Low fly height in-plane magnetic image sensor chip
Disclosed is a low fly height in-plane magnetic image sensor chip. This sensor chip comprises a silicon (Si) substrate with a pit on the surface, a magnetoresistive sensor, and an insulating layer. The magnetoresistive sensor is located on the bottom surface of the pit in the Si substrate. The insulating layer is located above the magnetoresistive sensor. The magnetic image surface detected during operation is coplanar or parallel with the surface of the Si substrate surface. The input and output ends of the magnetoresistive sensor are connected with leads directly, or bonded with leads through pads, or through a conducting post and pads to form connections. And the flying height of the leads is lower than the height of the surface of the Si substrate. This technical solution has several advantages, such as compact structure, high output signal, and direct contact with the magnetic image.
1. A low fly height in-plane magnetic image sensor chip for detecting a magnetic image, comprising:
a silicon (Si) substrate with a pit on a surface of the Si substrate,
a magnetoresistive sensor, and
an insulating layer,
wherein the magnetoresistive sensor is located on the bottom surface of the pit in the Si substrate, the insulating layer is located above the magnetoresistive sensor, and the insulating layer is provided with a window corresponding to input and output ends of the magnetoresistive sensor,
wherein the input and output ends of the magnetoresistive sensor are connected with leads directly, or bonded with leads through pads, or through a conducting post and pads to form connections at the window,
wherein the conducting post connects the input and output ends of the magnetoresistive sensor and the pads located on the input and output ends of the magnetoresistive sensor or the conducting post,
wherein the plane where the magnetic image is located is a magnetic image detection plane, and the direction of the magnetic image moving in the magnetic image detection plane when working relative to the magnetoresistive sensor is a scanning direction, wherein the fly height of the leads is lower than the height of the surface of the Si substrate, and the magnetic image detection plane is parallel or coplanar with the surface of the Si substrate.
2. The low fly height in-plane magnetic image sensor chip according to claim 1 , wherein a bottom plane of the pit is parallel with the surface of the Si substrate.
3. The low fly height in-plane magnetic image sensor chip according to claim 1 , wherein the magnetoresistive sensor is one of Hall, AMR, GMR or TMR magnetoresistive sensors.
4. The low fly height in-plane magnetic image sensor chip according to claim 1 , wherein the insulating layer is aluminum oxide, silicon nitride, silicon oxide, photoresist, polyimide or benzocyclobutene.
5. The low fly height in-plane magnetic image sensor chip according to claim 1 , wherein the surface of the Si substrate is higher than the upper surface of the magnetoresistive sensor by 1-10 um.
6. The low fly height in-plane magnetic image sensor chip according to claim 1 , wherein the magnetic image sensor chip further comprises a PCB, and the input and output ends of the magnetoresistive sensor or the pads are bonded to the PCB with leads to form connections.
7. The low fly height in-plane magnetic image sensor chip according to claim 6 , wherein the magnetic image sensor chip further comprises a permanent magnet assembly, and the magnetic field sensitive direction of the magnetoresistive sensor is parallel to the scanning direction.
8. The low fly height in-plane magnetic image sensor chip according to claim 7 , wherein the permanent magnet assembly is a concave permanent magnet, and a surface of the concave permanent magnet provided with a groove directly faces the back of the PCB, the grooving direction is parallel to the magnetic image detection plane and perpendicular to the magnetic field sensitive direction, and the magnetization direction of the concave permanent magnet is perpendicular to the direction of the PCB.
9. The low fly height in-plane magnetic image sensor chip according to claim 7 , wherein the permanent magnet assembly comprises two permanent magnets having the same magnetization direction, wherein the two permanent magnets are symmetrically located at two sides of the PCB along the scanning direction respectively, and the magnetization direction thereof is perpendicular to the front of the PCB.
10. The low fly height in-plane magnetic image sensor chip according to claim 7 , wherein the permanent magnet assembly comprises one back permanent magnet located at the back of the PCB and two side permanent magnets disposed symmetrically at two sides of the PCB along the scanning direction, wherein magnetization directions of the back permanent magnet and the two side permanent magnets are both perpendicular to the magnetic image detection plane, and the magnetization direction of the back permanent magnet is opposite to the magnetization direction of the two side permanent magnets.
11. The low fly height in-plane magnetic image sensor chip according to claim 1 , wherein the magnetic field sensitive direction of the magnetoresistive sensor is parallel/perpendicular to the magnetic image detection plane, and when the magnetic field sensitive direction of the magnetoresistive sensor is parallel to the magnetic image detection plane, the magnetic field sensitive direction is parallel/perpendicular to the scanning direction.
12. The low fly height in-plane magnetic image sensor chip according to claim 1 , wherein the magnetoresistive sensor is of a half-bridge structure comprising two, three or four magnetic sensitive units arranged into two rows and one column, three rows and one column or two rows and two columns, and magnetic field sensitive directions of the magnetic sensitive units are identical; the two magnetic sensitive units have the same resistance and directly constitute a half bridge; the resistance of the magnetic sensitive unit located in the middle row among the three magnetic sensitive units is half of the resistance of each of the two magnetic sensitive units located in two side rows, and the two magnetic sensitive units located in two side rows are connected in parallel to form a half-bridge structure with the magnetic sensitive unit located in the middle row; the four sensitive units have the same resistance, two magnetic sensitive units in the same row are connected in parallel, the two rows are connected in series to form a half-bridge structure, and the column direction thereof is parallel to the scanning direction.
13. The low fly height in-plane magnetic image sensor chip according to claim 12 , wherein the full-bridge or half-bridge structure is a single low fly height in-plane magnetic image sensor chip integrated with multiple magnetic sensitive units, or a combination of multiple discrete elements each integrated with one or more low fly height in-plane magnetic image sensor chips.
14. The low fly height in-plane magnetic image sensor chip according to claim 1 , wherein the magnetoresistive sensor is of a full-bridge structure comprising four magnetic sensitive units, the magnetic sensitive units have identical magnetic field sensitive directions and are arranged into two rows and two columns, two magnetic sensitive units comprised in the two half bridges constituting the full bridge are located in two rows but in different columns respectively, and column directions thereof are parallel to the scanning direction.
15. A micro-manufacturing method of a low fly height in-plane magnetic image sensor chip, wherein the micro-manufacturing method comprises:
forming a pit on a surface of a silicon substrate by DRIE or a wet etching process, and flattening the bottom of the pit;
depositing a magnetoresistive material thin film at the bottom of the pit, and patterning the magnetoresistive material thin film to form a magnetoresistive sensor;
depositing an insulating layer above the magnetoresistive sensor, and forming a window of input and output ends of the magnetoresistive sensor on the insulating layer; and
flattening the insulating layer.
16. The micro-manufacturing method of a low fly height in-plane magnetic image sensor chip according to claim 15 , wherein a pad is formed in the window of the input and output ends of the magnetoresistive sensor.
17. The micro-manufacturing method of a low fly height in-plane magnetic image sensor chip according to claim 15 , wherein a conducting post is deposited and shaped in the window of the input and output ends of the magnetoresistive sensor, a pad is formed on the conducting post, the conducting post passes through the insulating layer, and the pad is located above the insulating layer.
18. The micro-manufacturing method of a low fly height in-plane magnetic image sensor chip according to claim 15 , wherein the step (2) comprises:
depositing a bottom conducting layer at the bottom of the pit, and patterning the bottom conducting layer;
depositing a magnetic tunnel junction layer on the bottom conducting layer, and patterning the magnetic tunnel junction layer to form a magnetic tunnel junction element and a non-magnetic tunnel junction element;
depositing a second insulating layer on the magnetic tunnel junction layer, and flattening to expose the magnetic tunnel junction layer; and
depositing a top conducting layer above the second insulating layer and the magnetic tunnel junction layer, and patterning the top conducting layer.
19. The micro-manufacturing method of a low fly height in-plane magnetic image sensor chip according to claim 18 , wherein the input and output ends of the magnetoresistive sensor are located on the top conducting layer above the non-magnetic tunnel junction element, and the non-magnetic tunnel junction element is connected to a magnetic tunnel junction element in the adjacent magnetoresistive sensor by the bottom conducting layer or the top conducting layer.
20. The micro-manufacturing method of a low fly height in-plane magnetic image sensor chip according to claim 18 , wherein the second insulating layer comprises aluminum oxide, silicon nitride, silicon oxide, photoresist, polyimide, or benzocyclobutene.