Content addressable memory (CAM) device having substrate array line structure
View Patent ↗A content addressable memory (CAM) device can include a plurality of CAM cells each formed within a cell area of a substrate. Each cell area can have a cell length dimension in a first direction parallel to a substrate surface. The CAM device can also include at least one common line comprising a contiguous region of the substrate doped to a first conductivity type and formed in a base semiconductor region doped to a second conductivity type. The common line can extend in the first direction for more than one cell length and can be commonly coupled to non-power supply connections to the plurality of CAM cells.
1. A content addressable memory (CAM) device, comprising:
a plurality of CAM cells, formed in a substrate, coupled to a plurality of bit lines formed in a metallization layer over the substrate, each CAM cell of the plurality of CAM cells having a respective cell length in a first direction; and
a plurality of match lines coupled to the plurality of CAM cells,
wherein the plurality of match lines and transistor regions of the plurality of CAM cells are formed in their entirety in a contiguous region of the substrate.
2. The CAM device of claim 1 , further comprising:
a plurality of compare data lines, formed in a second metallization layer different from the metallization layer, coupled to the plurality of CAM cells.
3. The CAM device of claim 2 , wherein the second metallization layer is between the plurality of bit lines and the substrate.
4. The CAM device of claim 2 , wherein:
the plurality of match lines are formed parallel to one another in the substrate, each match line of the plurality of match lines being separated from an adjacent match line of the plurality of match lines on a first side by an isolation structure and by a row of CAM cells of the plurality of CAM cells on a second side.
5. The CAM device of claim 1 , wherein:
the substrate comprises silicon; and
each match line of the plurality of match lines comprises:
a portion of the substrate doped to a first conductivity type having a layer of silicide formed on a top surface of the match line.
6. The CAM device of claim 1 , wherein:
each match line of the plurality of match lines includes a portion of the substrate doped to a first conductivity type formed in a well of a second conductivity type.
7. The CAM device of claim 6 , further comprising:
a guard ring structure for each well that separates the well from adjacent portions of the substrate in a lateral direction, the guard ring structure being doped to the same conductivity type as the well, but at a higher concentration than the well.
8. The CAM device of claim 1 , wherein the plurality of CAM cells includes:
a plurality of store circuits that store data values, and
a plurality of compare circuits that compares data values stored in the plurality of store circuits with received compare data values.
9. The CAM device of claim 8 , wherein the plurality of CAM cells includes:
a plurality of local interconnect (LIC) structures formed from a second metallization layer that provides at least one conductive connection between the plurality of store circuits and the plurality of compare circuits,
wherein the second metallization layer is formed between the substrate and the metallization layer.
10. The CAM device of claim 1 , wherein:
the plurality of bit lines is formed in a column direction; and
the plurality of match lines is formed in a row direction substantially orthogonal to the column direction.
11. The CAM device of claim 1 , wherein the plurality of CAM cells and the plurality of match lines are formed in their entirety in the same layer.
12. A content addressable memory (CAM) device, comprising:
a plurality of CAM cells, formed in a substrate, coupled to a plurality of bit lines, each CAM cell of the plurality of CAM cells having a cell length in a column direction; and
a plurality of match lines coupled to the plurality of CAM cells, wherein the plurality of match lines and transistor regions of the plurality of CAM cells are formed in their entirety in a contiguous region of the substrate.
13. The CAM device of claim 12 , wherein:
the plurality of CAM cells is arranged into rows and columns, wherein each CAM cell of the plurality of CAM cells of a same column is coupled to at least one bit line of the plurality of bit lines; and
each match line of the plurality of match lines is coupled to a row of CAM cells of the plurality of CAM cells.
14. The CAM device of claim 12 , further comprising:
a plurality of compare data lines coupled to the plurality of CAM cells in the column direction.
15. The CAM device of claim 12 , wherein each CAM cell of the plurality of CAM cells includes:
a store circuit that stores data values, and
a compare circuit that compares data values stored in the store circuit with received compare data values.
16. The CAM device of claim 12 , wherein:
the plurality of bit lines are formed in a metallization layer over the substrate.
17. The CAM device of claim 12 , wherein:
each CAM cell of the plurality of CAM cells includes transistors of different conductivity types.
18. The CAM device of claim 17 , wherein each CAM cell of the plurality of CAM cells includes:
a store circuit that stores data values and includes transistors of first and second conductivity types, and
a compare circuit that compares data values stored in the store circuit with received compare data values, wherein the compare circuit does not include transistors of the second conductivity type.