KR20050014424A - Method and apparatus for inspecting a substrate - Google Patents

Abstract

PURPOSE: A method for inspecting a substrate is provided to detect foreign substances remaining on various layers formed on a semiconductor substrate, by irradiating the second laser beam with a wavelength selected from the first laser beams with a plurality of wavelengths to the semiconductor substrate, by detecting a surface defect of the semiconductor substrate from the light scattered from the substrate and by using a laser beam with a wavelength selected from the wavelengths with strongest spectrum. CONSTITUTION: The first laser beams with mutually different wavelengths are sequentially irradiated to a semiconductor substrate(S110). The first light scattered from the surface of the substrate by the irradiation of the first laser beams and the second light scattered from the particles on the substrate are detected(S120). The intensity of the first light is compared with the intensity of the second light to calculate difference values(S130). By the irradiation of the second laser beam, the second laser beam with a wavelength corresponding to the highest difference value among the difference values is irradiated to the substrate(S210). The defect of the substrate is detected from the third light scattered from the surface of the substrate and the fourth light scattered from the particles on the substrate. The first laser beam is supplied from a laser source with a plurality of resonators. The wavelength of the first laser beam is varied by the plurality of resonators.

Description

Substrate inspection method and apparatus {Method and apparatus for inspecting a substrate}

The present invention relates to a substrate inspection apparatus. More specifically, the present invention relates to an apparatus for detecting a defect on the surface of a semiconductor substrate by irradiating a laser beam on the semiconductor substrate, detecting light reflected from the semiconductor substrate.

In general, a semiconductor device includes a fabrication (FAB) process for forming an electrical circuit on a silicon wafer used as a semiconductor substrate, and an electrical die for inspecting electrical characteristics of the semiconductor devices formed in the fab process. sorting) and a package process for encapsulating and individualizing the semiconductor devices with epoxy resin, respectively.

The fab process includes a deposition process for forming a film on a semiconductor substrate, a chemical mechanical polishing process for planarizing the film, a photolithography process for forming a photoresist pattern on the film, and the photoresist pattern. An etching process for forming the film into a pattern having electrical characteristics, an ion implantation process for implanting specific ions into a predetermined region of the semiconductor substrate, a cleaning process for removing impurities on the semiconductor substrate, and the film and pattern Inspection process for detecting a defect of the formed semiconductor substrate, and the like.

Defects in semiconductor substrates, such as foreign matter remaining on the semiconductor substrate, are recognized as an important factor that lowers the reliability and productivity of the semiconductor device due to high integration of the semiconductor device, and the importance of the inspection process for detecting the foreign matter becomes more important. It is becoming.

As an example of an apparatus for detecting foreign matter remaining on the semiconductor substrate, US Pat. No. 6,215,551 (issued to Nikoonahad, et al.), Irradiates a laser beam onto a semiconductor substrate and scatters it from the surface of the semiconductor substrate. An apparatus for detecting light and detecting defects in a semiconductor substrate is disclosed.

When irradiating a laser beam on the semiconductor substrate, the intensity of light scattered on the semiconductor substrate is changed according to the wavelength of the laser beam and the material forming the film and pattern formed on the semiconductor substrate.

1 is a graph showing the refractive index and the absorption rate of light with respect to the silicon wafer, FIG. 2 is a graph showing the refractive index and the absorption rate of light with respect to the nitride film formed on the semiconductor substrate, Figure 3 is a refractive index of the light for the oxide film formed on the semiconductor substrate It is a graph showing.

1 to 3, the scattering efficiency of a laser beam having a specific wavelength is changed according to the refractive index and the absorption of the material, and the refractive index and the absorption of the material are changed according to the wavelength of the laser beam.

The conventional inspection apparatus has a disadvantage in that inspection efficiency for various films and patterns formed on a semiconductor substrate is changed because a laser beam having a specific wavelength is used. That is, since the intensity of the scattered light reflected from the semiconductor substrate by the irradiation of the laser beam having the specific wavelength varies in accordance with various films and patterns formed on the semiconductor substrate, the reliability of the inspection process is lowered. For example, since the intensity of light scattered from the semiconductor substrate on which the oxide film is formed is different from the intensity of light scattered from the semiconductor substrate on which the nitride film is formed, the inspection efficiency for the foreign matter remaining on the oxide film and the foreign matter remaining on the nitride film is different from each other. Will be different. In addition, since the intensity of light scattered from the foreign matter varies depending on the type of the foreign matter, the reliability of the inspection efficiency is further lowered.

An object of the present invention for solving the above problems is to select the wavelength of the laser beam in accordance with the components of the film and pattern formed on the semiconductor substrate and the components of the foreign material on the film and pattern, using a laser beam having a selected wavelength To provide a method for inspecting a defect of a semiconductor substrate.

Another object of the present invention is to provide an apparatus suitable for carrying out the method for inspecting a defect of the semiconductor substrate described above.

1 is a graph showing the refractive index and the absorbance of light for a silicon wafer.

2 is a graph showing the refractive index and the absorbance of light for a nitride film formed on a semiconductor substrate.

3 is a graph showing a refractive index of light with respect to an oxide film formed on a semiconductor substrate.

4 is a flowchart illustrating a substrate inspection method according to an embodiment of the present invention.

5 is a graph showing an emission spectrum of an argon laser.

FIG. 6 is a schematic diagram illustrating a substrate inspection apparatus for performing the substrate inspection method illustrated in FIG. 4.

FIG. 7 is a schematic diagram illustrating the laser source illustrated in FIG. 6.

8 are schematic cross-sectional views for showing examples of the arrangement method of the resonator.

FIG. 9 is a perspective view illustrating the substrate inspection apparatus illustrated in FIG. 6.

10A and 10B are schematic front views for explaining the first light and the second light scattered from the semiconductor substrate.

Explanation of symbols on the main parts of the drawings

10: substrate inspection device 12: sampling area

14: foreign matter 20: laser beam

30: scattered light 100: laser source

102 tube 104 resonator

106: wavelength selector 108: power supply

112: beam expander 114: beam deflector

116: focusing lens 120: detector

130: calculation unit 140: control unit

150: image processing unit 160: moving stage

164 drive unit 170 display unit

W: semiconductor substrate

The present invention for achieving the above object, the step of sequentially irradiating the first laser beams each having a different wavelength on the substrate, and the first light scattered from the surface of the substrate by the irradiation of the first laser beams And detecting second lights scattered from the foreign matter on the substrate, comparing the intensities of the first lights with the intensities of the second lights, respectively, and calculating difference values. Irradiating on the substrate a second laser beam having a wavelength corresponding to the largest difference value among the third light scattered from the surface of the substrate by the irradiation of the second laser beam and foreign matter on the substrate. And detecting a defect of the substrate from the scattered fourth light, wherein the first laser beam comprises a plurality of resonators. Is provided from which the laser source, wherein the wavelength change of the first laser beam and provides a substrate inspection method characterized in that the change by the number of the resonator.

According to another aspect of the present invention, there is provided a resonance tube including a laser medium, a plurality of resonators for selecting a wavelength of a laser generated from the laser medium, and one of the plurality of resonators. A laser source comprising a wavelength selector for positioning at both ends of the resonance tube, a power source for discharge excitation of the laser medium, and scattered from the substrate by irradiation of laser beams each having different wavelengths from the laser source. A detector for detecting lights and comparing the intensities of the first lights scattered from the surface of the substrate among the scattered lights with the intensities of the second lights scattered from the foreign matter on the substrate, respectively; Calculate difference values between the intensities of the light sources and the second lights, and among the difference values. An arithmetic unit for selecting a wavelength corresponding to the longest difference value, the laser source sequentially irradiating the laser beams onto the substrate, and irradiating the laser beam having the selected wavelength onto the substrate. A control unit for controlling the operation of a wavelength selector of the light source and a surface image of the substrate scattered from the substrate by irradiation of a laser beam having the selected wavelength, and detected by the detector, from the image It provides a substrate inspection apparatus comprising an image processing unit for detecting a defect of a substrate.

As described above, when the defect of the semiconductor substrate is inspected using the second laser beam having the selected wavelength, the inspection process efficiency of the semiconductor substrate is improved. That is, since the intensity of the third light scattered from the surface of the semiconductor substrate by the irradiation of the second laser beam and the intensity of the fourth light scattered from the foreign matter on the semiconductor substrate have the largest difference value, foreign substances on the semiconductor substrate can be easily detected. can do.

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

4 is a flowchart illustrating a substrate inspection method according to an embodiment of the present invention.

Referring to FIG. 4, the substrate inspection method according to the embodiment includes a first process for selecting a wavelength of a laser beam for inspecting a semiconductor substrate from among first laser beams each having a plurality of different wavelengths; And a second process for detecting defects in the semiconductor substrate using a second laser beam having a wavelength.

The first step will be described in detail. The first laser beam is irradiated to the sampling region set on the surface of the semiconductor substrate. (Step S110) Here, the first laser beam scans the sampling region in the x-axis direction, Moves in the y-axis direction orthogonal to the x-axis.

The first light scattered from the surface of the sampling region and the second light scattered from foreign matter remaining on the sampling region are detected by the irradiation of the first laser beam. (Step S120) At this time, a transistor is formed on the semiconductor substrate. Or films and patterns for forming a capacitor are formed.

The difference between the first light and the second light is calculated by comparing the detected intensity of the first light with the intensity of the second light (step S130).

Steps S110 to S130 are repeatedly performed while changing the wavelength of the first laser beam step by step. (Step S140) The first laser beam is preferably a gas laser beam, more preferably an argon laser beam. The wavelength change of the first laser beam is preferably changed in the order of 366nm, 488nm, 514nm. This is because the strongest spectrum is detected at the wavelengths as shown in FIG. 5 due to the characteristics of the argon laser beam. 5 shows the emission spectrum of the argon laser.

Next, a wavelength corresponding to the largest difference value is selected from the calculated difference values (step S150).

In detail, the second process is performed by irradiating the second laser beam having the selected wavelength on the substrate as a whole. (Step S210) In this case, the second laser beam scans the semiconductor substrate in the x-axis direction, and the semiconductor substrate Moves in the y-axis direction.

The third light scattered from the surface of the semiconductor substrate and the fourth light scattered from foreign matter on the semiconductor substrate are detected by the irradiation of the second laser beam. (Step S220).

The intensity of the third light and the intensity of the fourth light are converted into an electrical signal, and the electrical signal is converted into an image signal to obtain a surface image of the semiconductor substrate.

The defects of the semiconductor substrate are detected by analyzing the image. (Step S240) At this time, the difference between the intensity of the third light and the intensity of the fourth light is greater than the difference between the first and second lights. Foreign matter remaining on the semiconductor substrate is easily detected, and the efficiency of the semiconductor substrate inspection process is improved.

FIG. 6 is a schematic diagram illustrating a substrate inspection apparatus for performing the substrate inspection method illustrated in FIG. 4, and FIG. 7 is a schematic diagram illustrating the laser source illustrated in FIG. 6. 8 are schematic cross-sectional views for showing examples of the arrangement method of the resonator. FIG. 9 is a perspective view illustrating the substrate inspection apparatus illustrated in FIG. 6. 10A and 10B are schematic front views for explaining the first light and the second light scattered from the semiconductor substrate.

6 to 10, the substrate inspection apparatus 10 may include a laser source 100 for generating a laser beam 20 and a detector for detecting light 30 scattered from the semiconductor substrate W. 120, a computing unit 130 for analyzing the intensity of the scattered light 30, a controller 140 for controlling the operation of the laser source 110, and a semiconductor from the scattered light 30. And an image processing unit 150 for obtaining a surface image of the substrate W.

The laser source 100 sequentially irradiates the laser beams 20 having different wavelengths onto the semiconductor substrate W in sequence. That is, the laser source 100 irradiates the laser beams 20 onto the semiconductor substrate W while gradually changing the wavelength of the laser beam 20.

The laser source 100 is preferably a gas laser, more preferably an argon laser. The laser source 100 includes one of a tube 102 including a laser medium 100a, a plurality of resonators 104 for amplifying a laser generated from the laser medium 100a, and a plurality of resonators 104. And a power source 108 for discharge excitation of the laser medium 100a.

Argon gas may be used as the laser source 100, and the wavelengths that may be selected by the plurality of resonators 104 are preferably 366 nm, 488 nm, and 514 nm, respectively. This is a wavelength selected according to the characteristics of the argon laser, and the wavelength can be similarly selected even when other materials are used as the laser medium.

The resonator 104 consists of a combination of the total reflection mirror 104a and the partial transmission mirror 104b. The total reflection mirror 104a is disposed to correspond to the rear end of the tube 102, and the partial transmission mirror 104b is disposed to correspond to the front end of the tube 102. The laser generated from the argon gas filled in the tube 102 is amplified between the total reflection mirror 104a and the partial transmission mirror 104b and is emitted through the partial transmission mirror 104b. At this time, the total reflection mirror 104a reflects the laser at 100%, and the partial transmission mirror 104b reflects the laser at 90 to 95%. The arrow shown means the emission direction of the laser beam.

The wavelength selector 106 selects one of the plurality of resonators 104 and places it at the front and rear ends of the tube 102. The wavelength selector 106 may be a pneumatic cylinder operated by pneumatic. However, other configurations may be applied to the wavelength selector 106. For example, if a large number of resonators are placed radially on a disc shaped support, the wavelength selector may rotate the support to select the appropriate wavelength.

The arrangement method of the resonator 104 includes a case of employing a planar mirror, a case of employing a convex mirror, and a case of employing a concave mirror, as shown in FIG. 8. In Figure 8, R1, R2 means the radius of the mirror.

In Fig. 8, in the case of (a), it is a combination of convex mirrors that are nearly planar, in (b) is the combination of planar mirrors, and in (c), it is a combination of concave mirrors that are nearly planar. In the case of (d), it is a combination of concave mirrors which share almost a focus, in the case of (e) it is a combination of concave mirrors which share a focus, and in (f) it is a combination of a concave mirror which is almost spherical. (g) is a combination of spherical concave mirrors, (h) is a combination of almost spherical concave mirrors, and (i) is a combination of hemispherical concave mirrors and planar mirrors.

The semiconductor substrate W is supported on the movement stage 160, and the movement stage 160 moves in a horizontal direction so that the laser beam 20 generated from the laser source 100 scans the surface of the semiconductor substrate W. FIG. do. The movement stage 160 is connected to the drive unit 164 for moving the movement stage 160 by the drive shaft 162. The driving unit 164 includes a rectangular coordinate robot for moving the movement stage 160 in the horizontal direction, and the sampling region 12 or the semiconductor substrate W in which the laser beam 20 is set on the semiconductor substrate W. FIG. The movement stage 160 is moved in the x- and y-axis directions to scan the entire surface of the.

The beam expander 112 expands the cross-sectional area of the laser beam 20 generated from the laser source 100. The beam deflector 114 deflects the extended laser beam 22 such that the laser beam 22 extended by the beam expander 112 scans the surface of the semiconductor substrate W. As shown in FIG. The focusing lens 116 is adapted to maintain a constant size of the spot size on the surface of the semiconductor substrate W to which the laser beam 24 deflected by the beam deflector 114 is irradiated. Adjust the focal length of 24).

The detector 120 detects the scattered light 30 from the semiconductor substrate W by the irradiation of the laser beams, and converts the scattered light 30 into an electrical signal to calculate the operation unit 130 and the image processing unit. Transmit to 150.

The calculation unit 130 may be configured to intensify the first light 31 scattered from the surface of the semiconductor substrate W and the second light scattered from the foreign matter 14 on the semiconductor substrate W based on the electrical signal. Comparing the intensities of the (32), respectively, and calculates the difference between the intensities of the first light 31 and the intensities of the second light (32). The wavelength corresponding to the largest difference value is selected from the difference values.

The controller 140 is connected to the operation unit 130, and the laser source 100 sequentially receives the laser beams selected by one selected from the wavelength selector 106 and the plurality of resonators 104. The operation of the laser source 100 is controlled to irradiate the substrate W and irradiate a laser beam having a wavelength selected by the calculation unit 130 onto the semiconductor substrate W. In addition, the laser beam controls the operation of the beam deflector 14 to scan the surface of the semiconductor substrate (W) in the x-axis direction, and the driving unit (1) to scan the entire surface of the semiconductor substrate (W). 164 controls the operation.

The image processing unit 150 converts the electrical signal transmitted from the detector 120 into an image signal and displays the surface image of the semiconductor substrate W through the display unit 170. In addition, the image processing unit 150 analyzes the image signal to detect the position and size of the foreign matter 14 remaining on the semiconductor substrate W.

Hereinafter, the substrate inspection method according to an embodiment of the present invention will be described in detail with reference to FIGS. 6 to 10.

The semiconductor substrate W is placed on the moving stage 160. The first laser beam, which is generated from the laser source 100 and has the first wavelength, is extended through the beam expander 112, and on the predetermined semiconductor substrate W via the beam deflector 114 and the focusing lens 116. The sampling area 12 is irradiated. The beam deflector 114 deflects the first laser beam such that the first laser beam scans the surface of the sampling area 12 in the x-axis direction, and the driving unit 164 includes the first laser beam in the sampling area 12. The semiconductor substrate W is moved in the y-axis direction so as to scan the surface of the semiconductor substrate W. The width of the sampling area 12 corresponds to the scan width of the first laser beam deflected by the beam deflector 114, and the length is adjusted by the moving distance of the semiconductor substrate W controlled by the controller 140. do.

The first light 31 scattered from the surface of the sampling region 12 and the second light 32 scattered from the foreign matter 14 on the sampling region 12 are irradiated to the detector 120 by the irradiation of the first laser beam. Is detected. The detector 120 converts the intensity of the first light 31 and the intensity of the second light 32 into an electrical signal and transmits the electrical signal to the calculation unit 130. The difference between the intensity and the intensity of the second light 32 is calculated.

Subsequently, the laser source 100 generates a first laser beam having a second wavelength, and the first laser beam having the second wavelength is the beam expander 112, the beam deflector 114, and the focusing lens 116. Is irradiated to the sampling area 12 through. Subsequently, a difference value corresponding to the first laser beam having the second wavelength is calculated in the manner described above.

The calculation unit 130 selects the largest difference value among the difference values calculated by the above method.

The controller 140 controls the operation of the laser source 100 such that the laser source 100 generates a second laser beam having a wavelength selected by the operation unit 130, and the second laser beam is a semiconductor substrate. The operation of the beam deflector 114 is controlled to scan (W) in the x-axis direction, and the semiconductor substrate W is moved in the x-axis direction and the y-axis direction so that the second laser beam scans the semiconductor substrate W as a whole. The operation of the drive unit 164 is controlled to move to. Arrows shown in FIG. 6 mean a scanning direction of the second laser beam by the beam deflector 114 and a moving direction of the second laser beam by the driving unit 164, respectively.

The third light scattered from the surface of the semiconductor substrate W by the irradiation of the second laser beam and the fourth light scattered from the foreign matter on the semiconductor substrate W are detected by the detector 120. The detector 120 converts the intensity of the third light and the intensity of the fourth light into an electrical signal and transmits the electrical signal to the image processing unit 150.

The image processing unit 150 converts the electrical signal into an image signal, and the display unit 170 displays a surface image of the semiconductor substrate W according to the image signal. The image processing unit 150 analyzes the image signal to detect the location and size of foreign matter remaining on the semiconductor substrate W. At this time, the difference between the intensity of the third light scattered from the surface of the semiconductor substrate W and the fourth light scattered from the foreign matter on the semiconductor substrate W is determined between the intensities of the other first lights and the intensities of the second lights. The foreign matter on the semiconductor substrate W is easily detected because it is larger than the difference values.

According to the present invention as described above, a second laser beam having a wavelength selected from among the first laser beams each having a plurality of different wavelengths is irradiated to the semiconductor substrate, the surface of the semiconductor substrate from the light scattered from the semiconductor substrate Defects are detected. In addition, by using a laser beam having a wavelength selected from the wavelengths having the strongest spectrum, the efficiency and reliability of the inspection process for detecting foreign matter remaining on various films formed on the semiconductor substrate can be improved. Productivity is improved.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (6)

Sequentially irradiating first laser beams each having different wavelengths on a substrate, and first light scattered from a surface of the substrate by irradiation of the first laser beams and a second scattered from foreign matter on the substrate Detecting the lights, comparing the intensities of the first lights with the intensities of the second lights, and calculating difference values, and determining a wavelength corresponding to the largest difference value among the difference values. Irradiating a second laser beam having on the substrate, and defects of the substrate from third light scattered from the surface of the substrate by the irradiation of the second laser beam and fourth light scattered from foreign matter on the substrate. In the substrate inspection method comprising the step of detecting, Wherein the first laser beam is provided from a laser source having a plurality of resonators, wherein a wavelength change of the first laser beam is changed by the plurality of resonators. The method of claim 1, wherein the first laser beam and the second laser beam are argon laser beams. The method of claim 1, wherein the wavelengths of the first laser beam and the second laser beam are one selected from the group consisting of 366 nm, 488 nm, and 514 nm. A resonant tube comprising a laser medium, a plurality of resonators for selecting a wavelength of a laser generated from the laser medium, and a wavelength selector for selecting one of the plurality of resonators and placing them at both ends of the resonant tube And a power source for discharging and exciting the laser medium; A detector for detecting light scattered from the substrate by irradiation of laser beams each having different wavelengths from the laser source; Among the scattered lights, the intensities of the first lights scattered from the surface of the substrate and the intensities of the second lights scattered from the foreign matter on the substrate are respectively compared, and the intensities of the first lights and the intensities of the second lights are respectively compared. A calculation unit for calculating difference values therebetween, and selecting a wavelength corresponding to the largest difference value among the difference values; A controller for controlling the operation of the wavelength selector of the laser source such that the laser source irradiates the laser beams sequentially onto the substrate and irradiates a laser beam having the selected wavelength onto the substrate; And An image processing unit for scattering from the substrate by irradiation of a laser beam having the selected wavelength, obtaining a surface image of the substrate from the light detected by the detector, and detecting a defect of the substrate from the image Board inspection apparatus characterized in that. The apparatus of claim 4, wherein the laser medium is argon gas. 5. The apparatus of claim 4, wherein the resonators select laser beams having wavelengths of 366 nm, 488 nm and 514 nm, respectively.