Novel optimization device and method for improving bonding offset

Abstract

The invention discloses a novel optimization device and method for improving bonding offset, and the device comprises a device support, the bottom of the device support is provided with a fixed seat, the upper end of the device support is provided with a bonding support in a positioning manner, and the device support is provided with a slide rail at the side of the bonding support. A camera support is movably arranged on the sliding rail, an optical bracket is positioned at the upper end of the camera support, an optical alignment mechanism is mounted at the lower end of the end part of the optical bracket, a bonding plate is positioned on the inner side of the bonding support, a bonding cavity is formed in the bonding plate, and a lower hot plate, a wafer glass assembly, an upper hot plate and a transparent visible window are arranged on the bonding cavity. According to the novel optimization device and method for improving the bonding deviation, the bonding deviation is effectively prevented, the situation that after a large amount of bonding deviation occurs, a pressing machine still presses downwards, and consequently products are broken is effectively prevented, and the situation that a bonding deviation piece flows out and enters the next procedure, and consequently the product yield is reduced is effectively prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of bonding of semiconductor devices, and in particular to a novel optimization device and method for improving bonding deviation. Background Art

[0002] The new optimization device for bonding offset is a supporting device for semiconductor packaging. As the more popular packaging technologies that have emerged in China in recent years, 5D and 3D chip packaging technologies are very popular in the semiconductor back-end packaging industry. Wafer-level bonding is an indispensable process for 2.5D and 3D, and the bonding process accuracy is particularly important. With the continuous development of science and technology, people have higher and higher requirements for the manufacturing process of the new optimization device for bonding offset.

[0003] The existing new optimization device for bonding offset has certain drawbacks when used. At present, domestic bonding is only in its infancy, and there is little experience in wafer-level bonding. The bonding accuracy cannot meet the process requirements of high-end chip packaging, resulting in poor back-end process. Therefore, the improvement of bonding accuracy is particularly important. Whether the design of the bonding cavity is reasonable is particularly important. Therefore, in order to improve the bonding accuracy, this design is improved based on the mature foreign bonding cavity, which can effectively control the bonding offset and improve the bonding accuracy. To this end, we propose a new optimization device and method for improving bonding offset. Summary of the invention

[0004] Technical problems solved: In view of the deficiencies in the prior art, the present invention provides a new optimization device and method for improving bonding offset, which can effectively prevent bonding offset, effectively prevent the press from still pressing down after a large amount of bonding offset, causing product breakage, and effectively prevent the bond offset sheet from flowing out and entering the next process, causing a decrease in product yield, thereby effectively solving the problems in the background technology.

[0005] Technical solution: To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a new type of optimization device for improving bonding offset, including a device support, a fixed seat is positioned at the bottom of the device support, a bonding support is positioned and installed on the upper end of the device support, a slide rail is positioned on the device support at a position located on the side of the bonding support, a camera support is movably arranged on the slide rail, an optical bracket is positioned at the upper end of the camera support, an optical alignment mechanism is installed at the lower end of the end of the optical bracket, a bonding plate is positioned on the inner side of the bonding support, and a bonding cavity is arranged on the bonding plate.

[0006] As a preferred technical solution of the present application, the bonding chamber is provided with a lower hot plate, a wafer glass assembly, an upper hot plate and a transparent visual window, a detection sensor is provided in the middle of the transparent visual window, displacement sensors are provided around the upper end of the transparent visual window, a limit pin is provided on the lower hot plate for positioning the position of the wafer glass assembly, and a high-precision optical alignment camera is installed on the side of the transparent visual window.

[0007] As a preferred technical solution of the present application, the camera support moves horizontally on the slide rail, and the camera support drives the optical bracket and the optical alignment mechanism to move above the bonding plate, and the optical alignment mechanism moves back and forth to monitor the position of the bonding cavity.

[0008] As a preferred technical solution of the present application, the upper end of the lower heating plate is limited by a limit pin for the wafer glass assembly, and the displacement sensor and the detection sensor are detected at the upper end position of the transparent visual window.

[0009] As a preferred technical solution of the present application, a rail seat is positioned on the side of the outer side of the fixed seat, a sliding seat is movably provided on the upper end of the rail seat, a pillar is positioned on the upper end of the sliding seat, a cross bar is positioned on the inner top of the pillar, a cylinder is positioned in the middle of the upper end of the cross bar, a lifting rod is provided at the bottom of the cylinder, a lifting plate is installed at the bottom of the lifting rod, alignment monitoring cameras are installed on both sides of the bottom of the lifting plate, a compressor is positioned in the middle position of the bottom of the lifting plate, and an adsorption plate is positioned at the bottom of the compressor.

[0010] As a preferred technical solution of the present application, the slide is driven by a servo motor to move on the rail seat, the cylinder drives the lifting rod and drives the lifting plate to move up and down, the compressor drives the adsorption plate to adsorb and grasp the wafer assembly, and the position is monitored by a positioning monitoring camera.

[0011] A new optimization method to improve bonding offset includes the following steps:

[0012] S1: First, before entering the pre-alignment chamber, the optical alignment mechanism performs alignment detection on the wafer and glass. After meeting the requirements, the arm sends the glass and wafer to the pre-bonding chamber and transmits the size and offset data to the pre-bonding chamber;

[0013] S2: Secondly, the bonding device will perform pre-bonding in advance. After pre-bonding, an optical camera will be used in the pre-alignment cavity to pre-detect the bonding offset, and the detection data and wafer size will be sent to the pre-bonding cavity to facilitate the subsequent pre-bonding pin needle lifting;

[0014] S3: Then, after the pre-alignment detection is completed and the requirements are met, the arm pushes the wafer to the bonding chamber. When the bonding chamber is bonding, the outer ring uses the pin needles to control the offset of the bonding piece according to the size information of the optical alignment mechanism received. If the requirements are met, the outer ring pin needles can be lowered. If one side is blocked by the pin needles, the machine alarms and stops the pre-bonding operation.

[0015] S4: After the pin card control is completed, the upper and lower four groups of shooting sensors are offset and the presence of the wafer is detected;

[0016] S5: After the requirements are met, the upper heating plate descends and the bonding operation is carried out. After the wafer and glass bonding operations are completed, the peripheral pins rise again. If they encounter resistance, they stop moving and the machine alarms. If they can rise and fall normally, the accuracy meets the requirements and the bonding operation is completed.

[0017] As a preferred technical solution of the present application, the four groups of beam sensors in step S4 include one group of detection sensors and three groups of displacement sensors.

[0018] As a preferred technical solution of the present application, in the S1 step, an OCR camera is used to perform optical inspection on the glass and the wafer, and the offset in the X, Y, and θ angular directions and the dimensions of the wafer and the glass are measured, and the wafer and the glass are slightly adjusted to meet the needs, and then the data that meets the needs is sent to the pre-alignment cavity.

[0019] As a preferred technical solution of the present application, in the step S1, the glass and the wafer are optically aligned twice respectively, and the two images are compared, and the offset must be satisfied.

[0020] Beneficial effects: Compared with the prior art, the present invention provides a new optimization device and method for improving bonding offset, which has the following beneficial effects: This new optimization device and method for improving bonding offset can effectively prevent bonding offset, effectively prevent the press from still pressing down after a large amount of bonding offset, causing product breakage, and effectively prevent the bonding offset sheet from flowing out and entering the next process, causing the product yield to decrease. First, before entering the pre-alignment cavity, the optical alignment mechanism performs alignment detection on the wafer and the glass. After meeting the requirements, the arm sends the glass and the wafer to the pre-bonding cavity, and transmits the size and offset data to the pre-bonding cavity; secondly, the bonding device will perform pre-bonding in advance, and after pre-bonding, an optical camera will be used in the pre-alignment cavity to perform pre-detection of bonding offset, and the detection data and wafer size will be sent to the pre-bonding cavity, which is convenient for subsequent pre-bonding pin needles. Raise; then, after the pre-alignment detection is completed to meet the requirements, the arm pushes the wafer to the bonding chamber. When the bonding chamber is bonding, the outer circle uses the Pin needle to control the offset of the bonding piece according to the received optical alignment mechanism size information. If the requirements are met, the outer circle Pin needle can be lowered. If one side is blocked by the Pin needle, the machine alarms and stops the pre-bonding operation; after the Pin needle card control is completed, the upper and lower four groups of shooting sensors are offset and the existence of the wafer is detected; after meeting the requirements, the upper hot plate descends to carry out the bonding operation. After the wafer and glass bonding operation is completed, the outer pin needle rises again. If it encounters resistance, it stops and the machine alarms. If it can be raised and lowered normally, the accuracy meets the requirements and the bonding operation is completed. The new optimization device for the entire bonding offset has a simple structure and is easy to operate, and the effect of use is better than that of the traditional method. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the overall structure of a new type of optimization device for improving bonding offset according to the present invention.

[0022] Figure 2 This is a schematic diagram of the process structure of a new type of optimization device for improving bonding offset in the present invention.

[0023] Figure 3 The figure is a schematic diagram of the structure of a bonding cavity in a novel optimization device for improving bonding deviation according to the present invention.

[0024] Figure 4 The present invention is a schematic diagram of the structure of a displacement sensor and a detection sensor in a new type of optimization device for improving bonding offset.

[0025] Figure 5 The figure is a schematic diagram of the structure of an adsorption plate in a novel optimization device for improving bonding deviation according to the present invention.

[0026] Figure 6 This is a schematic diagram of a new optimization method for improving bonding offset according to the present invention.

[0027] In the figure: 1. device support; 2. bonding support; 3. bonding plate; 4. bonding cavity; 5. optical bracket; 6. optical alignment mechanism; 7. slide rail; 8. camera support; 9. fixed seat; 10. transparent visual window; 11. displacement sensor; 12. detection sensor; 13. upper heating plate; 14. high-precision optical alignment camera; 15. limit pin; 16. wafer glass assembly; 17. lower heating plate; 18. rail seat; 19. slide seat; 20. pillar; 21. cylinder; 22. cross bar; 23. lifting rod; 24. lifting plate; 25. compressor; 26. alignment monitoring camera; 27. adsorption plate. DETAILED DESCRIPTION

[0028] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0029] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] like Figure 1-6As shown, a new optimization device for improving bonding offset includes a device support 1, a fixing seat 9 is positioned at the bottom of the device support 1, a bonding support 2 is positioned and installed at the upper end of the device support 1, a slide rail 7 is positioned on the device support 1 at the side of the bonding support 2, a camera support 8 is movably arranged on the slide rail 7, an optical bracket 5 is positioned at the upper end of the camera support 8, an optical alignment mechanism 6 is installed at the lower end of the end of the optical bracket 5, a bonding plate 3 is positioned on the inner side of the bonding support 2, and a bonding cavity 4 is arranged on the bonding plate 3, which effectively prevents bonding offset, effectively prevents the press from still pressing down after a large amount of bonding offset, causing product breakage, and effectively prevents the bonding offset sheet from flowing out and entering the next process, causing a decrease in product yield.

[0032] Furthermore, the bonding chamber 4 is provided with a lower hot plate 17, a wafer glass assembly 16, an upper hot plate 13 and a transparent visual window 10, a detection sensor 12 is provided in the middle of the transparent visual window 10, displacement sensors 11 are provided around the upper end of the transparent visual window 10, a limit pin 15 is provided on the lower hot plate 17 for positioning the position of the wafer glass assembly 16, and a high-precision optical alignment camera 14 is installed on the side of the transparent visual window 10.

[0033] Furthermore, the camera support 8 moves in translation on the slide rail 7 , and the camera support 8 drives the optical bracket 5 and the optical alignment mechanism 6 to move above the bonding plate 3 , and the optical alignment mechanism 6 moves back and forth to monitor the position of the bonding cavity 4 .

[0034] Furthermore, the upper end of the lower heat plate 17 limits the position of the wafer glass assembly 16 through the limiting pin 15 , and the displacement sensor 11 and the detection sensor 12 perform detection at the upper end position of the transparent visual window 10 .

[0035] Furthermore, a rail seat 18 is positioned on the side of the outer side of the fixed seat 9, a slide seat 19 is movably provided on the upper end of the rail seat 18, a pillar 20 is positioned on the upper end of the slide seat 19, a cross bar 22 is positioned on the inner top of the pillar 20, a cylinder 21 is positioned in the middle of the upper end of the cross bar 22, a lifting rod 23 is provided at the bottom of the cylinder 21, a lifting plate 24 is installed at the bottom of the lifting rod 23, alignment monitoring cameras 26 are installed on both sides of the bottom of the lifting plate 24, a compressor 25 is positioned in the middle of the bottom of the lifting plate 24, and an adsorption plate 27 is positioned at the bottom of the compressor 25.

[0036] Furthermore, the slide 19 is driven by a servo motor to move on the rail seat 18, the cylinder 21 drives the lifting rod 23 and drives the lifting plate 24 to move up and down, the compressor 25 drives the adsorption plate 27 to adsorb and grasp the wafer assembly, and the position is monitored by the alignment monitoring camera 26.

[0037] A new optimization method to improve bonding offset includes the following steps:

[0038] S1: First, before entering the pre-alignment chamber, the optical alignment mechanism performs alignment detection on the wafer and glass. After meeting the requirements, the arm sends the glass and wafer to the pre-bonding chamber and transmits the size and offset data to the pre-bonding chamber;

[0039] S2: Secondly, the bonding device will perform pre-bonding in advance. After pre-bonding, an optical camera will be used in the pre-alignment cavity to pre-detect the bonding offset, and the detection data and wafer size will be sent to the pre-bonding cavity to facilitate the subsequent pre-bonding pin needle lifting;

[0040] S3: Then, after the pre-alignment detection is completed and the requirements are met, the arm pushes the wafer to the bonding chamber. When the bonding chamber is bonding, the outer ring uses the pin needles to control the offset of the bonding piece according to the size information of the optical alignment mechanism received. If the requirements are met, the outer ring pin needles can be lowered. If one side is blocked by the pin needles, the machine alarms and stops the pre-bonding operation.

[0041] S4: After the pin card control is completed, the upper and lower four groups of shooting sensors are offset and the presence of the wafer is detected;

[0042] S5: After the requirements are met, the upper heating plate descends and the bonding operation is carried out. After the wafer and glass bonding operations are completed, the peripheral pins rise again. If they encounter resistance, they stop moving and the machine alarms. If they can rise and fall normally, the accuracy meets the requirements and the bonding operation is completed.

[0043] Furthermore, in step S4, the four groups of beam sensors include one group of detection sensors and three groups of displacement sensors.

[0044] Furthermore, in step S1, an OCR camera is used to perform optical inspection on the glass and wafer, and to measure the X, Y, and θ angular offsets and the wafer and glass sizes, and to make slight adjustments to the wafer and glass to meet the requirements, and then the data that meets the requirements is sent to the pre-alignment cavity.

[0045] Furthermore, in step S1, the glass and the wafer are optically aligned twice, and the two images are compared to meet the offset.

[0046] In the first step, the OCR camera performs optical inspection on the glass and wafer, and measures the X, Y, θ angular offset, wafer and glass dimensions, and makes slight adjustments to the wafer and glass to meet the requirements, and then sends the data that meets the requirements to the pre-alignment chamber.

[0047] Wafer&Glass performs optical alignment twice and compares the two images to meet the offset requirement.

[0048] In the second step, the arm sends the glass and wafer to the pre-bonding chamber, and transmits data such as size and offset to the pre-bonding (hereinafter referred to as Pre-Bond) chamber.

[0049] In the third step, Pre-Bond will be performed before Bonding. After Pre-Bond, an optical camera will be used in the pre-alignment cavity to pre-detect the bonding offset, and the detection data and wafer size will be sent to the Bonding cavity (to facilitate the subsequent Bond pin lifting).

[0050] In the fourth step, after the pre-alignment detection is completed and the requirements are met, the arm pushes the wafer to the bonding cavity. When the bonding cavity is bonding, the outer ring uses the pin needles to control the offset of the bonding wafer according to the size information received from the optical alignment mechanism. If the requirements are met, the outer ring pin needles can be lowered. If one side is blocked by the pin needles, the machine alarm will stop the bonding operation.

[0051] Step 5. After the requirements are met, the upper hot plate descends and the Bonding operation is carried out. After the wafer and glass bonding operations are completed, the peripheral pins rise again. If they encounter resistance, they stop moving and the machine alarms. If they can rise and fall normally, the accuracy meets the requirements and the Bonding operation is completed.

[0052] Working principle: The present invention includes a device support 1, a bonding support 2, a bonding plate 3, a bonding cavity 4, an optical bracket 5, an optical alignment mechanism 6, a slide rail 7, a camera support 8, a fixed seat 9, a transparent visual window 10, a displacement sensor 11, a detection sensor 12, an upper hot plate 13, a high-precision optical alignment camera 14, a limit pin 15, a wafer glass assembly 16, a lower hot plate 17, a rail seat 18, a slide seat 19, a pillar 20, a cylinder 21, a cross bar 22, a lifting rod 23, a lifting plate 24, a compressor 25, an alignment monitoring camera 26, and an adsorption plate 27, which can effectively prevent bonding deviation, effectively prevent the press from still pressing down after a large amount of bonding deviation, causing product breakage, and effectively prevent the bonding deviation sheet from flowing out and entering the next process, causing a decrease in product yield.

[0053] It should be noted that, in this article, relational terms such as first and second (number one, number two), etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0054] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A novel optimization device for improving bonding offset, comprising a device support (1), characterized in that: A fixing seat (9) is positioned at the bottom of the device support (1), a bonding support (2) is positioned and installed at the upper end of the device support (1), a slide rail (7) is positioned on the device support (1) at a position on the side of the bonding support (2), a camera support (8) is movably arranged on the slide rail (7), an optical support (5) is positioned at the upper end of the camera support (8), an optical alignment mechanism (6) is installed at the lower end of the end of the optical support (5), a bonding plate (3) is positioned on the inner side of the bonding support (2), and a bonding cavity (4) is arranged on the bonding plate (3).

2. A novel optimization device for improving bonding offset according to claim 1, characterized in that: The bonding chamber (4) is provided with a lower heating plate (17), a wafer glass assembly (16), an upper heating plate (13) and a transparent visual window (10); a detection sensor (12) is provided in the middle of the transparent visual window (10); displacement sensors (11) are provided around the upper end of the transparent visual window (10); a limit pin (15) is provided on the lower heating plate (17) for positioning the wafer glass assembly (16); and a high-precision optical alignment camera (14) is installed on the side of the transparent visual window (10).

3. The novel optimization device for improving bonding offset according to claim 1, characterized in that: The camera support (8) moves in translation on the slide rail (7), and the camera support (8) drives the optical bracket (5) and the optical alignment mechanism (6) to move above the bonding plate (3), and the optical alignment mechanism (6) moves back and forth to monitor the position of the bonding cavity (4).

4. A novel optimization device for improving bonding offset according to claim 2, characterized in that: The upper end of the lower heating plate (17) limits the position of the wafer glass assembly (16) through a limiting pin (15), and the displacement sensor (11) and the detection sensor (12) perform detection at the upper end position of the transparent visual window (10).

5. The novel optimization device for improving bonding offset according to claim 1, characterized in that: A rail seat (18) is positioned on the side of the outer side of the fixed seat (9), a slide seat (19) is movably provided on the upper end of the rail seat (18), a pillar (20) is positioned on the upper end of the slide seat (19), a cross bar (22) is positioned on the inner top of the pillar (20), a cylinder (21) is positioned in the middle of the upper end of the cross bar (22), a lifting rod (23) is provided at the bottom of the cylinder (21), a lifting plate (24) is installed at the bottom of the lifting rod (23), and alignment monitoring cameras (26) are installed on both sides of the bottom of the lifting plate (24), a compressor (25) is positioned at the middle position of the bottom of the lifting plate (24), and an adsorption plate (27) is positioned at the bottom of the compressor (25).

6. A novel optimization device for improving bonding offset according to claim 5, characterized in that: The slide (19) is driven by a servo motor to move on the rail seat (18), the cylinder (21) drives the lifting rod (23) and drives the lifting plate (24) to move up and down, the compressor (25) drives the adsorption plate (27) to adsorb and grasp the wafer assembly, and the position is monitored by the alignment monitoring camera (26).

7. A novel optimization method for improving bonding offset, characterized in that: The specific steps include the following: S1: First, before entering the pre-alignment chamber, the optical alignment mechanism performs alignment detection on the wafer and glass. After meeting the requirements, the arm sends the glass and wafer to the pre-bonding chamber and transmits the size and offset data to the pre-bonding chamber; S2: Secondly, the bonding device will perform pre-bonding in advance. After pre-bonding, an optical camera will be used in the pre-alignment cavity to pre-detect the bonding offset, and the detection data and wafer size will be sent to the pre-bonding cavity to facilitate the subsequent pre-bonding pin needle lifting; S3: Then, after the pre-alignment detection is completed and the requirements are met, the arm pushes the wafer to the bonding chamber. When the bonding chamber is bonding, the outer ring uses the pin needles to control the offset of the bonding piece according to the size information of the optical alignment mechanism received. If the requirements are met, the outer ring pin needles can be lowered. If one side is blocked by the pin needles, the machine alarms and stops the pre-bonding operation. S4: After the pin card control is completed, the upper and lower four groups of shooting sensors are offset and the presence of the wafer is detected; S5: After the requirements are met, the upper heating plate descends and the bonding operation is carried out. After the wafer and glass bonding operations are completed, the peripheral pins rise again. If they encounter resistance, they stop moving and the machine alarms. If they can rise and fall normally, the accuracy meets the requirements and the bonding operation is completed.

8. A novel optimization method for improving bonding offset according to claim 7, characterized in that: In the step S4, the four groups of beam sensors include one group of detection sensors and three groups of displacement sensors.

9. A novel optimization method for improving bonding offset according to claim 7, characterized in that: In the S1 step, an OCR camera is used to perform optical inspection on the glass and the wafer, and the X, Y, and θ angular offsets and the wafer and glass sizes are measured. The wafer and the glass are slightly adjusted to meet the requirements, and the data that meets the requirements is then sent to the pre-alignment chamber.

10. The novel optimization method for improving bonding offset according to claim 7, characterized in that: In the step S1, the glass and the wafer are optically aligned twice respectively, and the two images are compared to meet the offset.

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