CN114944422B - Floating island device and manufacturing method thereof - Google Patents
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Abstract
The invention relates to a floating island device and a manufacturing method thereof in the technical field of semiconductors, and the floating island device comprises an epitaxial layer, a surface layer, a bottom layer, a first doping region, a second doping region and ohmic contact metal, wherein a plurality of epitaxial layers are arranged between the surface layer and the bottom layer, and the first doping region and the second doping region are arranged in at least one epitaxial layer; the ohmic contact metal is connected with the first doping region and the second doping region by forming ohmic contact; the floating island device has the advantages of eliminating the obstruction of space charge to current and communicating the epitaxial layer with the first doping region, and the problem of voltage overshoot or turn-on delay of the traditional floating island device when the device is in a recovery conducting state is solved.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a floating island device and a manufacturing method thereof.
Background
In recent years, energy conservation and emission reduction are more and more emphasized internationally, which puts higher requirements on loss control and efficiency improvement of large-scale power electronic equipment. Semiconductor power devices have received much attention from the industry as an important component of power electronic equipment.
Breakdown voltage is an important indicator of a semiconductor power device and represents the maximum voltage that the device can withstand. A floating island device (or referred to as a floating junction device) refers to a special power device in which a region that is not directly connected to an electrode and has a doping type opposite to that of a drift region is present in the drift region. At the moment that the drift region is doped into the N-type floating island device and is changed from a blocking state to a conducting state, because the P-type doped region in the drift region is not directly connected with the electrode, hole carriers cannot enter the P-type doped region, negative charges are left in the P-type doped region, meanwhile, a large number of positive charges are attracted into the N-type drift region, the drift region is occupied by the positive charges in a space charge mode, energy bands are bent, and accordingly, the flow of the electron carriers is hindered. I.e., floating island devices with a floating doped region in the drift region, cannot complete conduction recovery at low voltage. In this case, charge can only conduct through the drift region if the bias voltage is sufficiently large. Therefore, when the conventional floating island device is turned on, voltage overshoot or turn-on delay occurs, resulting in a large energy loss.
Disclosure of Invention
The invention provides a floating island device and a manufacturing method thereof aiming at the defects in the prior art, the floating island device has the advantage of eliminating current obstruction, and the problem of voltage overshoot or turn-on delay of the traditional floating island device when the traditional floating island device is recovered to a conducting state is solved.
In order to solve the technical problem, the invention is solved by the following technical scheme:
the floating island device comprises a surface layer and a bottom layer, wherein a plurality of epitaxial layers are arranged between the surface layer and the bottom layer, a first doping area and a second doping area are formed in at least one epitaxial layer, ohmic contact metal is formed on the at least one epitaxial layer, and the ohmic contact metal and the first doping area and the second doping area form ohmic contact.
Optionally, at least a portion of the second doped region is disposed in the first doped region, the doping type of the first doped region is opposite to that of the epitaxial layer, and the doping type of the second doped region is the same as that of the epitaxial layer.
Optionally, the doping concentration of the second doping region is higher than the doping concentration of the epitaxial layer.
Optionally, the epitaxial layers are stacked to form a step shape.
Optionally, in the three-dimensional structure, the three-dimensional structure includes a first dimension, a second dimension, and a third dimension, and the ohmic contact metal extends to the whole cell or only a part of the cell in a certain dimension.
Optionally, in the three-dimensional structure, the three-dimensional structure includes a first dimension, a second dimension, and a third dimension, and the first doped region and the second doped region extend to the entire cell in the third dimension; or the first doped region extends to the whole unit cell in the third dimension, and only a part of the second doped region extends in the third dimension; or only a portion of the first doped region and the second doped region extend in the third dimension.
Optionally, the ohmic contact metal is distributed on one side or both sides of the unit cell.
Optionally, when a plurality of the second doped regions are included in the at least one epitaxial layer, the ohmic contact metal forms the ohmic contact with at least one of the second doped regions.
Optionally, the ohmic contact metal, the first doped region, and the second doped region are formed on each epitaxial layer, and the ohmic contact metals on different epitaxial layers are not in contact with each other.
Optionally, a stepped trench is formed in a cell of the floating island device, and the ohmic contact metal is formed on a horizontal mesa of the stepped trench.
Optionally, when the floating island device is a schottky diode, the surface layer includes an anode metal, and the bottom layer includes a cathode-drain metal; when the floating island device is a PN diode, the surface layer comprises anode metal and an anode doped region, the doping type of the anode doped region is opposite to that of the epitaxial layer, and the bottom layer comprises cathode and drain metal; when the floating island device is a junction barrier Schottky diode, the surface layer comprises anode metal, an anode doped region and an anode epitaxial region or the surface layer comprises anode metal, an anode doped region, an anode epitaxial region and a second doped region, the doping type of the anode doped region is opposite to that of the epitaxial layer, the doping type of the anode epitaxial region is the same as that of the epitaxial layer, and the bottom layer comprises cathode and drain metal; when the floating island device is an MOSFET, the surface layer comprises source metal, a channel well doped region, a source doped region, a gate oxide layer and grid metal, and the bottom layer comprises cathode and drain metal; and when the floating island device is an IGBT, the surface layer comprises source metal, a channel well doped region, a source doped region, a gate oxide layer and gate metal, and the bottom layer comprises cathode and drain metal and a drain doped region.
According to the manufacturing method of the floating island device, the manufacturing method is used for manufacturing any floating island device.
According to the embodiment of the invention, the manufacturing method of the floating island Schottky diode comprises the following steps: an epitaxial layer is obtained by epitaxial growth, the epitaxial layer is made of N-type semiconductor material and has the doping concentration of
~
Forming a first doped region and a second doped region in the epitaxial layer by photoetching and P-type ion implantation, and repeating the operations to form a drift region, wherein the drift region comprises a plurality of epitaxial layers, a plurality of first doped regions and a plurality of second doped regions; after the drift region is prepared, etching a part of region from the surface of the wafer to expose the first doped region and the second doped region through a dry etching process, and forming ohmic contact metal on the exposed first doped region and the exposed second doped region through a metal sputtering method or a metal evaporation method; forming a surface layer and a bottom layer at two ends of the drift region by a metal sputtering method or a metal evaporation method; and then carrying out high-temperature annealing to form ohmic contacts between the bottom layer and the epitaxial layer, between the ohmic contact metal and the first doped region and between the ohmic contact metal and the second doped region.
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
by introducing the second doping region with the doping type opposite to that of the first doping region, at the moment that the floating island device is changed from a blocking state to a conducting state, along with the reduction of external potentials at two ends of the drift region, an electric field opposite to that of the blocking electric field appears in the epitaxial layer, so that positive charges in the epitaxial layer are pushed into the second doping region, space charges in the epitaxial layer are gathered in the second doping region instead of being dispersed in the whole epitaxial layer, the charges in the drift region can be prevented from generating a blocking effect on current due to charge accumulation when the bias voltage is lower, the drift region can smoothly conduct current, and the floating island device can still quickly recover the conducting capacity even under the lower bias voltage. When the doping concentration of the second doping region is very high, the tunneling effect of a PN junction formed between the second doping region and the floating island can be increased, so that at the moment of opening, along with the reduction of the external potential at two ends of the drift region, space charges in the epitaxial layer are accumulated in the second doping region, and the recombination of current carriers between the second doping region and the floating island can be realized by utilizing the tunneling effect, thereby further reducing the width of a depletion region around the floating island and increasing the current conduction capability;
by introducing the ohmic contact metal, when the floating island device is changed from a blocking state to a conducting state, the first doping region and the second doping region can be communicated through the ohmic contact metal, so that carriers and charges are supplemented to the first doping region and the second doping region, and the device is completely switched on.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic cross-sectional structure diagram of a floating island device according to an embodiment;
fig. 2 is a schematic cross-sectional structural diagram of a first doped region and a second doped region of a floating island device according to a second embodiment;
fig. 3 is a schematic cross-sectional structure diagram of a first doped region and a second doped region of a floating island device according to a third embodiment;
fig. 4 is a schematic cross-sectional structure diagram of a first doped region and a second doped region of a floating island device according to a fourth embodiment;
fig. 5 is a schematic cross-sectional structure diagram of a first doped region and a second doped region of a floating island device according to a fifth embodiment;
fig. 6 is a schematic cross-sectional structure diagram of a first doped region and a second doped region of a floating island device according to a sixth embodiment;
fig. 7 is a schematic cross-sectional structure diagram of the first doped region and the second doped region of a floating island device according to the seventh embodiment;
fig. 8 is a schematic cross-sectional structure diagram of the first doped region and the second doped region of a floating island device according to an eighth embodiment;
fig. 9 is a schematic cross-sectional structure view of the first doped region and the second doped region of the floating island device according to the ninth embodiment;
fig. 10 is a schematic structural diagram of a top view of a first doped region and a second doped region of a floating island device according to the tenth embodiment;
fig. 11 is a schematic structural diagram of a top view of a first doped region and a second doped region of a floating island device according to an eleventh embodiment;
fig. 12 is a schematic cross-sectional view of a surface layer of a floating island schottky diode according to the twelfth embodiment;
fig. 13 is a schematic cross-sectional structure diagram of a surface layer of a floating island PN diode according to a thirteenth embodiment;
fig. 14 is a schematic cross-sectional view of a surface layer of a floating island junction barrier schottky diode according to the fourteenth embodiment;
fig. 15 is a schematic cross-sectional view of a surface layer of a floating island junction barrier schottky diode according to the fifteenth embodiment;
fig. 16 is a schematic cross-sectional view of a surface layer of a floating island MOSFET according to the sixteenth embodiment;
fig. 17 is a schematic cross-sectional view of a bottom layer according to the twelfth embodiment to the sixteenth embodiment;
fig. 18 is a schematic cross-sectional structure of a bottom layer of a floating island IGBT according to the seventeenth embodiment;
fig. 19 is a schematic cross-sectional view of a floating island schottky diode according to the twelfth embodiment;
fig. 20 is a schematic cross-sectional structure diagram of a floating island PN diode according to the thirteenth embodiment;
fig. 21 is a schematic cross-sectional view of a floating island junction barrier schottky diode according to the fourteenth embodiment;
fig. 22 is a schematic cross-sectional view of a floating island junction barrier schottky diode according to the fifteenth embodiment;
fig. 23 is a schematic cross-sectional view of a floating island MOSFET according to the sixteenth embodiment;
fig. 24 is a schematic cross-sectional structure diagram of a floating island IGBT according to the seventeenth embodiment;
fig. 25 is a schematic cross-sectional structure diagram of a fast-on three-layer floating-island device according to an eighteen embodiment;
fig. 26 is a schematic cross-sectional structure diagram of a fast-on three-layer floating-island device according to nineteenth embodiment;
fig. 27 is a schematic three-dimensional structure diagram of a fast turn-on three-layer floating island junction barrier schottky diode according to the twenty first embodiment;
fig. 28 is a schematic diagram of a three-dimensional structure of a fast turn-on three-layer floating island junction barrier schottky diode according to twenty-first embodiment;
fig. 29 is a schematic diagram of a three-dimensional structure of a fast turn-on three-layer floating island junction barrier schottky diode according to twenty-two embodiments;
fig. 30 is a schematic cross-sectional diagram of a fast-on floating island device according to twenty-three embodiments;
fig. 31 is a schematic cross-sectional view of a fast-on floating island device according to twenty-four embodiments.
Reference numerals: 1. an epitaxial layer; 2. a surface layer; 3. a bottom layer; 4. a first doped region; 5. a second doped region; 6. an ohmic contact metal; 7. a drift region; 8. an anode metal; 9. an anode doped region; 10. an anode epitaxial region; 11. a source metal; 12. a channel well doped region; 13. a source doped region; 14. a gate oxide layer; 15. a gate metal; 16. a trench filler; 17. a cathode drain metal; 18. and a drain doped region.
Detailed Description
The present invention will be further described in detail with reference to the following examples, which are illustrative of the present invention and are not intended to limit the present invention thereto.
Example one
At the moment that the existing floating island device is changed from a blocking state to a conducting state, due to the fact that a P-type doped region in a drift region is not directly connected with an electrode, hole carriers near an anode cannot enter the P-type doped regions, negative charges are left in the P-type doped regions, a large number of positive charges are attracted in the drift region, the N-type drift region is occupied by the positive charges in a space charge mode, energy bands are bent, and accordingly the flow of the electron carriers is hindered. I.e., floating island devices with a floating doped region in the drift region, cannot complete conduction recovery at low voltage. In this case, charge can only conduct through the drift region if the bias voltage is sufficiently large. Therefore, when a conventional floating island device is turned on, voltage overshoot or turn-on delay occurs, resulting in a large energy loss.
As shown in fig. 1, in order to solve the problem that the floating island device cannot recover the conduction capability under the condition of a low bias voltage, the present embodiment proposes a basic structure of the floating island device, which includes an epitaxial layer 1, a surface layer 2, a bottom layer 3, a first doped region 4, a second doped region 5, and an ohmic contact metal 6. Wherein, a plurality of epitaxial layers 1 are arranged between the surface layer 2 and the bottom layer 3; a first doping region 4 and a second doping region 5 are arranged in at least one epitaxial layer 1; the ohmic contact metal 6 connects the first and second doped regions 4 and 5 by forming an ohmic contact. The ohmic contact metals 6 formed on the epitaxial layers 1 do not contact each other.
In the embodiment shown in fig. 1, the epitaxial layer 1 may be doped to a concentration of
~
The semiconductor material of (1). />
In the embodiment shown in fig. 1, the first doped region 4 has a doping type opposite to that of the epitaxial layer 1, and the second doped region 5 has a doping type identical to that of the epitaxial layer 1.
In the embodiment shown in fig. 1, the doping concentration of the second doped region 5 is higher than the doping concentration of the epitaxial layer 1.
Taking the epitaxial layer 1 as an N-type semiconductor material as an example, the first doped region 4 may have a doping concentration of
~
The second doped region 5 may be doped with a doping concentration of
~
The doping concentration of the second doping region 5 is higher than the doping concentration of the epitaxial layer 1.
As shown in fig. 1, the length of the second doped region 5 distributed in the first doped region 4 is less than the length of the first doped region 4, the upper edge of the second doped region 5 coincides with the upper edge of the first doped region 4, the upper edge of the second doped region 5 is in direct contact with the epitaxial layer 1, and the lower edge of the second doped region 5 is not lower than the lower edge of the first doped region 4. In other embodiments of the present invention, the upper edge of the second doped region 5 may be higher or lower than the upper edge of the first doped region 4.
In embodiments of the present invention, the shape and position of the second doped region 5 may vary widely. When the length of the second doping region 5 is greater than or equal to the length of the first doping region 4, the depletion region is blocked by the second doping region 5 when the device is blocked and the depletion region expands from top to bottom, so that the depletion region is blocked when the depletion region expands to the first second doping region 5, and advanced breakdown is caused, and therefore, the length of the second doping region 5 can be set to be smaller than the length of the first doping region 4. Since the second doping region 5 is hardly depleted by the first doping region 4 at the time of blocking when the lower edge of the second doping region 5 is lower than the lower edge of the first doping region 4, leading to premature breakdown, the lower edge of the second doping region 5 is set not lower than the lower edge of the first doping region 4. In other embodiments of the present invention, variations of the second doped region 5 may be as shown in fig. 2 to 11.
In other embodiments of the invention the surface layer 2 and the bottom layer 3 may have various designs to form various devices together with the drift region, for example the design of the surface layer 2 may be as shown in fig. 12 to 16 and the design of the bottom layer may be as shown in fig. 17 and 18.
Therefore, by introducing the second doping region 5, when the floating island device is changed from a blocking state to a conducting state, the space charges in the epitaxial layer 1 are gathered in the second doping region 5 instead of being dispersed in the whole epitaxial layer 1, so that the charges in the drift region can avoid the blocking effect on the current due to the charge accumulation when the bias voltage is lower, the current can be smoothly conducted in the drift region, and the conducting capability of the floating island device can still be rapidly recovered even under the lower bias voltage; by introducing the ohmic contact metal 6, when the floating island device is changed from a blocking state to a conducting state, the first doping region 4 and the second doping region 5 can be communicated through the ohmic contact metal, so that carriers are supplemented to the first doping region 4 and the second doping region 5, charges are neutralized, and the device is completely switched on.
Example two
The second doped region 5 in fig. 1 can have various designs. As shown in fig. 2, the position of the second doped region 5 relative to the first doped region 4 may be shifted to the left, e.g. the left edge of the second doped region 5 coincides with the left edge of the first doped region 4, or the right edge of the second doped region 5 coincides with the right edge of the first doped region 4.
EXAMPLE III
The second doped region 5 in fig. 1 can have various designs. As shown in fig. 3, the position of the second doped region 5 relative to the first doped region 4 may be shifted to the left, for example, the left edge of the second doped region 5 protrudes to the left of the left edge of the first doped region 4, or the right edge of the second doped region 5 protrudes to the right of the right edge of the first doped region 4. The length L2 of the portion of the second doped region 5 located in the first doped region 4 is set to be smaller than the length L1 of the first doped region 4.
Example four
The second doped region 5 in fig. 1 can have various designs. As shown in fig. 4, the second doping region 5 may be disposed at one side of the first doping region 4 and the second doping region 5 may not be disposed at the other side.
EXAMPLE five
The second doped region 5 in fig. 1 can have various designs. As shown in fig. 5, the upper edge of the second doped region 5 may be higher than the upper edge of the first doped region 4, i.e. a portion of the second doped region 5 lower than the upper edge of the first doped region 4 is distributed in the first doped region 4.
Example six
The second doped region 5 in fig. 1 can have various designs. As shown in fig. 6, the upper edge of the second doped region 5 may be lower than the first doped region 4, and as in the embodiment shown in fig. 6, the upper edge of the second doped region 5 is directly in contact with the epitaxial layer 1, i.e. the second doped region 5 is not completely surrounded by the first doped region 4, and only the bottom and both sides are surrounded by the first doped region 4. In other embodiments, it is within the scope of the present invention to provide that the upper edge of the second doped region 5 is directly in contact with the epitaxial layer 1.
EXAMPLE seven
The second doped region 5 in fig. 1 can have various designs and the shape can be varied. For example, as shown in fig. 7, the shape of the second doped region 5 may be a zigzag shape.
Example eight
The second doped region 5 in fig. 1 can have various designs. As shown in fig. 8, the second doping regions 5 may be composed of discontinuous portions, for example, the second doping regions 5 distributed in the same first doping region 4 are arranged at intervals in the lateral direction. The sum of the lengths (L21, L22, L23, L24, etc.) of the portions at this time is set to be smaller than the length L1 of the first doped region.
Example nine
The second doped region 5 in fig. 1 can have various designs. As shown in fig. 9, the second doped region 5 may also be composed of several discontinuous portions in the longitudinal direction, for example, each second doped region 5 distributed in the same first doped region 4 is arranged at intervals in the longitudinal direction, in one embodiment, one group or several groups of second doped regions 5 may be distributed in the first doped region 4 (that is, the periphery of one or several second doped regions 5 may be surrounded by the first doped region), and the lower edge of the topmost second doped region 5 may be flush with the upper edge of the first doped region 4 or lower than the upper edge of the first doped region 4. In other embodiments of the present invention, the second doping regions 5 are not limited to be spaced in the longitudinal or transverse direction, but may be spaced in any other direction.
Example ten
The second doped region 5 in fig. 1 can have various designs in the top view, and the shape of the second doped region 5 in the top view can be varied. For example, as shown in fig. 10, the top view of the second doped region 5 may be square, star-shaped, circular, etc.
EXAMPLE eleven
The top view of the first doped region 4 in fig. 1 can have various designs, and the top view shape of the first doped region 4 can have various changes. For example, as shown in fig. 11, the top view of the first doping region 4 may be an ellipse or the like.
Example twelve
As shown in fig. 12, the surface layer 2 may comprise only one layer of anodic metal 8.
As shown in fig. 17, the bottom layer 3 may include only one layer of the cathode/drain metal 17.
As shown in fig. 19, by replacing the surface layer 2 in the first embodiment with the structure shown in fig. 12 and replacing the bottom layer 3 in the first embodiment with the structure shown in fig. 17, a floating island schottky diode can be formed.
Therefore, by introducing the second doping region 5, when the floating island schottky diode is changed from a blocking state to a conducting state, space charges in the epitaxial layer 1 are gathered in the second doping region 5 instead of being dispersed in the whole epitaxial layer 1, so that when the bias voltage is low, charges in the drift region can also avoid the blocking effect on current due to charge accumulation, the drift region can smoothly conduct the current from the anode metal 8 to the cathode and drain metal 17, and the floating island schottky diode can still quickly recover the conducting capability even under the low bias voltage; by introducing the ohmic contact metal 6, when the floating island device is changed from a blocking state to a conducting state, the first doping region 4 and the second doping region 5 can be communicated through the ohmic contact metal 6, so that carriers are supplemented to the first doping region 4 and the second doping region 5, charges are neutralized, and the device is completely switched on.
EXAMPLE thirteen
As shown in fig. 13, the surface layer 2 may comprise a layer of anode metal 8 and a layer of anode doped region 9.
As shown in fig. 17, the bottom layer 3 may include only one layer of the cathode/drain metal 17.
As shown in fig. 20, another floating island PN diode can be formed by replacing the surface layer 2 in the first embodiment with the structure shown in fig. 13 and replacing the bottom layer 3 in the first embodiment with the structure shown in fig. 17.
Wherein, the doping type of the anode doping region 9 is opposite to that of the epitaxial layer 1. Taking the epitaxial layer 1 as an N-type semiconductor material as an example, the anode doped region 9 may be doped with a doping concentration of
~
P-type semiconductor material of (1).
Therefore, by introducing the second doping region 5, when the floating island PN diode is changed from a blocking state to a conducting state, space charges in the epitaxial layer 1 are gathered in the second doping region 5 instead of being dispersed in the whole epitaxial layer 1, so that the charges in the drift region can also avoid the blocking effect on current due to charge accumulation when the bias voltage is low, the drift region can smoothly conduct the current from the anode metal 8 to the cathode and drain metal 17, and the floating island PN diode can still quickly recover the conducting capability even under the low bias voltage; by introducing the ohmic contact metal 6, when the floating island device is changed from a blocking state to a conducting state, the first doping region 4 and the second doping region 5 can be communicated through the ohmic contact metal 6, so that carriers are supplemented to the first doping region 4 and the second doping region 5, charges are neutralized, and the device is completely switched on.
Example fourteen
As shown in fig. 14, the surface layer 2 may comprise an anode metal 8, an anode doped region 9 and an anode epitaxial region 10.
As shown in fig. 17, the bottom layer 3 may include only one layer of the cathode/drain metal 17.
As shown in fig. 21, by replacing the surface layer 2 in the first embodiment with the structure shown in fig. 14 and replacing the bottom layer 3 in the first embodiment with the structure shown in fig. 17, a floating island junction barrier schottky diode can be formed.
The doping type of the anode doping region 9 is opposite to that of the epitaxial layer 1, the doping type of the anode epitaxial region 10 is the same as that of the epitaxial layer 1, and the anode epitaxial region 10 is located on two sides or one side of the anode doping region 9. For example, when the epitaxial layer 1 is an N-type semiconductor material, the anode doped region 9 may have a doping concentration of
~
The anode epitaxial region 10 may be doped with a concentration of ≥ h>
~
The N-type semiconductor material of (1).
Therefore, by introducing the second doping region 5, when the floating island junction barrier schottky diode is changed from a blocking state to a conducting state, space charges in the epitaxial layer 1 are gathered in the second doping region 5 instead of being dispersed in the whole epitaxial layer 1, so that when the bias voltage is lower, the charges in the drift region can also avoid the blocking effect on the current due to the charge accumulation, the drift region can smoothly conduct the current from the anode metal 8 to the cathode and drain metal 17, and the floating island junction barrier schottky diode can still quickly recover the conducting capability even under the lower bias voltage; by introducing the ohmic contact metal 6, when the floating island device is changed from a blocking state to a conducting state, the first doping region 4 and the second doping region 5 can be communicated through the ohmic contact metal 6, so that carriers are supplemented to the first doping region 4 and the second doping region 5, charges are neutralized, and the device is completely switched on.
Example fifteen
As shown in fig. 15, the surface layer 2 may comprise an anode metal 8, an anode doped region 9, an anode epitaxial region 10 and a second doped region 5.
As shown in fig. 17, the bottom layer 3 may include only one layer of the cathode/drain metal 17.
As shown in fig. 22, by replacing the surface layer 2 in the first embodiment with the structure shown in fig. 15 and replacing the bottom layer 3 in the first embodiment with the structure shown in fig. 17, a floating island junction barrier schottky diode can be formed.
The doping type of the anode doping region 9 is opposite to that of the epitaxial layer 1, the doping type of the second doping region 5 is the same as that of the epitaxial layer 1, the doping type of the anode epitaxial region 10 is the same as that of the epitaxial layer 1, and the anode epitaxial region 10 is located on two sides or one side of the anode doping region 9. Taking the epitaxial layer 1 as an N-type semiconductor material, the doped concentration of the anode doped region 9 is
~
The second doped region 5 has a doping concentration ^ or ^ greater than or equal to>
~
Of N-type semiconductor materialThe anodic epitaxial region 10 can be doped in a concentration +>
~ 
Of (3) an N-type semiconductor material.
Therefore, by introducing the second doping region 5 into the surface layer 2 and the drift region, when the floating island junction barrier schottky diode is changed from a blocking state to a conducting state, space charges in the epitaxial layer 1 are gathered in the second doping region 5 instead of being dispersed in the whole epitaxial layer 1, so that when the bias voltage is lower, charges in the drift region can also avoid the blocking effect on current due to charge accumulation, the drift region can smoothly conduct the current from the anode metal 8 to the cathode and drain metal 17, and the floating island junction barrier schottky diode can still rapidly recover the conducting capability even under the lower bias voltage; by introducing the ohmic contact metal 6, when the floating island device is changed from a blocking state to a conducting state, the first doping region 4 and the second doping region 5 can be communicated through the ohmic contact metal 6, so that carriers are supplemented to the first doping region 4 and the second doping region 5, charges are neutralized, and the device is completely switched on.
Example sixteen
As shown in fig. 16, the surface layer 2 may include a source metal 11, a channel well doped region 12, a source doped region 13, a gate oxide layer 14, a gate metal 15, and a trench filler 16.
As shown in fig. 17, the bottom layer 3 may include only one layer of the cathode/drain metal 17.
As shown in fig. 23, by replacing the surface layer 2 in the first embodiment with the structure shown in fig. 16 and replacing the bottom layer 3 in the first embodiment with the structure shown in fig. 17, a floating island MOSFET can be formed. In other embodiments of the present invention, the floating island MOSFET structure is not limited to a trench MOSFET, and may be any other MOSFET structure such as a planar MOSFET, where the MOSFET includes a source metal, a cathode drain, a channel well doped region, a source doped region, a gate oxide layer, and a gate metal.
Wherein, theThe doping type of the channel well doping region 12 is opposite to that of the epitaxial layer 1, the doping type of the source doping region 13 is the same as that of the epitaxial layer 1, the gate oxide layer 14 can be an insulating oxide layer, and the trench filler 16 can be an insulator, a conductor or a semiconductor. For example, when the epitaxial layer 1 is made of N-type semiconductor material, the doped region 12 of the channel well may have a doping concentration of
~
The source doped region 13 may be doped with a doping concentration of
~
The N-type semiconductor material of (1).
Therefore, by introducing the second doping region 5, when the floating island MOSFET is changed from a blocking state to a conducting state, the space charges in the epitaxial layer 1 are gathered in the second doping region 5 instead of being dispersed in the whole epitaxial layer 1, so that the charges in the drift region can also avoid the blocking effect on the current due to charge accumulation when the bias voltage is low, the drift region can smoothly conduct the current from the cathode-drain metal 17 to the source metal 11, and the floating island MOSFET can still quickly recover the conducting capability even under the low bias voltage; by introducing the ohmic contact metal 6, when the floating island device is changed from a blocking state to a conducting state, the first doping region 4 and the second doping region 5 can be communicated through the ohmic contact metal 6, so that carriers are supplemented to the first doping region 4 and the second doping region 5, charges are neutralized, and the device is completely switched on.
Example seventeen
As shown in fig. 16, the surface layer 2 may include a source metal 11, a channel well doped region 12, a source doped region 13, a gate oxide layer 14, a gate metal 15, and a trench filler 16.
As shown in fig. 18, the bottom layer 3 may include a layer of drain doped region 18 and a layer of drain metal 17.
As shown in fig. 24, by replacing the surface layer 2 in the first embodiment with the structure shown in fig. 16 and replacing the bottom layer 3 in the first embodiment with the structure shown in fig. 18, a floating island IGBT can be formed.
The doping type of the channel well doping region 12 is opposite to that of the epitaxial layer 1, the doping type of the source doping region 13 is the same as that of the epitaxial layer 1, the doping type of the drain doping region 18 is opposite to that of the epitaxial layer 1, the gate oxide layer 14 is an insulating oxide layer, and the trench filler 16 can be an insulator, a conductor or a semiconductor. For example, when the epitaxial layer 1 is made of N-type semiconductor material, the doped region 12 of the channel well may have a doping concentration of
~
The source doped region 13 can be doped with a doping concentration->
~
The drain doped region 18 may be doped with a doping concentration->
~
P-type semiconductor material of (1).
Therefore, by introducing the second doping region 5, when the floating island IGBT is changed from a blocking state to a conducting state, space charges in the epitaxial layer 1 are gathered in the second doping region 5 instead of being dispersed in the whole epitaxial layer 1, so that when the bias voltage is lower, charges in the drift region can also avoid the blocking effect on current due to charge accumulation, the drift region can smoothly conduct the current from the cathode-drain electrode metal 17 to the source electrode metal 11, and the floating island IGBT can still quickly recover the conducting capability even under the lower bias voltage; by introducing the ohmic contact metal 6, when the floating island device is changed from a blocking state to a conducting state, the first doping region 4 and the second doping region 5 can be communicated through the ohmic contact metal 6, so that carriers are supplemented to the first doping region 4 and the second doping region 5, charges are neutralized, and the device is completely switched on.
EXAMPLE eighteen
As shown in fig. 25, different from the eleventh embodiment, the three second doping regions 5 are designed differently (for example, a design scheme is adopted in which the second doping region 5 is located at the right of the first doping region 4, and the second doping region 5 is composed of discontinuous portions, as shown in the embodiments of fig. 1, fig. 2, and fig. 8).
Example nineteen
As shown in fig. 26, unlike the eleventh embodiment, the upper edges of the three second doping regions 5 may be higher than or equal to or lower than the upper edge of the first doping region 4 (for example, the structures shown in the embodiments of fig. 1, 5 and 6 are respectively adopted).
Example twenty
The structure in fig. 1 may vary in the dimension perpendicular to the page.
Fig. 27 shows a three-dimensional structure of the triple-layer floating island junction barrier schottky diode of the present embodiment, which includes three dimensions x, y, and z, and the first doped region 4 and the second doped region 5 extend to the entire unit cell in the third dimension z.
Example twenty one
The structure in fig. 1 may vary in the dimension perpendicular to the plane of the paper.
Fig. 28 shows a three-dimensional structure of a three-layer floating island junction barrier schottky diode according to the present embodiment, which includes three dimensions x, y, and z, wherein the first doped region 4 extends to the whole cell in the third dimension z, and only a part of the second doped region 5 extends in the third dimension z.
Example twenty two
The structure in fig. 1 may vary in the dimension perpendicular to the page.
Fig. 29 shows a three-dimensional structure of the three-layer floating island junction barrier schottky diode of the present embodiment, which includes three dimensions x, y, and z, and only a portion of the first doped region 4 and the second doped region 5 extends in the third dimension z.
Example twenty three
The location of the ohmic contact metal 6 in figure 1 can vary in many ways.
For example, in one floating island device shown in fig. 30, the ohmic contact metal 6 may be located on the left or right side of the cell. In other embodiments, the ohmic contact metal 6 may be located on both sides of the vertical paper direction (the z direction of the third dimension in the twenty embodiment).
Example twenty-four
The floating island device in fig. 1 can be spliced with an original structure after being horizontally turned over, a stepped groove (which may be a U-shaped or V-shaped groove) is formed in the middle of the device, and the ohmic contact metal 6 is formed on a horizontal mesa of the stepped groove as shown in fig. 31.
Example twenty-five
A method of fabricating a floating island device, comprising the steps of: forming an epitaxial layer 1 by an epitaxial growth method, and forming a first doped region 4 and a second doped region 5 in the epitaxial layer 1 by a photolithography method, an ion implantation method, or the like; repeating the steps for a plurality of times to form an epitaxial layer 1 containing a first doping area 4 and a second doping area 5; etching part of the device by etching until the second doping region 5 and the first doping region 4 are exposed; the metal electrode composition surface layer 2 and the bottom layer 3 are formed at both ends of the drift region and the surfaces of the first doped region 4 and the second doped region 5 by sputtering, evaporation or annealing.
The manufacturing method described in this embodiment takes the first embodiment as an example, and first, the epitaxial layer 1 is obtained by epitaxial growth, and the doping concentration of the epitaxial layer 1 is as follows
~
The method comprises the steps of forming a first doping region 4 and a second doping region 5 in an epitaxial layer 1 through photoetching and P-type ion implantation, repeating the operation times according to actual production requirements, and forming a drift region, wherein the drift region comprises a plurality of epitaxial layers 1, a plurality of first doping regions 4 and a plurality of second doping regions 5.
After the drift region is prepared, etching the partial region from the surface of the wafer to expose the first doped region 4 and the second doped region 5 by a dry etching process; surface layer 2 and bottom layer 3 are formed at two ends of the drift region by a metal sputtering method or a metal evaporation method, then ohmic contact is formed between bottom layer 3 and epitaxial layer 1, between ohmic contact metal 6 and first doping region 4, and between ohmic contact metal and second doping region 5 by high-temperature annealing, and the temperature of high-temperature annealing in the embodiment can be set to one thousand degrees, so that the manufacturing process is completed.
In addition, it should be noted that the specific embodiments described in the present specification may differ in the parts, the shapes of the components, the names given, and the like. All equivalent or simple changes of the structure, the characteristics and the principle of the invention which are described in the patent conception of the invention are included in the protection scope of the patent of the invention. Various modifications, additions, combinations, or substitutions for the specific embodiments described herein may be made by those skilled in the art without departing from the scope of the invention as defined in the claims.
Claims (13)
1. A floating island device is a diode device and comprises a surface layer and a bottom layer, wherein the surface layer comprises anode metal, the bottom layer comprises cathode drain metal, when the floating island device is switched on, current flows from the anode metal to the cathode drain metal, a plurality of epitaxial layers are arranged between the surface layer and the bottom layer, a first doping region and a second doping region are formed in at least one epitaxial layer, ohmic contact metal is formed on at least one epitaxial layer, the ohmic contact metal and the first doping region and the second doping region form ohmic contact, the doping type of the first doping region is opposite to that of the epitaxial layer, the doping type of the second doping region is the same as that of the epitaxial layer, the doping concentration of the second doping region is higher than that of the epitaxial layer, and when the floating island device is changed from a blocking state to a conducting state, the first doping region and the second doping region are communicated through the ohmic contact metal.
2. A floating island device according to claim 1 wherein the ohmic contact metal, the first doped region and the second doped region are formed on each epitaxial layer, the ohmic contact metals on different epitaxial layers being not in contact with each other.
3. The floating island device of claim 2, wherein the epitaxial layers are stacked to form a ladder shape, and the ohmic contact metal is distributed on one or both sides of the unit cell.
4. A floating island device according to claim 1, wherein when a plurality of said second doped regions are included in said at least one epitaxial layer, said ohmic contact metal forms said ohmic contact with at least one of said second doped regions.
5. The floating island device of claim 1, wherein the cells of the floating island device are formed with stepped trenches, and the ohmic contact metal is formed on horizontal mesas of the stepped trenches.
6. A floating island device according to claim 1, wherein the ohmic contact metal extends over a dimension of the three-dimensional space to the whole cell or only a part of the cell.
7. A floating island device is an MOSFET device or an IGBT device and comprises a surface layer and a bottom layer, and is characterized in that the surface layer comprises source metal, a channel well doped region, a source doped region, a gate oxide layer and gate metal, the bottom layer comprises cathode and drain metal, when the floating island device is switched on, current flows to the source metal from the cathode and drain metal, a plurality of epitaxial layers are arranged between the surface layer and the bottom layer, a first doped region and a second doped region are formed in at least one epitaxial layer, ohmic contact metal is formed on the at least one epitaxial layer, the ohmic contact metal and the first doped region and the second doped region form ohmic contact, the first doped region is opposite to the doping type of the epitaxial layer, the doping type of the second doped region is the same as the doping type of the epitaxial layer, the doping concentration of the second doped region is higher than that of the epitaxial layer, and when the floating island device is changed from a blocking state to a conducting state, the first doped region and the second doped region are communicated through the ohmic contact metal.
8. A floating island device according to claim 7 wherein the ohmic contact metal, the first doped region and the second doped region are formed on each epitaxial layer, the ohmic contact metals on different epitaxial layers being not in contact with each other.
9. The floating island device according to claim 8, wherein the epitaxial layers are stacked to form a ladder shape, and the ohmic contact metal is distributed on one side or two sides of the unit cell.
10. A floating island device according to claim 7, wherein said ohmic contact metal forms said ohmic contact with at least one of said second doped regions when a plurality of said second doped regions are included in said at least one epitaxial layer.
11. A floating island device according to claim 7 wherein the cells of the floating island device are formed with stepped trenches, the ohmic contact metal being formed on the horizontal mesas of the stepped trenches.
12. A method of manufacturing a floating island device, the method being used to manufacture a floating island device according to any one of claims 1 to 11.
13. A method of fabricating a floating island schottky diode, comprising:
epitaxial layer is obtained by epitaxial growth, and is N-type semiconductor material with doping concentration of 1 × 10 15 cm -3 ～1×10 19 cm -3 Then, forming a first doped region and a second doped region in the epitaxial layer by photoetching and P-type ion implantation, and repeating the operations to form a drift region, wherein the drift region comprises a plurality of epitaxial layers, a plurality of first doped regions and a plurality of second doped regions;
after the drift region is prepared, etching a part of region from the surface of a wafer to expose the first doping region and the second doping region through a dry etching process, and forming ohmic contact metal on the exposed first doping region and the exposed second doping region through a metal sputtering method or a metal evaporation method, wherein the doping type of the first doping region is opposite to that of the epitaxial layer, the doping type of the second doping region is the same as that of the epitaxial layer, and the doping concentration of the second doping region is higher than that of the epitaxial layer;
forming a surface layer and a bottom layer at two ends of the drift region by a metal sputtering method or a metal evaporation method, wherein the surface layer comprises anode metal, an anode doped region and an anode epitaxial region, the doping type of the anode doped region is opposite to that of the epitaxial layer, the doping type of the anode epitaxial region is the same as that of the epitaxial layer, the bottom layer comprises cathode and drain metal, and when the floating island device is switched on, current flows from the anode metal to the cathode and drain metal;
and then, forming ohmic contacts between the bottom layer and the epitaxial layer, between the ohmic contact metal and the first doping region and between the ohmic contact metal and the second doping region through high-temperature annealing, wherein when the floating island Schottky diode is changed from a blocking state to a conducting state, the first doping region and the second doping region are communicated through the ohmic contact metal.
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