JPS6131638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a shot barrier type electrode.

The conventional method for manufacturing a shot barrier type electrode is to first deposit a metal layer on the surface of an n-type semiconductor to make shot contact with the n-type semiconductor, and then to form an electrode on the metal layer using a normal photoresist method. The metal layer on the surface of the n-type semiconductor is selectively removed by chemical etching or anodic oxidation to form a shot barrier type electrode. With the manufacturing method, it is extremely difficult to control the shape and width to be uniform across all electrodes.
When trying to form a 1.0 μm linear electrode, there are problems such as unevenness in the shape of the electrode and disconnection, and it is also difficult to control the dimensions of the electrode to a specific value. It was hot. on the other hand,
The conventional manufacturing method using the anodic oxidation method solves the problems encountered with the chemical etching method, but it also oxidizes the semiconductor directly under the metal along with the electrode metal, and therefore does not oxidize the semiconductor at all. However, there was a drawback that it was not possible to shorten the electrode dimensions by anodizing the metal under the mask for electrode formation.

An object of the present invention is to eliminate the above-mentioned drawbacks and problems, to selectively form a short barrier type electrode with a width on the order of submicrons in a uniform shape, and to also provide a mask for forming the electrode (referred to as an electrode forming mask). )
An object of the present invention is to provide a method for manufacturing a shot barrier type electrode that can be made smaller in size than the above.

According to the present invention, a metal layer having a high oxidizing power and making a sudden contact with the n-type semiconductor is deposited on the surface of the n-type semiconductor, and an insulator serving as a mask for anodic oxidation is applied to the electrode formation portion on the surface of the metal layer. After depositing the film, the voltage applied to the anode is changed to the fluctuation of the shot contact.
The anodic oxidation of the metal layer performed below the take-down voltage and the removal of the formed oxide film are repeated to remove all of the metal layer on the n-type semiconductor except for the electrode forming portion, and then the insulating film is removed. By removing , it is possible to obtain a method for manufacturing a shot barrier type electrode that can always form a shot barrier type electrode with uniform width and shape on the surface of an n-type semiconductor with good controllability and reproducibility.

This invention can also be applied to a recess structure in which the electrode formation portion is dug, and furthermore, an n-type semiconductor conductive layer having a different electron concentration from that of the n-type semiconductor, and furthermore a p-type semiconductor conductive layer are formed on the surface of the n-type semiconductor. It can also be applied to structures with

Since the electrode metal is selected to make a shot contact with the n-type semiconductor, as long as the voltage applied to the anode is below the breakdown voltage of the shot contact, the n-type semiconductor will not be oxidized at all. First, only the electrode metal is oxidized.

Furthermore, even if the metal directly under the insulating film is further anodized and the formed oxide film is repeatedly removed, the n-type semiconductor will not oxidize at all.
Only the dimensions of the electrode metal are shortened.

Next, a method for forming an electrode formation mask for anodic oxidation will be described. In order to manufacture electrode shapes with small dimensions, it is necessary that the sides of the electrode be as vertical as possible, but photoresist films, which are generally easy to handle, have poor adhesion, so anodization using such an electrode formation mask is difficult. If this is done, the side surfaces of the electrode metal will not be vertical but will have a gentle slope. In such a case, it is preferable to form a thin oxide film on the surface of the electrode metal in advance and then cover it with a photoresist film to serve as an electrode formation mask.

As described above, according to the present invention, an easy-to-handle photoresist film can be used as an electrode formation mask, and electrodes can be formed with good controllability.

The present invention will be explained in detail below using the drawings.

FIG. 1 is a diagram for explaining a conventional method of manufacturing a shot barrier type gate electrode, and shows cross-sectional views of a wafer in each main process. Figure 1 a is n type
Formed on the surface of GaAs11 (n=1×10 ¹⁷ cm ^-3 )
The Al film 12 is shown. In FIG. 1b, CVF (Chemical Vapor
SiO ₂ with a thickness of 3000 Å formed by
Membrane 13 is shown. Figure 1c shows that the Al film 12 was anodized using the SiO ₂ film as an electrode formation mask at a power supply voltage of 100 V and a current density of 2 mA cm ^-2 , and the formed oxide film was removed by repeating the process. Show the situation. FIG. 1d shows that in order to further shorten the size of the Al film 13 under the SiO ₂ film 13, the Al film 13 is
This shows how the sides of No. 3 were repeatedly anodized and removed. At this time, the surface of the n-type semiconductor 11 that is in contact with the electrolyte for anodic oxidation is also anodized at the same time. FIG. 1e shows an Al electrode obtained by removing the SiO ₂ film 13. Compared to the conventional manufacturing method using chemical etching, the shot barrier type electrode produced by this conventional manufacturing method is more uniform and has better controllability over the entire wafer surface, but it has the disadvantage that the shape of the n-type semiconductor surface changes. However, if an attempt was made to prevent this drawback, a new problem occurred in that it was impossible to shorten the dimensions of the electrode to below the dimensions of the electrode forming mask.

FIG. 2 is a diagram for explaining the first embodiment of the present invention, and shows cross-sectional views of a GaAs wafer in each main process.

Figure 2a shows n-type GaAs21 (n=1×10 ¹⁷ cm
^-3 ) shows the state in which the Al film 22 is deposited to a thickness of 3000 Å on the entire surface.

In Fig. 2b, a SiO ₂ film with a thickness of 3000 Å is deposited on the surface of the Al film 22 using the CVD method, and the SiO ₂ film 23 except for the electrode forming portion is coated with HF using the photoresist method.
This figure shows how it was removed using an etching solution.

FIG. 2c shows the SiO ₂ film 23 used as an electrode formation mask at a power supply voltage of 15 V and an initial current density of 2 mA cm.
^-2 in a 2.5% oxalic acid aqueous solution under anodizing conditions
When forming the oxide film of the Al film 22, the oxide film is made of Al ₂ O ₃ consisting of CrC ₃ , H ₃ PO ₄ and H ₂ O.
In the process of chemically etching and removing with a liquid, the process is first repeated until all of the Al film 22 on the n-type GaAS is removed except for the Al film directly below _{the SiO 2 film} 23, and then the This figure shows how the dimension of the Al film under the SiO ₂ film was shortened by repeatedly anodizing the side surface of the Al film 22 and removing the formed oxide film.

Here, the depth of wear of the Al film directly under the SiO ₂ film can be easily calculated from the value of the potential drop of the oxide film due to anodic oxidation, so if the dimensions of the SiO ₂ film are constant, Set the electrode dimensions to any value〓〓〓〓〓
Can be controlled.

FIG. 2d shows an Al electrode 24 obtained by removing the SiO ₂ film 23 with an HF-based aqueous solution.

As described above, according to the present invention, electrodes can be selectively formed in a uniform shape without oxidizing the n-type semiconductor at all, that is, without changing the shape of the surface of the n-type semiconductor, and furthermore, the electrode formation mask can be Electrodes smaller than the above dimensions can be formed with uniform dimensions over the entire surface of the wafer with good controllability.

FIG. 3 is a diagram for explaining the second embodiment of the present invention, showing cross-sectional views of a GaAs wafer in each main process. The embodiment shown in FIG. 3 is different from that shown in FIG.
This is a wafer in which an n + -type semiconductor conductive layer having a higher electron concentration than the n ^- type semiconductor conductive layer is provided on a part of the surface of the n-type semiconductor conductive layer.

Figure 3a shows an n-type semiconductor 31 (n=1×10 ¹⁷ cm
^-3 ) N-type semiconductor conductive layer (n=5×10 ¹⁷ cm ^-3 ) formed on a part of the surface and an Al film 33 with a thickness of 3000 Å deposited on the entire surface of the n-type semiconductor 31. shows.

FIG. 3b shows SiO ₂ with a thickness of 3000 Å formed on the Al film 33 in the electrode formation area using the usual photoresist method.
A state in which the film 34 is formed is shown.

FIG. 3c shows that the Al film 33 is anodized by using the SiO ₂ film 34 as an electrode formation mask at a power supply voltage of 8 V and a current density of 2 mA·cm ^-2 to chemically etch and remove the formed oxide film. is repeatedly removed, and the Al film 33 immediately below the SiO ₂ film 34 is also removed from the side, thereby reducing the dimension of the Al film 33 to be smaller than the SiO ₂ film 34.
Here, the power supply voltage for anodic oxidation is selected to be less than the breakdown voltage in the n ⁺ -type semiconductor conductive layer plus the potential drop in the electrolyte, etc.

FIG. 3d shows a shot barrier type Al electrode 35 obtained by removing the SiO ₂ film. As described above, according to the present invention, even in a wafer in which an n-type semiconductor conductive layer having a different electron concentration from that of the n-type semiconductor is formed on the surface of the n-type semiconductor, the power supply voltage for anodization is changed to that of the n-type semiconductor having a higher electron concentration. By lowering the breakdown voltage to below the breakdown voltage, a shot barrier type electrode can be formed in a uniform manner over the entire wafer surface with good controllability without changing the n-type semiconductor surface at all.

FIG. 4 is a diagram for explaining the third embodiment of the present invention, showing cross-sectional views of a GaAs wafer in each main process. The embodiment of FIG. 4 is different from that of FIG. 2 in that it is a wafer in which a P-type semiconductor conductive layer is formed on a part of the n-type semiconductor surface.

Figure 4a shows an n-type semiconductor 41 (n=1×10 ¹⁷ cm
^-3 ) The thickness of the P-type semiconductor conductive layer 42 formed on a part of the surface is
A 3000 Å SiO ₂ film 43 is applied to the P-type semiconductor conductive layer 42.
This figure shows how it is formed so as to completely cover it.

FIG. 4b shows a film with a thickness of 3000 Å formed on the entire surface of the SiO ₂ film 43 and the exposed n-type semiconductor 41.
The Al film 44 of FIG.

FIG. 4c shows the difference on the surface of the n-type semiconductor 41.
A CVD SiO ₂ film 45 with a thickness of 3000 Å is deposited on the electrode forming portion of the Al film 44 surface using the usual photoresist method.
The figure shows how it was formed to a thickness of .

FIG. 4d shows that the Al film is selectively anodized using the SiO ₂ film 45 as an electrode formation mask at a power supply voltage of 15 V and a current density of 2 mA cm ^-2 , and the formed oxide film is removed by chemical etching. This process is repeated to remove the Al film 4 immediately below the SiO ₂ film 45.
This figure shows how the size of the Al film 44 was shortened by repeating anodic oxidation and removal from the side surface of the Al film 44.

FIG. 4e shows a shot barrier type electrode 46 obtained by removing the SiO ₂ film. As described above, according to the present invention, even in a wafer consisting of a P-type semiconductor conductive layer formed on the surface of an N-type semiconductor, the P-type semiconductor conductive layer is covered with an insulating layer, so that the same method as in the embodiment shown in FIG. effect can be obtained. Furthermore, in FIG. 4, the semiconductor conductive layer covered with the insulating layer has been described using a P type semiconductor layer, but the P type
type semiconductor conductive layer with extremely high electron concentration n≧2×
The idea of the present invention can be applied even when replacing with an n ⁺ type semiconductor conductive layer of 10 ¹⁸ cm ⁻³ .

FIG. 5 is a diagram for explaining the fourth embodiment of the present invention, showing cross-sectional views of a GaAs wafer in each main process. The embodiment shown in FIG. 5 differs from the embodiment shown in FIG. 2 in that the electrode forming portion has a recessed structure.

FIG. 5a shows how a recess is formed on n-type GaAs (n=1×10 ¹⁷ cm ⁻³ ) using the first SiO ₂ film 52 formed by CVD as a mask.

FIG. 5b shows a state in which an Al film 53 with a thickness of 3000 Å is formed on the surface of the SiO ₂ film 52 and the n-type GaAs.
vinegar.

FIG. 5c shows that the entire surface of the Al film 53 is coated by CVD.
A second SiO ₂ film 54 with a thickness of 3000 Å is deposited, and the SiO ₂ film is selectively left within the recess at a size below the recess using a conventional photoresist method.

FIG. 5 d shows, similar to FIG. 2 c, the second
The Al film 5 is formed using the SiO ₂ film 54 as an electrode formation mask.
3 is selectively removed, and the dimension of the Al film 53 immediately below the SiO ₂ film 54 is also shortened. Normally, the thickness of the Al film in the difference part of the recess is thinner than in other parts, so the Al film in the recess and the Al film on the SiO ₂ film 52 (first) are cut during anodization, and the Al film on the SiO 2 film 52 (first) is cut. Although the Al film on the SiO ₂ film may remain without being removed, this Al film will be removed together with the SiO ₂ film in the next step.

Figure 5e shows the Al electrode 5 in the recessed structure obtained by completely removing the first and second SiO ₂ films.
5 is shown. As described above, according to the present invention, even in an n-type semiconductor having a recessed structure, electrode metal can be selectively formed into a uniform shape without changing the surface of the n-type semiconductor, and furthermore, the electrode metal can be formed in a uniform shape even in an n-type semiconductor having a recessed structure. can be formed with uniform dimensions over the entire wafer surface with good control.

FIG. 6 is a diagram for explaining the fifth embodiment of the present invention, showing cross-sectional views of a GaAs wafer at each main step. Fig. 6 shows the embodiment of Fig. 2. Fig. 2b
The subsequent steps, especially the method of forming an electrode formation mask for anodic oxidation, are different.

The following explanation is a simplified explanation of the same process as in FIG. 2a.

Figure 6a shows n-type GaAs61 (n=1×10 ¹⁷ cm
^-3 ) An Al film 62 is deposited on the surface to a thickness of 4000 Å, and
The Al oxide film 63 is formed on the surface of the Al film 62 to a thickness of 2000 mm.
Å formation is shown.

FIG. 6b shows a photoresist film (AZ1350, trademark) formed on the oxide film 63 at the electrode formation part.
64 is shown.

FIG. 6c shows the exposed Al film 62 using the photoresist film 64 as an electrode formation mask at a power supply voltage of 15V and an initial current density of 2mA, as in FIG. 2c.
In the step of forming an oxide film on the Al film 62 in a 2.5% oxalic acid aqueous solution under anodizing conditions of cm ^-2 and removing the oxide film by chemical etching, first, immediately below the photoresist film 64. This process is repeated until all of the Al film 62 except for the Al film 62 is removed, and then the Al film 62 directly under the photoresist film 64 is
This figure shows the process of repeatedly oxidizing the side surface of the film 62 and removing the formed oxide film.

FIG. 6d shows the photoresist film 64 with a thickness of 2000 Å.
An Al electrode 65 obtained by removing the Al oxide film 63 is shown. According to the present invention, by forming a thin oxide film on the gate metal surface, an easily handled photoresist film can be used as an electrode formation mask for anodic oxidation of the electrode metal. Electrode metal can be selectively formed into a uniform shape without oxidizing the n-type semiconductor at all, and electrodes smaller than the size of the electrode formation mask can be formed with uniform dimensions over the entire wafer with good controllability. .

As explained using the above example, the disadvantages of the conventional method of forming electrodes using chemical etching are the non-uniformity and uncontrollability of the electrode shape, and furthermore, the formation of electrodes using conventional anodic oxidation. The disadvantages of this method, such as shape change due to oxidation of the semiconductor surface, can all be solved by using the present invention. The present invention also solves the problem of forming electrodes in recess structures with minute dimensions, which was impossible with conventional chemical etching because the etching solution did not penetrate uniformly.

In the embodiments of the present invention, the power supply voltage is selected to be a value smaller than the voltage obtained by adding the breakdown voltage of shot contact and the potential drop in the electrolytic solution. Although the invention has been explained using GaAs as an embodiment, it goes without saying that it is also applicable to semiconductor elements using other semiconductor materials such as Si, GaP, and InSb. Although the SiO ₂ film and the photoresist film have been used in the explanation, other insulating materials that have good adhesion to the electrode metal or the oxide film of the electrode metal can also be used.

[Brief explanation of the drawing]

Figures 1a to 1e are diagrams for explaining a conventional method of manufacturing a shot barrier type electrode, and Figures 2a to d,
Figures 3 a to d, Figures 4 a to e, Figures 5 a to e, and Figures 6 a to d show the first manufacturing method of the present invention, respectively.
, the second example, the third example, the fourth example, and the fifth example.
A cross-sectional view of a GaAs wafer in each main process is shown. In these figures, 11, 21, 31, 4
1, 51 and 61 are n-type GaAs, 32 is n ⁺ type
GaAs conductive layer, 12, 22, 33, 44, 53 and 62 are Al films, 63 is Al oxide film, 13,
23, 34, 43, 45, 52 and 54 are
SiO ₂ film, 64 is photoresist film, 14,2
4, 35, 46, 55 and 65 represent shot barrier type electrodes. 〓〓〓〓〓

Claims (1)

[Scope of Claims] 1. A metal layer having a high oxidizing power and in direct contact with the n-type semiconductor is deposited on the surface of the n-type semiconductor, and an insulating coating is deposited on the electrode forming portion of the surface of the metal layer, Using the insulating film as a mask, the metal layer is anodized and the formed oxide film is removed so that the voltage applied to the anode is below the breakdown voltage of the shot contact. All of the metal layer on the n-type semiconductor surface except the bottom part is removed, and the side surface of the metal layer under the mask is anodized and the formed oxide film is removed to reduce the dimensions of the metal layer. A method for manufacturing a shot barrier type electrode, comprising shortening the electrode to a size smaller than that of a mask, and then removing the oxide film serving as a mask. 2. In forming an insulating film for anodic oxidation, a thin oxide film is formed on the surface of the gate electrode, a photoresist film is formed on the gate electrode formation portion on the oxide film, and the photoresist film is used as an insulating film for anodization. A method for manufacturing a shot barrier type electrode according to claim 1.