JP2005019600A - Wafer evaluation method, and management method of wafer manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer evaluation method by which a pit cluster can be easily evaluated and thereby a contamination occurring in a wafer processing process can be correctly evaluated, and also to provide a management method of a wafer manufacturing process using the wafer evaluation method. <P>SOLUTION: The wafer evaluation method is characterised in that a wafer to be evaluated is dipped in an etchant formed of ammonia and hydrogen peroxide for a long period of time, and thereafter, a defect corresponding to the pit cluster is evaluated using a light scattering-method particle counter or a defect of 0.3 μm or above is evaluated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an evaluation of a wafer capable of suitably detecting, inspecting and managing defects (mainly pit clusters) caused by an abnormality such as impurity contamination in a wafer manufacturing process for a wafer such as a silicon wafer. The present invention relates to a method for managing a wafer manufacturing process and a method for managing an abnormality that may occur in the wafer manufacturing process using the wafer evaluation method.
[0002]
[Related technologies]
In general, a method for manufacturing a semiconductor wafer such as a silicon wafer includes a single crystal manufacturing process for growing a single crystal ingot using a Czochralski (CZ) method and the like, and slicing the single crystal ingot so that at least one principal surface is a mirror surface. It consists of a wafer processing step that is processed into Further, in the wafer processing step, as shown in FIG. 9, a single crystal ingot is sliced to obtain a thin disk-shaped wafer (step 300), and the wafer obtained by the slicing step is prevented from cracking or chipping. Therefore, a chamfering process for chamfering the outer peripheral portion (step 302), a lapping process for flattening the wafer (step 304), and an etching process for removing processing distortion remaining on the chamfered and lapped wafer (step 306). And a polishing (polishing) step (step 308) for mirroring the wafer surface, and a cleaning step (step 310) for cleaning the polished wafer and removing abrasives and foreign substances adhering thereto. Yes.
[0003]
The above steps show main steps, and other processes such as a heat treatment process are added, the order of the processes is changed, and the processes are performed in multiple stages. The silicon wafer thus manufactured is finally subjected to quality inspection, then placed in a container for storing the wafer and packaged, and then a device is formed using the manufactured mirror-polished wafer (also referred to as PW). Therefore, it is sent to a device manufacturing company (device process). In addition, in order to add value to the mirror-polished wafer before forming the device, an annealing process for heat-treating the mirror-polished wafer and an epitaxial growth process for forming an epitaxial layer on the wafer may be included. In addition, a bonded SOI wafer or the like may be manufactured by bonding a wafer to a mirror-polished wafer via an oxide film.
[0004]
In such a wafer manufacturing process, device characteristics to be achieved have become increasingly severe as device miniaturization has progressed, and silicon wafers are required to have more complete crystal quality and clean surfaces. Yes.
[0005]
Accordingly, it is necessary to precisely evaluate the quality of the silicon wafer and improve the silicon wafer fabrication and device fabrication process. In other words, in the manufacture of semiconductor wafers, defects existing on the wafer and foreign matter adhering to the wafer cause the yield to decrease, and these defects and foreign matter attached to the wafer are inspected to control the amount of defects and foreign matter generated. In some cases, a defect existing on the wafer or an attached foreign substance is analyzed to analyze a generation source (generation process) of the defect or the foreign substance.
[0006]
Defects and foreign substances detected in the semiconductor wafer include defects caused by crystals introduced in the above-mentioned single crystal manufacturing process, defects caused by processing introduced in the wafer processing process, or foreign substances such as impurities (particles, heavy metals, etc.) It is divided roughly by the thing.
[0007]
Conventionally, an inspection device called a particle counter based on the principle of light scattering has been mainly used for such inspection of a silicon wafer surface. A light scattering particle counter scans the wafer surface with laser light and measures the intensity of light scattering from the particle (wafer surface) to identify the position and (optical) size of the particle. is there.
[0008]
The light scattering type particle counter will be further described with reference to FIG. FIG. 6 is a partial sectional side view schematically illustrating the basic structure of a light scattering type particle counter. In FIG. 6, reference numeral 30 denotes a light scattering type particle counter, which has a sample stage 32 on which a sample wafer W is mounted and rotatable. The laser beam L incident from one side is reflected downward by the first reflecting plate 34 and is reflected again by the surface of the rotating evaluation wafer W. A part of the reflected light is collected by a light collecting plate 36 erected around the first reflecting plate 34 and guided to a first detector 38 provided above. The rest of the reflected light is collected by the condenser lens 40 provided above the first reflector 34, then reflected to the other side by the second reflector 42, and the second provided on the other side. Guided to detector 44.
[0009]
In order to make the configuration of FIG. 6 easy to understand, the first detection mode is shown separately in FIG. 7A and the second detection mode is shown separately in FIG. 7B. The first detection mode (referred to as the DWN mode) is a mode in which the laser is irradiated perpendicularly to the wafer as shown in FIG. 7 (a), and the state of irregular reflection due to defects is collected and observed at a position close to the wafer. In particular, this mode is effective for detecting particles, COPs, and the like. In the second detection mode (referred to as the DNN mode), as shown in FIG. 7B, the wafer is irradiated with the laser perpendicularly, and the irregular reflection due to the defect is collected and observed in a portion close to regular reflection. This mode is particularly effective for detecting depressions and the like. In addition to the above configuration, the light scattering type particle counter includes, for example, an optical system in which a laser is incident obliquely.
[0010]
This device detects scattering intensity and detects particles on the wafer. However, in addition to particles, etc., various defects are detected if they are larger than a certain size, and it is difficult to distinguish them. The defects and foreign matters detected by this method are counted together without being distinguished, and the generation amount of defects is managed under the name of LPD (Light Point Defect).
[0011]
Conventionally, COP (Crystal Originated Particle) that appears near the surface of a wafer is known as a defect that causes a problem in a device process. These are crystal-induced defects that are introduced when the crystal is pulled up. As a method for evaluating such defects, before each defect is evaluated, the silicon wafer itself is pre-processed to improve the sensitivity for specific defects (defects are actualized), and then visually or with an electron microscope, etc. The defect is observed directly. For example, in the inspection of COP, COP is a defect of 0.1 μm or less, but it is manifested by treatment with an ammonia-hydrogen peroxide solution (also called SC-1 solution) and appears as pits on the wafer surface. This is detected. In recent years, a wafer with few defects such as COP can be manufactured by improving the crystal pulling technique.
[0012]
For other defects, the position of a bright spot on the wafer detected by a particle counter is specified, and the same point as the bright spot is measured by another measuring device, thereby identifying the defect. For example, a defect in which micro defects are gathered in a colony shape (hereinafter referred to as a pit cluster) is known as a defect of a silicon wafer. The position is measured with a scattering type particle counter or the like, and then observed and evaluated with a probe microscope (AFM or the like), an electron microscope (SEM), an optical microscope or the like.
[0013]
As another defect evaluation method for the silicon wafer surface, a laser microscope of a confocal optical system has recently been used in addition to a particle counter. The confocal optical system focuses the laser beam on the sample, irradiates it with a minute spot, refocuses the reflected light on the pinhole located on the entire surface of the receiver, and detects the amount of light that has passed through the pinhole. It is.
[0014]
A laser microscope using a confocal optical system will be described with reference to FIG. FIG. 8 is a schematic explanatory view showing the basic structure of a laser microscope using a confocal optical system. In FIG. 8, reference numeral 10 denotes a laser microscope using a confocal optical system, and a laser light source 14 such as an argon laser is provided corresponding to the microscope main body 12.
[0015]
The microscope main body 12 includes a laser light source 14, a beam splitter 16, an objective lens 18 for converging the laser beam B on the surface of the wafer W to be evaluated, and the laser beam B reflected from the surface of the wafer W into the pinhole 20 a of the pinhole member 20. The condenser lens 22 converges and the photodetector 24 that receives the laser beam B that has passed through the pinhole 20a.
[0016]
With such a configuration, the operation principle will be described below. The laser beam B converges on the surface of the wafer W by the objective lens 18 and irradiates the wafer surface with a spot of about 0.5 μm, for example. The laser beam B reflected from the surface of the wafer W returns to the optical system, is converged by the condenser lens 22, and enters the photodetector 24 through the pinhole 20 a of the pinhole member 20.
[0017]
When there is a defect on the surface of the wafer W, the wave front of the reflected light from the defective part is disturbed, and the spot of the laser beam B spreads in the photodetector 24, and the light detection signal is lowered. A defect detection circuit (not shown) detects a signal difference in the light detector 24, thereby making a portion where a signal intensity difference equal to or larger than a set value occurs as a defect portion, and records the size and coordinates. The inspection is performed while moving at a constant speed, and each beam spot scans the entire wafer W precisely.
[0018]
In this method, defects and foreign matter on the wafer surface are evaluated with higher sensitivity than conventional particle counters. According to the laser microscope of such a confocal optical system, it is possible to evaluate what kind of defects and foreign matters exist on the wafer and how each defect and foreign matter are distributed. An apparatus for automatically identifying the defect according to the shape of the defect has also been developed. In such an apparatus, since the wafer adhesion state of defects and foreign matters can be seen at a glance, it becomes easier to clarify the cause of the occurrence of defects and foreign matters. As a result, defects such as pit clusters can be identified even in a bare wafer.
[0019]
[Problems to be solved by the invention]
The presence of pit clusters has a serious adverse effect on yield in the device process. This is because the pit cluster forms a deep pit aggregate in the device process and the wiring is cut.
[0020]
In addition, it is known that pit clusters are defects caused by contamination. By grasping the number of pit clusters, the contamination state of the wafer manufacturing process can be confirmed. Therefore, it is important to accurately and easily evaluate the presence of pit clusters.
[0021]
However, the conventional method of repeating the SC-1 solution repeatedly to widen the defects, measuring the position with a light scattering type particle counter, etc., and then observing with a probe microscope, electron microscope, optical microscope, etc. requires a lot of man-hours. It is a problem.
[0022]
Further, when inspecting with a laser microscope of a confocal optical system having an automatic identification function, a very expensive apparatus is required. It is desirable to evaluate using an inexpensive device.
[0023]
Accordingly, the present invention provides a wafer evaluation method capable of simply evaluating pit clusters and accurately evaluating contamination generated in a wafer processing process, and a method for managing a wafer manufacturing process using this wafer evaluation method. For the purpose.
[0024]
[Means for Solving the Problems]
The present inventor found that a defect of a specific size obtained after SC-1 repeated cleaning was found to be proportional to the number of pit clusters obtained with a laser microscope of a confocal optical system detected with high sensitivity, The present invention has been completed.
[0025]
That is, the first aspect of the wafer evaluation method of the present invention is equivalent to a pit cluster by immersing the wafer to be evaluated in an etching solution made of ammonia-hydrogen peroxide for a long time, and then using a light scattering type particle counter. It is characterized by evaluating defects to be performed.
[0026]
The second aspect of the wafer evaluation method of the present invention is to immerse the wafer to be evaluated in an etching solution comprising ammonia-hydrogen peroxide for a long time, and then use a light scattering type particle counter to detect defects of 0.3 μm or more. It is characterized by evaluating.
[0027]
According to a third aspect of the wafer evaluation method of the present invention, the number of pit clusters existing on the surface of a predetermined wafer and the predetermined wafer are immersed in an etching solution composed of ammonia-hydrogen peroxide for a long time, A correlation equation with the number of defects evaluated as defects of 0.3 μm or more using a light scattering type particle counter is obtained in advance, and the wafer to be evaluated is immersed in the same etching solution as the etching solution for a long time under the same conditions. Then, using a light scattering type particle counter, the number of defects evaluated as a defect of 0.3 μm or more is obtained, and the number of pit clusters of the wafer to be evaluated is evaluated from the number of defects by using the above correlation equation. Features.
[0028]
In any of the first to third aspects of the wafer evaluation method of the present invention, the defects are widened by repeated cleaning of an etching solution (SC-1 solution) made of ammonia-hydrogen peroxide solution, and a light scattering type particle counter is used. The position is measured by the above method, and then the defect is not identified by another apparatus, but the defect corresponding to the pit cluster is evaluated only by the evaluation information obtained by the light scattering type particle counter.
[0029]
By evaluating such a large defect obtained by a light scattering type particle counter, it is possible to easily evaluate a defect caused by contamination, particularly a defect corresponding to a pit cluster.
[0030]
In the wafer evaluation method of the present invention, the number of defects evaluated as a defect of 0.3 μm or more using a light scattering type particle counter is, for example, 0.12 μm or more in the DWN mode of SP-1 manufactured by KLA-Tencor. This corresponds to the number of LPDs detected as a defect of 0.3 μm or more when this defect is evaluated.
[0031]
If evaluated using such an apparatus, the correlation between the number of defects evaluated for defects of 0.3 μm or more and the number of pit clusters becomes very good.
[0032]
By applying the wafer evaluation method of the present invention to the process management of the wafer manufacturing process, the process management of the wafer manufacturing process can be easily performed.
[0033]
The method of managing the wafer manufacturing method of the present invention is based on the number of LPDs evaluated as defects of 0.3 μm or more using a light scattering type particle counter by immersing the wafer in an etching solution comprising ammonia-hydrogen peroxide solution for a long time. It is characterized by managing the contamination status of the wafer.
[0034]
If managed in this way, it can be managed with an inexpensive evaluation apparatus, the process can be easily improved, and a stable wafer can be manufactured.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the illustrated examples are illustrative only, and various modifications can be made without departing from the technical idea of the present invention. .
[0036]
FIG. 1 is a flowchart showing an example of the order of steps in the first aspect of the wafer evaluation method of the present invention. In the first aspect of the wafer evaluation method of the present invention, a mirror polished wafer such as a silicon semiconductor that has been subjected to wafer processing is used as the wafer to be evaluated (preparation of wafer to be evaluated, step 100), and SC-1 solution (ammonia-pass After the treatment with hydrogen oxide water (step 102), evaluation is performed using a light scattering type particle counter (step 104a).
[0037]
FIG. 2 is a flowchart showing an example of the order of steps in the second aspect of the wafer evaluation method of the present invention. In the second aspect of the wafer evaluation method of the present invention, the preparation of the wafer to be evaluated (step 100) and the treatment with ammonia-hydrogen peroxide solution (step 102) are the same as in the first aspect of the method of the present invention. Subsequently, the difference is that a defect of 0.3 μm or more is evaluated by a light scattering type particle counter (step 104b).
[0038]
The process of step 102 reveals defects by immersing the wafer to be evaluated in an etching solution (SC-1 solution) made of ammonia-hydrogen peroxide solution for a long time. Conventionally, such treatment has been performed and evaluated. However, defects of 0.12 μm or more are usually evaluated, and evaluation information for large defects of 0.3 μm or more has not been particularly utilized. In the present invention, the surface of the wafer to be inspected is inspected by using a light scattering type particle counter in particular, and the number of defects of 0.3 μm or more revealed by the SC-1 solution is evaluated. It is. As described above, by evaluating the pit cluster based on information on a large defect of 0.3 μm or more that has not been used for evaluation in the past, the state of metal contamination can be easily evaluated.
[0039]
Since the light scattering type particle counter used in the wafer evaluation method of the present invention has already been described with reference to FIGS. 6 and 7A and 7B, description thereof will not be repeated. The light scattering type particle counter used in the method of the present invention evaluates the number of defects of 0.3 μm or more by identifying defects based on such a principle (optical system).
[0040]
In order to obtain such a defect, for example, evaluation is performed with the number of LPDs detected as a defect of 0.3 μm or more when a defect of 0.12 μm or more is evaluated in the DWN mode of the commercially available KLA-Tencor SP-1. Just do it.
[0041]
As a process for revealing the defects of the wafer to be evaluated, the wafer is immersed in an etching solution composed of ammonia-hydrogen peroxide solution for a long time. For long-time etching, treatment may be performed for any set time at one time, or immersion may be repeated so that the total time becomes the (set) set time.
[0042]
Usually, this long immersion treatment is performed for about 30 to 100 minutes, preferably about 40 to 60 minutes. An immersion time of less than 30 minutes is not preferable because the etching time is short and defects do not appear, and if it exceeds 100 minutes, the wafer surface becomes rough and haze increases. Note that the number of LPDs obtained after processing changes depending on the etching time. Therefore, when quality assurance or process management is performed, processing is performed at a fixed time.
[0043]
The etching solution comprising ammonia-hydrogen peroxide solution is not particularly limited. For example, it is a solution prepared by adjusting 28% by weight ammonia water, 30% by weight hydrogen peroxide solution, and pure water at about 10: 2: 100. Etching treatment is good. The liquid temperature is preferably adjusted to about 80 ° C.
[0044]
As described above, in the present invention, defects corresponding to pit clusters known as the cause of metal contamination can be evaluated by the number of LPDs of defects of 0.3 μm or more obtained by the light scattering method after SC-1 treatment. In addition, evaluation can be performed with an inexpensive inspection device. A defect of 0.3 μm or more obtained by the light scattering method usually detects a large foreign matter (dust) or the like, but in the method of the present invention, since it has been washed in advance with the SC-1 solution, Has been removed.
[0045]
On the other hand, a defect in which micro pits such as pit clusters are gathered in a colony has a large defect size due to the etching action of the SC-1 solution, and is different from other single defects. Therefore, it is considered that the defect size suddenly increases, and the defect size evaluated as a large defect of 0.3 μm or more is increased by processing with the SC-1 solution. Therefore, the correlation between information obtained as defects of 0.3 μm or more and pit clusters appears, and the number of pit clusters is indirectly determined by evaluating the number of LPDs of defects of 0.3 μm or more after such processing. Can be guessed.
[0046]
Before performing such an evaluation, the number of pit clusters existing on the wafer surface and the wafer is immersed in an etching solution made of ammonia-hydrogen peroxide for a long time, and then a light scattering type particle counter is used. The correlation of the number of defects detected as the number of defects of 0.3 μm or more is confirmed. That is, processing conditions (concentration and processing time) and evaluation conditions (measurement apparatus and measurement conditions) with the SC-1 solution are fixed, a correlation equation is obtained under certain conditions, and the sample to be evaluated The number of pit clusters can be evaluated.
[0047]
FIG. 3 is a flowchart showing an example of the process sequence of the third aspect of the wafer evaluation method of the present invention. (A) is a procedure for creating a correlation formula between the number of defects and a pit cluster in a predetermined wafer. Shows the procedure for evaluating the number of pit clusters on the wafer to be evaluated. In the third aspect of the wafer evaluation method of the present invention, first, a predetermined processed wafer is prepared (step 150). The number of pit clusters on the wafer surface is evaluated by a laser microscope or AFM of a confocal optical system (step 152). The wafer is treated with ammonia-hydrogen peroxide solution (step 154), and then the number of defects of 0.3 μm or more on the wafer surface is evaluated by a light scattering type particle counter (step 156). Next, a correlation formula between the number of defects of 0.3 μm or more and the number of pit clusters is created (step 158). This correlation equation can be created as, for example, the correlation equation shown in FIG.
[0048]
Next, the wafer to be evaluated is evaluated as follows using the above correlation equation. First, a wafer to be evaluated is prepared (step 160). This wafer to be evaluated is treated with ammonia-hydrogen peroxide solution under the same conditions as in step 154 (step 162). The number of defects of 0.3 μm or more on the surface of the processed wafer to be evaluated is evaluated using a light scattering type particle counter (step 164). The evaluation conditions at this time are the same as those in step 156. The number of pit clusters on the surface of the wafer to be evaluated is calculated and evaluated from the number of defects of 0.3 μm or more using the above-described correlation equation (step 166). Thus, the number of pit clusters can be calculated and evaluated from the evaluation of the number of defects of 0.3 μm or more for the wafer to be evaluated.
[0049]
Next, a method for managing the wafer manufacturing process of the present invention will be described with reference to FIG. FIG. 4 is a flowchart showing an example of the process sequence of the method for managing a wafer manufacturing process according to the present invention. In the wafer manufacturing process management method of the present invention, a predetermined wafer that has been subjected to wafer processing is prepared (step 200), and the wafer is treated with ammonia-hydrogen peroxide solution (SC-1 solution) (step 202). Next, the number of defects of 0.3 μm or more on the wafer surface is evaluated by a light scattering type particle counter (step 204). It is determined whether or not the evaluated number of defects (LPD) is within a predetermined standard value (step 206), and if it is within the standard value, it is determined that the defect is acceptable (step 208). This wafer has no problem and is transported to the next process, and it is determined that there is no abnormality in the wafer processing process and that process improvement is unnecessary (step 210).
[0050]
On the other hand, when the number of defects is not within a predetermined standard value, that is, when a large number of defects (LPD) exceeding an arbitrary predetermined standard value are detected, it is determined as a failure (step 212), and a defect due to contamination. It is determined that there are many pit clusters (step 214). In this case, it is necessary to pursue the cause of contamination, and the wafer processing process is improved (feedback to the wafer manufacturing process) (step 216).
[0051]
In wafer manufacturing processes, processes that are prone to contamination are known to some extent through experience. As an example, it is known that a process that easily causes contamination is likely to occur in a process of temporarily storing a wafer between a polishing process and a cleaning process, for example. Therefore, based on the result obtained by the evaluation as described above, the defect due to the contamination is quickly grasped, fed back to a possible process, and the process is improved.
[0052]
By evaluating the number of LPDs detected as defects of 0.3 μm or more after SC-1 treatment and managing the wafer manufacturing process, it is possible to easily grasp the problem process and improve productivity. And quality improvement.
[0053]
【Example】
The present invention will be described more specifically with reference to the following examples. However, it is needless to say that these examples are shown by way of illustration and should not be construed in a limited manner.
[0054]
(Example 1)
A silicon wafer having a diameter of 300 mm was evaluated by the wafer evaluation method of the present invention. The wafer to be evaluated is, for example, a wafer that is mirror-polished by a wafer manufacturing process as shown in FIG. Specifically, after cutting with a wire saw, chamfering, lapping with loose abrasive grains of # 1500 or more, alkali etching with 50% NaOH, and in the polishing process, double-side polishing, single-side polishing, single-side polishing Three-stage polishing was performed to obtain a wafer having a mirror surface with high flatness, followed by washing to obtain a silicon mirror wafer having a diameter of 300 mm. In the wafer manufacturing process, as long as at least one main surface of the wafer is mirror-finished and a wafer with high flatness is obtained, the process is not particularly limited. Actually, wafers obtained by a plurality of production lines and production conditions are evaluated.
[0055]
A part of this mirror-polished wafer was extracted and first treated with ammonia-hydrogen peroxide solution (SC-1 solution). The concentration of the chemical solution of ammonia-hydrogen peroxide solution (SC-1 solution) is a solution prepared by adjusting 28% by weight ammonia water, 30% by weight hydrogen peroxide solution, and pure water at 10: 2: 100. This chemical solution was put in a water tank, adjusted at a solution temperature of 80 ° C., and the wafer was etched by immersing the wafer to be inspected in this chemical solution for 40 minutes.
[0056]
Next, the number of LPDs after SC-1 treatment was confirmed using a light scattering type particle counter. As an evaluation condition, a defect of 0.32 μm or more when a defect of 0.12 μm or more is evaluated in the DWN mode of SP-1 manufactured by KLA-Tencor (defect detected in an area expressed as AreaCount in this apparatus) Was evaluated by the number of LPD detected. The LPD number of defects of 0.3 μm or more after the treatment with ammonia-hydrogen peroxide solution (SC-1 solution) was evaluated.
[0057]
In order to identify defects, in order to identify the types of defects obtained by defects of 0.3 μm or more, each evaluation unit is specifically used by using another evaluation apparatus such as a laser microscope and an AFM of a confocal optical system. When the defects were observed closely, it was found that the defects obtained by this method were pit clusters.
[0058]
FIG. 5 shows the relationship between the number of pit clusters and the number of defects (LPD) of 0.3 μm or more after SC-1 treatment evaluated by the wafer evaluation method of the present invention. As can be seen from FIG. 5, there is a good correlation.
[0059]
Under this evaluation condition, approximately pit clusters (pieces / cm ² ) = 0.81 × {0.3 μm or more defects (pieces / cm ² )}-0.012 There was a correlation that can be expressed by the relational expression. Since this correlation formula varies depending on the processing conditions with the SC-1 solution, the inspection apparatus, the inspection conditions, etc., the processing conditions and the evaluation conditions are fixed in advance, and the correlation under the conditions is confirmed. It is preferable.
[0060]
It is known that such a defect corresponding to a pit cluster is a defect that is likely to occur due to contamination.
[0061]
Therefore, by using this evaluation method, it is possible to easily provide feedback to the manufacturing site as described above, such as revising the wafer quality assurance and the manufacturing conditions of the wafer processing.
[0062]
(Example 2)
An embodiment of a method for managing a wafer manufacturing process will be described. For example, it is known that a certain device process (post-process) has a problem when there are 20 or more pit clusters (on the surface of a silicon wafer having a diameter of 300 mm). In addition, this numerical value differs with a preferable numerical value by a post process. Therefore, the number of pit clusters is set as appropriate for each process.
[0063]
Basically, it is preferable that there is no pit cluster, but if it is managed with 20 or less (on the surface of a wafer having a diameter of 300 mm), it can be guaranteed as a problem-free wafer with the wafer of most specifications at present.
[0064]
In this example, two types of wafers (silicon wafers having a diameter of 300 mm) having different manufacturing processes were evaluated.
[0065]
As described above, the evaluation conditions were first treated with a chemical solution of ammonia-hydrogen peroxide solution (SC-1 solution). The treatment conditions were 28 wt% ammonia water, 30 wt% hydrogen peroxide water and pure water adjusted at 10: 2: 100, and the wafer was immersed in a water bath at a liquid temperature of 80 ° C. for 40 minutes. Etched. Next, it evaluated by the number of LPD detected as a 0.3 micrometer or more defect when the defect of 0.12 micrometer or more was evaluated in DWN mode of SP-1 made from KLA-Tencor.
[0066]
As a result of the evaluation, one of the wafers had 30 (0.042 / cm2) LPD numbers of Area Count after SC-1 treatment (LPD number of defects of 0.3 μm or more) obtained by the light scattering method. ² )Met. When the number of LPDs is converted into the amount of pit clusters, under the above processing conditions, as shown in Example 1, pit clusters (pieces / cm ² ) = 0.81 × {0.3 μm or more defects (pieces / cm ² )}-0.012 relational expression, there are about 16 pit clusters (0.022 / cm2). ² In the method for managing a wafer manufacturing process of the present invention, since the control value of pit clusters is 20 or less, this is judged as a non-defective product and is accepted.
[0067]
In the other wafer, the LPD number of Area Count after SC-1 treatment obtained by the light scattering method is 65 (0.092 / cm2). ² )Met. The number of LPDs is approximately 44 (0.062 / cm2) in terms of the amount of pit clusters. ² In the wafer manufacturing process management method of the present invention, this was judged as a defective product and rejected.
[0068]
In the method for managing a wafer manufacturing process of the present invention, the cause of the failure can be further investigated. Since this is a defect corresponding to a pit cluster, it was determined that the defect was caused by contamination, and was fed back to a process where contamination could occur.
[0069]
In the wafer of this example, as a result of checking a temporary storage place of a wafer called a pit tank between the polishing process and the cleaning process, it was found that there was a problem in this pit tank and a defect occurred. By improving the metal impurities in the pit tank, the occurrence of defects was reduced, and a wafer that was within the specifications could be manufactured by the subsequent wafer evaluation method of the present invention.
[0070]
The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and has the same function and effect can be used. Included in the technical scope
[0071]
For example, a defect of 0.3 μm or more is evaluated using a light scattering type particle counter, but this was adopted because the correlation with the pit cluster was very good in this embodiment, If there is a correlation with the cluster, it is not necessarily limited to 0.3 μm or more, and may be a defect of 0.25 μm or more, a defect of 0.5 μm or more, etc. depending on the processing conditions and measurement conditions with the SC-1 solution. . Evaluate defects larger than normally detected defects.
[0072]
As for the management method, the management value is set by the number of pit clusters in the above embodiment, but the number of defects obtained as a defect of 0.3 μm or more using a light scattering type particle counter from the beginning is used as the management value. May be set.
[0073]
【The invention's effect】
As described above, the wafer evaluation method of the present invention can easily evaluate wafer defects corresponding to pit clusters, and can accurately evaluate and manage contamination generated in the wafer processing step. Further, according to the method for managing a wafer manufacturing process of the present invention, it is possible to manage an abnormality that may occur in the wafer manufacturing process.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an example of a process sequence of a wafer evaluation method of the present invention.
FIG. 2 is a flowchart showing another example of the process order of the wafer evaluation method of the present invention.
FIG. 3 is a flowchart showing another example of the order of steps of the wafer evaluation method of the present invention, where (a) shows a procedure for creating a correlation equation, and (b) shows a procedure for calculating and evaluating the number of pit clusters.
FIG. 4 is a flowchart showing an example of the order of steps in a method for managing a wafer manufacturing process according to the present invention.
5 is a graph showing the correlation between the number of defects of 0.3 μm or more and the number of pit clusters in Example 1. FIG.
FIG. 6 is a partial sectional side view schematically illustrating a basic structure of a light scattering type particle counter.
7 is a view similar to FIG. 6, in which (a) is a cutaway view showing a measurement mechanism in a first detection mode, and (b) is a measurement mechanism in a second detection mode.
FIG. 8 is a schematic explanatory view showing a basic structure of a laser microscope using a confocal optical system.
FIG. 9 is a flowchart showing an example of a conventional wafer processing step.
[Explanation of symbols]
10: laser microscope using confocal optical system, 12: microscope main body, 14: laser light source, 16: beam splitter, 18: objective lens, 20: pinhole member, 20a: pinhole, 22: condenser lens, 24: light Detector: 30: Light scattering type particle counter, 32: Sample stage, 34: Reflector, 36: Light collector, 38: First detector, 40: Condenser lens, 42: Reflector, 44: Second detector B, laser beam, L: laser beam, W: wafer.

Claims (6)

A wafer evaluation method, wherein a wafer to be evaluated is immersed in an etching solution comprising ammonia-hydrogen peroxide solution for a long time, and thereafter defects corresponding to pit clusters are evaluated using a light scattering type particle counter. A wafer evaluation method, wherein a wafer to be evaluated is immersed in an etching solution comprising ammonia-hydrogen peroxide for a long time, and thereafter a defect of 0.3 μm or more is evaluated using a light scattering type particle counter. The number of pit clusters existing on the surface of a predetermined wafer, and the predetermined wafer is immersed in an etching solution made of ammonia-hydrogen peroxide for a long time, and then a defect of 0.3 μm or more using a light scattering type particle counter. A correlation equation with the number of defects evaluated as above is obtained in advance, the wafer to be evaluated is immersed in an etching solution having the same composition as the etching solution for a long time under the same conditions, and then 0.3 μm using a light scattering type particle counter. A wafer evaluation method characterized in that the number of defects evaluated as the above defects is obtained, and the number of pit clusters of the wafer to be evaluated is evaluated from the number of defects by using the correlation equation. The wafer evaluation method according to claim 1, wherein a defect caused by contamination is evaluated. The number of defects evaluated for defects of 0.3 μm or more using the light scattering type particle counter is 0.3 μm or more when the defects of 0.12 μm or more are evaluated in the DWN mode of SP1 manufactured by KLA-Tencor. 5. The wafer evaluation method according to claim 1, wherein the number of detected LPDs. The wafer is immersed in an etching solution composed of ammonia-hydrogen peroxide solution for a long time, and the contamination status of the wafer is controlled by the number of defects evaluated as a defect of 0.3 μm or more using a light scattering type particle counter. A method for managing the wafer manufacturing process.

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