JP3383737B2 - Manufacturing method of hydrogen-terminated diamond FET by self-alignment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a field effect transistor (FET) using hydrogen-terminated diamond with elements isolated from each other.

[0002]

2. Description of the Related Art FET using hydrogen-terminated diamond
Is Japanese Patent Application Laid-Open No. 8-139109 filed by the applicant of the present application .
It has already been disclosed in the gazette (Japanese Patent Application No. 7-64035 ) "Hydrogen-terminated diamond semiconductor element with element isolation and method of manufacturing the semiconductor element".

In the Si semiconductor device, for example, a LOCOS technique for insulating and isolating elements by providing an oxide layer as disclosed in Japanese Patent Publication No. 49-45629 is used as an element isolation technique. However, in a semiconductor element using diamond, it is difficult to thickly oxidize diamond itself, so that an oxide film cannot be formed on the diamond surface, and the LOCOS technique like silicon cannot be used. Therefore, in order to separate the diamond semiconductor element, for example, “Diamond Thin-Film Recessed Gate Field-Eff
ect Transistors Fabricated by Electron Cyclotron R
esonance Plasma Etching: SAGrot, G.Sh.Gildenbla
t, and ARBadzian: IEEE ELECTRON DEVICE LETTERS:
As shown in VOL.13, NO.9, SEPTEMBER 1992: p462-463 ", it is conceivable to remove the semiconductor region by etching or the like to separate each element.
A complicated process such as etching is required. From this, it can be said that the technique for insulating and separating each element, which is required when a plurality of diamond semiconductor elements are formed on the same diamond substrate, has not been established yet.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a manufacturing method by a self-alignment method for forming a plurality of semiconductor elements on the surface of the same hydrogen-terminated homoepitaxial diamond substrate by insulating the elements from each other by a simple method. The purpose is to do.

Further, the present invention provides a simple manufacturing method which reduces the number of processes in the production of a mask for a semiconductor device in which the devices formed on the surface of the same hydrogen-terminated homoepitaxial diamond substrate are isolated from each other. The purpose is to do.

[0006]

SUMMARY OF THE INVENTION The invention of this application is a method for manufacturing a hydrogen-terminated diamond FET, in which a field-effect transistor (F) is formed on a diamond whose surface is hydrogen-terminated.
ET), a step of forming a mask covering a channel formation region including a source electrode region, a drain electrode region, and a region to be a gate electrode region, and FE using the mask.
The process includes the steps of destroying hydrogen terminations in regions other than the T formation region to form an insulating region, forming a gate electrode formation region in the mask, and forming a gate electrode in the gate electrode formation region.

Further, according to the present invention, in the above method for manufacturing a hydrogen-terminated diamond FET, the mask is made of ohmic contact materials for the source electrode and the drain electrode.

Further, according to the present invention, in the above method of manufacturing a hydrogen-terminated diamond FET, the insulating region is formed by irradiation with argon ions.

Further, the hydrogen-terminated diamond FET
In the manufacturing method of 1., the gate electrode formation region is formed by isotropic etching.

Further, according to the present invention, in the above method for manufacturing a hydrogen-terminated diamond FET, the gate electrode is formed by an anisotropic film forming method.

[0011]

Although diamond is generally an insulator at room temperature, a p-type semiconductor region can be formed by terminating the surface of diamond with hydrogen. As a method for terminating hydrogen, hydrogen plasma (H ₂ plasma) is applied to the diamond surface.
There is a method of terminating the surface with hydrogen by treating the surface with hydrogen, and a method of terminating the surface with hydrogen by using hydrogen gas as the atmosphere in the reactor after completion of diamond synthesis by the CVD method or the like. On the other hand, non-hydrogen termination (such as by subjecting the diamond surface to oxygen plasma (O ₂ plasma) treatment, exposing the synthesized diamond substrate to air (oxygen), or irradiating the diamond surface with argon ions ( When it is oxygen-terminated, an insulating region can be formed on the diamond surface. By separately forming two types of regions, that is, the semiconductor region and the insulating region, a plurality of hydrogen-terminated diamond semiconductor elements can be formed on the same substrate with isolation between the elements.

Further, the hydrogen-terminated diamond FE of the present invention
In the manufacturing method of T, since the metal thin films used as the source contact and the drain contact are used as the mask for the non-hydrogen termination treatment, the number of processes can be reduced. In addition, according to the present invention, the isotropic etching is used for forming the gate electrode forming region and the anisotropic film forming method is used for forming the gate electrode. Therefore, the gate electrode is formed by using the same mask as the source contact and the drain contact. Can be provided separately, and the number of masks can be reduced.

[0013]

1 is a conceptual diagram of a semiconductor device in which a plurality of MESFETs are provided on the surface of a homoepitaxial diamond obtained by a manufacturing method by a self-alignment method according to the present invention, and FIG. It is a conceptual diagram which shows the cross section of the AA line of FIG.

As shown in FIG. 1, a plurality of MESFETs 1, 1 are formed on the surface of a homoepitaxial diamond obtained by the manufacturing method by the self-alignment method according to the present invention.
The semiconductor element provided with 1 ′ is a hydrogen-terminated homoepitaxial diamond 10 obtained by epitaxially growing a diamond single crystal on a substrate made of diamond by a microwave plasma CVD method, and a region 11 whose surface is hydrogen-terminated. And a non-hydrogen-terminated region 13, and a drain electrode contact 31 and a source electrode contact 32 obtained by vapor-depositing gold to obtain an ohmic contact on the hydrogen-terminated region 11 and chromium (Cr), aluminum. (Al), nickel (Ni), lead (Pb), iron (Fe), tungsten (W), copper (C)
u), tantalum (Ta), zinc (Zn), indium (I
The gate electrode 51 is formed by depositing a metal that forms a Schottky barrier including n).

As shown in FIG. 2, when the surface of the diamond is hydrogen-terminated, the lower surface of the hydrogen-terminated region 11 is
The p-type semiconductor layer 12 is formed. When a metal forming the gate electrode is brought into contact with this region, a Schottky barrier is formed in a portion in contact with the metal, and a depletion layer 14 is formed in the p-type semiconductor layer 12 located below the gate electrode. The thickness of the surface conductive layer formed of the p-type semiconductor layer 12 is several hundred Å
Since it is extremely thin, 1000 Å, the thickness of the depletion layer can be controlled by selecting the material of the gate electrode, and any FET that performs an enhancement operation or a depletion operation can be obtained. On the other hand, insulation is obtained on the lower surface of the non-hydrogen-terminated region 13, and the insulating region separates the elements.

In the present invention, the term "hydrogen termination" refers to a state in which hydrogen atoms are bound to the dangling bonds of carbon atoms on the surface of the grown diamond crystal, that is, hydrogen atoms are bound to the terminating bonds. For example, a hydrogen-terminated homoepitaxial diamond film can be obtained by forming a diamond film in the presence of hydrogen. What is non-hydrogen termination?
A state in which the surface of diamond is terminated with atoms other than hydrogen, for example, an oxygen-terminated region can be obtained by treating the surface of diamond terminated with hydrogen with argon ions.

An example of manufacturing conditions of the hydrogen-terminated homoepitaxial diamond used in the present invention will be shown. The temperature of the diamond substrate is set to 850 ° C., a mixed gas of 5% methane (CH ₄ ) and 2.5% oxygen (O ₂ ) and the remaining hydrogen gas (H ₂ ) is used as a source gas, and the pressure is 35 Torr. A diamond single crystal was epitaxially grown at. As the raw material gas, other than this example, various hydrocarbons such as ethane, butane, and ethylene can be used in addition to carbon monoxide.

A method of manufacturing a hydrogen-terminated diamond FET by the self-alignment method according to the present invention will be described with reference to FIGS. In these figures, the left side is a plan view and the right side is a sectional view. The diamond substrate 10 was inserted into a plasma CVD apparatus using a microwave as an excitation source, and methane (CH ₄ ), ethane (C ₂ H ₆ ), butane (C ₄
H ₁₀ ), ethylene (C ₂ H ₄ ), carbon monoxide (CO), carbon dioxide (CO ₂ ), etc. and a mixed gas of hydrogen (H ₂ ) as a carbon source is supplied into the plasma CVD apparatus. Then, the homo-epitaxial diamond film 10 is obtained by being excited by microwaves to be turned into plasma and epitaxially growing a diamond crystal on the surface of the diamond substrate. After the film formation, this substrate is rapidly cooled in the presence of hydrogen gas so that hydrogen atoms are bonded to dangling bonds of carbon atoms on the surface of the diamond crystal to terminate hydrogen 11 and hydrogen having a surface conductive layer 12. Obtain a terminated homoepitaxial diamond substrate. A resist is applied to the surface of the hydrogen-terminated homoepitaxial diamond substrate by spin coating and exposed to form a mask 20 having an opening 21 in a portion to be left as a p-type semiconductor region (FIG. 3A).

After that, gold is vapor-deposited on the p-type semiconductor region 11 and the mask 20 to form a gold thin film 30 which serves as a mask and covers the channel forming region including the regions to be the source electrode region, the drain electrode region and the gate electrode region. Formed (FIG. 3B). A part of this gold thin film 30 is used as a source ohmic contact and a drain ohmic contact.

Next, the mask 20 is peeled off (FIG. 3C).
The gold thin film 30 remaining at this time is used as a mask for the subsequent processing.

After that, using a medium current ion implanter,
By irradiating the surface of the diamond substrate with, for example, argon ions, hydrogen atoms at the hydrogen termination on the surface other than the portion covered with the mask 30 are replaced with other atoms to obtain the non-hydrogen terminated surface 13. Below the non-hydrogen termination surface 13, the P-type semiconductor region 11 disappears and exhibits an insulating property, so that elements to be formed later are separated from each other (FIG. 3D).

Next, a resist having resistance to a potassium iodide (KI) solution used as an etching solution for gold used in a later step is applied, and then a mask 40 having an opening 41 in a region where a gate electrode is arranged. Are formed (FIG. 4A).

After that, the gold thin film 30 in the opening 41 of the mask 40 is etched using a potassium iodide (KI) solution. Since this etching is isotropic, a side wall of the opening 41 of the mask 40 is also etched to form a cavity 42 under the mask 40, and a source contact and a drain contact are formed separately (FIG. 4B). .

Next, a gate metal is vapor-deposited using the mask 40. Since this vapor deposition is anisotropic, the gate metal 50 is formed only on the projection surface of the opening 42 on the device. Therefore, the gate metal and the source contact or the drain contact are formed separately, and the depletion region 14 due to the gate metal is formed in the surface conductive layer 12 in contact with the gate metal 50 (FIG. 4C).

Finally, by peeling off the mask 40, the FET in which the source contact 32, the drain contact 31, and the gate electrode 51 are separated from each other can be separately formed by the self-alignment method (FIG. 4D).

Specific experimental conditions in the above manufacturing method will be described. As the mask 40, positive OEBR-200cp (manufactured by Tokyo Ohka) is dropped on the hydrogen-terminated diamond,
The mask obtained by spin coating by rotating at 00 rpm for 5 seconds and 4000 rpm for 10 seconds has a thickness of 2 to 3 μm.
Had a thickness of. The thickness of the gate metal is 18
It was 00Å. As a gold etching solution, 40 ml of 4 g of potassium iodide (KI) and 1 g of iodine (I ₂ )
The solution diluted with water (H ₂ O) of 10 to 100 times was used. The lateral etching rate of gold at this time was 0.5 μm / mm. The vapor deposition of gold was vapor deposition by resistance heating using a tungsten basket.

Next, the characteristics of the FET obtained by the present invention will be described. FIG. 5 shows an example in which chromium (Cr) is used as the gate electrode material, and FIG. 6 shows an example in which aluminum (Al) is used as the gate electrode material. In both figures, the horizontal axis represents the drain-source voltage Vds (V) and the vertical axis represents the drain-source current Ids (mA).
The gate-source voltage Vgs (V) is used as a parameter. The FET used in FIG. 5 uses chromium as the gate electrode and has a gate length (Lg) of 5.5 (μm) and a gate width (W
g) was set to 65 (μm). This FET operates in the depletion mode with a threshold voltage of 0.46 (V) and a mutual conductance (gm) of 12.3 (m).
S / mm) was obtained. The FET used in FIG. 6 uses aluminum as a gate electrode and has a gate length (Lg) of 6
(Μm) and the gate width (Wg) were set to 78 (μm). The threshold voltage of this FET is -1.6
It operated in the enhancement mode (V), and a transconductance (gm) of 7.48 (mS / mm) was obtained.
By selecting the gate metal as shown in these Vds-Ids characteristic curves, either depletion mode or enhanced mode MESFETs can be obtained.

According to the present invention, a plurality of element-separated MESFETs can be formed by a self-alignment method on a diamond film whose surface is formed with an extremely thin p-type semiconductor layer on its lower surface and whose surface is terminated with hydrogen. Since any Schottky barrier can be formed by selecting the electrode material, the gate can be easily formed with an extremely simple structure, and the MESFET operates in the enhancement mode or the depletion mode.
Can be manufactured by an extremely simple process.

Although gold has been described as the ohmic electrode material in the above-described embodiments, any material having a high electronegativity may be used as the ohmic electrode material, and platinum (P
t) can be used. Further, as the gate electrode material forming the Schottky barrier, chromium (Cr),
In addition to aluminum (Al), nickel (Ni), lead (P
It is also possible to use a metal that forms a Schottky barrier, including b), iron (Fe), tungsten (W), copper (Cu), tantalum (Ta), zinc (Zn), indium (In), and the like.

Further, in the above embodiment, the hydrogen-terminated homoepitaxial diamond obtained by microwave plasma CVD was described as an example. However, the growth method is not only microwave plasma CVD method, but also hot filament method and high frequency thermal plasma. CVD, DC arc plasma CVD, combustion flame method, etc. can also be used. further,
Diamond is not limited to homoepitaxially grown diamond, but can be any of other vapor phase synthetic diamonds such as heteroepitaxial diamond, natural diamond single crystal, and hydrogen-terminated diamond obtained by treating a diamond single crystal synthesized by the high pressure method in a hydrogen plasma atmosphere. It is clear from the principle that the p-type semiconductor conductive layer can be obtained by terminating the surface of diamond with hydrogen.

Further, in the above embodiment, the non-hydrogen termination treatment was performed by irradiating argon ions. However, the hydrogen termination surface of diamond is subjected to oxygen plasma (O ₂ plasma) treatment so as to be non-hydrogen termination (oxygen termination). An insulating region can be formed.

Of the steps shown in FIGS. 3 and 4, FIGS.
By repeating the above process using different gate metal materials, FETs with different operation modes can be formed on the same substrate.

[0033]

As described above, according to the present invention, a gate electrode is formed on a surface of a hydrogen-terminated homoepitaxial diamond by vapor-depositing a metal forming a Schottky barrier. By forming the source electrode and the drain electrode by vapor deposition of metal such as platinum or platinum, it is possible to obtain a MESFET having a large mutual conductance by operating in any mode of depletion mode or enhancement mode. With the non-hydrogen termination, the elements can be insulated and separated by a simple manufacturing process and means, and a diamond semiconductor device in which a plurality of semiconductor elements are integrated can be formed.

A plurality of diamond semiconductor elements can be formed on the same substrate by a simple process, and
For example, in the FET, since the element can be made into a simple shape without making it circular, miniaturization and high integration are possible.

Further, according to the present invention, in manufacturing the semiconductor layer, it is not necessary to introduce impurities, so that a toxic gas such as B ₂ H ₆ is not required and the semiconductor layer can be manufactured safely. Moreover, it is not necessary to deal with toxic gas, and the manufacturing apparatus can be simplified.

According to the present invention, the gate electrode, the source ohmic contact and the drain ohmic contact can be formed by vapor deposition, and the manufacturing process can be simplified.

Further, since the FET according to the present invention uses diamond having a large band gap, it can be used at high temperature and can be stably operated even under strong radiation.

Further, according to the present invention, since the metal film to be the electrode of the FET is used as a mask for dehydrogenating the hydrogen-terminated diamond, the number of masks can be reduced and the dehydrogenation treatment can be performed. It is not necessary to make an alignment and the processing steps can be greatly simplified. Further, since it is not necessary to design the source and the drain to be large in consideration of the alignment accuracy, the transconductance is improved and a high value of 12.3 mS / mm can be obtained.

[Brief description of drawings]

FIG. 1 is an FE obtained by a manufacturing method according to the present invention.
The top view which shows the concept of the structure of T.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a view (No. 1) for explaining the method of manufacturing the hydrogen-terminated diamond FET according to the present invention.

FIG. 4 is a diagram (No. 2) for explaining the method of manufacturing the hydrogen-terminated diamond FET according to the present invention.

FIG. 5 is a diagram showing characteristics of a depletion mode hydrogen-terminated diamond FET obtained by a manufacturing method according to the present invention.

FIG. 6 is a diagram showing the characteristics of an enhancement-mode hydrogen-terminated diamond FET obtained by the manufacturing method according to the present invention.

[Explanation of symbols]

10 Homoepitaxial diamond thin film 11 Hydrogen termination surface (conductive area) 12 Surface conductive layer (p-type conductive layer) 13 Non-hydrogen termination surface (insulation area) 14 depletion layer 20 masks 21 opening 30 gold thin film 31 Drain ohmic contact (drain electrode) 32 source ohmic contact (source electrode) 40 mask (potassium iodide resistant) 41 opening 42 cavities 51 gate electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Ito 1-1-16 Nishioginami, Suginami-ku, Tokyo (72) Inventor Akira Sozono 2--1549 Misumicho, Higashimurayama, Tokyo (56) Reference References Proceedings of the 42nd Applied Physics Joint Lecture in Spring 1995 (Japan), Japan, March 28, 1995, p. 423 Proceedings of the 56th Autumn Meeting of the Society of Applied Physics, 1995, Japan, August 26, 1995, p. 385 (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/338 H01L 29/812

Claims (3)

(57) [Claims] 1. A step of forming a mask on a diamond whose surface is terminated with hydrogen so as to cover a channel forming region including a source electrode region, a drain electrode region and a gate electrode region of a field effect transistor (FET), forming an insulating region by breaking the hydrogen-terminated region other than the FET forming region by using a mask to form a mask having a gate electrode forming opening on the mask, the gate electrode forming opening Isotropic with a mask that has
Of forming gate electrode formation area by reactive etching
And using an anisotropic film formation method in the gate electrode formation region using a mask having the gate electrode formation opening.
A method of manufacturing a hydrogen-terminated diamond FET, comprising the step of separating a contact and a drain contact to form a gate electrode. 2. The source electrode region and the drain electrode
Channel including a region and a region to be a gate electrode region
The method for manufacturing a hydrogen-terminated diamond FET according to claim 1, wherein the mask covering the formation region is an ohmic contact material for the source electrode and the drain electrode. 3. The method of manufacturing a hydrogen-terminated diamond FET according to claim 1, wherein the insulating region is formed by irradiation with argon ions.