JPH0778747A - Formation of pattern - Google Patents

Abstract

PURPOSE:To suppress an irregularity in the line width of a spectral line and to improve a dimensional controllability of a resist pattern. CONSTITUTION:1) When a resist film is adhered on a base, exposed and developed to form a resist pattern, the reflectivity of the base is adjusted in such a way that a difference between the maximum value and the minimum value of the minimum developable exposure (Eth) in the relational diagram between the Eth and the film thickness of the resist film is reduced. 2) The absorption coefficient of the resist film to exposure light is adjusted. 3) The adjustment in the 1) and the 2) are combined with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist pattern forming method in a semiconductor device manufacturing process or the like.

In recent years, semiconductor devices have become faster and more highly integrated, and accordingly, patterns have been miniaturized.
Therefore, it is required to stably form a fine pattern even on an uneven base.

[0003]

2. Description of the Related Art The determination of the resist film thickness in a conventional lithography process is performed by the Eth film in the relationship diagram between the minimum exposure amount (Eth) that can be exposed on a flat wafer and the resist film thickness shown in FIGS. A film thickness corresponding to a point called a mountain is selected. This film thickness is called the optimum film thickness,
Good pattern size controllability.

However, in the actual process, there is a portion where the base has unevenness and is not coated with the optimum film thickness obtained from the above relational diagram. For this reason, the pattern dimension control is not performed under the optimum conditions at present.

[0005]

In the conventional example, the dimensional controllability after patterning could not be optimized, and there was a problem that the pattern dimensions varied.

An object of the present invention is to suppress variations in line width and improve dimensional controllability of resist patterns.

[0007]

[Means for Solving the Problems] To solve the above problems, 1) the minimum developable exposure amount when a resist film is formed on a base, exposed and developed to form a resist pattern.
Pattern formation method that adjusts the reflectance of the underlayer so as to reduce the difference between the maximum value and the minimum value of Eth in the relationship diagram between (Eth) and resist film thickness, or 2) resist film on the underlayer Minimum exposure that can be developed when a resist pattern is formed by depositing, exposing and developing
(Eth) and the resist film thickness The pattern formation method that adjusts the absorptance of the resist with respect to exposure light so that the difference between the peak and valley values of Eth in the diagram is reduced, or 3) above 1) and above This is achieved by a pattern forming method that combines the adjustment of 2).

[0008]

FIG. 1 is a diagram for explaining the principle of the present invention. Figure 1 (A)
(C) is a relationship diagram of Eth-resist film thickness.
This is due to the case of lowering in the order of (A) → (C) or the case of increasing the absorption of the exposure light of the resist in the order of (A) → (C).

FIGS. 1D to 1F are diagrams showing the relationship between the pattern line width and the resist film thickness, and the line width variation decreases in the order of (D) → (F). Where (D) is (A), (E) is (B),
(F) corresponds to (C).

The present invention utilizes this result to adjust the reflectance of the base or the absorptance of the exposure light of the resist,
By making the peaks and valleys of Eth in the relationship diagram of Eth-resist film close to each other, it is possible to suppress variations in line width.

As is clear from the results shown in FIG. 1, the reason why the dimensional controllability of the pattern is improved as the difference between the peak a and the valley b of Eth becomes smaller will be described. When a resist having a low light absorptivity is selected on a base having a high reflectance, the Eth-resist film thickness relationship diagram shown in FIG. 6 is obtained. As described above, it is generally said that the optimum choice of the film thickness of the resist to be used is the film thickness corresponding to the point a (80 mJ), which is the peak of Eth, whereas the exposure dose showing the line width is , Usually expressed as Eth × K. Here, K is called the Eth coefficient. Now, assuming that K = 2 as a normally used value, the optimum exposure amount is 80 mJ × 2 = 160 mJ.

However, when forming a pattern on an actual device, the thickness of the resist film becomes uneven due to the unevenness of the base. At this time, there is a portion where the resist is thickly applied, and assuming that the film thickness at that time corresponds to the valley of Eth (b (60 mJ)), the Eth coefficient at that time is × 2.67.
(= 160mJ / 60mJ), which is too large for the exposure dose, and the line width becomes thinner in the case of positive resist. Therefore, by eliminating the difference between the peaks and valleys of Eth, the variation in line width can be suppressed.

[0013]

【Example】

Example (1): In order to adjust the reflectance of the underlayer, a film having different reflectance is grown. For example, titanium nitride (TiN) has a reflectance of -14%, Bare-Si of -23%, and Al of -50%. The relationship between Eth-resist film thickness for these three films is shown in Figure 2. 3,4.

2, 3 and 4 are explanatory views of the embodiment (1).
It is a figure which shows the background dependence of th. From the figure, it can be seen that the lower the reflectance is, the less the difference between Eth peak a and valley b is. Example (2): Generally, a resist is formed of a resin, a photosensitizer, a dye, an additive and the like. To adjust the light absorption of the resist, the constituent components of the resist are changed as follows.

A photosensitizer having a large absorptance for the light used is used. Adjust the amount of dye absorbed for the light used. FIG. 5 is an explanatory diagram of the embodiment (2), and is a diagram showing the dependence of the resist on the light absorption rate with respect to Eth.

In the figure, resist A is a resist without dye, resist B is a resist with dye, and resist B is
It can be seen that there is less difference between the mountain a and the valley b of Eth. It is possible to further reduce the difference by adjusting the type of dye and the amount added.

FIG. 6 is an explanatory view of the embodiment (3), which is an example in which a low reflectance of the base and a resist having an increased light absorptivity are combined. The white circles in the figure show the relationship between the Eth-resist film thickness for a Bare-Si substrate with a high underlayer reflectance, and the black circles show the Eth-resist film thickness for a substrate with a reduced underlayer reflectance (WSi film deposited on the surface). It is a relationship diagram. The resist used here is the resist B described above. By combining various resists with low reflectance and high light absorption of the base,
You can eliminate the difference between mountain a and valley b of Eth.

[0018]

According to the present invention, the variation in line width is suppressed and the dimensional controllability of the resist pattern is improved. As a result, it was possible to contribute to the miniaturization of the pattern of the semiconductor device.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is an explanatory diagram of Example 1 (1)

FIG. 3 is an explanatory diagram of Example 1 (2)

FIG. 4 is an explanatory diagram of Example 1 (3)

FIG. 5 is an explanatory diagram of the second embodiment.

FIG. 6 is an explanatory diagram of Example 3.

[Explanation of symbols]

 a Maximum value of predetermined resist film thickness b Minimum value of predetermined resist film thickness

Claims (3)

[Claims] 1. A resist film is deposited on a base, exposed,
When the resist pattern is formed by development, E in the relationship between the minimum developable exposure amount (Eth) and the resist film thickness
A pattern forming method characterized by adjusting the reflectance of the underlayer so as to reduce the difference between the maximum value and the minimum value of th. 2. A resist film is deposited on a base, exposed,
When the resist pattern is formed by development, E in the relationship between the minimum developable exposure amount (Eth) and the resist film thickness
A pattern forming method, which comprises adjusting the absorptance of the resist for exposure light so as to reduce the difference between the peak and valley values of th. 3. A pattern forming method, wherein the adjustments according to claim 1 and claim 2 are combined.