JPS61140187A - Semiconductor current detector - Google Patents

Abstract

PURPOSE:To obtain large current detection sensitivities with small collector current by restricting the collector current path to the neighborhood of the surface of an element having a strong magnetic field by a method wherein a buried layer of reverse conductivity type to that of the collector region is formed in the region immediately under a part which performs magnetic detection. CONSTITUTION:An n<+> buried layer 23 line immediately under a base region 15 are prevents holes from flowing out of the base into the Si substrate 11. A P-type buried layer 22 lines immediately under Hall electrode n<+> regions 17, 17' for magnetic detec tion. Thereby, when a high voltage is impressed on the collector terminal, a base- collector junction is reversely biased, and a depletion layer 25 keeps on spreading to the part between the region 17. Because of the installation of the p-type Si substrate 11, the buried layer 22 and an n-type epitaxial layer 14 are reversely biased, and a depletion layer 24 spreads upward. At this time, the electrons flowing into the epitaxial layer 14 out of the base flow only over the layer 14 in the neighborhood of the part of magnetic detection. This part is strong in magnetic field generated by flowing current. This strengthens the interaction between collector current and magnetic field and improves the sensitivity because of effective utilization of the collector current.

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 magnetic sensor using a semiconductor integrated circuit, for example, 1
rNE of Nikkei Electronics April 13, 1981 issue
There are nine things described in the report "Development of a highly sensitive bipolar Si magnetic sensor with good temperature characteristics and linearity."

The present inventor used the semiconductor magnetic sensor as described above to
A semiconductor current detection device has already been invented which detects the value of the current flowing through the current path by detecting the strength of the magnetic field generated by the current flowing through the current path provided on the surface of a semiconductor integrated circuit. ``Figure 2 is an example of the above semiconductor current detection device,'' where (A) is a plan view, (B) is a cross-sectional view taken along line AA' in (A), and (C) is a cross-sectional view taken along line B-- in (A). It is a B' sectional view.

In FIG. 2, 11 is a low resistivity p-type Si substrate;
2 is a channel stopper region for preventing the depletion layer from expanding near the surface, and is a phosphorus ion implantation layer.

Further, 13 is a p+ element isolation region, and 14 is an SL substrate 11.
The n- epitaxial layer formed above, 15 is the base diffusion region, 16 is the n+ region for the emitter, 17.17' is the n+ region for the hole electrode, and 18 is the n'' region for the collector. is forming.

In addition, 19 is an M wiring layer, 204tSiO,l[,21,
21' and 21' are current paths, for example, SiO□llI
20 by Ag plating.

In the above configuration, if a sufficiently large reverse bias is applied to the collector-base junction of the bipolar transistor so that the depletion layer reaches n+ regions 17 and 17' for the hole electrode, 17 and 17 ′, a Hall voltage Vh=fVan+axWB is generated.

Here, f is a coefficient representing the shape effect, V(IIIIII
X is the saturation drift velocity of electrons in the depletion layer, W is 17 and 1
7', B is the effective magnetic flux density.

As can be seen from the above equation, by increasing the distance between the pair of n+ regions 17 and 17' for hole electrodes, the sensitivity can be improved without increasing the collector current.

Then, current paths 21 and 21 formed on the Sin film 20
When a current is passed through ', 21', a magnetic field 22 proportional to the current is generated, so by detecting the Hall voltage Vh due to the above magnetic field, the value of the current flowing in the current path can be detected.

Note that the current paths 21.21' and 21' are formed so as to surround the n+ region 17.17' for hole electrodes, and are formed by plating 30 to 50 t, for example, with Ag or Au.
It is formed to a thickness of 1 m.

If, for example, a load current in a current control type load driving integrated circuit is used as the current flowing through the current path, it becomes possible to accurately detect the load current without causing a voltage drop or the like.

[Problem that the invention seeks to solve]

The semiconductor current detection device described above has a structure in which the current flowing from the base to the collector is distributed over a wide range from the surface toward the depth.
The strength of the magnetic field is strongest at the surface and weakens as it gets deeper, so essentially only the current flowing near the surface contributes to the Hall voltage, and other currents flow in vain, consuming excess power. There was a problem that there was a problem.

The present invention aims to solve the above problems.

[Means to solve the problem]

In order to achieve the above object, in the present invention, a portion where magnetic detection is performed (the above-mentioned n+ region for hole electrode 17, 17
′) By forming a buried layer of the opposite conductivity type to the collector region, the path of the collector current is limited to the vicinity of the element surface where the magnetic field is strong, and the interaction between the magnetic field and the collector current is strengthened. As a result, it is configured to obtain high current detection sensitivity with a small collector current.

[Embodiments of the invention]

FIG. 1 is a diagram showing an embodiment of the present invention, and (A) is a sectional view;
(B) is a partially enlarged view of (A).

In FIG. 1, 22 is a p-type buried layer, 23 is an n+ buried layer, and 24.25 is a depletion layer.

Moreover, (B) is an enlarged view of the part surrounded by the broken line 26 in (A).

In addition, the same symbols as in FIG. 2 indicate the same parts.

Further, the M wiring layer 19, S i O, film 20, current paths 21, 21', 21', etc. in FIG. 2 are omitted from illustration.

As shown in FIG. 1(B), there is an n+ buried layer 23 directly under the base region 15, and electrons from the base are transferred to the Si substrate 1.
This prevents it from flowing into 1.

Further, there is a p-type buried layer 22 directly below the n'' region 17, 17' for a hole electrode for magnetic detection.

Therefore, when a high voltage is applied to the collector terminal, the base-collector junction is reverse biased, and the depletion layer 25 becomes n+ region 1.
It spreads to the part between 7.17'.

Further, since the p-type Si substrate 11 is provided, a reverse bias is also applied between the p-type buried layer 22 and the n-type epitaxial layer 14, and the depletion layer 24 expands upward.

At this time, the electrons flowing from the base into the epitaxial layer 14 are transferred to the epitaxial layer 14 near the magnetic detection part.
Flows only at the top of the

This part is a current path (not shown) provided on the element surface.
This is the part of the magnetic field where the magnetic field is strong due to the current flowing through the magnetic field, and therefore the interaction between the collector current and the magnetic field is strong, and the collector current can be used effectively, improving sensitivity.

Next, FIG. 3 is an embodiment diagram showing the manufacturing process of the above element.

In Figure 3, first in (A), the specific resistance is 10Ω.
- The p-type (111) side Si substrate 11 of the opening is thermally oxidized to form an approximately 1-Sio2 film (not shown) on the entire surface.

Next, the Sin film is partially etched and sb is diffused to form an n+ buried layer 23 having a sheet resistance of about 30Ω.

Next, the Sio2 film is etched again by photolithography, and boron is diffused for the p-type buried layer 22 by depositing BBr.

The amount of boron doped at this time is approximately 1 to 2×10″/d.

After that, the above Sio film is completely removed.

Next, in (B), the specific resistance is 10 Ω, the thickness is 1
An n-type epitaxial layer 14 of 5 Ωm is grown.

Next, in (C), approximately 5,000 5in2 films (not shown) are formed by thermal oxidation, and after opening the window, BB
r, and is diffused at 200''C for about 100 hours to form a P+ element isolation region 13.

At this time, the p-type buried layer 22 is also outwardly diffused by about 6 to 7 times.

Next, in (D), the surface concentration of boron is 2 to 5
A p-type base diffusion region 1 is formed by performing normal base diffusion so that the diffusion depth is approximately 3 am.
form 5.

Next, in (E), a window (not shown) of the 5in2 film is opened, pocn3 is deposited, and n+ emitter diffusion is performed.

The surface concentration of the n+ region 16 for emitter is 5×10”/d
The diffusion depth is approximately 2°5IIIa.

At this time, at the same time, n+ regions 17 and 17' for hole electrodes,
A collector n+ region 18 is formed.

After that, the Sin film on the magnetic detection part is partially etched, a thin oxide film of about 500 layers is formed by thermal oxidation, and phosphorus ions of about 5X1011/cd are ion-implanted at 30 kaV to form the channel stopper region 12. do.

Here, annealing is performed at 900° C. for about 1 hour in a N2 atmosphere.

After that, although not shown, the contact hole Sio
, evaporate and pattern the gunwale, and deposit PSG on it.

Furthermore, in order to form a current path for generating a magnetic field, Ni or Ag is deposited as a base metal and masked with a resist to a thickness of 30 to 50 mm. Perform Ag plating.

〔Effect of the invention〕

As described above, in the present invention, a pair of n+ regions for hole electrodes are provided between the base region and the collector region, and a p-type buried layer is provided at the bottom of the epitaxial layer directly under the n+ regions for hole electrodes. Since the configuration is
Since the part where the collector current substantially flows can be limited to the upper part of the epitaxial layer where the magnetic field is strong, and the interaction between the magnetic field and the collector current can be strengthened, it is possible to obtain high current detection sensitivity with a small collector current. You can get the effect that you can.

Furthermore, in the present invention, since the substantial flow path of the collector current can be limited to the upper part of the epitaxial layer,
There is also the effect that variations in current density within the cross section of the epitaxial layer are reduced, and fluctuations in sensitivity due to changes in collector current can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of a semiconductor current detection device previously developed by the present inventor, and FIG. 3 is a diagram showing a manufacturing process of the present invention. Explanation of symbols 11...Si substrate 12...Channel stopper region 13...Element isolation region 14...Low epitaxial layer 15...Base diffusion region 16...N+ region for emitter 17.17'. ...N1 region 18 for hole electrode...N+ region 19 for collector...M wiring layer 20...SiO□ film 21, 21', 21'...Current path 22...P-type buried layer 23...n+ buried layer 24, 25...depletion layer 26...enlarged part

Claims (1)

[Claims] an epitaxial layer provided on a semiconductor substrate and having a conductivity type opposite to that of the semiconductor substrate; a base region and a collector region of a bipolar transistor formed in the epitaxial layer; and a pair of opposing regions formed between the two regions. a diffusion region of the same conductivity type as the collector region; a buried layer of the opposite conductivity type to the collector region provided below the diffusion region at the boundary between the semiconductor substrate and the epitaxial layer; and a current path formed so as to surround the diffusion region.