JP5638098B2 - Inspection device and inspection condition acquisition method - Google Patents

Description

  The present invention relates to an inspection method and an inspection apparatus, for example, a method and an inspection apparatus for inspecting a defect on the surface of an inspection object such as a semiconductor wafer.

  In the surface inspection, for example, in a semiconductor device manufacturing process, a pattern is formed on a bare wafer by transferring a pattern and etching it. In the manufacturing processes of various semiconductor devices that form circuits, foreign matters and defects adhering to the wafer surface are major factors that reduce yield. Foreign matter and defects adhering to the wafer surface are managed in each manufacturing process, and foreign matter adhering to the bare wafer surface and defects existing on the wafer surface are detected with high sensitivity and high throughput. Inspection equipment.

  As a method for inspecting foreign matter and defects on a wafer, a method using a charged particle beam such as an electron beam and a method using light are roughly classified. A method using light is to take an image of the wafer surface using a camera, Some analyze image information, and others analyze the degree of light scattering by detecting light scattered on the wafer surface with a light receiving element such as a photomultiplier tube. An example of the latter is disclosed in Patent Document 1. Further, as a conventional technique related to the present invention, Patent Document 2 discloses that a foreign object on a sample having a large surface state is removed by direct current offset to make a margin in an amplifier dynamic range and increase a gain. A method is described in which small defects can be seen.

JP-A-63-143830 Japanese Patent Application Laid-Open No. 06-249791

  For example, a dark field inspection apparatus using a dark field condensing optical system scans illumination laser light and detects scattered light only when a light source is irradiated to a defect. Signal). On the other hand, the irradiation range is sufficiently larger than the target foreign matter, and widely illuminates the range to be detected. By the way, the mirror wafer has a very small uneven structure (microroughness) called “Haze”, and scattered light is also generated from the surface uneven structure when irradiated with a laser. Since this scattered light generally has a sufficiently low frequency component compared to the signal from an independent defect, it can be separated by circuit filtering. However, the shot noise inherent to the sensor is a pulse component in the low frequency Haze scattered light input. Because of the superposition, a wafer with a certain amount of Haze counts shot noise as a defect, not an actual defect, and cannot perform correct measurement. Moreover, if the inspection is not performed under an appropriate sensitivity condition according to the Haze level, the output signal of the sensor is saturated, and there is a possibility of causing problems such as failure to correctly recognize the size of the defect. In addition, in order to avoid such problems, the task of setting inspection conditions for new processes depends on trial and error methods, and it takes time to create inspection conditions and the difference in the skill level of the setting operator is sufficient. The problem is that it is impossible to bring out the proper inspection performance. As described above, the method of determining the inspection condition while actually measuring the signal takes time, and the determination whether the set sensitivity condition is appropriate depends on the discretion of the operator.

  One object of the present invention is to provide an inspection apparatus and an inspection method capable of obtaining desired inspection conditions in a short time while suppressing the influence of the inspection operator's skill in the inspection based on scattered light.

The present invention obtains a low frequency component lower than a frequency component indicating an abnormality of the sample, normalizes the low frequency component, and obtains a range of anomalous dimensions that can be detected from the normalized signal. One feature.

  Another feature of the present invention is that the scattered light generated by the irradiation light irradiated on the sample is detected, the scattered light detected by the scattered light detection optical system is converted into an electrical signal, and the converted electrical signal In the inspection method for determining the size of the foreign matter from the size of the scattered light from the foreign matter on the wafer surface, the scattered light information from the sample surface is used to determine the detection condition of the scattered light. It is in the inspection method to be used.

  These and other features of the present invention are further illustrated by the following description.

  According to the aspect of the present invention, there is an effect that desired inspection conditions can be obtained in a short time while suppressing the influence of the skill of the inspection operator.

It is a figure which shows schematic structure of the Example of this invention. It is a figure which shows the illumination spot of the Example of this invention. It is a figure which shows Haze, the foreign material signal, and shot noise waveform of the Example of this invention. It is the figure which showed the procedure which calculates | requires a limit sensitivity from the normalized Haze amount of the Example of this invention. It is the figure which showed the sequence at the time of the test condition preparation of the Example of this invention. It is the figure which showed the sequence at the time of the normal test | inspection of the Example of this invention. It is the figure which showed the inspection condition creation screen of the Example of this invention. It is the figure which carried out the test | inspection with the Haze monitoring function validated by the test result of the Example of this invention, determined the validity of the measurement condition as NG, and displayed the warning. It is the figure which displayed that the inspection result of the example of the present invention enabled the Haze monitoring function, checked that the validity of the measurement condition was NG, automatically corrected the sensitivity, and the result of the minimum size was invalid. . It is a figure which shows the optical system schematic structure of Example 2 of this invention.

  After the general description of the present invention, embodiments will be described.

  In the present invention, the Haze signal (direct current) and the foreign substance signal (pulse) are information associated with each other as the ratio of the amount of scattered light to the irradiation power, and the magnitude of shot noise is statistically proportional to the square root of the Haze signal. Utilizing the physical phenomenon of increasing, predicting the detection limit of foreign matter and the maximum detectable size from Haze information (surface roughness) acquired in advance, preventing false generation and maintaining high inspection accuracy It is something to try.

For this purpose, the second measurement quantity called Haze is used to maintain the accuracy of the foreign object inspection, which is the first measurement object, and provide a technique that anyone can obtain without trial and error in the limit performance. I was able to. That is, for example,
1) Focusing on the correlation between the pseudo and roughness induced by scattered light due to extremely fine roughness on the wafer surface, the roughness information (Haze) is directly measured when setting the sensitivity of the foreign material and automatically appropriate. The inspection device calculates the foreign object detection sensitivity and the detectable range (minimum, maximum size) and provides information to the operator.

  2) Similarly, a large Haze increases the DC component of the sensor and causes saturation. Focusing on the correlation between Haze and saturation, the maximum sensitivity that does not saturate is determined and information is provided to the operator. Also, when inspecting under registered conditions, whether or not Haze is out of range is automatically determined before inspection, and saturation is avoided by automatically shifting the sensitivity.

  3) A wafer with a small Haze can raise the sensitivity to a level where saturation and pseudo defects are allowed. Focusing on the relationship between Haze, the limit sensitivity, and saturation, the maximum sensitivity that does not cause pseudo and does not cause saturation is determined and information is provided to the operator.

  Further, the roughness (roughness) of the wafer surface targeted by the present invention is defined as Haze in the SEMI standard, and the effective value of height is 0.1 to 10 nm, and the repetition period of unevenness is 0. It is about 1 to 10 μm and is measured with an AFM (Atomic Force Microscope). However, AFM can inspect only a very small area, and it is considered impractical to inspect the entire wafer surface.

  On the other hand, in the dark field inspection method that irradiates the wafer surface with a laser and collects the scattered light, the scattered light correlated with the average height of the fine roughness from the range irradiated with the laser. As a result, Haze can be obtained as a signal having a frequency component sufficiently lower than LLS (Localized Light Scatter) correlated with the rms value.

  That is, there is a difference in Haze between a smooth surface and a rough surface. On the other hand, the detection limit of an inspection apparatus such as a mirror surface wafer is noise. In addition to the base circuit noise, noise generated from a detector that is several times larger than an order of magnitude is added to this noise. This noise form is a single-shot signal that is randomly generated without depending on time and position, and is indistinguishable from a signal from the LLS. It has been confirmed that the magnitude of this noise has a correlation with the amount of Haze. The smaller the Haze, the smaller the defect can be detected. However, how far the small defect can be seen requires the operator's experience and a process of changing parameters by trial and error.

  On the other hand, in the prior art, the relationship between Haze and shot noise in surface inspection is not considered.

  The inventors of the present invention have focused on the point that it is not sufficient to simply cancel the DC component with an offset from a sample having a large Haze. Furthermore, in the semiconductor wafer surface inspection technology using the dark field method, which is an issue of the application field of the present invention, it is not the amplifier range that must be taken into account when the Haze is large. The sensor itself is saturated. Since this characteristic is directly related to Haze, it must be reduced by changing the light amount or the bias condition of the sensor to an appropriate sensitivity. Specifically, the voltage applied to the photomultiplier tube is controlled to optimize the amplification degree of the sensor itself. As a result, a signal saturated by the sensor may become apparent.

  The present invention provides an optimization technique of how much the sensitivity of a signal saturated with a sensor is lowered.

  The effect expected by the present invention is not to provide a means for optimally setting the sensitivity on a surface where the Haze is so large that the signal of the target independent defect is buried, but within an allowable range of Haze. Thus, automatic correction is applied to a Haze wafer that affects the inspection accuracy. Further, in terms of creating conditions, it is possible to determine the conditions for extracting the limit performance without taking time from the photometric Haze data.

  The present invention provides a technique for directly determining an appropriate sensitivity from the amount of Haze.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment of a foreign matter / defect inspection apparatus using the foreign matter / defect detection method of the present invention. A semiconductor wafer 100 that is an object to be inspected is vacuum-sucked by a chuck 101, and this chuck 101 is mounted on an object to be inspected stage 102 and a Z stage 105 that are composed of a rotary stage 103 and a translation stage 104. The rotary stage 103 performs rotational movement θ, and the translation stage 104 performs translational movement r. These stage controls are performed via the stage control mechanism 107 based on control signals from the host CPU 108 and the arithmetic unit 121. The illumination / detection optical system 110 includes a light source 200 and a sensor 207, and generates scattered light when the illumination spot irradiated from the light source strikes a foreign matter or a defect 206 on the wafer surface. The sensor 207 detects this scattered light, converts it into an electrical signal, and amplifies it by the amplifier 111. The scattered light signal detected by the amplifier 111 is divided into a foreign matter / defect signal processing system 115 having a high frequency and a Haze signal processing system 119 having a low frequency.

  In the foreign matter / defect signal processing system 115, the pulse component is extracted by the high pass filter 112, converted into the foreign matter / defect digital signal by the AD converter a113, and then the foreign matter / defect determination mechanism 114 for each unit area divided in advance. The size and position of the foreign matter or defect is sent to the host CPU 108 via Haze and the defect data transfer mechanism 120 in synchronization with the foreign matter / defect coordinate.

  The Haze signal processing system 119 extracts DC and low frequency components by the low-pass filter 116, converts them to Haze digital signals by the AD converter b 117, and then converts the Haze coordinates from the Haze coordinates for each unit area divided in advance. The Haze measurement value is sent to the host CPU 108 via the Haze and the foreign object / defect data transfer mechanism 120 in synchronization. At this time, the defect / foreign object coordinate being inspected is detected by the inspection coordinate detection mechanism 106, and a coordinate synchronization signal for synchronizing with the coordinate position is generated by the calculator 121, and the current position is reported to the host CPU 108. In this way, the illumination spot scans the entire surface of the wafer, thereby determining the size and position of the foreign matter / defect and Haze, and outputting the inspection result to the input / output device 109. The method for outputting the inspection results is a map showing the distribution of foreign matter / defects or Haze on the screen and / or a text file describing the position and size of each foreign matter / defect, the type of defect, etc. Etc. Also, the input / output device 109 inputs conditions such as sensitivity and threshold value for inspecting foreign matter / defects, and inputs commands such as start of inspection, analysis of inspection results, and storage.

  The sensitivity of the sensor when inspecting the entire surface of the wafer is performed by the sensor sensitivity controller 122 based on the data sent to the computing unit 121 according to the set conditions. Further, the Haze signal processing system 119 measures the amount of Haze and reports it to the host CPU 108 for the purpose of acquiring information for determining the sensor sensitivity before starting the entire surface inspection.

  FIG. 2 is a diagram showing illumination spots according to the embodiment of the present invention. Further, FIG. 2 shows an illumination / detection optical system disposed above the semiconductor wafer 100. A laser light source is used as the illumination light source 200. The irradiation beam 201 emitted from the light source 200 enters the irradiation lens 202 to form an illumination spot 203 having a predetermined size. The illumination light is, for example, P-polarized light, and is configured so as to be obliquely incident on the surface of the semiconductor wafer 100, which is an object to be inspected, approximately at a Brewster angle with respect to crystal Si. In this way, the irradiation beam trajectory on the wafer becomes spiral by the mechanism in which the irradiation beam is fixed and the wafer is translated while rotating. When this locus is called a helical scan 208, the illumination spot 203 has a substantially elliptical shape consisting of a long axis component 204 long in the radial direction r and a short axis component 205 short in the radial direction θ with respect to the helical scan 208. Here, the inside of the contour line where the illuminance decreases to 1 / square of e at the center of the illumination spot (e is the base of the natural logarithm) will be defined again as an illumination spot. In order to avoid a gap area that is not irradiated and not inspected in the spiral scan on the wafer 100, the normal illumination spot 203 has a predetermined amount in an arbitrary track of the spiral scan and the next track. Set to overlap. In this embodiment, the illumination spot 203 is scanned from the inner periphery to the outer periphery of the semiconductor wafer 100, but the reverse is also possible. When a foreign object or defect 206 on the surface of the wafer 100 is irradiated with an illumination spot irradiated from a light source, scattered light is generated. The sensor 207 detects this scattered light via the light receiving system condensing lens 209 and converts it into an electrical signal.

  The amount of light scattered from a foreign material that is smaller than the wavelength of the laser beam irradiated on the wafer is generally the sample optical constant (refractive index, sub-refractive index), thin film thickness, refractive index of the target foreign material, size of the foreign material, and detection optics It is determined if the irradiation angle of the system, the polarization direction, the arrangement of the light receiver, and the light analysis are determined. Here, the optical constant of a sample is usually determined by a deposited material and can be measured by a well-known method. The amount of scattered light can be normalized as a ratio to the irradiation power density, that is, the power per irradiation area, regardless of the irradiation area or irradiation power, and can be calculated by simulation with an amount called BRDF (Bidirectional Reflectance Distribution Function).

This calculation result is generally given by a table of the foreign matter size to normalized scattered light ratio, but in a region sufficiently smaller than the measurement wavelength, the Rayleigh (Reighly) that the amount of scattered light decreases in proportion to the sixth power of the foreign matter size. Since it can be considered that the law is obeyed, the normalized scattered light ratio from particles, Particle _BRDF is

但しｒは異物の直径

Where r is the diameter of the foreign material

The scattered light amount P _dp entering the sensor is

但しｐは照明のパワー、ｓは照射面積と表すことができる。

However, p can be expressed as illumination power, and s can be expressed as an irradiation area.

  On the other hand, when there is Haze (fine concavo-convex structure) on the wafer surface, if the laser beam is squeezed well and irradiated, scattered light is uniformly generated in the irradiated range, and the detector integrated the scattered light from each point. The amount will be detected.

  This Haze incident light amount can also be treated as a BRDF amount by being normalized by the ratio of the scattered light to the irradiation power, regardless of the sensitivity of the sensor and the irradiation power. When the Haze light quantity Meas Haze measured with a certain limited NA is known among the irradiation power p and all solid angles for measuring scattered light, this BRDF is

Here, S _k is the cathode radiation sensitivity of the sensor, that is, the current ratio to the incident light amount on the photoelectric conversion surface, g (PMTHV) is the multiplication factor of the sensor, and P _dh is the amount of light incident on the sensor (the amount of light scattered from Haze). , C is a conversion coefficient of the Haze processing system, and K is an appropriate proportionality constant. The sensor is a photomultiplier tube, and the multiplication factor is variable by the applied voltage PMTHV.

According to (Equation 3), C, because S _k is the sensor or inspection device specific constants used, predetermined conditions measured amount of Haze that (g (PMTHV), p is known) was measured by (Meas Haze) This shows that it is possible to calculate Haze _BRDF , which is a normalized Haze amount.

On the other hand, if fine irregularities on the wafer surface enter the sensor as Haze scattered light, this causes shot noise. When the shot noise superimposed by the photomultiplier tube becomes the same as the size of the foreign matter signal, the size of the foreign matter becomes the limit detection size of the pattern-less wafer foreign matter inspection apparatus. The magnitude of this noise is known to increase in proportion to the square root of the cathode current. The cathode current is proportional to the amount of light Phd entering the sensor, and Phd is proportional to Haze _BRDF. This leads to the relationship that the noise signal increases in proportion to the square root of Haze _BRDF .

  FIG. 3 is a diagram showing Haze, a foreign substance signal, and a shot noise waveform according to the embodiment of the present invention. FIG. 3 shows a state of a detection signal when a defect on a wafer having a certain roughness is detected by this inspection apparatus. This is a signal before the low frequency component and the high frequency component are independently extracted from the output signal of the amplifier 111 of FIG. The horizontal axis represents time, and the vertical axis represents the signal magnitude from the ground level 300. The detection signal 302 has a magnitude obtained by adding a component having a signal magnitude of S, a signal 301 from a foreign object having a magnitude of S1, and a component having a magnitude of S2 in the Haze signal 303, that is, S = S1 + S2. Here, the foreign substance signal 301 is generated as a pulse signal because the signal is generated only during the irradiation time of the laser spot. In the region where the magnitude S1 is sufficiently smaller than the measurement wavelength, the amount of scattered light is proportional to the sixth power of the foreign substance size. It is proportional to the irradiation power density and the sensitivity of the sensor. On the other hand, the magnitude S2 of the Haze signal 303 correlates with the surface roughness and is proportional to the irradiation power and the sensitivity of the sensor. Furthermore, when shot noise 304 proportional to the square root of the Haze component is superimposed on the pulse component, and the shot noise that is the pulse component has the same magnitude as the foreign substance signal from the detection limit size, the noise smaller than that size is detected. Can not do it. This is the detection limit. This limit is determined by the size of Haze regardless of the sensitivity of the sensor if the power to be irradiated is fixed.

When shot noise generated when illuminating a Haze _BRDF wafer with power p is converted into an incident light quantity P _sn equivalent to the noise level,

Ｃ_nは適当な比例定数

C _n is an appropriate proportionality constant

On the other hand, a foreign substance size such that P _dp = P _sn can be obtained from (Expression 2) and (Expression 4). That is

That is, if Haze _BRDF can be obtained from (Equation 3) under certain conditions, it is possible to predict the minimum detectable foreign material size on the wafer from (Equation 5).

  FIG. 4 is a diagram showing a procedure for obtaining the limit sensitivity from the normalized Haze amount according to the embodiment of the present invention.

  A graph 400 showing the relationship between the minimum detected foreign material size and the normalized Haze is shown on the right side of FIG. The horizontal axis is the normalized Haze amount, and the vertical axis is the limit size.

  The signal including Haze shown in FIG. 3 is extracted by the Haze signal processing system shown in FIG. 1, and the normalized Haze is calculated by the upper CPU according to the algorithm described above. On the other hand, since the inspection apparatus has the relationship shown in the graph 400 of FIG. 4 in the storage unit in the inspection apparatus as, for example, a text data table, the minimum size that can be detected under the optical conditions can be obtained immediately. Here, the relationship shown in the graph 400 may be directly calculated by the inspection apparatus in the form of a function.

  A graph 401 on the left in FIG. 4 shows the relationship between the normalized detected light amount and the foreign substance size. Once the limit size is determined from the normalized Haze amount, it is possible to control the sensor sensitivity by calculating the sensitivity condition most suitable for the size that can be processed by the foreign substance / defect signal processing system shown in FIG. is there.

  FIG. 5 is a diagram showing a sequence at the time of creating inspection conditions as an embodiment of the present invention. An initial condition is set or selected from the input / output device 109, and a wafer to be inspected is loaded (Wafer load). During wafer transfer until the illumination spot reaches the inspection start position with respect to the wafer, the pre-Haze measurement process 501 temporarily activates the Haze signal processing system 119 to measure the Haze amount (Get Haze data) and normalize it. A Haze process 503 calculates a normalized Haze value. At this time, if an effective Haze amount cannot be measured under the initially set sensitivity condition (NO in Haze within range?), The sensor sensitivity is automatically adjusted by the measurement condition shift processing 502 so that Haze is within the measurement range. The Then, a normalized Haze value is calculated by the normalized Haze processing 503 (Normalaization). In other words, when the Haze measurement value exceeds the upper limit of the range, the sensitivity is automatically adjusted to decrease, and when the Haze measurement value cannot be detected, the sensitivity is automatically adjusted to increase (sensor sensitivity optimization processing 504).

  The sensor sensitivity optimization process 505 prompts the input / output device 109 whether or not to optimize the sensitivity based on the normalized Haze value before starting the inspection. When performing the optimization, the minimum detection size is checked. Then, the initial input conditions are finely adjusted to inspect the entire wafer surface. Thereafter, after confirmation, conditions are saved (Save recipe), and the condition creation sequence is completed.

  FIG. 6 is a diagram showing a sequence during normal inspection as an embodiment of the present invention. The inspection condition 600 registered in advance from the input / output device 109 is selected to start the inspection (measurement condition selection processing 600). During the wafer transfer process until the wafer is loaded (Wafer load) and the illumination spot is at the inspection start position with respect to the wafer, the normal inspection Haze monitoring process 601 starts from collecting information on the normalized Haze amount (Get Haze data). Calculation (Normalization), saturation / detection limit check processing 602 and inspection condition validity determination processing 603 are automatically performed by using the functions of the respective parts constituting the inspection apparatus. If the measurement conditions are validated and determined to be contradictory (Yes in Incoherence?), The conditions are temporarily changed and measured by the warning transmission and temporary sensitivity correction processing 604, and the result is output. (Output result) and end (End). Further, a warning indicating that the sensitivity has been temporarily lowered is output to the input / output device together with the inspection result. The input / output device can select whether to enable or disable the Haze monitoring process 601 at the time of normal inspection and to permit temporary change of conditions at the time of determination NG or to only give a warning.

  FIG. 7 is an example of a screen for creating an inspection condition. FIG. 7 shows an inspection condition selection menu button 700, a sensitivity condition selection menu button 701, an irradiation condition setting area 702, a sensor sensitivity setting area 703, a scanning condition setting area 704, a threshold value and a detected defect size. Setting area 705, output display method and inspection area setting area 706, Haze monitoring function setting button 707, Haze monitoring function setting item sub-display area 708, command button arrangement area 709, wafer load button 710, wafer An inspection start button 711, an optimization execution button 712 based on Haze information, a wafer unload button 713, and a work mode switching button arrangement area 714 are displayed.

  When a new inspection condition for the inspection target wafer is newly created, an illumination condition 702 that is most suitable for the type and thickness of the thin film first generated on the surface of the inspection target wafer is previously set as the initial condition as the inspection condition menu 700 or Registered in the sensitivity condition menu 701. The registered initial condition is selected from the inspection condition menu 700 or the sensitivity condition menu 701. The sensor sensitivity 703 at this time is a sensitivity necessary for capturing 0.1 μm of foreign matter on the wafer surface, for example, and is a provisional value before being optimized. The setting of the scanning condition setting area 704, the output display method, and the inspection area setting area 706 is appropriately set according to the purpose of the inspection regardless of the optimization of the sensitivity condition. The defect size registration area 705 is set according to the purpose of use after the optimization of sensitivity conditions is completed. When optimizing the sensitivity based on the normalized Haze value, when the Haze monitoring function setting button 707 is pressed, the Haze monitoring function setting item sub display area 708 is displayed, and the switch “Haze pre-check for enabling the function is displayed. When “enable” is set to ON, the normalized Haze amount is measured and calculated before the wafer is loaded and the inspection is performed, and the validity of the sensitivity condition is determined. The item below the Haze monitoring function setting item sub display area 708 is an item that allows the inspection device to select an action to be performed when the sensitivity condition is determined to be NG when measuring in the normal mode. The inspection is selected by shifting the sensitivity, or simply displaying a warning. The Haze monitoring function setting button 707 may be omitted and the Haze monitoring function setting item sub display area 708 may be directly arranged. The Haze monitoring function may or may not be necessary for each type of wafer to be inspected, so it can be registered independently for each condition, but it can be set in common for all inspection conditions. good. In this case, the location of the Haze monitoring function setting item sub display area 708 may be an initial setting area, an initialization file, or the like to which special access authority is given.

  Here, an example of operating the work flow of FIG. 5 on the screen of FIG. 7 is shown. After the initial inspection condition is selected from the menu 700 or the sensitivity condition menu 701, 704 to 706 are appropriately set, and the wafer to be inspected is loaded by the wafer load button 710. The Haze monitoring function setting item sub display area 708 is checked as “valid”. At this point, the sensitivity is not optimized, and the provisional sensitivity is given as the initial condition. When the wafer is loaded, the Haze value is measured under the conditions registered in the initial conditions, and the normalized Haze amount is calculated. When the wafer inspection start button 711 is pressed here, the inspection apparatus performs the inspection under the initial conditions. When the optimization execution button 712 based on the Haze information is pressed, the inspection is performed in a state where the sensitivity set in the initial condition based on the normalized Haze amount is temporarily shifted upward or downward.

  The shift amount is a position at which the minimum detection size enables the effective measurement range to the maximum extent. However, by adding a setting item to the display area 708, input of a target size larger than the minimum detectable size is prompted, and the specified input is performed. The size may be optimized to maximize the effective measurement range. After the actual inspection is performed and confirmed by the wafer inspection start button 711 under the conditions corrected optimally in this manner, sensitivity conditions and inspection conditions are newly stored as new conditions. When the wafer unload button 713 is pressed, the wafer is unloaded and the sensitivity optimization operation ends.

  FIG. 8 is a diagram in which the Haze monitoring function is validated and the inspection result of the embodiment of the present invention is inspected, the validity of the measurement condition is determined to be NG, and a warning is displayed. That is, FIG. 8 shows a measurement condition / inspection information display area 800, a detection number display area 801 by defect size, a display area 802 such as a detection number by Haze value and defect category, a defect map 803, and detection by defect size. A number histogram 804 and a display 805 warning that the defect size is not correctly recognized are displayed. When the wafer inspection is performed with the Haze monitoring function enabled in the Haze monitoring function setting item sub display area 708, the validity of the condition measured by the normalized Haze value is determined as NG. It is an example of an inspection result display when the operation of the inspection device is set to only display a warning. The result of measurement without correcting the sensitivity condition is displayed in the detected number display area 801 for each defect size, and a warning 805 is displayed to the effect that “the defect size may not be recognized correctly”. Other than the warning, it is the same as the normal inspection result.

  FIG. 9 shows that the inspection result of the embodiment of the present invention is inspected with the Haze monitoring function enabled, the validity of the measurement condition is judged as NG, the sensitivity is automatically corrected, and the result of the minimum size is invalid. FIG. That is, FIG. 9 shows a case where the wafer is inspected with the Haze monitoring function enabled in the display area 708, when the validity is determined for the condition measured by the normalized Haze value and it is determined as NG. It is an example of an inspection result display when the operation of the inspection apparatus at that time is set to inspect with a sensitivity temporarily lowered. Since the minimum detection size is automatically changed, a special symbol such as an asterisk is displayed on the size classification display 900 out of the counting range instead of the detection number, and the sensitivity is automatically corrected. A display 901 is displayed to warn that measurement has been performed.

  FIG. 10 is a diagram illustrating a schematic configuration of an optical system according to the second embodiment of the present invention. In the first embodiment, the wafer 100 is illuminated obliquely from above, whereas in the second embodiment, the irradiation beam 1001 irradiated from the laser light source 1000 is narrowed in a spot shape by the irradiation lens 1002 and vertically aligned on the wafer surface. Irradiate. Scattered light 1003 from the foreign matter or defect is collected by the light receiving system condenser lens 1004 and guided to the sensor 1005. The installation angle of the light receiving condensing lens 1004 may be different from that of the light receiving condensing lens 209 shown in FIG. One inspection device may have an optical path switching mechanism that can select illumination from obliquely above and vertically, and the light receiving condenser lens also collects light scattered at a low angle. A method of processing both signals of the light receiving system condensing lens 1004 that collects light scattered at a high angle with 209 may be used.

  Further, in addition to the method in which the sample is translated while being rotated and spirally scanned, a method in which the sample is moved in the XY directions may be used.

  In any of the embodiments, the Haze amount is measured before wafer inspection based on the algorithm using (Expression 1) to (Expression 5) as described in paragraphs 0031 to 0051, and normalized from the conditions. A method and a function for determining the optimum size that can be inspected for the limit size and the size from the relationship between the limit size specified for each film type and optical condition and the normalized Haze amount are provided. Is.

  As described above, in the present specification, for example, a stage that holds a sample, an illumination optical system that irradiates illumination light onto the surface of the sample held on the stage, and an irradiation light that irradiates the sample. A dark field optical system that detects the generated scattered light, a photoelectric conversion unit that converts the scattered light detected by the scattered light detection optical system, and an electrical signal converted by the photoelectric conversion unit into a digital signal Equipped with a changing AD converter, equipped with a determination unit that determines the size of the foreign matter from the size of the scattered light from the foreign matter on the sample surface, and optimized using the scattered light information from the sample surface to determine the detection conditions An inspection device is disclosed.

  In addition, the inspection apparatus can previously acquire scattered light from the sample surface before performing the inspection. As conditions for acquiring scattered light from the sample surface in advance, selection of the most suitable optical system for each film type and film thickness is registered as an initial condition. Further, the inspection apparatus selects whether or not to optimize the condition setting using the scattered light information from the sample surface.

  In addition, the detection optical system and the signal processing unit for acquiring the scattered light from the sample surface before the inspection by the inspection apparatus have the same configuration as the state of the sample surface and the entire surface of the foreign material, and only the timing for the inspection is used. Is different. Further, the timing of inspecting the sample surface is performed by partially sampling at least one point on the sample before loading the sample on the stage and before starting the entire surface inspection. In this sampling, the sensitivity of the sensor is changed stepwise from the initial condition, and the sensitivity is made variable until the measured value of the scattered light on the sample surface falls within a desired range.

  The inspection device calculates the normalized Haze amount of the sample from the acquired scattered light information of the sample surface and the inspection condition, and the inspection device automatically calculates the optimization condition and the minimum detectable size immediately. Can be determined. At this time, the optimum condition determined by the inspection apparatus is displayed on the input / output device, and the validity or invalidity of the optimum condition can be selected.

  Further, when the inspection apparatus inspects under the already registered conditions, the inspection apparatus can determine whether or not the conditions to be inspected are appropriate for inspecting the sample. To do. At this time, the inappropriate determination of the condition is determined as inappropriate when the measured scattered light on the sample surface exceeds the set condition range.

  In addition, the treatment of the inspection apparatus when the determination result before inspection is inappropriate is as follows: 1) A warning is displayed in the inspection result that the amount of scattered light on the sample surface is out of range.

  2) The inspection is automatically performed with the sensitivity lowered so that the optimum condition is obtained within a range set in advance. The inspection result indicates that the amount of scattered light on the sample surface is out of range and that the sensitivity is automatically corrected according to the inspection result. If the amount of scattered light on the sample surface deviates beyond the correctable range, a warning is displayed as “abnormally scattered light amount on the sample surface” without correction.

  Any one of the above 1) and 2) can be selected from the input device.

  In addition, the sample to be inspected is a non-patterned mirror bare silicon wafer or a silicon wafer with a non-patterned deposition film, and the object to be inspected is locally, such as foreign matter, scratches, stains and crystal defects present on the wafer surface. It is a defect that exists and that scattered light is generated when irradiated with laser light, and the size of the detected defect is determined by converting it to the standard particle size for sensitivity calibration, and the position and number on the wafer are determined. An inspection apparatus characterized by outputting is disclosed.

  Also, a stage for holding the sample, an illumination optical system for irradiating the surface of the sample held on the stage with illumination light, and scattered light detection optics for detecting scattered light generated by the illumination light irradiated on the sample A system, a photoelectric conversion unit that converts the scattered light detected by the scattered light detection optical system into an electric signal, and an AD conversion unit that converts the electric signal converted by the means into the photoelectric conversion unit into a digital signal, In the method for determining the size of foreign matter from the size of scattered light from the foreign matter on the wafer surface, it has a function of optimizing using the scattered light information (haze) from the wafer surface in determining the detection condition. An optical wafer surface foreign matter inspection method is disclosed.

  In the above method, the normalized Haze amount of the wafer is calculated from the acquired Haze data and the inspection condition, and the inspection apparatus automatically calculates and determines the optimization condition and the minimum detectable size immediately.

  In addition, according to the embodiment of the present invention, it is possible to ensure the accuracy of the size of the foreign matter when the surface state changes within an allowable range. In addition, when the surface state fluctuates within an allowable range, it is possible to inspect a foreign material having a certain size or more. And or more than the standard performance can be pulled out without relying on the skill level of the worker at the time of creating conditions. And / or the optimum conditions can be created in a short time when creating the conditions.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above, and various modifications can be made within the scope of the technical idea of the present invention.

100 Semiconductor wafer 101 Chuck 102 Inspected object moving stage 103 Rotating stage 104 Translation stage 105 Z stage 106 Inspection coordinate detection mechanism 107 Stage control mechanism 108 Host CPU
109 Input / Output Device 110 Illumination / Detection Optical System 111 Amplifier 112 High Pass Filter 113 A / D Converter a
114 Foreign matter / defect determination mechanism 115 Foreign matter / defect signal processing system 116 Low-pass filter 117 A / D converter b
118 Haze determination mechanism 119 Haze signal processing system 120 Haze and foreign substance / defect data transfer mechanism 121 calculator 122 sensor sensitivity controller 200, 1000 laser light source 201, 1001 irradiation beam 202, 1002 irradiation lens 203 illumination spot 204 long axis of illumination spot Component 205 Short axis component of illumination spot 206 Foreign object or defect 207, 1005 Sensor 208 Spiral scanning 209, 1004 Light receiving system condenser lens 300 Ground level 301 Signal waveform from foreign object 302 Detection signal waveform 303 Haze signal waveform 304 Shot noise waveform 400 Graph 401 showing relationship between minimum detected foreign matter size and normalized Haze 500 Graph showing relationship between foreign matter size and normalized detected light quantity Initial condition (when creating new condition) selection process 501 Pre-Haze measurement process 502 Inspection condition shift process 50 3 Normalized Haze processing 504 Sensor sensitivity optimization processing 505 Defect detection sensitivity optimization processing based on Haze information 600 Measurement condition selection processing 601 Normal inspection Haze monitoring processing 602 Saturation / detection limit check processing 603 Inspection condition validity determination processing 604 Warning transmission And temporary sensitivity correction processing 700 Inspection condition selection menu button 701 Sensitivity condition selection menu button 702 Irradiation condition setting area 703 Sensor sensitivity setting area 704 Scanning condition setting area 705 Threshold and detection defect size setting area 706 Output display method and inspection area Equivalent setting area 707 Haze monitoring function setting button 708 Haze monitoring function setting item sub display area 709 Command button arrangement area 710 Wafer load button 711 Wafer inspection start button 712 Optimization execution button based on Haze information 713 Wafer unload button 714 Work mode switching Arrangement area 800 Display area for measurement conditions and inspection information 801 Detected number display area for each defect size 802 Display area such as Haze value and detected number for each defect category 803 Defect map 804 Detected number histogram for each defect size 805 Defect size is not recognized correctly Display 900 for warning that the size classification is displayed when the sensitivity is automatically lowered and measured 901 Display for warning that the measurement is automatically performed after correcting the sensitivity 1003 Scattered light

Claims (12)

An illumination optical system for supplying light to the sample;
A detection optical system for detecting light from the sample;
A processing unit,
The processing unit obtains a low frequency component lower than a frequency component indicating an abnormality of the sample, performs a normalization process on the low frequency component, and obtains a range of anomalous dimension that can be detected from the normalized signal. Inspection device. The inspection apparatus according to claim 1, wherein the low frequency component is a haze signal, and the normalized signal is a normalized haze signal. The inspection apparatus according to claim 2,
The processing unit is an inspection apparatus that determines sensitivity of the detection optical system from the range. The inspection apparatus according to claim 3, wherein
The acquisition of the normalized haze is an inspection apparatus that is performed while the sample is loaded into the inspection apparatus and the inspection is performed. The inspection apparatus according to claim 1,
The normalized signal is acquired while the sample is loaded into the inspection apparatus and the inspection is performed. The inspection apparatus according to claim 1,
The processing unit is an inspection apparatus that determines sensitivity of the detection optical system from the range. An inspection condition acquisition method for an apparatus for inspecting the sample by irradiating the sample with light and detecting scattered light from the sample,
Obtain a low-frequency component that is lower than the frequency component that indicates the abnormality of the sample,
Normalizing the low frequency component,
An inspection condition acquisition method for obtaining a range of anomalous dimensions that can be detected from a normalized signal. In the inspection condition acquisition method according to claim 7,
The inspection condition acquisition method, wherein the low-frequency component is a haze signal, and the normalized signal is a normalized haze signal. The inspection condition acquisition method according to claim 8, wherein the sensitivity of the detection optical system is determined from the range. The inspection condition acquisition method according to claim 9, wherein acquisition of the normalized haze is performed until the sample is loaded into an inspection apparatus and inspection is performed. The inspection condition acquisition method according to claim 7, wherein the sensitivity of the detection optical system is determined from the range. The inspection condition acquisition method according to claim 7, wherein the acquisition of the normalized signal is performed until the sample is loaded into the inspection apparatus and the inspection is performed.

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