Papers by Keyword: Wet Etching

Abstract: Strain relief etching is a critical wet process technique use in high volume manufacturing of semiconductor substrates and device wafers. The goal of a strain relief etch is application dependent but can generally be considered for removal of warp/bow or improving mechanical strength by removing sub-surface damage thereby optimizing yields. Silicon Carbide (SiC) has a high chemical resistance which has blocked SiC wafer manufacturers from using strain relief etching to date. In this work, we demonstrate strain relief etching using an Advanced Chemical Etching (ACE) process of the full wafer surface on commercial grade 4H-SiC wafers and poly-SiC wafers at high etch rates (μm’s/hr) which enable ACE as a production technique. The data shows a 4 times improvement of breakage strength, from 13 to 55N, in laser split wafers. Bow and warp of ground wafers is reduced from 70/250µm to -5/25µm approx. respectively, matching Chemical Mechanical Polished (CMP) wafers which is the industrial method for preparing wafers. Thus showing the potential of stronger, flatter wafers being available for chemical mechanical polishing.

Abstract: Etch profile control of the wafer surface is a key application for single-wafer wet process equipment. Wet etch processes are grouped into two types, either uniform flat etch profiles or specific non-flat etch profiles that are required for downstream processes. For both groups of etch profile it can consume time and resources to obtain the processing conditions to achieve the desired etch profile due to the complex interactions in the process. Etch profile prediction models can provide process engineers a valuable tool to identify processing conditions to get the desired etch profile in less time. In this paper, we introduce an etch profile prediction model using a Convolutional Neural Network [1] and validation of the prediction model against actual experimental data. We also investigated methods on how to select the comprehensive learning conditions and understand the relationship with prediction accuracy and the number of learning conditions. We found the choice of parameter type to describe a process condition can affect prediction accuracy. The prediction model reproduced the trend of etch profiles even when learned on a small dataset.

Abstract: Abstract. Advanced semiconductor technology features complicated three-dimensional nanostructures and nanoconfined spaces such as nanosheets, supervias, deep contact holes and nanocavities. Uniform wet etching of such nanoconfined spaces across different feature sizes or critical dimensions (CD) is extremely challenging. Typically, etch rate decreases with decrease in CD size. In this paper we report methods to achieve uniform wet etch rate (ER) of SiO₂ across different CD sizes by mixing organic solvents in the etching solution. We also report a reversal of etch rate trend where SiO₂ structure of smaller CD etches faster than a larger CD, by tuning the ratio of organic to water solvents in the etching solution. We also investigate the impact of parameters such as solvent type, wall material, surface tension and ionic strength on ER. Our data suggests, while surface tension and ionic strength show no impact, the type of wall material, surface potential and organic solvent amount in the etching solution show a strong influence on SiO₂ ER. Also, zeta potential could explain most of our results but not all, suggesting that surface potential is not the only factor impacting CD dependent ER in a nanoconfined spaces.

Abstract: We achieved the controlled recess of molybdenum (Mo), which is alternative interconnect material for copper (Cu), by wet chemical etching. This wet etching process includes two main steps which are chemical oxidation of Mo and its subsequent dissolution, respectively. Firstly, Mo nanowires (NWs) are uniformly oxidized with potassium permanganate (KMnO₄) solution in acetone. Secondly, the Mo oxide is dissolved using an aqueous solution of HCl. Mo NWs are characterized through transmission electron microscopy (TEM) imaging after each of the above steps. Cyclic etching experiments including oxidation and dissolution of Mo showed that Mo recess is linear and can be controlled for each cycle, where the etching produced the smooth Mo surface. This controlled Mo recess is crucial for the fabrication of next-generation metal interconnects.

Abstract: Wet chemicals for ruthenium (Ru) etching are required for the formation of reliable Ru interconnects in advanced semiconductor technology nodes. In the present study, a novel alkali wet etchant, referred to as TK-1, has been developed in order to overcome issues with conventional Ru etchants, such as a low etch rate and the formation of toxic RuO₄ gas. Regardless of the Ru deposition process, TK-1 exhibits a high Ru etching selectivity of greater than 100 relative to dielectric and liner materials. It also suppresses the production of RuO₄ during the etching process. TK-1 has potential applications for Ru recess etching during fully self-aligned via fabrication.

Abstract: In 4H-silicon carbide crystals, basal plane slip is the predominant deformation mechanism. However, prismatic slip is often observed in single crystals grown by the physical vapor transport method as the diameter expands to 6 inches or larger. Thermal modeling has shown that occurrence of prismatic slip is attributed to increased radial thermal gradients. While X-ray topography can be used to characterize the presence and extent of prismatic slip, the feasibility of using the chemical etching method to assess the extent of prismatic slip in an industrial setting is investigated. The distribution of scallop shaped etch pits oriented along the directions that correspond to prismatic dislocations, correlate well with the results of the thermal model that predicts the occurrence of prismatic slip dislocations. This capability of the etch pit method to characterize prismatic slip can be used to manage radial thermal gradients during PVT growth.

Abstract: Wet etching in nanometer-sized three-dimensional spaces creates new challengesbecause of the scaling of semiconductor devices with complex 3D architecture. Wet etching withinspaces is affected by the mass transport of the etchant ions that are impacted by the hydrophobicityand surface potential of surface. However, the kinetics of chemical reactions within the spaces is stillunclear.In this paper, we studied the effect of hydrophobicity and surface potential of silicon surface on SiO2etching in nanometer-sized narrow spaces by adding various additive components to etching solutions.We found that the transport of etchant ions into narrow spaces is governed by controlling thehydrophobicity and surface potential of the confined system walls.

Abstract: In this work investigation on wet etching of ion implanted 4H-SiC has been performed. Starting with the search for a suitable etching solution is followed by investigations on how to damage 4H-SiC in an efficient way involving different implantation species in various doses. With the help of Monte Carlo simulations a model for the experimental findings is proposed to derive the limitations for the wet etch capability.

Abstract: Deep wet etching for polished fused silica glass in HF solutions was investigated to manufacture quartz pendulous reed with better surface quality and higher size precision. It is widely believed that etching rate was mostly decided by the temperature and concentration of HF solutions. But, in the beginning it was found difficult to control the uniformity of etching depth when the glass was etched for 0.3 ~ 0.5 mm each side. Now, it is detected with help from new designed etching machine that depth of 0.5mm or more can be achieved very easily. And the uniformity about ±0.002 mm would also be realized easily by keeping the sample glass at same depth and moving all the time in HF solution with the temperature and concentration are 45°C and 40% HF

Abstract: We investigated the effect of Si wet etching on the vertical step at wafer edge. We found that the concave-convex shape appeared at the wafer edge after Si etching by the Atomic Force Microscopy analysis. From the liquid simulation and the detailed evaluation of Si etching rate, we revealed that the concave-convex shape was formed by the distribution of the fluid velocity at the wafer edge.