JPH0455328B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming fine, high-density patterns such as integrated circuit patterns with high precision.

[Conventional technology]

To form patterns for semiconductor integrated circuits, etc., a resist that is sensitive to high-energy rays such as light, X-rays, electron beams, or ion beams is applied to the semiconductor substrate.
This is done by irradiating this with the above-mentioned high-energy rays and developing it.

When the pantane becomes finer, the resolution of the formed pattern decreases due to diffraction phenomena, standing waves, etc. during light exposure. Therefore, high-energy rays such as electron beams and X-rays are advantageous, but even when these high-energy rays are used, resolution deteriorates due to backscattering phenomena or the generation of secondary electrons.

The present inventors filed an application for a pattern forming method that solved the above problems as Japanese Patent Application No. 1983-74690. This method is illustrated in Figures 1a-e. That is, when forming a pattern, a resist (sensitive material) 2 coated on a substrate 3 is irradiated with high-energy rays 1 such as light, electron beams, X-rays, or ion beams, and a concave pattern is formed on the surface of the resist through a development process. form. (FIG. 1a, b) A material having an etching selectivity with the resist 2, such as silicone resin (adhering material) 4, is applied to the sample to flatten the concave pattern portion (FIG. 1c). Etching the silicone resin uniformly and leaving the silicone resin in the concave pattern part,
Using this as a mask, the resist is removed by reactive ion etching (RIE) using O ₂ gas (Fig. 1d, e). As a result, the resist under the silicone resin remains and the other resist is removed, so that a resist pattern is formed on the substrate. The most important step in these steps is the step of etching the planarized silicone resin to form a mask. The concave pattern formed on the resist surface layer reflects the profile of high-energy rays and generally has a tapered or sine curved shape. Therefore, since the pattern size widens or narrows depending on the depth at which etching of the silicone resin is stopped, it is necessary to determine the end point of etching with high precision.

[Problem that the invention seeks to solve]

In the method disclosed in Japanese Patent Application No. 59-74690, the end point of silicone resin etching is determined based on the etching time calculated from the silicone resin coating thickness and etching rate. The ethylate is
It has been difficult to control these with high precision because they change due to changes in gas pressure, substrate temperature, etc. It has been found that when silicone resin is etched using CF ₄ gas, the etching rate change is as high as about 10%. If the silicone resin coating thickness is 2μm, the etching time is 0.2μm.
An etching error occurs. This becomes an error of 0.1 to 0.15 μm when converted into a pattern dimensional error.

As described above, in the pattern forming method described above, since the etching accuracy of the mask material in the mask forming process is directly reflected in the pattern dimensional accuracy, control using the etching time calculated from the etching rate of the mask material was insufficient.

In order to solve these drawbacks, the present invention provides a method for detecting the interface between a resist and a mask material.The purpose of the present invention is to improve pattern formation accuracy by determining the end point of etching of a mask material with high precision. There is a particular thing.

[Means for solving problems]

According to the present invention, the above problems are solved by detecting the interface between the deposited material and the sensitive material and determining the etching end point of the deposited material based on this detection.

〔Example〕

Figures 2a, b, and c show an embodiment of the present invention.
First, a phenyl methacrylate/methacrylic acid copolymer (φ-MAC) resist 5 containing 5% ZnBr as a label material is applied to the substrate 3 to a thickness of 1.5 μm. Prebake this at 200℃ for one hour.
After irradiating this sample with an electron beam, 1,4-dioxane
The phenomenon occurs with a mixed solution of 25% diisobutyl ketone and 75% diisobutyl ketone, and a concave pattern with a depth of 0.2 to 0.3 μm is formed on the resist surface layer. As shown in FIG. 2a, a silicone resin 4 is spin-coated on this to flatten the entire substrate. The entire substrate can be flattened by applying a silicone resin film with a thickness of 3 μm or more. Next, the silicone resin is etched with reactive ions 12 using CF ₄ gas in a reactive ion etching device. The etching status was monitored by a mass spectrometer 11 connected to the reactive ion etching device 10. As the etching of the silicone resin progressed and the flat portion of the resist began to be exposed, Zn contained in the resist was detected by a mass spectrometer at M/e = 32.5 in the mass spectrum. In this state, as shown in FIG. 2b, the silicone resin 4 is no longer present in the flat portions of the resist, but is present only in the concave pattern portions. After that, if the silicone resin is continued to be etched for an etching time calculated from the etching rate of the silicone resin and 1/2 of the remaining film thickness, the silicone resin 4 will be etched to a depth of 1/2 of the concave pattern, as shown in Figure 2c. It can be etched accurately up to the point. The etching accuracy of the silicone resin in this case was 200 to 300 Å. This translates into dimensional accuracy of approximately 150 to 200 Å, making extremely highly accurate dimensional control possible.

FIG. 3 shows another embodiment. Polymethyl methacrylate (PMMA) resist 2 is applied to substrate 3.
It is coated to a thickness of 1.5 μm, peribaked, irradiated with an electron beam, and developed with a mixture of methyl isobutyl ketone and isopropanol. As a label material after post-baking
A resist φ-MAC5 containing 5% ZnBr is applied to a thickness of about 0.1 μm, and after prebaking, the concave pattern is flattened with silicone resin 4.

This is etched by reactive ion etching using CF ₄ gas. As etching of silicone resin 4 progresses and φ-MAC is exposed, φ-
Zn ²⁺ contained in the MAC was detected by the mass spectrometer at M/e=32.5, indicating that the silicone resin was lost in the flat areas of the resist. In order to etch the silicone resin to the center depth of the concave pattern, it is sufficient to continue etching for the etching time calculated from the etching rate of the silicone resin and the remaining film thickness as described above. Even in the case of this example, the dimensional accuracy is
We were able to achieve a diameter of 0.05 μm or less. In this example, ZnBr
The containing φ-MAC was used as a label substance, but
Even if this is used as a resist instead of PMMA, the effect is exactly the same.

Other embodiments are shown in FIGS. 4a, b, c, and d. PMMA resist 2 is applied to the substrate 3 to a thickness of 1.5 μm and prebaked. To this, 500% dilute PMMA5 in which an organic metal such as aluminum tertiary butyrate (Al(OC ₄ H ₉ ) ₃ ) is dissolved is added as a labeling substance.
Apply about 100 yen and pre-bake. Furthermore, 0.1 μm of PMMA is applied to this sample and prebaked.

As shown in Figure 4a, the label material 5 is PMMA.
You will be stuck in between. When this is irradiated with an electron beam and a phenomenon occurs, a concave pattern with a depth of 0.3 μm reflecting the beam shape can be formed on the resist surface layer as shown in FIG. 4b. The label material present approximately at the center of the depth of the concave pattern is very thin and is dissolved in the same manner as PMMA during the PMMA development process. When this sample is coated with silicone resin 4 and flattened, it becomes as shown in FIG. 4c. This was done using CF ₄ and O ₂ gas.
Etch by reactive ion etching. In this case, the mixing ratio of CF ₄ and O ₂ , gas pressure, and RF power were controlled so that the silicone resin and the PMMA resist were etched under the same etching conditions. Further, the etching state was monitored using an emission spectrum analyzer. As the etching of the silicone resin progresses and the surface of the label material is exposed, the wavelengths of aluminum, 3082Å, 3093Å,
Peaks with approximately 5 times the luminescence intensity obtained from etching of silicone resin were detected at 3944 Å and 3962 Å. When etching is stopped in this state, as shown in Figure 4d, the silicone resin has been etched to a depth that is half the depth of the concave pattern obtained after the development process, creating a mask pattern that reflects the beam dimensions very well. I was able to form it.

In addition to the label substances shown in this example, aluminum acetylacetonate, Al(CH ₂ COCH ₂ −
COCH ₃ ) ₃ and polymethylaluminoxane (−
Exactly the same effect was obtained using organic metals such as CH ₃ AlO) _o --.

In the examples so far, the label substance was mixed into the resist layer, but an example in which the label substance was mixed into the mask material will be described. Silicone resin and polyaluminoxane were dissolved in ligroin at a ratio of 10:1, and this was used as a mask material. The concave pattern formed on PMMA is flattened using the mask material. When this mask material was etched using a reactive ion etching device using CF ₄ gas, a strong emission spectrum with a wavelength of 3082 to 3962 Å was obtained from the Al atoms in the polyaluminoxane. Etching approx.
After continuing for 20 minutes, the luminescence intensity from the mask material decreased to less than 1/3, and it was possible to detect that the mask material in the flat part of the PMMA had disappeared. When etching was further performed for 2 minutes, the mask material was etched almost to the center of the concave pattern formed on the surface layer of PMMA, making it possible to control the pattern dimensions with high precision.

An example in which no label substance is used is shown. φ−
A concave pattern is formed on the MAC resist using an electron beam,
This sample was spin-coated with silicone resin and flattened. This was etched using a reactive etching device using CF ₄ and 20% O ₂ gas. When the mass spectrum was observed using a mass spectrometer, a peak was observed at M/e=85 approximately 20 minutes after the start of etching. This is because Si in the silicone resin and F in the CF ₄ gas reacted to form SiF ⁺ ₃ . After 20 minutes of etching time, the strength of M/e=85 decreased to 1/4, and it was detected that the silicone resin had disappeared. When this sample was etched for an additional 5 minutes, a mask pattern with good dimensional accuracy was formed.

Note that the sensitive material is not limited to those used in each example. For example, materials whose polymers can be decomposed only by electron beam irradiation and which can form a concave pattern without using a phenomenon liquid include homopolymers or copolymers selected from the first monomer group, or homopolymers or copolymers selected from the first monomer group. Copolymers consisting of a combination of the second monomer group can be used, the first monomer group being α,α-dimethylbenzyl methacrylate, α-methylbenzyl methacrylate, diphenyl methacrylate, triphenyl methacrylate, phenyl methacrylate, etc. Aleem methacrylate and tert-butyl methacrylate, as the second monomer group CH ₂ =C(CH ₃ )COOR
represented by an alkyl group or a haloalkyl group R
There are alkyl methacrylates and halogen alkyl methacrylates in which the number of carbon atoms is 5 or less.

〔Effect of the invention〕

As explained above, according to the present invention, the end point of etching of a mask material can be determined using a label material or
Since this is performed based on the mass or emission spectrum of the resist and mask material, it is possible to determine the end point with high accuracy without depending on changes in etching conditions, which has the advantage of improving pattern formation accuracy.

[Brief explanation of the drawing]

FIG. 1 is a pattern forming process diagram of Japanese Patent Application No. 59-74690, and FIGS. 2 to 4 are pattern forming process diagrams of an embodiment of the present invention. 1...High energy ray, 2...Resist, 3...
...Substrate, 4...Silicone resin, 5...Label substance.

Claims (1)

[Claims] 1. A sensitive material that is sensitive to the light is irradiated with high-energy rays such as light, electron beams, X-rays, or ion beams to form a concave pattern on the upper layer of the sensitive material. A material that has an etching selectivity with the sensitive material is deposited on the pattern forming area, and after the deposited material is uniformly etched, the pattern is transferred to the lower layer of the sensitive material using the deposited material remaining in the recess as a mask. A pattern forming method comprising:
The interface between the adhered material and the sensitive material is detected based on a change in the mass or emission spectrum intensity of an element contained in either the adhered material or the sensitive material and not contained in the other; A pattern forming method characterized by determining the end point of etching of a material. 2. A label substance containing an element different from the elements constituting the sensitive material or the adhering material is mixed into the sensitive material or the adhering material, and the etching of the adhering material is determined based on changes in the mass or emission spectrum intensity of the label substance. A pattern forming method according to claim 1, characterized in that: 3. The pattern forming method according to claim 1, characterized in that a label substance layer is provided at the interface between the sensitive material and the adhering material, and this is detected. 4. The pattern forming method according to claim 1, wherein the sensitive material and the label material layer are formed into a sandwich structure in advance so that the label material is located at the center of the depth of the formed concave pattern. 5. The pattern forming method according to claim 2, 3, or 4, wherein an organic metal is used as the label substance.