Circuits: VLSI

Puzzle 4 of 100

Polysilicon and contacts

Goal

Connect A to Y. This puzzle offers only Polysilicon and Contact.

Die
12 by 7 squares
Layers
Polysilicon, Contact
Input
A
Output
Y

Go to the solution

New in this puzzle

Polysilicon

Polysilicon is a second conductor. It lies on a level below metal and resists current more than metal does.

Contact

A contact is a hole through the insulation, filled with metal, that joins the metal above to the layer below. Placing a contact also paints metal over it.

Guide

  1. Choose Polysilicon and paint a strip from the square beside A to the square beside Y.
  2. Choose Contact and place one on each end of the strip. Each contact joins a pad's metal to the polysilicon.

Hint

  1. Hint 1 of 3

    Paint a row of polysilicon between the two pads, then place a contact on the square at each end. A contact joins the pad's metal to the polysilicon under it.

  2. Hint 2 of 3

    Look between the two end contacts. The marked square is in the polysilicon strip.

  3. Hint 3 of 3

    Join the contacts with polysilicon. Keep metal off the middle of the strip so that it does not bypass the resistance.

These hints describe one valid approach. Other drawings can pass.

Solution

This is the game's reference drawing for the puzzle. It meets the goal and passes the design rules. Other drawings can pass as well.

Top View of the solved die for puzzle 4, Polysilicon and contacts, with the Side View below it.
Top View of the solved die, captured from the game. Paths that carry a high level at the moment shown are lit. The Side View below cuts through the row between the dashed lines.
The game window in Isometric View with the solved die for puzzle 4, Polysilicon and contacts, the guide, and the scope.
The whole game window in Isometric View. The scope on the right compares each output with its target band, and the message above it confirms that the drawing passes.
Solution drawing for puzzle 4, Polysilicon and contacts, drawn on a numbered grid with every layer in its game color and pattern.
The solution on the grid. Squares are numbered from the top left corner, so you can count them.

Legend

  • Metal4 squares
  • Polysilicon10 squares
  • Contact2 squares
  • Input padA
  • Output padY

About the drawing

  • The drawing uses 12 of the die's 84 squares.
  • The die starts empty, so you draw every square.
  • 2 contacts join metal to the polysilicon or active silicon under it.

After the puzzle

Polysilicon contributes resistance as well as capacitance. The measured output records their combined effect in this drawing.

Experiment: Strip width

Before records your passing drawing. Widen part of its polysilicon strip by adding a parallel row that touches it. Keep the end contacts and metal routes unchanged. Compare the output delay and waveform. Resistance and capacitance both change, so use the measured result rather than assuming that wider is always faster.

The experiment is optional. It does not change the puzzle target.