JP3417036B2 - Hall element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Hall element, and more particularly to a high sensitivity compound semiconductor Hall element using GaInAs. 2. Description of the Related Art A Hall element is a type of magnetic sensor. Conventionally, compound semiconductor materials such as GaAs and InP have been used for Hall elements in addition to elemental semiconductors such as Si. The GaAs Hall element uses a high-resistance semi-insulating GaAs crystal as a substrate. On the substrate, a semiconductor layer serving as a magneto-sensitive layer is deposited by an epitaxial growth method. Various processes for device formation are performed on such an epitaxial wafer to form a Hall device. This may be referred to as an epitaxial Hall element. Also,
There is also a conventional general method of forming a conductive layer having a desired electric conductivity by implanting ions into the surface of a GaAs semi-insulating crystal substrate and using this to obtain a Hall element. This may be called an ion implantation type Hall element. GaAs
In the case of an s Hall element, generally, Si or the like is ion-implanted. [0003] Regardless of the epitaxial type or the ion implantation type, the surface of a crystal used as a substrate is usually a mirror surface polished mechanically and chemically. Here, the surface refers to the surface of the crystal on which the crystal layer is deposited or on which the ion implantation is performed. Conventionally, an epitaxial layer is deposited on such a mirror-like crystal substrate surface. Also,
In the ion implantation type Hall element, ions are implanted into such a mirror surface. Before the epitaxial layer is grown, the mirror surface may be further etched. Before the ion implantation, the surface of the substrate may be etched. In obtaining a Hall element, a conventional etching process is a process for removing a surface layer of a substrate. Conventionally, there has been no surface processing that intentionally changes the carrier concentration or the distribution of the same concentration inside the substrate near the surface. In addition to the etching of the GaAs crystal surface,
A surface treatment method for applying a chemical to modify the surface is also known. An example is a method of applying ammonium sulfide to the surface of a GaAs crystal to achieve surface stabilization (for example, Minoru Sakata, Kenji Sato, Hideaki Ikoma, Proceedings of the 54th JSAP, 1993) , 29a-Z
H-4). This type of technique allows the drug to be adsorbed on the crystal surface,
This is a surface treatment method for stabilizing the surface by coating the surface. This is a surface treatment method different from etching and removing the crystal surface layer.
The surface treatment method of the aAs crystal was not intended to modify the inside of the crystal substrate. Further, a processing and processing method extending to the inside of the crystal substrate suitable for increasing the sensitivity of the Hall element has not been proposed yet. One of the characteristics representing the performance of the Hall element is product sensitivity. The product sensitivity usually refers to a Hall voltage output under a unit control current and a unit magnetic flux density (for example, Terutaka Kataoka, “Magnetoelectric conversion element”, February 1967, Nikkan Kogyo Shimbun, p. 56). The higher the Hall output voltage under certain device operating conditions, that is, the higher the product sensitivity, the higher the sensitivity of the Hall device. In order to obtain high product sensitivity, it is necessary to form a Hall element from a semiconductor material having high electron mobility. Although the product sensitivity of the conventional ion-implanted GaAs Hall element depends on the input resistance, it is approximately 10 mV /
It is about mA · kG. It is 5 to 30 mV / mA · kG in the epitaxial Hall element. The difference in product sensitivity between the epitaxial type and the ion implantation type is due to the difference in electron mobility of the base material. That is, it depends on the difference in electron mobility between the epitaxially grown GaAs layer and the ion-implanted GaAs layer. Recently, a high sensitivity Hall element using a ternary mixed crystal of a compound such as GaInAs has been newly realized in accordance with a demand for higher sensitivity of the Hall element (Shinobu Okuyama, Toshiichi Goto, Nakamura) Hiroshi, Proceedings of the 53rd JSAP Academic Conference, 1992, 16a-SZC-1
6). The product sensitivity is about 75mV with input resistance of 1100Ω
/ MA · kG product sensitivity. This GaInA
The s Hall element is formed using an InP buffer layer and a GaInAs magneto-sensitive layer provided on a semi-insulating high-resistance InP single crystal substrate. GaInAs has higher electron mobility than GaAs or the like conventionally used as a magnetic sensing layer (for example, K. Heime, “InGaAs F”).
field-Effect Transistor ", R
ESEARCH STUDIES PRESS Lt
d. , 1989). Therefore, there is an advantage that the sensitivity of the Hall element can be improved by using GaInAs as the magneto-sensitive layer. In the formation of a GaInAs Hall element, etching is conventionally performed as a pretreatment for growing an epitaxial layer on the surface of an InP crystal serving as a substrate. However, even in such a GaInAs Hall element, surface treatment such as intentionally changing the carrier concentration or the like near the surface in the InP crystal substrate has not been performed conventionally. Furthermore, a two-dimensional electron Hall element of high sensitivity using a structure similar to a base material for a high mobility transistor utilizing a high mobility characteristic of two-dimensional electrons has been reported. An example of a two-dimensional electron Hall element using a semi-insulating GaAs crystal as a substrate is an AlGaAs / GaAs heterojunction Hall element (Takashi Taguchi et al., IEICE Journal C, Vol. J70-C, No. 5, May 1987, 758
page). As a two-dimensional electron Hall element using a semi-insulating InP crystal substrate, there is an AlInAs / GaInAs heterojunction Hall element (Y. Sugiyama, T.)
technicalDigest of the 11t
h Sensor Symposium, 1992,
p. p. 79-82. ). For example, AlGaAs / GaAs
For an s-based heterojunction two-dimensional electron Hall element, 100 m
V / mA · kG and unprecedentedly high product sensitivity have been obtained (Yoshinobu Sugiyama, Material of the 5th meeting of the Next Generation Sensor Council,
1992, pp. 1-7). This is due to the application of high electron mobility manifested by two-dimensional electrons. 3
Since the electron mobility expressed by two-dimensional electrons is higher than that of electrons that behave two-dimensionally, the Hall element using two-dimensional electrons has high sensitivity. [0010] Even in a two-dimensional electron Hall element using either GaAs or InP as a substrate, these crystal substrates are generally not subjected to any processing other than removal of a substrate crystal surface layer by etching. Was. [0011] Among the two-dimensional electron Hall elements, GaInAs
In a Hall element using the layer as a channel layer of a two-dimensional electron gas, the GaInAs layer is generally not directly deposited on the InP substrate. GaInAs
The channel layer is usually made of InP deposited on an InP single crystal substrate.
It is formed on a buffer layer such as P or AlInAs. For devices operated under relatively high electric field strength, such as high mobility field effect transistors, the buffer layer should be p-type to prevent the infiltration of the electric field into the buffer layer and to fully extract the characteristics of the two-dimensional electron gas. It is common. FIG. 3 shows a conventional epitaxial layer structure for a general high mobility field effect transistor. The structure of the epitaxial wafer used for the two-dimensional electron Hall element is the same as that in FIG.
The carrier concentration of the p-type buffer layer is generally 10 ¹⁴ to 10 ¹⁵ cm.
^-3 , which is a conventional example deposited just above the substrate crystal. Without providing a p-type buffer layer, the region near the surface
If a shaped crystal is used as a substrate, there is a possibility that electric field diffusion can be prevented without providing a p-type buffer layer. Moreover, if a crystal processed inside such a crystal is used as a substrate, as shown in FIG. 4, the buffer layer in the epitaxial layer structure can be omitted, and the layer structure can be simplified. In other words, high mobility due to two-dimensional electrons is manifested even with a simplified structure, and for example, high sensitivity of a Hall element can be easily achieved. However, at present, there is no device such as a Hall element that uses a crystal in which a specific region inside the crystal is consciously converted into a p-type as a substrate. [0012] The p-type impurity acting on GaAs is Z which belongs to Group II of the periodic table.
n or Mg. Group IV carbon (C) also functions as a carrier. These p-type impurities are contained in the GaAs crystal and constitute a main part of the carrier. In particular, in a GaAs crystal grown by the liquid encapsulation Czochralski (LEC) method, the main impurity is assumed to be carbon. However, the carbon originally contained in the GaAs crystal is mainly mixed from the crystal growth environment, and the carbon concentration in the crystal is generally about 10 ¹⁵ cm ⁻³ . In addition, carbon is generally distributed almost uniformly in the depth direction from the surface of the crystal. In a specific region near the crystal surface, the carbon concentration, that is, the acceptor concentration (may be regarded as almost the carrier concentration) Has no corresponding change inside the crystal. Conventionally, a crystal having the same carrier concentration as the inside in the vicinity of the surface is used as the substrate. Therefore, a Hall element has been manufactured using a crystal that has not been devised to intentionally change the concentration or distribution of carbon impurities in a specific region inside the crystal, that is, the carrier concentration or distribution. This hinders easily obtaining a Hall element having a high sensitivity characteristic comparable to a two-dimensional electron Hall element using a two-dimensional electron gas with a simple structure. According to the present invention, the structure of a host material for high sensitivity Hall elements is simplified by employing, as a substrate, a crystal which has been processed to reach the inside of a crystal for converting a specific region near the surface into a p-type. Further, the present invention provides a Hall element having excellent sensitivity characteristics. That is, according to the present invention, a p-type impurity is ion-implanted into a specific region from the surface of a single crystal, and the carrier concentration of the specific region inside the crystal near the surface of the single crystal is reduced. A Hall element is formed from a compound semiconductor magnetosensitive layer formed on a substrate made of a crystal having a carrier concentration other than the above. The substrate used in the present invention is GaAs.
And InP single crystals. In order to make a specific region from the crystal surface p-type, p-type impurities such as carbon (C), zinc (Zn), and magnesium (Mg) may be diffused from the crystal surface to the inside or may be ion-implanted. Compared with the diffusion method, the ion implantation method is advantageous in terms of productivity because a large amount of crystals can be processed at the same time. In the ion implantation method, the depth from the crystal surface on which impurities are to be ion-implanted can be controlled by adjusting the acceleration voltage at the time of implantation. In addition, the impurity concentration in a specific region from the crystal surface may be adjusted by adjusting the dose at the time of ion implantation. By controlling the acceleration voltage and the dose, the carrier concentration can be controlled by the impurity concentration in a specific region from the crystal surface. In the ion implantation, the implanted impurities are distributed from the crystal surface in a normal distribution curve. This distribution is schematically shown in FIG. Therefore, according to the ion implantation method, not only the carrier concentration in the specific region near the crystal surface but also the concentration distribution can be uniformly controlled. One example of a p-type impurity ion-implanted into a specific region from the crystal surface is carbon. In a GaAs single crystal, Zn, Mg, etc. also act as carriers. However, these elements have a larger diffusion coefficient in GaAs than carbon. For example, the diffusion coefficient of Zn in a GaAs crystal is as large as 1.5 × 10 ⁻⁸ cm ² / s at 1100 ° C. (Japanese Industrial Technology Promotion Association, New Materials Technology Committee, “Compound Semiconductor Device”, 1973, p. 360). . Elements with a larger diffusion coefficient are more likely to diffuse deeper into the crystal due to heat treatment for electrically activating implanted ions performed after ion implantation. In addition, since the ions are not always diffused uniformly, it is not possible to maintain a uniform distribution having a normal curve originally exhibited by the implanted ion species. Therefore, it is difficult to obtain a uniform distribution of the carrier concentration. Therefore, carbon having a small diffusion coefficient is preferable as the p-type impurity. GaAs is used as a crystal for implanting carbon ions.
The explanation is given with reference to a crystal. The maximum value of the carrier concentration in a region of 10 ⁻⁴ cm or less in depth from the GaAs crystal surface is set to 8 × 10 ¹⁶ cm ⁻³ or less. Even if the carrier concentration exceeds this value, the expansion of the depletion layer can be prevented, which is effective for infiltration of the electric field. However, on the contrary, the junction capacitance of the p / n junction with the n-type magnetosensitive layer increases and the Hall element Is not preferred in terms of responsiveness. The maximum value of the carrier concentration is the peak concentration when the carrier concentration is distributed in a normal curve as shown in FIG. In the case where carbon ions are implanted multiple times while changing the acceleration voltage, and a flat carrier concentration profile as shown in FIG. Carrier concentration. As described above, carbon ions are implanted into the crystal near the crystal surface, and a GaAs crystal in which the carrier concentration in a specific region near the surface is higher than that inside the crystal is used as a substrate. The specific resistance of the GaAs crystal into which carbon is ion-implanted may be 10 ⁴ to 10 ⁸ Ω · cm. In practice, a crystal of 10 ⁶ to 10 ⁷ Ω · cm is generally used. Although the plane orientation of the crystal is not limited, {100} is appropriate in consideration of the epitaxial growth of the magneto-sensitive layer on the substrate crystal. In order to change the carrier concentration in a specific region within a depth of 10 ⁻⁴ cm from the surface of the GaAs crystal, the accelerating voltage is set so that the peak concentration is located at a depth corresponding to の of the specific region. Set. In the case of multiple injections, the injection may be performed at an acceleration voltage lower than this acceleration voltage value. As the acceleration voltage is lowered, the peak concentration position is located at a position shallower from the crystal surface. In order to electrically activate the implanted carbon ions, the GaAs crystal may be heat-treated after the implantation. 700-850 as heat treatment temperature
C is appropriate. A compound semiconductor magnetosensitive layer formed on a single crystal substrate into which p-type impurity ions have been implanted is Ga _x In _{1 -x} As.
(X represents a composition ratio). This is because Ga _x In _1-x As can obtain a higher electron mobility than GaAs or InP, which are conventional magneto-sensitive layer materials. When the composition ratio of Ga _x In _1-x As is deposited on a GaAs single crystal substrate, it is appropriate that x = 0.7 to 0.9. In a conventional structure for a high mobility field effect transistor, x is generally around 0.8. Since the film thickness is not lattice-matched with GaAs and Ga _x In _1-x As, by setting an extremely thick Ga _x In _1-x As
The strain cannot be confined in the layer. Therefore, x = 0.8
In this case, it is appropriate to set the thickness to about 10 nm (see P. BHATTACHARYA, “PROPERTI”).
ES OF LATTICE-MATCHED AND
STRAINEDIndium Galium A
rsenide ", INSPEC, 1993, Chapter 1, section 1.2). The GaInAs free layer is directly bonded to the single crystal substrate. It is not deposited on a p-type buffer layer as in the prior art. Thereby, the structure can be simplified. GaI
What is necessary is just to deposit another compound semiconductor layer on the nAs magnetic sensing layer. For example, GaInP has a large band gap difference from GaInAs, and is advantageous in that the temperature change of Hall element characteristics can be suppressed to a low level. Incidentally, the band gap at room temperature of Ga _0.51 In _0.49 P lattice-matched with GaAs is 1.8.
8 eV, and for example, the band gap of Ga _0.8 In _0.2 As is 1.21 eV (HC Casey a.
nd M. B. Panish "HETERO Stru
CTURE LASERS "-Part B, Acdem
ic Press, 1978, p. 16. ). Therefore,
The band gap difference between the two layers is 0.67 eV. On the GaInP layer, a GaAs layer having a high carrier concentration may be provided as an ohmic contact layer. This is because the input / output electrodes of the Hall element can be easily provided with ohmic properties. The carrier concentration is 10 ¹⁸ c
It is suitable to be about m ⁻³ and the film thickness is around 100 nm. The carrier concentration may be adjusted by the doping amount of the n-type impurity. As a dopant, Si of Group IV of the periodic table is used.
And Se and S of Group VI can be used. The GaInP layer on the GaInAs magnetic sensing layer may be undoped. Alternatively, doping may be performed by intentionally adding an impurity. As the doping gas, for example, hydrogen sulfide (chemical formula: H ₂ S) or silane (chemical formula: SiH
₄ ) etc. are available. The doping may be performed in consideration of a desired input resistance of the Hall element and the like. The Hall element may be formed by using a known process technique. No special process technology is required to form the device. The method for growing the GaInAs or GaInP layer is not particularly limited, and may be a liquid phase epitaxy (LPE) or a molecular beam epitaxy (MBE).
MOVPE) and MOVPE
(In some cases, it is also referred to as MOCVD or OMVPE.) Alternatively, an MO / MBE method combining both MOVPE and MBE may be used. Function G in which carbon ions are implanted into a specific region near the surface
By using the aAs crystal as the substrate, it is possible to suppress the penetration of the electric field into the substrate crystal with a simple material configuration. EXAMPLES The present invention will be described in detail based on examples. FIG.
FIG. 3 is a schematic plan view of a Hall element made of a material according to the present invention. FIG. 2 is a schematic cross-sectional view taken along the direction of a broken line AA ′ in the schematic plan view shown in FIG. The substrate (101) has a plane orientation of about 10 ⁶ Ω · cm and a plane orientation of ｛1.
A semi-insulating GaAs single crystal of 00 ° was used. Carbon ions having an atomic weight of 12 were implanted into the surface of the substrate crystal (101) at an acceleration energy of 250 KeV to form a p-type carbon ion implanted region (101a). The dose of carbon ions was 3 × 10 ¹² cm ⁻² . The activation heat treatment after the implantation was performed at a temperature of 850 ° C. for 15 minutes. Under these activation conditions, the peak concentration is about 7.1 × 10 ¹⁶ cm ⁻³ ,
The position of the peak concentration was 4.7 × 10 ⁻⁵ cm from the surface of the GaAs crystal substrate (101). A GaAs substrate (10
1) On top, n-type Ga _0.8 I having a composition ratio (x) of 0.8
An n _0.2 As layer (102) was deposited by MOVPE.
The carrier concentration in the undoped layer of the Ga _0.8 In _0.2 As layer (102) was about 8 × 10 ¹⁵ cm ⁻³ . The film thickness is about 8
nm. The n-type Si-doped Ga _0.51 In layer is similarly formed on the Ga _0.8 In _0.2 As layer (102) by the MOVPE method.
_{A 0.49} P layer (103) was deposited. The carrier concentration of the same layer (103) was 2 × 10 ¹⁸ cm ⁻³ . The film thickness is about 120
nm. Next, the surface of the Ga _0.51 In _0.49 P layer (103) is coated with a normal organic photoresist material, and then, by using well-known photolithography and etching techniques, areas where input / output electrodes are to be formed. In addition, a region (104) to be a magnetically sensitive portion was processed into a mesa shape. Thereafter, a Ga _0.51 In _0.49 P layer (103)
Was again entirely coated with the organic resist material. Next, a pair of the input electrode (105) and the output electrode (1
06), only the resist material in the region where the film is to be formed is removed using a known photolithography technique, and Ga _0.51 I
The surface of the n _0.49 P layer (103) was exposed. After that, G
Au / Ge alloy containing about 13% by weight of e was vacuum deposited. After that, the wafer was immersed in an organic solvent mixed solution to remove the resist material, and at the same time, remove the Au / Ge alloy film which was unnecessary for the production of the device adhered on the resist material by vapor deposition by a so-called lift-off method. Next, the wafer on which the alloy film serving as an electrode was applied was heated at 420 ° C. for several minutes.
Alloying was performed to obtain an ohmic electrode. Further, a pad electrode (107) was provided on each electrode in electrical connection with the input / output electrodes (105 and 106). The pad electrode (107) was placed on the surface layer of the GaAs single crystal substrate (101) exposed by mesa etching as described above. Next, the surface of the heterojunction material having undergone the above steps was covered with a silicon dioxide film (108) by a plasma CVD method, except for the above-mentioned input / output electrode portions. The deposited film thickness of the oxide film was about 400 nm. In this embodiment, a plasma CVD method was used to form the coating film. However, this film formation method is merely an example, and it does not matter if other methods do not cause a problem in insulation, film quality, and the like. Absent. Further, the entire surface of the device is covered again with a general photoresist material, and the Hall device formed on the entire surface of the wafer is separated into single components and patterned to form a dicing line (109) for forming a Hall device chip. Was given. Thereafter, in a portion corresponding to the dicing line (109), the oxide film (108) and the Ga
_0.51 In _0.49 P layer (103) and Ga _0.8 In _0.2 As
Layer (102) was sequentially removed by etching. Further, the etching is further performed to form a GaAs single crystal substrate (101).
The dicing line (109) was etched until reaching the surface layer portion of (1). The electrical characteristics of the formed Hall element were evaluated. The results are summarized in Table 1. As a conventional example, the characteristics of a Hall element using a normal GaAs crystal into which carbon ions were not implanted as a substrate were also evaluated. The structure of the conventional Hall element and the epitaxial layer is the same as that of the Hall element according to the present invention. In the Hall element according to the present invention, higher product sensitivity and lower unbalance rate were achieved as compared with the conventional element. The product sensitivity obtained by the present invention has been conventionally equivalent to that of a high-sensitivity hole obtained by a complicated structure similar to that of a high-mobility field-effect transistor. [Table 1] The present invention has the effect of achieving a high-quality Hall element having excellent uniformity of the unbalance rate and excellent sensitivity characteristics with a simple structure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic plan view of a Hall element according to the present invention. 2 is a line A- of a schematic plan view of the Hall element shown in FIG. 1;
FIG. 4 is a schematic cross-sectional view along A ′. FIG. 3 is a cross-sectional structural view of a general epitaxial material for a high mobility transistor. FIG. 4 is a cross-sectional view showing an example of a simplified epitaxial structure. FIG. 5 is a diagram showing a distribution of carrier concentration in a normal curve. FIG. 6 is a diagram showing an example of a flat carrier concentration distribution obtained by multi-stage injection. [Description of References] (101) GaAs single crystal substrate (101a) Carbon ion implanted region (102) GaInAs layer (103) GaInP layer (104) Magnetically sensitive region (105) Input electrode (106) Output electrode (107) Pad Electrode (108) Oxide film (109) Dicing line (110) GaAs substrate (110a) P-shaped specific region (111) GaAs buffer layer (112) GaInAs layer (113) Undoped AlGaAs layer (114) n-type AlGaAs layer ( 115) n-type GaAs layer (116) Concentration profile of ion-implanted element (117) Carrier concentration profile (118) Synthesized carrier concentration profile (119) Peak concentration

Continuation of the front page (56) References JP-A-5-74705 (JP, A) JP-A-5-75177 (JP, A) JP-A-55-48927 (JP, A) JP-A-57-32687 (JP, A) JP-A-63-70583 (JP, A) JP-A-6-97530 (JP, A) JP-A-6-244475 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H01L 43/06 G01R 33/07 JICST file (JOIS)

Claims (1)

(57) Patent Claims 1. A in the depth from the crystal surface 10 ^-4 cm following areas, a p-type impurity of carbon ion implantation, the carrier concentration of the <br/> region It was used as a high and 8 × 10 ¹⁶ cm ^-3 or less than the carrier concentration of the crystal inside other than the region GaA
a substrate made of s crystals, Hall elements formed by and a sensitive layer consisting of GaInAs which is formed by directly bonded thereon.