EE 147/247A Prof. Pister

Fall 2016

Homework 10

Due Wed 11/16/2016 (9am Thursday)

CoventorWare and SEMulator 3D are installed on computers in Cory 125 (c125m-{1…24}). To run the tools, open a terminal and run the command:/share/instsww/Coventor/<program>

where program is the program you are running.

A helpful tutorial on CoventorWare can be found at:

The SEMulator3D tutorial can be found at:

Necessary files for this assignment can be found at:

  1. The following layout is made in polyMUMPs.
  2. Draw cross-section AA by hand
  3. Layout the cross-section in SEMulator3D. Use the process filespolyMUMPs.vmpdpolyMUMPs.vproc and the starter layout file polyMUMPs_starter.catfound under the piazza resources tab.Use the labeled dimensions. Submit your layout file
  4. Build the model with 0.1 resolution. Take a screenshot of your device.
  5. Look at cross-section AA of the device (Under the menu go under “View>Enable Cross Sections” and press ctrl+shift+f). Take a screenshot of the cross-section.

  1. The polyMUMPs design guide suggests a combination of the DIMPLE, P1P2VIA, and ANCHOR2 masks to breach the nitride layer for contact to the substrate. In a layout editor working with the polyMUMPS process, you create a new layer called “PIT”. The minimum size of a PIT feature is 30um. When you draw a features on layer PIT, what you get is features on three masks in the final layout: DIMPLE is the same size as PIT. P1P2VIA is 7um smaller than PIT in every direction. ANCHOR2 is 5um smaller in every direction than P1P2VIA (these recommendations are very conservative). Assuming a 40um square on PIT is the only feature in your layout. In the polyMUMPs.vprocprocess file, add a 6:1 selectivity for the nitride layer to the POLY2 etch step. Draw a 40um square of PIT and look at the resulting 3D model cross-section. Why would you want to have access to the substrate?
  2. You could potentially remove both polysilicon layers using the POLY2 etch by a combination of POLY1 and P1P2VIA. Using the modified process file from problem 2 and a combination of ANCHOR1, POLY1, and P1P2VIA, what is the issue with doing this if your sole intention is to remove the polysilicon?
  3. You could potentially use a combination of ANCHOR1 and P1P2VIAto form a hole to anchor a POLY2 structure instead of using ANCHOR2. Simulate this in SEMulator3D by placing overlapping 3umx3um ANCHOR1 and P1P2VIA squares and a 5umx5um POLY2 square that encloses them. Why is this an inadvisable combination? What happens when there is a (very serious) 1um misalignment between the masks? What is advantageous about using only ANCHOR2 for the contact?
  4. In SEMulator3D, create a (very) simplified process file for the SOIMUMPs process. You can use Conformal Depositions of materials “SiO2_BOX” and “Si_Xtal” to form the SOI wafer. Use depositions and etches (define masks in etches) to pattern materials like the pad metal, silicon, and blanket metal. Finally use an isotropic etch to etch the silicon dioxide according to the SOIMUMPs design rules. Draw a sample structure using your process to make sure it is correct and take a screenshot. Upload your process file on bcourses along with your assignment. See reference [1] for specifics on the process.
  5. We will analyze a prebuilt cantilever using CoventorWare. Start a new CoventorWare project and open the Build Solid Model interface. Load MUMPs.mpd, PolyMUMPs.proc, and cantilever.cat into the Materials, Process, and Layout fields respectively. First some hand analysis:
  6. Calculate, by hand, the spring constant of the cantilever beam, the mass of the plate at the end of the beam, and the resonant frequency of the structure, and the capacitance between the plate and the poly0 pad. You can open the layout file for dimensions and layer names.
  7. How much will the end of the plate deflect with a 1uN load at the tip of the plate?
  8. How much will the tip of the plate deflect with 10V between the cantilever structure and the poly0 pad underneath the plate? You can assume the electrostatic force is a point load at the center of the plate.

Now we will analyze the structure using CoventorWare:

  1. Build the solid model of the layout in CoventorWare.Take a screenshot of your solid model. Hide the substrate and the nitride layers and add the poly0 and the poly1 layers to the mesh model.Mesh the model using 1x1x1 Manhattan brick elements. Take a screenshot of the meshed model.

Select and name the bottom face of the each poly0 part asAnchorand name the end face of the cantilever plate Tip.Name the cantilever conductor (expand the Conductors/Dielectrics tab to see the different conductors available)ActuatorElectrode and name the poly0 pad under the plate GroundElectrode. Image examples are shown below.

Anchor

Tip

ActuatorElectrode

GroundElectrode

Begin a new MemElectroanalysis. Put 1V between ActuatorElectrode and GroundElectrode to simulate charging the plate. Run the analysis and view the results.

  1. Open the capacitance matrix. Why is the capacitance different from your analytically calculated capacitance?
  2. View the 3D results of the charge density. Zoom into the corners of the structure and take a screenshot. Why is the charge density greatest at the edges and corners?

Begin a new MemMech analysis. Under SurfaceBCs, put the fixall condition on patch Anchor and put a LoadPatchNodes condition on patch Tip. Define LoadPatchNodes with a vector LoadValue and -1 in Z. Units for this boundary condition are in uN and act on the entire face. Run the analysis.

  1. How much did the end of the plate deflect? Is there good agreement with your hand calculation?
  2. Open the deflected structure in the visualizer. Use the “Deform using displacements” option under the CoventorWare menu. Take a screenshot.

Begin a new MemMech analysis, this time change the physics in the first drop menu of the MemMech Settings window to “Modal (non-equilibrium).”Under SurfaceBCs place the fixall condition on Anchor. Calculate the first 5 mode shapes.

  1. Open the results and look at the modeDomain table. Record the frequency of each mode shape. How does your calculated resonant frequency compare to the first mode? Why would it be different from your simple analysis?
  2. In the 3D visualizer you can see the mode shapes and animate them using the Coventor> Mode Shapes menu option. Animate the mode shapes to see what is happening to the beam.

Begin a new CoSolveEM analysis. Under the DC_ConductorsBCs place 10V on ActuatorElectrode and 0V on GroundElectrode. Under SurfaceBCs place the fixall condition on Anchor. Run the analysis. It may take a while. You can increase the amount of memory the MemMech solver uses under the advanced options of the solver settings tab.

  1. How much did the tip of the plate deflect? Why is it different from your hand calculation?

[1] SOIMUMPs design rules: