JPS59114819A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the positioning mark from etching even if the protective film on that mark is thin by filling the groove for a mark pattern formed on the semiconductor substrate with a first material of large atomic weight and by forming the protective film consisting of a second material of small atomic weight on said first material in the groove and on the substrate around the groove thereby forming the positioning mark. CONSTITUTION:A photoresist layer 12 is formed on a semiconductor substrate 11 consisting of Si or GaAs and a hole 13 for a predetermined positioning mark pattern is formed by exposure and development. Next, a material of large atomic weight is stuck to the whole surface of the substrate by deposition or the like, thereby forming a mark 15 in a groove 14 and a film 16 on said photoresist layer 12. Then the photoresist layer 12 is removed by a proper solvent and simultaneously the film 16 on the layer 12 is removed. Next, a material of smaller atomic weight than that of the mark 15 is formed by coating or the like on the mark 15 and the substrate 11 around the mark 15, as a protective film 17.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical field of the invention The present invention relates to a method for manufacturing a semiconductor device.
More specifically, the present invention relates to a method of forming alignment marks for electron beam exposure.

(2) Background of the technology In semiconductor devices, especially LSIs, pattern dimensions have become smaller in order to increase the degree of integration, and as a result, electron beam exposure technology (electron beam lithography technology) has been adopted. It has become. When writing with an electron beam, alignment is very important, and it is necessary to accurately detect alignment marks. Generally, alignment marks include wafer marks and tip marks, relatively large wafer marks are formed near the outer periphery of the semiconductor wafer, and wafer mounting is useful for measuring errors and wafer expansion and contraction, while tip marks is formed for each chip and serves to detect relative positional errors and rotational errors between the beam and the mark.

(3) Prior Art and Problems In order to obtain a reflection signal with good SA from an alignment mark, marks made of a material with a relatively large atomic weight are formed on a semiconductor substrate (wafer). The process of forming alignment marks in this case will be explained with reference to FIGS. 1 to 4. First, as shown in FIG.
Alternatively, a photorenost layer 2 having a mark pattern is formed on a GaAs semiconductor substrate 1. Next, the metal that is the mark material, such as titanium (TI) and gold (Au),
The gold layer mark 3 and the metal film 4 are formed by (continuous) depositing the metal on the entire surface by evaporation or the like. The photoresist layer 2 is removed using an organic solvent and at the same time the metal film 4 thereon is removed (lifted off) to form a metal mark 3 on the semiconductor substrate l as shown in FIG.

Then, to prevent the metal mark 3 from being etched in the etching process in the manufacturing process, the mark 3 is covered with a protective film 5, for example, a silicon dioxide (Si0,2) film formed by the CVD method (FIG. 3). In such a case, when forming the protective film 5 on the metal mark 3, the shape (
Step coverage (step coverage) is a problem, and a contact surface 7 reaching a peen hole 6 or a metal mark may occur as shown in FIG. When an etching process is performed in a subsequent process, the etching agent reaches the metal mark 3 through the peenhole or the contact surface and etches the metal mark 3. Unfortunately, part of the metal mark 3 is removed and the edge shape changes, causing the S/S of the mark detection signal to change.
This may result in a decrease in N or a shift in the mark detection position.

In order to clearly obtain a signal reflected from the alignment mark by the electron beam, it is better to make the mark thicker, and in order not to reduce the reflected signal, it is better to make the protective film on the mark thinner. However, if the protective film is made thinner, defects such as peen holes may occur in the protective film at the stepped portions, and the mark shape may change due to etching.

(4) Purpose of the Invention The purpose of the present invention is to prevent the mark from being etched even if the protective film on the alignment mark is thin.

Another object of the present invention is to provide a method for manufacturing a semiconductor device having alignment marks that can obtain accurate and good SA reflection signals.

(5) Structure of the invention
)~shio): A process of forming a mark tree groove in a semiconductor substrate; (a) a process of filling this groove with a first material having a large atomic weight; and (ii) a process of filling the first material in this groove and its surroundings. forming a protective film made of a second material having a smaller atomic weight than the first material on a semiconductor substrate; and forming an alignment mark.

(6) Embodiments of the invention Hereinafter, the present invention will be described in detail by way of embodiments of the invention with reference to the accompanying drawings.

As shown in FIG. 5, a photoresist layer 12 is formed on a semiconductor substrate (wafer) 11 of Sl, GaA, or S, and holes 13 having a predetermined alignment mark pattern are formed by exposure and development. The semiconductor substrate 11 exposed in the hole 13 of the photoresist layer 12 is etched to form a groove 14 with four turns of marks (for example, depth 0.4 μm). Next, a material with a large atomic weight, such as titanium, tungsten, molybdenum, platinum, gold, or a silicide thereof, is deposited on the entire surface by vapor deposition or slatting, as shown in FIG. 6, and a mark 15 is formed in the groove 14. A film 16 is then formed on the photoresist layer 12. For example, the grooves 14 are filled and the marks 15 are formed by successively depositing a titanium layer with a thickness of 0.1 μm and a gold layer with a thickness of 0.3 μm.

Then, when the photoresist layer 12 is removed with a suitable solvent, the film 16 thereon can be removed (lifted off) at the same time (FIG. 7). Since the marks 15 are embedded in the semiconductor substrate 11 in this manner, the semiconductor substrate 11 becomes substantially flat. mark 15
Even if there is some dent or protrusion, the difference in height from the semiconductor substrate 11 can be made much smaller than in the conventional case. As the protective film 17 (FIG. 8), a material having an atomic weight smaller than that of the mark 15, such as diprotic silicon, polycrystalline silicon, silicon nitride, aluminide, or polyimide resin, is formed by chemical vapor deposition (CVD). ) is formed on the mark 15 and the semiconductor substrate 11 around the mark 15 by coating or the like.

For example, silicon dioxide (thickness 0.1 μm) made by CVD method
If the protective film 17 is formed, there will be no step portion in the mark, so defects such as bean holes will not occur, and the mark 15 will not be etched during the etching process in the subsequent process. The mark 15 thus formed is detected and aligned before electron beam exposure, and then electron beam exposure is performed to obtain a predetermined fine pattern. Then, a semiconductor device is manufactured according to normal manufacturing.

(7) Effects of the Invention In the manufacturing method according to the present invention, the thickness of the alignment mark can be appropriately determined by the depth of the groove formed in the semiconductor substrate and the thickness of the mark material adhered to the mark and the semiconductor substrate. Since the surface can be made flat, there are no defects in the protective film due to steps, and the film thickness can be reduced. Therefore, since the mark thickness is appropriate, the protective film is thin, and the mark shape is as specified, an accurate reflection signal with good S/['J can be obtained. The alignment marks formed by the manufacturing method according to the present invention are used in the manufacturing of semiconductor devices (MO8 ICs, bipolar ICs, GaAs FETs and their ICs, low-noise HEMTs, HEMTICs, etc.) that are microfabricated by electron beam lithography.

[Brief explanation of the drawing]

1 to 3 are partial sectional views of a semiconductor device illustrating a conventional alignment mark forming process, and FIG. 4 is a partial sectional view of a semiconductor device illustrating defects in conventional alignment mark formation. FIGS. 5 to 8 are partial cross-sectional views of a semiconductor device for explaining the alignment mark forming step in the semiconductor device manufacturing method according to the present invention. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 3... Metal mark, 5... Protective film, 11... Semiconductor substrate, 12... Photoresist layer, 14... Groove, 15... Mark, 17... ·Protective film. Patent applicant Fujitsu Limited Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney 1) Yukio Patent attorney Akira Yamaguchi Figure 1 Figure 400!

Claims (1)

[Claims] 1. Before performing electron beam exposure, the following steps (7) to
(7) Forming a mark pattern groove in the semiconductor substrate; (A) Filling this groove with a first material having a large atomic weight; and (1) Filling the groove with the first material and forming a protective film made of a second material having a smaller atomic weight than the first material on the semiconductor substrate surrounding the semiconductor substrate; forming an alignment mark; a method for manufacturing a semiconductor device; . 2. The manufacturing method according to claim 1, wherein the first material is titanium, tungsten, molybdenum, platinum, gold, or a silicide thereof. 3. The manufacturing method according to claim 1, wherein the second material is silicon dioxide, polycrystalline silicon, silicon nitride, aluminide, or polyimide resin.