Structure for Measuring Body Pinch Resistance of High Density Trench MOSFET Array

• US 20090256149A1
• Filed: 04/10/2008
• Published: 10/15/2009
• Est. Priority Date: 04/10/2008
• Status: Active Grant

• Current Assignee: Alpha & Omega Semiconductor, Ltd.
• Original Assignee: Alpha & Omega Semiconductor, Ltd.
• Inventors: Ho, Moses, Li, Tiesheng, Lee, Il Kwan
• Granted Patent: US 7,683,369 B2
• Time in Patent Office: Days
• US Class Current: 257/48
• CPC Class Codes: H01L 22/34 Circuits for electrically characterising or monitoring manufacturing processes, e. g. whole test die, wafers filled with test structures, on-board-devices incorporated on each die, process control monitors or pad structures thereof, devices in scribe line switching, multiplexing, gating devices G01R19/25; process control with lithography, e.g. dose control, G03F7/20; structures for alignment control by optical means G03F7/70633
• CPC Class Codes: H01L 29/41 characterised by their shape, relative sizes or dispositions
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236
• CPC Class Codes: H01L 29/7815 with voltage or current sensing structure, e.g. emulator section, overcurrent sensing cell

Abstract

A structure is disclosed for measuring body pinch resistance Rp of trench MOSFET arrays on a wafer. The trench MOSFET array has a common drain layer of first conductivity type and a 2D-trench MOSFET array atop the common drain layer. The 2D-trench MOSFET array has an interdigitated array of source-body columns and gate trench columns. Each source-body column has a bottom body region of second conductivity type with up-extending finger structures. Each source-body column has top source regions of first conductivity type bridging the finger structures. The structure includes:

• • a) A source-body column wherein each finger structure of the bottom body region has a formed top contact electrode.
  • b) Two gate trench columns flank the source-body column and both have a formed top common gate contact electrode.

Upon connection of the structure to external voltage/current measurement devices, Rp can be measured while mimicking the parasitic effect of neighboring trench MOSFETs.

Claims

1. A structure for measurement of body pinch resistance of high density trench MOSFET array co-located on a semiconductor wafer with a wafer substrate of first conductivity type, the high density trench MOSFET array having a common drain foundation layer of first conductivity type atop the wafer substrate, a two-dimensional (2D) trench MOSFET array atop the common drain foundation layer, the 2D-trench MOSFET array having an interdigitated column array of source-body columns and insulated gate trench columns, each source-body column having a bottom body region of second conductivity type with a first plurality of finger structures extending upwards therefrom and, correspondingly, each source-body column also having a second plurality of top source regions of first conductivity type bridging the finger structures, the structure for measurement comprises:

a) a source-body column, atop the common drain foundation layer, wherein each top surface of a selected number of finger structures of the bottom body region further comprises a contact electrode formed thereon resulting in a corresponding number of contact electrodes; and

b) two insulated gate trench columns, each atop the common drain foundation layer, flanking said source-body column and both further comprise a common gate contact electrode formed thereon

whereby, upon electrical connection of the contact electrodes and the common gate contact electrode with a corresponding number of external biasing power supplies and voltage/current measurement devices, said body pinch resistance can be measured as the body pinch resistance through the bottom body region while mimicking the parasitic effect of neighboring trench MOSFET devices of the high density trench MOSFET array.

2. The structure for measurement of claim 1 wherein each of said two insulated gate trench columns further comprises a conductive gate material and a surrounding insulating gate dielectric layer separating the gate material from the source-body column and the common drain foundation layer.

3. The structure for measurement of claim 2 wherein said gate material is made of polysilicon.

4. The structure for measurement of claim 2 wherein said gate dielectric layer is made of silicon dioxide.

5. The structure for measurement of claim 1 wherein said bottom body region further comprises two selected finger structures and, correspondingly:

5a) the common gate contact electrode is connected to an external biasing voltage supply; and

5b) the corresponding two contact electrodes are connected to an external 2-terminal resistance measurement means for measuring the pinch resistance through the bottom body region.

6. The structure for measurement of claim 1 wherein said bottom body region further comprises four selected finger structures and, correspondingly:

6a) the common gate contact electrode is connected to an external biasing voltage supply; and

6b) the corresponding four contact electrodes are connected to an external 4-terminal resistance measurement means for measuring the pinch resistance through the bottom body region.

7. The structure for measurement of claim 1 wherein said common drain foundation layer is an epitaxial layer.

8. The structure for measurement of claim 1 wherein said first conductivity type is P-type and said second conductivity type is N-type.

9. The structure for measurement of claim 1 wherein said first conductivity type is N-type and said second conductivity type is P-type.

10. A semiconductor wafer comprises a wafer substrate of first conductivity type, a plurality of high density trench MOSFET arrays and at least one co-located structure for measurement thus monitoring body pinch resistance of the high density trench MOSFET arrays, wherein:

1. each high density trench MOSFET array further comprises a common drain foundation layer of first conductivity type atop the wafer substrate, a two-dimensional (2D) trench MOSFET array atop the common drain foundation layer, the 2D-trench MOSFET array further comprises an interdigitated column array of source-body columns and insulated gate trench columns, each source-body column further comprises a bottom body region of second conductivity type with a first plurality of finger structures extending upwards there from and, correspondingly, each source-body column further comprises a second plurality of top source regions of first conductivity type bridging the finger structures; and

2. the structure for measurement further comprises;

2a) a source-body column, atop the common drain foundation layer, wherein each top surface of a selected number of finger structures of the bottom body region further comprises a contact electrode formed thereon resulting in a corresponding number of contact electrodes; and

2b) two insulated gate trench columns, each atop the common drain foundation layer, flanking said source-body column and both further comprise a common gate contact electrode formed thereon

whereby, upon electrical connection of the contact electrodes and the common gate contact electrode with a corresponding number of external biasing power supplies and voltage/current measurement devices, said body pinch resistance can be measured as the pinch resistance through the bottom body region while mimicking the parasitic effect of neighboring trench MOSFET devices of the high density trench MOSFET array.

11. A method for measuring thus monitoring body pinch resistance of high density trench MOSFET arrays on a semiconductor wafer with a wafer substrate of first conductivity type, each high density trench MOSFET array having a common drain foundation layer of first conductivity type atop the wafer substrate, a two-dimensional (2D) trench MOSFET array atop the common drain foundation layer, the 2D-trench MOSFET array having an interdigitated column array of source-body columns and insulated gate trench columns, each source-body column having a bottom body region of second conductivity type with a first plurality of finger structures extending upwards there from and, correspondingly, each source-body column also having a second plurality of top source regions of first conductivity type bridging the finger structures, the method for measuring body pinch resistance comprises:

1) providing a structure for measurement, co-located on the semiconductor wafer with the high density trench MOSFET arrays, having;

1a) a source-body column, atop the common drain foundation layer, wherein each top surface of a selected number of finger structures of the bottom body region further comprises a contact electrode formed thereon resulting in a corresponding number of contact electrodes; and

1b) two insulated gate trench columns, each atop the common drain foundation layer, flanking said source-body column and both further comprise a common gate contact electrode formed thereon; and

2) electrically connecting the contact electrodes and the common gate contact electrode with a corresponding number of external biasing power supplies and voltage/current measurement devices and measuring said body pinch resistance as the pinch resistance through the bottom body region while mimicking the parasitic effect of neighboring trench MOSFET devices of the high density trench MOSFET arrays.

12. The method for measuring body pinch resistance of claim 11 wherein providing a structure for measurement further comprises forming a contact electrode on each top surface of two selected finger structures and, correspondingly, electrically connecting the contact electrodes and the common gate contact electrode further comprises:

2a) connecting the common gate contact electrode to an external biasing voltage supply; and

2b) connecting the corresponding two contact electrodes to an external 2-terminal resistance measurement means.

13. The method for measuring body pinch resistance of claim 11 wherein providing a structure for measurement further comprises forming a contact electrode on each top surface of four selected finger structures and, correspondingly, electrically connecting the contact electrodes and the common gate contact electrode further comprises:

2a) connecting the common gate contact electrode to an external biasing voltage supply; and

2b) connecting the corresponding four contact electrodes to an external 4-terminal resistance measurement means.