JPH05313349A - Reticule for stepper - Google Patents

Abstract

PURPOSE:To enable transfer without generating out-of-focus even if there is a level difference exceeding the focal depth of a projecting lens on the surface of a semiconductor substrate. CONSTITUTION:The level difference (DELTAepsilon=MDELTAh; M is the reduction magnification of the projecting lens) is formed on the surface of the reticule 1 is formed according to the level difference (DELTAh) existing on the surface of the semiconductor substrate 3 and pattern 2 of the projecting surface and recessed surface of the reticule 1 are formed according to the area of the projecting surface and recessed surface of the semiconductor substrate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reticle for a reduction projection exposure apparatus, and more particularly to a reticle for a reduction projection exposure apparatus that transfers a pattern onto a semiconductor substrate having a step on a projected surface.

[0002]

2. Description of the Related Art A conventional reticle for a reduction projection exposure apparatus has a pattern formed on its surface, and the pattern is reduced to 1/5 or 1/10 by a projection lens and transferred onto a semiconductor substrate. Focusing of the pattern at this time was performed according to the surface of the semiconductor substrate. However, as the integration of semiconductor integrated circuits has progressed in recent years, steps such as transfer, etching, and film formation have been repeated, and the depth of focus of the projection lens has been exceeded on the surface of the semiconductor substrate by repeating these steps. In this way, when there is a step on the semiconductor substrate, even if focusing is performed on one surface, the other surface is out of focus. This tendency became more strongly influenced as the NA of the projection lens was improved.

4A to 4C are cross-sectional views of a semiconductor substrate showing the order of steps for explaining a method of flattening. Conventionally, for a semiconductor substrate having such a step, a method of eliminating the step and flattening has been conventionally adopted. The method is
For example, the photoresist itself is used, or, as shown in FIGS. 4A and 4B, the semiconductor substrate 9 in a portion where a large step is formed in a later step is dug down,
As shown in FIG. 4C, as the process progresses, the dug-down substrate is filled with the pattern film 10, and finally, as shown in FIG. 4A, the surface is flattened with the insulating film 11. The method of eliminating the step was adopted.

On the other hand, on the exposure apparatus side, for the purpose of alleviating the focus shift of each step, a method of transferring the focused focus position by vertically oscillating and transferring is applied.

[0005]

In the above-described method of planarizing a semiconductor substrate, the semiconductor substrate itself is dug into a considerable amount, and the processes such as pattern film formation and insulating film formation become complicated, and the semiconductor formed on the semiconductor substrate is complicated. The performance of the device may be adversely affected. Further, in the latter measure against the exposure apparatus side, since the focus is vibrated up and down, the controllability of dimensions is poor.

An object of the present invention is to provide a reduction projection exposure apparatus capable of transferring a focused pattern to a semiconductor substrate without performing special processing or special control on the apparatus even if the semiconductor substrate has a step. To provide a reticle.

[0007]

In a first reticle for a reduction projection exposure apparatus of the present invention, a step is formed on a surface of a transparent substrate in accordance with a step of a semiconductor substrate on which a pattern is reduced and transferred by a projection lens. At the same time, the pattern is formed in an uneven area of the transparent substrate corresponding to the uneven surface of the semiconductor substrate. The second reduction projection exposure apparatus reticle is characterized in that a transparent film having a refractive index similar to that of the transparent substrate is applied to the concave surface of the transparent substrate to planarize it.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a reticle and a semiconductor substrate for explaining an embodiment of a reticle for a reduction projection exposure apparatus of the present invention. As shown in FIG. 1, the optical system in the reduction projection exposure apparatus has a reticle 1 with a projection lens interposed therebetween.
And the semiconductor substrate 3 are arranged on the same optical axis. If the projection lens is considered as a thin single lens, the distance between the principal surface 6 of the projection lens and the reticle is the distance obtained by multiplying the distance between the principal surface 6 of the projection lens and the semiconductor substrate 3 by the reduction ratio.

The present invention focuses on this point and forms the step Δε of the reticle 1 in accordance with the step Δh of the semiconductor substrate 3. The step Δε of the reticle 1 is Δε = MΔh, where M is the reduction ratio as described above. For example, the step difference of the semiconductor substrate is 1 μm, and the reduction ratio is 5
If it is twice, it is sufficient if there is a step of 5 μm on the reticle 1.

FIG. 2 is a cross-sectional view of the reticle for explaining the method of manufacturing the reticle of FIG. Next, a method of manufacturing a reticle having a step will be described. First, as shown in FIG. 2A, the pattern 2a of the convex region of the semiconductor substrate is formed on the transparent substrate 1a. Next, as shown in FIG. 2B, the region where the pattern 2a is formed is covered with the mask 4. Then, as shown in FIG. 2C, a desired thickness is removed by a method such as etching. Next, a pattern 2b corresponding to the concave region of the semiconductor substrate is formed in the formed concave portion 4a.
To form. Although not shown in the drawing, the pattern may be formed on the entire surface after the unevenness is previously formed on the transparent substrate according to the unevenness of the semiconductor substrate.

FIG. 3 is a sectional view showing another embodiment of the reticle for a reduction projection exposure apparatus of the present invention. This reticle is
As shown in FIG. 3, the transparent film 8 having the same refractive index of the transparent substrate 1a is provided between the pattern 2b corresponding to the convex region and the pattern 2b corresponding to the concave region of the semiconductor substrate.

As a result, there is an advantage that the pattern distortion due to the diffraction of light at the step portion is eliminated as compared with the reticle in the above-mentioned embodiment. Also, since the step on the reticle surface is only the step of non-translucent material such as chromium,
When performing particle check on the surface of the reticle with a laser beam, there is an advantage that it is easier to identify dust and patterns as compared with the first implementation. On the other hand, in this reticle manufacturing method, the pattern 2b corresponding to the convex region of the semiconductor substrate is formed on the transparent substrate 1a, and then the transparent film 8 having the refractive index of the transparent substrate is formed by a method such as CVD.
Then, a pattern 2a corresponding to the recessed area of the semiconductor substrate is formed on the transparent film 8.

[0014]

As described above, according to the present invention, the surface on which the pattern of the reticle surface is formed according to the step of the semiconductor substrate surface is formed to have the step according to the step of the semiconductor substrate surface. Even if there is a step on the semiconductor substrate, the focus can be achieved within the depth of focus of the projection lens, so that the in-focus pattern can be transferred.

[Brief description of drawings]

FIG. 1 is a sectional view showing a reticle and a semiconductor substrate for explaining an embodiment of a reticle for a reduction projection exposure apparatus of the present invention.

2A to 2D are cross-sectional views showing a method of manufacturing the reticle shown in FIG. 1 in order of steps.

FIG. 3 is a cross-sectional view of a reticle for illustrating a reticle for a reduction projection exposure apparatus according to another embodiment of the present invention, which is shown in the order of steps.

FIG. 4 is a cross-sectional view showing the order of steps for explaining a planarizing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 reticle 1a transparent substrate 2, 2a, 2b pattern 3 semiconductor substrate 4 mask 4a concave portion 5a convex portion 6 main surface of projection lens 8 transparent film

Claims (2)

[Claims] 1. A step is formed on a surface of a transparent substrate according to a step of a semiconductor substrate on which a pattern is reduced and transferred by a projection lens, and an uneven area of the transparent substrate corresponding to an uneven surface of the semiconductor substrate is formed. A reticle for a reduction projection exposure apparatus, wherein the pattern is formed. 2. The reticle for a reduction projection exposure apparatus according to claim 1, wherein a transparent film having a refractive index similar to that of the transparent substrate is deposited on the concave surface of the transparent substrate to planarize it. ..