A fluxgate magnetometer is formed in a semiconductor wafer fabrication sequence, which significantly reduces the size and cost of the fluxgate magnetometer. The semiconductor wafer fabrication sequence attaches a die, which has drive and sense circuits, to the bottom surface of a cavity formed in a larger structure, and forms drive and sense coils around a magnetic core structure on the top surface of the larger structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fluxgates and, more particularly, to a semiconductor fluxgate magnetometer.

2. Description of the Related Art

A magnetometer is a device that measures the strength of an external magnetic field. There are a number of different approaches to measuring magnetic fields, and various different types of magnetometers have been developed based on these different approaches. One type of magnetometer based on flux variations in a magnetic core is a fluxgate magnetometer.

FIG. 1shows a block diagram that illustrates an example of a prior art fluxgate magnetometer100. As shown inFIG. 1, fluxgate magnetometer100includes a drive coil110, a sense coil112, and a magnetic core structure114that lies within drive coil110and sense coil112.

As further shown inFIG. 1, fluxgate magnetometer100also includes a drive circuit120that is connected to drive coil110, and an sense circuit122that is connected to sense coil112and drive circuit120. Sense circuit122generates an output voltage VOUTthat is proportional to the magnitude of an external magnetic field.

FIGS. 2A-2Eshow views that illustrate the operation of fluxgate magnetometer100.FIG. 2Ashows a graph that illustrates a BH curve200for magnetic core structure114, whileFIG. 2Bshows a graph that illustrates an alternating current input to drive coil110,FIG. 2Cshows a graph that illustrates the magnetic induction field B that results from the alternating current input to drive coil110,FIG. 2Dshows a graph that illustrates an induced voltage in sense coil112plotted in the time domain that results from the magnetic induction field B, andFIG. 2Eshows a graph that illustrates the induced voltage in sense coil112plotted in the frequency domain that results from the magnetic induction field B.

As shown by BH curve200inFIG. 2A, when the magnitude of a magnetic field H increases, magnetic core structure114increases the magnitude of the magnetic induction field B until magnetic core structure114saturates. Once in saturation, further increases in the magnitude of the magnetic field H lead to very little increase in the magnitude of the magnetic induction field B.

As a result, saturation is commonly illustrated as inFIG. 2Aas the region where increases in the magnitude of the magnetic field H lead to no additional increase in the magnitude of the magnetic induction field B. In the present example, the magnitude of the magnetic field H is increased by increasing the magnitude of the alternating current flowing through drive coil110.

As shown inFIGS. 2A-2C, when no external magnetic field is present and an alternating current waveform210, which has an amplitude that is sufficient to drive magnetic core structure114into saturation, is input to drive coil110from drive circuit120, an alternating magnetic induction field B, as represented by waveform212, is generated in response.

In other words, when alternating current waveform210is input to drive coil110, magnetic core structure114is driven through cycles (magnetized, un-magnetized, inversely magnetized, un-magnetized, magnetized again, and so on) that generate an alternating magnetic induction field B as represented by waveform212. In the present example, the alternating current waveform210is triangular, while the magnetic induction field waveform212has flat tops and bottoms that represent the periods of saturation.

As shown inFIG. 2D, the alternating magnetic induction field B induces an alternating voltage214in sense coil112. The induced alternating voltage214is proportional to the change in the magnetic induction field B over time (dB/dt). In addition, the induced alternating voltage214is processed by sense circuit122to generate the output voltage VOUT, which is proportional to the external magnetic field.

As shown inFIG. 2E, in the frequency domain, the induced alternating voltage214has a fundamental frequency1f, but only odd harmonics, such as a third harmonic3f, of the fundamental frequency1f. As a result, when no external magnetic field is present, the induced alternating voltage214has no second harmonic.

However, when an external magnetic field is present, the external magnetic field interacts with magnetic core structure114and changes the alternating magnetic induction field B. In other words, magnetic core structure114is more easily saturated when magnetic core structure114is in alignment with the external magnetic field, and less easily saturated when magnetic core structure114is in opposition to the external magnetic field.

In the present example, as shown by waveform220inFIG. 2C, alignment to the external magnetic field increases the duration of the positive magnetic induction field B and decreases the duration of the negative magnetic induction field B. As a result, as shown by waveform222inFIG. 2B, the external magnetic field has the effect of shifting alternating current waveform210to the right.

In other words, when no external magnetic field is present, each half cycle of the waveform210drives magnetic core structure114into positive and negative saturation by substantially an equal amount. However, when exposed to an external magnetic field, as illustrated by the waveform222, the external magnetic field causes one half-cycle of the waveform222to drive magnetic core structure114more deeply into saturation, and one half-cycle of the waveform222to drive magnetic core structure114less deeply into saturation.

In addition, as shown inFIG. 2D, the change in the alternating magnetic induction field B phase shifts the induced alternating voltage214to generate a phase-shifted induced alternating voltage224. Further, as shown inFIG. 2E, in the frequency domain, the phase-shifted induced alternating voltage224that results from the external magnetic field includes even harmonics, specifically a second harmonic2f.

The magnitude of the second harmonic2f, in turn, is proportional to the magnitude of the external magnetic field. Thus, by filtering the phase-shifted induced alternating voltage224to isolate the second harmonic2f, and then detecting the magnitude of the second harmonic2f, the magnitude of the external magnetic field can be determined.

FIG. 3shows a block diagram that illustrates an example of a prior art fluxgate magnetometer300. Fluxgate magnetometer300is similar to fluxgate magnetometer100and, as a result, utilizes the same reference numerals to designate the structures which are common to both fluxgate magnetometers.

As shown inFIG. 3, fluxgate magnetometer300differs from fluxgate magnetometer100in that fluxgate magnetometer300includes a feedback coil310that is wrapped around magnetic core structure114along with drive coil110and sense coil112, and a feedback circuit312that is connected to feedback coil310and sense circuit122. Feedback circuit312generates an output voltage VCANthat has an amplitude which is proportional to the magnitude of an external magnetic field.

Fluxgate magnetometer300operates the same as fluxgate magnetometer100, except that feedback coil310and feedback circuit312are utilized to generate a magnetic field that opposes the external magnetic field.FIG. 2Cshows that alignment to the external magnetic field increases the duration of the positive magnetic induction field B and decreases the duration of the negative magnetic induction field B.

In addition, as the strength of the external magnetic field increases, the duration of the positive magnetic induction field B increases while the duration of the negative magnetic induction field B decreases. Thus, as the strength of an external magnetic field increases, the duration of the negative induction field B decreases until the fluxgate magnetometer reaches saturation where there is substantially no negative magnetic induction field B. Once the fluxgate magnetometer saturates, further increases in the strength of the external magnetic field can not be detected by the fluxgate magnetometer.

To prevent a strong external magnetic field from saturating a fluxgate magnetometer, the alternating current input to feedback coil310is selected to generate a magnetic field that cancels out the external magnetic field, and effectively make the output voltage VOUTappear as though no external magnetic field were present.

The magnitude of the alternating current input to feedback coil310when the output voltage VOUTappears as though no external magnetic field were present can then be used to generate the output voltage VCAN. Since the amplitude of the output voltage VCANis proportional to the magnitude of the external magnetic field, the magnitude of the external magnetic field can then be determined. Thus, the advantage of fluxgate magnetometer300is that fluxgate magnetometer300can be used in very strong magnetic fields.

FIG. 4shows a block diagram that illustrates an example of a prior art fluxgate magnetometer400. As shown inFIG. 4, fluxgate magnetometer400includes a drive coil410, a sense coil412, and a pair of magnetic core structures414and416that lie within drive coil410and sense coil412.

As further shown inFIG. 4, fluxgate magnetometer400also includes a drive circuit420that is connected to drive coil410, and a sense circuit422that is connected to sense coil412. Sense circuit422generates an output voltage VDIFthat has an amplitude which is proportional to the magnitude of an external magnetic field.

In operation, drive coil410is wrapped around the magnetic core structures414and416so as to generate equal and opposing alternating magnetic induction fields when drive circuit420outputs an alternating current to drive coil410. Thus, when no external magnetic field is present, no voltage is induced in sense coil412because no alternating magnetic induction field is present.

FIG. 5shows a graph that further illustrates the operation of fluxgate magnetometer400. As shown inFIG. 5, although no current is induced in sense coil412when no external magnetic field is present, the presence of an external magnetic field induces an alternating voltage in sense coil412.

Sense circuit422detects the induced alternating voltage in sense coil412and generates in response the output voltage VDIF, which has an amplitude that is proportional to the magnitude of the external magnetic field. Thus, by detecting the amplitude of the output voltage VDIF, the magnitude of the external magnetic field can be determined.

One of the advantages of fluxgate magnetometer400over fluxgate magnetometer100is that fluxgate magnetometer400requires less support circuitry than fluxgate magnetometer100. For example, drive circuit120commonly generates a second harmonic clock signal which drive circuit410need not generate. The second harmonic clock signal, which has a frequency that is equal to the second harmonic of the fundamental frequency of the clock signal used to input current to drive coil, is typically required by sense circuit122.

FIG. 6shows a block diagram that illustrates an example of a prior art fluxgate magnetometer600. Fluxgate magnetometer600is similar to fluxgate magnetometer100and, as a result, utilizes the same reference numerals to designate the structures which are common to both fluxgate magnetometers.

As shown inFIG. 6, fluxgate magnetometer600differs from fluxgate magnetometer100in that fluxgate magnetometer600utilizes a magnetic core structure610in lieu of magnetic core structure114. Magnetic core structure610differs from magnetic core structure114in that magnetic core structure610has flared ends. Fluxgate magnetometer600operates the same as fluxgate magnetometer100except that the flared ends of magnetic core structure610capture additional flux and channel the additional flux into the body of magnetic core structure610, thereby functioning as a flux concentrator.

FIG. 7shows a block diagram that illustrates an example of a prior art fluxgate magnetometer700. Fluxgate magnetometer700is similar to fluxgate magnetometer100and, as a result, utilizes the same reference numerals to designate the structures which are common to both fluxgate magnetometers.

As shown inFIG. 7, fluxgate magnetometer700differs from fluxgate magnetometer100in that fluxgate magnetometer700utilizes a magnetic core structure710in lieu of magnetic core structure114. Magnetic core structure710differs from magnetic core structure114in that magnetic core structure710has a narrow center section. In addition, fluxgate magnetometer700differs from fluxgate magnetometer100in that sense coil112of fluxgate magnetometer700is only wrapped around the narrow center section of magnetic core structure710.

Fluxgate magnetometer700operates the same as fluxgate magnetometer100except that the narrow section of magnetic core structure710saturates faster than the remaining sections of magnetic core structure710. As a result, less current is required to saturate the section of magnetic core structure710that is wrapped by sense coil112.

Although the fluxgate magnetometers100,300,400,600, and700each measures the strength of an external magnetic field, the fluxgate magnetometers100,300,400,600, and700tend to be bulky and expensive to manufacture. Thus, there is a need for a smaller and less expensive fluxgate magnetometer.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 8A-8Cshow views that illustrate an example of a semiconductor fluxgate magnetometer800in accordance with the present invention.FIG. 8Ashows a plan view, whileFIG. 8Bshows a cross-sectional view taken along line8B-8B inFIG. 8A, andFIG. 8Cshows a cross-sectional view taken along line8C-8C inFIG. 8A. As described in greater detail below, the present invention provides a smaller and less expensive semiconductor fluxgate magnetometer.

As shown inFIGS. 8A-8C, semiconductor fluxgate magnetometer800includes a semiconductor structure810that has a bottom surface8106, a top surface810T, and a cavity814that extends from the top surface810T down into semiconductor structure810. Cavity814, in turn, has a side wall surface814S and a bottom surface814B that lies above and vertically spaced apart from the bottom surface810B of semiconductor structure810. In addition, bottom surface814B can be either conductive or non-conductive.

As further shown inFIGS. 8A-8C, semiconductor fluxgate magnetometer800includes a die816that lies in cavity814, and an adhesive818that attaches die816to the bottom surface814B of cavity814. Die816has a side wall surface816S, a bottom surface816B that touches adhesive818, and a number of conductive pads820that provide external electrical connection points for die816. Further, a side wall space819lies between the side wall surface814S of cavity814and the side wall surface816S of die816.

In addition, die816includes the drive and sense circuits. In the present example, the drive circuit is conventionally implemented, and includes all of the electrical components that are required to output an alternating current to a drive coil, and a clock signal to the sense circuit that is equal to second harmonic of the fundamental frequency of the alternating current that is output to the drive coil.

In addition, the sense circuit is conventionally implemented, and includes all of the electrical components that are required to detect an alternating voltage that has been induced in a sense coil, isolate the second harmonic of the induced alternating voltage, and generate an output voltage that represents the magnitude of the second harmonic of the induced alternating voltage (which is proportional to the magnitude of an external magnetic field).

Adhesive818, in turn, can be implemented with, for example, a conductive or non-conductive epoxy or die attach film. In addition, adhesive818, which can be, for example, 25 μm thick, can be selected based on any isolation and thermal requirements of die816and whether the bottom surface814B of cavity814is conductive or non-conductive.

Semiconductor fluxgate magnetometer800also includes a non-conductive structure822that touches die816and semiconductor structure810. Non-conductive structure822, which fills up the remainder of cavity814, has a number of openings822P that expose the conductive pads820on die816.

Further, semiconductor fluxgate magnetometer800includes a number of metal lower structures830that touch non-conductive structure822. The metal lower structures830include a number of via structures830V that extend through non-conductive structure822to touch a first group of the conductive pads820which represent power and input/output signal pads, a number of via trace structures830T with via sections that extend through non-conductive structure822to touch a second group of the conductive pads820which represent input/output coil pads, and a number of lower coil structures830C.

In addition, semiconductor fluxgate magnetometer800includes a non-conductive structure850that touches the via structures830V, the via trace structures830T, the lower coil structures830C, and non-conductive structure822. Non-conductive structure850has a substantially planar top surface850T, and a number of openings850P that expose the via structures830V, one end of each via trace830T, and the opposite ends of each lower coil structure830C.

Semiconductor fluxgate magnetometer800also includes a number of via structures854that lie in the openings850P to make electrical connections to the via structures830V, one end of each via trace830T, and the opposite ends of each lower coil structure830C. Magnetometer800additionally include a magnetic core structure872that touches the top surface850T of non-conductive structure850. In the present example, magnetic core structure872is uniaxially anisotropic, and has a rectangular shape with opposing ends.

Further, semiconductor fluxgate magnetometer800includes a non-conductive structure874that touches non-conductive structure850, the via structures854, and magnetic core structure872. Non-conductive structure874has a substantially planar top surface874T, and a number of openings874P that expose the via structures854.

In addition, semiconductor fluxgate magnetometer800includes a number of metal upper structures880that touch non-conductive structure874. The metal upper structures880include a number of upper via structures880V that touch the via structures854which are connected to the via structures830V, and a number of upper coil structures880C that touch the via structures854which are connected to the lower coil structures830C, and the via structures854which are connected to the ends of the via traces830T.

The electrical connection of the upper coil structures880C, the lower coil structures830C, and the via structures854that are connected to the upper coil structures880C and the lower coil structures830C form a fluxgate magnetometer that has a drive coil C1and a sense coil C2which are wrapped around magnetic core structure872.

Semiconductor fluxgate magnetometer800also includes a passivation layer882that touches the top surface874T of non-conductive structure874and the metal upper structures880. As further shown inFIGS. 8A-8C, passivation layer882is formed to have a number of pad openings882P that expose portions of the top surfaces of the upper via structures880V.

Further, semiconductor fluxgate magnetometer800includes metal pads884, such as aluminum pads, that lie in the pad openings882P to touch the upper via structures880V. The metal pads884can be connected by way of bonding wires886to external connection structures (e.g., pins or pads) on a lead frame as illustrated inFIG. 8A, or by way of solder balls888to a printed circuit board as illustrated inFIG. 8C.

Thus, semiconductor fluxgate magnetometer800includes a non-conductive structure890, which includes non-conductive structures822,850, and874, that touches die816and the top surface810T of the semiconductor structure810. In addition, fluxgate magnetometer800includes a first conductor892and a second conductor894that touch non-conductive structure890.

First conductor892includes the lower coil structures830C, the upper coil structures880C, and the via structures854which are connected together to form drive coil C1, along with a pair of via traces structures830T that are electrically connected to die816and drive coil C1. Thus, first conductor892, which is electrically isolated from magnetic core structure872by non-conductive structure890, is wound around magnetic core structure872in a spiral to form drive coil C1.

Further, the lower coil structures830C of drive coil C1touch non-conductive structure890, and lie in a horizontal plane H1that lies below and vertically spaced apart from the bottom surface of magnetic core structure872. In addition, in the present example, the horizontal plane H1lies above and vertically spaced apart from the top surface810T of semiconductor structure810. In addition, the upper coil structures880C of drive coil C1touch non-conductive structure890, and lie in a horizontal plane H2that lies above and vertically spaced apart from the top surface of magnetic core structure872.

Second conductor894includes the lower coil structures830C, the upper coil structures880C, and the via structures854which are connected together to form sense coil C2, along with a pair of via traces structures830T that are electrically connected to die816and sense coil C2. Thus, second conductor894, which is electrically isolated from magnetic core structure872by non-conductive structure890, is wound around magnetic core structure872in a spiral to form sense coil C2. Further, the lower coil structures830C of sense coil C2touch non-conductive structure890and lie in horizontal plane H1, while the upper coil structures880C of sense coil C2touch non-conductive structure890and lie in horizontal plane H2.

In operation, the drive circuit of die816outputs an alternating current to the drive coil C1, and a clock signal to the sense circuit of die816that is equal to second harmonic of the fundamental frequency of the alternating current that is output to the drive coil C1. The alternating current in the drive coil C1sets up an alternating magnetic induction field that induces an alternating voltage in sense coil C2.

The sense circuit detects the alternating voltage in sense coil C2, isolates the second harmonic of the alternating voltage in sense coil C2, identifies a magnitude of the second harmonic, and generates an output voltage with a magnitude that is proportional to the magnitude of the external magnetic field.

FIGS. 9A-9Cthrough56A-56C show a series of views that illustrate an example of a method of forming a semiconductor fluxgate magnetometer in accordance with the present invention.FIGS. 9A-56Ashow a series of plan views, whileFIGS. 9B-56Bshow a series of cross-sectional views taken along lines9B-56B, respectively, inFIGS. 9A-56A, andFIGS. 9C-56Cshow a series of cross-sectional views taken along lines9C-56C, respectively, inFIGS. 9A-56A.

As shown in theFIGS. 9A-9C, the method of forming a semiconductor fluxgate magnetometer utilizes a conventionally-formed semiconductor wafer910. Wafer910, in turn, can be implemented with a conducting material, such as silicon, or a non-conducting material such as quartz or G10-FR4 glass epoxy laminates. As further shown inFIGS. 9A-9C, the method begins by forming a patterned photoresist layer912on the top surface of wafer910.

Patterned photoresist layer912is formed in a conventional manner, which includes depositing a layer of photoresist, projecting a light through a patterned black/clear glass plate known as a mask to form a patterned image on the layer of photoresist that softens the photoresist regions exposed by the light, and removing the softened photoresist regions.

As shown inFIGS. 10A-10C, after patterned photoresist layer912has been formed, the exposed region of wafer910is etched in a conventional manner to form a large number of cavities914, which each has a bottom surface914B, in wafer910. (Only one cavity914is shown for simplicity.) Wafer910can be etched using a dry etch such as reactive ion etching, or a timed wet etch.

After the etch, the resulting structure is rinsed, and patterned photoresist layer912is then removed in a conventional manner, such as with acetone. Once patterned photoresist layer912has been removed, the resulting structure is conventionally cleaned to remove organics, such as with a Piranha etch (e.g., using a solution of 50H2SO4:1H2O2@ 120° C. removes approximately 240 nm/minute). If wafer910is conductive, a conformal non-conducting material, such as oxide or nitride, can be optionally formed on wafer910to line cavity914so that the bottom surface914B of cavity914is non-conductive.

Next, as shown inFIGS. 11A-11C, a die916is placed in each cavity914and attached to the bottom surface914B of the cavity914using an adhesive918such as, for example, a conductive or non-conductive epoxy or die attach film. Adhesive918, which can be, for example, 25 μm thick, can be selected based on any isolation and thermal requirements of die916and whether the bottom surface914B of cavity914is conductive or non-conductive. Die916, which includes the drive and sense electronics and a number of conductive pads920, can be placed in and attached to the bottom surface914B of cavity914using a conventional pick and place machine.

As shown inFIGS. 12A-12C, after die916has been attached to the bottom surface914B of cavity914, a non-conductive structure922is formed to touch die916and wafer910. Non-conductive structure922, which fills up the remainder of cavity914, has a number of openings922P that expose the conductive pads920on die916.

In the present example, as shown inFIGS. 13A-13C, non-conductive structure922is formed by depositing a layer of photoimageable epoxy or polymer924, such as SU-8, benzocyclobutene (BCB), or polybenzoxazole (PBO), which are substantially self planarizing. Once the photoimageable epoxy or polymer has been deposited, a number of openings924P are formed in photoimageable epoxy or polymer layer924by projecting a light through a mask to form a patterned image on layer924that softens the regions of layer924that are exposed by the light, and then removing the softened regions of layer924.

After the openings924P have been formed, as shown inFIGS. 14A-14C, a layer of nitride926approximately 0.6 μm thick is conventionally formed on photoimageable epoxy or polymer layer924to line the openings924P using, for example, plasma-enhanced chemical vapor deposition (PECVD).

Following this, a patterned photoresist layer928is conventionally formed on nitride layer926. The exposed regions of nitride layer926are then etched to expose the conductive pads920on die916. Patterned photoresist layer928is then removed in a conventional manner to complete the formation of non-conductive structure922. (The formation and etch of nitride layer926are optional and can be omitted.)

As shown inFIGS. 15A-15C, after non-conductive structure922has been formed, a number of metal lower structures930are formed to touch non-conductive structure922. The metal lower structures930include a number of via structures930V that also touch a first group of the conductive pads920, a number of via trace structures930T that also touch a second group of the conductive pads920, and a number of lower coil structures930C. The metal lower structures930can be formed in a number of different ways.

As shown inFIGS. 16A-16C, in a first embodiment, the metal lower structures930can be formed by depositing a seed layer932to touch non-conductive structure922and the conductive pads920. For example, seed layer932can be implemented with a layer of aluminum copper. Seed layer932can alternately be formed by depositing 300 Å of titanium, 3000 Å of copper, and 300 Å of titanium. After seed layer932has been formed, a plating mold934is formed on the top surface of seed layer932.

As shown inFIGS. 17A-17C, following the formation of plating mold934, copper is electroplated in a conventional manner to form a number of copper regions936approximately 5 μm thick. After the electroplating, as shown inFIGS. 18A-18C, plating mold934and the underlying regions of seed layer932are removed to form the via structures930V, the via trace structures930T, and the lower coil structures930C.

Alternately, in a second embodiment, as shown inFIGS. 19A-19C, the metal lower structures930can be formed by first depositing a liner layer940on non-conductive structure922to line the openings922P. Liner layer940can be implemented with, for example, titanium/titanium nitride. After liner layer940has been formed, a metal layer942, such as tungsten, is conventionally deposited on liner layer940to fill up the openings922P.

Following this, as shown inFIGS. 20A-20C, metal layer942is planarized, such as with chemical-mechanical polishing, to expose the top surface of non-conductive structure922, and form via plug structures942P in the openings922P that make electrical connections to the conductive pads920of die916.

As shown inFIGS. 21A-21C, after the via plug structures942P have been formed, a metal layer944, such as aluminum, is sputter deposited onto non-conductive structure922to a depth of approximately 5 μm. Alternately, metal layer944can include multiple layers of metal such as, for example, a layer of titanium, a layer of titanium nitride, a layer of aluminum copper, a layer of titanium, and a layer of titanium nitride.

Once metal layer944has been formed, a patterned photoresist layer946approximately 1.0 μm thick is formed on the top surface of metal layer944in a conventional manner. Following the formation of patterned photoresist layer946, metal layer944is etched to remove the exposed regions of metal layer944and form the metal lower structures930.

Metal layer944can be etched using a dry etch such as reactive ion etching, or a timed wet etch. For example, aluminum can be wet etched in a 10:1 hydrogen fluoride solution for the necessary period of time. After the etch, the resulting structure is rinsed, and patterned photoresist layer946is then removed in a conventional manner, such as with acetone. Once patterned photoresist layer946has been removed, the resulting structure is conventionally cleaned to remove organics, such as with a Piranha etch.

As shown inFIGS. 22A-22C, after the via structures930V, the via trace structures930T, and the lower coil structures930C have been formed, a non-conductive structure950is formed on the via structures930V, the via trace structures930T, the lower coil structures930C, and non-conductive structure922. Non-conductive structure950has a substantially planar top surface950T, and a number of openings950P that expose the via structures930V, one end of each via trace930T, and the opposite ends of each lower coil structure930C. Dielectric structure950can be formed in a number of different ways.

For example, as shown inFIGS. 23A-23C, in a first embodiment, non-conductive structure950can be formed by conventionally depositing a silicon nitride layer950N approximately 0.6 μm thick on non-conductive structure922and the metal lower structures930. After this, a layer of silicon dioxide950X is conventionally formed on the top surface of silicon nitride layer950N.

Following the formation of oxide layer950X, oxide layer950X is planarized in a conventional manner, such as with chemical-mechanical polishing, until oxide layer950X has a substantially planar top surface950F. Once oxide layer950X has been planarized, a hard mask952is formed on substantially planar top surface950F of oxide layer950X.

As shown inFIGS. 24A-24C, hard mask952can be formed by conventionally depositing a layer of masking material952M, such as a layer of aluminum, or a layer of oxide with an overlying layer of nitride, followed by the conventional formation of a patterned photoresist layer952H. After this, the exposed regions of masking material952M are etched to form the openings in hard mask952. Patterned photoresist layer952H is then removed in a conventional manner to complete the formation of hard mask952.

After hard mask952has been formed, as shown inFIGS. 25A-25C, the exposed regions of oxide layer950X and nitride layer950N are etched away to form the openings950P that exposes the via structures930V, one end of each via trace930T, and the opposite ends of each lower coil structure930C. After the via structures930V, one end of each via trace930T, and the opposite ends of each lower coil structure930C have been exposed, hard mask952is removed in a conventional manner to form non-conductive structure950. Alternately, depending on the thickness of the dielectric to be etched, a thick patterned photoresist layer can be used in lieu of hard mask952.

When the metal lower structures930are formed as in the first embodiment (electroplated), nitride layer926of non-conductive structure922and nitride layer950N of non-conductive structure950surround the copper structures and prevent copper diffusion. Alternately, when the metal lower structures930are formed as in the second embodiment (metal deposition, mask, and etch), silicon nitride layers926and950N can be omitted when a copper diffusion barrier is not required.

Alternately, as shown inFIGS. 26A-26C, non-conductive structure950can be formed by depositing a layer of photoimageable epoxy or polymer950E on non-conductive structure922. The photoimageable epoxy or polymer layer950E can be implemented with, for example, SU-8, benzocyclobutene (BCB), or polybenzoxazole (PBO), which are substantially self planarizing.

Once photoimageable epoxy or polymer layer950E has been deposited, the openings950P are formed in photoimageable epoxy or polymer layer950E by projecting a light through a mask to form a patterned image on layer950E that softens the regions of layer950E that are exposed by the light, and then removing the softened regions of layer950E.

As shown inFIGS. 27A-27C, after non-conductive structure950has been formed, a number of via structures954are formed in the openings950P to make electrical connections to the via structures930V, one end of each via trace930T, and the opposite ends of each lower coil structure930C. The via structures954can be formed in a number of different ways.

In a first embodiment, as shown inFIGS. 28A-28C, the via structures954are formed by first depositing a copper diffusion barrier layer956on non-conductive structure950to line the openings950P. Barrier layer956can be implemented with, for example, nitride, titanium nitride, titanium, or tantalum.

If barrier layer956is non-conductive, then a patterned photoresist layer is formed on barrier layer956, followed by an etch to remove a portion of barrier layer956. The portion of barrier layer956removed by the etch exposes the top surfaces of the via structures930V, one end of each via trace930T, and the opposite ends of each lower coil structure930C.

After barrier layer956, which is illustrated as a conductive barrier layer, has been formed, a seed layer958is conventionally formed on barrier layer956(and the exposed top surfaces of the via structures930V, one end of each via trace930T, and the opposite ends of each lower coil structure930C when a non-conductive barrier layer is used). For example, seed layer958can be implemented with a layer of aluminum copper. Seed layer958can alternately be formed by depositing 300 Å of titanium, 3000 Å of copper, and 300 Å of titanium. After seed layer958has been formed, a plating mold960is formed on the top surface of seed layer958.

As shown inFIGS. 29A-29C, following the formation of plating mold960, copper is electroplated in a conventional manner approximately 5 μm thick to form copper structures961in the openings950P. After this, as shown inFIGS. 30A-30C, plating mold960and the exposed regions of seed layer958and barrier layer956are removed in a conventional manner to complete the formation of the via structures954.

In a second embodiment, as shown inFIGS. 31A-31C, the via structures954are formed by first depositing a liner layer962on non-conductive structure950to line the openings950P. Liner layer962can be implemented with, for example, titanium/titanium nitride. After liner layer962has been formed, a metal layer964, such as tungsten, is conventionally deposited on liner layer962to fill up the openings950P.

Following this, as shown inFIGS. 32A-32C, metal layer964is planarized, such as with chemical-mechanical polishing, to expose the top surface of non-conductive structure950, and form via plug structures966in the openings950P that make electrical connections to the via structures930V, one end of each via trace930T, and the opposite ends of each lower coil structure930C.

As shown inFIGS. 33A-33C, after the via plug structures966have been formed, a metal layer968, such as aluminum, is sputter deposited onto the non-conductive top surface950T of non-conductive structure950to a depth of approximately 5 μm. Alternately, metal layer968can include multiple layers of metal such as, for example, a layer of titanium, a layer of titanium nitride, a layer of aluminum copper, a layer of titanium, and a layer of titanium nitride.

Once metal layer968has been formed, a patterned photoresist layer970approximately 1.0 μm thick is formed on the top surface of metal layer968in a conventional manner. Following the formation of patterned photoresist layer970, metal layer968is etched to remove the exposed regions of metal layer968and form the via structures954in the openings950P that make electrical connections to the via structures930V, one end of each via trace930T, and the opposite ends of each lower coil structure930C.

Metal layer968can be etched using a dry etch such as reactive ion etching, or a timed wet etch. For example, aluminum can be wet etched in a 10:1 hydrogen fluoride solution for the necessary period of time. After the etch, the resulting structure is rinsed, and patterned photoresist layer970is then removed in a conventional manner, such as with acetone. Once patterned photoresist layer970has been removed, the resulting structure is conventionally cleaned to remove organics, such as with a Piranha etch.

As shown inFIGS. 34A-34C, after the via structures954have been formed, a magnetic core structure972is formed on the top surface950T of non-conductive structure950. Magnetic core structure972, in turn, can be formed in a number of ways.

In a first embodiment, as shown inFIGS. 35A-35C, a layer of silicon nitride972N approximately 0.6 μm thick is deposited on the top surface of non-conductive structure950and the via structures954, followed by the deposition of a seed layer972S on the top surface of nitride layer972N. For example, seed layer972S can be implemented with a layer of aluminum copper. Seed layer972S can alternately be formed by depositing 300 Å of titanium, 3000 Å of copper, and 300 Å of titanium.

After seed layer972S has been formed, a magnetic material with a high permeability and a low resistance, such as an alloy of nickel and iron like permalloy, is electroplated to a thickness of, for example, 5 μm to form a magnetic material layer972Y. Following this, a patterned photoresist mask972M is formed on magnetic material layer972Y.

Next, as illustrated inFIGS. 36A-36C, the exposed regions of magnetic material layer972Y and seed layer972S are etched and removed to form magnetic core structure972. In this example, nitride layer972N is left in place, but the exposed regions of nitride layer972N could alternately be removed. Patterned photoresist layer972M is then removed in a conventional manner, such as with acetone. Once patterned photoresist layer972M has been removed, the resulting structure is conventionally cleaned to remove organics. In addition, a plating mold can alternately be used to define the regions where the magnetic material is to be electroplated.

In a second embodiment, as shown inFIGS. 37A-37C, a magnetic material layer972L is sputter deposited on the top surface950T of non-conductive structure950and the via structures954. Magnetic material layer972L can be implemented with, for example, cobalt tantalum zirconium (CoTaZr) or permalloy, materials which have a high permeability and a low resistance.

Following this, a patterned photoresist layer972P is formed on magnetic material layer972L. After patterned photoresist layer972P has been formed, the exposed regions of magnetic material layer972L are etched and removed to form magnetic core structure972. Patterned photoresist layer972P is then removed in a conventional manner, such as with acetone. Once patterned photoresist layer972L has been removed, the resulting structure is conventionally cleaned to remove organics.

In the present example, the magnetic materials972Y and972L are subjected to the presence of a strong magnetic field that so that the magnetic materials972Y and972L are uniaxially anisotropic. The strong magnetic field can be applied during the plating or deposition of the magnetic material. Alternately, the strong magnetic field can be applied during an anneal at elevated temperatures after the plating or deposition of the magnetic material.

Following the formation of magnetic core structure972, as shown inFIGS. 38A-38C, a non-conductive structure974is formed on non-conductive structure950, the via structures954, and magnetic core structure972. Non-conductive structure974has a substantially planar top surface974T, and a number of openings974P that expose the via structures954. Dielectric structure974can be formed in a number of different ways.

For example, as shown inFIGS. 39A-39C, in a first embodiment, non-conductive structure974can be formed by conventionally depositing a silicon nitride layer974N approximately 0.6 μm thick on non-conductive structure950, the via structures954, and magnetic core structure972. After this, a layer of silicon dioxide974X is conventionally formed on the top surface of silicon nitride layer974N.

Following the formation of oxide layer974X, oxide layer974X is planarized in a conventional manner, such as with chemical-mechanical polishing, until oxide layer974X has a substantially planar top surface974F. Once oxide layer974X has been planarized, a hard mask976is formed on substantially planar top surface974F of oxide layer974X.

As shown inFIGS. 40A-40C, hard mask976can be formed by conventionally depositing a layer of masking material976M, such as a layer of aluminum, or a layer of oxide with an overlying layer of nitride, followed by the conventional formation of a patterned photoresist layer976H. Following this, the exposed regions of masking material976M are etched to form the openings in hard mask976. Patterned photoresist layer976H is then removed in a conventional manner to complete the formation of hard mask976.

After hard mask976has been formed, as shown inFIGS. 41A-41C, the exposed regions of oxide layer974X and nitride layer974N are etched away to form the openings974P that expose the via structures954. After the via structures954have been exposed, hard mask976is removed in a conventional manner to form non-conductive structure974. Alternately, depending on the thickness of the dielectric to be etched, a thick patterned photoresist layer can be used in lieu of hard mask976.

When the via structures954are formed as in the first embodiment (electroplated), nitride layer950N of non-conductive layer950, barrier layer956, and nitride layer974N surround the copper structures and prevent copper diffusion. Nitride layers972N and974N also surround magnetic core structure972. Alternately, when the via structures954are formed as in the second embodiment (metal deposition, planarization, metal deposition, mask, and etch), silicon nitride layers950N and974N can be omitted when a copper diffusion barrier is not required.

Alternately, as shown inFIGS. 42A-42C, non-conductive structure974can be formed by depositing a layer of photoimageable epoxy or polymer974E on non-conductive structure950. The photoimageable epoxy or polymer layer974E can be implemented with, for example, SU-8, benzocyclobutene (BCB), or polybenzoxazole (PBO), which are substantially self planarizing.

Once photoimageable epoxy or polymer layer974E has been deposited, the openings974P are formed in photoimageable epoxy or polymer layer974E by projecting a light through a mask to form a patterned image on layer974E that softens the regions of layer974E that are exposed by the light, and then removing the softened regions of layer974E.

As shown inFIGS. 43A-43C, after non-conductive structure974has been formed, a number of metal upper structures980are formed to touch non-conductive structure974. The metal upper structures980include a number of upper via structures980V that are connected to the via structures954which are connected to the via structures930V, and a number of upper coil structures980C that are connected to the via structures954which are connected to the lower coil structures930C, and the via structures954which are connected to the ends of the via traces930T.

The electrical connection of the upper coil structures980C, the lower coil structures930C, and the via structures954that are connected to the upper coil structures980C and the lower coil structures930C form a fluxgate magnetometer that has a drive coil C1and a sense coil C2which are wrapped around magnetic core structure972. The metal upper structures980can be formed in a number of different ways.

In a first embodiment, as shown inFIGS. 44A-44C, the metal upper structures980are formed by first depositing a copper diffusion barrier layer980B on non-conductive structure974to line the openings974P. Barrier layer980B can be implemented with, for example, nitride, titanium nitride, titanium, or tantalum.

If barrier layer980B is non-conductive, then a patterned photoresist layer is formed on barrier layer980B, followed by an etch to remove a portion of barrier layer980B. The portion removed by the etch exposes the top surfaces of the via structures954. After barrier layer980B, which is illustrated as a conductive barrier layer, has been formed, a seed layer980S is conventionally formed on barrier layer980B (and the top surfaces of the via structures954when a non-conductive barrier layer is used).

For example, seed layer980S can be implemented with a layer of aluminum copper. Seed layer980S can alternately be formed by depositing 300 Å of titanium, 3000 Å of copper, and 300 Å of titanium. After seed layer980S has been formed, a plating mold980M is formed on the top surface of seed layer980S.

As shown inFIGS. 45A-45C, following the formation of plating mold980M, copper is electroplated in a conventional manner to form a number of copper regions980R approximately 5 μm thick. After the electroplating, as shown inFIGS. 46A-46C, plating mold980M and the underlying regions of seed layer980S and barrier layer980B are removed to form the upper via structures980V and the upper coil structures980C. (If non-conductive, barrier layer980B can optionally remain.)

In a second embodiment, as shown inFIGS. 47A-47C, the metal upper structures980are formed by first depositing a liner layer980L on non-conductive structure974to line the openings974P. Liner layer980L can be implemented with, for example, titanium/titanium nitride. After liner layer980L has been formed, a metal layer980Z, such as tungsten, is conventionally deposited on liner layer980L to fill up the openings974P.

Following this, as shown inFIGS. 48A-48C, metal layer980Z is planarized, such as with chemical-mechanical polishing, to expose the top surface of non-conductive structure974, and form via plug structures980P in the openings974P that make electrical connections to the via structures954.

As shown inFIGS. 49A-49C, after the via plug structures980P have been formed, a metal layer980Y, such as aluminum, is sputter deposited onto the non-conductive top surface974T of non-conductive structure974to a depth of approximately 5 μm. Alternately, metal layer980Y can include multiple layers of metal such as, for example, a layer of titanium, a layer of titanium nitride, a layer of aluminum copper, a layer of titanium, and a layer of titanium nitride.

Once metal layer980Y has been formed, a patterned photoresist layer980X approximately 1.0 μm thick is formed on the top surface of metal layer980Y in a conventional manner. Following the formation of patterned photoresist layer980X, metal layer980Y is etched to remove the exposed regions of metal layer980Y and form the upper via structures980V and the upper coil structures980C.

Metal layer980Y can be etched using a dry etch such as reactive ion etching, or a timed wet etch. For example, aluminum can be wet etched in a 10:1 hydrogen fluoride solution for the necessary period of time. After the etch, the resulting structure is rinsed, and patterned photoresist layer980X is then removed in a conventional manner, such as with acetone. Once patterned photoresist layer980X has been removed, the resulting structure is conventionally cleaned to remove organics, such as with a Piranha etch.

As shown inFIGS. 50A-50C, after the upper via structures980V and the upper coil structures980C have been formed, a passivation layer982is formed on the top surface974T of non-conductive structure974and the metal upper structures980. As further shown inFIGS. 50A-50C, passivation layer982is formed to have a number of pad openings982P. The pad openings982P expose portions of the top surfaces of the upper via structures980V.

Passivation layer982can be formed in a number of different ways. As shown inFIGS. 51A-51C, in a first embodiment, passivation layer982can be formed by depositing a layer of silicon nitride982N approximately 0.6 μm thick on the top surface974T of non-conductive structure974. Following this, a layer of silicon dioxide982X approximately 10-20 μm thick is deposited on nitride layer982N. Oxide layer982X and silicon nitride layer982N can be deposited in a conventional manner, and oxide layer982X can optionally be omitted in cases where lateral isolation will be provided by a molding compound. Once oxide layer982X has been formed, a patterned photoresist layer982M approximately 1.0 μm thick is formed on the top surface of oxide layer982X in a conventional manner.

As shown inFIGS. 52A-52C, following the formation of patterned photoresist layer982M, the exposed regions of oxide layer982X and nitride layer982N are etched to expose the upper via structures980V. Patterned photoresist layer982M is then removed in a conventional manner, followed by a conventional cleaning. Next, as shown inFIGS. 53A-53C, a layer of silicon nitride982S approximately 0.6 μm thick is deposited on the top surface of oxide layer982X and the exposed regions of the upper via structures980V.

Following this, a patterned photoresist layer982Y approximately 1.0 μm thick is formed on the top surface of nitride layer982S in a conventional manner. The openings in patterned photoresist layer982Y are made slightly smaller that the openings in patterned photoresist layer982M to ensure that oxide layer982X is completely sealed against moisture absorption. After patterned photoresist layer982Y has been formed, the exposed regions of nitride layer982S are etched to form passivation layer982with the pad openings982P. Patterned photoresist layer982Y is then removed in a conventional manner, followed by a conventional cleaning.

Alternately, in a second embodiment, as shown inFIGS. 54A-54C, passivation layer982can be formed by depositing a layer of photoimageable epoxy or polymer982E on non-conductive structure974and the metal upper structures980. The photoimageable epoxy or polymer layer982E can be implemented with, for example, SU-8, benzocyclobutene (BCB), or polybenzoxazole (PBO), which are substantially self planarizing.

Once photoimageable epoxy or polymer layer982E has been deposited, the openings982P are formed in photoimageable epoxy or polymer layer982E by projecting a light through a mask to form a patterned image on layer982E that softens the regions of layer982E that are exposed by the light, and then removing the softened regions of layer982E.

As shown inFIGS. 55A-55C, after passivation layer982has been formed, metal pads984, such as aluminum pads, are next formed in the pad openings982P to touch the upper via structures980V and complete the formation of a fluxgate magnetometer wafer986. The metal pads984make electrical connections with the upper via structures980V.

The metal pads984can be formed, as shown inFIGS. 56A-56C, by sputter depositing a metal layer984L, such as aluminum, approximately 1000 Å thick, followed by the deposition of a patterned photoresist layer984M. Once patterned photoresist layer984M has been formed, the exposed regions of metal layer984L are etched to form the metal pads984. Patterned photoresist layer984is then removed in a conventional manner, followed by a conventional cleaning.

After fluxgate magnetometer wafer986has been formed (following the formation of the metal pads984), the back side of fluxgate magnetometer wafer986can be ground down as necessary so that the completed assembly can fit into a package. Following this, fluxgate magnetometer wafer986is diced to form a large number of fluxgate magnetometer dice.

Thus, a semiconductor fluxgate magnetometer and a method of forming a semiconductor fluxgate magnetometer have been described. One of the advantages of the present invention is that the fluxgate magnetometer of the present invention is formed in a semiconductor process which, in turn, substantially reduces the size and cost of fluxgate magnetometers.

FIGS. 57A-57Cshow views that illustrate an example of a semiconductor fluxgate magnetometer5700in accordance with an alternate embodiment of the present invention.FIG. 57Ashows a plan view, whileFIG. 57Bshows a cross-sectional view taken along line57B-57B inFIG. 57A, andFIG. 57Cshows a cross-sectional view taken along line57C-57C inFIG. 57A. Semiconductor fluxgate magnetometer5700is similar to semiconductor fluxgate magnetometer800and, as a result, utilizes the same reference numerals to designate the structures which are common to both magnetometers.

As shown inFIGS. 57A-57C, semiconductor fluxgate magnetometer5700differs from semiconductor fluxgate magnetometer800in that semiconductor fluxgate magnetometer5700utilizes a die5710in lieu of die816. Die5710, which has a side wall surface5710S and a bottom surface5710B, differs from die816in that die5710further includes a cancellation circuit.

Third conductor5720includes a number of the lower coil structures930C, a number of the upper coil structures880C, and a number of the via structures954, which are connected together in the same manner as the drive and sense coils C1and C2to form a cancellation coil C3. Thus, third conductor5720, which is electrically isolated from magnetic core structure872, first conductor892, and second conductor894by non-conductive structure890, is wound around magnetic core structure872in a spiral to form cancellation coil C3. Third conductor5720further includes a pair of via trace structures830T that are electrically connected to die5710and cancellation coil C3.

Semiconductor fluxgate magnetometer5700operates the same as semiconductor fluxgate magnetometer800, except that the cancellation circuit in semiconductor fluxgate magnetometer5700outputs an alternating current to the cancellation coil C3. The alternating current in the cancellation coil C3sets up an alternating magnetic induction field that is equal and opposite to the alternating magnetic induction field which is generated by the alternating current in drive coil C1.

The cancellation circuit also adjusts the magnitude of the alternating current that is output to the cancellation coil C3until the output voltage from the sense circuit appears to indicate that no external magnetic field is present, and then determines the magnitude of the external magnetic field based on the magnitude of the alternating current output to the cancellation coil C3.

Semiconductor fluxgate magnetometer5700is formed in the same manner that semiconductor fluxgate magnetometer986is formed, except that the method is modified to add a pair of via traces structures930T, a number of the lower coil structures930C, a number of the upper coil structures980C, and a number of the via structures954, which are connected together to form third conductor5720in the same manner that the first and second conductors892and894are formed.

FIGS. 58A-58Cshow views that illustrate an example of a semiconductor fluxgate magnetometer5800in accordance with an alternate embodiment of the present invention.FIG. 58Ashows a plan view, whileFIG. 58Bshows a cross-sectional view taken along line58B-58B inFIG. 58A, andFIG. 58Cshows a cross-sectional view taken along line58C-58C inFIG. 58A. Semiconductor fluxgate magnetometer5800is similar to semiconductor fluxgate magnetometer800and, as a result, utilizes the same reference numerals to designate the structures which are common to both magnetometers.

As shown inFIGS. 58A-58C, semiconductor fluxgate magnetometer5800differs from semiconductor fluxgate magnetometer800in that semiconductor fluxgate magnetometer5800utilizes a die5810in lieu of die816. Die5810, which has a side wall surface5810S and a bottom surface5810B, differs from die816in that die5810utilizes simplified drive and sense circuits in lieu of the drive and sense circuits utilized in die816.

As additionally shown inFIGS. 58A-58C, semiconductor fluxgate magnetometer5800also differs from semiconductor fluxgate magnetometer800in that semiconductor fluxgate magnetometer5800further includes a magnetic core member5820that lies spaced apart from magnetic core member872.

Further, in addition to being wound around magnetic core structure872as a spiral to form drive coil C1, first conductor892is also wound around magnetic core structure5820as a spiral to form a drive coil C3. Also, in addition to being wound around magnetic core structure872as a spiral to form sense coil C2, second conductor894is further wound around magnetic core structure5820as a spiral to form a sense coil C4.

In operation, first conductor892is wrapped around the magnetic core structures872and5820so as to generate equal and opposing alternating magnetic induction fields when the drive circuit in die5810outputs an alternating current to drive coils C1and C3. Thus, when no external magnetic field is present, no voltage is induced in the sense coils C2and C4because no alternating magnetic induction field is present.

When an external magnetic field is present, the presence of the external magnetic field induces an alternating voltage in the sense coils C2and C4. The sense circuit in die5810detects the alternating voltage in the sense coils C2and C4and generates in response a sensed output voltage, which has an amplitude that is proportional to the magnitude of the external magnetic field. The sense circuit in die5810does not detect or utilize the second harmonic of the fundamental frequency of the alternating current that is output to the drive coils C1and C3.

Semiconductor fluxgate magnetometer5800is formed in the same manner that semiconductor fluxgate magnetometer986is formed. Magnetic core structure5820is formed at the same time that magnetic core structure872is formed, and the sections of drive coil C3and sense coil C4are formed at the same time that the corresponding sections of drive coil C1and sense coil C2are formed.

FIGS. 59A-59Cshow views that illustrate an example of a semiconductor fluxgate magnetometer5900in accordance with an alternate embodiment of the present invention.FIG. 59Ashows a plan view, whileFIG. 59Bshows a cross-sectional view taken along line59B-59B inFIG. 59A, andFIG. 59Cshows a cross-sectional view taken along line59C-59C inFIG. 59A. Semiconductor fluxgate magnetometer5900is similar to semiconductor fluxgate magnetometer5800and, as a result, utilizes the same reference numerals to designate the structures which are common to both magnetometers.

As shown inFIGS. 59A-59C, semiconductor fluxgate magnetometer5900differs from semiconductor fluxgate magnetometer5800in that semiconductor structure810of semiconductor fluxgate magnetometer5900has two cavities: cavity814and cavity5910which is formed at the same time and in the same manner that cavity814is formed.

Cavity5910, in turn, has a side wall surface59105and a bottom surface5910B that lies above and is vertically spaced apart from the bottom surface810B of semiconductor structure810. In addition, the bottom surface5910B of cavity5910can be either conductive or non-conductive.

As further shown inFIGS. 59A-59C, semiconductor fluxgate magnetometer5900also differs from semiconductor fluxgate magnetometer5800in that semiconductor fluxgate magnetometer5900utilizes a drive die5912and a sense die5914in lieu of die816. In the present example, drive die5912, which has a number of conductive pads5912P that provide external electrical connection points for die5912, includes all of the electrical components that are required to output an alternating current to the drive coils C1and C3.

Sense die5914, which has a number of conductive pads5914P that provide external electrical connection points for die5914, includes all of the electrical components that are required to detect an alternating voltage that has been induced in the sense coils C2and C4, and generate an output voltage from the alternating voltage in the sense coils C2and C4that has a magnitude which is proportional to an external magnetic field.

Drive die5912and sense die5914are attached to semiconductor structure810by way of adhesive818at the same time and in the manner that die816is attached to semiconductor structure810. In the present example, sense die5914does not detect or utilize the second harmonic of the fundamental frequency of the alternating current that is output to the drive coils C1and C3.

Semiconductor fluxgate magnetometer5900further differs from semiconductor fluxgate magnetometer5800in that semiconductor fluxgate magnetometer5900includes additional via structures830V that touch the pads5914P, additional via structures854, additional upper via structures880V, and additional pads884as required to provide power and input/output connections to die5914.

One of the advantages of semiconductor fluxgate magnetometer5900is that semiconductor fluxgate magnetometer5900provides galvanic isolation between the drive and sense dice5912and5914and, therefore, provides galvanic isolation between the drive and sense circuits. As a result, the drive and sense dice5912and5914can utilize different voltages, such as 0V and 200V, for ground.

FIGS. 60A-60Cshow views that illustrate an example of a semiconductor fluxgate magnetometer6000in accordance with an alternate embodiment of the present invention.FIG. 60Ashows a plan view, whileFIG. 60Bshows a cross-sectional view taken along line60B-60B inFIG. 60A, andFIG. 60Cshows a cross-sectional view taken along line60C-60C inFIG. 60A.

Semiconductor fluxgate magnetometer6000is similar to semiconductor fluxgate magnetometer800and, as a result, utilizes the same reference numerals to designate the structures which are common to both magnetometers. As shown inFIGS. 60A-60C, semiconductor fluxgate magnetometer6000differs from semiconductor fluxgate magnetometer800in that semiconductor fluxgate magnetometer6000utilizes a magnetic core structure6010in lieu of magnetic core structure872.

Magnetic core structure6010, which is a single unified structure, differs from magnetic core structure872in that magnetic core structure6010has a body region6012with a rectangular shape, and a pair of flared end regions6014that extend away from opposing ends of body region6012so that the maximum width of a flared end region6014is greater than a maximum width of body region6012.

Semiconductor fluxgate magnetometer6000operates the same as semiconductor fluxgate magnetometer800. In addition, semiconductor fluxgate magnetometer6000is formed in the same manner as semiconductor fluxgate magnetometer800, except that the mold or mask used to form magnetic core structure872is modified to form the magnetic core structure with flared ends.

FIGS. 61A-61Cshow views that illustrate an example of a semiconductor fluxgate magnetometer6100in accordance with an alternate embodiment of the present invention.FIG. 61Ashows a plan view, whileFIG. 61Bshows a cross-sectional view taken along line61B-61B inFIG. 61A, andFIG. 61Cshows a cross-sectional view taken along line61C-61C inFIG. 61A.

Semiconductor fluxgate magnetometer6100is similar to semiconductor fluxgate magnetometer800and, as a result, utilizes the same reference numerals to designate the structures which are common to both magnetometers. As shown inFIGS. 61A-61C, semiconductor fluxgate magnetometer6100differs from semiconductor fluxgate magnetometer800in that semiconductor fluxgate magnetometer6100utilizes a magnetic core structure6110in lieu of magnetic core structure872.

Magnetic core structure6110, which is a single unified structure, differs from magnetic core structure872in that magnetic core structure6110has a center region6112that has a first width, and a pair of end regions6114that are connected to opposite sides of center region6112. In addition, each end region6114has a second width that is greater than the first width of center region6112.

As additionally shown inFIGS. 61A-61C, semiconductor fluxgate magnetometer6100also differs from semiconductor fluxgate magnetometer800in that sense coil C2is only wound around the center region6112of magnetic core structure6110. Further, in the present example, semiconductor fluxgate magnetometer6100also includes a third conductor6120that touches non-conductive structure890.

Third conductor6120includes a number of the lower coil structures930C, a number of the upper coil structures880C, and a number of the via structures954, which are connected together in the same manner as the drive and sense coils C1and C2to form a supplemental drive coil C3. Thus, third conductor6120, which is electrically isolated from magnetic core structure6110, first conductor892, and second conductor894by non-conductive structure890, is wound around magnetic core structure6110in a spiral to form supplemental drive coil C3. Third conductor6120further includes a pair of via trace structures830T that are electrically connected to die816and supplemental drive coil C3.

Semiconductor fluxgate magnetometer6100operates the same as semiconductor fluxgate magnetometer800, except that the alternating current output to drive coil C1is also output to supplemental drive coil C3. In addition, semiconductor fluxgate magnetometer6100is formed in the same manner as semiconductor fluxgate magnetometer800, except that the mold or mask used to form magnetic core structure872is modified to form the magnetic core structure with a narrower center region. (The coils C1, C2, and C3are illustrated with one or two loops for simplicity, and can have any number of loops.)

In an alternate embodiment of the present invention, the sense circuit in die816is replaced with all of the electrical components that are required to measure the inductance of drive coil C1and sense coil C2in a conventional manner, and then compare the drive coil inductance to the sense coil inductance in a conventional manner to determine a difference in inductance. The difference in inductance is proportional to the magnitude of the external magnetic field, and the alternate sense circuit in die816determines the magnitude of the external magnetic field based on the difference in inductance.

It should be understood that the above descriptions are examples of the present invention, and that various alternatives of the invention described herein may be employed in practicing the invention. Thus, it is intended that the following claims define the scope of the invention and that structures and methods within the scope of these claims and their equivalents be covered thereby.