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STT-RAM Project

Initial Estimates and Results of Cell Sizing

Expected MTJ Parameters (Ilya/Pedram)

I-STT– RP ≈ 500-700Ω

– TMR ≈ 100-120%– Lowest write energy:

● VWRITE ≈ 0.6-1V

● tPULSE ≈ 1-5ns

C-STT– RP ≈ 600-800Ω

– TMR ≈ 30-50%– Lowest write energy:

● VWRITE ≈ 1.2-2.0V

● tPULSE ≈ 0.2-0.5ns

2

Reference SRAM Cell

For IBM65: F = 0.1μm SRAM Size: 0.625μm2 = 62.5F2

3

~0.

575μ

m

~1.087μm

STT-RAM Cell Sizing

For a 2 finger device, cell area is approx:0.61μm x (WFINGER + 0.2μm)

– 50F2 → 620nm/50nm x2

– 35F2 → 380nm/50nm x2

– 25F2 → 220nm/50nm x2

4

WL

BL

SL

fingersnm

m

L

W2

80

27.1

52.5 F2

27.5 F2

(OLD CELLS)

I-STT Results for “Balanced” Voltage

VWL = 1.0V

– VDD = 1V; RP ≈ 500-700Ω; TMR ≈ 100-120%

VWL = 1.2V (15-40% increase in IWRITE/VWRITE)

– VDD = 1V; RP ≈ 500-700Ω; TMR ≈ 100-120%

5

  VAP→P [mV] VP→AP [mV]

50F2 300-350 410-540

35F2 250-300 270-360

25F2 190-240 160-220

  IAP→P [μA] IP→AP [μA]

50F2 230-310 760-820

35F2 200-250 520-540

25F2 160-190 320-330

  VAP→P [mV] VP→AP [mV]

50F2 410-470 540-667

35F2 360-480 340-410

25F2 260-330 220-300

  IAP→P [μA] IP→AP [μA]

50F2 300-410 950-1100

35F2 260-340 690-730

25F2 210-260 430-450

I-STT Results for “Balanced” Current

VWL = 1.0V

– VDD = 1V; RP ≈ 500-700Ω; TMR ≈ 100-120%

VWL = 1.2V (15-40% increase in IWRITE/VWRITE)

– VDD = 1V; RP ≈ 500-700Ω; TMR ≈ 100-120%

6

  VAP→P [mV] VP→AP [mV]

50F2 680-800 230-260

35F2 490-660 175-210

25F2 310-450 120-160

  IAP→P [μA] IP→AP [μA]

50F2 520-680 380-460

35F2 430-490 300-350

25F2 290-310 220-250

  VAP→P [mV] VP→AP [mV]

50F2 770-850 310-360

35F2 620-750 240-290

25F2 420-580 170-210

  IAP→P [μA] IP→AP [μA]

50F2 550-770 510-620

35F2 490-620 410-480

25F2 380-420 300-340

C-STT Results for “Balanced” Voltage

VWL = 1.0V

– VDD = 1V; RP ≈ 600-800Ω; TMR ≈ 30-50%

VWL = 1.2V (15-40% increase in IWRITE/VWRITE)

– VDD = 1V; RP ≈ 600-800Ω; TMR ≈ 30-50%

7

  VAP→P [mV] VP→AP [mV]

50F2 280-330 480-590

35F2 220-270 320-410

25F2 170-220 200-250

  IAP→P [μA] IP→AP [μA]

50F2 270-360 740-800

35F2 230-290 510-530

25F2 180-210 315-325

  VAP→P [mV] VP→AP [mV]

50F2 380-440 610-710

35F2 300-370 430-540

25F2 230-290 270-340

  IAP→P [μA] IP→AP [μA]

50F2 360-480 890-1020

35F2 310-390 670-710

25F2 240-290 430-440

C-STT Results for “Balanced” Current

VWL = 1.0V

– VDD = 1V; RP ≈ 600-800Ω; TMR ≈ 30-50%

VWL = 1.2V (15-40% increase in IWRITE/VWRITE)

– VDD = 1V; RP ≈ 600-800Ω; TMR ≈ 30-50%

8

  VAP→P [mV] VP→AP [mV]

50F2 580-740 250-280

35F2 400-560 200-230

25F2 250-370 140-170

  IAP→P [μA] IP→AP [μA]

50F2 610-740 350-410

35F2 470-510 290-330

25F2 300-320 210-230

  VAP→P [mV] VP→AP [mV]

50F2 700-800 340-380

35F2 530-680 270-310

25F2 330-480 190-230

  IAP→P [μA] IP→AP [μA]

50F2 670-900 480-560

35F2 570-670 390-440

25F2 400-430 290-320