Body-contacted field effect transistors configured for test and methods

Patent metadata

Field	Value
Publication number	US-11367790-B2
Application number	US-201916551794-A
Country	US
Kind code	B2
Filing date	Aug 27, 2019
Priority date	Aug 27, 2019
Publication date	Jun 21, 2022
Grant date	Jun 21, 2022

Abstract

Test structures for a body-contacted field effect transistor (BCFET) include: a single-pad structure with body contact and probe pad regions connected to a channel region at first and second connection points with a known separation distance between the connection points; and a multi-pad structure with a body contact region connected to a channel region at a first connection point and multiple probe pad regions connected to the channel region at second connection points that are separated from the first connection point by different separation distances. A method includes: determining separation distance-dependent internal body potentials at the second connection points in response to different bias conditions by using either multiple single-pad structures, each having a different separation distance between the connection points, or by using a multi-pad structure; and based on the separation distance-dependent internal body potentials, generating a model representing the BCFET with body-contacted and floating body devices.

First claim

What is claimed is:

1. A method comprising:
providing multiple different instances of a test structure,
wherein each of the multiple different instances of the test structure comprises:
a channel region;
a source region adjacent to a first side of the channel region;
a drain region adjacent to a second side of the channel region opposite the first side;
a body contact region electrically connected to a first connection point in the channel region and electrically isolated from the source region and the drain region; and
a probe pad region electrically connected to a second connection point in the channel region and electrically isolated from the source region and the drain region, and

wherein, in the multiple different instances of the test structure, the first connection point and the second connection point are separated by different separation distances, respectively;

applying different sets of bias conditions to each instance of the test structure;
measuring a voltage level on the probe pad region of each instance of the test structure in response to application of each set of bias conditions, wherein the voltage level on the probe pad region is indicative of an internal body potential of the channel region at the second connection point; and
based on results of the measuring, developing an internal body potential profile for a body-contacted field effect transistor, wherein the profile indicates expected internal body potential variations of the body-contacted field effect transistor as a function of both the different separation distances and different drain voltages.

2. The method of claim 1 ,
wherein the developing of the internal body potential profile comprises generating initial graphs, where each initial graph is associated with specific gate, source and body contact bias conditions and comprises multiple first curves with each first curve representing, for the specific gate, source and body contact bias conditions and for a given separation distance between first and second connection points, a relationship between changes in internal body potential and changes in drain voltage, and
wherein the developing of the internal body potential profile further comprises generating final graphs, where each final graph is associated with the specific gate, source and body contact bias conditions and comprises multiple second curves with each second curve representing, for the specific gate, source and body contact bias conditions and for a given drain voltage, a relationship between the changes in the internal body potential and changes in the separation distance between the first and second connection points.

3. The method of claim 1 , further comprising, based on the profile, generating a model to predict electrical characteristics of the body-contacted field effect transistor,
wherein the body-contacted field effect transistor has a total channel width,
wherein, within the model, the body-contact field effect transistor is represented by a combination of body-contacted and floating body devices, and
wherein a sum of channel widths of the body-contacted and floating body devices is equal to the total channel width.

4. The method of claim 3 , wherein, within the model, the channel widths of the body-contacted and floating body devices remain constant irrespective of application of the different sets of bias conditions.

5. The method of claim 3 , wherein, within the model, the channel widths of the body-contacted and floating body devices vary as a function of application of the different sets of bias conditions.

6. The method of claim 3 , further comprising employing the model during integrated circuit design.

7. A method comprising:
applying different sets of bias conditions to a test structure, wherein the test structure comprises:
a channel region;
a source region adjacent to a first side of the channel region;
a drain region adjacent to a second side of the channel region opposite the first side;
a body contact region electrically connected to a first connection point in the channel region and electrically isolated from the source region and the drain region; and
multiple probe pad regions electrically connected to corresponding second connection points in the channel region and electrically isolated from the source region and the drain region, wherein the corresponding second connection points are separated from the first connection point by different separation distances, respectively;

measuring voltage levels on the multiple probe pad regions in response to application of each set of bias conditions, wherein voltage levels on the probe pad regions are indicative of internal body potentials at the corresponding second connection points; and
based on results of the measuring, developing an internal body potential profile for a body-contacted field effect transistor, wherein the profile indicates expected internal body potential variations of the body-contacted field effect transistor as a function of both the different separation distances and different drain voltages.

8. The method of claim 7 ,
wherein the developing of the internal body potential profile further comprises generating graphs, where each graph is associated with specific gate, source and body contact bias conditions and comprises multiple curves with each curve representing, for the specific gate, source and body contact bias conditions and for a given drain voltage, a relationship between changes in the internal body potential and changes in separation distance between the first and second connection points.

9. The method of claim 7 , further comprising, based on the profile, generating a model to predict electrical characteristics of the body-contacted field effect transistor,
wherein the body-contacted field effect transistor has a total channel width,
wherein, within the model, the body-contact field effect transistor is represented by a combination of body-contacted and floating body devices, and
wherein a sum of channel widths of the body-contacted and floating body devices is equal to the total channel width.

10. The method of claim 9 , wherein, within the model, the channel widths of the body-contacted and floating body devices remain constant irrespective of application of the different sets of bias conditions.

11. The method of claim 9 , wherein, within the model, the channel widths of the body-contacted and floating body devices vary as a function of application of the different sets of bias conditions.

12. A test structure for a body-contacted field effect transistor, the test structure comprising:
a channel region;
a source region adjacent to a first side of the channel region;
a drain region adjacent to a second side of the channel region opposite the first side;
a body contact region electrically connected to a first connection point in the channel region and electrically isolated from the source region and the drain region; and
a probe pad region electrically connected to a second connection point in the channel region and electrically isolated from the source region and the drain region, wherein the probe pad region is adapted to output an output voltage and to be electrically connected to a voltmeter that measures the output voltage and wherein the output voltage is indicative of an internal body potential of the channel region at the second connection point.

13. The test structure of claim 12 ,
wherein the test structure is a single-pad test structure comprising a single probe pad region,
wherein the first connection point is at a first end of the channel region,
wherein the second connection point is at a second end

Assignees

• Globalfoundries Us Inc

Inventors

• Dutta Anupam
• Swaminathan Balaji

Classifications

• H10D86/201

  the substrates comprising an insulating layer on a semiconductor body, e.g. SOI (H10D86/40 take precedence) · CPC title

• H10D62/364

  of IGFETs · CPC title

• H10D30/6711 Primary

  by using electrodes contacting the supplementary regions or layers · CPC title

• G01R31/2623 Primary

  for measuring break-down voltage therefor · CPC title

• G06F30/367

  Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods · CPC title