Basic Bipolar Process Description

• Bipolar Process Flow– Vertical npn– Lateral pnp– JFET

– Prepared by Randy Geiger, September 2001

Bipolar Process Flow

P-substrate

n+ buried collector implant

n-epitaxy

Buried collector

Isolation Diffusionp-base diffusion n+ emitter diffusionOxidationContact OpeningsMetalization Bipolar Process Flow

n+ buried collector implantBuried collector

Base Emitter Collector

Vertical npn BJT

B E C

Lateral pnp Modification

E C B

Lateral pnp BJT

B E C

JFET Modification

S DG

BJT Layout and Area Issues

• BJT Layout

• BJT Area Requirements

• Comparison of Area between MOS and Bipolar Processes

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

15

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

19

2

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

19

14 14

43

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

19

14 14

43

14

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

19

14

47

14

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

19

14

47

14

4

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

14

47

14

46

12

22

NOT TOSCALE

Note: 24 requiredBetween p-base and isolation diffusion

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

14

63

6

12

2

2

Note: 24 requiredBetween p-base and isolation diffusion

Note: Not to vertical Scale

58

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

3 2

14

63

6

12

2

2

Note: 24 requiredBetween p-base and isolation diffusion

Note: Not to vertical Scale

58

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

63

Note: Not to vertical Scale

58

67

62

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

Note: Not to vertical Scale

67

62

Bounding Area = 41542

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

16

13

Bounding Area = 208

Comparison with Area for n-channel MOSFET in Bulk CMOS

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

14

12

Bounding Area = 168

Active Area = 62

Minimum-Sized MOSFET

1 5 10 15 20 25 30 35 40 45 50 6055 7065 751

5

10

20

15

30

25

40

35

50

45

55

Note: Not to vertical Scale

67

62

MOSFET BJT

Area Comparison between BJT and MOSFET

• BJT Area = 4154 2

• n-channel MOSFET Area = 168 2

• Area Ratio 25:1

That’s all folks!