Apparatus for current ballasting ESD sensitive devices

• US 6,587,320 B1
• Filed: 05/30/2000
• Issued: 07/01/2003
• Est. Priority Date: 01/04/2000
• Status: Expired due to Term

• Current Assignee: Sofics BVBA
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: Verhaege, Koen Gerard Maria, Russ, Christian Cornelius
• Primary Examiner(s): Sircus, Brian
• Assistant Examiner(s): KITOV, ZEEV V
• Application Number:
  US09/583,141
• Time in Patent Office: 1,127 Days
• Field of Search: 361/56, 361/91.1, 361/91.5, 257/361, 257/357, 257/355, 257/360
• US Class Current: 361/56
• CPC Class Codes: H01L 23/60 Protection against electrostatic charges or discharges, e.g. Faraday shields
• CPC Class Codes: H01L 27/0266 using field effect transistors as protective elements
• CPC Class Codes: H01L 27/0288 using passive elements as protective elements, e.g. resistors, capacitors, inductors, spark-gaps
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/3011 Impedance

Abstract

A current ballasting circuit for an ESD protection device couples nonintersecting conductive strips between a common contact pad and the contact electrodes of the ESD protection device. The connecting strips form respective electrically isolated ballasting resistors between the external contact pad and the contact electrodes of the ESD device. In addition, lateral resistances are formed between the contact strips which enhance the operation of the multiple ballasting resistors. The conductive strips may be made from metal, polysilicon or by a vertically meandering series connection of polysilicon layers, metal layers and interconnecting vias. The lateral resistance between the parallel conductive paths may be enhanced by segmenting both the drain and source electrodes. In one example, the gate electrode of an MOS ESD device extends locally between each pair of strips to segment the drain and source regions. The lateral resistance between the conductive strips is further enhanced by defining an additional gate electrode, having a portion that is parallel to the gate electrode of the ESD device and further portions that extend between the conductive strips. Multiple ESD devices may be connected in parallel to provide additional paths for shunting ESD current.

Claims

1. Apparatus for current ballasting an electrostatic discharge (ESD) sensitive device having a first region and a second region, for protecting a node in an electronic circuit from over voltage conditions by providing a conductive path through the first and second regions to a terminal configured to be coupled to a source of reference potential when said ESD device is turned on, said apparatus comprising:

a plurality of spaced connecting terminals in the first region of the ESD sensitive device for providing respective electrical contacts to the first region, the first region and the spaced connecting terminals being configured to exhibit a lateral resistance in the first region between successive ones of the spaced connecting terminals, wherein the lateral resistance is greater than a resistance of the conductive path when the ESD device is turned on; and

a plurality of isolated nonintersecting conductive strips, each having a first end and a second end, the first end of each of the isolated nonintersecting conductive strips being electrically coupled to the node and the second end of each of the isolated nonintersecting conductive strips being coupled to a respectively different one of the plurality of spaced connecting terminals.

2. Apparatus according to claim 1 further comprising:

a plurality of further spaced connecting terminals in the second region of the ESD sensitive device for providing respective electrical contacts to the second region, the second region and the spaced connecting terminals being configured to exhibit a lateral resistance between successive ones of the further spaced connecting terminals; and

a plurality of further nonintersecting conductive strips, each having a first end and a second end, the first end of each of the further nonintersecting conductive strips being electrically coupled to a respectively different one of the further spaced connecting terminals and the second end of each of the further nonintersecting conductive strips being coupled to the terminal which is configured to be coupled to the source of reference potential.

3. Apparatus according to claim 2 wherein the ESD sensitive device comprises an NMOS ESD device that forms a parasitic bipolar transistor, the first region being a drain region, the second region being a source region, and a third region being a gate region, said apparatus comprising a plurality of conductive elements, each conductive element being electrically coupled to the third region of the ESD device and extending into the first region between a respective pair of adjacent ones of the plurality of spaced connecting terminals and into the second region of the ESD device between a respective pair of adjacent ones of the plurality of further spaced connecting terminals.

4. Apparatus according to claim 1 wherein at least one of the plurality of isolated nonintersecting conductive strips is made of metal.

5. Apparatus according to claim 1 wherein at least one of the plurality of isolated nonintersecting conductive strips is segmented and includes at least one segment made of polysilicon.

6. Apparatus according to claim 5 wherein the at least one segmented nonintersecting conductive strip includes a plurality of series connected resistive elements selected from a group consisting of contacts, vias, polysilicon films and metal films.

7. Apparatus according to claim 1, wherein each of the isolated nonintersecting conductive strips exhibits a resistance and the first region and the plurality of spaced connecting terminals are configured such that the lateral resistance between successive ones of the spaced conducting terminals in the first region of the ESD device is relatively large compared to the resistance exhibited by the at least one nonintersecting conductive strip.

8. Apparatus according to claim 7 further including a plurality of conductive elements, insulated from and entirely above the first region of the ESD device, each element having a first end and a second end, the first ends of the elements being electrically connected above the first region of the ESD device and the second ends, extending across the first region of the ESD device between respective pairs of the spaced connecting terminals.

9. Apparatus according to claim 1 wherein the ESD sensitive device is selected from the group consisting of an NMOS transistor, a zener diode, an avalanche diode, a silicon controlled rectifier, a PMOS transistor, an NPN transistor, and a PNP transistor.

10. An electrostatic discharge (ESD) protection device for protecting a node in an electronic circuit from over voltage conditions by providing a conductive path through the ESD device to a terminal configured to be coupled to a source of reference potential when said ESD device is turned on, the ESD device comprising:

a drain region of a first semiconductor type, the drain region including a plurality of spaced connecting terminals which provide respective electrical contacts to the drain region, wherein the drain region and the spaced connecting terminals are configured to exhibit a lateral resistance between successive ones of the spaced connecting terminals, which lateral resistance is greater than a resistance of the conductive path through the ESD device when the ESD device is turned on;

a channel region of a second semiconductor type, having a length and a width, the channel region being in physical contact with the drain region along the width of the channel region;

a source region of the first semiconductor type, the source region being in physical contact with the channel region along the width of the channel region and separated from the drain region by the length of the channel region, the source region being connected to the terminal which is configured to be connected to a source of reference potential;

a gate electrode, insulated from and positioned above the channel region;

a plurality of isolated nonintersecting conductive strips, each having a first end and a second end, the first end of each of the isolated nonintersecting conductive strips being electrically coupled to the node and the second end of each of the nonintersecting conductive strips being coupled to a respectively different one of the plurality of spaced connecting terminals.

11. An ESD device according to claim 10, further comprising:

a plurality of further spaced connecting terminals in the source region of the ESD protection device for providing respective electrical contacts to the source region, the source region and the spaced connecting terminals being configured to exhibit a lateral resistance between successive ones of the further spaced connecting terminals; and

a plurality of further nonintersecting conductive strips, each having a first end and a second end, the first end of each of the further nonintersecting conductive strips being electrically coupled to a respectively different one of the further spaced connecting terminals and the second end of each of the further nonintersecting conductive strips being coupled to the terminal which is configured to be connected to the source of reference potential.

12. An ESD device according to claim 10 wherein the plurality of isolated nonintersecting conductive strips are made from metal.

13. An ESD device according to claim 10 wherein the plurality of isolated nonintersecting conductive strips are segmented and each strip includes at least one segment made of polysilicon.

14. An ESD device according to claim 10, wherein the plurality of segmented nonintersecting conductive strip includes a plurality of series connected vertically meandering resistive elements selected from a group consisting of contacts, vias, polysilicon films and metal films.

15. An ESD device according to claim 10, wherein:

the drain region is segmented into a plurality of drain regions, each segmented drain region including a respectively different one of the spaced connecting terminals, the segmented drain regions being separated by respective channels of a semiconductor of the second type; and

the source region is segmented into a plurality of source regions, each segmented source region including a respectively different one of the further spaced connecting terminals, the segmented source regions being separated by respective channels of a semiconductor of the second type.

16. An ESD device according to claim 10, further comprising a further gate electrode, including:

a plurality of conductive elements, the conductive elements being insulated from and positioned above respective areas of the drain region that are between adjacent ones of the spaced connecting terminals; and

a connecting element, for interconnecting the plurality of conductive elements, the connecting element being insulated from and positioned above the drain region in an area of the drain region adjacent to the gate electrode but separate from the gate electrode.

17. A composite electrostatic discharge (ESD) protection device for protecting a node in an electronic circuit from over voltage conditions by providing a conductive path through the ESD device to a reference terminal configured to be coupled to a source of reference potential when said ESD device is turned on, the ESD device comprising:

a plurality of component ESD devices, each component ESD device including;

a drain region of a first semiconductor type, the drain region including a plurality of spaced connecting terminals which provide respective electrical contacts to the drain region, wherein the drain region and the spaced connecting terminals are configured to exhibit a lateral resistance between successive ones of the spaced connecting terminals, the lateral resistance being greater than a resistance exhibited by the conductive path when the composite ESD device is turned on;

a channel region of a second semiconductor type, having a length and a width, the channel region being in physical contact with the drain region along the width of the channel region;

a source region of the first semiconductor type, the source region being in physical contact with the channel region along the width of the channel region and separated from the drain region by the length of the channel region, the source region including a plurality of further spaced connecting terminals which provide respective electrical contacts to the source region, wherein the source region and the further spaced connecting terminals are configured to exhibit a lateral resistance between successive ones of the further spaced connecting terminals;

a gate electrode, insulated from and positioned above the channel region;

first and second common electrically conductive terminals;

a plurality of first nonintersecting conductive strips, each having a first end and a second end, the first end of each of the first nonintersecting conductive strips being electrically coupled to the first common electrically conductive terminal and the second end of each of the first nonintersecting conductive strips being coupled to a respectively different one of the plurality of spaced connecting terminals for making electrical contact with the drain region;

a plurality of second nonintersecting conductive strips, each having a first end and a second end, the first end of each of the second nonintersecting conductive strips being electrically coupled to the second common electrically conductive terminal and the second end of each of the second nonintersecting conductive strips being coupled to a respectively different one of the plurality of further spaced connecting terminals for making contact with the source region; and

a first conductor connecting the first common electrically conductive terminals of all of the component ESD devices;

a second conductor connecting the second common electrically conductive terminals of all of the component ESD devices to the reference terminal.

18. An electrostatic discharge (ESD) protection device comprising:

a plurality of component ESD devices, each component ESD device including;

a first region of a first semiconductor type, the first region including a plurality of spaced connecting terminals which provide respective electrical contacts to the first region, wherein the first region and the spaced connecting terminals are configured to exhibit a lateral resistance between successive ones of the spaced connecting terminals;

a second region of a second semiconductor type, the second region including a plurality of further spaced connecting terminals which provide respective electrical contacts to the second region, wherein the second region and the further spaced connecting terminals are configured to exhibit a lateral resistance between successive ones of the further spaced connecting terminals;

first and second common electrically conductive terminals;

a plurality of first nonintersecting conductive strips, each having a first end and a second end, the first end of each of the first nonintersecting conductive strips being electrically coupled to the first common electrically conductive terminal and the second end of each of the first nonintersecting conductive strips being coupled to a respectively different one of the plurality of spaced connecting terminals for making electrical contact with the first region;

a plurality of second nonintersecting conductive strips, each having a first end and a second end, the first end of each of the second nonintersecting conductive strips being electrically coupled to the second common electrically conductive terminal and the second end of each of the second nonintersecting conductive strips being coupled to a respectively different one of the plurality of further spaced connecting terminals for making contact with the second region; and

a first conductor connecting the first common electrically conductive terminals of all of the component ESD devices;

a second conductor connecting the second common electrically conductive terminals of all of the component ESD devices.