JPS6410058B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a far-ultraviolet negative resist material used to form a fine resist pattern in a lithography process, for example, in the production of high-density integrated circuit devices, and a method for forming a resist pattern using this material. In recent years, demands for higher performance and higher integration of semiconductor integrated circuit elements have become extremely high. short electron beam,
Efforts are being made to establish microfabrication techniques that can obtain finer processing dimensions than those obtained by photolithography, using lithography techniques that irradiate high-energy beams such as X-rays and deep ultraviolet rays. Resist materials used in lithography using these high-energy beams are extremely important because they have a significant impact on the dimensional accuracy and efficiency of microfabrication. Due to the above-mentioned importance, many attempts have been made to develop resist materials for high-energy beams, but in general, positive resist materials have excellent resolution but low sensitivity, and negative resist materials Although the resist material has high sensitivity, it does not have high enough resolution to control the cross-sectional shape of the pattern, and there is a strong desire to develop a resist material that has both excellent sensitivity and resolution. Conventionally, several high-sensitivity resist materials have been known as resist materials for electron beams, and it is known that the sensitivity of a resist material to X-rays is approximately parallel to the sensitivity to electron beams. However, since the sensitivity of a resist material to far ultraviolet rays is not in a parallel relationship with the sensitivity to electron beams, a highly sensitive resist material for electron beams does not necessarily become a highly sensitive resist material for far ultraviolet rays. Therefore, it is necessary to develop resist materials suitable for deep ultraviolet lithography. In particular, the recently developed method of batch transfer of patterns from a mask to a wafer using deep ultraviolet light (deep ultraviolet reflection projection exposure method) eliminates damage to the mask and wafer because the mask and wafer are completely separated. , has advantages such as low defectivity, but the amount of light effective for transfer is small, and for this reason, there is a demand for higher sensitivity of resist materials. Resist materials are largely unknown.
Until now, photoresist AZ-2400 and white resist have been known as highly sensitive resists for deep ultraviolet rays. However, since the former uses an alkaline solution as a developer, contamination with alkali metals adversely affects the electrical characteristics of IC elements, etc., and the absorption coefficient of far ultraviolet rays is large (absorption coefficient: 1.73 μm ^-1 at 250 mm). If the resist film was too thick, far ultraviolet rays would not reach the bottom, resulting in a disadvantage that sufficient resolution could not be obtained. The latter white resist had the disadvantage that sufficient processing accuracy could not be obtained because the film loss after development was as large as 30% to 40%. The inventors of the present invention have conducted numerous experiments and researches in order to solve the above-mentioned drawbacks and obtain a new negative resist material for deep ultraviolet rays with high sensitivity and high resolution, and as a result, they have arrived at the present invention. It is something. That is, the first invention of the present invention is a repeating unit This is a negative resist material for deep ultraviolet rays, characterized by being made of a polymer of Further, the second invention of the present invention is to form a film on a base material using the negative resist material for far ultraviolet rays according to the first invention, and after irradiating it with far ultraviolet rays, a developer made of carbon tetrachloride is applied. This is a method for forming a resist pattern using a negative type resist material for deep ultraviolet rays, which is characterized by developing with a negative type resist material to obtain a negative type resist pattern. The polymer of the present invention comprising repeating units according to the above formula, ie, polynormal propyl α-chloroacrylate (hereinafter abbreviated as PnPCA), has extremely high sensitivity and resolution as a resist material, as described below. It has been found that the above object can be fully achieved by using this PnPCA as a resist material and using carbon tetrachloride as a developer. To explain this in detail, PnPCA is dissolved in a suitable solvent to prepare a resist solution, which is applied onto a substrate by a rotation method, dried, and then irradiated with far ultraviolet rays according to a predetermined pattern. Then, development is performed using carbon tetrachloride as a developer to obtain a negative resist pattern. In this way, according to the present invention, the γ value that shows contrast to far ultraviolet rays is
1.65, it shows high contrast as a negative resist material, and can resolve a 1.0 μm resist pattern while maintaining a rectangular cross-sectional shape. The sensitivity was 75 times higher than that of Since the resist material according to the present invention contains a halogen element that is highly sensitive to high-energy beams, it is presumed to exhibit high sensitivity as described above, but the ease of reaction is generally determined from the structural formula. This value far exceeds the expected value, and this characteristic was revealed for the first time by the present inventors. Further, the resist material according to the present invention has photosensitivity in the deep ultraviolet wavelength range. FIG. 1 shows the extinction coefficient of the resist material of the present invention. In FIG.
This is the extinction coefficient of PMMA. As is clear from FIG. 1, the resist material of the present invention has absorption in the wavelength range of 180 to 260 nm, and the extinction coefficient at the absorption peak in these wavelength ranges is
It is 0.34 μm ^-1 , which is smaller than PMMA's 0.44 μm ^-1 . This means that energy is supplied to the bottom of a sufficiently thick resist layer, thus making it possible to process a high shape ratio, and further improving the yield due to the reduction of pinholes. Furthermore, since the resist material of the present invention is not sensitive to visible light and ultraviolet light (wavelength of 260 nm or more),
It can be handled under normal light and has the advantage of being easy to handle in terms of production process and management. In addition, since the resist pattern forming method according to the present invention uses an organic solvent as the developer used in the development process of the resist material, contamination by alkali metals such as when AZ-2400 is used, and contamination of IC elements etc. due to this, can be avoided. This has the effect of not causing any adverse effects on electrical characteristics. It goes without saying that the resist material of the present invention exhibits higher sensitivity with higher molecular weight resist materials, similar to general negative resist materials. The PnPCA monomer used in the present invention is a known compound. For example, normal propyl α-chloroacrylate monomer is disclosed in British Patent No. 514619 (1939
It can be manufactured according to the method described in 2010). In addition, the PnPCA polymer can be manufactured by common methods such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. Examples of the present invention will be described below. Monomer synthesis example: In a container equipped with a thermometer, stirrer and reflux device,
Trichlorethylene 180.2g, 98% while stirring
379.7 g of concentrated sulfuric acid and 0.2716 g of hydroquinone were added, and the liquid temperature was raised to 70°C. While maintaining the liquid temperature at 70°C, 112 g of 35% formalin was gradually added dropwise over 1.5 to 2.0 hours. After addition of formalin, the temperature was gradually raised to 100-110°C, and this temperature was maintained until the reflux of trichlene stopped. Then, the temperature suddenly increased to 140℃.
After raising the temperature to 100 and holding this temperature for 30 minutes,
Cooled to ℃. Next, while maintaining the temperature at 100℃, add 159.2g of purified normal propyl alcohol and water.
After gradually dropping 60.6 g of the mixed solution and maintaining the liquid temperature at 100° C. for 1 hour, stirring was stopped and steam distillation was performed to collect a fraction at 106 to 120° C. (separated into two layers). The lower layer of the fraction was washed with a 5 to 10 ^wt % aqueous solution of sodium carbonate until the washing liquid became neutral, and then a molecular sieve was added to dehydrate it. Thereafter, a small amount of hydroquinone was added and vacuum distillation was performed to obtain 41.58 g of a fraction having a temperature of 46 to 48° C. at 10 mmHg, that is, purified n-propyl α-chloroacrylate monomer (hereinafter referred to as nPCA). Polymer Synthesis Example 29.7 g of nPCA obtained as described above, 118.7 g of dimethylformamide and 0.297 g of azobisisobutyronitrile were mixed and polymerized at a temperature of 50° C. for 17 hours with stirring in a nitrogen stream. After the polymerization was completed, the solution was poured into 2 methanol, and the resulting precipitate was dried under vacuum. Next, the product was purified by dissolving it in chloroform, reprecipitating with methanol, and then vacuum drying to obtain about 20.7 g of the desired PnPCA polymer. The weight average molecular weight (w) of this polymer was determined by gel permeation chromatography (GPC) to be 215,000, and the polydispersity (d) was 1.84. Additionally, as a result of differential scanning calorimetric analysis (DSC) and thermogravimetric analysis (TG), the glass transition temperature (Tg) was 86-87℃, and the decomposition temperature (Td) was 216-217℃.
It was warm at ℃. Next, an example of a method for forming a resist pattern will be described. Example 1 1.4 g of PnPCA was added to methyl cellosolve acetate 10
ml and filtered through a 0.45 μm filter to prepare a resist solution. This resist solution
It was dropped onto a Si substrate, spin-coated at 2000 rpm, and heat-treated at 100°C for 30 minutes in air. The film thickness of the resist after heat treatment was approximately 1.0 μm. Next, the resist layer was irradiated with far ultraviolet light generated from a 200W deuterium lamp at varying exposure doses. After the irradiation, the substrate was immersed for 2 minutes in a developer made of carbon tetrachloride at a temperature of 26.2° C., and then dried by blowing dry nitrogen. At this time, the portions of the resist that were irradiated with deep ultraviolet light remain. After that, it was heated to 100℃ in the air.
After heat treatment for 30 minutes, the remaining film thickness at each exposure dose was measured using a thin film step measuring device (Talystep). The characteristic curve obtained as described above upon exposure to deep ultraviolet rays is shown in FIG. 2, and the sensitivity and contrast (γ value) are shown in Table 1 below. To explain Figure 2, the vertical axis shows the film thickness of the irradiated area after development as a relative value (normalized residual film thickness) when the film thickness before irradiation is set to 1, and the horizontal axis shows the film thickness of the irradiated area after development as a relative value (normalized residual film thickness). It is the common logarithm of the far ultraviolet irradiation amount (m ^J /cm ² ). And here γ
The value refers to the slope of the tangent line at the normalized residual film thickness of 0.5 in the relationship between the normalized residual film thickness and the irradiation dose shown in FIG. 2, and this value is a measure of the resolution of the resist. Generally, the larger the gradient, the better the resolution of the resist. Sensitivity is determined by the usual method.
The irradiation dose was taken as the normalized residual film thickness of 0.5.

[Table] As described above, in the case of this example, the γ value of the resist material of the present invention is 1.65, which indicates that it exhibits high contrast as a negative type resist material for deep ultraviolet rays. In addition, the sensitivity is 8.0 mJ/cm ² for PMMA.
The sensitivity was approximately 75 times higher than that of 600 mJ/cm ² . Furthermore, the resist material of the present invention has
It goes without saying that if a resist material with a higher molecular weight is used like a general negative resist material, the sensitivity will be higher. Example 2 In exactly the same manner as in Example 1, a resist film was formed on a Si substrate to a thickness of about 0.8 μm.
Next, the resist layer was irradiated with far-ultraviolet light generated from a 200W deuterium lamp through a mask having lines and spaces with a minimum line width of 0.5 μm. Regarding the irradiation amount, the minimum exposure amount at a residual film rate of 100% was set as 39 mJ/cm ² in the characteristic curve. After irradiation, development and drying were carried out in exactly the same manner as in Example 1. In the resist pattern obtained as described above, lines and spaces of 1.0 μm were clearly resolved, and when the cross section of the resist pattern was observed by SEM, it had a rectangular shape with good rise. At this time, the decrease in film thickness in the irradiated area was almost zero. As explained above, the resist material according to the present invention is 75 times more sensitive than PMMA to deep ultraviolet rays and has high contrast, making it possible to perform microfabrication with high resolution in a short exposure time. The effect is obtained. Furthermore, since the method for forming a resist pattern according to the present invention uses a developer made of carbon tetrachloride, it has the advantage that there is no contamination by alkali metals and the accompanying adverse effects on the electrical characteristics of ICs, etc. It will be done. In addition to semiconductor integrated circuit devices, the present invention is also effective when applied to the formation of fine patterns for optical application components, magnetic bubble devices, surface acoustic wave devices, and the like.

[Brief explanation of the drawing]

FIG. 1 shows resist materials according to the present invention and
FIG. 2 is a diagram showing the exposure characteristic curve of the resist material of the present invention to deep ultraviolet rays.

Claims (1)

[Claims] 1. Repeating unit A negative-tone resist material for deep ultraviolet rays, characterized by consisting of a polymer of 2 Repeat unit Forming a film on a base material using a negative resist material for deep ultraviolet rays made of a polymer of A method for forming a resist pattern using a negative resist material for deep ultraviolet rays, characterized by: