JPH0554628B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a device for detecting the value of current flowing in a current path in a semiconductor integrated circuit, for example, a device for detecting a load current in a current-controlled load driving integrated circuit. It is related to.

[Prior art]

As a conventional current measuring circuit, there is one described, for example, on page 1264 of "Electrical Measurement Handbook, published by Ohmsha, 1971."

FIG. 2 is a configuration diagram of a conventional current-controlled load driving integrated circuit.

In FIG. 2, 1 is a power transistor for driving a load, 2 is a load, 3 is a current detection resistor, 4 is a control circuit, and 5 is a power supply terminal.

In the above circuit, the current flowing through the load 2 is converted into a voltage by the current detection resistor 3, and the control circuit 4 adjusts the control voltage or duty of the power transistor 1 based on the value. It is configured to apply negative feedback to control the current flowing through the circuit.

Generally, in a power control integrated circuit that incorporates a current detection resistor of several ampere class, an emitter diffusion resistor of about 0.1Ω is used as the current detection resistor 3.

[Problem that the invention seeks to solve]

In conventional devices such as those described above, a resistor is inserted in series with the load in order to detect the current flowing through the load. Therefore, when controlling a large current, the resistor causes a voltage drop, causing the load There is a problem in that the voltage applied to the device decreases.

In order to solve this problem, attempting to realize a resistor with a large capacity and a low resistance value requires a large area, resulting in a large and expensive integrated circuit.

Furthermore, since the current detection resistor generates heat, there is also the problem that heat dissipation design becomes difficult.

The present invention aims to solve the problems of the prior art as described above.

[Means to solve the problem]

In order to achieve the above object, in the present invention,
Forming a current path on an insulating film on the surface of a semiconductor integrated circuit, forming a magnetic detection element within the semiconductor integrated circuit,
A groove is provided in the vicinity of the magnetic detection element of the semiconductor integrated circuit chip, and a current path is provided in the groove, so that the strength of the magnetic field generated by the current flowing through the current path is detected by the magnetic detection element. In this way, the current value is detected, and the distance between the magnetic detection element and the current path is reduced to improve the detection sensitivity.

FIG. 3 is a conceptual diagram of the present invention, and the same reference numerals as in FIG. 2 indicate the same parts.

In FIG. 3, 6 is a magnetic detection element, and 7 is a current path for generating a magnetic field.

In the above device, when a load current flows through the current path 7, a magnetic field corresponding to the current value is generated.

By detecting the strength of the magnetic field with the magnetic detection element 6, the value of the current flowing through the current path 7 can be detected.

In the present invention, the magnetic detection element 6 and the current path 7 are formed on a semiconductor integrated circuit chip on which other elements are formed.

[Embodiments of the invention]

FIG. 1 is an example of a current detection device devised by the present inventor, which is the premise of the present invention, where A is a plan view and B is a plan view.
shows a sectional view taken along line A-A' of A.

In Figure 1, 11 is p with a specific resistance of 10Ω・cm.
(111) type Si substrate, 12 is n ⁺ buried layer, 13 is
p ⁺ element isolation region, 14 is an n ^- epitaxial layer with a resistivity of 10 Ω cm and a thickness of 16 μm, 15 is a p-type base diffusion region, 16 is an n ⁺ region for emitter,
17 and 17' are n ⁺ regions for hole electrodes (although they should not be visible in the A-A' cross-sectional view, they are also shown in B for explanation), 18 is n ⁺ region for collectors, and 19
is an Al wiring layer, 20 is a SiO ₂ film, and 21 is a 30 μm thick
Current path (21′, 21″) formed with Ag plating layer
is a part of the current path), and Ag is on the Al wiring layer 19.
After forming a vapor-deposited film, it is formed thereon by a plating method.

In FIG. 1A, the part inside the broken line is the magnetic detection element, and the part outside the broken line is the part of the element isolation region 13.

The above magnetic sensing element also includes an n ^- epitaxial layer 14, a base diffusion region 15, and an n ⁺ emitter layer.
It is composed of a region 16 ^, an n ⁺ region 17, 17' for a hole electrode, and an n ⁺ region 18 for a collector. ⁺
Regions 17 and 17' are provided.

In the device shown in FIG. 1, when a load current flows through the current path 21, a magnetic field is generated on the magnetic detection element formed inside the current path 21.

By detecting the strength of this magnetic field with a magnetic detection element, the value of the current flowing through the current path 21 can be detected.

In addition, in order to strengthen the magnetic field and increase detection sensitivity, the current path 21 is formed thickly by, for example, Ag plating.
Moreover, by narrowing the width, the effective distance between the magnetic field detection area and the current path is set small.

In the above configuration, an effective magnetic flux density of 50 to 100 Gauss is obtained for a current of 2 to 4 A.

Moreover, the magnetic sensing element is made of an n ^- epitaxial layer 14.
By increasing the specific resistance to 10 Ω·cm, the depletion layer of the base-collector coupling is made to reach the hole electrode n ⁺ regions 17, 17'.

At this time, a voltage of fV _dnax WB is generated between the hole electrode n ⁺ regions 17 and 17'.

Here, f is a coefficient expressing the shape effect, V _dnax is the saturation drift velocity of electrons in the depletion layer, W is the distance between 17 and 17', and B is the effective magnetic flux density.

For example, when W = 50 μm, collector n ⁺ region 18
If a voltage of 8 to 10 V is applied to the base diffusion region 15 with a current mirror and a collector current of several mA flows, an output of several tens of mV can be obtained when the load current is 2 to 4 A.

Note that the n ⁺ buried layer 12 is formed only directly under the base diffusion region 15 so as not to serve as a path for collector current.

In the above configuration, Ag of the current path 21
Since the steps other than plating can be formed by a normal bipolar process, it is possible to form a load driving integrated circuit having a current detection function in a compact manner.

Next, problems with the device shown in FIG. 1 will be explained.

FIG. 4 is a sectional view taken along line BB' in FIG.
Reference numeral 22 indicates a magnetic field, and the same reference numerals as in FIG. 1 indicate the same elements.

In the apparatus of FIG. 4, when currents in opposite directions flow through the current paths 21', 21'', a magnetic field 22 as shown is produced.

When a current is passed through the n ^- epitaxial layer 14 in a direction perpendicular to the plane of the paper, a voltage is generated between the n ⁺ diffusion regions 17 and 17 due to the Hall effect.

However, as in the configuration shown in Fig. 4, the current path 2
1', 21'' are formed on the surface of the semiconductor integrated circuit chip, the n ^- epitaxial layer 14
The magnetic field is weaker in the region below the current paths 21' and 22'', and the interaction with the bias current flowing through the n ^- epitaxial layer 14 is reduced, so the bias current can be fully utilized. It may disappear.

For example, the thickness of the n ^-epitaxial layer 14 is
When the diameter is 12 μm, the magnetic field is 5% or more smaller at the bottom end than at the top end, resulting in lower sensitivity, and the inside of the n ^-epitaxial layer is more susceptible to variations in bias current distribution, resulting in sensitivity variations. becomes larger.

FIG. 5 is a sectional view of an embodiment of the present invention that solves the above problems.

In FIG. 5, 23, 23' are current paths, 24,
25 is a groove provided in the semiconductor integrated circuit chip; 26 is a groove provided in the semiconductor integrated circuit chip;
It is a SiO ₂ film, and the same symbols as in FIG. 4 indicate the same parts.

In the configuration shown in FIG. 5, the thickness of the n ^- epitaxial layer 14 is 12 μm, and the grooves 24 and 25 are formed of p-type
If it is formed to the extent that it reaches the Si substrate 11, the current path 2
Assuming that the distance from the center of 3, 23' to the center of ^the n ^-epitaxial layer 14 is 50 μm, the magnetic field is stronger at the upper and lower ends of the n -epitaxial layer than at the center.
It will only decrease by 0.7%.

In this way, the changes in the magnetic field are much smaller than in the configuration shown in Figure 4, which not only improves the sensitivity, but also makes it less susceptible to variations in the bias current distribution inside the n ^-epitaxial layer, resulting in lower sensitivity. Variation becomes smaller.

Next, a manufacturing process for integrating the device shown in FIG. 5 with a bipolar integrated circuit will be described.

First, an n ⁺ buried layer is diffused into the p-type Si substrate 11,
After growing the n ^- epitaxial layer 14, a p ⁺ element isolation region is formed by diffusion, and a p type base diffusion,
Up to n ⁺ emitter diffusion, the process can be performed in the same way as a standard bipolar process.

Next, grooves 24 and 25 penetrating the n ^- epitaxial layer 14 are formed by anisotropic etching or reactive etching to form current paths 23 and 2.
3', for example, an Al wire is fitted into this groove.

Next, a device as shown in FIG. 5 can be formed by reflowing the Al wire at about 700° C. and performing contact etching, Al vapor deposition, patterning, PSG deposition, and pad etching.

In the previous examples, a one-chip type current detection device based on a bipolar integrated circuit was explained, but a MOS type magnetic detection element and a one-chip type current detection device were explained.
Of course, it can also be applied to integrated circuits such as those integrated with CMOS circuits.

〔Effect of the invention〕

As explained above, in the present invention, the current is detected by the current path and the magnetic detection element, so unlike the conventional resistance detection method, the current value flowing to the load is limited. There is no problem such as internal heat generated by the detection resistor, and the current path and magnetic detection element are formed on the same chip as the load driving integrated circuit. The excellent effect of being able to control the load with a single-chip integrated circuit is achieved.

In addition, since everything other than the formation of the current path can be constructed using only a standard bipolar process, it is possible to easily manufacture a compact and inexpensive semiconductor integrated circuit for load control having a current detection function.

Furthermore, since the semiconductor integrated circuit chip is configured to have a groove and a current path is formed in the groove, it not only has better detection sensitivity than a device that forms a current path on the chip surface. It has the effect of reducing variations in sensitivity even when the bias current is unevenly distributed, and since the current path is formed in the groove, there are no protrusions on the surface.
It also has the effect of facilitating mask alignment during PSG etching.

[Brief explanation of drawings]

Fig. 1 is an example of a current detection device devised by the present inventor and is the premise of the present invention, Fig. 2 is an example of a conventional device, Fig. 3 is a conceptual diagram of the present invention, and Fig. 4 is the same as Fig. 1. FIG. 5 is a cross-sectional view taken along line B-B' of FIG. Explanation of symbols 1...Transistor, 2...Load, 3...Resistor for current detection, 4...Control circuit, 5
...Power terminal, 6...Magnetic detection element, 7...Current path, 11...Si substrate, 12...n ⁺ buried layer, 13...
...Element isolation region, 14...n ^- epitaxial layer,
15...Base diffusion area, 16...For emitter
n ⁺ region, 17, 17'... n ⁺ region for hole electrode,
18...N ⁺ region for collector, 19...Al wiring layer,
20... SiO ₂ film, 21, 21', 21''... Current path, 22... Magnetic field, 23, 23'... Current path, 2
4, 25...groove, 26...SiO ₂ film.

Claims (1)

[Claims] 1 Forming a magnetic detection element in a semiconductor integrated circuit,
Further, a groove is provided in the vicinity of the magnetic detection element of the semiconductor integrated circuit chip, and a high conductivity current path is provided in the groove, and the strength of the magnetic field generated by the current flowing through the current path is measured by the upper magnetic field. A semiconductor current detection device characterized in that a current value flowing in the current path is detected by detection with a detection element.