JPH07176501A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a metal film for electrodes and wirings by evaporation with out leaving resist on a substrate. CONSTITUTION:A silicon oxide film 22 is formed on the surface of a semiconductor substrate 21, and a photoresist pattern 24, having an aperture 23, is formed thereon. An aperture 25, through which the surface of the substrate 21 is exposed, is formed by etching the silicon oxide film 22 from the aperture 23. Electrode materials 261 and 262 are deposited from above the photoresist pattern 24, then the photoresist pattern 24 is lifted off together with the electrode material 261, and the silicon oxide film 22 is removed by etching. When the electrode material is deposited, no resist remains on the substrate 21 because the silicon oxide film 22 is located between the resist pattern 24 and the substrate 21 even when the aperture part 23 of the photoresist pattern 24 is modified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an improved semiconductor device, in which an electrode or wiring layer made of a metal material such as Au is formed on a semiconductor substrate by metal lift-off.

[0002]

2. Description of the Related Art In a semiconductor integrated circuit device having a high density, a technique for increasing the frequency as well as for increasing the frequency of a high frequency circuit using an FET (Field Effect Transistor) or the like is being developed. In order to enable higher speeds and higher frequencies in such integrated circuits, it is necessary to reduce the resistance of the electrode material of each device that constitutes the integrated circuit and the metal wiring material that connects the devices. For this purpose, a low resistance material such as Au is used as a wiring metal material, and fine processing of wiring using these materials is required.

A metal material such as Au used as a wiring material can effectively reduce loss because it is a low resistance element, but on the other hand, it is difficult to process it easily by a method such as etching. Therefore, the metal lift-off method is used for finely processing a difficult-to-etch material such as Au.

That is, as shown in FIG. 4, the semiconductor substrate 11
A photoresist is applied to the surface of the photoresist film, and a photoresist pattern 12 having openings formed in the photoresist film is set corresponding to the portions where wiring is to be formed. Then, an electrode material such as Au is deposited on the surface of the photoresist pattern 12 by electron beam vapor deposition or the like, and is formed on the surface of the substrate 11 corresponding to the opening of the photoresist pattern 12 and the surface of the photoresist film. Metal deposition films 131 and 132 are formed.

Thereafter, the photoresist pattern 12 and the metal vapor deposition film 132 on the surface of the resist pattern 12 are removed by immersing in a solvent that dissolves the resist, such as acetone or a resist stripping agent, to form an electrode or wiring. The metal vapor deposition film 131 is left on the substrate 11.

However, in the electron beam deposition process for forming the metal deposition films 131 and 132, a large amount of heat acts on the resist, and due to this heat, particularly in the openings of the resist pattern 12, the peripheral portion 14 is transformed. Occurs. When such an altered portion 14 occurs, in the case where the resist is strongly adhered to the substrate 11 and is difficult to dissolve in a solvent, etc., a resist residue remains on the substrate 11 after lift-off for removing the resist pattern 12. Therefore, an adverse effect occurs in the subsequent process.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and in a metal lift-off in which a photoresist pattern is removed after a metal material is vapor-deposited, a resist residue is not left on the substrate. Thus, the present invention is intended to provide a method for manufacturing a semiconductor device in which adverse effects are not left in the subsequent semiconductor device manufacturing process.

[0008]

According to the method of manufacturing a semiconductor device of the present invention, an oxide film is formed on the surface of a semiconductor substrate, and then a photoresist pattern having an opening pattern is formed on the oxide film. The oxide film corresponding to the opening of the photoresist pattern is removed. And
On the photoresist pattern, a metal deposition layer is formed by depositing a metal material layer including the semiconductor substrate surface portion corresponding to the opening portion of the pattern, and forming the metal deposition layer on the photoresist layer. After removing the oxide film, the oxide film remaining on the semiconductor substrate is removed by etching.

Here, the oxide film layer is appropriately side-etched in an area range larger than the opening of the photoresist pattern, or the oxide film layer is etched corresponding to the opening portion of the photoresist pattern in the etching step. Further, the surface of the semiconductor substrate is also etched to form a recess, so that a vapor deposition layer of a metal material is formed on the exposed substrate surface or recess corresponding to the opening of the photoresist pattern. To do.

[0010]

According to such a semiconductor device manufacturing method, Ga
A photoresist pattern is formed after forming an oxide film such as silicon oxide on the surface of a semiconductor substrate of As or the like, and a metal wiring layer corresponding to the photoresist pattern is formed. In order to form this metal wiring layer, for example, Au
A metal material such as is vapor-deposited on the photoresist pattern. In this case, an altered portion due to heat is generated in the vicinity of the opening of the photoresist pattern. Since the oxide film is interposed, the residue of the altered portion does not remain on the substrate when removing the resist pattern. Therefore, if the oxide film on the substrate is removed by etching after removing the photoresist pattern, it is possible to reliably prevent the resist residue from remaining on the substrate surface.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1A to 1C sequentially show steps of forming a metal layer such as an electrode or a wiring on a semiconductor substrate 21 such as GaAs. First, as shown in FIG.
A thin silicon oxide film 22 is formed on the surface of P by a method such as P-CVD. After the silicon oxide film 22 is formed in this way, a photoresist is applied on the silicon oxide film 22 and, as shown in FIG. 6B, an opening 23 is formed corresponding to the electrode forming portion or the wiring forming portion. A photoresist pattern 24 having the above is formed. Then, the silicon oxide film 22 exposed through the opening 23 of the photoresist pattern 24.
Are etched with hydrofluoric acid or the like, and an opening 25 reaching the surface of the semiconductor substrate 21 is formed in the silicon oxide film 22 so as to match the shape of the opening 23.

In this way, the photoresist pattern 24
If an opening 25 corresponding to the opening 23 is formed in the silicon oxide film 22, as shown in FIG.
The semiconductor substrate 21 exposed above the opening 23 through the opening 23.
Electrode materials 261 and 262 such as Au or Pt are vapor-deposited by the electron beam vapor deposition method including the surface portion of. After that, the photoresist pattern 24 is dissolved and removed by the solvent of the resist.
As a result of the dissolution and removal of, the electrode material 261 on the photoresist pattern 24 is also removed at the same time as shown in FIG.
So-called metal lift-off is performed.

After the photoresist pattern 24 and the electrode material 261 have been removed by metal lift-off in this way, the silicon oxide film 22 remaining on the semiconductor substrate 21 is etched with an etchant such as dilute hydrofluoric acid, (E). As shown in the figure, the structure is such that the layer of the electrode material 262 remains on the semiconductor substrate 21. In this case, the layer of the electrode material 262 needs to be composed of a material such as Au which is not attacked by an etching solution for silicon oxide such as dilute hydrofluoric acid.

Here, according to the metal lift-off as in the conventional example shown in FIG. 4, since the photoresist pattern 12 is formed by directly coating the surface of the semiconductor substrate 11, the photoresist pattern 12 is formed on the semiconductor substrate 11. A resist residue is generated at.

However, as shown in the embodiment, the semiconductor substrate
Since the silicon oxide film 22 is formed on 21 and the photoresist pattern 24 is formed thereon, the electrode material
A resist residue due to an altered portion generated during vapor deposition of 261 and 262 is generated on the silicon oxide film 22. The resist residue thus generated on the silicon oxide film 22 comes to be removed together with the etching of the silicon oxide film 22,
Therefore, it is possible to reliably prevent the occurrence of adverse effects on the post-process such as uneven etching of the substrate 21 and deterioration of reliability due to the resist residue.

Further, according to the metal lift method described in the embodiment, even if heat is applied to the resist by vapor deposition of an electrode material or the like, a resist residue is not generated, and therefore, in a photo step of forming a resist pattern. The resist can be sufficiently baked, the resist pattern is not deformed by heat applied in the electrode material vapor deposition step, etc., and a stable and reliable metal lift-off step can be performed.

FIG. 2 shows a second embodiment of the present invention. As shown in FIG. 2A, a silicon oxide film 22 is formed on a semiconductor substrate 21 as shown in FIG. A photoresist pattern 24 is formed by coating on the silicon film 22. In this case, the opening 23 is formed in the photoresist pattern 24 corresponding to the electrode formation site.

After the photoresist pattern 24 is formed in this way, the silicon oxide film 22 is etched by dry etching by RIE using CF ₄ or wet etching using hydrofluoric acid or the like, as shown in FIG. The opening 251 of the silicon oxide film 22 is formed in the above.

Here, the etching of the silicon oxide film 22 is performed under the condition that side etching is performed. Therefore, the opening 251 formed by the etching of the silicon oxide film 22 is etched so as to be deeper than the edge portion of the opening 23 of the photoresist pattern 24, and the substrate formed on the silicon oxide film 22. The opening 251 that exposes the surface of 21 is formed with a larger diameter than the opening 23 of the photoresist pattern 24.

If a large-diameter opening 251 corresponding to the opening 23 of the photoresist pattern 24 is formed in the silicon oxide film 22 in this way, as shown in FIG. In addition, electrode materials 261 and 262 such as Au are deposited by a method such as electron beam deposition including the surface portion of the semiconductor substrate 21 exposed corresponding to the opening 251. After that, as shown in FIG. 7D, the photoresist 24 is dissolved and removed by a predetermined solvent to perform metal lift-off, and the silicon oxide film 22 is removed by etching as shown in FIG. Only the electrode material 261 is left on the surface as an electrode or the like.

In order to facilitate lift-off, the conventional metal lift-off resist pattern 12 shown in FIG. 4 is immersed in monochlorochlorobenzene or the like to modify the resist surface before development in the resist photo process, and then the developer is removed. The resist etching rate is slowed down so that the surface side of the opening of the resist is narrowed. If such a reverse taper shape of the resist opening end is not formed, a vapor deposition film 131 made of an electrode material on the semiconductor substrate 11 corresponding to the resist opening and a vapor deposition film 132 being an electrode material on the resist 12 are formed. Therefore, lift-off cannot be easily performed.

On the other hand, in the second embodiment shown in FIG. 2, the side etching of the silicon oxide film 22 is performed so that the surface treatment of the photoresist before the development is not performed. The electrode material 262 on the semiconductor substrate 21 corresponding to the opening 23 of the pattern 24 and the electrode material 261 on the resist pattern 24 are separated. Therefore, the metal lift-off is easily performed as it is.

FIG. 3 shows a third embodiment. A silicon oxide film 22 is formed on the surface of a semiconductor substrate 21 by the same steps as shown in FIGS. A photoresist pattern 24 is formed on top. Then, the silicon oxide film 22 is side-etched from the opening 23 of the photoresist pattern 24 to form an opening 251 having a larger diameter than the opening 23.

Thus, the silicon oxide film on the semiconductor substrate 21
After the opening 251 is formed in the semiconductor substrate 22, the surface of the semiconductor substrate 21 is etched through the opening 23 of the photoresist pattern 24 and the opening 251 of the silicon oxide film 22 as shown in FIG. A recess 27 is formed on the surface of the substrate 21. Then, as shown in FIG. 6B, with the recess 27 formed, electrode materials 281 and 282 such as Au are deposited on the photoresist pattern 24 through the opening 23 and into the recess 27 by electron beam evaporation or the like. Vapor deposition. Subsequently, as shown in FIG. 7C, the photoresist pattern 24 is dissolved and removed by a predetermined solvent to perform metal lift-off.

This embodiment is applied to the Schottky recess gate process of a field effect transistor (FET), and the semiconductor substrate 21 is opened through the opening 23 of the photoresist pattern 24 and the opening 251 of the silicon oxide film 22. The surface is being etched. Here, when a photoresist pattern is directly applied and formed on a semiconductor substrate as in the conventional example of FIG. 4, the etching rate on the surface of the semiconductor substrate is affected by the effect of the resist residue remaining in the resist opening after development. Variation occurs.

On the other hand, according to the method of this embodiment, the resist residue does not exist on the semiconductor substrate 21 and the etching rate of the semiconductor substrate 21 does not vary in the subsequent process. Further, even if side etching of the silicon oxide film 22 occurs due to overetching of the silicon oxide film 22, the shape of the electrode material 282 is determined by the opening 23 of the photoresist pattern 24, and the side etching of the opening 251 of the silicon oxide film 22 is prevented. Not affected.

In particular, since the Schottky recess gate of the field effect transistor has a fine structure, a resist residue is likely to be generated in the opening 23 of the photoresist pattern 24, and precise etching is required. However, by adopting the manufacturing method as shown in the embodiment, it becomes possible to easily manufacture the field effect transistor having high accuracy and reliability.

[0028]

As described above, according to the method of manufacturing a semiconductor device of the present invention, an oxide film such as silicon oxide is formed on a semiconductor substrate, and then a photoresist pattern is formed by coating on the oxide film to form an electrode. The metal material such as wiring and wiring was vapor-deposited. Therefore, it is possible to surely avoid the situation where the heat generated by the vapor deposition process causes a change in the opening of the photoresist pattern and the like, and a resist residue remains on the semiconductor substrate after removing the resist pattern.
A highly reliable post-process can be performed.

[Brief description of drawings]

1A to 1E are cross-sectional configuration diagrams sequentially explaining a semiconductor manufacturing method according to an embodiment of the present invention.

2A to 2E are cross-sectional configuration diagrams sequentially explaining a second embodiment of the present invention.

FIGS. 3A to 3C are views for further explaining the third embodiment of the present invention.

FIG. 4 is a diagram illustrating a process of forming an electrode on a conventional semiconductor substrate.

[Explanation of symbols]

21 ... Semiconductor substrate, 22 ... Silicon oxide film, 23 ... Opening, 24 ... Photoresist pattern, 25, 251 ... Opening, 261, 262, 28
1, 282 ... Electrode material, 27 ... Recess.

Front Page Continuation (72) Inventor Yoshiki Ueno 1-1, Showa-cho, Kariya City, Aichi Prefecture

Claims (3)

[Claims] 1. An oxide film forming step of forming an oxide film on a surface of a semiconductor substrate; a pattern forming step of forming a photoresist pattern having openings corresponding to wiring portions on the oxide film; and the photoresist pattern. An etching step of removing the oxide film corresponding to the opening portion, and a metal deposition for depositing a layer of a conductive metal material on the photoresist pattern including the semiconductor substrate surface portion corresponding to the opening portion of the pattern. And a resist removing step of removing the photoresist layer including the metal material layer thereon, and the oxide film remaining on the semiconductor substrate is etched away together with the metal vapor deposition layer thereon. A method for manufacturing a semiconductor device, characterized in that. 2. The method of manufacturing a semiconductor device according to claim 1, wherein in the etching step, the oxide film layer is etched in a larger area range than the opening of the photoresist pattern. 3. In the etching step, the oxide film layer is etched corresponding to the opening of the photoresist pattern, and the surface of the semiconductor substrate is further etched to form a recess, and the photoresist is formed in the recess. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the vapor deposition layer of the metal material is formed corresponding to the opening of the pattern.