JPH04176143A - Wafer pattern form inspecting device - Google Patents

Abstract

PURPOSE:To make it possible to handle more easily the title device than the handling of a scanning electron microscope, such as without needing a vacuum or the like, and to make it possible to know the form of a pattern on the surface of a wafer in a short measurement time by a method wherein a laser beam is emitted on the wafer and reflected light and diffracted lights are photodetected by a two-dimensional photodetector and are compared with data on reference wafers which are previously stored. CONSTITUTION:A wafer pattern form inspecting device comprises a laser beam source (an HeNe laser) 1, a beam expander 2, a means (a mirror) 3 for directing a laser beam 10 having passed through the expander 2 onto an object semiconductor wafer 9, a a condenser lens 4, which condenses regular reflected light (0-order diffracted light) 12 generated by directing the beam 10 onto the wafer 9 and lights (primary diffracted light and primary diffracted light) 11 and 13 diffracted by a pattern on the wafer 9 and is set larger the distance between the lens 4 and the wafer 9 than a focal length (f), a two-dimensional photodetector (a two-dimensional CCD) 5, which is positioned by the focal length (f) apart from the lens 4 and photodetects the laser beam condensed by the lens 4, a storage device 7 for storing the output values of pixels, which correspond to a multitude of kinds of reference wafers, of the element 5, and a decision device 8 for deciding the kinds of the reference wafers, which correspond to the output values of the pixels of the element 5 to photodetect the beam directed onto the wafer 9 and are stored in the device 7.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a wafer pattern shape inspection device, and in particular, a wafer pattern shape inspection device that includes inspection of the three-dimensional shape of the wafer surface, which can be applied to semiconductor wafers having repetitive patterns such as memories. This invention relates to a shape inspection device.

[Conventional technology]

Conventional wafer pattern shape inspection includes a direct device that uses, for example, a scanning electron microscope to capture the shape of a desired portion as an image. The two-dimensional shape of a semiconductor wafer can be determined by observing the surface of the semiconductor wafer with a scanning electron microscope and obtaining an image. It becomes clear by observing it with a scanning electron microscope and obtaining an image of it.

[Problem to be solved by the invention]

The above-described conventional wafer pattern shape inspection apparatus uses a scanning electron microscope, so it has the disadvantage that it takes time and effort to conduct measurement inspections, such as by creating a vacuum.

[Failure to solve the problem]

A wafer pattern shape inspection apparatus according to the present invention includes a laser light source, a beam expander that expands the diameter of a laser beam emitted from the laser light source, and a target semiconductor wafer that is a target object with the laser beam passing through the beam expander.
(ii) a means for guiding the target semiconductor wafer, and condensing specularly reflected light generated when the laser beam is irradiated onto the target semiconductor wafer and light diffracted by a pattern on the semiconductor wafer to make the distance between the target semiconductor wafers larger than the focal length; a condensing lens; a two-dimensional light receiving element located at a distance from the condensing lens by a focal length and receiving the laser beam condensed by the condensing lens; a storage device that stores the output value of each pixel of the light-receiving element; and a determination that determines the type of the reference semiconductor wafer stored in the storage device that corresponds to the output of each pixel of the two-dimensional light-receiving element by the target semiconductor wafer. A device is characterized in that it includes a device.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 shows the semiconductor wafer 9 shown in FIG. 5 is a partially enlarged view showing the state of the laser beam 10 in the condenser lens 4, the two-dimensional CCD 5, and the diffracted light reflected by the semiconductor wafer 9. FIG.

In this embodiment, a HeNe laser 1 as a laser light source,
A beam expander 2 that expands the diameter of the laser beam 10 emitted by the HeNe laser 1, a mirror 3 that guides the laser beam 10 that has passed through the beam expander 2 to a semiconductor wafer 9 that is an object, and the laser beam 10. specularly reflected light (O-order diffracted light) 12 generated by irradiating the semiconductor wafer 9 with first-order diffracted light 11 diffracted by the pattern on the semiconductor wafer 9. -1st order diffracted light 13. and a condensing lens 4 that condenses the multi-high order diffraction light, a two-dimensional CCD 5 that receives the laser beam condensed by the condensing lens 4,
The distance between the condenser lens 4 and the two-dimensional CCD 5 is the focal length f of the condenser lens 4, and the distance between the condenser lens 4 and the semiconductor wafer is the focal length f of the condenser lens 4. a COD controller 6 for reading out the output of each pixel of the two-dimensional CCD from the two-dimensional CCD 5, and a means for positioning the two-dimensional CCD'5 to make it larger (as shown in the figure); A storage device 7 that stores pixel output values and a COD controller 6
The output value of each pixel of the two-dimensional CCD 5 read from
The data corresponding to the output of each pixel of the dimensional CCD 5 is compared, and it is determined which standard semiconductor wafer of the data stored in the storage device the output from the COD controller 6 corresponds to, and the corresponding storage device is 7 is the same as the shape of the set semiconductor wafer 9.

A laser beam 10 emitted from a HeNe laser 1 is expanded in beam diameter by a beam expander 2 so that the diameter of the laser beam 10 is the same as the reference area on the semiconductor wafer 9, and is reflected by a mirror 3 and directed onto the semiconductor wafer. 9
irradiated at a relatively small angle of incidence. The three-dimensional shape of the semiconductor wafer pattern includes grooves that are deep relative to the opening width, so the incident angle is set small so that the laser beam hits the bottom of the groove. A regularly repeating pattern on the semiconductor wafer 9 causes the laser beam 10 to generate diffracted light, the emission angle of which is determined by the planar pattern shape.

Also, due to the three-dimensional shape in the thickness direction, the light reflected from the pattern surface and the light reflected from the bottom of the groove will have a positional difference corresponding to the difference in optical distance. It can be regarded as a phase grating, and since it is affected by interference, each diffraction from the semiconductor wafer 9=6= The light intensity of the light depends on the three-dimensional shape of the pattern.

These diffracted lights are collected by a condenser lens 4 having a focal length f and received by a two-dimensional CCD 5.
By setting the distance between the dimensional CCDs 5 to f, the reflected light and each diffracted light that reach the condenser lens are 2
The distance between the condenser lens 4 and the semiconductor wafer 9 is set larger than f so that each diffracted light beam is focused on the two-dimensional CCD l and each diffracted light beam is separated from the other.
The distance is set so that each diffracted light is collected so that it enters the light receiving part of the CD5.

Reflected light obtained from the two-dimensional CCD 5, the position of each diffracted light,
As mentioned earlier, the intensity is determined by the exit angle, that is, the two-dimensional CC
The position of the beam on D5 depends on the planar pattern shape 2, and the intensity depends on the three-dimensional pattern shape, and is unique to semiconductor wafers of the same type and process. This data is taken into the determination device 8 via the CCD controller 6 and stored in the storage device 7.
The determination device 8 determines which of the reference semiconductor wafers stored in the storage device 7 the semiconductor wafer 9 currently being measured corresponds to by comparing it with various data stored in the storage device 7 .

〔Effect of the invention〕

The wafer pattern shape inspection apparatus of the present invention irradiates a semiconductor wafer with a laser beam (1), and separates the reflected light (1) and diffracted light beams on a two-dimensional light receiving element (2) and a relatively narrow beam (2).
The positions of the condenser lens and the two-dimensional light receiving element are determined so that each diffracted light beam enters the light receiving surface of the two-dimensional light receiving element and is slightly focused, and the nine diffracted lights reflected from the semiconductor wafer are received by the two-dimensional light receiving element. Measure the distribution and intensity of the 5-diffracted light reflected by the shiso,
By comparing this measurement result with the pre-memorized distribution intensity of the one-diffracted light reflected from a reference semiconductor wafer on a two-dimensional light receiving element, it is easier to handle than a scanning electron microscope, as it does not require a vacuum. This method has the advantage of being able to determine the pattern shape on the surface of a semiconductor wafer in a short measurement time.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
Semiconductor wafer 9 shown in the figure. Condensing lens 4.2-dimensional CCD
Laser beam of part 5, reflected light by semiconductor wafer 9
It is a partially enlarged view showing the state of diffracted light. DESCRIPTION OF SYMBOLS 1... HeNe laser, 2... Beam expander, 8... Mirror, 4... Condenser lens, 5... Two-dimensional CCD16... CCD controller, 7... Storage device, 8 ... Determination device, 9 ... Semiconductor wafer, 1o
...Laser beam, 11...1st order diffracted light, 12...
・Specular reflection light (0th order diffraction light), 13...-1st order diffraction light.

Claims (1)

[Claims] a laser light source; a beam expander that expands the diameter of the laser beam emitted from the laser light source; a means for guiding the laser beam that has passed through the beam expander onto a target semiconductor wafer; A condensing lens that condenses the specularly reflected light irradiated onto the target semiconductor wafer and the light diffracted by the pattern on the semiconductor wafer so that the distance between the target semiconductor wafers is larger than the focal length; A two-dimensional light-receiving element that is located a distance apart and receives the laser beam focused by the condenser lens, and an output value of each pixel of the two-dimensional light-receiving element with respect to various types of reference semiconductor wafers as a reference is stored. A wafer pattern comprising: a storage device; and a determination device that determines the type of the reference semiconductor wafer stored in the storage device corresponding to the output of each pixel of the two-dimensional light receiving element by the target semiconductor wafer. Shape inspection device.