JP3968768B2 - Semiconductor wafer evaluation apparatus and evaluation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a defect evaluation apparatus and method for a semiconductor wafer such as a silicon wafer (hereinafter sometimes simply referred to as a wafer), and more particularly, distribution of surface defects on a semiconductor wafer by depositing copper on the wafer surface. The present invention relates to a semiconductor wafer evaluation apparatus and evaluation method using a Cu deposition method for accurately analyzing density and the like.
[0002]
[Related technologies]
As the degree of integration of semiconductor elements increases, the quality of the wafer has a great influence on the yield and reliability of the semiconductor elements. The quality of semiconductor wafers is determined throughout the crystal growth process, wafer processing process, and device manufacturing process, but defects in the wafer are mainly crystal defects and processing that occur during silicon ingot growth. It is broadly divided into processing damage that is sometimes formed and defects due to external contamination sources.
[0003]
In general, a silicon wafer is manufactured by a crystal growth step of manufacturing a single crystal ingot using a Czochralski (CZ) method or a floating zone (FZ) method, slicing the single crystal ingot, This is performed through a wafer processing process in which one main surface is processed into a mirror surface. In more detail, the wafer processing process includes a slicing process in which a single crystal ingot is sliced to obtain a thin disk-shaped wafer, and the wafer obtained by the slicing process is prevented from cracking or chipping. A chamfering process for chamfering the outer periphery, a lapping process for flattening the wafer, an etching process for removing processing distortion remaining on the chamfered and lapped wafer, and a polishing (polishing) process for polishing the wafer surface. The cleaning step is performed to clean the polished wafer and remove the abrasive and foreign matter adhering thereto. The wafer processing process is a main process, and other processes such as a heat treatment process are added, or the order of processes is changed.
[0004]
In general, external contamination sources such as dust are easily removed by etching or cleaning processes among defects in wafers. However, in the case of metals such as Cu, there are some contamination sources that are taken into the wafer and difficult to remove. is there. This contamination can induce defects. In addition, defects such as defects, oxygen precipitates, stacking faults, and metal precipitates existing in the grown single crystal are mainly generated during the growth process of the single crystal and are not removed by the cleaning process. . In particular, since defects such as COP (Crystal Originated Particles) known as micropits are not removed by a conventional general cleaning process as a surface defect of a semiconductor wafer, a crystal growth process or a wafer processing It must be suppressed in the process.
[0005]
Such defects such as COP continuously affect the oxide film breakdown voltage characteristic, that is, the process of forming a semiconductor element on a semiconductor wafer, and cause a decrease in yield and reliability of the semiconductor element. Therefore, it is very important in terms of yield management of semiconductor elements to confirm the exact distribution and density of these defects before forming the semiconductor elements on the wafer in the device manufacturing process.
[0006]
Conventionally, a laser scattering method has been mainly used to analyze surface crystal defects of a wafer immediately after mirror polishing. For example, NH called SC1 composition _Four OH: H ₂ O ₂ : H ₂ After cleaning the wafer with a chemical solution of O = 1: 1: 8, etc., using a laser scattering particle counter, the surface of the wafer was irradiated with a laser having a certain wavelength and scattered. A signal is detected to analyze defects on the surface of the wafer.
[0007]
However, the conventional method has the following problems. That is, when a conventional laser scattering particle counter is used, since the detection limit for defects is about 0.12 μm, a COP below this size cannot be detected. However, even undetected fine defects of 0.12 μm or less affect the quality such as the oxide film breakdown voltage.
[0008]
In other words, since accurate information about defects on the wafer surface could not be obtained, the yield of semiconductor elements manufactured in subsequent processes could not be managed, and the generation of defects during wafer manufacturing was suppressed. I could not find an effective way to do this. As an evaluation method for solving this problem, a Cu deposition method has been considered.
[0009]
The Cu deposition method is a wafer evaluation method that can accurately measure the position of defects in a semiconductor wafer, improve the detection limit for defects in a semiconductor wafer, and accurately measure and analyze even finer defects. .
[0010]
A specific method for evaluating a wafer is to form an insulating film having a predetermined thickness on the wafer surface, destroy the insulating film on the defective portion formed near the surface of the wafer, and use an electrolytic substance such as Cu in the defective portion. Is deposited (deposition). That is, in the Cu deposition method, when a copper electrode is used in a solvent and a potential is applied to the oxide film formed on the wafer surface, a current flows through a portion where the oxide film is degraded, and Cu ions dissolved in the solvent are generated. This is an evaluation method utilizing the precipitation as Cu. It is known that a defect such as COP exists in a portion where the oxide film easily deteriorates.
[0011]
Defects of Cu deposited wafers can be analyzed under a condenser lamp or directly with the naked eye to evaluate their distribution and density. Further, they can be observed with a microscope, transmission electron microscope (TEM) or scanning electron microscope (SEM). ) Etc.
[0012]
A semiconductor wafer evaluation method and apparatus using the Cu deposition method will be described.
[0013]
FIG. 5 is a flowchart showing an example of a process order of a semiconductor wafer evaluation method using a Cu deposition method. First, an evaluation target wafer W to be evaluated is prepared (step 100 in FIG. 5). Necessary preprocessing is performed on the wafer W. As a pretreatment, this wafer is cleaned (step 102 in FIG. 5), and then the wafer W is put into an oxidation furnace and thermally oxidized to form an oxide film F on the wafer (step 104 in FIG. 5). ). The thickness of this oxide film is not particularly limited, but is usually about 25 nm.
[0014]
Next, in order to secure an electrical path between the wafer and the lower electrode, a part of the back side of the wafer is etched in the wafer W whose surface is covered with an insulating film F called a thermal oxide film. (Step 106 in FIG. 5). Although the entire backside of the wafer can be etched, it is sufficient in this method to ensure a minimum electrical path. In general, this etching may be performed using hydrogen fluoride (HF) vapor.
[0015]
The wafer is then cleaned with pure water to remove residues such as etching gas (step 108 in FIG. 5). Thereafter, Cu deposition is performed on the wafer to be evaluated on which the oxide film is formed (step 112 in FIG. 5).
[0016]
The Cu deposition is performed by a Cu deposition apparatus 10 schematically shown in FIG. The Cu deposition apparatus 10 has a processing container 12. In the processing container 12, a lower electrode (plate) 14 plated with copper and an upper electrode (plate) 16 made of copper are arranged at a predetermined interval. The wafer W whose surface is covered with the oxide film F is set on the wafer holder 18 so that the surface thereof is on the upper electrode side and is positioned between the lower electrode 14 and the upper electrode 16.
[0017]
Connection terminals 14a and 16a are connected to the lower electrode 14 and the upper electrode 16, respectively. The connection terminals 14a and 16a are connected to a DC external power source 20. A voltage is applied to the lower and upper electrodes 14 and 16 in a variable state by the external power source 20, and a constant electric field is formed between the electrodes 14 and 16.
[0018]
A solvent (electrolytic agent) 22 is injected into the processing container 12. Methanol is used as the solvent 22.
[0019]
Normally, seasoning is performed with a dummy wafer at the stage of starting Cu deposition. Seasoning is usually performed for about 1 hour (step 110 in FIG. 5). The reason why such a long time is required is to secure a sufficient time for cleaning the electrode and for ionizing copper. Specifically, methanol is injected as a solvent, and a negative bias is applied to a copper plate (upper plate) immersed in methanol to ionize copper.
[0020]
Next, after removing and attaching the dummy wafer, a target wafer (evaluation wafer) W is mounted on the wafer holder 18. Next, an external voltage is applied to the lower electrode 14 and the upper electrode 16 to deposit copper ions on the defective portion of the target wafer W (step 112 in FIG. 5). The strength of the electric field applied in the step of depositing copper is usually in the range of 3 to 10 MV / cm.
[0021]
The wafer on which such Cu deposition has been performed is washed and dried (step 114 in FIG. 5), and the number and distribution of deposited copper formed on the wafer are visually and microscopically evaluated (step 116 in FIG. 5).
[0022]
[Problems to be solved by the invention]
The above is a general method and apparatus for Cu deposition, but it takes time for seasoning. Further, in order to use methanol or the like efficiently, it is necessary to process a plurality of wafers using the same methanol. The overall evaluation time was very long.
[0023]
Moreover, although the above-described Cu deposition method has good sensitivity, there is a difficulty in stability of measured values. About this stability, it turned out that Cu concentration in the solvent used for Cu deposition is important, and it improves by adjusting in the range of 0.4-30 ppm. However, in addition to this, it was confirmed that the evaluation becomes unstable when Fe or Ni is present. When processing a plurality of wafers, if the same methanol is used, impurities are brought in and accumulated, and there is a problem that the metal of such instability is mixed.
[0024]
The present invention has been made in view of the above-described problems. In the Cu deposition method, the solvent can be efficiently exchanged for each wafer, and the wafer can be evaluated in a short time. An object of the present invention is to provide an evaluation apparatus and an evaluation method for a semiconductor wafer by a Cu deposition method that can eliminate the instability factor of wafer evaluation due to contamination and can accurately evaluate the defect of the wafer. To do.
[0025]
[Means for Solving the Problems]
In order to solve the above problems, a semiconductor wafer evaluation apparatus of the present invention is an apparatus for evaluating a semiconductor wafer by a Cu deposition method, and is provided with an upper electrode and a predetermined interval with respect to the upper electrode. A lower electrode and an external power source that generates an electric field between these electrodes, By drilling a solvent inlet in the upper electrode, and injecting a solvent from the solvent inlet, A solvent is injected into the surface of the semiconductor wafer placed on the upper surface of the lower electrode, and the injected solvent can be held on the surface of the semiconductor wafer by surface tension. Specifically, the solvent is accumulated on the wafer surface by surface tension by reducing the distance between the wafer and the upper electrode.
[0026]
If a solvent injection port is formed in the upper electrode and the solvent is injected from the solvent injection port, the injection operation is easy.
[0027]
It is preferable that the interval between the upper electrode and the lower electrode can be adjusted and maintained by an electrode interval adjusting member. This distance may be adjusted as appropriate in consideration of the range in which the solvent can be maintained by the surface tension and the thickness of the wafer. That is, it may be set according to the nature of the solvent used and the measurement environment (room temperature, etc.). For example, when methanol with a Cu concentration adjusted is used as a solvent, it is preferable to adjust so that an interval of about 0.3 mm to 1.5 mm is provided from the wafer surface. If the interval is more than 1.5 mm, it is difficult to maintain by surface tension, and the solvent may spill with a slight inclination. In addition, if the interval is narrower than 0.3 mm, the Cu concentration (the absolute amount of Cu) in methanol is reduced, and sufficient precipitation may not occur. Although the wafer thickness varies depending on the size of the wafer, the distance between the upper electrode and the lower electrode may be set to about 1 mm to 2.3 mm in a 6-inch wafer or an 8-inch wafer. Further, even for a wafer having a larger diameter, the thickness may be set appropriately in consideration of the thickness.
[0028]
By further providing a horizontal holder having an adjustment function for maintaining the lower electrode in a horizontal state, the entire apparatus can be maintained in a horizontal state, and good wafer evaluation can be realized.
[0029]
As the upper electrode, a glass electrode in which a transparent electrode film such as tin oxide or ITO (indium-tin oxide) is attached to a glass substrate or an electrode plated with gold on copper can be used.
[0030]
By further providing a means for fixing the semiconductor wafer placed on the upper surface of the lower electrode, there is no inconvenience such as the wafer floating due to surface tension.
[0031]
The method for evaluating a semiconductor wafer of the present invention is as follows. Using the evaluation device of the present invention, Forming an insulating film having a predetermined thickness on the surface of the semiconductor wafer; destroying the insulating film on the defect site formed near the surface of the semiconductor wafer; and depositing copper in a solvent on the defect site And depositing copper in a state where the solvent is held on the surface of the semiconductor wafer by surface tension.
[0032]
The basic process flow of the method of the present invention can be said to be the same as that of the conventional method shown in FIG. Since it is held on the surface, the configuration of the apparatus used in the Cu deposition step (step 112 in FIG. 5) is different and the procedure is also different.
[0033]
In the method of the present invention, it is preferable to adjust the copper concentration by adding a Cu standard solution to the solvent.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a semiconductor wafer evaluation apparatus according to the present invention will be described below with reference to FIG. 1, but various modifications can be made to this embodiment without departing from the technical idea of the present invention. Needless to say. FIG. 1 is a schematic explanatory view showing one embodiment of a semiconductor wafer evaluation apparatus of the present invention.
[0035]
In FIG. 1, reference numeral 30 denotes a semiconductor wafer evaluation apparatus of the present invention, which is used as an apparatus for performing Cu deposition.
[0036]
The evaluation device 30 has a lower electrode 32. As the lower electrode 32, copper plated with gold is used. An upper electrode 34 is provided above the lower electrode 32 so as to face it at a predetermined interval. The facing distance between the lower electrode 32 and the upper electrode 34 is maintained by an electrode spacing adjusting member 36 installed at the edge of the electrodes 32, 34 and can be appropriately adjusted. The electrode interval adjusting member 36 is made of glass or the like.
[0037]
Connection terminals 32 a and 34 a are connected to the lower electrode 32 and the upper electrode 34. The connection terminals 32 a and 34 a are connected to the DC external power supply 20. A voltage is applied to the lower and upper electrodes 32 and 34 in a state where the external power supply 20 can be varied, and a constant electric field is formed between the electrodes 32 and 34.
[0038]
The wafer W whose surface is covered with the oxide film F is set on the upper surface of the lower electrode 32 so as to be positioned between the lower electrode 32 and the upper electrode 34. A wafer holder 38 made of silicone rubber or the like is provided on the upper surface of the lower electrode 32 between the wafer W and the electrode interval adjusting member 36 so as to support the side surface of the wafer W.
[0039]
In the example of FIG. 1, the wafer holder 38 is formed on a flat plate, and the upper side of the wafer holder 38 is surrounded by the lower surface of the upper electrode 34, the side surface of the electrode interval adjusting member 36, and the side surface of the wafer W. A space 44 is formed. However, the space 44 does not need to be formed over the entire wafer holder 38. For example, an auxiliary support 45 formed of a fluororesin or the like is disposed as shown by an imaginary line in FIG. The upper electrode 34 can be supported in an auxiliary manner, and a protective cover (not shown) can be provided so that dirt does not enter from the outside and the electrodes 34 and 36 are not touched.
[0040]
Reference numeral 40 denotes a solvent injection hole formed in the upper electrode 34. There is no particular limitation on the drilling position of the solvent injection port 40, but it is preferable to drill in the center as shown in the illustrated example. The solvent 22 is injected onto the surface of the wafer W from the solvent injection port 40. The injected solvent 22 causes the surface of the wafer W and the upper electrode 34 to have an appropriate proximity distance, thereby causing the surface of the wafer W to have the solvent 22 applied to the surface of the wafer W by the force of surface tension as shown in FIG. A held state can be obtained.
[0041]
A horizontal holder 42 is attached to the lower surface of the lower electrode 32. The horizontal holder 42 can hold the lower electrode 32 horizontally. In other words, the horizontal holder 42 has a horizontal adjustment function so that the entire evaluation apparatus 30 can be held horizontally. As described above, in the evaluation apparatus 30 of the present invention, the solvent 22 is held on the surface of the wafer W by the surface tension. Therefore, when the evaluation apparatus 30 is tilted, the solvent 22 spills from the surface of the wafer W. However, it is possible to prevent an accident that the solvent 22 spills from the surface of the wafer W by holding the evaluation apparatus 30 so as to be horizontal by the horizontal holder 42. Therefore, in the present invention, it is important to start Cu deposition with the evaluation device 30 leveled out in advance.
[0042]
Since the wafer W may float due to the influence of the surface tension acting between the upper electrode 34 and the wafer W, a wafer fixing means for fixing the wafer W placed on the upper surface of the lower electrode 32, for example, As indicated by phantom lines in FIG. 1, it is preferable to provide a suction mechanism 46 that holds the back surface of the wafer W by vacuum suction so that the wafer W can be fixed.
[0043]
Thus, the evaluation apparatus 30 does not use a conventional container for storing a solvent, such as a processing container (reference numeral 12 in FIG. 4). For this reason, since it is not necessary to make contact with an extra container or the like, metal contamination caused by dirt or the like of the container or the like can be avoided.
[0044]
Moreover, in this evaluation apparatus 30, the solvent (methanol) which added Cu standard solution of a fixed density | concentration is used. Thereby, it is not necessary to use a Cu electrode as the upper electrode 34, and therefore seasoning time such as a cleaning process of the Cu electrode can be saved.
[0045]
A solvent controlled to a constant Cu concentration can be used, and a glass electrode or an electrode plated with gold on copper can be used as the upper electrode 34. By using the solvent having a constant Cu concentration in this way, the upper electrode 34 need not be particularly limited.
[0046]
That is, as the upper electrode 34, the same electrode as the lower electrode 32 in which gold is plated on copper, a glass electrode, a gold electrode, a platinum electrode, a carbon electrode, and other electrodes can be used.
[0047]
As described above, by using an electrode other than copper as the upper electrode 34, the seasoning time for cleaning the electrode, which has conventionally taken time, can be omitted. That is, it is easier and easier to clean the electrode than the Cu electrode. Further, the surface of the Cu electrode is oxidized during use, and becomes a non-conductive state. These can be evaluated stably for a long time without being oxidized by using a glass electrode or an electrode obtained by plating gold on copper.
[0048]
In particular, by using a glass electrode as the upper electrode 34, the state where the injected solvent spreads on the wafer can be observed, the solvent can be stably supplied, and ultraviolet light is applied to the wafer surface through the electrode. The optical effect can be used for increasing sensitivity. The glass electrode is obtained by attaching a transparent electrode film to a glass substrate such as a quartz plate. The electrode may be an electrode film formed on a transparent substrate other than glass.
[0049]
Next, the semiconductor wafer evaluation method of the present invention will be described with reference to FIG. FIG. 2 is a flowchart showing an example of the method for evaluating a semiconductor wafer according to the present invention.
[0050]
The semiconductor wafer evaluation method of the present invention is characterized in that copper is deposited in a state where a solvent is held on the wafer surface by surface tension.
[0051]
As an overall semiconductor wafer evaluation method, the same processing as the conventional method shown in FIG. 5 is basically performed before seasoning. That is, an evaluation target wafer W to be evaluated is prepared (step 100 in FIG. 2), and necessary preprocessing is performed on the wafer W. As a pretreatment, the wafer is cleaned (step 102 in FIG. 2), and then the wafer W is put into an oxidation furnace and thermally oxidized to form an oxide film F on the wafer (step 104 in FIG. 2). ). Next, in order to secure an electrical path between the upper part and the lower part of the wafer W, a part of the back side of the wafer W is etched with hydrogen fluoride (HF) vapor or the like (step 106 in FIG. 2). . Next, the wafer is cleaned with pure water to remove residues such as etching gas (step 108 in FIG. 2), and then Cu deposition is performed on the wafer to be evaluated on which this oxide film is formed (FIG. 2). Step 112 of 2).
[0052]
In the present invention, the method for performing Cu deposition is different from the conventional one, and the Cu deposition apparatus (FIG. 1) used in the method of the present invention is completely different from the conventional Cu deposition apparatus (FIG. 4). In the method of the present invention, using the Cu deposition apparatus of the present invention shown in FIG. 1, first, the wafer to be evaluated W is set, and the upper electrode 34 and the surface of the wafer to be evaluated W are set to about 1 mm. This interval is appropriately adjusted according to the thickness of the wafer W, the surface tension of the solvent 22, and the amount of solvent necessary for Cu deposition.
[0053]
Next, a methanol solution (solvent) 22 in which the Cu concentration is controlled is injected from the solvent injection port 44 of the upper electrode 34. At this time, the methanol (solvent) 22 travels between the surface of the wafer W and the electrodes 32 and 34 and gradually spreads. It holds so that methanol (solvent) 22 exists only on the surface of the wafer W.
[0054]
At this time, since the wafer W may be attracted (floated) to the upper electrode 34 side due to the surface tension of the methanol (solvent) 22, the back surface of the wafer W is vacuumed so as not to be lifted due to the surface tension. It is preferable that the adsorption mechanism 46 or the like be adsorbed and held.
[0055]
In this state, an external electrode is applied to the upper electrode 34 and the lower electrode 32 to deposit copper ions on the defective portion of the wafer W (step 112 in FIG. 2). By doing in this way, copper precipitates on the wafer surface.
[0056]
The wafer subjected to such Cu deposition is cleaned and dried (step 114 in FIG. 2), and the number and distribution of deposited copper (deposited at a defective place) formed on the wafer by visual inspection or microscope are evaluated. (Step 116 in FIG. 2).
[0057]
In addition, after Cu deposition, the solvent 22 is thrown away, and a to-be-inspected wafer is evaluated sequentially using a new solvent. That is, the method of the present invention can be said to be an evaluation method using methanol (solvent) on a single wafer.
[0058]
In the method of the present invention, since the surface tension is used well and methanol (solvent) exists only on the wafer W, contamination from the outside is small. Moreover, since methanol (solvent) is thrown away every time Cu deposition is performed once, there is an advantage that there is no accumulation of impurities.
[0059]
In the conventional method, a large amount of methanol (solvent) has been used from the beginning. When there are many wafers to be evaluated, the amount of methanol (solvent) used is not particularly problematic, but when you want to evaluate several wafers, the solvent is wasted because a large amount of methanol is required as well. Often. In the present invention, the solvent (methanol) needs only to be supplied onto the wafer in an amount that can be maintained by the surface tension, which has the advantage of reducing the solvent. Further, in the method (apparatus) of the present invention, since a conventional processing container is not used, wafers having different diameters can be easily processed by the same apparatus. Conventionally, it is necessary to prepare a processing container corresponding to each diameter, or to enlarge the processing container according to a large diameter in advance and use a useless solvent. In the apparatus of the present invention, since the solvent is only held on the wafer surface, there is basically no need to change the size of the apparatus itself. For example, if the apparatus is made for an 8-inch wafer, the electrode interval is adjusted. Wafers with other diameters can be easily evaluated with slight adjustment of the members and wafer holding (fixing) means.
[0060]
Further, in the method of the present invention, by using a solvent whose Cu concentration is adjusted in advance, the time required for seasoning such as electrode cleaning and ionization of the Cu electrode, which previously took time, can be omitted, and the efficiency can be reduced. Time wafer evaluation can be performed.
[0061]
【Example】
Hereinafter, the method of the present invention will be described in more detail with reference to examples, but it is needless to say that these are shown by way of example and should not be interpreted in a limited manner.
[0062]
Example 1
As an evaluation target wafer to be evaluated, a 6-inch CZ silicon wafer (wafer after mirror polishing) was prepared. As a pretreatment for this wafer, the wafer is cleaned, and then the wafer is put into an oxidation furnace, and heat treatment is performed in an oxygen atmosphere at 900 ° C. for 95 minutes to form a thermal oxide film of 25 nm.
[0063]
Next, in order to secure an electrical path between the wafer and the lower electrode, a part of the back side of the wafer is etched with hydrofluoric acid vapor. Next, in order to remove residues such as etching gas, it was washed with pure water. Thereafter, Cu deposition was performed on the wafer to be evaluated on which the oxide film was formed.
[0064]
The Cu deposition of the present invention uses the Cu deposition apparatus shown in FIG. 1, and first holds the outer periphery of the wafer to be evaluated with silicone rubber or the like so that the position does not shift, and the electrodes are spaced at a distance of about 1.6 mm ( Set at about 1 mm from the surface of the wafer to be evaluated. The distance may be adjusted by holding a certain thickness of glass that does not allow current to flow between the upper electrode and the lower electrode. Next, a solvent in which the Cu concentration is controlled (in this embodiment, a methanol solution) is injected into the center of the wafer from a solvent injection port opened in the upper electrode.
[0065]
By doing in this way, it can hold | maintain so that methanol exists only on the wafer surface under the influence of surface tension.
[0066]
A methanol solution whose Cu concentration is controlled in advance is used. Specifically, Cu standard solution, for example, commercially available CuSO _Four ・ 5H ₂ It prepared by adding O (made by Kanto Chemical Co., Inc.) etc. in a solvent. It is preferable to adjust the Cu concentration to be about 0.4 to 30 ppm using this standard solution.
[0067]
In this example, methanol having a Cu concentration of about 1 ppm was used. The methanol was dropped using a pipette and dropped to the extent that it did not spill from the wafer using surface tension. Methanol spreads throughout the wafer between the wafer and the top electrode. In this example, approximately 18 mL of solvent was dropped per wafer.
[0068]
An applied electric field was applied between the upper electrode and the lower electrode at 5 MV / cm for 5 minutes. After Cu deposition, clean with pure water, dry naturally, and scan the copper deposits on the wafer in a straight line in the diameter direction of the wafer under a microscope (50 times, approximately 3.5 mm field of view) to observe defects, Number of deposited copper per unit area (pieces / cm ² ) Was calculated. The result of microscopic observation is shown in FIG. As is clear from FIG. 3, donut-shaped precipitated copper was observed.
[0069]
As described above, according to the method of the present invention, it was confirmed that the inspection time was remarkably shortened because seasoning was not performed. Moreover, although the said operation was repeated and several wafers were evaluated, as a result of repeated measurement, the defect was able to be observed stably.
[0070]
(Comparative Example 1)
Using a conventional Cu deposition apparatus (FIG. 4), 1 liter of solvent was placed in the processing vessel to perform Cu deposition. In addition, seasoning is performed for 1 hour before depositing on the wafer to be evaluated. As a result of Cu deposition, defects similar to those in FIG. 3 were detected even in this conventional apparatus.
[0071]
This operation was repeated without exchanging the solvent (methanol), and a plurality of wafers were evaluated, but as a result of repeated measurement, it was sometimes difficult to see defects. When this cause was investigated, it turned out that the density | concentration of Fe and Ni is increasing. It is considered that these metals were brought in from the wafer to be evaluated, or the metal adhering to the processing container was eluted.
[0072]
As described above, in the present invention, since it is carried out without using a processing container for storing a solvent, there is little external contamination, and by exchanging and processing the solvent one by one, from another wafer Accumulation of brought-in pollution etc. is reduced, and unstable factors due to pollution can be remarkably reduced. In addition, the amount of solvent can be reduced.
[0073]
Furthermore, the use of a solvent whose Cu concentration has been adjusted in advance eliminates the need for seasoning such as electrode cleaning and ionization of the Cu electrode, enabling rapid evaluation. Further, a glass electrode or a gold-plated copper electrode can be used as the upper electrode, and the deterioration of the electrode and the source of contamination are further reduced.
[0074]
【The invention's effect】
As described above, according to the present invention, a wafer can be evaluated in a short time, and further, an instability factor in wafer evaluation due to contamination can be eliminated, and a wafer defect can be evaluated with high accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing one embodiment of a semiconductor wafer evaluation apparatus of the present invention.
FIG. 2 is a flowchart showing an example of a process order of the semiconductor wafer evaluation method of the present invention.
3 is a photograph showing a result of microscopic observation of copper precipitates on a wafer in Example 1. FIG.
FIG. 4 is a schematic explanatory view showing a conventional Cu deposition apparatus.
FIG. 5 is a flowchart showing an example of a process order of a conventional semiconductor wafer evaluation method.
[Explanation of symbols]
10, 30: Deposition device, 12: Processing vessel, 14, 32: Lower electrode, 14a, 16a, 32a, 34a: Connection terminal, 16, 34: Upper electrode, 18: Wafer holder, 20: External power supply, 22 : Solvent, 36: Electrode spacing adjusting member, 38: Wafer holder, 40: Solvent inlet, 42: Horizontal holder, 44: Space, 45: Auxiliary support, 46: Wafer fixing means, F: Insulating film, W : Wafer.

Claims (7)

An apparatus for evaluating a semiconductor wafer by a Cu deposition method, comprising an upper electrode, a lower electrode provided at a predetermined interval with respect to the upper electrode, and an external power source for generating an electric field between these electrodes A solvent injection port is formed in the upper electrode, and a solvent is injected from the solvent injection port to inject a solvent into the surface of the semiconductor wafer placed on the upper surface of the lower electrode. An apparatus for evaluating a semiconductor wafer, wherein the solvent can be retained on the surface of the semiconductor wafer by surface tension.   2. The semiconductor wafer evaluation apparatus according to claim 1, further comprising an electrode interval adjusting member that adjusts and maintains an interval between the upper electrode and the lower electrode. 3. The semiconductor wafer evaluation apparatus according to claim 1, further comprising a horizontal holder having an adjustment function for maintaining the lower electrode in a horizontal state. Wherein the upper electrode, a semiconductor wafer evaluation apparatus according to any one of claims 1 to 3, characterized in that the use of electrodes plated with gold to a glass electrode or copper. Evaluation device for a semiconductor wafer according to any one of claims 1 to 4, wherein the further provided with that the means for fixing the semiconductor wafer mounted on the upper surface of the lower electrode. A semiconductor wafer evaluation method using the semiconductor wafer evaluation apparatus according to claim 1 , wherein an insulating film having a predetermined thickness is formed on a surface of the semiconductor wafer, and the semiconductor A semiconductor wafer surface is formed by using a Cu deposition method comprising a step of destroying an insulating film on a defect site formed near the surface of the wafer and depositing copper in the solvent on the defect site. A method for evaluating a semiconductor wafer, characterized in that copper is deposited in a state of being held in a wafer. The method for evaluating a semiconductor wafer according to claim 6 , wherein the copper concentration is adjusted by adding a Cu standard solution to the solvent.

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