Chuck and deformation method for realizing wafer deformation

Abstract

The present application relates to the technical fields of semiconductor wafer packaging, in particular to a chuck for realizing wafer deformation and a deformation method. The chuck comprises a chuck deformation part, which is located on a base. The upper part of the chuck deformation part is a plane, and the lower part is a convex part protruding downward. An upper sensor is arranged above the chuck deformation part, and a lower sensor is arranged at the center of the upper surface of the base. The upper and lower sensors are distance measuring sensors, which can monitor the deformation amount before each bonding and can feedback the deformation amount so that the deformation amount is more in line with the process requirements. When the chuck is deformed, the wafer and the chuck deformation part are deformed synchronously, protruding upward or sinking downward, so that the distance between the mark points on the wafer changes by nanometers. The mark point error generated by different batches of wafers is compensated by the method of the present application, so that the distance between the two mark points required during alignment is changed, and the alignment accuracy is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor wafer packaging, in particular to a chuck for wafer deformation and a deformation method. BACKGROUND

[0002] With the increasing demand for chip functions, it is increasingly difficult to improve performance by reducing transistor size, so integrated circuit technology is gradually developing from 2D plane to 3D integration. In 3D integration technology, wafer bonding is the most important link in the technology. In addition, with the increasing demand for wafer bonding accuracy, the alignment pre-bonding accuracy in the hybrid bonding field has been improved to 50 nm level. Under the bonding accuracy requirement of below 200 nm, the error introduced by the warping of the wafer itself has a more and more prominent influence on the accuracy.

[0003] Currently, equipment manufacturers mainly use negative pressure to adsorb the wafer at the edge, and use pneumatic blowing at the center to make the middle part of the wafer bulge upward and deform. This method has high requirements for pressure control, and the wafer is very thin and has poor rigidity. The arc-shaped protrusion generated after deformation under pneumatic driving and the height difference with the chuck itself will have a great influence on the visual recognition accuracy. SUMMARY

[0004] The purpose of the present application is to provide a chuck for wafer deformation and a deformation method. The wafer adsorbed on the chuck is deformed by physical method, so that the arc shape of the wafer and the chuck deformation is consistent, thereby solving the problem of wafer warping.

[0005] In order to solve the above technical problems, the present application provides the following technical solutions:

[0006] A chuck for wafer deformation, comprising a chuck deformation part, the chuck deformation part is located on a base, the upper part of the chuck deformation part is a plane, and the lower part is a downward protruding protruding part; an upper sensor is arranged above the chuck deformation part, and a lower sensor is arranged at the center of the upper surface of the base. The upper and lower sensors are distance measuring sensors, which can monitor the deformation amount before each bonding and can feedback the deformation amount to make the deformation amount more meet the process requirements.

[0007] The material of the chuck deformation part is silicon nitride. Compared with the traditional ceramic material, silicon nitride has lower thermal expansion coefficient and better mechanical properties.

[0008] The upper surface of the chuck deformed part is arranged with a wafer, and the upper sensor is located above the wafer; the upper sensor is used for scanning and measuring the distance between a plurality of measuring points on the upper surface of the wafer and the upper sensor; the lower sensor is used for measuring the distance between the center point of the lower surface of the chuck deformed part and the lower sensor. Further, the plurality of measuring points are equidistant points on a straight line passing through the center point of the upper surface of the wafer.

[0009] The chuck is uniformly arranged with at least three wafer transmission jacks, and the wafer transmission jacks can move up and down along the guide pipe on the base and the top pin hole through the chuck deformed part.

[0010] The center of the chuck deformed part is provided with a gas hole, the gas hole passes through the upper plane and the lower convex part of the chuck deformed part; the upper part and the lower part of the chuck deformed part are fixed together through a flange.

[0011] Further, the inside of the base is provided with a first air channel and a second air channel; the first air channel is in communication with the gas hole.

[0012] Further, one end of the first air channel is connected with a vacuum pumping device.

[0013] The cross-sectional shape of the convex part of the lower part of the chuck deformed part is an arc structure similar to a parabola; the thickness of the central part of the chuck deformed part is greater than the thickness of the edge part. If the bottom of the chuck deformed part is a plane, in the case of being fixed at the edge, after the positive pressure fluid is introduced to make the chuck deformed part protrude, the shape of the protrusion of the middle part will produce a structure similar to a plane, which makes the center not "point" contact but "surface" contact in the bonding process (while the center point of the wafer after protrusion is required in actual production). Thus, it is possible to produce bonding holes between the two wafers after bonding. The convex part of the lower part of the chuck deformed part of the present application adopts an arc structure similar to a parabola, which can give the upper surface of the chuck deformed part a structure similar to a parabolic protrusion under the action of gas pressure, so that the center of the chuck deformed part produces the highest point protrusion, and the wafer adsorbed on the upper surface of the chuck deformed part presents a protrusion similar to a parabola, producing "point" contact at the beginning of bonding, and then recovering the initial shape due to material elasticity after the upper and lower wafers are released from vacuum, producing a bonding wave, discharging the atmosphere between the wafers, and solving the problem of bonding holes.

[0014] The upper surface of the deformable portion of the chuck is provided with multiple protrusions. This bump structure reduces the actual contact area between the wafer and the chuck, thus reducing the risk of contamination from metal particles and particulate matter generated during contact. Another advantage of using the bump structure is that, due to the reduced contact area, the wafer can undergo "micro-slippage" as it deforms with the chuck, allowing it to deform more effectively and adaptively conform to the chuck.

[0015] The base and the protruding part at the bottom of the deformable part of the chuck form an independent cavity.

[0016] Furthermore, an injection hole is provided in the middle of the upper surface of the base, and the second air passage is connected to the independent cavity through the injection hole.

[0017] Alternatively, another approach can be adopted, namely: at least one air chamber is formed between the base and the protrusion at the lower part of the deformable portion of the chuck; each air chamber is connected to an air passage, and the pressure in the corresponding air chamber is controlled through the air passage.

[0018] Furthermore, the center of the chuck deformation part and the base is provided with a vacuum channel that runs through the upper and lower bottom surfaces of the chuck deformation part and the base.

[0019] The air chamber is an annular air chamber. When there are two or more air chambers, all the air chambers are arranged sequentially from the inside to the outside around the vacuum channel, and adjacent air chambers are separated from each other. The vacuum channel and the corresponding air chamber are separated from each other and sealed by a sealing ring. By setting an annular partition to form multiple independent air chambers, when the deformable part of the chuck deforms, the air chambers can control the micro-deformation to meet the deformation structure requirements.

[0020] Furthermore, there are four air chambers, which are arranged from the inside out as the first air chamber, the second air chamber, the third air chamber, and the fourth air chamber. The first air chamber, the second air chamber, the third air chamber, and the fourth air chamber are connected to the third air passage, the fourth air passage, the fifth air passage, and the sixth air passage, respectively. The third air passage, the fourth air passage, the fifth air passage, and the sixth air passage all penetrate the upper and lower bottom surfaces of the base.

[0021] The conduit and the corresponding air chamber are separated from each other, and a sealing ring ensures a seal.

[0022] The method for modifying the chuck described in this invention specifically includes the following steps:

[0023] (1) When positive pressure fluid is introduced, the chuck deformed part bulges upward, which in turn causes the wafer vacuum adsorbed on the upper surface of the chuck deformed part to bulge upward as well; the upper sensor scans multiple measurement points on the upper surface of the wafer, the chuck deformed part causes the wafer to gradually flatten, and the distance of each measurement point from the upper sensor is recorded. When the difference between the maximum and minimum values ​​is less than the preset value, the wafer is considered to be flattened; at the same time, the lower sensor records the distance d1 between the center point of the lower surface of the chuck deformed part and the lower sensor.

[0024] (2) Continue to apply positive pressure to make the chuck bulge and deform. The lower sensor monitors in real time the distance between the center of the lower surface of the chuck and the lower sensor until it reaches d1+Δd. Maintain the pressure to fix the degree of deformation of the chuck and record the pressure as F1. Wherein, Δd is a preset value, representing the preset deformation amount of the center point of the chuck.

[0025] (3) The upper sensor continues to scan multiple measurement points on the upper surface of the wafer to obtain the actual deformation of each point. The actual deformation of each point is subtracted from the distance measured when the wafer is flattened in step (1), and the deformation curve is obtained by fitting. If the deformation curve meets the requirements, the subsequent bonding process is continued; if it does not meet the requirements, the pressure is finely adjusted based on the pressure F1, and the detection of this step is repeated.

[0026] Compared with the prior art, the chuck and deformation method for wafer deformation of the present invention have at least the following advantages:

[0027] Beneficial effects:

[0028] (1) The chuck and deformation method of the present invention are mainly applied to wafer-level bonding. Before bonding two wafers, it is necessary to compensate for the overlay accuracy of the wafer. The wafer is adsorbed to the deformed part of the chuck by negative pressure. When the chuck is deformed, the wafer and the deformed part of the chuck are synchronously deformed upward or downward, so as to make the distance between the marking points on the wafer change at the nanometer level.

[0029] (2) The method of the present invention compensates for the mark point error generated by different batches of wafers, thereby changing the distance between the two mark points required for alignment, and thus improving the alignment accuracy.

[0030] (3) The present invention uses a combination of upper and lower sensors to measure the degree of wafer deformation: First, the upper sensor can measure the degree of slight collapse of the wafer itself before positive pressure is introduced into the cavity, so that the chuck can deform upward to compensate for the collapse and make the wafer flat; Second, after positive pressure is introduced into the cavity, when the lower sensor detects that the center of the lower surface of the protrusion reaches a preset distance from the lower sensor, the upper sensor can also measure the degree of deformation of the upper surface of the wafer with high precision, that is, the actual deformation of the wafer. Since the upper surface of the wafer is the bonding surface, the bonding effect can be guaranteed more intuitively and accurately; Third, the lower sensor can measure the distance between the center of the chuck protrusion and the lower sensor in real time during the deformation process to provide a criterion for stopping the deformation and improve work efficiency.

[0031] (4) The lower part of the chuck deformation section adopts a parabolic arc structure. Under the action of gas pressure, this structure can give the upper surface of the chuck deformation section a parabolic upward convex structure. When the subsequent bonding begins, it can make "point" contact with another wafer to be bonded, thus solving the problem of voids generated during wafer bonding.

[0032] The chuck and deformation method for wafer deformation according to the present invention will be further described below with reference to the accompanying drawings. Attached Figure Description

[0033] Figure 1 This is a three-dimensional schematic diagram of the chuck for wafer deformation according to the present invention;

[0034] Figure 2 A three-dimensional schematic diagram of the deformed part of the chuck;

[0035] Figure 3 This is a three-dimensional schematic diagram of the base;

[0036] Figure 4 This is the front view of the deformed part of the chuck;

[0037] Figure 5 This is a top view of the deformed part of the chuck;

[0038] Figure 6 This is a longitudinal section view of the base;

[0039] Figure 7 This is a top view of the base;

[0040] Figure 8 This is a schematic diagram showing the state before fluid is introduced.

[0041] Figure 9 This is a schematic diagram showing the state when filled with positive pressure fluid;

[0042] Figure 10 This is a schematic diagram showing the state when a negative pressure fluid is introduced.

[0043] Figure 11 This is a longitudinal cross-sectional view of another structural form of the chuck for wafer deformation according to the present invention;

[0044] Figure 12 This is a magnified view of the upper surface of the deformed part of the chuck.

[0045] Among them, 1-chuck deformation part, 2-base, 101-ejector hole, 102-air hole, 21-conduit, 22-lower sensor, 23-first air channel, 24-second air channel, 25-injection hole; 3-wafer transfer ejector, 4-first O-ring, 5-second O-ring, 6-third O-ring, 7-vacuum channel, 8-third air channel, 9-fourth air channel, 10-fifth air channel, 11-sixth air channel, 12-first air chamber, 13-second air chamber, 14-third air chamber, 15-fourth air chamber, 16-protrusion, 17-upper sensor. Detailed Implementation

[0046] like Figures 1-6 and Figure 9 As shown, a chuck for wafer deformation is provided. The chuck is a lower chuck and includes a chuck deformation part 1. The chuck deformation part 1 is located on a base 2. The upper part of the chuck deformation part 1 is a flat surface used to support the wafer. The lower part is a downward protruding part. An upper sensor 17 is provided above the chuck deformation part 1, and a lower sensor 22 is provided at the center of the upper surface of the base 2.

[0047] A wafer is placed on the upper surface of the chuck deformation portion 1, and the upper sensor 17 is located above the wafer. The upper sensor 17 is used to scan and measure the distance between multiple measurement points on the upper surface of the wafer and the upper sensor. The lower sensor 22 is used to measure the distance between the center point of the lower surface of the chuck deformation portion and the lower sensor 22. The multiple measurement points are multiple equally spaced points on a straight line passing through the center point of the upper surface of the wafer.

[0048] like Figure 3 , 5 As shown in -6 and 11, three wafer transfer push rods 3 (for transferring wafers) are evenly distributed on the chuck. The wafer transfer push rods 3 can move up and down along the push pin hole 101 that passes through the deformed part 1 of the chuck and the guide tube 21 on the base 2.

[0049] The chuck deformation section 1 has a central vent 102, which extends through the upper plane and lower protrusion of the chuck deformation section 1. The upper and lower parts of the chuck deformation section 1 are fixed together by a flange, and the joint is sealed with an O-ring. After the force driving the deformation is released, the chuck deformation section 1 can still restore a high degree of surface flatness (i.e., the upper plane returns to flatness, and the downward protrusion returns to its state when no positive or negative pressure is applied). Both the upper and lower parts of the chuck deformation section are made of silicon nitride, which has a certain degree of elasticity. Compared with traditional ceramic materials, silicon nitride has a lower coefficient of thermal expansion and better mechanical properties.

[0050] like Figure 12 As shown, the upper surface of the chuck deformation portion 1 has multiple protrusions 16. This structure can reduce the actual contact area between the wafer and the chuck, reducing the risk of contamination from metal particles and particulate matter generated by contact; moreover, because the contact area is reduced, the wafer can generate "micro-slip" when deforming with the chuck, and deform better with the chuck, so that the wafer can adaptively conform to the chuck.

[0051] like Figure 5 , 7 As shown, the base 2 has a first air channel 23 and a second air channel 24 inside; the first air channel 23 is connected to the air hole 102. A vacuum pumping device is connected to one end of the first air channel 23 to provide negative pressure and to provide a vacuum for wafer adsorption by drawing a vacuum through the first air channel 23.

[0052] The base 2 and the protruding part at the bottom of the deformable part 1 of the chuck form an independent cavity. For example... Figure 7 As shown, an injection hole 25 is provided in the middle of the upper surface of the base 2, and the second air passage 24 is connected to the independent cavity through the injection hole 25. The second air passage 24 is used to pass positive pressure fluid or negative pressure fluid. By filling the independent cavity with positive pressure, the plane on the upper part of the chuck deformation part 1 can be deformed.

[0053] In another advantageous embodiment, such as Figure 11As shown, four air chambers are formed between the base 2 and the protrusion at the lower part of the chuck deformation section 1; each air chamber is connected to an air passage, and the pressure in the corresponding air chamber is controlled through the air passage. A vacuum passage 7 is provided at the center of the chuck deformation section 1 and the base 2, penetrating the upper and lower bottom surfaces of the chuck deformation section 1 and the base 2. The air chambers are annular, and all the air chambers are arranged sequentially from the inside to the outside around the vacuum passage 7, with adjacent air chambers separated from each other; the vacuum passage 7 is separated from the corresponding air chamber by a sealing ring to ensure a seal. The four air chambers, from the inside out, are designated as first air chamber 12, second air chamber 13, third air chamber 14, and fourth air chamber 15. These chambers are connected to third air passage 8, fourth air passage 9, fifth air passage 10, and sixth air passage 11, respectively. All four air passages (8, 9, 10, and 11) penetrate the upper and lower bottom surfaces of the lower chuck 2. The conduit 21 is separated from the corresponding air chambers by sealing rings to ensure a tight seal.

[0054] like Figure 8 As shown, the top is the wafer, the middle is the chuck deformation section, and the bottom is the base. All remain in their initial state before fluid is introduced into the cavity. The wafer is placed on the upper surface of the chuck deformation section 1. When no positive pressure is applied, the wafer rests on the upper surface of the chuck. The wafer is not perfectly flat; due to the gravity of the wafer and the chuck, as well as the warping of the wafer itself, there is a very slight indentation or collapse on the wafer as a whole.

[0055] The method for modifying this chuck specifically includes the following steps:

[0056] (1) As Figure 9 As shown, when positive pressure fluid is introduced into the second air passage 24, the deformable part of the chuck bulges upward, which in turn causes the wafer vacuum-adsorbed on the upper surface of the deformable part of the chuck to bulge upward as well. The upper sensor scans multiple measurement points on the upper surface of the wafer, and the deformable part of the chuck causes the wafer to gradually flatten. The distance h1, h2, h3, etc. from each measurement point to the upper sensor is recorded. When the difference between the maximum and minimum values ​​is less than the preset value, it is considered that the wafer has been flattened (that is, the wafer collapse has been compensated, and the distance between each point on the wafer surface and the sensor is basically the same). At the same time, the lower sensor records the distance d1 between the center point of the lower surface of the deformable part of the chuck and the lower sensor.

[0057] (2) Continue to apply positive pressure to make the chuck bulge and deform. The lower sensor monitors in real time the distance between the center of the lower surface of the chuck and the lower sensor until it reaches d1+Δd. Maintain the pressure to fix the degree of deformation of the chuck and record the pressure as F1. Wherein, Δd is a preset value, representing the preset deformation amount of the center point of the chuck.

[0058] (3) The upper sensor continues to scan multiple measurement points on the upper surface of the wafer to obtain the actual deformation of each point. The actual deformation of each point is subtracted from the distance measured when the wafer is flattened in step (1), and the deformation curve is obtained by fitting. If the deformation curve meets the requirements, the subsequent bonding process is continued; if it does not meet the requirements, the pressure is finely adjusted based on the pressure F1, and the detection of this step is repeated.

[0059] (4) Figure 10 As shown, when negative pressure fluid is introduced into the second air passage 24, the deformed part of the chuck is concave downwards, which in turn causes the wafer that is vacuum-adsorbed on the upper surface of the deformed part of the chuck to also be concave downwards and deformed.

[0060] The chuck of this invention can deform the wafer upwards or downwards through positive and negative pressure fluid control, whereas existing chucks can often only bulge upwards and cannot dent downwards. The deformation method of this invention can precisely adjust the height of the upward bulge and the deformation curve by adjusting the pressure.

[0061] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A chuck for wafer deformation, characterized in that: Includes a chuck deformation part (1), which is located on the base (2). The upper part of the chuck deformation part (1) is a flat surface, and the lower part is a downward protruding part. An upper sensor (17) is provided above the chuck deformation part (1), and a lower sensor (22) is provided at the center of the upper surface of the base (2). The upper surface of the chuck deformation part (1) is provided with multiple protrusions (16). A wafer is placed on the upper surface of the chuck deformation portion (1), and the upper sensor (17) is located above the wafer; the upper sensor (17) is used to scan and measure the distance between multiple measurement points on the upper surface of the wafer and the upper sensor; the lower sensor (22) is used to measure the distance between the center point of the lower surface of the chuck deformation portion and the lower sensor (22); The cross-sectional shape of the protrusion at the lower part of the chuck deformation part (1) is a parabolic arc structure; the thickness of the central part of the chuck deformation part (1) is greater than the thickness of the edge part; The base (2) and the protrusion at the bottom of the chuck deformation part (1) form an independent cavity.

2. The chuck for wafer deformation according to claim 1, characterized in that: The multiple measurement points are multiple equally spaced points on a straight line passing through the center point of the upper surface of the wafer.

3. The chuck for wafer deformation according to claim 1, characterized in that: The center of the chuck deformation part (1) is provided with an air hole (102), which penetrates the upper plane and the lower protrusion of the chuck deformation part (1); the upper and lower parts of the chuck deformation part (1) are fixed together by a flange.

4. The chuck for wafer deformation according to claim 3, characterized in that: The base (2) is provided with a first air passage (23) and a second air passage (24); one end of the first air passage (23) is connected to the air hole (102), and the other end is connected to the vacuum device.

5. The chuck for wafer deformation according to claim 4, characterized in that: An injection hole (25) is provided in the middle of the upper surface of the base (2), and the second air passage (24) is connected to the independent cavity through the injection hole (25).

6. The chuck for wafer deformation according to claim 1, characterized in that: At least one air chamber is formed between the base (2) and the protrusion at the lower part of the chuck deformation part (1); each air chamber is connected to an air passage, and the pressure in the corresponding air chamber is controlled by the air passage.

7. The chuck for wafer deformation according to claim 6, characterized in that: The center of the chuck deformation part (1) and the base (2) is provided with a vacuum channel (7) that runs through the upper and lower bottom surfaces of the chuck deformation part (1) and the base (2).

8. The chuck for wafer deformation according to claim 7, characterized in that: The air chamber is an annular air chamber. When there are two or more air chambers, all the air chambers are arranged in sequence from the inside to the outside around the vacuum channel (7), and the adjacent air chambers are separated from each other. The vacuum channel (7) is separated from the corresponding air chambers, and the sealing is ensured by the sealing ring.

9. A method for modifying the chuck according to any one of claims 1-8, characterized in that, Includes the following steps: (1) When positive pressure fluid is introduced, the chuck deformed part bulges upward, which in turn causes the wafer vacuum adsorbed on the upper surface of the chuck deformed part to bulge upward and deform together; the upper sensor scans multiple measurement points on the upper surface of the wafer, the chuck deformed part causes the wafer to gradually flatten, and the distance of each measurement point from the upper sensor is recorded. When the difference between the maximum and minimum values ​​is less than the preset value, it is considered that the wafer has been flattened; at the same time, the lower sensor records the distance d1 between the center point of the lower surface of the chuck deformed part and the lower sensor at this time. (2) Continue to apply positive pressure to make the chuck bulge and deform. The lower sensor monitors the distance between the center of the lower surface of the chuck and the lower sensor in real time until it reaches d1+Δd. Maintain the pressure to fix the degree of deformation of the chuck and record the pressure as F1. Wherein, Δd is a preset value, representing the preset deformation amount of the center point of the chuck. (3) The upper sensor continues to scan multiple measurement points on the upper surface of the wafer to obtain the actual deformation of each point. The actual deformation of each point is subtracted from the distance measured when the wafer is flattened in step (1), and the deformation curve is obtained by fitting. If the deformation curve meets the requirements, the subsequent bonding process is continued; if it does not meet the requirements, the pressure is finely adjusted based on the pressure F1, and the detection of this step is repeated.

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