JP2023117041A - Method for manufacturing semiconductor element - Google Patents

Abstract

To provide a method for manufacturing a semiconductor element, which can suppress electrode detachment when forming electrodes using photoresist.SOLUTION: A method for manufacturing a semiconductor element of the present disclosure includes depositing a Ni electrode layer on a p-type semiconductor layer of NiO using a photoresist, performing a heat treatment at a temperature of 150°C to 200°C after depositing the Ni electrode layer, and lifting off the photoresist after the heat treatment. The p-type semiconductor layer may be formed, for example, on an Al2O3 semiconductor layer.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to methods for manufacturing semiconductor devices.

Patent document 1 includes an n-type semiconductor layer made of an n-type Ga ₂ O ₃ -based single crystal, and a p-type semiconductor layer made of a p-type semiconductor in which the volume of the amorphous portion is larger than the volume of the crystalline portion. , a diode wherein said n-type semiconductor layer and said p-type semiconductor layer form a pn junction.

JP 2019-36593 A

In general, when a photoresist is used to form an electrode on a NiO p-type semiconductor layer, there is a problem that the electrode tends to peel off from the semi-NiO p-type semiconductor layer.

An object of the present disclosure is to provide a method for manufacturing a semiconductor device that can suppress peeling of electrodes when electrodes are formed using a photoresist.

The present discloser has found that the above objects can be achieved by the following means:
forming a Ni electrode layer using a photoresist on the NiO p-type semiconductor layer;
performing a heat treatment at a temperature of 150° C. to 200° C. after forming the Ni electrode layer; and lifting off the photoresist after the heat treatment;
A method of manufacturing a semiconductor device, comprising:

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a method for manufacturing a semiconductor device that can suppress peeling of an electrode when forming the electrode using a photoresist.

FIG. 1A is a schematic diagram showing one step of a method for manufacturing a semiconductor device according to the first embodiment of the present disclosure. FIG. 1B is a schematic diagram showing one step of the method for manufacturing a semiconductor device according to the first embodiment of the present disclosure. FIG. 1C is a schematic diagram showing one step of the method for manufacturing a semiconductor device according to the first embodiment of the present disclosure. FIG. 1D is a schematic diagram showing one step of the method for manufacturing a semiconductor device according to the first embodiment of the present disclosure. FIG. 1E is a schematic diagram showing one step of the method for manufacturing a semiconductor device according to the first embodiment of the present disclosure. FIG. 1F is a schematic diagram showing one step of the method for manufacturing a semiconductor device according to the first embodiment of the present disclosure. FIG. 1G is a schematic diagram showing one step of the method for manufacturing a semiconductor device according to the first embodiment of the present disclosure. FIG. 1H is a schematic diagram showing one step of the method for manufacturing a semiconductor device according to the first embodiment of the present disclosure. 2A is a photograph showing the state of the electrodes of the semiconductor device manufactured by the method of Example 1. FIG. 2B is a photograph showing the state of the electrodes of the semiconductor device manufactured by the method of Comparative Example 1. FIG. FIG. 3 is a graph showing the residual rate of electrodes in semiconductor devices manufactured by the methods of the respective examples.

Hereinafter, embodiments of the present disclosure will be described in detail. It should be noted that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the disclosure.

The manufacturing method of the present disclosure includes forming a Ni electrode layer using a photoresist on a NiO p-type semiconductor layer, and performing a heat treatment at a temperature of 150° C. to 200° C. after forming the Ni electrode layer. and, after thermal treatment, lifting off the photoresist;
A method of manufacturing a semiconductor device, comprising:

In a semiconductor device such as a power device using gallium oxide or aluminum oxide, a p-type semiconductor layer of NiO can be employed as the p-type semiconductor layer. In forming an electrode layer such as an ohmic electrode layer on the NiO p-type semiconductor layer, it is conceivable to form a Ni electrode layer on the NiO p-type semiconductor layer using a photoresist.

In this regard, Ni is a metal with a high work function. Such a metal has insufficient adhesion to the NiO p-type semiconductor layer in the as-depo state. Therefore, when the photoresist is lifted off, the electrode layer may be peeled off together with the surrounding metal portions.

Therefore, when the Ni electrode layer is formed using a photoresist, there is a problem that the Ni electrode layer is easily separated from the NiO p-type semiconductor layer.

In contrast, the manufacturing method of the present disclosure includes heat treatment at a temperature of 150° C. to 200° C. after forming the Ni electrode layer using photoresist and before lifting off the photoresist.

Although the principle is not clear, by performing heat treatment at a temperature of 150 ° C. or higher, for example, O atoms in the NiO p-type semiconductor layer form chemical bonds with Ni in the Ni electrode, thereby forming a NiO p-type semiconductor layer. It is considered that the bonding force between the Ni electrode layer and the Ni electrode layer is strengthened. Note that if the heating temperature exceeds 200° C., the photoresist is degraded, and the subsequent lift-off using an organic solvent is considered to be difficult.

It should be noted that the manufacturing method of the present disclosure can include providing a substrate and forming a p-type semiconductor layer of NiO on the substrate before depositing the Ni electrode layer. Although the substrate is not particularly limited, gallium oxide substrates can be mentioned, for example. More specifically, as the substrate, a Ga ₂ O ₃ single crystal substrate produced by any method or a commercially available Ga ₂ O ₃ single crystal substrate can be used. A β-Ga ₂ O ₃ single crystal is particularly preferable for the Ga ₂ O ₃ single crystal substrate. The substrate may also be an alumina substrate, ie an Al ₂ O ₃ substrate.

1A-H are schematic diagrams showing one step of a method for manufacturing a semiconductor device according to the first embodiment of the present disclosure. Note that FIGS. 1A and 1B are not essential in the manufacturing method of the present disclosure. Figures 1A-H are also not intended to limit the manufacturing methods of the present disclosure.

In the manufacturing method according to the first embodiment of the present disclosure, first, as shown in FIG. 1A, an Al ₂ O ₃ semiconductor layer 10 is provided as a base material.

Next, as shown in FIG. 1B, a NiO semiconductor layer 20 is formed on the Al ₂ O ₃ semiconductor layer 10 . The NiO semiconductor layer 20 can be formed, for example, by sputtering using a NiO target.

After that, as shown in FIG. 1C, a photoresist layer 30 is formed on the NiO semiconductor layer 20, and as shown in FIG. A pattern 35 is formed on the NiO semiconductor layer 20 by dissolving the exposed portion of the layer 30 with a developer.

Next, the Ni electrode layer 45 having the shape of the pattern 35 is formed by forming the Ni layer 40 from the photoresist layer 30 side.

After that, in the method of manufacturing a semiconductor device according to the first embodiment of the present disclosure, heat treatment is performed at a temperature of 150° C. to 200° C. in a lamp furnace 300, as shown in FIG. 1G.

Finally, the photoresist layer 30 is lifted off from the NiO semiconductor layer 20 by, for example, immersion in an organic solvent to obtain the NiO semiconductor layer 20 on which the Ni electrode layer 45 having the shape of the pattern 35 is formed.

<Deposition of Ni electrode layer using photoresist>
The manufacturing method of the present disclosure includes forming a Ni electrode layer on a NiO p-type semiconductor layer using a photoresist.

Here, the thickness of the NiO p-type semiconductor layer may be, for example, 50 nm to 200 nm. The thickness of the NiO p-type semiconductor layer may be 50 nm or more, 60 nm or more, 70 nm or more, or 80 nm or more, and may be 200 nm or less, 180 nm or less, 150 nm or less, or 120 nm or less.

The film formation of the Ni electrode layer using a photoresist is performed, for example, by forming a photoresist layer on a NiO p-type semiconductor layer, and irradiating ultraviolet rays from above the photoresist layer through a pattern forming filter. forming a photoresist layer pattern on the NiO p-type semiconductor layer by removing the portion irradiated with the ultraviolet rays with a developer; and forming a Ni electrode layer from the photoresist layer side of the NiO p-type semiconductor layer depositing a.

The photoresist may be deposited, for example, by depositing a resist solution on the NiO p-type semiconductor layer, specifically, for example, by coating and drying.

As the resist liquid, any resist liquid used for forming a photoresist used when forming a pattern electrode of a semiconductor element can be adopted. OFPR-800 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), for example, can be used as the resist solution.

The thickness of the photoresist may be between 500 nm and 2000 nm. The thickness of the photoresist may be 500 nm or more, 800 nm or more, 1000 nm or more, or 1200 nm or more, and may be 2000 nm or less, 1800 nm or less, 1600 nm or less, or 1400 nm or less.

The film formation of the Ni electrode layer may be performed, for example, by electron beam evaporation using metallic Ni as a target.

The thickness of the Ni electrode layer may be 10 nm to 100 nm. The thickness of the Ni electrode layer may be 10 nm or more, 20 nm or more, 30 nm or more, or 40 nm or more, and may be 100 nm or less, 90 nm or less, 80 nm or less, or 70 nm or less.

<Heat treatment>
The manufacturing method of the present disclosure includes heat treatment at a temperature of 150° C. to 200° C. after forming the Ni electrode layer.

The heat treatment temperature may be 150° C. or higher, 155° C. or higher, 160° C. or higher, or 165° C. or higher, and may be 200° C. or lower, 190° C. or lower, 180° C. or lower, or 170° C. or lower.

The heat treatment may be carried out, for example, in a furnace, more particularly in a lamp furnace.

The atmosphere of the heat treatment is an atmosphere inert to the substrate, the p-type semiconductor layer of NiO, the Ni electrode layer, and the photoresist, for example, an atmosphere substantially free of oxygen, more specifically a rare gas atmosphere or N ₂ atmosphere or the like is preferable.

The heat treatment may be performed under atmospheric pressure.

The heat treatment time may range from 1 minute to 60 minutes. The heat treatment time may be 1 minute or more, 3 minutes or more, 5 minutes or more, or 10 minutes or more, and may be 60 minutes or less, 30 minutes or less, 20 minutes or less, or 15 minutes or less.

<Photoresist lift-off>
The fabrication method of the present disclosure includes lifting off the photoresist after thermal treatment.

The photoresist lift-off can use any solvent, such as an organic solvent, that can dissolve the photoresist and has low reactivity with the substrate, the NiO p-type semiconductor layer, and the Ni electrode layer. Lift-off is performed by, for example, attaching a solvent to a photoresist layer, more specifically, by immersing, for example, a laminate of a substrate, a NiO p-type semiconductor layer, a Ni electrode layer, and a photoresist in a solvent. may

<<Examples 1 and 2, and Comparative Examples 1 to 3>>
<Example 1>
A NiO semiconductor layer was deposited on an Al ₂ O ₃ substrate by high-frequency sputtering using a NiO target. The high-frequency sputtering was performed under the conditions of an output of 200 W, a substrate temperature of room temperature, an atmosphere of Ar:O ₂ =40:60 during film formation, an internal chamber pressure of 0.2 Pa, and a target thickness of 100 nm.

Next, a resist solution (OFPR-800, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied onto the NiO semiconductor layer to form a photoresist layer with a thickness of 1500 nm. After that, the photoresist layer is irradiated with ultraviolet rays through a filter, and the ultraviolet-exposed portion is dissolved by a developer (NMD-3, manufactured by Tokyo Ohka Kogyo Co., Ltd.), and a diameter of 0.3 mm is formed on the NiO semiconductor layer. A resist pattern was formed which was capable of producing 25 circular Ni electrodes.

After that, from the photoresist layer side, a Ni electrode layer was formed on the NiO semiconductor layer by electron beam evaporation using a Ni metal target. The target thickness of the Ni electrode layer in electron beam evaporation was 50 nm.

After that, the laminate of the Al ₂ O ₃ substrate, NiO semiconductor layer, and Ni electrode layer was placed in a lamp furnace and subjected to heat treatment. The conditions of the heat treatment were as follows: the reached temperature was 150° C., the heat treatment time at the reached temperature was 5 minutes, the atmosphere was N ₂ atmosphere, and the pressure was 1 atm.

Finally, the laminate was immersed in an organic solvent, and the photoresist layer was removed from the laminate to obtain the semiconductor device of Example 1.

<Example 2>
A semiconductor device of Example 2 was manufactured in the same manner as in Example 1, except that the heat treatment temperature was set to 200.degree.

<Comparative Example 1>
A semiconductor device of Comparative Example 1 was manufactured in the same manner as in Example 1, except that the heat treatment was not performed.

<Comparative Example 2>
A semiconductor device of Comparative Example 2 was manufactured in the same manner as in Example 1, except that the heat treatment temperature was 100.degree.

<Comparative Example 3>
A semiconductor device of Comparative Example 3 was manufactured in the same manner as in Example 1, except that the heat treatment temperature was 250°C.

<Observation of Ni electrode>
The Ni electrode was confirmed with a microscope for the semiconductor element of each example.

<result>
2A and 2B are microscopic images showing the states of the Ni electrodes in the semiconductor devices of Example 1 and Comparative Example 1, respectively.

As shown in FIG. 2A, all the Ni electrodes remained in the semiconductor device of Example 1, which was heat-treated at 150.degree. On the other hand, as shown in FIG. 2B, in the semiconductor device of Comparative Example 1 in which the heat treatment was not performed, most of the Ni electrode was separated from the NiO semiconductor layer.

FIG. 3 shows the residual ratio of the Ni electrode in the semiconductor device of each example.

In the semiconductor element of Comparative Example 1 in which no heat treatment was performed and in Comparative Example 2 in which the heat treatment temperature was 100° C., the residual ratios of the Ni electrodes were about 20% and 12%, respectively. In addition, in the semiconductor device of Comparative Example 3 in which the heat treatment temperature was 250° C., the photoresist layer was denatured by heat, and lift-off could not be performed.

On the other hand, in the semiconductor devices of Examples 1 and 2 in which the heat treatment temperatures were 150° C. and 200° C., respectively, the Ni electrode survival rates were 100% and about 71%, respectively.

REFERENCE SIGNS LIST 10 Al ₂ O ₃ semiconductor layer 20 NiO semiconductor layer 30 photoresist layer 35 pattern 40 Ni layer 45 Ni electrode layer 100 filter member 200 and 210 ultraviolet rays 300 lamp furnace

Claims (1)

forming a Ni electrode layer using a photoresist on the NiO p-type semiconductor layer;
performing a heat treatment at a temperature of 150° C. to 200° C. after forming the Ni electrode layer; and lifting off the photoresist after the heat treatment;
A method of manufacturing a semiconductor device, comprising:

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