JP3155670B2 - Manufacturing method of magnetoelectric conversion 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 method for manufacturing a magnetoelectric conversion element, and more particularly to a method for manufacturing an indium-antimony-based magnetoelectric conversion element having excellent reliability.

[0002]

^2. Description of the Related Art Indium antimony (hereinafter abbreviated as InSb) is a compound semiconductor such as indium arsenide (InAs, mobility 30,000 cm ² / V / sec).
Gallium arsenide (GaAs, mobility 7,000 cm ² /
V / sec), which is much higher than the electron mobility (78,0).
(00 cm ² / V / sec), it is known that it is suitable as a material for a magnetoelectric conversion element. here,
VTR, floppy disk, C
Hall elements used as rotational position detection sensors for drive motors such as D-ROMs; semiconductor magnetoresistors used as potentiometers, rotation detection sensors for gears, or magnetic sensors for banknote recognition for detecting magnetic ink patterns applied to banknotes And the like.

In order for a magnetoelectric conversion element using InSb as a material to function as a sensor, it is necessary to reduce the thickness of InSb to about 1 μm in order to secure a practical resistance value.

Further, in order to use the high sensitivity characteristics of InSb, it is necessary to secure high electron mobility at the same time as thinning the film. One method to meet this demand is to cut out a single crystal and polish it to form a thin film. However, according to this method, although electron mobility comparable to that of a single crystal can be secured, it is difficult to uniformly form a desired thin film having a thickness of about 1 μm. In addition, this method has a problem that the cost is very high.

Accordingly, various methods for thinning InSb that can be mass-produced and obtain desired characteristics have been studied. For example, Japanese Patent Publication No. 51-45234 discloses that
A so-called transfer method is shown. That is, after forming an InSb thin film on a crystalline substrate such as mica by vapor deposition, this thin film is bonded to another insulating substrate using an adhesive such as an epoxy resin, and then the crystalline substrate is removed. is there. In this case, since a crystalline substrate is used, there is an advantage that an InSb thin film having a desired film thickness can be formed with a relatively high mobility and good mass productivity if the deposition conditions are selected.

Further, the present inventors have proposed various conditions for forming a high mobility InSb thin film. Tokuhei 1-1
In JP 3211, the atomic ratio of In to Sb is 1.
It has been clarified that an excess of In of 1.1 to 1.7 instead of 0 is a necessary condition for forming a high mobility InSb thin film. Further, the substrate temperature, In and Sb
And other necessary conditions for increasing the mobility such as flux (Japanese Patent Publication No. 1-13211, Japanese Patent Publication No.
No. 15135, Japanese Patent Publication No. 2-47849, Japanese Patent Publication No. 3-59571). Thus, I
The mobility is extremely high, for example, 6
A thin film that reaches as much as 000 cm ² / V / sec can be formed. Then, such a thin film was transferred to another insulating substrate such as ferrite or ceramic via a resin, and was patterned and assembled, whereby a Hall element and a semiconductor magnetoresistive element were formed.

On the other hand, Japanese Patent Application Laid-Open No. 59-202677 discloses that 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, and then Sb is vapor-deposited. Finally, it is shown that a thin film having an atomic ratio close to 1.0 is obtained. In other words, it is shown that by preparing an InSb-based composite crystal thin film containing excess In in advance and then reducing the amount of single In, a magneto-electric conversion element having a high Hall coefficient and high resistance can be formed.

[0008]

However, when such a thin film is used, a passivation layer is provided between the package resin and the thin film in order to secure practical reliability, and particularly to improve moisture resistance. For example, it was necessary to take an additional step of forming an alumina thin film.

The inventors of the present invention have studied the reliability problem in more detail, but have come to find that the problem is basically related to a deposited thin film.

In the case of the Hall element, the reliability such as moisture resistance can be secured by evaporating alumina before the transfer, but in the case of the semiconductor magnetoresistive element, the sensitivity is particularly important. It is necessary to perform a treatment for preventing humidity from entering without performing alumina deposition.

On the other hand, with the development of technology, the required level of reliability has been increased, and there has been a demand for cost reduction. Therefore, high reliability can be achieved without introducing complicated steps, that is, without depositing alumina. It has been demanded to manufacture an element having the same.

The present invention has been made in view of the above circumstances, and has as its object to provide a method of manufacturing a magnetoelectric conversion element capable of producing a highly reliable magnetoelectric conversion element.

[0013]

According to the present invention, InSb itself is a very stable compound that is difficult to be oxidized, and the factor that degrades the reliability is excessive elemental In and excessive elemental In.
n can be eliminated, and the use of the thin film formed in this way makes it possible to produce a device with extremely improved reliability without any other processing. Was.

That is, according to the present invention, a composite crystal of a crystal of an indium antimony (InSb) compound and a simple element of indium (In) is provided on a substrate, and all the indium (I)
The atomic ratio of n) to antimony (Sb) is 1.1 to 1.1.
Indium antimony (InSb) in the range of 1.7
A composite crystal thin film is formed by vapor deposition, and then the excess amount of antimony (S) is twice or more the amount required to convert the remaining indium (In) into indium antimony (InSb).
b) vapor-depositing at a substrate temperature higher than that at which re-evaporation of antimony (Sb) occurs.

The substrate used in the present invention is preferably a mica that allows the InSb crystal to grow well and that can be peeled immediately after the InSb thin film does not strongly adhere.

In order to form an InSb thin film on this substrate, a vapor deposition method such as ordinary vapor deposition, molecular beam epitaxy (MBE), and sputtering can be used. On this occasion,
From the viewpoint of practical characteristics, the thickness of the thin film is preferably in the range of 0.1 to 2 μm.

In the present invention, first, in the InSb-based thin film, the total In of S and In in InSb and S
It is necessary to control so that the atomic ratio to b is in the range of 1.1 to 1.7. 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 the crystallinity is poor and the noise is large. On the other hand, when the ratio exceeds 1.7, pinholes are generated, and the yield is reduced. A particularly preferred atomic ratio is 1.2 to 1.6.
In this range, the crystallinity of the thin film is good,
In addition to the high mobility, the noise level is low and the uniformity is good.

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

For example, according to Japanese Patent Publication No. 3-59571, when the average atomic ratio of In to Sb is vapor-deposited in the range of 1.1 to 1.7, the arrival speed ratio of In to Sb in the initial stage of vapor deposition is 1 0.0 or less, and when the substrate temperature (absolute temperature) T is selected so as to fall within the range of the following equation, a high mobility InSb-based composite thin film can be obtained.

[0020]

Tc ≦ T ≦ Tc + 30 where Tc is the substrate temperature T at the boundary given by the following equation.
c.

[0021]

1 / Tc = 1.29 × 10 ⁻³ −3.84 × 10
^-5 logP (Tc is the substrate temperature at the boundary (absolute temperature), P is the degree of vacuum during deposition (Torr)) At this stage, the InSb-based composite crystal thin film
In this embodiment, simple In deposited from the inside of the InSb film is distributed on the nSb film surface.

Next, InS in which In is extremely excessive
In the b-type composite crystal thin film, an excess of at least 2 times, more preferably, 4 times more than the amount required to convert the single In into InSb.
More than twice the amount of Sb is deposited at a substrate temperature higher than that at which re-evaporation of Sb occurs. As a result, the single element In in the composite crystal becomes InS
b, but the mobility is kept high. If it is less than twice, In remains, and it is not possible to secure more reliability than in the case of a method of depositing alumina later.

The temperature of the substrate depends on the degree of vacuum in the vapor deposition chamber, but can be estimated from thermodynamic data. See, for example, Stul, a book by Sinke Quantum, Thermodynamic Properties of the Elements (Thermodynamic Properties).
s of The Elements, D.C. R. St
ul and G. C. Sinke, America
n Chemical Society, 1956), 9.9 × 10 ⁻⁵ Torr at 427 ° C.
r, the vapor pressure becomes 6.5 × 10 ⁻³ Torr at 527 ° C., so that if the degree of vacuum of the evaporator is, for example, 10 ⁻⁶ Torr, Sb is re-evaporated at a substrate temperature of 427 ° C. Become.

In the present invention, re-evaporation is suppressed by excessively depositing Sb, and excess single element In is converted to In.
A condition is selected in which Sb is formed and excess Sb does not adhere.
For example, in a vacuum of 10 ¹⁶ Torr, the substrate temperature is set to 500 ° C.
Under such a condition, Sb is deposited in an amount of 10 times the amount necessary for converting excess In into InSb. In this manner, a thin film having an atomic ratio of In to Sb of 1.0 can be finally obtained.

As the Sb evaporation source, not only Sb alone but also InSb or GaSb can be used. Further, Sb may be added to these. In this case, Sb evaporates,
It is necessary to select a boat temperature condition under which In and Ga do not evaporate.

Next, the InSb thin film formed on the mica substrate as described above is bonded to another insulating substrate via a resin. In this case, since the insulating substrate is a substrate for semi-permanently holding the element, a highly reliable substrate is preferable. For example, inorganic materials include alumina,
Ferrite, silicon nitride, quartz, sapphire, or the like can be used. As described in JP-B-51-45234, when ferrite is used, the sensitivity can be further greatly increased by newly mounting a magnetic focusing chip.

The resin for bonding the InSb thin film to the insulating substrate can be selected from a thermosetting resin, a thermoplastic resin and the like, for example, an epoxy resin and a polyimide resin. In addition, an extremely simple method can be used for adhesion. For example, there is a method in which a resin is dropped on a thin film, an insulating substrate is placed thereon, and the film is heated or further pressurized and left for a predetermined time. Screen printing may be used instead of dropping. In general, under an appropriate viscosity of the resin, the thickness of the resin layer as the adhesive layer can be uniformly transferred to several μm.

Next, the mica is peeled off, and an InSb thin film carried on a semi-permanent insulating substrate is formed.

In the substrate carrying the InSb thin film formed as described above, electrodes are formed and individual elements are formed in a patterning step. Al, Ni,
Cr, Cu, Pd, Au or the like is used, and the electrode generally has a laminated structure of these metals. Further, individual pellets are formed by a dicing process, these pellets are fixed to a lead frame by a die bonder or the like, the electrodes of the pellets are connected to the lead frame by a wire bonder or the like, and a magnetoelectric conversion element is formed by a molding process or the like.

[0030]

The magneto-electric conversion device thus manufactured can produce an InSb thin film free of excessive In, and has extremely high reliability.

[0031]

Next, the present invention will be described in more detail by way of examples.

First, mica was used as a substrate for crystal growth,
These 12 substrates for crystal growth are set on a disk-shaped substrate holder. Holes having a size of 52 mm square are formed concentrically on the substrate holder that is driven to rotate, and the substrate for crystal growth is placed in these holes. The substrate holder is 3
InSb was installed in a vacuum evaporation apparatus having two evaporation source boats, and InSb was evaporated on a substrate for crystal growth using the vacuum evaporation apparatus. At the time of vapor deposition, the degree of vacuum is 7 ×
Set to 10 ^-6 Torr, set the substrate temperature to 400 ° C,
Total deposition time is 17 minutes, final temperature is 480 ° C
And During this time, the substrate temperature rising rate is set to 0 to 0 after the start of vapor deposition.
0 ° C./min for 6 minutes, 6 to 14 minutes, and 14 to 17 minutes, 1
It was set to 2.5 ° C / min and 0 ° C / min.

Assuming that the amounts of In and Sb flying from the boat under these conditions are 2 g and 3 g, respectively, the ratio of In to Sb in the first 14 minutes is about 30% excess of In.

In the last three minutes, only Sb was converted to the amount of flight from the equivalent of the excess single element In by about 1.5 times,
Sb was vapor-deposited in excess of 2, 4 and 8 times, respectively.
Note that, for comparison, the case where only Sb was not deposited (0
Times) were also prepared.

Under each of the deposition conditions, each of the 12 thin films showed the same properties. In addition, when the composition was excessively increased by 8 times, the composition analysis of one of the 12 wafers was performed by XMA, and the composition ratio of the entire wafer was 1.0. further,
When the mobility of this thin film was measured by the van der Pauw method, 45,000 ± 500 cm ² / V / sec.
c. The thickness was 0.7 ± 0.05 μm (measured by Dick tack after patterning).

Of the obtained thin films, evaporation of only Sb was carried out for 2 hours.
Although it was close to a golden color when it was performed at twice or more times, those without Sb only deposition (0 times) and those with 1.5 times Sb deposition had a whitish appearance,
Thin films made according to the invention can be visually identified. Observation of the film surface with a metallurgical microscope magnified 700 times or more shows that, before Sb vapor deposition, single element In deposited in a hemispherical shape is crushed after Sb vapor deposition. The difference in shape between the surface states and the simple substance In
It is considered that the difference between the film constituents that gives InSb changes the appearance color tone.

Next, a 50 mm square ferrite is prepared,
A polyimide resin was dropped on the InSb thin film, ferrite was overlaid thereon, and a weight was placed and left at 200 ° C. for 12 hours. Next, the temperature was returned to room temperature, and the mica was peeled off. This InS
Photolithography was used to form a Hall element pattern from a wafer carrying the thin film b.

FIGS. 1 and 2 show the structure of the Hall element after patterning. FIG. 1 is a plan view thereof, and FIG.
It is a line sectional view. As shown, a polyimide resin layer 2 and an InSb thin film layer 3 are sequentially laminated on an insulating substrate 1. A conductor layer 4 made of ohmic contact Cu or the like is formed in a portion of the InSb thin film layer 3 other than the center magneto-sensitive portion 3a, and a Ni layer 5 as an electrode layer for bonding is further formed thereon. An Au layer 6 is laminated. In this embodiment, Cu, Ni, Au
The thickness of each layer was about 3 μm. The size of the pellet was 0.8 mm square.

Next, dicing is performed to divide the individual elements, these pellets are die-bonded to the island portions on the lead frame, and furthermore, the leads and the electrode portions of the pellets are connected by an Au wire by wire bonding to make electrical connection. did. Further, the Hall element was completed through processes such as transfer molding and electrical inspection.

After removing 100 pieces from these elements and performing solder dip at 300 ° C. for 5 seconds, 85 ° C.
A reliability test was performed in which the sample was left in a thermo-hygrostat at 85% RH for 200 hours.

Before and after this reliability test, the change in the resistance value indicating the electro-magnetic characteristics of the Hall element and the value of the Hall voltage in the 0.05 terrace were converted into a change rate and evaluated.

An excess of 8 times, such as an excess of simple In, etc.
When only b is deposited, the rate of change of the resistance value is about 0.6%,
The change rate of the Hall voltage was about 0.5%, and even with the deviation of the change rate, the resistance value was about 0.3% and the Hall voltage was about 0.4%, and good results were obtained.

An excess of 4 times the equivalent amount of the excess In
When only b is deposited, in the component analysis by XMA,
The composition ratio was 1.0. After conducting a reliability test,
The average change rate of the resistance value was 0.9%, and the change rate of the Hall voltage in the 0.05 terrace was 0.5%. Also, in the deviation of the change rate, the resistance value is 0.3% and the Hall voltage is 0.5%.
%, And good results were obtained.

An excess of two times the equivalent amount of the excess elemental In
When only b is deposited, in the component analysis by XMA,
The composition ratio was 1.0. After conducting a reliability test,
The average change rate of the resistance value was 1.7%, and the change rate of the Hall voltage in the 0.05 terrace was 0.7%. Also, in the deviation of the change rate, the resistance value is 0.3% and the Hall voltage is 0.6%.
%, And good results were obtained.

In the case where only Sb was vapor-deposited with an excess of 1.5 times the equivalent amount of the excess single element In, the In (10
1) A peak was observed. An element was fabricated using this thin film, and a reliability test was performed. As a result, the rate of change in resistance was 9.7%, and the rate of change in Hall voltage in 0.05 terraces was about 8.9%. Although this is slightly improved as compared with the case where Sb is not deposited (0 times), the rate of change is larger than the case where only Sb is deposited with twice the equivalent amount of the excess single element In. This result also indicates that the presence of a small amount of In lowers the reliability.

When the latter half of Sb alone was not deposited, that is, when the equivalent amount of the excess elemental In was excessively increased by 0 times, S
When only b is deposited, the average of the rate of change of the resistance value is 11.
1%, 0.05 Hall voltage change rate in terrace is 1
0.5%. Also, the deviation of the rate of change was 0.8% for the resistance value and 0.7% for the Hall voltage.

When the deposition of Sb alone was not performed, that is, in a state of excess In, a Hall element was prepared using a thin film obtained by evaporating alumina at about 2,500 ° on the thin film, and a similar reliability test was performed. As a result, the average rate of change in resistance was about 2.5%, and the average rate of change in Hall voltage in the 0.05 terrace was about 3.2%. From this Sb
It can be seen that the case where the excess amount of elemental In is vapor-deposited at least twice as much as the equivalent amount of the elemental In is more reliable than the vapor-deposition of alumina. Further, this result indicates that the excess In
Indicates that it has an adverse effect on moisture resistance.

The ratio between the excess equivalent of the single element In and the equivalent amount of Sb calculated from the Sb jump amount and the solder dip (300
Table 1 shows the results of a humidity storage test (85 ° C., 85% RH) after (5 ° C., 5 seconds).

[0049]

[Table 1]

Next, as another embodiment, in the same manner as in the above embodiment except that the amounts of In and Sb jumped from the boat were changed to 2.1 g, 4 g, 1.5 g and 3 g, respectively. An InSb thin film having a composition of 1.0 was formed. Each of these mobilities is 41,000 ± 500c
m ² / V / sec and 37,000 cm ² / V / sec. When a Hall element was formed from these thin films in the same manner as in the above embodiment, and subjected to a reliability test,
Was excessively deposited at least twice the equivalent amount of the elemental In, the average of the rate of change and the average of the deviations were both 1% or less, and good results were obtained.

Further, only the electrode structure is made of 3 μm Cu,
Even when the laminated structure was changed to 5 μm Ni and 0.5 μm Pd, the result of the reliability test was as excellent as the above.

Next, a semiconductor magnetoresistive element was prepared using the same thin film as that for forming the Hall element.

A 50 mm square alumina substrate was prepared, and In
A polyimide resin was dropped on the Sb thin film, an alumina substrate was overlaid on the thin film, and a weight was placed and left at 200 ° C. for 12 hours. Then it was returned to room temperature and the mica was stripped off. This In
Photolithography was used to form a semiconductor magnetoresistive element pattern from a wafer carrying an Sb thin film.

FIGS. 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, the insulating substrate 11
On top are the polyimide resin layer 12 and the InSb thin film layer 1
3 are sequentially stacked. A conductor layer 16 made of ohmic contact, such as Cu, is formed in a strip shape in a portion other than the magnetically sensitive portion of the InSb thin film layer 13 to form a portion called a raster electrode for short-circuiting an electric field. 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 17 for connecting to an external circuit was formed with solder, and a lead terminal made of phosphor bronze foil having a thickness of 0.03 mm was soldered. On top of that, 0.15m
An m-thick protective glass was adhered with a silicone resin to prepare a semiconductor magnetoresistive element for a potentiometer.

After 100 pieces were taken out of these elements and subjected to a solder dip at 300 ° C. for 5 seconds,
A reliability test was conducted in which the sample was left for 200 hours in a thermo-hygrostat at 85 ° C. and 85% RH. Before and after this reliability test, the resistance value, which is an item indicating the electro-magnetic characteristics of the semiconductor magnetoresistive element, and the degree of change in the magnetoresistance in the 0.4 terrace were each converted and evaluated. The rate of change of the resistance value and the rate of change of the magnetoresistance were both 1% or less on average. Also, the deviation of the change rate was 0.2% in the resistance value and 0.3% in the magnetoresistance change rate.

However, a semiconductor magnetoresistive element was prepared without performing the latter deposition, and the same reliability test was performed. As a result, both the rate of change of the resistance value and the rate of change of the magnetoresistance were 10%.
% Or more. In a semiconductor magnetoresistive element, when alumina is vapor-deposited on a vapor-deposited film, the magnetoresistance ratio decreases by 10%. Therefore, sensitivity is emphasized and alumina is not vapor-deposited. Therefore, the reliability of the semiconductor magnetoresistive element is significantly improved by the present invention.

[0059]

As is apparent from the above description, the magnetoelectric conversion element of the present invention is excellent in moisture resistance and extremely excellent in reliability without forming passivation of alumina or the like.

[Brief description of the drawings]

FIG. 1 is a plan view of a Hall element to which the present invention is applied.

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

FIG. 3 is a plan view of a semiconductor magnetoresistive element to which the present invention is applied.

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]

 REFERENCE SIGNS LIST 1 insulating substrate 2 resin layer 3 InSb thin film layer 4 conductive layer 5 bonding electrode layer 6 raster electrode layer 7 lead terminal soldering electrode layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C30B 23/06 C30B 23/06 G01R 33/09 H01L 43/12 H01L 43/12 G01R 33/06 R (72) Inventor Hideki Araki Asahi Kasei Electronics Co., Ltd., 6-4100 Asahicho, Nobeoka City, Miyazaki Prefecture (72) Inventor Fujimi Kumazawa 6-4100 Asahicho, Nobeoka City, Miyazaki Prefecture Asahi Kasei Electronics Corporation (56) -40672 (JP, B1) JP-B-62-50993 (JP, B2) JP-B-62-50994 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 14/00- 14/58 C01G 30/00 C30B 23/06 G01R 33/09 H01L 43/12

Claims (1)

(57) [Claims] 1. A substrate comprising a composite crystal of a crystal of an indium antimony compound and a simple element of indium, and having an atomic ratio of all indium to antimony of 1.1 to 1.
The indium-antimony composite crystal thin film in the range of 7 is formed by vapor deposition, and then at least a two-fold excess of antimony in excess of the amount required to convert indium to indium-antimony is deposited at a substrate temperature higher than the re-evaporation of antimony. A method for manufacturing a magnetoelectric conversion element, comprising: