United States Patent
Amerasekera et al.
(10) Patent N0.:
(45) Date of Patent:
(54) ELECTROSTATIC DISCHARGE DEVICE 5,374,838 A * 12/1994 Sawada et a1. ........... .. 257/369
AND METHOD
FOREIGN PATENT DOCUMENTS
(75) Inventors: E. Ajith Amerasekera, Plano; Vikas
GMucpKtian,n eDya,l laalsl; oSf tTanXt o(nU SI))I Ashburn, * . . . . . . . ..
* cited by examiner
(73) Assignee: Texas Instruments Incorporated,
Dallas, TX (US)
Primary Examiner—Tom Thomas
( * ) Notice: Subject to any disclaimer, the term of this Assistant Examiner—Ori Nadav
patent is extended or adjusted under 35 (74) Attorney, Agent, or Firm—Carlton H. Hoel; W. James
U.S.C. 154(b) by 0 days. Brady; Frederick J. Telecky, Jr.
(21) Appl. No.: 09/456,036 (57) ABSTRACT
(22) Filed: Dec‘ 3’ 1999 The 'high current capabilities of a lateral npn transistor for
application as a protection device agamst degradation due to
Related US. Application Data electrostatic discharge (ESD) events are improved by adjust
(60) ligg‘gsional application NO- 60/081419’ ?led on APL 8’ ing the electrical resistivity of the material through Which
' 7 the collector current ?oWs from the avalanching pn-junction
(51) Int. Cl. ........................ .. H01L 23/62; H01L 29/76 to the Wafer backside Contact AS expressed in terms of the
(52) US. Cl. ..................... .. 257/355; 257/357; 257/369; Second threshold Current improvements by a factor of 4 are
257/372; 438/510; 438/518; 438/519; 438/521; _ _ _
438/529 reported. TWo implant sequences are described WhlCh apply
(58) Field of Search ............................... .. 257/355—363, local masking and Standard implant Conditions to achieve
257/369—372; 438/510, 518, 519, 521, 527, the improvements Without adding to the total number of
529 process steps. The principle of p-Well engineering is
(56) References Cited extended to ESD protection devices employing SCR-type
4,760,433 A *
U.S. PATENT DOCUMENTS
7/1988 Young et a1. .......... .. 357/2313
devices.
2 Claims, 7 Drawing Sheets
N CHANNEL [MPLANTS
mmmwmm“,
LOW VOLTAGE Vtn
RWH'ML\\\\\\\
P CHANNEL