JPH05315213A - Formation method of pattern by exposure and transfer - Google Patents

Abstract

PURPOSE:To provide a method wherein an exposure amount user to transfer a pattern truely can be decided and confirmed when the pattern is formed by using a photolithographic technique. CONSTITUTION:A photoresist film is formed on a substrate on which a pattern is to be formed; an optimum exposure amount used to transfer the pattern truely is decided on the basis of the residual-film characteristic of an exposed part. Consequently, when the light sensitivity of the photoresist is confirmed in this manner, a fluctuation in the light sensitivity can be grasped accurately and it is possible to obtain a transferred pattern which is truer to a size than that in conventional methods in which an optimum exposure amount is decided by means of the size of a transferred pattern. In addition, since an operation to confirm the residual film in the exposed part of the photoresist is very simple, the optimum exposure amount can be decided and confirmed with good efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern transfer method using a photolithography technique which is implemented in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, for example, pattern formation is carried out using photolithography to form transistor elements, wirings and the like. In this photolithography technique, one semiconductor substrate surface is coated with a photosensitizer called a photoresist, and this photoresist is selectively exposed to ultraviolet rays or X-rays through an exposure mask having a predetermined pattern. This is a technique of developing and transferring the pattern of the exposure mask onto the surface of the semiconductor substrate.

For example, in an integrated circuit or the like, it is required to faithfully transfer the pattern of the exposure mask onto the surface of the semiconductor substrate. If the dimensions of the pattern of the exposure mask are not faithfully transferred, a fatal defect may occur in the integrated circuit. Therefore, in the transfer formation of the pattern of this exposure mask, sufficient care must be taken to control the pattern size, and for this reason the amount of exposure such as ultraviolet rays and X-rays for controlling the pattern size must be set. It becomes important.

This exposure amount is optimized and set in advance so that it is transferred in a dimension faithful to the pattern of the exposure mask. In reality, however, the amount of the photoresist applied on the semiconductor substrate is set. Due to the influence of various factors such as variations in coating film thickness, variations in illuminance of the light source used for exposure, and variations in temperature and humidity in the clean room where the pattern is formed, dimensions that are faithful to the pattern of the exposure mask It is difficult to maintain the optimum exposure amount for transfer as a constant set value.

Therefore, when the photoresist is applied to one semiconductor substrate to be exposed, the photoresist is applied to another substrate of the same type at the same time, immediately before the exposure process of the photoresist applied to the one semiconductor substrate. Then, the photoresist coated on the other substrate of the same type is exposed and further developed to transfer and form a predetermined exposure mask pattern.

The size of the pattern formed through the above process is used as a monitor to find the optimum exposure amount for transferring with a size faithful to the pattern of the exposure mask.

The exposure method for finding the optimum exposure amount is to transfer the photoresist coated on the another substrate serving as a monitor through a predetermined exposure mask in advance with a dimension faithful to the pattern of the exposure mask. The exposure amount is distributed to the front and back with the optimized exposure amount for performing the exposure. Then, the photoresist applied on the substrate is developed, and the dimension of the obtained photoresist pattern is measured for each exposure amount distributed and exposed, and the exposure transferred with the most faithful dimension to the pattern of the exposure mask. Find the amount.

By exposing the photoresist applied on one semiconductor substrate in accordance with the exposure amount thus obtained, the pattern can be transferred and formed with a dimension faithful to the pattern of the exposure mask, and it can be formed in an integrated circuit or the like. No fatal defects will occur.

[0009]

However, in the above-mentioned method, since the size of the pattern formed by the photoresist is used to find the exposure amount capable of transferring the pattern with a size faithful to the pattern of the exposure mask, High precision is required for the measuring device and the measuring method for measuring the dimensions of. For example, depending on the measuring device, there is a device that cannot measure the pattern dimension with high accuracy, and there is a possibility that an incorrect exposure amount may be set depending on the dimension obtained by the measuring instrument.

Further, in recent years, an electron scanning microscope is often used in order to measure a pattern dimension with high accuracy.
It takes a long time to measure the dimension of the pattern by using the electron scanning microscope, and when it is used in a mass production plant or the like, it is very problematic in terms of production operability.

[0011]

SUMMARY OF THE INVENTION The present invention is for the purpose of obtaining a dimension faithful to the pattern of an exposure mask as in the prior art.
The optimum exposure dose is not found by dimensional measurement, but the photosensitivity of the photoresist, that is, the optimum exposure dose is found by finding the minimum exposure dose at which the photoresist in the portion exposed by ultraviolet rays or X-rays is opened after development. Then, the pattern is transferred and formed on the semiconductor substrate with a dimension faithful to the pattern of the exposure mask.

Generally, the optimum exposure amount (a) for transferring with a dimension faithful to the pattern of the exposure mask is the photosensitivity of the above-mentioned photoresist, that is, the portion exposed by ultraviolet rays or X-rays is developed. It is said to be an amount obtained by multiplying the minimum exposure amount (b) opened later by a constant (c). The constant (c) at this time is different depending on the type of photoresist, the difference in reflectance of the substrate surface, and the like, but if the same photoresist and the same substrate are used, the portion exposed by ultraviolet rays or X-rays will not be developed after development. It is invariable even if the value of the minimum exposure amount (b) to be opened fluctuates.

Therefore, the constant (c) is the optimum exposure amount (a).
Is divided by the minimum exposure dose (b) that the photoresist is opened. The present invention utilizes this principle.

[0014]

According to the structure of the present invention, variations in the coating film thickness of the photoresist that hinders keeping a constant optimum exposure amount for transferring with a dimension faithful to the pattern of the exposure mask, and of the light source used for exposure The effects of various factors such as variations in illuminance, fluctuations in temperature and humidity in the clean room where the pattern is formed, and the photosensitivity of the photoresist described above, that is, the portions exposed by ultraviolet rays or X-rays are opened after development. This can be grasped by managing only the minimum exposure amount (b), and the optimum exposure amount (a) for transferring with a dimension faithful to the pattern of the exposure mask can be easily found.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described. However, the present invention is applicable only to a positive photoresist in which an exposed portion is dissolved by a developing process.

First, the exposure amount transferred with a dimension faithful to the pattern of the exposure mask is optimized in advance, and the optimum exposure amount (a) obtained by dimension measurement when setting is performed.
Then, it is necessary to find the minimum exposure amount (b) which is opened after the photoresist development of the exposed portion, and to find the constant (c) from the above formula.

Then, as in the method described in the prior art, when a photoresist is applied on one semiconductor substrate to be exposed, the photoresist is simultaneously applied on another substrate of the same kind and applied on the one semiconductor substrate. Immediately before the exposure process of the formed photoresist, the photoresist coated on the other substrate of the same type is exposed.

The exposure method at this time is that the photoresist in the exposed portion becomes unopened after development through a predetermined exposure mask, and the photoresist in the exposed portion is more exposed than the exposure amount in which the photoresist film is slightly left. Exposure is performed by dividing the exposure amount into several conditions at equal intervals until the exposure amount is completely opened after development. Then, the minimum exposure amount (b) at which the residual film of the photoresist is completely eliminated is found from the exposure amounts distributed under several conditions after the development processing. Since the positive photoresist contains a dye, the residual resist film can be easily confirmed by observation with an optical microscope.

Then, by multiplying the obtained exposure dose (b) by a constant (c), the exposure dose (a) transferred with the most faithful dimension to the pattern of the exposure mask is found.
By exposing the thus obtained exposure amount as the exposure setting amount of the photoresist applied on one semiconductor substrate, it is possible to transfer and form a pattern with a dimension faithful to the pattern of the exposure mask.

Further, when the reduction projection exposure apparatus is used, it is possible to grasp the variation in the upper surface of the substrate by performing a plurality of exposures on the surface of another substrate to be the monitor, and to consider the variation. Then, the exposure amount can be set by averaging. According to this method, the dimensional control of the transferred pattern can be made more precise.

[0021]

As described above, according to the method of the present invention,
The pattern can be easily transferred and formed in a dimension that is faithful to the pattern of the predetermined exposure mask, and the precision of the transfer pattern dimension control is higher than that of the conventional method for confirming the optimum exposure dose. Can be achieved.

Further, in recent years, a development end point detection system for photoresist and the like utilizing the above-described principle has been developed and studied, but the present invention achieves the same object without requiring the above system.

Claims (1)

[Claims] 1. A step of applying a photoresist on the surface of another substrate of the same type as that of one substrate, and exposing the photoresist applied on the surface of another substrate of the same type with several types of exposure doses, A step of developing, a step of finding an optimum exposure amount by the residual film in the exposed portion of the photoresist, exposing the photoresist coated on the surface of the one substrate with the optimum exposure amount, and developing. Pattern formation method.