated etching gas (Fluorine) inside a chemical etching reactor that does not require any plasma or vacuum. The work was done at Fraunhofer IWS in Dresden with a reactor from Nines Photovoltaics. The reactor is designed to be single sided, i.e. the etching is applied only on one side of the wafer. The two main applied solar cell processes being targeted were front side texturing of the wafer in order to increase the amount of light absorbed, and back side etching of the cell in order to remove the emitter and provide a flatter surface.

A lot of the work focussed on better understanding of the etching mechanism for this particular type of reactor, in order to be able to get a better control of the final surface result. The texturing work resulted in excellent optical properties and uniformity across the 156x156 solar wafers. The weighed reflectivity reached for the bare wafer was as low as 2%. Highly controlled anisotropic etching of Si by thermally activated F2 was achieved. The anisotropy is the result of a self-masking effect in F2-Si reaction mechanism that has been exploited to create anisotropic structures with different aspect ratios. The amount of silicon removed to achieve this type of performance was less than a micrometer. A removal of very small amount of Si during texturing process is of high importance for advanced cell concepts that uses thinner wafers and also for the economical cell concepts that make use of thin epitaxial Si layers grown on top of low-cost substrates. The features etched on the silicon surface were of the nanometre scale, and the wafer substrates as a result look black, similar to the “black silicon” commonly obtained with reactive ion etching(RIE) machines. The “black silicon” process developed is very attractive from a cost point of view, because of the very small amount of etching required. This resulted in a process with a lot less silicon wasted than for a standard texturing process. Furthermore, the reflectivity obtained after the etch is so low that potentially, there would be no need to apply an anti-reflective (AR) layer during the cell manufacturing process. The AR manufacturing step is a standard step that requires the deposition of a thin, usually Silicon Nitride layer, by mean of expensive vacuum deposition machines. This could be another source of cost saving if this AR coating is not required anymore for its optical properties. In any case, this provides more freedom with the selection of dielectric layers used for passivation.

After carrying out modelling of the reactor and hardware changes, and furthering our understanding of the etching process at atmospheric pressure, we experimented with several modifications of the way the etching gas was delivered to the silicon wafer, and exhausted from the chemical reactor. This led to very different texture results. The texture produced has much wider surface features, comparable in scale to the current textures achieved with wet processes. This means that it should be relatively easy to integrate in a standard cell process.

Novel etching process recipes were also developed to produce a flattening effect, and applied to the back side of cells that had already been textured with micron-size pyramids. The process was monitored by a FT-IR instrument that gave very useful information on the etching behaviour for various recipes and wafer types.

Another etching process recipe combined with a specific hardware modification of the reactor lead to a configuration where potentially both saw damage etch and texture etch could be carried out at the same time. Saw damage removal is required for crystalline silicon wafers produced by the ingoting process, where the ingot is sliced into wafers in a subsequent step, leaving damage on the wafer up to several micron meters deep. In this particular case, combining saw damage etch and texture etch is preferable.

Full solar cells have been processed by Fraunhofer ISE and Solartec, who both integrated the dry process step in their cell manufacturing process. After installing and setting up the required gas supplies and scrubbing facilities in Fraunhofer ISE in order to be able to use safely the etching gas required, a new prototype tool, specifically built by Nines Photovoltaics for this project, was shipped over and installed. This new single wafer process prototype offered more automated process control and stable operation. It allowed the scientists of Fraunhofer to come up with a stable texturing process that could be used in the overall cell process, and fully focus on the development of the downstream process steps required for solar cell manufacturing in order to integrate them together. It was an essential part of the work to be carried out within this project: identifying interactions between the processes and adapting each step to each other in order to reach an optimised overall cell manufacturing process. After characterisation and validation of the texture etch results described earlier on (nano-texture, black silicon), the scientists focussed on improving the passivation of the front surface, in order to reduce the recombination induced by the novel texture. Because the nano-texture strongly enlarges the effective surface of the wafer, the increased amount of recombination, a main loss mechanism in a solar cell, has to be compensated by an effective passivation of the surface. This was achieved by using an atomic layer deposition process to deposit aluminium oxide (Al2O3), providing both a highly conformal deposition and a very strong passivation quality. Thin ALD Al2O3 layers form an excellent chemical interface with Si minimizing the interface defect density (Dit). The inherent high density of negative charges present in Al2O3 layers also provides an excellent field effect passivation. This process was optimized leading to effective surface recombination velocities below 100 cm/s which is a very good value on such rough and lowly reflecting surfaces.

A novel pre-ALD process step was also developed, leading to consistent surface passivation results, and reducing the effect of the texture depth on the final result.

The phosphorus emitter diffusion process was also optimised to suit the increased surface area of the textured surface, and to reduce heavily doped areas. The results of the work on these two steps were quite successful, and lead to equal or better results than reference wafers. Here, emitter saturation currents J0e of below 200 fA/cm2 for samples including the nano-texture and ALD Al2O3 passivation were achieved which is slightly lower (better) than the reference process at ISE including a standard wet-chemical texture, standard emitter and a PECVD SiNx passivation. However, in the top parts of the nano-texture at the actual process sequence still remains a very highly phosphorus-doped area from which the generated minority charge carriers cannot contribute to the solar cell current due to too-low diffusion lengths (high recombination). At the moment, this leads to a loss in short-circuit current in comparison to reference solar cells. Finally, the work tasks were focussed on achieving a good contacting of the cell. This last step is closely related to the diffusion step, hence numerous iterations were necessary. Several batches of dry etched wafers were processed through the various manufacturing steps in the pilot line of Fraunhofer ISE, either as partial cell or full solar cell in order to assess the influence of the various parameters and strategies deployed to improve the final electrical performances of the solar cell. The contacting together with the parasitic absorption within highly doped top parts of the nano-texture of the cell remain the most challenging and is still holding back the overall efficiency of the best cell produced so far. However, we are very confident that further optimisation of the interlinked production processes nano-texturisation, emitter diffusion and solar cell contacting will overcome these issues.

During the lifetime of this project, an in-line monitoring solution was being developed in order to provide a good etching process control. All requirements specific to this type of process have been compiled in a specification document and several design options were proposed, involving technologies such as mass spectrometry by ALYXAN. In-line process monitoring of the etching reactor was pursued by installing an FT-IR instruments on the exhaust of the reactor. After calibration, FT-IR could detect the main product of the etching reaction (SiF4), and the time signal was used in order to estimate the efficiency and stability of the etch. Very relevant results were obtained, in particular results showing a clear correlation between the surface texture and the evolution of the FT-IR signal. This helped the understanding of the etching process and constitutes in itself a very good tool for development of the texturing process, as the evolution of surface changes during the etch is reflected by the time signal. In parallel, several proof of concept experiments were carried out by Alyxan using their mass spectrometer technology (FT-ICR), in order to devise a sampling and ionisation strategy that would meet the specific requirements of the etch process. The main difference here is that F2 can be monitored directly, circumventing the limitations of the FT-IR optical method. Quantitative experiments were carried out showing good suitability for the relevant gas concentration. Other experiments included sensitivity for lower concentration. A soft chemical ionisation method was also devised. Overall, the results lead to the detailed design specifications of a modified MS instruments, based on Alyxan ‘s current product that would be much more adapted to the task in terms of detection range, sensibility but also cost for such a product, keeping in mind that this would need to be integrated inside an etch equipment.

Vestlandforsking have carried out a review of emission regulations. They also gathered all the relevant data required for the Life Cycle Analysis of this new manufacturing process, in order to compare it to the standard wet chemical route. The results show that the dry process is better than the wet process on all impact categories, though this LCA is limited in scope and based on preliminary values.

Potential Impact:

SOLNOWAT focuses on dry atmospheric pressure silicon etching technologies using non GWP gases and chemistries, to achieve the precise textures required for efficient solar cell manufacturing. This etching equipment had to be developed to produce efficient texturing chemistry and will require in an industrial environment the added value provided by a high performance process monitoring solution and a non-contact wafer handling technology. It was also integrated in an overall solar cell manufacturing process.

THE PRIME INDUSTRIAL OBJECTIVES ARE:

+ Reduce overall cost of solar cell production
+ Deliver a process with increased throughput that can meet future needs
+ Reduce production costs related to GWP emission and water consumption
+ Streamline the production process
+ Reduce the footprint of equipment required for etching steps
+ Enable a number of advanced cell technologies

THE SOCIETAL OBJECTIVES ARE

+ Reduce unnecessary water usage of the PV industry
+ Reduce and control CO2 emission compared to current process
+ Disseminate to global solar cell manufacturers
+ Produce accurate measure of manufacturing process emissions
+ Preserve the PV industry‘s image as truly green

SOLNOWAT will decrease the cost related to solar cell production mainly by:

+ enabling new technologies that require less raw material (thin cells)
+ improving the cell efficiency
+ developing a flexible process compatible with various wafer types
+ increase the potential throughput of the process

A 60 μm decrease in wafer thickness leads to approximately to 10‐15 % cost reduction. SOLNOWAT‘s novel process technology allows for further cell conversion efficiency improvements and will also translate into cost reduction. Enhancing light trapping through better front surface texturing can potentially lead to a 1.4% efficiency cell improvement. Tweaking the back‐surface reflector to get better light trapping and passivation could lead to an extra 2%. According to cell manufacturers, each 1% cell improvement leads to 7% cost reduction at all levels of the value chain.

To be adopted by the cell manufacturing industry, the successful process will have to demonstrate strong controllability and be able to scale. The SMEs believes that by combining their interest and capabilities through SOLNOWAT, they can develop and bring this dry process to market in the very near future, and offer it to large cell manufacturing companies.

The impacts of this project are directly aligned with the targets & goals outlined by the European

Commission in relation to research activities in PV: “Research and development should lead to reduced material consumption, higher efficiencies and improved manufacturing processes, based on environmentally sound processes and cycles.”

Following a European investment of circa €1.1m this project has the potential to increase

participating SME’s sales revenue to in excess of €273 M and employ in excess of 146 people within the Union over a 5 year period following completion, representing a cost/revenue ratio of over 200. There will be a considerable economic impact with the adoption of this technology. It is expected that the cost per Watt Peak (Wp) of the specific etching step can be reduced by close to 30% in some cases. The initial targeted cost per wafer we have set is under 7 Euro cents for a 2μm etch depth. The Current Wet Etch technology is circa 10 Euro cents per wafer. There is an economic impact of reducing the water consumption; currently it is estimated that the cost of water consumption for 1 GW PV manufacturing plant is circa €4‐6 Million per year. Plants running advanced cell concepts, utilising significantly more etching steps, cost close to €10 million per year.

The output of SOLNOWAT is a new proprietary solar cell process, designed and engineered for crystalline silicon PV solar cell production, including novel dry zero GWP etching steps. This is a complete step change from the state of the art. It is anticipated that following successful completion of the FP7 programme a fully developed process will be brought to market between 6 and 12 months. Once this technology has been successfully demonstrated, there will be increased interest in applying it to other cell technologies.

IP benefiting all participating SME’s has been generated through this project, relating to c‐Si solar PV cell manufacturing techniques, hardware, process knowledge and data. The IP generated will enable European SME’s offer higher value add products to the PV cell manufacturing market.

Working at a trans‐national level allowed all partners to gain access to core competencies, and permit an efficient dissemination of relevant knowledge to each of the participating countries. It enabled participants from smaller economies to benefit fully from available industrial EU infrastructures. This is a unique opportunity for SOLNOWAT's SMEs to work with the best R&D facilities available in Europe in the PV sector, facilities that they could not have accessed otherwise. They have now developed a lasting relationship with these R&D Institutes, and increased collaborations at the European level.

The documented results and dissemination already provide SMEs with a real advantage when facing future customers; it enhances their credibility. The quality of the consortium and its RTD performers backs up the claims presented and increase the customer's confidence and willingness to engage with the SMEs of SOLNOWAT. This program constitutes a very significant marketing tool, and bring clear advantages to the SMEs.

Given that SOLNOWAT is an applied research technology it is important to ensure that no confidential information about the project and its developments are disclosed which could jeopardise the commercial potential of the results. To this end, even though the dissemination of the foreground of the project is essential, all project results are confidential because of the need to protect the intellectual property and interests of the participating SMEs. The non-confidential information that has been so far identified can be found in the following documents and reports:

• Content of the SOLNOWAT website- http://nines-pv.com/solnowat
• SOLNOWAT project summary or factsheet (can be downloaded from www.nines-pv.com/solonwat)
• Key scientific and technological achievements and milestones, without including protected technical details.
• Scientific publications, posters and presentations.
• SEMI & ITRPV meeting

In terms of disseminating SOLNOWAT to industry, the aim is to promote the uptake of the technology by all potential industrial stakeholders. As a result, the core message is hinged on the Unique Selling Points (USPs) of SOLNOWAT, which also include the basic technologies and their novelty, as well as the impact for profitability. Solid technical and scientific proofs of concept have been compiled over the past few months which will help to substantiate the claims that are made. We have been active with both the SEMI PV group and the ITRPV (International Technology Roadmap PV) both of which are instrumental is mapping out the way the industry will go as it grows into the future. Members of these two groups include both cell manufacturers and equipment developer and providers.

For the public, the key message focuses on the socio-economic impact of SOLNOWAT particularly the potential impact in terms of raising the profile and viability of PV solar for electricity production. The communications has been in plain language and without unnecessary technical jargon. The aim was to stimulate interest in SOLNOWAT and provide evidence of the need and possibilities for technology for PV solar cell manufacturing, as well as to transmit the social benefits that can be derived from public funding.

The presentation of new findings and the stimulation of further research are the drivers to communicate the findings of the SOLNOWAT project to the research community.

Most companies consulted expressed their desire to be provided with up-to-date information on the progress and success of the SOLNOWAT project, and the consortium is doing its best to ensure that such non-confidential information is provided to the public once it was available. A number of end-users (PV solar cell manufactures), upon learning about SOLNOWAT, expressed an interest in taking part in the validation stage of the project, as they could envisage tangible benefits from such a technology.

Consortium members have also presented the SOLNOWAT project via leaflets, posters and presentations disseminated at a number of conferences in the US and Europe. Conference attendance has played a significant role in the direct dissemination of information about the SOLNOWAT project to industry players.

The summary of dissemination actions highlights the intense dissemination of the SOLNOWAT project that has taken place, both by both face-to-face via industry consultations and conference attendance. This emphasis will be maintained over the post-project months.

Further efforts will be put into disseminating the results of the project to the general public via Press releases and Video production. Efforts so far have yielded positive results, with a number of Press and Web releases published. As more results emerge from the project, more substantial Press releases can be prepared and distributed to as wide an audience as possible.

At the end of this 24 month project the exploitable results comprise solar cell processing data and processes developed at the Fraunhofer ISE facility in Freiburg Germany, etching process recipes, characteristics and hardware configurations, various hardware prototype set up trials and a LCA analysis of the proposed new Dry Etch techniques in the context of solar cell manufacturing.

Solar Cell processing Data & Dry Etching processing data:

The data collected here is of critical importance, there has been some IP developed that has the potential to be protected under patent but in the main the exploitable value here is in the process validation and design-in arena. The fact that the consortium have made solar cells that work well and are comparable with cells manufactured using the standard solar cell manufacturing techniques is an important milestone. There have been a number of process integration issues identified and solutions developed and tried. The consortium has taken its lead from commercial cell manufacturers in this regard. We have shared our results and progress with a number of tier one manufacturers and looked for feedback in relation to our efforts, asking what they would need to see to adopt such an approach.

Process monitoring:

The development from this work has led to a method of real time monitoring of the etch process itself. The consortium sees a real potential for this real time monitoring to be used for quality control and process optimization in a volume production environment. This approach could lead to deployment of SPC (Statistical Process Control) techniques that could really improve the yield from a high volume production line. The exploitation of such work will once again come in the form of the deployment of the PV tool in volume production customer sites. There may be an opportunity to develop software for analysis, the data could then be licensed to manufacturing customers.

Hardware development for atmospheric reactor technology:

Along with this process work, another very promising development was the work on the non-contact wafer transport mechanism so that it can be applied to the process reactor. Once integrated into a fully automated tool it will help to eliminate contamination from the reactor which will lead to an improved quality of the resulting process. A number of gas delivery configurations leading to direct influence on the etching results were also developed.

LCA analysis

The Life Cycle Analysis carried out by the Stiftinga Vestlandforsking (VEST) goes a long way to showing the industry how this new technology is future proofed. It shows that there is a viable alternative with respect to the overall carbon footprint for solar cell manufacturing.

List of Websites:

http://www.solnowat.com


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