JPS60177627A - Formation of pattern - Google Patents

Abstract

PURPOSE:To remove the influence of light reflected from a substrate, and to obtain a fine pattern of high precision by a method wherein exposure and development are performed according to light of 200-550nm wavelength through the light reflecting layer of an amorphous material mainly consisting of Si and having density of 1.9g/cm<3> or less. CONSTITUTION:A low density amorphous Si layer 2 is deposited to 0.2mum thickness in Ar gas of 12mTorr at the room temperature on a substrate 1 having an Al topmost layer according to the DC sputtering method, a resist 3 of 1mum thickness is put thereon, and exposure and development are performed to form a resist pattern. RIE according to SiCl4 gas is performed to etch the layer 2 and the substrate 1, and the resist 3 is removed. The amrophous Si layer of density of 1.9g/cm<3> or less can be obtained easily according to the DC sputtering method, and when the forming condition is selected, reflectivity becomes to 0.2 or less at the wavelength of 436nm to be used for the most part at an exposure process, becomes to 0.3 or less at the wavelength of 200nm, and the high absorption coefficiency of 10<5>/cm or more is obtained. Accordingly, a high precise and fine pattern can be formed even on the substrate of high reflectivity such as Al. Moreover a fine process according to RIE can be also performed in gas such as SiCl4, etc., and this method is convenient for formation of the pattern.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a pattern forming method in the manufacture of various solid-state devices including semiconductor integrated circuits.
In particular, it is intended to eliminate the influence of reflected light from the substrate to enable highly accurate fine pattern formation.

[Background of the invention]

In pattern formation by light exposure, if the material directly under the resist is a highly reflective material such as aluminum, there will be significant light interference in the resist.Furthermore, in pattern formation on a substrate with steps, interference from adjacent patterns may occur. It is difficult to form fine patterns because side reflections occur and the pattern narrows. Conventionally, in order to reduce the light reflection from the layer directly under the resist, we used materials such as titanium/tungsten, vanadium, organic polymer films containing light-absorbing dyes, amorphous Ge-5e, and amorphous silicon, which have low reflectivity. A two-layer construction method has been adopted in which a light reflection reducing layer is first formed on the surface of a substrate to be processed, and a photosensitive resist is formed on this light reflection reducing layer.

However, with the method of using a metal layer as the light reflection reduction layer, the process is complicated because the metal layer and the substrate layer to be processed must be etched separately, and corrosion phenomena are likely to occur after etching. There is a problem. The method of using an organic polymer film containing a light-absorbing dye in the light reflection reducing layer has a problem in that it is sensitive to the baking time and temperature after formation and has poor reproducibility. Further, although the method using amorphous Ge-8e has a low reflectance to air of about 0.3, there is a problem in that the process becomes complicated. The method using amorphous silicon has good compatibility with the process, as it does not become a contaminant, can be etched at the same time, and is less prone to corrosion. ), and the reflectance is as high as about 0.4 to 0.6 in the wavelength range of 550 to 200 nm, and silicon-based materials with lower reflectance are desired as the light reflection reducing layer.

[Purpose of the invention]

The purpose of the present invention is to meet the above-mentioned needs, and to make it possible to almost completely eliminate the influence of reflected light from the substrate, even when processing a substrate with high reflectance such as aluminum, and to form a fine pattern with high precision. The object of the present invention is to provide a pattern forming method.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized by a step of forming a light reflection reducing layer on a substrate surface with or without an organic polymer layer, and a process of forming a photoresist on the light reflection reducing layer. A pattern forming method including a step of forming a resist pattern, a step of forming a resist pattern by subsequent exposure and development treatment, and a step of etching using this resist pattern as a mask, the wavelength range of the light used for exposure is 200 nm to 200 nm. The light reflection reducing layer in the case of 550 nm has a density of 1.9 g/a+ mainly composed of silicon.
? The following is a pattern forming method using an amorphous material.

[Embodiments of the invention]

The conditions that the light reflection reducing layer used during pattern formation must have are that it has a low light reflectance, a large light absorption coefficient, and is capable of microfabrication. Density 1.9g/cn, mainly composed of silicon? The following amorphous material (hereinafter referred to as low-density amorphous silicon) satisfies all of the above conditions, has good compatibility with silicon processes, can be formed at room temperature, and can be formed into fine patterns using a simple process. Formation is possible. The low reflectance of low-density amorphous silicon is shown in Figure 1 in comparison with amorphous silicon (density 2.2) and amorphous GeSe. Wavelength range is 200-550n
Low-density amorphous silicon exhibits a low reflectance for light at wavelengths of 436 nm, which is often used in photolithography.
is approximately 1/2 that of amorphous silicon (density 2.2).
, is about 2/3 that of amorphous Ge-8e.

The low-density amorphous silicon with densities of 1.9 and 1.8 shown in Figure 1 both have 105
It has an absorption coefficient greater than or equal to "-". Therefore, even on a substrate with high reflectance such as aluminum, it is possible to almost completely eliminate the influence of reflected light from the substrate, making it easy to form a high-precision pattern. By further lowering the density,
Although it is possible to obtain a material with a lower reflectance, in practical terms, the density of the low-density amorphous silicon material to be employed may be determined based on the relationship with the reflectance of the substrate to be processed. Etching methods for low density amorphous silicon include CCD, 4.5iCQ,
A reactive ion etching method using, for example, etching can be applied, and high-speed etching can be performed without causing undercuts, and patterns can be formed without pattern conversion differences.

Formation of low-density amorphous silicon is possible by direct current sputtering. When the distance between the target and the substrate is constant, low density amorphous silicon can be formed by varying the argon pressure.

The argon pressure during formation of the amorphous silicon shown in FIG. 1 is 1.5 mTorr for amorphous silicon with a density of 2.2;
9 is 5mTorr, density -1,8 is 12m
Torr. Note that sputtering was performed with a DC power of 700W. The creation method mentioned here is just an example.
Other methods, such as direct current sputtering using a gas other than argon, RF (radio frequency) sputtering, plasma CVD (chemical vapor deposition), or photo-CVD, can be used to create a direct current using argon. A low-density amorphous silicon layer similar to that obtained by sputtering can be formed.

Next, the basic steps of pattern formation when a two-layer structure is adopted in which a low-density amorphous silicon layer is formed on a substrate to be processed and a photosensitive resist layer is formed thereon will be explained. Second
Figures (a) to (c) are linear sectional views showing the order of steps. First, as shown in FIG. 2(a), a substrate 11 to be processed, for example, a substrate to be processed in which aluminum is present as the top layer,
A low-density amorphous silicon layer 2 is deposited on top by direct current sputtering at room temperature and an argon pressure of 12 mTorr at 0.2I.
Formed to a thickness of Irn. Next, a photosensitive resist layer 3 is formed to a thickness of 1.0 cape. Next, the second film is exposed through a mask pattern (not shown), and then subjected to development processing.
A resist pattern shown in Figure (b) is formed.

Next, the low-density amorphous silicon layer 2 and the substrate 1 to be processed are simultaneously etched by reactive ion etching using 5iCQ4 gas, resulting in a substrate pattern with no difference in pattern conversion (aluminum If it exists in the top layer, an aluminum pattern) can be formed. Subsequently, the photosensitive resist layer 3 is stripped using a commercially available J-100 resist stripping solution.

If the remaining low-density amorphous silicon layer is also desired to be removed, a CF 4 + 02 plasma etching step may be added.

Next, pattern formation when adopting a three-layer structure in which an organic polymer layer is formed on the substrate to be processed, a low-density amorphous silicon layer is formed on top of that, and a photosensitive resist is further formed on top of that. Explain and explain the basic process. Figure 3(a)-(c)
) is a line cross-sectional view showing the steps in order. First, as shown in FIG. 3(a), an organic polymer layer 2' is deposited to a thickness of, for example, 2 um on a substrate 1 to be processed on which aluminum is present as the uppermost layer.
After baking and baking, a low-density amorphous silicon layer 2 was formed to a thickness of 0.27 m at room temperature and an argon pressure of 12 m' Torr by direct current sputtering. , and further a photosensitive resist layer 3
is formed to have a thickness of, for example, 1.0 cape. Subsequently, a resist pattern is formed by exposure using an exposure device and further development, as shown in FIG. 3(b). Next, using this resist pattern as a mask, the low-density amorphous silicon layer 2 is etched with 5iCQ4 gas, and then the organic polymer layer 2' is etched with reactive etching using 02 gas to form a pattern. [Figure 3 (C)]. At this time, the uppermost layer resist pattern is etched at the same time as the lower layer resist etching. Next, the low density amorphous silicon layer 2 is removed by plasma etching in CF4+02 gas. Furthermore, if the substrate to be processed is aluminum, using the lower resist pattern as a mask, 5iCQ4
Fine patterns can be formed using reactive ion etching such as gas. Finally, the remaining organic polymer layer is removed using J-100 resist removal solution.

〔Effect of the invention〕

As explained above, the present invention relates to a pattern forming method characterized by employing a low-density amorphous silicon layer as a light reflection reducing layer. There are many benefits mentioned. Low-density amorphous silicon materials can be easily fabricated at room temperature by direct current sputtering.
Kuri Toinu - Two Use de Mashi 1 - Upper 11 and γ Kaikan Zo 11
0.2 or less for light with a wavelength of 136 nm, which is often used in photolithography, and 0 for light with a wavelength of 200 nm.
．． It is possible to achieve a low reflectance of 3 or less and a high light absorption coefficient of 105 -1 or more. Therefore, by applying the present invention to a substrate with a high reflectance such as aluminum, the influence of reflected light from the substrate can be reduced. It can be almost completely removed, making it possible to form fine patterns with high precision. Also, CCD,
Microfabrication is possible by reactive ion etching in a gas such as 4 or 5iC11, and it also has good compatibility with conventional silicon processes and can be a simple pattern forming process.

[Brief explanation of drawings]

Figure 1 shows aluminum and amorphous silicon (density 2.2)
, a comparison diagram of the light reflectance of amorphous Ge-8e and low-density amorphous silicon (density 1.9 or less), and FIGS. 2 and 3 respectively show the basic steps of the pattern forming method according to the present invention in order of process. FIG. Explanation of symbols 1...Substrate to be processed 2...Low density amorphous silicon layer 2'...Organic polymer layer 3...Photosensitive resist layer Patent applicant Nakamura, patent attorney representing Nippon Telegraph and Telephone Public Corporation Junnosuke Sai 1 Izuoi 5 Taiji) 'IP2 Figure 3

Claims (1)

[Claims] A process of forming a light reflection reducing layer on the substrate surface with or without an organic polymer layer, a process of forming a photosensitive resist on this light reflection reducing layer, and a subsequent exposure and development process. In a pattern forming method including a step of forming a resist pattern and a step of etching using the resist pattern as a mask, the light reflection reducing layer has a density of 1.9 g/a containing silicon as a main component! It is made of the following amorphous material, and the wavelength range of the light used for the exposure is 2.
A pattern forming method characterized in that the thickness is 00 nm to 550 nm.