JPS6340305B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical exposure mask, and more particularly to the structure of an optical exposure mask that uses a charged beam to draw a pattern.

Conventionally, optical exposure masks use a glass substrate covered with a thin film made of a light-shielding material such as chromium, and an organic polymer resist that is sensitive to light or a charged beam is coated on top of the light-shielding material. They were manufactured by drawing and developing a pattern using a charged beam, and using the resist pattern as an etching protection mask to remove the light-shielding material and transferring the pattern onto the light-shielding material.

However, when these masks are used to manufacture semiconductor devices, the pattern on the mask becomes finer as semiconductor devices become more highly integrated and performant.
As an etching method, a dry method is being used more often than a wet method. Currently, among the charged beams, electron beams are at the stage of practical use, and in this case, the proximity effect and resistance to dry etching have become major problems. In other words, the proximity effect means that when an electron beam is irradiated, secondary electrons generated in the resist, substrate, etc. are scattered in the resist, so the resist sensitivity of the area where the electron beam is irradiated changes depending on the size of the nearby pattern. It is the action of changing. FIG. 1 is a schematic cross-sectional view showing the manufacturing process of a conventional optical exposure mask, in which 1 indicates a glass substrate, 2 indicates a light-shielding material, and 3 indicates an organic polymer resist. In order to form a pattern with a minimum line width of about 1 μm, an example was shown in which an electron beam was used as the drawing means. When four fine patterns with the same dimensions are drawn with a relatively large pattern adjacent to them using an electron beam, the pattern shown in A in Figure 1b is affected by the secondary electron dispersion of the nearby large pattern. The dimensions of the area become larger than the other dimensions, resulting in a mask pattern that partially differs from the designed dimensions, as shown in FIG. 1c. For this reason, proximity effect correction programs have been developed using software, such as reducing the amount of electron beam incident when drawing patterns that are susceptible to the proximity effect, but the time required for this correction is enormous, and the electron beam This was the cause of the delay in the practical application of the pattern drawing method.

In addition, high-resolution electron beam resists such as PMMA and PGMA have a high etching speed during dry etching, and are not sufficient as etching masks for light-shielding materials.They have relatively high dry etching resistance even at the expense of high resolution. It was necessary to use resist. These problems have made it difficult to manufacture optical masks having fine patterns with excellent controllability and reproducibility.

The present invention provides an optical exposure mask having a novel patterned structure without using a resist. That is, the gist of the present invention is to provide a transparent substrate, a silicon layer on the substrate, and a metal layer that reacts with the silicon layer to form a metal silicide, or by a multi-layer structure, or by a silicide layer of the metal. The present invention relates to an optical exposure mask, characterized in that a pattern to be transferred is formed on the mask.

According to this invention, the surface of the glass substrate is made of silicon and metal as a light-shielding material, and a silicidation reaction is caused by pattern drawing using a charged beam to form metal silicide. . When a charged beam is incident on a silicon or metal surface, the beam energy is converted into thermal energy by collision, resulting in a metal silicide reaction that occurs at a relatively low temperature. Furthermore, since there is no organic polymer resist with low thermal conductivity on the surface as in the prior art, thermal energy is instantaneously dissipated through the metal or silicon film, so proximity effects due to charge accumulation are less likely to occur. If an etching solution is used in which the formed silicide has a low etching ratio with respect to silicon or metal, the silicide will remain only in the area where the electron beam is incident, and it can be used as a light-shielding area. Conversely, if an etching solution with a high etching ratio for silicide to silicon or metal is used, the light-shielding material is removed only in the area where the electron beam is incident, and the two-layer structure region of silicon and metal can be made into a light-shielding area. .

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a schematic cross-sectional view of the manufacturing process of an optical exposure mask according to the present invention. Glass substrate 1 is coated with silicon 102 of about 500 Å and platinum 103 of 500 Å.
When deposited by vacuum evaporation method to a certain degree continuously, the second
Obtain diagram a. Next, using electron beam exposure technology,
Perform pattern drawing. Pattern drawing is repeated as many times as the number of chips that can be accommodated within the wafer size used at this time. The silicon-platinum structure in the region where the electron beam is incident is completely changed to platinum silicide (Pt ₂ Si or PtSi) 104 . This state is shown in FIG. 2b. Thereafter, platinum is completely etched away using aqua regia, and silicon is further etched off completely using a mixed solution of acetic acid, nitric acid, and hydrofluoric acid. Since each etching solution hardly attacks platinum silicide, the etching time for substantially selectively etching platinum and silicon does not have to be very strict. Furthermore, regardless of the size of the pattern, even if a constant electron beam charge amount is used, there is no influence of the proximity effect, and patterns close to the designed dimensions can be obtained on all masks. The finished state is shown in Figure 2c.

Although this embodiment has been described in which silicon is formed as a first layer and platinum is formed as a second layer thereon, the same effect can be obtained even if the order of formation is reversed.

Although the above is an example in which platinum is used as the metal, it can be inferred that it may be replaced with another metal that forms silicide at a relatively low temperature. For example, corresponding metals include magnesium, nickel, hafnium, titanium, iron, tungsten, molybdenum, and the like.

As explained above, the optical exposure mask according to the present invention has a multilayer structure of silicon and a metal that forms silicide with silicon on a transparent substrate, a pattern is drawn using a charged beam, and the drawn portion is converted into silicide. Patterns are formed by utilizing the difference in etching speed between silicide and silicon, and between metal and silicide. Therefore, this mask can form either a positive type or a negative type pattern by changing the etching solution using the same charged beam irradiation.

In addition, the silicon-metal multilayer and silicide film have good light-shielding properties, and since there is no proximity effect due to charged beam irradiation, it is possible to achieve high sensitivity and high resolution, and it is possible to realize fine dimensions with high precision.

Further, conventional masks using chromium were cleaned using organic solvents, but the present invention has the effect of making the exposure process easier because silicide and the like can be cleaned with acid.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view schematically showing the manufacturing process of a conventional optical exposure mask, and FIG.
It is a schematic cross-sectional view shown in contrast with the figure. The numbers in the figure are 1,101...Glass substrate, 2
... Light shielding material, 3 ... Organic polymer resist, 10
2...silicon, 103...metal forming silicide, such as platinum, and 104...metal silicide, respectively. In Fig. 1b, A is a region whose dimensions have been deformed due to the proximity effect.

Claims (1)

[Claims] 1. A pattern to be transferred is formed on a transparent substrate by a multi-layer stack of a silicon layer and a metal layer that can react with the silicon to form silicide, or by a silicide layer of the metal. An optical exposure mask characterized by: