As LSI advances to a higher integration and a further facilitation in speed, miniaturization of a pattern size is rapidly progressing. In accordance with this miniaturization movement, the lithography technology has achieved formation of a fine pattern by shifting the wavelength of a light source shorter and by proper selection of a resist composition responding to such shift in the light source. The main factor of this is a positive photoresist composition used in a monolayer. In this monolayer positive photoresist composition, a skeleton having an etching resistance to dry etching by a gas plasma of chlorine-based or fluorine-based is incorporated into a resist resin and a switching mechanism to dissolve an exposed part is constructed in a resist resin, and thereby a pattern is formed by dissolving the exposed part, and then, a substrate to be processed is dry-etched by using the remained resist pattern as an etching mask.
However, if miniaturization is pursued without changing a film thickness of the photoresist film to be used, namely, if the pattern width thereof is made further narrower, resolution of the photoresist film decreases; in addition, if the photoresist film is pattern-developed by using a developer, a so-called aspect ratio thereof becomes so large that a problem of the pattern fall occurs. In view of the above-mentioned, the thickness of the photoresist film has been made thinner in accordance with this miniaturization movement.
On the other hand, for processing of a substrate to be processed, the method wherein this substrate is dry-etched by using a photoresist film having a formed pattern as an etching mask has been usually used. However, practically there is no dry etching method having a complete etching selectivity between the photoresist film and the substrate to be processed. Because of this, during processing of the substrate, the resist film is also damaged to cause collapse of the resist film so that there has been a problem that the resist pattern cannot be precisely transcribed to the substrate to be processed. Because of this, the resist composition has been required to have a further higher dry etching resistance in accordance with the movement to a finer pattern. On the other hand, however, in order to increase a resolution, the resin used for the photoresist composition has been required to have a smaller light absorbance at the wavelength of the exposure light. Therefore, as the exposure light shifts to a shorter wavelength, i.e., shifting to i-beam, KrF, and ArF, the resin has also been shifting to a novolak resin, polyhydroxystyrene, and a resin having an aliphatic polycyclic skeleton. Realistically however, the etching rate under the dry etching condition during the substrate processing has been increased so that recent photoresist compositions having a high resolution tend to have rather a lower etching resistance.
In the situation as mentioned above, a substrate to be processed must be processed by dry etching by using a photoresist film having a thinner thickness and a lower etching resistance than ever; and thus, securement of a material and a process in this patterning process has become an acute imperative.
One means to solve the problems mentioned above is a multilayer resist method. In this method, an intermediate film having the etching selectivity different from that of a photoresist film (namely, a resist upper layer film) is put between the resist upper layer film and a substrate to be processed; and after a pattern is formed on the resist upper layer film, this pattern is transcribed to the intermediate film by dry etching using the pattern on the upper layer film as a dry etching mask, and then, the pattern is transcribed further to the substrate to be processed by dry etching using the intermediate film as a dry etching mask.
One of the multilayer resist methods is a three-layer resist method in which a general resist composition used in a monolayer resist method can be used. In this three-layer resist method, for example, an organic film formed of a novolak resin or the like is formed on the substrate to be processed as the resist underlayer film, on it a silicon-containing film is formed as the resist intermediate film, and further on it a usual organic photoresist film is formed as the resist upper layer film. Because the organic resist upper layer film can have a good selectivity relative to the silicon-containing resist intermediate film in dry etching by a fluorine-based gas plasma, the resist upper layer film pattern can be transcribed to the silicon-containing resist intermediate film by using dry etching by the fluorine-based gas plasma. According to this method, even if a resist composition with which a pattern having a sufficient film thickness to directly work on the substrate to be processed is difficult to be formed is used, or a resist composition whose dry etching resistance is insufficient to work on the substrate is used, the pattern can be transcribed to the silicon-containing film (the resist intermediate film), and then, by transcribing the pattern by the dry etching using an oxygen-based or a hydrogen-based gas plasma, the pattern of the organic film (resist underlayer film) formed of a novolak resin or the like having a sufficient dry etching resistance to the substrate processing can be obtained. Many of the resist underlayer films as mentioned above have already been in the public domain, such as, for example, those described in Patent Document 1.
On the other hand, in recent years, production of the semiconductor device having a novel structure such as a multi-gate structure is being actively investigated; and with this movement, requirements for better planarization and gap-filling characteristics than before are increasing more than before in the resist underlayer film. For example, when there is a very fine pattern structure such as a hole, a trench, or a fin in the underlayment substrate to be processed, the gap-filling characteristic to fill up inside the pattern by the resist underlayer film without a void becomes necessary. Further, when there are steps on the underlayment substrate to be processed, or when a dense pattern area and a scarce pattern area co-exist on the same wafer, the film surface needs to be planarized by the resist underlayer film. By planarizing the underlayer film surface, variance of the film thickness of the resist intermediate film and the resist upper layer film to be formed thereupon can be suppressed; and as a result, the decrease in a focus margin of the lithography as well as in a margin in the subsequent process step of the substrate to be processed can be suppressed. Alternatively, in order to remove, by dry etching, the resist underlayer film used for gap-filling and planarization without leaving the residue thereof after the substrate processing, the resist underlayer film having the dry etching characteristics different from those of the above-mentioned, for example, the resist underlayer film having the dry etching rate faster than that of the resist upper layer film, is sometimes required. Further, there is also a case that the substrate processing by wet etching using a chemical is required, wherein the resist underlayer film acting as the processing mask is required to have a resistance to a wet etching solution.
Meanwhile, the background for requirement of the material matching to the wet etching process in the multilayer resist method will be explained in detail. In order to improve the semiconductor device performance, technologies such as a three-dimensional transistor and a through wiring are being used in the most advanced semiconductor devices. The patterning by using the multilayer resist method is carried out also in the patterning process used for forming the inner structure of the semiconductor device as mentioned above. In the patterning like this, there is a case that after the patterning a process in which the silicon-containing resist intermediate film is removed without damaging the said pattern is required. If this removal is insufficient, namely if the wafer is sent to subsequent manufacturing process steps while still having residual substances to be cleaned, yield of the device manufacturing definitely decreases. With the miniaturization movement of the device as mentioned above, a higher cleanness is required in the cleaning step. In many cases, however, the main constituent element in the conventional silicon-containing resist intermediate film and in the semiconductor device substrate is silicon; and thus, even if the attempt is made to selectively remove the silicon-containing resist intermediate film by dry etching, the constituent ingredients are so similar with each other that it has been difficult to suppress the damage to the semiconductor device substrate. This problem cannot be solved even with the wet etching using a usual fluorine-based removing agent. Therefore, a basic hydrogen peroxide aqueous solution, which is called as SC1 (Standard Clean-1) that is generally used in the semiconductor manufacturing process, may be used as the removing solution (namely, wet etching solution) not damaging the semiconductor device substrate. In this case, conversely the resist underlayer film needs to have a resistance to the basic hydrogen peroxide aqueous solution.
Besides, the process is being studied in which the substrate to be processed such as titanium nitride is processed by wet etching using the basic hydrogen peroxide aqueous solution and the resist underlayer film as a mask. In this case, too, the resist underlayer film needs to have the resistance to the basic hydrogen peroxide aqueous solution.
As the resist underlayer film composition having a fast dry etching rate and being capable of planarizing the substrate having steps to be used for the semiconductor device manufacturing, for example, a composition containing a polymer compound such as polyglycidyl methacrylate is proposed in Patent Document 2. Also as the resist underlayer film composition having a fast dry etching rate to be used for the semiconductor device manufacturing, in Patent Document 3, a composition containing a copolymer that is produced by using monomers such as (meth)acrylic acid and glycidyl (meth)acrylate is proposed, and in Patent Document 4, a composition containing a crosslinking agent and a copolymer that is produced by using monomers such as hydroxypropyl methacrylate is proposed. However, in these heretofore known compositions there has been a problem that the resistance to the basic hydrogen peroxide aqueous solution is insufficient.
As the resist underlayer film composition having the resistance to the basic hydrogen peroxide aqueous solution, in Patent Document 5, a composition containing, among others, a polymer having an epoxy group and a carboxyl group protected by using a vinyl ether compound (acetal-protected ester) is proposed for a two-layer resist process not using the resist intermediate film. However, this composition is insufficient in the planarization characteristic, and thus, this is not suitable for patterning of the substrate to be processed having irregular surface or steps highly required especially in the most advanced process, and in addition, there has been problem that the resistance to the basic hydrogen peroxide aqueous solution is still insufficient in view of practical use.
As the resist underlayer film which is excellent in the dry etching characteristic, in the resistance to the basic hydrogen peroxide aqueous solution, and in the planarization characteristic, in Patent Document 6, a composition containing among others a polymer having an epoxy group and a carboxyl group protected by using a tertiary alkyl group is proposed. However, there has been a problem in this composition that the resistance to the basic hydrogen peroxide aqueous solution is still insufficient in view of practical use.
Therefore, there have been requirements of the resist underlayer film composition to be used for the semiconductor device manufacturing having a high conformity to a wet etching process (namely, high resistance to the basic hydrogen peroxide aqueous solution) and having at the same time good gap-filling and planarization characteristics and dry etching characteristic, as well as the patterning process using this composition.
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