Structure of semiconductor device and method for bonding two substrates

A structure of semiconductor device is provided. The structure includes a first bonding pattern, formed on a first substrate. A first grating pattern is disposed on the first substrate, having a plurality of first bars extending along a first direction. A second bonding pattern is formed on a second substrate. A second grating pattern, disposed on the second substrate, having a plurality of second bars extending along the first direction. The first bonding pattern is bonded to the second bonding pattern. One of the first grating pattern and the second grating pattern is stacked over and overlapping at the first direction with another one of the first grating pattern and the second grating pattern. A first gap between adjacent two of the first bars is different from a second gap between adjacent two of the second bars.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a semiconductor fabrication technology, in particular, to a structure of semiconductor device and method for bonding two substrates.

Description of Related Art

In development for the semiconductor fabrication technology, the fabrication may be divided into two parts, in which the corresponding circuits are respectively fabricated on two substrates. To the individual substrate, after accomplishing the fabrication of the circuit, the surface of the substrate, which is to be bonding to the circuit of another substrate, would be formed with a plurality of bonding pads at the corresponding locations. Then, the two substrates are bonded according to the packaging technology. At the ideal condition, the bonding pads of the two substrates would be precisely bonded together, to form the whole integrated circuit.

In bonding process for the two substrates, the two substrates need to be aligned therebetween, before performing the bonding the substrates. In a conventional way, each substrate is fabricated to have an alignment mark together with the actual integrated circuit. The alignments marks in the two substrates are compared to measure the aligning quality between the two substrates.

As usually known, if the misalignment occurs, at least the bond pads such as the metal pads in the two substrates would also shift to each other, and a bond surface would be in contact with the dielectric layer, which is an inter-layer dielectric and surrounds the bond pad. The bonding process usually includes an annealing process in high temperature to bond the metallic material of the bond pads. Then, under the situation with severe misalignment, a void would occur at the interface between the metal pad and the dielectric layer. It causes a defect in bonding quality. To the alignment marks, if the void occurs on the metal alignment marks, the alignment quality with the capability to measure the alignment quality would get worse.

A design of the alignment marks to improve the bonding process for boding two substrates is still under development.

SUMMARY OF THE INVENTION

The invention proposes the alignment marks respectively formed in two substrates. When the two substrates are bonded, the alignment marks are in overlapping when looking over the plane of the substrate. In addition, patterns of the alignment marks allow to efficiently measure the alignment quality between the two substrates.

In an embodiment, the invention provides a structure of semiconductor device. The structure includes a first bonding pattern, formed on a first substrate. A first grating pattern is disposed on the first substrate, having a plurality of first bars extending along a first direction. A second bonding pattern is formed on a second substrate. A second grating pattern, disposed on the second substrate, having a plurality of second bars extending along the first direction. The first bonding pattern is bonded to the second bonding pattern. One of the first grating pattern and the second grating pattern is stacked over and overlapping at the first direction with another one of the first grating pattern and the second grating pattern. A first gap between adjacent two of the first bars is different from a second gap between adjacent two of the second bars.

In an embodiment, as to the structure of semiconductor device, a bar end of the first bars is matched to a bar end of the second bars at one side of the first bars.

In an embodiment, as to the structure of semiconductor device, a bar end of the first bars is constantly shifted from a bar end of the second bars at one side of the first bars.

In an embodiment, as to the structure of semiconductor device, one of the first bars and the second bars is numbered as a plurality of numbered bars while another one is a plurality of comparison bars. The numbered bars have a reference bar assigned with a reference number, wherein a misalignment level is determined by a shift from the reference bar for a detected one of the numbered bars being most matching to one of the comparison bars.

In an embodiment, as to the structure of semiconductor device, the reference number as assigned to the reference bar is “0”, a first side with respect to “0” is negatively numbered and a second side with respect to “0” is positively numbered.

In an embodiment, as to the structure of semiconductor device, the first bars are longer than the second bars or the first bars are shorter than the second bars.

In an embodiment, as to the structure of semiconductor device, further, a third grating pattern is disposed on the first substrate, having a plurality of third bars extending along a second direction perpendicular to the first direction. a fourth grating pattern is disposed on the second substrate, having a plurality of fourth bars extending along the second direction. One of the third grating pattern and the fourth grating pattern is stacked over and overlapping at the second direction with another one of the third grating pattern and the fourth grating pattern. A third gap between adjacent two of the third bars is different from a fourth gap between adjacent two of the fourth bars.

In an embodiment, as to the structure of semiconductor device, a bar end of the third bars is matched to a bar end of the fourth bars at one side of the first bars.

In an embodiment, as to the structure of semiconductor device, a bar end of the third bars is constantly shifted from a bar end of the fourth bars at one side of the first bars.

In an embodiment, as to the structure of semiconductor device, one of the third bars and the fourth bars is numbered as a plurality of numbered bars while another one is a plurality of comparison bars. The numbered bars have a reference bar assigned with a reference number, wherein a misalignment level is determined by a shift from the reference bar for a detected one of the numbered bars being most matching to one of the comparison bars.

In an embodiment, as to the structure of semiconductor device, the reference number as assigned to the reference bar is “0”, a first side with respect to “0” is negatively numbered and a second side with respect to “0” is positively numbered.

In an embodiment, as to the structure of semiconductor device, the third bars are longer than the fourth bars or the third bars are shorter than the fourth bars.

In an embodiment, the invention also provides a method for bonding two substrates. The method includes providing a first substrate, having a first bonding pattern and a first grating pattern at a top of the first substrate, wherein the first grating pattern has a plurality of first bars extending along a first direction. In addition, a second substrate is provided, having a second bonding pattern and a second grating pattern at a top of the second substrate, wherein the second grating pattern has a plurality of second bars extending along the first direction. The first bonding pattern is dielectric bonding to the second bonding pattern, wherein an alignment condition between the first grating pattern and the second grating pattern is optically checked and accordingly adjusted to satisfy within a range. Annealing bonding is performed on the first bonding pattern and the second bonding pattern to have metal bonding. One of the first grating pattern and the second grating pattern is stacked over and overlapping at the first direction with another one of the first grating pattern and the second grating pattern. A first gap between adjacent two of the first bars is different from a second gap between adjacent two of the second bars.

In an embodiment, as to the method for bonding two substrate, a bar end of the first bars is matched or constantly shifted from a bar end of the second bars at one side of the first bars.

In an embodiment, as to the method for bonding two substrate, one of the first bars and the second bars is numbered as a plurality of numbered bars while another one is a plurality of comparison bars. The numbered bars have a reference bar assigned with a reference number, wherein a misalignment level is determined by a shift from the reference bar for a detected one of the numbered bars being most matching to one of the comparison bars.

In an embodiment, as to the method for bonding two substrate, the reference number as assigned to the reference bar is “0”, a first side with respect to “0” is negatively numbered and a second side with respect to “0” is positively numbered.

In an embodiment, as to the method for bonding two substrate, the first bars are longer than the second bars or the first bars are shorter than the second bars.

In an embodiment, as to the method for bonding two substrate, the first substrate and the second substrate as provided further includes: a third grating pattern, disposed on the first substrate, having a plurality of third bars extending along a second direction perpendicular to the first direction; and a fourth grating pattern, disposed on the second substrate, having a plurality of fourth bars extending along the second direction. One of the third grating pattern and the fourth grating pattern is stacked over and overlapping at the second direction with another one of the third grating pattern and the fourth grating pattern. A third gap between adjacent two of the third bars is different from a fourth gap between adjacent two of the fourth bars.

In an embodiment, as to the method for bonding two substrate, one of the third bars and the fourth bars is numbered as a plurality of numbered bars while another one is a plurality of comparison bars. The numbered bars have a reference bar assigned with a reference number, wherein a misalignment level at the second direction is determined by a shift from the reference bar for a detected one of the numbered bars being most matching to one of the comparison bars.

In an embodiment, as to the method for bonding two substrate, the third bars are longer than the fourth bars or the third bars are shorter than the fourth bars.

In an embodiment, as to the method for bonding two substrate, the alignment condition is optically checked by analyzing an overlapping image of the first grating pattern and the second grating pattern as shot by infra-red light.

DESCRIPTION OF THE EMBODIMENTS

The invention is directed to the semiconductor device, which is formed from two circuit parts respectively formed in two substrates. The two parts of the integrated circuit are then bonded as a whole circuit of the integrated circuit.

To have the alignment of the bond pads in the two substrates, each substrate has also been fabricated with an alignment mark. The two alignment marks are used to properly align to each other, so that the bond pads in the two substrates are properly aligned.

However, the alignment of the bond pads belonging to the integrated circuit is determined by the alignment of the alignment marks in the two substrates. The quality of the alignment marks is essential to decide the alignment condition. If the design of the alignment marks is not proper, the alignment performance between the two substrates may be not at the intend quality. It implies that a misalignment may occur. Then bonding condition between the bond pad would get misalignment, too.

The invention has looked into the issues of misalignment and proposes the structure of alignment marks. The alignment condition may be effectively improved. Multiple embodiments are provided for describing the invention but the invention is not just limited to the embodiments.

FIG. 1is a is a drawing, schematically illustrating a cross-section structure of two substrates as separately fabricated, according to an embodiment of the invention. Referring toFIG. 1, the while integrated circuit are divided into two circuit parts, which are respectively fabricated in one substrate100and another substrate200. In the substrate100, the device layer102are formed on the substrate. In an embodiment, the device layer102includes the circuit part without illustrated in detail, in which the interconnection is shown. The bond pattern104with multiple bonds as surrounded by the dielectric layer106is formed on the device layer102in connection to the interconnection, so as to be bonded with another circuit part in the substrate200.

Likewise, the substrate200has also been fabricated with the device layer202, the bond pattern204and the dielectric layer206surrounding the bond pattern204. The device layer202includes another circuit part of the whole integrated circuit.

In an embodiment, the bond pattern104in the substrate100and the bond pattern204in the substrate200are identical and to be bonded together for electric connection.

In addition, to precisely bonded for the bond patterns104,204, the alignment mark108and the alignment mark208are also respectively formed in the two substrates100,200.

FIG. 2is a drawing, schematically illustrating a cross-sectional structure of two substrates as bonded, according to an embodiment of the invention. Referring toFIG. 2, after the bonding process, the substrate100and the substrate200are bonded together, in which the alignment mark108and the alignment mark208may be monitored by IR device to check whether or not the two substrates100,200are well aligned, and then to make sure the bonds of the bond patterns104,204are properly bonded as well. After binding, the alignment mark108and the alignment mark208form the structure300, as viewed or monitored by the IR device.

The alignment condition between the alignment mark108and the alignment mark208would be essential to decide the bonding condition of the bond patterns104204. The structure of the alignment mark108and the alignment mark208may also determine the aligning quality in measurement.

The invention has looked into alignment mechanism between the alignment mark108and the alignment mark208.FIG. 3AandFIG. 3Bare drawings, schematically illustrating structures of the alignment marks of the two substrates in plane view after bonding, according to an embodiment of the invention.

Referring toFIG. 3A, in a design of the alignment mark108and the alignment mark208, they may be a grating pattern, like the indication bars of a ruler. The geometric relation in theFIG. 3Ais the image taken by the IR device from top plane of the substrate as also referring toFIG. 2. As viewed in the plane view after bonding the two substrates100,200, the grating patterns of the alignment marks108,208in ruler structures for comparison, in which the measurement of alignment may be like the measurement mechanism of a Vernier caliper. Here, in a straight way, the grating patterns of the alignment mark108and the alignment mark208as viewed from the IR device in a plane image are not overlapped but abutting at the interfacing edges. The alignment condition is determined by the location of the matched bars, which is located at the center, in an embodiment.

Referring toFIG. 3B, as noted, the grating patterns of the alignment marks108,208may have various designs in size for easy detection. The measurement mechanism is the same.

As to the alignment marks108,208inFIG. 3AandFIG. 3B, the alignment marks108,208are abutting at the interface without overlapping. The material of the alignment marks108,208is the same as the bonds of the bond patterns104,205. Usually, the dielectric material of one substrate would cover over the grating pattern of the alignment mark in another substrate.

As looking into in the invention, the bonding process including two stages of dielectric bonding and annealing bonding. The dielectric bonding is to preliminarily align the bonds such as copper bond of the bonding pattern104,204based on alignment marks108,208. In an embodiment, the location of the substrate mat be adjusted during the dielectric bonding since the bonding force at this stage is rather weak and then the substrate is still movable. Therefore, before actually performing the annealing bonding, the alignment marks108,208are monitored by the IR device to have the alignment as intended.

Then, the annealing bonding in relative high temperature is to firmly connect the metal bonds of the bonding pattern104,204. In the high temperature, the interface between the substrate100,200may include the portion between dielectric and metal. Further noted, according to the structure inFIG. 3AorFIG. 3B, the alignment mark108,208in one of the two substrates100,200would be fully covered by dielectric layer106,206of another one of the two substrate100,200. In an example, the alignment mark108of the substrates100would be fully covered by dielectric layer106of the substrates200.

Further looking into the interface between the dielectric and metal bond at the high annealing temperature, a void would occur.

As to the bonding condition between the bonds of the bond patterns104,204. The situations of proper alignment and misalignment are illustrated.FIG. 4Ais a drawing, schematically illustrating a cross-section structure of bonds in two substrates with misalignment after bonding, according to an embodiment of the invention.

Referring toFIG. 4A, one bond of the bond pattern104surrounded by the dielectric layer106and one bond of the bond pattern204surrounded by the dielectric layer206are illustrated. The bonds between the bond patterns104,204, ideally, are well aligned. In this situation, the dielectric layers106,206and the bonds204,204are well matched at the interface between the two substrates. The metal material, such as copper, are well connected during the annealing bonding stage and the dielectric layers106,206are also well bonded during the dielectric bonding stage.

FIG. 4Bis a drawing, schematically illustrating a cross-section structure of bonds in two substrates as well aligned after bonding, according to an embodiment of the invention. Referring toFIG. 4B, a misalignment between the bonds of the bond patterns204,204are illustrated. When severe misalignment occurs between the bonds of the bond patterns204,204, the electric contact portion is greatly reduced and the portion of the interface between the dielectric layer106,206are also greatly increased. It would at least cause an issue at this portion of the interface.

FIG. 5is a drawing, schematically illustrating a potential defect at the interface between the dielectric and the metal bond, according to an embodiment of the invention. Referring toFIG. 5, as looking into in the invention, a void54would potentially occur at the interface between the dielectric material52and the metal material50under the high temperature, such as the annealing temperature.

Further, the void would be more potentially occur between the dielectric layer106,206and the alignment masks108,208. In this situation, the quality of the alignment marks108,208as viewed by the IR device may gets larger error. The alignment precision would get worse. The alignment between the bond patterns104,204may be affected, accordingly.

After looking into the issues above, the invention in an embodiment proposes the structure of the alignment mark with overlapping as viewed in plane view.FIG. 6Ais a drawing, schematically illustrating a structure of the alignment marks of the two substrates in plane view after bonding, according to an embodiment of the invention.

Referring toFIG. 6A, in an embodiment, in the plane view of the substrate, the bars of the grating pattern of the alignment mark108is overlapping with the bars of the grating pattern of the alignment mark208. In an embodiment, the bars are extending along a direction, such as the Y-axis while the bars are distributed along the direction such as X-axis. Here, in an embodiment, the alignment mark208of the substrate200may be disposed on the alignment mark108of the substrate100. However, the grating patterns of the two substrates100,200may be exchanged, without specific limitation in the invention.

In the structure ofFIG. 6Aas an embodiment, the bars of the grating pattern of the alignment mark108may be shorter than the bars of the grating pattern of the alignment mark208. The bars of the grating pattern of the alignment mark108,208are like the indication bars of a ruler, in which every five bars is relative longer than the adjacent bars. However, the gap between the adjacent two bars of the alignment mark108is different from the gap between the adjacent two bars of the alignment mark208.

This setting is similar to the measurement mechanism of the Vernier caliper to look for the match bars of the two grating patterns of the alignment marks104,204for determining the relative locations between the two substrate100,200. Generally, the central bar of the grating pattern of the alignment mark108,208is set to be matched when the substrate100is aligned to the substrate200in ideal condition. If the matched bars are shifted from the central bar, a misalignment occurs and the shifted amount is determined by the location of the matched bars.

The overlap between the two gating patterns of the alignment marks104,204may have other arrangement.FIG. 6Bis a drawing, schematically illustrating a structure of the alignment marks of the two substrates in plane view after bonding, according to an embodiment of the invention. Referring toFIG. 6B, one side of each bar may be set to distribute along a straight line. The other geometric settings may be the same as those inFIG. 6A.

As noted, the two gating patterns of the alignment marks104,204overlapped in plane view. The geometric relation in theFIG. 6AorFIG. 6Bis the image taken by the IR device from top plane of the substrate, as also referring toFIG. 2. In this situation, a significant portion of the bars are overlapped during the annealing bonding stage at high temperature. The void54inFIG. 5is effectively reduced for the alignment marks104,204because the less portion of the bars is covered by the dielectric layer from the opposite substrate.

FIG. 7is a drawing, schematically illustrating schematically illustrating a structure of the alignment marks of the two substrates in plane view after bonding as well aligned, according to an embodiment of the invention. Referring toFIG. 7, in an embodiment, to easily measure the shift between the two substrates. The bars of the grating pattern of the alignment mark of one of the substrates100,200may be numbered for easy measuring the shift between the two substrates. In an example, the bars of the grating pattern of the alignment mark208are numbered for easy discerning the bars. As usual, one of the bars is the reference bar and numbered as 0 in an example. Basically, one of the bars in the grating pattern of the alignment mark108would match to one of the bars in the grating pattern of the alignment mark208because the gap between adjacent two bars in two alignment marks104,204are different.

In a situation with precise alignment between the alignment mark108and the alignment mark208, the match bar is located at the reference bar, as numbered by 0.

FIG. 8is a drawing, schematically illustrating structure of the alignment marks of the two substrates in plane view after bonding with misalignment as measured, according to an embodiment of the invention. Referring toFIG. 8, when misalignment occurs, the shift amount may be easily measured. In an example, a misalignment by shift toward right by 5 bars, the bars of the alignment mark208and the bars of the alignment mark108have a match bar at the fifth bar. Further in an example, when more misalignment occurs, the bars of the alignment mark208and the bars of the alignment mark108have a match bar at the tenth bar. This, the misalignment with the shift amount may be easily measured.

Due to overlapping between the bars, the portion for bars being contacting to the dielectric material is also effectively reduced. The void54as illustrate inFIG. 5in an example may be reduced.

In bonding process, as previously stated, the dielectric bonding stage causes the weak bonding of the dielectric layers106,206at the interface between the two substrates100,200. The alignment condition is optically checked by analyzing an overlapping image of the grating pattern of the alignment mark108and the grating pattern of the alignment mark208. The image may be shot by infra-red light of IR device. Once the alignment is done, in which the match bar is located t the reference bar numbered by “0”, the annealing process may be performed to actually bond the be bond pads104,204, while the alignment marks108,208are also bonded.

FIG. 9is a drawing, schematically illustrating a structure of the alignment marks of the two substrates in plane view after bonding, according to an embodiment of the invention. Referring toFIG. 9, to actually align the two substrate100,200, it needs to align in both the X direction and the Y direction. In this situation, the alignment marks108,208may be additional set in another direction, in which the bars are extending along the X direction while the bars are distributed along the Y direction. Two-dimension alignment may be done with the same design aspect.

Further in an embodiment, a method for bonding two substrates may be also provided. In an embodiment, the method includes providing a first substrate100, having a first bonding pattern of104and a first grating pattern of alignment mark108at a top of the first substrate100. The first grating pattern of alignment mark108has a plurality of first bars extending along X direction. In addition, a second substrate200is provided, having a second bonding pattern204and a second grating pattern of alignment mark208at a top of the second substrate200. The second grating pattern of alignment mark208has a plurality of second bars extending along the X direction. The first bonding pattern of alignment mark108is dielectric bonding to the second bonding pattern of alignment mark208, wherein an alignment condition between the first grating pattern and the second grating pattern is optically checked and accordingly adjusted to satisfy within a range. Annealing bonding is performed on the first bonding pattern104and the second bonding pattern204to have metal bonding. One of the first grating pattern of alignment mark108and the second grating pattern of alignment mark208is stacked over and overlapping at the X direction with another one of the first grating pattern of alignment mark108and the second grating pattern of alignment mark208. A first gap between adjacent two of the first bars of the first grating pattern of alignment mark108is different from a second gap between adjacent two of the second bars of the first grating pattern of alignment mark208.

The invention has provided the alignment marks with overlapping as viewed at the plane view. The misalignment may be easily detected and measured, and the alignment marks may be fabricated in improved structure with reducing the occurrence of void at the interface between dielectric and metal during the bonding process.

Although the invention is described with reference to the above embodiments, the embodiments are not intended to limit the invention. A person of ordinary skill in the art may make variations and modifications without departing from the spirit and scope of the invention. Therefore, the protection scope of the invention should be subject to the appended claims.