JP7201194B1 - Method for manufacturing magnetic field detection element - Google Patents

Abstract

【Task】
When creating a magnetic field detection element on a Si substrate, if the coil pitch is reduced in the groove of an inverted trapezoid, disconnection is likely to occur due to the step at the top of the groove and the edge of the bottom surface. Formation of the coil and lower coil is difficult.
[Solution]
By applying a negative resist resin film to the groove and curing heat treatment, the bottom of the groove is formed into an R shape, thereby preventing disconnection of the lower coil. In addition, the step between the upper part of the groove and the magnetic wire is smoothed by applying a positive resist resin film and curing heat treatment to prevent disconnection of the upper coil.
[Selection drawing] Fig. 3

Description

The present invention relates to a method of manufacturing a magnetic field detecting element having a fine coil pitch of 10 μm or less by forming inverted trapezoidal grooves in a Si substrate.

High-sensitivity magnetic sensors include Hall sensors, GMR sensors, TMR sensors, high-frequency carrier sensors, FG sensors, MI sensors, GSR sensors, and the like. Among these sensors, Hall sensors, GMR sensors, TMR sensors, and high-frequency carrier sensors have been made smaller and thinner by integrating elements with ASICs, but improvement in detection sensitivity is a problem.
On the other hand, the FG sensor, MI sensor, and GSR sensor have high sensitivity, but the element and ASIC are arranged separately and joined by wire bonding, and the problem is to make the sensor thinner and smaller, and to further increase its sensitivity. be.

In order to solve this problem, the present inventors worked on the development of technology for miniaturizing the coil pitch of the magnetic field detection element to increase sensitivity and miniaturization. Reference 1).
Patent Document 1 discloses an MI element with a coil pitch of 14 μm. However, although the manufacturing method has been continuously improved since then, no detailed disclosure of the technology has been made at present.
In addition, 10 μm, 5 μm, and 3 μm are the issues for further miniaturization of the coil pitch.

In addition, the present inventors have found the optimum tension heat treatment conditions for achieving both magnetic properties and GSR properties (Patent Document 2). However, although the manufacturing method has been continuously improved since then, no detailed disclosure of the technology has been made at present.

Japanese Patent No. 5747294 Japanese Patent No. 6924453

RIE (Reactive Ion Etching) is generally known as a method of forming a groove in a substrate for arranging a magnetic wire of a magnetic field detecting element. However, a groove formed by RIE has a rectangular parallelepiped shape, and it is difficult to form a coil on the side surface of the groove.

In order to form a trapezoidal groove, the etching rate differs depending on the orientation of the Si substrate. Therefore, by using the Si substrate 10 with the <100> crystal orientation, an inverse trapezoidal groove as shown in FIG. 1 is formed by anisotropic etching. of grooves 11 can be formed.
However, even with such an inverted trapezoidal shape, sharp edges peculiar to the Si substrate are generated at the upper portion 101 and the bottom portion 102 of the groove. With such an edge, the more the coil pitch becomes finer, the more likely it is that the metal film will be disconnected (disconnection) during coil formation, making it more difficult to form a fine coil pitch.

A thermal oxide film made of SiO ₂ having a thickness of about 100 nm is formed on a Si substrate of crystal orientation <100>.
First, in order to remove the thermal oxide film 12, a resist is applied to the entire Si substrate 10, exposed using a line-shaped mask corresponding to a band-shaped range for arranging the lower coil, the upper coil and the magnetic wire. Development is performed, and the thermal oxide film is removed by RIE to expose the Si surface of the groove forming portion. At this time, in the portion corresponding to the alignment mark portion, a cross mark type mask and a plurality of rectangular masks are used, and exposure, development, and RIE are performed at the same time as the line mask to form alignment marks at the same time.

Next, it is immersed in an alkaline etchant (for example, potassium hydroxide solution). Since the Si substrate has different etching rates depending on its orientation, the use of the Si substrate 10 with the <100> crystal orientation enables the formation of the inverted trapezoidal groove 11 as shown in FIG. 1 by anisotropic etching.
Since it is necessary to form a coil having a fine coil pitch around the magnetic wire in the vicinity of the magnetic wire, it is essential that the shape of the groove is an inverted trapezoid.

After etching to a predetermined groove depth, the thermal oxide film 12 remaining on the Si substrate other than the groove is removed by RIE. This is because wet etching progresses not only in the groove depth direction but also in the groove width direction, so that the Si under the thermal oxide film is etched, leaving the thermal oxide film in the form of eaves 121 . Since the metal film used for forming the lower coil is not attached to the underside of the eaves, disconnection may occur. Also, the edge 102 of the bottom of the groove remains sharp, which also causes disconnection.

Next, as shown in FIG. 2, after forming a Si ₃ N ₄ insulating film 21 for insulating the Si substrate and the lower coil over the entire substrate, a negative resist-based resin film 22 is applied, exposed, baked, and developed. After that, the resin film is left only in the grooves and cured by heat treatment. As a result, an R shape (R portion) 201 is formed at the bottom of the groove. Here, the temperature of the curing heat treatment is 250-350.degree.

Next, a metal film is deposited to form the lower coil. Thereafter, a lower coil pattern is formed through resist coating, exposure, and development processes. At this time, an alignment mark is also formed at the same time by arranging a cross pattern and a plurality of rectangular shapes for processes after the lower coil in the alignment mark portion.
By removing the resist after plating and wetting, a lower coil having a thickness of 0.2 to 1.0 μm is formed in the groove. An R portion is formed at the bottom of the groove, and even fine wiring with a line width of 0.5 to 2 μm can form the lower coil without disconnection.

Next, a magnetic wire is placed in the groove in which the lower coil is formed by applying a tension of 50 to 100 kg/mm ² . At this time, the magnetic wire is fixed to the jig with an adhesive, tape, or the like in order to maintain its tension. After that, a negative resist resin film is applied, and heat treatment is performed at 90° C. for temporary fixing of the magnetic wire. Then, the magnetic wires are fixed inside the grooves by performing exposure, baking, development, and curing heat treatment, and the wires are heat-treated while maintaining tension, so that the GSR characteristics can be improved. Here, the temperature of the curing heat treatment is 250-350.degree.

A portion of the insulating glass covering the magnetic wire is removed in order to provide wire terminals (both ends of the magnetic wire) to the magnetic wire fixed inside the groove.
Generally, hydrofluoric acid treatment is known, but as a result of the trial production, the damage around the wire terminal is large, and it has a great influence on the device formation. Therefore, after intensive investigation, it was found that the glass can be removed by the RIE method using CF ₄ gas, and henceforth the glass is removed by the RIE method.

Next, a positive resist resin film is applied to the upper portion of the magnetic wire, and a curing heat treatment is performed. Thereby, the step between the groove and the magnetic wire can be eliminated.

Generally, a negative type resist is known as a resist to be left as a structure. However, since the negative-type resist has sharp edges, the metal film necessary for the upper coil does not stick well to this portion in the subsequent processes, and there is a concern of disconnection.
Therefore, a positive resist-based resin film, which is not generally used as a resist to be left as a structure because the shape changes after the curing heat treatment, was investigated. As a result, the edge shape of the positive resist resin coating can be smoothly improved after the curing heat treatment, and steps can be eliminated without fear of disconnection.

Then, a metal film is deposited to form the upper coil. After that, the upper coil is formed on the magnetic wire and the electrode pattern (including wire terminals and wiring) is formed on the substrate by resist coating, exposure, and development processes. A coil is formed.
The connecting portion with the lower coil has a gentle shape, and the upper coil can be formed without wire breakage, so that a detection coil that encircles the magnetic wire can be obtained.

Formation of a fine pitch coil of 10 μm or less by making the shape of the inverted trapezoidal groove bottom of the Si substrate on which the magnetic wire is arranged and the shape of the connecting portion between the upper coil and the lower coil smooth with an R shape. becomes possible.

According to the present invention, it is possible to prevent disconnection of the coil and to manufacture a highly sensitive magnetic field detection element having a fine pitch coil of 10 μm or less on a Si substrate.

FIG. 4 is a diagram showing upper edges, lower edges, and eaves in an inverted trapezoidal groove formed in a Si substrate; FIG. 10 is a diagram showing an Si ₃ N ₄ insulating film formed on the entire surface of the Si substrate, and the bottom of the groove having an R shape due to the negative resist resin coating. A plan view showing a magnetic field detection element and alignment marks arranged on a Si substrate. A plan view of a magnetic field detection element provided with a magnetic wire coated with insulating glass on a Si substrate, a detection coil composed of a lower coil and an upper coil surrounding the magnetic wire, and electrodes. Cross-sectional view of A1-A2 line in FIG.

A method of manufacturing a GSR element comprising a Si substrate 10 having a width of 0.40 mm and a length of 0.50 mm will be described below with reference to FIGS.

step (a)
A thermal oxide film made of SiO ₂ with a thickness of about 100 nm is formed on a Si substrate having a crystal orientation <100>.
First, in order to remove this thermal oxide film, the entire substrate is coated with a resist, exposed using a line _- shaped mask, developed, and CF4 gas is used to remove the thermal oxide film by RIE (Reactive Ion Etching). is removed to expose the Si surface.

step (b)
Next, it is immersed in a potassium hydroxide solution. Since the Si substrate has different etching rates depending on its orientation, the use of the Si substrate 10 with the <100> crystal orientation enables the formation of the inverted trapezoidal groove 11 as shown in FIG. 1 by anisotropic etching.

step (c)
After etching to a predetermined groove depth, the thermal oxide film 12 is removed by CF ₄ RIE.

step (d)
After a Si ₃ N ₄ insulating film 21 for insulating the Si substrate and the lower coil is formed over the entire substrate to a thickness of 300 nm, a negative resist-based resin film 22 is applied, and after exposure, baking, and development, the resin film is applied only to the grooves. A curing heat treatment is performed at 280° C. for 1 hour. As a result, an R shape (R portion) 201 is formed at the bottom of the groove (FIG. 2).

step (e)
Next, in order to form the lower coil, a metal film is formed to a thickness of about 100 nm. Thereafter, a lower coil pattern is formed through resist coating, exposure, and development processes.
By removing the resist after plating and wetting, a lower coil having a line width of 1.2 μm and a thickness of 0.7 μm is formed in the groove. An R portion is formed at the bottom of the groove, and the lower coil can be formed without disconnection even with fine wiring having a line width of 1 μm.

step (f)
A magnetic wire is placed in the groove in which the lower coil is formed with a tension of 70 kg/mm ² applied. At this time, the magnetic wire is fixed to the jig with an adhesive, tape, or the like in order to maintain its tension. After that, a negative resist resin film is applied, and heat treatment is performed at 90° C. for temporary fixing of the magnetic wire. Then, exposure, baking, development, and curing heat treatment at 280° C. for 1 hour fix the magnetic wire inside the groove, and the wire is heat treated while maintaining tension, so that the GSR characteristics can be improved.

step (g)
In order to provide wire terminals (both ends of the magnetic wire) to the magnetic wire, part of the insulating glass covering the magnetic wire is removed by RIE using CF ₄ gas.

process (h)
Next, in order to eliminate the step between the groove and the magnetic wire, the entire substrate is coated with a positive resist resin film, exposed, developed, and cured at 280° C. for 1 hour to be fixed inside the groove.

step (i)
A metal film having a thickness of about 100 nm is formed to form the upper coil. After that, an upper coil and an electrode pattern are formed on the upper part of the magnetic wire by resist coating, exposure, and development processes. After plating and wetting, the resist is removed to form a line width of 1.2 μm and a thickness of 0.2 μm on the upper part of the magnetic wire. An 8 μm top coil is formed. The connecting part with the lower coil has a gentle shape, and the upper coil is also formed without disconnection. At the same time, wire terminals, electrodes and wiring are also formed.

Regarding the GSR element manufactured by the above steps, a plan view (a) showing a plurality of magnetic field detection elements (aggregates) arranged on a Si substrate and a plurality of alignment marks, and insulating glass on the Si substrate. A plan view (b) of a magnetic field detection element including a coated magnetic wire, a detection coil consisting of a lower coil and an upper coil surrounding the magnetic wire, and electrodes, and a cross-sectional view of the A1-A2 line in the plan view (b) ( c) is shown and described.
First, the plan view of FIG. 3(a) will be described.
The Si substrate 30 is cut into 20 mm squares, on which a large number of magnetic field detection elements 30a and alignment marks 30b are arranged at the four corners of the substrate. The magnetic field detection element is manufactured in units of this substrate, and finally separated into individual pieces.

Next, the plan view of FIG. 3(b) will be described.
The entire surface of the Si substrate 30 is covered with a Si ₃ N ₄ insulating film 301 and has a width (horizontal direction) of 0.4 mm and a length (vertical direction) of 0.5 mm. The thickness is 0.55 mm.

An inverted trapezoidal groove 31 and a lower coil 32 are formed on a Si substrate 30, and a magnetic wire 33 is arranged and fixed. A detection coil consisting of a lower coil 32 and an upper coil 34 wraps around the magnetic wire. The detection coil has a coil pitch of 3.0 μm, a line width of 1.2 μm, and a thickness of 0.7 μm.

Two wire terminals 331 are formed on the magnetic wire 33, and a wire 332 and a wire electrode 333 are formed to be connected to the wire terminals 331, respectively. Two wirings 321 and 341 and two coil electrodes 342 are formed to connect the lower coil 32 and the upper coil 34 .

Next, description will be made with reference to a cross-sectional view taken along the line A1-A2 shown in FIG. 3(c).
An inverted trapezoidal groove 31 is formed on a Si substrate 30 , and the surface in the groove 31 is covered with a Si ₃ N ₄ insulating film 301 . A negative resist resin film 302 having an R shape (104) is formed on the bottom of the trench covered with the Si ₃ N ₄ insulating film 301 .

After forming the lower coil 32 on the negative resist resin film 302 , the magnetic wire 33 is arranged and fixed by the negative resist resin film 303 .
The magnetic wire 33 is covered with insulating glass with a thickness of 1.0 μm and has a diameter of 12 μm.

A positive resist-based resin film 304 is formed between the groove 31 and the magnetic wire 33 in order to eliminate the step between the groove 31 covered with the Si ₃ N ₄ insulating film 301 and the magnetic wire 33 .
This positive resist-based resin film 304 is also spread over the magnetic wire 33, and the upper coil 34 is formed thereon.
The lower coil 32 and the upper coil 34 are connected in a gentle shape with respective connecting portions (321, 341).

Through the above steps, the bottom of the groove where the magnetic wire is arranged and the connecting portion of the upper coil and the lower coil using the Si substrate are each rounded to form a gentle R shape, thereby forming a fine coil pitch of 10 μm or less. It becomes possible to manufacture a highly sensitive magnetic detection element.

INDUSTRIAL APPLICABILITY The present invention realizes the manufacture of a magnetic field detection element having a fine coil pitch using a Si substrate, and is expected to be used as a highly sensitive magnetic field detection device.

1: Si substrate with grooves formed 10: Si substrate 101: Edge of top of groove 102: Edge of bottom of groove 121:
Eaves 11: Inverted trapezoidal groove formed in Si substrate ₂ : R shape at groove bottom 201: R portion at groove bottom 21: _Si3N4 insulating film 22: Resin coating 3a: Magnetic field detection element (aggregate) Plan view of alignment mark 3b: Plan view of magnetic field detection element 3c: Cross-sectional view of magnetic field detection element 30: Si substrate,
30a: magnetic field detection element 30b: alignment mark 301: _Si3N4 insulating film, 302: negative resist resin coating, 303: negative resist resin coating ₍ for fixing magnetic wires), 304: positive resist resin coating (removing steps) for)
31: inverted trapezoidal groove 32: lower coil 33: magnetic wire 331: wire terminal, 332: wiring, 333: wire electrode 34: upper coil 341: wiring, 342: coil electrode

Claims (2)

A Si substrate coated with a thermally oxidized _SiO2 film, a magnetic wire coated with insulating glass on the Si substrate, a detection coil consisting of a lower coil and an upper coil surrounding the magnetic wire, and a plurality of electrodes. In a method for manufacturing a magnetic field detection element comprising a magnetic field detection element,
(1) A resist is applied to the entire surface of the Si substrate, and exposure is performed using a line-shaped mask in the element forming portion and a mask having a cross shape and a plurality of rectangular shapes arranged as alignment marks in the alignment mark forming portion, a step of developing and removing the thermal oxide film SiO ₂ by RIE using CF ₄ gas to expose the Si surface;
(2) A step of immersing the Si substrate with the Si surface exposed in a potassium hydroxide solution (40 wt %) to form alignment marks in which a plurality of inverted trapezoidal grooves, a cross shape, and a plurality of rectangular shapes are arranged. When,
( ₃ ) removing the thermal oxide film _SiO2 remaining outside the groove by RIE using CF4 gas;
(4) After a Si ₃ N ₄ insulating film is formed on the entire surface of the Si substrate, a negative resist-based resin film is applied, exposed and developed to leave the resin film only in the grooves, and the bottoms of the grooves are cured by heat treatment. forming an R shape in the
(5) forming alignment marks for the lower coil, the electrode wiring on the substrate, and the lower coil and thereafter along the inverted trapezoidal groove;
(6) a step of inserting, temporarily fixing, cutting, arranging and temporarily fixing the magnetic wires along the plurality of grooves while applying a tension of 50 to 100 kg/ ^mm2 ;
(7) Applying a negative resist resin film on the entire surface of the substrate, exposing and developing to leave the negative resist resin film only on the magnetic wire portion, and performing a curing heat treatment while applying the tension to remove the wire from the wire. fixing in the groove;
(8) removing, by CF ₄ -RIE, the insulating glass covering the wire in the wire electrode portion for joining the wire and the electrode wiring;
(9) a step of applying a positive resist-based resin coating to the entire surface of the substrate, exposing and developing to leave the positive resist-based resin coating only in the grooves and magnetic wire portions, and performing a curing heat treatment to smooth the steps;
(10) forming an upper coil and electrode wiring;
(11) singulating an assembly of the magnetic field detection elements each composed of the magnetic wire, the detection coil, and the electrode;
A method of manufacturing a magnetic field detection element, comprising: In step (6) of claim 1,
After aligning the magnetic wires along the grooves on the substrate by applying a tension higher than the elastic limit, the magnetic wires are temporarily fixed with an adhesive, leaving a tension of 10 kg/mm ² to 76 kg/mm ² , and performing the process. A method of manufacturing a magnetic field detecting element according to (7), characterized in that tension heat treatment is performed at a temperature of 250°C to 350°C.

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