JPH05223704A - Standard sample for fine foreign matter detecting device - Google Patents

Abstract

PURPOSE:To evaluate the performance and to easily make quantitative measurement by controlling the size of a fine structure by controlling the distance between the tip of a probe and a substrate and the voltage applied across the probe and giving coordinate positions by using random numbers to obtain the distributed density per unit area of an object. CONSTITUTION:A gas pressure, distance 5 between a probe 1 and substrate 4, and voltage to be applied which are appropriate to the kind of a used gas are selected through preliminary experiments and inputted in advance. The distance 5 becomes nearly the same as the size of an aimed fine structure and the voltage to be applied becomes about 5-80V. In addition, the distribution of dots is controlled and stored by giving the coordinate position corresponding to the distributed density per unit area of the object by using a random number and setting the distance between adjacent dots so that the distance can be maintained higher than a fixed value. By forming a film in a very small area on a substrate 4 by resolving a gas under a scanning tunnel microscope by using this method and directly preparing the standard sample of the objective material, the performance of a fine foreign material detecting device can be evaluated or the diameter of the objective material can be easily and quantitatively measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign substance inspection device for inspecting a foreign substance on a surface to be inspected.

[0002]

2. Description of the Related Art As semiconductor patterns continue to shrink,
In 64M DRAM, the LSI has a width of 0.3 μm, and even a foreign matter of 0.07 μm may cause a defect. At present, a fine foreign matter detecting device utilizing scattered light of light as described in Japanese Patent Application Laid-Open No. 1-185434 is used for detecting fine foreign matter at the time of forming a fine pattern in a semiconductor process. One of the major materials used as is a polymer particle. The smallest polymer particle is about 0.05 micron, and the size is not strictly uniform. In order to evaluate the performance of the device for detecting minute foreign matter, first, the polymer particles are attached onto a substrate, and then the state of adhesion and distribution is confirmed with an optical microscope or an electron microscope. There is a need for a process of comparing the same standard sample with a pattern obtained as a result of observing the same standard sample.

[0003]

As described above, the mainstream of the fine foreign matter detecting apparatus currently used is the one that utilizes the scattering of light. For the evaluation of the apparatus performance or the detection limit, for example, a particle is used. A polymer particle with a uniform diameter is attached to the wafer and used. However, even if the intensity of scattered light is the same material and particles having the same particle size, there is a great variation.

Regarding the adhesion state of the polymer particles, the number and distribution of the adhered particles are not controlled and are unknown. Therefore, under the present circumstances, there is a possibility that many particles are detected and dropped even if the material is limited. This point can be avoided to some extent by using different means such as an electron microscope under the present circumstances, but for this purpose, it is necessary to go through a plurality of steps of particle adhesion and confirmation of distribution. Moreover, in reality, the scattering probability of light varies depending on the material. Therefore, using particles of one material as a standard sample cannot cope with actual foreign substances that may be composed of various materials.

Further, the smallest polymer particle is about 0.05 micron, which is insufficient as a standard sample for detection of minute foreign matters when forming a fine pattern in a semiconductor process, which will be further miniaturized in the future. It is easily inferred. In addition, the smaller the particle size, the more difficult it is to adhere to the substrate. When it is observed with a scanning electron microscope or the like widely used in the semiconductor process, it evaporates, making it impossible to observe, and worsening the vacuum and contaminating the device. In addition, the smaller the size, the more difficult it becomes to observe with an optical microscope, so there is no means for confirming the actual particle size, shape, distribution, etc.

[0006]

According to the present invention, for detecting a foreign substance having a minute structure made of an inorganic material or an organic material, the material, size and distribution of which are controlled, for evaluating the performance of an apparatus, or for calibration. In preparing the standard sample, a scanning tunnel microscope that has been calibrated or corrected in advance is used, and the following means are taken according to the purpose.

For the purpose of manufacturing a plurality of minute structures on a conductive substrate, a standard sample is directly manufactured by forming a minute region on the substrate by decomposing gas by using a scanning tunneling microscope. The gas used is Ag (C
₆ H ₅ ), AuBr (CH ₃ ) ₂ , Fe (CO) ₅ , GeC
10O, Mo (CO) ₆ , Ni (C ₈ H ₁₂ ) ₂ , Pd (C ₃ H
₅ ) ₂ , Pt (C ₈ H ₁₂ ) ₂ , W (CO) ₆ , Si ₃ H ₈ , T
Use i (NO ₃ ) ₄ etc. properly according to the target substance. The above-mentioned gas is introduced into the chamber, and the chamber is preferably a vacuum because it may have an atmospheric pressure or a vacuum depending on the type of gas. The diameter of the produced dot is determined by the radius of curvature of the tip of the probe, the distance between the probe and the substrate, the gas pressure, the gas species, and the applied voltage. Therefore, the appropriate gas pressure according to the gas type used in the preliminary experiment, the distance between the probe and the substrate,
Select the applied voltage and input it. Since a proper gas pressure depends greatly on the gas species, it is not limited here, but the distance 5 between the probe and the substrate is almost equal to the size 3 of the target minute structure as shown in FIG. 1, and the applied voltage is Generally, it falls within the range of about several 5 to about 800V. The dot distribution is controlled and stored as follows. That is,
The coordinate position corresponding to the desired distribution density per unit area is given by a random number. However, at this time, it is important to set such that the distance between adjacent dots is maintained at a certain value or more. Then, at the same time when the dots are formed, a line or the like formed by film formation similar to the dot formation is marked near the standard sample preparation region. The marking has a size that can be reliably detected by the existing foreign matter detection device (for example, 3
Depending on the performance of the current foreign matter detection device,
Alternatively, it is for confirming the position of the microstructure produced instantly with a low-magnification electron microscope. According to the method, the substrate and the structure can be made of the same material or different materials.

When it is desired to form a structure made of the same material on an insulating substrate or a conductive substrate, first, etching gas using a scanning tunneling microscope is used, or etching of a minute region without gas is performed. A pattern is formed on the conductive first substrate. At this time, the distribution of dots is controlled in the same manner as the above method. When gas is used, this step is preferably performed in a vacuum for the same reason as described above, but is not limited to this when gas is not used. Next, a target substance is formed on the pattern by a CVD method, a vapor deposition method, a sputtering method or the like. The initial film formation may be performed in the same chamber as the above etching, but the initial film formation is continued. Since the film formation requires a high film formation rate in order to increase the film thickness, it is preferable to carry out the film formation in a chamber different from the above etching. The material used for film formation is the gas used in the first method, solid metal, carbon, or the like. Also,
Finally, the first substrate is removed by macro etching, but chemical etching is convenient at this stage. The etchant depends on the material of the first substrate, but is, for example, nitric acid or mixed acid.

Alternatively, a mask material is formed on a minute area by decomposing a gas on a conductive substrate using a scanning tunneling microscope, and subsequently, an unmasked area is macro-etched to prepare a standard sample. .. According to the method, the substrate and the structure are made of different materials.

By comparing the detection result of the standard foreign material detecting device for evaluating the standard sample manufactured by the above method with the dot distribution on the standard sample stored at the time of manufacturing, It has become possible to quantitatively and easily evaluate the detection probability of minute foreign substances of various materials and sizes.

[0011]

When a plurality of minute structures are formed on a conductive substrate, a standard sample is directly formed on the substrate by film formation of a minute region by gas decomposition using a scanning tunneling microscope. The diameter of the dot to be produced is determined by the radius of curvature of the tip of the probe, the distance between the probe tip and the substrate, the gas pressure, and the applied voltage. It is possible to obtain a dot of In particular, according to this method, an insulating substrate cannot be used, but the substrate and the structure can be made of the same material or different materials. In addition, by controlling the computer's dot distribution and storing it at the same time, it is possible to intentionally obtain standard samples that show various distributions according to the target distribution density per unit area. The performance of the foreign material inspection method or apparatus can be quantitatively grasped by collating with the above. The mark in the vicinity of the area where the dots exist is a target when the drive mechanism for fine movement and the drive mechanism for coarse movement are used continuously. Alternatively, it serves as a mark for searching for a target area on the substrate when the detection is performed by the minute foreign matter detection device.

In the second method, for the purpose of producing a structure made of the same material on an insulating substrate or a conductive substrate, first, an etching gas using a scanning tunneling microscope is used, or a gas is used. A pattern is formed on the first substrate by etching the unused minute regions. Again, the dot distribution adopts the same computer control as the above method. Next, a target substance is formed on the pattern. In the initial film formation, the target substance is slowly formed by vapor deposition or the like in the same chamber as that used for the etching to form the pattern formed by the etching. Can be accurately reproduced. Subsequent film formation can obtain a substrate in a short time by CVD or the like performed in a chamber different from the above etching. Further, in the final step, the first substrate is simply and accurately removed by using chemical etching to obtain a target standard sample.
The second method is particularly advantageous for producing dots made of organic matter.

As a third method, a mask material is formed on a minute area by decomposing a gas on a conductive substrate by using a scanning tunneling microscope, and then an unmasked area is macro-etched. Make a standard sample.
According to the method, the substrate and the structure are made of different materials.

It is desirable to use the above three methods properly according to the selection of the material.

According to the above method, a wide variety of materials,
Moreover, it has become possible to easily and quantitatively perform performance evaluation or calibration of the minute foreign matter detection device using a standard sample whose size and distribution are controlled and stored.

[0016]

【Example】

Example 1 First, an example of a standard sample prepared by depositing a palladium film on a silicon substrate to detect foreign matter is shown. FIG. 2 shows an outline of the apparatus used in this example. The above device is an example incorporated in a minute foreign matter detection device using laser light.
First, the surface of the silicon substrate 9 is etched with a hydrofluoric acid aqueous solution and then introduced into the vacuum chamber 15. Here, the in chamber 15 by introducing a bis (allyl) palladium _{(Pd (C 3 H 5)} 2)) becomes the reaction gas, the pulse to be引加a predetermined voltage to the probe, the gas in this case The pressure, voltage, and the distance between the probe and the substrate were several mTorr, about 100 V, and 10 nm, depending on other conditions. In this embodiment, both the coarse-movement driving body and the fine-movement piezoelectric element driving body are controlled by the computer 12, and the density (2 μm) set within the set range (2 μm square) is set.
A structure having random dots (diameter: 10 nm) with particles / 1 micron square) was continuously formed at 9 positions. An outline of the flow chart used in FIG. 3 is shown, and the prepared standard sample is shown in FIG. In this embodiment, since the area of the prepared standard sample is small, a mark is also formed around the area so that the area can be immediately detected by the minute foreign matter detecting device. Next, when the standard sample was compared with the distribution pattern of particles as a result of detection with a minute foreign matter detection device using an argon laser and a photomal, and the pattern when the standard sample was stored in the computer, the above-mentioned minute foreign matter detection was detected. It was found that the detection probability of palladium (diameter 10 nm) of the device was 30%.

As described above, in the present embodiment, it becomes possible to easily and quantitatively evaluate the performance of the minute foreign matter detecting device.

COMPARATIVE EXAMPLE 1 As a comparative example, an example of evaluating the performance of a fine foreign matter detecting device using scattered light by using a polymer particle (particle size 50 nm) which is generally commercially available as a standard particle size product will be shown.
First, including polymer particles (particle size 50 nm),
After diluting 10 microliters of the aqueous suspension with water, the solution is dropped on a silicon wafer and dispersed on the wafer using a spinner. In this state, the average distribution density of particles is about 1 particle / 1 micron square. By the way, generally, in the case of a minute foreign matter detection device that uses scattered light, the relationship between the particle diameter and the output signal intensity of scattered light cannot be made to correspond one-to-one. The probability of being detectable must be determined. For this purpose, it is necessary to check the distribution of the foreign matter detected by the minute foreign matter detection device and the distribution of the minute foreign matter in the same field of view observed by the SEM. However, since the particle size of the polymer particles used in this comparative example is small, the polymer particles evaporate during SEM observation and SE
The vacuum of M was aggravated and it became impossible to continue observation.

Example 2 Next, an example in which a nickel dioxide first substrate was used to detect foreign matter and a pattern was formed to prepare a standard sample of silicon dioxide will be described.

FIG. 5 shows an outline of the apparatus used in this embodiment. The surface of the nickel substrate is light-etched with dilute nitric acid and then introduced into a vacuum chamber. After this,
The driver for coarse movement and the piezoelectric element for fine movement are both controlled by a computer, and the distance between the probe and the substrate is 40 nm.
Applying a voltage of about 400V to the probe in a pulsed state with the temperature kept at, the density set within the set range (2 micron square) (2 particles / 2 micron square)
To produce a random etching pattern (40 nm in diameter). Subsequently, silicon is vapor-deposited while introducing oxygen gas in the vacuum chamber shown in FIG. 4, and then it is moved to another vacuum chamber to form silicon dioxide as a substrate by sputtering. Finally, nickel was removed with sulfuric acid in the air to obtain a standard sample.

By directly comparing the distribution pattern of the particles of the standard sample detected by the objective fine foreign matter detection device for performance evaluation with the distribution pattern of the particles of the standard sample stored in the computer, It has been found that the performance of the fine foreign matter detector in the examples is about 70% for particles of silicon dioxide having a diameter of 40 nm.

[0022]

As described above, according to the present invention, the size and distribution of a material which can be selected from a wide range on a conductive or insulating substrate manufactured by using a scanning tunneling microscope are calculated by a computer. It has become possible to easily and quantitatively perform performance evaluation or calibration of a microscopic foreign matter detection device using a standard sample having a microstructure controlled and stored by.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the distance between a probe and a substrate and the size of a microstructure.

FIG. 2 is a schematic diagram of an apparatus used in Example 1.

FIG. 3 is a schematic diagram of a flow chart used in Example 1.

FIG. 4 is a schematic diagram of a standard sample produced and used in Example 1.

5 is a schematic diagram of an apparatus used in Example 2. FIG.

[Explanation of symbols]

1 ... Probe (probe), 2 ... Microstructure, 3 ... Diameter of microstructure, 4 ... Substrate, 5 ... Distance between probe (probe) and substrate, 6 ... Laser, 7 ... Detector, 8 ... Gas cylinder , 9 ...
Gas introduction path, 10 ... Sample chamber, 11 ... Tunnel unit,
12 ... Gate valve, 13 ... Substrate, 14 ... Magnetic support,
15 ... Sample stand, 16 ... Computer (control system), 17
... sample stage moving mechanism, 18 ... stage, 19 ... chamber, 20 ... valve, 22 ... marking, 23 ... pump (exhaust system).

Claims (6)

[Claims] 1. A method for forming a microscopic region by decomposing a gas using a scanning tunneling microscope or a combination of etching a microscopic region using a scanning tunneling microscope and another film forming method and macro etching, and The size is controlled by controlling the distance between the probe tip of the scanning tunneling microscope and the substrate and the voltage applied to the probe with a computer, and a random number coordinate position is obtained by the computer to obtain the target distribution density per unit area. A standard sample for a minute foreign matter detecting device, which has a minute structure made of an inorganic substance or an organic substance on a substrate, the distribution of which is controlled and recorded by giving 2. A method for producing a standard sample for a fine foreign matter detection device, which comprises using the computer according to claim 1 and a scanning tunneling microscope. 3. A voltage of about 5 to about 800 V is applied to the probe while the distance between the probe tip of the scanning tunneling microscope and the substrate is kept substantially equal to the size of the target minute structure. The standard sample for the fine foreign matter detection device according to claim 1, which was produced. 4. A voltage of about 5 to about 800 V is applied to the probe while the distance between the probe tip of the scanning tunneling microscope and the substrate is kept substantially equal to the size of the target minute structure. The method for producing a standard sample for a fine foreign matter detection device according to claim 2, wherein the standard sample is produced. 5. A performance evaluation system characterized in that it is possible to quantitatively evaluate the performance of a fine foreign matter detection device by using the standard sample according to claim 1. 6. The position of the standard sample according to claim 1 is confirmed by a scanning electron microscope incorporated in the same apparatus,
A performance evaluation system characterized by being able to quantitatively evaluate the performance of a minute foreign matter detection device.