Etching of SiO2 layer in SOI substrate using RIE

In summary, the conversation discusses etching SiO2 buried layers for MEMS suspended structures using CHF3+2% O2 plasma. Both vertical and lateral etching of SiO2 should have similar etch rates, but the depth and feature definition may vary.
  • #1
sandeep4442
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Hello all,
I am trying to etch SiO2 buried layer for MEMS suspended structures using RIE and the receipe is CHF3 + 2% O2 Plasma. In my structures, the sacrificial layer is SiO2. How does the etching process vary from vertical to lateral (underneath of top Si) etching of SiO2.
 
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  • #2
Thank you.The etching process won't vary much between vertical and lateral etching of SiO2. Both should have a similar etch rate, since the CHF3+2% O2 plasma should be able to etch in both directions. The main difference will be the depth of the etch, as the lateral etches will only go as deep as the top Si layer, while the vertical etches can go much deeper. Additionally, you may get more feature definition with the lateral etch, since it will be easier to control the etch depth.
 

1. What is RIE and how does it work in etching SiO2 layers in SOI substrates?

RIE stands for reactive ion etching, which is a type of dry etching technique used in semiconductor processing. In RIE, a gas is introduced into a plasma chamber where it is ionized and creates reactive ions. These ions are then accelerated towards the surface of the substrate, where they react with the material and etch it away. This process is highly controlled and allows for precise etching of materials such as SiO2 in SOI substrates.

2. Why is RIE preferred over other etching methods for SiO2 layers in SOI substrates?

RIE is preferred over other etching methods for SiO2 layers in SOI substrates because it offers several advantages. It is a dry etching technique, which means it does not use any liquid chemicals that can cause damage to sensitive electronic components. RIE also allows for highly anisotropic etching, meaning that the etched features have vertical sidewalls, which is important for creating precise and uniform structures in semiconductor devices.

3. What are the key parameters to consider when using RIE for etching SiO2 layers in SOI substrates?

Some key parameters to consider when using RIE for etching SiO2 layers in SOI substrates include the gas composition, pressure, power, and temperature. The gas composition determines the type of ions that will be generated in the plasma and their reactivity with the material. Pressure affects the ion density and energy, while power and temperature control the etch rate and selectivity of the process.

4. How can the etch selectivity between SiO2 and SOI layers be controlled in RIE?

The etch selectivity between SiO2 and SOI layers in RIE can be controlled by adjusting the gas composition and process parameters. By using a gas that is more reactive towards SiO2, the etch rate of SiO2 can be increased relative to the SOI layer. Additionally, by optimizing the process parameters, the etch rate of SiO2 can be further increased while minimizing the etch rate of the SOI layer.

5. What are some potential challenges or limitations when using RIE for etching SiO2 layers in SOI substrates?

One potential challenge when using RIE for etching SiO2 layers in SOI substrates is achieving uniform etching across a large area. This can be addressed by optimizing the process parameters and using a gas distribution system that ensures consistent gas flow. Additionally, RIE can result in damage to the underlying layers due to ion bombardment, which can be mitigated by using lower power and optimizing the gas composition for more selective etching.

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