JP2009049177A - Method for rapidly evaluating surface quality of semiconductor substrate in packing state - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for rapidly evaluating the surface quality of a semiconductor substrate in a packing state. <P>SOLUTION: The method packs a semiconductor substrate with a packing material at ambient temperature Tam, and (1) increases the temperature Tam up to high temperature Thi and keeps the high temperature Thi for a time period thi, (2) decreases the high temperature Thi down to low temperature Tlow and keeps the low temperature Tlow for a time period tlow, (3) increases the temperature Tlow up to the ambient temperature Tam and keeps the ambient temperature Tam for a time period tam, and then checks the semiconductor substrate for deterioration in the surface quality. Therefore, the method allows rapid evaluation for the degree of deterioration in the surface quality of the semiconductor substrate in a packing state, estimation of a prior-to-use storage time limit for the semiconductor substrate, evaluation for deterioration in the quality of a packing material, and identification of the deterioration factors. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  For the purpose of moving, transporting or storing a semiconductor substrate or glass substrate (hereinafter referred to as “semiconductor substrate” in this specification) outside a clean room while maintaining the surface quality of the semiconductor substrate, Cases, carriers, cassettes, and the like are used, and the cases, carriers, cassettes, and the like are packaged with appropriate packaging materials in order to avoid environmental influences.

  The semiconductor substrate is transported, moved, and stored in such a packaged state under various means (for example, land, sea, air route) and various environmental conditions (for example, temperature, humidity, pressure). In addition, the packaging material is first unwound after use for a certain period of storage, and the surface quality of the semiconductor substrate is inspected when used for implementation.

  Since the surface quality of semiconductor substrates is confirmed to be defect-free (no degradation) as a result of inspection, the surface quality degradation found during use is maintained for a certain period in the packaged state. As a result.

  However, such deterioration of surface quality is caused by various causes acting in a complex manner, so far the degree of deterioration of the surface quality of the semiconductor substrate in the packaged state has been evaluated directly and quickly, In addition, it has been extremely difficult to estimate the shelf life of the semiconductor substrate before use. Moreover, it has been extremely difficult to identify a deterioration factor of the surface quality of the semiconductor substrate in such a packaged state (see Non-Patent Documents 1 and 2).

Therefore, development of a method for quickly (and directly) evaluating the degree of deterioration of the surface quality of the semiconductor substrate in the packaged state is strongly desired.
Larry W. Shive, Richard Blank and Karen Lamb: “Investigating the Formation of Time-Dependent Haze on Stored Wafers”, Micro Magazine, (March, 2001). N. Muenter, B.M. O. Kolbesen, W.M. Storm, and T.M. Mueller: "Analysis of Time-Dependent Haze on Silicon Surfaces", Journal of The Electrochemical Society, 150 (3) G192-G197 (2003)

  The present invention is a new method for satisfying such a demand, and a method for quickly evaluating the surface quality of a semiconductor substrate in a packaged state, thereby estimating the shelf life before use of the semiconductor substrate, and further improving the quality of the packaging material. A method for evaluating degradation and identifying a degradation factor is provided.

  As a result of diligent research to solve such problems, the present inventor succeeded in finding a method for quantitatively identifying the direct cause of the deterioration of the surface quality of the semiconductor substrate in the packaged state, and completed the present invention.

That is, the present invention 1 is a method for quickly evaluating the degree of deterioration of the surface quality of a semiconductor substrate in a packaged state,
Package the semiconductor substrate with packaging material at room temperature Tam,
(1) The temperature is raised from the temperature Tam and maintained at the high temperature Thi for a time thi.
(2) The temperature is lowered and maintained at a low temperature Tlow for a time tlow,
(3) After raising the temperature and maintaining at the room temperature Tam for a time tam time,
It is characterized by inspecting deterioration of the surface quality of the semiconductor substrate.

  Further, the present invention 1 is characterized in that the inspection of the deterioration of the surface quality is a measurement of a haze value of a semiconductor substrate surface or a foreign matter adhesion amount.

In addition, the present invention 2 is a method for estimating a storage period before use of a semiconductor substrate,
Package the semiconductor substrate with packaging material at room temperature Tam,
(1) The temperature is raised from the temperature Tam and maintained at the high temperature Thi for a time thi.
(2) The temperature is lowered and maintained at a low temperature Tlow for a time tlow,
(3) After raising the temperature and maintaining at the room temperature Tam for a time tam time,
(4) The deterioration of the surface quality of the semiconductor substrate is inspected to determine the maintenance time thi until the deterioration of the surface quality at Thi,
(5) Based on the relational expression between Thi and thi, determine thi in any Thi,
(6) It is characterized in that the storage period before use of the semiconductor substrate is estimated.

  Further, the present invention 2 is characterized in that the relational expression (5) is obtained by plotting the reciprocal of Thi on the horizontal axis and the logarithm of the maintenance time thi until deterioration on the vertical axis to obtain a linear relational expression.

Further, the present invention 3 is a method for identifying a quality deterioration factor of a semiconductor substrate surface caused by a packaging material,
Package the semiconductor substrate with packaging material at room temperature Tam,
(I) The temperature is raised from the temperature Tam and maintained at the high temperature Thi for a time thi,
(Ii) The temperature is lowered and maintained at the low temperature Tlow for a time tlow,
(Iii) After heating and maintaining at room temperature Tam for a time tam time,
(Iv) Inspecting the deterioration of the surface quality of the semiconductor substrate to determine the maintenance time thi until the deterioration of the surface quality at Thi,
(V) The relational expression between Thi and thi is plotted with the reciprocal of Thi on the horizontal axis and the logarithm of the maintenance time thi until deterioration on the vertical axis to determine the slope of the straight line as a linear relational expression,
Packaging materials
(Vi) After raising the temperature from the temperature Tam and maintaining the time thi at the high temperature Thi,
(Vii) determining the degassing amount MGa of each degassing component Ga of the packaging material;
(Viii) plotting the reciprocal of Thi on the horizontal axis and the logarithm of each MGa on the vertical axis, and determining the slope of each decomponent straight line as a linear relational expression;
(Ix) Compare the slope obtained in (v) with the slope of each component obtained in (viii),
The degassing component of the packaging material which is a deterioration factor of the surface quality of a semiconductor substrate is identified.

  By the method of the present invention, quickly assessing the degree of deterioration of the surface quality of the semiconductor substrate in the packaged state, estimating the shelf life before use of the semiconductor substrate, evaluating the deterioration of the quality of the packaging material, and It becomes possible to identify the deterioration factor.

Substrate There is no particular limitation on the material of the semiconductor substrate whose surface quality can be evaluated by the present invention, and various known metal and non-metal semiconductor substrates are included. In particular, examples of the metal substrate include silicon, silicon carbide, gallium arsenide compound semiconductor substrate, and gallium nitride compound semiconductor substrate. In particular, the present invention is preferably applicable to a silicon substrate. The non-metallic material substrate is preferably applicable to a silicon dioxide glass substrate.

  There is no particular limitation on the shape of the semiconductor substrate that can be evaluated for deterioration in surface quality according to the present invention, and various shapes that are usually used are included. Specific examples include a circular shape, an elliptical shape, a plate shape, and a rod shape, and are particularly applicable to a circular substrate. The size is not particularly limited, and various sizes that are usually used are included. For example, in the case of a circular shape, it can be preferably applied to a substrate having a diameter of 100 mm to 300 mm.

Packaging material, packaging state Packaging material as used in the present invention means not only a semiconductor substrate case, carrier, cassette, etc., but also a material for packaging a semiconductor substrate itself, and a semiconductor substrate case containing a semiconductor substrate, It means a material for packaging carriers, cassettes and the like. Specific examples of the case, carrier, cassette and the like for the semiconductor substrate include a case, carrier, cassette and the like for a semiconductor substrate made of a resin material, a metal material, or a composite material thereof.

  Here, there are no particular limitations on the shape and size of the case, carrier, and cassette, and the present invention can be applied to a case, carrier, cassette, and the like for a semiconductor substrate of a generally known size and shape.

  Resin materials are not particularly limited and are generally known materials such as polyolefin resins, polyester resins, polyamide resins, polyether resins, polycarbonate resins, polypropylene resins, polyethylene resins, PBT resins, poly resins. Ether ether ketone resin is raised. These resins include those containing various additives for adding various functions. Examples of the additive include a plasticizer, an antioxidant, a flame retardant, an ultraviolet absorber, an antistatic agent, and a release agent.

  Furthermore, there are no particular limitations on the metal material, and examples thereof include stainless steel, aluminum, and titanium, which are commonly known materials.

  The material for packaging the semiconductor substrate itself means a packaging material that directly touches the surface of the semiconductor substrate, and specifically means a pressing member used to hold the position of the semiconductor substrate in the case, carrier, or cassette. To do. Specific examples include generally known resin materials, such as polyolefin resins, polyester resins, polyamide resins, polyether resins, polycarbonate resins, polypropylene resins, polyethylene resins, PBT resins, polyether ethers. It is a ketone resin. These resins include those containing various additives for adding various functions. Examples of the additive include a plasticizer, an antioxidant, a flame retardant, an ultraviolet absorber, an antistatic agent, and a release agent.

  In the present invention, the packaging state means that the semiconductor substrate is held using a pressing member to hold the position of the semiconductor substrate in the case, carrier, and cassette, and the entire case and the like are packaged with the packaging material. Means (hereinafter “external packaging material”). Here, the external packaging material is not particularly limited, and usually includes known materials and shapes. Examples of such materials include polyester resins, polyethylene resins, nylon resins, PET resins, and silica deposited films. These resins include those containing various additives for adding various functions. Examples of the additive include a plasticizer, an antioxidant, a flame retardant, an ultraviolet absorber, an antistatic agent, and a slip agent. Examples of the shape include a film shape and a bag shape. There are no particular restrictions on the method of packaging with external packaging materials, which are generally known packaging methods, regardless of whether automatic packaging or manual packaging, the semiconductor substrate held in the case etc. is directly exposed to the external environment and contaminated. Any method that does not work.

  In the present invention, the surface quality of the semiconductor substrate is not particularly limited, and means a quality item to be satisfied with respect to the surface state of the semiconductor substrate, which is defined in various known qualitative and quantitative methods. These quality items are items that should be inspected and cleared before packaging the semiconductor substrate. For example, generation of fogging on the surface, adhesion of particles, adhesion of organic gas, adhesion of inorganic ions, adhesion of metal components can be mentioned. In the method of the present invention, the generation of haze and particle adhesion generated on the surface of the semiconductor substrate are particularly mentioned. If these qualities show values that are unacceptable compared to before the semiconductor substrate is packaged, the quality of the surface is considered to have deteriorated.

  In the present invention, the method for evaluating the degree of deterioration is not particularly limited, and various measurement methods suitable for the surface quality item to be evaluated are used, and the degree of deterioration is evaluated by quantitative measurement when necessary. Is possible. Specifically, examples of the evaluation method for occurrence of fogging on the surface of the semiconductor substrate include visual confirmation and an automatic measurement method using a surface foreign matter inspection apparatus. In the present invention, the visual method is preferably applicable qualitatively, and when a quantitative evaluation is required, a surface foreign matter measuring device and a measuring method based on the optical measurement principle can be applied. Moreover, about the evaluation of the particle adhesion which adheres to the surface, the visual measurement and the automatic measuring method by a surface foreign material inspection apparatus are mentioned. In the present invention, a visual method is preferably applicable for confirmation of particles having a large particle diameter of 0.3 μm or more, and when a quantitative evaluation is necessary, a measuring device based on an optical measurement principle, and All other evaluation methods to which the measurement method can be applied are listed.

(Method of quickly evaluating the degree of deterioration of the surface quality of the semiconductor substrate in the packaged state)
The method for quickly evaluating the degree of deterioration of the surface quality of the semiconductor substrate in the packaging state of the present invention is based on a specific packaging material after confirming that the surface quality of the semiconductor substrate satisfies the requirements after manufacturing the semiconductor substrate. When packaged and presupposed to be held in a predetermined storage state (especially storage temperature) for a predetermined period, the degree of deterioration of the surface quality of the semiconductor substrate is awaited for the passage of the period, and In this method, the package is opened, the semiconductor substrate is directly taken out, and the degree of surface degradation is not measured, and the evaluation is quickly performed at an earlier time (for example, before shipment).

That is, according to the method of the present invention, after confirming that there is no deterioration of the surface quality, the semiconductor substrate is packaged with a packaging material at room temperature Tam,
(1) The temperature is raised from the temperature Tam and maintained at the high temperature Thi for a time thi.
(2) The temperature is lowered and maintained at a low temperature Tlow for a time tlow,
(3) After raising the temperature and maintaining at the room temperature Tam for a time tam time,
Each step is for inspecting the deterioration of the surface quality of the semiconductor substrate.

  Here, the inspection of the deterioration of the surface quality is, for example, measurement of a haze value of the semiconductor substrate surface or a foreign matter adhesion amount.

  The temperature (Tam) at the time of packaging is usually the temperature in the factory of the packaging process, and is set and maintained in the range of 20 to 25 ° C.

  (1) to (3) are processes assuming a temperature change and a period that the semiconductor substrate in a packaged state will receive during transfer and transportation and storage. Therefore, in the present invention, only the temperature and time are defined, but the present invention is not limited to this, and includes a step of changing the humidity and pressure if necessary.

  (1) is not particularly limited as long as it is from the packaging temperature to the maximum temperature (Thi) that the semiconductor substrate in the packaging state may receive, that is, the temperature resistance of the packaging material. Specifically, it may be in the range of 30 to 100 ° C. In the present invention, as Thi, it is preferable that the temperature is about 5 ° C. or higher and about 100 ° C. or lower than the packaging temperature (Tam). When the temperature is lower than this range, the time for evaluation becomes longer. When the temperature is higher than this range, the accuracy of evaluation may not be sufficient. Further, the maintenance time is not particularly limited, and may be in a range sandwiching the time until deterioration occurs at the temperature Thi. Usually several days to a year. Such a high temperature condition activates a factor that degrades the surface of the semiconductor substrate and accelerates the degradation phenomenon.

  (2) is not particularly limited as long as it is from the packaging temperature to the lowest temperature (Tlow) that the semiconductor substrate in the packaging state may receive, that is, the cold resistance temperature of the packaging material. Specifically, it may be in the range of −60 to 10 ° C. In the present invention, Tlow is preferably -40 to -20 ° C, particularly about -30 ° C. In this temperature range, the packaged internal water vapor is almost completely condensed. Further, the maintenance time is not particularly limited, and may be in a range sandwiching the time until deterioration due to condensed water occurs at the temperature Tlow. Usually several days to a year. The deterioration phenomenon occurs due to water (or other volatile components) aggregated on the surface of the semiconductor substrate due to such a low temperature state.

  The time tam (3) is a time sufficient to return the temperature to Tam in order to evaluate the deterioration of the surface of the semiconductor substrate caused by the processes (1) to (2). Usually, it may be 1 hour to 4 hours. After the elapse of this time, the packaging material is destroyed, the semiconductor substrate is taken out, and the deterioration of the surface quality is evaluated.

  In the method of the present invention, the above steps (1) to (3) are performed not only once but also repeatedly at the same temperature and time in order to perform the degree of deterioration more accurately and more quickly. A method of changing the temperature and time and repeating once or a plurality of times is included.

(Method of estimating the shelf life of semiconductor substrates before use)
The method for estimating the pre-use shelf life of the semiconductor substrate according to the present invention is to confirm how much the surface quality of the semiconductor substrate satisfies the requirements after manufacturing the semiconductor substrate, and how much is in a state of being packaged with a specific packaging material. This is a method for estimating whether the semiconductor substrate can be used as it is without deterioration in the surface quality of the semiconductor substrate when it is held in a predetermined storage state (particularly storage temperature) and later opened.

  That is, this method is an application of the present invention described above, applies (1) to (3) of the method for rapidly evaluating the degree of deterioration of the surface quality of the semiconductor substrate in the packaged state, and further the semiconductor substrate. Determine the maintenance time thi until the surface quality degradation at Thi seen as a result of the inspection of the surface quality degradation, and create an empirical formula that expresses the relationship between Thi and thi. By determining thi in Th i, the shelf life before use of the semiconductor substrate is estimated.

  Here, the method of creating the relational expression is not limited in any way, and can be determined by various known statistical methods for deriving the correlation between Thi and thi. With this method, the relationship between these two values can be statistically expressed, and thi at any Thi can be estimated including a statistical error. Specifically, in the present invention, it is preferable to apply the Arrhenius method or the Eyring method.

  In the present invention, when the inverse of Thi is plotted on the horizontal axis and the logarithm of the maintenance time thi until deterioration is plotted on the vertical axis, a linear relational expression with good correlation is often obtained. In this case, the slope of the straight line obtained is similar to the activation energy derived from the Arrhenius plot obtained by the thermal acceleration test of the specific material itself, but its technical meaning is different. This is because the method of the present invention does not evaluate the deterioration of the semiconductor substrate itself.

  According to the method of the present invention, when a semiconductor substrate is shipped from a manufacturing factory in a packaged state, it is given in advance what kind of movement, transportation and storage conditions it will be exposed to (especially the exposure temperature and time). It is possible to quantitatively calculate whether or not the surface of the packaged semiconductor substrate has deteriorated for a certain period of time, and thus it is possible to estimate the storage period before using the semiconductor substrate. Such a result is extremely important for the purpose of estimating the shelf life before use of the semiconductor substrate.

(Method of identifying quality degradation factors on the surface of semiconductor substrates caused by packaging materials)
The present invention is a method for identifying a deterioration factor when the surface quality of a semiconductor substrate in a packaged state is deteriorated due to a packaging material. That is, the method for estimating the pre-storing period of the present invention The relational expression between Thi and thi obtained by the method for evaluating the deterioration of the quality of the packaging material, the reciprocal number of Thi and the maintenance time thi until deterioration is shown. The logarithm is plotted on the vertical axis, the slope of the line as a linear relational expression, and the packaging material is heated from the temperature Tam and maintained at the high temperature Thi for a time thi, and then the degassing amount of the degassing component from the packaging material is determined. This method consists of comparing and verifying the slopes of the straight lines obtained by measurement.

  Here, the degassed component from the packaging material is unique to the packaging material, and there is no particular limitation on the identification method and quantitative method of the component, and conventionally known gas component analyzers and methods can be preferably used. Specific examples include a gas chromatograph device, a mass spectrometer, and an analyzer that combines them. Based on the result obtained by such measurement, the degassing component / degassing amount depending on the temperature Thi of each component is determined.

  As a well-known method, when the inverse of Thi is plotted on the horizontal axis and the logarithm of the release amount of each degassed component is plotted on the vertical axis, a linear relational expression with good correlation is often obtained. The slope of the straight line obtained in this case is known as the Arrhenius plot of volatilization / diffusion of each degassed component, and the technical meaning of the obtained activation energy value is well understood (Oki, Osawa, Tanaka, Edited by Chihara: Dictionary of Chemistry, “Arrhenius Formula”, Tokyo Kagaku Doujin (1989), by GM BARROW, written by Ryoichi Fujishiro: Physical Chemistry (below), 4th edition, pages 664-647, Tokyo Chemistry Doujin, PW ATKINS, Hideaki Chihara and Nobuo Nakamura: Physical Chemistry (bottom) 2nd edition, p. 1056, Tokyo Chemical Doujin).

  Therefore, the method of estimating the pre-storing time limit of the present invention, the relational expression between Thi and thi obtained by the method of evaluating the deterioration of the quality of the packaging material, the reciprocal of Thi on the horizontal axis, The logarithm is plotted on the vertical axis to compare the slope of the straight line as a linear relational expression with the slope of the straight line of each degassing component obtained by the method of evaluating deterioration of the quality of the packaging material. Can be determined as a factor that degrades the surface quality of the semiconductor substrate in the packaged state.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
(Invention 1: Method for quickly evaluating the degree of surface quality degradation of a semiconductor substrate in a packaged state)
First, a predetermined number of wafers having a diameter of 200 mm used for evaluation were collected, and the product wafer was cleaned under the same conditions as for cleaning before shipment, for example, the RCA cleaning method. After that, the number of wafer surface defects having a particle diameter of 100 nm or more is 100 nm or more, 120 nm or more, 160 nm or more, 200 nm or more, 280 nm or more, large-scale foreign matter (SurfScan-SP1-TBI manufactured by KLA-Tencor) It was measured separately for each grade (common name: area count). This is in order to understand the size at which quality degradation that appears on the wafer typically appears, and it is preferable to measure the particle size to the measurable limit as much as possible in that era. The number of defects measured after cleaning is an initial condition value before the start of the evaluation, and the number of increase / decrease from this value is recognized as an effect on the surface quality due to storage.

  Next, the wafer was set in a wafer storage container as an evaluation target material. As the first material to be evaluated, we used our original storage container and a storage container made by a major foreign manufacturer. Usually, the storage container has 25 grooves so that 25 wafers can be stored. In the evaluation, the case where 25 wafers were stored and the case where only 3 wafers of 1 groove (first groove), 13 grooves (center of the storage container) and 25 grooves (last groove) were stored were used in combination. Since the obtained results were not significantly different, a method of storing only three wafers in each storage container as described above was used for the convenience of the experiment.

  After storing the wafer, the lid of the container was closed, and the storage container was double-packed under normal pressure in the same manner as the product wafer. First, in order to eradicate particulate foreign substances from the external environment, the storage container is packed with a colorless and transparent gusset bag (common name: inner bag) mainly composed of polyethylene, and then water and inorganic ions from the external environment are continuously used. In order to eradicate the contamination of the wafer due to the above, it was wrapped in a gusset bag (common name: outer bag) in which an aluminum film and a polyethylene film were laminated. By this double packaging, the environment inside the storage container is completely isolated from the outside world. By the way, a desiccant mainly composed of zeolite may be installed between the inner bag and the outer bag to absorb the moisture present in the bag's environment. Whether or not it is installed depends on the product shipment. It should be the same as the packing form, and no desiccant was used in this evaluation. In this evaluation, the packaging conditions were normal pressure, but reduced pressure packaging may be used, and it is important that the packaging conditions be the same as the product shipment. In addition, the packaging bag used a special grade product made by Showa Denko Packaging Co., Ltd., and the influence of inorganic ions, metal ions and organic outgas generated from the packaging bag on this evaluation was eliminated as much as possible.

  From the wafer collection to the completion of packaging, as a matter of course, it was carried out in the same clean room as inspecting and packaging the product wafer, and the production environment inherent in the packaging bag was made equal between the product wafer and the evaluation wafer. Incidentally, the clean room used in this evaluation is always managed at a temperature of 23 ± 1 ° C. and a relative humidity of 40 ± 10%.

  After packaging is completed, take the storage container out of the clean room, leave it in the constant temperature bath IG-46H manufactured by Yamato Scientific (maximum temperature reached: 85 ° C, temperature control accuracy: ± 0.5 ° C), and close the temperature chamber door. It was. In addition, the thermostat was preheated to the temperature used for evaluation beforehand, and the temperature rising time of the thermostat was shortened as much as possible. As for the heating temperature in this thermostat, in Example 1, the main experimental temperature was 60 ° C., and the main heating time was 168 hours.

  Immediately after the heating in the thermostatic bath, the storage container was put into a Hitachi freezer RS-M30 (minimum temperature reached: -32 ° C, temperature control accuracy: ± 1 ° C). This freezer is sufficient to be a general-purpose storage of so-called ice candy in a candy store. The freezer is always set to -30 ° C and immediately cooled to a predetermined temperature after the storage container is put in. I was able to do it. In this evaluation, the cooling time was 12 hours, but this was 2 hours even if the temperature transition time from 80 ° C. to −30 ° C. when the storage container heated to 80 ° C. was immediately left in the freezer was excluded. Considered to be cooled. Of course, this cooling time is determined by the capacity of the freezer. In order to stabilize the evaluation result, it is preferable to keep the cooling temperature at a predetermined cooling temperature for at least two hours.

  After completion of cooling for a predetermined time, the storage container was taken out of the freezer and left on the spot for about 2 hours to raise the temperature of the storage container to near room temperature. Subsequently, the storage container was brought into the clean room, and after further accommodating the storage container to room temperature for 2 hours, the packaging bag was opened and the storage container was taken out. And the lid of the storage container is opened, the wafer is taken out, and the number of wafer surface defects having a particle diameter of 100 nm or more is 100 nm or more, 120 nm or more, 160 nm or more with a wafer surface foreign substance inspection apparatus SurfScan-SP1-TBI manufactured by KLA-Tencor. 200 nm or more, 280 nm or more, and remeasured for each grade of large-scale foreign matter (common name: area count). Note that the measurement conditions used for remeasurement need to be the same as the conditions under which the initial condition values were measured.

  Next, the initial condition value was compared with the remeasured value, and it was verified whether there was a difference in the number of surface defects measured. FIG. 1 shows the appearance of surface defects after evaluation obtained with our original storage container. In the figure, the outline of the wafer and the surface defects measured on the wafer are indicated by dots. The wafer before evaluation shown in FIG. 1A has few dots indicating the presence of surface defects in the wafer outline, but the wafer after application of this evaluation method shown in FIG. It can be seen that defects are concentrated and appear.

  On the other hand, the appearance state of surface defects after evaluation obtained in a storage container made by a major foreign manufacturer is shown in FIG. 2, but the wafer before evaluation shown in FIG. 2 (a) and the main evaluation shown in FIG. 2 (b). In the wafer after application of the method, it can be seen that there is no difference in the dots indicating the presence of surface defects in the outline of the wafer, that is, the surface defects are not increased at all.

  From the above, in this evaluation, it was possible to make the surface defect generated during wafer storage caused by the wafer storage container appear by the temperature acceleration method in a form depending on the storage container.

(Embodiment 2) (Invention 2: Method for Estimating Storage Period before Use of Semiconductor Substrate)
First, a predetermined number of wafers having a diameter of 200 mm used for evaluation were collected, and the product wafer was cleaned under the same conditions as for cleaning before shipment, for example, the RCA cleaning method. After that, the number of wafer surface defects having a particle diameter of 100 nm or more is 100 nm or more, 120 nm or more, 160 nm or more, 200 nm or more, 280 nm or more, large-scale foreign matter (SurfScan-SP1-TBI manufactured by KLA-Tencor) It was measured separately for each grade (common name: area count). This is in order to understand the size at which quality degradation that appears on the wafer typically appears, and it is preferable to measure the particle size to the measurable limit as much as possible in that era. The number of defects measured after cleaning is an initial condition value before the start of this evaluation, and the number of increase / decrease from this value is recognized as an effect on the surface quality due to storage.

  Next, the wafer was set in a wafer storage container as an evaluation target material. An original storage container made by our company was used as an evaluation target material. Usually, the storage container has 25 grooves so that 25 wafers can be stored. In the evaluation, the case where 25 wafers were stored and the case where only 3 wafers of 1 groove (first groove), 13 grooves (center of the storage container) and 25 grooves (last groove) were stored were used in combination. Since there was not much difference in the obtained results, a method of storing only three wafers as described above was used for the convenience of the experiment.

  After storing the wafer, the lid of the storage container was closed, and the storage container was double-packed under normal pressure in the same manner as the product wafer. First, in order to eradicate particulate foreign substances from the external environment, the storage container is packed with a colorless and transparent gusset bag (common name: inner bag) mainly composed of polyethylene, and then water and inorganic ions from the external environment are continuously used. In order to eradicate the contamination of the wafer due to the above, it was wrapped in a gusset bag (common name: outer bag) in which an aluminum film and a polyethylene film were laminated. By this double packaging, the environment inside the storage container is completely isolated from the outside world. By the way, a desiccant mainly composed of zeolite may be installed between the inner bag and the outer bag to absorb the moisture present in the bag's environment. Whether or not it is installed depends on the product shipment. It should be the same as the packing form, and no desiccant was used in this evaluation. In this evaluation, the packaging conditions were normal pressure, but reduced pressure packaging may be used, and it is important that the packaging conditions be the same as the product shipment. In addition, the packaging bag used a special grade product made by Showa Denko Packaging Co., Ltd., and the influence of inorganic ions, metal ions and organic outgas generated from the packaging bag on this evaluation was eliminated as much as possible.

  From the wafer collection to the completion of packaging, as a matter of course, it was carried out in the same clean room as inspecting and packaging the product wafer, and the production environment inherent in the packaging bag was made equal between the product wafer and the evaluation wafer. Incidentally, the clean room used in this evaluation is always managed at a temperature of 23 ± 1 ° C. and a relative humidity of 40 ± 10%.

  After packaging is completed, take the storage container out of the clean room, leave it in the constant temperature bath IG-46H manufactured by Yamato Scientific (maximum temperature reached: 85 ° C, temperature control accuracy: ± 0.5 ° C), and close the temperature chamber door. It was. In addition, the thermostat was preheated to the temperature used for evaluation, and the temperature rising time of the thermostat was shortened as much as possible. The heating temperature in this constant temperature bath is set to 80 ° C., and the main experimental temperatures are 40 ° C., 60 ° C., and 80 ° C. However, the evaluation time is long at 40 ° C. for the purpose of verifying the validity of this evaluation. When it became too much, evaluation at 30 ° C. and 50 ° C. was additionally performed. The main heating time was 12 hours to 744 hours, and evaluation was started from the condition of heating at 60 ° C. for 12 hours.

  Immediately after the heating in the thermostatic bath, the storage container was put into a Hitachi freezer RS-M30 (minimum temperature reached: -32 ° C, temperature control accuracy: ± 1 ° C). This freezer is sufficient to be a general-purpose storage of so-called ice candy in a candy store. The freezer is always set to -30 ° C and immediately cooled to a predetermined temperature after the storage container is put in. I was able to do it. In this evaluation, the cooling time was 12 hours, but this was 2 hours even if the temperature transition time from 80 ° C. to −30 ° C. when the storage container heated to 80 ° C. was immediately left in the freezer was excluded. Considered to be cooled. Of course, this cooling time is determined by the capacity of the freezer. In order to stabilize the evaluation result, it is preferable to keep the cooling temperature at a predetermined cooling temperature for at least two hours.

  After completion of cooling for a predetermined time, the storage container was taken out of the freezer and left on the spot for about 2 hours to raise the temperature of the storage container to near room temperature. Subsequently, the storage container was brought into the clean room, and after further accommodating the storage container to room temperature for 2 hours, the packaging bag was opened and the storage container was taken out. And the lid of the storage container is opened, the wafer is taken out, and the number of wafer surface defects having a particle diameter of 100 nm or more is 100 nm or more, 120 nm or more, 160 nm or more with a wafer surface foreign substance inspection apparatus SurfScan-SP1-TBI manufactured by KLA-Tencor. 200 nm or more, 280 nm or more, and remeasured for each grade of large-scale foreign matter (common name: area count). Note that the measurement conditions at the time of remeasurement need to be the same as the conditions under which the initial condition values were measured.

  Next, the initial condition value was compared with the remeasured value, and it was verified whether there was a difference in the number of surface defects measured. Since no obvious increase in surface defects was observed under the heating condition of 60 ° C. for 12 hours, in the next evaluation, the heating time at 60 ° C. was extended to 24 hours, 48 hours and 72 hours, and a clear difference appeared. Extended the time. A clear increase in surface defects in this evaluation appeared in the area count, which is indicated by dots in FIG. The area count increased either when a new area count appeared or when the initial condition value changed a surface defect with a small particle size to an area count. When the area count was increased by one, it was determined that the storage limit date before using the wafer was reached. Since the storage container and the wafer are not reused after one heating / cooling cycle is applied, several (4 to 8) storage containers can be left at a time to shorten the overall evaluation period. It is desirable to use a constant-temperature bath having a capacity and to take out one storage container from the thermostat after a predetermined heating time. As the number of evaluations actually increased, we did so to make the evaluation more efficient.

  At 60 ° C., a clear increase in surface defects including an area count could not be confirmed until 96 hours, and the area count clearly increased after 120 hours. Therefore, it was found that the storage limit date before use of the wafer at 60 ° C. was between 96 hours (4 days) and 120 hours (5 days). Therefore, the same procedure as described above was repeated except that the heating temperature of the storage container was raised to 80 ° C. Since the increase in surface defects was not clearly observed when the heating time was 12 hours, the heating time was extended to 18 hours, 24 hours, 36 hours, 48 hours, 72 hours, 168 hours. As a result, from 24 hours to 48 hours, one of the three sheets increased the area count by one to two. However, after 72 hours or more, the three wafers clearly increased the area count. Therefore, it was found that the storage limit date before wafer use at 80 ° C. was 48 hours (2 days) to 72 hours (3 days). Next, the above-described evaluation method was repeated at a heating temperature of 40 ° C. As a result, the area count did not increase during the heating time of 336 hours and 504 hours, but the area count increased clearly when the heating time was 744 hours. Therefore, it was found that the storage limit date before using the wafer at 40 ° C. is 504 hours (21 days) to 744 hours (31 days).

  From the above-mentioned results, it can be seen that the storage limit date before use of the wafer is accelerated as the heating temperature decreases. From this, it is clear that the estimated storage limit date before use of the wafer is several months or more at 20 to 30 ° C. which is the actual storage temperature of the wafer. In order to estimate the storage limit date before wafer use at the actual storage temperature of the wafer from the storage limit dates before wafer use at 80 ° C., 60 ° C., and 40 ° C., the storage limit date before wafer use at each heating temperature described above is used as the heating temperature. Was plotted against the inverse of the absolute temperature. The results are shown in FIG.

  In FIG. 3, the horizontal axis indicates a value obtained by multiplying the reciprocal of the heating temperature converted into the absolute temperature by 1000, and the vertical axis indicates the storage limit time before using the wafer. The plots in the figure indicate that the circle mark indicates that the area count does not increase, the triangle mark indicates that the area count has increased for some wafers, and the x mark indicates that the area count has increased for three wafers. The figure also shows data on the storage limit date before using the wafer at the actual storage temperature of the wafer (20 ° C.), in which the wafers stored in our shipping warehouse were inspected. The range marked with ○ is the storage date that guarantees the quality of the wafer, and the range marked with X is the storage date that cannot guarantee the quality of the wafer. It turns out that it becomes a straight line when connected by temperature. Therefore, by extending the straight line to the low temperature side (in the direction closer to the wafer storage temperature), it was possible to estimate the storage limit date before using the wafer at the actual wafer storage temperature. The estimation results were about 2 months at 30 ° C, about 4 months at 25 ° C, and about 7 months at 20 ° C.

  In Fig. 1, it can be seen that the result of extending this straight line to the low temperature side is in good agreement with the data on the storage limit date before using the wafer at the actual storage temperature of the wafer that was inspected for the wafer stored in our shipping warehouse. The validity of this evaluation method was demonstrated. Note that the slope of the extrapolated line in FIG. 3, that is, the activation energy, was calculated to be approximately 1.05 ± 0.05 eV.

Example 3 (Invention 3: Method for Identifying Degradation Factors Caused by Packaging Materials)
The wafer storage limit date in our original storage container is as shown in Example 2.

  After that, three components of our original storage container were collected for each type. The sample was in the shape of a square plate after molding, the size was unified to 75 mm × 125 mm × 2 mm, and all samples were stored in a refrigerator until the start of analysis. As a pretreatment, put one sample in a 4 liter glass container and seal it, and then heat each sample for 2 hours at 40 ° C., 60 ° C. or 80 ° C. to fill the glass container with the outgas from the sample. (Each sample heated only under one temperature condition. Therefore, three identical samples were required). Thereafter, the air in the container was immediately concentrated and sampled in a collecting agent (TENAX-TA: 100 mg). Sampling was performed in a clean booth, and the sampling amount was 8 liters, which is twice the volume of the glass container. The outgas component was collected from the sample by heating the glass container from room temperature to 400 ° C. at a rate of temperature increase of 25 ° C./min while flowing helium gas, and holding at 400 ° C. for 15 minutes for a total of 30 minutes.

  Next, the generated organic outgas was analyzed using GC-MS in which a gas chromatography device GC6890 manufactured by GL Science and a mass spectrometer MSD5973N manufactured by Agilent were combined with a collector (TENAX-TA: 100 mg), The type of each outgas generated per gram of the structural member and the amount of outgas generated for each heating temperature were investigated. The conditions for thermally desorbing the gas collected from the collection agent (TENAX-TA: 100 mg) were 280 ° C. × 15 minutes. The temperature conditions for gas analysis with the GC-MS apparatus were as follows: first, waiting at 40 ° C. for 8 minutes, then increasing the temperature to 300 ° C. at a rate of 10 ° C./minute, and holding at 300 ° C. for 10 minutes. That is, a total of 44 minutes of analysis was performed. This analysis was performed on each component sample.

As a result of the analysis, there were _six main outgas types: C ₁₂ H ₂₄ , C ₁₂ H ₂₆ , decanal (Decanal), dibutyl phthalate (BHT), C ₁₂ H ₂₅ SH, and C ₁₆ H ₃₄ . The weight of the outgas amount at each heating temperature in terms of carbon atom weight was plotted against the reciprocal of the heating temperature in terms of absolute temperature with respect to these six types of outgas amount and total organic outgas amount. This is shown in FIG.

In FIG. 4, the horizontal axis indicates a value obtained by multiplying the reciprocal of the heating temperature converted into the absolute temperature by 1000, and the vertical axis indicates the outgas generation amount. Plots in the figure are: C ₁₂ H ₂₄ , ◯ marks C ₁₂ H ₂₆ , □ marks decanal, ◇ marks dibutyl phthalate (BHT), + marks C ₁₂ H ₂₅ SH, × The symbol indicates C ₁₆ H ₃₄ , and the symbol * indicates the total organic outgas amount. In the figure, a straight line indicating an activation energy of 1.05 ± 0.05 eV is indicated by a dotted line. Among the six types of plots described above, the amount of outgas monotonously increases as the heating temperature rises, and the activation energy is close to 1.05 ± 0.05 eV because C ₁₂ H ₂₄ , C ₁₂ H ₂₆ , There were only three types, Decalal. It was also found that the activation energy was significantly different from the total organic outgas amount. From this, it was estimated that any or all of these three types of substances are suspicious as wafer surface defect inducers that regulate the wafer storage deadline. Therefore, in our original storage container, we prototyped an improved storage container that reduced the above three suspicious substances, and performed outgas evaluation similar to the above on the components of the improved storage container. The wafer storage limit due date was evaluated.

FIG. 5 shows the result of outgas evaluation similar to that described above for the components of the improved storage container. In FIG. 5, the horizontal axis indicates a value obtained by multiplying the reciprocal of the heating temperature converted into the absolute temperature by 1000, and the vertical axis indicates the outgas generation amount. In the plots in the figure, ◯ indicates the C ₁₂ H ₂₄ in the conventional storage container, Δ indicates the C ₁₂ H ₂₆ in the conventional storage container, and □ indicates the decanal outgas amount in the conventional storage container. Further, the black triangle mark indicates the C ₁₂ H ₂₆ in the improved storage container, and the black square mark indicates the amount of decanal (Decanal) outgas in the improvement storage container. In the improved storage container, C ₁₂ H ₂₄ was not detected, and the outgas amount of both C ₁₂ H ₂₆ and Decanal was reduced. The activation energies of these two types of outgas were calculated to be 0.9 eV or less.

  On the other hand, FIG. 6 shows the heating temperature dependency of the wafer storage limit date obtained by applying the evaluation method described in Example 2 to the improved storage container. In FIG. 6, the horizontal axis represents a value obtained by multiplying the reciprocal of the heating temperature converted into an absolute temperature by 1000, and the vertical axis represents the storage limit time before using the wafer. The plots in the figure indicate that the circle mark indicates that the area count does not increase, the triangle mark indicates that the area count has increased for some wafers, and the x mark indicates that the area count has increased for three wafers. The figure also shows data on the storage limit date before using the wafer at the actual storage temperature of the wafer (20 ° C.), in which the wafers stored in our shipping warehouse were inspected. The range marked with ○ is the storage date that guarantees the quality of the wafer, and the range marked with X is the storage date that cannot guarantee the quality of the wafer. It was found that when connected by temperature, it was almost a straight line. Therefore, by extending the straight line to the low temperature side (in the direction closer to the wafer storage temperature), it was possible to estimate the storage limit date before using the wafer at the actual wafer storage temperature. The result of the estimation was 4 years or more at 30 ° C., and it was found that the result was significantly higher than 1 year or more, which is a standard for customer requirements.

The activation energy of the wafer storage limit time is 1.15 ± 0.05 eV, which is different from the activation energy of the wafer storage limit time in the conventional storage container, and C ₁₂ H ₂₆ detected in the improved storage container. And also the activation energy of Decanal. From the above results, the main suspicious substance that has constrained the wafer storage limit time in the conventional storage container is C ₁₂ H ₂₄ , and in the improved storage container excluding it, different activation energy can be obtained and the wafer storage limit date Was also able to improve significantly. This demonstrates the effectiveness of the method of identifying suspicious substances by comparing and verifying the outgas activation energy of the packaging member and other packaging members and the activation energy of the wafer storage limit date. It was done.

  As a result of investigating the wafer storage limit date for various packaging containers in order to verify the validity of the above-described evaluation method, this method is not only for wafer storage containers having a diameter of 200 mm, but also for 100 mm, 150 mm and 300 mm. It was proved to be effective for wafer storage containers. It was also shown that it is effective not only for shipping containers but also for temporary wafer storage containers in the wafer manufacturing process. As a fact found from these evaluations, 1.15 ± 0.05 eV can be obtained as the activation energy of the wafer storage limit date by properly selecting the determination condition of the occurrence of wafer surface defects. By using the wafer storage limit date at a single heating temperature higher than room temperature, it becomes possible to more easily know the wafer storage limit date at the actual wafer storage temperature.

In addition, C ₁₂ H _24, which is a suspicious substance indicated in this evaluation method, is not suitable for the purpose of wafer storage. Therefore, a storage case manufactured by a component member intentionally containing it is not used for wafer storage. It goes without saying that it doesn't happen.

  Note that the methods described in the above embodiments are not limited to storage containers but are also effective for evaluation of other packaging materials such as packaging bags.

  The present invention provides a method for quickly evaluating the surface quality of a semiconductor substrate in a packaged state of the semiconductor substrate, thereby estimating the shelf life before use of the semiconductor substrate, as well as evaluating the deterioration of the quality of the packaging material and identifying the deterioration factors Enable the method.

The appearance of surface defects that appeared after application of this evaluation method ((a): initial measurement result, (b): remeasurement result after application of this evaluation method). The appearance of surface defects that appeared after application of this evaluation method ((a): initial measurement result, (b): remeasurement result after application of this evaluation method). Results of plotting the storage limit date before wafer use at each heating temperature as the reciprocal of the absolute temperature of the heating temperature. The result of having plotted the various outgas amounts from the storage container structural member in each heating temperature by the reciprocal number of the absolute temperature of heating temperature. The result which plotted the various outgas amounts from the storage container structural member in each heating temperature in the improvement container by the reciprocal number of the absolute temperature of heating temperature. Results of plotting the storage limit date before wafer use at each heating temperature in the improved storage container as the reciprocal of the absolute temperature of the heating temperature.

Claims (5)

Package the semiconductor substrate with packaging material at room temperature Tam,
(1) The temperature is raised from the temperature Tam and maintained at the high temperature Thi for a time thi.
(2) The temperature is lowered and maintained at a low temperature Tlow for a time tlow,
(3) After raising the temperature and maintaining at the room temperature Tam for a time tam time,
A method for quickly evaluating the surface quality of a semiconductor substrate in a packaged state, wherein the deterioration of the surface quality of the semiconductor substrate is inspected.   The method according to claim 1, wherein the inspection of the deterioration of the surface quality is a measurement of a haze value of a semiconductor substrate surface or a foreign matter adhesion amount. Package the semiconductor substrate with packaging material at room temperature Tam,
(1) The temperature is raised from the temperature Tam and maintained at the high temperature Thi for a time thi.
(2) The temperature is lowered and maintained at a low temperature Tlow for a time tlow,
(3) After raising the temperature and maintaining at the room temperature Tam for a time tam time,
(4) The deterioration of the surface quality of the semiconductor substrate is inspected to determine the maintenance time thi until the deterioration of the surface quality at Thi,
(5) Based on the relational expression between Thi and thi, determine thi in any Thi,
(6) A method for estimating a storage period before use of a semiconductor substrate.   4. The method according to claim 3, wherein the relational expression (5) is obtained by plotting the reciprocal of Thi on the horizontal axis and the logarithm of the maintenance time thi until deterioration on the vertical axis to obtain a linear relational expression. . In the method of identifying the quality degradation factor of the semiconductor substrate surface caused by the packaging material,
Package the semiconductor substrate with packaging material at room temperature Tam,
(I) The temperature is raised from the temperature Tam and maintained at the high temperature Thi for a time thi,
(Ii) The temperature is lowered and maintained at the low temperature Tlow for a time tlow,
(Iii) After heating and maintaining at room temperature Tam for a time tam time,
(Iv) Inspecting the deterioration of the surface quality of the semiconductor substrate to determine the maintenance time thi until the deterioration of the surface quality at Thi,
(V) The relational expression between Thi and thi is plotted with the reciprocal of Thi on the horizontal axis and the logarithm of the maintenance time thi until deterioration on the vertical axis to determine the slope of the straight line as a linear relational expression,
Packaging materials
(Vi) After raising the temperature from the temperature Tam and maintaining the time thi at the high temperature Thi,
(Vii) determining the degassing amount MGa of each degassing component Ga of the packaging material;
(Viii) plotting the reciprocal of Thi on the horizontal axis and the logarithm of each MGa on the vertical axis, and determining the slope of each decomponent straight line as a linear relational expression;
(Ix) Compare the slope obtained in (v) with the slope of each component obtained in (viii),
A method for identifying a degassing component of a packaging material, which is a deterioration factor of a surface quality of a semiconductor substrate.