JP3417009B2 - Hall element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Hall element, and more particularly to a GaInAs / InP heterojunction Hall element.

[0002]

2. Description of the Related Art A Hall element is a kind of magnetic sensor and is already used as a rotation or current sensor. Recently, in response to the demand for higher device performance, G
A Hall element using a heterojunction of aInAs and InP has been developed (Okuyama Shinobu et al., Autumn 1992 53rd).
Proceedings No.3 (published by Japan Society of Applied Physics, 1992), 16a-SZC-16,1078
page). This GaInAs / InP heterojunction Hall element has a relatively small change in characteristics with temperature. Further, it is attracting attention because of its excellent sensitivity characteristics.

Even in such a heterojunction Hall element, the input and output electrodes are formed as in the conventional case to form a Hall element. An operating current is passed through the input electrode. The Hall voltage is taken out from the output electrode side. Usually, a DC voltage of about 5 to 12 V is applied between the input electrodes. An operating current corresponding to the resistance of the magnetosensitive layer flows between the opposing input electrodes. It is desirable that the operating current does not change with time. This is because the change over time of the operating current causes the change over time of the characteristics. The sensitivity and the like increase in proportion to the operating current value. If the operating current value changes, the sensitivity also changes.

The input / output electrodes must have ohmic properties. It is necessary to subject the electrode material to alloying heat treatment in order to impart ohmic properties. Conventional GaIn
In the As / InP heterojunction Hall element, the current changes with time (drift) depending on this alloying condition. An example of current drift is shown in FIG. The alloying condition is 42
8 minutes at 0 ° C. In the example shown in the figure, the current value gradually decreases immediately after the operating current of 5 mA flows. This is what is called a reduced drift. Conversely, an increase in the operating current value is called an increase drift. Generally, the current value largely changes in a few minutes. Regardless of the alloying conditions, the current value becomes almost constant 10 minutes after the current flows.

The current value 10 minutes after the operating current is passed is I (mA). Let I _m (mA) be the maximum value or the minimum value of the current before 10 minutes have passed. Here, the drift amount (D
%) Is defined by the following equation (1). D (%) = (I−I _m ) / I _m × 100 Equation (1) In the conventional GaInAs / InP Hall element, as shown in FIG. The value occurs within a few minutes after the start of energization. In the conventional example, D reaches ± 20 to 30%.

[0006]

[Problems to be Solved by the Invention] GaInAs / InP
In the heterojunction Hall element, D changes depending on the alloying conditions. If ohmic properties are imparted to the electrode without the need for alloying heat treatment, a reduction in D value can be expected. There is also a conventional method of forming an ohmic electrode by providing a low resistance semiconductor layer having a carrier concentration of 10 ¹⁹ to 10 ²⁰ cm ⁻³ on the magnetic sensing layer. This is called a non-alloy contact method. Since many carriers are present in this method, there is an advantage that an ohmic electrode can be obtained without alloying treatment. However, even if the non-alloy method is adopted, the D amount cannot be reduced stably. There has been no effective conventional technique for stably reducing the D amount. Therefore, GaInA with less drift
The s / InP heterojunction Hall device was not stably manufactured. Practically, it is necessary to keep the D content within ± 15%.

Since the D amount is not reproducible even in the non-alloy method, another factor affecting the drift was examined. As a result, it was found that the drift is related to the P concentration in the GaInAs layer. P diffuses from the InP side during film growth and during alloying heat treatment. Since the diffusion amount of P to the GaInAs side is different, a difference appears in the D amount. Ga in the conventional example
The P concentration in the InAs layer is 10 near the heterojunction interface.
More than ¹⁷ cm ^-3 and poor reproducibility. In addition, the width of the region from the hetero interface in the GaInAs layer in which P is present in a high concentration is also variable. If this P concentration is specified, the D amount can be expected to be reduced, but there has been no related specification. The present invention provides a GaI for stably reducing drift.
The purpose is to clarify the P concentration in the nAs layer.

[0008]

A Hall element is manufactured from a GaInAs layer in which a region having a P concentration of 10 ¹⁵ cm ^-3 or less is specified. The specified region is from the surface of the GaInAs magnetosensitive layer to a depth of 50% or more of the film thickness of the layer. As a result, the change over time of the operating current is within ± 15% G
An aInAs / InP heterojunction Hall element is obtained.

The GaInAs / InP heterojunction Hall element is grown on a high-resistance InP single crystal substrate. Fe
Doped semi-insulating InP single crystal is generally used as the substrate. An InP layer is deposited on the InP substrate as a buffer layer. This is to reduce the diffusion amount of Fe impurities of the InP substrate into the magnetosensitive layer. A GaInAs layer is deposited on the buffer layer as a magnetosensitive layer.

There is no limitation on the growth method of the InP buffer layer and the GaInAs layer. Molecular beam epitaxial growth method (MB
E method) or metalorganic pyrolysis vapor deposition method (MOCVD method). MO / M that combines MOVPE and MBE
The BE method or the like may be used.

Ga _x In _1-x As Ga composition ratio x of the magnetosensitive layer x
Is preferably 0.37 ≦ x ≦ 0.57. In
This is because the degree of lattice mismatch becomes remarkable with the deviation from x = 0.47, which is lattice-matched to P, and the crystallinity is lowered due to the occurrence of crystal defects and the like. The electron mobility is also reduced, and this also hinders the improvement of the product sensitivity of the Hall element.

There is no particular limitation on the film thickness of the Ga _x In _1-x As layer. However, as the thickness of the conductive layer increases, the time required for mesa etching inevitably increases. The increase in the etching amount causes a remarkable difference in mesa shape depending on the crystal orientation. This causes an increase in the unbalance rate, which is one of the important characteristics of the Hall element. Therefore, good results are obtained when the film thickness of the Ga _x In _1-x As magnetosensitive layer is smaller than approximately 2 to 3 μm.

The carrier concentration of the GaInAs magnetosensitive layer is 1 ×
It is generally adjusted to 10 ^{14 to} 5 × 10 ¹⁶ cm ^-3 .
However, since P diffuses as an impurity from the hetero interface with InP, it is not preferable for the Hall element. P
The concentration is 1 from the surface of the magneto-sensitive layer to the region of 50% or more of the film thickness
It should be 0 ¹⁵ cm ^-3 or less. Set the thickness of the GaInAs magnetosensitive layer to 1 μm
If m, it means a region of 0.5 μm or more from the surface. I
The diffusion of P from the nP side is promoted when the growth temperature of the GaInAs layer is high. It is better to grow at a temperature below 700 ° C. 600-650 degreeC is suitable. Also, MOCV
In the D method, if the source gas of the V group element is completely switched, the P concentration of the GaInAs layer is lowered. MOCVD
The method uses PH ₃ to grow InP. GaInA
The As source during As layer growth is AsH ₃ . After growing the InP layer, when growing the GaInAs layer, a group V source material was added to P
It is necessary to switch from H ₃ to AsH ₃ . This is because if PH ₃ remains in the growth system, it is mixed in the GaInAs layer. The distribution of P concentration in the depth direction in the case of performing such an operation is shown in FIG. 4 in comparison with the conventional example. If the growth temperature is appropriate and the emission of PH ₃ is sufficient, GaInAs /
Even in the vicinity of the InP hetero interface, the P concentration satisfies the regulation of the present invention. The distribution of P concentration in the depth direction can be measured by secondary ion mass spectrometry (SIMS) or Auger spectroscopy (AES).

Input and output electrodes are provided on the GaInAs magnetosensitive layer. Alloying heat treatment is performed to impart ohmic property to the electrode. As mentioned above, P depends on the alloying conditions.
The concentration changes. The longer the heat treatment at high temperature, the more GaI of P
Promotes diffusion into the nAs layer. Alloying temperature 400
It is advisable to set the temperature within the range of up to 450 ° C. and set the alloying time within 5 minutes. If the region where the P concentration is 1 × 10 ¹⁵ cm ⁻³ or less is 50% or more of the layer thickness of the same layer from the surface of the magnetosensitive layer, the current drift amount can be reliably accommodated within ± 15%. Electrodes alloyed at high temperatures will drift. In addition, a decreasing drift is observed when the alloying time exceeds 5 minutes. If the P concentration of the Ga _x In _1-x As layer is 10 ¹⁵ cm ^-3 or less, the drift is not affected.

[0015]

When the concentration of P impurities in the GaInAs magnetosensitive layer is kept low, the current drift is eliminated.

[0016]

EXAMPLES The present invention will be described in detail based on examples. Figure 1
FIG. 3 is a schematic plan view of a Ga _0.47 In _0.53 As / InP heterojunction Hall element according to the present invention. FIG. 2 is a schematic sectional view taken along the direction of broken line AA ′ in FIG. Board (10
1) is a Fe-doped semi-insulating InP single crystal. The specific resistance was about 10 ⁶ Ω · cm. The plane orientation was (100). Undoped InP on InP single crystal substrate (101)
A buffer layer (102) was deposited. The same layer (102) is PH ₃
Was grown by atmospheric pressure MOCVD using P as a P source. The growth temperature was 610 ° C. The film thickness was about 100 nm. The carrier concentration was about 2 × 10 ¹⁵ cm ^-3 .

After the growth of the InP buffer layer (102), the addition of PH ₃ gas into the growth system was stopped. The In source was also stopped. After stopping the PH ₃ gas, only the hydrogen carrier gas was circulated in the growth system for 2 minutes. The temperature was kept at 610 ° C. The period of 2 minutes was set in order to sufficiently reduce the PH ₃ concentration in the system. After 2 minutes, the supply of AsH ₃ was started. In addition, the supply of In source was restarted. Ga
_{A 0.47} In _0.53 As magnetosensitive layer (103) was grown.
The carrier concentration was about 2 × 10 ¹⁶ cm ^-3 . Film thickness is 40
It was set to 0 nm. In this example, a supply stop period of 2 minutes was provided in order to sufficiently reduce the PH ₃ concentration. The point is PH ₃
It is sufficient to set the stop period as the time during which the gas can be completely discharged. PH
_{If 3} is completely discharged, the P concentration in the GaInAs layer can be stored within the range specified in the present invention.

Mesa-shaped hole cloths (104) were formed in the Ga _0.47 In _0.53 As magnetosensitive layer (103) by using a known photolithography technique or the like. Hall cross (1
In 04), the mesa-shaped rectangles having a width of 100 μm and a length of 200 μm are orthogonal to each other. Hall cross (10
An input ohmic electrode (105) and an output ohmic electrode (106) were formed on the surface of the Ga _0.47 In _0.53 As magnetosensitive layer (103) at the end of 4). The electrode was composed of an Au.Ge alloy film. Ohmic alloying at 420 ℃ 3
I went for a minute.

After alloying, Ga _0.47 In by AES method
The P concentration of the _0.53 As magnetosensitive layer (103) was analyzed. The results are shown in Fig. 4. The P concentration of 10 ¹⁵ cm ^-3 or less is in the same layer (1
It was a region having a depth of 280 nm from the surface of (03). This is 70% of the film thickness of the Ga _0.47 In _0.53 As magnetosensitive layer (103).
%.

Further, the surface was covered with a silicon dioxide (SiO ₂ ) oxide film (107) by the plasma CVD method. On
The output ohmic electrode portion (105, 106) is not covered. Further, a part of the SiO ₂ oxide film (107) was processed to form a dicing line (108).

The current drift when the operating current was 5 mA was compared with that of the conventional GaInAs Hall element. In the new GaInAs Hall element according to the present invention, the current drift was ± 2% (Fig. 4: A). On the other hand, a conventional example in which the P concentration exceeds 10 ¹⁵ cm ^-3 in the entire magnetosensitive layer (Fig. 4: B).
, A decrease drift of about 22% was observed.

[0022]

EFFECT OF THE INVENTION The drift of the operating current is eliminated, and thus a GaInAs Hall element with stable operation can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a Hall element according to the present invention.

FIG. 2 is a schematic cross-sectional view taken along the direction of broken line AA ′ in FIG.

FIG. 3 is a diagram showing an example of current drift.

FIG. 4 is a diagram showing a distribution of P concentration.

[Explanation of symbols]

(101) InP single crystal substrate (102) InP buffer layer (103) Ga _0.47 In _0.53 As Magnetosensitive layer (104) Hole cross (105) Input ohmic electrode (106) Output ohmic electrode (107) SiO ₂ oxide film (108) Dicing line (109) Hetero interface (110) Magnetosensitive layer surface

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 43/06 G01R 33/07

Claims (2)

(57) [Claims] 1. An InP deposited on an InP single crystal substrate
And a GaI provided by being joined to the buffer layer
A magnetic sensitive layer made of nAs and a magnetic sensitive layer opposite to the buffer layer side.
The input and output electrodes on the opposite surface
In the Hall element provided, the magnetic sensitive layer is provided with an electrode.
Distance from the surface toward the heterojunction interface with the buffer layer
In the region of 50% or more of the layer thickness of the magnetic sensitive layer, phosphorus (P) is
The concentration of HO is 10 ¹⁵ cm ^-3 or less
Le element. 2. The operating current flowing between the opposing input electrodes.
The Hall element according to claim 1, wherein the lift amount (D) is within ± 15%.