JPH0147009B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for forming fine and highly accurate patterns in pattern formation for semiconductor integrated circuits and the like. [Technical background of the invention and its problems] Pattern formation for semiconductor integrated circuits, etc. involves coating a semiconductor substrate with a resist that is sensitive to high-energy rays such as light or electron beams, irradiating the resist with the high-energy rays, and then A pattern is formed by performing a phenomenon.
For example, in the case of a positive resist, the resist absorbs energy when irradiated with high-energy rays, which causes the main chain or side chain of the resist to be cut, decomposes, and becomes soluble in a developing solvent. For this reason,
After development, the resist in the areas irradiated with high-energy rays is removed to form a pattern. When a pattern becomes finer, the resolution of the formed pattern decreases due to a diffraction phenomenon in light exposure, so high-energy rays such as electron beams and X-rays are advantageous. However, these high-energy rays also have factors that degrade resolution. A conventional pattern forming method using an electron beam is shown in FIGS. 1a, 1b, and 1c. In FIG. 1a, when a sensitive material (resist 2) coated on a substrate 3 is irradiated with an electron beam 1, the electrons that have entered the resist and the substrate collide with molecules and atoms.
The electrons become backscattered electrons 4 and are emitted to the outside of the substrate. The range of backscattered electrons is determined by the energy of the electron beam and the density of the substrate, but usually ranges from a few to more than ten microns. During this process, the resist becomes sensitized again by the backscattered electrons, and as shown by the dotted line in Figure 1b,
The resist decomposition region extends over a wider range than the dimensions (beam dimensions) of the irradiated electron beam. In this way, the amount of stored energy brought about by the electron beam in the resist has a smaller spread from the beam size in the upper layers of the resist, and reflects the beam size. In the developing process, the resist is dissolved from the upper layer of the resist, so when the developing solvent reaches the substrate, the pattern width becomes larger than the beam dimension, as shown in FIG. 1c. That is, although the amount of energy stored in the upper layer of the resist is smaller than that in the lower layer of the resist, the resist is immersed in the developing solvent for a longer time and dissolution progresses in the lateral direction.
On the other hand, in the lower layer of the resist, the amount of energy stored in the resist is large, and the dissolution of the resist proceeds rapidly, so that the melted region expands in a short period of time. This forms a resist pattern that is wider than the beam dimension. In particular, when the pattern density is high, the resolution of the pattern is significantly reduced due to the effect of backscattered electrons generated when adjacent pattern portions are irradiated. Such circumstances are X
This is a common problem from the viewpoint of resolution degradation caused by the influence of the substrate, such as a decrease in resolution caused by the generation of secondary electrons during line exposure, or non-uniformity of pattern edges due to the presence of standing waves during light exposure. . [Purpose of the Invention] The present invention aims to eliminate the reduction in resolution and dimensional accuracy caused by backscattered electrons in electron beam lithography, secondary electrons in X-ray exposure, and standing waves in light exposure. This method is characterized by transferring the pattern formed on the upper layer to the lower layer of the resist, and its purpose is to obtain a desired fine pattern with high precision. [Embodiment of the Invention] Figures 2a to 2e show an embodiment of the invention. As shown in FIG. 2a, a sensitive material (resist 2) coated on a substrate 3 is drawn with an electron beam 1. As shown in FIG. At this time, the irradiation amount is sufficiently small, for example, 1/5 to 1/1 of the appropriate irradiation amount.
Set to 0. As a result, when the resist is developed, a concave pattern reflecting the beam size is formed in the upper layer of the resist 2, as shown in FIG. 2b. A material 5 having a slower etching speed than the resist 2 is applied to the pattern as shown in FIG. 2c. For this purpose, a material having a high etching selectivity with respect to the resist, such as siloxane resin or spin-on glass, is used. These materials can be applied easily and with good uniformity using a spin coater, which greatly simplifies the process. For example, when a siloxane resin is applied, the siloxane resin is etched uniformly when etched in a CF ₄ gas atmosphere. When the etching time is set appropriately, the siloxane resin is etched to approximately the center of the concave portion of the pattern formed in the upper layer of the resist, as shown in FIG. 2d. Then, using an anisotropic etching device,
When etching is carried out in an O ₂ gas atmosphere, all of the resist except the lower part of the siloxane resin is removed as shown in FIG. 2e, and a pattern reflecting the beam dimensions is formed under the siloxane resin. In this example, if the etching of the siloxane resin by CF ₄ gas is made deeper than the center of the concave portion of the pattern formed in the upper layer of the resist, it is also possible to form a pattern smaller than the beam size. Furthermore, since a pattern formed in the upper layer of the resist is used, which is less affected by backscattered electrons, both arcuate patterns and adjacent patterns can be drawn under the same conditions.
Furthermore, the amount of radiation required for pattern formation is significantly reduced, leading to improved productivity. Next, specific examples of the present invention will be shown. A 1 μm thick positive resist and phenyl methacrylate-methacrylic acid copolymer (φ-MAC) are applied to a silicon wafer substrate, and prebaked at 200°C for one hour. This sample is irradiated with an electron beam (30keV) with a size of 0.2μm. The irradiation dose was set at 10 μC/cm ^2, which is approximately 1/10 of the irradiation dose required by conventional pattern formation methods. When this is immersed in a mixed solution of 25% 1,4-dioxane and 75% diisobutyl ketone and developed, the electron beam irradiation area has a depth of 0.15 μm to reflect the beam size.
A concave pattern of 0.2 μm was obtained. When 0.6 μm thick siloxane resin is applied onto this using a spin coater, the sample surface becomes flat. This sample was processed using CF ₄ at a flow rate of 50 sccm using a reactive ion etching device.
Etching was performed for 12 minutes at a power density of 0.3 W/cm ² by flowing gas. As a result, the siloxane resin was etched to almost the center of the recessed portion of the resist pattern. After that, power density was determined using _O2 gas at a flow rate of 50 sccm using the reactive ion etching device again.
After etching at 0.3 W/cm ² for 10 minutes, a resist pattern with a high aspect ratio was formed under the siloxane resin. In this case, the siloxane resin is hardly etched, and only φ-MAC is etched. The pattern dimensions obtained reflected the beam dimensions extremely faithfully, with a dimensional accuracy of 0.05 μm or less. In the conventional method shown in Figure 1,
Although the pattern size spreads by as much as 0.2 μm due to backscattered electrons, this method enabled highly accurate pattern formation. An example using light exposure will be described. Positive resist through a mask with a 1μm wide pattern
I transferred a concave pattern to AZ1350J. The amount of light irradiation was set at 6 mJ/cm ² , about 1/10 of the normal amount. G-line (0.436 μm) was used as the wavelength of light. This sample was coated with siloxane resin in the same manner as described above, and the siloxane resin was etched using a reactive ion etching device. In the siloxane resin etching step, the siloxane resin was etched a little over-etching, and the siloxane resin was etched to a distance of about 500 Å from the tip of the recess formed in the resist. The resist of this sample was etched in the same manner as described above. The pattern size obtained as a result was a pattern with a width of 0.8 μm, which was smaller than the mask size.
In this method, by controlling the etching conditions of the deposited material, it was possible to form a pattern finer than the designed pattern. Furthermore, in these Examples, pattern formation was performed with approximately 1/10 the irradiation dose of the conventional method, and the irradiation time was also significantly shortened. An example in which the sensitive material is changed will be shown. A 1 μm thick polymer film made of polyα,α-dimethylbenzyl methacrylate is coated on a silicon wafer. When this is irradiated with an electron beam of 20 μC/cm ² , a concave pattern with a depth of 0.2 μm is formed on the surface of the polymer film. A siloxane resin was attached to this, and a polymer film made of the siloxane resin and poly α, α-dimethylbenzyl methacrylate was etched using the method described above to obtain a 1 μm pattern having the same beam size. In such sensitive materials, as is well known, electron beam irradiation causes the main chains and side chains of the polymer to break, decompose, and evaporate the molecules, which can omit the development step and simplify the pattern formation process. . In addition to the above-mentioned poly α, α-dimethylbenzyl methacrylate, homopolymers or copolymers selected from the M1 monomer group are materials whose polymers are decomposed by electron beam irradiation and can form concave patterns without development using a developer. Alternatively, a copolymer consisting of a combination of M1 monomer group and M2 monomer group is used, where the M1 monomer group includes α,α-dimethylbenzyl methacrylate, α-methylbenzyl methacrylate,
Aryl methacrylates such as diphenyl methacrylate, triphenyl methacrylate, phenyl methacrylate and tert-butyl methacrylate, as the M2 monomer group, CH ₂ = C (CH ₃ )
The effects of the present invention can also be achieved using alkyl methacrylates and haloalkyl methacrylates represented by COOR in which the alkyl group or haloalkyl group R has 5 or less carbon atoms. Table 1 shows examples of sensitive materials that can provide the same effect as in this example. The amount of irradiation required to form a concave pattern with a depth of 0.2 μm is shown. These are characterized by a wide range of material selection because it is only necessary to form a concave pattern in the upper layer of the sensitive material by irradiation with high-energy rays.

〔Effect of the invention〕

As explained above, the present invention transfers the pattern formed on the upper layer of the resist to the lower layer of the resist, so that backscattered electrons in electron beam lithography, secondary electrons in X-ray exposure, and fixed electrons in light exposure are This has the advantage that the effects of waves, etc. can be reduced and it is possible to form a pattern that is faithful to the design pattern. Furthermore, since the amount of irradiation can be significantly reduced, there is an advantage that the pattern formation time can be shortened.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the conventional pattern forming method, Figure 2
The figure is a pattern forming process diagram showing an embodiment of the present invention. 1...Electron beam, 2...Resist, 3...Substrate, 4...Backscattered electrons, 5...Adhesive material whose etching rate is different from that of the sensitive material.

Claims (1)

[Claims] 1. Light. Electron beam. In a method of forming a pattern using high-energy rays such as X-rays or ion beams, the high-energy rays are irradiated onto a sensitive material to form a concave pattern on the upper layer of the sensitive material. After depositing a material that has an etching selectivity with the sensitive material on the pattern forming portion to flatten the entire surface layer of the sensitive material and uniformly etching the deposited material, the deposited material remaining in the recesses is removed. A method for forming a pattern, which comprises transferring the mask pattern to a lower layer of the sensitive material as a mask. 2. The pattern forming method according to claim 1, wherein a positive resist is used as the sensitive material. 3. The pattern forming method according to claim 1, wherein silicon or a silicon compound is used as the adhesion material. 4. As the above-mentioned sensitive material, a homopolymer or copolymer selected from the M1 monomer group or a copolymer consisting of a combination of the M1 monomer group and the M2 monomer group can form a concave pattern simply by irradiation with high-energy rays without developing using a developer. It uses
The M1 monomer group includes aryl methacrylates and tert-butyl methacrylate such as α,α-dimethylbenzyl methacrylate, α-methylbenzyl methacrylate, diphenyl methacrylate, triphenyl methacrylate, and phenyl methacrylate; the M2 monomer group includes CH ₂ =C
The pattern forming method according to claim 1, characterized in that an alkyl methacrylate and a haloalkyl methacrylate represented by (CH ₃ )COOR and in which the alkyl group or haloalkyl group R has 5 or less carbon atoms are used.