JPH0544174B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a semiconductor device, and more specifically, to a semiconductor device having alignment marks for electron beam exposure.

(2) Background of the technology In semiconductor devices, especially LSIs, pattern dimensions have become smaller in order to achieve higher levels of integration, and electron beam exposure technology (electron beam lithography technology) has been adopted for this purpose. I'm getting old. When writing with an electron beam, alignment is very important, and it is necessary to accurately detect alignment marks. In general, alignment marks include wafer marks and chip marks. Relatively large wafer marks are formed near the outer periphery of a semiconductor wafer and are useful for measuring wafer mounting errors and wafer expansion/contraction, while chip marks It is formed for each chip and is useful for detecting relative position errors and rotation errors between the beam and the mark.

(3) Prior art and problems In order to obtain a reflection signal with a good S/N ratio from an alignment mark, marks made of a material with a relatively large atomic weight are formed on a semiconductor substrate (wafer). There is. The process of forming alignment marks in this case will be explained with reference to FIGS. 1 to 4. First, as shown in FIG. 1, a photoresist layer 2 having a mark pattern is formed on a Si or GaAs semiconductor substrate 1. form. Next, the metal that is the mark material, such as titanium (Ti) and gold (Au),
is deposited on the entire surface by (continuous) vapor deposition or the like to form the metal mark 3 and the metal film 4. 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 1 as shown in FIG. Then, in order to prevent the metal mark 3 from being etched during the etching process in the manufacturing process, the mark 3 is covered with a protective film 5, for example, a silicon dioxide (SiO ₂ ) film made by CVD method.
figure). In such a case, when forming the protective film 5 on the metal mark 3, the shape at the step part (step coverage) becomes a problem, and as shown in FIG. This may occur. When etching 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. for that,
A part of the metal mark 3 is removed and the edge shape changes, resulting in a decrease in the S/N of the mark detection signal and 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) Object of the invention The object of the invention is to provide an alignment mark that will not be etched even if the protective film on the mark is thin.

Another object of the present invention is to provide a semiconductor device having alignment marks that can obtain a reflected signal with an accurate and good S/N ratio.

(5) Structure of the Invention In a semiconductor device having an alignment mark for electron beam exposure, the alignment mark has a groove of a mark pattern dug in a semiconductor substrate, and a first groove with a large atomic weight that fills the groove almost flatly. It is characterized by comprising a material mark, and a protective film formed on the first material mark and the semiconductor substrate surrounding the mark and made of a second material having a smaller atomic weight than the first material. This is achieved by a semiconductor device that

(6) Embodiments of the invention The present invention will be described in detail below 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 Si or GaAs semiconductor substrate (wafer) 11, and holes 13 having a predetermined alignment mark pattern are formed by exposure and development. This photoresist layer 1
The semiconductor substrate 11 exposed in the hole 13 of No. 2 is etched to form the groove 14 of the mark pattern (for example, the 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, sputtering, etc., as shown in FIG. A membrane 16 is formed on layer 12. For example, 0.1μm
The grooves 14 are filled and marks 15 are formed by successively depositing a titanium layer with a thickness of 0.3 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. Even if the mark 15 is slightly depressed or protruded, 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 a smaller atomic weight than the material of the mark 15, such as silicon dioxide, polycrystalline silicon, silicon nitride, aluminum nitride, or polyimide resin, is formed by chemical vapor deposition (CVD), Mark 15 by coating etc.
It is formed on the semiconductor substrate 11 above and around it. For example, silicon dioxide (thickness
If the protective film 17 is formed with a thickness of 0.1 .mu.m), there will be no stepped portion in the mark, so defects such as peen 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 element (such as a transistor) can be manufactured through a normal manufacturing process, and a semiconductor device having alignment marks can be manufactured.

(7) Effects of the Invention In the semiconductor device 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 deposited. Since the surface of the semiconductor substrate 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 reflected signal with a good S/N ratio can be obtained. The alignment marks formed on the semiconductor device according to the present invention are used in the manufacture of semiconductor devices (MOSIC, bipolar IC, GaAs FET and its IC, low-noise HEMT, HEMTIC, 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. , and Figure 5~
FIG. 8 is a partial cross-sectional view of a semiconductor device illustrating the alignment mark forming step in the semiconductor device manufacturing method according to the present invention. 1...Semiconductor substrate, 3...Metal mark, 5...
Protective film, 11... Semiconductor substrate, 12... Photoresist layer, 14... Groove, 15... Mark, 17...
Protective film.

Claims (1)

[Claims] 1. In a semiconductor device having an alignment mark for electron beam exposure, the alignment mark is a groove 14 of a mark pattern dug in a semiconductor substrate 11.
The first layer with a large atomic weight fills the groove almost flatly.
a mark 15 made of a material, and a protective film 17 formed on the first material mark and the semiconductor substrate surrounding the mark and made of a second material having a smaller atomic weight than the first material. A semiconductor device characterized by: 2. The semiconductor device according to claim 1, wherein the first material is titanium, tungsten, molybdenum, platinum, gold, or a silicide thereof. 3. The semiconductor device according to claim 1, wherein the second material is silicon dioxide, polycrystalline silicon, silicon nitride, aluminum nitride, or polyimide resin.