Bonding process method

Abstract

The invention discloses a bonding process method, which comprises the following steps that: a first wafer is placed on a top vacuum chuck of bonding equipment, the top vacuum chuck comprises a plurality of circles of vacuum suction holes, and the vacuum degree of the outer circle of vacuum suction holes of the top vacuum chuck is set to be greater than that of the inner circle of vacuum suction holes; therefore, the central inner ring of the first wafer is in a sinking state. And during bonding, the central inner ring is in a sinking form to ensure that the central point of the first wafer is contacted firstly, so that bonding waves are uniformly diffused outwards from the central point of the first wafer. According to the invention, the morphology of the wafer on the top vacuum chuck can be ensured to be stable, so that uniform bonding can be realized.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a semiconductor integrated circuit, and more particularly to a bonding process method. Background Art

[0002] Existing bonding equipment has inner ring vacuum suction holes and outer ring vacuum suction holes in the top chuck. During bonding, the top chuck fixes the wafer through vacuum suction. In the existing method, the vacuum degree (Vacuum) of each vacuum suction hole of the top chuck is set to be the same, that is, the vacuum suction force is the same. However, in the existing method, the wafer itself is prone to warping (BOW). When the warping is too large, the deformation of the wafer is unstable after being fixed on the top chuck, which will affect the contact position during bonding, making it easy to generate bubbles during bonding, thereby affecting the bonding quality.

[0003] As Figure 1 shown, it is a schematic structural diagram of a wafer with a warped morphology placed on a chuck in the existing bonding process method; before bonding, the wafer 103a will be fixed on the top chuck 101, and the wafer 103b will be fixed on the bottom chuck 102. When the wafer 103a itself has a large warping, the vacuum suction force setting of the top chuck 101 cannot flatten the wafer 103a, the deformation of the wafer 103a is unstable, and the lowest point position of the wafer 103a is uncertain. In this way, during bonding, the first contact position between the wafers 103a and 103b is uncertain, and finally the bonding quality will be affected, such as bubbles are likely to be generated. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a bonding process method that can ensure the stable morphology of the wafer on the top vacuum chuck, so as to achieve uniform bonding.

[0005] To solve the above technical problem, the bonding process method provided by the present invention includes the steps of:

[0006] Place the first wafer on the top vacuum chuck of the bonding equipment. The top vacuum chuck includes multiple circles of vacuum suction holes. Set the vacuum degree of the outer ring vacuum suction holes of the top vacuum chuck to be greater than that of the inner ring vacuum suction holes to ensure that the central inner ring of the first wafer is in a sunken state.

[0007] Perform bonding. During the bonding, the sunken state of the central inner ring ensures that the center point of the first wafer contacts first, so that the bonding wave spreads evenly outward from the center point of the first wafer.

[0008] A further improvement is that there are two circles of vacuum suction holes on the top vacuum chuck.

[0009] A further improvement is that the vacuum degree of the outer ring vacuum suction holes of the top vacuum chuck is more than 50 mbar greater than that of the inner ring vacuum suction holes.

[0010] A further improvement is that the first wafer has a warped morphology.

[0011] A further improvement is that the number of the outer ring vacuum suction holes of the top vacuum chuck includes six, and each of the outer ring vacuum suction holes is equally angularly distributed on the same circle.

[0012] A further improvement is that the number of the inner ring vacuum suction holes of the top vacuum chuck includes three, and each of the inner ring vacuum suction holes is equally angularly distributed on the same circle.

[0013] A further improvement is that before the bonding, it further includes setting the second wafer on the bottom chuck.

[0014] The bonding bonds the first wafer and the second wafer together.

[0015] A further improvement is that the bottom chuck uses a vacuum chuck.

[0016] A further improvement is that when the second wafer is fixed, the vacuum degrees of the vacuum suction holes on the bottom chuck are the same.

[0017] The present invention makes a special setting on the vacuum degree, i.e., the suction force, of the vacuum suction holes of the top vacuum chuck. A greater vacuum degree means a greater suction force. That is, the vacuum degree of the outer ring vacuum suction holes is set to be greater than that of the inner ring vacuum suction holes. In this way, it can be ensured that the first wafer sinks in the center inner ring under the combined action of gravity and vacuum suction force. That is, even if the first wafer has a warped morphology, finally, it can be ensured that the position of the center inner ring is the lowest. In this way, the situation where the lowest position of the first wafer appears randomly when the first wafer has a warped morphology can be eliminated. Therefore, finally, it can be ensured that the center point of the first wafer first contacts during bonding and further ensure uniform bonding. Therefore, the present invention can ensure the stable morphology of the wafer on the top vacuum chuck, thereby realizing uniform bonding. Description of the Drawings

[0018] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments:

[0019] Figure 1 is a schematic structural diagram of a warped wafer placed on a chuck in the existing bonding process method;

[0020] Figure 2 is a flowchart of the bonding process method of the embodiment of the present invention;

[0021] Figure 3AIt is a schematic structural diagram after the wafer is placed on the chuck in the bonding process method of the embodiment of the present invention;

[0022] Figure 3B It is a schematic structural diagram during bonding in the bonding process method of the embodiment of the present invention;

[0023] Figure 4 It is a distribution diagram of the vacuum suction holes of the top vacuum chuck in the bonding process method of the embodiment of the present invention. Detailed implementation manners

[0024] As Figure 2 shown, it is a flowchart of the bonding process method of the embodiment of the present invention; as Figure 3A shown, it is a schematic structural diagram after the wafer is placed on the chuck in the bonding process method of the embodiment of the present invention; as Figure 3B shown, it is a schematic structural diagram during bonding in the bonding process method of the embodiment of the present invention; the bonding process method of the embodiment of the present invention includes the steps:

[0025] Step S101, as Figure 3A shown, place the first wafer 203a on the top vacuum chuck 201 of the bonding equipment. The top vacuum chuck 201 includes multiple circles of vacuum suction holes. Set the vacuum degree of the outer - circle vacuum suction holes 301a of the top vacuum chuck 201 to be greater than that of the inner - circle vacuum suction holes 301b to ensure that the central inner circle of the first wafer 203a is in a sunken state.

[0026] In the embodiment of the present invention, there are two circles of vacuum suction holes on the top vacuum chuck 201. As Figure 4 shown, it is a distribution diagram of the vacuum suction holes of the top vacuum chuck 201 in the bonding process method of the embodiment of the present invention. The two circles of vacuum suction holes on the top vacuum chuck 201 are respectively the outer - circle vacuum suction holes 301a and the inner - circle vacuum suction holes 301b.

[0027] In some embodiments, the vacuum degree of the outer - circle vacuum suction holes 301a of the top vacuum chuck 201 is more than 50 mbar greater than that of the inner - circle vacuum suction holes 301b.

[0028] In some embodiments, the first wafer 203a has a warped morphology. It can be seen from Figure 3A this that even if the first wafer 203a warps, the lowest position is ensured to be at the central inner circle of the first wafer 203a.

[0029] In some embodiments, as Figure 4 shown, the number of the outer - circle vacuum suction holes 301a of the top vacuum chuck 201 is 6, and each of the outer - circle vacuum suction holes 301a is equally - angularly distributed on the same circle.

[0030] The number of inner - ring vacuum suction holes 301b of the top vacuum chuck 201 is 3, and each of the inner - ring vacuum suction holes 301b is equally - angularly distributed on the same circle.

[0031] In the embodiment of the present invention, as Figure 3A shown, before the bonding, it further includes setting the second wafer 203b on the bottom chuck 202.

[0032] The bottom chuck 202 adopts a vacuum chuck.

[0033] Meanwhile, referring to Figure 3B shown, when the second wafer 203b is fixed, the vacuum degrees of the vacuum suction holes 302 on the bottom chuck 202 are the same.

[0034] Step S102: As Figure 3B shown, perform bonding. During the bonding, the central inner - ring presents a sunken shape to ensure that the center point of the first wafer 203a contacts first, so that the bonding wave spreads uniformly outward from the center point of the first wafer 203a.

[0035] The bonding bonds the first wafer 203a and the second wafer 203b together.

[0036] By Figure 3B shown, during the bonding, the ejector pin 303 also passes through the top vacuum chuck 201 to press down the first wafer 203a. The ejector pin 303 is located in the central area of the top vacuum chuck 201.

[0037] In the embodiment of the present invention, the vacuum degree (i.e., suction force) of the vacuum suction holes of the top vacuum chuck 201 is specially set. The larger the vacuum degree, the greater the suction force. That is, the vacuum degree of the outer - ring vacuum suction holes 301a is set to be greater than that of the inner - ring vacuum suction holes 301b. In this way, it can be ensured that the first wafer 203a presents a sunken shape in the central inner - ring under the combined action of gravity and vacuum suction force. That is, even if the first wafer 203a has a warped morphology, finally, it can be ensured that the position of the central inner - ring is the lowest. In this way, the situation where the lowest position of the first wafer 203a will randomly appear when the first wafer 203a has a warped morphology can be eliminated. Therefore, finally, it can be ensured that the center point of the first wafer 203a contacts first during bonding and further ensure uniform bonding. Therefore, the embodiment of the present invention can ensure the stable morphology of the wafer on the top vacuum chuck 201, thereby realizing uniform bonding.

[0038] In the embodiments of the present invention, according to the bonding principle, the vacuum settings of the inner and outer rings of the top chuck are optimized, and the vacuum suction force of the outer ring is about 50 mbr greater than that of the inner ring, so that the shape of the wafer with a relatively large BOW value on the top chuck is stably in the shape of slightly sinking in the central inner ring. Ensure that during the bonding process, the center point, that is, the mechanical action point, contacts first, and the bonding wave uniformly and stably diffuses from the center point to the outer ring perimeter.

[0039] In the embodiments of the present invention, the shape of the wafer with a large BOW value is stabilized on the top chuck, so that the bonding wave is uniform and stable, ensuring that the probability of product bubble generation is reduced.

[0040] The present invention has been described in detail through specific embodiments above, but these do not constitute a limitation to the present invention. Without departing from the principle of the present invention, those skilled in the art can also make many modifications and improvements, which should also be regarded as the protection scope of the present invention.

Claims

1. A bonding process method, characterized in that, Including the steps: Place the first wafer on the top vacuum chuck of the bonding equipment. The top vacuum chuck includes multiple circles of vacuum suction holes. Set the vacuum degree of the outer - circle vacuum suction holes of the top vacuum chuck to be greater than that of the inner - circle vacuum suction holes to ensure that the central inner circle of the first wafer is in a sunken shape; Perform bonding. During the bonding, the sunken shape of the central inner circle ensures that the center point of the first wafer contacts first, so that the bonding wave spreads uniformly outward from the center point of the first wafer.

2. The bonding process method according to claim 1, characterized in that: There are two circles of vacuum suction holes on the top vacuum chuck.

3. The bonding process method according to claim 2, wherein: The vacuum degree of the outer - circle vacuum suction holes of the top vacuum chuck is more than 50 mbar greater than that of the inner - circle vacuum suction holes.

4. The bonding process method according to claim 1, characterized in that: The first wafer has a warped topography.

5. The bonding process method according to claim 2, characterized in that: The number of the outer - circle vacuum suction holes of the top vacuum chuck is 6, and each of the outer - circle vacuum suction holes is equally - angularly distributed on the same circle.

6. The bonding process method according to claim 5, wherein: The number of the inner - circle vacuum suction holes of the top vacuum chuck is 3, and each of the inner - circle vacuum suction holes is equally - angularly distributed on the same circle.

7. The bonding process method according to claim 1, characterized in that: Before the bonding, it also includes setting the second wafer on the bottom chuck; The bonding bonds the first wafer and the second wafer together.

8. The bonding process method according to claim 7, characterized in that: The bottom chuck uses a vacuum chuck.

9. The bonding process method according to claim 8, characterized in that: When the second wafer is fixed, the vacuum degrees of the vacuum suction holes on the bottom chuck are the same.

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