A method for filling silicon grooves with organic dielectric without voids

Abstract

The present invention discloses a void-free organic medium filling method. Aiming at the high-depth-ratio narrow groove structure formed between the embedded chip and the filling groove in the silicon wafer reconstruction process, the groove structure is first prepared on the silicon wafer, the chemical stains and particle residues on the groove surface are removed, the groove structure on the silicon wafer is treated with pure oxygen plasma, the tackifier is spread on the groove structure surface, the groove structure surface is pre-wetted with an organic solvent, and the organic solvent is adsorbed on the groove structure surface; then the organic medium is spin-coated on the silicon wafer with the groove structure; finally, the bubbles in the groove structure are removed by vacuuming at least twice, and the organic medium is solidified. The method can significantly improve the uniformity and stability of the filling process, reduce the process risk of medium filling voids in the groove structure on silicon, and significantly improve the reliability of the product.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic packaging and relates to a method for filling a silicon groove with a void-free organic medium. Background Art

[0002] The ever-increasing and diverse system demands continue to drive the development of various new packaging structures towards small size, lightweight, and low cost. With the development of bumping, RDL, TSV, wafer bonding, debonding, and wafer forming technologies, fan-out wafer-level packaging (FOWLP) technology has achieved long-term development. Compared with traditional packaging technology, FOWLP technology reconstructs the known good die (KGD) using a mold and surrounds the chip with epoxy molding compound (EMC) material, which extends the chip package pins beyond the mold surface. The FOWLP package size is not limited by the chip size, making it suitable for multi-chip integration. It is currently used in large-scale production, such as baseband, RF transceiver, and power management chips.

[0003] Although FOWLP has been used in large-scale production, many challenges still need to be addressed. From a process perspective, handling EMC reconstructed wafers is very troublesome because the thermal expansion coefficient of EMC wafers and silicon wafers differs significantly, which usually results in large warpage. In addition, it is also difficult to create a fine-pitch redistribution layer on the surface of EMC reconstructed wafers. By using Si materials instead of EMC materials, the thermal expansion coefficient mismatch between the reconstructed new product and the substrate material can be reduced. By preparing a groove slightly larger than the size of the KGD chip on the Si, the KGD chip is mounted into the large groove on the carrier Si. However, there is a high-aspect-ratio narrow groove structure between the buried chip and the filled groove. When the structure is filled with organic dielectrics, voids may form, thereby increasing the risk of failure in subsequent process steps. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the prior art and provide a method for filling a silicon groove with an organic medium without voids.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for filling a silicon groove with a void-free organic medium comprises the following steps:

[0007] S1, preparing a groove structure on a silicon wafer and removing chemical stains and particle residues on the groove surface;

[0008] S2, pure oxygen plasma treatment of the groove structure on the silicon wafer;

[0009] S3, spreading the tackifier onto the surface of the groove structure;

[0010] S4, pre-wetting the surface of the groove structure with an organic solvent, so that the organic solvent is adsorbed on the surface of the groove structure;

[0011] S5, spin coating an organic medium on the silicon wafer with the groove structure;

[0012] S6, removing air bubbles from the groove structure by vacuuming at least twice;

[0013] S7, curing the organic medium.

[0014] A further improvement of the present invention is:

[0015] The groove structure in S1 has an opening of 10 to 60 μm, a depth of 100 to 150 μm, and a groove spacing of 100 μm to 10,000 μm.

[0016] The plasma treatment time in S2 is 60 to 360 seconds.

[0017] In the S3, the tackifier is spin-coated at a speed of 600 to 1200 rpm, and the tackifier is allowed to stand for 60 to 300 seconds after being spin-coated.

[0018] The organic solvent used in S4 is PGMEA or PGME, the pre-wetting spin coating speed is 50 to 300 rpm, and the pre-wetting is allowed to stand for 30 to 180 seconds.

[0019] The spin coating of the organic medium in S5 comprises the following steps:

[0020] S5.1, glue dripping stage, speed 10-30 rpm, lasting 10-30 s;

[0021] S5.2, medium filling stage, rotation speed 100-200 rpm, lasting 120-360 s, allowing the surface medium to flow into the groove structure;

[0022] S5.3, the coating stage, the rotation speed is increased to 400-800 rpm, the residual adhesive is removed, and the adhesive medium is initially formed on the surface of the silicon wafer;

[0023] S5.4, surface medium film forming stage, the rotation speed is increased to 1000-1500 rpm to obtain an organic medium film with a smooth surface.

[0024] The step of curing the organic medium in S7 includes the following steps:

[0025] S7.1, solvent evaporation stage, heating rate 0.5-2°C / min;

[0026] S7.2, bubble volatilization stage, heating rate 0.5-2°C / min, duration 30-120 min;

[0027] S7.3, medium curing stage, heating rate 1-2°C / min, holding time 60-120 min;

[0028] S7.4, cooling stage, cooling rate 3~5℃ / min.

[0029] When the organic medium is a photosensitive material, the following steps are further included between S6 and S7:

[0030] The silicon wafer filled with the photosensitive organic medium is soft-baked and exposed; the photosensitive organic medium is a positive photoresist, which protects the medium in the groove structure during exposure, and the medium on the surface of the groove is removed by development after exposure; the photosensitive organic medium is a negative photoresist, which solidifies the medium in the groove after exposure, and the excess organic medium on the surface of the groove structure is removed by development.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention discloses a void-free organic dielectric filling method. Targeting the high-aspect-ratio narrow groove structure formed between the embedded chip and the filled groove in the silicon wafer reconstruction process, the method can significantly improve the uniformity and stability of the filling process, reduce the risk of dielectric filling voids in the groove structure on silicon, and significantly improve product reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 is a process flow chart of the present invention;

[0035] Figure 2 Schematic diagram of the cross-sectional structure of the groove structure on silicon;

[0036] Figure 3 This is a schematic diagram of the relationship between the rotation speed and time of organic medium spin coating;

[0037] Figure 4 Schematic diagram of the vacuum bubble removal device;

[0038] Figure 5 This is the vacuum degree change curve during the vacuum bubble removal process;

[0039] Figure 6 Curing temperature profile after filling the organic dielectric in the silicon groove;

[0040] Figure 7Filling the grooved organic medium on silicon with exposed photoresist structure;

[0041] Figure 8 A cross-sectional view of a large-sized meandering groove structure on silicon used in one embodiment of the present invention;

[0042] Figure 9 A top view of a large-scale meandering groove structure on silicon used in one embodiment of the present invention;

[0043] Figure 10 This is a cross-sectional view after the first filling using WPR 5100 according to one embodiment of the present invention;

[0044] Figure 11 This is a cross-sectional view after the second filling using WPR 5100 according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0046] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0047] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0048] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0049] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0050] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0051] The present invention is described in further detail below with reference to the accompanying drawings:

[0052] See also Figure 1 , is a process flow chart of a method for filling a silicon groove with a void-free organic dielectric in the present invention, comprising the following steps:

[0053] S1, prepare a high aspect ratio groove structure on a silicon wafer by dry or wet method. The groove structure opening is 10-60μm, the depth is 100-150μm, and the groove spacing is 100μm-10000μm. The chemical stains and particle residues on the groove surface are removed by wet process to ensure the cleanliness of the silicon wafer surface. The cross-sectional structure diagram of the groove structure on silicon is shown in Figure 2 shown.

[0054] S2, using pure oxygen plasma atmosphere to change the hydrophilicity of the groove surface on the silicon, the plasma treatment time is 60 to 360 seconds.

[0055] S3, use 600-1200 rpm spin coating speed to ensure that the adhesion agent completely covers the entire groove surface. After the adhesion agent is spin coated, let it stand for 60-300 seconds to allow the adhesion agent to be completely spread on the surface of the groove structure on the silicon.

[0056] S4, pre-wetting the surface of the groove structure with PGMEA or PGME organic solvent, with a pre-wetting spin coating speed of 50 to 300 rpm. After pre-wetting, let it stand for 30 to 180 seconds until the PGEMA or PGME molecules are completely adsorbed on the silicon sidewalls in the groove and the excess organic solvent on the surface evaporates.

[0057] S5, spin coating an organic medium on a silicon wafer with a groove structure. The relationship between the spin coating speed and time is shown in the figure below. Figure 3 Shown, including:

[0058] S5.1, AB section is the glue dripping stage, the speed is 10-30 rpm, and it lasts for 10-30 seconds;

[0059] S5.2, BC section is the medium filling stage, with a rotation speed of 100-200 rpm and a duration of 120-360 s, allowing the surface medium to flow into the groove structure;

[0060] S5.3, DE section is the glue spreading stage, the rotation speed is increased to 400-800 rpm, the excess glue on the surface is removed, and the glue medium is initially formed on the surface of the silicon wafer;

[0061] S5.4, FG section is the surface medium film forming stage, the rotation speed is increased to 1000-1500 rpm to obtain an organic medium film with a smooth surface.

[0062] S6, remove the bubbles in the groove structure by vacuuming at least twice. The vacuum equipment requires a minimum vacuum degree of 1Pa. The schematic diagram of the vacuum bubble removal device is as follows Figure 4 As shown, the first vacuuming can make the cavity in a high vacuum state, and at the same time, it can also discharge a large number of bubbles that were not discharged when the organic medium was spin-coated at the bottom of the groove. The cavity at the bottom of the groove is also basically in a vacuum state. After the vacuum is broken, the interior of the cavity is at atmospheric pressure, and the cavity at the bottom of the groove is in a low vacuum state. The pressure difference between the inside and outside can further make the organic medium on the side wall of the groove and the surface of the silicon wafer flow into the interior of the groove; the second vacuuming further discharges the bubbles in the medium at the bottom of the groove, completing the bubble discharge process. The vacuum degree change curve during the vacuum bubble discharge process is shown in FIG. Figure 5 For groove structures with high aspect ratios, the number of vacuum breaks can be increased to remove the bubbles in the organic medium within the grooves.

[0063] S7, solidify the organic medium. When the organic medium is non-photosensitive, it is directly solidified after vacuuming and removing bubbles. After solidification, it is subjected to chemical mechanical polishing to remove excess impurities on the surface. The solidification temperature curve after the organic medium is filled in the groove on the silicon is as follows: Figure 6 As shown, curing of the organic medium includes the following steps:

[0064] S7.1, AB section is the solvent volatilization stage, the heating rate is 0.5~2℃ / min;

[0065] S7.2, BC section is the bubble volatilization stage, with a heating rate of 0.5-2°C / min and a duration of 30-120 min;

[0066] S7.3, CD section is the medium curing stage, the heating rate is 1-2°C / min, and the holding time is 60-120min;

[0067] S7.4, DE section is the cooling stage, and the cooling rate is 3-5℃ / min.

[0068] When the organic medium is a photosensitive material, after completing the vacuum and bubble removal, the silicon wafer filled with the photosensitive organic medium needs to be soft-baked and exposed. The organic medium filling exposure photomask structure on the silicon groove is as follows: Figure 7 As shown in Figure 2, if the filling medium used is positive photoresist, then Figure 7 The middle shaded area is the light-transmitting area, and the blank area, that is, the groove area, is not light-transmitting. During exposure, the medium in the groove is protected, and the medium on the surface of the groove can be developed and removed after exposure. If the filling medium used is a negative photoresist, then Figure 7 The middle shaded area is a light-proof area, and the blank area is a light-transmitting area. After exposure, the medium in the groove is solidified, and the excess organic medium on the surface is removed by development before solidification.

[0069] If a single spin coating fails to completely fill the groove structure on the silicon with the organic medium, the above steps are repeated to repeatedly fill the groove with the organic medium, thereby achieving complete filling of the groove with the organic medium without voids.

[0070] One embodiment of the present invention is to fill organic medium with large-scale meandering groove structure on silicon without voids. The structure of large-scale meandering groove is shown in FIG. Figure 8 and Figure 9 As shown, the size of the meander groove used is 10mm*10mm, the groove depth is 125μm, and the groove opening width is 25μm. The above steps are used to fill the large-size meander groove structure on silicon with organic medium without voids. The cross-sectional view after the first filling is as shown Figure 10 As shown, the cross-section after the second filling is as follows Figure 11 shown.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for filling a silicon groove with a void-free organic medium, characterized in that: The following steps are involved: S1, preparing a groove structure on a silicon wafer and removing chemical stains and particle residues on the groove surface; S2, treating the groove structure on the silicon wafer with pure oxygen plasma; S3, spreading the tackifier onto the surface of the groove structure; S4, pre-wetting the surface of the groove structure with an organic solvent, so that the organic solvent is adsorbed on the surface of the groove structure; S5, spin coating an organic medium on the silicon wafer having the groove structure; S6, removing bubbles in the groove structure by vacuuming at least twice; S7, curing the organic medium; The groove structure in S1 has an opening of 10-60 μm, a depth of 100-150 μm, and a groove spacing of 100 μm-10000 μm; When the organic medium is a non-photosensitive medium, it is directly cured after the bubbles are removed by vacuum, and then the surface excess impurities are removed by chemical mechanical polishing process after curing; When the organic medium is a photosensitive material, the steps between S6 and S7 also include: soft baking and exposure of the silicon wafer filled with the photosensitive organic medium; the photosensitive organic medium is a positive photoresist, and the medium in the groove structure is protected during exposure, and the medium on the surface of the groove is removed by development after exposure; the photosensitive organic medium is a negative photoresist, and the medium in the groove is solidified after exposure, and excess organic medium on the surface of the groove structure is removed by development; The spin coating of the organic medium in S5 comprises the following steps: S5.1, glue dripping stage, speed 10~30rpm, lasting 10~30s; S5.2, medium filling stage, the rotation speed is 100~200rpm, and the duration is 120~360s, so that the surface medium flows into the groove structure; S5.3, the glue spreading stage, the rotation speed is increased to 400~800rpm, the residual glue is removed, and the glue medium is initially formed on the surface of the silicon wafer; S5.4, surface medium film formation stage, the rotation speed is increased to 1000~1500rpm to obtain an organic medium film with a smooth surface; The step of curing the organic medium in S7 comprises the following steps: S7.1, solvent volatilization stage, heating rate 0.5~2℃ / min; S7.2, bubble volatilization stage, heating rate 0.5~2℃ / min, duration 30~120min; S7.3, medium solidification stage, heating rate 1~2℃ / min, holding time 60~120min; S7.4, cooling stage, cooling rate 3~5℃ / min.

2. The method for filling a silicon groove with a void-free organic medium as claimed in claim 1, characterized in that: The plasma treatment time in S2 is 60 to 360 seconds.

3. The method for filling a silicon groove with organic medium without voids as claimed in claim 1, characterized in that: In the S3, the tackifier is spin-coated at a speed of 600-1200 rpm, and the tackifier is allowed to stand for 60-300 seconds after being spin-coated.

4. The method for filling a silicon groove with organic medium without voids as claimed in claim 1, characterized in that: The organic solvent used in S4 is PGMEA or PGME, the pre-wetting spin coating speed is 50-300 rpm, and the pre-wetting is allowed to stand for 30-180 seconds.

Images