Array architecture and operating methods for digital multilevel nonvolatile memory integrated circuit system

• US 6,282,145 B1
• Filed: 01/14/1999
• Issued: 08/28/2001
• Est. Priority Date: 01/14/1999
• Status: Expired due to Term

• Current Assignee: Silicon Storage Technology Incorporated (Microchip Technology Incorporated)
• Original Assignee: Silicon Storage Technology Incorporated (Microchip Technology Incorporated)
• Inventors: Tran, Hieu Van, Korsh, George J., Khan, Sakhawat M.
• Primary Examiner(s): Dinh, Son T.
• Application Number:
  US09/231,928
• Time in Patent Office: 957 Days
• Field of Search: 365/63, 365/230.06, 365/51
• US Class Current: 365/230.06
• CPC Class Codes: G11C 11/5621 using charge storage in a floating gate
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 11/5635 Erasing circuits
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 11/5678 using amorphous/crystalline phase transition storage elements
• CPC Class Codes: G11C 13/0004 comprising amorphous/crystalline phase transition cells
• CPC Class Codes: G11C 16/08 Address circuits; Decoders; Word-line control circuits
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 16/24 Bit-line control circuits
• CPC Class Codes: G11C 16/28 using differential sensing or reference cells, e.g. dummy cells
• CPC Class Codes: G11C 2211/5634 Reference cells
• CPC Class Codes: G11C 27/005 with non-volatile charge storage, e.g. on floating gate or MNOS

Abstract

Memory array architectures and operating methods suitable for super high density in the giga bits for multilevel nonvolatile memory integrated circuit system. The array architectures and operating methods include: (1) an Inhibit and Select Segmentation Scheme; (2) a Multilevel Memory Decoding Scheme that includes a Power Supply Decoded Decoding Scheme, a Feedthrough-to-Memory Decoding Scheme, a Feedthrough-to-Driver Decoding Scheme, and a Winner-Take-All Kelvin Memory Decoding Scheme; (3) a constant-total-current-program scheme; (4) includes fast-slow and 2-step ramp rate control programming; and a reference system method and apparatus, which includes a Positional Linear Reference System, a Positional Geometric Reference System, and a Geometric Compensation Reference System. The apparatus and method enable multilevel programming, reading, and margining.

Claims

1. An integrated circuit data storage system comprising:

a plurality of memory cells, each memory cell being configurable to store one of a plurality of signal levels;

a decoding circuit coupled to the plurality of memory cells and configured to generate a first and a second control signal based on a set of input data bits; and

a supply source operatively coupled to selected ones of the plurality of memory cells based on the first control signal from the decoding circuit, the supply source configured to provide programming signals based on the second control signal, and

wherein the selected memory cells are programmed in accordance with the programming signals from the supply source.

2. The system of claim 1, wherein each of the plurality of memory cells is configurable to store one of 2^N signal levels, where N is two or greater.

3. The system of claim 2, wherein N is two.

4. The system of claim 2, wherein N is three.

5. A device comprising the data storage system of claim 1, wherein the plurality of memory cells are configurable to store at least one giga bits of data.

6. The system of claim 1 wherein the plurality of memory cells is formed at the surface of a semiconductor substrate and the decoding circuit is further configured to generate a set of control signals based on an address;

and further comprising

a plurality of bit lines, each bit line interconnecting a subset of the plurality of memory cells formed in a memory array, each bit formed as a main metal bit line and a plurality of segmented metal bit lines, the main metal bit line traversing a length of the memory array, the segmented metal bit lines each traversing a portion of the length of the memory array, selectively connected to the main bit line responsive to the control signals from the decoding circuit and connected to semiconductor substrate regions of the memory cells along the portion of the length of the memory array, the segmented metal bit lines passing over the semiconductor substrate and the main bit line passing over the segmented metal bit lines so that capacitance of each bit line is reduced.

7. The device of claim 6, wherein the plurality of memory cells are arranged into a plurality of memory arrays, each memory array including P rows by Q columns of memory cells.

8. The device of claim 7, wherein each memory array is partitioned into a plurality of memory segments, each memory segment including R rows by S columns of memory cells, wherein each memory segment is further partitioned into a plurality of memory blocks, each memory block including X rows by Y columns of memory cells.

9. The device of claim 8, wherein each segmented bit line couples to memory cells in a column of a memory block.

10. The device of claim 8, wherein each main bit line couples to segmented bit lines associated with a column of a memory segment.

11. The device of claim 6, wherein the segmented bit lines couple to the main bit lines via a first set of transistors.

12. The device of claim 11, wherein the transistors in the first set are enabled by associated bit line select lines.

13. The device of claim 6, further comprising:

a plurality of bit line decoding circuits, each bit line decoding circuit coupled to an associated segmented bit line and including

at least one deselect transistor coupled between a control line and a supply ground, wherein a control gate for each deselect transistor couples to a low voltage control signal, and

at least one select transistor coupled between the control line and a supply source.

14. The device of claim 6, further comprising:

a plurality of common lines positioned transverse to the main bit lines, the main bit lines traversing the memory array in a first direction, each common line interconnecting a set of memory cells disposed along a second direction of the memory array.

15. The device of claim 14, wherein the main bit lines are disposed over the segmented bit lines and under the common lines.

16. The device of claim 14, wherein the common lines are disposed under the main bit lines and over the segmentcd bit lines.

17. The device of claim 6, wherein the main bit lines are positioned above the segmented bit lines and in the space between pairs of segmented bit lines, to reduce capacitive coupling between the main and segmented bit lines.

18. The device of claim 6, wherein the bit lines are implemented with a hierarchical interconnection structure comprised of a plurality of first segment bit lines and a plurality of second segment bit lines, wherein each first segment bit line couples to a set of memory cells and each second segment bit line couples to a set of first segment bit lines.

19. The device of claim 18, wherein the first segment bit lines are disposed within a first metal layer and the second segment bit lines are disposed within a second metal layer.

20. The device of claim 18, wherein the first segment bit lines couple to the second segment bit lines via a set of transistors.

21. The device of claim 18, wherein the hierarchical interconnection structure further comprises a plurality of third segment bit lines, wherein each third segment bit line couples to a set of second segment bit lines.

22. The device of claim 18, further comprising:

one or more inhibit lines operatively coupled to the plurality of bit lines via a set of transistors.

23. The device of claim 22, wherein the inhibit lines operatively coupled to bit lines associated with one memory segment.

24. The device of claim 22, wherein the inhibit lines operatively coupled to bit lines associated with two or more memory segments.

25. The device of claim 18, further comprising:

a plurality of control gate lines, each control gate line coupled to control gates of memory cells in a row of a memory segment.

26. The device of claim 25, wherein each control gate line comprises a plurality of segmented control gate lines.

27. The device of claim 25, further comprising:

a plurality of control gate circuits, each control gate circuit coupled to an associated control gate line.

28. The device of claim 27, wherein each control gate circuit includes

a first transistor coupled between the associated control gate line and a predecoded control gate line, and

a second transistor coupled between the associated control gate line and a low voltage line.

29. The device of claim 28, further comprising:

a control gate predecoder configured to receive an input address and generate predecoded control gate lines.

30. The device of claim 6, further comprising:

a plurality of common lines positioned transverse to the bit lines, each common line interconnecting a second subset of the plurality of memory cells.

31. The device of claim 30, wherein each common line traverses a width of a plurality of memory arrays.

32. The device of claim 30, wherein each common line traverses a width of one memory array.

33. The device of claim 30, wherein each common line is implemented with a set of segmented common lines that collectively traverses a width of a plurality of memory arrays.

34. The device of claim 30, wherein each common line is driven from at least two locations along the common line.

35. The device of claim 30, further comprising:

a plurality of control gate drivers, at least one control gate driver coupled to each control gate line.

36. The device of claim 34, wherein each control gate driver is coupled to a middle, and configured to drive both sidcs, of the control gatc line.

37. The device of claim 30, wherein a width of each common line is dimensioned to provide a voltage drop across a length of the common line of less than a particular voltage level.

38. The device of claim 30, wherein the common lines are implemented with diffusion common lines and metal common lines, wherein the diffusion common lines are periodically strapped to the metal common lines via metal strapping lines.

39. The device of claim 30, wherein the common lines are operated to conduct approximately constant amounts of program current during programming of the memory cells.

40. The device of claim 39, wherein the approximately constant amounts of program current are achieved by switching into the common lines additional amounts of current to replace currents associated with memory cells inhibited from programming.

41. The device of claim 30, wherein each common line is implemented with a plurality of line sections, each line section being driven by drivers located on both sides of the line section.

42. The device of claim 30, further comprising:

a plurality of common line circuits, each common line circuit coupled to an associated common line.

43. The device of claim 42, wherein each common circuit includes

a first transistor coupled between the associated common line and a predecoded common line, and

a second transistor coupled between the associated common line signal and a low voltage line.

44. The device of claim 43, wherein the predecoded common line is generated based on a received input address.

45. The device of claim 30, further comprising:

a Kelvin decoder coupled to the plurality of common lines.

46. The device of claim 45, wherein the Kelvin decoder comprises a plurality of diode-connected transistors, one transistor coupled to each common line, the transistors further coupled together.

47. The memory system of claim 1, wherein the memory unit is configured to provide a status signal indicative of an operational state of the memory unit.

48. The memory system of claim 47, wherein the indicated operational state is either ready or busy.

49. The memory system of claim 1, wherein the memory unit is configured to activate a restore flag indicative of a need to restore at least one memory cell after a read operation.

50. The memory system of claim 1, wherein the memory unit is configured to set a flag indicative of a program, erase, or restore state of the memory unit.

51. The memory system of claim 1, wherein the memory unit further includes test circuitry configured to provide signals used to test the memory unit.

52. The memory system of claim 1, wherein the memory unit further includes

at least one redundant array of memory cells, each redundant array configurable to substitute for a subset of the plurality of memory cells in the memory unit.

53. The memory system of claim 1, wherein the memory unit further includes

a power unit configured to provide a set of voltages used by the memory unit.

54. The memory system of claim 53, wherein power unit is configured to power down circuit blocks not in used.

55. The memory system of claim 53, wherein power unit is configured to step down one or more input voltages to lower voltages used by circuitry within the memory unit.

56. The memory system of claim 53, wherein power unit is operative to receive an analog input voltage and to provide an analog output voltage to selected circuitry within the memory unit.

57. The memory system of claim 53, wherein power unit includes a set of supply regulators configured to provide different voltages to different sections of the memory unit.

58. The memory system of claim 1, wherein the memory unit further includes

a set of fuses configured to direct selected operations of the memory unit.

59. The memory system of claim 58, wherein at least one fuse is configured to identify a particular number of pages of memory cells that can be erased in a single erase operation.

60. The memory system of claim 58, wherein at least one fuse is configured to identify a particular number of memory cells that can be programmed in a single program operation.

61. The memory system of claim 58, wherein at least one fuse is configured to identify a particular number of memory cells that can be read in a single read operation.

62. An integrated circuit memory device having a semiconductor substrate, said memory device comprising:

a plurality of memory cells at a surface of said semiconductor substrate;

a decoding circuit configured to generate a set of control signals based on an address; and

a plurality of bit lines, each bit line interconnecting a subset of the plurality of memory cells formed in a memory array, each bit formed as a main metal bit line and a plurality of segmented metal bit lines, the main metal bit line traversing a length of the memory array, the segmented metal bit lines each traversing a portion of the length of the memory array, selectively connected to the main bit line responsive to the control signals from the decoding circuit and connected to semiconductor substrate regions of the memory cells alone the portion of the length of the memory array, the segmented metal bit lines passing over the semiconductor substrate and the main bit line passing over the segmented metal bit lines so that capacitance of each bit line is reduced.

63. The device of claim 62, wherein the plurality of memory cells are arranged into a plurality of memory arrays, each memory array including P rows by Q columns of memory cells.

64. The device of claim 63, wherein each memory array is partitioned into a plurality of memory segments, each memory segment including R rows by S columns of memory cells, wherein each memory segment is further partitioned into a plurality of memory blocks, each memory block including X rows by Y columns of memory cells.

65. The device of claim 64, wherein each segmented bit line couples to memory cells in a column of a memory block.

66. The device of claim 64, wherein each main bit line couples to segmented bit lines associated with a column of a memory segment.

67. The device of claim 62, wherein the segmcnted bit lines couple to the main bit lines via a first set of transistors.

68. The device of claim 67, wherein the transistors in the first set are enabled by associated bit line select lines.

69. The device of claim 62, further comprising:

a plurality of bit line decoding circuits, each bit line decoding circuit coupled to an associated segmented bit line and including

at least one deselect transistor coupled between a control line and a supply ground, wherein a control gate for each deselect transistor couples to a low voltage control signal, and

at least one select transistor coupled between the control line and a supply source.

70. The device of claim 62, further comprising:

a plurality of common lines positioned transverse to the main bit lines, the main bit lines traversing the memory array in a first direction, each common line interconnecting a set of memory cells disposed along a second direction of the memory array.

71. The device of claim 70, wherein the main bit lines are disposed over the segmented bit lines and under the common lines.

72. The device of claim 70, wherein the common lines are disposed under the main bit lines and over the segmented bit lines.

73. The device of claim 62, wherein the main bit lines are positioned above the segmented bit lines and in the space between pairs of segmented bit lines, to reduce capacitive coupling between the main and segmented bit lines.

74. The device of claim 62, wherein the bit lines are implemented with a hierarchical interconnection structure comprised of a plurality of first segment bit lines and a plurality of second segment bit lines, wherein each first segment bit line couples to a set of memory cells and each second segment bit line couples to a set of first segment bit lines.

75. The device of claim 74, wherein the first segment bit lines are disposed within a first metal layer and the second segment bit lines are disposed within a second metal layer.

76. The device of claim 74, wherein the first segment bit lines couple to the second segment bit lines via a set of transistors.

77. The device of claim 74, wherein the hierarchical interconnection structure further comprises a plurality of third segment bit lines, wherein each third segment bit line couples to a set of second segment bit lines.

78. The device of claim 62, further comprising:

a plurality of common lines positioned transverse to the bit lines, each common line interconnecting a second subset of the plurality of memory cells.

79. The device of claim 78, wherein each common line traverses a width of a plurality of memory arrays.

80. The device of claim 78, wherein each common line traverses a width of one memory array.

81. The device of claim 78, wherein each common line is implemented with a set of segmented common lines that collectively traverses a width of a plurality of memory arrays.

82. The device of claim 78, wherein each common line is driven from at least two locations along the common line.

83. The device of claim 78, further comprising:

a plurality of control gate drivers, at least one control gate driver coupled to each control gate line.

84. The device of claim 82, wherein each control gate driver is coupled to a middle, and configured to drive both sides, of the control gate line.

85. The device of claim 78 wherein a width of each common line is dimensioned to provide a voltage drop across a length of the common line of less than a particular voltage level.

86. The device of claim 78, wherein a width of each common line is dimensioned to provide a voltage drop across a length of the common line of less than a particular voltage level.

87. The device of claim 78, wherein the common lines are operated to conduct approximately constant amounts of program current during programming of the memory cells.

88. The device of claim 87, wherein the approximately constant amounts of program current are achieved by switching into the common lines additional amounts of current to replace currents associated with memory cells inhibited from programming.

89. The device of claim 78, wherein each common line is implemented with a plurality of line sections, each line section being driven by drivers located on both sides of the line section.

90. The device of claim 78, further comprising:

a plurality of common line circuits, each common line circuit coupled to an associated common line.

91. The device of claim 90, wherein each common circuit includes

a first transistor coupled between the associated common line and a predecoded common line, and

a second transistor coupled between the associated common line signal and a low voltage line.

92. The device of claim 91, wherein the predecoded common line is generated based on a received input address.

93. The device of claim 78, further comprising:

a Kelvin decoder coupled to the plurality of common lines.

94. The device of claim 93, wherein the Kelvin decoder comprises a plurality of diode-connected transistors, one transistor coupled to each common line, the transistors further coupled together.

95. The device of claim 64, further comprising:

one or more inhibit lines operatively coupled to the plurality of bit lines via a set of transistors.

96. The device of claim 95, wherein the inhibit lines operatively coupled to bit lines associated with one memory segment.

97. The device of claim 95, wherein the inhibit lines operatively coupled to bit lines associated with two or more memory segments.

98. The device of claim 64, further comprising:

a plurality of control gate lines, each control gate line coupled to control gates of memory cells in a row of a memory segment.

99. The device of claim 98, wherein each control gate line comprises a plurality of segmented control gate lines.

100. The device of claim 98, further comprising:

a plurality of control gate circuits, each control gate circuit coupled to an associated control gate line.

101. The device of claim 100, wherein each control gate circuit includes

a first transistor coupled between the associated control gate line and a predecoded control gate line, and

a second transistor coupled between the associated control gate line and a low voltage line.

102. The device of claim 101, further comprising:

a control gate predecoder configured to receive an input address and generate predecoded control gate lines.

103. The device of claim 101, wherein the first and second transistors are implemented as NMOS transistors.

104. A multilevel memory system comprising:

a multilevel integrated circuit memory unit that includes

a plurality of memory cells, each memory cell being programmable to one of a plurality of levels in response to a set of programming signals,

a decoding circuit coupled to the plurality of memory cells and configured to generate first and second control signals based on an address, and

a supply source coupled to selected ones of the plurality of memory cells based on the first control signal, the supply source configured to provide the set of programming signals based on the second control signal; and

a microcontroller coupled to the memory unit and operative to control operation of the memory unit.

105. The memory system of claim 104, wherein the memory unit is configured to provide a status signal indicative of an operational state of the memory unit.

106. The memory system of claim 105, wherein the indicated operational state is either ready or busy.

107. The memory system of claim 104, wherein the memory unit is configured to activate a restore flag indicative of a need to restore at least one memory cell after a read operation.

108. The memory system of claim 104, wherein the memory unit is configured to set a flag indicative of a program, erase, or restore state of the memory unit.

109. The memory system of claim 104, wherein the memory unit further includes

test circuitry configured to provide signals used to test the memory unit.

110. The memory system of claim 104, wherein the memory unit further includes

at least one redundant array of memory cells, each redundant array configurable to substitute for a subset of the plurality of memory cells in the memory unit.

111. The memory system of claim 104, wherein the memory unit further includes

a power unit configured to provide a set of voltages used by the memory unit.

112. The memory system of claim 111, wherein power unit is configured to power down circuit blocks not in used.

113. The memory system of claim 111, wherein power unit is configured to step down one or more input voltages to lower voltages used by circuitry within the memory unit.

114. The memory system of claim 111, wherein power unit is operative to receive an analog input voltage and to provide an analog output voltage to selected circuitry within the memory unit.

115. The memory system of claim 111, wherein power unit includes a set of supply regulators configured to provide different voltages to different sections of the memory unit.

116. The memory system of claim 104, wherein the memory unit further includes

a set of fuses configured to direct selected operations of the memory unit.

117. The memory system of claim 116, wherein at least one fuse is configured to identify a particular number of pages of memory cells that can be erased in a single erase operation.

118. The memory system of claim 116, wherein at least one fuse is configured to identify a particular number of memory cells that can be programmed in a single program operation.

119. The memory system of claim 116, wherein at least one fuse is configured to identify a particular number of memory cells that can be read in a single read operation.

120. An electronic camera system that includes the memory unit and microcontroller of claim 105.

121. The electronic camera system of claim 120, further comprising:

an analog-to-digital converter (ADC) coupled to the memory unit, the ADC configured to receive and digitize an input signal to generate data samples that are provided to the memory unit.

122. The electronic camera system of claim 121, wherein the memory unit, ADC, and processor are implemented within one integrated circuit.

123. The electronic camera system of claim 120, further comprising:

an image sensor operative to receive an image; and

an analog-to-digital converter (ADC) coupled to the image sensor and the memory unit, the ADC configured to receive and digitize an output from the image processor to generate data samples that are provided to the memory unit.

124. The electronic camera system of claim 123, wherein the memory unit and ADC are implemented within one integrated circuit.

125. The electronic camera system of claim 123, wherein the memory unit, ADC, and image processor are implemented within one integrated circuit.

126. The electronic camera system of claim 123, wherein the memory unit, ADC, image processor, and microcontroller are implemented within one integrated circuit.

127. An electronic audio system that includes the memory system and microcontroller of claim 105.

128. The electronic audio system of claim 127, further comprising:

a first filter operative to receive an input signal; and

an analog-to-digital converter (ADC) coupled to the first filter and the memory unit, the ADC configured to receive and digitize an output from the first filter to generate data samples that are provided to the memory unit.

129. The electronic audio system of claim 128, further comprising:

a digital-to-analog converter (DAC) coupled to the memory unit and configured to receive and convert data samples from the memory unit into an analog signal; and

a second filter configured to DAC and configured to receive and filter the analog signal.

130. The electronic audio system of claim 127, further comprising:

an analog-to-digital converter (ADC) coupled to the memory unit, the ADC configured to receive and digitize an input signal to generate data samples that are provided to the memory unit; and

a digital-to-analog converter (DAC) coupled to the memory unit and configured to receive and convert data samples from the memory unit into an analog signal.

131. The electronic audio system of claim 130, wherein the memory unit, ADC, and DAC are implemented within one integrated circuit.

132. The electronic audio system of claim 130, wherein the memory unit, ADC, DAC, and micro are implemented within one integrated circuit.

133. The electronic audio system of claim 128, wherein the memory unit, microcontroller, first filter, and ADC are implemented within one integrated circuit.

134. The electronic audio system of claim 129, wherein the memory unit, first and second filters, ADC, and DAC are implemented within one integrated circuit.

135. The electronic audio system of claim 129, wherein the memory unit, first and second filters, ADC, DAC, and microprocessor are implemented within one integrated circuit.