CVD Tool Research Articles

Taguchi Design of Experiments to Optimize Material Removal Rate in Turning AISI 4340 Steel

In this work, an effort is prepared to optimize turning process by maximising the material removal rate (MRR). For experimentation, CNC Spinner 15 lathe machine is used. The input factors are spindle speed, feed rate, depth of cut and type of tool under the 3 altered values of noise factor. Output parameter is MRR. The work piece material is AISI4340 steel. The Taguchi robust design is achieved by implementing spindle vibration as a noise factor. The orthogonal Array L9 is used for experimentation. The MRR is calculated by the defined formula. The data analysis is done by Taguchi technique. The Higher-the-better signal-noise ratio is adopted to compute the quality characteristics S by N fraction of MRR for every run of experiment. Response table is then computed. The main effect plot is the base to discover the best situation of the response parameter. ANOVA is used to guess the significant parameters. The best setting is A-1 B-2 C-2 D-3 and E-3) i.e. spindle speed 780rpm, feed rate = 2.42 mm/rev, coated CVD tool, nose radius=1.2 mm whereas depth of cut = 1.5 mm.

Studying the Effect of un Coated and Multilayer Coated Tools on Cutting Temperature in Turning Operation

The present work studies three variables (cutting velocity, feed rate, and cut depth) on hard turning cutting temperature of uncoated and multilayer-coated carbide (TiN, TiN/TiCN, TiN /Al2O3/ TiCN) inserts are used in AISI 1045 alloy steel. The tool's temperature was measured simultaneously, measuring the temperature of the tool-chip interface using infrared radiation (IR) pyrometer in this investigation. This study investigated the performance of four distinct coated and uncoated PVD and CVD tools during turning operations. Four cutting speeds (56, 88, 112, 141) m/min, four feed rates (0.065, 0.08, 0.16, 0.228) mm/rev., in the experiments, a constant cutting depth of (1) mm was used. The results also show that Coarse cutting tools have a lower tool temperature than uncoated ones. In comparison to uncoated and other coated tools, the three-layer (TiN/ Al2O3/ TiCN) coating is especially effective in a range of (32% to 39%) than uncoated inserts at various cutting velocity and constant feed rates, with varying feed rates and consistent cutting velocity and lower by approximately( 34% to 40%) than uncoated inserts.

HARD TURNING PERFORMANCE EVALUATION USING CVD AND PVD COATED CARBIDE TOOLS: A COMPARATIVE STUDY

This study emphasizes the comparative cutting performance evaluation of CVD- and PVD-coated carbide inserts in hard turning of AISI D2 steel. The cutting factors, namely cutting speed (100[Formula: see text]m/min), tool feed rate (0.08[Formula: see text]mm/rev), and depth of cut 0.2[Formula: see text]mm, have been fixed for the entire study. The comparative study is based on the analysis of the obtained test results of flank wear, tool life, auxiliary flank wear, surface roughness, and surface texture. Both tools are catastrophically failed when tool wear reached limiting flank wear ([Formula: see text][Formula: see text]mm) criteria. SEM and EDS analysis of both the tools (at their end of tool life) are carried. Diffusion followed by adhesion is found to be the prime mechanism at the end of tool life. Based on limiting flank wear criteria, the tool life of CVD and PVD tools was estimated as 65 and 57[Formula: see text]min, respectively, i.e. the tool life of the CVD tool is 14% longer than that of the PVD tool. Considering the limiting criteria of surface roughness ([Formula: see text]m), the tool life of the CVD tool was estimated as 63[Formula: see text]min while for the PVD tool, it was found as 54[Formula: see text]min i.e. about 14.3% higher tool life was found for the CVD tool relative to the PVD tool. The auxiliary flank wear was observed to be lower for the CVD tool relative to the PVD tool. Surface roughness for both the tools increased with cutting time and the relatively larger rough surface was obtained with the PVD tool. The machining cost of one pass of the CVD tool is 2.5% less than that of the PVD tool. However, for mass production, the CVD tool is more efficient than the PVD tool for machining hard D2 steel ([Formula: see text] HRC).

Grey-Fuzzy Hybrid Optimization and Cascade Neural Network Modelling in Hard Turning of AISI D2 Steel

Nowadays hard turning is noticed to be the most dominating machining activity especially for difficult to cut metallic alloys. Attributes of dry hard turning are highly influenced by the amount of heat generation during cutting. Some major challenges are rapid tool wear, lower tool-life span, and poor surface finish but simultaneously generated heat is enough to provide thermal softening of hard work material and facilitates easier shear deformation thus easy cutting. Also, plenty of works reported the utilization of various cooling methods as well as coolants which successfully retard the intensity of cutting heat but this leads to additional cost as well as environmental and health issues. However, still, there is scope to select proper cutting tool materials, its geometry, and appropriate values of cutting parameters to get favorable machining outcomes under dry hard turning and avoid the cooling cost, environmental, and health issue. Considering these challenges, current work utilizes PVD-coated (TiAlN) carbide insert in dry hard turning of AISI D2 steel. The multi-responses like tool-flank wear, chip morphology, and chip reduction coefficient are considered. The amalgamation of input processing variables must be optimum for the effectual performance of hard to process materials turning. Generally, the Fuzzy logic hypothesis represents the uncertainties co-related with fuzziness, and deficiency in the data concerned with the problem. Further, to achieve the best combination of input cutting terms, grey-fuzzy hybrid optimization (Type I and Type II) is utilized considering the Gaussian membership function. Type II grey-fuzzy system attributed to 15 % less error (between GRG and GFG) compared to Type I. Hence, Type II grey-fuzzy system is utilized to get the optimal set of input terms. The optimal combination of input terms is found as t-1 (0.15 mm), s-4 (0.25 mm/rev) and is Vc-2 (100 m/min) which is comparable to the results obtained under spray impingement cooling using CVD tool in the literature. However, hard turning can be assessed under the dry condition with a PVD tool at the obtained optimal input condition for industrial uses. Further, six different types of cascade-forward-back propagation neural network modelling is accomplished. Among all models, CFBNN-4 model exhibited the best prediction results with a mean absolute error of 2.278% for flank wear (VBc) and 0.112% for the chip reduction coefficient (CRC). However, this model can be recommended for other engineering modelling problems. The outcomes of this research may be of immense importance to the tool manufacturers and machining industry.

Achievement of Low Carrier Concentration of High-Uniformity SiC Films Grown by High Speed Wafer Rotation Vertical CVD Tool

N-type 4H-SiC homo-epitaxial films were grown by high speed wafer rotation vertical CVD tool, and effect of surface C/Si ratios on in-wafer uniformity and lower limit of carrier concentration of the SiC films on 150 mm diameter wafers was investigated. From analysis of in-wafer distribution by mapping of whole wafers, it was found that high in-wafer thickness uniformity was obtained for the films grown both at lower introduced C/Si ratio of about 1.35, which corresponds to surface C/Si ratio is lower than 1.0, and at higher introduced C/Si ratio of about 1.80, which corresponds to surface C/Si ratio is higher than 1.0. However, larger fluctuation of the carrier concentration at wafer edge was observed for the film grown at lower introduced C/Si ratio, compared with the film grown at higher introduced C/Si ratio. Lower fluctuation of the carrier concentration for the film grown at higher introduced C/Si ratio is thought to be due to lower sensitivity of carrier concentration on growth temperature, which is observed for the film grown at surface C/Si ratio higher than 1.0. Also, the film grown at higher introduced C/Si ratio showed longer carrier lifetime with higher uniformity, although the film grown at lower introduced C/Si ratio indicated shorter carrier lifetime with lower uniformity. The mean carrier concentration of the films grown at higher introduced C/Si ratio was reduced by two digits compared with those grown at lower introduced C/Si ratio, and low carrier concentration of 1.7 x 1014 cm-3 with high in-wafer uniformity for intentionally doped SiC film grown at higher introduced C/Si ratio was achieved. Based on the results mentioned above, fabrication of thick and low-doped epi layer on 150 mm diameter wafer with high in-wafer uniformity was demonstrated.

Improvement of Repeatability on N-Type 4H-SiC Epitaxial Growth by High Speed Wafer Rotation Vertical CVD Tool

N-type 4H-SiC homo-epitaxial films were grown on 150 mm diameter wafers by high speed wafer rotation vertical CVD tool, and effect of surface C/Si ratio on short-term and long-term repeatability of the SiC films was investigated. By tuning of growth condition, high uniform SiC film with in-wafer thickness uniformity of ±2.8 % (1.6 % σ/mean) and carrier concentration uniformity of ±3.1 % (1.9 % σ/mean) was successfully grown at higher introduced C/Si ratio of about 1.80, which corresponds to surface C/Si ratio higher than 1.0 on the whole wafer. This result was comparable to the film grown at lower introduced C/Si ratio of about 1.35, which corresponds to surface C/Si ratio lower than 1.0 on the whole wafer. On the other hand, the films on 13 wafers successively grown at higher introduced C/Si ratio indicated low fluctuation from 1.85 to 3.09 % (σ/mean), and the short-term repeatability of the in-wafer carrier concentration uniformity of the films grown at higher introduced C/Si ratio was improved compared with the films grown at lower introduced C/Si ratio. Additionally, in-wafer carrier concentration uniformity of the films on 171 wafers grown at higher introduced C/Si ratio showed 75 % quartile of 4.26 % (σ/mean), and this result was greatly superior to that of 8.21 % (σ/mean) for the films on 130 wafers grown at lower introduced C/Si ratio.

Repeatability of Epitaxial Growth of n-Type 4H-SiC Films by High Speed Wafer Rotation Vertical CVD Tool

N-type 4H-SiC homo-epitaxial films were grown by high speed wafer rotation vertical CVD tool, and both short term repeatability and long term repeatability of epitaxial growth were investigated. In the short term repeatability investigated by 6 epitaxial wafers chosen from successively grown 12 epitaxial wafers using same recipe, it was found that total variation of thickness and carrier concentration for all measurement points of 6 wafers is 1.44 and 4.64 % respectively, which indicates excellent repeatability as well as high uniform thickness and carrier concentration. In the long term repeatability investigated by a very large number of growth experiments, probability achieving target uniformity of thickness and carrier concentration of the SiC films was increased up to 1.32 times by optimizing gas nozzle structure in gas inlet compared with in the case of conventional gas nozzles. Moreover, adjustment range of C/Si ratio necessary to achieve target uniformity of thickness and carrier concentration of the films was considerably reduced to 22 % by optimized gas nozzles.

Continuous Growth of Buffer/Drift Epitaxial Stack Based on 4H-SiC by Quick Change of N<sub>2 </sub>Flow Rate under High Growth Rate Condition

N-type 4H-SiC homo-epitaxial films were grown under high growth rate condition by high speed wafer rotation vertical CVD tool, and dependence on N2 flow rate for in-wafer distribution of thickness and carrier concentration was investigated. By adjusting only the N2 flow rate from 0.33 to 130 sccm, average carrier concentration of the SiC film was controlled within a range from 3 x 1015 to 1 x 1018 cm-3, while maintaining good in-wafer uniformity less than ±7.0%. Average growth rate higher than 54 μm/h and in-wafer uniformity less than ±3.1% were maintained and no dependence for thickness distribution on N2 flow rate was observed. Buffer/drift epitaxial stack using quick change of N2 flow rate was fabricated, and the crystalline quality and steepness of N concentration at buffer/drift interface were also investigated. The epitaxial stack showed lower defect density compared with single drift layer and showed steep interface between buffer layer and drift layer.

Influence of machining parameters on surface quality during high speed edge trimming of carbon fiber reinforced polymers

CVD diamond-coated carbide tools could provide an economical alternative for trimming CFRPs components compared to their PCD tools counterpart. Nevertheless, there are still some technical issues to understand related to wear resistance and surface quality. In this work, a CVD tool with six straight flutes was used to investigate the relationship between surface roughness, surface damage, tool wear, cutting force and cutting parameters during the high speed trimming of CFRPs. Statistical techniques for identifying and selecting the best cutting conditions for CVD tool are developed. In terms of tool wear, results show that the best operational condition to minimize the tool wear is achieved at lower feed rates and higher cutting speeds. Experimental results show also that a 0° ply orientation represents the worst case and produces the maximum tool wear. Furthermore, a strong correlation between the feed force and the tool wear was observed. It was found that the surface roughness decreases as a reciprocal function of cutting length. This decrease was due to the matrix burning/sticking and the thermal damage related to the low thermal conductivity of CFRP. In such situation, Ra becomes inappropriate indicator for roughness evaluation. On the other hand, it wasn’t seen any type of delamination or fiber pull-out on the trimmed surface of all coupons for the three tool life tests. Accordingly, delamination can be avoided using high fixture rigidity, high quality of CFRP laminates, a suitable cutting tool and stable operational conditions.

Reduction of Surface and PL Defects on n-Type 4H-SiC Epitaxial Films Grown Using a High Speed Wafer Rotation Vertical CVD Tool

4H-SiC homo-epitaxial films were grown using a high speed wafer rotation vertical CVD tool, and effects of wafer rotation speed during initial temperature ramping before epitaxial growth were investigated. Also, the effects of conditions during growth of the highly doped buffer layer on both surface and PL defect densities were investigated. It was found that the wafer rotation speed during the temperature ramping has a large influence on the surface defect density of the films. Especially, triangles generated from small pits were considerably reduced in the samples grown at a higher wafer rotation speed during the temperature ramping. The phenomena could be explained as a result of suppressed interfacial reaction between down-falls (DFs) and the wafer surface. Additionally, it was found that the density of basal plane dislocations (BPDs) on a drift layer is remarkably reduced by adjusting the C/Si ratio during growth of the buffer layer grown prior to the drift layer. By applying higher wafer rotation speed during the temperature ramping and optimizing the C/Si ratio for the growth of the buffer layer, a total defect density of 0.75 cm-2 on the film, which includes DFs, triangles, DF-triangles, stacking faults (SFs) and BPDs, was achieved.

High In-Wafer Uniformity of Growth Rate and Carrier Concentration on n-Type 4H-SiC Epitaxial Films Achieved by High Speed Wafer Rotation Vertical CVD Tool

In this study, influence of both Si/H2 ratio and C/Si ratio on growth rate uniformity and carrier concentration uniformity of n-type 4H-SiC epitaxial films grown by high speed wafer rotation vertical CVD tool was investigated. It was found that changes in radial profile of the growth rate and the carrier concentration obtained by varying Si/H2 ratio showed quite similar behavior to those obtained by varying C/Si ratio. Such a similar trend would suggest that the distribution of local C/Si ratio near the wafer surface changes depending on total Si/H2 ratio similarly to total C/Si ratio. Additionally, by using this relationship, both the growth rate uniformity of 49.2 μm/h ±1.78% (1.15% σ/mean) and carrier concentration uniformity of 1.08 ×1016cm-3 ±6.15% (3.40% σ/mean) was achieved.

Optimisation of turning parameters on heat treated INCOLOY 800H using cryogenically treated CVD tool with grey-based entropy method

This research work is focused on examining the turning behaviour of heat treated INCOLOY 800H superalloy by varying turning parameters like cutting speed, feed rate, depth of cut and nose radius of tool in dry turning, using cryogenically treated (24 hrs) CVD coated tool of TiAlN. The samples are heated to the temperature of 1,050°C; maintained for 1 hr inside the induction furnace and then cooled in air, after solution treatment. Micro structure, compression test, fractography and wear test were conducted to study the material behaviour. Thrust force, cutting force, surface roughness, cutting tool-tip temperature, material removal rate (MRR) and coefficient of friction (CoF) were considered as output responses. Grey relational analysis (GRA) with an entropy weight method was used to optimise turning parameters. Analysis of variance (ANOVA) was employed to identify most influencing parameters on the responses. The machining performance could be improved (39.07%) efficiently by this projected approach.

Optimisation of turning parameters on heat treated INCOLOY 800H using cryogenically treated CVD tool with grey-based entropy method

Optimisation of turning parameters on heat treated INCOLOY 800H using cryogenically treated CVD tool with grey-based entropy method

Environmental-Friendly Fluorine Mixture for CVD Cleaning Processes to Replace C2F6, CF4 and NF3

The target of this work was to find viable alternative CVD-cleaning gas mixtures for the semiconductor industry, which are environmental-friendly and in addition can be used as a “drop in” to avoid high investment costs from equipment modification. Our study has demonstrated that this can be achieved with F2-based gas mixtures, which also provide a more efficient and faster cleaning behavior for most applications. A cleaning efficiency gain of a factor 1.3 up to 17 can be expected, relative to the F2-amount required for cleaning. This gain in efficiency depends on the cleaning gas to be replaced and on the reactor type. A shorter cleaning time can lead into a higher equipment throughput and more cost effective usage of thin film tools. To generate data on particle and tool attrition, a first “mini marathon” test run has been performed. The test reactor, a 200mm wafer size CVD tool, was equipped with a mass spectrometer to monitor the end point of the chamber cleaning and to gain an overview of the waste gases going into the abatement system

Environmental Friendly Fluorine Mixture for CVD Cleaning Processes to Replace C2F6, CF4 and NF3

Since the beginning of the 1980’s per fluorinated carbons (PFC’s) such as C2F6 and CF4 have been used as cleaning gases in thin film deposition technology and since the 1990’s NF3 has been used in the same way. PFC’s and NF3 have long atmospheric lifetimes and therefore high global warming potentials. The main applications of these gases are to remove residual films left behind after a chemical vapor deposition process (CVD). The most important materials to remove are dielectric layers like silicon oxides (SiO2), carbon-containing silicon oxides, silicon nitrides (Si3N4) and, to a certain extent, conducting films like doped poly-silicon and silicide layers. According to the World Semiconductor Council the semiconductor industry in 2013 used 7512 t NF3, 1133 t CF4 and 708 t C2F6 on a global basis. Approximately 72% of all semiconductor industry gaseous emissions are caused from these three gases (C2F6, CF4 and NF3). Fraunhofer EMFT and Solvay Special Chem have developed an alternative cleaning process, which can be a replacement for the currently used PFC’s and NF3in semiconductor CVD tools. The target of this work was to find viable alternative gas mixtures for the semiconductor industry, which could be used as a “drop in” to avoid additional high investment costs from equipment modification. Our study has demonstrated that these more environment friendly gas mixtures also provide a more efficient and faster cleaning behavior for most applications. A cleaning efficiency gain of a factor 1.3 up to 17 can be expected, relative to the F2-amount required for cleaning; this gain in efficiency depends on the cleaning gas to be replaced and on the reactor type. A shorter cleaning time can lead directly into a higher equipment throughput and more cost effective usage of thin film tools. To generate data on particle and tool attrition, a first “mini marathon” test run has been performed. The test reactor, a 200mm wafer size CVD tool, was equipped with a mass spectrometer, to verify the end point of the chamber cleaning and to gain an overview of the waste gases going into the abatement system. Figure 1

Machining of Carbon Fibre: Optical Surface Damage Characterisation and Tool Wear Study

Better control of fibre composites machining requires reliable surface roughness and damage characterisation measurements. The performance and tool wear rate of three different state of the art CVD and PCD cutting tools manufactured for carbon fibre machining were compared in wet and dry conditions. Machined surfaces were characterised by areal surface roughness parameters using a novel focus variation optical system. The tool wear and cutting forces were recorded up to 50 linear meters of machining or until tool failure. Results showed that wet machining conditions reduced tool failure; and that the CVD tool in wet conditions machined the greatest distance of 26m before reaching an average roughness limit of 3μm. The tool type was found to be the most significant parameter on the surface quality. The optical system was found to be a useful tool for measuring roughness of individual plies and characterising machining induced surface damage.

Research on Wear Characteristics of CVD Composite Coated Tool in Natural Marble Cutting

The high speed milling test of CVD composite coated tool cutting natural marble is carried out. Measured milling forces of different parameters by the dynamometer and analyzed the influence of different parameters on the cutting force. Observed the wear appearance by the SEM and analyzed the wear mechanism of CVD tool. The results of the experiment show that the cutting force increases along with the cutting depth and feed speed increase, decreases along with the spindle speed and the influence of the cutting depth is the largest. The wear mechanisms of CVD tool when milling the natural marble include the removal of mechanical loss on the tool substrate, oxidation wear and adhesion wear. The removal of mechanical loss and adhesion wear couple with the whole process of CVD composite coated tool.

Performance of carbide cutting tools when machining of nickel based alloy

This paper was investigated the behavior of cutting tools when machining of nickel based alloys 242. Experiments were conducted using four different cutting tool materials under wet condition. Tool failure modes and wear mechanism were examined at various cutting parameters. Flank wear found to be the predominant tool wear for all cutting tools especially with CVD tools. Attrition lead to exposure and build up edge of the wear mechanisms were observed in all cutting tools. Coating is observed to be delaminated as main phenomena on cutting tools surfaces. The obtained results are PVD cutting tools perform better than CVD in terms of tool life with machining parameters.

Transparent conducting oxides superstrate for thin film solar cells: an industrial prospective

The demand for a TCO coated glass substrate as a base material and front electrode of the solar cells is expected to grow very strongly in the next few years. Therefore it is crucial to prepare the industrial tools and proper glass compositions to meet this very impressive demand. Mass production of extra clear glass and atmospheric pressure thermal CVD tool installed directly on the float glass line are adapted processes to mass produce in a cost effective way fluorine doped tin oxide based TCO superstrates for PV application. From an industrial prospective, opto electrical trade off is an important issue. But maintaining the performances of the electrode during 20 years of function is a major concern too. In this paper, we will underline the durability issue of the SnO2 : F based electrode and specifically, electrochemical corrosion phenomenon due to electrical field assisted diffusion of alkaline ions from the glass toward the interface between the glass substrate and the TCO film. The DC electrical field responsible for this phenomenon is due to the difference of potentials between the grounded metallic frame of the PV modules and the TCO electrodes which are strongly negatively biased.

Use of SIMS in SiGe process control

Epitaxial processes are increasingly used in semiconductor technology to cope with the requirement of ultra thin layers and ultra shallow junctions. A variety of MBE and CVD tools are used for process development and in production. Monitoring of the processed EPI-wafers is required. SIMS is a method of choice for this task. Quantifiability and even more repeatability delivered by the SIMS tool are of key importance. This paper reports the use of the FEI SIMS 4500 with a special optical conductivity enhancement (OCE) device to monitor a SiGe process in industrial routine.