Dry etching method of high-aspect-ratio large-angle silicon-based inclined hole and packaging structure

Abstract

The invention discloses a dry etching method for a silicon-based inclined hole with a high aspect ratio and a large angle, which improves the aspect ratio of the silicon-based inclined hole and is simple in operation steps, thereby improving the performance of a packaging structure and ensuring that the density of the packaging structure per unit area can be improved. The method is characterized in that a straight hole structure is etched in a silicon groove through a Bosch process, and then the straight hole structure is expanded into the dry etching of the inclined hole structure through a non-Bosch process.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor chip packaging, in particular to a dry etching method for high aspect ratio and large angle silicon-based oblique holes. The present invention also provides a packaging structure corresponding to the method. Background Art

[0002] Figure 1 A known chip packaging structure is disclosed, in which a Si wafer and a glass are bonded together through a bonding layer, and a circuit redistribution circuit is formed on the back of the Si wafer through a TSV (Through Silicon Via), and then cut into a single package. However, due to the limitation of dry etching technology, the depth and angle of the oblique hole in the Si groove are difficult to increase. Usually, the depth is less than 70 μm and the angle is less than 73°, resulting in a large spacing between pads that need to be arranged during design, and it is difficult to increase the density of the package structure per unit area. At the same time, the silicon thickness of the package body is thin and the structural strength is low. In addition, there are a series of problems in the previous multi-step etching technology of high aspect ratio oblique holes, such as obvious sharp corners at the top of the hole, large protrusions on the side walls of the hole, and uneven hole contours. These problems will directly or indirectly lead to leakage or reliability failure of the package. For this reason, it is urgent to develop a dry etching method suitable for high aspect ratio and large angle silicon-based oblique holes, so as to improve the performance of the package structure and ensure that the density of the package structure per unit area can be increased. Summary of the invention

[0003] In response to the above problems, the present invention provides a dry etching method for high aspect ratio and large angle silicon-based inclined holes, which improves the aspect ratio of the silicon-based inclined holes and has simple operation steps, thereby improving the performance of the packaging structure and ensuring that the density of the packaging structure per unit area can be increased.

[0004] A dry etching method for high aspect ratio and large angle silicon-based inclined holes, characterized in that the inclined holes are firstly formed by etching a straight hole structure in a silicon groove through a Bosch process, and then expanding the straight hole structure into an inclined hole structure through a non-Bosch process.

[0005] It is further characterized by:

[0006] First, the glass is bonded to the Si wafer, and then the Si wafer is thinned to the target thickness. Then, a groove structure is etched on the back of the Si. Then, a straight hole structure is etched in the Si groove through the Bosch process. Then, an inclined hole structure is etched through a non-Bosch process. Then, an insulating layer is covered on the TSV to form a redistribution line. Then, photoresist is used as a solder mask layer, and the wafer is cut into single chips to complete the packaging.

[0007] It is further characterized in that it comprises the following steps:

[0008] S1, forming a bonding layer 200 on the glass 100 by coating;

[0009] S2, bonding the Si wafer 300 and the glass with the bonding layer together, grinding and stress-relief etching the Si wafer to a target thickness, and presetting a Pad on the Si wafer;

[0010] S3, making a groove opening on the Si back side of the Si wafer by coating, exposing, and developing;

[0011] S4, etching a Si groove on the back side of Si by a non-Bosch process;

[0012] S5, making hole openings and cutting path openings in the Si groove by coating, exposing, and developing;

[0013] S6, a straight hole structure is etched in the Si groove by Bosch process, and the pad does not leak out at this time;

[0014] S7, expanding the straight hole structure into an oblique hole structure through a non-Bosch process to expose the pad, and etching out a cutting path at the same time, the cutting path is located between two adjacent pads;

[0015] S8, forming a passivation layer 400 on the back of Si by coating or vacuum lamination, and then opening the Pad position by exposure and development;

[0016] S9, obtaining a metal redistribution line 500 by metal redistribution on the passivation layer to extend the pad lead;

[0017] S10, forming a solder resist layer 600 on the metal redistribution circuit 500 by coating, then exposing the redistribution circuit that needs to be electrically led out by exposure and development, and then forming solder balls 700 by printing solder paste or planting balls;

[0018] S11, cutting the whole wafer into individual packages by wafer cutting.

[0019] It is further characterized by:

[0020] Step S8 can be replaced by forming an oxide or nitride insulating layer by plasma chemical vapor deposition, and then opening the pad position by a yellow light process and an oxide etching process;

[0021] In step S9, when the metal is re-wired, a seed layer is first deposited, then electroplated to the target Cu thickness, and then the circuit is etched out, and then Ni / Au is electrolessly plated to form protection on the metal re-wired circuit 500.

[0022] A packaging structure of a silicon-based inclined hole with a high aspect ratio and a large angle is obtained by a dry etching method of a silicon-based inclined hole with a high aspect ratio and a large angle, and is characterized in that the high aspect ratio of the silicon-based inclined hole is not less than 100:50 and the angle is not less than 73°.

[0023] The present invention adopts a two-step etching method, which has simple steps, is easy to implement, has good hole morphology, a large process window and high mass production stability. In addition, it can reduce the pad spacing, greatly improve the interconnection density, and at the same time increase the silicon thickness of the package, thereby improving the structural strength and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of an existing chip packaging structure;

[0025] Figure 2 is a process flow chart of the dry etching method of the present invention;

[0026] Figure 3 is a schematic diagram of the packaging structure of the present invention;

[0027] The names corresponding to the serial numbers in the figure are as follows:

[0028] Pad1, silicon-based oblique hole 2;

[0029] Glass 100 , bonding layer 200 , Si wafer 300 , groove opening 301 , Si groove 302 , hole opening 303 , cutting path opening 304 , straight hole structure 305 , oblique hole structure 306 , passivation layer 400 , metal redistribution line 500 , solder resist layer 600 , solder ball 700 . DETAILED DESCRIPTION

[0030] A dry etching method for high aspect ratio and large angle silicon-based inclined holes, see Figure 2 The inclined hole adopts dry etching which first etches a straight hole structure in the silicon groove through the Bosch process, and then expands the straight hole structure into an inclined hole structure through a non-Bosch process.

[0031] First, the glass 100 is bonded to the Si wafer 300, and then the Si wafer 300 is thinned to the target thickness. Then, a Si groove is etched on the Si back side of the Si wafer, and then a straight hole structure is etched in the Si groove through the Bosch process. Then, an inclined hole structure is etched through a non-Bosch process, and then an insulating layer is covered on the TSV to form a redistribution line. Then, photoresist is used as a solder mask layer, and then the wafer is cut into single chips to complete the packaging.

[0032] It includes the following steps:

[0033] S1, a bonding layer 200 is formed on the glass 100 by coating. The bonding layer 200 uses a gapless bonding adhesive, such as TOK A01. The thickness of the bonding layer varies according to the total thickness requirement of the package.

[0034] S2, bonding the Si wafer 300 and the glass 100 with the bonding layer 200 together, grinding and stress-relief etching the Si wafer to a target thickness, presetting a Pad1 on the Si wafer 300, and reserving a cutting distance between two Pad1s of the pre-set packaging structure;

[0035] S3, making a groove opening 301 on the Si back side of the Si wafer 300 by coating, exposing and developing;

[0036] S4, through non-Bosch process (using SF 6 , C 4 F 8 , O 2 Three mixed gases) etch Si groove 302 on the back of Si;

[0037] S5, making a hole opening 303 and a cutting path opening 304 in the Si groove 302 by coating, exposing and developing;

[0038] S6, through Bosch process (using SF 6 , C 4 F 8 Two gases) etch a straight hole structure 305 along the hole opening 303 and the cutting road opening 304 in the Si groove 302, and the Pad does not leak out at this time;

[0039] S7, through non-Bosch process (using SF 6 , C 4 F 8 , O 2 The three mixed gases are used to expand the straight hole structure 305 into an oblique hole structure 306 and expose the Pad. At the same time, a cutting path is etched out. The cutting path is also an oblique hole structure and is located between two adjacent Pad1s.

[0040] S8, forming a passivation layer 400 on the back side of Si by coating or vacuum lamination, and then opening the Pad1 position by exposure and development;

[0041] Alternatively, an oxide or nitride insulating layer is formed by plasma chemical vapor deposition (PECVD), and then the pad position is opened by a yellow light process and an oxide etching process;

[0042] S9, obtaining a metal redistribution line 500 by metal redistribution on the passivation layer 400 to extend the pad lead;

[0043] During metal rewiring, a seed layer, such as Ti / Cu, is first deposited, then electroplated to a target Cu thickness, then the circuit is etched out, and then Ni / Au is chemically plated to form protection on the metal rewiring circuit 500;

[0044] S10, forming a solder resist layer 600 on the metal redistribution circuit 500 by coating, the solder resist layer 600 adopts a green or black photolithography material, and then exposing and developing the redistribution circuit that needs to be electrically led out, and then forming solder balls 700 by printing solder paste or planting balls;

[0045] S11, cutting the whole wafer into individual packages by wafer cutting.

[0046] A packaging structure of a silicon-based oblique hole with a high aspect ratio and a large angle, Figure 3 : It is obtained by a dry etching method for a high aspect ratio and large angle silicon-based inclined hole, which includes glass 100 and Si wafer 300. A bonding layer 200 is arranged on the upper surface of the glass 100, Pad1 is arranged on the bottom periphery of the Si wafer 300, a silicon-based inclined hole 2 is arranged at the thickness position of the Si wafer 300 corresponding to Pad1, a passivation layer 400 is arranged on the surface of the Si wafer 300, the solder balls on the Si wafer 300 are connected to PAD1 through metal rewiring 500, and the surface of the exposed metal rewiring 500 is provided with a solder resist layer 600. The aspect ratio of the silicon-based inclined hole 2 is not less than 100:50, and the angle is not less than 73°. In a specific embodiment, the aspect ratio of the silicon-based inclined hole 2 is 100:50, and the angle is 80°.

[0047] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0048] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A dry etching method for high aspect ratio and large angle silicon-based inclined holes, characterized in that: The inclined hole is formed by first etching a straight hole structure in a silicon groove through a Bosch process, and then expanding the straight hole structure into an inclined hole structure through dry etching using a non-Bosch process.

2. The dry etching method for high aspect ratio and large angle silicon-based inclined holes according to claim 1, characterized in that: First, the glass is bonded to the Si wafer, and then the Si wafer is thinned to the target thickness. Then, a groove structure is etched on the back of the Si. Then, a straight hole structure is etched in the Si groove through the Bosch process. Then, an inclined hole structure is etched through a non-Bosch process. Then, an insulating layer is covered on the TSV to form a redistribution line. Then, photoresist is used as a solder mask layer, and the wafer is cut into single chips to complete the packaging.

3. The dry etching method for high aspect ratio and large angle silicon-based inclined hole according to claim 2, characterized in that , which includes the following steps: S1, forming a bonding layer 200 on the glass 100 by coating; S2, bonding the Si wafer 300 and the glass with the bonding layer together, grinding and stress-relief etching the Si wafer to a target thickness, and presetting a Pad on the Si wafer; S3, making a groove opening on the Si back side of the Si wafer by coating, exposing, and developing; S4, etching a Si groove on the back side of Si by a non-Bosch process; S5, making hole openings and cutting path openings in the Si groove by coating, exposing, and developing; S6, a straight hole structure is etched in the Si groove by Bosch process, and the pad does not leak out at this time; S7, expanding the straight hole structure into an oblique hole structure through a non-Bosch process to expose the pad, and etching out a cutting path at the same time, the cutting path is located between two adjacent pads; S8, forming a passivation layer 400 on the back of Si by coating or vacuum lamination, and then opening the Pad position by exposure and development; S9, obtaining a metal redistribution line 500 by metal redistribution on the passivation layer to extend the pad lead; S10, forming a solder resist layer 600 on the metal redistribution circuit 500 by coating, then exposing the redistribution circuit that needs to be electrically led out by exposure and development, and then forming solder balls 700 by printing solder paste or planting balls; S11, cutting the whole wafer into individual packages by wafer cutting.

4. The dry etching method for high aspect ratio and large angle silicon-based inclined holes according to claim 3, characterized in that: Step S8 can be replaced by forming an oxide or nitride insulating layer by plasma chemical vapor deposition, and then opening the Pad position by a yellow light process and an oxide etching process.

5. The dry etching method for high aspect ratio and large angle silicon-based inclined holes according to claim 3, characterized in that: In step S9, when the metal is re-wired, a seed layer is first deposited, then electroplated to the target Cu thickness, and then the circuit is etched out, and then Ni / Au is electrolessly plated to form protection on the metal re-wired circuit 500.

6. A packaging structure of a silicon-based oblique hole with a high aspect ratio and a large angle, obtained by a dry etching method of a silicon-based oblique hole with a high aspect ratio and a large angle as claimed in any one of claims 1 to 5, characterized in that: The aspect ratio of the silicon-based inclined hole is not less than 100:50, and the angle is not less than 73°.

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