Circuit for encoding identification information on circuit dice using FET capacitors

• US 5,056,061 A
• Filed: 12/20/1989
• Issued: 10/08/1991
• Est. Priority Date: 12/20/1989
• Status: Expired due to Fees

• Current Assignee: North American Philips Corp. (Koninklijke Philips N.V.)
• Original Assignee: NJ Phillips Pty Ltd. (Province of Québec)
• Inventors: Akylas, Victor R., De Zeeuw, Cornelis J. H.
• Primary Examiner(s): CLAWSON JR, JOSEPH
• Application Number:
  US07/453,546
• Time in Patent Office: 657 Days
• Field of Search: 365/96, 365/102, 365/104, 365/103, 365/225.7, 365/189.02, 365/182
• US Class Current: 365/96
• CPC Class Codes: G06K 1/128 by electric registration, e.g. electrolytic, spark erosion recording apparatus for measuring instruments G01D15/06; information storage in general G11
• CPC Class Codes: H01L 2223/5444 for electrical read out
• CPC Class Codes: H01L 27/02 including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers

Abstract

A programmable circuit for inclusion in an integrated circuit die for encoding information identifying or otherwise relating to such die, such circuit utilizing a plurality of single bit information storage and reading bit cells, each bit cell including a MOSFET or IGFET capacitor structure as a bit storage element. A gate of the MOSFET or IGFET acts as a positive voltage plate of the capacitor, while a source and drain are both connected to ground and act as ground plates of the capacitor. Normally, an open circuit is present between the gate and the source and drain, however, when a programming high voltage is applied to the gate, the capacitor structure physically breaks down and a conduction path is formed between the gate and the source or drain. The presence or absence of this conduction path enables the MOSFET or IGFET capacitor structure to act as a binary bit. Read circuitry selectively senses the presence or absence of the conduction path of each bit cell, and a multiplexer can be employed to connect the read circuitry to the successive bit cells sequentially. Protection circuitry is provided to prevent the read circuitry from being damaged by the applied programming voltage. The programmable circuit can be fabricated by the same integrated circuit fabrication techniques used to fabricate the remaining circuits on the die.

Claims

1. A programmable circuit for encoding and storing information, comprising:

(a) a plurality of single bit information storage and reading bit cells, each bit cell including

(i) a field effect transistor having a gate, a source and a drain, the source and drain being connected in common to ground so as to constitute one plate of a capacitor structure of which said gate serves are the other plate thereof, there normally being an open circuit between said plates;

(ii) means to selectively apply a high voltage to said gate so as to cause said capacitor structure to physically break down and form closed circuit between the plates thereof, whereby the capacitor structure acts as a single bit binary store representing a first binary value when there is an open circuit between said plates and representing a secondary binary value when there is a closed circuit between said plates; and

(iii) a pass transistor for selectively connecting the gate of said bit cell to a sensing bus;

(b) a read circuit connected to said sensing bus for sensing whether there is a closed or open circuit between the plates of the capacitor structure of a bit cell when the gate of such bit cell is connected to said sensing bus; and

(c) multiplexer means for selectively enabling the pass transistors of successive bit cells to connect the gates thereof to said sensing bus, so that said read circuit successively senses whether there is a closed or an open circuit between the plates of the capacitor structures of the successive bit cells.

2. A circuit as claimed in claim 1, further comprising

means for protecting said read circuit and the pass transistors of said bit cells from high voltage on the gates thereof, said protecting means comprising a resistor in each bit cell disposed between said gate and said pass transistor and means to connect the pass transistor side of such bit cell to ground when high voltage is applied to said gate.

3. An integrated circuit die which includes one or more circuits other than a programmable memory and further includes a programmable circuit for encoding and storing information relating to said die, said programmable circuit comprising:

(a) a plurality of single bit information storage and reading bit cells, each bit cell including

(i) a capacitor structure having a first plate and a second plate between which there is normally an open circuit, said capacitor structure being formed by a field effect transistor having a gate which constitutes said second plate and a source and drain which are connected together to ground and constitute said first plate; and

(ii) means to selectively apply a high voltage to said second plate so as to cause said capacitor structure to physically break down and form a closed circuit between said first and second plates; and

(b) means to sense whether there is an open or closed circuit between the plates of each of said bit cells, said means to sense comprising;

(iii) a read circuit for sensing whether there is a closed or open circuit between the gate and the source or drain of each of said bit cells;

(iv) a pass transistor in each bit cell which when enabled connects said read circuit to the gate of such bit cell; and

(v) multiplexer means for successively enabling each of said pass transistors so that said read circuit is successively connected to the gates of the successive bit cells,

whereby the capacitor structure of each bit cell acts as a single bit binary store which represents a first binary value when there is a closed circuit between the plates of such bit cell and which represents a second binary value when there is an open circuit between said plates.

4. The integrated circuit die of claim 3, further including means to protect said read circuit and the pass transistors of said bit cells from high voltage on the gates of said bit cells.