KR950006347B1 - Patterning method - Google Patents

Abstract

The photoresist pattern generation provides a good profile without overhang when a photolithography is executed by DISIRE (diffusion enhanced silyating resist process). The process is as follows. The photoresist formed over the wafer is silyated selectively. Not silyated area of the resist is given the first etching to be treated for the second silyation and form the silyated resist on the side walls of the first silyating resist. Finally the process is complete by removing all resist which is not exposed by the second etching.

Description

Pattern Formation Method

1A to 1D are schematic diagrams of a conventional DESIRE method.

2 shows a step of etching a wafer substrate using a lace pattern formed by a conventional DESIRE method.

3A to 3F are schematic diagrams showing an embodiment of the present invention.

4a to 4d are views for explaining the secondary silylation process in more detail in the process of the present invention.

The present invention relates to a pattern forming method. More specifically, it relates to a method of forming a resist pann for improving the resist profile of the present invention.

In the manufacture of microcircuits, it is necessary to precisely control and inject impurities into small regions of the silicon substrate, and these regions are interconnected to form devices and VLSI circuits. The pattern defining such an area is formed by a lithography process. That is, initially a layer of photoresist material is spin coated onto the wafer substrate. Next, it is selectively exposed to ultraviolet rays, electron beams or X-rays. An exposure apparatus mask, an electron beam lithography data tape, and the like are used to perform the desired selective exposure. This remaining resist protects the applied substrate. In addition, the areas where the resist is removed are subjected to various additional or extractive processes on the substrate surface using patterns.

Although the photolithography process can be replaced by other methods to form submicron fine patterns, photolithography is still widely used according to the progress of the photolithography apparatus, resist material, and processing technology. BACKGROUND ART With the higher integration of semiconductor devices, technologies for forming finer resist patterns have been developed. Particularly in the megabit era, lithography using conventional single layer resists has become difficult to form submicron size patterns.

That is, the resolution on a flat plane is limited by the lithographic contrast and exposure contrast of the resist, and in order to achieve a high resolution image, a high exposure resist must be used to expose with a good exposure machine, but the surface of the substrate is irregular. In one case, it becomes difficult.

Thus, as a limiting factor of the resolution of the resist, the bulk effect generated from the light absorption by the resist material, the isotropic property of the developing solution, the difference in thickness of the resist formed on the irregular substrate, and the end of the structure formed on the substrate Light scattering and reflection of light on the substrate. In order to solve this problem, a method using a multilayered resist having a trilayer structure has been proposed (G, N Taylor, LE Stillwagon, and T. Venkantesan, J. Electroshem. Soc, 7,1658). 984)) has the disadvantage that the process is very complicated and expensive.

Therefore, in order to simplify the above-mentioned process, it is proposed to the method of forming a pattern like the above-mentioned resist layer of a multilayer structure using a single layer. (F. Coopmans and B. Roland, Solid State Technology, June 1987, PP 93-99). This method is called DESIRE (Diffusion Enhanced Silyating Resist Process). The silylation method is a method of containing silicon in a polymer by exposing the polymer material to a gaseous or liquid silicon-containing compound such as hexamethyldisilazane (HMDS) or SiCl ₄ . The main feature of the DESIRE method is that it converts a potential light image into a potential silicon image using silylation, which is highly selective from the weather, and then by a dry etching in oxygen using this silicon image, a relief image. To form.

1A to 1D are schematic diagrams showing a conventional DESIRE method.

First, a resist layer 2 is formed by spin coating a photoresist on the semiconductor wafer 1. Next, the resist layer 2 is exposed to the ultraviolet light 4 using the photomask 3 having the mask pattern formed thereon. Then, the resist layer 3 is divided into an exposed portion 6 and an unexposed portion 5, and the resist of the exposed portion 6 decomposes the photosensitive compound so that the resin of the resist is free of molecules.

[Figure 1a]

Next, the exposed resist layer 2 is baked (first b). The baking process is performed at 140 ° C. or higher, and when the resist layer 2 is baked, the resin particles of the unexposed portion 5 of the resist layer 2 crosslink with the photosensitive compound to form the polymer layer 7. Done. This is called a PSB (Pre-Silylation Bake) process.

After the PSB process, silicon-containing compound HMDS or TMDS (Tetra Methl DiSilazane) is flowed 8 onto the resist in the gas phase. The resin particles in the exposed portion 6 of the resist 2 then react with the Si of the HMDS or TMDS to form the silized resist layer 9 (Fig. 1C). This is called a silylation process.

Next, the resist layer 2 is developed to form a resist pattern (FIG. 1D). The development is carried out by a dry developing method using an oxygen plasma. At this time, oxygen combines with Si of the silized resist layer 9 to form a SiO structure and acts as a barrier layer during resist development. Therefore, the lower resist of the silylated resist layer 9 is not removed and other resists are removed to form a desired resist pattern. The dry development is generally carried out by the RIE method. Therefore, the above phenomenon is also referred to as resist etching and hereinafter referred to as resist etching process.

In the case of forming a resist pattern by the above-described DESIRE method, the resist profile after development is changed by factors such as the etching equipment and the gas used, power, and gas flow rate during etching. In addition, even under optimal process conditions, as shown in FIG. 1D, an overhang portion 10 is generated, which makes it difficult to measure the line width of the pattern, and when etching the resist sheet as shown in FIG. ) May interfere with the overhang portion 10, resulting in a poor profile of the resist.

Accordingly, it is an object of the present invention to provide a method for forming a good resist pattern without generating an overhang portion upon performing the above DESIRE method.

In order to achieve the above object, according to the present invention, the resist layer formed on the semiconductor substrate is selectively silylated to form a silylated resist layer on the surface portion of the resist, and the first unsilylated resist layer is etched. There is provided a resist pattern forming method comprising secondary silylation to form a silicided resist layer on a sidewall of a resist layer below the silylated resist layer, and second etching to remove all of the unexposed resist layer. do.

The step of selectively silylating the surface portion of the resist layer to form a silylated resist layer, for example, after exposing the resist layer, selectively silylates exposed or unexposed portions of the resist layer. . The exposure may be performed by pattern exposure using a photomask or exposure using an electron beam.

The method of forming a pattern by selectively silylating exposed portions of the resist layer to remove unexposed portions is called a negative tone process, and on the contrary, a portion exposed by silylating an unexposed portion of the resist. The method of removing a pattern to form a pattern is called a positive tone process. This varies depending on the type of resist used.

As a light source which can be used by this invention, any conventional UV light can be used. For example, g-line (436 nm), h-line (405 nm) i-line (365 nm), KrF excimer laser (248 nm), ArF excimer and resin (193 nm) and light with a broad wavelength of 240-255 nm can be used. have. It may also be exposed using an electron beam.

Although the resist which can be used in the present invention can be changed depending on the light source to be used, any of the resists that can be silylated can be used. For example, when i-line or g-line is used as the light source, plasma-150g (Plasmask-150g: trade name of Belgian UCB) or plasma-200 GC (Plasmask-200GC: Belgian UCB) Or a plasma mask 301U (Plasmask-301U; a Belgian USB company name) or a plasma mask 302U (Plasmask-), which is a polyvinyl phenolic resist when using a KrF excimer laser or a broadband wavelength of 240 nm to 250 nm as a light source. 302U; trade name of UCB, Belgium. In addition, SAL601-ER7 (trade name of Shipley, USA) can be used because it is a chemically amplified resist XP-8913.

When the chemically amplified resist is used, a silicide layer is formed on the surface portion of the resist layer that is not exposed.

In the primary etching of the unsilylated resist layer, the etching amount is preferably etched back to about 20-70% of the total thickness of the zest layer.

As the etching method, MERIE (Magnetic Enhanced Reactive Ion Etching ), RIE, ECR (Electron Cyclotron Resonance) using a dry etching, pure O ₂ gas to the system, such as, or O ₂ gas and N ₂ or a dry etching process by the addition of He, etc., etc. Can be mentioned.

The etching may be performed in one step, but a two-step etching method of etching in one step using CF ₄ or C ₂ F ₆ and O ₂ and then etching in two steps using O ₂ may be used. In such a case, at the time of one step etching, about 100-200 microseconds is etched simultaneously in the silylated resist layer and the unsilylated resist layer. At this time, the flow rate of the CF ₄ or C ₂ F ₆ and O ₂ is 5 ~ 20sccm, respectively, it is preferable that the flow rate of O _{2 in} the two-step etching is 15 ~ 100sccm. When only O ₂ gas, dry etching using a flow rate of O ₂ is 20 ~ 100sccm, it is preferable that the RF (Radio Frequency) power of the dry etching apparatus of 0.5kw ~ 2.0kw.

As the silylating agent that can be used in the present invention, any compound containing a silicone can be used. Among them, HMDS (Hexamethy Disilazane) or TMDS (Tetramethyl Disilazane) may be mentioned. The silylation step is preferably carried out for 30 seconds to 5 minutes at 120 ℃ to 250 ℃ temperature.

It is preferable to perform a PSB (Pre-Silylation Back) process before the first salicylation. Then, in the negative tone method, the resin particles react with the photosensitive compound present in the resist at the unexposed portions of the resist layer to form a polymer layer. The PSB process is preferably carried out at 140 ℃ ~ 250 ℃ 30 seconds to 5 minutes.

In addition, in the positive tone method using a chemical medium width resist, the base resin and the crosslinking agent react at the exposed portions of the resist to form a polymer layer. At this time, it is preferable to perform a PSB process for 5 minutes in 30 second at 80 degreeC-150.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

Example 1

3A to 3F are schematic diagrams showing an example of a pattern forming method according to the present invention.

Referring to FIG. 3A, a resist layer 12 having a thickness of 1.0 to 1.2 mu m is spin-coated on the semiconductor wafer 11 by using a novolak-based resin plasma mask-200GC (Plasmask-200GC; trade name of Belgian USB) as a resist material. ). Next, the resist layer 12 is exposed using the photomask 13 on which a mask pattern is formed. The exposure is performed using light line 14 of i-line (365 nm). When the resist layer 12 is exposed, the resist layer 12 formed on the semiconductor wafer 11 is divided into an exposed portion 16 and an unexposed portion 15, and the exposed portion 16 is exposed. The photosensitive compound of the resist collapses and the resin molecules of the resist are free. Referring to FIG. 3B, the exposed resist layer 12 is subjected to a PSB process using a conventional hot plate bake track at 125 ° C. for 120 seconds. Then, the resin particles in the unexposed portion 15 crosslink with the photosensitive compound to form the polymer layer 17. Pre-silylation bake (PSB).

Referring to FIG. 3C, the first silylation is performed by flowing plasmaster-Si (trade name of Plasmaster-Si JSR; TetraMethyl DiSilazane (TMDS) as a silylating agent in a gas phase at 130 ° C. for 150 ° C.). The resin particles in the exposed portion 16 react with the Si group of the siliciding agent to form the silylated resist layer 19.

Referring to FIG. 3D, 1.0KW RF (Radio Fregcercy) power using BMC-600 (trade name; product of MRC Co., Ltd.) employing MERIE (Megnetic Enhanced Reactive Ion Etching) method as a resist dry etching apparatus. And first etch the resist for 1 minute at an O ₂ flow rate of 50 sccm (standard cubic centimeter per minute). Then, the polymer layer 17 of the resist is removed to a depth of about 0.5㎛.

The etching may be performed in one step as described above but may be performed in two steps.

In other words, as the first step, the unsilylated polymer layer 17 and the silylated resist layer 19 were etched for 15 seconds at about 15 seconds using a CF ₄ flow rate of 15 sccm and an O ₂ flow rate of 150 sccm. Further etching is performed at an O ₂ flow rate of 50 sccm.

Referring to FIG. 3e, after partially etching the polymer layer 17 as described above, a second silylation process is performed.

The secondary silylation process is performed in the same manner as the primary silylation process. The silylation reaction also occurs on the sidewalls of the exposed resist layer 16 under the silicided resist layer 19 by this secondary silylation process, and the sidewalls serve as a protective film in a subsequent resist etching process. Patterns can be formed.

4A to 4D are views for explaining the second silicidation step in more detail.

The sidewall silylation reaction is increased to the thickness of the silylated resist layer 19 in the upper layer, and the depth at which the silylation reaction occurs in the depth direction is changed.

4A shows a cross-sectional view of the resist layer before secondary silylation.

4b shows a secondary silylation process. When the second silylation process is performed, an upper layer portion of the silylated resist layer 19 is deepened as shown in (40) of FIG. 4B and a silylated resist layer 20 having an inclination on the sidewall is formed. This is due to the difference in the amount of light to which the light beam is exposed. More specifically with reference to FIG. 4d, the profile of the silylated resist is formed as 43, but swelling occurs during dry etching with O ₂ , as in 44. This acts as a mask layer in dry etching to form a pattern. At the time of exposure, the distribution of orphans is absorbed into the resist and the photosensitive compound is decomposed in the resist as shown in (45) of FIG. At the surface portion of the resist, the amount of exposure to light increases, so that the amount of the photosensitive compound decomposes and increases. Resin particles, such as a resist, are surrounded by the photosensitive compound, and reaction of another molecule | numerator is suppressed. When the photosensitive compound is decomposed, the resin molecules react more easily than other molecules. Therefore, the closer to the surface of the resist layer, the more resin particles can bind to TMDS, and the lower the lower part, the smaller amount of resin molecules will react with TMDS, resulting in inclined silylated resists such as (20) in Figure 4b. A layer is formed.

In addition, crosslinking of the photosensitive compound and the resin particles occurs by heat during the PSB process, but the unbonded resin particles react with TMDS to form dozens of microns to several hundreds of silylated resist layers as shown in (42) of FIG. 4b. The first etched polymer layer 16 is formed on the surface.

Referring to FIG. 3f, after the secondary silylation process, the secondary etching is performed in the same manner as the primary etching. At this time, the silylated resist layer 20 formed on the sidewall becomes a protective film to obtain a resist pattern having a good profile.

4C is a cross-sectional view showing the obtained resist pattern in more detail.

Example 2

Plasma mask-301U (Plasmask-301u; manufactured by UCB, Belgium) was used as a resist material, and exposed using a KrF excimer laser, and then the PSB process was performed at 170 ° C. for 120 seconds, and the silylation process was performed at 145 ° C. A resist pattern was obtained in the same manner as in Example 1 except for performing for 150 seconds.

Example 3

Using a chemically amplified resist, SAL 601-ER7 (trade name: Shipley, Inc.) as a resist material, using a KrF excimer laser or an electron beam (acceleration voltage 20 KeV), the PSB process was performed at 100 ° C. for 60 seconds. After that, a first silylation process is performed. Then, in contrast to Example 1, a crosslinking reaction occurs between the base resin and the crosslinking agent in the exposed PSB process to form a polymer layer, and a silylation reaction occurs on the surface portion of the unexposed resist layer. A resist layer is formed.

Perform primary etching for 30 seconds. After the same as in Example 1 to obtain a resist pattern.

Since the resist is a chemically amplified resist, it is possible to form a pattern even when the exposure energy of the KrF excimer laser is 100 mJ / cm 2 or less, and 5 to 30 when using an electron beam. Pattern formation is possible even at C / cm 2 or less.

According to the present invention, the resist profile was vertically formed after the secondary etching of the resist, thereby improving the resist profile.

In addition, since the overhang portion does not occur on the resist pattern, there is no difficulty in measuring the resist line width. In addition, since there is no overhang portion, the etching radicals are not disturbed during the etching of the substrate, so that a good profile of the substrate can be obtained.

In addition, the swelling occurs as the sidewalls of the resist are silized, and thus the KfF excimer laser can lower the exposure energy to 150-200 m J / cm 2, thereby increasing the wafer throughput.

Claims (14)

Selectively silylating the resist layer formed on the semiconductor substrate to form a silylated resist layer on a surface portion of the resist, first etching the unsilylated resist layer, and second silylating the silylated resist layer. Forming a silylated resist layer on the sidewalls of the silylated resist layer below the resist layer, and performing secondary etching to remove all of the unsilylated resist layers. 2. The negative tone method of claim 1, wherein the method exposes a resist layer formed on a semiconductor substrate and then selectively sililates the unexposed portions or the negative tone method of selectively primary silylating exposed portions of the resist layer. A resist pattern forming method characterized by a positive tone method. The method of claim 2, wherein the exposure is performed using a patterned photomask or exposed using an electron beam. The method of claim 1, wherein the unsilified resist layer is firstly etched to about 20 to 70% of the total thickness of the resist layer and then subjected to second silicification. The method of claim 1, wherein the dry etching method such as RIE MERIE (Magnetic Enhanced Reactioc Ion Etching), ECR (Electron Cyclotron Resonace), or the like using pure O ₂ gas or mixed gas such as O ₂ gas and N ₂ or He A resist pattern forming method characterized by performing by an etching method. The method of claim 5, wherein the flow rate of the O ₂ is 20 to 100 sccm, and the RF power of the dry etching apparatus is 0.5 to 2.0 KW. The method of claim 1, wherein the etching is performed in one step using CF ₄ or C ₂ F and O ₂ , and two step etching using O ₂ . The method of claim 7, forming a resist pattern according to that characteristic the city step etching CF _4, or C ₂ F ₆ and O ₂ in the flow rate that each 5 ~ 20sccm, and the flow rate of O ₂ with 2-step etching 15 ~ 100sccm Way. The method of claim 1, wherein the silylation is performed using hexamethyldisilazane (HMDS) or tetra methyldislan-zane (TMDS) as the silylating agent. The method of claim 9, wherein the silylation process is performed at 120 to 250 ° C. for 30 seconds to 5 minutes. The method of claim 2, wherein a pre-silicon bake (PSB) process is performed before the first silicification. 12. The method according to claim 11, wherein the PSB process is performed for 30 seconds to 5 minutes at 140 ° C to 250 ° C in the case of a negative tone method, and 30 seconds to 5 minutes at 80 ° C to 150 ° C for a positive tone method. A resist pattern forming method characterized by the above-mentioned. The method of claim 1, wherein the resist is a novolak-based, polyvinyl phenol-based, or chemically amplified resist. The method of claim 3, wherein the exposure is performed with g-line (436 nm), h-line (405 nm), i-line (365 nm), KrF excimer laser (248 nm), ArF excimer laser (193 nm), or E-beam ( Electron beam), a resist pattern forming method characterized in that performed using a light ray having a broadband wavelength of 240nm ~ 255nm.