JP2585676B2 - Pattern formation method - Google Patents

Description

The present invention relates to a method of forming a resist pattern used in a lithography step in a process of manufacturing a semiconductor device, and particularly to forming a pattern by a silylation process. About the method.

(Prior Art) With the advance of the semiconductor technology, the speeding up and the integration of a semiconductor device and a semiconductor element have been promoted. Along with this, the necessity of pattern miniaturization is increasing, and the pattern dimensions are also required to have higher precision. In the current process, the underlying thin film is etched by RIE using the photosensitive polymer (resist) pattern as a mask, so lithography technology can form a fine resist pattern with high aspect ratio and high dimensional accuracy on the surface of a stepped device Conventional single-layer processes in the required photolithography technology are difficult to meet these requirements, and the significance of a multilayer resist process has become increasingly important.

The multi-layer resist method is intended to share the role of the resist by making the resist multi-layer. First two
A resist layer having a thickness of about 3 μm is provided to flatten the steps on the element surface and absorb light reflected from the base. If patterning is performed thereon with a high-resolution resist, exposure and development can be performed under ideal conditions separated from the base, and a pattern with high resolution and high dimensional accuracy is formed.

This is the basic idea of a multilayer resist, but specific methods are more diverse than the number of layers and the method of pattern transfer to a lower layer. As a typical multilayer process, there is a three-layer resist method in which an intermediate layer is provided between upper and lower resist layers. The pattern transfer from the upper layer to the intermediate layer and from the intermediate layer to the lower layer is performed by two-stage reactive ion etching (RIE, hereinafter abbreviated as RIE). Here, the intermediate layer plays two roles of preventing interaction between the upper and lower resist layers and giving the lower resist layer RIE a breakdown voltage. Therefore, the material of the intermediate layer can be formed by spin coating.
OG (Spin On Glass: organic silicon glass) is most often used. Although this method is a considerably stable process compared to other technologies, the process is considerably complicated, such as two RIE steps, and is not suitable for practical use for mass production. Therefore, simplification of the process has become a major issue, and various processes are being studied. One promising technology is the silylation process. The silylation process realizes the functions of the above-described three-layer resist with a single-layer resist, and can be said to be the ultimate and ideal resist process.

According to JP-A-61-107346, a typical silylation process is as shown in FIGS.
(FIG. 1), and exposed through an exposure line 4 such as an ultraviolet ray through a mask 3 to form an exposed portion 5 (see FIG. 1).
(FIG. 3), a silylated layer 6 is formed by resisting the exposed portion 5 and selectively absorbing a silicon compound (FIG. 3), and the non-exposed portion is selectively removed by reactive ion etching to obtain a desired negative. This is to obtain a pattern (FIG. 4). However, in the conventional silylation process, not only the exposed part but also the unexposed part is silylated, and therefore, the selectivity of the pattern is poor, and it has been difficult to put it to practical use.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned points, and the interaction between the exposed photosensitive substance and the polymer is achieved by performing the silylation treatment in a gaseous atmosphere of a basic substance. It is an object of the present invention to provide a method for forming a pattern by a silylation process in which the precision of silylation is improved by reducing the absorption of silicon compounds in the exposed area, and the processing time of the silylation is shortened.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to carry out a silylation treatment in a gaseous atmosphere of a basic substance.

(Function) When a photosensitive agent undergoes a decomposition reaction by light irradiation to generate a carboxylic acid, the carboxylic acid causes a hydrogen bond with a —OH group in the polymer, and this development is caused by absorption of a silicon compound into the polymer. Work in the direction that hinders. On the other hand, it is generally known that a carboxylic acid causes a decarboxylation reaction by a base substance. According to the present invention, by causing this decarboxylation reaction to occur at the same time as the silylation treatment, the absorption of the silicon compound into the polymer is promptly caused, and as a result, a pattern with a high selectivity can be formed in the exposed area.

(Example) Example 1 Hereinafter, the present invention will be described in detail using examples. 8 g of a novolak resin and 2 g of a photosensitive agent containing naphthoquinonediazide were dissolved in 23 g of ethyl cellosolve acetate to prepare a photosensitive resin. The silicon wafer was previously exposed to an atmosphere of hexamethyldisilazane for 120 seconds to perform surface modification for improving adhesiveness, and then the photosensitive resin was spin-coated on the silicon wafer at 3500 rpm and baked at 90 ° C. for 5 minutes. Was done. After exposing this wafer to g-rays from a mercury lamp, the wafer was placed in a chamber, the inside air was replaced with nitrogen, and the pressure was increased to 5 Torr.
Then, ammonia gas was injected into the reactor, and vapor of hexamethyldisilazane was injected to perform silylation treatment. Oxygen gas is introduced into the decompression vessel, high-frequency discharge is generated between the parallel plate electrodes to convert the oxygen gas into plasma, the sample is placed on the cathode side, and the wafer is subjected to oxygen reactive ion etching to form a 0.5 μm pattern. Accurately obtained.

Example 2 Using polyvinylphenol as a polymer, a photosensitizer containing naphthoquinonediazide was dissolved in ethyl cellosolve acetate, applied to a silicon wafer in the same manner as in Example 1, and exposed to imidazole in a nitrogen atmosphere. A silylation treatment was performed using a mixed gas of hexamethyldisilazane, and oxygen-reactive ion etching was performed on the silylation treatment, whereby a 0.5 μm pattern was obtained with high accuracy.

[Effects of the Invention] As described above, by performing the silylation treatment in a gas atmosphere of a basic substance, it is possible to form a pattern with high accuracy in a short time.

[Brief description of the drawings]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are process diagrams of a conventional Si process. 1 ...... substrate, 2 ...... photosensitive resin, 3 ...... mask, 4 ...... ultraviolet, 5 ...... exposed areas, 6 ...... silylated zone, 7 ...... SiO ₂ region

Claims (4)

(57) [Claims] 1. A step of applying a photosensitive resin layer containing a polymer mixed or combined with a photoactive substance to a substrate, and a step of applying radiation such as visible light, ultraviolet light, far ultraviolet light, X-ray, or electron beam.
A step of exposing with a charged particle beam such as an ion beam, a step of selectively absorbing a silicon compound in accordance with the amount of external exposure, and a step of anisotropically etching the photosensitive resin layer using oxygen plasma to form silicon having a predetermined value or less. In the step of selectively removing the concentration portion and obtaining a desired pattern, the step of absorbing the silicon compound is performed by exposing the base material to a gaseous atmosphere of a basic substance, and then exposing the base material to a gaseous atmosphere of the basic substance. A method of forming a pattern, wherein the pattern is formed by absorbing a silicon compound. 2. The pattern forming method according to claim 1, wherein said basic substance includes at least one of the above compounds, which are imidazole, dimethylamine, trimethylamine and derivatives thereof. 3. The pattern forming method according to claim 1, wherein said basic substance is ammonia. 4. The method according to claim 1, wherein the portion for selectively absorbing the silicon compound is a portion having a large exposure amount.
The pattern forming method described in the above.