JP3124325B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lateral MOSFET and a current detecting MOS built in the lateral MOSFET.
The present invention relates to a semiconductor device including an FET.

[0002]

2. Description of the Related Art A conventional semiconductor device comprising a lateral MOSFET having a built-in current detecting MOSFET will be described with reference to FIGS. 3, 4 and 5. FIG. 3 is a plan view showing a configuration of a conventional semiconductor device, FIG. 4 is a cross-sectional view taken along line BB 'of FIG. 3, and FIG. 5 is a cross-sectional view taken along line CC' of FIG. In FIG. 3, reference numeral 15 denotes a contact window,
8, 19 and 20 are aluminum wirings, 200 is an insulating film, and in FIGS. 4 and 5, 23 is a gate terminal, 24 is a drain terminal, and 25 is a source terminal.

As shown in FIG. 3 and FIG.
In the FET, a band-shaped n-type drain region 17, a band-shaped source region 30, and a drain region 1 are formed on a semiconductor substrate 100.
A gate electrode 16 made of polysilicon is provided between the gate electrode 7 and the source region 30. The source region 30 has an n-type diffusion region 4 for improving avalanche withstand capability.
And p-type diffusion regions 21 are provided alternately in the belt-like direction A.

A current detecting MOSFET is built in the above-mentioned lateral MOSFET. That is, as shown in FIGS. 3 and 5, the drain region and the gate electrode of the current detecting MOSFET are common to the drain region 17 of the lateral MOSFET, and the source region 1 of the current detecting MOSFET is It is composed of only an n-type diffusion region and is interposed between p-type diffusion regions 21 constituting a source region 30 of a lateral MOSFET. Such a current detecting MOSFET is a lateral MOSFET.
This is for detecting a current flowing between the drain region 17 and the source region 30 of FIG. Note that the current detection MO
The side surface 2 on the gate electrode side of the n-type diffusion region 1 serving as the source region 1 of the SFET is formed linearly.

[0005]

However, in the conventional semiconductor device configured as described above, the current detecting MO
The avalanche withstand capability of the source region 1 of the SFET is not sufficient. Therefore, when a breakdown is caused by a surge from the drain terminal 24 shown in FIG. 5, there is a possibility that the breakdown is easily caused.

As shown in FIG. 6, which is a cross-sectional view taken along line DD 'of FIG. 3, the width W5 of the source region 1 of the current detecting MOSFET in the band direction A constitutes the source region 30 of the lateral MOSFET. Direction A of n-type diffusion region 4
Is wider than the width W6. Therefore, per unit width, the total width of the overlapping portion 22a of the source region 1 of the current detecting MOSFET and the p-type diffusion region 21 forming the source region 30 of the lateral MOSFET, and the lateral MOSFET
Comparing the total width of the overlapping portion 22b of the n-type diffusion region 4 and the p-type diffusion region 21 constituting the T source region, the difference was clearly different.

As a result, the current detecting MOS on the mask
A width W5 of the n-type source region 1 of the FET in the band direction A;
The ratio of the total width W6 in the band direction A of the n-type diffusion region 21 constituting the source region 30 constituting the lateral MOSFET to the sense ratio (the current flowing between the drain-source region of the lateral MOSFET and the drain of the sensing MOSFET If the mask is designed by determining the width of the gate electrode 16 so as to match the given current, the sense ratio after diffusion becomes different from the design value. there were.

An object of the present invention is to provide a semiconductor device capable of improving the avalanche resistance of a current detecting MOSFET and obtaining a highly accurate sense ratio in view of the above problems.

[0009]

According to a semiconductor device of the present invention, a lateral MOSF having a width in a band direction is provided in a third diffusion region of a first conductivity type serving as a source region of a current detecting MOSFET.
A fourth diffusion region of the second conductivity type having the same width as the width of the second diffusion region of the second conductivity type constituting the source region of the ET in the band direction is provided to form a third diffusion region of the source region of the current detection MOSFET. The width in the band direction is the same as the width of the first diffusion region of the first conductivity type forming the source region of the lateral MOSFET in the band direction.

[0010]

According to the structure of the present invention, the current detecting MOSF
Since the fourth diffusion region of the second conductivity type is provided in the third diffusion region of the first conductivity type, which is the source region of the ET, a voltage drop due to a breakdown current below the third diffusion region.
Is the lower part of the source region of the conventional current detection MOSFET.
Is smaller than the voltage drop at Accordingly
Must have a larger breakdown current than before.
If the parasitic bipolar transistor does not operate,
No destruction. That is, the current detection MO
Avalanche resistance of SFET can be improved
You.

The width of the fourth diffusion region of the second conductivity type forming the source region of the current detecting MOSFET in the band direction is set to the width of the second diffusion region of the second conductivity type forming the source region of the lateral MOSFET. The width of the third diffusion region of the first conductivity type constituting the source region of the current detection MOSFET in the band direction is set to be equal to the width of the lateral MOSFET.
The width of the second diffusion region of the first conductivity type forming the source region is equal to the width in the band direction. Therefore, when the total width of the source region of the current detecting MOSFET in the strip direction is compared with the total width of the source region of the lateral MOSFET in the strip direction per unit width, the two become equal.

[0012]

FIG. 1 is a plan view showing the structure of a semiconductor device according to one embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA 'of FIG. 1 and 2, 12, 13
And 14 are aluminum wiring, 15 is a contact window,
100 denotes a semiconductor substrate, and 200 denotes an insulating film.

As shown in FIG. 1, a lateral MOSFET is
An n-type drain region 11 serving as a band-shaped first conductivity type drain region; a band-shaped source region 50;
1 and a source electrode 50 and a gate electrode 10 made of polysilicon. The source region 50
The first diffusion regions 9 of the n-type and the second diffusion regions 7 of the p-type are alternately provided in the belt-like direction A, thereby improving the avalanche withstand capability.

The current detecting MOSFET is built in the above-mentioned lateral MOSFET. That is, FIG.
As shown in (1), the drain region and the gate electrode of the current detecting MOSFET are shared with the drain region 11 and the gate electrode 10 of the lateral MOSFET, and the source region 60 of the current detecting MOSFET is an n-type third diffusion. The region 5 is interposed between the p-type second diffusion regions 7 constituting the source region 50 of the lateral MOSFET, and a p-type fourth diffusion region 6 is provided in the third diffusion region 5. It is a thing. As shown in FIG. 2, the width W1 of the p-type fourth diffusion region 6 in the strip direction A is the same as the width W2 of the p-type second diffusion region 7 in the strip direction A. The region 6 is provided so that the width W3 of the n-type third diffusion region 5 in the band direction A is the same as the width W4 of the n-type first diffusion region 9 in the band direction A. Such a current detecting MOSFE
T is for detecting a current flowing between the drain region 11 and the source region 50 of the lateral MOSFET.

As described above, the p-type fourth diffusion region 6 is provided in the n-type third diffusion region 5 constituting the source region 60 of the current detection MOSFET , and the n-type third diffusion region 5 has a band-like shape.
The width W3 in the direction A is defined as the width A of the n-type
Since the width is the same as the width W3, the n-type third diffusion region 5 is formed.
Voltage drop at the bottom of the semiconductor device (breakthrough through the semiconductor substrate 100)
Down) is the conventional semiconductor shown in FIG.
N-type saw for current detection MOSFETs constituting body device
Lower than the voltage drop at the bottom of
Of the n-type first diffusion region 9 constituting the n-type MOSFET
Voltage drop at the same level. Therefore, for current detection
The same level of fluctuation as the lateral MOSFET
If no down current flows, the parasitic bipolar transistor
The register does not operate and does not break down.
That is, the avalanche withstand capability of the current detection MOSFET
To the same level as the avalanche withstand capability of the lateral MOSFET.
Can be up.

Further, as shown in FIG.
The width W1 of the p-type fourth diffusion region 6 forming the source region 60 of the SFET is equal to the width W2 of the p-type second diffusion region 7 forming the source region 50 of the lateral MOSFET, and the current detection MOSFET The width W3 of the n-type third diffusion region 5 constituting the source region 60 of FIG.
Is equal to the width W4 of the n-type second diffusion region 9 constituting the source region 50 of FIG.

Therefore, the total width of the overlapping portion 8a of the source region 60 of the current detecting MOSFET in the strip direction A is:
The total width of the overlapping portion 8b in the band direction A of the source region 50 of the lateral MOSFET becomes equal when compared per unit width in the band direction A. As a result, the sense ratio after diffusion (the ratio of the current flowing between the drain and source regions of the lateral MOSFET to the current flowing between the drain and source regions of the MOSFET for sensing) is reduced by the lateral MOSFET on the mask.
The total width of the width W3 of the n-type first diffusion region 9 constituting the source region 50 and the source region 60 of the current detecting MOSFET
And the ratio with the total width of the width W4 of the n-type third diffusion region 5 that constitutes the above-mentioned configuration, it is possible to obtain a sense ratio with a highly accurate design value.

The side surface 12 on the gate side of the source region 60 of the current detecting MOSFET is formed in an uneven shape. Thereby, the avalanche resistance can be further improved. In the above embodiment, the n-channel type has been described.

[0019]

According to the semiconductor device of the present invention, the third region of the first conductivity type, which is the source region of the current detecting MOSFET.
By providing the fourth diffusion region of the second conductivity type in the diffusion region , a breakdown current below the third diffusion region can be reduced .
Voltage drop is the source of a conventional current sensing MOSFET.
Smaller than the voltage drop at the bottom of the region
Wear. That is, the source region of the current detecting MOSFET
Of the third diffusion region of the first conductivity type constituting the
Improve avalanche resistance by making it smaller
Can be.

The width of the fourth diffusion region of the second conductivity type forming the source region of the current detecting MOSFET in the band direction is set to the width of the band of the second diffusion region of the second conductivity type forming the source region of the lateral MOSFET. The width of the third diffusion region of the first conductivity type constituting the source region of the current detection MOSFET in the band direction is set to be equal to the width of the lateral MOSFET.
The width of the second diffusion region of the first conductivity type forming the source region is equal to the width in the band direction. Therefore, when the total width of the source region of the current detecting MOSFET in the strip direction is compared with the total width of the source region of the lateral MOSFET in the strip direction per unit width, the two become equal.

As a result, the sense ratio after diffusion (horizontal MOS
The ratio of the current flowing between the drain and source regions of the FET to the current flowing between the drain and source regions of the sensing MOSFET) is the first diffusion of the first conductivity type constituting the source region of the lateral MOSFET on the mask. The ratio is the ratio of the total width of the region to the total width of the third diffusion region of the first conductivity type that constitutes the source region of the current detection MOSFET, and it is possible to obtain a highly accurate sense ratio as designed.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a semiconductor device according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line A-A 'of FIG.

FIG. 3 is a plan view showing a configuration of a conventional semiconductor device.

FIG. 4 is a sectional view taken along line B-B 'of FIG.

FIG. 5 is a sectional view taken along line C-C ′ of FIG. 3;

FIG. 6 is a sectional view taken along line D-D ′ of FIG. 3;

[Brief description of reference numerals]

9 n-type first diffusion region (first conductivity type first diffusion region) 7 p-type second diffusion region (second conductivity type second diffusion region) 5 n-type third diffusion region (first conductivity type) 6th p-type fourth diffusion region (second conductivity type fourth diffusion region) 11 drain region 50 lateral MOSFET source region 60 current detection MOSFET source region A band direction

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-138773 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 29/78

Claims (1)

(57) [Claims] 1. A first diffusion region of a first conductivity type and a second diffusion region of a second conductivity type are alternately arranged in the band direction as source regions in order to form a drain region of the first conductivity type in a band shape and increase avalanche withstand capability. And a drain region for detecting a current flowing between a drain region and a source region of the lateral MOSFET.
A semiconductor device comprising a drain region and common to current sensing MOSFET having a source region and a third diffusion region of the first conductivity type is interposed between the second diffusion region of SFET, the third diffusion region A fourth diffusion region of the second conductivity type having a width in the band direction equal to the width of the second diffusion region in the band direction is provided therein, and the width of the third diffusion region in the band direction is set to the first width. A semiconductor device, wherein the width of the diffusion region is the same as the width in the strip direction.