Integrated Circuit Technology Faculty-in-charge: Dr. Sitangshu Bhattacharya Department of ECE Indian Institute of Information Technology-Allahabad Room No. 2221, CC-I Telephone: 2131 Email: sitangshu@iiita.ac.in Integrated Circuit Technology Contents: o o o o o o o Introduction to VLSI Design Bipolar Junction Transistor Fabrication MOSFET Fabrication for IC Crystal Structure of Si Defects in crystal and crystal growth Epitaxy Vapor Phase Epitaxy Doping During Epitaxy Oxidation Kinetics Oxidation Rate Constants Doping Redistribution Oxide Charges Diffusion Theory of Diffusion Diffusion-Infinite Source Actual Doping Profiles, Diffusion Systems Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 o o o o o o o o o o o o o o Ion Implantation Process Annealing of Damages Masking During Implantation Lithography Etching Wet Chemical Etching Dry Etching Plasma Etching Etching of Si, SiO2, SiN and other materials Plasma Deposition Process Metalization Problems in Aluminium Metal IC BJT-From Junction Isolation to LOCOS Problems in LOCOS+Trench Isolation Metal Gate vs Self Aligned Poly-gate MOSFET-Tailoring of Device Parameters CMOS Technology Latch-up in CMOS BiCMOS Technology Reading Materials: a) VLSI Technology, S M Sze b) VLSI Fabrication Principles, S K Gandhi c) Fundamentals of Semiconductor Fabrication, G S May and S M Sze Integrated Circuit Technology Ion Implantation Doping can be either done by diffusion or by Ion Implantation Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Merits and de-merits of diffusion over Ion implantation: Diffusion ❑ Contamination: You cannot use the same furnace or same Quartz boat or push rod for B and P. You must have separate booths for every thing. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 Ion Implantation ❑ Contamination: It is a cleaner process as it is done under high vacuum. Any high vacuum process is cleaner. See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Merits and de-merits of diffusion over Ion implantation: Diffusion ❑ Contamination: You cannot use the same furnace or same Quartz boat or push rod for B and P. You must have separate booths for every thing. Ion Implantation ❑ Contamination: It is a cleaner process as it is done under high vacuum. Any high vacuum process is cleaner. ❑ Control of doping profile is within 5-10% of the predicted value. Controlling ambient is difficult. ❑ Control of doping profile (ion dose) is within ±1% of the predicted value. Controlling ambient is easy. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Merits and de-merits of diffusion over Ion implantation: Diffusion ❑ Contamination: You cannot use the same furnace or same Quartz boat or push rod for B and P. You must have separate booths for every thing. Ion Implantation ❑ Contamination: It is a cleaner process as it is done under high vacuum. Any high vacuum process is cleaner. ❑ Control of doping profile is within 5-10% of the predicted value. Controlling ambient is difficult. ❑ Control of doping profile (ion dose) is within ±1% of the predicted value. Controlling ambient is easy. ❑ Diffusion is high temperature process (here you have to grow oxide for masking or selective masking). ❑ Ion implantation is room temperature process (here you can use photo-lithography for masking or selective masking). Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Merits and de-merits of diffusion over Ion implantation: Diffusion ❑ Contamination: You cannot use the same furnace or same Quartz boat or push rod for B and P. You must have separate booths for every thing. Ion Implantation ❑ Contamination: It is a cleaner process as it is done under high vacuum. Any high vacuum process is cleaner. ❑ Control of doping profile is within 5-10% of the predicted value. Controlling ambient is difficult. ❑ Control of doping profile (ion dose) is within ±1% of the predicted value. Controlling ambient is easy. ❑ Diffusion is high temperature process (here you have to grow oxide for masking or selective masking). ❑ Ion implantation is room temperature process (here you can use photo-lithography for masking or selective masking). ❑ Low concentration and a shallow junction is not possible. ❑ Low concentration and a shallow junction is possible. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Low concentration and shallow junction at same time is not possible in diffusion: Here junction width increases as concentration decreases. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Merits and de-merits of diffusion over Ion implantation: Diffusion Ion Implantation ❑ Contamination: You cannot use the same furnace or same Quartz boat or push rod for B and P. You must have separate booths for every thing. ❑ Contamination: It is a cleaner process as it is done under high vacuum. Any high vacuum process is cleaner. ❑ Control of doping profile is within 5-10% of the predicted value. Controlling ambient is difficult. ❑ Diffusion is high temperature process (here you have to grow oxide for masking or selective masking). ❑ Low concentration and a shallow junction is not possible. ❑ Diffusion is based on laws of diffusion (conc. gradient) so that the upper limit of the concentration is determined by the solid solubility. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 ❑ Control of doping profile (ion dose) is within ±1% of the predicted value. Controlling ambient is easy. ❑ Ion implantation is room temperature process (here you can use photo-lithography for masking or selective masking). ❑ Low concentration and a shallow junction is possible. Here you have two independent control: 1. Ion dose, which control total impurity and 2. Ion energy, which determine how deep the ion should go. ❑ This is non equilibrium process. Here you are using energy to direct the impurity by force, so the concentration can exceed solid solubility limit. Instead of surface, you can have the peak concentration inside the bulk. See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Merits and de-merits of diffusion over Ion implantation: Diffusion ❑ Not costlier. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 Ion Implantation ❑ Very costly. See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets discuss some merits and de-merits of diffusion over Ion implantation: Diffusion Ion Implantation ❑ Not costlier. ❑ Very costly. ❑ Diffusion process, not much damage of the surface. ❑ Layer will be completely damaged because of bombardment, but this can be thermally annealed at 800 degC. However, annealing is a diffusion process. Thus doping profile is going to get modified. Fortunately for Si, 𝐷𝑡 , that determines the diffusion depth is not very high at 950 degC. But for compound semiconductors, this is a problem. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation The main physics of ion implantation is divided into two parts Ion Implantation Nuclear Stopping Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 Electron Stopping See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Nuclear stopping: When the energetic ion (dopant) goes inside the surface (penetration), they begin to loose their energy by colliding elastically to the lattice atoms. This also causes the damages and cause point defects. Ion Implantation Nuclear Stopping Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 Electron Stopping See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Electron stopping: When the energetic ion (dopant) supplies its energy to the bound electrons. This makes the bound electrons free to move inside the crystal. It does not create the defects. Ion Implantation Nuclear Stopping Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 Electron Stopping See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation The rate of energy loss of the ion can be mathematically written as − dE = N ( Sn ( E ) + Se ( E ) ) dx N is the number of target atoms per unit volume. Sn(E) = nuclear stopping Sp(E) = electronic stopping Notice that the two Ss are function of energy. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation The rate of energy loss of the ion can be mathematically written as − dE = N ( Sn ( E ) + Se ( E ) ) dx N is the number of target atoms per unit volume. Sn(E) = nuclear stopping Sp(E) = electronic stopping Notice that the two Ss are function of energy. I am interested to know where the ion has gone finally? What is the resting place of these ions? Ions − 2 2 How far the dopant has dopants has gone inside: Range of ions (R) Surface Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Range of Ions (R): It is the distance travelled when the energy has fallen to zero from its initial energy. R R = dx 0 Ions − 2 2 Surface Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Range of Ions (R): It is the distance travelled when the energy has fallen to zero from its initial energy. R − R = dx 0 Or dE = N ( Sn ( E ) + Se ( E ) ) dx 1 E0 dE R= N 0 ( Sn ( E ) + Se ( E ) ) Now, you can integrate this if you know how the stopping powers are related to energy. R is going to be the function of initial energy E0. Ions − 2 2 Surface Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Projected Range (Rp): is the distance travelled by the ions in the direction of the incident ion. This is characterized by the mean value of RP. Rp Ions − 2 2 Surface Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Projected Range (Rp): is the distance travelled by the ions in the direction of the incident ion. This is characterized by the mean value of RP. Straggle (∆Rp) : In statistics, this is actually the standard deviation or the variation of RP. Rp Ions − 2 2 Surface Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Projected Range (Rp): is the distance travelled by the ions in the direction of the incident ion. This is characterized by the mean value of RP. Straggle (∆Rp) : In statistics, this is actually the standard deviation or the variation of RP. These two parameters tells you how deep the ions are going to penetrate. Rp Ions − 2 2 Surface Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation How is the doping profile look like in case of ion implantation? If we assume that the target is perfectly amorphous (no symmetry in target), then the profile is given by a Gaussian function. 2 1 x−R p N ( x ) = N Rp exp − 2 R p RP Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Now the assumption is that the target is perfectly amorphous. 1 x − R 2 p N ( x ) = N Rp exp − 2 R p But my target here is crystalline! And VLSI technology is done on single crystal. So, what I will do, I will make this target to look like an amorphous. For crystal sample, the ions can go to long distances without colliding and the mathematical process becomes difficult to analyse. RP Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Now the total concentration is given by the area under the curve N vs x 1 x − R 2 p N ( x ) = N Rp exp − 2 R p The dose (i.e., the concentration) is given by = N ( x ) dx − RP Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Now the total concentration is given by the area under the curve N vs x 1 x − R 2 p N ( x ) = N Rp exp − 2 R p The dose (i.e., the concentration) is given by = N ( x ) dx − As Gaussian function is even function 1 x − R 2 p = N Rp exp − dx 2 R p 0 Or with z= x − Rp 2R p We get = 2NR 2RP exp ( − z 2 )dz = 2 N Rp 2RP = 2 RP N Rp 2 0 p Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 RP See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Now the total concentration is given by the area under the curve N vs x 1 x − R 2 p N ( x ) = N Rp exp − 2 R p The dose (i.e., the concentration) is given by = N ( x ) dx − As Gaussian function is even function 1 x − R 2 p = N Rp exp − dx 2 R p 0 Or with z= x − Rp 2R p We get = 2NR 2RP exp ( − z 2 )dz = 2 N Rp 2RP = 2 RP N Rp 2 0 p Thus the peak concentration is given by Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 N Rp = RP 2 RP See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation is the ion dose, so most often, you have to control the dose. 1 x − R 2 p NR = − N x = N exp ( ) R 2 RP 2 R p p p The dose is controlled by the ion beam current, so that in the instrument you need to control the ion beam current. Now, how do you make the crystal Si to look like amorphous ? RP Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation is the ion dose, so most often, you have to control the dose. 1 x − R 2 p NR = − N x = N exp ( ) R 2 RP 2 R p p p The dose is controlled by the ion beam current, so that in the instrument you need to control the ion beam current. Now, how do you make the crystal Si to look like amorphous ? You do this by misaligning the crystal by 7-10% from its crystallographic axis. If the crystal is misaligned to the direction of the ion beam, then for the ion bean the crystal symmetry will be lost. And the crystal would appear as an amorphous to the beam. RP Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation is the ion dose, so most often, you have to control the dose. 1 x − R 2 p NR = − N x = N exp ( ) R 2 RP 2 R p p p The dose is controlled by the ion beam current, so that in the instrument you need to control the ion beam current. Now, how do you make the crystal Si to look like amorphous ? You do this by misaligning the crystal by 7-10% from its crystallographic axis. If the crystal is misaligned to the direction of the ion beam, then for the ion bean the crystal symmetry will be lost. And the crystal would appear as an amorphous to the beam. If it is aligned along the crystallographic axis, then there will be a lot of variation in the expected Gaussian distribution. The ions will find several empty ways to move deeper into the crystal resulting channelling. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation is the ion dose, so most often, you have to control the dose. 1 x − R 2 p NR = − N x = N exp ( ) R 2 RP 2 R p p p The dose is controlled by the ion beam current, so that in the instrument you need to control the ion beam current. Now, how do you make the crystal Si to look like amorphous ? You do this by misaligning the crystal by 7-10% from its crystallographic axis. If the crystal is misaligned to the direction of the ion beam, then for the ion bean the crystal symmetry will be lost. And the crystal would appear as an amorphous to the beam. If it is aligned along the crystallographic axis, then there will be a lot of variation in the expected Gaussian distribution. The ions will find several empty ways to move deeper into the crystal resulting channelling. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation is the ion dose, so most often, you have to control the dose. 1 x − R 2 p NR = − N x = N exp ( ) R 2 RP 2 R p p p The dose is controlled by the ion beam current, so that in the instrument you need to control the ion beam current. Now, how do you make the crystal Si to look like amorphous ? You do this by misaligning the crystal by 7-10% from its crystallographic axis. If the crystal is misaligned to the direction of the ion beam, then for the ion bean the crystal symmetry will be lost. And the crystal would appear as an amorphous to the beam. If it is aligned along the crystallographic axis, then there will be a lot of variation in the expected Gaussian distribution. The ions will find several empty ways to move deeper into the crystal resulting channelling. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Channelling: 1 x − R 2 p NR = − N x = N exp ( ) R 2 RP 2 R p NR = 2 RP p is the dose and the dose is increasing from top to bottom. Here the beam is aligned along [110] direction. p p ❑ The channelling is more for low dose and becomes less as dose increases. This is because as you dose the crystal, the damages occurs and the sample resembles as amorphous. The profile reaches Gaussian. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Channelling: 1 x − R 2 p NR = − N x = N exp ( ) R 2 RP 2 R p NR = 2 RP p is the dose and the dose is increasing from top to bottom. Here the beam is aligned along [110] direction. p p ❑ The channelling is more for low dose and becomes less as dose increases. This is because as you dose the crystal, the damages occurs and the sample resembles as amorphous. The profile reaches Gaussian. Ways to make amorphous surface: ❑ Self-implantation: Prior to the actual implantation, use Si ion beams to dose Si ions into Si crystal. This will make the surface amorphous and a more Gaussian profile. ❑ Make a thin oxide. This will not stop the beam, but to the ion beam it will resemble the amorphous surface. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Channelling: is the dose and the dose is increasing from top to bottom. Here the beam is aligned along [110] direction. ❑ The channelling is more for low dose and becomes less as dose increases. This is because as you dose the crystal, the damages occurs and the sample resembles as amorphous. The profile reaches Gaussian. 1 x − R 2 p N ( x ) = N Rp exp − 2 R p N Rp = 2 RP Ways to make amorphous surface: ❑ Self-implantation: Prior to the actual implantation, use Si ion beams to dose Si ions into Si crystal. This will make the surface amorphous and a more Gaussian profile. ❑ Make a thin oxide. This will not stop the beam, but to the ion beam it will resemble the amorphous surface. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets go back to nuclear stopping: Ion Implantation Nuclear Stopping Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 Electron Stopping See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets go back to nuclear stopping: The plot of the energy loss with energy Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets go back to nuclear stopping: The plot of the energy loss with energy The ion beam starts with this energy (enters the semiconductor, with high energy). Energy transfer is less. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets go back to nuclear stopping: The plot of the energy loss with energy Energy of the beam slows down. Maximum loss at RP. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets go back to nuclear stopping: The plot of the energy loss with energy Energy becomes zero. There is nothing to be loss now. The energy is zero, means the ion beam is at rest. This is nuclear stopping. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets go back to nuclear stopping: The plot of the energy loss with energy Now this exact variation of Sn(E) is difficult to model so one takes a constant Sn0. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets go back to nuclear stopping: So, in nuclear stopping, for simplicity one uses a constant Sn which is independent of energy. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets go back to electron stopping: In electron stopping, the energy loss varies as square root of energy. Sn ( E ) E Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Lets go back to electron stopping: In electron stopping, the energy loss varies as square root of energy. Sn ( E ) E This is critical energy. When the energy is greater than Ec, electron stopping dominates while less than that nuclear stopping dominates. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Thus, the range for these two process can be written in the extreme regimes as 1 E0 dE 1/2 R= = K E 1 N 0 KE1/2 Electron stopping Sn ( E ) E This is critical energy. R R = dx 0 − dE = N ( Sn ( E ) + Se ( E ) ) dx R= Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 1 E0 dE N 0 ( Sn ( E ) + Se ( E ) ) See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Thus, the range for these two process can be written in the extreme regimes as 1 E0 dE 1/2 R= = K E 1 N 0 KE1/2 Electron stopping Sn ( E ) E 1 E0 dE R= = K2 E N 0 C Nuclear stopping This is critical energy. R R = dx 0 − dE = N ( Sn ( E ) + Se ( E ) ) dx R= Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 1 E0 dE N 0 ( Sn ( E ) + Se ( E ) ) See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Thus, the range for these two process can be written in the extreme regimes as 1 E0 dE 1/2 R= = K E 1 N 0 KE1/2 Electron stopping Sn ( E ) E 1 E0 dE R= = K2 E N 0 C Nuclear stopping So, in both cases you have R as a function of energy. This is critical energy. R R = dx 0 − dE = N ( Sn ( E ) + Se ( E ) ) dx R= Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 1 E0 dE N 0 ( Sn ( E ) + Se ( E ) ) See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation The mean projected range (Rp) can be found out as (derivation not important at this stage) Sn ( E ) E Rp = R M 1+ 1 3M 2 M1 = mass of target atom and M2 = mass of incident ion. This is critical energy. R R = dx 0 − dE = N ( Sn ( E ) + Se ( E ) ) dx R= Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 1 E0 dE N 0 ( Sn ( E ) + Se ( E ) ) See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Rp = R M 1+ 1 3M 2 M1 = mass of target atom and M2 = mass of incident ion. Sn ( E ) E The critical energy can be shown (derivation not important at this stage) as 15 KeV for Boron: As Boron is much lighter atom. So you need lesser energy to push it inside. 150 KeV for Phosphorous This is critical energy. R R = dx 0 − dE = N ( Sn ( E ) + Se ( E ) ) dx R= Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 1 E0 dE N 0 ( Sn ( E ) + Se ( E ) ) See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation Now as in case of diffusion, if you have a window and if you want to have a junction depth of 1 um, the lateral width will be then 0.8 + 0.8 + 1 um = 2.6 um 1 um 1 um Si 1 um 1 um Si 0.8 um Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 0.8 um See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation In case of Ion implantation, you also have a similar thing and that is extremely difficult to model. One may model the 2D spreading effect via the relation N ( x, y ) = N ( x ) 1 um 1 y−a y+a erfc + erfc 2 2Rt 2Rt 1 um Si -a 2a 0 y a Si x Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi Integrated Circuit Technology Ion Implantation In case of Ion implantation, you also have a similar thing and that is extremely difficult to model. One may model the 2D spreading effect via the relation N ( x, y ) = N ( x ) 1 y−a y+a erfc + erfc 2 2Rt 2Rt -a 2a 0 y a Si x The fallout is the following figure. Assignment: Work it out to show numerically. Faculty-in-charge: Dr. Sitangshu Bhattacharya 2015 See VLSI fabrication Principles By S K Gandhi
