JPH0964006A - Method for evaluating cleaning effect of semiconductor surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an effective evaluation method for cleaning effect by which the cleaning effects of a plurality of surface conditions during manufacturing process can be evaluated through one evaluation experiment. SOLUTION: A plurality of processing areas corresponding respectively to a plurality of surface conditions are formed on the surface of a semiconductor wafer, and they are contaminted by contaminating substance labelled with a radioactive isotope. Then, the radioactive intensity distribution on the contaminated surface is stored in a first stimulable phosphor layer, and its surface is cleaned by a cleaning method to be evaluated, then the radioactive intensity distribution on the cleaned surface is stored in a second accelerated luminescent layer. Further, the radioactive intensity distributions stored in the first and second accelerated luminescent layers are read out as a picture, and they are analyzed so as to compare the radioactive intensities before and after cleaning in the respective processing areas.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the evaluation of cleaning methods used in the process of manufacturing semiconductor devices.

[0002]

2. Description of the Related Art In addition to silicon, compound semiconductors such as gallium arsenide and gallium phosphide are known as semiconductors used for manufacturing semiconductor devices. Silicon devices make up the majority of such semiconductor devices. Most of LSIs and individual semiconductors form a film such as an oxide film, a nitride film or a polysilicon film on the surface of a silicon wafer. Etching is performed on the opening of the film by using the fine processing of the photoresist film. It is formed by repeating processing steps such as forming a region or forming an impurity-doped region by thermal diffusion or ion implantation. Such processing is, of course, performed in a clean room, but there are many opportunities for chemical contamination by elements such as heavy metals and alkali metals that deteriorate electrical characteristics and fine particle contamination that impairs fine processing. Therefore, it is necessary to repeat the cleaning of the wafer at each stage of processing. Naturally, a cleaning method having excellent cleaning power is required, and a method for evaluating the cleaning effect is necessary to select the cleaning method.

The cleaning method adopted at each processing stage of manufacturing should ideally be selected as necessary and sufficient according to the surface condition of the wafer at the processing stage. It is necessary to prepare a cleaning device according to the cleaning method, which not only lowers productivity but is also disadvantageous in terms of cost. Therefore, in reality, some limited cleaning methods and cleaning devices are all used for cleaning.

Conventionally, a radioactive tracer method has been known as a method for evaluating the cleaning effect of cleaning a silicon wafer. For example, as a cleaning method for heavy metal contamination, cleaning with a mixed solution of hydrochloric acid-hydrogen peroxide-water called SC-2 cleaning is widely used in almost all processes. The developer of the cleaning method evaluates the cleaning effect of this cleaning method by the radioactive tracer method as follows. Ie radioisotope ¹⁹⁸
A silicon wafer is immersed in a hydrofluoric acid-based solution containing Au labeled with Au to deposit this Au on the entire surface of the wafer to contaminate it, and the radioactivity of the contaminated wafer is counted with a scintillation counter (count value A). Then, SC-2 cleaning is performed, and the radioactivity of the cleaned wafer is counted (count value B). The cleaning effect was evaluated to be better as the residual rate of contaminants shown in (3) was smaller. The radioactive impurity tracer method is an effective cleaning evaluation method because it was difficult to measure the metal impurity concentration on the surface cleaned to the extent that defects did not occur with a highly reliable chemical analysis method before 1980. It was

Since 1980, the wafer surface is subjected to vapor phase decomposition with hydrofluoric acid, and the decomposition products are collected, and the average metal concentration on the wafer surface is quantified by a highly sensitive analysis method such as the flameless atomic absorption method. It became possible (VPD-AA method). According to this analysis method, it is possible to analyze the amount of metal deposited on the order of 10 ⁹ atoms / cm ² which indicates that the cleanliness is sufficient after cleaning. To quantitatively evaluate the cleaning effect,
Although it is necessary to analyze the concentration of impurities on the wafer surface before cleaning without destructing it and further contaminating it, the total reflection fluorescence X-ray analysis method (TRXRF) was developed. Various analyzes have become possible. Therefore, at present, the evaluation of the cleaning effect of semiconductor wafers is performed by contaminated the wafer surface with the metal element to be evaluated almost uniformly, then the contamination concentration is analyzed by TRXRF analysis, and then the evaluation target is cleaned, and after cleaning. The residual contamination amount of is analyzed by VPD-AA, and the method of obtaining the residual rate of contaminant elements after cleaning is used.

[0006]

However, in TRXRF, the elements that can be analyzed are limited to those heavier than silicon, and the detection sensitivity is insufficient at about 10 ¹⁰ atoms / cm ² . Further, it has a drawback that an accurate analysis value cannot be obtained in a sample having extremely high unevenness of contamination concentration. The impurity concentration distribution on the wafer can be obtained to some extent, but the resolution is not good at around 10 mm. In addition, on the surface to be cleaned in the semiconductor manufacturing process,
Not only silicon surface but also surface with oxide film, nitride film or polysilicon film is formed, but TRXRF method
It is essentially unsuitable for the analysis of uneven wafer surfaces having patterns such as oxide films, nitride films, or polysilicon films.

Also, what can be quantified by VPD-AA is the average metal concentration on the wafer surface as described above, and the impurity concentration distribution in the wafer cannot be measured at all. Moreover, since the surface contamination is a destructive inspection, it is not possible to directly carry out an experiment for evaluating the cleaning effect on the analyzed sample.

The present inventor has found that Cu or Au depends on whether the silicon surface is p-type or n-type, the difference in electrical conductivity, and the presence or absence of crystal defects due to ion implantation or reactive ion etching. It has been found that there is a difference in cleaning effect with respect to heavy metal contamination such as. However, when trying to evaluate the cleaning effect on such various surfaces at each stage of the manufacturing process by the above-mentioned conventional method, a large number of evaluation wafer samples corresponding to each surface state are prepared, and the number of cleaning experiments and Analysis must be done. This is a very complicated task. for that reason,
Until now, accurate evaluation of the cleaning effect at each processing stage has not been carried out, and it is unavoidable to evaluate various cleaning methods at academic societies.
The actual situation is that the silicon bare wafer as a starting material has been announced as a standard. Then, the objective of this invention is to provide the efficient cleaning effect evaluation method which can evaluate the cleaning effect with respect to several surface states which appear in a manufacturing process by one evaluation experiment.

[0009]

In order to achieve the above object, the present invention is directed to cleaning by a specific cleaning method against the contamination of various surface states that appear in the process of processing a semiconductor wafer surface to manufacture a semiconductor device. A method of evaluating the effect all at once, (A) forming a plurality of processing regions corresponding to each of a plurality of surface states on the surface of a semiconductor wafer for evaluation, and (B) thus forming a plurality of processing regions. The surface of the semiconductor wafer is contaminated with a radioactive isotope-labeled contaminant, and (C) the radioactivity intensity distribution of the contaminated surface is then used as a latent image on the first photostimulable phosphor layer. (D) Next, the contaminated surface is cleaned by the cleaning method to be evaluated, and (E) the radioactivity intensity distribution of the surface thus cleaned is hidden in the second photostimulable phosphor layer. (F) Next, the first and the second The radioactivity intensity distribution stored in the photostimulable phosphor layer of is read out as an image and analyzed to compare the radioactivity intensities before and after washing in each processing region. It is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be described for each step. The description will be given by taking a silicon wafer as an example, but the semiconductor to which the method of the present invention is applied is not limited to silicon,
It goes without saying that it may be GaAs or GaP, for example.

Step (A) First, a plurality of processed regions corresponding to a plurality of surface states to be evaluated among the various surface states appearing in the semiconductor device manufacturing process are independently formed on the surface of the semiconductor wafer. . Such surface conditions include, for example, a surface on which a film such as an oxide film, a nitride film, or a polysilicon film is formed when manufacturing a MOS LSI device using a silicon wafer, a photoresist opening region. An etched surface formed by etching, a surface on which various concentrations of donors or acceptors formed in this opening region are thermally diffused, a surface subjected to reactive ion etching (RIE) under conditions similar to those for forming a trench structure, In addition, the state of the surface or the like in which various donors or acceptors are ion-implanted into the film opening or the resist film opening is mentioned.

Since such a processed region is usually formed by a photolithography technique, it can be formed in any shape on a silicon wafer. However, in order to improve the measurement efficiency, a square or circular shape is desirable. In addition, in the photostimulable phosphor layer (step (B)), which will be described later, a scattered spot-like background is generated during exposure, so to ensure the reliability of the detection limit of residual radiation after cleaning. It is desirable that the processing area area be 10 mm ² or more.

In an actual LSI, fine processing with a line width of 1 μm or less is performed. Therefore, such a square or circular processed area is used as a fine pattern film, an impurity doped area or
By forming the RIE region as a set, the influence of the fine pattern on the cleaning effect can be evaluated at the same time. Minimum resolution of commercially available imaging plates is 50 μm
Although the radioactivity in the fine pattern as described above can be measured as an average of the entire processed area, the cleaning effect can be sufficiently evaluated.

(B) Step The semiconductor wafer having the plurality of processed regions formed as described above is then contaminated with a radioactive isotope-labeled contaminant. Here, the term "contaminants" means non-metals such as harmful metals, halogens, sulfuric acid, nitric acid and phosphoric acid, organic substances and fine particles which have been conventionally evaluated for cleaning.

The radioactive isotope used in the present invention is a representative harmful metal in the semiconductor manufacturing process, namely, Na, Fe, Cr, N.
²² Na, ⁵⁹ Fe, ⁵¹ Cr, ⁵⁷ N for i, Cu, Au, Zn, Ca, etc.
i, ⁶⁴ Cu, ¹⁹⁷ Au, ⁶⁵ Zn, ⁴³ Ca, etc. As for these labeled metals, the residual amount of 10 ⁸ atoms / cm ² can be quantified after the washing, even if the specific metal having high specific activity is taken into consideration. For example, for ⁶⁴ Cu, which has a short half-life, it is desirable that the specific activity is 5 TBq / g or more.

In the method of the present invention, β-rays can be measured with high sensitivity due to the characteristics of the imaging plate. Therefore, not only such metal contamination but also non-metal ion contamination, which has been attracting attention recently, is ³⁶ Cl or ³⁵ SO. By using ₄ and by using a labeled compound with ¹⁴ C, it is possible to evaluate organic contamination in the same manner as in the case of metal contamination. Further, for fine particles, a device for labeling with ^99m Tc is commercially available, and thus the same evaluation can be performed.

In order to contaminate a semiconductor wafer with such a radioactive isotope-labeled contaminant, a method of immersing the wafer in a solution containing these elements and adsorbing the wafer is generally used. The metal is chloride, acetate, or
May be used in the form of water-soluble salts of nitrates, Cl ^-,
SO ₄ ^-, as an aqueous solution which dissolves in or organics water if use a state of the acid with respect to non-metal ions of PO ₄ ^{3 -,} etc., in other cases may be used dissolved in a solvent. In the case of a substance that can be vaporized by heating such as NaCl or an organic substance that can be evaporated by heating, in the case of fine particles generated in the vapor phase, the vapor phase can contaminate the wafer in the closed container.

Step (C) Next, the radioactivity intensity distribution on the surface of the wafer, which is contaminated with the pollutant, is stored in the first photostimulable phosphor layer. below
The steps (C) to (F) are performed by Computed Radiography (CR) (digita) which is already established as a medical diagnostic technology.
l radiography by imaging plate).

A "stimulable fluorescent substance" is a photostimulated luminescent material that accumulates its energy when it is exposed to radiation and is re-excited when it is subsequently exposed to visible light and has a short life proportional to the radiation that was first applied. fluorescence, PSF). As such a stimulable phosphor,
For example, a barium fluoride halide (typically BaFBr) doped with Eu ⁺² is known.

When the radiation applied to the phosphor has an intensity distribution, a latent image (that is, a distribution of accumulated energy) is generated in the phosphor according to the distribution. When the phosphor is exposed to visible light, it is re-excited and stimulated emission (Ph
otostimulated fluorescence (PSF) is generated, but since this luminescence has a short life, a latent image can be imaged by scanning visible light with a reader and calibrating the stimulated luminescence with a photomultiplier tube. . A photostimulable phosphor layer formed on a substrate made of polyester, for example, is known as an imaging plate (IP) and is commercially available from Fuji Photo Film Co., Ltd.

In this step (C), when the photostimulable phosphor layer of the imaging plate is brought into close contact with the wafer surface on which the contaminant labeled with the radioisotope is adsorbed in the step (B) to expose the wafer surface, The isotope concentration distribution is stored as a latent image in the photostimulable phosphor layer.

(D) Step Next, the contaminated wafer is cleaned by the cleaning method that is an evaluation target. The cleaning method is not particularly limited, and any wet cleaning or dry cleaning can be evaluated. Wet cleaning, jet liquid jet scanning, scrubber cleaning, etc. can also be evaluated by the method of the present invention when the device can be installed in the radioactivity controlled area. Clarification of cleaning conditions is important for accurate evaluation. For example, in the case of wet cleaning with a chemical solution, the type of chemical solution, its composition, cleaning temperature, cleaning time, immersion cleaning or spray cleaning,
It is necessary to clarify whether or not ultrasonic waves are used together.

Step (E) Next, the radioactivity intensity distribution on the surface of the cleaned semiconductor wafer is stored in the second photostimulable phosphor layer again using another imaging plate in the same manner as in the step (C).

Step (F) Next, the radiation intensity distributions stored in the first and second photostimulable phosphor layers are read out as an image and analyzed to obtain radiation before and after cleaning in each processing region. Compare performance intensity. The reading of the radioactivity distribution on the wafer surface stored in the photostimulable phosphor layer is usually performed by scanning the surface of the photostimulable phosphor layer with a red laser. Then, since blue light that is proportional to the stored radiation dose (latent image) is emitted (stimulated emission), the radioactivity distribution on the wafer surface can be known by separating and measuring this blue light with a color filter. .

For example, when an imaging analyzer BAS2000 sold by Fuji Photo Film Co., Ltd. is used, the emitted blue color is converted into an electric signal and temporarily recorded on a magnetic disk, and the recorded data is then imaged on the CRT surface of the analyzer. Be converted. That is, the concentration distribution of the radioactive isotope-labeled contaminant on the wafer surface can be obtained as an image.
By specifying the area to measure the radioactivity intensity (shown in relative units called PSL in BAS2000) on the image,
Analysis is performed automatically, and the radioactivity intensity within the designated area is 1 mm ² after subtracting the background PSL value (displayed as BG).
It is displayed on the screen as strength per hit (PSL-BG). If a standard sample containing a known amount of the same radioisotope is exposed at the same time as the test wafer and the (PSL-BG) value is calculated for the standard sample in the same manner, the (PSL-BG) value By comparison, the element concentration in the designated area can be quantified.

In the present invention, in each of the wafer image planes obtained by exposing the wafer to the imaging plate before and after cleaning, the measurement region is designated as large as possible within the region to be processed, and the substrate region is the same area or larger. By specifying the measurement area of, the elemental amount of each area is quantified, and the residual rate after cleaning can be obtained by the ratio of the elemental quantity after cleaning to that before cleaning, and the cleaning effect on each area can be known at once. .

[0027]

EXAMPLES Next, examples will be described in detail, but the present invention is not limited to these examples. The most important factor preventing the removal of metal contamination by cleaning in the semiconductor device manufacturing process is the crystal defect occurring on the wafer surface and the interface between the wafer and the film where the cross section of the film such as the formed oxide film is exposed. Is. Among the contaminant elements, Cu, which has the fastest diffusion rate in silicon and at the interface, is most susceptible to these factors. Moreover, Cu is one of the elements most commonly exposed to wafer contamination in the general manufacturing process. Therefore, in the examples, the following experiments were performed using Cu as the element to be removed. However, it goes without saying that the same cleaning effect can be evaluated for the other elements described above. ⁶⁴ Cu was used as the radioisotope of Cu. That is, at the time of initial use, that is, in the evaluation wafer contamination stage, the specific activity is about 10 TBq / g, a calculated amount of copper acetate labeled with ⁶⁴ Cu was added to a solution with a predetermined concentration, and a plurality of processing regions were provided. A silicon wafer was immersed at room temperature for 10 minutes to prepare a test wafer sample.

Example 1 Cleaning in which cleaning with hydrofluoric acid and SC-2 cleaning were combined
Evaluation of Method In this example, after forming a processing area consisting of a bare silicon surface, an oxide film formed surface, a surface where B was thermally diffused in silicon, and a surface where RIE was performed on the silicon wafer surface, the wafer was formed. The entire surface was contaminated with Cu and then the contaminated wafer was cleaned by SC-2 cleaning method. The cleaning effect on each processing area was evaluated simultaneously. 6-inch diameter n-type (100) Si wafer [10-20
As shown in FIG. 1, a processing region (1 to 5) having a size of 3 × 3 cm having each surface state was formed on the surface of Ωcm], and a wafer for cleaning effect evaluation was prepared (to be exact, FIG. Images obtained from the imaging plate as described below). The procedure is shown below.

First, the silicon wafer was subjected to standard precision cleaning, and then the silicon wafer was oxidized to form an oxide film having a thickness of 1000 Å on the wafer surface. Then, the oxide film was selectively removed by photoetching to expose the silicon surface and form a region 1. Next, B was thermally diffused from the silicon surface of the region 1 to make the region 1 a p-type having a B concentration of 10 ¹⁸ atoms / cm ² .

Next, the oxide film was selectively removed in regions 2 and 3 by the same photolithography to expose the bare silicon surface. At this time, the oxide film newly formed in the region 1 was also removed at the same time. Further, after the oxide film is removed in the regions 4 and 5 by the same photolithography, the region 4 is left with the photoresist as a mask.
An etching region having a depth of 1 μm was formed on each of the electrodes 5 and 5 by RIE.

The photoresist layer used as a mask in each lithographic step was removed by oxygen plasma treatment on the surface layer, and the residual resist was treated with a sulfuric acid / hydrogen peroxide aqueous solution.
Further, an RCA ammonia / hydrogen peroxide aqueous solution [ammonia / hydrogen peroxide / water (volume ratio) = 1/1/5] cleaning (hereinafter, referred to as SC-1 cleaning) was performed to completely remove it.

The cleaning effect evaluation wafer in which the processed regions 1 to 5 were formed in this manner was immersed in hydrofluoric acid [hydrogen fluoride / water (weight ratio) = 1/100] at room temperature for 20 seconds in advance and each region was processed. After removing the natural oxide film generated in 1), it was immersed at room temperature for 10 minutes in a solution prepared by adding 2 ppb of Cu labeled with ⁶⁴ Cu to pure water containing 1 ppm HF. Then, the wafer was pulled up and rinsed with pure water for 1 minute to contaminate the wafer with ⁶⁴ Cu.

Next, after spin-drying the contaminated wafer, the stimulability of the surface of the wafer on which regions 1 to 5 are formed and the imaging plate (manufactured by Fuji Photo Film Co., Ltd.) (hereinafter referred to as imaging plate 1). The surface having the fluorescent layer was brought into close contact with the surface for 30 minutes, and the imaging plate was exposed. Next, the radioactivity intensity distribution of the wafer recorded on the exposed imaging plate 1 was read by the imaging analyzer BAS2000. An image of the imaging plate 1 at that time is shown in FIG.

Then, 24 hours after the exposure, the wafer was previously subjected to hydrofluoric acid [hydrogen fluoride / water (weight ratio) = 1.
/ 50] for 20 seconds to remove the natural oxide film formed in the regions 1 to 5, and then to a hydrochloric acid / hydrogen peroxide aqueous solution at 70 ° C. [hydrochloric acid / hydrogen peroxide / water (volume ratio) = 1/1 / 6] was immersed in a cleaning solution (hereinafter, referred to as SC-2 cleaning solution) for 10 minutes.

Next, the thus washed wafer was rinsed with pure water for 10 minutes, spin-dried and immediately exposed to another imaging plate (referred to as imaging plate 2) in the same manner as described above. Regarding the exposure time, the specific activity was reduced by about 2 TBq / g because the half-life of ⁶⁴ Cu was 12.7 hours, and the concentration of ⁶⁴ Cu was lowered by the effect of the above-mentioned cleaning. Was predicted to be 12 hours.

Next, the radioactivity intensity distribution of the wafer recorded on the exposed imaging plate 2 was read by the imaging analyzer BAS2000. An image of the imaging plate 2 at that time is shown in FIG. Area 1
.About.5 and ⁶⁴ Cu concentration before and after cleaning in regions 6 and 7 selected from the peripheral region of the wafer (composed of an oxide film) other than the above region.
It was determined by comparing the PSL measured at 000 with the PSL of a standard sample of known Cu concentration. The results are shown in Table 1.

In Table 1, in summary, each region has been processed as follows. Area number 1: Thermally diffused silicon surface of B Area numbers 2 and 3: Bare silicon surface Area numbers 4 and 5: Silicon surface subjected to RIE Area numbers 6 and 7: Oxide film surface

[0038]

[Table 1] In the table, * indicates that it was below the detection limit.

Example 2 Evaluation of Cleaning Method Using SC-1 Cleaning Solution n-type (100) silicon wafer having a diameter of 6 inches [10
.About.20 .OMEGA.cm] on the surface, as shown in FIG.
A cleaning effect evaluation wafer having regions (8 to 14) for dividing the processed state of m was prepared (to be precise, FIG. 3 shows an image obtained from an imaging plate as described later). The procedure is shown below. First, the silicon wafer was subjected to standard precision cleaning, and then the silicon wafer was oxidized to form an oxide film having a thickness of 100 Å on the wafer surface.

Next, the oxide film surface was selectively exposed in the region 8 by photolithography, and B was ion-implanted in the region 8 using the resist as a mask. Ion implantation is B
F ₂ ⁺ ions were applied at 35 keV and implanted so that the concentration of B in the region 8 was 5 × 10 ¹³ atoms / cm ² . Then, by similar photolithography, regions 9 and 10 are formed.
In, the ion implantation of B having a higher concentration was performed. That is, the implantation was performed so that the B concentration was 5 × 10 ¹⁴ atoms / cm ^{2 in this} region.

Further, by the same photolithography, As was ion-implanted at 30 keV through the oxide film in the regions 11 and 12 so that the As concentration became 5 × 10 ¹⁴ atoms / cm ² . Annealing was performed at 900 ° C. for 30 minutes to activate the ions implanted above. The resist layer used in each lithography process was removed in the same manner as in Example 1.

The cleaning effect evaluation wafer having the regions 8 to 12 thus formed was immersed in a solution of 0.5 ppb of Cu labeled with ⁶⁴ Cu in an NH ₄ F buffered HF solution at room temperature for 10 minutes, and then the wafer was cleaned. And then add 10
The wafer was contaminated with ⁶⁴ Cu by rinsing for a minute.

Next, the contaminated wafer was spin-dried, and immediately thereafter, the first imaging plate (imaging plate 1) was exposed in the same manner as in Example 1. next,
The radioactivity intensity distribution of the wafer recorded on the exposed first imaging plate is analyzed by the imaging analyzer BAS.
Read at 2000. An image of the imaging plate 1 at that time is shown in FIG.

Then, 24 hours after the exposure, the wafer was immersed in a SC-1 cleaning solution at 70 ° C. for 10 minutes. The thus washed wafer was rinsed with pure water for 10 minutes, spin-dried and immediately exposed to the second imaging plate (imaging plate 2) in the same manner as above. Exposed imaging plate 2
The radioactivity intensity distribution of the wafer recorded in 1. was read by the imaging analyzer BAS2000. An image of the imaging plate 2 at that time is shown in FIG.

Further, the ⁶⁴ Cu concentration before and after the cleaning of the regions 13 and 14 selected from the regions 8 to 12 and the peripheral region of the wafer other than the regions (consisting of the bare silicon surface peeled by HF) are used. Imaging analyzer B
It was measured by AS2000. Table 2 shows the results.

In the table, in summary, each region has undergone the following processing. Region number 8: Silicon surface implanted with 5 × 10 ¹³ atoms / cm ² ions of B Region numbers 9 and 10: Silicon surface implanted with 5 × 10 ¹⁴ atoms / cm ^{2 of} B Region numbers 11 and 12: 5 × As 10 ¹⁴ atoms / cm ²
Ion-implanted silicon surface Region numbers 13 and 14: Bare silicon surface

[0047]

[Table 2] In the table, * indicates that it was below the detection limit.

Example 3 Evaluation of Cleaning Method with Hydrofluoric Acid / Hydrogen Peroxide Solution p-type (100) silicon wafer 6 inches in diameter [10
.About.20 .OMEGA.cm] at the position corresponding to regions 8 to 12 shown in FIG. 3 using a photomask in which the LSI chips are arranged in 2 rows and 2 columns per region, and the photolithography and ion implantation methods The minimum width in the area is 0.6 μm
An ion implantation pattern including the fine pattern array of was formed. In forming the fine ion implantation pattern, the ion implantation and annealing conditions were the same as in Example 2. This wafer was used in the same manner as in Example 1 except that the SC-1 cleaning solution was replaced with a hydrofluoric acid / hydrogen peroxide aqueous solution [hydrogen fluoride 0.5% by weight, hydrogen peroxide 1% by weight] at room temperature for 3 minutes. Then, the cleaning effect was evaluated. The results are shown in Table 3.

[0049]

[Table 3] In the table, * indicates that it was below the detection limit. Thus, at first glance by comparing FIG. 1 and FIG. 2 and FIG. 3 and FIG. 4, it is possible to numerically evaluate the effect of cleaning from Tables 1 to 3.

[0050]

According to the cleaning effect evaluation method of the present invention, it is possible to easily and accurately evaluate the cleaning effect for a large number of surface states appearing on the wafer surface during the semiconductor device manufacturing process by using only one wafer. Can be done at. In addition, the evaluation of the cleaning effect can be numerically grasped as the difference between the concentrations of the contaminants contained in the wafer before and after the cleaning. Therefore, it is possible to easily configure an optimum cleaning system supported by specific numerical values throughout the semiconductor device forming process.

[Brief description of drawings]

FIG. 1 is a diagram showing the radioactivity intensity distribution on the wafer surface before cleaning in Example 1 as a difference in brightness.

FIG. 2 is a diagram showing the radioactivity intensity distribution on the wafer surface after cleaning in Example 1 as a difference in brightness.

FIG. 3 is a diagram showing a radioactivity intensity distribution on a wafer surface before cleaning in Example 2 as a difference in brightness.

FIG. 4 is a diagram showing the radioactivity intensity distribution on the wafer surface after cleaning in Example 3 as a difference in brightness.

Claims (2)

[Claims] 1. A method for collectively evaluating the cleaning effect of a specific cleaning method against contamination of various surface states that appear in the process of processing a semiconductor wafer surface to manufacture a semiconductor device, comprising: A plurality of processed regions corresponding to each surface state is formed on the surface of the evaluation semiconductor wafer, and (B) the surface of the semiconductor wafer on which the plurality of processed regions are formed is treated with a radioactive isotope-labeled contaminant. (C) Next, the radioactivity intensity distribution of the surface thus contaminated is stored as a latent image in the first photostimulable phosphor layer, and (D) Next, the contaminated surface is stored. Washing with the cleaning method of the evaluation object, (E) the radioactive intensity distribution of the surface thus washed is stored as a latent image in the second photostimulable phosphor layer, (F) Next, the first and second The radioactivity intensity distribution stored in the photostimulable phosphor layer of Then, the radioactivity intensity before and after cleaning in each processing region is compared by reading out and analyzing the result, and a cleaning effect evaluation method. 2. The plurality of processed regions formed in step (A) includes a region having a fine pattern film formed thereon, a region doped with impurities, and a region etched. Cleaning effect evaluation method.