JP2831757B2 - Method of forming resist pattern - Google Patents

Description

The present invention relates to a method for forming a resist pattern, and more particularly to a method for forming a resist pattern for forming a submicron fine pattern.

(Prior Art) In semiconductor integrated circuit technology, with rapid progress of high density, microfabrication technology using a thin film has become an extremely important elemental technology. Among these, in the microfabrication resist process, which is one of the most important technologies for forming a fine pattern on the resist layer, a high-resolution and high-sensitivity resist is used to compensate for the decrease in throughput accompanying pattern miniaturization. There is a need for a patterning method.

However, since the sensitivity and resolution of the resist layer are opposite to each other, a pattern is formed at the time of actual pattern formation at the expense of either resolution or sensitivity depending on the application. For example, during the actual production process, the throughput is improved by increasing the sensitivity of the resist layer as much as possible, even if the resolution is somewhat sacrificed, thereby improving the productivity. For this reason, in the actual production process, it is necessary to control the sensitivity of the resist layer with high sensitivity and stably.

Many proposals have been made for increasing the sensitivity of the resist layer. Among these proposals, there is a method of controlling the sensitivity of a resist layer by heat treatment as a method that is relatively easy and effective to apply to an actual production process. According to this method, a highly sensitive resist layer is obtained by pre-baking the applied resist layer and then performing an emergency command.
-132127, JP-A-59-132128, JP-A-59-132
132618 JP, JP-A-59-132619, JP-A-60-14
0824, JP-A-61-80247).

However, when forming a fine resist pattern of submicron, a higher resolution is required than before, and thus such a pattern forming method requires:
Sensitivity cannot be significantly improved. As a result, the throughput is reduced, and it is difficult to adapt to an actual production process.

(Problems to be Solved by the Invention) The conventional resist pattern forming method has insufficient resolution and sensitivity, and it is difficult to form a fine resist pattern of submicron.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a resist pattern having high resolution and high sensitivity and capable of forming a fine resist pattern of submicron.

[Constitution of the Invention] (Means and Actions for Solving the Problems) In the present invention, a resist layer made of a polymer material is formed on a substrate, and the resist layer is irradiated with fine pattern light or charged particles. After exposure, in the method of forming a resist pattern to form a resist pattern by removing the soluble portion of the soluble portion and the hardly soluble portion of the resist layer generated by exposure by developing the resist layer, after the exposure After the resist layer is annealed at a temperature just below the glass transition temperature (Tg ₁ ) of the hardly dissolvable part, subsequently, it is rapidly cooled near the glass transition temperature of the fusible part (Tg ₂ and Tg ₂ <Tg ₁ ). A resist pattern forming method characterized by performing a cooling process.

The principle of the present invention can be explained as follows from the change in the aggregation state of molecules during heating, cooling, and annealing of the resist layer.

In a heating state at or above the glass transition temperature (Tg), the molecular main chain in the resist polymer undergoes a rotational motion (micro-Brownian motion), and other molecular chains in the vicinity are eliminated, thereby forming a large free volume space. When rapidly cooled from such a heating state at a temperature equal to or higher than Tg, the rotational motion of the molecular main chain is rapidly stopped, so that the wide free volume space is frozen and remains almost as it is. On the other hand, when gradually cooled,
The rotational motion gradually stops, and adjacent molecular chains penetrate and approach, so that the free volume space becomes narrow. Also,
The large free volume space shrinks even in annealing in a temperature region immediately below Tg where the molecular chains are easy to move, and is in the same state as that after the slow cooling. It is considered that such a change in the free volume space has a great effect on the dissolution rate of the resist layer in the solvent of the developer during development. That is, when a large free volume space is formed by rapid cooling, the solvent molecules in the developer can easily enter the resist molecules, and the diffusion rate of the solvent increases. As a result, the dissolution rate of the resist layer increases. Conversely, when a narrow free volume space is formed by slow cooling or annealing, penetration of solvent molecules becomes difficult, and the diffusion rate of the solvent decreases. as a result,
It is considered that the dissolution rate of the resist layer is reduced.

In addition, when the temperature of the heat treatment is equal to or lower than Tg, the sensitivity of the resist layer does not change even if it is rapidly cooled. For example, FIG. 4 shows the change in the sensitivity of the electron beam resist EBR-9 to the temperature of the resist layer before quenching. As can be seen from this graph, near the glass transition temperature (Tg) of EBR-9,
If the temperature before quenching is lower than Tg, the dissolution rate, in other words, the sensitivity, has not changed at all.

By the way, the molecular weight of a polymer material is greatly affected by the glass transition temperature (Tg), and it is generally known that, within a certain molecular weight range, the relationship between Tg and the number average molecular weight Mn is expressed by the formula (1). Have been.

Tg = Tg (∞) −h / Mn (1) Here, Tg (∞) is Tg when Mn is infinite, and h is a constant.

Therefore, when the molecular weight of the resist changes due to exposure, that is, for a positive resist in which the molecular weight decreases, Tg
In the negative type in which the molecular weight increases and Tg increases, the Tg increases. In any of the resists, the portion having a low molecular weight is a soluble portion and its Tg is lowered, and the portion having a high molecular weight is a hardly soluble portion and its Tg is high.
That is, the glass transition temperature of the low solubility portion and availability dissolved part after exposure, respectively, when the Tg ₁ and Tg _2, in the case of utilizing a change of the dissolution rate by the change in molecular weight resist layer, whether in the positive negative However, there is always a relationship of Tg ₁ > Tg ₂ . For example, FIG. 5 shows that the positive electron beam resist layer has a thickness of 20 kV and 20 A / cm.
² shows the relationship between the electron beam irradiation amount D and Tg. From this graph, in the positive resist layer, since Mn is inversely proportional to the electron beam irradiation amount D, the glass transition temperature Tg decreases as the electron beam irradiation amount D increases from the above equation (1).

The present invention controls the sensitivity (dissolution rate) between the soluble portion and the hardly soluble portion of the resist layer by utilizing such a difference in the glass transition temperature between the soluble portion and the hardly soluble portion, thereby achieving high sensitivity. A resist pattern with high sensitivity and high resolution can be formed. The method of forming a resist pattern according to the present invention will be further described with reference to FIG. FIG. 1 shows a change in the dissolution rate of a positive resist when the present invention is carried out. Before exposure, the glass transition temperature (Tg ₁ ) and dissolution rate of the entire resist layer are uniform. When the resist layer is exposed by irradiating it with patterned light or an electron beam, the glass transition temperature of the exposed fusible portion decreases from Tg ₁ to Tg ₂ and the dissolving rate of the fusible portion increases. At this time, the dissolution rate of the resist layer around the fusible portion that has not been exposed actually increases due to the influence of heating during exposure.

Next, when annealed at a temperature of Tg ₁ vicinity, dissolution rate of the entire sparingly portion that has not been exposed is reduced uniformly. At this time, the dissolution rate of the resist layer around the dissolvable part where the dissolution rate has increased is also made uniform with the other hardly dissolvable parts that were not exposed.

Finally, when the material is rapidly cooled from the annealed state to room temperature, only the exposed dissolvable portion has undergone rapid cooling from the glass transition temperature (Tg ₂ ) or higher, and the dissolution rate increases.

As a result, the difference in the dissolution rate between the exposed soluble portion and the non-exposed hardly soluble portion increases, and the contrast improves. That is, the hardly-dissolved portion that has not been exposed has low sensitivity, and the sensitivity is improved as a whole, thereby increasing the throughput. Furthermore, the dissolution rate of the peripheral portion of the exposed portion due to the thermal influence at the time of exposure can be made uniform with the dissolution speed of the other hardly-dissolved portions that have not been exposed, and the resolution can be improved. Therefore, both sensitivity and resolution are improved.

The same applies to the negative type resist as to the positive type resist. That is, as shown in FIG. 2, in the case of a negative resist, contrary to the positive resist, annealing after exposure reduces the exposed fusible portion to low sensitivity, thereby lowering the dissolution rate. By increasing the dissolution rate by increasing the dissolution rate of the hardly-dissolved portion that has not been exposed due to the subsequent rapid cooling, both the sensitivity and the resolution are improved as a whole.

In the present invention, the glass transition temperature (Tg ₁ ) of the hardly melted part
Annealing at a temperature immediately below means a heat treatment for narrowing the free volume space of the molecular main chain in the resist polymer in the hardly soluble portion as described above. Therefore, Tg ₁
Includes slow cooling that is maintained for a certain time within the temperature range immediately below.
For example, at a temperature in the range (Tg ₁ -10) ° C,
The effect of the present invention appears when the time is set to 0 minutes or more, preferably 30 minutes or more. However, this temperature range and time depend on the resist material used and can be set arbitrarily. As this resist material, (Tg ₁ −T
g ₂ )> 40 ° C. is preferred. Further, the temperature immediately below Tg ₁ is preferably a temperature lower by 5 ° C. to 10 ° C. than Tg ₁ .

As described above, rapid cooling around the glass transition temperature (Tg ₂ ) of the fusible portion requires a cooling rate at which a large free volume space is fixed to the molecular main chain in the resist polymer of the fusible portion. Good. This cooling rate depends on the resist material and can be arbitrarily selected.

The resist material to which the present invention is applied includes polymethyl methacrylate (PMMA), poly (trichloroethyl methacrylate), poly (trifluoroethyl α-chloroacrylate), poly (butene sulfone), and poly (glycidyl methacrylate). And chloromethylated polystyrene.

As described above, according to the present invention, the resist layer after exposure is annealed at a temperature just below the glass transition temperature (Tg ₁ ) of the hardly-dissolved portion, thereby reducing the dissolution rate of the hardly-dissolved portion in the developer. Then, when the resist layer is cooled, the melting rate of the fusible portion is increased by rapidly cooling the vicinity of the glass transition temperature (Tg ₂ ) of the fusible portion. To improve the sensitivity of the resist layer. Furthermore, by heating at the time of exposure, non-uniformity of the dissolution rate in the unexposed area around the exposed area due to rapid cooling, annealing at a temperature just below Tg ₁ makes it possible to achieve the same dissolution rate as other unexposed areas. As a result, the "cut" at the boundary between the exposed portion and the unexposed portion is good, and the resolution can be improved.

(Example) Hereinafter, an example of the present invention will be described. In FIG.
1 shows a processing apparatus used in this embodiment. As shown in FIG. 3, in this processing apparatus (1), a substrate (3) supporting an exposed resist layer (2) is disposed in a housing (4) having heat insulation, and a nozzle (5). and N ₂ gas (8) is blown a dry gas heated to a predetermined temperature by the heater (6) and a thermocouple (7) through, it is annealed. The resist material is made of poly (trichloroethyl methane acrylate), and the annealing temperature is controlled to be just below the glass transition temperature of the hardly soluble part (5-10 ° C lower than Tg ₁ ), and the annealing time is 60 minutes. And

After the completion of the annealing, the supply of the N ₂ gas (8) is stopped, and at the same time, the N ₂ gas as the cooling and drying gas is
Gas (10) was blown onto the resist layer (2) to quench it. The temperature of this N ₂ gas was −30 ° C., and the cooling time was set until the entire substrate (3) was completely cooled to room temperature or lower.

Thereafter, the supply of the N ₂ gas (10) is stopped, and the heater (6)
A dried N ₂ gas (8) at room temperature without heating was blown onto the substrate (3) through the nozzle (5) to return the temperature of the cooled substrate (3) to room temperature. This is because when the substrate (3) is taken out of the housing (4), it does not condense on the resist layer (2). The gas was discharged from the housing (4) through the exhaust ports (11) and (12).

When this resist layer was developed, a clear resist pattern was obtained.

Heated in the above embodiments, the drying gas used for cooling, if an inert gas that does not react with the resist layer, can be used a He gas and Ar gas other than N ₂ gas or the like.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a method for forming a resist pattern that can form a fine resist pattern with high resolution and high sensitivity and a submicron size. it can.

[Brief description of the drawings]

FIG. 1 is a graph showing the change in the dissolution rate and the glass transition temperature when using a positive resist material according to an embodiment of the present invention, and FIG. 2 is a graph when using a negative resist material according to another embodiment. FIG. 3 is a cross-sectional view showing a processing apparatus used in an embodiment of the present invention, and FIG. 4 is a graph showing the relationship between the heating temperature and the sensitivity of the resist EBR-9 before quenching. FIG. 5 is a graph showing the relationship between the electron beam irradiation dose of the positive electron beam resist layer and the glass transition temperature. 1 ...... processor, 2 ...... resist layer, 3 ...... substrate, 4 ...... housing, 5 ...... nozzles, 6 ...... heater, 7 ...... thermocouple, 8 ...... N ₂ gas, 9 ...... nozzle , 10 ...... N ₂ gas, 11 ...... outlet, 12 ...... outlet.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shigemitsu Civilization 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Tamagawa Plant (56) References JP-A-63-81820 (JP, A) JP-A-61-89632 (JP, A) JP-A-60-117627 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/027 G03F 7/38 511

Claims (1)

(57) [Claims] 1. A resist layer made of a polymer material is formed on a substrate, and the resist layer is exposed to light or charged particles in the form of a fine pattern. The resist layer is developed and exposed to light. In the method of forming a resist pattern by forming a resist pattern by removing a dissolvable part between a dissolvable part and a hardly dissolvable part of the layer, the resist layer after the exposure is placed just below the glass transition temperature (Tg ₁ ) of the hardly dissolvable part And then subjecting the meltable portion to a quenching process to rapidly cool the glass transition temperature (Tg ₂ , Tg ₂ <Tg ₁ ). .