JP7704431B2 - Glass Substrate and Glass Interposer - Google Patents

Description

The present invention relates to a glass substrate and a glass interposer using the same.

Traditionally, silicon-based and resin-based materials have been widely used as interposer materials.

However, when considering the need to narrow the pitch of connection pads (bumps) and to accommodate finer wiring, silicon-based materials have the disadvantage of higher production costs, while resin-based materials have the disadvantage of making it difficult to achieve finer wiring.

Therefore, some prior art technologies use glass materials to construct glass interposers (see, for example, Patent Document 1). This technology is said to solve the technical problem of metallization, which is unique to glass, and realize suitable glass interposers.

JP 2019-044212 A

However, conventional glass interposers, including those described in Patent Document 1 above, have a multi-layer wiring layer formed on a glass substrate and made of multiple materials other than glass, which can make it difficult to narrow the pitch of the connection pads (bumps) and to miniaturize the wiring.

For example, there were disadvantages such as warping due to the difference in thermal expansion coefficient between the glass and the multilayer wiring layer, and deformation of the multilayer wiring layer due to external forces during stacking.

Furthermore, when the multi-layer wiring layer is made of resin, it is difficult to achieve finer detail as described above, and the process for forming the multi-layer wiring layer requires multiple steps, which tends to increase production costs.

The object of the present invention is to provide a glass substrate that can realize a narrow pitch of a glass interposer while suppressing production costs, and a glass interposer using this glass substrate.

The glass substrate according to the present invention has a plurality of micro through holes. The diameter of the micro through holes is in the range of about 5 μm to 500 μm, and the micro through holes are formed, for example, by laser-assisted etching.

This glass substrate has a recess for filling wiring and a wiring portion. The recess for filling wiring is provided at a position on the main surface of the glass substrate where wiring is to be formed. Examples of the recess for filling wiring include, but are not limited to, a fine groove in which fine wiring is arranged and a recess that expands to cover a desired area.

The wiring parts are made of conductive materials, including metal materials such as copper and chromium, and are placed in the micro through holes and recesses for filling wiring.

The upper surface of the wiring portion arranged in the recess for filling wiring and the main surface of the glass substrate are arranged on the same plane, and each has a smooth surface. To achieve this configuration, for example, after filling the recess for filling wiring with the wiring portion, the entire main surface of the glass substrate may be polished by chemical mechanical polishing or the like.

In the above configuration, the surface roughness Ra of the smooth surface of the upper surface of the wiring portion arranged in the recess for filling wiring and the smooth surface of the main surface of the glass substrate may each be 10 nm or less, and preferably 1 nm or less.

The reason for this is that the smoother the main surfaces of the glass substrates are, the easier it is to bond the glass substrates together to form a glass interposer. Furthermore, if the surface roughness Ra of the smooth surface is smoothed to 0.5 nm or less (more preferably 0.1 nm or less) by chemical mechanical polishing or other processes, the glass substrates can be easily bonded by room temperature bonding.

By increasing the adhesion between multiple glass substrates and stacking them to form an interposer with a multilayer wiring structure, it is possible to inexpensively form a multilayer wiring structure that does not warp due to thermal expansion and is resistant to deformation due to external forces.

In particular, glass substrates are easy to make large and ultra-thin, making it easier to keep costs down when producing narrow-pitch interposers compared to using other materials such as resin, ceramics, and silicon.

This invention makes it possible to achieve a narrow pitch for glass interposers while keeping production costs down.

1 is a diagram showing a schematic configuration of a glass interposer according to an embodiment of the present invention; 1A to 1C are diagrams illustrating an example of a manufacturing method for a glass interposer. 1A to 1C are diagrams showing an example of a method for forming a recess for filling wiring. 1A to 1C are diagrams illustrating an example of a method for forming a through hole. FIG. 1 is a diagram showing an example of an etching apparatus used in manufacturing a glass interposer. 1A to 1C are diagrams illustrating an example of a method for forming a through wiring portion and an in-plane wiring portion. FIG. 13 is a diagram showing another example of an etching apparatus used in manufacturing a glass interposer. 11A to 11C are diagrams showing another example of a method for forming recesses for filling wiring and through holes.

Figures 1(A) to 1(D) show an outline of a glass interposer 10 according to one embodiment of the present invention. The glass interposer 10 is supported by a probe card 2 so that its position can be freely adjusted. In this embodiment, an example in which the glass interposer 10 is used in a probe card 2 is described, but the glass interposer 10 can also be used for other purposes such as a semiconductor memory.

The probe card 2 is attached to a prober 4 that is connected to a tester or the like and is configured to be freely movable. The probe card 2 is configured to measure the electrical characteristics of a measurement object 6 (e.g., a silicon wafer on which a semiconductor integrated circuit is formed) on a stage (not shown).

A probe support substrate 8 is connected to the main surface of the glass interposer 10 that faces the measurement target 6. This probe support substrate 8 has multiple probes 9. Note that only the number of probes 9 is shown for the sake of convenience. The probe support substrate 8 is made of resin, ceramics, silicon, etc., with multiple through holes, but it is also possible to use a glass material, as with the glass interposer 10.

The glass interposer 10 is configured to match the pitch of the probes 9 provided on the probe support substrate 8 with the pitch of the spring electrodes 7 provided on the probe card 2. Specifically, it is configured to provide electrical continuity between the connection pads 70 and 90, which are arranged at different pitches as shown in FIG. 1(B).

As shown in FIG. 1B, the glass interposer 10 is configured by stacking multiple glass substrates 12. In this embodiment, the glass interposer 10 is configured by bonding three glass substrates 12 at room temperature, but the number of glass substrates 12 and the bonding method are not limited to these.

The glass substrates 12 that make up the glass interposer 10 are almost identical in configuration, so for convenience, we will describe a single glass substrate 12 here.

As shown in FIG. 1(C) and FIG. 1(D), the glass substrate 12 has a through wiring portion 122 provided on the inner wall surface of the through hole 126, and an in-plane wiring portion 124 provided as a circuit pattern from the opening of the through hole 126 to a predetermined portion of the main surface of the glass substrate 12. The in-plane wiring portion 124 is arranged so as to fill the wiring filling recess 128.

In this embodiment, both the through wiring portion 122 and the in-plane wiring portion 124 are made of a copper plating layer, but this is not limited to this as long as the layer has conductivity. The probe 9 and the spring electrode 7 are electrically connected by the through wiring portion 122, the in-plane wiring portion 124, the connection pad 70, the connection pad 90, and a conductive paste (silver, chromium, silicon nitride, etc.) provided in or near the through hole 126 as necessary.

In the glass substrate 12, the upper surface of the in-plane wiring portion 124 in the wiring filling recess 128 and the main surface of the glass substrate 12 are arranged on the same plane, and further, the upper surface of the in-plane wiring portion 124 and the main surface of the glass substrate 12 are each surface-treated so that the surface roughness 1Ra is 1 nm or less.

The reason for adopting such a configuration is to make it easier to bond the glass substrates 12 together. If the bonding surfaces of the glass substrates 12 are uneven, it becomes difficult to stack the glass substrates 12 to form the glass interposer 10, but by smoothing the entire main surface of the glass substrate 12, including the top surface of the in-plane wiring portion 124, it becomes easier to bond the glass substrates 12 together. For example, when bonding the glass substrates 12 together by room temperature bonding, it is preferable that the surface roughness 1Ra is 1 nm or less, more preferably about 0.1 nm to 0.5 nm, and even more preferably 0.1 nm or less. Even when an adhesive or the like is used, it is preferable that the glass substrate 12 has a smoothness of about 10 nm or less in surface roughness.

Next, an example of a method for manufacturing the glass substrate 12 will be described with reference to Figures 2(A) to 2(E). First, as shown in Figures 2(A) and 2(B), a wiring-filling recess 128 is provided at the circuit pattern formation position on the main surface of the glass substrate 12. The wiring-filling recess 128 is formed by selective etching using, for example, photoresist, a chrome mask, an etching-resistant film, etc.

Then, as shown in FIG. 2(C), through holes 126 are provided. The through holes 126 are formed by so-called laser-assisted etching or the like. In this embodiment, through holes 126 with a diameter of about 50 μm to 100 μm are formed, but the diameter of the through holes 126 can be appropriately set in the range of about 5 μm to 500 μm by adjusting the laser beam diameter.

Next, as shown in FIG. 2(D), the through-hole wiring section 122 and the in-plane wiring section 124 are formed. Here, a copper seed layer of about 1 μm is formed by electroless copper plating, and then a copper plating layer of 50 to 60 μm is formed by electrolytic plating. Furthermore, if necessary, a conductive paste such as chromium is filled into the through-hole 126.

However, the method for forming the through wiring portion 122 and the in-plane wiring portion 124 is not limited to this. For example, it is also possible to adopt a method for forming an adhesion layer such as Ti or TiW and a copper seed layer by sputtering for the through wiring portion 122 and the in-plane wiring portion 124. In addition, a metal oxide film formed by the sol-gel method or a primer may be used when forming the copper seed layer.

Then, as shown in FIG. 2(E), the entire main surface of the glass substrate 12, including the upper surface of the in-plane wiring portion 124, is surface-treated by a CMP (Chemical Mechanical Polishing) process, i.e., a chemical mechanical polishing process.

In this embodiment, the surface chemical action of the abrasive (abrasive grains) such as SeO and the action of the chemical components contained in the slurry increase the mechanical polishing effect caused by the relative movement between the main surface of the glass substrate 12 and the slurry. As a result, it is possible to obtain a polished surface that is sufficiently smooth for room temperature bonding with a surface roughness 1Ra of 0.1 nm or less.

The glass substrates 12, whose main surfaces have been subjected to CMP processing, are stacked by room temperature bonding in the number required to form the glass interposer 10. Room temperature bonding methods include known bonding methods such as surface activation and atomic diffusion bonding.

Figures 3(A) to 3(C) show how the wiring filling recess 128 is formed on the main surface of the glass substrate 12 as described with reference to Figure 2(B).

First, as shown in FIG. 3(A), an etching-resistant photoresist 30 is applied to the main surface of the glass substrate 12, and the photoresist 30 is removed at the desired position by exposure, development, etc., to expose the formation position of the wiring filling recess 128.

After that, as shown in FIG. 3B, the desired position of the glass substrate 12 is dissolved by etching to form a wiring-filling recess 128. Then, as shown in FIG. 3C, the photoresist 30 is removed after the wiring-filling recess 128 is formed. Note that instead of processing with the photoresist 30, an etching-resistant film may be attached to the main surface of the glass substrate 12, and the film may be removed at the desired position by laser processing to expose the formation position of the wiring-filling recess 128, or a similar process may be performed using a chrome mask or other methods.

Figures 4(A) and 4(B) show an example of a method for forming a through hole 126 in a glass substrate 12. In this method, a laser beam is irradiated onto the position in the glass substrate 12 where the through hole 126 is to be formed, forming a modified portion at this position that is easily etched.

The type and irradiation conditions of the laser beam are not particularly limited as long as the laser beam can modify the intended position of the through hole 126 in the glass substrate 12 so as to make it easier to etch. In this embodiment, a laser beam emitted from a short pulse laser (e.g., a picosecond laser or a femtosecond laser) is irradiated from the laser head, but a _CO2 laser, a nanosecond laser, or the like may also be used.

In addition, in this embodiment, the output is controlled so that the average laser energy of the laser beam is approximately 30 μJ to 300 μJ, but this is not limited to this.

It is preferable that the focal area of the laser beam is adjusted appropriately. Here, the focal area of the laser beam is adjusted to cover the entire thickness of the glass substrate 12, which makes it easier to form the through-hole 126.

Following the above-mentioned laser processing, the modified portion is etched to form a through hole 126 in the glass substrate 12.

The etching process is performed, for example, using an etching apparatus 50 of a single-wafer spray etching type as shown in Figures 5(A) and 5(B). The glass substrate 12 is introduced into the etching apparatus 50, and is etched using an etching solution containing hydrofluoric acid, hydrochloric acid, and the like. Typically, an etching solution containing about 1 to 10% by weight of hydrofluoric acid and 5 to 20% by weight of hydrochloric acid is used, and a surfactant or the like is used in combination as appropriate, if necessary.

In the etching device 50, as shown in Figures 5(A) and 5(B), the glass substrate 12 is etched by contacting the main surface of the glass substrate 12 with an etching solution in the etching chamber 52 while the glass substrate 12 is transported by a transport roller.

In the etching device 50, a cleaning chamber 53 is provided downstream of the etching chamber 52 to wash away the etching liquid adhering to the glass substrate 12, so that the glass substrate 12 is discharged from the etching device 50 with the etching liquid removed.

This method of assisting etching with laser processing makes it possible to minimize the etching process time.

As a result, the surface of the glass substrate 12 is less likely to become roughened when the through holes 126 are formed, and the shape of the through holes 126 is less likely to become distorted. The diameter of the through holes 126 can be adjusted appropriately within the range of approximately 5 μm to 500 μm.

As a general rule, if the thickness of the glass substrate 12 is thin, it is easier to make the diameter of the through hole 126 smaller. This is because, during the etching process, the diameter of the through hole 126 increases slightly more than the laser beam diameter.

As a countermeasure against this slight increase, the applicant's experiments have revealed that adding a fluorine complexing agent such as titanium oxide or an alkali such as potassium hydroxide or sodium hydroxide to the etching process suppresses the slight increase in the groove width of the through hole 126 during the etching process. Therefore, by adding an appropriate amount of a fluorine complexing agent or alkali to the etching solution as necessary, it is possible to adjust the diameter and shape of the through hole 126.

Next, as shown in Figures 6(A) and 6(B), the formation process of the through wiring section 122 and the in-plane wiring section 124 and the CMP process of the glass substrate 12 are performed. As described above, a copper seed layer of about 1 μm is formed by electroless copper plating, and then a copper plating layer of 50 to 60 μm is formed by electrolytic plating.

When the diameter of the through-holes 126 exceeds 100 μm, it tends to be difficult to fill the through-holes 126 with a conductive material using electrolytic plating alone, so it is preferable to appropriately fill the through-holes 126 with a conductive paste such as chromium. Typically, a copper plating layer with a thickness of about 1.1 to 1.5 times the thickness of the copper plating layer in the through-holes 126 is formed on both main surfaces of the glass substrate 12.

Then, as shown in FIG. 6(E), the entire main surface of the glass substrate 12, including the upper surface of the in-plane wiring portion 124, is surface-treated by a CMP (Chemical Mechanical Polishing) process, i.e., a chemical mechanical polishing process.

In this embodiment, the surface chemical action of the abrasive (abrasive grains) such as SeO and the action of the chemical components contained in the slurry increase the mechanical polishing effect caused by the relative movement between the main surface of the glass substrate 12 and the slurry. As a result, the surface roughness 1Ra can be adjusted to a range from 10 nm to 0.1 nm or less, making it possible to obtain a polished surface that is sufficiently smooth for room temperature bonding.

The glass substrates 12, whose main surfaces have been subjected to CMP processing, are then stacked by room temperature bonding in the number required to form the glass interposer 10.

The above-described embodiment makes it possible to efficiently form micro-holes and perform metallization on the glass substrate, and also makes it possible to inexpensively realize a glass interposer 10 that is compatible with narrower pitches of connection pads.

By appropriately using the above-mentioned laser-assisted etching for external shape processing, it is possible to appropriately process the external shape of the glass substrate 12 even if it has an irregular shape (e.g., a polygon with rounded corners, a circle, an ellipse, etc.).

In the above embodiment, an example of performing the etching process using a spray etching type etching device 50 has been shown, but the present invention is not limited to this. For example, as shown in FIG. 7(A), it is also possible to adopt a configuration in which the glass substrate 12 is transported in an overflow type etching chamber 54 while being in contact with the overflowing etching solution.

Furthermore, as shown in FIG. 7(B), it is also possible to employ a dip-type etching method in which one or more glass substrates 12 stored in a carrier are immersed in an etching tank 56 containing an etching solution.

Of course, as shown in this figure, the shape of the glass substrate 12 is not limited to a circle, but may also be a rectangle. Also, by preparing an appropriate jig, it is possible to accommodate glass substrates 12 of any shape.

When the size of the glass substrate 12 is small and transportation or handling may be difficult, it is possible to use a carrier member such as a support tray, basket, or jig made of an etching-resistant mesh material.

Also, as shown in Figures 8(A) to 8(C), it is possible to simultaneously form the through-hole 126 and the recess 128 for filling the wiring by using laser-assisted etching.

In this case, as shown in FIG. 8(A), the area of the glass substrate 12 where the wiring filling recess 128 is to be formed is modified by irradiating the area with a laser beam while adjusting the laser focus.

Furthermore, as shown in FIG. 8(B), the formation position of the through hole 126 is modified by a laser beam. Then, as shown in FIG. 8(C), the modified portion is dissolved by an etching process, so that the through hole 126 and the recess 128 for filling the wiring are formed at the same time.

The above description of the embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, not by the above-described embodiments. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope of the claims.

10--glass interposer 12--glass substrate 122--through wiring portion 124--in-plane wiring portion 126--through hole 128--recess for filling wiring

Claims (3)

A glass substrate having a plurality of fine through holes,
a recess for filling wiring provided at a position on a main surface of the glass substrate where wiring is to be formed;
wiring portions made of a conductive material and disposed in the fine through-holes and the recesses for filling wiring,
A glass substrate characterized in that the upper surface of the wiring portion arranged in the recess for filling wiring and the main surface of the glass substrate are arranged on the same plane, and each has a polished surface that is sufficiently smooth for room temperature bonding . 2. The glass substrate according to claim 1, wherein the surface roughness Ra of the smooth surface of the upper surface of the wiring portion arranged in the recess for filling wiring and the smooth surface of the main surface of the glass substrate are each 1 nm or less, and the glass substrate has a polished surface that is sufficiently smooth for room temperature bonding . 3. A glass interposer comprising a plurality of glass substrates each having a polished surface sufficiently smooth for room temperature bonding according to claim 1 or 2 bonded together.

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