Dry etching crystal face protection process

Abstract

The invention discloses a dry etching crystal face protection process, which comprises the following steps of: 1, providing a wafer of which the back surface is provided with a to-be-etched film layer; 2, forming a protective layer on the front surface of the wafer, wherein the protective layer is an electrostatic film or protective glue; 3, performing dry etching on the back surface of the wafer so as to remove the film layer to be etched; and 4, removing the protective layer on the front surface of the wafer. According to the method, a traditional oxide layer protection scheme is replaced by a physical film pasting or gluing mode, the wafer scratch risk is reduced, meanwhile, the process cost is remarkably reduced, the operation time is shortened, and the method is suitable for wafer back etching scenes of soft film layers such as polycrystalline silicon and oxide layers.

Description

Technical Field

[0001] This invention relates to the field of semiconductor integrated circuit manufacturing, and in particular to a dry etching process for protecting the crystal surface. Background Technology

[0002] In semiconductor integrated circuit manufacturing, when depositing thin films such as polysilicon and silicon dioxide using furnace tube processes, film layers are formed simultaneously on both the front and back sides of the wafer. When device manufacturing only requires retaining the front film layer, the back film layer needs to be removed. When the film layer is polysilicon or silicon dioxide, its relatively soft texture means that the front side of the wafer will directly contact the table (carrier) during back-side etching, posing a risk of scratches. Currently, the common practice is to first grow a layer of oxide on the front side of the wafer to protect it before performing back-side etching, and then etch away this oxide layer after the back-side etching is completed. This approach requires a second high-temperature oxide layer deposition, which has drawbacks such as high energy consumption and long processing time. The subsequent second etching to remove the protective layer further increases the process complexity.

[0003] Therefore, the present invention aims to provide a dry etching process for protecting the crystal surface, which replaces the traditional oxide layer protection scheme by physically applying a film or coating adhesive. This reduces the risk of wafer scratches while significantly reducing process costs and shortening operation time, and is suitable for back etching scenarios of soft films such as polysilicon and oxide layers. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a dry etching process for protecting crystal surfaces, comprising the following steps: Step 1: Provide a wafer, the back of which has a film layer to be etched; Step 2: Form a protective layer on the front side of the wafer. The protective layer is an electrostatic film or a protective adhesive. Step 3: Dry etching is performed on the back side of the wafer to remove the film layer to be etched; Step 4: Remove the protective layer from the front side of the wafer.

[0005] Before performing step two, the wafer is cleaned to remove surface particles from the front side of the wafer. Furthermore, before growing the protective layer on the crystal surface, the crystal surface is cleaned to remove particles, preventing bubbling during the protective layer growth process and ensuring effective protection of the crystal surface.

[0006] The protective layer in step two is an electrostatic film with a thickness ≤ 5 μm. Furthermore, when applying a protective film to the front side of the wafer, the protective film used must be an electrostatic film with a thickness ≤ 5 μm; thicker, more adhesive blue films cannot be used to avoid residue buildup when removing the film due to patterns on the wafer surface.

[0007] The wafer is placed on a carrier stage, and the stage is heated to maintain a temperature ≥120°C. When the adhesion of the electrostatic film is low, the stage needs to be heated to ensure the effective adhesion of the electrostatic film.

[0008] In step two, the film feeding speed is controlled at 5~30m / sec, and the electrostatic film is cut with a blade. Controlling the film feeding speed to 5~30m / sec prevents wrinkles from forming on the electrostatic film.

[0009] The blade is heated during the cutting process to ensure a stable and high-performance cutting effect.

[0010] In step four, when removing the electrostatic film, the tearing angle is 45±1°, and the tearing speed is controlled in three stages: the first stage is 0.2~0.5 mm / s, the second stage is 2~6 mm / s, and the third stage is 5~8 mm / s.

[0011] The protective layer in step two is a protective adhesive. The wafer is placed on a carrier stage, and the stage temperature is <120℃. When applying adhesive to protect the front side of the wafer, the stage temperature must be kept below 120℃. If the stage temperature is too high, the protective adhesive will soften, causing stage contamination.

[0012] The protective adhesive material is polyimide with a thickness of 0.2~0.3 μm.

[0013] In step four, the protective adhesive is removed using dry etching.

[0014] The beneficial effects of this invention are: The dry etching crystal surface protection process provided by this invention replaces the traditional oxide layer protection scheme by applying a film or adhesive to the front side of the wafer, thus avoiding scratches on the front side of the wafer during the dry etching process. At the same time, it significantly reduces process costs and shortens operation time by saving two process steps: oxide layer growth and secondary etching. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart of a dry etching process for protecting crystal surfaces provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure for applying a protective film to the front side of a wafer, provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the structure for applying adhesive to protect the front side of a wafer, as provided in Embodiment 2 of the present invention.

[0017] Figure label: 1. Wafer; 2. Electrostatic film; 3. Protective adhesive. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in and described with reference to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0019] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0020] Example 1 like Figure 1 and Figure 2 As shown, this invention provides a dry etching wafer protection process, which involves attaching an electrostatic film to the front side of the wafer before dry etching the back side, and includes the following steps: Step 1: Provide a wafer, the back of which has a film layer to be etched; Step 2: Form a protective layer on the front side of the wafer, the protective layer being an electrostatic film; Step 3: Dry etching is performed on the back side of the wafer to remove the film layer to be etched; Step 4: Remove the protective layer from the front side of the wafer.

[0021] Specifically, in step one, when growing the film using the furnace tube process, the film layers grow simultaneously on both the front and back sides of the wafer. Now, it is necessary to remove the unwanted film layer from the back side using dry etching. A wafer 1 to be etched is provided. First, the wafer is cleaned to remove surface particles on the front side to prevent air bubbles from forming during film application. During cleaning, the front side of the wafer is rinsed with high-pressure deionized water and then dried.

[0022] Step two: An electrostatic film 2 is attached to the crystal surface, with a thickness ≤ 5 μm. During the attachment process, the film feed speed is controlled at 5~30 m / sec, and the feed speed and roller height are adjusted according to the type of electrostatic film. After attachment, excess electrostatic film is cut off using a heated blade to ensure cutting effectiveness. When the adhesion of the electrostatic film is low, the stage needs to be heated during attachment to maintain a stage temperature ≥ 120°C. Traditional protection methods require approximately 14 minutes to grow the oxide layer, while this embodiment reduces the time to approximately 1 minute through film attachment protection, significantly shortening the operation time and reducing process costs.

[0023] Step 3: Dry etching is performed on the back of the wafer. In this step, wafer 1 is flipped over and held in place on its front side, and dry etching is performed on the back of the wafer. Only dry etching can be used for the back of the wafer; wet etching solutions cannot be used to avoid damaging the electrostatic film. After etching, the wafer is cleaned with EKC cleaning agent, and the critical dimension (CD) is measured. Simultaneously, the appearance of the wafer is checked to determine if it meets the requirements.

[0024] Step 4: After the back etching is completed, flip the wafer 1 and peel off the electrostatic film 2 on the front side of the wafer. When peeling off the electrostatic film, control the peeling angle to be 45±1° and control the peeling speed in three stages: the first stage is 0.2~0.5 mm / s, the second stage is 2~6 mm / s, and the third stage is 5~8 mm / s.

[0025] Example 2 This embodiment provides a dry etching process for protecting the wafer surface. Unlike Embodiment 1, which uses an electrostatic film to protect the front side of the wafer from scratches, this embodiment protects the front side of the wafer by applying a protective adhesive.

[0026] Specifically, such as Figure 3 As shown, after cleaning the wafer, polyimide material is spin-coated on the front side of wafer 1, and then spin-coated and dried to form a protective layer 3 on the front side of wafer 1. The thickness of the polyimide is 0.2~0.3um, which can effectively protect the wafer surface without increasing the process cost too much.

[0027] Step 3: Dry etching of the back of the wafer. In this step, wafer 1 is flipped over and held in place on the front side, and dry etching is performed on the back of the wafer. Only dry etching can be used for the back of the wafer; wet etching solutions cannot be used to avoid damaging the protective layer. During the etching process, the stage temperature must be kept below 120°C to prevent the protective adhesive from softening and causing stage contamination due to excessively high temperatures.

[0028] Step four: After the back-side etching is completed, flip wafer 1 and remove the polyimide protective layer 3 using dry etching. Clean the wafer with EKC cleaning agent after etching.

[0029] The dry etching wafer protection process provided in this embodiment can save about 1 hour of process time and significantly reduce process costs compared to the traditional method of first growing an oxide layer on the front side of the wafer for protection and then etching away the oxide layer after the back side is etched.

[0030] Furthermore, it should be noted that in this specification, "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A dry etching process for protecting crystal surfaces, characterized in that, Includes the following steps: Step 1: Provide a wafer, the back of which has a film layer to be etched; Step 2: Form a protective layer on the front side of the wafer. The protective layer is an electrostatic film or a protective adhesive. Step 3: Dry etching is performed on the back side of the wafer to remove the film layer to be etched; Step 4: Remove the protective layer from the front side of the wafer.

2. The dry etching crystal surface protection process according to claim 1, characterized in that, Before performing step two, the wafer is cleaned to remove surface particles on the front side of the wafer.

3. The dry etching crystal surface protection process according to claim 1, characterized in that, The protective layer in step two is an electrostatic film with a thickness ≤ 5 μm.

4. The dry etching crystal surface protection process according to claim 3, characterized in that, The wafer is placed on a carrier stage, and the carrier stage is heated to maintain a temperature ≥120°C.

5. The dry etching crystal surface protection process according to claim 3, characterized in that, In step two, the film feeding speed is controlled at 5~30m / sec, and the electrostatic film is cut with a blade.

6. The dry etching crystal surface protection process according to claim 5, characterized in that, In step two, the blade is subjected to heat treatment.

7. The dry etching crystal surface protection process according to claim 3, characterized in that, In step four, when removing the electrostatic film, the tearing angle is 45±1°, and the tearing speed is controlled in three stages: the first stage is 0.2~0.5 mm / s, the second stage is 2~6 mm / s, and the third stage is 5~8 mm / s.

8. The dry etching crystal surface protection process according to claim 1, characterized in that, The protective layer in step two is a protective adhesive, and the wafer is placed on a stage with a stage temperature of <120°C.

9. The dry etching crystal surface protection process according to claim 8, characterized in that, The protective adhesive material is polyimide with a thickness of 0.2~0.3 μm.

10. The dry etching crystal surface protection process according to claim 8, characterized in that, In step four, the protective adhesive is removed using dry etching.

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