JP2006171187A - Microscope apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microscope apparatus capable of remarkably reducing dust-sticking on a sample such as a semiconductor wafer using an immersion objective lens and the occurrence of watermarks on the sample by quickly drying liquid remaining on the sample after the visual inspection of the sample. <P>SOLUTION: The visual inspection of the wafer is performed by supplying the liquid by a supply nozzle in between the leading end of the objective lens and the wafer, after finishing the visual inspection, the liquid is sucked from the wafer by a suction nozzle, the microscope apparatus is provided with a fan filter unit arranged above the microscope apparatus so as to generate the downward air current, a wafer transporting apparatus for transporting the wafer from an inspection stage to a cassette, and a drying mechanism for blowing at speed higher than that of the air current generated by the fan filter unit, and when transporting the wafer where the liquid is already sucked by the suction nozzle from the inspection stage to the cassette by the wafer transporting apparatus after the visual inspection, the air is sprayed by the drying mechanism to thereby dry the liquid remaining on the surface of the wafer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a microscope apparatus for inspecting the appearance of a specimen such as a semiconductor wafer, and more particularly to a microscope apparatus incorporating a microscope observation apparatus having an immersion objective lens.

  In the manufacturing process of a semiconductor circuit element, observation (appearance inspection) of a defect or a foreign substance in a circuit pattern formed on a specimen such as a semiconductor wafer is performed using a microscope apparatus (see, for example, Patent Document 1). . The microscope apparatus is a combination of a mechanism for automatically transporting a specimen and an optical microscope observation apparatus.

  In such a microscope observation apparatus for the purpose of observing a semiconductor wafer or the like, a higher-resolution objective lens is required with the recent miniaturization of the pattern line width. The resolution R in such an objective lens can be expressed by the following equation (1), where λ is the wavelength of light involved in image formation and NA is the numerical aperture of the objective lens.

                R = 0.61 × (λ / NA) (1)

  From the above formula (1), it can be seen that it is effective to increase the numerical aperture NA and shorten the wavelength λ in order to achieve a high resolution R in the objective lens. The numerical aperture NA is expressed by the following equation (2), where n is the refractive index of the medium between the sample and the objective lens, and θ is the angle between the optical axis and the light beam entering the outermost side of the objective lens. Can be expressed.

              NA = n × sin θ (2)

Therefore, in order to increase the numerical aperture NA, a microscope observation apparatus for observing a living organism is not a dry objective lens that fills the space between the specimen and the tip of the objective lens, but a specimen and an objective lens. There is known a lens equipped with an immersion objective lens that fills the space with a liquid such as water or oil.
JP 2004-172480 A

  By the way, in the microscope observation apparatus provided with the immersion objective lens, the operator wipes and collects the liquid filled between the specimen and the objective lens after the observation is completed. Even in a microscope observation apparatus used for observing a semiconductor wafer, it is assumed that an immersion objective lens is used in order to perform high-resolution observation. In this case, after the appearance inspection is completed, if a small amount of liquid remains on the wafer without wiping and recovering the liquid, dust or the like adheres to the remaining small amount of liquid, and when a device is formed, a short circuit or connection of the pattern There was a risk of causing defects.

  Further, the liquid used in the appearance inspection of the semiconductor wafer by such an immersion type objective lens is ultrapure water, and the time that the ultrapure water remaining on the wafer remains on the semiconductor wafer is extended. As a result, the possibility of forming a watermark increases, and the semiconductor wafer is damaged. The watermark refers to a stain (silicon oxide) in which silicon in the wafer elutes in the remaining liquid (ultra pure water) and remains after drying. When such a watermark, that is, silicon oxide is formed on the wafer surface, there is a risk of causing contact failure when a device is formed.

  The present invention has been made in view of such problems, and after the appearance inspection of a specimen such as a semiconductor wafer using an immersion objective lens, the liquid remaining on the specimen is quickly dried to obtain the specimen. An object of the present invention is to provide a microscope apparatus that can significantly reduce the adhesion of dust and the like and the generation of watermarks.

  In order to achieve such an object, the present invention provides an inspection stage for holding a specimen such as a semiconductor wafer, an immersion objective lens, and a liquid (for example, this embodiment) between the tip of the objective lens and the specimen. A microscope observation apparatus having a supply means (for example, supply nozzle 22c in the present embodiment) and a suction means (for example, suction nozzle 22d in the present embodiment) for sucking the liquid from the specimen. A microscope apparatus for supplying a liquid between the tip of the objective lens and the specimen by the supply means to inspect the appearance of the specimen, and sucking the liquid from the specimen by the suction means after completion of the inspection. A filter unit (for example, a fan filter unit in the present embodiment) that is provided on the microscope apparatus and generates a downward air flow. 50), a transfer means (for example, wafer transfer device 40 in the present embodiment) for transferring the sample from the inspection stage to a predetermined position, and drying for blowing out air at a speed higher than the air flow generated by the filter unit. Means (for example, the lower overhanging portion 13, the upper overhanging portion 14, and the fan filter unit 50 in the present embodiment), and after the appearance inspection is completed, the sample in which the liquid is sucked by the suction means is transported. When transporting from the inspection stage to the predetermined position (for example, the cassette 41 in the present embodiment) by means, air is blown by the drying means to dry the liquid remaining on the surface of the specimen. The

  The difference between the speed of the air flow generated by the filter unit and the speed of the air blown by the drying means is preferably 0.10 m / s or more.

  Further, the speed of the air flow generated by the filter unit is 0.2 m / s to 0.5 m / s, and the speed of the air blown out by the drying means is about 0.5 m / s. desirable.

  In addition, an illumination unit that illuminates the specimen on the inspection stage is provided, and the illumination unit raises the temperature inside the microscope apparatus to heat the liquid remaining on the surface of the specimen after visual inspection. It is desirable to have a heater function.

  As described above, according to the present invention, after a visual inspection of a specimen such as a semiconductor wafer using an immersion objective lens, air is blown by a drying unit when the sample is transferred from the inspection stage to a predetermined position by the transfer unit. As a result, it was possible to realize a microscope apparatus that can rapidly dry the liquid remaining on the specimen and significantly reduce the adhesion of dust and the like to the specimen and the generation of watermarks.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1A and 1B, a microscope apparatus 1 according to the present invention performs an appearance inspection of a specimen such as a semiconductor wafer (hereinafter referred to as a wafer W). The microscope 10 includes a microscope observation device 20, a wafer transfer device 40, and a fan filter unit 50 housed in the frame 10. The white arrows in FIG. 1 indicate the direction of downflow by the fan filter unit 50.

  The apparatus frame 10 is provided with an outer wall (not shown), and the microscope apparatus 1 is isolated from the outside by the outer wall (the cassette mounting table 12 and the cassette 41 described later are located outside the apparatus frame 10. ).

  As shown in FIGS. 2 and 3, the microscope observation apparatus 20 is installed on a horizontal table 11 in the apparatus frame 10 and covers an inspection stage 21 that holds a wafer W and covers the inspection stage 21. And an observation device 22 installed. 2 indicates the direction of downflow by the fan filter unit 50, and the hatched arrow in FIG. 3 is blown out from the outside to the wafer W via the ULPA filter-equipped fan 22f described later. This shows the flow of air.

  The inspection stage 21 includes a sample stage 21a, an XYZ stage 21b, and an automatic focus detection device (not shown).

  The sample stage 21a is instructed to be movable in the vertical direction by the XYZ stage 21b and movable in the horizontal plane. In this embodiment, the wafer W is transferred from the cassette 41 and placed on the upper surface of the sample stage 21a, and is fixedly supported by, for example, vacuum suction.

  The XYZ stage 21b moves the sample stage 21a in the vertical direction when the wafer W is focused. This focusing operation is performed by an automatic focus detection apparatus (not shown) using an autofocus function. The XYZ stage 21b moves the sample stage 21a in the horizontal plane when positioning a predetermined observation point on the wafer W within the visual field of the eyepiece 22a and the objective lens 22b.

  The observation device 22 includes an eyepiece 22a, an objective lens 22b, a supply nozzle 22c (see FIG. 2), a suction nozzle 22d (see FIG. 2), an illumination light source 22e (see FIG. 3), and a fan 22f with a ULPA filter. (See FIG. 3).

  The objective lens 22b is an immersion type objective lens, and is designed so that the aberration of the optical system is corrected when the space between the tip (lower surface) and the wafer W is filled with the liquid E. Note that the tip of the objective lens 22b is a part that touches the liquid E. In the present embodiment, ultrapure water is assumed as the liquid E, but the present invention is not limited to this.

  The supply nozzle 22 c supplies the liquid E between the tip of the objective lens 22 b and the wafer W. The supply of the liquid E is automatically performed by a control unit (not shown) before the immersion observation. The suction nozzle 22d sucks the liquid E from the wafer W at the end of the appearance inspection. The supply nozzle 22c and the suction nozzle 22d are fixed around the objective lens 22b, respectively, and their tips are arranged near the tip of the objective lens 22b.

  The illumination light source 22e is turned on when the appearance inspection of the wafer W is performed to illuminate the wafer W. In this embodiment, a visible range is assumed as the observation wavelength. The illumination light source 22e not only illuminates the wafer W, but also raises the temperature inside the apparatus frame 10 using residual heat. After the appearance inspection of the wafer W, the illumination light source 22e is not completely sucked by the suction nozzle 22d and is applied to the surface of the wafer W It also functions as a heater for drying the remaining liquid E.

  Note that the observation wavelength in the illumination light source 22e is not limited to the above. For example, when the observation wavelength is in the ultraviolet region, observation from the eyepiece lens 22a is not possible, and thus an image is taken by providing a CCD camera or the like instead of the eyepiece lens 22a. Display on the monitor and observe.

  The fan 22f with a ULPA filter is a fan to which a high-performance filter called an ULPA filter (Ultra Low Penetration Air Filter) is attached. Fresh air is blown onto the wafer W. By installing the fan 22 with a ULPA filter in addition to the illumination light source 22e, the liquid E remaining on the surface of the wafer W can be dried more efficiently.

  In the observation apparatus 22 configured as described above, an enlarged image (pattern image) of the wafer W is formed at the visual field position of the eyepiece 22a, and the appearance inspection of the wafer W is performed using this image. Further, the numerical aperture of the objective lens 22b can be made larger than 1 in accordance with the refractive index (> 1) of the liquid E that fills the space between the tip of the objective lens 22b and the wafer W. Therefore, the resolution can be reliably improved as compared with the numerical aperture ≦ 1).

  The wafer transfer device 40 includes a cassette 41 and a transfer arm 42.

  The cassette 41 is a box that is installed on a cassette mounting table 12 provided outside the apparatus frame 10 and that is open on one side of the side surface. Inside this box, a plurality of horizontal slots are provided side by side, and one wafer W is stored in each slot.

  The transfer arm 42 can be operated including bending and stretching in a horizontal plane by the operation of an electric motor (not shown), and the wafer W adsorbed by the adsorption mechanism 42a provided at the tip thereof can be freely moved in a horizontal posture. Can be made. With the transfer arm 42 having such a configuration, the wafer W is transferred inside the apparatus frame 10, specifically, the wafer W is transferred between the cassette 41 and the inspection stage 21 of the microscope observation apparatus 20.

  The fan filter unit 50 generates a downward air flow by three blowers 50a, 50b, 50c and 50d provided at different positions on the upper part of the apparatus frame 10, and air containing dust or the like enters the inside from the outside. In order to prevent this, the air pressure inside the apparatus frame 10 is kept higher than the external air pressure. In addition, the speed of the airflow which each blower 50a-50d generate | occur | produces is 0.2 m / s-0.5 m / s.

  Further, a high-performance chemical filter 50e such as a ULPA filter is provided between the blower 50d and the apparatus frame 10 (see FIG. 1), and dust in the air blown by the blower 50d is removed. Clean air is supplied (particularly around the microscope observation apparatus 20 on which the wafer W is placed).

  In order to properly guide the clean air supplied into the apparatus frame 10 to the periphery of the microscope observation apparatus 20 on which the wafer W is placed, as shown in FIG. A lower projecting portion 13 projecting upward from the surface and an upper projecting portion 14 projecting downward from the ceiling portion are provided, and a structure for separating the air chambers inside the apparatus frame 10 with these as a boundary. Has been taken.

  Note that the lower overhanging portion 13 and the upper overhanging portion 14 not only have a role of partitioning the inside of the apparatus frame 10 as described above, but also serve as a drying mechanism that dries the surface of the wafer W after the appearance inspection. Have. More specifically, a first pipe line 13a having one end (on the floor surface side) connected to an exhaust port (not shown) and the other end opened is formed in the lower projecting portion 13, A second pipe line 14a is formed in the overhanging part 14 so that one end (on the ceiling side) is connected to the fan filter unit 50 and the other end is opened to face the opening of the first pipe line 13a. After the appearance inspection of the wafer W, the air supplied from the fan filter unit 50 when the wafer W from which the liquid E has been sucked by the suction nozzle 22d is transported from the inspection stage 21 to the cassette 41 by the transport arm 42. Is blown to the wafer W through the overhanging portion 14 (second conduit 14a), and the liquid E remaining on the surface of the wafer W can be dried. The air blown out from the upper overhanging portion 14 is opened to the atmosphere from a discharge port (not shown) through the lower overhanging portion 13 (first pipe line 13a).

  In order to supply clean air to the overhanging portion 14, the fan filter unit 50 is provided with a high-performance chemical filter (not shown) such as a ULPA filter between the blower 50c and the apparatus frame 10. ing.

  The difference between the speed of the air flow generated by the fan filter unit 50 and the speed of the air blown from the overhanging portion 14 is preferably 0.10 m / s or more. In this embodiment, the speed of the air blown out by the overhanging portion 14 is about 0.5 m / s, and the speed of the air flow generated by the fan filter unit 50 is 0.2 m / s to 0.5 m / s. Faster than.

  Thus, in order to secure the speed of the air blown from the overhanging portion 14, a chemical filter (not shown) provided between the blower 50c and the apparatus frame 10 is selected to have a low pressure loss. Alternatively, the rotational speed of the fan of the blower 50c may be set high.

  Further, the blower 50c and the apparatus frame 10 are arranged so that the difference between the speed of the air blown from the overhanging portion 14 and the speed of the air passing through the chemical filter 50e of the fan filter unit 50 is 0.1 m / s or more. You may select the filter (not shown) provided between these, and the chemical filter 50e. Specifically, each filter is adjusted so that the speed of the air blown from the overhanging portion 14 is 0.55 m / s and the speed of the air passing through the chemical filter 50e is 0.45 m / s or less. If selected, good performance can be exhibited in both dustproof performance and drying.

  Further, by providing a suction device in the second conduit 13a of the lower overhanging portion 13 to suck air blown out from the upper overhanging portion 14 or the like, by increasing the wind speed blown out from the upper overhanging portion 14, the wafer W The liquid E remaining on the surface can be blown off more effectively to promote drying.

  Next, the operation of the microscope apparatus 1 will be described. First, when an operator gives an instruction to start an appearance inspection using the microscope observation apparatus 20 (for example, turning on a switch), the transfer arm 42 sucks and holds the wafer W stored in the cassette 41. And is taken out of the cassette 41 and placed on the sample stage 21a of the microscope observation apparatus 20. When the wafer W is placed on the sample stage 21a, the sample stage 21a now vacuum-sucks the wafer W. When the wafer W is sucked and held by the sample stage 21a, the XYZ stage 21b is moved, and a desired portion of the wafer W is moved directly below the objective lens 22b of the microscope observation apparatus 20. Then, the liquid E is supplied between the tip of the objective lens 22b and the wafer W by the supply nozzle 22c, thereby enabling the appearance inspection of the surface of the wafer W from the eyepiece lens 22a.

  Subsequently, when the appearance inspection of the wafer W using the microscope observation apparatus 20 is completed, the liquid E is sucked from between the tip of the objective lens 22b and the wafer W by the suction nozzle 22d, and the wafer W is inspected by the transfer arm 42. When the wafer W is transferred from the stage 21 to the cassette 41, more specifically, when the wafer W passes between the lower overhanging portion 13 and the upper overhanging portion 14 (the lower overhanging portion 13 and the upper overhanging portion 14). The air supplied from the fan filter unit 50 is blown by the drying mechanism (consisting of the fan filter unit 50) through the overhanging portion 14, and the liquid E remaining on the surface of the wafer W is dried. At this time, the speed of the air blown out by the overhanging portion 14 is about 0.5 m / s, which is faster than the speed of the air flow blown out by the fan filter unit 50 from 0.2 m / s to 0.5 m / s. Is set to In addition, the air blown onto the wafer W is released to the atmosphere from a discharge port (not shown) through the lower overhanging portion 13 (first conduit 13a). The wafer W thus dried is stored in the cassette 41 by the transfer arm 42. Thereby, a series of operation | movement of the microscope apparatus 1 is complete | finished.

  The present invention as described above is not limited to the above embodiment, and can be improved as appropriate without departing from the gist of the present invention.

It is a block diagram of the microscope apparatus which concerns on this invention, (a) is a top view, (b) is a (partial) side sectional view. It is a block diagram of the drying apparatus installed in the inside of the microscope apparatus which concerns on this invention. It is a side view of the microscope observation apparatus installed in the inside of the microscope apparatus which concerns on this invention.

Explanation of symbols

1 Microscope device 13 Underhanging part (Drying means)
13a 1st pipe line 14 Overhang part (drying means)
14a Second pipe 20 Microscope observation device 21 Inspection stage 21a Sample stage 21b XYZ stage 22 Observation device 22a Eyepiece 22b Objective lens 22c Supply nozzle (supply means)
22d Suction nozzle (suction means)
22e Illumination light source 22f ULPA filter fan 40 Wafer transfer device (transfer means)
41 cassette 42 transfer arm 50 fan filter unit (filter unit / drying means)
W Wafer E Liquid

Claims (4)

An inspection stage for holding a specimen such as a semiconductor wafer, an immersion objective lens, a supply means for supplying a liquid between the tip of the objective lens and the specimen, and a suction means for sucking the liquid from the specimen Having a microscope observation device,
In the microscope apparatus for supplying a liquid between the tip of the objective lens and the specimen by the supply means and performing an appearance inspection of the specimen, and sucking the liquid from the specimen by the suction means after the inspection is completed.
A filter unit that is provided at the top of the microscope observation device and generates a downward air flow;
Transport means for transporting the sample from the inspection stage to a predetermined position;
Drying means for blowing out air at a speed faster than the air flow generated by the filter unit;
After the appearance inspection is completed, when the specimen, the liquid of which has been sucked by the suction means, is transported from the inspection stage to the predetermined position by the transport means, air is blown by the drying means to the surface of the specimen. A microscope apparatus, wherein the remaining liquid is dried.   2. The microscope apparatus according to claim 1, wherein a difference between a speed of the air flow generated by the filter unit and a speed of the air blown by the drying unit is 0.10 m / s or more. The speed of the air flow generated by the filter unit is 0.2 m / s to 0.5 m / s,
The microscope apparatus according to claim 1 or 2, wherein a speed of air blown out by the drying means is about 0.5 m / s. Illuminating means for illuminating the specimen on the inspection stage;
The said illuminating means has a function of a heater for raising the temperature inside the microscope apparatus and drying the liquid remaining on the surface of the specimen after visual inspection. A microscope apparatus according to any one of the above.

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