Method for improving metal step coverage of device
By rotating the card angle of the wafer and changing the distribution direction of the metal strips, the problem of gradually deteriorating metal step coverage was solved, achieving efficient step coverage and a stable evaporation process, improving product yield and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-26
- Publication Date
- 2026-03-31
AI Technical Summary
In existing metal evaporation processes, particularly in planetary evaporation, the coverage of metal steps gradually deteriorates from bottom to top, leading to the risk of metal breakage, especially in large-scale production where the coverage is poor.
By rotating the card angle of the wafer, the metal strips are distributed from top to bottom to left to right, maximizing their parallelism to the tangent direction of the planetary disk's edge. This changes the card form of the metal evaporation process and optimizes the metal step coverage.
It improves the coverage of metal steps, increases product yield and the stability of the evaporation process, reduces costs, and requires no equipment modification or menu adjustment.
Smart Images
Figure CN121772618A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor manufacturing process technology, and specifically relates to a method for improving the metal step coverage of devices. Background Technology
[0002] In semiconductor manufacturing, metal processing is typically performed using Physical Vapor Deposition (PVD). PVD methods mainly fall into two categories: evaporation and sputtering. Evaporation offers several significant advantages over sputtering: it can produce thin films with higher purity; evaporation equipment is relatively simple in structure, resulting in lower manufacturing and maintenance costs; furthermore, for low-melting-point metals such as aluminum and gold, evaporation is easier to implement, consumes less energy, and offers simpler process control.
[0003] In semiconductor manufacturing, typical device products such as TVS (Transient Voltage Suppressor Diode), PD (Photodiode), and PT (Phototransistor) are relatively simple in structure, focused on specific electrical properties or core characteristics of optoelectronic devices, and characterized by shallow and wide dimensions and stepped structures. They do not require high aspect ratio filling capabilities in metal deposition processes, so metal processing is generally completed using evaporation. This effectively reduces the manufacturing cost of these devices and shortens the manufacturing cycle.
[0004] Metal evaporation methods are divided into revolution-type and planetary-type. Revolution-type evaporation is vertical evaporation, which generally has better step coverage, but its disadvantage is low production capacity. For example, for 6-inch silicon wafers, only 9 wafers can be processed per batch, making it unsuitable for mass production. Planetary-type evaporation, on the other hand, can process 24 wafers per batch, with high efficiency, making it suitable for large-scale production. However, planetary-type evaporation is not vertical; the wafer holder is usually evaporated at a certain angle (60±5°). This results in a step coverage that gradually deteriorates from the 6 o'clock position to the 12 o'clock position (6 o'clock for the tangent edge, 12 o'clock for the large round edge; 12 o'clock is above, 6 o'clock is below), i.e., from bottom to top. This characteristic leads to a risk of metal strip breakage at the metal steps in the upper part of the wafer during subsequent metal corrosion. Summary of the Invention
[0005] The purpose of this invention is to provide a method for improving metal step coverage in a device. Based on the characteristics of metal evaporation step coverage, this invention effectively improves metal step coverage by rotating the card angle to change the distribution direction of the metal strips inside the device. The principle is to change the metal strip distribution from top-to-bottom to left-to-right, maximally parallel to the tangent direction of the planetary disk's edge. The fundamental purpose is to change the step direction of the metal strips, thus altering the card form of the metal evaporation process.
[0006] To address the aforementioned technical problems, this invention provides a method for improving the metal step coverage of a device, comprising:
[0007] Provide wafers;
[0008] The wafer is mounted onto the small target of the planetary disk, and the planetary disk is inserted into the device. By rotating the card angle of the wafer, the distribution direction of the metal strips inside the device is changed, and the metal step coverage is improved. The rotation angle is 45° to 135°.
[0009] Metal thin films are prepared by metal evaporation on the surface of a wafer.
[0010] Metal lithography;
[0011] Metal corrosion;
[0012] Inspection and measurement were performed using microscopy and electron microscopy. The appearance and morphology of the wafer surface were examined under a microscope, and the width of the metal strip was measured.
[0013] Preferably, in the provided wafer, the wafer is 6 inches in size and its material includes monocrystalline silicon, SOI, or SiGe.
[0014] Preferably, the provision of the wafer further includes a pretreatment of the wafer, the pretreatment including: cleaning the wafer with an acid solution, the cleaning steps specifically being: using a No. 1 cleaning solution mixed with H2O2, ammonia and water in a certain proportion, and cleaning with BOE / HF etching solution to obtain a clean wafer surface.
[0015] Preferably, the metal evaporation process includes:
[0016] Evacuate the vacuum chamber; after installation, close and lock the vacuum chamber door. Once the equipment is evacuated to 5E-4, start the main menu process.
[0017] Low-power pre-melting; start the electron beam gun and within 30 seconds, adjust the electron beam power to 30% to 40%, which is 1 / 3 to 1 / 2 of the material's melting point, to avoid direct melting; then focus the electron beam on the surface of the crucible material and scan slowly for about 1 minute.
[0018] Melting; gradually increase the electron beam power to 50%–70% within 20 seconds, adjust the scanning range to cover the entire crucible material, keep the material uniformly heated, and make the material reach a completely molten state within 4 minutes;
[0019] Evaporation; within 10 seconds, increase the evaporation rate to 12 A / s and maintain it to ensure stable electron beam scanning and uniform metal vapor coverage of the wafer surface; start the film thickness monitor to monitor the metal film thickness on the wafer surface in real time; when the film thickness reaches the target value, turn off the electron beam gun and stop evaporation;
[0020] Cooling and vacuum breaking; maintain vacuum, wait for the remaining metal in the crucible to cool to room temperature, turn off the vacuum pump, and slowly introduce inert gas into the vacuum chamber to atmospheric pressure;
[0021] Remove the wafer; open the vacuum chamber and remove the deposited wafer.
[0022] Preferably, in the low-power pre-melting, the electron beam power is adjusted to 35%.
[0023] Preferably, during the melting process, the electron beam power is adjusted to 60%.
[0024] Preferably, the metal corrosion includes: performing metal corrosion via a wet process; the wet corrosion material is an Al corrosion solution, the composition of which is hydrochloric acid-nitric acid, and the corrosion rate is [missing information]. The overall corrosion time is 2 minutes, and the adhesive is removed after corrosion is completed.
[0025] Preferably, the width of the metal strip is 45 μm and the height of the lower step of the metal strip is 0.6 μm.
[0026] Preferably, the metal film is made of Al material and has a thickness of 2.2 μm.
[0027] Preferably, the card angle needs to be adjusted according to the distribution direction of the metal steps of the device so that the optimal angle is that the step direction is parallel to the cutting edge direction of the planetary disk.
[0028] Compared with the prior art, the present invention has the following beneficial effects:
[0029] This invention utilizes the characteristic that the metal evaporation step coverage gradually improves from 12 points to 6 points. By changing the wafer mounting angle during the pre-evaporation process, the direction of the metal steps is altered, thus improving the step morphology of the metal strips inside the device. The wafer rotation angle can be automatically adjusted according to the distribution direction of the metal strips within the chip, with 45° to 135° as a reference adjustment direction. The final direction can be adjusted according to the properties of each evaporation stage. This method optimizes operator technique and wafer mounting method, requiring no equipment modification, menu adjustments, or other costs, thus minimizing costs and achieving optimized step coverage. Attached Figure Description
[0030] Figure 1 This is a schematic diagram showing the orientation of the disc at 6 o'clock and 12 o'clock.
[0031] Figure 2 This is a microscopic image showing the top-to-bottom morphology of the metal strip steps within the chip after metal etching, under the conditions of a conventional metal evaporation process.
[0032] Figure 3 This is a top-to-bottom morphology image of the metal strip steps inside the chip after metal etching, taken under an electron microscope at the location of the metal evaporation process card.
[0033] Figure 4 Location diagram of a standard metal evaporation process card.
[0034] Figure 5 This is a schematic diagram of a conventional metal evaporation process card rotated 45°.
[0035] Figure 6 This is a schematic diagram of a conventional metal evaporation process card rotated 135°.
[0036] Figure 7 This is a schematic diagram of a conventional metal evaporation process card rotated 90°.
[0037] Figure 8 This is a schematic diagram showing the parallel effect of the distribution direction of the metal strips and the tangent direction of the planetary disk's circular edge.
[0038] Figure 9 This is a topographical image of the step at the metal strip after rotating 45°.
[0039] Figure 10 This is a topographical image of the metal strip step after rotating 135°.
[0040] Figure 11 This is a topographical image of the metal strip step after rotating 90°. Detailed Implementation
[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.
[0042] like Figures 1-11 As shown, this embodiment of the invention provides a method for improving the metal step coverage of a device, the method comprising the following steps:
[0043] (1) Provide wafers;
[0044] (2) Cleaning, usually acid cleaning is used. The common cleaning steps are BOE / HF plus No. 1 liquid cleaning (H2O2, ammonia and water are mixed in a certain proportion) to obtain a clean wafer surface.
[0045] (3) Perform the evaporation process:
[0046] 1) Determine the rotation angle based on the characteristics of each evaporation stage and the distribution direction of the metal strip steps of the device products, and install the discs at the specified angle.
[0047] 2) Install the planetary disk into the device.
[0048] 3) Select the menu to perform the metal evaporation process. The metal film is made of Al material, with a deposition thickness of 2.2 μm. The equipment used is the Ulvac EI-501 series system.
[0049] The main evaporation process includes the following five stages:
[0050] Vacuuming: After installation, close and lock the vacuum chamber door. Once the equipment is evacuated to 5E-4, start the main menu process.
[0051] First stage pre-melting (low-power pre-melting): Start the electron beam gun and within 30 seconds, adjust the beam power to 35% (30%-40%), which is 1 / 3 to 1 / 2 of the material's melting point, to avoid direct melting. Then, focus the electron beam on the surface of the crucible material and scan slowly for about 1 minute.
[0052] Second stage melting: Gradually increase the electron beam power to 60% (50%-70%) within 20 seconds, adjust the scanning range to cover the entire crucible material, keep the material uniformly heated, and make the material reach a completely molten state within 4 minutes.
[0053] Formal evaporation stage: Increase the evaporation rate to 12 A / s within 10 seconds and maintain it, ensuring stable electron beam scanning and uniform metal vapor coverage of the wafer surface. Activate the film thickness monitor to monitor the surface film thickness in real time. Once the film thickness reaches the target value, turn off the electron beam gun and stop evaporation.
[0054] Cooling and vacuum breaking: Maintain a vacuum state and wait for the remaining metal in the crucible to cool to room temperature. Then, turn off the vacuum pump and slowly introduce inert gas into the vacuum chamber until atmospheric pressure is reached.
[0055] 4) Open the vacuum chamber and remove the deposited disc.
[0056] (4) Select the correct photolithography template number according to the device product model and perform metal photolithography.
[0057] (5) Metal corrosion is carried out using a wet etching process. The wet etching material is an Al etching solution, whose main components are hydrochloric acid and nitric acid, with a corrosion rate of approximately [missing information]. The overall corrosion time is 2 minutes. After corrosion is complete, a descaling process is performed.
[0058] (6) Inspect the appearance of the disc, examine its morphology under a microscope, and measure the width of the metal strip.
[0059] When mounting discs on a metal evaporation table, the conventional card design is changed—the cut edge of the disc faces the outer edge of the planetary disk—by rotating the disc as a whole by 45°-135° from the original card angle. This method effectively solves the problem of poor step coverage in the metal evaporation process, greatly improving product yield and the stability of the evaporation process.
[0060] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.
Claims
1. A method of improving device metal step coverage, comprising: The application relates to a method for preparing a metal film on a wafer surface. The method comprises the following steps: providing a wafer; mounting the wafer on a small target of a planet disc and loading the planet disc into a device; rotating the wafer by a card angle to change the distribution direction of a metal strip inside a device and improve metal step coverage; the rotating angle is 45 DEG to 135 DEG ; preparing a metal film on the wafer surface by using a metal evaporation process; metal photoetching; metal etching; 2. The method of claim 1, wherein the metal layer is deposited by physical vapor deposition (PVD) or atomic layer deposition (ALD). inspection and measurement, microscopic mirror inspection and electron microscope testing are adopted to inspect the wafer surface appearance and shape and measure the metal strip width.
3. The method of claim 1, wherein the metal layer is deposited by physical vapor deposition (PVD) or atomic layer deposition (ALD). In the step of providing the wafer, the wafer size is 6 inches, and the wafer material comprises monocrystalline silicon, SOI or SiGe.
4. The method of claim 1, wherein the metal layer is deposited by physical vapor deposition. In the step of providing the wafer, the wafer is pretreated, and the pretreatment comprises the following steps: cleaning the wafer by using an acid liquid, wherein the cleaning step is specifically: cleaning by using a No. 1 cleaning liquid mixed by H2O2, ammonia and water in a certain proportion and cleaning by using a BOE / HF etching liquid to obtain a clean wafer surface. The metal evaporation process comprises the following steps: vacuumizing; after mounting, closing the vacuum chamber door and locking, starting the main process of the menu after the device is vacuumized to 5E-4; low-power pre-melting; starting an electron beam gun, adjusting the electron beam power to 30% to 40% within 30s, that is, 1 / 3 to 1 / 2 of the material melting point to avoid direct melting; then the electron beam is focused on the material surface of the crucible and slowly scanned for about 1 min; melting; gradually increasing the electron beam power to 50% to 70% within 20s, adjusting the scanning range to cover the whole material in the crucible, keeping the material uniformly heated, and making the material reach a completely molten state within 4 min; evaporation; increasing the evaporation rate to 12 A / s within 10s and keeping the same to ensure the electron beam scanning stable and ensure that the metal vapor uniformly covers the wafer surface; starting a film thickness monitor to monitor the wafer surface metal film thickness in real time, and when the film thickness reaches the target value, the electron beam gun is closed and the evaporation is stopped; cooling and breaking the vacuum; keeping the vacuum state, closing the vacuum pump, and slowly introducing inert gas into the vacuum chamber to normal pressure after the remaining metal in the crucible is cooled to room temperature; 5. The method for improving the metal step coverage of a device as described in claim 4, characterized in that, taking out the wafer; opening the vacuum chamber and taking out the deposited wafer.
6. The method of claim 4, wherein the metal layer is deposited by physical vapor deposition. In the step of low-power pre-melting, the electron beam power is adjusted to 35%.
7. The method of claim 1, wherein the metal step coverage of the device is improved. The metal corrosion includes: carrying out metal corrosion through a wet process; the wet etching material is selected from Al etching liquid, the composition of the Al etching liquid is hydrochloric acid-nitric acid, and the etching rate is 0.5-1.5 μm / min. The overall over-etching time is 2 min, and after the etching is completed, a photoresist removing treatment is carried out.
8. The method of claim 1, wherein the metal step coverage of the device is improved. In the step of melting, the electron beam power is adjusted to 60%.
9. The method of claim 1, wherein The metal strip width is 45 mu m, and the metal strip lower step height is 0.6 mu m.
10. A method of improving device metal step coverage as claimed in any one of claims 1 to 9, wherein, The metal film adopts Al material, and the thickness is 2.2 mu m. The card angle needs to be adjusted according to the metal step distribution direction of the device to make the optimal angle parallel to the planet disc cutting edge direction.