JPH0536584A - Mask alignment method - Google Patents

Abstract

PURPOSE:To perform a mask alignment and exposure operation a plurality of times by exposing an alignment mark in an element manufacturing process and to enhance its alignment accuracy in order to perform an alignment and photolithographic operation a plurality of times so as to correspond to a multilayer structure. CONSTITUTION:When a clad 7 is formed, a substrate-side alignment mark 2 is exposed by using a substrate-side alignment-mark cover 15 composed of Si or the like so that the clad 7 is not deposited on the substrate-side alignment mark 2. When a resist is coated for a second photolithographic operation, it is arranged that the substrate-side alignment mark 2 is not coated with the resist. Consequently, since the substrate-side alignment mark 2 is exposed in the second alignment and photolithographic operation, a mask alignment operation can be performed with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask alignment method (mask alignment) in photolithography technology.

[0002]

2. Description of the Related Art Electronic circuit elements and optical circuit elements are densified by patterning using photolithography.
Researches for high integration have been actively conducted. As shown in FIG. 3, among others, when patterning is performed on one substrate 1 with a plurality of masks, first, positioning of the alignment mark 2 for mask alignment on the substrate 1, FIG. Then, the alignment mark 4 of the second photomask 3 is superposed on the alignment mark 2 and FIG.
After that, the method of exposing FIG. 3C is used.

[0003]

When patterning with a plurality of masks in FIG. 3, patterning by exposure using the first photomask and first patterning by using the second photomask are performed. Although the alignment mark is not hidden during the patterning by the mask alignment exposure described in (1), in the case of stacking multiple layers of metal to form a higher-performance element as a pattern structure, The second alignment mark may be hidden by the next metal coating, making it impossible to perform the second alignment photolithography. For example, as in the glass waveguide formation process, after the first alignment mark is formed, the cladding film is coated on the alignment mark. Therefore, the alignment mark formed at the first time during the second photolithography May be hidden under the metal coating and cannot be aligned with the second alignment mark.

An object of the present invention is to eliminate the above-mentioned problems of the prior art and to enable alignment photolithography a plurality of times corresponding to a multi-layer structure, by exposing the alignment mark a plurality of times during the device manufacturing process. Another object of the present invention is to provide a mask aligning method that enables the mask aligning exposure described above and can improve the aligning accuracy.

[0005]

That is, the above object of the present invention is to provide a metal film on a first metal film on a first metal film when manufacturing a circuit in which a metal film is laminated in multiple layers on a substrate by using a photolithography technique. When a pattern with a substrate side alignment mark is formed on the substrate using the first mask and the next metal film is laminated on the pattern, the substrate side alignment mark is not covered with the metal film. After stacking the next metal film using the cover of the mark part, remove the mark cover, apply photoresist to a place other than the mark cover, and use the next mask to mark the substrate side alignment mark and the mark of the next mask. The mask alignment method is characterized in that the photolithography is performed in accordance with the above.

In the present invention, the "next" meaning of the next metal film and the next mask means the number of layers when a multilayer or laminated circuit is manufactured.

In the present invention, when the resist applied at the next photolithography is also applied on the exposed alignment mark on the substrate side, exposure is performed by using a negative target mask to align the substrate side. It is also possible to remove the resist on and near the mark.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustration of the present invention will be described in detail below with reference to an embodiment.

FIG. 2 is a plan view (A) of an optical switch element produced by using the combined photolithography technique of the present invention and an enlarged view (B) of its AA cross section. The optical waveguide 5 is
It is formed by a structure in which layers of silicon oxide having different refractive indexes are stacked on a flat substrate 1 of single crystal silicon,
A substantially rectangular core (refractive index nw) 6 through which light propagates, and a low-refractive-index clad (refractive index nc) 7, which covers the core from above and below,
8 and. The optical waveguide core 6 on the substrate has at least three linear paths 6a-6b and three paths 6a constituted by branch paths 6c arranged so as to be orthogonal thereto.
6b and 6c are provided, and these three branch paths are placed in a positional relationship in which the axes intersect as shown in FIG. 2 (A). Among these, the branch path 6a functions as a light incident portion on the optical waveguide core, and the remaining two branch paths 6b and 6c function as a light emitting portion. Here, the optical waveguide core (branch 6) of the incident light end 9 of light is used.
In contrast to a), the branch 6b of one exit light end 10 is on an extension of the branch 6a of the entrance light end 9, and the branch 6c of the other exit light end 11 is the branch 6a of the entrance light end 9. It is formed so as to be orthogonal to.

In the middle of the optical waveguide 5, there is one slit 13 for holding a liquid 12 (eg fluorenebenzene, cyclohexanol, etc.) having a refractive index substantially equal to that of the core 6.
About 45 ° to the optical path propagating in each core branch
The slit 13 cuts the intersecting portion of the optical waveguide.

A liquid 12 having a refractive index substantially equal to the refractive index of the core 6 of the optical waveguide 5 is filled in the groove of the slit 13, and the temperature controller 14 is provided just below the slit 13.
Is formed, and the temperature controller 14 is energized to heat the vicinity of the slit 13 to vaporize the liquid in the slit 13. As a result, the light propagating in the core 6 in the direction from the incident light end 9 to the outgoing light end 10 is reflected by the inner surface of the slit 13 because the liquid in the slit is heated and vaporized. Bent to core branch 6c,
Propagate to the outgoing light end 11. On the other hand, when the vicinity of the slit 13 is cooled by the temperature control unit 14, the vaporized liquid is condensed and becomes a liquid and returns to the inside of the slit, so that the light goes straight toward the outgoing light end 10 again. In this way, by performing the liquid injection and removal operations in the slit 13 by vaporizing and condensing the liquid by heating and cooling, high-speed switching operation can be realized.

When the switch element is manufactured, there are a step of forming the optical waveguide 5 (first photolithography) and a step of forming the slit 13 (second photolithography), and the inside of the optical waveguide 5 is in between. The step of forming the clad 7 for closing and closing the light is included. In the conventional method, since the substrate side alignment mark 2 is covered with the clad during the second alignment photolithography, it is difficult to perform highly accurate mask alignment.

However, in the method according to the present invention shown in FIG. 1, when the clad 7 is formed (step), the clad 7 is prevented from being deposited on the substrate side alignment mark 2 so that the clad 7 is not deposited.
The step of exposing the substrate-side alignment mark 2 by the substrate-side alignment mark cover 15 by i or the like, and the resist is not coated on the substrate-side alignment mark 2 during the resist application in the second photolithography. Therefore,
At the time of the second alignment photolithography, since the substrate side alignment mark 2 is exposed, highly accurate mask alignment becomes possible.

[0014]

As described above, according to the present invention, the following effects can be obtained.

(1) When a device having a multi-layer structure is formed by using the photolithography technique, mask alignment can be performed a plurality of times.

(2) In the second and subsequent alignment photolithography, the resist on the exposed alignment mark on the substrate side is removed to improve the visibility of the alignment mark and enable more accurate mask alignment.

(3) By the method of exposing the substrate side alignment mark, higher functionality and higher integration can be expected by multiplexing the elements.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of steps of a mask alignment method of the present invention.

FIG. 2 is a plan view (A) and an AA cross-sectional view (B) of an optical switch element manufactured by the mask alignment method of the present invention.

FIG. 3 is a plan view of a photomask and a mask alignment example of a conventional mask alignment method, positioning (A), mask overlay (B), and exposure (C).

[Explanation of symbols]

 1 substrate 2 substrate side alignment mark 3 next photomask 4 alignment mark 5 optical waveguide 6 6a, 6b, 6c core 7 clad 8 clad 9 incident light end 10 emission light end 12 liquid 13 slit 14 temperature control part 15 mask cover

Claims (1)

[Claims] 1. A pattern with a substrate side alignment mark using a first mask on a first metal film when manufacturing a circuit in which a metal film is laminated in multiple layers on a substrate using a photolithography technique. And when a next metal film is laminated on the pattern, after the next metal film is laminated by using the cover of the substrate side alignment mark part so that the substrate side alignment mark is not covered with the metal film. A mask characterized in that the mark cover is removed, a photoresist is applied to a place other than the mark cover, and the substrate side alignment mark and the mark of the next mask are aligned using the next mask to perform photolithography. Matching method.