JP2506133B2 - Pattern formation method - Google Patents

Description

The present invention relates to a pattern forming method using a two-layer resist method, which is a method for forming a fine pattern on a substrate for a semiconductor or various devices with high accuracy. It is a thing.

“Conventional Technology and Problems” As a method for forming a fine pattern on a substrate for semiconductors and various devices with high accuracy, a multilayer resist method has been developed. This method can eliminate the adverse effect on the pattern formation characteristics caused by the local fluctuation of the resist film thickness due to the step remaining on the substrate surface, as compared with the case where the pattern formation is performed on the resist single layer film. Moreover, since the resist film thickness of the uppermost layer for forming an image can be made thinner than that of the resist single layer film, there is an advantage that even a fine pattern can be formed with high accuracy.

However, on the other hand, there are some practical problems such as complicated process steps and the need for a special resist material.

The technology currently being developed as a multilayer resist method includes
There are a three-layer resist method and a two-layer resist method. The three-layer resist method has a problem that the process is complicated and the number of steps is large because the dry etching process for forming the intermediate layer and processing the intermediate layer and the lower layer film is performed twice. On the other hand, the two-layer resist method was developed as a more practical pattern forming method by halving the number of steps of the three-layer resist method. The feature is that a silicon-containing resist having oxygen plasma resistance is used as the upper layer resist. It was used.

However, in general, when silicon is contained as a constituent element of a polymer, it affects basic characteristics required as a resist such as solubility and sensitivity in a solvent and pattern resolution, and there is a practical problem.

Therefore, a silylated two-layer resist method was developed (Japanese Patent Application Nos. 60-165041 and 61-116844). This method uses a commercially available resist that has excellent characteristics in sensitivity and resolution as it is, and it is possible to obtain O ₂ RIE resistance by performing silylation treatment after pattern formation. This is a highly versatile method that can be applied to exposure methods such as X-rays.

3A to 3D are process diagrams of pattern formation by the normal transfer process. As shown in FIG. 3 (a), a resist film (for example, polyimide) 6 that is not silylated is applied onto the substrate 3. Then, a resist for electron beam exposure (for example, PMMA) is thinly applied as the upper layer resist film 7. Next, the upper layer resist 7 is exposed and developed using an electron beam exposure apparatus to form a pattern as shown in FIG. 3 (b). After this, by irradiation with far-ultraviolet light using an organic silane such as a halogenated alkylsilane, a silylated layer 8 is formed on the surface layer portion of the upper resist film 7, as shown in FIG. Finally, when the entire substrate is dry-etched with oxygen gas, the lower resist film 6 is etched using the silylated layer as a mask, and a pattern can be formed as shown in FIG. 3 (d).

On the other hand, FIGS. 4A to 4D show pattern formation process diagrams of the anti-transfer process. As shown in FIG. 4A, a lower layer resist film (for example, a novolak resin hard-baked at about 200 ° C.) 6 that can be silylated is applied onto the substrate 3. Next, a resist for electron beam exposure (for example, PMMA, FBM, etc.) is thinly applied as the upper resist film 7. Next, if exposure and development are performed, a pattern can be formed as shown in FIG. Thereafter, a silylation treatment is performed in a halogenated alkylsilane atmosphere. Here, the upper resist film 7 is used.
Can be selectively silylated by using far-ultraviolet light such that only the lower resist film 6 is silylated and the lower resist film 6 is silylated. As shown in FIG. 4C, only the lower resist film 6 is silylated. The chemical conversion layer 8 can be formed. Finally, if the entire substrate is dry-etched in oxygen gas, the fourth
As shown in FIG. 3D, the remaining portion of the unsilylated upper layer film 7 is etched by using the silylated layer 8 as a mask, and an anti-transfer pattern can be formed.

As described above, according to the silylated two-layer resist method, a commercially available resist material is used for the upper layer resist film 7, and the lower layer resist material and the wavelength of the far-ultraviolet light source at the time of silylation are selected to perform the normal transfer or the anti-transfer. This is a technology that allows easy formation of patterns.

By the way, Japanese Patent Application Nos. 60-165041 and 61
In the case of forming a positive transfer pattern, Japanese Patent Laid-Open No. 116844 describes the use of a polymer material which is originally non-silylated, such as polyimide, polyethylene, polypropylene and polyvinyl chloride, which is originally inert to organosilane. However, when considering application in the current LSI process, polyethylene, polypropylene, polyvinyl chloride, etc. have no actual use record, and polyimide is a material that has recently begun to be used as a semiconductor process, so it is applied to mass production processes. In order to do so, more thorough examination is needed.

For this reason, in order to use the silylated two-layer resist method in a mass production process, it is necessary to study a material with a proven track record, and it is also the same as the material used for the anti-transfer pattern. Desired in the process. From this idea, in the invention (polymer film silylation method) just applied prior to the present invention, a photoresist that has been used in a VLSI mass production process is used, and the polymer surface is silylated or non-silvered depending on the processing conditions. It is silylated. However, in the present invention, the conditions for desilylation of the polymer surface are such that a treatment of about 1 hour is required at a temperature of 280 ° C. and a treatment of about 30 minutes is required at a temperature of 300 ° C. Such a high temperature treatment causes various problems in the VLSI process steps (for example, when aluminum is used for the wiring, hillocks are generated when the high temperature treatment is performed), and it is not practical. Therefore, it is desired to be able to desilylate at a lower temperature.

"Means for Solving Problems" The present invention has been made in view of the above circumstances, and in a pattern forming method using a two-layer resist method, a lower layer resist film containing a novolac resin as a main component is formed on a substrate. A step of forming, a step of irradiating the entire surface of the lower layer resist film with ultraviolet rays while heating the substrate at 180 ° C. or higher and 250 ° C. or lower, and desilylating the surface of the lower layer resist film; Forming an upper resist film having a property of silylating the surface by irradiation on the lower resist film; forming a desired pattern on the upper resist film; and lower resist film and patterning Exposing the upper resist film to organic silane and irradiating with ultraviolet light to selectively silylate only the upper resist film; It is characterized in that the step of transferring the pattern of the upper layer resist film to the lower layer resist film by performing etching with oxygen plasma on the substrate for which the steps have been completed is sequentially performed.

In order to solve the above conventional problems, in the present invention, as an organic polymer material, it is premised that a photoresist with a proven track record in the process of VLSI is used, and the temperature is as low as possible as a treatment condition for desilling the polymer surface, and as short as possible. It is characterized by what can be done in. Therefore, the damage to the element can be reduced as compared with the conventional technique, and the normal rotation and anti-transfer patterns can be easily formed with the same material. Regarding the silylation method utilizing the photochemical reaction according to the present invention, Japanese Patent Application No. 60-165041 and Japanese Patent Application No. 61-116844, and the invention (polymer film silylation method) filed prior to the present application The patents are the same, but are a further development of this principle.

The present invention will be described in more detail below. In the present invention, as a polymer material for the lower resist film, a positive photoresist (MP1400-27, manufactured by Shipley Co.) used in VLSI is used, and as shown in Table 1, curing conditions by ultraviolet rays (UV), that is, Samples with different non-silylation conditions were prepared. Sample A is a case where only heat treatment at 280 ° C. for 3 minutes was performed without UV irradiation. Sample B is from the temperature of 110 ℃ 5
This is the case where the temperature was raised to 180 ° C in 0 second and UV irradiation was performed during that time. Sample C is the case where UV irradiation is performed while raising the temperature from 110 ° C to 180 ° C for 140 seconds. Sample D is the case where UV irradiation is performed while raising the temperature to 110 ° C to 250 ° C for 140 seconds. Sample E is a case where UV irradiation was performed for 180 seconds while increasing the temperature from 110 ° C to 200 ° C.

Next, the outline of the silylation process will be described with reference to FIG. The container 1 is filled with an organic silane (for example, trimethylchlorosilane) liquid 2. Further, various resist films 4 with different processing conditions are formed on the substrate 3. Then, the container 1 is covered with a quartz glass 5 and far ultraviolet light is irradiated from the upper surface thereof to silylate the resist film 4. Next, in order to confirm the silylation reaction state, etching was carried out in a parallel plate type sputter etching apparatus in which oxygen gas was introduced,
The etching amount with respect to the etching time was measured and examined by comparing with the non-silylated one. The results are shown in Table 1 above. The silylation treatment was performed by irradiating deep ultraviolet light with a low pressure mercury lamp for 20 minutes. The conditions of the tri-etching were an oxygen pressure of 2 Pa, a flow rate of 50 SCCM, and a high-frequency output of 100 W, and the etching amounts at the etching times of 1 minute 30 seconds and 6 minutes were determined to determine whether or not desilylation was possible.

As a result, in the sample A, the etching amount did not increase even if the etching time was lengthened, and it was found that the resist surface was silylated. In sample B, the resist surface is slightly silylated, but if the etching time is lengthened, an almost same etching amount tends to be obtained as compared with the case of non-silylation. Sample C has a lower degree of silylation on the resist surface than Sample B, and an etching amount equivalent to that in the case of non-silylation is obtained by increasing the etching time. It was found that the samples D and E obtained almost the same etching amount as in the case of non-silylation, and the resist surface was not silylated.

From these results, the silylation state varies depending on the UV irradiation time and the curing temperature, and the longer the irradiation time and the higher the curing temperature, the better the results obtained. All of these good results were obtained by desilylation at low temperature and in a short time, compared with the case of the invention (method of silylating polymer film) filed prior to the present application. The reason for this is considered to be that the crosslinking reaction occurs in the resist by the application of UV irradiation and heat and the OH group in the benzene nucleus in the resist is decomposed, and as a result, the alkylsilane does not bond. Therefore, by adopting UV cure, a normal or reverse pattern can be realized with the same material.

Examples of the present invention will be shown below.

“Example” FIGS. 2A to 2C show, as an example, specific process diagrams of a positive transfer pattern by light exposure. First, the second
As shown in FIG. 3A, a photoresist (MP1400 or the like) having a thickness of about 1.5 μm is applied on the substrate 3 to form a lower resist film 6. Next, after performing UV curing for 3 minutes at 110 ℃ to 30 ℃ / minute, apply a photoresist (AZ1350 etc.) with a thickness of about 0.4μm on it and bake at 90 ℃ for 20 minutes to form the upper resist film. Form 7. After that, exposure and development are performed by a stepper or the like to form a desired pattern on the upper resist film 7.

In this case, the lower layer resist film 6 is made sufficiently thick to reduce the influence of the step of the substrate 3, and the thin layer of the upper layer resist film can be applied to form a fine pattern with good reproducibility. Then, using an alkylsilane (for example, dimethylchlorosilane) liquid, irradiating with far-ultraviolet light,
Only the patterned upper resist film 7 is shown in FIG.
A silylated layer 8 is formed as shown in FIG. After that, if the entire substrate is transferred to a reactive ion etching apparatus and etching is performed, a pattern can be formed as shown in FIG. 2 (c).

If pattern processing is performed by the method described above, any lithography technique such as electron beam, deep ultraviolet ray, X-ray, excimer laser, and plasma can be applied as the upper resist film 7.

On the other hand, the anti-transfer pattern is not shown in the embodiment, but the conventional method (for example,
By using a bake at 200 ° C. for about 30 minutes), silylation can be performed, and thus an anti-transfer pattern can be formed.

"Effects of the Invention" As described above, in the pattern forming method using the two-layer resist method, according to the present invention, the surface of the lower resist film is exposed by simultaneously performing heating at 180 ° C to 250 ° C and ultraviolet irradiation. It is characterized by non-silylation. Therefore, according to the present invention, one of the two-layer resist is
When selectively silylating only the layer, a commonly used conventional photoresist can be used as it is. In addition to this, since the condition for desilylation is relatively low temperature as compared with the conventional method and does not affect the semiconductor process at all, a fine pattern is formed on the substrate for various devices such as semiconductors. Can be formed with high precision.

[Brief description of drawings]

Figure 1 is for explaining the outline of the silylation process.
FIG. 2 is a schematic configuration diagram of an apparatus suitable for this silylation treatment, FIG. 2 is a process diagram of a normal transfer pattern according to the present invention, and FIGS. 3 and 4 are process diagrams of pattern formation by a conventional method. 1 ... Container, 2 ... Organosilane liquid, 3 ... Substrate, 4 ...
Resist film, 5 ... Quartz glass plate (lid), 6 ... lower resist film, 7 ... upper resist film, 8 ... silylated layer.

Claims (1)

(57) [Claims] 1. A step of forming a lower layer resist film containing a novolac resin as a main component on a substrate, and irradiating the entire surface of the lower layer resist film with ultraviolet rays while heating the substrate at 180 ° C. to 250 ° C. A step of desilylating the surface of the lower resist film; a step of forming an upper resist film having the property of silylating the surface by exposing it to organic silane and irradiating it with ultraviolet light; A step of forming a desired pattern on the resist film, and a step of selectively silylating only the upper layer resist film by exposing the lower layer resist film and the patterned upper layer resist film to organic silane and performing ultraviolet irradiation, By subjecting the substrate on which the process is completed to etching with oxygen plasma, the pattern of the upper layer resist film is formed into the lower layer. Pattern forming method and performing the step of transferring the resist film, sequentially.