JP3681425B2 - GaAs Hall element - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a Hall element that has a small variation in Hall output voltage over a wide temperature range, has sufficient sensitivity for practical use, and is suitable for high-accuracy measurement.
[0002]
[Prior art]
The Hall element is a magnetic sensor that detects the magnetic field strength by converting the magnetic field into a Hall output voltage using the Hall effect of semiconductors such as InSb, InAs, and GaAs, and is widely used for motors, non-contact switches, etc. ing. Among the applications of the Hall element, the magnetic field strength measurement gauss meter, current sensor, and the like require the Hall output voltage stability with respect to fluctuations in ambient temperature in addition to the linearity of the Hall output voltage with respect to the magnetic field strength. However, although the temperature change rate of the Hall output voltage of the conventional Hall element depends on the Hall element driving method, it is about 2% / ° C. for the InSb Hall element and 0.06 even for the GaAs Hall element having a small temperature dependency of characteristics. Since it was about% / ° C., an IC for correcting the temperature change of the Hall output voltage was indispensable in the above-described applications.
[0003]
Incidentally, the method of correcting the temperature change of the Hall output voltage with the IC has the following problems. First, since the Hall output voltage generally does not change linearly with respect to temperature, the temperature correction method, and thus the configuration of the temperature correction IC, becomes very complicated, and the manufacturing cost of the IC is very expensive. It was a thing. In addition, if the variation in temperature characteristics of the Hall elements is large, temperature correction cannot be performed with sufficient accuracy even with a temperature correction IC, so it is necessary to select the Hall elements. It was a big factor pushing up. Further, since the temperature correcting IC chip is relatively large, there is a problem in mounting.
[0004]
Moreover, in recent years, applications of Hall elements that require temperature change correction of the Hall output voltage over a wider temperature range than before have appeared. For example, in automobile-related applications, temperature correction in a temperature range of about −50 ° C. to 150 ° C. is required. In such a very wide temperature range, the above-described problem becomes more remarkable in the method of correcting the temperature change of the Hall output voltage by the IC.
[0005]
Thus, in applications where the stability of the Hall output voltage with respect to fluctuations in the ambient temperature is required, a method of correcting the temperature change of the Hall output voltage with an IC has been used exclusively, but it is very expensive in terms of cost. There are problems of becoming things and implementation problems, and these problems are becoming more and more prominent in the future.
[0006]
[Problems to be solved by the present invention]
An object of the present invention is to provide a Hall element that has a sufficiently high Hall output voltage stability with respect to a change in ambient temperature, has a sufficiently high sensitivity in practical use, and is suitable for highly accurate measurement.
[0007]
[Means for Solving the Problems]
The present inventors paid attention to a GaAs Hall element having the smallest temperature change rate of the Hall output voltage among the conventional Hall elements, and as a result of research for further reducing the temperature change rate, the temperature of the Hall output voltage The present invention succeeded in realizing a GaAs Hall element having a sufficiently low change rate that does not require a correction IC and having a sufficiently high Hall output voltage in practical use.
[0008]
That is, the present invention is as follows.
1. A GaAs hole having a conductive layer made of GaAs having a sheet carrier concentration of 8 × 10 ¹² / cm ² or more and an input resistance value being 1.6 times or more of a sheet resistance value of the conductive layer. element.
2. 2. The GaAs Hall element according to 1 above, wherein a conductive layer is formed by ion implantation with an acceleration voltage of 400 keV or less.
[0009]
As a result of the study by the present inventors, increasing the sheet carrier concentration of the GaAs conductive layer serving as the magnetosensitive layer in the GaAs Hall element can reduce the temperature change rate of the Hall output voltage. As the concentration increased, the product sensitivity of the Hall element decreased, and it became clear that the problem that it was not suitable for high-precision measurement occurred at the same time. Therefore, the sheet carrier concentration of the GaAs conductive layer and the pattern shape of the Hall element are comprehensively studied. In the GaAs hole element, a conductive layer made of GaAs having a sheet carrier concentration of 8 × 10 ¹² / cm ² or more is formed. And the desired Hall element is obtained by making the input resistance value 1.6 times or more the sheet resistance value of the conductive layer.
[0010]
Hereinafter, the present invention will be described in detail.
FIG. 1 is a plan view of the Hall element according to the present invention, and FIG. 2 is a sectional structural view taken along line AA ′ in FIG. In FIG. 1, 1 is a substrate, 2 is a GaAs conductive layer which is a magnetosensitive layer, 3a and 3a ′ are input-side ohmic electrodes electrically connected to the GaAs conductive layer, and 3b and 3b ′ are electrically connected to the GaAs conductive layer. The connected output-side ohmic electrode 4 is a protective film for protecting the GaAs conductive layer 2 and the ohmic electrode 3 from moisture and the like. The substrate 1 is a semi-insulating GaAs substrate, a Si substrate on which a GaAs thin film is grown, or the like, but is not particularly limited in the present invention.
[0011]
The GaAs conductive layer 2 is made of a GaAs thin film containing donor impurities. As a forming method, a method of ion-implanting donor impurities into a semi-insulating GaAs substrate, a method of ion-implanting donor impurities into a GaAs thin film grown on a semi-insulating GaAs substrate or Si substrate, a semi-insulating GaAs substrate There is a method of growing a GaAs thin film containing a donor impurity on or on a Si substrate, and the ion implantation method is particularly preferable among them. Any donor impurity may be used as long as it becomes a donor in GaAs, but Si, Ge, Se, and the like are preferable. When the GaAs conductive layer 2 is formed by ion implantation, the thickness of the conductive layer is determined by the acceleration voltage. However, since high-voltage ion implantation is expensive and the carrier concentration is low, 400 keV or less is preferable. 250 keV or less is more preferable. Moreover, since it will become difficult to form a conductive layer under the influence of a surface depletion layer when it becomes less than 100 keV, 100 keV or more is preferable. The annealing process for activating the ion-implanted donor impurity is not particularly limited with respect to the method and conditions.
[0012]
In the present invention, the sheet carrier concentration in the GaAs conductive layer 2 is preferably 8 × 10 ¹² / cm ² or more, and more preferably 1 × 10 ¹³ / cm ² or more. If the sheet carrier concentration is less than this value, a Hall element having a sufficiently high Hall output voltage stability with respect to fluctuations in ambient temperature, which is an object of the present invention, cannot be realized. Further, when the sheet carrier concentration is 8 × 10 ¹³ / cm ² or more, impurities are not easily activated, and a concentration higher than this is not realistic.
[0013]
In the present invention, the input resistance value between the input-side ohmic electrodes 3a and 3a ′ needs to be 1.6 times or more the sheet resistance value of the GaAs conductive layer 2, and preferably 1.8 to 3.5. Double the range. When the ratio is lower than 1.6 times, the product sensitivity of the Hall element is low, a practically sufficient sensitivity cannot be obtained, and it is not suitable for high-accuracy measurement. The input resistance value is controlled by changing the planar shape of the GaAs conductive layer, which is the magnetic sensitive part.
[0014]
The ohmic electrode 3 may be anything as long as it is in ohmic contact with the GaAs conductive layer 2, but an electrode including an AuGe / Ni / Au structure is particularly preferable. The formation method is not particularly limited.
The protective film 4 is formed for the purpose of preventing contamination or deterioration of the GaAs conductive layer 2 due to moisture or oxidation, and is made of an inorganic insulating film such as SiO ₂ or SiN, or an organic thin film such as polyimide, and has a thickness of About 0.1 to 5 μm is preferable.
[0015]
【Example】
Next, an example explains the present invention.
[0016]
[Example 1]
First, a photosensitive resist pattern was formed on a semi-insulating GaAs substrate. The planar shape of the magnetic sensitive part was designed so that the input resistance of the element was 1.8 times the sheet resistance of the conductive layer. Thereafter, ions are implanted at an acceleration voltage of 250 keV and an implantation dose of 1.2 × 10 ¹³ / cm ² to form a conductive layer, and then annealed at 850 ° C. for 15 minutes to activate the implanted ions. Went. At this time, the sheet carrier concentration was 9.2 × 10 ¹² / cm ² and the sheet resistance was 418Ω. The difference between the dose and the sheet carrier concentration is due to the fact that the activation rate of the ion-implanted impurities is not 100%. Next, after forming a resist pattern for electrode formation, AuGe 200 nm, Ni 50 nm, and Au 300 nm were sequentially deposited on the entire surface of the wafer as an electrode metal in this order from the substrate side. Thereafter, lift-off was performed, and ohmic contact with the conductive layer portion was obtained by alloying. Furthermore, 300 nm of SiO ₂ was formed on the entire surface of the wafer by plasma CVD to form a protective film. The wafer was diced, die-bonded and wire-bonded to complete an element molded in epoxy resin. The input resistance of the element thus fabricated was 752Ω, which was 1.8 times the sheet resistance as designed. The product sensitivity was 12 mV / mAkG, which was sufficiently high for practical use, and the deviation of the unbalanced voltage was 0.2 mV / mA. The temperature coefficient of Hall output was 0.01%. In consideration of the fact that the fluctuation range of the Hall output is as small as 2% or less in the operating temperature range of −50 ° C. to 150 ° C. and the error of the measurement system is 2 to 3%, the Hall element of the present invention is for temperature correction. The conventional measurement accuracy can be sufficiently obtained without using the IC. Therefore, by using the Hall element according to the present invention, it is possible to perform highly accurate measurement at low cost. Further, when the deviation of the unbalanced voltage is considered to be three times the deviation of the unbalanced voltage, the ratio of the unbalanced voltage to the product sensitivity is as low as 5%, which indicates that it is suitable for high-accuracy measurement.
[0017]
[Comparative Example 1]
In order to clarify the relationship between the sheet carrier concentration and the temperature dependence, the same mask and process as in Example 1 were used, and the sheet carrier concentration only differed. The element structure is the same as that shown in FIG. 1, the shape of the magnetosensitive part is the same, and the ion implantation conditions are an acceleration voltage of 250 keV and a dose of 4 × 10 ¹² / cm ² .
At this time, the sheet carrier concentration is 3.2 × 10 ¹² / cm ² and the sheet resistance is about 700Ω. The input resistance of the device was 1260Ω, the product sensitivity was 20 mV / mAkG, and the deviation of the unbalanced voltage was 0.2 mV / mA.
[0018]
FIG. 3 shows the temperature characteristics of the Hall elements shown in Example 1 and Comparative Example 1 according to the present invention. In the figure, the horizontal axis represents the ambient temperature, and the vertical axis represents the hall output during constant current driving. For easy comparison, the vertical axis represents the change when the Hall output at room temperature is 100%. As is apparent from the figure, in Comparative Example 1, the temperature coefficient is 0.06%, and in the temperature range from −50 ° C. to 150 ° C., it is found that there is a fluctuation of about 12% in the fluctuation range. . Therefore, an IC for correcting output according to temperature is separately required, which is not only expensive in cost, but also requires space for the IC for temperature correction, which causes a problem in mounting of the element.
[0019]
[Comparative Example 2]
Next, in order to clarify the difference in element characteristics depending on the shape of the magnetic sensing portion of the element, a Hall element having a different magnetic sensing portion shape was manufactured by the same process as in Example 1. In Comparative Example 2, the input resistance is 1.4 times the sheet resistance. The input resistance of the device was 590Ω, the product sensitivity was 8.5 mV / mAkG, and the deviation of the unbalanced voltage was 0.9 mV / mA.
[0020]
The Hall element of Comparative Example 2 has the same sheet carrier concentration as Example 1 according to the present invention, and the temperature dependency of the characteristics is the same as that of the prototype according to the present invention, but the product sensitivity is low. Moreover, since the deviation of the unbalanced voltage is large in Comparative Example 2, the ratio of the unbalanced voltage to the product sensitivity is high. For this reason, when the unbalanced voltage variation is 3 times the deviation, the comparative example 2 has an unbalanced voltage exceeding 30% with respect to the product sensitivity. Is not suitable for high-precision measurement.
[0021]
【The invention's effect】
The Hall element of the present invention is sufficiently sensitive to be suitable for high-accuracy measurement, and the temperature change rate of the Hall output voltage is very small, so that there is no need for a temperature correction IC for the Hall output voltage, or Even when using a temperature compensation IC, a very simple configuration is sufficient. Therefore, stable magnetic field strength measurement that does not depend on variations in ambient temperature can be performed at a very low cost.
[Brief description of the drawings]
FIG. 1 is a top view of a Hall element in which a protective film is omitted according to the present invention (omitted for easy understanding of the shapes of a conductive layer and an electrode).
FIG. 2 is a sectional structural view of a Hall element according to the present invention.
3 is a graph showing a temperature change of the Hall output voltage of the Hall element according to Example 1 and Comparative Example 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 2 GaAs conductive layer 3a Input side ohmic electrode 3a ^, Input side ohmic electrode 3b Output side ohmic electrode 3b ^, Output side ohmic electrode 4 Protective film 5 Example 1
6 Comparative Example 1

Claims (2)

It has a conductive layer made of GaAs having a sheet carrier concentration of 8 × 10 ¹² / cm ² or more and less than 8 × 10 ¹³ / cm ² , and the input resistance value is 1.6 to 3.5 times the sheet resistance of the conductive layer. There is a GaAs Hall element. 2. The GaAs Hall element according to claim 1, wherein the conductive layer is formed by ion implantation with an acceleration voltage of not less than 100 keV and not more than 400 keV .

Images