JPS6052026A - Formation of fine pattern - Google Patents

Abstract

PURPOSE:To form a fine pattern with high accuracy by shaping a polymer layer flattening a stepped section, an intermediate layer, which has ashing resistance better than the polymer layer and can see through the surface of a substrate, and a resist layer on the substrate coated with a thin-film is succession and etching them. CONSTITUTION:A conductor layer 3 is formed on a substrate 1, the surface thereof has stepped sections, through a sputtering method, etc., and a polymer layer 8 flattening the stepped sections is formed on the substrate. A substance, which is degenerated by the irradiation of shortwave ultraviolet rays and the speed of ashing thereof is increased, is used as a material for the polymer layer 8, an intermediate layer 9 consisting of SiO2, which has ashing resistance better than the polymer layer 8 and can see through the surface of the substrate, is shaped on the layer 8, and a mask pattern composed of a photo-resist layer 10 is formed. The resist layer 10 and the intermediate layer 9 are etched and windows are bored, shortwave ultraviolet rays are projected to the whole surface of the substrate, and the window sections are etched by reactive ions, thus forming a thin-film pattern.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a method for forming a fine pattern on a substrate with significant steps. - (b) Background of the technology The degree of integration of semiconductor devices such as ICs and LSIs is Semiconductor devices are getting smaller and larger, and as a result, electrode pattern widths and conductor pattern widths are also getting smaller. At the same time, due to the multilayer structure, the unevenness of the substrate is increasing, and the formation of semiconductor devices requires advanced technology. .

The present invention relates to an improvement in a method of forming a fine pattern on a substrate-F with a significant step difference.

(cl) Problems in the Prior Art Thin film formation technology and photolithography (+-) are used as methods for forming fine patterns made of conductors or insulators on substrates.

That is, a thin film made of metal, non-metal, insulating material, etc. is formed by vacuum evaporation, sputtering, etc., and then a photoresist is coated on top of the thin film, and a mask pattern is projected onto the thin film or contact exposure is performed to selectively expose the photoresist. It is exposed to light and causes a difference in its resolution with respect to the developer.

There are two types of photoresists: positive type, in which the light irradiated area becomes soluble in the present 1i1&N, and negative type, in which the light irradiated area becomes insoluble.Next, chemical etching or dry etching is applied to the areas partially opened by the development process. The thin film on the substrate is etched by etching, and the photoresist used as a mask is then dissolved and removed to form a fine pattern made of the thin film. In this example, the substrate 1 in this case is a substrate surface formed with a multilayer structure on a silicon (Sl) wafer.
), aluminum (hereinafter referred to as AA), and materials such as silicon dioxide (hereinafter referred to as SIN) are used as the insulating layer.
The thickness of the poly 81 layer should be 0.4 to 0.5 [μ] to reduce the conductor resistance and avoid the insulation layer.
m], the positions where these conductor patterns intersect have unevenness with significant steps.

Figure 1 shows a case where a conductor pattern 2 made of poly-Si or AZ is formed on a substrate 1 with various unevenness, and the figure shows a cross-sectional view, and (B) shows a plan view of the conductor pattern 2 after pattern formation. be. Now, as in the conventional method, a photoresist layer (positive type in this case) 4 is formed on the f-KWj 3 by the spin code method, and it is directly applied to the step part as shown in Figure (4). When forming a thin line pattern as shown in FIG. 7 will occur.

In other words, since the paddle 1 in this embodiment is a positive resist, the exposed area decomposes and becomes easily soluble in the developer, but in this exposure process, the resist 2 thick flat area 6 is used to prevent the development from remaining. The exposure is carried out under conditions such that the exposed area is sufficiently exposed.

However, under this condition, the photoresist layer 4 on the protruding portion 5 of the substrate is overexposed, and even the mask portion is partially exposed due to reflection from the substrate surface, resulting in the formation of a constriction 7 in the conductor pattern 2.

The constriction 7 is formed with a pattern width of 3 [μ] as in the conventional method.
This has little effect on conductor patterns with a pattern width of 1 [μm], but it will have a large effect on future fine patterns with pattern widths of 1 [μm]. A dry etching method that takes a three-layer structure has been proposed as a pattern forming method. Figures 2 (A) to (G) show a pattern forming method using this method. 3 is formed by a sputtering method or the like, and then a polymer layer 8 is formed thicker to eliminate unevenness caused by steps on the substrate.

Here, the polymer is used to eliminate the unevenness of the base mt, and it is not necessary to have photosensitivity, and any transparent polymer may be used.The reason for this is that it is advantageous in terms of mask alignment with the substrate 1. 0 In this example, the coating thickness of the polymer layer 8 was set at 2.5 to 3 [μm], but this means that even if there is a step difference of 0.5 to 1 (μm) due to unevenness on the substrate surface, The surface of the polymer layer 8 is planarized in the same figure (A).

Next, an intermediate layer 9 of approximately t
The same figure (Bl.

This intermediate layer 9 acts as a mask when performing ashing (ashing) processing, and the necessary conditions for this are that it be made of a material with low reflectance and that it be formed thinly to facilitate mask alignment. ET)Q In other words, in order to align the mask while the surface of the substrate 1 is visible, it is necessary to form the conductor layer 3 with a material that has a lower reflectance than the conductor layer 3, and it is necessary to use a material that is corrosion resistant during the ashing process that will be performed later. It has to be something. When the conductor layer 3 is made of polySt, the material that satisfies this condition is 51
If 02 is also made of Ai, 81 or 5ins is suitable as the material used for the intermediate layer 9.

Next, a mask made of a photoresist layer 10 is formed on this layer, and anisotropic dry etching such as Cl, reactive ion etching is applied to the intermediate layer 11j.
9 is etched, and the same figure 01 is further etched with polymer layer 8 and conductor layer 3.
．． ! (2) in the same figure in which a fine pattern is formed by selectively etching -. When using a dry etching method with a three-layer structure like this, anisotropic etching is used in which etching progresses in the vertical direction, so there is no constriction of the conductor pattern, but since the polymer layer 8 is thick, etching is difficult. 0(d), which takes time and tends to cause side etching.
OBJECTS OF THE INVENTION It is an object of the present invention to provide a pattern forming method that does not cause side etching of the pattern and has a high etching speed when forming a fine pattern on a substrate having a significant step difference.

(e) Structure of the Invention An object of the present invention is to provide a polymer layer that flattens the steps on a substrate coated with a thin film when forming a fine pattern made of a thin film on a substrate with steps on the surface, and a polymer layer that is more durable than the polymer layer. An intermediate layer and a resist layer, which have excellent ashing properties and can be seen through the substrate surface, are formed in 11 m order, and the resist layer and intermediate layer are selectively etched to remove the fine pattern forming area and a window is opened. This can be achieved by irradiating ultraviolet rays and then performing reactive ion etching to form a thin film pattern by etching the part to the thin film part. After etching the intermediate layer 9 shown in Fig. 2 (0), the entire surface of the substrate is irradiated with ultraviolet rays, using a material that changes in quality when exposed to short-wavelength ultraviolet irradiation and has a high ashing rate (ashing rate). By performing reactive ion etching, a highly accurate pattern can be formed with an extremely fast etching speed.

The inventor discovered that not only ordinary positive resists but also polymer layers such as polyimide can be treated with ultraviolet rays, especially short wavelength ultraviolet rays (Dee
p Ultra Violet Ray wavelength 220~3
It has been found that the ashing rate by active ion etching method increases significantly when irradiated with 00 (nm)).

In other words, similar to the case of positive resists, UV irradiation causes the desorption of radicals constituting the polymer, resulting in a change from a stable structure to an unstable structure. Ion etching is also called sputter etching, and the object to be etched is placed on a cathode that is connected to a 13.56 (MHz) high-frequency plate power supply on one side of parallel plate electrodes, and the material to be etched is placed in a gas plasma using a cathode drop voltage. Sputter etching is carried out by the impact of positive ions on the object to be etched on the cathode, and the present invention is characterized in that anisotropic etching progresses in a direction perpendicular to the electrode surface.The present invention will now be described with reference to Examples.

As polymer rf #8 in Figure 2, a commercially available positive resist (OFPR-800) was used with a thickness of 2.5 to 3 (/1rn).
) with a thickness of approximately 10 mm as the intermediate layer 9 provided thereon.
A layer of Sin of 00IAl is formed, and a mask pattern consisting of a photoresist layer 10 is formed on this to create a structure shown in FIG. The structure shown is the same as the conventional method up to 0. Next, the wavelength is 220 (nm) and the illuminance is 10 (mw/(m)
) After irradiating the polymer layer 8 with ultraviolet rays of 30 [seconds] to 1 [minute] alternately, reactive ion etching is performed using oxygen (zero bagasse) as a medium, and etching is performed to the state shown in Figure 2 (G). .

When dry etching a polymer using O and gas as a medium, the main chain of the polymer is made of carbon, so even stable polymers may be 0. In gas plasma, the main chain is easily broken and vaporized into carbon dioxide (COx) and water vapor (HtO), resulting in ashing.
However, the polymer irradiated with ultraviolet rays according to the present invention has an etching rate of 6 because the irradiated area is altered.
000-8000 (A/min) and the conventional 4000-50.
00 (A/min), and since the ultraviolet rays are irradiated perpendicularly to the substrate surface, the polymer layer 8 is altered by creating a clear boundary, so combined with the straightness of reactive ion etching, the polymer layer 8 Although the conductor pattern 3 is thick, it is formed with high accuracy.

(X) Effects of the Invention The present invention is capable of forming fine patterns in etching of 3J-structures, but etching takes time, and the accuracy tends to decrease due to the thick polymer layer.1 Implementation of the present invention ameliorates these drawbacks,
Fine patterns can now be formed with high precision◎

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the conventional fine pattern formation method, (4)
03) is a cross-sectional view, and Figure 2 (03) is a plan view of the fine pattern.
4) to (g) are cross-sectional views illustrating the steps of the etching method for a three-layer structure according to the present invention. , 8 is a polymer layer, and 9 is an intermediate layer. 11-

Claims (1)

[Claims] When forming a fine pattern made of a thin film on a substrate with steps on the surface, a polymer layer is used to flatten the steps on the substrate coated with an rfJi film, which has better ashes resistance than the polymer layer and allows the substrate surface to be seen through. The intermediate layer and resist layer are sequentially formed, and the resist layer and intermediate layer 1- are selectively etched to remove the fine pattern forming area and a window is opened.The entire surface of the base is irradiated with short wavelength ultraviolet rays, and then reactive ions are applied. A method for forming a fine pattern, characterized in that etching is performed (1), and a thin film pattern is formed by etching the window opening in a thin manner.