News Article
Advancement of wet processing technology
Siconnex Customized Solutions GmbH provides an insight into their BATCHSPRAY technology and its research and development.
FOR COMPANIES in the fast changing semiconductor industry, constant and effective innovation is the key to success. To ensure a high process quality, reliable equipment is essential. Process quality is one important factor. Another one is economy and environment. Cutting down on or replacing hazardous chemicals is beneficial for both of these.
Siconnex customized solutions GmbH, located in Hof bei Salzburg, Austria, develops wet batch spray processes and manufactures the associated BATCHSPRAY systems. The company's goal is to provide solutions, including optimal processes for best results with high throughput and low cost of ownership.
Siconnex puts a lot of effort into developing and improving processes in this area. Therefore a fully equipped laboratory with innovative and highly skilled technicians is located at their headquarters in Austria. Siconnex offers proven economically advantageous processes for BATCHSPRAY systems. Together with customers, Siconnex is developing customized processes for individual requirements and R&D. The achievement of this innovation results in reliable equipment with optimal process results. One mature process of Siconnex is metal etching.
Etching with precision
The main task in etching is to ensure repeatability and uniformity of process results. To comply with these requirements two basic options are available. One opportunity is using a recipe with a fixed time and accepting a higher overetch. The other is automatic adaption of etch time. With this the chemical can be used more often with a lower underetch. This solution is of course the more cost-effective.
The main question is how to calculate the etching time? The etch rate of used, decomposing mixtures is almost impossible to predict, since there are many factors which influence it. Due to this fact, a calculation via etch rate is not very accurate. A better way is to make the process independent from the etch rate and consequently independent of the current chemical composition.
This is possible by using the characteristics of spectroscopy. Different layers reflect different wave lengths. This system makes it possible to identify exactly the moment when one layer is etched completely.
Run-to-run uniformity improves significantly with this feature, without changing the mixture at each run.
Intensive investment into process and equipment development for Siconnex Systems made it possible to achieve typical etch uniformity rates of less than 2% within wafer for etching processes on 200mm and 300mm substrates. A further benefit of using this so called "end point detection system" is the reduction of chemical consumption due to a longer usage of the decomposing etchant.
Cost effective cleaning
Cleaning steps are essential for the performance of the final product. Processes with reclaimed chemicals or in baths can hardly guarantee that required quality. As a result the trend in the past was tending towards single wafer cleaning for small features and 300mm applications, although the costs are higher than with batch processes. Cost effective production together with product quality is the main objective for each fabrication plant. Thus, the cost of ownership and the price are becoming more and more important.
Altogether, low costs with high throughput and an optimal result is the main goal. This objective is achievable with the so-called "SicOzone process" of Siconnex. So what is the difference between this process and common cleaning processes? When it comes to cleaning, the main objective is "less is more". Processes with diluted chemicals are more effective than processes with concentrated chemicals as has long been proven in the field. Peroxide as an oxidizing agent is essential for the chemical reaction in these processes. Peroxide is however a potential source of metal contamination.
So, how to solve this issue? The solution is to substitute the peroxide with another oxidizing agent, namely ozone. This gas can not only be generated extremely cleanly and cheaply, it also leads to better results than peroxide.
In baths, ozone is mainly used dissolved in water. The concentration of ozone in these baths is very low because it decomposes very quickly in warm water. The optimal utilization of ozone is to apply it directly and in high concentrations to the substrate.
The SicOzone process combines concentrated ozone with highly diluted chemicals for single use. For this process the ozone does not have to be dissolved in the deionized water. The BATCHSPRAY Clean system of Siconnex was developed especially for this cleaning process.
With that knowledge, Siconnex can achieve optimal results using BATCHSPRAY technology. The chemical consumption is very low due to high dilution, even for single use. It results in an efficient and cost effective process.
Stripping without solvent
Resist stripping is a well discussed topic in every fabrication plant. Most of the time, solvents are used for stripping that are not only very expensive, but also very harmful for humans and the environment. So nowadays the trend is tending towards solvent free fabrication plants.
Implementing this is a very tough task, as there is a high number of different resists and solvents used throughout the industry. Even more important for resist stripping are the processes between the developing and the stripping of the resist.
Here again, just like for etching, the usage of ozone is emphasized because of the large range of resist types, for which ozone is applicable for stripping. Many resists can be removed just with water and ozone. For stressed resists, Siconnex adds different chemicals to enhance the stripping. This technique improves the strip rate significantly. When using ozone, the exposed materials have to be taken into consideration as some materials, like copper, oxidize when exposed to ozone.
The Siconnex process department has conducted a number of tests with different stressed resists using the SicOzone stripping process. The success is shown in the results; they achieved strip rates of about 1µm per minute for a wide range of resists. For special resists or layers which are sensitive to ozone, Siconnex can also provide appropriate solutions with the use of different chemicals in their BATCHSPRAY system.
The beauty of automation
In a modern state of the art fabrication plant, automation is not an option nowadays, but a necessity.Especially for small features, contamination due to manual handling must be prevented to ensure optimal results. Safe and clean automation is therefore necessary. So how best to fulfill these needs? Siconnex provides a clear answer and the perfect solution. The BATCHSPRAY Autoload system. It is the company's latest development which provides a reliable and clean automation system. A piece of equipment which can reach throughputs of up to 400 wafers per hour in less than 8m2 "“ fully automated.
