Crystal defect treatment method for aluminum gasket
By first wet etching to remove crystals with smaller surfaces of the aluminum liner, and then dry etching to remove larger crystals, the problem of difficulty in removing two types of crystal defects in the prior art is solved, and the flatness and uniformity of the wafer surface are achieved.
Patent Information
- Application Number
- CN202411215511.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-03-14
AI Technical Summary
After large-scale wafer production, crystallization is easily formed on the surface of the aluminum liner, which affects subsequent packaging. It is difficult for the prior art to effectively remove two types of crystallization defects of different sizes.
The smaller first type of crystals are removed by first performing wet etching to make the surface of the aluminum liner flat, and then the larger second type of crystals are removed by dry etching. Combined with the specific etching gas and processing time, in-plane uniformity is ensured.
It effectively reduces crystal defects on the wafer surface, ensures the flatness and uniformity of the aluminum pad surface, and avoids the re-formation of crystal defects.
Smart Images
Figure CN119626899A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor technology, and in particular to a method for processing crystal defects of an aluminum liner. Background Art
[0002] Currently, due to large market fluctuations, after large-scale wafer production is completed, BSI (Backside illuminated CMOS image sensor) / UTS (stacked CMOS image sensor) customers will have a long backlog of wafer products in warehouses and clients for various reasons, resulting in the formation of crystals (PDCY) on the Al Pad (aluminum pad or aluminum liner) on the surface of the wafer products, affecting subsequent packaging.
[0003] It should be noted that the information disclosed in the background technology section of the invention is only intended to deepen the understanding of the general background technology of the invention, and should not be regarded as an admission or suggestion in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention
[0004] The object of the present invention is to provide a method for processing crystal defects of an aluminum liner to solve the problem of crystallization on the surface of the aluminum liner.
[0005] In order to solve the above technical problems, the present invention provides a method for processing crystal defects of an aluminum liner, comprising the following steps:
[0006] Providing a wafer having an aluminum liner, wherein the aluminum liner has a first type of crystal and a second type of crystal, wherein the first type of crystal is smaller in size than the second type of crystal;
[0007] The wafer is wet-etched to remove the first type of crystals, and then the wafer product is dry-etched to remove the second type of crystals.
[0008] Preferably, NE111 chemical solution is used to perform wet etching on the wafer product.
[0009] Preferably, in dry etching the wafer, the main etching gas used is one of CHF3, CF4, N2, and Ar.
[0010] Preferably, the main etching gas is used to etch the wafer for 60 seconds.
[0011] Preferably, after dry etching using the main etching gas, treatment is performed using 1000 sccm of Ar.
[0012] Preferably, the treatment time of 1000 sccm Ar is 10 s.
[0013] Preferably, after dry etching using the main etching gas, treatment is performed using 1800 sccm of O2.
[0014] Preferably, the treatment time of 1800 sccm O2 is 30 seconds.
[0015] Preferably, the size of the second type of crystals is 2-5 μm.
[0016] Preferably, the wafer is used to manufacture a stacked CMOS image sensor or a back-illuminated CMOS image sensor.
[0017] In the crystal defect processing method of the aluminum pad provided by the present invention, the wafer surface is first wet-etched to make the wafer surface flat while removing the first type of crystals, and then the larger second type of crystals are processed by dry etching, thereby effectively reducing the crystal defects on the surface of the storage wafer. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.
[0019] Figure 1 This is a schematic diagram of large crystals on the surface of a wafer product;
[0020] Figure 2 It is a schematic diagram of tiny particles on the surface of wafer products;
[0021] Figure 3 It is a schematic diagram of the defect formation mechanism on the surface of the wafer product;
[0022] Figure 4 is an execution flow chart of an embodiment of the present invention;
[0023] Figure 5 It is a schematic diagram of dry etching alone;
[0024] Figure 6 The defect morphology is shown before and after the crystal defect processing method of the aluminum liner provided by the present invention is adopted. DETAILED DESCRIPTION
[0025] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.
[0026] As used in the present invention, the singular forms "a", "an" and "the" include plural objects, the term "or" is generally used in a sense including "and / or", the term "several" is generally used in a sense including "at least one", and the term "at least two" is generally used in a sense including "two or more". In addition, the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features. The term "proximal end" is usually the end close to the operator, and the term "distal end" is usually the end close to the patient. "One end" and "the other end" as well as "proximal end" and "distal end" usually refer to two corresponding parts, which include not only the endpoints. The terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of the two elements or the interaction relationship between the two elements. In addition, as used in the present invention, an element is arranged on another element, which usually only means that there is a connection, coupling, matching or transmission relationship between the two elements, and the connection, coupling, matching or transmission between the two elements can be direct or indirect through an intermediate element, and it cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, one element can be in any position such as inside, outside, above, below or on one side of another element, unless the content clearly indicates otherwise. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0027] The inventors have found that there are often fluorine-containing gases and polysilicon in the microenvironment where Al PAD is stored. Long-term storage of Al PAD is prone to react with H2O / O2 in the air to form crystals. In this process, the reaction Al+HF+H2O→AlOxFy occurs, and further reactions will occur. The reaction mechanism is as follows: Figure 3 As shown in the figure, the system composed of the aluminum oxide film and the metal aluminum film on the surface of the aluminum liner generates aluminum hydroxide under the joint action of fluoride ions and water vapor; the second step is the acid-base neutralization reaction, and the aluminum hydroxide on the surface generates a crystalline compound AlOxFy containing aluminum fluoride and oxygen under the action of hydrofluoric acid. This substance is crystalline (PDCY).
[0028] The inventors further discovered that for the crystals formed on the aluminum liner (PDCY), there are generally two types of crystal sizes, such as Figure 1 The large crystals (Crystal) shown and Figure 2There are two types of tiny particles (Yellow Pad) shown, and their composition is Al / O / F.
[0029] The inventors further studied and found that in the actual process of removing crystal defects, the wet etching method was first used, but it was unable to remove large crystal defects; dry etching was then used to try to remove the crystals. Although a series of influencing factors such as the gas composition, ratio and time of the dry etching were adjusted during the operation, only large crystal defects were removed, such as Figure 5 As shown, it is difficult to control the in-plane uniformity, there is no improvement on tiny particles (Yellow Pad), and new tiny particles are formed after some of the tiny particles are removed, causing abnormalities at the edge of the wafer. Using dry etching or wet etching alone has limited effect on improving the crystallization of the wafer surface, and when removing one type of defects, the other type of defects is difficult to remove while ensuring the in-plane uniformity, and new crystallization defects are easily formed again.
[0030] Based on this, the core idea of the present invention is to first remove smaller crystal defects by wet etching to make the surface of the aluminum pad smooth, and then further process it by dry etching to effectively remove the crystal defects on the surface of the aluminum pad.
[0031] For details, please refer to Figure 4-Figure 6 , which is a schematic diagram of an embodiment of the present invention. Figure 4 As shown, a method for processing crystal defects of an aluminum liner comprises the following steps:
[0032] S1, providing a wafer with an aluminum liner, wherein the aluminum liner has a first type of crystals and a second type of crystals, and the size of the first type of crystals is smaller than that of the second type of crystals.
[0033] The size of the second type of crystals is 2-5 μm, and the second type of crystals are shaped like lotus leaves or petals. Figure 5 The first type of crystals are much smaller than the second type of crystals, and the first type of crystals are distributed on the entire aluminum liner. Figure 5 The second type of crystals are surrounded by densely packed protrusions.
[0034] Specifically, the wafer is used to manufacture a stacked CMOS image sensor (UTS) or a back-illuminated (BSI) CMOS image sensor. For a stacked CMOS image sensor, different process methods are used to manufacture pixel and logic chips on two wafers respectively, and then bond them to form a UTS CIS chip.
[0035] S2, wet etching the wafer to remove the first type of crystals, and then dry etching the wafer product to remove the second type of crystals, such as Figure 6 As shown, the left picture is a schematic diagram of the wafer surface and the local schematic diagram of the aluminum pad without processing crystal defects, and the right picture is a schematic diagram of the wafer surface and the local schematic diagram of the aluminum pad after wet etching and dry etching. It can be seen that the crystal defects are significantly improved after treatment, and the in-plane uniformity is good.
[0036] Among them, when wet etching is performed alone, large pieces of second type crystals cannot be effectively removed. Similarly, when dry etching is performed alone, even if parameters such as the composition, proportion and time of the etching gas are adjusted, large pieces of second type crystals and smaller first type crystals cannot be removed while ensuring the uniformity within the surface, and there will be abnormalities at the edge of the wafer.
[0037] In one embodiment, the wafer is wet-etched using NE111 chemical solution to remove the first type of crystals, improve the crystal distribution on the wafer surface, and make the wafer surface flat.
[0038] Exemplarily, in dry etching the wafer product, the main etching gas used is one of CHF3, CF4, N2, and Ar. The wafer is etched for 60 seconds using the main etching gas.
[0039] Specifically, after dry etching with the main etching gas, 1000 sccm of Ar is used for 10 seconds. After dry etching with the main etching gas, 1800 sccm of O2 is used for 30 seconds.
[0040] In one embodiment, the main etching gas used for dry etching is CHF3 / CF4 / N2 / Ar for 60 seconds, and then 1000 sccm of Ar is introduced for 10 seconds and 1800 sccm of O2 is introduced for 30 seconds respectively.
[0041] It can be understood that in RWK flow, the etching amount can be determined by measuring the before and after values to ensure the uniformity within the wafer surface.
[0042] In the crystal defect processing method of the aluminum pad provided by the present invention, for the aluminum pad with crystal defects on the surface, since there are two types of crystal defects of different sizes distributed on the surface, in the existing process flow, using dry etching and wet etching alone to remove the crystal defects both have certain defects. When dry etching is used alone, although large pieces of second-type crystals can be removed, even if the parameters such as the composition, proportion and time of the etching gas are adjusted, the uniformity within the surface cannot be guaranteed, and the removal effect of smaller first-type crystals is limited. It is difficult to remove large pieces of second-type crystal defects using wet etching alone. The present invention first performs wet etching on the wafer surface to make the wafer surface flat while removing the first-type crystals, and then uses dry etching to process larger second-type crystals, thereby effectively reducing the crystal defects on the surface of the storage wafer.
[0043] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.
Claims
1. A method for treating crystal defects of an aluminum liner, characterized in that: The following steps are involved: Providing a wafer having an aluminum liner, wherein the aluminum liner has a first type of crystal and a second type of crystal, wherein the first type of crystal is smaller in size than the second type of crystal; The wafer is wet-etched to remove the first type of crystals, and then the wafer product is dry-etched to remove the second type of crystals.
2. The method for processing crystal defects of an aluminum liner according to claim 1, characterized in that: The wafer product is wet-etched using NE111 chemical solution.
3. The method for processing crystal defects of an aluminum liner according to claim 1, characterized in that: When the wafer is dry-etched, the main etching gas used is one of CHF3, CF4, N2, and Ar.
4. The method for processing crystal defects of an aluminum liner according to claim 3, characterized in that: The wafer is etched with the main etching gas for 60 seconds.
5. The method for processing crystal defects of an aluminum liner according to claim 3, characterized in that: After dry etching using the main etching gas, treatment is performed using 1000 sccm of Ar.
6. The method for treating crystal defects of an aluminum liner according to claim 5, characterized in that: The treatment time of 1000 sccm Ar was 10 s.
7. The method for processing crystal defects of an aluminum liner according to claim 3, characterized in that: After dry etching using the main etching gas, treatment is performed using 1800 sccm of O2.
8. The method for processing crystal defects of an aluminum liner according to claim 7, characterized in that: The treatment time of O2 at 1800sccm is 30s.
9. The method for processing crystal defects of an aluminum liner according to claim 1, characterized in that: The size of the second type of crystals is 2-5 μm.
10. The method for processing crystal defects of an aluminum liner according to claim 1, characterized in that: The wafer is used to manufacture a stacked CMOS image sensor or a back-illuminated CMOS image sensor.