TMBS photoetching process capable of preventing photoresist on surface of silver film layer from falling off during development

Abstract

The invention discloses a TMBS photoetching process capable of preventing photoresist on the surface of a silver film layer from falling off during development, and belongs to the technical field of semiconductor device manufacturing. In the prior art, photoresist is easy to fall off during development. The method comprises the following steps: depositing an aluminum film layer on a wafer substrate; the surface of the aluminum film layer is coated with a first layer of photoresist, the edge washing width is j, and an electrode pattern is exposed and developed; under the masking of a first layer of photoresist, corroding the aluminum film layer to form the electrode pattern, synchronously corroding the edge of the aluminum film layer, and then removing the first layer of photoresist; an intermetallic bonding layer is deposited on the aluminum film layer, and then a silver film layer is deposited, and the distance between the silver film layer and the boundary of the wafer substrate is klt; j; continuously depositing a titanium film layer on the surface of the silver film layer; coating a second layer of photoresist on the surface of the titanium film layer, and exposing and developing an electrode pattern; sequentially corroding the titanium film layer, the silver film layer and the intermetallic bonding layer to form the electrode pattern under the masking of a second layer of photoresist; and removing the second layer of photoresist, and corroding the titanium film layer. The method is used for manufacturing the electrode of the TMBS semiconductor device.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor device manufacturing. Background Art

[0002] In the electrode manufacturing process of TMBS (Trench MOS Barrier Schottky) semiconductor devices, a process structure of depositing a silver film layer on an aluminum film layer is often used. Silver has good conductivity and is a commonly used welding material in semiconductor packaging. Using silver as an electrode can ensure extremely low resistance and good welding strength during packaging, greatly improving device performance.

[0003] However, in the silver film layer photolithography process, since the silver film layer is deposited on the surface of the aluminum film layer, the surface roughness of the silver film layer is poor due to the large aluminum grains, which will affect the adhesion between the photoresist and the surface of the silver film layer, and the photoresist is likely to fall off in the subsequent development. In addition, in the subsequent development, the silver on the surface of the silver film layer in the developing solution and the aluminum at the edge of the wafer substrate that is not completely covered by the silver film layer are likely to form a galvanic cell model, that is, when immersed in the developing solution together, aluminum is more active than silver and is likely to lose electrons, and aluminum is oxidized to trivalent aluminum and enters the developing solution, and electrons flow to silver. The hydrogen ions in the developing solution obtain electrons from the silver and are reduced to hydrogen atoms, forming hydrogen gas release, which will result in the photoresist on the surface of the silver film layer falling off.

[0004] Therefore, a large number of wafer substrates will have photoresist falling off during development, resulting in pattern defects, which will make it impossible to carry out the subsequent wet etching process and require rework. In order to prevent the outflow of defective products, all wafer substrates need to be inspected, which consumes a lot of manpower and time. Even if the photoresist of the wafer substrate does not fall off during development, there is still a risk of photoresist falling off during the subsequent wet etching. Summary of the invention

[0005] In order to prevent the photoresist on the surface of the silver film layer from falling off during development in the TMBS photolithography process, the present invention provides a technical solution named "TMBS photolithography process capable of preventing the photoresist on the surface of the silver film layer from falling off during development".

[0006] The present invention comprises the following steps:

[0007] S1: Figure 1 As shown, an aluminum film layer 2 is deposited on a wafer substrate 1, the thickness of the aluminum film layer 2 is 3 μm to 5 μm, and the distance between the aluminum film layer 2 at the edge of the wafer substrate 1 and the boundary of the wafer substrate 1 is i=1.2 mm to 1.4 mm;

[0008] S2: Figure 2As shown, a first layer of photoresist 3 is coated on the surface of the aluminum film layer 2. The trimming width j of the first layer of photoresist 3 is 2.5 mm to 3 mm, and the error of the trimming width j is within the range of ±0.1 mm. The first layer of photoresist 3 is exposed and developed to form an electrode pattern;

[0009] S3: As Figure 3 shown, under the masking of the first layer of photoresist 3, the aluminum film layer 2 is etched to form the electrode pattern. The edge of the aluminum film layer 2 is etched synchronously. The distance i is equal to the distance j. After that, the first layer of photoresist 3 is removed, as Figure 4 shown;

[0010] S4: As Figure 5 shown, a titanium layer with a thickness of and a nickel layer with a thickness of are sequentially deposited on the aluminum film layer 2. The titanium layer and the nickel layer form an intermetallic bonding layer 4. Then, a silver film layer 5 is deposited. The silver film layer 5 covers the surface of the intermetallic bonding layer 4 and the side circumferential surfaces of the intermetallic bonding layer 4 and the aluminum film layer 2. The thickness of the silver film layer 5 is The distance k between the part of the silver film layer 5 covering the side circumferential surface and the boundary of the wafer substrate 1 is < j, and k = 0 mm to 2 mm;

[0011] S5: As Figure 6 shown, a titanium film layer 6 with a thickness of is continuously deposited on the surface of the silver film layer 5;

[0012] S6: As Figure 7 shown, a second layer of photoresist 7 is coated on the surface of the titanium film layer 6. The trimming width of the second layer of photoresist 7 is equal to the distance k. The second layer of photoresist 7 is exposed and developed to form an electrode pattern;

[0013] S7: Under the masking of the second layer of photoresist 7, the titanium film layer 6, the silver film layer 5, and the intermetallic bonding layer 4 are sequentially etched to form the electrode pattern;

[0014] S8: As Figure 8 shown, the second layer of photoresist 7 is removed, and then the titanium film layer 6 is etched away.

[0015] The present invention adjusts the edge washing width of the first layer of photoresist 3 to j to ensure that the edge portion of the aluminum film layer 2 is corroded in a circle in the subsequent etching process. The intermetallic bonding layer 4 serves as an intermediate transition layer between the aluminum film layer 2 and the silver film layer 5, and can improve the adhesion between the two. The distance between the deposited silver film layer 5 and the edge of the wafer substrate 1 at the edge position of the wafer substrate 1 is k, which completely covers the aluminum film layer 2, forming a covering of the silver-aluminum metal electrode structure, and no aluminum is exposed at the edge position of the wafer substrate 1, thereby avoiding the formation of a primary battery reaction between the two metals of silver and aluminum in the developing solution. After the deposition of the silver film layer 5 is completed, the titanium film layer 6 is continuously deposited. Since titanium is easy to form a natural oxide in the air at room temperature, it is easy to undergo a substitution reaction with HMDS to form a hydrophobic group in the process of photolithography hydrophobic treatment, thereby increasing the adhesion between the silver film layer 5 and the photoresist 7, and since the thickness of the deposited titanium film layer 6 is very thin, it is easy to be corroded, and does not affect the conductivity of the silver film layer 5. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of S1 of the present invention.

[0017] Figure 2 This is a schematic diagram of S2 of the present invention.

[0018] Figure 3 It is a schematic diagram of the synchronous corrosion of the edge of the aluminum film layer 2 in S3 of the present invention.

[0019] Figure 4 It is a schematic diagram of removing the first layer of photoresist 3 in S3 of the present invention.

[0020] Figure 5 This is a schematic diagram of S4 of the present invention.

[0021] Figure 6 This is a schematic diagram of S5 of the present invention.

[0022] Figure 7 This is a schematic diagram of S6 of the present invention, which also serves as a summary figure.

[0023] Figure 8 This is a schematic diagram of S8 of the present invention. DETAILED DESCRIPTION

[0024] The edge cleaning method of the first photoresist layer 3 and the second photoresist layer 7 is the same, and is implemented by using an EBR (Edge Bead Removal, silicon wafer edge exposure) or WEE (Wafer Edge Exposure, silicon wafer edge exposure) process method.

[0025] The aluminum film layer 2 and the silver film layer 5 are deposited in the same manner, using a sputtering or evaporation process.

[0026] The aluminum film layer 2 and the silver film layer 5 are corroded and developed in the same way, using dry etching or wet etching methods.

[0027] A specific example of the TMBS lithography process of the present invention that can prevent the photoresist on the surface of the silver film layer from falling off during development is described as follows.

[0028] As Figure 1 shown, an aluminum film layer 2 is deposited on the wafer substrate 1. The thickness of the aluminum film layer 2 is 3 μm, and the distance from the edge of the aluminum film layer 2 to the boundary of the wafer substrate 1 at the edge of the wafer substrate 1 is i = 1.2 mm; as Figure 2 shown, a first layer of photoresist 3 is coated on the surface of the aluminum film layer 2, and the trimming width of the photoresist 3 is adjusted to j = 2.5 mm, and the error of the trimming width j is within the range of ±0.1 mm, and the electrode pattern is exposed and developed; as Figure 3 shown, under the masking of the first layer of photoresist 3, the aluminum film layer 2 is corroded, and the edge of the aluminum film layer 2 is also corroded to a position where the distance from the boundary of the wafer substrate 1 is j = 2.5 mm, and then the first layer of photoresist 3 is removed, as Figure 4 shown; as Figure 5 shown, a thick titanium layer and a thick nickel layer are sequentially deposited on the aluminum film layer 2 to form an intermetallic adhesion layer 4, and then a silver film layer 5 is deposited. The silver film layer 5 covers the surface of the intermetallic adhesion layer 4 and the side circumferential surfaces of the intermetallic adhesion layer 4 and the aluminum film layer 2. The thickness of the silver film layer 5 is The silver film layer 5 is k < j from the boundary of the wafer substrate 1 at the edge position of the wafer substrate 1, and k = 1 mm; as Figure 6 shown, a thick titanium film layer 6 is continuously deposited on the silver film layer 5; as Figure 7 shown, a second layer of photoresist 7 is coated on the surface of the titanium film layer 6. The trimming width of the second layer of photoresist 7 is k = 1 mm, and the electrode pattern is exposed and developed; under the masking of the second layer of photoresist 7, the titanium film layer 6, the silver film layer 5, and the adhesion layer 4 are sequentially corroded to form the electrode pattern; as Figure 8 shown, the second layer of photoresist 7 is removed and the surface titanium film layer 6 is corroded away.

Claims

1. A TMBS photolithography process capable of preventing the photoresist on the surface of the silver film layer from falling off during development, characterized in that: The following steps are involved: S1: depositing an aluminum film layer (2) on a wafer substrate (1), wherein the thickness of the aluminum film layer (2) is 3 μm to 5 μm, and the distance between the aluminum film layer (2) at the edge of the wafer substrate (1) and the border of the wafer substrate (1) is i=1.2 mm to 1.4 mm; S2: coating a first layer of photoresist (3) on the surface of the aluminum film layer (2), wherein the edge wash width j of the first layer of photoresist (3) is 2.5 mm to 3 mm, and the error of the edge wash width j is within the range of ±0.1 mm, and exposing the first layer of photoresist (3) to develop an electrode pattern; S3: Under the masking of the first layer of photoresist (3), the aluminum film layer (2) is etched to form the electrode pattern, the edge of the aluminum film layer (2) is etched synchronously, the distance i is equal to the distance j, and then the first layer of photoresist (3) is removed; S4: Deposit successively on the aluminum film layer (2) a titanium layer with a thickness of and a nickel layer with a thickness of to form an intermetallic bonding layer (4), and then deposit a silver film layer (5). The silver film layer (5) covers the surface of the intermetallic bonding layer (4) and the side circumferential surfaces of the intermetallic bonding layer (4) and the aluminum film layer (2). The thickness of the silver film layer (5) is The distance k between the part of the silver film layer (5) covering the side circumferential surface and the boundary of the wafer substrate (1) is less than j, and k = 0 mm to 2 mm; S5: Continue to deposit on the surface of the silver film layer (5) A titanium film layer (6) having a thickness of 1000 mm; S6: coating a second layer of photoresist (7) on the surface of the titanium film layer (6), wherein the edge width of the second layer of photoresist (7) is equal to the distance k, and exposing and developing an electrode pattern; S7: Under the masking of the second photoresist layer (7), the titanium film layer (6), the silver film layer (5), and the intermetallic bonding layer (4) are sequentially etched to form the electrode pattern; S8: removing the second photoresist layer (7), and then etching away the titanium film layer (6).

2. The TMBS photolithography process according to claim 1, which is capable of preventing the silver film layer surface photoresist from falling off during development, is characterized in that: The edge washing method of the first layer of photoresist (3) and the second layer of photoresist (7) is the same, and is implemented by using an EBR or WEE process method.

3. The TMBS photolithography process according to claim 1, which is capable of preventing the silver film layer surface photoresist from falling off during development, is characterized in that: The aluminum film layer (2) and the silver film layer (5) are deposited in the same manner, using a sputtering or evaporation process.

4. The TMBS photolithography process capable of preventing the silver film layer surface from falling off during photoresist development according to claim 1, characterized in that: The etching and developing methods of the aluminum film layer (2) and the silver film layer (5) are the same, using dry etching or wet etching.

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