Vertical Hall Effect sensor

A complimentary metal oxide semiconductor (CMOS) sensor system in one embodiment includes a doped well extending along a first axis of a doped substrate, a first electrical contact positioned within the doped well, a second electrical contact positioned within the doped well and spaced apart from the first electrical contact along the first axis, a third electrical contact positioned within the doped well and located between the first electrical contact and the second electrical contact along the first axis, and a fourth electrical contact electrically coupled to the doped well at a location of the doped well below the third electrical contact.

BACKGROUND

The invention relates to magnetic field sensors and more specifically to CMOS Hall Effect sensors.

BACKGROUND

Hall Effect sensors are among the most widely used magnetic sensors. Hall Effect sensors incorporate a Hall Effect plate, which is either an n− or p-doped area, supplied with bias current/voltage. In presence of a magnetic field the carriers that are moving in the doped area are deflected by the Lorentz force, and a Hall electrical field appears. The Hall voltage Vh appears across the positive and negative contacts of the Hall Effect plate. Front-end circuitry provided with the sensor converts the Hall voltage to a data indicative of the sensed magnetic field.

Magnetic detection by standard CMOS Hall devices is thus limited to the field perpendicular to the chip surface. In many scenarios, however, measurement of the magnetic field in two or even three dimensions is desired. Packaging sensors for measuring multiple dimensions of a magnetic field can be accomplished by packaging chips perpendicular to each other. This approach, however, requires the use of specialized technology during the manufacturing process and special alignment of the equipment resulting in increased manufacturing costs.

Alternatively, vertical Hall effect devices may be used. U.S. Pat. No. 4,929,993, issued on May 29, 1990 discloses one such device. In these devices, the current flows in the Z (out of plane) direction. These devices, however, exhibit low sensitivity, instability, and excessive cross-talk between different dimensions of the magnetic field. Yet another approach is to use a single chip with magnetic concentrators. This approach results in higher post processing costs.

An out of plane sensor that can be combined with other circuits on a chip is beneficial. A packaged sensor capable of sensing the out of plane component of a magnetic field is useful. The ability to package a sensor capable of measuring more than one dimension of a magnetic field would also be useful. A method of manufacturing such a device in a commonly used semiconductor process, e.g. CMOS, would be beneficial.

SUMMARY

In accordance with one embodiment, a complimentary metal oxide semiconductor (CMOS) sensor system includes a doped well extending along a first axis of a doped substrate, a first electrical contact positioned within the doped well, a second electrical contact positioned within the doped well and spaced apart from the first electrical contact along the first axis, a third electrical contact positioned within the doped well and located between the first electrical contact and the second electrical contact along the first axis, and a fourth electrical contact electrically coupled to the doped well at a location of the doped well below the third electrical contact.

In accordance with another embodiment, a complimentary metal oxide semiconductor (CMOS) sensor system includes a first doped contact on a top surface of a doped substrate, a second doped contact on the top surface of the doped substrate, a third doped contact on the top surface of the doped substrate and located between the first doped contact and the second doped contact, a first doped well conductively coupled to each of the first doped contact, the second doped contact, and the third doped contact, and a fourth electrical contact on the top surface of the doped substrate and electrically coupled to the first doped well at a location of the first doped well directly underneath the third electrical contact.

In yet another embodiment, a method of sensing a magnetic field includes supplying a current to a first doped well portion through a first doped contact at a top surface of a substrate, discharging at least a first portion of the current from the first doped well portion through a second doped contact at the top surface of the substrate, exposing the at least a first portion of the current moving along the first doped well portion between the first doped contact and the second doped contact to a magnetic field, generating a first Hall voltage between the top surface of the substrate and a portion of the substrate underlying the top surface with the at least a first portion of the current, and detecting the first Hall voltage using a third doped contact at the top surface of the substrate and a fourth doped contact at the top surface of the substrate.

DESCRIPTION

A vertical Hall Effect sensor100is depicted inFIGS. 1-4. The sensor100is formed in a substrate102which in this embodiment is p-doped. The doping of the substrate102and the other components of the sensor100may be reversed if desired.

Within the p-doped substrate102, an n− doped well104extends between an n+ doped contact106and another n+ doped contact108. A third n+ doped contact110is located within the n− doped well104at a location midway between the n+ doped contact106and the n+ doped contact108.

A second n− doped well112includes a first portion114that extends from a beneath the n− well104to an upwardly extending portion116of the n− doped well112located on a first side of the n− well104. A second upwardly extending portion118is located on the opposite side of the n− well104. The portions116and118extend upwardly to the top surface120of the substrate102at a location spaced apart from the n− doped well104. One n+ doped contact122is located within the portion116at the top surface120of the substrate102and another n+ doped contact124is located within the portion118at the top surface120of the substrate102.

In operation, a Hall voltage measuring device130is positioned across the contacts110and124. The Hall voltage measuring device130may be a circuit on the substrate102or an off chip device which amplifies the Hall voltage. Next, a current is supplied to the contact106as indicated by the arrow132inFIG. 2with a return path (arrow134) provided through the contact108. Within the substrate102, the current will flow through the n− doped well104from the contact106to the contact108.

In the presence of a magnetic field with a component that is parallel to the upper surface120and orthogonal to the axis defined by the n− doped well104between the contact106to the contact108, the Lorentz force influences the path of the current travelling within the n− doped well104. For example, in n type doped materials the electrons, depending upon the direction of the magnetic field, may be forced toward the upper surface120or toward the lower surface140.

Accordingly, a Hall voltage is established between the contact110and the upper part of the portion114of the well112, which is in contact with the well104. Consequently, the Hall voltage that is established between the contact110and the contact122, by way of the buried well112, is detected by the Hall voltage measuring device130. If desired, another voltmeter may be connected between the contact110and the contact124.

An alternative sensor system150is shown inFIG. 5. The sensor system150is formed in a substrate152which in this embodiment is p-doped. The doping of the substrate152and the other components of the sensor system150may be reversed if desired.

The sensor system150includes two sensors1541and1542. The sensors154xare substantially identical to the sensor100. Thus, each of the sensors154xinclude an n− doped well156xwhich extends between an n+ doped contact158xand another n+ doped contact160x. A third n+ doped contact162xis located within the n− doped well156xat a location midway between the n+ doped contact156xand the n+ doped contact158x.

A second n− doped well164xincludes a first portion166xthat extends from a beneath the n− well156xto an upwardly extending portion168xof the n− doped well164located on a first side of the n− well156x. A second upwardly extending portion170xis located on the opposite side of the n− well156x. The portions168xand170xextend upwardly to the top surface172xof the substrate152xat a location spaced apart from the n− doped well156x. One n+ doped contact174xis located within the portion168xat the top surface172xof the substrate152xand another n+ doped contact176xis located within the portion170xat the top surface172xof the substrate152x.

The sensor system150functions in substantially the same manner as the sensor100. The primary difference results from the orientation of the second n− doped wells1641and1642. Specifically, the centerline1781of the sensor1541defines an axis that is orthogonal to an axis defined by the centerline1782of the sensor1542. Accordingly, while the path of a current travelling within the n− doped well1561is not influenced by the Lorentz force by a component of a magnetic field that is parallel to the upper surface172and parallel to the centerline1781, that same magnetic field component will be orthogonal to the centerline1782. Thus, the sensor1542will sense the magnetic field component that is not sensed by the sensor1541. Similarly, the sensor1541will sense a component of a magnetic field that is parallel to the upper surface172and parallel to the centerline1782that is not sensed by the sensor1542.

Accordingly, the sensor system150provides sensing of a magnetic filed in both the x-axis and the y-axis.

An alternative sensor200for sensing a magnetic field in the x-axis, the y-axis, and the z-axis is depicted inFIGS. 6-7. The sensor200is formed in a substrate202which in this embodiment is p-doped. The doping of the substrate202and the other components of the sensor200may be reversed if desired.

Within the p-doped substrate202, an n− doped well204extends between an n+ doped contact206and another n+ doped contact208along a first leg210. A third n+ doped contact212is located within the n− doped well204at a location midway between the n+ doped contact206and the n+ doped contact208. A second leg214of the n− doped well204extends between an n+ doped contact216and another n+ doped contact218. The n+ doped contact212is located within the n− doped well204at a location midway between the n+ doped contact216and the n+ doped contact218.

A second n− doped well220includes a first leg222that extends beneath the intersection of the leg210and the leg214of the n− well204from an upwardly extending portion224of the n− doped well220to an upwardly extending portion226of the n− doped well220. The portion224extends upwardly to the top surface228of the substrate202at a location spaced apart from the leg210and the leg214of the n− doped well204. One n+ doped contact230is located within the portion224at the top surface228of the substrate202. The portion226also extends upwardly to the top surface228of the substrate202at a location spaced apart from the leg210and the leg214of the n− doped well204. Another n+ doped contact232is located within the portion226at the top surface228of the substrate202.

Another leg240of the that n− doped well220extends beneath the intersection of the leg210and the leg214of the n− well204from an upwardly extending portion242of the n− doped well240to an upwardly extending portion244of the n− doped well240. The portion242extends upwardly to the top surface228of the substrate202at a location spaced apart from the leg210and the leg214of the n− doped well204. One n+ doped contact246is located within the portion242at the top surface228of the substrate202. The portion244also extends upwardly to the top surface228of the substrate202at a location spaced apart from the leg210and the leg214of the n− doped well204. Another n+ doped contact248is located within the portion244at the top surface228of the substrate202.

The sensor200functions in fundamentally the same manner as the sensor100. The difference in structure, however, allows the sensor200to be configured and/or operated in a variety of ways to sense components of a magnetic field. By way of example, a current may be introduced into the sensor200through the contact206and drawn out through the contact208. Accordingly, within the substrate202, the current will flow through the n− doped well204along the leg210from the contact206to the contact208. Consequently, in the presence of a magnetic field with a component that is parallel to the upper surface228, and orthogonal to the axis defined by the leg210of the n− doped well204, the Lorentz force influences the path of the current travelling within the leg210of the n− doped well204. For example, in n type doped materials the electrons, depending upon the direction of the magnetic field, may be forced toward the upper surface228or toward the lower surface250.

Accordingly, a Hall voltage is generated between the upper surface228and the lower surface250within the leg210. The Hall voltage is thus established between the contact212and the upper part of the intersection of the legs222and240of the well220, which is in contact with the well204. Consequently, the Hall voltage may be measured between the contact212and any of the contacts230,232,246, or248.

Additionally, a current may be introduced into the sensor200through the contact216and drawn out through the contact218. Accordingly, within the substrate202, the current will flow through the n− doped well204along the leg214from the contact216to the contact218. Consequently, in the presence of a magnetic field with a component that is parallel to the upper surface228, and orthogonal to the axis defined by the leg214of the n− doped well204, the Lorentz force influences the path of the current travelling within the leg214of the n− doped well204. For example, in n type doped materials the electrons, depending upon the direction of the magnetic field, may be forced toward the upper surface228or toward the lower surface250.

Accordingly, a Hall voltage is generated between the upper surface228and the lower surface250within the leg214. The Hall voltage is thus established between the contact212and the upper part of the intersection of the legs222and240of the well220, which is in contact with the well204. Consequently, the Hall voltage may be measured between the contact212and any of the contacts230,232,246, or248.

The sensor200may also be used to sense a magnetic field with a component that is perpendicular to the upper surface228. By way of example, a current may be introduced into the sensor200through the contact216and drawn out through the contact218. Accordingly, within the substrate202, the current will flow through the n− doped well204along the leg214from the contact216to the contact218. Consequently, in the presence of a magnetic field with a component that is perpendicular to the upper surface228, the Lorentz force influences the path of the current travelling within the leg214of the n− doped well204. For example, in n type doped materials the electrons, depending upon the direction of the magnetic field, may be forced toward the contact206or toward the contact208.

Accordingly, a Hall voltage is generated between the contact206and the contact208within the leg210. Consequently, the Hall voltage may be measured between the contact206and the contact208.

Moreover, current may likewise be caused to flow through the leg210(e.g., through the contact206), the leg222(e.g., through the contact232), and the leg240(e.g., through the contact246), to produce a Hall voltage measurable across the contacts in the intersecting leg in response to a component of a magnetic field perpendicular to the surface228.

The sensor200is thus capable of sensing magnetic fields along the x-axis, the y-axis, and the z-axis of the sensor200. As such, the sensor200may be used in various applications such as, but not limited to, a complimentary metal oxide semiconductor (CMOS) compass, a sensor for detecting and measuring the components of a magnetic field generated by different magnetic sources, and the detection of a magnetic bead fielding order to detect a cell or molecule.