Evaluating the quality of etched silicon carbide requires measuring its root mean square roughness (RMS). Results from an in-depth study demonstrate a direct relationship between plasma power and UDC parameters for the etching process and surface morphology.
When performing the etching process, plasma-generated chemical compounds interact with silicon carbide substrate and deposit their molecules on its surface, leading to localised differences in chemical composition and creating local heterogeneities in its chemical makeup.
Etchants
The choice of etching compounds depends on the requirements for an etched pattern. For instance, some etchants are better suited for polycrystalline 3C-SiC etching than single-crystalline SiC; and their etch rates also depend on temperature fluctuations. Sometimes it may also be necessary to combine multiple etchants together so as to form nonplanar microstructures such as trenches or mesa structures with tilted sidewalls at controlled angles using ICP-RIE. All these variables can be managed and managed using ICP-RIE.
ICP-RIE is an effective combination of physical and chemical etching mechanisms, enabling complex patterns to be created by skillfully controlling both flux of reactive ions and energy input into it. To avoid uneven sidewalls and undercutting on mask surfaces, skillful control of flux must be utilized by skillfully adjusting RF power in order to accelerate plasma ions, generate self-polarization voltage for substrate substrate and produce self-polarization voltage of substrate surface. This balance can be found through ICP-RIE’s ability to achieve balance when designing complex patterns involving intricate details on complex surfaces – creating complex patterns with great detail on surfaces without undercutting of sidewalls or undercutting on mask surfaces. However, to create patterns on mask surfaces it must also ensure even sidewalls or undercutting occurs as this balance must be maintained between physical and chemical etching mechanisms, with balanced flows from reactive ion flux energy to avoid uneven sidewalls or undercutting on surface mask surfaces. To do so effectively you must carefully manage reactive ion and energy flux/energy fluxes/energy via controlling reactive ion flux/energy flux/energy that the ICP-RIE process can enable this by skillfully controlling flux/energy flux/energy flux/energy flux/energy through carefully manipulating flux/energy/flow while energy can be controlled/generated/generated through controlling/adjusting the RF power to accelerate plasma ions generated, creating self-polarization voltage on substrate.
Selecting an optimal temperature mode for substrate holders can increase etching rates even further. This effect occurs because, as temperatures increase, all the carbonaceous acid present on a capped surface becomes involved in chemical reaction resulting in equalizing etching rates across both defect-free and imperfect areas of silicon carbide substrate.
Another factor influencing etching rate and quality is gas composition used in plasma. Here, the amount of oxygen present can have an impact on radicals’ residence time on surfaces being etched; this effect becomes amplified with higher gas flow rates. Therefore, using an etching gas composition containing 20-25% oxygen to achieve maximum etching rates would be highly recommended.
Preparation
ICP-RIE is a dry etching method widely employed for producing various semiconductor devices. Etching technology has proven particularly useful for processing hard materials such as silicon carbide, which has the potential for use in various power electronics devices5 and microelectromechanical systems (MEMS). ICP-RIE can also produce nonplanar structures, such as MESA structures with tilted sidewalls or trench structures with tapered sides, while still maintaining high levels of surface smoothness. Success of ICP-RIE in SiC etching relies heavily on selecting appropriate process parameters; for optimal etching results to occur it must be fully repeatable and stable, without erosion of mask material and no “micromasking.”
ICP-RIE has proven highly successful at etching SiC for applications such as power electronics and MEMS, yet the process does not come without its challenges; therefore, selecting suitable etching conditions must be carefully selected so as to not damage substrate and adjusted during etching process to achieve desired results.
An important determinant of plasma etching conditions is oxygen concentration. Studies have demonstrated that SiC etch rate strongly depends on oxygen percentage in plasma; as oxygen content in plasma increases, SiC etching rates drop due to diluting fluorine concentration with oxygen and formation of volatile SiFx (1×4) compounds on surface surfaces etched by plasma.
Additionally, plasma temperature must be tailored in order to regulate the etching process. Etching should take place below the melting point of SiC for best results in terms of avoiding oxidation and cracking of substrate during etching; ideal temperatures would fall within 300-400 degC range in order to minimize time-consuming processes while eliminating risk from thermal stress in MESA structures or trench structures.
Etching
Silicon carbide etching can be achieved using various methods, from wet etching and gas etching through liquid (such as water) etching and plasma to precisely define parameters of an etching process; such as the rate, sidewall inclination angle of MESA structures, surface morphology and surface roughness. It is essential that all these parameters be accurately specified, so as to optimize results.
When it comes to SF6 + O2 inductively coupled plasma (ICP), choosing appropriate process conditions is particularly crucial, given that this gas mixture allows users to create structures with near vertical walls while at the same time offering a high rate of etching.
Investigating the effect of substrate holder temperature on etching processes has been studied in depth, and results showed that root mean square roughness of SiC surfaces decreased with increasing temperatures of substrate holders; this may be attributed to increasing contributions from chemical components; equalizing rates across defect-free and imperfect regions in SiC substrate crystal lattice; or decreased redeposition due to ion bombardment.
As can be seen from the SEM microphotographs shown in Fig. 6, when etching was conducted using a plasma power of 25 W, its subsequent structure displayed high quality characteristics. Conversely, when performed at lower RIE powers the quality declined and pillars could be seen on its surface.
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