CN109509705B - Low barrier height Schottky diode and method of making the same - Google Patents

Abstract

The present invention provides a low barrier height Schottky diode and a preparation method thereof, comprising the following steps: 1) providing a substrate; 2) forming a graphene film on the surface of the substrate; 3) fluorinating the graphene film to 4) depositing a metal electrode on the surface of the fluorinated graphene insulating layer; 5) removing the fluorinated graphene insulating layer outside the area where the Schottky junction is located; 6) forming an ohmic layer on the exposed substrate surface contact electrodes. The invention utilizes the fluorinated graphene insulating layer as the intercalation layer between the metal electrode and the substrate, and the fluorinated graphene insulating layer does not produce MIGS pinning effect in the substrate; the fluorinated graphene insulating layer can block the connection between the metal electrode and the substrate. The mutual diffusion between the two can form a highly uniform Schottky junction; it can greatly reduce the Fermi level pinning effect of the metal electrode to the substrate, thereby reducing the Schottky diode formed between the substrate and the metal electrode. Turkey junction barrier height.

Description

Low barrier height Schottky diode and method of making the same

technical field

The invention belongs to the technical field of semiconductors, and in particular relates to a Schottky diode with a low potential barrier height and a preparation method thereof.

Background technique

With the rapid development of the semiconductor industry, it has become a common trend to find new materials to replace traditional silicon-based materials. Currently, germanium is considered to be the most promising semiconductor material due to its extremely high carrier mobility and compatibility with semiconductor processes. Schottky barrier diodes (SBDs) have been extensively studied for decades in materials, device physics, design and applications due to their technological importance. It is well known that the performance and reliability of SBDs are greatly affected by the quality of the interface between the deposited metal and the semiconductor surface. The main parameters for current control in metal-semiconductor (M-S) structures are the doping concentration Nd of the semiconductor and the Schottky barrier height (SBH) at the interface of the M-S structure. The SBH value depends on the work function of the metal. For Ge (germanium), the charge neutrality level (CNL) is just above the valence band, resulting in metal Fermi level pinning. Although the reason for pinning is not fully understood, it is mainly believed to be the effect of metal-induced gap states (MIGS), that is, the free electron wavefunction in the metal enters the semiconductor band gap-induced gap acceptor or donor-like state. The existence of Fermi level pinning significantly increases the barrier height of Schottky diodes, and the barrier height of Schottky diodes is relatively independent of the metal work function, thus affecting the performance of Schottky diodes.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a low barrier height Schottky diode and a preparation method thereof to solve the problem of metal Fermi level pinning in the Schottky diode in the prior art Therefore, the potential barrier height of the Schottky diode is higher, which in turn affects the performance of the Schottky diode.

In order to achieve the above object and other related purposes, the present invention provides a method for preparing a Schottky diode with a low barrier height, and the method for preparing a Schottky diode with a low barrier height includes the following steps:

1) provide a base;

2) forming a graphene film on the surface of the substrate;

3) fluorinating the graphene film to form a fluorinated graphene insulating layer;

4) depositing a metal electrode on the surface of the fluorinated graphene insulating layer to form a Schottky junction between the metal electrode and the substrate;

5) removing the fluorinated graphene insulating layer outside the area where the Schottky junction is located, and exposing the substrate;

6) forming an ohmic contact electrode on the exposed surface of the substrate.

Optionally, the substrate provided in step 1) includes a germanium substrate.

Optionally, the germanium substrate includes an N-type germanium substrate.

Optionally, in step 2), the graphene film is grown in situ on the surface of the substrate by chemical vapor deposition.

Optionally, in step 3), sulfur hexafluoride gas is used to perform plasma fluorination treatment on the graphene film, so that all the graphene film is converted into a fluorinated graphene insulating layer.

Optionally, in step 5), an inductively coupled plasma etching process is used to remove the fluorinated graphene insulating layer outside the region where the Schottky junction is located.

The present invention also provides a low barrier height Schottky diode, the low barrier height Schottky diode includes:

base;

a metal electrode, located on the substrate, to form a Schottky junction between the metal electrode and the substrate;

a fluorinated graphene insulating layer, located on the surface of the substrate and between the metal electrode and the substrate;

The ohmic contact electrode is located on the surface of the substrate outside the area where the fluorinated graphene insulating layer is located.

Optionally, the substrate comprises a germanium substrate.

Optionally, the germanium substrate includes an N-type germanium substrate.

Optionally, the metal electrodes include titanium/gold electrodes.

As described above, a low barrier height Schottky diode and a preparation method thereof of the present invention have the following beneficial effects:

In the method for preparing a Schottky diode with a low barrier height of the present invention, a graphene film is fluorinated to form a fluorinated graphene insulating layer, and then a metal electrode is formed, and the fluorinated graphene insulating layer is used as the space between the metal electrode and the substrate. The intercalation of the fluorinated graphene insulating layer does not produce MIGS (metal induced band gap state) pinning effect in the substrate; at the same time, the fluorinated graphene insulating layer can block the interdiffusion between the metal electrode and the substrate, which can form Highly uniform Schottky junction; due to the existence of the fluorinated graphene insulating layer between the metal electrode and the substrate, the Fermi level pinning effect of the metal electrode to the substrate can be greatly reduced, thereby reducing the Schottky diode. The height of the Schottky junction barrier formed between the substrate and the metal electrode;

In the low barrier height Schottky diode of the present invention, a fluorinated graphene insulating layer is arranged between the metal electrode and the substrate, and the fluorinated graphene insulating layer will not generate MIGS (metal induced band gap) nails in the substrate. At the same time, the fluorinated graphene insulating layer can block the mutual diffusion between the metal electrode and the substrate, and can form a highly uniform Schottky junction; between the metal electrode and the substrate, due to the fluorinated graphene insulating layer Exist, can greatly reduce the Fermi level pinning effect of the metal electrode to the substrate, thereby reducing the height of the Schottky junction barrier formed between the substrate and the metal electrode in the Schottky diode.

Description of drawings

FIG. 1 is a flow chart of a method for fabricating a Schottky diode with a low barrier height provided in Embodiment 1 of the present invention.

FIG. 2 is a schematic three-dimensional structure diagram of the structure obtained in step 1) of the manufacturing method of the low-barrier-height Schottky diode provided in the first embodiment of the present invention.

FIG. 3 is a schematic three-dimensional structure diagram of the structure obtained in step 2) of the manufacturing method of the low barrier height Schottky diode provided in the first embodiment of the present invention.

FIG. 4 is a schematic three-dimensional structure diagram of the structure obtained in step 3) of the manufacturing method of the low-barrier height Schottky diode provided in the first embodiment of the present invention.

FIG. 5 is a schematic three-dimensional structure diagram of the structure obtained in step 4) of the method for fabricating a Schottky diode with a low barrier height provided in Embodiment 1 of the present invention.

FIG. 6 is a schematic three-dimensional structure diagram of the structure obtained in step 5) of the manufacturing method of the low-barrier-height Schottky diode provided in the first embodiment of the present invention.

FIG. 7 is a schematic view of the cross-sectional structure of FIG. 6 along the AA direction.

FIG. 8 is a schematic three-dimensional structure diagram of the structure obtained in step 6) of the method for fabricating a Schottky diode with a low barrier height provided in Embodiment 1 of the present invention.

FIG. 9 is a schematic view of the cross-sectional structure of FIG. 8 along the AA direction.

Component label description

10 base

11 Graphene film

12 Fluorinated graphene films

13 Metal electrodes

14 Ohm Contact Electrode

S1～S6 steps

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

See Figures 1 to 9. It should be noted that the diagrams provided in this embodiment are only to illustrate the basic concept of the present invention in a schematic way, although the diagrams only show the components related to the present invention rather than the number, shape and the number of components in actual implementation. For dimension drawing, the shape, quantity and proportion of each component can be arbitrarily changed during actual implementation, and the component layout shape may also be more complicated.

Example 1

Referring to FIG. 1, the present invention provides a method for preparing a Schottky diode with a low barrier height. The method for preparing a Schottky diode with a low barrier height includes the following steps:

1) provide a base;

2) forming a graphene film on the surface of the substrate;

3) fluorinating the graphene film to form a fluorinated graphene insulating layer;

4) depositing a metal electrode on the surface of the fluorinated graphene insulating layer to form a Schottky junction between the metal electrode and the substrate;

5) removing the fluorinated graphene insulating layer outside the area where the Schottky junction is located, and exposing the substrate;

6) forming an ohmic contact electrode on the exposed surface of the substrate.

In step 1), referring to step S1 in FIG. 1 and FIG. 2 , a substrate 10 is provided.

As an example, the substrate 10 may include any substrate with a neutral charge level in the valence band; preferably, the substrate 10 may include but not limited to a germanium (Ge) substrate; more preferably, in this embodiment , the substrate 10 includes an N-type germanium substrate.

In step 2), referring to step S2 in FIG. 1 and FIG. 3 , a graphene film 11 is formed on the surface of the substrate 10 .

As an example, the graphene film 11 can be grown in-situ on the surface of the substrate 10 by, but not limited to, chemical vapor deposition.

As an example, the graphene film 11 may be a single-atomic-layer graphene film, or a multi-atomic-layer graphene film. Preferably, in this embodiment, the graphene film 11 is a graphene film with a thickness of 1-3 atomic layers, and the graphene film with a thickness of 1-3 atomic layers can ensure that the obtained fluorinated graphene insulating layer can act as a barrier The mutual diffusion between the metal electrode and the substrate 10 can form a highly uniform Schottky junction, which can greatly reduce the Fermi level pinning effect of the metal electrode on the substrate 10, thereby reducing the Schottky level. The effect of the Schottky junction barrier height formed between the substrate 10 and the metal electrode in the diode.

In step 3), referring to step S3 in FIG. 1 and FIG. 4 , the graphene film 11 is fluorinated to form the fluorinated graphene insulating layer 12 .

As an example, a fluorine-containing gas may be used to form plasma and then the graphene film 11 may be subjected to fluorination treatment. Preferably, in this embodiment, sulfur hexafluoride (SF ₆ ) gas is used to perform a fluorination treatment on the graphene film 11 . Plasma fluorination treatment.

As an example, when the graphene film 11 is a single atomic layer graphene film, after the graphene film 11 is subjected to fluorination treatment, the graphene film 11 is completely converted into the fluorinated graphene insulating layer 12 and when the graphene film 11 is a multi-atomic layer graphene film, in the process of carrying out the fluorination treatment to the graphene film 11, only the top atomic layer graphene is converted into the fluorinated graphene insulating layer 12, and other graphene films 11 will not be fluorinated, but still maintain the state of graphene films, that is, after the fluorination treatment of the graphene films 11, only part of the graphene films 11 are converted into The fluorinated graphene insulating layer 12 , that is, after the fluorination treatment, the graphene thin film 11 remains between the fluorinated graphene insulating layer 12 and the substrate 10 . But preferably, in this embodiment, after the graphene film 11 is fluorinated, all the graphene film 11 is converted into the fluorinated graphene insulating layer 12, so that the fluorinated graphene can be ensured The insulating layer 12 can block the interdiffusion between the subsequently formed metal electrode and the substrate 10 to the greatest extent, so as to minimize the Fermi level pinning effect between the metal electrode and the substrate 10 .

In step 4), please refer to step S4 in FIG. 1 and FIG. 5 , a metal electrode 13 is deposited on the surface of the fluorinated graphene insulating layer 12 to form a small hole between the metal electrode 13 and the substrate 10 Teckie knot.

As an example, the metal electrode 13 may be formed by, but not limited to, an electron beam evaporation method. Of course, in other examples, any other deposition method can also be used to form the metal electrode 13 . Specifically, a patterned mask layer may be formed on the surface of the fluorinated graphene insulating layer 12, and an opening defining the position and shape of the metal electrode 13 is formed in the patterned mask layer, and then The metal electrode 13 is formed on the surface of the fluorinated graphene insulating layer 12 in the opening.

Of course, in other examples, a metal electrode material layer may be formed on the surface of the fluorinated graphene insulating layer 12 by an electron beam evaporation method first, and then a patterned layer may be formed on the metal electrode material layer. A mask layer, a pattern defining the position and shape of the metal electrode 13 is formed in the patterned mask layer, and finally the metal electrode material layer is etched according to the patterned mask layer to obtain the Metal electrode 13 .

As an example, the metal electrode 13 includes a titanium (Ti)/gold (Au) electrode, that is, the metal electrode 13 includes a titanium metal layer and a gold metal layer, and the titanium metal layer is located on the fluorinated graphene insulating layer 12 The gold metal layer is located on the surface of the titanium metal layer away from the fluorinated graphene insulating layer 12 . Of course, in other examples, the metal electrode 13 can also be a titanium metal electrode, a gold metal electrode, a copper metal electrode, a nickel metal electrode, or the like.

As an example, the specific shape of the metal electrode 13 can be set according to actual needs, which is not limited here.

In step 5), referring to step S5 in FIG. 1 and FIG. 6 to FIG. 7 , the fluorinated graphene insulating layer 12 outside the area where the Schottky junction is located is removed, and the substrate 10 is exposed .

As an example, an inductively coupled plasma etching (ICP) process may be used to remove the fluorinated graphene insulating layer 12 outside the region where the Schottky junction is located. Specifically, the fluorinated graphene insulating layer 12 may be etched according to the metal electrode 13 as an etching stopper. After etching, only the fluorinated graphene insulating layer 12 is located on the metal electrode 13 The part directly below is retained, and the fluorinated graphene insulating layer 12 exposed outside the metal electrode 13 is removed. Of course, in order to cause damage to the metal electrode 13 during the process of removing the fluorinated graphene insulating layer 12, a protective layer can also be formed on the surface of the metal electrode 13 first, and then the fluorinated graphene is insulated. Layer 12 is removed by etching.

It should be noted that, in this step, the fluorinated graphene insulating layer 12 exposed outside the metal electrode 13 is completely removed; and when the graphene fluoride insulating layer 12 has the graphene under it When the thin film 11 is formed, the graphene thin film 11 located outside the metal electrode 13 is also removed together to expose the substrate 10 after etching.

In step 6), referring to step S6 in FIG. 1 and FIGS. 8 to 9 , ohmic contact electrodes 14 are formed on the exposed surface of the substrate 10 .

As an example, a large-area electrode can be formed as the ohmic contact electrode 14 by depositing on the exposed surface of the substrate 10 . The area of the ohmic contact electrode 14 can be set according to actual needs. For example, the ohmic contact electrode 14 can cover 5/1 to 1/2 of the surface of the substrate 10 on which the ohmic contact electrode 14 is formed. Wait.

As an example, the ohmic contact electrode 14 may include a metal electrode, and the material of the ohmic contact electrode 14 may be the same as that of the metal electrode 13 .

In the method for preparing a low barrier height Schottky diode of the present invention, the graphene film 11 is fluorinated to form a fluorinated graphene insulating layer 12, and then the metal electrode 13 is formed. The insulating layer 12 acts as an intercalation layer between the metal electrode 13 and the substrate 10, and the fluorinated graphene insulating layer 12 does not generate MIGS (metal induced band gap state) pinning effect in the substrate; The fluorinated graphene insulating layer 12 can block the mutual diffusion between the metal electrode 13 and the substrate 10, and can form a highly uniform Schottky junction; Due to the existence of the fluorinated graphene insulating layer 12, the Fermi level pinning effect of the metal electrode 13 on the substrate 10 can be greatly reduced, thereby reducing the relationship between the substrate 10 and the substrate 10 in the Schottky diode. The height of the Schottky junction barrier formed between the metal electrodes 13 .

Embodiment 2

Please continue to refer to FIGS. 8 to 9 in conjunction with FIGS. 2 to 7 . The present invention further provides a low barrier height Schottky diode. The low barrier height Schottky diode includes:

base 10;

a metal electrode 13, the metal electrode 13 is located on the substrate 10 to form a Schottky junction between the metal electrode 13 and the substrate 10;

a fluorinated graphene insulating layer 12, the fluorinated graphene insulating layer 12 is located on the surface of the substrate 10 and between the metal electrode 13 and the substrate 10;

The ohmic contact electrode 14 is located on the surface of the substrate 10 outside the area where the fluorinated graphene insulating layer 12 is located.

As an example, the substrate 10 may include any substrate with a neutral charge level in the valence band; preferably, the substrate 10 may include but not limited to a germanium (Ge) substrate; more preferably, in this embodiment , the substrate 10 includes an N-type germanium substrate.

As an example, the fluorinated graphene insulating layer 12 is a structure obtained by performing a fluorination treatment on the in-situ growth of the graphene film 11 on the surface of the substrate 10. Specifically, a fluorine-containing gas can be used to form a plasma after the The graphene film 11 is subjected to fluorination treatment to obtain the fluorinated graphene insulating layer 12. Preferably, in this embodiment, sulfur hexafluoride (SF ₆ ) gas is used to perform plasma on the graphene film 11 The fluorinated graphene insulating layer 12 is obtained by the fluorination treatment.

As an example, the metal electrode 13 includes a titanium (Ti)/gold (Au) electrode, that is, the metal electrode 13 includes a titanium metal layer and a gold metal layer, and the titanium metal layer is located on the fluorinated graphene insulating layer 12 The gold metal layer is located on the surface of the titanium metal layer away from the fluorinated graphene insulating layer 12 . Of course, in other examples, the metal electrode 13 can also be a titanium metal electrode, a gold metal electrode, a copper metal electrode, a nickel metal electrode, or the like.

As an example, the specific shape of the metal electrode 13 can be set according to actual needs, which is not limited here.

As an example, a large-area electrode can be formed as the ohmic contact electrode 14 by depositing on the exposed surface of the substrate 10 . The area of the ohmic contact electrode 14 can be set according to actual needs. For example, the ohmic contact electrode 14 can cover 5/1 to 1/2 of the surface of the substrate 10 on which the ohmic contact electrode 14 is formed. Wait.

As an example, the ohmic contact electrode 14 may include a metal electrode, and the material of the ohmic contact electrode 14 may be the same as that of the metal electrode 13 .

As an example, the low-barrier-height Schottky diode further includes a graphene film, and the graphene film is located between the fluorinated graphene insulating layer 12 and the substrate 10 .

In the low barrier height Schottky diode of the present invention, by disposing the fluorinated graphene insulating layer 12 between the metal electrode 13 and the substrate 10, the fluorinated graphene insulating layer 12 will not MIGS (metal induced band gap state) pinning effect is generated in the substrate 10; at the same time, the fluorinated graphene insulating layer 12 can block the mutual diffusion between the metal electrode 13 and the substrate 10, and can form a uniform Due to the existence of the fluorinated graphene insulating layer 12 between the metal electrode 13 and the substrate 10, the cost of the metal electrode 13 to the substrate 10 can be greatly reduced meter level pinning effect, thereby reducing the height of the Schottky junction barrier formed between the substrate 10 and the metal electrode 13 in the Schottky diode.

To sum up, the low barrier height Schottky diode and the preparation method thereof of the present invention, the preparation method of the low barrier height Schottky diode includes the following steps: 1) providing a substrate; 2) on the substrate A graphene film is formed on the surface; 3) fluorination treatment is performed on the graphene film to form a fluorinated graphene insulating layer; 4) a metal electrode is deposited on the surface of the fluorinated graphene insulating layer, so that the metal electrode and the forming a Schottky junction between the substrates; 5) removing the fluorinated graphene insulating layer outside the area where the Schottky junction is located, and exposing the substrate; 6) on the exposed surface of the substrate Ohmic contact electrodes are formed. In the method for preparing a Schottky diode with a low barrier height of the present invention, a graphene film is fluorinated to form a fluorinated graphene insulating layer, and then a metal electrode is formed, and the fluorinated graphene insulating layer is used as the space between the metal electrode and the substrate. The intercalation of the fluorinated graphene insulating layer does not produce MIGS (metal induced band gap state) pinning effect in the substrate; at the same time, the fluorinated graphene insulating layer can block the interdiffusion between the metal electrode and the substrate, which can form Highly uniform Schottky junction; due to the existence of the fluorinated graphene insulating layer between the metal electrode and the substrate, the Fermi level pinning effect of the metal electrode to the substrate can be greatly reduced, thereby reducing the Schottky diode. The barrier height of the Schottky junction formed between the substrate and the metal electrode; the low barrier height Schottky diode of the present invention is provided with a fluorinated graphene insulating layer between the metal electrode and the substrate, and the fluorinated graphene insulating layer The layer does not produce MIGS (metal induced band gap state) pinning effect in the substrate; at the same time, the fluorinated graphene insulating layer can block the interdiffusion between the metal electrode and the substrate, and can form a highly uniform Schottky junction surface; due to the existence of the fluorinated graphene insulating layer between the metal electrode and the substrate, the Fermi level pinning effect of the metal electrode to the substrate can be greatly reduced, thereby reducing the formation of the Schottky diode between the substrate and the metal electrode. Turkey junction barrier height.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can make modifications or changes to the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (10)

1. A preparation method of a low barrier height Schottky diode is characterized by comprising the following steps:

1) providing a substrate;

2) forming a graphene film on the surface of the substrate;

3) performing fluorination treatment on the graphene film to form a fluorinated graphene insulating layer;

4) depositing a metal electrode on the surface of the fluorinated graphene insulating layer to form a Schottky junction between the metal electrode and the substrate;

5) removing the fluorinated graphene insulating layer outside the region of the Schottky junction, and exposing the substrate;

6) and forming an ohmic contact electrode on the exposed surface of the substrate.

2. The method of claim 1, wherein the substrate provided in step 1) comprises a germanium substrate.

3. The method of claim 2, wherein the germanium substrate comprises an N-type germanium substrate.

4. The method according to claim 1, wherein in step 2), the graphene film is grown in situ on the surface of the substrate by chemical vapor deposition.

5. The method for preparing a schottky diode with a low barrier height as claimed in claim 1, wherein in the step 3), the graphene film is subjected to plasma fluorination treatment by using sulfur hexafluoride gas, so that the graphene film is completely converted into a fluorinated graphene insulating layer.

6. The method for preparing a schottky diode with a low barrier height as claimed in claim 1, wherein in the step 5), the fluorinated graphene insulating layer outside the region where the schottky junction is located is removed by using an inductively coupled plasma etching process.

7. A low barrier height schottky diode, comprising:

a substrate;

the metal electrode is positioned on the substrate so as to form a Schottky junction between the metal electrode and the substrate;

the fluorinated graphene insulating layer is positioned on the surface of the substrate and is positioned between the metal electrode and the substrate;

and the ohmic contact electrode is positioned on the surface of the substrate outside the area where the fluorinated graphene insulating layer is positioned.

8. The low barrier height schottky diode of claim 7 wherein the substrate comprises a germanium substrate.

9. The low barrier height schottky diode of claim 8 wherein the germanium substrate comprises an N-type germanium substrate.

10. The low barrier height schottky diode of claim 7, wherein the metal electrode comprises a titanium/gold electrode.

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