Manufacturing Silicon Chips

Micrometer scale precision manufacturing processing at Micronit demands the use of dedicated and consistent quality materials, such as silicon, glass, and polymers. 

When it comes to silicon, Micronit has built up a strong track record in developing and manufacturing microfabricated devices for life science, health applications and aerospace. 

In this article we will tell you about the most important aspects of manufacturing processing using silicon. 

Benefits of Silicon Chips – from a Manufacturer perspective 

Silicon is the material of choice when it comes to fabrication of integration of sensors, electronic circuits and CMOS, for example in bioMEMS applications. It allows combining CMOS technology with MEMS technology and microfluidics, which are becoming essential traits of the newest labs-on-chips for health and life science applications. 

Silicon's appeal in microsystems lies in its high-temperature stability, resistance to a wide range of chemicals, excellent mechanical properties, and monocrystalline structure utilized in silicon wafer production. Furthermore, silicon has a high degree of chemical inertness, and it does not react with oxygen, water, and most acids. However, it does react with dilute alkalis and halogens. Its relatively high thermal conductivity, compared to thermally insulating materials like glass, enables the ability of increasing the density of the on-chip components.  

A typical silicon wafer surface has a roughness of tens of nanometer with a significant low defect density that is realized by a dedicated polish process allowing for the high precision surface processing. Additionally, the autofluorescence property of silicon is relatively low and its transparency to infra-red wavelength radiation allows for specific optical applications. 

Microfabrication methods of Silicon Chips 

The large range of available micromachining technologies make it possible to structure and functionalize silicon substrates to a very high degree of accuracy: 

• Deep Reactive Ion Etching (DRIE) facilitates the creation of high aspect ratio structures such as comb-drives and trenches. 
• Batch-wise wet etching in alkaline solutions achieves anisotropic structures like cavities, ensuring reproducible and predictable outcomes based on silicon's monocrystalline nature.  
• Thin film deposition and patterning of materials like PZT layers and metal vias enable the creation of functional structures or serve as masks for selective etching. 

Types of Wafers for Silicon Chips  

The Micronit MEMS foundry offers silicon wafers processing up to a diameter of 200 mm. 

• Wafer thickness: 0.1mm-2mm . 
• Silicon on Insulator (SOI) and double-SOI (DSOI) wafers.. 
• Resistivity: ranging from <.01 Ohm cm to intrinsic silicon. 

Best Practices for your Design for Manufacturing process  

Besides the fact that Micronit has dedicated technology for silicon processing, we can assist you in your design for manufacturing (DFM) process. Understanding design rules and manufacturing processes is crucial to optimize costs and efficiency. Key considerations include: 

• In production we use standard-size, round, silicon wafers. Here industrial standard wafer thicknesses (coupled to the diameter) are attained, although a specific thickness is possible depending on our supplier availability.  
• The larger the wafer diameter and the smaller the chip size, the more chips will fit on a substrate, therefore, the lower the costs per chip and potentially a higher yield. Hence, it is worthwhile to consider a design in which such a small silicon chip can be added to a universal adapter, for example a larger cartridge or polymer microfluidic circuit board, towards an easy-to-handle but cost-effective solution.  
• Aspect ratio is a crucial factor for costs. Aspect ratio is the relation between feature width and height. Small features, like fluidic channels, that need to be realized relatively large depth, are in general more complex from a manufacturing point-of-view.  
• Keep the amount of functionality on each silicon chip to a minimum, preferably by transferring complexity and functionality to the readout station or an universal adapter.  
• Limit the amount of different channel depths in a single silicon chip as each depth will require the addition of a new etch mask with many process steps associated. 
• Silicon is a highly inert material and as such the chip could be up for reuse, especially in an application test phase.  

Getting started 

Are you working on a silicon device, such as a MEMS sensor, microfluidic structure, or hybrid device? Do you need CMOS post-processing services? Or would you like to discuss the best type of material for your project? Please, feel free to contact us directly. Our Sales and R&D teams will be happy to assist you!