JPH06120551A - Semiconductor device - Google Patents

Abstract

PURPOSE:To make prominent and stabilized electric characteristics possible by a method wherein the configurations of four corners of an island type projections are shaped so as to have polygonal or circular shapes when they are seen from the upper side thereof. CONSTITUTION:In the process of leaving a resist film so as to have a rectangular shape when it is seen from the upper side thereof among the manufacturing processes of rectangular island-type projections on a substrate, chamfering is applied on the rectangular four corners two times and photo mask is used so that the resist film remains. Thereafter, etching is applied by water phosphate. Thus, the upper surface 1 of the substrate, the upper surface 2 as well as the side surface 3 of rectangular island-type projection and the side surface 5 produced by chamfering can be obtained. Next, a protecting film is formed on the whole surfaces of the substrate having the rectangular island-type projection and, then, the resist film is formed. Such a configuration is provided whereby the thickness of the resist film on four corners of the island-type projection can be a necessary thickness and the working of the protecting film as well as the formation of an electrode unit can be effected with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a device having a structure having a rectangular island-shaped projection on a substrate.

[0002]

2. Description of the Related Art Conventionally, a semiconductor device, for example, a photodiode is manufactured by a method described below. N-type, I-type, and P-type semiconductor thin film layers are sequentially formed by a MOCVD method or the like on a flat substrate of a semiconductor or an insulator. The total thickness of the semiconductor thin film layers is about 10 μm. A resist film is formed thereon by a spin coat method or the like. The unnecessary portion of the resist film is removed by the photo etching method. The remaining resist film has a rectangular shape of about 200 μm square when viewed from the upper surface side. This substrate is etched to remove the P-type and I-type semiconductor thin film layers other than the portion covered with the resist film. As a result, the portion protected by the resist film remains as a rectangular island-shaped protrusion. This finally becomes each photo diode.

After that, the resist film is removed, and then a protective film is formed on the entire surface of the substrate by a sputtering method or the like. Further, in order to form an electrode portion, a part of the protective film on the N-type semiconductor thin film layer is removed by photoetching. Furthermore, in order to insulate each diode,
The N-type semiconductor thin film layer in the portion without the protective film is removed by etching. After that, an electrode material such as Al is formed by a sputtering method or the like, and further shaped into a required shape. The upper surface of the rectangular island-shaped projection portion is composed of an electrode portion and a light receiving portion, but normally the electrode portion is arranged in the peripheral portion and the light receiving portion is arranged in the central portion surrounded by the electrodes. The above is the outline of the manufacturing method. FIG. 3 is a partially enlarged cross-sectional view after forming a resist film in an example of a conventional semiconductor device. Figure 4
FIG. 4 is a partially enlarged perspective view of the device of FIG. 3. FIG. 5 shows FIG.
It is a partial enlarged top view of the apparatus of FIG. As shown in the figure, in the conventional semiconductor device, a rectangular island-shaped protrusion 11 is formed on the upper surface of the substrate 10.

By the way, the performance of the photodiode is determined by how the electrode portion arranged on the upper surface of the rectangular island-shaped projection portion is arranged on the outer peripheral portion and the light receiving portion area is made large. In addition, if the photo-etching of the protective film on the upper surface of the rectangular island-shaped projection portion where the electrode is arranged is incomplete,
The I-type semiconductor thin film layer may short-circuit with the electrode. That is, the photoetching process of the protective film is a factor that determines the device performance and the manufacturing yield.

[0005]

With respect to the conventional photodiode having the above-mentioned structure, a protective film is formed on the entire surface of a substrate having rectangular island-shaped protrusions, and then the electrode portion is formed. There is a step of forming a resist film in the step of etching the portion of the protective film and the step of etching the N-type semiconductor thin film layer.

This will be described with reference to FIG. Generally, the resist film is applied by a spin coat method or the like, but if the substrate surface is flat, a uniform film thickness can be obtained over the entire substrate surface. Considering the resistance to etching and the accuracy of patterning that follow, the thickness of the resist film after coating is preferably in the range of 0.5 to 1 μm. To satisfy this, the type of resist and coating conditions Is selected.

However, when the resist film 9 is formed on the substrate 10 having the rectangular island-shaped protrusions 11, the process is as follows. That is, as the height H of the rectangular island-shaped protrusions 11 increases, the thickness t ₂ of the resist film on the upper surface 8 of the rectangular island-shaped protrusions becomes smaller, and the thickness t ₁ on the substrate surface 6 becomes Get thicker. This ratio differs depending on the resist coating conditions. The thickness of the resist film on the side surface 7 of the rectangular island-shaped protrusion has an intermediate value between t ₂ and t ₁ . The thickness of the resist film near the side of the upper surface 8 of the rectangular island-shaped protrusion is smaller than the thickness of the central portion thereof. The thickness of the resist film at the corner is thinner than the thickness near the side. When the resist coating conditions are set so that the thickness of the resist film near the center of the upper surface 8 of the rectangular island-shaped protrusions is set appropriately, the resist is applied at the four corners of the upper surface 8 of the rectangular island-shaped protrusions. The thickness of the film becomes extremely thin. Therefore, the resist film at the four corners of the upper surface 8 of the rectangular island-shaped protrusion disappears in the developing process or peels off in the etching process, and normal etching cannot be performed.

For this reason, the resist coating conditions are used to properly secure the thicknesses of the resist films at the four corners of the upper surface 8 of the rectangular island-shaped projection. As a result, the rectangular island-shaped projection is formed. The thickness of the resist film on the central portion of the upper surface 8 of the portion and on the side surface 7 of the rectangular island-shaped protrusion, particularly on the substrate surface 6,
The etching accuracy of the protective film and the P-type semiconductor thin film layer was deteriorated, and it was difficult to obtain a photodiode device having good characteristics. Therefore, according to the present invention, when the resist film is formed on the entire surface of the substrate having the rectangular island-shaped projections, the thickness of the resist film at the four corners of the upper surface of the rectangular island-shaped projections is required. To make it thicker, so that
It is an object of the present invention to provide a semiconductor device having excellent and stable electrical characteristics by enabling the processing of the protective film and the formation of the electrode portion with high accuracy.

[0009]

The semiconductor device of the present invention comprises:
In a semiconductor device in which at least one rectangular island-shaped protrusion is formed on a substrate, the shapes of the four corners of the island-shaped protrusion are polygonal or arc-shaped when viewed from the upper surface side. Thus, the above-mentioned object is achieved.

[0010]

EXAMPLES Examples of the present invention will be described below. First, a method of forming a rectangular island-shaped protrusion on a substrate will be described. In the conventional example, the first and second embodiments of the present invention, the method is basically the same, and the difference is that the resist film used as a mask in etching when forming the rectangular island-shaped protrusions. Because of the difference in shape seen from the upper surface side, FIG. 3, FIG. 4 and FIG. 5 used in the description of the above-mentioned conventional example and FIG. 1 and FIG. It demonstrates using. FIG. 1 is a partially enlarged top view of the first embodiment of the semiconductor device of the present invention. Figure 2
FIG. 7 is a partially enlarged top view of the second embodiment of the semiconductor device of the present invention. As shown in the drawings, Example 1 of the present invention chamfers the four corners of the upper surface of the rectangular island-shaped projection on the substrate once, and Example 2 describes the rectangular island-shaped projection on the substrate. It has a shape in which the four corners of the upper surface of the part are chamfered twice.

An N-type semiconductor thin film layer having a thickness of 2 μm is formed on an insulating substrate having a diameter of 2 ″ by MOCVD.
An I-type semiconductor thin film layer is formed thereon with a thickness of 5 μm by the same method. Further, a P-type semiconductor thin film layer is formed thereon with a thickness of 1 μm. Next, a resist film is formed to a thickness of 0.5 μm by the spin coat method. The resist used is, for example, OFPR manufactured by Tokyo Ohka Kogyo Co., Ltd.
-8600, the resist solution is dropped on the plurality of semiconductor thin film layers formed on the substrate, the rotation speed is 2000 rpm,
The coating is performed under the coating condition that the rotation time is 20 seconds.

After drying the resist film, a pattern is exposed to the resist film using a photomask. The unexposed portion remains without being dissolved in the step of developing the resist film. That is, this portion serves as a mask in the etching process. This shape is the shape of the upper surface of the rectangular island-shaped protrusion. The size of this rectangular shape is 200 μm × 200 μm
To 2000 μm × 2000 μm, which is selected according to the type of photodiode.

Next, the P-type and I-type semiconductor thin film layers are removed by etching. However, those portions protected by the resist film remain without being etched. This becomes a rectangular island-shaped protrusion 11. Usually, phosphoric acid / hydrogen peroxide (a mixed solution of phosphoric acid, hydrogen peroxide, and water) is used as an etching solution, and the etching amount is controlled by the etching time. In this case, the etching is 7 μm. After that, when the resist film is removed, a rectangular island-shaped protrusion 11 on the substrate 10 shown in FIG. 4 is obtained. The substrate is shown with its top surface 6 and side surfaces 12. The rectangular island-shaped protrusion has an upper surface 8
And side 7 is shown. The height of the rectangular island-shaped protrusion is
It is 7 μm. The rectangular island-shaped protrusion includes an I-type semiconductor thin film layer that serves as a photoelectric conversion unit and a P-type semiconductor thin film layer that serves as a light receiving unit and an electrode unit.

Next, a SiN film serving as a protective film is formed to a thickness of 0.5 μm on the entire surface of the substrate having the rectangular island-shaped protrusions. Of this SiN film, a part of the upper surface of the rectangular island-shaped protrusion and a part of the N-type semiconductor thin film are removed to form an electrode part. For this, the photoetching method used when forming the rectangular island-shaped protrusions is used again. First, a resist film is applied over the entire surface of a substrate having rectangular island-shaped protrusions. FIG. 3 is a sectional view showing the state at that time. t ₁ is the resist film 9 on the upper surface 6 of the substrate
, And t ₂ represents the thickness of the resist film on the upper surface 8 of the rectangular island-shaped protrusion. Although t ₁ and t ₂ differ depending on the type of resist and its coating conditions, t ₂ is 0.
They are chosen to be 5 μm.

When the thickness distribution of the resist film 9 on the upper surface 8 of the rectangular island-shaped projection is examined, it is thick in the central portion and thin in the peripheral portion. Focusing on the sides and corners of the periphery, the corners are the thinnest. Next, there is an etching step for removing unnecessary portions of the SiN film, but the thickness of the resist film at the corners of the four corners must be thick enough to protect the necessary portions to be left. In addition, the thickness t of the resist film 9 on the upper surface 6 of the substrate
₂ varies depending on the type of resist and the coating conditions, but when the height of the rectangular island-shaped protrusions is 7 μm and the resist film thickness t _{2 on} the upper surface 8 of the rectangular island-shaped protrusions is 0.5 μm, 1
From 3 μm to μm. When the thickness t ₁ of the resist film on the upper surface 6 of the substrate becomes 3 μm, the dimensional accuracy of the resist film on the substrate after exposure to light and development is extremely poor and the next etching step cannot be performed accurately. The thickness of the resist film 9 on the side surface 7 of the rectangular island-shaped protrusion is 0.5 μm to 3 μm. The resist film in this portion is
Since it serves as a protective layer, it may have a sufficient thickness.

Next, the results of a comparative examination of the conventional example and the example will be described. As the shape of the four corners of the rectangular island-shaped protrusion on the substrate, a rectangular island shape is formed depending on the type of resist, as compared to the right angle of the conventional example, the chamfering once of Example 1 and the chamfering twice of Example 2. It was clarified whether or not the resist film formed on the substrate having the protrusion was good.

As the resist, those manufactured by Tokyo Ohka Kogyo Co., Ltd. were used, and the difference in effect depending on the viscosity was clarified. OFPR-8 is a low-viscosity resist.
600 was used. Its viscosity is 30 cp. The coating conditions were a rotation speed of 2000 rpm and rotation for 20 seconds. ODUR-1013 was used as the medium viscosity resist. Its viscosity is 170 cp. The coating condition is 30 rotations.
Spinned at 00 rpm for 20 seconds. OFPR-800 was used as the high-viscosity resist. Its viscosity is 500
cp. The coating conditions are 2500 rpm and 2
Spin for 0 seconds.

FIG. 5 shows a conventional example. Here, the upper surface 6 of the substrate, the upper surfaces 8 and the side surfaces 7 of the rectangular island-shaped protrusions are shown. In the conventional example, when the low-viscosity or medium-viscosity resist is applied to the entire surface of the substrate having the rectangular island-shaped protrusions, the upper surface 8 of the rectangular island-shaped protrusions is shown in FIG.
There are areas where the resist film is not applied at the four corners. The length L of one side thereof is 20 μm or less. This L
The magnitude of the value of is not important, and it is important that the resist film surely remains at the four corners of the upper surface 8 of the rectangular island-shaped protrusion, and that this part functions as a mask in the subsequent etching step. Is. In the conventional example, when the high-viscosity resist is applied to the entire surface of the substrate having the rectangular island-shaped protrusions, the missing portion of the resist film shown by the hatched portion in FIG. 5 does not appear. However, since the resist film thickness on the substrate upper surface 6 shown by t ₁ in FIG. 3 exceeds 3 μm, an accurate resist pattern cannot be formed on the substrate upper surface 6. Therefore, since only etching with low accuracy can be performed, this condition is not actually adopted.

[Example 1] In the step of forming a rectangular island-shaped projection on a substrate, in a step of leaving a rectangular resist film when viewed from the upper surface side, a chamfering was performed once at four corners of the rectangle. A resist film is left using a mask, and then etching is performed with phosphoric acid / hydrogen peroxide mixture. FIG. 1 is a partially enlarged top view of the rectangular island-shaped protrusion thus obtained. In this figure, the upper surface 1 of the substrate, the upper surface 2 of the rectangular island-shaped protrusions and their side surfaces 3 and the side surfaces 4 obtained by chamfering are shown. The chamfer width L ₁ is 5 μm. A protective film is formed on the entire surface of the substrate having the rectangular island-shaped protrusions, and then a resist film is formed.

When the low-viscosity resist is used, the resist film is not formed over the width of 2 μm along the chamfered line of the corner of the upper surface 2 of the rectangular island-shaped protrusion. All parts except this part are covered with the resist film. However, when the medium viscosity resist is used, the resist film is formed also on the portion along the chamfered line of the corner of the upper surface 2 of the rectangular island-shaped protrusion. This resist film sufficiently functions as a mask in the next etching step. Under the condition of applying the medium viscosity resist, the resist film thickness t ₁ on the upper surface of the substrate is 2 μm, and even when the protective film on the upper surface of the substrate is etched, its accuracy can be sufficiently ensured, and good results are obtained. Was given.

[Embodiment 2] In a process of forming a rectangular island-shaped projection on a substrate, a resist film is left in a rectangular shape when viewed from the upper surface side, and four corners of the rectangle are chamfered twice. A resist film is left using a mask, and then etching is performed with phosphoric acid / hydrogen peroxide mixture. FIG. 2 is a partially enlarged top view of the rectangular island-shaped protrusion thus obtained. In this figure, the upper surface 1 of the substrate, the upper surface 2 of the rectangular island-shaped projections and their side surfaces 3 and the side surfaces 5 obtained by chamfering are shown. The shape of the double chamfer is L ₂ = 20 μm, θ =
It is 155 °. A protective film is formed on the entire surface of the substrate having the rectangular island-shaped protrusions, and then a resist film is formed.

When a low-viscosity resist is used, the resist film is also formed on the corners of the upper surface 2 of the rectangular island-shaped protrusions along the chamfered line. At this time, the resist film thickness t ₁ on the upper surface of the substrate 1 is 1 [mu] m, even when the etching of the protective film on the substrate, it is possible to sufficiently ensure the accuracy,
Very good results have been obtained. Similarly, when the medium viscosity resist and the high viscosity resist are used, the resist film is formed also on the portion along the chamfered line of the corner of the upper surface 2 of the rectangular island-shaped protrusion. The medium viscosity resist film sufficiently functions as a mask in the next etching step. The conditions for applying the medium viscosity resist, resist film thickness t ₁ on the upper surface of the substrate 1 is 2 [mu] m, even when the etching of the protective film on the substrate, it is possible to sufficiently ensure the accuracy, good results Was obtained. However, under the condition of applying the high-viscosity resist, the resist film thickness t ₁ on the upper surface of the substrate shown in FIG.
Is 3 μm, and is not actually used when the protective film on the substrate is etched, because its accuracy cannot be sufficiently ensured.

The above results are shown in Table 1. Table 1 clarifies the quality of the resist film formed on the upper surface of the rectangular island-shaped protrusion in the relationship between the shapes of the four corners of the upper surface of the rectangular island-shaped protrusion and the viscosity of the resist used. It is the one.

[0023]

[Table 1]

In Table 1, the shapes of the corners are such that the corners at the four corners of the rectangular island-shaped protrusions on the substrate are viewed from the upper surface side, and the chamfering of Example 1 is once and the chamfering of Example 2 is two. Shows a right angle for a turn and a conventional example. In Table 1, the resist viscosity represents the viscosity of a resist used when forming a resist film on the entire surface of a substrate having rectangular island-shaped protrusions. Low represents low viscosity (30 cp), medium represents medium viscosity (150 cp), and high represents high viscosity (500 cp). The result is that when a resist film is formed on the entire surface of a substrate having rectangular island-shaped protrusions,
It is shown whether or not the rectangular island-shaped protrusions are well formed on the upper surface. A circle indicates good, and a cross indicates defective.

In the above-described embodiment of the present invention, the results obtained when the four corners of the rectangular island-shaped projection on the substrate are chamfered once or twice when viewed from the upper surface side have been described. . That is, when a resist film is formed on the entire surface of a substrate having such rectangular island-shaped protrusions, the resist film is also formed on the four corners of the upper surface of the rectangular island-shaped protrusions. As a result, it was stated that good results can be obtained in the subsequent etching. In addition, the corners of the four corners of the rectangular island-shaped protrusions on the substrate are larger than the results obtained when chamfering the corners of the four corners of the rectangular island-shaped protrusions on the substrate once from the top surface side. It was shown that the result obtained when chamfering twice was superior when viewed from the top side.

Therefore, the present invention is not limited to the above-described embodiment, but the four corners of the rectangular island-shaped projection on the substrate are polygonal or arcuate when viewed from the upper surface side. It can be seen that good results are obtained even when

[0026]

According to the semiconductor device of the present invention having the above-described structure, the four corners of the rectangular island-shaped projection on the substrate are polygonal or arcuate when viewed from the upper surface side. By doing so, the thickness of the resist film at this corner can be set to the required thickness, and the processing of the protective film and the formation of the electrode part can be performed accurately, so that an excellent and stable electrical A semiconductor device having characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a partially enlarged top view of a first embodiment of a semiconductor device of the present invention.

FIG. 2 is a partially enlarged top view of a second embodiment of the semiconductor device of the present invention.

FIG. 3 is a partial enlarged cross-sectional view after forming a resist film in an example of a conventional semiconductor device.

4 is a partially enlarged perspective view of the device of FIG.

5 is a partially enlarged top view of the device of FIG.

[Explanation of symbols]

 1 Upper surface of substrate 2 Upper surface of rectangular island-shaped projection portion 3 Side surface of rectangular island-shaped projection portion 4 Side surface of rectangular island-shaped projection portion after chamfering once 5 Side surface of rectangular island-shaped projection portion after chamfering twice 9 resist film 10 substrate 11 rectangular island-shaped protrusions

Claims (1)

[Claims] 1. In a semiconductor device in which at least one rectangular island-shaped protrusion is formed on a substrate, the shape of the four corners of the island-shaped protrusion is a polygon or a polygon when viewed from the upper surface side. A semiconductor device having an arc shape.