JPS62149138A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a resistive contact characterized by small resistance and good reproducibility, by completely removing resist before evaporating a metal layer, washing a device, and sufficiently washing the surface of a GaAs substrate, on which the resistive contact is obtained. CONSTITUTION:Photoresist 4 is applied on a gallium arsenide substrate 1 through an SiO2 film, and a pattern is formed. With the resist 4 as a mask, the SiO2 film 2 is removed. The resist 4 is removed, and the surface is masked with phosphoric acid. Then, Au.Ge.Ni are evaporated, and alloy reaction is carried out. An organic material 5 is applied, and heat treatment is performed. Then etching is performed. An unnecessary metal layer 3 and the compound 5 are simultaneously removed, and the thickness of the metal layer 3 is made thin. Finally, the SiO2 film 2 is removed by using fluoric acid. Thus, a resistive contact characterized by small resistance and good reproducibility is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a full resistive contact area on a gallium arsenide semiconductor device.

[Conventional technology]

Conventionally, the following methods have been used to obtain a resistive contact 2 to a gallium arsenide (GaAs) substrate. FIG. 2 is a cross-sectional view showing a companion process for explaining the first conventional example of obtaining resistive contact by performing lift-off using photoresist 4;
The figure shows a silicon dioxide (Si02) film 2 and a photoresist 4.
FIG. 7 is a cross-sectional view showing a predetermined process for explaining a second conventional example in which a resistive contact is obtained by performing lift-off using a conventional method.

For example, as shown in FIG.
- Deposit. Next, as shown in FIG. 2A, the entire photoresist 4 is applied by ultrasonic treatment in an organic solvent, lift-off is performed to remove unnecessary metal layer 3, and alloying reaction gold is then performed.

Alternatively, as shown in FIG. 3A, a 5i02 film 2 is grown and a photoresist 4 is applied on a 7'CGaAs substrate 1 to form a pattern. Next, as shown in FIG. 3A, the portions of the Sin film 2 where a resistive contact is to be made are removed, and then a metal layer 3t is deposited on the entire surface. Thereafter, as shown in FIG. 3, the unnecessary metal layer 3 is removed by a lift-off method using the photoresist, and then an alloying reaction t6 is carried out. There was a method like the one above.

[Problem that the invention seeks to solve]

According to the method of forming a resistive contact by the above-mentioned conventional cross-cutoff method using a photoresist, a pattern is formed using a photoresist, and then a metal layer is deposited to a predetermined thickness of 3Vf.
After removing unnecessary metal layer 3 by lift-off method, G
The a As substrate 1 and the metal layer 30 are alloyed.

At this time, since patterning is performed by lift-off, it is necessary to perform the entire vacuum deposition of the metal layer 3 while the photoresist 4, which is an organic substance, is completely attached. Therefore, gas is generated from the photoresist 4 during vapor deposition, resulting in resistive contact between GaAs and GaAs.
Gas adheres to the surface of the substrate 1. In addition, since water is adsorbed to the photoresist 4 by cleaning before vapor deposition, gas is likely to be generated during vapor deposition, making it difficult to perform sufficient cleaning and obtaining a clean surface of the GaAs substrate 1, resulting in a decrease in contact resistivity. There was a problem that the number of particles increased and the reproducibility was poor.

Furthermore, since strong ultrasonic waves are applied during lift-off for cleaning, there is a problem in that the GaAs substrate 1 may be destroyed.

However, in the method shown in FIG. 2, protrusions 6 remain at the edges of the trap metal layer 3 shown in FIG. 2A.

This protrusion 6 loses its shape when an alloying reaction occurs, so if another metal layer exists near the metal layer 3,
The problem arises that the

In addition, a level difference due to the metal layer 3 remains on the surface of the GaAs substrate 1, making it difficult to obtain a flat surface, so that if the wiring is connected, there is a risk of disconnection at the level difference.

[Elaborate means to solve problems]

The object of the present invention is to eliminate the above-mentioned drawbacks, and to eliminate the metal layer edge protrusion 6 as shown in FIG.
The object of the present invention is to provide a method for forming a resistive contact with low resistivity and good reproducibility.

According to the present invention, (11) forming a first layer made of an insulator entirely on a GaAs substrate, and then opening the first layer in a region where a resistive contact is to be formed to expose the GaAs substrate; depositing a second metal layer over the entire surface of the first layer including the openings in the first layer, the metal layer exposed in the openings in the first layer making resistive contact with the surface of the semiconductor substrate; In order to obtain a resistive contact, the second metal layer and the semiconductor substrate are subjected to an alloying reaction. a step of forming a third layer made of an organic material so as to alleviate a step difference on the second metal layer caused by a step difference in the second metal layer; selectively removing the surface of the third layer and the second metal layer at the same time; a step of leaving the second metal layer only in the opening of the first layer and reducing the thickness of the second metal layer on the semiconductor substrate; and a step of removing the first layer. There is obtained a method for manufacturing semiconductor electrical equipment, which is characterized by comprising the steps of:

[Effect]

According to the present invention, when obtaining a resistive contact on the surface of the GaAs substrate 1, the photoresist 4 is removed and cleaned before the metal layer 3 is deposited, so that a clean surface of the GaAs substrate 1 can be obtained, thereby reducing the contact resistivity. Very good reproducibility. Also,
Since lift-off processing is not performed, substrate destruction during the ultrasonic cleaning process can be prevented. Moreover, 8i0□ membrane 2
Since the GaAs substrate 1 and the metal 3 undergo an alloying reaction only at the opening, the metal layer 3 and other metal layers are not damaged. Furthermore, after alloying the GaAs substrate 1 and the metal layer 3, an organic compound 5f is applied to the surface of the GaAs substrate 1 to form a flat surface, and the thickness of the metal layer 3 becomes smaller than the original thickness. By removing the unnecessary metal layer 3 and organic compound 5 on the 5iOz film 2 at the same time, the protrusions are eliminated as shown in FIG. 2.

In addition, since the difference in level caused by the metal layer 3 on the GaAs substrate 1 can be reduced, disconnection of the wiring at the difference in level is prevented.

Details will be explained using FIG. 1, which is an embodiment of the present invention. As shown in Figure 1A, the first 〇H1r is twisted by 8i02.
2? After the formation, a photoresist 4t is applied to form a pattern, and the 5i02 film 2 is etched away to form an opening. Next, as shown in FIG. 1A, after the photoresist 4 is removed, cleaning is performed, a second metal layer 3 is deposited, and an alloying reaction is performed. At this time, since the photoresist 4 is removed before vapor deposition, no gas is generated during vapor deposition. Therefore, the problem of gas adhering to the surface of the GaA@substrate 1 that provides resistive contact and causing an increase in contact resistance does not occur.

Next, as shown in FIG. 1, a third layer 5t made of an organic compound is applied and heat treated, and the surface is flattened. As shown in Figure 1, the removal rates of organic compound 5, organic compound 5, and metal layer 3 are the same, or organic compound 5 is slower (,8i0
2 Film 2 is not removed or the removal rate is lower than organic compound 5.
The unnecessary metal layer 3 and organic compound 5 on the first layer other than the opening are simultaneously removed using etching conditions that are much slower, and the thickness of the metal layer 3 on the GaAs substrate 1 is also reduced. (Fig. 1). Therefore, the protrusion 6 exerts a strong force. In addition, since a flat surface with almost no steps can be obtained on the As substrate 1, there is no disconnection of the wiring at the step, and the gap between the GaAs substrate 1 and the metal layer is only at the opening of the Si film 2. In order for the alloying reaction with 3 to occur, the sheet between the metal layers must be large. Since this is after the t1 alloying reaction, the surface GaA of the metal layer 30 is
Even if it is removed close to the surface of the s-substrate 1, the contact resistivity is not affected. GaAs substrate 1 surface tisich other than metal layer 3
Since the GaAl1 substrate 1 is covered with the film 2, it is not damaged at all by etching during the process of removing the organic compound 5 and the metal layer 3. The above process has no drawbacks as described above.

〔Example〕

Next, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating an embodiment of the present invention and illustrating the process of obtaining resistive contact to a 90aAs substrate.

First, an 8i0z film of 3000AQ is grown. A photoresist 4 is applied to a gallium-arsenide substrate 1 to form a pattern, and this photoresist 4 is applied as a mask to form an i02 film 2.
(Figure 1 A).

Next, the photoresist 4 is removed and washed with phosphoric acid. After that, AuGe*Ni 2000A t" is deposited and the alloying reaction is carried out (Fig. 1A).Organic compound s
By applying 1ooooX and heat-treating, four almost flat surfaces can be obtained (Figure 1). Etching is performed in CC4Ft gas to remove unnecessary metal layer 3 and organic compound 5 at the same time to reduce the thickness of metal layer 3 (first drawing).

Since the alloying reaction has already taken place at this time, etching the surface of the metal layer 3 within the opening will not affect the resistive contact.

Finally, the 5i02 film 2 is removed using hydrofluoric acid (see Figure 1). According to the embodiment described above, the photoresist 4 is completely removed before the metal layer 3 is vapor deposited, and then cleaning is performed and the vapor deposition is performed. Therefore, the surface of the GaAs substrate 1 on which resistive contact is to be made can be sufficiently cleaned.

In addition, it is possible to obtain a resistive contact with a small indentation resistance and good reproducibility, since gas is generated from the resist during vapor deposition and is unlikely to adhere to the surface of the GaAs substrate 1 to obtain a resistive contact. Further, since the photoresist 4 is used and the photoresist 7 is strongly removed, the substrate is not destroyed in the ultrasonic cleaning process. In addition, the alloying reaction between the GaAs substrate and the substrate waste layer 3 is Sio,
Since this occurs only at the opening of the membrane 2, there is no atomization between the metal layer 3 and other metal layers. There are no protrusions 6 because the etching is performed so that the thickness of the metal layer 3 is thinner than the original thickness.

Furthermore, since the step formed by the metal layer 3 is clearly visible on the GaAs substrate 1, there is no disconnection of wiring at the narrow step portion where four flat surfaces can be obtained.

〔Effect of the invention〕

As explained above, in the present invention, before depositing the metal layer 3, the resist is completely removed and then the resist is cleaned and then the deposition is performed. Therefore, the surface of the GaAs substrate 1 to obtain resistive contact can be cleaned nine times. . Furthermore, gas is not generated from the photoresist 4 during the evaporation step 1 and adheres to the surface of the GaAs substrate 1 from which a resistive contact is obtained, so that a resistive contact with low resistance and good reproducibility can be obtained. In addition, since photoresist 4 is used and the foot-off is strong, there is no substrate destruction during the ultrasonic cleaning process, which greatly improves the cleanliness. Further, since the alloying reaction of the GaAs substrate 1 substrate waste layer 3 occurs only at the opening of the Sin film 2, no sheeting occurs between the metal layer 3 and other metal layers. Furthermore, since the unnecessary metal layer 3 is etched after performing the alloying reaction, the protrusion 6 can be easily removed without affecting the contact resistivity. can be alleviated.

Although the EHOt film is used as the first layer in the embodiment, the same effect can be obtained by replacing it with a silicon nitride film. ! ! In addition, the metal layer 3Fi is often fixed only to AuGe-Ni, and AuGe-Pt, AuGe
-AuAuGe-Ni -Au A metal such as AuZn may be used.

Excitation ν' 4, Brief Description of the Figures Figures 1A to 1O show an embodiment according to the present invention.
FIG. 3 is a cross-sectional view showing the entire process of forming resistive contact on the substrate.

Figures 2A and 3A are cross-sectional views of a GaAs substrate showing all the steps of the prior art.

l...Gallium-arsenic substrate 2...First layer 3...Second metal layer 4...Photoresist 5...Third layer 6...Second metal layer edge portion Protrusion 7...Alloy layer of gallium-arsenic substrate and second metal layer

Claims (1)

[Claims] forming a first layer made of an insulator on a semiconductor substrate, and then opening the first layer in a region where a resistive contact is to be formed to expose the semiconductor substrate; depositing a second metal layer over the entire surface of the first layer, the second metal layer to provide resistive contact to the surface of the semiconductor substrate exposed in the opening of the first layer; The step of alloying and reacting the semiconductor substrate with the second metal layer surface including the openings of the first layer that has obtained resistant contact due to the step difference in the openings of the first layer. a step of forming a third layer made of an organic substance so as to reduce the step difference on the second metal layer; selectively removing the surface of the third layer and the second metal layer at the same time; The method includes the steps of: leaving the second metal layer only in the opening of the layer and reducing the thickness of the second metal layer on the semiconductor substrate; and removing the first layer. A method for manufacturing a semiconductor device.