JP2002116184A - Instrument and system for analyzing foreign matter in semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the yield of a high-integration semiconductor device, and to enhance the speed and efficiency of analysis. SOLUTION: The analysis method is provided for analyzing semiconductor devices by obtaining a two-dimensional ion image from ions obtained from a foreign matter or a contaminated part by a laser abrasion method, and a manufacturing method including an analyzing process is provided for manufacturing the semiconductor devices. The above methods include an ion optical system satisfying both space resolution and detection sensitivity allowing a 0.1 mm foreign matter, in particular, to be analyzed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a memory, an ASIC, and the like.
The present invention relates to an analysis / removal device suitable for chemical analysis and removal of minute foreign matter and contaminated portions necessary for improving the yield of semiconductor devices such as LSIs, magnetic disk devices, and liquid crystals, and a semiconductor device manufacturing method using the same.

[0002]

2. Description of the Related Art In order to improve the yield and quality of an LSI, it is necessary to analyze foreign substances and contaminants having a diameter of 1 μm or less, which are mainly adhered in a manufacturing process, to clarify the cause of the generation and to develop a removal method. is there. On the other hand, the processing dimensions are becoming finer every year, and have recently become very thin, 0.3 to 0.5 μm. Especially 16M
DRAM has a width of 0.5 μm and a depth of 0.5 μm (aspect ratio (depth /
Width): 1) Deep groove type or single hole structure. For analysis of foreign matter adhering to this, the minimum analysis diameter is 0.3 μm and the analysis sensitivity is 10 ⁻¹⁴ g (0.1 μm ^{3 in} terms of volume). ) As described above, a high-performance device capable of reliably performing the analysis up to the bottom of the deep groove is required. For 64M, 256M, and 1GDRAM, the wiring rule is also 0.
As a result, the size of the target foreign substance and the contaminated region is 0.1 μm or less, and the aspect ratio reaches 3 to 5.

[0003] As for inorganic foreign substances, there are a minute portion secondary ion mass spectrometer, a scanning Auger electron spectrometer, and the like, and these needs can be sufficiently satisfied. On the other hand, for the analysis of organic contaminants, a micropart ultra-high sensitivity surface analyzer that can perform fluorescence spectroscopic analysis and Raman analysis of microparts is close to this requirement, but the minimum analysis diameter is 0.5 μm and the aspect ratio is 0.6, In addition, it is not possible to analyze organic foreign substances and mixtures on a SiO ₂ film, an organic film, and the like, and thus, it is not sufficient to cope with a 0.1 to 0.3 μmL SI process.

As an analysis method which can cope with this, a purpose is set for a foreign substance or a contaminated portion, and a laser beam squeezed to the size of the target is irradiated.
It is considered that the laser mass spectrometry described in Japanese Patent Publication No. 66 is optimal in sensitivity. However, for a future 0.1 to 0.3 μm process, the focusing of the laser beam is, in principle, one wavelength.
Since it cannot be reduced to about / 2 or less, analysis including even very small foreign substances cannot be handled by extension of the current technology. TOF that irradiates a focused primary ion beam such as Ga or Cs instead of a laser as a probe and performs time-of-flight mass spectrometry of secondary ions
-SIMS can be applied to the analysis of minute foreign substances because the beam can be narrowed down to several tens of nanometers. However, in a semiconductor device having many insulating parts such as an oxide film, there are problems of charging and contamination of the sample by primary ions.

Therefore, in the present invention, a laser beam is applied to a relatively large area including a foreign matter / contaminated portion with a laser beam to a laser-induced mass spectrometer which basically does not cause the problems of TOF-SIMS, and an ion image of the area is formed. 0.1m by imaging at the detector end
The aim was to establish a technology that possesses a spatial resolution that can respond to the analysis of foreign particles with a diameter of m or more.

Research on a method of performing surface analysis by using a secondary ion image of a projection type instead of a scanning type has been advanced with a SIMS apparatus using an ion optical system as shown in FIG. Then, the beam diameter is narrowed down by the primary ion lens system 2, and a flat extraction electrode (W
Primary ions are radiated from the side of the ehnelt electrode 4, secondary ions generated are extracted directly above, and are scattered almost right above by the contrast aperture (several tens of mm in diameter) 6 while preventing the divergence of ions by the intermediate electrode 5. Only the ions that have passed therethrough are imaged by a detector 8 such as a CCD camera with an image intensifier by an imaging lens system 7 at the subsequent stage. Up to 0.1 with this method
It is reported that spatial resolution of about μm can be obtained
(MT Bernius, Anal.Chem. 58, pp. 94-101, (198
6), MT bernius, et al., J. Appl. Phys., 6
0, 1904 (1986), MT Bernius, et al., J. Appl. Ph.
ys. 61, 1677 (1987)). If the same ion optical system is used, a spatial resolution of 0.1 μm can be obtained, but this ion optical system extracts only ions in the scattering direction included in a small solid angle, as described in detail later, so sacrifices sensitivity. And cannot be applied to the analysis of minute foreign matter.

[0007] For semiconductor devices such as DRAMs and ASICs, the size of a wafer is increasing year by year, and the outer diameter will be increased in the future.
12 inches are becoming mainstream. In addition, as a result of the high integration of the elements, it is inevitable that the amount of foreign matter and contaminants that cause a problem becomes extremely small. Therefore, a higher degree of vacuum is required for the apparatus in the future. As the size of the wafer increases, the size of the container increases. As a result, it is difficult to achieve and maintain a high vacuum. Since the devices are usually arranged in a grid at equal intervals, it is desirable to position the sample using XYZ coordinates, but the inner diameter of the vacuum vessel must be twice as large as the outer diameter of the wafer to be able to scan the whole. , Large containers are required. In order not to make the container large, a positioning mechanism of Rz-θ is preferable, but the resolution of positioning depends on θ,
It gets worse at the outer periphery. Further, there is a disadvantage that it is difficult to intuitively operate on scanning.

[0008]

In the above prior art, 0.3
It is difficult to achieve both a spatial resolution of μm or less and a detection sensitivity of tens of femtograms or less, and therefore it is difficult to provide efficient feedback of analytical information to the production line process, or it is highly integrated such as ULSI Analysis suitable for direct integration into production lines, including semiconductor devices /
A foreign matter removing device could not be provided. For large diameter wafers, the XYZ scanning type sample stage, which is suitable for positioning accuracy, requires a large vacuum vessel,
There were difficulties in terms of operability and maintainability. Also,
As the degree of integration of devices increases, the number of single holes increases like contact holes, but it is difficult to analyze the bottom of such a structure with an oblique primary ion injection method such as SIMS as the aspect ratio increases as the aspect ratio increases It is.

An object of the present invention is to simultaneously satisfy a spatial resolution of 0.3 mm or less and a sensitivity of several tens of femtograms, including the bottom of a single-hole structure, and contaminate a device,
It is an object of the present invention to provide a compact device which has a function of removing foreign matter and surface contamination without being destroyed and which can be incorporated into a semiconductor device production line.

[0010]

According to the present invention, based on laser-induced time-of-flight mass spectrometry, (1) a two-dimensional ion image is formed on a detector by a projection method to form an image.
A spatial resolution exceeding the laser beam focusing limit is secured. In particular, aberrations, which are problematic in imaging, are solved by specially devising the extraction electrode. (2) The NA is small for the component analysis at the bottom of a single hole, and therefore, an optical lens system having a large depth of focus requires a foreign substance /
The focused laser beam reaches the bottom of the deep hole by irradiating and evaporating / ionizing the contaminated area from above. (3) The X-Y-Z--θ drive stage ensures the spatial resolution of position control, while miniaturizing the vacuum vessel.
Incorporate the analyzer itself into the production line and make it easy to produce single wafers. Hereinafter, means for solving the problems will be described in detail.

Desorption and ionization of foreign matter / contaminated components When a laser beam is focused on the foreign matter / contaminated part and irradiated, the temperature of the foreign matter / contaminated surface instantaneously rises, and when it reaches the boiling point of the material or more, it evaporates explosively. Cause ablation. Mostly neutral atoms. Scattered as molecules, the direction of which obeys the cosine law,
It has been. Assuming that the wavelength of the laser is λm and the beam radius of the irradiation part is b, b is due to the so-called Rayleigh diffraction limit.
The minimum value of b _min is

[0012]

B _min = kλ / 2NA (1) where NA is the numerical aperture, k is a constant, and the radial strength is １ ／.
It is 0.52 at the point where becomes, 0.82 at the point where it becomes 1 / e2, and 1.22 at the point where it becomes zero. Depth of focus h

[0013]

H = λ / 2 (NA) 2 (2) If an excimer laser with a wavelength of 0.193 μm is used, the beam can be narrowed down to about 0.1 μm in principle,
In reality, there is a problem in processing the lens, which involves difficulty. On the other hand, the temperature rise of the foreign matter by laser irradiation changes the pulse output to P (J / p
ulse), and the irradiation time is t (s).

[0014]

[Equation 3] F = 4P / πb ² (3)

[0015]

(Equation 4)

[0016] In this case, λ _t is the thermal conductivity (cal / cmdegs), c
Is specific heat (cal / kg) and r is density (kg.m3). Foreign matter during irradiation depends on the beam diameter, but actually reaches the boiling point in a very short time with respect to the laser pulse width and decomposes. Heating does not proceed uniformly, and because it progresses locally due to unevenness of heat input and relative relationship with the focal position, a part of the particles dissolves and evaporates.As a result, foreign particles are not neutral molecules, It is thought that many decompose as clusters of molecular groups. The physical process after laser ablation is conceptually summarized in FIG. It is thought that some of the molecules and clusters are ionized from the beginning.
Further, since the ionization efficiency varies depending on the underlying material (matrix effect), there is a problem that the detection sensitivity varies depending on the substance. In order to solve the problem, there is a method (post-ionization) in which laser irradiation is further performed after ablation and ionization is performed under a condition free from a matrix effect. For post-ionization, a method of directly exciting and ionizing valence electrons (resonance method, using a laser beam having a wavelength corresponding to ionization energy) and a non-resonance method (multiphoton absorption, time during which a virtual metastable state is excited ( The next photon is absorbed within 10 to 10 ^-15 S) to obtain the energy required for ionization), and an energy density of at least 10 ⁸ W / cm ² and 10 ¹⁰ W / cm ² is required. In recent years, if the beam is sufficiently focused, it is easy to reduce the intensity to the intensity required for the non-resonance method. Therefore, if imaging of ions can be realized,
It is not necessary to narrow the laser beam to a small size, and it is only necessary that the area including the foreign matter can be roughly covered. That is, it is not necessary to consider the restrictions on the working distance, NA, and the like for the laser focusing optical system.
On the other hand, for imaging with high spatial resolution, it is necessary to control various aberrations of the ion optical system as small as possible.
Especially during ablation, ions have a certain initial thermal energy and scatter in a specific direction.
It is particularly important to estimate the magnitude of the aberration due to the magnitude of the thermal energy.

[0017] Mass m _i kg the initial velocity of the ion when a v0, kinetic energy Ev is

[0018]

(Equation 5)

Ablation is not strict because it is not a thermal equilibrium process, but if this is considered equivalent to the temperature at the time of ablation,

[0020]

(Equation 6)

FIG. 4 shows a rough approximation of E _v and v ₀ as a function of the temperature T, and it is considered that the particles actually scatter at an energy corresponding to the boiling point. Acceleration energy due to the electric field of ions is thousands of volts by common sense, so the initial thermal energy can be said to be smaller than this. However, when an ion image is directly formed, the initial thermal motion can cause various aberrations. Therefore, it is necessary to quantitatively evaluate the thermal motion and suppress the aberrations.

For this purpose, an electrostatic field / ion orbit analysis code SIMION (DA Dahl, INEL-95 / 0403, S
Ion trajectories were analyzed by numerical simulation using IMION3D, Version 6.0, 1995). As will be described later, the electrostatic lens system is composed of an Einzel lens, and a reflectron is provided in the middle to improve the mass resolution. When the ion trajectory is analyzed under the condition of (several mm), it can be seen that ions flying vertically from a point 1 μm apart on the sample surface 3 can be sufficiently separated at the detector as shown in FIG. At this time, the ion trajectory having 10% and 20% higher energy than the thermal energy corresponding to the boiling point was also analyzed (three orbits close to each other in the figure). It turns out that it cannot be the cause. However, it has been found that the dispersion in the scattering direction causes a large aberration, and in some cases, the imaging itself becomes impossible. FIG. 6 shows an example of this analysis. FIG. 6 shows the results of analyzing the ion trajectories in three directions deflected vertically and vertically by 60 degrees from three points 1 μm apart on the sample surface as in the previous example. The trajectories of ions emerging from one point do not intersect On the contrary, it can be seen that the ions scattered in the same direction behave as if they jumped out from the same point. In the SIMS of the projection method with high spatial resolution described in the description of the prior art, the Contrast diaphragm scatters in a specific direction shown in FIG. 6 (substantially transmits only ions that have protruded in the vertical direction from the sample surface to transmit spatial resolution. Therefore, the sensitivity cannot be expected inevitably.

The reason why the aberration increases when the scattering direction of the ions is large can be explained as follows with reference to FIG. The ions that fly out of the sample surface fly out in the initial direction for a very short time, but when they are accelerated by the electric field of the extraction electrode and become sufficiently high-speed, they effectively move linearly in the direction of the electric field. As a result, when viewed from the extraction electrode, the ions appear to have jumped out of the position shifted by the distance moved by the initial thermal motion. Assuming that the position where the extraction electrode 'sees' the ions is the electrode surface on the sample side, and assuming that the ions seem to have flew from the direction of the tangent to the ion trajectory at this position, FIG. The equation of motion of the ion is calculated using the system shown in the figure, and the apparent displacement of the starting position is apparently different.
It is assumed that the expression of d is obtained, and that twice this deviation (the ion orbits from adjacent points do not overlap) gives the spatial resolution r _sol . The following equation is obtained.

[0024]

(Equation 7)

Here, w = qV / Ev (relative acceleration energy = acceleration energy by electric field / initial heat energy) S = spatial resolution factor α: correction coefficient (compare with the result of numerical simulation) it can. The spatial resolution is primarily determined by the characteristics of the extraction electrode portion. (1) It is determined only by the three variables of the allowable scattering angle of ions, the relative acceleration energy, and the electrode distance.

(2) It is proportional to the extraction electrode distance.

(3) It does not depend on the mass of ions.

(4) Depends on the temperature at the time of ablation.

FIG. 8 shows the relationship of equation (7) as a function of relative energy.

For example, if the potential difference of the extraction electrode and the evaporation temperature of the foreign matter are determined, the relative acceleration energy is determined from the lower plot of FIG. On the other hand, if it is determined how far the scattering angle of ions should be taken into image formation, the spatial resolution factor f can be obtained from the upper half surface of FIG. The correction coefficient a in equation (7) is the lens effect of the extraction electrode (a divergent lens with a focal length of 3d).
And the divergence angle is proportional to 2a / d. Actually, as the opening 2a is larger than d, the correction coefficient a becomes larger, and has a linear relationship with the opening 2a as shown in FIG. 9 in the range read from the SIMION plot result.

The above evaluation results indicate that the closer the extraction electrode is to the sample surface, the smaller the spatial resolution can be. Assuming that the applied voltage is 2000 V and the evaporation temperature is 2500 ° C. as the correction coefficient 1, the spatial resolution is about 0.01 even if the scattering angle is expected to be 89 °, that is, the electrode interval is 100 μm.
If it can be controlled below, if it approaches 1 μm or less, 10 μm
A spatial resolution of 0.1 μm can be expected. If placed in a position close to the electrode so far, the first becomes a problem is a breakdown, the breakdown voltage V _b in the following vacuum conditions 10- ⁴ Torr obtained by the following equation.

[0032]

(Equation 8)

When d is 10 μm, the value is 1897 V. In this case, approximately 1500 V is the maximum value of the voltage that can be applied.

As described above, it can be seen that the required spatial resolution can be obtained without sacrificing sensitivity by reducing the distance between the sample surface and the extraction electrode within a range where dielectric breakdown does not occur. In particular, in order to assume an analysis region of 1 μm or less, it is understood that the space between the extraction electrode and the sample should be about 100 μm or less and the aperture diameter should be as small as possible under the condition where the spatial resolution factor is actually assumed.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows an overall view of the analyzer for analyzing fine foreign matter / contaminated portions according to the present invention. In the example of FIG. 1, the entire apparatus includes a sample stage drive system, a sample observation / laser irradiation unit, and a TOF chamber (including a reflectron 10, detectors 12, 13). A magnetic disk, a silicon wafer, or the like, in which the position and approximate dimensions of the foreign matter have been confirmed in advance by a laser light scattering method or the like, are transported in a vacuum shuttle chamber or the like, and introduced into the analyzer without being exposed to the outside air, so that the foreign matter can be analyzed. This apparatus can be incorporated as a part of a single-wafer integrated production apparatus without using a shuttle chamber.

The overall features are as follows: 1) A scanning electron microscope having a spatial resolution of at least a few nm is used for visually recognizing the position and shape of a foreign substance including a very small foreign substance. In this microscope, a laser beam is perpendicularly incident on the sample surface 3 and ions are similarly emitted perpendicularly. Therefore, the electron gun 15 of the electron microscope is mounted obliquely in the sample chamber. Also,
Using an electron microscope, the surface of the sample 3 of the ion extraction electrode 9 was
In order to grasp the distance and the positional relationship with the analysis target part, the secondary electron detector 16 is arranged not at the side opposite to the electron gun but at a position adjacent to the electron gun. In this embodiment, a rotation mechanism around the Z axis (vertical direction) was added to the XYZ drive mechanism in order to make the vacuum vessel main body compact while ensuring high sample positioning resolution. That is, after scanning and analyzing a quarter surface of a certain wafer by XYZ drive, the wafer is rotated 90 ° to drive the next quarter surface. By doing so, the driving distance in the X-Y (parallel to the wafer surface) direction is only half that of the wafer, and the rotation angle accuracy is 0 °, 90 °, 180 °, 270 °.
Therefore, it is sufficient to cut a groove on the outer periphery of the sample table in the corresponding four directions and fix the groove with a holding spring or the like. In addition, it is possible to combine the compactness of the R-θ scan with the X-Y scan having a good positioning resolution.

2) As described above, it is difficult to secure a spatial resolution by a method of squeezing a laser beam. Therefore, evaporation / ionization of foreign matter is a fixed area (for example, 1 μm diameter)
Laser beam irradiation, and a two-dimensional ion image
The desired spatial resolution is ensured by imaging at 2 and 13. Since the ion extraction electrode 9 needs to be arranged very close to the sample, and the tip of the electron gun 15 needs to be close to within 20 to 30 mm to secure the spatial resolution, the optical system 17 for condensing the laser is It cannot be placed near, but is placed just above the extraction electrode 9 and the electrostatic objective lens 18. The laser beam passes through the extraction electrode 9 and the hollow portion of the electrostatic objective lens 18, and the ions pass through a hole formed along the central axis of the optical objective lens 17.

3) When the diameter of the foreign matter becomes one third, for example, from 0.3 μm to 0.1 μm, the number of molecules contained therein becomes 1/27, and therefore, to obtain the same signal output level, the sensitivity is improved by almost three orders of magnitude. is necessary. In the example of the present invention, the laser 19 for ablation and the laser 20 for ionization are separated, and post-ionization in which the evaporated molecules are irradiated again with the laser for ionization is employed. FIG. 10 shows a typical example of a laser optical system. In the present invention, it is necessary to irradiate the post ion laser within a short time (10 to several tens of ns) when the vapor reaches the extraction electrode, and preferably within several ns.
The G laser and the modulator 22 are used to realize the incident light with a very short time difference by the optical delay line 24 using the second harmonic wave and the fifth harmonic wave.

The sample surface can be observed by the CCD camera 31 via the imaging lens 28. For example, even if different lasers are used, such as using the excimer laser 20 for post-ionization, the injection of the post-ionization laser light can be realized in a short time by the same method. The incident laser light is reflected by a perforated mirror 30 for passing ions through a glass window provided in the sample chamber, and is incident from just above the sample. Mirror 30
The laser beam is expanded by the expander 27a, converted into a parallel beam by the lens 27b, then incident on the mirror 30, and focused again by the optical system 27. A glass window may be provided directly above the reflectron 10 in the TOF room, and laser light may be incident therethrough.

In the present invention, in order to obtain a necessary spatial resolution, an ion extraction portion is particularly important.

FIG. 11 shows an embodiment of the extraction electrode. It is desirable that the extraction electrode be conical in order to prevent unexpected contact with the sample surface, and that the enlargement of the ion image as early as possible reduces the burden of countermeasures against aberrations in the subsequent electrostatic lens system. Therefore, a structure in which the second electrode 63 is disposed immediately behind the extraction electrode 9 and as a result, the electrostatic lens is brought as close as possible to the sample surface is optimal. On the other hand, if the two electrodes are too close together, a problem of dielectric breakdown may occur,
The potential difference between the first-stage extraction electrode 9 and the sample surface 3 gives a sufficient kinetic energy to the ions within a range that does not cause dielectric breakdown. The second-stage electrode 63 has a sufficient magnification without causing dielectric breakdown. In order to obtain a deceleration lens. To prevent the expansion of aberration due to thermal energy due to deceleration,
The Einzel lens 18 is arranged at a position where a sufficient distance does not cause dielectric breakdown to accelerate and expand. Further, a stop 68 may be provided at a subsequent stage to obtain better aberration by excluding ions having a large scattering angle. Each of the electrodes is cylindrical and is electrically insulated by an insulator 64 such as Teflon (registered trademark) or polyimide, and is fixed by a clamp 65.

Further, in this embodiment, the piezo stage 66 is used to enable high-precision position control of the extraction electrode, so that the field of view and the spatial resolution can be adjusted according to the size of the target foreign matter. The position and posture of the extraction electrode 9 and the second-stage electrode 63 may be separately controlled. FIG. 12 shows a detailed structure of the extraction electrode. The extraction electrode is formed by making the end of a pipe into a cylindrical shape, and having a hole having an outer diameter of about 100 mm or less at the end of the cylinder. Such an electrode can be formed, for example, by drilling a hole in a copper rod with a cylindrical tip, and then performing cutting from the outside. Further, the hole at the tip can be formed by electric discharge machining, focused laser machining, or focused ion beam machining. Terminals for connecting lead wires are joined to the electrodes by welding or the like. FIG. 13 shows another embodiment of the extraction electrode. In the illustrated example, the extraction electrode 9, the second-stage electrode 63, and the subsequent acceleration / magnification lens system 71
Have an integral structure with an insulator 70 interposed therebetween. If the tip is capped with an insulator, careless contact between the sample surface and the extraction electrode can be avoided. Also, the electrode is made of an insulator 71
A similar structure can be obtained by forming an electrode film at a specific position on the insulator 71 by an operation such as vapor deposition / etching instead of a structure sandwiching the insulator 71.

FIG. 14 shows the result of calculation using SIMION for such a system. As can be seen from FIG.
It has been shown that a spatial resolution of 0.1 μm can be achieved even when the electrode spacing is 20 mm with a scatter angle of degrees, and that the lens is located at a close position using the electrode 63 in the second stage based on simple calculation by equation (7). Has the effect of improving aberration. An outline of a control system and a signal processing system of the apparatus will be described with reference to FIG. ON / OFF of the laser 20 for ablation and the laser 19 for post-ionization is performed manually or automatically by the sequencer 43.
Is controlled by Either the target foreign matter may be evaporated at once with a single pulse, or the target foreign matter may be evaporated little by little with a plurality of pulses. The former is advantageous in terms of S / N because many ions can be generated at one time. The latter is the non-destructive point of the sample,
This is advantageous in that the end point of foreign matter removal can be confirmed.

The emission of the laser can be confirmed by input to the power meter 46, and the output of the power meter 46 can trigger the measurement system and the timer 45. The ion beam is guided to a detector such as the MCP 12 or the CCD 13 with the image intensifier only during the measurement start time and the measurement end time after laser emission recorded in the sequencer 43 in advance, and the ion pulse beam having a specific mass / charge ratio range is obtained. The charge amount and the two-dimensional ion image can be taken into the data logger 53 and the computer 60. The secondary electron image of the SEM is taken into the computer 60 via the image converter 61, the video adapter 62 and the like, and the ion image and the SEM image are superimposed to obtain a clearer cat image of the foreign matter. As a method of forming a two-dimensional ion image, several methods described below can be applied.

1) Method using MCP / CCD: The first example is MC
An avalanche generated from ions incident on a specific channel with a P (Micro Channel Plate) CCD (IC
(CD) This is a method in which light enters the camera surface and is captured as a two-dimensional optical image. In this method, if the number of pixels of the CCD is N _c and the transfer time of one pixel is t _c , it takes N _c t _c to capture one screen, which is 12000 frames / sec even with the fastest CCD camera at present. The time resolution per frame is slightly less than several hundred ms. When the ion is subjected to mass spectrometry of the TOF flag under normal conditions, the TOF is several to several hundreds of ms, so that it is limited to focus on only a few types of molecules with a single shot of the laser to capture an image image. In this case, the spectrum is first calibrated in advance on the normal surface of the sample, and then the target is squeezed to a specific molecule contained in the foreign matter, and is introduced into the reflectron 10 by the blanker 42 according to the timing at which the molecule passes. The units 12 and 13 form an image image. Alternatively, usually, while passing through the reflectron 10 and obtaining a spectrum, the reflectron 10 is turned off in accordance with the timing at which the corresponding molecule comes in, and an image is formed on a detector provided at the top of the TOF chamber by ions traveling straight. The latter method has the advantage that more information can be obtained, but in any case, some judgment is necessary in advance regarding the structure of the foreign matter.

2) Method using MCP / RAE: A method using RAE (Resistive Anodic Encoder) instead of CCD is also possible. A RAE is arranged at the latter stage of the MCP 12 to receive electrons from the MCP, measure the quantity of electricity at the four electrodes at that time, and determine the location where the electrons are incident from the relative large and small system. If the time is long (for example, 400 ns) and a plurality of ions are incident within this time range, it becomes difficult to specify the position. Therefore, in MCP / RAE, there is a device that suppresses the amount of ions generated so that the number of flying ions is, for example, 1/400 ns or less, and integrates a signal with many weak laser shots to form an image. become.

3) Method using a framing camera: A framing streak camera is known as a method for recording image information at the highest speed. This allows recording tens of millions of frames per second. The principle is basically simple. That is, films are arranged on the inner surface of a cylindrical drum,
In this method, an image is sequentially transferred by arranging a mirror rotating at a very high speed in the center or rotating a drum around a fixed imaging lens system at a very high speed. Although this method is fast, it is difficult to signal information directly and it is expensive. In the future, a two-dimensional imaging array may be arranged on the inner surface of the fixed drum instead of the film, or a processing method may be used in which the film is separately processed and converted into an electric signal.

In this apparatus, since the analysis is performed while evaporating the foreign matter, the foreign matter is also removed. The incident energy of the laser beam is set lower, the results of multiple beam irradiations are integrated, and the analysis is performed. After the analysis is completed or during the analysis, the ion component specific to the foreign substance / contamination component is focused on and output. It is sufficient to confirm the removal of foreign matter / contaminants by reducing the number of particles.

[0050]

According to the present invention, chemical analysis of minute foreign matter is performed in a production line of various highly integrated semiconductor devices to quickly identify the source of the foreign matter and obtain data necessary for improving the process. Since removal is also possible, the analyte can be returned to the production line again.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a minute foreign matter / contaminated portion analyzer by time-of-flight mass spectrometry according to an embodiment of the present invention.

FIG. 2 is a diagram showing a static electromagnetic lens system of a two-dimensional image projection SIMS.

FIG. 3 is a diagram conceptually showing a physical phenomenon in a measured part at the time of laser irradiation.

FIG. 4 is a diagram showing an example of a calculated value of a flight time per 1 mm corresponding to an evaporation temperature and a thermal motion velocity of ions / neutral particles during laser irradiation.

FIG. 5 is a diagram showing an example of the results of ion trajectory calculation in a laser-induced time-of-flight mass spectrometer.

FIG. 6 is a diagram showing the influence of the initial scattering direction on the ion trajectory in the laser-induced time-of-flight mass spectrometer.

FIG. 7 is a diagram for explaining an initial relationship between the scattering direction of ions and a spatial resolution based on a positional relationship with an extraction electrode.

FIG. 8 is a diagram showing an example of a calculation procedure for obtaining a spatial resolution (factor).

FIG. 9 is a diagram showing the influence of the opening diameter of the extraction electrode on the spatial resolution.

FIG. 10 is a diagram showing one embodiment of a laser optical system of the present invention.

FIG. 11 is a diagram showing one embodiment of the electrostatic objective / optical objective lens system of the present invention.

FIG. 12 is a view showing a detailed structure of an extraction electrode of the present invention.

FIG. 13 is a view showing another embodiment of the extraction electrode of the present invention.

14 is a diagram illustrating an example of ion trajectory calculation when the extraction electrode illustrated in FIG. 11 is used in the overall configuration illustrated in FIG. 1;

FIG. 15 is a block diagram illustrating a laser system, an electrostatic lens system, a control system of an ion detection unit, and a signal processing system according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ion source, 2 ... Primary ion lens system, 3 ... Sample, 4
... Extraction electrode (Wehnelt electrode), 5 ... Ion transport electrode system, 6 ... Contrast aperture, 7 ... Imaging lens system,
8: imaging surface, 9: extraction electrode, 10: reflectron,
11 intermediate lens, 12 MCP, 13 ICCD, 1
4 Shuttle chamber, 15 Electron gun, 16 Secondary electron detector, 17 Optical objective lens, 18 Intermediate lens, 1
9 post-ionization laser, 20 laser for ablation,
21: beam splitter, 22: modulator, 23: half mirror, 24: delay line, 25: guide laser,
26: laser power meter, 27: beam splitter,
26: perforated mirror, 29: imaging lens, 30: objective lens, 31: CCD camera, 32: laser light introduction window,
33: observation window for optical microscope, 34: high vacuum pump, 35
... bellows for driving the sample stage, 36 ... gate valve,
37 turntable, 38 wafer, 39 vacuum pump for shuttle chamber, 40, 41 vacuum roughing port, 42 blanker, 43 sequencer, 44 timer, 45 time / voltage converter, 46 laser Power meter, 47: Blanker control system, 48: High voltage DC power supply, 4
9: MCP signal processing system, 50: ICCD signal processing system, 5
1: sample stage, 52: sample stage drive system, 53:
Data logger, 54: SEM control system, 55: SEM image processing system, 56: Workstation for data analysis, 57
... Hard disk, 58 ... Film printer, 59 ... Printer, 60 ... Data processing computer, 61 ... Image converter, 62 ... Video card, 63 ... Electrode, 64 ... Insulator, 65 ... Clamp, 66 ... Piezo stage, 67 ... Guide rail, 68 ... diaphragm, 69 ... terminal, 70 ... insulator,
71 ... electrode, 72 ... Einzel lens electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Asao Nakano 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi, Ltd.Production Technology Laboratory (72) Inventor Yutoshi Sugimoto 6-16, Shinmachi, Ome-shi, Tokyo (3) Inside the Device Development Center, Hitachi, Ltd. (72) Inventor Fumio Mizuno 882, Omo, Oaza, Hitachinaka-shi, Ibaraki F-term in the Measuring Instruments Group, Hitachi, Ltd. 4M106 AA01 CA70 CB21 CB30 DH01 DH24 DH32 DJ04

Claims (11)

[Claims] 1. A device positioning drive device aligns a laser beam irradiation spot with an area including a minute foreign matter or a contaminated portion on a surface of a semiconductor device such as a memory, an ASIC, a liquid crystal, a disk, and irradiates a laser beam. By evaporating and ionizing foreign matter or contaminated parts,
A method for manufacturing a semiconductor device, comprising an apparatus and a process for analyzing a chemical composition and a structure of a contaminated portion and removing the chemical composition and structure as necessary. 2. A method for measuring the chemical composition and structure of the foreign matter / contaminated portion according to claim 1 wherein the mass of the ions is determined by the time of flight of the generated ions in an external electric field (hereinafter referred to as "laser-induced time-of-flight mass spectrometry"). A method for manufacturing a semiconductor device. 3. The method for removing foreign matter / contamination according to claim 1, wherein the confirmation of removal is performed by irradiating a laser beam with a detection amount of one or a plurality of ion components specific to the foreign matter / contaminated portion being a predetermined amount or less. A method for manufacturing a semiconductor device. 4. The foreign matter / contaminated portion according to claim 1 having an outer diameter of 1
A method for manufacturing a semiconductor device, which is not less than Å and not more than 0.3 μm. 5. A method for manufacturing a semiconductor device, wherein the laser beam according to claim 1 is perpendicularly incident on a device surface. 6. The method for analyzing foreign matter / contamination according to claim 1, wherein the mapping is a map including two pieces of information of a position and an emission amount of ions emitted from a specific area within a laser beam irradiation range. A method for manufacturing a semiconductor device. 7. The device according to claim 1, wherein the positioning of the device is based on a distance from a predetermined reference position along an orthogonal three-dimensional axis and a rotation angle around one of the orthogonal three-dimensional axes. A method for manufacturing a semiconductor device. 8. A distance d ₁ (= aV ² , where a is a constant) at which a discharge does not occur when an applied voltage is set to V, wherein a distance between the electrode for extracting ions from the foreign matter / contaminated portion and the sample surface according to claim 1 is V. ) Is the distance d ₂ (= bδ, b is the scattering angle of the ions reaching the detector from the sample surface from the sample surface in the vertical direction, the voltage V, and the heat of the ions. energy,
A constant depending on the opening equivalent diameter of the extraction electrode) or less. 9. The method for manufacturing a semiconductor device according to claim 8, wherein the distance d ₂ between the tip of the extraction electrode and the sample surface is 100 μm or less. 10. A method for manufacturing a semiconductor device according to claim 8, wherein the extraction electrode has a hollow shape with a triangular pyramid at the tip, and passes a laser beam through a hollow portion of the electrode. 11. A method for manufacturing a semiconductor device, comprising: arranging at least one electrode having a potential different from that of the extraction electrode on the side opposite to the sample surface of the extraction electrode according to claim 8.