SOI semiconductor structure and method for manufacturing an SOI semiconductor structure

Abstract

An SOI semiconductor structure, including a substrate layer formed on a back side and a semiconductor layer of a second conductivity type formed on a front side, an insulating layer being disposed between the substrate layer and the semiconductor layer, a three-dimensional Hall sensor structure having a sensor region made up of a monolithic semiconductor body being formed in the semiconductor layer, and the semiconductor body extending from an underside up to the front side, at least three first metallic terminal contacts being formed on the upper side, and at least three second metallic terminal contacts being formed on the underside, the first terminal contacts being offset with respect to the second terminal contacts in a projection perpendicular to the front side, each first terminal contact and each second terminal contact being formed in each case on a highly doped semiconductor contact region of a second conductivity type.

Claims

1. A method for manufacturing an SOI semiconductor structure, including a three-dimensional Hall sensor structure, the method comprising: manufacturing, in a first process stage, at least three second highly doped semiconductor contact regions of a second conductivity type that are assigned to each of the second terminal contacts, via implantation in a plurality of process steps on a first front surface of a first semiconductor wafer, which includes a semiconductor layer having the first front surface and a first back surface; joining, in a second process stage, the first front surface of the first semiconductor wafer to a second front surface of a second semiconductor wafer formed as a substrate layer; forming an insulating layer between the first semiconductor wafer and the second semiconductor wafer after the joining, wherein, due to the joining, the first back surface of the first semiconductor wafer becomes a front side of the SOI semiconductor wafer, and the second back surface of the second semiconductor wafer becomes the back side of the SOI semiconductor wafer, and wherein the semiconductor surface of the first front surface of the first semiconductor wafer becomes a buried lower surface above the insulating layer after the joining; thinning, in a third process stage, a front side of the first semiconductor wafer and highly doped first semiconductor contact regions are created via implantation; and forming first terminal contacts on each of the first semiconductor contact regions.

2. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein a trench structure completely surrounding the sensor region is formed on the front side in a fourth process stage.

3. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein a doped polysilicon is deposited and structured during the first process stage for connecting the highly doped second semiconductor contact regions as second contact regions.

4. The method for manufacturing an Sal semiconductor wafer according to claim 1, wherein the structured polysilicon is covered with the aid of a dielectric during the first process stage.

5. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein an oxide is formed in the second process stage as an insulating layer.

6. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein the semiconductor layer is formed with two different thicknesses in the third process stage, wherein the area of the sensor region has a greater thickness than the thickness of the area of the semiconductor layer surrounding the sensor region.

7. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein a semiconductor layer having a thickness between 2 μm and 30 μm or less than 100 μm is formed in the third process stage via a CMP process.

8. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein a semiconductor layer having a uniform thickness is formed in the third process stage.

9. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein the trench etching outside the sensor region is carried out in the third process stage.

10. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein the second buried terminal contacts are connected from the front side of the semiconductor layer in another process stage.

11. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein the second terminal contacts are connected from the back side in another process stage.

12. The method for manufacturing an SOI semiconductor wafer according to claim 1, wherein the first terminal contacts and the second terminal contacts are electrically connected to the integrated circuit in a fifth process stage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 shows a cross-sectional view of a semi-finished product for manufacturing an SOI semiconductor structure;

(3) FIG. 2 shows a cross-sectional view of a first specific embodiment of an SOI semiconductor structure, including a sensor region;

(4) FIG. 3 shows a top view of an upper side of the sensor region illustrated in FIG. 2;

(5) FIG. 4 shows a cross-sectional view of the SOI semiconductor structure with two different thicknesses of a semiconductor region; and

(6) FIG. 5 shows cross-sectional view of the SOI semiconductor structure, including a connection of buried terminal contacts from the back side.

DETAILED DESCRIPTION

(7) The illustration in FIG. 1 shows a cross-sectional view of an SOI semiconductor structure WF. SOI semiconductor structure WF comprises a first semiconductor wafer WF1, joined or bonded to a second semiconductor wafer WF2. An insulating layer OXS made from a silicon dioxide is formed between the two semiconductor wafers WF1 and WF2 by the bonding of the two semiconductor wafers WF1 and WF2. Semiconductor wafers WF1 and WF2 are preferably designed as silicon wafers.

(8) First semiconductor wafer WF1 includes a semiconductor layer HLS of a second conductivity type, which has a first front surface VF1 and a first back surface RF1.

(9) Second semiconductor wafer WF2, which has a second front surface VF2 and a second back surface RF2, comprises a substrate layer. The substrate layer is designed as a carrier layer.

(10) The two front surfaces VF1 and VF2 of the two semiconductor wafers WF1 and WF2, each preferably covered with a silicon dioxide, are joined in an integral and force-fitting manner along a joining surface BF, also referred to as a bond surface. Joining surface BF runs within insulating layer OXS, the insulating layer being essentially made up of silicon dioxide, i.e. by more than 50%.

(11) Before the joining process, first front surface VF1 forms a surface of first semiconductor wafer WF1, three highly doped second semiconductor contact regions HG21, HG22 and HG23 of a second conductivity type being preferably created by means of implantation on the surface of first semiconductor wafer WF1 in a plurality of process steps before the joining process.

(12) A second terminal contact K21, K22 and K23 is subsequently formed on each of second semiconductor contact regions HG21, HG22 and HG23. Second terminal contacts K21, K22 and K23 are preferably formed from doped polysilicon or metal.

(13) It should be noted that second semiconductor contact region HG23 and second terminal contact K23 are only illustrated in a subsequent top view for reasons of clarity.

(14) The illustration in FIG. 2 shows a cross-sectional view of a first specific embodiment of an SOI semiconductor structure having a sensor region. Only the differences from the illustration in FIG. 1 are explained below.

(15) Due to the joining, first back surface RF1 of first semiconductor wafer WF1 becomes a front side VS of semiconductor layer HLS, semiconductor layer HLS of first semiconductor wafer WFI being thinned from a thickness D of several hundred μm to a thickness D in the range between 2 μm and 30 μm, preferably by means of a CMP process.

(16) Second back surface RF2 of second semiconductor wafer WF2 becomes back side RS of SOI semiconductor structure WF.

(17) The semiconductor surface of first front surface VF1 of first semiconductor wafer WF1 becomes a buried lower surface above insulating layer OXS after the joining.

(18) After the joining, highly doped first semiconductor contact regions HG11, HG12, HG13 are created in subsequent process steps by means of implantation, and first terminal contacts K11, K12, K13 are subsequently formed on each of first semiconductor contact regions HG11, HG12, HG13.

(19) To form a sensor region for forming a three-dimensional Hall sensor structure HSENS, a semiconductor body HLK is electrically insulated from remaining semiconductor layer HLS with the aid of a circumferential trench structure TR, the ratio of thickness D of semiconductor layer HLS or semiconductor body HLK to a length L of semiconductor body HLK comprising a range between 0.6 and 1.4 or a range between 0.8 and 1.2 in the sensor region. The ratio is preferably 1. The lateral extension of the sensor region results from length L of semiconductor body HLK between two first terminal contacts K11, K12 and K13.

(20) Second terminal contacts K21, K22 and K23 are electrically connected from front side VS in additional process steps.

(21) Semiconductor layer HLS outside the sensor region, i.e. remaining semiconductor layer HLS, has the same thickness D as within the sensor region. An integrated circuit—not illustrated—is formed in an area of remaining semiconductor layer HLS. The integrated circuit is electrically connected to terminal contacts K11, K12, K13, K21, K22 and K23 with the aid of printed conductors—not illustrated.

(22) One advantage is that an easy and cost-effective manufacturing results with the aid of a monolithic design of the integrated circuit and Hall sensor structure HSENS in semiconductor layer HLS.

(23) The illustration in FIG. 3 shows a top view of a front side VS of the sensor region illustrated in FIG. 2. Only the differences from the illustration in FIG. 2 are explained below.

(24) Semiconductor body HLK, and thus the sensor region, is designed to be electrically insulated from the other regions of semiconductor layer HLS with the aid of trench structure TR, which is provided with a square design for reasons of clarity. Semiconductor body HLK is preferably provided with a hexagonal design or is designed in the shape of a polygon.

(25) Second semiconductor contact regions HG21, HG22 and HG23—drawn with a dashed line—have a multiple, in particular a ternary, symmetry with regard to an axis of symmetry SA.

(26) First semiconductor contact regions HG11, HG12 and HG13, formed on front side VS, also have a multiple, in particular a ternary, symmetry with regard to axis of symmetry SA.

(27) First semiconductor contact regions HG11, HG12 and HG13 on front side VS are disposed, offset with respect to second semiconductor contact regions HG21, HG22 and HG23, on burred lower surface OS.

(28) The illustration in FIG. 4 shows a cross-sectional view of SOI semiconductor structure WF in an embodiment having two different thicknesses D of semiconductor layer HLS. Only the differences from the illustration in FIG. 2 are explained below.

(29) The thickness of semiconductor layer HLS outside the sensor region, i.e. in remaining semiconductor layer HLS, is much lower than the thickness of semiconductor layer HLS within the sensor region. The thickness of semiconductor body HLK directly outside the sensor region is reduced, so that trench structure TR is already formed in the region having a low thickness.

(30) One advantage is that the reliability is increased and the manufacturing costs reduced by designing a trench structure with a reduced depth.

(31) An integrated circuit IS having a plurality of CMOS transistors is formed in remaining semiconductor layer HLS, which has, for example, a thickness of 0.5 μm. The individual transistors or other components or groups of transistors or groups of components may be disposed in regions separated from each other with the aid of the trench structure.

(32) Integrated circuit IS is connected to Hall sensor structure HSENS—which is not illustrated.

(33) The illustration in FIG. 5 shows a cross-sectional view of SOI semiconductor structure WF, including a connection of buried terminal contacts K21, K22 and K23 from back side RS. Only the differences from the illustration in FIG. 4 are explained below.

(34) Back side RS, except for insulating layer OXS, is etched away beneath the sensor structure. Second terminal contacts K21, K22 and K23—the latter is not illustrated—are subsequently contacted from the back side with the aid of a mask process, i.e. second terminal contacts K21, K22 and K23 are brought out in the etched-away region and may be easily electrically connected thereby.

(35) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.