Method for monitoring degradation state of surface of lense

Abstract

The method for monitoring the deterioration state of a lens surface according to the present invention comprises the steps of: a laser beam diagnostic device generating and outputting a profile of a laser beam transmitted through an objective lens; a control device converting the laser beam profile into digital data; and the control device quantifying the deterioration of the objective lens surface using the fluctuation range of the digital data to obtain a single quantified value.

Description

Technology Field

[0001] The present invention relates to a method for monitoring the deterioration state of a lens surface. Background Technology

[0002] The scribing process is a process for cutting silicon wafers used in semiconductor chip manufacturing. A scriber is a device that forms scribe lines with a very thin width and a predetermined depth on the wafer. After wafer processing is complete, the wafer is cut along the scribe lines formed between the dies.

[0003] A laser scriber performs the scribing process by scanning a laser beam onto a wafer. Specifically, a laser beam with a wavelength capable of penetrating the wafer is focused by an objective lens, and the focused light is concentrated at a single point inside the wafer. If the laser beam is continuously incident on the objective lens, degradation occurs on the lens surface due to factors such as the laser beam's heat or contamination. If degradation occurs on the lens surface, wafer breakage or cracking may occur when the wafer is cut after the scribing process. The problem to be solved

[0004] One of the objectives of the technical concept of the present invention is to provide a method for quantifying the degradation of a lens surface using data representing the state of a laser beam transmitted through an objective lens in order to monitor the degradation state of the lens surface. means of solving the problem

[0005] A method for monitoring the deterioration state of a lens surface according to one embodiment of the present invention comprises the steps of: a laser beam diagnostic device generating and outputting a profile of a laser beam transmitted through an objective lens; a control device converting the laser beam profile into digital data; and the control device quantifying the deterioration of the objective lens surface using the fluctuation range of the digital data to obtain a single quantified value. Effects of the invention

[0006] According to one embodiment of the present invention, by quantifying the degradation of the lens surface and monitoring the quantified values, preliminary measures such as replacing the lens can be taken before a semiconductor chip defect occurs. Accordingly, there is an effect of reducing the defect rate of the semiconductor chip.

[0007] The various and beneficial advantages and effects of the present invention are not limited to those described above, and may be more easily understood in the process of explaining specific embodiments of the present invention. Brief explanation of the drawing

[0008] FIG. 1 is a simplified block diagram of a laser scriber according to one embodiment of the present invention. FIG. 2 is a block diagram illustrating a method for measuring a laser beam according to an embodiment of the present invention. FIG. 3 is a block diagram showing a control device according to one embodiment of the present invention. FIG. 4 is a drawing showing a laser beam profile according to one embodiment of the present invention. FIG. 5 is a graph showing digital data according to one embodiment of the present invention. Figure 6 is a graph quantifying the degradation of the lens surface according to one embodiment of the present invention. Figure 7 is a graph showing the defect rate of a semiconductor chip according to one embodiment of the present invention. Specific details for implementing the invention

[0009] Hereinafter, preferred embodiments of the present invention are described as follows with reference to the attached drawings.

[0011] FIG. 1 is a simplified block diagram of a laser scriber according to one embodiment of the present invention.

[0012] Referring to FIG. 1, a laser scriber (100) can irradiate a wafer (W) with a laser beam (L) to form a scribe line (SL) between dies (D). The laser scriber (100) may include a laser power supply (110), a laser head (120), one or more beam splitters (130-1 to 130-5), an objective lens (140), and a work stage (150).

[0013] A laser head (120) may be a laser beam source that receives power from a laser power supply (110) to form a laser beam (L) and irradiates the laser beam (L). One or more beam splitters (130-1 to 130-5) may split the laser beam (L) irradiated from the laser head (120) into one or more beams. An objective lens (140) may focus the laser beam (L) split through one or more beam splitters (130-1 to 130-5) onto a wafer (W).

[0014] The work stage (150) may be movable in the horizontal direction, that is, in the xy plane. When a wafer (W) is loaded onto the work stage (150), the wafer (W) can be moved under the objective lens (140) by adjusting the position of the work stage (150). The objective lens (140) can focus a laser beam (L) branched through one or more beam splitters (130-1 to 130-5) and irradiate it onto the wafer (W). After the wafer (W) processing is finished, dies (D) can be cut along the scribe line (SL) to form a semiconductor chip.

[0015] When a laser beam (L) is continuously incident on the objective lens (140), deterioration occurs on the lens surface due to heat or contamination from the laser beam (L). If deterioration occurs on the lens surface, wafer breakage or cracking may occur when cutting the wafer (W) after the scribing process. This may increase the defect rate of the semiconductor chip.

[0016] According to one embodiment of the present invention, the state of a laser beam (L) transmitted through an objective lens (140) is measured, and digital data output from measuring the state of the laser beam (L) is processed to quantify the degradation of the lens surface. The quantified value may indicate the degradation state of the entire surface of the objective lens (140). By monitoring the periodically calculated quantified values, precautionary measures, such as replacing the objective lens, can be taken before a semiconductor chip defect occurs. Accordingly, the defect rate of the semiconductor chip can be reduced.

[0018] FIG. 2 is a block diagram illustrating a method for measuring the state of a laser beam according to an embodiment of the present invention, FIG. 3 is a block diagram showing a control device according to an embodiment of the present invention, and FIG. 4 is a drawing showing a laser beam profile according to an embodiment of the present invention.

[0019] Referring to FIG. 2, a laser scriber (200) and a control device (300) can be used to quantify the degradation of a lens surface. The laser scriber (200) may include a laser power supply (210), a laser head (220), one or more beam splitters (230-1 to 230-5), an objective lens (240), and a work stage (250).

[0020] Unlike the laser scriber (100) of FIG. 1, in the laser scriber (200) of FIG. 2, a laser beam diagnostic device (260) can be placed on the work stage (250) instead of a wafer (W). That is, the laser beam diagnostic device (260) can be positioned at the end of the path of the laser beam (L). By adjusting the position of the work stage (250), the laser beam diagnostic device (260) can be moved below the objective lens (240). The objective lens (240) can concentrate the laser beam (L) branched through one or more beam splitters (230-1 to 230-4) and irradiate it onto the laser beam diagnostic device (260). The laser beam diagnostic device (260) can generate a profile of the laser beam that has passed through the objective lens (240) and output it to the control device (300).

[0021] Referring to FIG. 3, the control device (300) may be implemented as a computer, etc. The control device (300) may include a storage unit (310), a display unit (320), a data conversion unit (330), and a digitization unit (340). The control device (300) may store a laser beam profile generated by the laser beam diagnostic device (260) in the storage unit (310). The control device (300) may display the laser beam profile through the display unit (320) so that the current state of the laser beam can be checked.

[0022] Referring to FIG. 4, the laser beam may have an intensity profile that oscillates according to the distance from the center. The laser beam profile can represent the intensity distribution of the laser beam and, ideally, may have the shape of a Gaussian distribution. The Gaussian distribution refers to a distribution in which the curve of the frequency distribution is symmetrical around the mean value. The laser beam diagnostic device can measure the intensity of the laser beam using a photodetector and generate a laser beam profile that can verify the current state of the laser beam.

[0023] Referring to FIG. 3 and FIG. 4 together, the data conversion unit (330) can convert a laser beam profile into digital data. Specifically, the data conversion unit (330) can output digital data representing the intensity distribution of a laser beam along an arbitrary diameter of a laser beam of Gaussian distribution. For example, the data conversion unit (330) can convert the intensity distribution of a laser beam (DATA1) along the diameter of a first direction (e.g., x-axis direction) of a laser beam of Gaussian distribution into first digital data. The data conversion unit (330) can convert the intensity distribution of a laser beam (DATA2) along the diameter of a second direction (e.g., y-axis direction) of a laser beam of Gaussian distribution into second digital data.

[0024] The digitization unit (340) can process the first digital data and the second digital data to digitize the deterioration of the lens surface. For example, the digitization unit (340) can digitize the deterioration of the lens surface for each of the first digital data and the second digital data using the fluctuation range of the digital data to obtain a single digitized value. The detailed operation of the digitization unit (340) will be explained with reference to FIG. 5.

[0026] FIG. 5 is a graph showing digital data according to one embodiment of the present invention.

[0027] The left graph of FIG. 5 represents digital data converted from a laser beam profile and may correspond to either the first digital data or the second digital data described in FIG. 4. The right graph of FIG. 5 is an enlarged view of a portion of the area (AREAR) in the left graph of FIG. 5. Here, the x-axis represents the position along an arbitrary diameter direction of the laser beam, and the y-axis represents the intensity of the laser beam.

[0028] Referring to the graph in Fig. 5, the range of variation in the intensity of the laser beam can vary depending on the degree of degradation of the lens surface. For example, the greater the degree of degradation of the lens surface, the greater the range of variation in the intensity of the laser beam. Therefore, if the range of variation in the digital data is known, the degradation state of the lens surface can be determined.

[0029] The digitization unit of the control device can process digital data to digitize the degradation of the lens surface and obtain a single digitized value. The digitization unit can process digital data using a macro program, etc. By periodically digitizing the degradation of the lens surface and obtaining the digitized values, the degradation status of the lens surface can be monitored.

[0030] To explain how the quantification unit (340) quantifies the deterioration of the lens surface, refer to the graph of FIG. 5, which is an enlarged view of a portion of the area. From the first position (x=0) to the last position (x=m), a single quantified value can be obtained by calculating the sum of the absolute values ​​of the difference between the laser beam intensity at the first position (x=n) and the laser beam intensity at the second position (x=n+1) following the first position (x=n). Here, n and m are natural numbers greater than 1, and m is greater than n. Since the greater the degree of deterioration of the lens surface, the greater the fluctuation range of the laser beam intensity, the larger the quantified value, the more severe the degree of deterioration of the lens surface.

[0032] FIG. 6 is a graph quantifying the degradation of a lens surface according to one embodiment of the present invention. In the graph of FIG. 6, the x-axis represents the date on which the intensity of the laser beam was measured, and the y-axis represents the value quantified from the digital data.

[0033] The first values ​​(VAL1) correspond to values ​​obtained by quantifying the first digital data, and the second values ​​(VAL2) may correspond to values ​​obtained by quantifying the second digital data. As described above, the first digital data may refer to the intensity distribution of a laser beam represented along the diameter of the first direction of a Gaussian distribution laser beam converted into digital data, and the second digital data may refer to the intensity distribution of a laser beam represented along the diameter of the second direction of a Gaussian distribution laser beam converted into digital data. Since the fluctuation range of the digital data increases as the degree of degradation of the lens surface becomes more severe, the first values ​​(VAL1) and the second values ​​(VAL2) may increase as the degradation of the lens surface becomes more severe.

[0034] A predetermined reference value (Dref) can be determined based on the timing of objective lens replacement. For example, the predetermined reference value (Dref) can be determined to be a value smaller than the value at which semiconductor chip failure occurs. The control device can determine whether any of the first values ​​(VAL1) and the second values ​​(VAL2) reach the predetermined reference value (Dref). If any of the first values ​​(VAL1) and the second values ​​(VAL2) reach the predetermined reference value (Dref) (A, B, C), the control device can predict that semiconductor chip failure will occur due to the deterioration of the lens surface. By taking precautionary measures, such as replacing the objective lens before semiconductor chip failure occurs, the failure rate of the semiconductor chip can be reduced.

[0036] Figure 7 is a graph showing the defect rate of a semiconductor chip according to one embodiment of the present invention.

[0037] In the graph of FIG. 7, the x-axis represents the date the laser beam intensity was measured, and the y-axis represents the defect rate of the semiconductor chip. The first section (D1) represents the defect rate before quantifying and monitoring the degradation of the lens surface, and the second section (D2) represents the defect rate after quantifying and monitoring the degradation of the lens surface and taking precautionary measures.

[0038] By quantifying and monitoring the degradation of the lens surface, it is possible to predict that semiconductor chip defects will occur due to the degradation of the lens surface and take preventive measures; thus, as shown in the graph of FIG. 7, the defect rate of the second section (D2) can be reduced compared to the defect rate of the first section (D1).

[0040] In this specification, the technical concept of the present invention has been explained with an example focusing on quantifying the degradation of the lens surface in a laser scriber. However, the technical concept of the present invention is not limited to laser scribers and can be applied to all devices that process a workpiece on a work stage by focusing a laser beam from an objective lens, such as laser dicing and laser markers, within a scope that is easily understood by a person skilled in the art.

[0042] The present invention is not limited by the embodiments described above and the attached drawings, but is intended to be limited by the appended claims. Accordingly, various substitutions, modifications, and changes may be made by those skilled in the art within the scope of the technical concept of the present invention as described in the claims, and such are also to be considered to fall within the scope of the present invention. Explanation of the symbols

[0043] 100, 200; Laser scribe 110, 210; laser power supply 120, 220; laser head 130-1 ~ 130-5; Beam Splitter 230-1 ~ 230-5; Beam Splitter 140, 240; objective lens 150, 250; Work stage 260; Laser beam diagnostic device 300; control unit

Claims

Claim 1 A method for monitoring the degradation state of a lens surface, comprising: a step in which a laser beam diagnostic device generates and outputs a profile of a laser beam transmitted through an objective lens; a step in which a control device converts the profile of the laser beam into digital data; and a step in which the control device quantifies the degradation of the objective lens surface using the variation range of the digital data to obtain a single quantified value, wherein the digital data includes first digital data corresponding to the intensity distribution of the laser beam along the diameter of a first direction of the laser beam and second digital data corresponding to the intensity distribution of the laser beam along the diameter of a second direction of the laser beam. Claim 2 delete Claim 3 A method for monitoring the degradation state of a lens surface according to claim 1, wherein the quantifying step comprises calculating the sum of the absolute values ​​of the difference between the intensity of the laser beam at a first position and the intensity of the laser beam at a second position following the first position from the first position to the last position of the laser beam to obtain a single quantified value. Claim 4 A method for monitoring the deterioration state of a lens surface according to claim 1, further comprising the step of the control device determining whether the quantified value has reached a predetermined reference value. Claim 5 A method for monitoring the deterioration state of a lens surface according to claim 4, further comprising the step of the control device predicting that a semiconductor chip defect will occur when the quantified value reaches a predetermined reference value. Claim 6 In paragraph 4, the above-determined reference value is a method for monitoring the deterioration state of the lens surface determined based on the replacement time of the objective lens. Claim 7 A method for monitoring the deterioration state of a lens surface according to claim 1, further comprising the step of moving the laser beam diagnostic device below the objective lens by adjusting the position of a work stage movable in the horizontal direction. Claim 8 A method for monitoring the deterioration state of a lens surface in which the numerical value increases as the degree of deterioration of the lens surface becomes more severe, in accordance with claim 1. Claim 9 A method for monitoring the deterioration state of a lens surface, wherein the laser beam profile is the intensity distribution of the laser beam in claim 1. Claim 10 In claim 1, the step of generating the laser beam profile is a method for monitoring the deterioration state of a lens surface, wherein the laser beam diagnostic device uses a photodetector to measure the intensity of the laser beam and generate the laser beam profile.

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