JPH01258420A - Protection of mark - Google Patents

Abstract

PURPOSE:To form a pattern with high precision by a method wherein the first radiation sensitive resin layer is formed on the part excluding an alignment mark part on a substrate and then the second radiation sensitive resin layer is formed on the mark part to equalize the thickness of resist film. CONSTITUTION:A recessed mark 12 is formed on a substrate 1 by etching process and then an oxide film 13 is formed on the substrate 11. The oxide film 13 is coated with a positive type resist film 14 to form a removed part 14A of the resist film 14. The mark 12 is irradiated with electron beams and a mark detecting signal is transmitted to make an alignment of the substrate 11 and then the first film 14 is selectively removed to form another removed part 14B. The resist film 14 is coated with a negative type resist 15 in an inverse soluble development characteristics and then the resist film 15 excluding the part 14A is removed by far ultraviolet ray exposure process to leave the negative type resist film 15 only on the part of the mark 12. The oxide film 13 is selectively removed to form a circuit pattern. Through these procedures, a pattern with high precision can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for protecting marks for forming highly accurate patterns in charged beam, particularly electron beam, exposure.

Conventional technology Generally, in electron beam exposure technology for manufacturing integrated circuits etc. on a substrate, the position of the electron beam itself relative to the substrate is detected by the irradiated electron beam, and the electron beam or the substrate is aligned at a predetermined position. In order to do this, marks for detecting the exposure position are provided on the substrate surface. Usually, this mark for detecting the exposure position (hereinafter referred to as mark) is manufactured by forming a concave or convex step on the surface of the substrate. The planar shape of the mark is often L-shaped or cross-shaped.

FIG. 2 shows a pattern forming method when manufacturing an integrated circuit using electron beam exposure technology.

First, in FIG. 2(a), a concave mark 2 is formed on the substrate l.
is formed by etching, and then a thin film is formed on the entire surface of the substrate 1.
For example, a silicon oxide film (hereinafter referred to as an oxide film) 3 is formed, and a radiation-sensitive resin layer (hereinafter referred to as a resist film) 4 is formed on this oxide film 3.

In FIG. 2 (1)), after forming the resist film 4,
The drawing position of the electronic circuit pattern is determined by irradiating the mark 2 with an electron beam (not shown), and the resist film 4 is selectively formed by exposing the resist film 4 to a desired circuit pattern and developing it. Remove. Note that since the part of the mark 2 is irradiated with the electron beam, the resist film 4 in this part is removed by development.

Next, in FIG. 2C, the oxide film 3 is selectively removed using the resist film 4 as a mask to form a circuit pattern. Thereafter, an integrated circuit is manufactured by repeating the same pattern forming method.

In addition, in FIG. 2(b), 4A and 4B indicate the removed portions of the resist film 4 corresponding to the mark 2 portion and the circuit pattern portion, and in FIG. 2(c), 3A and 3B
indicates the removed portion of the oxide film 3 corresponding to the mark 2 portion and the circuit pattern portion.

Problems to be Solved by the Invention However, as shown in FIG. 2, in the pattern forming method with the conventional structure, the top of the mark 2 remains covered with the resist film 4, making it difficult to detect the mark 2. Therefore, if the resist film 4 is thin, mark detection is possible, but it will not be able to withstand the subsequent etching of the oxide film 3, and conversely, if the resist film 4 is thick, the marks from the marks 2 will be detected. As the amount of electrons decreases, the detection signal weakens, leading to problems such as a decrease in mark positioning accuracy or the inability to perform one positioning.

In FIG. 3, the horizontal axis is H, which indicates (step difference in mark 2 - film thickness of resist 4), and the vertical axis is R, which indicates the rate at which the position detection signal meets the prescribed detection conditions, that is, the mark detection rate.
This shows the relationship between the two. As is clear from FIG. 3, as H increases, R increases. Therefore, in order to ensure R above a certain value and to increase the thickness of the resist film 4, the step of the mark 2 must be made very large. It won't happen. Furthermore, if the step difference in the mark 2 is increased, the unevenness of the substrate 1 becomes severe, the non-uniformity of the resist film 4 increases, and the pattern accuracy decreases.

The present invention solves the above-mentioned problems by eliminating the need for large step differences in marks, achieving high mark positioning accuracy in charged beam, especially electron beam exposure, and providing a resist film with a thickness that is sufficient to withstand etching in subsequent processes. The purpose of this invention is to provide a mark protection method that protects marks by ensuring that

Means for Solving the Problems In order to solve the above problems, the present invention includes a step of forming a first radiation-sensitive resin layer on a portion of the substrate surface other than the alignment mark portion, and selectively using a charged beam. The method further includes a step of removing the first radiation-sensitive resin layer, and a step of forming a second radiation-sensitive resin layer on the mark portion.

Further, in the present invention, resins exhibiting mutually opposite dissolution and development characteristics with respect to radiation are used as the first radiation-sensitive resin layer and the second radiation-sensitive resin layer.

Furthermore, the first and second radiation-sensitive resin layers are exposed using radiation other than a charged beam.

Effect If the above configuration is used, since the first radiation-sensitive resin layer (resist film) is not present in the mark portion, mark detection can be performed regardless of the film thickness, no matter how thick the first resist film is. In addition, in the etching process using the first resist film as a mask, the mark portion is covered by the second resist film, making it possible to prevent mark deformation due to etching and ensuring a good mark detection signal even if pattern formation is repeated. can.

Furthermore, by using a combination of the first resist film and the second resist film that exhibit opposite dissolution characteristics to each other in the exposure and development process, when the mark portion is processed, the same resist film is used when exposed using a charged beam. pattern data,
When performing light exposure using ultraviolet rays, far ultraviolet rays, X-rays, etc., the same photomask can be used.

In addition, when exposing the mark part, the detection accuracy of the substrate position may be low, so there is no need to expose using a charged beam, and light exposure by batch transfer is sufficient, and batch transfer is used to process the mark part. , without significantly reducing substrate processing speed.

Example An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows a process diagram for forming a pattern using a single layer resist using the mark protection method of the present invention.

First, in FIG. 1(a), a concave mark 12 is formed on a substrate 1 by etching, and a thin film, such as an oxide film 13, is formed on the substrate 11 to a thickness of 1 μm. A positive resist film 14 is formed on this oxide film 13. For example, AZ 2400 manufactured by Shipley Co., Ltd. is applied to a thickness of 1.5 μm, and then the resist film at the mark 12 portion is removed by a normal light exposure method to form the removed portion 14A of the positive resist film 14.

Next, in FIG. 1(b), the mark 12 is irradiated with an electron beam to obtain a mark detection signal, and the substrate 11 is positioned.
Thereafter, the electronic circuit pattern is exposed and developed to selectively remove the positive resist film 14 to form a removed portion 14B.

Next, in FIG. 1(C), a negative resist film 15 having dissolution and development characteristics opposite to that of the positive resist film 14 is placed on the substrate 11. Coat with a thickness of 1.5 μm.

Thereafter, the negative resist film 15 other than the removed portion 14A is removed by deep ultraviolet exposure, leaving the negative resist film 15 only at the mark 12 portion.

Next, in FIG. 1(d), the resist films 14 and 15
Using this as a mask, the oxide film 13 is selectively removed to form one circuit pattern. 13A indicates a location where the oxide film 13 has been removed.

In this way, when the mark 12 is irradiated with an electron beam for positioning in FIG. The uniformity of the resist film thickness is improved, and a highly accurate pattern can be formed.

Further, when the oxide film 13 is etched as shown in FIG. 1(d), since the mark 2 portion is covered with the negative resist film 15, deformation of the mark 12 can be prevented. Furthermore, since the resist films 14 and 15 are made of positive-type and negative-type resins having opposite dissolution and development characteristics, the same photomask can be used for exposing the marks 12.

Furthermore, in the exposure of the mark 12 in FIG. 1(a), the detection accuracy of the position of the substrate 11 may be low;
There is no need to use a charged beam, a light exposure method can be used, and a significant decrease in the processing speed of the substrate 11 can be avoided.

In this example, an example was shown in which pattern formation was performed using a single layer resist, but even when pattern formation is performed using a multilayer resist, the same structure can be achieved by replacing the positive resist film with a multilayer resist film. The present invention can be applied.

In addition, when the positive resist film 14 and the negative resist film 15 are mixed, the surface of the positive resist film 14 is treated with Freon plasma or a water-soluble organic film such as % previnyl alcohol is formed and mixed. By forming a film that prevents the formation of a mixed layer, it is possible to prevent the formation of a mixed layer.

Effects of the Invention As described above, according to the present invention, when the mark portion is irradiated with a charged beam for positioning, there is no radiation-sensitive resin layer (resist film), so there is no need to increase the step of the mark, and the resist film This improves the uniformity of the thickness and enables the formation of highly accurate patterns. Further, when the mark portion is etched using the first resist film as a mask, it is covered by the second resist film, so that damage to the mark is prevented and pattern formation can be repeated with high accuracy. Also, since the same mark can be used repeatedly,
There is no need to form a large number of marks, and a decrease in the utilization rate of the substrate can be prevented.

Furthermore, by using resins that exhibit opposite dissolving and developing characteristics for the first and second resist films, when processing the mark portion, when exposing using a charged beam, the same pattern data can be applied to ultraviolet rays, The same photomask can be used when performing light exposure using deep ultraviolet rays, X-rays, etc. Further, since the detection accuracy of the substrate may be low when exposing the mark portion, a light exposure method can be used without the need for exposure using a charged beam, and a significant decrease in substrate processing speed can be avoided.

[Brief explanation of the drawing]

FIGS. 1(a) to (d) are process diagrams sequentially showing a pattern forming method using the mark protection method of the present invention, and FIGS. 2(a) to (d) are
c) is a process diagram showing the conventional pattern forming method in order;
The figure is a characteristic diagram showing the relationship between (mark step difference - resist film thickness) and mark detection rate. DESCRIPTION OF SYMBOLS 11...Substrate, 12...Mark, 13...Oxide film, 14...Positive resist film (first radiation sensitive resin layer), 15...Negative resist film (second radiation sensitive resin layer) radiation-sensitive resin layer).

Claims (1)

[Claims] 1. A step of forming a first radiation-sensitive resin layer on a portion of the substrate surface other than the alignment mark portion, and selectively applying the first radiation-sensitive resin layer using a charged beam. A method for protecting a mark, comprising the steps of removing a layer and forming a second radiation-sensitive resin layer on the mark portion. 2. The mark protection method according to claim 1, wherein the first radiation-sensitive resin layer and the second radiation-sensitive resin layer are resins that exhibit mutually opposite dissolution and development characteristics with respect to radiation. 3. The mark protection method according to claim 1, wherein the first and second radiation-sensitive resin layers are exposed using radiation other than a charged beam.