JPS61112122A - Observing device - Google Patents

Abstract

PURPOSE:To position a circuit pattern and an wafer highly accurately by changing the wavelength of irradiated light in accordance with the difference of levels of a fine step-like structure on the surface of the wafer. CONSTITUTION:Light flux radiated from a light source 1 is converted by a wavelength variable means 2, the converted light flux is irradiated upon the wafer surface 6 of a semiconductor substrate by a half mirror 5 and the reflected light is observed by an observing optical system 8. If a fine step-like structure 7 due to photoetching exists on the wafer surface 6, the reflected light beams obtained from the upper and lower surfaces of the steps are interferred each other and the observation is interrupted. Therefore, the wavelength of the irradiated light is changed by operating a wavelength controller 9 manually to remove the interference. Thus, always proper observation can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention is directed to the observation and equipment (particularly in the production of ICs, LSIs, etc.) on the wafer surface of a silicon substrate on a circuit pattern such as a mask or V-chip. This is related to &Mfc direct alignment for aligning the two when projecting and exposing them.

Conventionally, photolithography, which forms circuit patterns such as 45 ZC and LSI on the wafer surface, involves repeating the process of projecting and exposing the circuit pattern onto the surface of the wafer many times to form the circuit pattern on the wafer surface. It is formed by photo-etching.

When projecting and exposing the circuit pattern image onto the wafer surface, align the circuit pattern image and the square surface with the naked eye for each exposure! ! This can be done while observing or automatically using a technique called auto-alignment. In general, a wafer is photo-etched by repeatedly projecting and exposing nine different circuits over and over again. For this reason, a step structure occurs in the circuit pattern image on the wafer surface. The amount of step difference at this time varies depending on the type of semiconductor to be manufactured, the process, etc.

If this 7% is maintained, when observing one wafer by irradiating a light beam onto the wafer surface and using the reflected light beam, the reflected light beams from the top and bottom surfaces of the step structure O on the wafer surface will interfere, making observation difficult. The case is ruru.

In other words, when the wavelength of the JR light directed at the object (queue) is λ, the step amount between the top and bottom surfaces of the step structure of the circuit pattern is d, and the step amount d is on the wavelength order and the coherence length is 6 (however, a - 0 , 1, 2, ·°°), the reflected light beams from the top and bottom surfaces of the stepped structure on the eight surfaces of the sea urchin interfere with each other, making it difficult to observe the circuit pattern. As a result, alignment between the circuit pattern and the wafer becomes a fixed point.

In addition, even if the light receiving means and the TV right camera are used to automatically align the circuit pattern and the wafer (so-called automatic alignment), even if the reflected light beam interferes with KvA, the S/N of the light receiving means will increase.
The ratio decreases, making it difficult to perform highly accurate positioning.

This is particularly likely to occur when a monochromatic light source with a long coherence length, such as a laser, is used as the high-intensity light source.

The present invention is a concept #I that allows the circuit pattern and the square to be matched with high precision even if there is any step structure in the circuit pattern image on the 8th surface of the sea urchin! The purpose is to provide equipment.

The main luminous percentage characteristics of the observation device for achieving the purpose of the present invention are:
The light flux 1c from the light source is irradiated onto the object, and the object t WA,
View to celebrate 1! In this case, the wavelength of the irradiated light changes continuously in accordance with the amount of the step in the fine step structure of the object.

In this way, in the present invention, by continuously changing the wavelength of the light irradiated to the object using, for example, a dye laser, etc., a circuit/<turn image t-p is repeatedly projected onto the eight surfaces of the sea urchin. - Even if a stepped structure of the circuit pattern occurs on the surface, it is possible to precisely align the circuit pattern and the wafer.

Next, one embodiment of the present invention will be described with reference to each drawing.

FIG. 1 is a schematic diagram of a portion of a nine-hole joint applied to the photolithography technique of the present invention.

In the figure, for the sake of simplicity, the circuit butter 71 - each 9. I'll omit the details.

Unlike the embodiment shown in FIG. 1, the nine beams emitted from the light source 1 are selectively converted into a desired wavelength by a wavelength variable means 2 which performs wavelength conversion or wavelength selection such as a spectroscope or filter.

In addition, if the wavelength variable means 2 is built in the light source 1, the wavelength variable means 2 is required. If the light source 1 is wavelength variable, such as a dye laser, the wavelength variable means 2 does not need to be provided. The luminous flux of is reflected by a total reflection mirror of 3°4.
The reflected light beam from the wafer surface 6 is incident on the wafer surface 6 which is a semiconductor substrate by the half mirror 5 and illuminates the surface of the sea urchin I. The reflected light beam from the wafer surface 6 passes through the -7 mirror and enters the observation optical system 8.

If there is a fine step structure 7 formed by photo-etching a circuit pattern image on the wafer surface 6, the reflected light beams from the top and bottom surfaces of the step structure will interfere with each other as shown in FIG. There may be times when it becomes difficult. For example, if the height difference between the top and bottom surfaces of the stepped structure is t-d, and the irradiation length of the irradiation source is λ, then 9 and z
When it is approximately equal to d-(n+4)λ (2) (however, n-0, 1, 2, . . .), the reflected light beams interfere, making observation difficult. Therefore, in this implementation, the wavelength controller 9 is manually operated to change the wavelength of the irradiated light so that the length of the reflected light beam does not completely satisfy equation (2), that is, it does not completely interfere with the wafer. The surface 6 can be observed clearly.

Here, since the step amount varies as described above, it must be kept continuously large accordingly even during the wavelength change. This is because even if the wavelengths that can be changed are discrete, it will not be possible to cope with the step amount of K, which is a common multiple of them.

As the wavelength variable means 2 in this embodiment, for example, a plurality of emission spectra of an ultra-high pressure mercury lamp may be selected and used, or a wavelength variable means included in a dye laser or the like may be used. In particular, dye lasers are ideal for this purpose because of their high brightness and wide wavelength tunable range from ultraviolet to infrared as shown in FIG. In Figure 3, the different peaks indicate the different pigments.

Figure 4 is Ki-ni F! The position of the circuit pattern and the wafer is shown in FIG.

In the same figure, as in FIG. 1, each element involved in projecting a circuit pattern onto a wafer surface is omitted.

Also, in FIG. 4, the same elements as in FIG. m1 are given the same numbers.

1 on the sea urchin halo by the aζl festival optical system 8 in this disaster or j
The elephant is formed on the TV camera 10, and the circuit pattern and the wafer are aligned using the sign from the camera.At this time, a stepped structure is formed on the surface 6 as shown in If this happens, the reflected light beams from the top and bottom surfaces of the stepped structure will interfere, resulting in a drop in the output signal.As a result, the accuracy of the alignment between the circuit pattern and the QF will deteriorate.For this reason, in this implementation-j, the TV camera lO While detecting the entire contrast on the wafer surface 6, the wavelength variable means 2 is automatically adjusted via the wavelength controller 9 as soon as the contrast is maximized.
Thus, the oscillation length v from the light source 1 can be increased.

As described above, according to the present invention, by changing the wavelength of the light irradiated to one object depending on the level difference structure generated on the wafer surface, it is possible to achieve an observation apparatus that can always perform good observation.

[Brief explanation of the drawing]

FIGS. 1 and 4 are schematic diagrams when applied to Kiyo BAt-photolithography, respectively, and FIG. 2 is an explanatory diagram of the optical path when observing the reflected light flux t-m from the step structure in the present invention,
FIG. 3 is a graph showing the oscillation wavelength and oscillation efficiency of a typical conventional dye laser. In the figure, 1 #'i light source, 2 wavelength variable means, 3.4 mirror, 5 half mirror, 16 wafer surface, 7 step structure, 8
Ha lol! The detection optical system 9 is a wavelength controller, 1oFiT
It is a V camera.

Claims (2)

[Claims] (1) An observation device for observing an object by irradiating the object with a light beam from a light source, including means for continuously changing the wavelength of the light irradiating the object to adjust the amount of step in the fine step structure of the object. An observation device characterized in that the wavelength of irradiation light is changed accordingly. (2) The observation device according to claim 1, wherein the light source is a dye laser.