Defect inspection method and device for electronic devices

Abstract

A method for inspecting a semiconductor package includes the steps of: generating and directing an excitation laser beam to an excitation region on a first side of the semiconductor package, thereby generating ultrasonic vibrations in the semiconductor package; generating and directing a measurement laser beam to a measurement region on a second side of the semiconductor package, wherein the first side and the second side are opposite to each other; and detecting the measurement laser beam reflected from the measurement region with a vibration detector to measure the ultrasonic vibration generated by the excitation laser beam to inspect the quality of the semiconductor package.

Description

Technical Field

[0001] The present invention generally relates to automatic inspection of defects or quality inconsistencies in electronic devices such as semiconductor packages, and more particularly to a method and apparatus for inspecting electronic devices so as to achieve non-contact, media-free in-line defect inspection during the manufacturing process of the electronic devices. Background Art

[0002] During the manufacturing of electronic devices such as semiconductor packages, various defects may occur in the semiconductor packages, and an effective and efficient quality or defect inspection solution must be available to ensure that the quality of the finished electronic devices is acceptable. Although non-destructive offline defect inspection methods have been adopted for automatic inspection after manufacturing, an online defect inspection solution is needed to prevent defective devices from being transferred to subsequent production processes, provide defect feedback in a timely manner to strengthen production process control, improve yield and reduce resource waste.

[0003] In the semiconductor industry, online inspection methods for packaging should be non-destructive, non-contaminating, and have high-speed scanning capabilities and high throughput, because the quality of electronic devices is very sensitive to humidity and contamination. However, the inspection equipment of the existing technology is not enough to achieve this goal. For example, the use of traditional X-ray inspection equipment with a limited operating life for online inspection will lead to increased costs related to radiation protection and reduce the inspection speed. Similarly, the effectiveness of piezoelectric ceramics and other ultrasonic generators is limited by the necessary transmission medium to carry the ultrasonic signal. However, the introduction of such a medium may compromise the quality and reliability of the electronic devices being inspected.

[0004] Several non-contact, medium-free ultrasonic measurement methods have been proposed for quality inspection of electronic devices. However, these methods have limited accuracy due to the slow propagation speed of ultrasonic waves in air, resulting in low resolution. In addition, due to the limited effective measurement area, it is necessary to frequently move the electronic device under inspection in order to measure the entire device, which will limit the inspection throughput.

[0005] For example, the laser ultrasonic measurement method generates ultrasonic waves by causing sudden thermal deformation on a target surface of a die included in an electronic device, and uses the optical Doppler effect to measure the ultrasonic vibration on the target surface in a non-contact manner, thereby inspecting defects in the electronic device based on the measurement results. However, since both the excitation laser beam and the measurement laser beam in this method (hereinafter referred to as the "reflection detection method") are directed to the same target surface of the semiconductor die, there is a risk of damaging the sensitive surface of the semiconductor die. Moreover, since the reflected laser beam may be less sensitive to defects in the electronic device, the accuracy of the quality inspection may be affected.

[0006] Therefore, it would be beneficial to provide an in-line inspection solution for electronic devices that can address at least some of the problems faced by traditional defect detection methods. Summary of the invention

[0007] It is therefore an object of the present invention to seek to provide an effective and efficient in-line defect inspection method for electronic devices during their manufacture.

[0008] According to a first aspect of the present invention, there is provided a method for inspecting a semiconductor package, the method comprising: generating an excitation laser beam and directing it to an excitation area on a first side of the semiconductor package, thereby generating ultrasonic vibrations in the semiconductor package; generating a measuring laser beam and directing it to a measuring area on a second side of the semiconductor package, the first side and the second side being opposite to each other; and detecting the measuring laser beam reflected from the measuring area to measure the ultrasonic vibrations generated by the excitation laser beam, thereby inspecting the quality of the semiconductor package.

[0009] Using the proposed inspection method, the excitation laser beam and the measuring laser beam are aimed at two opposite sides of the semiconductor package, so that the ultrasonic vibrations generated by the excitation laser beam in the semiconductor package are detected by a transmission-based detection method rather than a reflection inspection method used in the prior art. The transmission-based detection method means that the ultrasonic vibrations generated by the excitation laser beam on one side of the semiconductor package are transmitted to the other side of the semiconductor package and detected by the measuring laser beam directed to the opposite side. This can prevent damage to the sensitive surface of the semiconductor package because the excitation laser beam can be directed to the less sensitive or non-sensitive surface of the semiconductor package, such as the substrate.

[0010] The proposed method can be used to inspect various defects formed after a die is bonded to a substrate contained in a semiconductor package. In some embodiments, a first side of the semiconductor package may include a surface of a substrate contained in the semiconductor package, and a second side of the semiconductor package may include a surface of a semiconductor die attached to the substrate and / or a surface of an interconnect bonded to the die. Accordingly, inspecting the semiconductor package may include inspecting quality inconsistencies in the semiconductor package introduced during the manufacturing process, wherein the quality inconsistencies may include one or more of the following defects in the semiconductor package: voids and / or delamination defects formed in an adhesive layer between the die and the substrate contained in the semiconductor package, void defects formed in an adhesive layer between the die and the interconnect bonded to the die contained in the semiconductor package, cracks formed in the die, and uneven distribution of the adhesive layer between the die and the substrate contained in the semiconductor package.

[0011] In another embodiment, the proposed method can be used to inspect defects formed after molding the semiconductor package. The first side and the second side of the semiconductor package may include two opposing surfaces of a molded housing of the semiconductor package. Defects formed during the molding process may include cracks formed in the molded housing. Accordingly, the step of inspecting the semiconductor package also includes: inspecting whether cracks are formed in the molded housing.

[0012] In order to perform a comprehensive quality inspection on the semiconductor package, in some embodiments, the excitation laser beam can be sequentially directed to multiple excitation areas on the first side of the semiconductor package. For example, when the first side includes the surface of the substrate contained in the semiconductor package, the multiple excitation areas can substantially cover the entire surface. Correspondingly, the measurement laser beam can be directed to a fixed measurement area or multiple corresponding measurement areas on the second side.

[0013] Alternatively, in some embodiments, the measurement laser beam may be directed sequentially to a plurality of measurement regions on the second side of the semiconductor package. For example, when the second side includes a surface of a die attached to a substrate, the plurality of measurement regions may substantially cover the entire surface of the die. Accordingly, the excitation laser beam may be directed to a fixed excitation region or a plurality of excitation regions on the first side.

[0014] Each measurement region of the second side may have a predetermined spatial relationship with a corresponding excitation region of the first side of the semiconductor package. Preferably, to further improve the inspection accuracy, each measurement region of the second side and the corresponding excitation region of the first side may be positioned directly opposite to each other and extend together. In other words, each measurement region has a corresponding excitation region directly opposite to it and having the same shape and size.

[0015] In some embodiments of the present invention, the step of detecting the measuring laser beam may include: detecting frequency changes of the measuring laser beam at the plurality of measuring areas, thereby verifying whether there are quality inconsistencies in the semiconductor package during the manufacturing process. These quality inconsistencies can be inferred from the detected frequency changes. The vibration detector includes a vibrometer.

[0016] According to a second aspect of the present invention, there is provided an apparatus for inspecting a semiconductor package during its manufacture. The apparatus comprises: an excitation laser assembly, the excitation laser assembly being operated to generate an excitation laser beam and direct it to an excitation region on a first side of the semiconductor package, thereby generating ultrasonic vibrations in the semiconductor package; a measuring laser assembly, the measuring laser assembly being operated to generate a measuring laser beam and direct it to a measuring region on a second side of the semiconductor package, the second side being opposite to the first side, the excitation laser assembly and the measuring laser assembly being located on opposite sides of the semiconductor package; and a vibration detector, the vibration detector being operated to detect the measuring laser beam reflected from the second side of the semiconductor package to measure the ultrasonic vibrations generated by the excitation laser beam, thereby inspecting the quality of the semiconductor package.

[0017] The vibration detector and the measuring laser assembly can use a common optical system to make the entire device more compact. The common optical system may include a galvanometer and an f-θ lens. The galvanometer is configured and operated to direct the measuring laser beam to the measuring area on the second side of the semiconductor package, and through the f-θ lens, the measuring laser beam reflected from the measuring area is directed to the vibration detector. In some embodiments, the common optical system also includes a polarization beam splitter and a quarter wave plate, which are configured to direct the measuring laser beam from the measuring laser assembly to the galvanometer, and direct the measuring laser reflected from the measuring area to the vibration detector.

[0018] The inspection apparatus may further include a control system configured to record detection results from the vibration detector and analyze the detection results to identify quality inconsistencies in the semiconductor package.

[0019] The control system may include a control module that may be communicatively connected to the excitation laser assembly and / or the measurement laser assembly. The control module is configured to send control signals to the excitation laser assembly and / or the measurement laser assembly to adjust the direction of the excitation laser beam and / or the direction of the measurement laser beam. The control system may also include a controller clock for synchronizing operations in the excitation laser assembly and the measurement laser assembly.

[0020]

[0011] These and other features, aspects and advantages will become better understood with reference to the specification portion, appended claims and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0022] Figure 1is a schematic side view of an in-line device for inspecting a semiconductor package according to an embodiment of the present invention;

[0023] Figure 2 is a flow chart illustrating an in-line method for inspecting a semiconductor package according to some embodiments of the present invention;

[0024] Figure 3A shows a cross-sectional side view of a semiconductor package including voids formed in an adhesive layer between a substrate and a die attached to the substrate and in an adhesive layer between the die and a chip bonded to the die;

[0025] Figure 3B is a cross-sectional side view of a semiconductor package including a delamination defect in an adhesive layer between a substrate and a die attached to the substrate;

[0026] Figure 3C is a cross-sectional side view of a semiconductor package including a crack present in a die contained in the semiconductor package;

[0027] Figure 4 shows cross-sectional side views of four semiconductor packages, each semiconductor package comprising a standard adhesive layer, an adhesive layer that is too thick, an adhesive layer that is too thin, and an unevenly distributed adhesive layer;

[0028] Figure 5A shows a cross-sectional side view of a semiconductor package with a crack in the molded housing;

[0029] Figure 5B Shown in Figure 5A Waveforms obtained from different measurement areas on the bottom surface of the molded housing are shown;

[0030] Figure 6 is a flow chart illustrating a method for inspecting a semiconductor package according to one embodiment of the present invention.

[0031] In the drawings, the same components are denoted by the same reference numerals. DETAILED DESCRIPTION

[0032] Before discussing the embodiments in more detail, an overview is first given. Embodiments of the present invention provide a method and apparatus for online inspection of electronic devices. In the present invention, an excitation laser beam and a measuring laser beam are directed to two opposite sides of a semiconductor package, respectively. The excitation laser beam is used to excite ultrasonic vibrations in the semiconductor package, so that when the measuring laser beam is reflected from the semiconductor package, the frequency change of the measuring laser caused by various quality inconsistencies of the semiconductor package can be detected by a vibration tester, and used to identify such inconsistencies, such as gaps and delamination defects formed in the adhesive layer between the die and the substrate, cracks formed in the die, and / or uneven distribution of the adhesive layer between the die and the substrate. Further, at least one of the excitation laser beam and the measuring laser beam can be directed to different areas on the semiconductor package. Therefore, the vibration waveform generated thereby can be compared across at least one characteristic value of multiple regions to identify and quantify any defects or flaws in the semiconductor package.

[0033] Figure 1 1 is a schematic side view of an in-line apparatus 100 for inspecting semiconductor packages 102a-102c according to one embodiment of the present invention. The apparatus 100 includes an excitation laser assembly 120, a measurement laser assembly 140, a vibration detector 160, and a control system 180. Figure 1 The excitation laser assembly 120 and the measurement laser assembly 140 are respectively located at opposite sides of the semiconductor package 102a for inspecting the semiconductor package 102a. Each of the semiconductor packages 102a-102c includes a substrate 104 and a die 110 attached to the substrate 104.

[0034] The excitation laser assembly 120 is configured and operated to generate an excitation laser beam 121 and direct the excitation laser beam 121 to the bottom side (or first side) of the semiconductor package 102a. The bottom side includes the bottom surface of the substrate 104 included in the semiconductor package 102a. The excitation laser beam is directed to the excitation region 106 on the bottom surface of the substrate 104. Typically, the excitation laser beam 121 is a nanosecond laser energy pulse that can be absorbed by the excitation region 106 in nanoseconds in the micrometer range, thereby generating stress due to the deformation of the excitation region 106, which propagates in the semiconductor package 102a as ultrasonic waves for a short time. Figure 1 As shown, the excitation region 106 is located directly below the void defect 108. When the ultrasonic waves pass through the void defect 108, their waveforms will change due to the lower acoustic impedance of the material in the void defect 108. Such changes can be measured via the measurement laser assembly 140.

[0035] refer to Figure 1, the excitation laser assembly 120 may include an excitation laser generator 122 and an excitation beam steering device 124. The excitation laser generator 122 operates to generate an excitation laser beam 121 for actuating ultrasonic vibrations in the semiconductor package 102a. The excitation beam steering device 124 is configured to direct the excitation laser beam 121 to the excitation region 106 on the bottom surface of the substrate 104.

[0036] The excitation beam steering device 124 may be constituted by an optical system. For example, the excitation beam steering device 124 may include a galvanometer 126 and an f-θ lens 128. The galvanometer 126 is configured and operated to direct the excitation laser beam 121 from the excitation laser generator 122 to the excitation region 106 on the bottom surface of the substrate 104 through the f-θ lens 128. When the excitation laser beam 121 is aimed at the excitation region 106, an excitation ultrasonic laser spot will be generated at the excitation region 106.

[0037] The excitation beam steering device 124 may further include a galvanometer driver 127. The galvanometer driver 127 may be operated to change the direction of the excitation laser beam 121 by adjusting the orientation of the galvanometer 126. Thus, the position of the excitation region 106 on the bottom surface of the substrate 104 may be changed. In order to enhance the accuracy and thoroughness of defect inspection, the excitation beam steering device 124 may be operated to adjust the direction of the excitation laser beam 121 so as to sequentially direct the excitation laser beam 121 to a plurality of excitation regions on the first side of the semiconductor package 102a. The plurality of excitation regions may cover the entire bottom surface of the substrate 104 for comprehensive inspection. It should be noted that the excitation beam steering device 124 may be composed of different optical systems as long as the optical system can be used to direct the excitation laser beam to the target region on the first side of the semiconductor package 102a.

[0038] The apparatus 100 may further include a linear motor 190A configured to move the excitation laser assembly 120 to a position directly below a semiconductor package to be inspected (eg, any one of the semiconductor packages 102 a to 102 c ).

[0039] The measurement laser assembly 140 is configured and operated to generate a measurement laser beam 141 and direct the measurement laser beam 141 to the top side (or second side) of the semiconductor package 102a. The top side of the semiconductor package 102a includes the top surface of the semiconductor die 110 mounted on the substrate 104. The measurement laser beam 141 is directed to the measurement area 112 on the top surface of the die 110. Figure 1 As shown, in the present embodiment, the measurement region 112 is directly opposite to the excitation region 106 on the bottom surface of the substrate 104. Then, the measurement laser beam 141 reflected by the measurement region 112 is guided to the vibration detector 160 through the same optical system.

[0040] refer to Figure 1 , the measurement laser assembly 140 may include a measurement laser generator 142 and a measurement beam steering device 144. The measurement laser generator 142 is configured and operated to generate a measurement laser beam for inspecting the semiconductor package 102a. The measurement beam steering device 144 is configured to direct the measurement laser beam 141 from the measurement laser generator 142 to the second side of the semiconductor package 102a. In this embodiment, the second side of the semiconductor package 102a includes the top surface of each die 110.

[0041] The measurement beam steering device 144 may be composed of an optical system for directing the measurement laser beam to the second side of the semiconductor package 102a. For example, the measurement beam steering device 144 may include a galvanometer 146 and an f-θ lens 148. The galvanometer 146 is configured and operated to direct the measurement laser beam 141 from the measurement laser generator 142 to the second side of the semiconductor package 102a through the f-θ lens 148. The measurement laser beam is aimed at the measurement area on the top surface of the die 110. The measurement beam steering device 144 may also include a galvanometer driver 147. The direction of the measurement laser beam can be changed by adjusting the direction of the galvanometer 146 via the galvanometer driver 147. Therefore, the measurement area on the top surface of the die 110 can also be changed.

[0042] In order to enhance the accuracy and thoroughness of defect inspection, the measurement beam steering device 144 can be operated to adjust the direction of the measurement laser beam 141 so as to sequentially direct the measurement laser beam 141 to a plurality of measurement regions on the top surface of the die 110. These measurement regions can be arranged to cover the entire top surface of the die 110 during measurement. Each of the plurality of measurement regions on the top surface of the die 100 can have a predetermined spatial relationship with a corresponding excitation region on the bottom surface of the substrate 104. In one example, the excitation laser beam 121 can be directed to a fixed excitation region on the bottom surface of the substrate 104, while the measurement laser beam 141 can be directed to a plurality of measurement regions that can cover the entire top surface of the die 100. Alternatively, the excitation laser beam 121 can be directed to a plurality of excitation regions that can cover the entire surface of the substrate 104, while the measurement laser beam is directed to a fixed measurement region on the top surface of the die 100. Preferably, each measurement region on the top surface of the die 100 and the corresponding excitation region on the bottom surface of the substrate 104 are positioned opposite to each other and coextensive. In other words, when the excitation laser beam 121 is directed to a predetermined excitation region on the bottom surface of the substrate 104, the measurement laser beam 141 is correspondingly directed to a measurement region that is located directly opposite to the predetermined excitation region on the top surface of the die 110 and has the same shape and size. Using such an arrangement, the accuracy of defect inspection can be further improved.

[0043] The apparatus 100 may further include a linear motor 190B configured to move the measurement laser assembly 140 to a position directly above a semiconductor package to be inspected (eg, any one of the semiconductor packages 102 a to 102 c ).

[0044] The vibration detector 160 is configured and operated to detect the measurement laser beam 141 reflected from the measurement area 112 to measure the ultrasonic vibration generated at the measurement area 112 by the excitation laser beam 121 directed to the excitation area 106. The vibration detector 160 can be operated to detect the frequency change of the measurement laser beam 141 reflected from the measurement area 112, and convert the frequency change into a voltage amplitude change formed by multi-beam interference. The vibration detector 160 may include a vibrometer. The vibration detector 160 is communicatively connected to the control system 180 to transmit the detection result to the control system 180.

[0045] The control system 180 is configured to record the detection results from the vibration detector 160, and based on the recorded detection results, identify and quantify any quality inconsistencies of the semiconductor package 102a. The control system 180 can also be configured to synchronize the excitation laser assembly 120, the measurement laser assembly 140, and the vibration detector 160. The control system also sends control signals to the corresponding galvanometer drivers 127 and 147 to adjust the directions of the corresponding galvanometers 126, 146.

[0046] refer to Figure 1 , the control system 180 may include a digital-to-analog converter 182, a controller clock 184, and a control module 186. The digital-to-analog converter 182 may be configured to generate a waveform diagram based on the photocurrent signal received from the vibration detector 160. The controller clock 184 is configured to synchronize the operation of the excitation laser assembly 121, the measurement laser assembly 141, and the vibration detector 160. The control module 186 is configured to send a control signal to the galvanometer drivers 127, 147 to adjust the deflection angle of the galvanometers 126, 146 according to a preset rule. The preset rule may define one or a set of specific values ​​for adjusting the deflection angle of each galvanometer during semiconductor package inspection. The control module 186 may also record the waveform diagram generated by the digital-to-analog converter 182 and transmit the recorded information to a server computer communicatively connected thereto.

[0047] In this embodiment, the control system 180 can be operated to control the galvanometer driver 127 to adjust the deflection angle of the galvanometer 126 so that the excitation area will be able to traverse the entire bottom surface of the substrate 104. Accordingly, the control system 180 can also control the galvanometer driver 147 to adjust the deflection angle of the galvanometer 146 so that the measurement area can traverse the entire top surface of the die 110. Preferably, the galvanometers 126 and 146 are adjusted accordingly so that the excitation area on the top surface of the die 110 and the corresponding measurement area on the bottom surface of the substrate 104 are positioned directly opposite each other. However, it should be understood by those skilled in the art that for some embodiments, the excitation area and the measurement area may not necessarily cover the entire surface to which they can be directed.

[0048] After inspecting the semiconductor package 102a, the excitation laser assembly 120 and the measurement laser assembly 140 can be driven by the linear motors 190A and 190B, respectively, to move to a position just above or below the next semiconductor package to be inspected (e.g., the semiconductor package 102b or the semiconductor package 102c) to perform a similar inspection process. Figure 1 As shown, the excitation laser assembly 120 and the measurement laser assembly 140 can move along the horizontal direction Y.

[0049] Figure 2 1 is a flow chart illustrating a method for inspecting a semiconductor package during semiconductor package manufacturing according to some embodiments of the present invention. The method comprises the following steps:

[0050] At step 201 , an excitation laser beam is generated and directed to an excitation region on a first side of a semiconductor package, thereby generating ultrasonic vibrations in the semiconductor package.

[0051] At step 202, a measurement laser beam is generated and directed to a measurement area on a second side of the semiconductor package. The first side and the second side are opposite to each other.

[0052] In step 203, the measuring laser beam reflected from the measuring area is detected by a vibration detector to measure ultrasonic vibration generated by the exciting laser beam, thereby inspecting the semiconductor package.

[0053] In order to inspect defects that may be formed between the first side and the second side of the semiconductor package, at least one of the excitation laser beam and the measurement laser beam can be sequentially directed to multiple different areas on the first side and / or the second side of the semiconductor package. The multiple different areas on the first side and / or the second side of the semiconductor package may cover the entire target surface of the first side and / or the second side. In some embodiments, corresponding to the position change of the excitation beam relative to the multiple excitation areas, the measurement laser beam is sequentially directed to the multiple measurement areas on the second side of the semiconductor package, so that each measurement area on the second side has a predetermined spatial relationship with the corresponding excitation area on the first side of the semiconductor package. Preferably, the predetermined spatial relationship may refer to each measurement area on the second side being positioned directly opposite to the corresponding excitation area and having the same shape / pattern and size as the corresponding excitation area. Reference Figure 1 , the measurement region 112 and the excitation region 106 are positioned directly opposite each other and extend together.

[0054] In some embodiments, the above method can be used to verify whether there is a quality inconsistency between a substrate and a die attached to the substrate or within the die itself. In these embodiments, the first side of the semiconductor package may include the bottom side of the substrate, and the second side of the semiconductor package may include the top surface of the die attached to the substrate. The quality inconsistencies that can be identified include, but are not limited to, the following defects:

[0055] Voids formed in the adhesive layer between the substrate and the die

[0056] For example, a gap 108 is formed in the adhesive layer between the die 110 and the substrate 104, such as Figure 1 As shown, a gap 308 is formed in the adhesive layer between the substrate 304 and the die 310, as shown in FIG. Figure 3A shown.

[0057] Delamination defects in the adhesive layer between the substrate and the die

[0058] For example, a delamination defect 308B is formed in the adhesive layer between the die 310 and the substrate 304, such as Figure 3B As shown. The delamination defect 308B occurring in the adhesive layer may be due to delamination and / or separation of the solder material in the adhesive layer. Such delamination does not result in any loss of solder material. In the case of transmitting vibration in the form of ultrasonic waves, such an interface will exhibit total reflection, and the characteristic values ​​of the waveform will change significantly, such as a significant decrease in the amplitude of the measured vibration waveform.

[0059] Crack defects formed in the die

[0060] For example, a crack 308C exists in the die 310 attached to the substrate 304, such as Figure 3CAs shown. This type of defect present inside the wafer is generally similar to a delamination defect, where any change in mass density is negligible. However, due to the large difference in acoustic impedance between air and solid materials such as silicon, total reflection can be assumed. Therefore, when a crack 308C exists between the excitation area and the measurement area, a significant change can be identified from the characteristic values ​​of the measured waveform.

[0061] Uneven distribution of the adhesive layer or the thickness of the adhesive layer does not meet the desired or required standards.

[0062] Figure 4 Shown are side views of four semiconductor packages 402A-402D. In a semiconductor package 402A, the distribution and thickness of the adhesive layer all meet predetermined standards. On the other hand, other semiconductor packages 402B to 402D show different problems about the adhesive layer, including excessive thickness, insufficient thickness and uneven distribution. For the situation where the adhesive layer thickness is too large or insufficient thickness, measuring in a single measurement area is enough to identify this type of quality inconsistency. The measured vibration signal shows a delay and bandwidth reduction, indicating that the adhesive layer thickness is too large. On the contrary, if the measured vibration signal shows an advance and bandwidth increase, it indicates that the adhesive layer may be too thin. In order to evaluate this type of uneven distribution of the adhesive layer, it is necessary to measure at a plurality of spaced measurement areas.

[0063] When the method is used to inspect whether there is a quality inconsistency in the interface between the die and the chip bonded to the die, the first side of the semiconductor package may include the bottom side of the substrate to which the die is attached, and the second side of the semiconductor package may include the top surface of the chip bonded to the die. Such quality inconsistencies may include, but are not limited to, voids formed in the adhesive layer between the die and the chip, such as voids 308A formed in the adhesive layer between the interconnect 301 (which may be in the form of a clip) and the die 310, as shown in FIG. Figure 3A shown.

[0064] When the method is used to inspect whether there is quality inconsistency within a molded case of a semiconductor package, the first side and the second side of the semiconductor package generally comprise two opposite surfaces of the molded case. Figure 5A A cross-sectional side view of a semiconductor package 502 is shown, which includes a molded housing 505. Two cracks 508A, 508B are present in the molded housing 505. When inspecting these cracks 508A, 508B present in the molded housing 505 using the method, the excitation laser beam and the measurement laser beam can be directed to two opposite surfaces of the molded housing 505.

[0065] like Figure 5AAs shown, the excitation laser beam 521 is sequentially directed to two different excitation areas 506A and 506B on the top surface of the molded housing 505. Correspondingly, the measuring laser beam 541 is also sequentially directed to two different measuring areas 512A and 512B on the bottom surface of the molded housing 505. The excitation area 506A and the measuring area 512A are positioned directly opposite each other, and the excitation area 506B and the measuring area 512B are positioned directly opposite each other. The line passing through the excitation area 506A and the measuring area 512A does not encounter any cracks in the molded housing 505, while the line passing through the excitation area 506B and the measuring area 512B passes through the crack 508A in the molded housing 505. It should be noted that the arrangement of the excitation laser beam and the measuring laser beam may be different in other embodiments. For example, the excitation laser beam 521 may be directed to the bottom surface of the molded housing 505, and the measuring laser beam 541 may be directed to the top surface of the molded housing 505. In Figure 5B , waveforms 509A and 509B obtained at measurement areas 512A and 512B are indicated, respectively. The horizontal axis represents time (t), while the vertical axis represents the vibration amplitude (A) of the wave. It can be observed from the two waveforms that they exhibit different vibration amplitudes. This difference is due to total reflection when the ultrasonic vibration generated by the excitation laser beam 521 passes through the crack 508A. Therefore, based on the waveforms generated by the inspection method and apparatus provided in the embodiments of the present invention, any cracks in the molded housing 505 can be identified.

[0066] Figure 6 is a flow chart illustrating a method for inspecting a semiconductor package 102a according to one embodiment of the present invention.

[0067] In step 601, an excitation laser beam 121 is generated and directed to a predetermined excitation region on the bottom surface of the substrate 104, thereby generating ultrasonic vibrations in the semiconductor package 102a.

[0068] At step 602, a measurement laser beam 141 is generated and directed to a predetermined measurement area on the top surface of the die 110. The predetermined measurement area and the excitation area are positioned directly opposite each other and have the same shape and size.

[0069] At step 603, the measuring laser beam reflected from the measuring area is detected by a vibration detector to measure the ultrasonic vibration generated by the excitation laser beam 121, and the detection result is recorded in the control system 180 to identify any defects in the semiconductor package 102a.

[0070] At step 604 , if there is a next predetermined excitation region to be inspected on the bottom surface of substrate 104 , the process continues to step 605 , otherwise the process continues to step 607 .

[0071] At step 605, the excitation laser beam 121 is directed to the next excitation region on the bottom surface of the substrate 104, and the measurement laser beam 141 is directed to the next measurement region on the top surface of the die 110. The next measurement region is positioned directly opposite the next excitation region on the bottom surface of the substrate 104. For example, the excitation region 106' and the measurement region 112', as shown in FIG. Figure 1 shown.

[0072] At step 606, the measuring laser beam reflected from the next measuring area is detected by the vibration detector 160 to measure the ultrasonic vibration generated by the exciting laser beam 121, and the detection result is recorded in the control system 180 to identify defects in the semiconductor package 102a.

[0073] In step 607, defects in semiconductor package 102a are identified using the recorded inspection results. For example, if a waveform generated based on the inspection results obtained in one measurement area has a vibration amplitude significantly lower than that of other measurement areas, it can be determined that there may be a void or delamination defect in the adhesive layer between die 110 and substrate 104.

[0074] Using the method and apparatus provided by the embodiments of the present invention, online defect inspection can be performed at different stages during the manufacture of semiconductor packages without the need for additional radiation protection or ultrasonic transmission media. The semiconductor package can be inspected after the bonding process when the die is attached to the substrate, the interconnect is bonded to the die, and / or after the molding process of encapsulating the electronic device in the molded housing. By using such inspection methods and apparatus, any quality inconsistencies or defects in the semiconductor package can be identified in a timely manner during different production stages. This helps prevent defective devices from being used in subsequent production stages, thereby ultimately improving the control of the production process. Therefore, resource waste is minimized while increasing production. Further, since the excitation laser beam and the measurement laser beam are directed to opposite sides of the semiconductor package during inspection, the shortcomings faced by the traditional laser ultrasonic measurement method are successfully solved. Specifically, the risk of damaging the sensitive surface of the die can be avoided, the interference of the excitation laser beam and the measurement laser beam can be avoided, and high detection resolution can be achieved without the need for a high measurement bandwidth. Moreover, due to the sensitivity of the transmitted laser beam to defects and the high propagation speed of the ultrasonic wave generated by the excitation laser beam in the semiconductor package, the accuracy and efficiency of defect inspection can be improved. In addition, by changing the deflection angle of the optical element, the direction of the excitation laser beam and the measurement laser beam can be easily adjusted so that the excitation area and the measurement area can cover the entire surface of their corresponding target. This will further improve the accuracy and thoroughness of defect inspection, especially when each measurement area and its corresponding excitation area are positioned directly opposite each other and have the same pattern and size.

[0075] Variations, modifications and / or additions may be made to the invention described herein in addition to those specifically described, and it is to be understood that the invention includes all such variations, modifications and / or additions which fall within the spirit and scope of the above description.

Claims

1. A method for inspecting a semiconductor package, the method comprising: generating an excitation laser beam and directing it to an excitation region on a first side of the semiconductor package to generate ultrasonic vibrations in the semiconductor package, generating a measuring laser beam and directing it to a measuring area on a second side of the semiconductor package, the first side and the second side being opposite to each other, and The measuring laser beam reflected from the measuring area is detected by a vibration detector to measure the ultrasonic vibration generated by the exciting laser beam, thereby inspecting the quality of the semiconductor package. 2 . The method of claim 1 , wherein the first side of the semiconductor package comprises a surface of a substrate included in the semiconductor package. 3 . The method of claim 2 , wherein the second side of the semiconductor package comprises a surface of a die attached to the substrate and / or a surface of an interconnect bonded to the die attached to the substrate.

4. The method according to claim 3, wherein the step of inspecting the semiconductor package comprises: Inspecting whether there is quality inconsistency in the semiconductor package, wherein the quality inconsistency includes one or more of the following defects: voids and / or delamination defects formed in the adhesive layer between the die and the substrate, a void defect formed in an adhesive layer between the die and the interconnect bonded to the die, cracks formed in the die contained in the semiconductor package, and Uneven distribution of the adhesive layer between the die and the substrate. 5 . The method of claim 1 , wherein the first side and the second side of the semiconductor package comprise two opposing surfaces of a molded housing of the semiconductor package.

6. The method according to claim 5, wherein the step of inspecting the semiconductor package comprises: The molded housing was inspected for crack formation. 7 . The method of claim 1 , further comprising sequentially directing the excitation laser beam to a plurality of excitation regions on the first side of the semiconductor package. 8 . The method of claim 1 , further comprising sequentially directing the measurement laser beam to a plurality of measurement areas on the second side of the semiconductor package. 9 . The method of claim 7 , further comprising sequentially directing the measurement laser beam to a plurality of measurement regions on the second side of the semiconductor package, the plurality of measurement regions corresponding to positional changes of the excitation laser beam relative to the plurality of excitation regions. 10 . The method of claim 9 , wherein each measurement region on the second side of the semiconductor package has a predetermined spatial relationship with a corresponding excitation region on the first side of the semiconductor package. 11 . The method of claim 10 , wherein each measurement region of the second side and a corresponding excitation region of the first side are positioned directly opposite and coextensive with each other.

12. The method according to claim 9, wherein the step of detecting the measuring laser beam comprises: Frequency variations of the measuring laser beam at the plurality of measurement areas are detected, thereby inspecting the semiconductor package for quality inconsistencies that can be inferred from the detected frequency variations.

13. The method of claim 1, wherein the vibration detector comprises a vibrometer.

14. An apparatus for inspecting a semiconductor package, the apparatus comprising: an excitation laser assembly operative to generate an excitation laser beam and direct it to an excitation region on a first side of the semiconductor package to generate ultrasonic vibrations in the semiconductor package, and a measurement laser assembly operative to generate and direct a measurement laser beam to a measurement area on a second side of the semiconductor package, the second side being opposite the first side, and A vibration detector is operative to detect the measuring laser beam reflected from the second side of the semiconductor package to measure the vibration generated by the exciting laser beam at the measuring region, thereby inspecting the quality of the semiconductor package.

15. The apparatus of claim 14, wherein the excitation laser assembly and the measurement laser assembly are located on opposite sides of the semiconductor package.

16. The apparatus of claim 14, wherein the vibration detector and the measurement laser assembly use a common optical system.

17. The apparatus of claim 16 , wherein the common optical system comprises a galvanometer and an f-θ lens, the galvanometer being configured and operated to direct the measuring laser beam to the measuring area on the second side of the semiconductor package, and directing the measuring laser beam reflected from the measuring area to the vibration detector through the f-θ lens.

18. The apparatus of claim 17, wherein the common optical system further comprises a polarization beam splitter and a quarter wave plate, the polarization beam splitter and the quarter wave plate being configured to direct the measurement laser beam from the measurement laser assembly to the galvanometer, and to direct the measurement laser reflected from the measurement area to the vibration detector.

19. The apparatus of claim 14, wherein the vibration detector comprises a vibrometer.

20. The apparatus of claim 14, further comprising a control system configured to record detection results from the vibration detector and analyze the detection results to identify quality inconsistencies in the semiconductor package.

21. The apparatus according to claim 20, wherein the control system comprises a control module configured to send a control signal to the excitation laser assembly and / or the measurement laser assembly to adjust the direction of the excitation laser beam and / or the direction of the measurement laser beam.

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