JPH02210831A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To surely perform anodic oxidation when the connection position of an anode is arbitrary by covering the periphery of an element forming region or a circuit forming region of a semiconductor film, with an insulating film, and stretching said insulating film over the electrode connection position. CONSTITUTION:The periphery of an element forming region or a circuit forming region 6 of a conductive semiconductor film 1 is covered with an insulating film 4, which is stretched over an electrode connection region 7. As a result, current flows always from an electrode 8 to the element forming region or the circuit forming region 6 through the conductive semiconductor film 1 in the region where the insulating film 4 is formed. Thereby, even when the electrode 8 is connected with a region whose film thickness is the thinnest or a region whose impurity concentration is the lowest, anodic oxidation of a region whose film thickness is thick or a region whose impurity concentration is high can surely be performed.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for manufacturing a semiconductor device including a step of anodizing the surface of a semiconductor film epitaxially grown on a semiconductor substrate, regardless of the connection position of the electrode in the conductive semiconductor film,
In order to ensure that anodic oxidation is performed, the periphery of the element formation region or circuit formation region in the conductive semiconductor film formed on the substrate is covered with an insulating film, and the insulating film is used as the electrode in the conductive semiconductor film. extending to the vicinity of the connection region, connecting an electrode to the electrode connection region, and anodizing the surface of the element formation region or circuit formation region of the conductive semiconductor film; Alternatively, the structure includes a step of thinning the circuit forming region.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for manufacturing a semiconductor device including a step of anodizing a semiconductor film epitaxially grown on a semiconductor substrate.

[Conventional technology]

Methods for mixing impurities into a semiconductor film include a first method of implanting impurity ions onto a semi-insulating semiconductor substrate by an ion implantation method, a second method of epitaxial growth using an MBE method, and a liquid phase or vapor phase method. It can be roughly divided into the third method of epitaxial growth.

The first method has the advantage that the impurity concentration and depth can be controlled uniformly, but has the problem that the crystallinity of the semiconductor film deteriorates due to ion implantation.

Further, although the second method has no problems with uniformity or crystallinity, it has poor mass productivity and increases cost.

On the other hand, the third method has excellent crystallinity and mass productivity, and is generally widely used. However, the distribution of impurities and the thickness of the film become non-uniform, and when a semiconductor device is manufactured using this semiconductor film, there is a drawback that variations in operating current occur.

Therefore, as a means of making the operating current uniform by approximating the product of impurity concentration and film thickness, after growing a semiconductor film with impurities mixed in by epitaxial method,
The surface of the conductive semiconductor film is anodized to form an operating layer through which a uniform operating current flows.

Furthermore, in the case of GaAs FET, it is also possible to remove the surface of the semiconductor film, which will become the active layer, by etching only the gate electrode formation region to form a recess, and then thin the underlying semiconductor film to a predetermined thickness. It is being said. If the depletion layer formed by the Schottky electrode formed in the recess spreads to the periphery of the recess, the withstand voltage will change depending on the thickness of the semiconductor film around the recess. In order to make the thickness uniform, the entire surface of the semiconductor film is anodized before forming the recess to make the thickness uniform.

As shown in FIG. 4, anodic oxidation is performed by connecting an anode 41 of a DC power source to an epitaxially grown semiconductor layer 40 while irradiating visible light from above, and then irradiating the surface of the epitaxially grown semiconductor layer 40 in an electrolytic solution. According to this method, oxidation proceeds from the upper part of the depletion layer 42 generated on the surface of the semiconductor layer 40, and as the oxidized film 43 becomes thicker, the depletion layer 42 also moves downward. Become.

Therefore, when anodizing a semiconductor layer 40 with a uniform impurity concentration and non-uniform film thickness, as shown in FIG. 4(a), the thickest region of the semiconductor film 40 is A
When the positive electrode 41 is connected to the semiconductor film 40, a depletion layer 42 is uniformly generated near the surface of the semiconductor film 40, and the upper part of the depletion layer 42 is oxidized.

In this case, in the thin region B, the depletion layer 42 reaches the buffer layer 45 earlier and blocks the current from the anode 41 (FIG. 4(b)). In this case, the oxidation stops early (FIG. 4(C)), while the anodic oxidation continues in the thick region A, resulting in an increase in the thickness of the oxide film 43.

Therefore, by removing the anodized film 43, the thickness of the semiconductor film 40 can be made uniform.

[Invention tries to solve! ! i! However, when the anode electrode 41 is connected to the thin region B, as shown in FIG. As a result, the flow of current from the positive electrode 41 to the thick region A is blocked by the depletion layer 42, which results in the oxidation of the thick region A being stopped early. ,
A problem arises in that the film thickness cannot be made uniform.

Of course, it is possible to connect the positive electrode to the thickest part of the film, but it is impossible to find the thickest position in a non-destructive manner.

The present invention has been made in view of such problems, and an object of the present invention is to provide a method for manufacturing a semiconductor device that allows complete anodic oxidation regardless of the contact position of the anode.

[Means to solve the problem]

The above-mentioned problem is solved by the conductive semiconductor film 1 formed on the substrate 3.
The periphery of the element formation region or circuit formation region 6 is covered with an insulating film 4, and the insulating film 4 is extended to the vicinity of the electrode connection region 7 in the conductive semiconductor film 1,
An electrode 8 is connected to the electrode connection region 7 and the element formation region or circuit formation region 6 of the conductive semiconductor film 1 is anodized to thin the element formation region or circuit formation region 6 of the conductive semiconductor film. The present invention is solved by a method for manufacturing a semiconductor device characterized by having a step of:

[For production]

In the present invention, since the periphery of the element formation region or circuit formation region 6 of the conductive semiconductor film 1 is covered with the insulating film 4, and this insulating film 4 is extended to the electrode connection region 7, A current can be constantly passed from the electrode 8 to the element formation region or circuit formation region 6 through the conductive semiconductor film 1 in the region where the insulating film 4 is formed.

As a result, even if the electrode 8 is connected to the thinnest region of the conductive semiconductor lI21 or the electrode 8 is connected to the region with the lowest impurity concentration, the thick fII region or the region with high impurity concentration This makes it possible to reliably perform anodic oxidation.

〔Example〕

(a) Description of one embodiment of the invention FIG. 2 is a plan view and a sectional view showing a disk-shaped semiconductor wafer to be anodized, and reference numeral 1 in the figure indicates a buffer N2 made of a non-doped compound semiconductor. This n-type semiconductor film 1 is an n-type semiconductor film epitaxially grown on a semi-insulating semiconductor substrate 3 via a compound such as gallium arsenide (GaAs) formed by a vapor phase method, a liquid phase method, etc. It is made of a semiconductor and is formed so that impurities such as silicon (Si) contained therein are uniformly mixed in at the same time as the film grows.

Next, an embodiment of the present invention using the above-described semiconductor wafer will be described based on FIG. 1.2.

First, a silicon dioxide (Sing) film 4 is formed on the n-type semiconductor film 1 by a vapor phase growth method, and this Si
A resist 5 is applied on the O2 film 4. Then, this resist 5 is exposed and developed to form a plurality of semiconductor element forming regions 6 inside the n-type semiconductor film 1 and the n-type semiconductor 11! J
After forming a window of resist 5 above the electrode connection region 7 provided at one periphery (FIG. 1(a)), the SiO□ film 4 is etched using a hydrofluoric acid etching solution using the resist 5 as a mask, thereby forming a semiconductor. 5i02 around the element formation region 6
While the film 4 remains, the n-type semiconductor film 1 is exposed from the electrode connection region 7 (FIG. 1(b)).

Next, after removing the resist 5, propylene glycol is added to the tartaric acid aqueous solution while the clip-shaped positive electrode 8 is connected to the electrode connection area 7 of the n-type semiconductor substrate 1, as shown in FIG. 1(c). The semiconductor substrate 3 is immersed in the added electrolyte 9.

Then, the positive electrode of a DC power supply 1O is connected to the above-mentioned positive electrode 8, and the negative electrode 11 made of platinum immersed in the electrolyte 9 is connected to the negative electrode of the DC power supply 10.

In this state, when visible light is irradiated from above the SiO□ film 4 as shown in FIG.
, oxidation progresses from the surface to Ga2O3,
An oxide film 13 of AsO□ is formed, and its thickness increases with the passage of time, and as a result, the depletion 1112 moves toward the buffer layer 2 (FIG. 1(e)).

By the way, the n-type semiconductor film 1 covered with the SiO□ film 4
In the region, the surface is not oxidized and the depletion W412 below it is
Since the current does not reach the buffer M2, current can be constantly supplied to each semiconductor element forming region 6 through this region.

As a result, in the thin region B of the n-type semiconductor film l, even if the current flow is blocked by the depletion layer 12 below and the anodic oxidation is stopped, the SiO□ film 4 is formed. from the positive electrode 8 through the thick region A.
A current flows through the region A, and anodic oxidation is performed in the region A until the depletion layer 12 reaches the buffer layer 2 (FIG. 1(f)).

Therefore, the thickness of the unoxidized n-type semiconductor film 1 in the element formation region 6 becomes uniform.

At this stage, the oxide film 13 on the n-type semiconductor film 1 is reduced to 20%.
While selectively removing with concentrated hydrochloric acid, SiO
□Remove IFJ4 by photo etching method etc. (first
Figure (g)).

In the GaAs n-type semiconductor film 1 whose film thickness has been made uniform by anodic oxidation, the carrier distribution becomes uniform, so source and drain electrodes are formed using AuG5/Ni/Au on this film, and a gate electrode is bonded using ^l. In this way, a GaAs Schottky junction FET with uniform characteristics can be formed.

In this embodiment, an insulating film is formed around the semiconductor element formation region 6 and anodized. However, an insulating film is formed around the semiconductor circuit formation region including the semiconductor element formation region 6 and the wiring formation region. The semiconductor circuit forming region may be anodized by forming a semiconductor circuit forming region.

(b) Description of other embodiments of the present invention In the embodiments described above, the case where the impurity concentration in the n-type semiconductor film l is uniform is explained. In the case of anodic oxidation, as shown in FIG. 3(a), the n-type semiconductor film 21 is
The thickness of the depletion layer 25 generated in the region C where the impurity concentration is high is
Therefore, as shown in FIG. 3(b), the depth of the anodic oxidation increases and the oxide film 26 becomes thicker, and the thickness of the unoxidized film becomes thinner than in the region where the impurity concentration is low.

As a result, as shown in FIG. 3(c) after anodization, the thickness of the n-type semiconductor film 21 in the semiconductor element formation region or the semiconductor circuit formation region becomes non-uniform in each region. Since the number of carriers is distributed almost uniformly in the plane direction, it is possible to make the operating characteristics of the semiconductor device formed here uniform.

In the drawing, reference numeral 22 indicates a buffer layer, 23 indicates a semi-insulating semiconductor substrate, 24 indicates a SiO□ film, and 28 indicates a positive electrode.

By the way, 1. In the above two embodiments, the case where the film thickness is non-uniform and the impurity concentration is non-uniform is explained, but the same phenomenon occurs even when the film thickness is non-uniform, and the impurity distribution is uniform. It becomes almost uniform in the direction.

Further, in the above-described embodiment, the region where no semiconductor element or circuit is formed is covered with the SiOg film 4.24, but it can also be covered with a nitride film, a PSG film, a photoresist, or other insulating film.

Furthermore, although the n-type semiconductor layers 1 and 21 described above are formed of GaAs, the above embodiments can also be applied to cases where they are formed of compound semiconductors such as GaAs and InGaAs.

〔Effect of the invention〕

As described above, according to the present invention, the periphery of the element formation region or the circuit formation region of the semiconductor film is covered with an insulating film, and this insulating film is extended to the electrode connection position, so that the insulating film is It is possible to constantly flow a current M to a plurality of semiconductor formation regions through the semiconductor film in the formed region, and it becomes possible to perform anodization reliably even if the connection position of the anode electrode is arbitrary.

[Brief explanation of the drawing]

FIGS. 1(a) to (g) are process diagrams showing an example of the present invention in cross section; FIGS. 2(a) and (b) are a plan view and a sectional view showing an example of a semiconductor wafer; FIGS. 3(a) to (c) are process diagrams showing other embodiments of the present invention in cross section, and FIGS. 4(a) to (d) are sectional views showing a first example of the conventional method. , FIGS. 5(a) and 5(b) are cross-sectional views showing a second example of the conventional method. (Explanation of symbols) 1.21...n-type semiconductor l! J (conductive semiconductor film),
2.22...Buffer layer, 3.23...Semi-insulating semiconductor substrate, 4.24...Si0g film (insulating It' layer), 5...Resist, 6.26...Semiconductor element formation Region, 7... Electrode connection region, 8... Positive electrode, 9... Electrolyte, 10... DC power supply, 11... Negative electrode, 12°25... Depletion layer, 13... ·Oxide film.

Claims (1)

[Claims] Covering the periphery of an element forming region or a circuit forming region in a conductive semiconductor film formed on a substrate with an insulating film, and extending the insulating film to the vicinity of an electrode connection region in the conductive semiconductor film. connecting an electrode to the electrode connection region, anodizing the surface of the element formation region or circuit formation region of the conductive semiconductor film, and thinning the element formation region or circuit formation region of the conductive semiconductor film; A method for manufacturing a semiconductor device, comprising a step of layering.