Cooling method and system for semiconductor wafer

Abstract

The present invention relates to the field of semiconductor manufacturing, and more specifically, to a cooling method and system for semiconductor wafers, the method comprising: obtaining the mass, initial temperature and target temperature of the semiconductor wafer to be cooled, obtaining the heat released by the wafer during the cooling process; counting the time of each cooling process, calculating the power of the current semiconductor cooling process to be cooled; constructing an objective function of the cooling gas temperature and the cooling gas release rate and resource consumption in the semiconductor wafer cooling process, based on the accuracy of the cooling process and cooling gases with different preset temperatures, selecting the control parameters corresponding to the objective function that meet the relationship between power, density of the cooling gas, specific heat capacity and the heat released by the semiconductor wafer during the cooling process, and then using them as control parameters of the cooling process to perform semiconductor wafer cooling control. The present invention satisfies process requirements with different accuracy requirements and improves resource utilization efficiency by precisely controlling cooling parameters.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and more particularly to a method and system for cooling a semiconductor wafer. Background Art

[0002] In the semiconductor manufacturing process, wafer temperature control is crucial to production efficiency and product quality. As a common wafer temperature control technology, the gas back cooling system plays an important role in ensuring the stability of wafer temperature. In the semiconductor wafer manufacturing process, the gas back cooling system consumes a lot of energy to maintain the low temperature of the back of the wafer, especially in the process steps with high power density and high heat load. The temperature control in the semiconductor manufacturing process requires extremely high precision, and any slight temperature change may have a significant impact on product quality.

[0003] The existing Chinese patent application document with publication number CN110854010A discloses a method, device and semiconductor processing equipment for cooling wafers. It includes: step S110, real-time acquisition of the process time difference between the current wafer that has completed the process and is to be cooled and the process wafer that is undergoing the process; step S120, based on the preset functional relationship between the process time difference and the cooling gas flow value, the real-time cooling gas flow value of the current wafer is obtained through the real-time process time difference; step S130, according to the real-time cooling gas flow value, the current wafer is provided with cooling gas of the corresponding cooling gas flow value, so that when the process wafer completes the process or before the process wafer completes the process, the current wafer is just cooled to the preset temperature, and the cooling gas is stopped from being provided to the current wafer; when the process wafer is transformed into the current wafer that has completed the process and is to be cooled, the next wafer that is undergoing the process is used as the process wafer, and steps S110 to S130 are repeated.

[0004] In the above scheme, the wafer is cooled after the etching process to reach the target temperature before the next process. Since the gas back cooling system involves multiple components and parameters, such as gas flow, gas temperature, etc., which all need to be precisely controlled and adjusted, the current gas back cooling system faces high energy consumption and high temperature control accuracy requirements in the semiconductor manufacturing process. The cooling temperature of the wafer is different for different processes, which cannot be applied to multiple process production links, resulting in excessive consumption of resources. Summary of the invention

[0005] In order to solve the problem that the cooling temperatures for wafers under different processes are different and cannot be applied to multiple process production links, resulting in excessive consumption of resources, the present invention provides solutions in the following aspects.

[0006] In a first aspect, a semiconductor wafer cooling method includes: obtaining the mass, initial temperature and target temperature of the semiconductor wafer to be cooled, so as to obtain the heat that needs to be released by the semiconductor wafer to be cooled during the cooling process; counting the time of each cooling process of the semiconductor wafer to be cooled, and calculating the power of the current semiconductor cooling process to be cooled; constructing an objective function of the cooling gas temperature and the cooling gas release rate and resource consumption in the semiconductor wafer cooling process, and selecting the control parameter corresponding to the objective function in accordance with the power, the density of the cooling gas, the specific heat capacity and the heat released by the semiconductor wafer during the cooling process based on the accuracy of the cooling process and the cooling gas at different preset temperatures. The control parameter is used as the control parameter of the cooling process to perform semiconductor wafer cooling control; wherein the objective function satisfies the following relationship: , , where represents the total resources consumed by the cooling process, Indicates the cooling gas release rate, Indicates the cooling process time, Indicates the preset temperature per unit volume The resources required for cooling gas, Indicates the cooling gas release rate The power of the gas equipment during transportation, Indicates the maximum speed of cooling gas release.

[0007] The effect is: by constructing the objective function to obtain the minimum value of the objective function, the optimal cooling gas release rate and temperature can be found to minimize the total resource consumption of the cooling process; by considering the cost of cooling gas with different preset temperatures, a cost-benefit analysis can be performed to select the most suitable cooling gas to maximize cost-effectiveness; by real-time monitoring and adjustment of cooling process parameters, it can dynamically adapt to different wafer characteristics and process requirements to improve production flexibility and adaptability; by optimizing the cooling process, the waiting time and unnecessary energy consumption of the wafer during the cooling process can be reduced, thereby improving overall production efficiency; by precisely controlling the cooling process, the thermal stress and damage of the wafer can be reduced, and the quality and performance of the final product can be improved.

[0008] Preferably, the step of obtaining the heat that needs to be released by the semiconductor wafer to be cooled during the cooling process includes:

[0009] Calculating the difference between the initial temperature and the target temperature to obtain a cooling temperature range;

[0010] Calculating the product of the mass of the semiconductor wafer to be cooled and the specific heat capacity of the semiconductor wafer to be cooled to obtain a heat change;

[0011] The product of the cooling temperature range and the heat change is used as the heat that needs to be released by the semiconductor wafer to be cooled during the cooling process.

[0012] The effect is that by determining the specific temperature range in which the wafer needs to be cooled and the change in heat that the wafer needs to absorb or release under specific temperature changes, the efficiency and performance of the cooling system are optimized, while being suitable for cooling wafers of different materials and different process requirements.

[0013] Preferably, the cooling power of the current semiconductor cooling process to be cooled includes:

[0014] The ratio of the heat released by the semiconductor wafer during the cooling process to the cooling process is used as the cooling power of the semiconductor wafer to be cooled.

[0015] Preferably, the cooling power of the current semiconductor cooling process to be cooled also includes:

[0016] The temperature difference of the cooling gas before and after the cooling of the semiconductor wafer is calculated, and the product of the temperature difference of the cooling gas and the release rate, density and specific heat capacity of the cooling gas is taken as the cooling power of the semiconductor wafer cooling process, that is, the heat taken away from the wafer by the cooling gas per unit time.

[0017] The effect is: by calculating the temperature difference of the cooling gas and combining it with the gas release rate, density and specific heat capacity, the cooling efficiency can be optimized to ensure that the wafer is effectively cooled per unit time. While ensuring effective cooling, the best adjustment parameters are obtained to reduce economic losses.

[0018] Preferably, the accuracy of the cooling process includes:

[0019] The variance of the difference between the temperature after historical cooling and the set temperature is calculated, and the variance is normalized as the accuracy of the cooling process. In response to the accuracy of the cooling process being less than a preset accuracy threshold, the cooling process is of high accuracy, otherwise it is of low accuracy.

[0020] The effect is that by calculating the variance of the difference between the historical cooling temperature and the set temperature and normalizing it, the smaller the variance, the closer the actual cooling temperature is to the set temperature, that is, the higher the accuracy. Conversely, the larger the variance, the more dispersed the temperature distribution is, and the lower the accuracy is.

[0021] Preferably, the semiconductor wafer cooling control includes:

[0022] When the cooling process requires high precision, the minimum total resource consumption of the cooling process is selected. Corresponding cooling gas release rate and the temperature of the cooling gas , as the cooling gas release rate and the cooling gas temperature that need to be regulated;

[0023] In response to the requirement of the cooling process being low precision, the power range corresponding to the low precision of the cooling process is obtained, and the total resources consumed by the cooling process Sorting is performed, and the total resources that meet the power range are selected Minimum corresponding cooling gas release rate and the temperature of the cooling gas , as the cooling gas release rate and the cooling gas temperature that need to be regulated.

[0024] The effect is: by precisely controlling the release rate and temperature of the cooling gas, the wafer cooling process is optimized and cooled at different precisions, which improves production efficiency and enhances process flexibility and adaptability.

[0025] Preferably, the preset temperature per unit volume The resources required to produce cooling gas include:

[0026] The ratio of all costs involved in producing or obtaining cooling gas at a specific temperature to the total volume of cooling gas produced or obtained in the same period of time is used as the preset temperature. The cooling gas requires resources.

[0027] In a second aspect, a semiconductor wafer cooling system includes: a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the semiconductor wafer cooling method described above is implemented.

[0028] The present invention has the following effects:

[0029] 1. The present invention adopts a dynamic adjustment strategy for the cooling process so as to adjust the parameters of the cooling gas according to real-time feedback during the production process to adapt to the characteristics and process requirements of different wafers while reducing energy consumption and improving production efficiency.

[0030] 2. The present invention obtains the mass and initial temperature of the semiconductor wafer to be cooled and the target temperature to be cooled, calculates the heat that needs to be released by the semiconductor wafer to be cooled during the cooling process, obtains the cooling time of the semiconductor wafer to be cooled, and calculates the power of the semiconductor wafer cooling process in combination with the heat that needs to be released during the cooling process, constructs an objective function, and finds the cooling gas temperature and release rate that minimize the total resource consumption of the wafer cooling, thereby improving the efficiency of the wafer cooling process and saving resource consumption of the wafer cooling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0032] Figure 1 It is a method flow chart of steps S1 to S3 in the semiconductor wafer cooling method according to an embodiment of the present invention.

[0033] Figure 2 It is a structural block diagram of a cooling system for a semiconductor wafer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0035] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] Reference Figure 1 The semiconductor wafer cooling method includes steps S1 to S3, which are specifically as follows:

[0037] S1: Obtaining the mass, initial temperature, and target temperature of the semiconductor wafer to be cooled, so as to obtain the heat that needs to be released by the semiconductor wafer to be cooled during the cooling process.

[0038] To further explain, before the semiconductor wafer undergoes a cooling process, it is necessary to obtain the mass and initial temperature of the semiconductor wafer to be cooled through a sensor, and determine the target cooling temperature of the semiconductor wafer according to the corresponding manufacturing process requirements.

[0039] Calculate the difference between the initial temperature and the target temperature to obtain the cooling temperature range;

[0040] The heat change is obtained by calculating the product of the mass of the semiconductor wafer to be cooled and the specific heat capacity of the semiconductor wafer to be cooled;

[0041] The product of the cooling temperature range and the heat change is taken as the heat that the semiconductor wafer to be cooled needs to release during the cooling process.

[0042] Specifically, the heat released by the semiconductor wafer to be cooled currently satisfies the following relationship:

[0043] ;

[0044] In the formula, Indicates the amount of heat that the semiconductor wafer to be cooled needs to release during the cooling process. Indicates the mass of the semiconductor wafer to be cooled. represents the specific heat capacity of the semiconductor wafer to be cooled. Indicates the initial temperature of the semiconductor wafer to be cooled before cooling. Indicates the target cooling temperature of the semiconductor wafer to be cooled.

[0045] S2: Counting the time of each cooling process of the semiconductor wafer to be cooled, and calculating the power of the current cooling process of the semiconductor wafer to be cooled.

[0046] To further illustrate, the time for the cooling process of the current semiconductor wafer to be cooled is obtained, specifically, based on the completion time of the semiconductor wafer process of another process flow before the current cooling process. In the semiconductor manufacturing industry, it is very important to control the cooling power, because it directly affects the production efficiency and the final quality of the product. By adjusting the parameters of the cooling system, such as the flow rate, temperature and pressure of the cooling gas, the cooling power can be optimized to achieve efficient and uniform cooling effect.

[0047] The ratio of the heat released by the semiconductor wafer during the cooling process to the cooling process is taken as the cooling power of the semiconductor wafer to be cooled.

[0048] Specifically, the cooling power satisfies the following relationship:

[0049] ;

[0050] In the formula, represents the cooling power of the current semiconductor wafer cooling process, Indicates the amount of heat that the semiconductor wafer to be cooled needs to release during the cooling process. Indicates the cooling time of the semiconductor wafer to be cooled.

[0051] In addition, based on the definition of cooling power of the semiconductor wafer cooling process, that is, the heat removed from the wafer surface per unit time, the corresponding cooling gas release rate and the temperature of the cooling gas after the semiconductor wafer is cooled can be obtained according to the power, so as to make adaptive adjustments to the parameters;

[0052] The cooling power of the current semiconductor cooling process to be cooled also includes:

[0053] The temperature difference of the cooling gas before and after the cooling of the semiconductor wafer is calculated, and the product of the temperature difference of the cooling gas and the release rate, density and specific heat capacity of the cooling gas is taken as the cooling power of the semiconductor wafer cooling process, that is, the heat taken away from the wafer by the cooling gas per unit time.

[0054] Specifically, the cooling power satisfies the following relationship:

[0055] ;

[0056] In the formula, represents the cooling power of the current semiconductor wafer cooling process, Indicates the cooling gas release rate in the current semiconductor wafer cooling process. represents the density of the cooling gas, represents the specific heat capacity of the cooling gas, Indicates the temperature of the cooling gas before the current semiconductor wafer is cooled. Indicates the temperature of the cooling gas after the current semiconductor wafer is cooled.

[0057] That is, cooling power refers to the amount of heat removed from the wafer surface per unit time, measured in watts (W); cooling gas release rate refers to the volume flow rate of cooling gas flowing through the wafer, measured in cubic meters per second (m³ / s) or liters per second (L / s); cooling gas density refers to the mass of cooling gas per unit volume, measured in kilograms per cubic meter (kg / m³); cooling gas specific heat capacity refers to the amount of heat absorbed or released when the temperature of a unit mass of cooling gas changes by 1 degree Celsius, usually measured in joules per kilogram Celsius (J / kg·℃); during the cooling process of semiconductor wafers, the cooling gas flows over the wafer surface, absorbing the heat of the wafer, causing the gas temperature to rise. The total heat absorbed and removed from the wafer surface by the cooling gas per unit time, the cooling gas release rate ,density and specific heat capacity The difference in gas temperature determines the gas's ability to carry away heat. , which reflects the increase in temperature of the gas after absorbing heat from the wafer. That is, the greater the change, the more heat the gas absorbs.

[0058] It is further explained that the temperature of the cooling gas after the semiconductor wafer is cooled is obtained through a modified formula of the cooling power.

[0059] Specifically, the temperature of the cooling gas after the semiconductor wafer is cooled satisfies the following relationship:

[0060] ;

[0061] In the formula, Indicates the temperature of the cooling gas after the current semiconductor wafer is cooled. Indicates the temperature of the cooling gas before the current semiconductor wafer is cooled. Indicates the amount of heat that the semiconductor wafer to be cooled needs to release during the cooling process. Indicates the amount of heat that the semiconductor wafer to be cooled needs to release during the cooling process. represents the density of the cooling gas, represents the specific heat capacity of the cooling gas, Indicates the cooling time of the semiconductor wafer to be cooled.

[0062] That is to say, under specific cooling conditions, the temperature change of the cooling gas after absorbing the heat of the wafer can be obtained through the modified formula of the cooling power.

[0063] S3: Construct the objective function of cooling gas temperature, cooling gas release rate and resource consumption in the semiconductor wafer cooling process. Based on the accuracy of the cooling process and cooling gases with different preset temperatures, select the control parameters corresponding to the objective function that conform to the relationship between power, density of cooling gas, specific heat capacity and the heat released by the semiconductor wafer during the cooling process. Use them as control parameters of the cooling process to perform semiconductor wafer cooling control.

[0064] Specifically, the objective function satisfies the following relationship:

[0065] , ;

[0066] In the formula, represents the total resources consumed by the cooling process, Indicates the cooling gas release rate, Indicates the cooling process time, Indicates the preset temperature per unit volume The resources required for cooling gas, Indicates the cooling gas release rate The power of the gas equipment during transportation, Indicates the maximum speed of cooling gas release.

[0067] Further, the preset temperature is calculated by taking the ratio of all costs involved in manufacturing or obtaining cooling gas of a specific temperature to the total volume of cooling gas manufactured or obtained in the same period of time. The cooling gas requires resources.

[0068] That is, all the above costs, including but not limited to energy consumption (such as electricity, coolant, etc.), equipment depreciation, maintenance costs, labor costs, etc., are added up to obtain the total cost of manufacturing or obtaining a certain volume of cooling gas. This total cost calculation is not limited and can be calculated by time period (such as daily, weekly, monthly).

[0069] Among them, obtaining the accuracy of the cooling process includes:

[0070] The variance of the difference between the historical cooling temperature and the set temperature is calculated, and the variance is normalized as the accuracy of the cooling process. If the accuracy of the cooling process is less than the preset accuracy threshold, the cooling process is of high accuracy, otherwise it is of low accuracy.

[0071] In this embodiment, different preset temperatures, i.e., the release device of the cooling gas, can be set to 100 degrees, 90 degrees, 80 degrees, 70 degrees, 60 degrees, etc., and there is no limit on the preset temperature, which can be adjusted by those skilled in the art according to the nozzle of the release device. Specifically, the preset accuracy threshold is 0.3, and the variance of the difference between the historical cooling temperature and the set temperature is calculated using Normalize the exponential function with base .

[0072] When the cooling process requires high precision, the minimum total resource consumption of the cooling process is selected. Corresponding cooling gas release rate and the temperature of the cooling gas , as the cooling gas release rate and the cooling gas temperature that need to be regulated;

[0073] In response to the requirement of the cooling process being low precision, the power range corresponding to the low precision of the cooling process is obtained, and the total resources consumed by the cooling process Sorting is performed, and the total resources that meet the power range are selected Minimum corresponding cooling gas release rate and the temperature of the cooling gas , as the cooling gas release rate and the cooling gas temperature that need to be regulated.

[0074] It should be noted that under high precision requirements, the cooling system needs to control heat exchange very accurately to ensure that the temperature of the wafer reaches the target temperature accurately. Usually more sophisticated control and possibly higher costs are required.

[0075] Under low precision requirements, the cooling system can allow certain temperature fluctuations while ensuring a certain cooling effect. This can be achieved by selecting different cooling gas release rates and the temperature of the cooling gas before cooling. to optimize resource consumption and cost-effectiveness, among which, Indicates the preset temperature per unit volume The cooling gas needs to consume resources, preset temperature The temperature of the cooling gas before cooling , that is to say the preset temperature in the release device of the cooling gas.

[0076] The present invention also provides a cooling system for semiconductor wafers. Figure 2 As shown, the system includes a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the semiconductor wafer cooling method according to the first aspect of the present invention is implemented.

[0077] The system also includes other components familiar to those skilled in the art, such as a communication bus and a communication interface. The configuration and functions of these components are known in the art and will not be described in detail here.

[0078] In the present invention, the aforementioned memory may be any tangible medium containing or storing a program that can be used by or in combination with an instruction execution system, apparatus or device. For example, a computer-readable storage medium may be any appropriate magnetic storage medium or magneto-optical storage medium, such as a resistive random access memory RRAM (Resistive Random Access Memory), a dynamic random access memory DRAM (Dynamic Random Access Memory), a static random access memory SRAM (Static Random-Access Memory), an enhanced dynamic random access memory EDRAM (Enhanced Dynamic Random Access Memory), a high-bandwidth memory HBM (High-Bandwidth Memory), a hybrid memory cube HMC (Hybrid Memory Cube), etc., or any other medium that can be used to store the required information and can be accessed by an application, a module, or both. Any such computer storage medium may be part of a device or accessible or connectable to a device. Any application or module described in the present invention may be implemented using computer-readable / executable instructions that may be stored or otherwise maintained by such a computer-readable medium.

[0079] In the description of this specification, "plurality" or "several" means at least two, such as two, three or more, etc., unless otherwise clearly and specifically defined.

[0080] Although this specification has shown and described a number of embodiments of the present invention, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art will conceive of many modifications, changes and alternatives without departing from the ideas and spirit of the present invention. It should be understood that in the practice of the present invention, various alternatives to the embodiments of the present invention described herein may be employed.

Claims

1. A method for cooling a semiconductor wafer, characterized in that: include: Obtaining the mass, initial temperature, and target temperature of the semiconductor wafer to be cooled, so as to obtain the heat that needs to be released by the semiconductor wafer to be cooled during the cooling process; Counting the time of each cooling process of the semiconductor wafer to be cooled, and calculating the power of the current cooling process of the semiconductor wafer to be cooled; Constructing an objective function of cooling gas temperature, cooling gas release rate and resource consumption in a semiconductor wafer cooling process, and selecting a control parameter corresponding to the objective function that conforms to a relationship between the power, the density of the cooling gas, the specific heat capacity of the cooling gas and the heat released by the semiconductor wafer during the cooling process as a control parameter of the cooling process based on the accuracy of the cooling process and cooling gases of different preset temperatures, and performing semiconductor wafer cooling control; The objective function satisfies the following relationship: , , where represents the total resources consumed by the cooling process, Indicates the cooling gas release rate, Indicates the cooling process time, Indicates the preset temperature per unit volume The resources required for cooling gas, Indicates the cooling gas release rate The power of the gas equipment during transportation, Indicates the maximum speed of cooling gas release.

2. The semiconductor wafer cooling method according to claim 1, characterized in that: The step of obtaining the heat that needs to be released by the semiconductor wafer to be cooled during the cooling process includes: Calculating the difference between the initial temperature and the target temperature to obtain a cooling temperature range; Calculating the product of the mass of the semiconductor wafer to be cooled and the specific heat capacity of the semiconductor wafer to be cooled to obtain a heat change; The product of the cooling temperature range and the heat change is used as the heat that needs to be released by the semiconductor wafer to be cooled during the cooling process.

3. The method for cooling a semiconductor wafer according to claim 1, wherein: The cooling power of the current semiconductor cooling process to be cooled includes: The ratio of the heat released by the semiconductor wafer during the cooling process to the cooling process is used as the cooling power of the semiconductor wafer to be cooled.

4. The method for cooling a semiconductor wafer according to claim 1, wherein: The cooling power of the semiconductor cooling process to be cooled currently also includes: The temperature difference of the cooling gas before and after the cooling of the semiconductor wafer is calculated, and the product of the temperature difference of the cooling gas and the release rate, density and specific heat capacity of the cooling gas is taken as the cooling power of the semiconductor wafer cooling process, that is, the heat taken away from the wafer by the cooling gas per unit time.

5. The method for cooling a semiconductor wafer according to claim 1, wherein: The accuracy of the cooling process includes: The variance of the difference between the temperature after historical cooling and the set temperature is calculated, and the variance is normalized as the accuracy of the cooling process. In response to the accuracy of the cooling process being less than a preset accuracy threshold, the cooling process is of high accuracy, otherwise it is of low accuracy.

6. The semiconductor wafer cooling method according to claim 1, characterized in that: The semiconductor wafer cooling control includes: When the cooling process requires high precision, the minimum total resource consumption of the cooling process is selected. Corresponding cooling gas release rate and the temperature of the cooling gas , as the cooling gas release rate and the cooling gas temperature that need to be regulated; In response to the requirement of the cooling process being low precision, the power range corresponding to the low precision of the cooling process is obtained, and the total resources consumed by the cooling process Sorting is performed, and the total resources that meet the power range are selected Minimum corresponding cooling gas release rate and the temperature of the cooling gas , as the cooling gas release rate and the cooling gas temperature that need to be regulated.

7. The semiconductor wafer cooling method according to claim 1, characterized in that: The preset temperature per unit volume The resources required to produce cooling gas include: The ratio of all costs involved in producing or acquiring cooling gas of a specific temperature to the total volume of cooling gas produced or acquired in the same period of time is used as the preset temperature. The cooling gas requires resources.

8. A cooling system for a semiconductor wafer, characterized in that: include: A processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, a cooling method for a semiconductor wafer according to any one of claims 1 to 7 is implemented.

Images