Blazed gratings and methods of processing blazed gratings

Abstract

The application discloses a blazed grating and a processing method of the blazed grating. The processing method comprises the following steps: an ion beam with an included angle with the normal line of a grating base is used to etch after an etching gas is introduced through a mask matched with the blazed grating to be processed; and the grating base has self-rotation during the etching process. According to the method, the self-rotation of the grating base can make the part farthest from the ion source and the nearest part have a close etching rate, thereby effectively improving the uniformity. In addition, the self-rotation can reduce the area not covered by the mask, thereby facilitating the elimination of the reverse blazed surface turning. Overall, the method can effectively improve the product yield.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing equipment technology, and specifically to a blazed grating and a method for processing a blazed grating. Background Technology

[0002] A blazed grating is a type of phase grating that can separate the central maximum of a single grooved surface diffraction from the zero-order principal maxima of interference between grooved surfaces. Based on its zero-order beam splitting and ease of satisfying missing orders, as well as its high diffraction efficiency, blazed gratings are widely used in measurement, display, communication, and laser beam shaping.

[0003] Traditional methods for fabricating diffraction gratings include mechanical scribing, holographic lithography, and die-casting replication. The gratings produced by these methods are respectively called scribing gratings, holographic gratings, and replicated gratings. Each of these three grating fabrication processes has its own advantages and disadvantages. For example, the grooves in a holographic grating are generated simultaneously using interference phenomena, while the grooves in a scribing grating are generated sequentially. The latter has periodic and random displacement errors, leading to the generation of "ghost lines" (pseudo-spectral lines). Due to the presence of microscopic notches in the scribing blade, scribing gratings have stronger stray light compared to holographic gratings. Scribing gratings offer a wider range of line densities, specifically from tens of lines / mm to 6000 lines / mm, while holographic grating recording is less convenient for optical systems with line densities below 100 lines / mm, and its upper limit for line density recording with visible light is 3600 lines / mm. The fabrication cycle for holographic gratings is much shorter than that for scribing gratings. The biggest advantage of die-casting replication is that it can mass-produce replicated gratings with the same parameters using the same master grating, resulting in lower replication costs.

[0004] Ion beam etching, a dry etching process developed in the 1970s, has been widely adopted in modern microelectronic device manufacturing processes, primarily for ultra-fine, high-fidelity pattern transfer. Holographic ion beam etched diffraction gratings involve first fabricating a grating mask using holographic lithography, then transferring it to the grating substrate material via ion beam etching. This technique combines the high efficiency of mechanically etched gratings with the advantages of holographic gratings, such as no ghost lines, low stray light, and a high signal-to-noise ratio. It offers advantages such as controllable groove tilt angle, fast etching rate, good selectivity, and minimal surface damage, and has been used to fabricate holographic blazed gratings.

[0005] Please see Figure 1The diagram illustrates a typical etching principle for a blazed grating. Generally, the mask 10 is a trapezoidal structure. Mask etching can be simplified into two parts: the top edge vertically shrinks as etching progresses, and the sidewalls horizontally shrink as etching progresses. The ion beam incident angle Φ is fixed, and the ion beam incident angles of the top edge and sidewalls are constant values. Therefore, the vertical etching rate Vc and the horizontal etching rate Vs of the mask remain unchanged. As etching progresses, the mask height decreases, reducing the obstruction of the ion beam. The ion beam reaches the surface of the grating substrate 20 and then etches the substrate, initiating blazing. When the mask is etched vertically and horizontally simultaneously, it shrinks to a single point at the top, forming a triangular shape, i.e., a blazed grating.

[0006] The distance between the ion source 30 and different parts of the grating substrate 20 is different, such as... Figure 2 As shown, the etching rate is fastest at the location closest to the ion source, and slowest at the location farthest from the ion source. This difference in etching rates between near and far locations increases inhomogeneity. Furthermore, when the ion beam incident angle is small, such as... Figure 3 As shown, some areas are not masked, resulting in continuous ion beam etching of these areas. Furthermore, due to the influence of redeposition, these areas will exhibit a certain angular tilt, causing the reflective surface to produce... Figure 4 The discontinuity inflection points are shown. Therefore, due to the fixed angle between the ion beam and the normal to the grating substrate, and the fact that the grating substrate does not rotate, the etching uniformity is directly affected.

[0007] In view of this, it is urgent to optimize the existing processing technology of blazed gratings in order to effectively improve etching uniformity. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides a blazed grating and a method for processing the blazed grating, which can obtain good etching uniformity.

[0009] The present invention provides a method for processing a blazed grating, comprising the following steps: using a mask adapted to the blazed grating to be processed, introducing an etching gas, and then etching with an ion beam having an angle between the ion beam and the normal of the grating substrate, wherein the grating substrate rotates during the etching process.

[0010] Optionally, the etching process includes rotation etching and fixed etching, wherein the grating substrate rotates during the rotation etching and stops rotating during the fixed etching.

[0011] Optionally, after the self-rotating etching has been performed for a first time length, the fixed etching has been performed for a second time length.

[0012] Optionally, the rotational etching and the fixed etching are performed alternately multiple times.

[0013] Optionally, the angle between the normal of the grating substrate and the ion beam is θ, where -90° < θ < 90°.

[0014] Optionally, the rotational speed is n, where n ≤ 100 RPM.

[0015] Optionally, the etching gas is one of an inert gas, a chlorine-based gas, and a fluorine-based gas, or a combination of at least two of them. This includes, but is not limited to, the above gases and combinations.

[0016] Optionally, the grating substrate is one of Si, SiO2, SiC, and quartz, or a combination of at least two of them. This includes, but is not limited to, the above substrates and combinations.

[0017] The present invention also provides a blazed grating manufactured using the aforementioned method for processing blazed gratings.

[0018] This invention proposes a novel and optimized method for the fabrication of blazed gratings, effectively improving etching uniformity. Specifically, a mask adapted to the blazed grating to be processed is used. After introducing an etching gas, an ion beam with an angle between the beam and the normal to the grating substrate is used for etching, during which the grating substrate rotates. This rotation ensures that the areas furthest from the ion source and the closest areas have similar etching rates, effectively improving uniformity. Furthermore, the increased rotation reduces the area not obscured by the mask, facilitating the elimination of anti-blazed surface transitions. Overall, this significantly improves product yield.

[0019] In an optional embodiment of the present invention, the etching process includes rotation etching and fixed etching. When the grating substrate is subjected to rotation etching, based on the above-mentioned technical effects achieved by rotation, when the grating substrate stops rotating and is subjected to fixed etching, different morphological shapes can be obtained. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the typical etching principle of existing blazed gratings; Figure 2 This is a schematic diagram showing the relative positional relationship between the ion source and the grating substrate; Figure 3 This is a schematic diagram showing the processing status of a portion of the area not being covered by the mask. Figure 4 Based on Figure 3 A schematic diagram showing the reverse transition formed by the processing state shown; Figure 5 This is a schematic diagram showing the relative positional relationship between the ion source and the grating substrate in the method for fabricating a blazed grating as described in a specific embodiment. Figure 6A flowchart of the etching process described in a specific embodiment is shown.

[0021] Figures 1-2 middle: Mask 10, grating substrate 20, ion source 30; Figures 5-6 middle: 1. Ion source, 2. Grating substrate, 3. Mask. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0024] Secondly, this application is described in detail with reference to the schematic diagrams. When describing the embodiments of this application in detail, for ease of explanation, the cross-sectional views of the device structure will be partially enlarged without adhering to the general scale. Moreover, the schematic diagrams are only examples and should not limit the scope of protection of this application.

[0025] In the existing blazed grating processing technology, the fixed angle between the ion beam and the wafer normal (grating substrate normal) during ion beam etching of the blazed grating results in inconsistent arrival times of the ion beam on the wafer surface, which in turn affects etching uniformity and reduces economic efficiency.

[0026] Based on this, embodiments of this application provide a method for processing a blazed grating, and a blazed grating fabricated according to this method. The method for processing a blazed grating may include the following steps: using a mask adapted to the blazed grating to be processed, introducing an etching gas, and then etching with an ion beam at an angle to the normal of the grating substrate, wherein the grating substrate rotates during the etching process. That is, during ion etching, rotation is added to the grating substrate, thereby making the etching rates of the parts farthest from the ion source and the parts closest to it similar, improving uniformity; in addition, the increased rotation of the grating substrate can also reduce the area not blocked by the mask, which is beneficial for eliminating the inflection point of the anti-blazed surface, reducing the processing difficulty, and exhibiting good processability.

[0027] To better understand the technical solution and effects of this application, the specific embodiments will be described in detail below with reference to the accompanying drawings.

[0028] In this embodiment, the grating substrate 2 to be processed is first transferred to an ion beam etching machine, so that the surface normal of the grating substrate forms a certain angle with the ion beam, such as... Figure 5 As shown, the ion beam formed by ion source 1 forms an angle θ with the normal to the surface of the grating substrate. Etching gas is introduced into the discharge chamber, and rotation etching and fixed etching are performed sequentially. The grating substrate rotates during rotation etching and stops rotating during fixed etching.

[0029] Without loss of generality, this embodiment uses an ion beam etching machine to complete the fabrication of the blazed grating. The main functional components of the ion beam etching machine are not the core inventive point of this application, and can be implemented by those skilled in the art based on existing technology; therefore, they will not be described further here.

[0030] Under normal circumstances, adding a rotation step will result in an etching pattern resembling an isosceles triangle. If this isosceles triangle differs from the target shimmering pattern, adding another etching step without rotation can yield different shapes to meet design requirements. Please refer to [link / reference]. Figure 6 The figure shows a flowchart of the etching process described in this embodiment.

[0031] In other words, the etching process includes rotational etching and stationary etching. The grating substrate rotates during rotational etching and stops rotating during stationary etching. In practical applications, after a first time length of rotational etching, stationary etching can be performed for a second time length to meet different processing needs. Of course, the above etching steps can include at least one step of rotational etching and one step of stationary etching, or a combination of multiple steps of rotational and stationary etching, to maximize the conformity to the designed shape.

[0032] In addition, the process parameters can be selected according to the specific characteristics of the product during the execution of the above processing steps.

[0033] The angle θ between the grating substrate normal and the ion beam can be selected according to the actual product processing requirements. For example, it can be selected within the range of -90° < θ < 90°. Understandably, any method that meets the corresponding etching requirements is acceptable.

[0034] In practical applications, the rotational speed n of the grating substrate can be controlled by the stage of the ion beam etching machine, for example, but not limited to, n ≤ 100 RPM. Here, the rotational control of the stage of the ion beam etching machine can be achieved based on the conventional control functions of the equipment, and is not the core inventive point of this application, so it will not be elaborated here.

[0035] In other specific applications, the working medium etching gas introduced into the discharge chamber can also be selected according to the actual product processing requirements. For example, the grating substrate can be one of Si, SiO2, SiC, and quartz, or a combination of at least two of them. Correspondingly, the etching gas can be one of inert gas, chlorine-based gas, and fluorine-based gas, or a combination of at least two of them.

[0036] Example 1

[0037] (1) The mask is made of photoresist with a thickness of 300nm, a linewidth (CD) of 200nm, and a pitch of 400nm; (2) The grating substrate to be processed is transferred to the ion beam etching cavity; (3) Adjust the angle so that the angle between the ion beam and the normal of the grating substrate surface is 40°, and set the rotation of the grating substrate to 10 rpm; (4) Ar gas is introduced into the ion beam reaction chamber, and the discharge is initiated to extract the ion beam; (5) Open the baffle so that the ion beam can act on the grating substrate to be processed; (6) Maintain rotation and etch for 10 minutes; (7) Stop the rotation, keep other parameters the same, and etch for 5 minutes; (8) Obtain a blaze grating with a blaze angle of 35°, a height of 200nm, and a period of 200nm.

[0038] Example 2

[0039] (1) The mask is made of photoresist with a thickness of 300nm, a linewidth (CD) of 200nm, and a pitch of 400nm; (2) The grating substrate to be processed is transferred to the ion beam etching cavity; (3) Adjust the angle so that the angle between the ion beam and the normal of the grating substrate surface is 25°, and set the rotation of the grating substrate to 10 rpm; (4) Ar gas is introduced into the ion beam reaction chamber, and the discharge is initiated to extract the ion beam; (5) Open the baffle so that the ion beam can act on the grating substrate to be processed; (6) Maintain rotation and etch for 12 minutes; (7) Stop the rotation, keep other parameters the same, and etch for 6 minutes; (8) Obtain a blazed grating with a blaze angle of 40°, a height of 220nm, and a period of 200nm.

[0040] In addition to the aforementioned method for processing blazed gratings, this embodiment also provides a blazed grating manufactured using the same processing method.

[0041] It should be noted that the specific functional configuration of the ion beam etching machine used in the above embodiments provided in this implementation method is not the core inventive point of this application. Those skilled in the art can implement it based on existing technology, so it will not be described in detail here.

[0042] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a blazed grating, characterized in that, Includes the following steps: Using a mask adapted to the blazed grating to be processed, after introducing etching gas, an ion beam with an angle between the ion beam and the normal of the grating substrate is used for etching. During the etching process, the grating substrate rotates. The etching process includes rotation etching and fixed etching. During the rotation etching, the grating substrate rotates, and during the fixed etching, the grating substrate stops rotating. After the rotation etching is performed for a first time length, the area not covered by the mask is reduced to facilitate the elimination of the anti-flare surface transition. The fixed etching is performed for a second time length. The rotation etching and the fixed etching are performed alternately multiple times to obtain different morphological shapes according to different design requirements.

2. The method for processing a blazed grating according to claim 1, characterized in that, The angle between the normal of the grating substrate and the ion beam is θ, -90° < θ < 90°.

3. The method for processing a blazed grating according to claim 1, characterized in that, The rotational speed is n, where n ≤ 100 RPM.

4. The method for processing a blazed grating according to claim 1, characterized in that, The etching gas is one of an inert gas, a chlorine-based gas, and a fluorine-based gas, or a combination of at least two of them.

5. The method for processing a blazed grating according to claim 1, characterized in that, The grating substrate is one of Si, SiO2 and SiC, or a combination of at least two of them.

6. A blazed grating, characterized in that, It is manufactured using the processing method of any one of claims 1 to 5.

Images