How Optimum Particle Reduction is Achieved in a Wet Bench Process

When microscopic particles remain on the surface of silicon wafers during a wet bench process, the resulting semiconductor products may be of reduced quality or even defective. As semiconductor geometries and microscopic structures become smaller and are packed more densely on a silicon wafer, the presence of particles can influence the etch rate around the particle and compromise semiconductor fabrication. The smallest structures and conductor paths can be influenced by particles in the submicron size range and these particles are especially difficult to remove completely.

Modutek has developed innovative solutions that achieve particle reduction through reduced handling of wafers and excellent particle removal. The single chamber IPA Vapor Dryer and the use of megasonic cleaning deliver excellent results. The reduced particle count produces better yields and higher quality output. At the same time, Modutek’s solutions save money through the reduced use of chemicals.

The Single Chamber IPA Vapor Dryer Keeps the Particle Count Low

Modutek’s single chamber IPA Vapor Dryer incorporates rinsing and drying in a single system to save space, reduce costs, and minimize the handling of silicon wafers. The system initially rinses the wafers with de-ionized water and then introduces IPA vapor into the drying cabinet. The vapor comes from a one-gallon bottle that is located in the exhaust compartment for easy changing.

IPA vapor is introduced into the drying chamber from the top to ensure even distribution and reduce the amount of IPA required. When the IPA vapor condenses on the wafers, a surface tension gradient develops between the IPA and the remaining water. When water flows off the wafer surfaces it can remove the contaminating particles. The dry wafer surface doesn’t have any water marks and no particles are added.

One source of particles is the handling of wafers during transfers between stations. Reducing the number of transfers eliminates a source of particle contamination. Modutek’s Single Chamber IPA Vapor Dryer can handle an optional etching feature and drying in the same system. The wafers are rinsed and dried without transferring them to a new station. Since no additional particles are introduced during this process the particle count is kept to a minimum.

Megasonic Cleaning Effectively Removes Particles Without Toxic Chemicals

Megasonic cleaning relies on high-frequency sound waves in the cleaning solution to remove contaminating particles from wafer surfaces. Modutek has partnered with Kaijo Corporation, a world leader in megasonic cleaning systems to incorporate this technology in their wet bench equipment.

A megasonic generator feeds a high-frequency signal to a transducer immersed in the cleaning tank liquid. The transducer converts the signal into sound waves that travel throughout the tank. The sound waves generate microscopic cavitation bubbles that produce a scrubbing action to clean wafers. Particles on the surface of the wafer are dislodged and washed away.

The higher the megasonic frequency, the smaller the cavitation bubbles and the gentler the cleaning action. The microscopic structures etched into silicon wafers are very delicate and could be damaged with rough cleaning. Megasonic cleaning uses frequencies of 950 kHz and higher. The tiny bubbles of megasonic cleaning deliver gentle cleaning action without damaging fragile silicon structures.

Although megasonic cleaning works well with DI water or an SC1 process, adding a mild detergent or solvent can improve cleaning performance. Particles on silicon wafer surfaces often adhere to the surface and can be difficult to remove. Submicron particles may stay within a surface boundary layer, resisting removal. The microscopic bubbles can dislodge such particles, but the addition of solvents or detergents helps dissolve the bonds holding the particles to the surface and can improve particle removal.

Modutek Innovates to Help Meet Customer Challenges

Modutek works closely with customers to identify issues with wet process applications and continually works on developing new innovative solutions. The Single Chamber IPA Vapor Dryer and the megasonic cleaning process are innovations that help reduce particle counts while reducing chemical use and lowering costs. Modutek’s experience with wet processing equipment ensures customers will continually be able to improve their process performance results. Contact Modutek to schedule a free consultation to discuss your specific process requirements.

How Software Controls Achieve Best Results in Silicon Wafer Processing

Depending on the degree of automation, software controls can enhance wafer manufacturing facility performance and achieve improved results. Full automation lets operators take advantage of different operational modes to test new process steps and optimize process variables. The controls can then run the process with precise repeatability and often without operator intervention. The reduction in operator error, monitoring chemical concentration with dosing capability and the increased reliability can result in higher yields and reduced costs with more efficient silicon wafer processing.

Automation controls in wafer manufacturing equipment must be reliable and accurate enough to reproduce exact chemical doses and process times, but flexible enough to permit technicians to make changes when needed. An intuitive operator interface, transparent programming of process steps, and easy adaptation of variables to new requirements help achieve excellent results. Software controls that deliver reliable reproduction of existing processes along with flexible programming for responding to changing requirements can significantly improve facility output.

Software Must Combine Support for Current Operations and Meet Future Needs

Modutek’s software can set process parameters such as chemical dosage, wafer etching, and cleaning times as well as other process parameters. Touch screens with a Graphic User Interface (GUI) allow operators to see process status and intervene if necessary. The displayed process shows the information on the status of the processing equipment. In addition, all set points can be easily modified to reflect your requirements. The software Modutek provides combines operational reliability with the flexibility needed to adapt the programs to new situations or requirements.

Optional Equipment Interface Makes Sure Commands Are Executed Correctly

Modutek offers SECS/GEM protocol or Ethernet access for the data logging interface. This interface allows Modutek to make output changes and integrate new wafer manufacturing equipment while ensuring that software commands are executed properly and accurately. Operators can read displays of process characteristics on the GUI to ensure command execution takes place as expected. All these options are reviewed during the station design layout process to ensure it meets your process and budget requirements.

Peripheral Control Features Can Enhance Software Performance

Data logging can improve performance by providing operators with additional information that allows them to optimize operations. Data loggers can track indicators such as output, process temp, processing times, and all alarm features. All data can form the basis for an evaluation of facility performance and plans for targeted changes to reach clearly defined goals.

Modutek can integrate standard or custom peripheral control features as needed by customers for specific applications. Customers may require certain information to optimize their process or depend on output data for subsequent action. Modutek can analyze such requirements and add the necessary functionality, both in terms of sensors or additional equipment and to ensure the information is processed and presented in a useful format.

Designing and Building Advanced Software Controls to Improve Silicon Wafer Processing

As a leading wet bench manufacturer with extensive experience and expertise in designing and building equipment in-house, Modutek works with customers to ensure their software controls meet their needs. In addition to providing excellent customer support, Modutek can evaluate complex customer applications to propose the best possible solutions. Contact Modutek for a free consultation to discuss your manufacturing equipment needs.