CN117457483A - Low-doping type 4H-SiC ohmic contact and preparation method thereof - Google Patents

Low-doping type 4H-SiC ohmic contact and preparation method thereof Download PDF

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Publication number
CN117457483A
CN117457483A CN202311435683.9A CN202311435683A CN117457483A CN 117457483 A CN117457483 A CN 117457483A CN 202311435683 A CN202311435683 A CN 202311435683A CN 117457483 A CN117457483 A CN 117457483A
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CN
China
Prior art keywords
layer
seed layer
sic
ohmic contact
doped
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CN202311435683.9A
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Chinese (zh)
Inventor
袁昊
周瑜
韩超
杜丰羽
何艳静
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Wuhu Xijing Microelectronics Technology Co ltd
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Wuhu Xijing Microelectronics Technology Co ltd
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Priority to CN202311435683.9A priority Critical patent/CN117457483A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/0445—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising crystalline silicon carbide
    • H01L21/048—Making electrodes
    • H01L21/0485—Ohmic electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof  ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
    • H01L29/43—Electrodes ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
    • H01L29/45—Ohmic electrodes

Abstract

The invention relates to a low-doped 4H-SiC ohmic contact and a preparation method thereof, wherein the preparation method comprises the following steps: step 1: alternately growing a W seed layer and a C seed layer on the upper surface of the SiC layer of the device to form an alloy seed layer, wherein the W seed layer of a first layer in the alloy seed layer is contacted with the SiC layer; step 2: growing a Pad layer on the upper surface of the alloy seed layer, wherein the last C seed layer in the alloy seed layer is contacted with the Pad layer; step 3: and carrying out rapid thermal annealing treatment on the device so as to enable the alloy seed layer and the SiC layer to form ohmic contact. According to the preparation method of the low-doped 4H-SiC ohmic contact, the SiC layer is low-doped SiC, extra high-energy ion implantation is not needed, the process cost is saved, the device damage caused by ion implantation is avoided, and in addition, the prepared ohmic contact is good in performance and high in thermal reliability.

Description

Low-doping type 4H-SiC ohmic contact and preparation method thereof
Technical Field
The invention belongs to the technical field of SiC semiconductor devices, and particularly relates to a low-doped 4H-SiC ohmic contact and a preparation method thereof.
Background
SiC semiconductor devices and circuits are widely used in power devices and modules, harsh environments, electronic power transmission, and other fields and some of the scenarios cannot be replaced. As the basis for SiC semiconductor devices and circuits. Excellent metal/SiC ohmic contacts are the cornerstone for the operation of related devices and circuits. At present, ni and alloys thereof are mainly used as main choices of SiC ohmic contact metals, and Ni or alloys related to Ni, ti and Al and highly doped SiC are mainly used for forming SiC ohmic contact under the high-temperature annealing condition.
Ni and its related alloys require ohmic contact with SiC in the high concentration ion implantation region. The ion implantation process is expensive and can cause surface damage of SiC, high-temperature annealing activation is needed after ion implantation, and the activation temperature of the ion implantation of the SiC material is often more than 1500 ℃. This can introduce additional thermal budget that is detrimental to device cost reduction. In addition, ni has poor affinity for C, and C in SiC precipitates as free C during annealing, which is detrimental to the subsequent wire bonding process. Ohmic contact formed by SiC, ni and related alloys thereof has poor thermal stability and cannot exert the high-temperature working advantage of the SiC semiconductor device.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a low-doped 4H-SiC ohmic contact and a preparation method thereof. The technical problems to be solved by the invention are realized by the following technical scheme:
the invention provides a preparation method of a low-doped 4H-SiC ohmic contact, which comprises the following steps:
step 1: alternately growing a W seed layer and a C seed layer on the upper surface of a SiC layer of a device to form an alloy seed layer, wherein the W seed layer of a first layer in the alloy seed layer is in contact with the SiC layer;
step 2: growing a Pad layer on the upper surface of the alloy seed layer, wherein the last C seed layer in the alloy seed layer is in contact with the Pad layer;
step 3: and carrying out rapid thermal annealing treatment on the device so as to enable the alloy seed layer and the SiC layer to form ohmic contact.
In one embodiment of the invention, the SiC layer is doped n-type or p-type with a doping concentration in the range of 5X 10 15 cm -3 ～5×10 16 cm -3 。
In one embodiment of the present invention, the thickness of the W seed layer is 5nm to 10nm, and the thickness of the C seed layer is 5nm to 10nm.
In one embodiment of the present invention, the sum of the number of layers of the W seed layer and the C seed layer in the alloy seed layer is 8 to 12.
In one embodiment of the invention, the Pad layer is a W metal layer having a thickness of 1 μm to 2 μm.
In one embodiment of the present invention, the rapid thermal annealing process is as follows: annealing for 360 s-900 s under the condition of 1200-1250 ℃ in argon or nitrogen atmosphere.
The invention provides a low-doped 4H-SiC ohmic contact, which comprises the following steps:
a SiC layer;
the alloy seed layer is arranged on the SiC layer, wherein the alloy seed layer comprises a W seed layer and a C seed layer which are sequentially stacked from bottom to top;
a Pad layer disposed on the alloy seed layer;
wherein a W seed layer of a first layer of the alloy seed layers is in contact with the SiC layer, and a C seed layer of a last layer of the alloy seed layers is in contact with the Pad layer.
In one embodiment of the invention, the SiC layer is doped n-type or p-type with a doping concentration in the range of 5X 10 15 cm -3 ～5×10 16 cm -3 。
In one embodiment of the present invention, the thickness of the W seed layer is 5nm to 10nm, the thickness of the C seed layer is 5nm to 10nm, and the sum of the layers of the W seed layer and the C seed layer in the alloy seed layer is 8 to 12.
In one embodiment of the invention, the Pad layer is a W metal layer having a thickness of 1 μm to 2 μm.
Compared with the prior art, the invention has the beneficial effects that:
according to the preparation method of the low-doped 4H-SiC ohmic contact, the SiC layer is low-doped SiC, extra high-energy ion implantation is not needed, the process cost is saved, the device damage caused by ion implantation is avoided, and in addition, the prepared ohmic contact is good in performance and high in thermal reliability.
The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention, as well as the preferred embodiments thereof, together with the following detailed description of the invention, given by way of illustration only, together with the accompanying drawings.
Drawings
FIG. 1 is a flow chart of a method for preparing a low-doped 4H-SiC ohmic contact according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a low-doped 4H-SiC ohmic contact according to an embodiment of the invention;
FIG. 3 is a graph showing I-V characteristics of a low-doped 4H-SiC ohmic contact according to an embodiment of the invention in different temperature environments;
fig. 4 is a graph of the extraction result of specific contact resistance of a low-doped 4H-SiC ohmic contact in different temperature environments according to an embodiment of the present invention.
Icon: a 1-SiC layer; a 2-W seed layer; a 3-C seed layer; 4-Pad layer
Detailed Description
In order to further illustrate the technical means and effects adopted by the invention to achieve the preset aim, the following is a detailed description of a low-doped 4H-SiC ohmic contact and a preparation method thereof according to the invention with reference to the accompanying drawings and the detailed description.
The foregoing and other features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings. The technical means and effects adopted by the present invention to achieve the intended purpose can be more deeply and specifically understood through the description of the specific embodiments, however, the attached drawings are provided for reference and description only, and are not intended to limit the technical scheme of the present invention.
In a first aspect, an embodiment of the present invention provides a method for preparing a low-doped 4H-SiC ohmic contact, referring to fig. 1, fig. 1 is a flowchart of a method for preparing a low-doped 4H-SiC ohmic contact according to an embodiment of the present invention, where as shown in the drawing, the method for preparing a low-doped 4H-SiC ohmic contact according to the embodiment of the present invention includes:
step 1: alternately growing a W seed layer and a C seed layer on the upper surface of the SiC layer of the device to form an alloy seed layer, wherein the W seed layer of a first layer in the alloy seed layer is contacted with the SiC layer;
in an alternative embodiment, the alloy seed layer is formed by alternately growing a W seed layer and a C seed layer on the upper surface of the SiC layer of the device using a PECVD process.
In this embodiment, the SiC layer is low-doped SiC, optionally n-doped or p-doped, with a doping concentration in the range of 5×10 15 cm -3 ～5×10 16 cm -3 。
In an alternative embodiment, the W seed layer and the C seed layer are both on the order of nanometers in thickness, alternatively, the W seed layer is 5nm to 10nm in thickness and the C seed layer is 5nm to 10nm in thickness.
In an alternative embodiment, the sum of the number of layers of the W seed layer and the C seed layer in the alloy seed layer is 8 to 12. Wherein the number of layers of the W seed layer and the C seed layer in the alloy seed layer is equal. Alternatively, among the alloy seed layers, the number of layers of the W seed layer and the C seed layer may be 4, 5, or 6.
Step 2: growing a Pad layer on the upper surface of the alloy seed layer, wherein the last C seed layer in the alloy seed layer is contacted with the Pad layer;
in an alternative embodiment, the Pad layer is a W metal layer having a thickness of 1 μm to 2 μm.
In this embodiment, the Pad layer is used for subsequent wire bonding.
Step 3: and carrying out rapid thermal annealing treatment on the device so as to enable the alloy seed layer and the SiC layer to form ohmic contact.
In an alternative embodiment, the rapid thermal annealing process is as follows: annealing for 360 s-900 s under the condition of 1200-1250 ℃ in argon or nitrogen atmosphere.
In the preparation method of the low-doped 4H-SiC ohmic contact, the SiC layer is low-doped SiC, no extra high-energy ion implantation is needed, the process cost is saved, and the device damage caused by ion implantation is avoided. In addition, C and W are elements with excellent thermal stability, and react in an environment of 1200 ℃ to form WC related alloy, wherein the phase of the alloy is a stable phase and is not affected by temperature, so that ohmic contact has better thermal stability and thermal reliability.
In a second aspect, an embodiment of the present invention provides a low-doped 4H-SiC ohmic contact, which is prepared by using the method for preparing a low-doped 4H-SiC ohmic contact, and referring to fig. 2, fig. 2 is a schematic diagram of a low-doped 4H-SiC ohmic contact according to an embodiment of the present invention. As shown in the figure, the low-doped 4H-SiC ohmic contact of the present embodiment includes: the SiC seed layer comprises a SiC layer 1, an alloy seed layer and a Pad layer 4, wherein the alloy seed layer is arranged on the SiC layer, the alloy seed layer comprises a W seed layer 2 and a C seed layer 3 which are sequentially laminated from bottom to top, and the Pad layer 4 is arranged on the alloy seed layer. Wherein, the W seed layer 2 of the first layer of the alloy seed layers is contacted with the SiC layer 1, and the C seed layer 3 of the last layer of the alloy seed layers is contacted with the Pad layer 4.
In an alternative embodiment, the SiC layer 1 is n-doped or p-doped with a doping concentration in the range of 5×10 15 cm -3 ～5×10 16 cm -3 。
In an alternative embodiment, the thickness of the W seed layer and the C seed layer are both nanometer scale, the thickness of the W seed layer 2 is 5nm to 10nm, and the thickness of the C seed layer 3 is 5nm to 10nm. The number of layers of the W seed layer 2 and the C seed layer 3 in the alloy seed layer is equal.
Alternatively, the sum of the layers of the W seed layer 2 and the C seed layer 3 is 8 to 12. In this embodiment, the number of layers of the W seed layer and the C seed layer is 5 (as shown in fig. 2), and in other embodiments, the number of layers of the W seed layer and the C seed layer may be 4 or 6.
In an alternative embodiment, pad layer 4 is a W metal layer having a thickness of 1 μm to 2 μm. In this embodiment, the Pad layer is used for subsequent wire bonding.
Further, the performance of the low doped 4H-SiC ohmic contact of this embodiment is illustrated by experiments.
Referring to fig. 3 and fig. 4 in combination, fig. 3 is an I-V characteristic diagram of a low-doped 4H-SiC ohmic contact according to an embodiment of the present invention in different temperature environments; fig. 4 is a graph of the extraction result of specific contact resistance of a low-doped 4H-SiC ohmic contact in different temperature environments according to an embodiment of the present invention.
From the figure, it can be seen that the I-V characteristics of the ohmic contact are symmetrical about the origin and exhibit good linearity in a high temperature environment ranging from room temperature to 500 ℃. The specific contact resistance of the extracted ohmic contact at room temperature and 500 ℃ is 2.53×10 respectively -4 Ω·cm 2 And 1.29×10 -5 Ω·cm 2 The contact performance is good.
Note that the low-doped 4H-SiC ohmic contact of the present embodiment is not limited to the device type.
The low-doped 4H-SiC ohmic contact provided by the embodiment of the invention forms WC related alloy with extremely stable phase and no influence of temperature by using the elements C and W with excellent thermal stability, so that the ohmic contact can be ensured to have better thermal stability and thermal reliability.
It should be noted that in this document relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in an article or apparatus that comprises the element. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The orientation or positional relationship indicated by "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is merely for convenience of description and to simplify the description, and is not indicative or implying that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.

Claims (10)

1. The preparation method of the low-doped 4H-SiC ohmic contact is characterized by comprising the following steps:
step 1: alternately growing a W seed layer and a C seed layer on the upper surface of a SiC layer of a device to form an alloy seed layer, wherein the W seed layer of a first layer in the alloy seed layer is in contact with the SiC layer;
step 2: growing a Pad layer on the upper surface of the alloy seed layer, wherein the last C seed layer in the alloy seed layer is in contact with the Pad layer;
step 3: and carrying out rapid thermal annealing treatment on the device so as to enable the alloy seed layer and the SiC layer to form ohmic contact.
2. The method for fabricating a low doped 4H-SiC ohmic contact according to claim 1, wherein the SiC layer is doped n-type or p-type in a doping concentration range of 5X 10 15 cm -3 ～5×10 16 cm -3 。
3. The method for manufacturing a low doping type 4H-SiC ohmic contact according to claim 1, wherein the thickness of the W seed layer is 5nm to 10nm, and the thickness of the C seed layer is 5nm to 10nm.
4. The method of manufacturing a low-doped 4H-SiC ohmic contact according to claim 1, wherein the sum of the layers of the W seed layer and the C seed layer in the alloy seed layer is 8 to 12.
5. The method for manufacturing a low-doped 4H-SiC ohmic contact according to claim 1, wherein the Pad layer is a W metal layer having a thickness of 1 μm to 2 μm.
6. The method for preparing a low-doped 4H-SiC ohmic contact according to claim 1, wherein the rapid thermal annealing process is as follows: annealing for 360 s-900 s under the condition of 1200-1250 ℃ in argon or nitrogen atmosphere.
7. A low-doped 4H-SiC ohmic contact, comprising:
a SiC layer (1);
the alloy seed layer is arranged on the SiC layer, wherein the alloy seed layer comprises a W seed layer (2) and a C seed layer (3) which are sequentially stacked from bottom to top;
a Pad layer (4) disposed on the alloy seed layer;
wherein a W seed layer (2) of a first layer of the alloy seed layers is in contact with the SiC layer (1), and a C seed layer (3) of a last layer of the alloy seed layers is in contact with the Pad layer (4).
8. The low-doped 4H-SiC ohmic contact according to claim 7, characterized in that the SiC layer (1) is n-doped or p-doped with a doping concentration ranging from 5 x 10 15 cm -3 ～5×10 16 cm -3 。
9. The low-doped 4H-SiC ohmic contact according to claim 7, characterized in that the thickness of the W seed layer (2) is 5nm to 10nm, the thickness of the C seed layer (3) is 5nm to 10nm, and the sum of the layers of the W seed layer (2) and the C seed layer (3) in the alloy seed layer is 8 to 12.
10. The low-doped 4H-SiC ohmic contact according to claim 7, characterized in that said Pad layer (4) is a W metal layer having a thickness ranging from 1 μm to 2 μm.
CN202311435683.9A 2023-10-31 2023-10-31 Low-doping type 4H-SiC ohmic contact and preparation method thereof Pending CN117457483A (en)

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CN202311435683.9A CN117457483A (en) 2023-10-31 2023-10-31 Low-doping type 4H-SiC ohmic contact and preparation method thereof

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Application Number Priority Date Filing Date Title
CN202311435683.9A CN117457483A (en) 2023-10-31 2023-10-31 Low-doping type 4H-SiC ohmic contact and preparation method thereof

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CN117457483A true CN117457483A (en) 2024-01-26

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