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Expert help when you need it- Q1:Add or subtract the following measurements. Be sure each answer you enter contains the correct number of significant digits. 18.877 g 1.40 g 6.92 g 1.3 g 18.770 g + 0.77 g = = = g g 0 X SSee Answer
- Q2:1) a) A bare Si wafer is oxidized in dry O₂ at 1000 °C. The desired final thickness is 40 nm. i) Find the time required to perform the oxidation, ignoring rapid growth. ii) Find the time required to perform the oxidation, taking rapid growth into account. Do not use oxide growth curves. b) A <100> silicon wafer is oxidised using the following sequence i) 40 mins @ 1000°C in dry O₂. ii) 60 mins @ 1000°C in steam. iii) Etch 0.3 microns of oxide. iv) 20 mins @ 1100°C in dry O₂. Use growth curves to calculate the oxide thickness after each step. Nitride- Silicon Wafer Oxidation: Pad Oxide Oxide Nitride removal: "Bird's beak" [10 1/3 marks] [10 marks] Figure 1. LOCOS process c) The diagram above, Figure 1, shows a fully recessed LOCOS (Local Oxidation of Silicon) process. Explain, with reference to the diagram, how the process is used to produce areas of oxide on a wafer without a subsequent lithography and etch step. [5 marks] d) Discuss five of the features of SiO₂ which account for its widespread use in microelectronics. [5 marks]/nSee Answer
- Q3:2) a) A phosphorous doped n-type silicon wafer of 1 92-cm resistivity is subjected to a boron diffusion at a temperature of 1150 °C. A constant surface concentration of 2 x 10¹⁹ cm³ is maintained throughout the diffusion. i) Calculate the background concentration in the wafer. ii) How long should the diffusion be carried out for to obtain a junction depth of 4 microns. iii) Calculate the charge, Q. [15 1/3 marks] b) Describe with the aid of a diagram, a liquid source diffusion system. [5 marks] c) State Henry's Law. Explain why predeposition is performed at the solid solubility limit in industrial practice. [5 marks] excitation: primary ion beam: ot, Art, O, Cst ooooooooooooo Figure 2. SIMS Schematic Diagram analytical signal secondary ions: X*, X, X-Y*, X-Y- not used: neutrals, excited atom d) Figure 2, above, shows a schematic diagram illustrating Secondary Ion Mass Spectroscopy (SIMS) Briefly describe the technique. Why would SIMS be a poor method to use to profile dopant concentrations in a multi-quantum-well laser consisting of several ultra-thin layers of different materials? How is this measurement attempted in practice? [5 marks] e) Rapid Thermal Processors use several methods to compensate for higher radiant heat losses at the periphery of the wafer. Briefly discuss one of these methods. [3 marks]See Answer
- Q4:3) a) Describe, with the aid of suitable diagrams where necessary, the principal steps in a typical lithography process flow. Your answer should include a discussion of i) Wafer surface preparation ii) Resist application iii) Soft bake iv) Alignment and Exposure v) Development [15 1/3 marks] b) A proximity X ray mask is made up of tungsten absorbing patterns on a silicon nitride membrane. The minimum feature size is 0.1 microns. i) If the membrane heats up by 9°C during the exposure and the field is square with 3 cm sides, how much will the field be distorted due to thermal expansion of the membrane? Express your answer as a % increase in the length of a side. ii) If the maximum allowable distortion is 1/3 the minimum feature size, what is the maximum allowable temperature rise on the mask. Take the Thermal Coefficient of expansion for silicon nitride to be 2.7 X 10-6 (°C-¹). [10 marks] c) An optical lithographic system has an exposure power of 0.3 mW/cm². The required exposure energy for a positive resist is 150 mJ/cm² while the exposure energy needed for a negative resist is 12 mJ/cm². i) Neglecting load and unload times, calculate the wafer throughput for both the positive and negative resists. ii) Comment on your results, explaining why positive resist is preferred in general. [8 marks]See Answer
- Q5:4) a) The Deal Grove model for deposition determines the growth rate of a CVD film as kạng Cry kg + hg N v is the growth rate ks is the surface reaction rate v= hg is the mass transfer coefficient CT is the total concentration of the gas in the reactor N is the number of atoms per unit volume in the film Y is the mole fraction of the reactant Y= _CG CT i) Simplify the expression for growth rate assuming ks << hg. Is this the surface reaction-controlled case or the mass transfer controlled case? Why? ii) Simplify the expression for growth rate assuming kç » hg. Is this the surface reaction-controlled case or the mass transfer controlled case? Why? iii) Is the growth rate of a film dependent on temperature if it is mass transfer controlled? Why? iv) Is the growth rate of a film dependent on temperature if it is surface reaction controlled? Why? v) Is the growth rate of a film dependent on reactor geometry if it is mass transfer controlled? Why? vi) Is the growth rate of a film dependent on reactor geometry if it is surface reaction controlled? Why? [18 1/3 marks]/n[18 1/3 marks] b) Discuss concisely the differences between Chemical Vapour Deposition (CVD) and Molecular Beam Epitaxy (MBE). An engineer has designed a GaAs/InGaAs quantum well laser. She has specified that control of the layer thicknesses within the device is required to within a single molecular layer. Would CVD or MBE be an appropriate technology to realise her device? [10 marks] 2.0 1.5 2. 1.0 0.0 -0.5 -1.00 1.00 2.0 1.5 1.0 2. Jedn 0.0 -0.5 -1.00 1.00 Page 8 of 17 2.0 1.5 1.0 0.0 -0.5 0.0 0.0 microns microns (a.) (b.) (c.) Figure 3. Simulation of trench filling with LPCVD oxide with different sticking coefficients. -1.00 0.0 microns 1.00/nc) The sequence of diagrams in Figure 3 shows the results of a SPEEDIE simulation of trench filling using Low Pressure Chemical Vapour Deposition (LPCVD) of SiO₂ in a narrow trench. The same isotropic arrival angle distribution (n=1) is used for all 3 simulations but the sticking coefficient, Sc,is varied. i) Identify the plot with the highest value of the sticking coefficient. ii) Identify the plot with the lowest value of the sticking coefficient. iii) Figure 3 (b) indicates that void formation may be a problem with this process. Why are voids in trenches problematic? [5 marks]See Answer
- Q6:= 0+1866XLO 1) a) A bare Si wafer is oxidized in dry O2 at 1100 °C. The desired final thickness is 50 nm. J i) Find the time required to perform the oxidation, ignoring rapid growth. ii) Find the time required to perform the oxidation, taking rapid growth into account. tox Use Deal-Grove equations - do NOT use oxide growth curves. b) A <111> silicon wafer is oxidised using the following sequence i) 60 mins @ 1000°C in dry O₂. ATB 0,065 [10 1/3 marks] ii) 60 mins @ 1000°C in steam. 0.125 iii) Locally etch 0.1 microns of oxide to create a trench. iv) 30 mins @ 1100°C in dry O2. 0.009 Use growth curves to calculate the oxide thickness after each step. [10 marks c) It is possible to determine the thickness of oxide on oxidised wafers by visual inspection. Describe the method and discuss TWO disadvantages of this technique. [5 marks] d) Discuss FIVE of the features of SiO₂ which account for its widespread use in microelectronics. Breack down $h field [5 marks e) Dry oxidation is much slower than wet oxidation. Discuss briefly any advantages to using dry oxides instead of wet oxides. [3 mark -Excellent stable Passivation Excellent and stable Eelectricat Properties If the wet wild is s is day,See Answer
- Q7:3) a) Discuss, in detail, the following light sources used in lithography. i) Mercury lamps (Ultra Violet UV) ii) Excimer lasers (Deep Ultra Violet DUV) iii) Laser pulsed plasma (Extreme Ultra Violet EUV) Make sure you consider the mechanism by which the radiation is produced, the technology used to construct the light source and the advantages and disadvantages each technology. Include labelled diagrams where appropriate. [15 1/3 marks] b) An X ray mask is made up of tungsten absorbing patterns on a silicon nitride membrane. The minimum feature size is 0.13 microns. i) If the membrane heats up by 10° C during the exposure and the field is square w 4 cm sides, how much will the field be distorted due to thermal expansion? Express your answer as an increase in side length in microns. Take the Therma Coefficient of expansion for silicon nitride to be 2.7 X 10-6 (°C-¹). ii) If the maximum allowable distortion is 1/4 the minimum feature size, what is t maximum allowable temperature rise on the mask. Comment on your result. [10 m c) A lithographic scanner has an exposure power of 0.25 mW/cm². The required exposure energy for a positive resist is 160 mJ/cm² while the exposure energy ne for a negative resist is 11 mJ/cm². i) Neglecting load and unload times, calculate the wafer throughput, in wafers hour, for both the positive and negative resists. ii) Comment on your results, explaining why positive resist is preferred in gene [8 mSee Answer
- Q8:3. The reaction shown below occurs by a general acid-catalyzed pathway. Please propose a reasonable mechanism for this reaction. Me OH H-B (cat.)See Answer
- Q9:(A) Lil Time Rate (A)→ What reaction order is this? Based on your assessment, if the initial concentration of nitrate in the environment is 1.8 mol/L NO3, what will the concentration be after 21 days if the rate constant of the reaction is k = 0.5? Select the appropriate units for k based on what reaction order you believe this is: Zero (M/hr), First (1/hr) or Second (1/M.hr). Assume that there are no other inputs or outputs. (3 marks) c) How many MORE days will it take to reach a concentration that is below the Canadian drinking water guidelines of 10 mg/L of NO3-N? (2 marks) **Molar mass N (14.0067 g/mol) and O (15.999 g/mol).See Answer
- Q10:What is the ionic strength (I) of a solution when 1 mole of norsethite [BaMg(CO3)2] is completely dissolved in 2 liters of pure water? Show your work for full marks. (3 marks)See Answer
- Q11:1. The SA Water desalination plant in Lonsdale was officially opened in 2013 to assist with fresh water supply during the 2000s drought. As we are no longer drought- stricken in South Australia, the plant currently operates at 10% of its 300 megalitre/day capacity. The sea water feeding the desalination plant along the coast of Lonsdale has a salinity value of 35 grams/litre. The brine (salty water) output from desalination plant is has a salinity of 75 grams/litre. The density of sea water can be assumed to be 1020kg/m3 and the density of the brine as 1050kg/m3. a. Determine the mass flow rates of the brine and pure water streams leaving the desalination plant in kg/hr. [6.125 * 105 kg/hr] b. If the salinity meter used to determine the salt content in the water is accurate to the nearest 1g/L and has a precision level of ±5%, determine the uncertainty in the flow rate of the brine. [Assuming independent ±4.4*104 kg/hr]See Answer
- Q12:2. You have been tasked with preparing one litre of 1M, 2M and 3M solutions of sodium hydroxide. To complete the task, you have access to an analytical balance with a maximum capacity of 60g that is accurate to the nearest 0.01g, 3 one litre volumetric flasks, accurate to ±0.12mL. a. Determine the uncertainty in the concentration of each of the solutions using the balance and the one litre flasks. [8C₁ = ±1.73 10-4M, 8C₂ = ±2.98* 10-¹M, SC3= 4.01 10-4M] OR [8C₁ = +1.73 10-4M, 8C₂ = ±3.47*10-4M, 8C3 = 4.38 10-4M b. You accidentally break the flask for the 3M solution mid-way through preparing the solution. Instead, you now need to use four 250mL flasks accurate to ±0.08mL. Determine the total uncertainty in the concentration of 1L of 3M solution prepared this way. [SC3b = 4.33 * 10-³M OR 8C3b = 2.165 10-³M]See Answer
- Q13:3. Consider a hot automotive engine, which can be approximated as a 0.6 m high, 0.3 m wide, and 0.9 m long rectangular block. The bottom surface of the block is at a temperature of 90°C and has an emissivity of 0.9. The ambient air is at 23°C, and the road surface is at 28°C. The fluid properties of air are determined at the film temperature and can be found in the tables at the end of the tutorial. a. Determine the rate of heat transfer from the bottom surface of the engine block by convection and radiation as the car travels at a velocity of 60 km/h. [916W] b. If the temperatures were measured with a thermometer accurate to the nearest 1°C, what is the uncertainty in the resultant heat transfer rate? (You may ignore the uncertainties when calculating your fluid properties). [+10W] c. If the speedometer in the car is accurate to the nearest 2km/h, what is the uncertainty in the result? [+11W] [Uncertainties assumed as independent in all cases]See Answer
- Q14:4. Given the following experimental observations (errors determined as standard deviations): h₁ = 15 + 1mm (manometer reading) h₂ = 9±1mm (manometer reading) P₁ = 18.6 ± 0.1 psia Q=0.308 ± 0.06 ft³. (min)-¹ V = 1 + 0.05 gal m = 8.2 ± 0.05 lbm Calculate the following derived variables and their best-estimate uncertainties. Present the results in the form of x = x, ± 8x. a. Pressure drop reading from the manometer. AP(mmHg) = h₁ - h₂ [6±1.4mmHg] b. Pressure drop conversion from mmHg to psia. [0.12±0.027psi] c. Pressure ratio: [1.006±0.008794] d. Specific Gravity: SG = Psample Pwater (for liquids) [0.98+0.05] e. Valve sizing coefficient: C₂ = Q * SG So for Qin ΔΡ gal minute and AP in psi [6.7+1.5]See Answer
- Q15:Question 9 Not yet answered Points out of 1 P Flag question The product of the nucleophilic substitution reaction below is *SCH₂CH₂ Select one: O a. O b. O C. CH₂CH₂CH₂SCH₂CH₂ S-CH₂-CH; CH₂-CH-CH₂ Br ! CH₂CCH, S-CH₂-CH; O d. CH₂-CH₂-CH₂-CH₂-SH Br CH;CHCH; Previous page ob Quix #4 Next pageSee Answer
- Q16:Points out of 1 P Flag question Which of these compounds is a properly named 2° alcohol? Select one: a. 1,3-Propandiol O b. 2-Methyl-3-methyl-3-pentanol O c. 1-Propanol H H- H HH H H H m- -C- O d. 3-Hexanol m H B -- 8 -C- 8 D H -O HH -- Q сSee Answer
- Q17:Question 15 Not yet answered Points out of 1 P Flag question What is the product of the nucleophilic substitution reaction below? CH₂ OCH; CH,CH₂CHCH₂CH₂Br Select one: O a. O b. O C. O d. CH₂CH₂CHCH₂CH₂OCH; CH,CH,CHCH₂CH₂CH₂ CH₂ CH₂CH₂CHCH₂CH₂OH CH; CH₂CH₂CCH₂CH₂Br OCH, Previous page Next pageSee Answer
- Q18:Question 46 Not yet answered Points out of 1 P Flag question Which of the following is a carboxylic acid sugar? Select one: a. b. O d. OH COCH -OK CH₂OH a 2 сSee Answer
- Q19:Question 32 Not yet answered Points out of 1 PFlag question What is the product of the following reaction? H HO H HO- H -H OH -H -OH CH₂OH Select one: O a. H H H 32 A HO + -H -OH -H H -OH CH₂OH Benedict's Solution aSee Answer
- Q20:Question 19 Not yet answered Points out of 1 P Flag question What is the major organic product of the following reaction? || CH₂CH₂C-H + H₂ Select one: a. CH₂CH=CH₂ O b. CH₂CH₂CH₂OH OC. CH3CH, CH3 d. CH3CH₂COOH Previous page I Lab Quiz #4 Jump to... Pr Next pageSee Answer
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