{"id":29287,"date":"2004-05-01T00:05:53","date_gmt":"2004-05-01T00:05:53","guid":{"rendered":"https:\/\/silvaco.com\/uncategorized\/when-solving-for-the-static-cv-curve-for-a-mos-capacitor-due-to-the-absence-of-current-carriers\/"},"modified":"2021-07-08T18:30:35","modified_gmt":"2021-07-09T01:30:35","slug":"when-solving-for-the-static-cv-curve-for-a-mos-capacitor-due-to-the-absence-of-current-carriers","status":"publish","type":"post","link":"https:\/\/silvaco.com\/ja\/simulation-standard\/when-solving-for-the-static-cv-curve-for-a-mos-capacitor-due-to-the-absence-of-current-carriers\/","title":{"rendered":"When solving for the static CV curve for a MOS capacitor, due to the absence of current carriers"},"content":{"rendered":"
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Hints, Tips and Solutions – May 2004<\/strong><\/h1>\n

Q.<\/strong>\u00a0When solving for the static CV curve for a MOS capacitor, due to the absence of current carriers, convergence can be a real problem. Previous methods suggested in the hints and tips archive of Silvaco\u2019s simulation standard have made use of Silvaco\u2019s\u00a0Luminous<\/em>\u00a0module where a small amount of light intensity is incident on the device, the idea being to generate a small amount of carriers to aid convergence.<\/p>\n

A.<\/strong>\u00a0A recent addition to Silvaco\u2019s device simulator has supplanted such means for the use of\u00a0Luminous<\/em><\/strong>\u00a0in generating the static CV curve for a MOS capacitor.<\/p>\n

Use is made of the QSCV term in addition to the NOCURRENT term to the SOLVE statement to give the Quasi-static capacitance of the electrode being bias-ramped. This also includes electrodes linked to the electrode being bias ramped via the COMMON parameter of the CONTACT statement.<\/p>\n

This will output capacitance summed over electrodes and capacitance for each common electrode. They are calculated by numerically differentiating charge on each contact with respect to the applied bias, and so a fine voltage increment is required for accurate results.<\/p>\n

Such a solve statement can be described as follows:<\/p>\n

\n

solve init<\/span><\/p>\n

solve vanode=0 vstep=0.25 vfinal=10.0 name=anode<\/span><\/p>\n

log outfile=CV_AlGaAs_qscv.log<\/span><\/p>\n

solve vanode=10.0 vstep=-0.1 vfinal=-10 name=anode qscv nocurrent<\/span><\/p>\n

log off<\/span><\/p>\n<\/blockquote>\n

giving the following CV curve for a generated MOS capacitor:<\/p>\n

Q.\u00a0<\/strong>Can a previously created structure, once loaded into Atlas, have any of its REGION properties modified without having to recreate the complete structure?<\/p>\n

A.<\/strong>\u00a0If a previously created structure is loaded into\u00a0ATLAS<\/em><\/strong>\u00a0using the MESH INFILE statement properties of each individual region within the structure can now be modified. A recent addition to the REGION statement is the key word MODIFY. Use of the MODIFY statement provides a very convenient method for easily changing structure properties. By specifying MODIFY on the REGION statement any of the following parameters may be applied to that region:<\/p>\n

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MATERIAL, DONORS, ACCEPTORS, X.COMPOSE, Y.COMPOSE, WELL.CNBS, WELL.VNBS, WELL.NY, WELL.NX, WELL.GAIN, WELL.OVERLAP, PIEZO.SCALE, QWELL, LED, WELL.FIELD, PIEZOELEC FIXED.FERMI, and CALC.STRAIN.<\/span><\/p>\n<\/blockquote>\n

An example highlighting the use of such a statement is given below. The example makes use of a previously created structure called xcomp035.str in which the x.comp value for the AlGaAs is 0.35. Use is then made of the MODIFY keyword to change this value in both of the regions.<\/p>\n

Figure 2 shows the before and after structure property of the x.comp parameter obtained by taking a one dimensional cut line through the structure in\u00a0TonyPlot<\/em><\/strong>. Use of the MODIFY statement provides a very convenient method for easily changing structure properties.<\/p>\n<\/div><\/section><\/div>

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