JP2003109992A - Defect detector and method for detecting defect - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting defect by which the position of defect in an insulation film can be determined easily and accurately in a sample substrate with arbitrary size. SOLUTION: This method includes a step for masking where a sample substrate is masked to bring an electrolytic solution into contact with only a defect evaluation area on the surface of an insulation film formed on the front surface side of the sample substrate, a step for fixation where the sample substrate is fixed onto a fixing/holding means in a state where a cathode electrode is in contact with the rear surface of the masked sample substrate so that a negative voltage is uniformly applied to the insulation film, a dripping step where the electrolytic solution is dripped only onto the defect evaluation area on the surface of the insulation film and an anode electrode is brought into contact with a drip of the electrolytic solution, and an electrodeposition step where the sample substrate between the anode electrode and cathode electrode is energized while the anode electrode is in contact with the drip of the electrolytic solution, to uniformly apply a negative voltage to the insulation film, and noble metal in the electrolytic solution is precipitated on the surface of the insulation film, corresponding to the position of a defect existing in the insulation film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect detection processing apparatus and a defect detection method for detecting defects existing in an insulating film.

[0002]

2. Description of the Related Art As a method for detecting defects existing in an insulating film of a silicon substrate having an insulating film on its surface, various methods have been conventionally proposed based on various principles. For example, RCA
Review, Vol. 34, p. 656-690
(1973) and SolidStateTechnol.
ology, Vol. 17, p. 35-42 (1974), (1) electrical method using a capacitor, (2) chemical selective etching method, (3) electrochemical method such as bubble generation, (4) Normarski Methods such as chemical methods such as the method, (5) X-ray and electron probe microprobe analysis methods, and (6) mechanical probe profile observation.

However, in evaluating films (SiO2, SiN, SiON, etc.) used for insulating semiconductor elements and gate oxide films of MOS transistors, an electric field was applied in order to meet the purpose of the film. A method capable of detecting defects in the state is preferable.

As a first method satisfying the above requirements, the electrical characteristics of a MOS capacitor having a "metal (M) -oxide film (O) -semiconductor (S)" structure as in (1) is measured. There is a method. Since this method is a method of directly measuring the electrical characteristics of the insulating film to measure the presence or absence of defects, it is a highly reliable defect evaluation method. However, for the trial manufacture of a MOS capacitor, sputtering or vapor deposition in order to form a metal electrode that is insulated and separated,
Various processes such as a process requiring a vacuum such as low pressure CVD and a photo-etching process are required. For this reason, there is a drawback that the quickness and convenience of the evaluation are lost.

In order to overcome the above-mentioned first drawback, an electrochemical method capable of completing the evaluation by a small number of steps is very effective, and various methods have been conventionally proposed to realize this. ing. For example, RCA Re
view, Vol. 31, p. 431-438 (197)
In 0), as a second method for overcoming the first drawback, a copper anode is used with methyl alcohol as a solvent, and copper is deposited on a defect of a semiconductor silicon substrate having an insulating film as a cathode by an electrophoretic phenomenon. Proposing a method. However, in this method, the specific electric conductivity of methyl alcohol at 25 ° C. is extremely small at 3 × 10 −7 Ω−1 cm −1 and the influence of the voltage drop due to the solution resistance is large, so that the semiconductor silicon substrate having the insulating film that is the cathode is It is not easy to keep the surface potential uniform within the surface. For this reason, uneven deposition of copper is likely to occur in the plane. Further, since the solution has hygroscopicity and evaporation, there are many problems such that the liquid composition easily changes with time and reproducibility is poor.

As a third method for overcoming the above first and second drawbacks, Japanese Patent Laid-Open No. 1326822/1982 discloses that an aqueous solution containing a strong acid salt of copper is used as an electrolytic solution, and a conductive material which is not attacked by the electrolytic solution. And a cathode composed of a semiconductor silicon substrate having an insulating film, which is an object to be measured, are immersed in the electrolyte solution and formed on the surface of the silicon substrate between the anode and the cathode. There is disclosed a method of applying a DC voltage lower than the dielectric breakdown voltage of the insulating film thus formed to deposit copper on a defect of a semiconductor silicon substrate having an insulating film as a cathode by an electrochemical plating reaction. In this method, since the influence of the voltage drop due to the electrolyte solution is small, the surface potential of the silicon substrate can be kept uniform in the surface. Therefore, the in-plane uniformity of copper deposition is good. Further, since the electrolyte solution is an aqueous solution, the change over time in the liquid composition due to moisture absorption and evaporation does not pose a problem.

However, even the third conventional method has the following problems. When copper adheres to the surface of the insulating film as an impurity, copper is deposited even if there is no defect in the insulating film, so that there is a problem in that it appears as if there is a defect. In addition, the surface of the copper deposit is susceptible to chemical changes such as oxidation and dissolution depending on the surrounding environment. The smaller the copper deposit has a diameter of 1 μm or less, the greater the effect, and the deposit is once deposited. Copper disappears easily due to surface oxidation and dissolution, and copper easily adheres to a place unrelated to the insulating film defect due to secondary pollution from the environment.

On the other hand, in the case of the defect detection process as disclosed in Japanese Patent Laid-Open No. 11-248608, in which the precipitate becomes a noble metal, it is chemically stable and there is no secondary pollution from the environment. However, there is no problem like the above-mentioned copper.

FIG. 6 is a schematic diagram showing the structure of the conventional defect detection processing device disclosed in the above publication.

This defect detection processing apparatus comprises a preprocessing section 102.
The processing unit 102 includes a sample substrate (Si substrate) 106 having an insulating film 112, a cathode electrode 105a, a sample fixing holder 108, and an anode electrode 1.
05b and a container 104 for containing an electrolyte solution E containing a noble metal.

The processing control unit 103 includes a variable DC voltage generator 10 in which the direction and magnitude of the DC voltage to be supplied are variable.
9, an ammeter 110, and a voltmeter 111. The variable DC voltage generator 109 and the cathode electrode 105a are electrically connected by an ammeter 110 and a sample holder 10.
It is formed through 8.

The sample substrate (Si substrate) 106 having the insulating film 112, the cathode electrode 105a, the sample fixing holder 108, and the anode 105b are immersed in the electrolyte solution E in the container 104.

Insulating film 112 formed on sample substrate 106
By applying a negative voltage equally to the insulating film 112 so that the electrode becomes a negative electrode in the electrolyte solution E containing the noble metal, the surface of the insulating film 112 corresponding to the position of the defect 113 existing in the insulating film 112. The noble metal 114 in the electrolyte solution E is deposited on the upper portion, and the defect 113 of the insulating film 112 is detected.

[0014]

However, in the conventional example of the above publication, when the sample has an arbitrary shape other than the wafer,
It has been difficult to make a device structure for preventing the electrolyte solution from easily contacting the back surface of the sample.

In addition, when there is a large defect in the area outside the defect evaluation target, a large amount of precious metal is deposited, and the precipitation of the precious metal in the defect evaluation target area is very small. There is also a problem that it is difficult to accurately specify the position of the defective portion in the portion.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to easily and accurately determine the position of a defective portion of an insulating film of a sample substrate having an arbitrary size. It is to provide a defect detection processing device and a defect detection method that can be performed.

[0017]

In order to achieve the above object, in the present invention, an insulating film formed on a sample substrate is used as a negative electrode in an electrolyte solution containing a noble metal. A defect detection process for detecting defects in the insulating film by depositing a noble metal in the electrolyte solution on the surface of the insulating film corresponding to the positions of defects existing in the insulating film by applying a negative voltage equally. In the device, the electrolyte solution is dropped onto the defect evaluation target area on the surface of the insulating film that has been masked by a masking means to bring the electrolyte solution into contact only with the defect evaluation target area, and the electrolyte solution is also added. Electrolyte solution dropping means configured so that the anode electrode can be brought into contact with the liquid droplet and the sample substrate is fixedly held on the cathode electrode so that a negative voltage is equally applied to the insulating film. A sample fixing and holding means, and a processing control means for conducting an electric current to the sample substrate between the anode electrode and the cathode electrode in a state where the anode electrode is in contact with the droplet of the electrolyte solution. It is characterized by that.

In the present invention, a masking step of subjecting the sample substrate to a masking treatment so as to bring the electrolyte solution into contact with only the defect evaluation target region on the surface of the insulating film formed on the surface side of the sample substrate, and the masking step. A fixing step of fixing the sample substrate to a fixing holding means in a state in which a cathode electrode is in contact with the back surface side of the processed sample substrate so that a negative voltage is equally applied to the insulating film, Dropping the electrolyte solution only to the defect evaluation target region of the insulating film surface, and a dropping step of contacting the anode electrode to the droplet of the electrolyte solution, and contacting the anode electrode to the droplet of the electrolyte solution In this state, the sample substrate between the anode electrode and the cathode electrode is energized so that a negative voltage is equally applied to the insulating film, and the negative voltage is applied to the position of the defect existing in the insulating film. And executes the above electrolyte solution noble metal conductive precipitating during wear process on the insulating film surface is.

In the present invention, of the plurality of polysilicon films formed on the insulating film of the sample substrate, only the predetermined polysilicon film to be the defect evaluation target is brought into contact with the electrolyte solution so that the sample substrate is contacted with the sample substrate. A mask process of performing a mask process, and the sample substrate subjected to the mask process,
A fixing step of fixing the sample substrate to a fixing holding means in a state where the cathode electrode is in contact with the insulating film so that a negative voltage is equally applied, and the electrolyte solution is dropped only on the predetermined polysilicon film surface. With the dropping step of contacting the anode electrode with the droplet of the electrolyte solution, the sample substrate between the anode electrode and the cathode electrode in a state where the anode electrode is in contact with the droplet of the electrolyte solution. A negative voltage is equally applied to the insulating film by conducting an energization process to deposit the noble metal in the electrolyte solution on the surface of the polysilicon film corresponding to the position of the defect under the predetermined polysilicon film. And an electrodeposition step for performing the same.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[Outline] <Structure of Defect Detection Processing Device> FIG. 1 is a schematic diagram showing the structure of a defect detection processing device according to an embodiment of the present invention.

The defect detection processing apparatus 1 is composed of a preprocessing section 2 and a processing control section 3, and the processing section 2 includes an insulating film 12.
A sample fixing holder 8 for simultaneously holding and fixing a sample substrate (Si substrate) 6 with a mark, a plate-shaped conductive metal electrode 5a serving as a cathode, and a mask plate 21, and an anode paired with the cathode. Conductive noble metal electrode 5b and an electrolyte solution containing device (micropipette) 4 for containing the electrolyte solution E
Composed of and.

The sample substrate 6 has a constant thickness, and an insulating film (SiO 2 film) 12 having a predetermined thickness is formed on the sample substrate 6. The surface of the insulating film 12 has a rod-like shape arranged through the inside of the micropipette 4. It is arranged so as to be below the conductive noble metal electrode 5b. The material of the conductive noble metal electrode 5b of the anode may be any metal as long as it is a conductive solid at room temperature and has an ionization tendency smaller than hydrogen.
Copper, gold, platinum, palladium and the like can be mentioned, but noble metals such as gold and platinum are preferable because they are chemically stable.

A mask adhesive tape (mask means) 7 is attached to the surface of the insulating film 12 of the sample substrate (Si substrate) 6. The mask means 7 may be any as long as it does not interfere with the detection of defects directly or indirectly, and for example, it is preferable to attach the adhesive tape 7 to a region other than the defect evaluation target. That is, it is desirable to attach the adhesive tape 7 having a window (hole) of a predetermined size so that only the surface of the insulating film 12 in the defect evaluation target area comes into contact with the electrolyte solution E in advance.

As a material for the tape, it is preferable to use a material which is transparent and has strong acid resistance and is impermeable to water. Examples thereof include polyethylene terephthalate, polystyrene, polypropylene, polyvinyl chloride and the like. The adhesive of the adhesive tape is preferably one that does not stain the surface of the sample substrate when peeled off, has strong acid resistance, does not pass water, and does not soak in water, for example, silicone rubber or acrylic adhesive. Is preferred.

Further, the sample fixing holder 8 uses a transparent plastic mask plate, a rubber O-ring, a Teflon (registered trademark) container and a plastic screw to make a conductive metal electrode 5a having sharp irregularities. And the back surface of the sample substrate 6 are overlapped and fixedly held.

The reason why the conductive metal electrode 5a is provided with sharp irregularities is that it is possible to penetrate the natural oxide film on the back surface of the sample substrate 6 and become conductive, so that the ohmic electrode need not be formed. That is, since a natural oxide film is usually formed on the silicon substrate, the silicon of the conductive metal electrode 5a has sharp irregularities that penetrate the natural oxide film on the back surface of the silicon substrate and connect with the metal silicon inside. It is desirable to provide it on the contact surface with the substrate. The larger the difference in the unevenness, the greater the effect, but if it is too large, the conductive metal electrode 5a is easily damaged. On the other hand, if it is too small, it becomes difficult to penetrate the natural oxide film on the back surface of the silicon substrate when the silicon substrates are stacked and attached. Considering these, the size of the unevenness is preferably 0.02 to 200 μm, and more preferably 0.1 to 20 μm.

The means for forming irregularities on the surface of the conductive metal electrode 5a directly or indirectly hinders the deposition of a metal with a low ionization tendency on the upper surface of the insulating film 12 centering on the defect center. If not, any means may be used, and it may be produced by scratching the entire surface of the conductive metal thin plate with sharp metal tweezers or needles. By forming an electrical connection with the silicon substrate by penetrating the natural oxide film on the back surface of the silicon substrate with sharp irregularities, the formation of the ohmic electrode is not necessary and the operation is simple.

In order to use the sample substrate 6 as a cathode,
It is necessary to apply a cathode voltage to the sample substrate 6. this is,
For example, the sample substrate 6 is attached to the conductive metal electrode 5a which is a cathode electrode.
This can be done by fixing the back surface of the substrate (the surface opposite to the insulating film 12 to be evaluated) in contact and applying a cathode voltage to the conductive metal electrode 5a. The material for forming the conductive metal electrode 5a may be any material as long as it is a conductive solid at room temperature. Copper, aluminum, silver, iron, gold, platinum, palladium and the like can be mentioned, but copper, aluminum, silver and iron are preferable because they are inexpensive and have good workability.

The sample fixing holder 8 is constructed so as to press and hold an area of the sample substrate 6 which is not the object of defect evaluation so as to be able to correspond to the sample substrate 6 having an arbitrary shape and size. The substrate 6 and the conductive metal electrode 5a are overlapped and fixedly held. The sample fixing holder 8 has an insulating film 12
Any means may be used as long as it does not directly or indirectly impede the deposition of a metal having a low ionization tendency on the upper surface centering on the defect center portion in the sample substrate 6. Means such as sandwiching the end portion and squeezing with a screw of a plastic material is preferably used.

Further, the mask adhesive tape 7 has a window of a predetermined shape and size, and through the window of the mask adhesive tape 7, only the defect evaluation target region of the insulating film 12 is the electrolyte solution from the micropipette 4. It comes in contact with E.

As the electrolyte solution E, an acid solution in which a noble metal is dissolved is used. Noble metals include gold and platinum group elements, and platinum group elements include platinum, palladium, ruthenium,
Includes rhodium, iridium and osmium. Noble metal dissolves in aqua regia, so prepare a noble metal aqua regia solution,
An electrolyte solution can be prepared by appropriately blending this with an aqueous solution of an acid such as hydrochloric acid, sulfuric acid or nitric acid. Sulfuric acid tends to remain on the surface of the insulating film, and it is difficult to quickly remove it by washing with water.
When operating with an electrolyte solution using sulfuric acid, these metal components are likely to precipitate even on the surface of the insulating film having no defects. From these things, it is particularly preferable to use an aqueous solution of hydrochloric acid or an aqueous solution of nitric acid.

Since the electrolyte solution E contains the noble metal, the noble metal is deposited on the surface of the insulating film 12 corresponding to the position where the defect exists due to the energization. The electrodeposition accuracy of noble metal is much better than that of copper, and the chemical stability of the noble metal not only prevents it from disappearing after deposition, but also engraves it on the insulating film so that the location of defects can be easily identified. Etching or the like can be used in such applications. In particular, gold has a color different from that of other metals and thus is easy to visually identify, which is advantageous for identifying the center position of a defect.

The processing control section 3 comprises a variable DC voltage generator 9 in which the direction and magnitude of the DC voltage to be supplied are variable, an ammeter 10 and a voltmeter 11. The electrical connection between the variable DC voltage generator 9 and the conductive metal electrode 5a is
It is formed via an ammeter 10 and a sample fixing holder 8.

Although not shown in FIG. 1, a holder fixing for fixing and holding the sample fixing holder 8 itself, an electrode holding member for fixing and holding the other electrode portion 5b, and a DC voltage to be applied. If necessary, a resistor or the like for controlling the fluctuation of the above may be arranged.

<Operation of Defect Detection Processing Device> In the above structure, when the electrode portion 5a is applied so that it becomes the negative electrode and the electrode portion 5b becomes the positive electrode, the electrode portion 5a applies the same voltage to the insulating film 12. A difference in current value locally occurs depending on the presence or absence of the defect portion 13 on the surface of the insulating film 12, and the noble metal component in the electrolyte solution E begins to precipitate on the surface of the insulating film 12 at the position corresponding to the defect portion 13, and the deposited noble metal A spot is formed by 14.

By the detection processing device 1 of FIG.
The sample substrate 6 on which the noble metal is deposited at the corresponding position can be observed with a physical observation device such as an optical microscope or a scanning electron microscope. Therefore, such an observation device is arranged adjacent to the defect detection processing device.

In the above description, the present invention is described using the silicon substrate as the substrate having the insulating film.
Needless to say, the method of detecting defects in the insulating film of the present invention is not limited to application to a silicon substrate, but can be applied to a device in which an insulating film is formed on another conductive metal substrate. Further, the insulating film 12 can be applied not only to silicon dioxide but also to defect detection of oxides, nitrides, and carbides of silicon nitride and other metals. Further, not only the insulating film formed on the metal substrate but also the insulating film itself may be brought into direct contact with the electrode plate to apply a voltage evenly to detect defects.

<Defect Detection Method> A defect detection method executed by using the above defect detection processing apparatus will be described with reference to the flowchart of FIG.

The defect detection method according to the present embodiment uses a silicon substrate having an insulating film as a cathode in an electrolyte solution in which a noble metal ion or a noble metal complex in a concentration range in which electroless plating or electrochemical concentration polarization does not occur is dissolved in water. As a result of applying a voltage as an electric current, the noble metal in the electrolyte solution is selectively applied to the surface of the insulating film according to the position of the defect due to the difference in the current value between the position where the defect exists in the insulating film and the position where it does not exist. This is a defect detection method that utilizes the deposition (electrodeposition) of components to identify the position of the defect in the insulating film formed on the silicon substrate.

First, a cleaning step of cleaning the surface of the insulating film 12 with an oxidizing acid solution is performed (step S11).

Insulating film 12 of silicon substrate for defect detection
If the surface is previously washed with a solution containing an oxidizing acid solution, the attached copper can be removed. Therefore, when a direct current voltage is applied to the insulating film 12, the noble metal can be accurately deposited on the surface of the insulating film 12 centering on the defect center portion in the insulating film 12 by the electrochemical action.

Subsequently, the electrolyte solution E is applied only to the defect evaluation target region on the surface of the insulating film 12 formed on the surface side of the sample substrate 6.
In order to bring the sample substrate 6 into contact with the sample substrate 6, a masking process is carried out by the masking means 7 (step S1).
2). That is, as shown in FIG. 3, an adhesive tape 7 having a window (hole) 12a of a predetermined size is attached in advance so that only the surface of the insulating film 12 in the defect evaluation target region comes into contact with the electrolyte solution E.

Next, the mask plate 21 is placed on the surface of the sample substrate 6 (step S13) so that a negative voltage is equally applied to the insulating film 12 on the back surface side of the sample substrate 6 which has been subjected to the mask processing. A fixing step of fixing the sample substrate 6 to the sample fixing holder 8 is performed with the conductive metal electrode 5a being in contact with the sample fixing holder 8 (step S14).

Then, the tip of the micropipette 4 is made to face the defect evaluation target region on the surface of the insulating film 12,
A dropping step is performed in which the electrolyte solution E is dropped only on the surface defect evaluation target area and the conductive noble metal electrode 5b is brought into contact with the drop of the electrolyte solution E (step S1).
5).

Then, by the processing control unit 3, in a state where the conductive noble metal electrode 5b is brought into contact with the droplet of the electrolyte solution E,
The sample substrate 6 between the conductive noble metal electrode 5b and the conductive metal electrode 5a is energized (step S16), and a negative voltage is equally applied to the insulating film 12. As a result, the noble metal (noble metal precipitate 1) in the electrolyte solution E is formed on the surface of the insulating film 12 corresponding to the position of the defect portion 13 existing in the insulating film 12.
4) is deposited (electrodeposition step). This precious metal deposit 14
As shown in FIG. 4 (a), first, the central portion 14a that exactly corresponds to the position of the defect portion 13 is deposited, and then the noble metal is deposited in a substantially concentric shape.

After that, the surface of the insulating film 12 on which the noble metal is deposited is washed with an oxidizing acid solution (step S17). As a result, copper or the like other than the noble metal can be dissolved and removed. As the oxidizing acid solution, any solution may be used as long as it can remove the copper adhering to the surface of the insulating film 12 and does not interfere with the detection of defects directly or indirectly. A mixed solution of hydrogen oxide and hydrochloric acid, a dilute mixed solution of nitric acid and hydrochloric acid, and the like are preferable.

After depositing the noble metal, the outer periphery of the noble metal deposit 14 is marked, and a part or most of the noble metal deposit 14 is selectively etched with a solution containing aqua regia (step S18). By this etching,
Noble metal deposit 14 deposited as shown in FIG.
Are sequentially etched so that only the central portion 14a remains. By leaving only the central portion 14a that exactly corresponds to the position of the defect portion 13, it becomes possible to observe the defect portion 13 with high accuracy by observing the precipitate with a microscope or the like which will be performed later. As the marking means, the position of the deposited precious metal can be easily indicated, and unless the detection of defects is directly or indirectly obstructed,
Any material may be used, and for example, marking with a laser is preferable.

Then, the surface of the insulating film 12 of the sample substrate 6 is observed with an optical microscope and a scanning electron microscope to examine the noble metal precipitate 14 (step S19).

As described above, in the present embodiment, the position, size and distribution of the defective portion 13 of the insulating film 12 of the sample substrate 6 having an arbitrary size can be determined quickly, easily and accurately.

[Detailed Description Using Experimental Results] The embodiments of the present invention will be described in more detail below with reference to the experimental results using the sample substrate shown in FIG.

<Experimental Example 1> Diameter 150 mm (6 inches)
On the boron-doped Si wafer (specific resistance: 7.0 Ωcm, thickness: 625 μm), a SiO 2 film having a thickness of 200 Å was formed as the insulating film 12 by the thermal oxidation method. Further on this C
The poly Si film 50 (size 2) having a thickness of 300Å is formed by the VD method.
mm square 100) were formed. The following operations were performed using this sample substrate 6.

(Operation Example 1) About 3N-nitric acid and about 3N-hydrochloric acid were mixed at a ratio of 1: 1 (volume ratio) to prepare a mixed acid solution E. The sample substrate 6 was washed with this mixed acid solution E at about 25 ° C. for about 5 minutes, rinsed with pure water and dried.

The surface (rear surface) opposite to the insulating film of the dried sample substrate 6 is pressed against the electrode portion 5a as shown in FIG. 1 and detected so as to shield the electrode portion 5a and the rear surface of the sample substrate 6 from the surroundings. It was fixed to the sample fixing holder 8 of the processing apparatus 1. Details of each component of the detection processing device 1 are as follows.

The electrode portion 5a is a copper plate having a diameter of 150 mm (6 inches) × a thickness of 1 mm, which is scratched with stainless tweezers to form irregularities of 1 to 20 μm.

The electrode portion 5b has a diameter of 0.6 mm and a length of 30.
mm gold wire.

The sample fixing holder 8 has a diameter of 200 mm and a thickness of 23 mm and is made of Teflon. For fixing the sample substrate 6, a transparent polyvinyl chloride mask plate 21 (diameter 150 mm × thickness 1
Use 10 mm and 20 mm square windows), rubber O-rings, Teflon tools and acrylic screws.

The electrolyte solution E storage device 4 is a micropipette for storing the electrode portion 5b and the electrolyte solution E in a polyethylene microchip.

A mask adhesive tape (cellophane tape made by Nichiban, size 10) having a window (2 mm □) was provided to bring only a predetermined poly-Si film to be evaluated for defects into contact with the electrolyte solution E.
mm □) 7 is attached.

Gold was dissolved in aqua regia and hydrochloric acid was added to about 0.0
An electrolyte solution E was prepared by preparing an about 0.5 N hydrochloric acid solution E (containing a small amount of nitric acid) containing gold at a concentration of 001 mol / l.
5 μl of this electrolyte solution E is dispensed with a micropipette and dropped on the surface of a predetermined poly-Si film which is a target for defect evaluation. The tip of the microchip of the electrolyte solution E storage device is brought into contact with the droplet of the electrolyte solution E.

A voltage of +5 V (potential of electrode portion 5b-potential of electrode portion 5a) was applied to the electrode portions 5a and 5b for 10 minutes. As a result, gold was deposited on the surface of the poly-Si film on the insulating film 12 of the sample substrate 6. After that, the adhesive tape 7 was peeled off, the sample substrate 6 was washed with about 2N-nitric acid at about 25 ° C for about 5 minutes, then rinsed with pure water at about 25 ° C for about 5 minutes and dried.

Predetermined poly S on the insulating film 12 of the sample substrate 6
The i film surface is observed with an optical microscope and a scanning electron microscope,
The deposited gold was examined. Then, a predetermined poly-Si film was treated with aqua regia to remove gold.

Further, the steps from the gold deposition in the droplets of the electrolyte solution E to the dissolution removal of the deposited gold were repeated 10 times, and the deposited gold was microscopically observed 10 times. As a result, the precipitate was formed at the same position 10 times, and the diameter of the precipitate was 0.9 μm 10 times. Almost no copper was detected in the precipitate, and the golden metallic luster made it easy to identify gold by microscopic observation.

(Operation Example 2) A microscope of the deposited gold was obtained by repeating the same operation as in Operation Example 1, except that the cleaning treatment with dilute nitric acid in Operation Example 1 was performed instead of the cleaning treatment with dilute hydrochloric acid of about 3N. Observation was performed 10 times. As a result of microscopic observation, the deposits were formed at the same position 10 times, and the diameter of the deposits was 0.9 μm 10 times.

(Operation Example 3) Microscopic observation of the deposited gold was conducted by repeating the same operation as in Operation 1 except that the cleaning treatment with dilute nitric acid in Operation Example 1 was not performed.
I went 0 times. As a result of microscopic observation, the deposits were formed at the same position 10 times, and the diameter of the deposits was 0.9 μm 10 times.

(When the adhesive tape for mask 7 was not used) In the operation 1 of Experimental Example 1, the operation was repeated except that the adhesive tape 7 for the mask was not attached. The gold was microscopically observed 10 times. As a result of microscopic observation, gold was deposited 8 times, but not twice. Precipitates were formed at the same position eight times, and the diameter of the precipitates varied within the range of 0.4 to 0.8 μm. This is because the electrolyte solution E contacts not only the poly-Si film region of the defect evaluation target but also the non-target region, and moreover, there is a large defect in the non-target region, so that a large amount of gold is deposited. It is considered that gold deposition in the defect evaluation target area was significantly reduced.

<Experimental Example 2> 50 mm square phosphorus-doped Si
Wafer (specific resistance: 3.2 Ωcm, thickness: 625 μm)
In addition, 210N thick SiN as an insulating film
A film was formed. On top of this, a thickness of 300 is obtained by the CVD method.
A Å poly-Si film (25 pieces having a size of 2 mm □) was formed. The following operations were performed using this sample substrate 6.

(Operation Example 4) About 3N-nitric acid and about 3N-hydrochloric acid were mixed at a ratio of 1: 1 (volume ratio) to prepare a mixed acid solution E. The sample substrate 6 was washed with this mixed acid solution E at about 25 ° C. for about 5 minutes, rinsed with pure water and dried.

The surface (rear surface) opposite to the insulating film of the dried sample substrate 6 is pressed against the electrode portion 5a as shown in FIG. 1 and detected so as to shield the electrode portion 5a and the rear surface of the sample substrate 6 from the surroundings. It was fixed to the sample fixing holder 8 of the processing apparatus 1. Details of each component of the detection processing device 1 are as follows.

The electrode portion 5a is a copper plate having a diameter of 150 mm (6 inches) × a thickness of 1 mm, which is scratched with stainless tweezers to form irregularities of 1 to 20 μm.

The electrode portion 5b has a diameter of 0.6 mm and a length of 30.
mm gold wire.

The sample fixing holder 8 has a diameter of 200 mm and a thickness of 23 mm and is made of Teflon. To fix the sample substrate 65, a transparent polyvinyl chloride mask plate 21 (diameter 150 mm × thickness 1 mm, there are 10 windows of 20 mm □), a rubber O-ring, a Teflon instrument and an acrylic screw are used.

The electrolyte solution E storage device 4 is a micropipette for storing the electrode portion 5b and the electrolyte solution E in a polyethylene microchip. In order to bring only a predetermined poly-Si film, which is the object of defect evaluation, into contact with the electrolyte solution E, an adhesive tape for mask (Nichiban cellophane tape, size 10 mm □) 7 with a window (2 mm □) 7 is attached.

Gold is dissolved in aqua regia and hydrochloric acid is added to about 0.0
An electrolyte solution E was prepared by preparing an about 0.5 N hydrochloric acid solution E (containing a small amount of nitric acid) containing gold at a concentration of 001 mol / l.
5 μl of this electrolyte solution E is dispensed with a micropipette and dropped on the surface of a predetermined poly-Si film which is a target for defect evaluation. The tip of the microchip of the electrolyte solution E storage device 4 is brought into contact with the droplet of the electrolyte solution E.

A voltage of +5 V (potential of electrode portion 5b-potential of electrode portion 5a) was applied to the electrode portions 5a and 5b for 10 minutes. As a result, gold was deposited on the surface of the poly-Si film on the insulating film 12 of the sample substrate 6. Then, the adhesive tape 7 was peeled off, the sample substrate 6 was washed with about 2N-nitric acid at about 25 ° C for about 5 minutes, rinsed with pure water at about 25 ° C for about 5 minutes, and dried.

Predetermined poly S on the insulating film 12 of the sample substrate 6
The i film surface is observed with an optical microscope and a scanning electron microscope,
The deposited gold was examined. Then, a predetermined poly-Si film was treated with aqua regia to remove gold.

Further, the steps from the gold deposition in the electrolyte solution E droplet to the dissolution removal of the deposited gold were repeated 10 times, and the deposited gold was microscopically observed 10 times. As a result of the microscopic observation, the precipitate was formed at the same position 10 times,
The diameter of the precipitate was 0.8 μm for all 10 times.

Almost no copper was detected in the deposit, and the golden metallic luster facilitated the identification of gold by microscopic observation.

(Operation 5) A microscopic observation of the deposited gold was performed by repeating the same operation as in Operation 4, except that the cleaning treatment with dilute nitric acid in Operation 4 was performed instead of the cleaning treatment with dilute nitric acid. I went there. As a result of microscopic observation, deposits were formed at the same position 10 times, and the diameter of the deposits was 0.8 μm 10 times. The deposits sometimes contained a small amount of copper, and it was difficult to distinguish gold and copper by microscopic observation.

(Operation 6) The same operation as in Operation 4 was repeated except that the cleaning treatment with diluted nitric acid was not performed in Operation 4, and the deposited gold was observed with a microscope 10 times. As a result of microscopic observation, deposits were formed at the same position 10 times, and the diameter of the deposits was 0.8 μm 10 times. Since there was a small amount of copper deposited, it was slightly difficult to distinguish between gold and copper by microscopic observation.

(When the mask adhesive tape 7 was not used) In the operation 4 of Experimental Example 2, the gold deposited by repeating the same operation as the operation 4 except that the mask adhesive tape was not attached Was observed 10 times under a microscope. As a result of microscopic observation, gold was deposited 8 times,
It did not precipitate twice. Precipitates were formed at the same position every eight times, and the diameter of the precipitates varied in the range of 0.3 to 0.6 μm. This is because the electrolyte solution E is poly-Si whose defect is to be evaluated.
Contact not only the membrane area but also the non-target area, and
It is considered that the large amount of gold was deposited due to the large defect in the non-target region, and the gold deposition in the defect evaluation target region was significantly reduced.

[0082]

As described in detail above, according to the present invention, the position, size and distribution of the insulating film defect portion of a sample substrate of any size can be determined quickly, simply and accurately. As a result, detailed analysis and evaluation of the defective portion of the VLSI can be facilitated, the cause of the defect occurrence can be elucidated, and appropriate defect reduction measures can be taken. Therefore, the yield and performance of the VLSI can be improved at an early stage. Can be expected.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a defect detection processing apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a defect detection method according to the embodiment.

FIG. 3 is a top view showing a sample substrate with mask means attached.

FIG. 4 is a cross-sectional view showing a process of forming a noble metal deposit.

FIG. 5 is a sectional view of a sample substrate used in an experimental example.

FIG. 6 is a schematic diagram showing a configuration of a conventional defect detection processing device.

[Explanation of symbols]

E Electrolyte solution 1 Defect detection processor 2 Pretreatment section 3 Processing control unit 4 Electrolyte solution storage equipment 5a, 5b Electrode part (electrode plate) 6 Sample substrate (Si substrate) 7 Mask means (mask tape) 8 Sample holder 9 Variable DC voltage generator 10 ammeter 11 Voltmeter 12 Insulating film 13 defects 14 Precious metal deposits

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keiki Nagai             25-1 Honmachi, Kawasaki-ku, Kawasaki-shi, Kanagawa             Toshiba Microelectronics Co., Ltd. F term (reference) 2G052 AA13 FC02 FD00 FD09 GA32                       GA35                 4M106 AA01 AA13 BA14 BA20 CA45                       CA46 DH60

Claims (9)

[Claims] 1. A defect existing in the insulating film by equally applying a negative voltage to the insulating film so that the insulating film formed on the sample substrate becomes a negative electrode in an electrolyte solution containing a noble metal. In a defect detection processing apparatus for detecting a defect in the insulating film by depositing a noble metal in the electrolytic solution on the surface of the insulating film corresponding to the position of, in order to bring the electrolyte solution into contact with only the defect evaluation target region. An electrolyte solution dropping means configured such that the electrolyte solution is dropped onto the defect evaluation target region on the surface of the insulating film masked by a mask means, and an anode electrode can be brought into contact with the droplets of the electrolyte solution. And so that a negative voltage is equally applied to the insulating film,
Sample fixing and holding means for fixing and holding the sample substrate on the cathode electrode, with the anode electrode in contact with the droplets of the electrolyte solution, with respect to the sample substrate between the anode electrode and the cathode electrode A defect detection processing apparatus, comprising: a processing control unit that performs a power distribution process. 2. The defect detection processing apparatus according to claim 1, wherein the sample substrate has a structure in which a polysilicon film is formed on the surface of the insulating film. 3. A mask step of subjecting the sample substrate to a mask process for bringing the electrolyte solution into contact only with a defect evaluation target region on the surface of an insulating film formed on the surface side of the sample substrate; A fixing step of fixing the sample substrate to a fixing holding means in a state where a cathode electrode is in contact with the back surface side of the applied sample substrate so that a negative voltage is equally applied to the insulating film; While dropping the electrolyte solution only in the defect evaluation target region of the film surface, a dropping step of contacting the anode electrode with the droplet of the electrolyte solution, in a state of contacting the anode electrode with the droplet of the electrolyte solution. The sample substrate between the anode electrode and the cathode electrode is energized to apply a negative voltage equally to the insulating film, and the negative voltage is applied to the insulating film in correspondence with the position of the defect existing in the insulating film. Absence And a step of depositing a noble metal in the electrolyte solution on the edge film surface. 4. The defect detecting method according to claim 3, wherein a cleaning step of cleaning the sample substrate is performed before the mask step and after the electrodeposition step. 5. After marking the outer periphery of the noble metal deposit deposited on the surface of the insulating film after the electrodeposition step,
The defect detecting method according to claim 3, wherein an etching step of selectively etching the noble metal precipitate is performed. 6. A mask process is performed on the sample substrate to bring the electrolyte solution into contact only with a predetermined polysilicon film to be a defect evaluation target among a plurality of polysilicon films formed on the insulating film of the sample substrate. And a mask step of fixing the sample substrate to the fixing holding means in a state where the cathode electrode is in contact with the masked sample substrate so that a negative voltage is equally applied to the insulating film. Fixing step, and a dropping step of dropping the electrolyte solution only on the surface of the predetermined polysilicon film, and bringing an anode electrode into contact with the droplet of the electrolyte solution; and bringing the anode electrode into contact with the droplet of the electrolyte solution. In this state, the sample substrate between the anode electrode and the cathode electrode is energized so that a negative voltage is equally applied to the insulating film and the predetermined polysilicon is applied. A defect detection method comprising performing an electrodeposition step of depositing a noble metal in the electrolyte solution on the surface of the polysilicon film corresponding to the position of the defect under the film. 7. The defect detection method according to claim 6, wherein a cleaning step of cleaning the sample substrate is performed before the mask step and after the electrodeposition step. 8. After the electrodeposition step, after marking the outer periphery of the noble metal deposit deposited on the surface of the predetermined polysilicon film, an etching step of selectively etching the noble metal deposit is performed. The defect detection method according to claim 6 or 7. 9. The defect detection method according to claim 8, wherein a heating step of heating the surface of the sample substrate containing the noble metal precipitate is performed before the etching step.