JPH09148652A - Magnetoelectric conversion element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetoelectric conversion element of high sensitivity wherein the noise level appearing in the form of unbalance voltage is very low, by forming an indium antimony based thin film as a magnetosensitive part by evaporation, which film has stoichiometric composition, a specified thickness, thickness variation, and mobility. SOLUTION: In the title magnetoelectric conversion element, an indium antimony (InSb) based thin film formed by evaporation whose mobility is at least 30,000cm<2> /V/sec is used as a magnetosensitive part. The film has stoichiometric composition and is 0.5-1.5μm in thickness. When the thickness variation is measured with a pin type surface roughness meter, it is at most 10% of the total average thickness. That is, In and Sb, are deposited on a crystalline substrate 1 set at a temperature wherein Sb only does not attach to the substrate, and a composite crystal thin film 2 composed of composite crystal of InSb compound crystal and simple substance In is formed. The atomic ratio of the total In to Sb is 1.1-1.7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indium antimony-based magnetoelectric conversion element having a very low noise level appearing in the form of an unbalanced voltage, high sensitivity and excellent reliability, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Magnetoelectric conversion elements such as Hall elements and semiconductor magnetoresistive elements are VTRs, floppy disks and CDs.
It is widely used as a rotational position detection sensor for a drive motor such as a ROM or a magnetic sensor for bill recognition. An indium antimony-based thin film having high mobility is most suitable as the magnetic sensing part of such an element. Here, indium antimony-based refers to the general formula InSb _1-X V _X
(V is one or more elements selected from phosphorus and arsenic, and X is 0
To 0.5).

In order for the magnetoelectric conversion element using these compound semiconductors as the magnetic sensing portion to function as a sensor, it is necessary to secure a practical resistance value, and the thickness is 0.5 to 1.5 μm.
It is an essential requirement to thin the film to a certain degree. In addition, high mobility is also required to ensure high sensitivity. One method that meets this demand is a method in which a single crystal is cut out and polished to form a thin film. However, according to this method, although a mobility similar to that of a single crystal can be secured,
It is difficult to form a thin film having the above thickness uniformly. Further, this method has a problem that the cost is very high.

Therefore, various thinning methods of this system which can be mass-produced and can obtain desired characteristics have been studied. For example, Japanese Patent Publication No. 51-45234 discloses a so-called transfer method. That is, after forming an InSb thin film on a crystalline substrate such as mica by vapor deposition, this thin film is adhered to another insulating substrate using an adhesive such as an epoxy resin, and then the crystalline substrate is removed. is there.

On the other hand, the present inventors have proposed various conditions for forming a thin film of this system having high mobility. Tokuhei 1
According to Japanese Patent Laid-Open No. -13211, it is a necessary condition for forming a high mobility InSb thin film that the atomic ratio of In to Sb is not 1.0, but excessive In of 1.1 to 1.7. Revealed. Further, the necessary conditions for increasing the mobility such as the substrate temperature and the flux of In and Sb were clarified (Japanese Patent Publication No. 1-15135, Japanese Patent Publication No. 2135/1990).
-47849 gazette, Japanese Patent Publication No. 3-59571 gazette). In addition, Japanese Examined Patent Publication No. 2-47850 and JP-A-59
In JP-A-202674, an InSb-based composite crystal thin film having an atomic ratio of In to Sb in the range of 1.1 to 1.7 is formed by vapor deposition, then arsenic or Sb is vapor deposited, and finally chemical A method of forming a thin film of this system with a stoichiometric composition was clarified.

In recent years, along with the demand for higher sensitivity of the element, the demand for reduction of the above noise level has increased.
However, among the characteristics of the magnetoelectric conversion element having the indium antimony-based thin film formed as described above as the magnetic sensing part,
There are various noise levels that appear in the form of unbalanced voltage, from extremely high to extremely low.

[0007]

SUMMARY OF THE INVENTION The present invention provides an indium antimony-based magnetoelectric conversion element having a very low noise level appearing in the form of an unbalanced voltage, high sensitivity and excellent reliability, and a method for manufacturing the same. It is intended.

[0008]

The present inventors have found that the above noise level is caused by the difference in the uniformity of the thickness of the surface of the deposited film.
Further, it was found that the uniformity of the thickness depends on the condition of the first step in the thin film forming step, that is, the condition at the time of forming the In-excessive composite crystal thin film, and completed the present invention.

That is, the present invention has a stoichiometric composition and a thickness of 0.5 to 1.5 μm, and the thickness unevenness is 10% or less of the total average thickness measured by a needle type surface roughness meter. Yes,
The magnetoelectric conversion element is characterized in that an indium antimony-based thin film formed by vapor deposition having a mobility of 30,000 cm ² / V / sec or more is used as a magnetic sensing part. In addition, the present invention, on a crystalline substrate set to a temperature at which antimony alone does not adhere, vapor deposition of indium and antimony, consisting of a composite crystal of a crystal of indium antimony compound and elemental indium, and atoms of antimony of all indium. When forming a composite crystal thin film having a ratio in the range of 1.1 to 1.7, antimony is vaporized in excess of indium at the beginning of vapor deposition, and then indium alone or a large excess of indium is vaporized relative to antimony at the end of vapor deposition. And a step of depositing an element capable of forming a compound with the excess indium, thereby forming an indium antimony-based thin film.

As the element capable of forming a compound with indium, it is preferable to use one or more elements selected from phosphorus, arsenic and antimony. The mode in which the thin film is formed on the crystalline substrate as described above and then transferred to another substrate is also suitable for the present invention. At this time, mica is optimally used as the crystalline substrate.

The thickness unevenness of the thin film formed under various conditions was measured by a needle type surface roughness meter, and then the thin film was used as an element to investigate the correspondence between the noise level and the thickness unevenness. As a result, it was found that the noise level rapidly decreased when the total average thickness was 10% or less.
The method of the present invention has found optimum vapor deposition conditions based on these results.

In order to form an indium antimony-based thin film on a crystalline substrate, vapor deposition, molecular beam epitaxy (MBE), sputtering, or other vapor deposition method can be generally used. At this time, the thickness is 0.5-
A range of 1.5 μm is suitable. In the present invention, first, In in InSb in the InSb-based thin film and the simple substance I
The atomic ratio of total In and n to Sb is 1.1 to 1.7.
It is necessary to control it to be within the range. This range shows a particularly high mobility as compared with those outside the range, and can form a thin film having practical characteristics. When the atomic ratio is less than 1.1, only a brittle thin film is obtained and its mobility is low. Further, when it exceeds 1.7, pinholes are generated and the yield is lowered. A particularly preferable atomic ratio is 1.2.
In the range of up to 1.6, the crystallinity of the thin film is good and the mobility is high within this range.

A method previously proposed by the present inventors as a method for forming an InSb type composite crystal thin film (Japanese Patent Publication No. 1-13
No. 211, Japanese Patent Publication No. 2-47849, No. 3
-59571), it is possible to use a vapor deposition means for separately controlling the flying amounts of In and Sb and the substrate temperature. To obtain a thin film having a particularly high mobility,
Means such as increasing the substrate temperature are useful.

For example, according to Japanese Patent Publication No. 3-59571, when the average atomic ratio of In and Sb is vapor-deposited in the range of 1.1 to 1.7, the arrival rate ratio of In to Sb at the initial stage of vapor deposition is 1. 0.0 or less and the substrate temperature T
When the (absolute temperature) is selected so as to fall within the range of the following equation, an InSb-based composite thin film having a particularly high mobility is obtained. Tc ≦ T ≦ Tc + 30 where Tc is the boundary substrate temperature T given by the following equation.
c.

1 / Tc = 1.29 × 10 ⁻³ −3.84 ×
10 ^-5 log P (P is the degree of vacuum during vapor deposition (Torr)) When vapor deposition is performed under these conditions, a high mobility InSb-based composite thin film in which excess In is present can be formed. It was found that by adding the condition that a large excess of indium is vapor-deposited, a thin film with extremely good thickness uniformity can be obtained. This condition can be met by simple means.
At the end of vapor deposition, the power of the Sb vapor deposition source is reduced or reduced to zero, the power of the In vapor deposition source is increased, or another In vapor deposition source is prepared and the power is added.

Next, InS in which this In is extremely excessive
An element capable of forming a compound with the excess In is deposited on the b-based composite crystal thin film. At this time, one or more elements selected from phosphorus, arsenic and Sb are preferably used as the element capable of forming a compound with In. In this case, excess In
It is preferable to vapor-deposit the element in excess of 2 times or more, more preferably 4 times or more, than the amount required for converting into InSb at a substrate temperature above which re-evaporation of the element occurs.

Although the substrate temperature depends on the degree of vacuum in the vapor deposition machine, the line of sight can be estimated by thermodynamic data. For example, the books by Stur and Shinke, Thermodynamic Properties of the Elements (T
hermodynamic Properties o
f The Elements, D.F. R. Stulla
nd G. C. Sinke, American Che
Sb at 427 ° C. was 9.9 × 10 ⁻⁵ Tor, with reference to the data of the Medical Society, 1956).
Since the equilibrium vapor pressure becomes 6.5 × 10 ⁻⁵ Torr at r of 527 ° C., if the vacuum degree in the vapor deposition machine is, for example, 10 ⁻⁶ ,
This means that Sb re-evaporates at a substrate temperature of 427 ° C. or higher.

In the present invention, excessive evaporation of an element selected from phosphorus, arsenic, and Sb that combine with In suppresses re-evaporation, and excess In is InX (X is P, As, Sb alone or compound element) and extra P
Etc. select the condition that does not adhere. For example, 10 ^-6 Tor
In a vacuum of r, the substrate temperature is set to 500 ° C., and the above elements are
The conditions are such that excess In is vapor-deposited in an amount 10 times the amount necessary for converting to InX. In this way, an InSb-based thin film having a stoichiometric composition can be finally formed.

As a vapor deposition source of the above elements, simple substances and their compounds, that is, InSb, GaSb, InAs, G
aAs or the like can be used. Extra elements may be added to these. In this case, the above elements evaporate, but I
It is necessary to select a boat temperature condition where n and Ga do not evaporate. The vapor deposition thickness was measured with a needle type surface roughness meter. As described above, when In was excessively excessive at the end of vapor deposition, the thickness unevenness was 10% or less of the total average thickness.
It was found that the noise level appearing in the form of unbalanced voltage becomes extremely small when the device is formed by using such a thin film.

Vapor deposition is performed on a crystalline substrate. The above-mentioned vapor deposition process is a process in which crystals grow well, but unless a crystalline substrate is used, the initial crystal initial nuclei cannot be formed and the final mobility of 30,000 cm ² / V / sec cannot be secured. The high mobility InSb-based thin film according to the present invention is
It is possible to obtain an element having a flat surface and using the substrate used as the vapor deposition substrate at the beginning as an element and having a small noise level that appears in the form of a sufficient unbalanced voltage. Examples of such a substrate include an insulating GaAs and GaP substrate.

When mica or NaCl, which cannot be made into an element as it is, is used as the crystalline substrate, the insulating substrate is first adhered to another insulating substrate through an adhesive resin, and then these substrates are removed. Can be considered. The substrate at this time is preferably a substrate having high reliability because it is a substrate for holding the element semipermanently. For example, an inorganic material can be used, and alumina, ferrite, silicon nitride, quartz, sapphire, or the like can be used. Among them, as described in Japanese Patent Publication No. 51-45234, when ferrite is used, a magnetic focusing chip can be newly mounted to further increase the sensitivity.

The above-mentioned adhesive resin can be selected from thermosetting resins, thermoplastic resins and the like, such as epoxy resins and polyimide resins. Further, the adhesion can be performed by a very simple method. For example, there is a method in which a resin is dropped on a thin film, an insulating substrate is placed on the thin film, heated, or further pressurized and left for a predetermined time. Screen printing may be used instead of dropping. Generally, under the proper viscosity of the resin, it is possible to transfer the resin layer, which is an adhesive layer, to a thickness of several μm uniformly.

The substrate carrying the InSb-based thin film formed as described above is subjected to a patterning process to form electrodes and form individual devices. As the electrode metal, Al, Ni,
Cr, Cu, Pd, Au, etc. are used, and the electrode generally has a laminated structure of these metals. Further, the pellets are individually made by a dicing process, these pellets are fixed to a lead frame by a die bonder or the like, the electrodes of the pellet and the lead frame are connected by a wire bonder or the like, and a magnetoelectric conversion element is made by a molding process or the like.

The magnetoelectric conversion element thus manufactured has an extremely low noise level.

[0025]

Now, the present invention will be described in further detail with reference to Examples.

[0026]

Example 1 An insulating GaAs substrate was used as a crystalline substrate, and these 12 substrates were placed in a disk-shaped substrate holder. The substrate holder was installed in a vacuum vapor deposition machine having three boats for vapor deposition sources, and first, an In-excess composite crystal thin film was formed using the boats for In and Sb. Vacuum degree is 7 × 10
^-6 Torr, the substrate temperature was set to 420 ° C, the total deposition time was 17 minutes, and the final temperature was 515 ° C. During this period, the substrate temperature rising rate is 0 to 6 after the start of vapor deposition.
Minutes, 6 to 14 minutes, and 14 to 17 minutes, respectively, 0 ° C./minute, 12.
It was set to 5 ° C./min and 0 ° C./min. The power applied to the In and Sb boats was kept constant for 15 minutes from the start, and then the power applied to the Sb boat was set to zero. The flying amounts of In and Sb were set to 2.6 g and 3.5 g, but it was visually confirmed that In became excessive in the final stage and crystal growth proceeded.

Subsequently, the power of the In boat was set to zero, and the power was applied to the third boat on which Sb was placed 3
The substrate temperature was raised to 525 ° C. for minutes, and Sb was deposited. At this time, the equivalent amount of In, which is excessive, is converted from the flying amount to 8
Doubled. The mobility of the thus obtained InSb-based thin film was measured by the Van der Pau method.
It was 30,000 ± 350 cm ² / V / sec. Further, the composition analysis of one sheet was conducted by XMA, and the composition ratio was 1.0 on the entire surface of the wafer. 100 points or more on the entire surface of the wafer
When the thickness was measured with a needle type surface roughness meter, the average thickness was 0.7 μm and all points were within 10%.

A photolithography technique was used to form a Hall element pattern from this wafer. 1 is a plan view thereof, and FIG. 2 is a sectional view taken along line AA of FIG.
As shown, an InSb thin film layer is formed on the GaAs substrate 1. Ohmic contact was made to C in the central portion of the InSb thin film layer 2 other than the magnetic sensitive portion 2a.
A conductor layer 3 such as u is formed, and further,
Ni layer 4 and A as an electrode layer for bonding
The u layer 5 is laminated. In this embodiment, Cu, Ni,
The thickness of each Au layer was about 3 μm. The size of the pellet was 0.8 mm square.

Next, dicing is performed to divide into individual elements, these pellets are die-bonded to the island portion on the lead frame, and the leads and the electrode portions of the pellets are connected by Au wires for electrical connection. did. Further, a Hall element was created through steps such as transfer molding and electrical inspection. The unbalanced voltage of these devices is 0 ± 1.1 mV (average ± deviation, input voltage 1
V) was extremely small and the distribution was sharp.

[0030]

COMPARATIVE EXAMPLE 1 In Example 1, when the first InSb composite crystal containing excess In was prepared, the same vapor deposition was performed without turning off the power of the Sb boat. InS obtained
The composition of the b-based thin film was a stoichiometric composition, but the appearance was considerably uneven. In the same manner as in Example 1,
The thickness variation was measured and found to be 17% of the average thickness.
The unbalanced voltage after device formation is 2.3 ± 3.5 mV (average ±
The deviation and the input voltage were 1 V) and the distribution was wide.

[0031]

[Examples 2 to 4] In Example 1, an example will be given in which P and As were charged in the third boat. In this case as well, the conditions for producing the first InSb composite crystal containing excess In were set to a large excess of In at the final stage. When the thickness unevenness was measured in the same manner as in Example 1, it was within 10% of the average thickness. A Hall element was manufactured in the same manner as in Example 1. The unbalanced voltage after device formation is 0 ± 1.1 mV (average ± deviation, input voltage 1
V) was extremely small. It can be seen that the unbalanced voltage value and its variation can be suppressed to a small level by the conditions according to the present invention when forming the InSb composite crystal containing the initial excess In.

[0032]

Example 5 In Example 1, mica was used as the crystalline substrate. An InSb-based thin film was prepared in the same manner as in Example 1 except that the temperature was lowered from the set substrate temperature by 5 ° C. as compared with Example 1. The thickness unevenness of this thin film did not exceed 7% of the average thickness. Next, a 50 mm square ferrite was prepared, a polyimide resin was dropped on the InSb-based thin film prepared as described above, and the ferrite was superposed thereon.
A weight was placed and the plate was left at 200 ° C. for 12 hours. Next, the temperature was returned to room temperature, and the mica was peeled off. A Hall element was formed from the wafer carrying the InSb-based thin film in the same manner as in Example 1. The unbalanced voltage after device formation was 0 ± 0.8 mV (mean ± deviation, input voltage 1 V), which was a very small distribution and sharp distribution.

[0033]

Example 6 Using the InSb-based thin film obtained in Example 5,
A semiconductor magnetoresistive element was created. A 50 mm square alumina substrate is prepared, polyimide resin is dropped on the InSb-based thin film, the alumina substrate is overlaid thereon, and a weight is placed on the substrate.
It was left at 0 ° C. for 12 hours. Then, the temperature was returned to room temperature, and the mica was peeled off. A photolithography method was used to form a semiconductor magnetoresistive element pattern from the wafer carrying the InSb-based thin film.

3 to 5 show the structure of the semiconductor magnetoresistive element after patterning. 3 is a plan view thereof, FIG. 4 is a sectional view taken along line BB of FIG. 3, and FIG. 5 is a sectional view taken along line CC of FIG. As shown in these figures, a polyimide resin layer 12 and an InSb-based thin film layer 13 are formed on the insulating substrate 11.
Are sequentially laminated. A conductor layer 16 of ohmic contact such as Cu is formed in a strip shape on a portion other than the magnetic sensitive portion of the InSb thin film layer 13, and a portion called a raster electrode for short-circuiting an electric field is formed. The width W of the raster electrode was 200 μm, and the interval L of InSb between the raster electrodes was 30 μm.

Further, an electrode layer 1 for connecting to an external circuit
7 was formed by soldering, and a lead terminal made of 0.03 mm thick phosphor bronze foil was soldered. On top of that, 0.15 mm
A thick protective glass was adhered with a silicone resin to prepare a semiconductor magnetoresistive element for a potentiometer in which two semiconductor magnetoresistors were arranged so as to form a bridge circuit. 100 pieces were taken out from these elements and the characteristics were examined.
As a result, the magnetic resistance change rate at a magnetic flux density of 0.4 T is 3.4 times on average, and the difference in the midpoint potential between the magnetic field (0.4 T) and the non-magnetic field is within 0.1 V (input voltage 10 V). I was subdued.

[0036]

According to the present invention, it is possible to obtain an extremely excellent magnetoelectric conversion element in which the noise level appearing in the form of an unbalanced voltage is extremely low and the sensitivity is high.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a plan view of a semiconductor magnetoresistive element according to Example 6 of the present invention.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a sectional view taken along line CC of FIG. 3;

[Explanation of symbols]

 1 Crystalline Substrate 2 InSb System Thin Film Layer 3 Conductive Layer 4 Bonding Electrode Layer 16 Raster Electrode Layer 17 Lead Terminal Soldering Electrode Layer

Claims (7)

[Claims] 1. A stoichiometric composition having a thickness of 0.5-1.
At 5 μm, the thickness unevenness is 10% or less of the total average thickness measured by a needle type surface roughness meter, and the mobility is 30,
A magnetoelectric conversion element comprising an indium antimony-based thin film formed by vapor deposition of 000 cm ² / V / sec or more as a magnetic sensing part. 2. The magnetoelectric conversion element according to claim 1, wherein after the indium antimony-based thin film is formed on the crystalline substrate, only the thin film is transferred to another substrate to form a magnetic sensitive section. . 3. The magnetoelectric conversion element according to claim 1, wherein the crystalline substrate is mica. 4. Indium and antimony are vapor-deposited on a crystalline substrate set to a temperature at which antimony alone does not adhere, and the indium-antimony compound crystal is composed of a composite crystal of elemental indium, and the atomic ratio of all indium to antimony. When forming a composite crystal thin film having a range of 1.1 to 1.7, antimony is deposited in excess of indium at the beginning of deposition, and then indium alone or a large excess of indium is deposited at the end of deposition. A method of manufacturing a magnetoelectric conversion element, which comprises forming an indium antimony-based thin film by a step and a step of depositing an element capable of forming a compound with the excess indium. 5. The method for manufacturing a magnetoelectric conversion element according to claim 4, wherein the element capable of forming a compound with indium is one or more selected from phosphorus, arsenic and antimony. 6. The method for manufacturing a magnetoelectric conversion element according to claim 4, further comprising the step of forming an indium antimony-based thin film on a crystalline substrate and then transferring the thin film onto another substrate. . 7. The method of manufacturing a magnetoelectric conversion element according to claim 4, wherein the crystalline substrate is mica.