The Microwind MOS Generator

 Hello Dear Readers,

Today, I will explain how to use Microwind inbuilt MOS generator. My first post regarding Microwind got responses as expected so I will try to make complete series of the Microwind tutorial which makes you technically stronger. So Let's start with how to use Microwind to create our transistor layouts.

Launch Microwind and examine the screen. The palette window appears. The top portion of the palette menu is shown in Fig.1. Notice the button which is a circle by a blue pen that looks like a FET circuit symbol. This provides access to the MOS generator routine in Microwind. When you click on it will be brought up on the dialog screen.

Fig.1 MOS Layout Generator button

The MOS Layout Generator has several options, all of which are controlled by the screen shown in Fig.2. The Channel length L is preset by the selected process. Normally the channel length will be left at the default value, but the designer adjusts the value of W according to the circuit specification but this is only for the digital circuits in analog integrated circuit design length also may vary.

Fig.2 MOS Layout Generator dialog screen

To create NMOS push the nMOS button after specifying the W/L ratio and then push generate device button. This action will place you back on the drawing screen. Specify the location where you want the NMOS by positioning the cursor, then left-click the mouse. As shown in Fig.3 NMOS layout with color-coded layer according to the scheme appears. The red layout represents Poly gate, Metal1 which is represented by blue color, and n+ doping is represented by green color.

Fig.3 Generated NMOS

Similar Steps is for PMOS except that you push the pMOS button in the dialog screen and generated layout which Shown in Fig.4. Also noted is that the PMOS  is embedded within an n-well that is color-coded as a green rectangle with a green stipple pattern fill.

Fig.4 Generated PMOS

And the last feature of the MOS generator we will study here is the Add polarization box in Fig.2. In the terminology of Microwind, "polarization" means to add a positive or negative bias voltage. if you select this option by clicking box, both the generated NMOS and PMOS are modified to those shown in Fig.5 and Fig.6. The NMOS has an added section of Metal1 and contact to the substrate, this is used to insure that the P-substrate has a well defined voltage and is not a floating value. In practice , this is most commonly set at 0V(ground). Similarly PMOS device now has a contact to the n-well which is added for the same purpose and it is most commonly connected to the Vdd supply voltage.

Fig.5 Modified NMOS with Polarization

Fig.6 Modified PMOS with Polarization

The MOS Layout Generator can be used to create the MOSFETs needed for a circuit, and the transistors are wired together using metal layers with contacts and vias.

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