JPH04348018A - Alignment optical device - Google Patents

Abstract

PURPOSE:To provide an alignment device which enables incidence of light flux for alignment to a specified position of each grating mark at a specified angle even if the grating mark of a reticle and a wafer is displaced and enables precision alignment of the reticle and the wafer. CONSTITUTION:A device is provided with first alignment marks 6, 6' of a first substrate 8 and second alignment marks 12, 12' of a second substrate 10. An alignment optical device whereby a projection part of alignment optical source parts 26, 30, 33 which projects alignment light flux is supported to be displaced in radiation direction and rotation direction around a fixed position regarding an alignment optical device for positioning a relative position through an object lens 2 of the first substrate 8 and the second substrate 10 by using alignment light flux injected to the alignment marks.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a device for aligning two marks, and in particular for aligning marks provided on a mask used for pattern transfer and a wafer for alignment adjustment, etc. The present invention relates to an alignment device suitable for.

0002

2. Description of the Related Art In recent years, with the miniaturization of circuit patterns of semiconductor devices such as LSIs, optical projection exposure apparatuses having high resolution performance have been widely used as pattern transfer means. When performing transfer using this device, the mask and wafer are aligned with high precision prior to exposure.
There is a need to.

[0003] As a method for performing alignment, an optical system other than the projection optical system (off-axis microscope) is used.
The wafer is positioned by detecting marks formed in advance on the wafer, and then the wafer is moved with high precision to a predetermined position within the field of view of the projection optical system, and the position relative to the mask that has been precisely positioned in advance is determined. Perform alignment off-axis
TTL (Through TTL), which detects alignment marks pre-formed on both the mask and wafer through a projection optical system and directly aligns the mask and wafer.
There is a he Lens method.

The off-axis method has the advantage of requiring less time for alignment and high throughput (processing speed) because the number of alignments is small. However, it is necessary to move the aligned wafer a precise distance to the position where it should be transferred, and an additional absolute length measurement system must be installed, increasing the number of error factors. difficult to do. Under these circumstances, recently, in order to achieve more precise alignment, methods such as the TTL method, which detect marks provided on the mask and wafer through a projection optical system and perform direct alignment, are considered to be better. It recognized.

[0005] As one of the TTL alignment methods, there is a method of overlapping two grating marks (
Literature G. Dubroeucq. 1980, ME,
W. R Trutna. Jr. 1984, SPIE, etc.). As shown in FIG. 2, a one-dimensional grating mark 101 is provided on a reticle 111 which is an original mask for a transfer pattern, and a two-dimensional grating mark 102 is provided on a wafer 112. A laser beam from an alignment light source 104 illuminates a grating mark 101 on a reticle 111 through a mirror 113, and the transmitted diffracted light of the grating mark 101 is guided to a grating mark 102 on a wafer 112 through a projection lens 103. grating mark 102
The reflected and diffracted light passes through the projection lens 103 again, is transmitted and diffracted again by the grating mark 101 on the reticle 111, and is transmitted through the half mirror 106 to the photoelectric detector 10.
Enter 5. Alignment light source 104 and mirror 113 are attached to base 115. Then, by measuring the intensity of the diffracted light incident on the photoelectric detector 105, the relative position between the reticle 111 and the wafer 112 is detected.

According to this method, the intensity of the diffracted light reaches its maximum where the two grating marks 101 and 102 overlap, so by performing signal processing to detect the maximum, the reticle 111 and wafer 112 can be detected with high precision. Alignment is possible.

By the way, the positions of the grating marks 101 and 102 on the reticle 111 are not constant, but vary depending on the size, number, shape, etc. of the circuit patterns formed on the reticle 111. As shown in FIG. 2, when grating marks 101 and 102 are displaced to grating marks 101' and 102', the alignment laser beam emitted from alignment light source 104 must also be displaced so that it enters grating mark 101'. It won't happen.

[0008]

[Problem to be Solved by the Invention] When the grating mark 101 is displaced to a grating mark 101' located a distance d apart along the axis X as shown in FIG. 2, the direction of displacement of the grating mark and It is difficult to completely match the moving direction of the laser beam, and there is a high possibility that the laser beam will be displaced along the axis X1 which is inclined by ΔΘ with respect to the axis X. The laser beam is transmitted at a distance d (1-cos
ΔΘ) position shift, distance in Y-axis direction (d×sin
ΔΘ), and therefore highly accurate positioning cannot be performed. In order to eliminate this drawback, it is possible to actually measure the distance of the positional deviation and correct the position of the mirror 113', but the configuration for performing such control is complicated and imposes a heavy burden on the system, which is not preferable.

The present invention was developed in view of the above-mentioned problems of conventional alignment devices, and it is possible to direct the alignment light beam to the predetermined position of each grating mark even if the grating marks on the reticle and wafer are displaced. It is easy to make the beam enter at a predetermined angle, and the reticle and wafer can be aligned with high precision.
Moreover, it is an object of the present invention to provide a positioning device having a simple device configuration.

0010

[Means for Solving the Problems] The present invention uses a first alignment mark on a first substrate, a second alignment mark on a second substrate, and an alignment light beam incident on these alignment marks. In the alignment optical device for positioning the relative positions of the first substrate and the second substrate through an objective lens, the emission part of the alignment light source unit that emits the alignment light beam rotates in a radial direction and rotates about a certain position. This is an alignment optical device characterized in that it is supported so as to be displaceable in a direction.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A positioning apparatus according to an embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the positioning device includes a condenser lens 4 and a reticle 8 provided with a transmission grating mark 6 arranged above the optical axis O of the objective lens 2. Below the objective lens 2, a wafer 14 is placed on a wafer table 10 and provided with reflective grating marks 12.

Further above the condenser lens 4 on the optical axis O, an oblique half mirror 18 and an alignment light source section 20 are arranged. A receiving optical element 22 is arranged on the reflection optical axis OO of the half mirror 18.

The alignment light source section 20 includes a housing 2
4, an alignment light source 30 placed on the base 26 that emits a He-Ne laser beam, and a base 26.
A mirror 32 is supported on the mirror 32 so as to be slidable in the radial direction via a sliding body 33. An opening 34 is provided in the base 26 at a portion below the sliding range of the mirror 32, so that the laser beam emitted from the alignment light source 30 is not blocked. In addition, when the optical axis O is bent by a mirror, it will be rotated around the optical axis O bent by the alignment light source section.

Next, the operation of the positioning device having the above structure will be explained. First, the reticle 8 and the wafer 14 are aligned using the wafer table 10 by a known method. The mirror 32 is in the position shown in FIG. 1, and the laser beam emitted from the alignment light source 30 is reflected by the mirror 32 and reaches the grating mark 6 via the half mirror 18 and the condenser lens 4. The laser beam that has been transmitted and diffracted through the transmission grating mark 6 reaches the reflection grating mark 12 via the objective lens 2 . The laser beam reflected and diffracted by the reflective grating mark 12 reaches the half mirror 18 again via the objective lens 2, the transmission grating mark 6, and the condenser lens 4, and the laser beam reflected by the half mirror 18 passes through the light receiving element. Reach 22.

The light receiving element 22 outputs a detection signal corresponding to a change in the amount of received light caused by the relative positional relationship between the transmission type grating mark 6 and the reflection type grating mark 12. A microcomputer (not shown) connected to the light receiving element 22 performs arithmetic processing on the detection signal and outputs the relative positional relationship between the transmission grating mark 6 and the reflection grating mark 12 .

Next, the reticle 8 and wafer 14 are replaced, and the transmission grating mark 6 becomes 6'.
Assume that the reflective grating mark 12 has become 12'. First, as mentioned above, the reticle 8 and the wafer 14 are
The alignment is performed using the wafer table 10 by a known method. Subsequently, the mirror 32 is 32'
At the same time, the base 26 is rotated so that the light is incident on the transmission grating mark 6' through the condenser lens 4 at a predetermined angular direction. By doing so, it becomes possible to align the transmission type grating mark 6' and the reflection type grating mark 12' with high precision.

[0017]

As described above, according to the present invention, even if the grating marks on the reticle and wafer are displaced, it is possible to easily make the alignment light beam incident on the predetermined position of each grating mark at a predetermined angle. This has the advantage that the reticle and wafer can be aligned with high precision, and the configuration of the apparatus is simple.

[0018]

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional explanatory diagram of a positioning device according to an embodiment of the present invention.

FIG. 2 is an explanatory vertical cross-sectional view of a conventional alignment device.

[Explanation of symbols]

2 Objective lens 4
Condenser lens 6, 6'
Transparent grating mark 8
Reticle 10 Wafer table 12, 12'
Reflective grating mark 14
Wafer 20 Alignment light source section 22
Light receiving element 24 Housing 26 Base 30 Alignment light sources 32, 32
' mirror

Claims (3)

[Claims] Claim 1: A first alignment mark on a first substrate;
Alignment optics for positioning the relative positions of the first substrate and the second substrate via an objective lens using second alignment marks on the second substrate and an alignment light beam that irradiates these alignment marks. An alignment optical device characterized in that an emitting section of an alignment light source section that emits the alignment light beam is supported so as to be displaceable in a radial direction and a rotational direction centering on a fixed position. 2. A positioning device characterized in that the center of rotation of the injection section is the optical axis of the objective lens. 3. A positioning apparatus characterized in that the alignment light beam is a laser beam.