Programmable ROM - Revision history

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2025-11-10T17:05:51Z

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← Previous revision		Revision as of 17:05, 10 November 2025
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			{{redirect\|PROM\|other uses\|Prom (disambiguation)}}
	{{Memory types}}		{{Memory types}}
	{{short description\|~~Type of solid state~~ computer memory ~~that becomes read only after being written once~~}}		{{short description\|Write once computer memory}}
	A '''programmable read-only memory''' ('''PROM''') is a form of digital memory where the contents can be changed once after manufacture of the device. The data is then permanent ~~and cannot be changed~~. It is one type of [[read-only memory]] (ROM). PROMs are used in digital electronic devices to store ~~permanent data, usually~~ low level programs such as [[firmware]] or [[microcode]]. The key difference from a standard [[Read-only memory\|ROM]] is that the data is written into a ROM during manufacture, while with a PROM the data is programmed into them after manufacture. Thus, ROMs tend to be used only for large production runs with well-verified data. PROMs may be used ~~where the volume required does not make a factory-programmed ROM economical, or~~ during development of a system that ~~may~~ ultimately be converted to ROMs in a mass produced version.		A '''programmable read-only memory''' ('''PROM''') is a form of digital memory where the contents can be changed once after manufacture of the device. The data is then permanent. It is one type of [[read-only memory]] (ROM). PROMs are usually used in digital electronic devices to store low level programs such as [[firmware]] or [[microcode]]. PROMs may be used during development of a system that will ultimately be converted to ROMs in a mass produced version. These types of memories are used in [[microcontroller]]s, [[video game console]]s, mobile phones, radio-frequency identification ([[RFID]]) tags, implantable medical devices, high-definition multimedia interfaces ([[HDMI]]), and in many other consumer and automotive products.

	PROMs are manufactured blank and, depending on the technology, can be programmed at wafer, final test, or in system. Blank PROM chips are programmed by plugging them into a device called a ''PROM programmer''. Companies can keep a supply of blank PROMs in stock, and program them at the last minute to avoid large volume commitment. These types of memories are frequently used in [[microcontroller]]s, [[video game console]]s, mobile phones, radio-frequency identification ([[RFID]]) tags, implantable medical devices, high-definition multimedia interfaces ([[HDMI]]) and in many other consumer and automotive electronics products. A typical PROM device ~~is made up of~~ an array of memory cells~~, each made up of a transistor, which is a~~ [[bipolar transistor]], connected to a [[Fuse (electrical)\|fuse]] called a [[polyfuse (PROM)\|polyfuse]] ~~in the emitter of the transistor~~. A PROM ~~programmer~~ is ~~used~~ to blow the ~~polyfuse, programming the PROM~~.<ref>{{cite book \| url=https://books.google.com/books?id=9VHMBQAAQBAJ&dq=prom+fuse&pg=PA760 \| title=The Electronics Handbook \| isbn=978-1-4200-3666-4 \| last1=Whitaker \| first1=Jerry C. \| date=3 October 2018 \| publisher=CRC Press }}</ref>		PROMs are manufactured blank and, depending on the technology, can be programmed at the wafer, final test, or system stage. Blank PROM chips are programmed by plugging them into a device called a ''PROM programmer''. A typical PROM device has an array of memory cells. The [[bipolar transistor]]s in the cells have an emitter that is connected to a [[Fuse (electrical)\|fuse]] called a [[polyfuse (PROM)\|polyfuse]]. To program a PROM is to strategically blow the polyfuses.<ref>{{cite book \| url=https://books.google.com/books?id=9VHMBQAAQBAJ&dq=prom+fuse&pg=PA760 \| title=The Electronics Handbook \| isbn=978-1-4200-3666-4 \| last1=Whitaker \| first1=Jerry C. \| date=3 October 2018 \| publisher=CRC Press }}</ref>

	== History ==		== History ==
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	=== One time programmable memory ===		=== One time programmable memory ===
	OTP (one time programmable) memory is a special type of [[non-volatile memory]] (NVM) that permits data to be written to memory only once. Once the memory has been programmed, it retains its value upon loss of power (i.e., is non-volatile). OTP memory is used in applications where reliable and repeatable reading of data is required. Examples include boot code, encryption keys and configuration parameters for analog, sensor or display circuitry. OTP NVM is characterized, over other types of NVM like [[eFuse]] or EEPROM, by offering a low power, small area footprint memory structure. As such OTP memory finds application in products from microprocessors & display drivers to power management ICs (PMICs).		OTP (one time programmable) memory is a special type of [[non-volatile memory]] (NVM) that permits data to be written to memory only once. Once the memory has been programmed, it retains its value upon loss of power (i.e., is non-volatile). OTP memory is used in applications where reliable and repeatable reading of data is required. Examples include boot code, encryption keys and configuration parameters for analog, sensor or display circuitry. OTP NVM is characterized, over other types of NVM like [[eFuse]] or EEPROM, by offering a low power, small area footprint memory structure. As such, OTP memory finds application in products from microprocessors & display drivers to power management ICs (PMICs).

	Commercially available semiconductor antifuse-based OTP memory arrays have been around at least since 1969, with initial antifuse bit cells dependent on blowing a capacitor between crossing conductive lines. [[Texas Instruments]] developed a MOS [[gate oxide]] breakdown antifuse in 1979.<ref>See [http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE US Patent 4184207] {{Webarchive\|url=https://web.archive.org/web/20180427183945/http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE \|date=2018-04-27 }} - High density floating gate electrically programmable ROM, and [http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE US Patent 4151021] {{webarchive\|url=https://web.archive.org/web/20180427092847/http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE \|date=2018-04-27 }} - Method of making a high density floating gate electrically programmable ROM</ref> A dual-gate-oxide two-transistor (2T) MOS antifuse was introduced in 1982.<ref>[http://www.chipestimate.com/techtalk/techtalk_071218.html Chip Planning Portal]. ChipEstimate.com. Retrieved on 2013-08-10.</ref> Early oxide breakdown technologies exhibited a variety of scaling, programming, size and manufacturing problems that prevented volume production of memory devices based on these technologies.		Commercially available semiconductor antifuse-based OTP memory arrays have been around at least since 1969, with initial antifuse bit cells dependent on blowing a capacitor between crossing conductive lines. [[Texas Instruments]] developed a MOS [[gate oxide]] breakdown antifuse in 1979.<ref>See [http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE US Patent 4184207] {{Webarchive\|url=https://web.archive.org/web/20180427183945/http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE \|date=2018-04-27 }} - High density floating gate electrically programmable ROM, and [http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE US Patent 4151021] {{webarchive\|url=https://web.archive.org/web/20180427092847/http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE \|date=2018-04-27 }} - Method of making a high density floating gate electrically programmable ROM</ref> A dual-gate-oxide two-transistor (2T) MOS antifuse was introduced in 1982.<ref>[http://www.chipestimate.com/techtalk/techtalk_071218.html Chip Planning Portal]. ChipEstimate.com. Retrieved on 2013-08-10.</ref> Early oxide breakdown technologies exhibited a variety of scaling, programming, size and manufacturing problems that prevented volume production of memory devices based on these technologies.

imported>Nyq: /* One time programmable memory */ lc per MOS:EXPABBR

2025-06-15T02:44:23Z

One time programmable memory: lc per MOS:EXPABBR

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New page

{{Memory types}}
{{short description|Type of solid state computer memory that becomes read only after being written once}}
A '''programmable read-only memory''' ('''PROM''') is a form of digital memory where the contents can be changed once after manufacture of the device. The data is then permanent and cannot be changed. It is one type of [[read-only memory]] (ROM). PROMs are used in digital electronic devices to store permanent data, usually low level programs such as [[firmware]] or [[microcode]]. The key difference from a standard [[Read-only memory|ROM]] is that the data is written into a ROM during manufacture, while with a PROM the data is programmed into them after manufacture. Thus, ROMs tend to be used only for large production runs with well-verified data. PROMs may be used where the volume required does not make a factory-programmed ROM economical, or during development of a system that may ultimately be converted to ROMs in a mass produced version.

PROMs are manufactured blank and, depending on the technology, can be programmed at wafer, final test, or in system. Blank PROM chips are programmed by plugging them into a device called a ''PROM programmer''. Companies can keep a supply of blank PROMs in stock, and program them at the last minute to avoid large volume commitment. These types of memories are frequently used in [[microcontroller]]s, [[video game console]]s, mobile phones, radio-frequency identification ([[RFID]]) tags, implantable medical devices, high-definition multimedia interfaces ([[HDMI]]) and in many other consumer and automotive electronics products. A typical PROM device is made up of an array of memory cells, each made up of a transistor, which is a [[bipolar transistor]], connected to a [[Fuse (electrical)|fuse]] called a [[polyfuse (PROM)|polyfuse]] in the emitter of the transistor. A PROM programmer is used to blow the polyfuse, programming the PROM.<ref>{{cite book | url=https://books.google.com/books?id=9VHMBQAAQBAJ&dq=prom+fuse&pg=PA760 | title=The Electronics Handbook | isbn=978-1-4200-3666-4 | last1=Whitaker | first1=Jerry C. | date=3 October 2018 | publisher=CRC Press }}</ref>

== History ==
The PROM was invented in 1956 by [[Wen Tsing Chow]], working for the Arma Division of the American [[Bosch (company)|Bosch]] Arma Corporation in [[Garden City, New York|Garden City]], [[New York (state)|New York]].<ref name="Huang2008">{{cite book|author=Han-Way Huang|title=Embedded System Design with C805|url=https://books.google.com/books?id=3zRtCgAAQBAJ&pg=PA22|date=5 December 2008|publisher=Cengage Learning|isbn=978-1-111-81079-5|page=22|url-status=live|archive-url=https://web.archive.org/web/20180427092847/https://books.google.com/books?id=3zRtCgAAQBAJ&pg=PA22|archive-date=27 April 2018}}</ref><ref name="AufaureZimányi2013">{{cite book|author1=Marie-Aude Aufaure|author2=Esteban Zimányi|title=Business Intelligence: Second European Summer School, eBISS 2012, Brussels, Belgium, July 15-21, 2012, Tutorial Lectures|url=https://books.google.com/books?id=7iK5BQAAQBAJ&pg=PA136|date=17 January 2013|publisher=Springer|isbn=978-3-642-36318-4|page=136|url-status=live|archive-url=https://web.archive.org/web/20180427092847/https://books.google.com/books?id=7iK5BQAAQBAJ&pg=PA136|archive-date=27 April 2018}}</ref> The invention was conceived at the request of the [[United States Air Force]] to come up with a more flexible and secure way of storing the targeting constants in the Atlas E/F [[ICBM]]'s airborne digital computer. The patent and associated technology were held under secrecy order for several years while the Atlas E/F was the main operational missile of the United States ICBM force. The term ''burn'', referring to the process of programming a PROM, is also in the original patent, as one of the original implementations was to literally burn the internal whiskers of diodes with a current overload to produce a circuit discontinuity. The first PROM programming machines were also developed by Arma engineers under Chow's direction and were located in Arma's Garden City lab and Air Force [[Strategic Air Command]] (SAC) headquarters.

{{Anchor|OTPM}}

=== One time programmable memory ===
OTP (one time programmable) memory is a special type of [[non-volatile memory]] (NVM) that permits data to be written to memory only once. Once the memory has been programmed, it retains its value upon loss of power (i.e., is non-volatile). OTP memory is used in applications where reliable and repeatable reading of data is required. Examples include boot code, encryption keys and configuration parameters for analog, sensor or display circuitry. OTP NVM is characterized, over other types of NVM like [[eFuse]] or EEPROM, by offering a low power, small area footprint memory structure. As such OTP memory finds application in products from microprocessors & display drivers to Power Management ICs (PMICs).

Commercially available semiconductor antifuse-based OTP memory arrays have been around at least since 1969, with initial antifuse bit cells dependent on blowing a capacitor between crossing conductive lines. [[Texas Instruments]] developed a MOS [[gate oxide]] breakdown antifuse in 1979.<ref>See [http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE US Patent 4184207] {{Webarchive|url=https://web.archive.org/web/20180427183945/http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE |date=2018-04-27 }} - High density floating gate electrically programmable ROM, and [http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE US Patent 4151021] {{webarchive|url=https://web.archive.org/web/20180427092847/http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE |date=2018-04-27 }} - Method of making a high density floating gate electrically programmable ROM</ref> A dual-gate-oxide two-transistor (2T) MOS antifuse was introduced in 1982.<ref>[http://www.chipestimate.com/techtalk/techtalk_071218.html Chip Planning Portal]. ChipEstimate.com. Retrieved on 2013-08-10.</ref> Early oxide breakdown technologies exhibited a variety of scaling, programming, size and manufacturing problems that prevented volume production of memory devices based on these technologies.

Another form of one-time programmable memory device uses the same semiconductor chip as an ultraviolet-[[EPROM|erasable programmable read-only memory]] (UV-EPROM), but the finished device is put into an opaque package, instead of the expensive ceramic package with transparent quartz window required for erasing. These devices are programmed with the same methods as the UV EPROM parts but are less costly. Embedded controllers may be available in both field-erasable and one-time styles, allowing a cost saving in volume production without the expense and lead time of factory-programmed mask ROM chips. <ref>Ken Arnold, "Embedded Controller Hardware Design", Newnes, 2004, ISBN 1-878707-52-3, page 102</ref>

Although antifuse-based PROM has been available for decades, it wasn’t available in standard [[CMOS]] until 2001 when Kilopass Technology Inc. patented 1T, 2T, and 3.5T antifuse bit cell technologies using a standard CMOS process, enabling integration of PROM into logic CMOS chips. The first process node antifuse can be implemented in standard CMOS is 0.18 um. Since the gate oxide breakdown is less than the junction breakdown, special diffusion steps were not required to create the antifuse programming element. In 2005, a split channel antifuse device<ref>See [http://patimg2.uspto.gov/.piw?Docid=7402855&idkey=NONE US Patent 7402855] {{Webarchive|url=https://web.archive.org/web/20150904051044/http://patimg2.uspto.gov/.piw?Docid=7402855&idkey=NONE |date=2015-09-04 }} split channel antifuse device</ref> was introduced by Sidense. This split channel bit cell combines the thick (IO) and thin (gate) oxide devices into one transistor (1T) with a common [[Polycrystalline silicon|polysilicon]] gate.

== Programming ==
[[File:ANT Nachrichtentechnik DBT-03 - Texas Instruments TBP18SA030N-0019.jpg|thumb|Texas Instruments PROM type TBP18SA030N]]
A typical PROM comes with all bits reading as "1". Burning a fuse bit during programming causes the bit to be read as "0" by "blowing" the fuses, which is an irreversible process. Some devices can be "reprogrammed" if the new data replaces "1"s with "0"s. Some CPU instruction sets (e.g. [[MOS Technology 6502#Bugs and quirks|6502]]) took advantage of this by defining a break (BRK) instruction with the operation code of '00'. In cases where there was an incorrect instruction, it could be "reprogrammed" to a BRK causing the CPU to transfer control to a patch. This would execute the correct instruction and return to the instruction after the BRK.

The bit cell is programmed by applying a high-voltage pulse not encountered during a normal operation across the gate and substrate of the thin oxide transistor (around 6{{nbsp}}V for a 2 nm thick oxide, or 30{{nbsp}}MV/cm) to break down the oxide between gate and substrate. The positive voltage on the transistor's gate forms an inversion channel in the substrate below the gate, causing a tunneling current to flow through the oxide. The current produces additional traps in the oxide, increasing the current through the oxide and ultimately melting the oxide and forming a conductive channel from gate to substrate. The current required to form the conductive channel is around 100{{nbsp}}μA/100{{nbsp}}nm{{sup|2}} and the breakdown occurs in approximately 100{{nbsp}}μs or less.<ref>{{cite web |url=http://www.sidense.com/images/stories/designcon_8_a_eval_embedded_nvm_65nm_and_beyond.pdf |title=Evaluating Embedded Non-Volatile Memory for 65nm and Beyond |author=Wlodek Kurjanowicz |year=2008 |access-date=2009-09-04 |url-status=dead |archive-url=https://web.archive.org/web/20160304025935/http://www.sidense.com/images/stories/designcon_8_a_eval_embedded_nvm_65nm_and_beyond.pdf |archive-date=2016-03-04 }}</ref>

==See also==
* [[Intel HEX]]

==References==
{{Reflist}}

==References==
* [https://archive.org/details/bitsavers_inteldataBMay77_21293903 1977 Intel Memory Design Handbook] - archive.org
* {{usurped|1=[https://web.archive.org/web/20130812120201/http://www.intel-vintage.info/intelmemory.htm Intel PROM datasheets]}} - intel-vintage.info
* View the US "Switch Matrix" Patent #3028659 at [http://patimg2.uspto.gov/.piw?Docid=03028659&idkey=NONE US Patent Office] {{Webarchive|url=https://web.archive.org/web/20151016080757/http://patimg2.uspto.gov/.piw?Docid=03028659&idkey=NONE |date=2015-10-16 }} or [https://patents.google.com/patent/US3028659 Google]
* View Kilopass Technology Patent US "High density semiconductor memory cell and memory array using a single transistor and having variable gate oxide breakdown" Patent #6940751 at [http://patimg2.uspto.gov/.piw?Docid=6940751&idkey=NONE US Patent Office] {{Webarchive|url=https://web.archive.org/web/20150904051044/http://patimg2.uspto.gov/.piw?Docid=6940751&idkey=NONE |date=2015-09-04 }} or [https://patents.google.com/patent/US6940751 Google]
* View Sidense US "Split Channel Antifuse Array Architecture" Patent #7402855 at [http://patimg2.uspto.gov/.piw?Docid=7402855&idkey=NONE US Patent Office] {{Webarchive|url=https://web.archive.org/web/20150904051044/http://patimg2.uspto.gov/.piw?Docid=7402855&idkey=NONE |date=2015-09-04 }} or [https://patents.google.com/patent/US20060244099 Google]
* View the US "Method of Manufacturing Semiconductor Integrated Circuits" Patent #3634929 at [http://patimg2.uspto.gov/.piw?Docid=3634929&idkey=NONE US Patent Office] {{Webarchive|url=https://web.archive.org/web/20150904051044/http://patimg2.uspto.gov/.piw?Docid=3634929&idkey=NONE |date=2015-09-04 }} or [https://patents.google.com/patent/US3634929 Google]
* CHOI et al. (2008). {{usurped|1=[https://wayback.archive-it.org/all/20081031153339/http://www.ee.ucla.edu/~ipl/New_Non-Volatile_Memory_Structures_for_FPGA_Architectures.pdf "New Non-Volatile Memory Structures for FPGA Architectures"]}}
* For the Advantages and Disadvantages table, see Ramamoorthy, G: "Dataquest Insight: Nonvolatile Memory IP Market, Worldwide, 2008-2013", page 10. Gartner, 2009

==See also==
* [[EPROM]]
* [[EEPROM]]

==External links==
* [http://www.righto.com/2019/07/looking-inside-1970s-prom-chip-that.html Looking inside a 1970s PROM chip that stores data in microscopic fuse] - shows die of a 256x4 MMI 5300 PROM

{{Authority control}}
{{DEFAULTSORT:Programmable Read-Only Memory}}

[[Category:Non-volatile memory]]
[[Category:Computer memory]]
[[Category:Computer-related introductions in 1956]]
[[Category:American inventions]]

← Previous revision		Revision as of 02:44, 15 June 2025
Line 1:		Line 1:
	{{Memory types}}		{{Memory types}}
	{{short description\|Type of solid state computer memory that becomes read only after being written once}}		{{short description\|Type of solid state computer memory that becomes read only after being written once}}
	A '''programmable read-only memory''' ('''PROM''') is a form of digital memory where the contents can be changed once after manufacture of the device. The data is then permanent and cannot be changed. It is one type of [[read-only memory]] (ROM). PROMs are used in digital electronic devices to store permanent data, usually low level programs such as [[firmware]] or [[microcode]]. The key difference from a standard [[Read-only memory\|ROM]] is that the data is written into a ROM during manufacture, while with a PROM the data is programmed into them after manufacture. Thus, ROMs tend to be used only for large production runs with well-verified data. PROMs may be used where the volume required does not make a factory-programmed ROM economical, or during development of a system that may ultimately be converted to ROMs in a mass produced version.		A '''programmable read-only memory''' ('''PROM''') is a form of digital memory where the contents can be changed once after manufacture of the device. The data is then permanent and cannot be changed. It is one type of [[read-only memory]] (ROM). PROMs are used in digital electronic devices to store permanent data, usually low level programs such as [[firmware]] or [[microcode]]. The key difference from a standard [[Read-only memory\|ROM]] is that the data is written into a ROM during manufacture, while with a PROM the data is programmed into them after manufacture. Thus, ROMs tend to be used only for large production runs with well-verified data. PROMs may be used where the volume required does not make a factory-programmed ROM economical, or during development of a system that may ultimately be converted to ROMs in a mass produced version.

	PROMs are manufactured blank and, depending on the technology, can be programmed at wafer, final test, or in system. Blank PROM chips are programmed by plugging them into a device called a ''PROM programmer''. Companies can keep a supply of blank PROMs in stock, and program them at the last minute to avoid large volume commitment. These types of memories are frequently used in [[microcontroller]]s, [[video game console]]s, mobile phones, radio-frequency identification ([[RFID]]) tags, implantable medical devices, high-definition multimedia interfaces ([[HDMI]]) and in many other consumer and automotive electronics products. A typical PROM device is made up of an array of memory cells, each made up of a transistor, which is a [[bipolar transistor]], connected to a [[Fuse (electrical)\|fuse]] called a [[polyfuse (PROM)\|polyfuse]] in the emitter of the transistor. A PROM programmer is used to blow the polyfuse, programming the PROM.<ref>{{cite book \| url=https://books.google.com/books?id=9VHMBQAAQBAJ&dq=prom+fuse&pg=PA760 \| title=The Electronics Handbook \| isbn=978-1-4200-3666-4 \| last1=Whitaker \| first1=Jerry C. \| date=3 October 2018 \| publisher=CRC Press }}</ref>		PROMs are manufactured blank and, depending on the technology, can be programmed at wafer, final test, or in system. Blank PROM chips are programmed by plugging them into a device called a ''PROM programmer''. Companies can keep a supply of blank PROMs in stock, and program them at the last minute to avoid large volume commitment. These types of memories are frequently used in [[microcontroller]]s, [[video game console]]s, mobile phones, radio-frequency identification ([[RFID]]) tags, implantable medical devices, high-definition multimedia interfaces ([[HDMI]]) and in many other consumer and automotive electronics products. A typical PROM device is made up of an array of memory cells, each made up of a transistor, which is a [[bipolar transistor]], connected to a [[Fuse (electrical)\|fuse]] called a [[polyfuse (PROM)\|polyfuse]] in the emitter of the transistor. A PROM programmer is used to blow the polyfuse, programming the PROM.<ref>{{cite book \| url=https://books.google.com/books?id=9VHMBQAAQBAJ&dq=prom+fuse&pg=PA760 \| title=The Electronics Handbook \| isbn=978-1-4200-3666-4 \| last1=Whitaker \| first1=Jerry C. \| date=3 October 2018 \| publisher=CRC Press }}</ref>

	== History ==		== History ==
Line 11:		Line 11:

	=== One time programmable memory ===		=== One time programmable memory ===
	OTP (one time programmable) memory is a special type of [[non-volatile memory]] (NVM) that permits data to be written to memory only once. Once the memory has been programmed, it retains its value upon loss of power (i.e., is non-volatile). OTP memory is used in applications where reliable and repeatable reading of data is required. Examples include boot code, encryption keys and configuration parameters for analog, sensor or display circuitry. OTP NVM is characterized, over other types of NVM like [[eFuse]] or EEPROM, by offering a low power, small area footprint memory structure. As such OTP memory finds application in products from microprocessors & display drivers to ~~Power Management~~ ICs (PMICs).		OTP (one time programmable) memory is a special type of [[non-volatile memory]] (NVM) that permits data to be written to memory only once. Once the memory has been programmed, it retains its value upon loss of power (i.e., is non-volatile). OTP memory is used in applications where reliable and repeatable reading of data is required. Examples include boot code, encryption keys and configuration parameters for analog, sensor or display circuitry. OTP NVM is characterized, over other types of NVM like [[eFuse]] or EEPROM, by offering a low power, small area footprint memory structure. As such OTP memory finds application in products from microprocessors & display drivers to power management ICs (PMICs).

	Commercially available semiconductor antifuse-based OTP memory arrays have been around at least since 1969, with initial antifuse bit cells dependent on blowing a capacitor between crossing conductive lines. [[Texas Instruments]] developed a MOS [[gate oxide]] breakdown antifuse in 1979.<ref>See [http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE US Patent 4184207] {{Webarchive\|url=https://web.archive.org/web/20180427183945/http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE \|date=2018-04-27 }} - High density floating gate electrically programmable ROM, and [http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE US Patent 4151021] {{webarchive\|url=https://web.archive.org/web/20180427092847/http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE \|date=2018-04-27 }} - Method of making a high density floating gate electrically programmable ROM</ref> A dual-gate-oxide two-transistor (2T) MOS antifuse was introduced in 1982.<ref>[http://www.chipestimate.com/techtalk/techtalk_071218.html Chip Planning Portal]. ChipEstimate.com. Retrieved on 2013-08-10.</ref> Early oxide breakdown technologies exhibited a variety of scaling, programming, size and manufacturing problems that prevented volume production of memory devices based on these technologies.		Commercially available semiconductor antifuse-based OTP memory arrays have been around at least since 1969, with initial antifuse bit cells dependent on blowing a capacitor between crossing conductive lines. [[Texas Instruments]] developed a MOS [[gate oxide]] breakdown antifuse in 1979.<ref>See [http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE US Patent 4184207] {{Webarchive\|url=https://web.archive.org/web/20180427183945/http://patimg2.uspto.gov/.piw?Docid=4184207&idkey=NONE \|date=2018-04-27 }} - High density floating gate electrically programmable ROM, and [http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE US Patent 4151021] {{webarchive\|url=https://web.archive.org/web/20180427092847/http://patimg2.uspto.gov/.piw?Docid=4151021&idkey=NONE \|date=2018-04-27 }} - Method of making a high density floating gate electrically programmable ROM</ref> A dual-gate-oxide two-transistor (2T) MOS antifuse was introduced in 1982.<ref>[http://www.chipestimate.com/techtalk/techtalk_071218.html Chip Planning Portal]. ChipEstimate.com. Retrieved on 2013-08-10.</ref> Early oxide breakdown technologies exhibited a variety of scaling, programming, size and manufacturing problems that prevented volume production of memory devices based on these technologies.

	Another form of one-time programmable memory device uses the same semiconductor chip as an ultraviolet-[[EPROM\|erasable programmable read-only memory]] (UV-EPROM), but the finished device is put into an opaque package, instead of the expensive ceramic package with transparent quartz window required for erasing. These devices are programmed with the same methods as the UV EPROM parts but are less costly. Embedded controllers may be available in both field-erasable and one-time styles, allowing a cost saving in volume production without the expense and lead time of factory-programmed mask ROM chips. <ref>Ken Arnold, "Embedded Controller Hardware Design", Newnes, 2004, ISBN 1-878707-52-3, page 102</ref>		Another form of one-time programmable memory device uses the same semiconductor chip as an ultraviolet-[[EPROM\|erasable programmable read-only memory]] (UV-EPROM), but the finished device is put into an opaque package, instead of the expensive ceramic package with transparent quartz window required for erasing. These devices are programmed with the same methods as the UV EPROM parts but are less costly. Embedded controllers may be available in both field-erasable and one-time styles, allowing a cost saving in volume production without the expense and lead time of factory-programmed mask ROM chips. <ref>Ken Arnold, "Embedded Controller Hardware Design", Newnes, 2004, ISBN 1-878707-52-3, page 102</ref>

	Although antifuse-based PROM has been available for decades, it wasn’t available in standard [[CMOS]] until 2001 when Kilopass Technology Inc. patented 1T, 2T, and 3.5T antifuse bit cell technologies using a standard CMOS process, enabling integration of PROM into logic CMOS chips. The first process node antifuse can be implemented in standard CMOS is 0.18 um. Since the gate oxide breakdown is less than the junction breakdown, special diffusion steps were not required to create the antifuse programming element. In 2005, a split channel antifuse device<ref>See [http://patimg2.uspto.gov/.piw?Docid=7402855&idkey=NONE US Patent 7402855] {{Webarchive\|url=https://web.archive.org/web/20150904051044/http://patimg2.uspto.gov/.piw?Docid=7402855&idkey=NONE \|date=2015-09-04 }} split channel antifuse device</ref> was introduced by Sidense. This split channel bit cell combines the thick (IO) and thin (gate) oxide devices into one transistor (1T) with a common [[Polycrystalline silicon\|polysilicon]] gate.		Although antifuse-based PROM has been available for decades, it wasn’t available in standard [[CMOS]] until 2001 when Kilopass Technology Inc. patented 1T, 2T, and 3.5T antifuse bit cell technologies using a standard CMOS process, enabling integration of PROM into logic CMOS chips. The first process node antifuse can be implemented in standard CMOS is 0.18 um. Since the gate oxide breakdown is less than the junction breakdown, special diffusion steps were not required to create the antifuse programming element. In 2005, a split channel antifuse device<ref>See [http://patimg2.uspto.gov/.piw?Docid=7402855&idkey=NONE US Patent 7402855] {{Webarchive\|url=https://web.archive.org/web/20150904051044/http://patimg2.uspto.gov/.piw?Docid=7402855&idkey=NONE \|date=2015-09-04 }} split channel antifuse device</ref> was introduced by Sidense. This split channel bit cell combines the thick (IO) and thin (gate) oxide devices into one transistor (1T) with a common [[Polycrystalline silicon\|polysilicon]] gate.

	== Programming ==		== Programming ==
	[[File:ANT Nachrichtentechnik DBT-03 - Texas Instruments TBP18SA030N-0019.jpg\|thumb\|Texas Instruments PROM type TBP18SA030N]]		[[File:ANT Nachrichtentechnik DBT-03 - Texas Instruments TBP18SA030N-0019.jpg\|thumb\|Texas Instruments PROM type TBP18SA030N]]
	A typical PROM comes with all bits reading as "1". Burning a fuse bit during programming causes the bit to be read as "0" by "blowing" the fuses, which is an irreversible process. Some devices can be "reprogrammed" if the new data replaces "1"s with "0"s. Some CPU instruction sets (e.g. [[MOS Technology 6502#Bugs and quirks\|6502]]) took advantage of this by defining a break (BRK) instruction with the operation code of '00'. In cases where there was an incorrect instruction, it could be "reprogrammed" to a BRK causing the CPU to transfer control to a patch. This would execute the correct instruction and return to the instruction after the BRK.		A typical PROM comes with all bits reading as "1". Burning a fuse bit during programming causes the bit to be read as "0" by "blowing" the fuses, which is an irreversible process. Some devices can be "reprogrammed" if the new data replaces "1"s with "0"s. Some CPU instruction sets (e.g. [[MOS Technology 6502#Bugs and quirks\|6502]]) took advantage of this by defining a break (BRK) instruction with the operation code of '00'. In cases where there was an incorrect instruction, it could be "reprogrammed" to a BRK causing the CPU to transfer control to a patch. This would execute the correct instruction and return to the instruction after the BRK.

	The bit cell is programmed by applying a high-voltage pulse not encountered during a normal operation across the gate and substrate of the thin oxide transistor (around 6{{nbsp}}V for a 2 nm thick oxide, or 30{{nbsp}}MV/cm) to break down the oxide between gate and substrate. The positive voltage on the transistor's gate forms an inversion channel in the substrate below the gate, causing a tunneling current to flow through the oxide. The current produces additional traps in the oxide, increasing the current through the oxide and ultimately melting the oxide and forming a conductive channel from gate to substrate. The current required to form the conductive channel is around 100{{nbsp}}μA/100{{nbsp}}nm{{sup\|2}} and the breakdown occurs in approximately 100{{nbsp}}μs or less.<ref>{{cite web \|url=http://www.sidense.com/images/stories/designcon_8_a_eval_embedded_nvm_65nm_and_beyond.pdf \|title=Evaluating Embedded Non-Volatile Memory for 65nm and Beyond \|author=Wlodek Kurjanowicz \|year=2008 \|access-date=2009-09-04 \|url-status=dead \|archive-url=https://web.archive.org/web/20160304025935/http://www.sidense.com/images/stories/designcon_8_a_eval_embedded_nvm_65nm_and_beyond.pdf \|archive-date=2016-03-04 }}</ref>		The bit cell is programmed by applying a high-voltage pulse not encountered during a normal operation across the gate and substrate of the thin oxide transistor (around 6{{nbsp}}V for a 2 nm thick oxide, or 30{{nbsp}}MV/cm) to break down the oxide between gate and substrate. The positive voltage on the transistor's gate forms an inversion channel in the substrate below the gate, causing a tunneling current to flow through the oxide. The current produces additional traps in the oxide, increasing the current through the oxide and ultimately melting the oxide and forming a conductive channel from gate to substrate. The current required to form the conductive channel is around 100{{nbsp}}μA/100{{nbsp}}nm{{sup\|2}} and the breakdown occurs in approximately 100{{nbsp}}μs or less.<ref>{{cite web \|url=http://www.sidense.com/images/stories/designcon_8_a_eval_embedded_nvm_65nm_and_beyond.pdf \|title=Evaluating Embedded Non-Volatile Memory for 65nm and Beyond \|author=Wlodek Kurjanowicz \|year=2008 \|access-date=2009-09-04 \|url-status=dead \|archive-url=https://web.archive.org/web/20160304025935/http://www.sidense.com/images/stories/designcon_8_a_eval_embedded_nvm_65nm_and_beyond.pdf \|archive-date=2016-03-04 }}</ref>

	==See also==		==See also==