WO2024060361A1 - Alignment mark structure and forming method therefor - Google Patents

Abstract

The present disclosure provides an alignment mark structure and a forming method therefor. The alignment mark structure comprises: a substrate (1); a marking region (2), comprising an alignment structure (2-2) and a chamfer structure layer (2-1), the alignment structure (2-2) being formed in the substrate (1) and being a recessed structure, the chamfer structure layer (2-1) being formed on the surface of the substrate (1) and being a raised structure, and the chamfer structure layer (2-1) forming a raised chamfer structure at an edge of the alignment structure (2-2); and a non-marking region (6), disposed around the periphery of the marking region (2), an upper surface of the non-marking region (6) being lower than a lower surface of the chamfer structure layer (2-1) in the marking region (2). According to the alignment mark structure of the present disclosure, the definition and contrast of alignment mark detection can be effectively improved.

Description

Alignment mark structure and method of forming the same

This disclosure claims priority from the Chinese patent application with application number 202211147128.1 filed on September 20, 2022, the entire content of which is incorporated into this disclosure by reference.

Technical field

The present disclosure relates to the field of photolithographic alignment technology, and in particular to an alignment mark structure and a method of forming the same.

Background technique

In actual IC manufacturing, from wafer to final test package, the entire manufacturing process often requires dozens of processes to be completed by stacking in the middle. Therefore, alignment marks must be used to ensure that the alignment value of the current layer and the previous layer is within the allowable error range. Usually, the alignment mark will be affected by the previous process and the photolithography alignment accuracy will be reduced. This is because before a certain layer of photolithography, the surface of the alignment mark may have been covered with thin films such as silicon oxide, silicon nitride, metal layer, photoresist layer, etc., which affects the clarity and contrast of the alignment mark. In particular, with the gradual reduction of IC process technology, more film layers are covered on the surface of the wafer to realize the etching transfer of the pattern. These film layers will interfere with the alignment signal to a certain extent, causing the alignment mark to be distorted, affecting the detection of the alignment mark in the previous photolithography process.

Figure 1 is a schematic cross-sectional structural diagram of a common alignment mark before the photolithography process, including the alignment mark on the substrate structure and the multi-layer film covering the surface of the alignment mark. The multi-layer film has filled the bottom of the alignment mark, and the surface of the multi-layer film forms an obtuse angle at the edge of the alignment mark. Due to the uneven thickness of the multi-layer film at the edge of the alignment mark, the alignment light incident on the edge of the alignment mark cannot be reflected vertically in one direction, resulting in unclear alignment signals. Since the bottom of the alignment mark is basically filled with the multi-layer film, the contrast between the bottom of the alignment mark and the surface of the substrate is greatly reduced.

Therefore, the low contrast of the alignment mark will make it difficult for the CCD camera to detect the alignment mark signal, and the unclear edges of the alignment mark will distort the alignment signal detected by the CCD camera, resulting in a reduction in alignment accuracy and Affect photolithography quality.

Summary of the invention

(1) Technical problems to be solved

In response to the above problems, the present disclosure provides an alignment mark structure and a forming method thereof to solve technical problems such as unclear edges of alignment signals and low contrast of traditional alignment mark structures during detection.

(2) Technical solutions

On the one hand, the present disclosure provides an alignment mark structure, including: a substrate; a mark area, including an alignment structure and a chamfer structure layer; the alignment structure is formed in the substrate through etching and is a recessed structure; and the chamfer structure The layer is formed on the surface of the substrate through deposition and is a protruding structure. The chamfering structure layer forms a protruding chamfering structure at the edge of the alignment structure; the non-marking area is set around the periphery of the marking area, and the upper surface of the non-marking area Below the lower surface of the chamfered structural layer in the marked area.

Further, a high reflectivity thin film layer is provided on the bottom and side walls of the alignment structure; the thickness of the high reflectivity thin film layer does not exceed 100 nm, and its material includes one of Au, Al, and Ag.

Further, the planar size of the alignment structure ranges from 0.5 to 50 μm, and the depression depth of the alignment structure ranges from 100 to 4000 nm.

Further, the alignment structure includes one of a cross-shaped alignment mark and a grid-type alignment mark.

Further, the thickness of the chamfer structure layer does not exceed 100nm, and the inclination angle of the chamfer structure is 35 to 55°; the material of the chamfer structure layer is a non-transparent medium that is easy to be etched and controlled, including silicon nitride and aluminum nitride. , silicon carbide, and polysilicon.

Furthermore, the non-marking area is a U-shaped structure, which is arranged around the alignment structure within a range of 1 to 1000 μm; the non-marking area is formed in the substrate by etching, and its etching depth does not exceed 1/2 of the depth of the recessed structure.

Another aspect of the present disclosure provides a method for preparing an alignment mark structure according to the foregoing, including: S1, forming a chamfer layer on the substrate; S2, coating the first photosensitive layer; etching the mark area after exposure and development, It includes sequentially etching the chamfer layer and the substrate to obtain an alignment structure; S3, etching the chamfer layer at the edge of the alignment structure to obtain a convex chamfer structure, and removing the first photosensitive layer; S4, coating the third Two photosensitive layers; after exposure and development, etching the periphery of the marking area, including sequentially etching the chamfering layer and the substrate, to obtain the non-marking area and the chamfering structural layer; S5, remove the second photosensitive layer to obtain the target alignment mark structure.

Further, after S3, it also includes: S31, depositing a high reflectivity thin film layer with a thickness of no more than 100 nm.

Further, S5 also includes: removing the high reflectivity thin film layer on the chamfer structure layer.

Further, the etching method in S3 is dry etching. Dry etching includes one of reactive ion etching and inductively coupled plasma etching. The etching gases include SF ₆ , O ₂ , N ₂ , One of CHF ₃ , Cl ₂ , Ar and C ₄ F ₈ ; the tilt angle of the convex chamfer structure obtained by etching is 35 to 55°.

(3) Beneficial effects

The alignment mark structure and its formation method of the present disclosure make the surface of the mark area closer to the mask by arranging a higher-height chamfer structure layer on the mark area and arranging a lower-height non-mark area on the periphery of the mark area. The surface of the non-marking area is further away from the mask. During detection, the contrast between the marking area and the non-marking area is greater, making it easier to obtain the detection signal of the alignment mark; further, by forming protrusions in the chamfered structural layer The chamfer structure can effectively prevent the deposited multi-layer films from accumulating at the edge of the alignment structure, thereby allowing the incident light at the edge of the alignment structure to be reflected in one direction, significantly improving the edge clarity of the alignment structure.

Description of the drawings

Figure 1 schematically shows the cross-sectional structure and light reflection diagram of common alignment marks before the photolithography process;

Figure 2 schematically shows the cross-sectional structure and light reflection of the alignment mark before the photolithography process according to an embodiment of the present disclosure;

Figure 3 schematically shows a top view of the positional relationship between the marking area and the non-marking area and a schematic diagram of the contrast relationship between the two according to an embodiment of the present disclosure;

Figure 4 schematically illustrates a flow chart of a method for preparing an alignment mark structure according to an embodiment of the present disclosure;

Figure 5 schematically illustrates a process flow chart of the alignment mark structure according to an embodiment of the present disclosure;

Figure 6 schematically shows an image of an alignment mark with a chamfer structure and a marked area under a CCD camera according to Embodiment 1 of the present disclosure;

Figure 7 schematically shows an image of the alignment mark without chamfer structure and mark-free area according to Comparative Example 1 of the present disclosure under a CCD camera;

Figure 8 schematically shows an image of the alignment mark in the mark-free area according to Comparative Example 2 of the present disclosure under a CCD camera;

Figure 9 schematically shows an image of the alignment mark without chamfer structure in Comparative Example 3 of the present disclosure under a CCD camera;

Explanation of reference symbols:

1. Substrate; 2. Marking area; 3. Multilayer film; 4. Incident light; 5. Reflected light; 5-1, Illumination light reflected on the surface of the multilayer film; 5-2, Illumination directly on the substrate Reflected light; 5-3, the sum of irregular scattered light reflections at the edge of the marking area; 5-4, the light that is reflected multiple times inside the multi-layer film and then reflected back to the air; 2-1, chamfered structural layer; 2-2, alignment structure; 6-non-marking area; 7, chamfering layer; 8-1, first photosensitive layer; 8-2, second photosensitive layer; 9-1, first mask; 9-2 , the second mask; 10, exposure light source; 11, high reflectivity thin film layer.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present disclosure more clear, the present disclosure will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. The terms "comprising," "comprising," and the like, as used herein, indicate the presence of stated features, steps, operations, and/or components but do not exclude the presence or addition of one or more other features, steps, operations, or components.

It should be noted that if there is a directional indication in the embodiment of the present disclosure, the directional indication is only used to explain the relative positional relationship, movement, etc. between the components in a specific posture. If the specific posture changes, , the directional indication will also change accordingly.

The embodiment of the present disclosure provides an alignment mark structure, see Figure 2, including: a substrate 1; a marking area 2, including an alignment structure 2-2 and a chamfer structure layer 2-1; the alignment structure 2- 2 is formed in the substrate 1 and has a concave structure; the chamfer structure layer 2-1 is formed on the surface of the substrate 1 and has a protruding structure. The chamfer structure layer 2-1 forms a protrusion on the edge of the alignment structure 2-2. The non-marking area 6 is arranged around the periphery of the marking area 2, and the upper surface of the non-marking area 6 is lower than the lower surface of the chamfering structure layer 2-1 in the marking area 2.

The alignment mark structure disclosed in the present invention includes a mark area 2 formed on a substrate 1 and a non-mark area 6 arranged around the mark area 2. The mark area 2 includes a preset alignment structure 2-2 and a chamfered structure layer 2-1 higher than the initial surface of the substrate 1; the non-mark area 6 is formed in the substrate 1 and is lower than the lower surface of the chamfered structure layer 2-1 (i.e., the initial surface of the substrate 1), so that the height of the mark area 2 is higher and the height of the non-mark area 6 is lower, and in close contact lithography (such as super-resolution lithography), the surface of the mark area 2 can be closer to the mask, and the non-mark area 6 has a larger gap relative to the mask. That is, when the alignment mark is detected, the distance of the non-mark area 6 relative to the mask is greater than the distance of the mark area 2 relative to the mask. This structure can make the non-mark area 6 darker and the mark area 2 brighter under the entire CCD camera, and the contrast between the mark area 2 and the non-mark area 6 is greater, so that the alignment structure 2-2 is easier to find under the CCD camera, especially for close contact lithography, this structural optimization is very necessary. Thereby, the problem that the reflected light in the non-marking area 6 is too bright and the contrast of the alignment structure 2 - 2 in the marking area 2 is reduced is solved.

Further, by forming a convex chamfer structure in the chamfer structure layer 2-1, the deposited multi-layer film 3 can be effectively prevented from accumulating on the edge of the alignment structure 2-2. As shown in Figure 2, the multi-layer film 3 3. Form a smooth and uniform transition on the chamfered structure, so that the incident light illuminated on the edge of the alignment structure 2-2 can be reflected in one direction, including the light reflected on the surface of the multi-layer film 5-1. The illumination on the substrate The sum of the light directly reflected 5-2 and the illumination irregularly scattered light reflected at the edge of the marking area 5-3 significantly improves the edge definition of the alignment structure 2-2.

On the basis of the above embodiment, a high reflectivity thin film layer 11 is provided on the bottom and side walls of the alignment structure 2-2; the thickness of the high reflectivity thin film layer 11 does not exceed 100 nm, and its materials include Au, Al, and Ag. A sort of.

The alignment mark structure of the present disclosure can further be provided with a high reflectivity thin film layer 11 on the bottom and side walls of the alignment structure 2-2. The high reflectivity thin film layer 11 is made of materials with high reflectivity, including Au, Al, Ag and other metal films can enhance the reflected light intensity of the alignment structure 2-2, thereby further improving the contrast of the alignment structure 2-2.

Based on the above embodiments, the planar size of the alignment structure 2-2 ranges from 0.5 to 50 μm, and the depression depth of the alignment structure 2-2 ranges from 100 to 4000 nm.

The alignment structure 2-2 forms an alignment mark pattern on a plane. In order to facilitate finding the position of the alignment mark pattern, its plane size range is usually set within the above range. The etching depth of the alignment structure 2-2 should not be too small, otherwise it will affect the clarity of the alignment structure 2-2 and make it difficult to accurately identify it.

Based on the above embodiment, the alignment structure 2-2 includes one of a cross-shaped alignment mark and a grid-type alignment mark.

Cross-shaped alignment marks are usually used in rough alignment scenarios, with the advantage of quickly finding the relative position between the mask and the wafer; grid-type alignment marks are usually used in fine alignment scenarios, with the ability to finely adjust the relationship between each exposure field and the wafer. Advantages of relative positioning of reticle.

Based on the above embodiment, the thickness of the chamfered structure layer 2-1 does not exceed 100nm, and the inclination angle of the chamfered structure is 35 to 55°; the material of the chamfered structure layer 2-1 is an easy-to-etch and non-transparent medium, including one of silicon nitride, aluminum nitride, silicon carbide, and polycrystalline silicon.

Although the chamfer structure layer 2-1 is used to bring the surface of the marking area 2 closer to the mask, its thickness should not exceed 100 nm, otherwise it will affect the duty cycle of the alignment structure 2-2 observed under CCD. The inclination angle of the chamfer structure is within the above range, which has the technical effect of uniformly covering the multi-layer film 3 . The chamfer structure layer 2-1 uses a non-transparent medium to increase the reflectivity of the surface of the marking area 2.

On the basis of the above embodiment, the non-marking area 6 has a zigzag structure and is arranged in a range of 1 to 1000 μm around the periphery of the alignment structure 2-2; the non-marking area 6 is formed in the substrate 1 by etching. The corrosion depth shall not exceed 1/2 of the depth of the depressed structure.

The zigzag structure is a fully enclosed structure, and the non-marking area 6 surrounds the entire marking area 2. As shown in Figure 3, the marking area 2 and the non-marking area 6 form a complete alignment mark structure. The etching depth of the non-marking area 6 does not exceed 1/2 of the depth of the recessed structure. Too deep an etching depth will also affect the contrast between the bottom of the alignment structure 2-2 and the bottom of the non-marking area 6.

Embodiments of the present disclosure also provide a preparation method according to the aforementioned alignment mark structure, as shown in Figures 4 to 5, including: S1, forming the chamfer layer 7 on the substrate 1; S2, coating the third A photosensitive layer 8-1; after exposure and development, etching the mark area 2, including sequentially etching the chamfer layer 7 and the substrate 1 to obtain the alignment structure 2-2; S3, etching the edge of the alignment structure 2-2 Etch the chamfer layer 7 to obtain a convex chamfer structure, remove the first photosensitive layer 8-1; S4, coat the second photosensitive layer 8-2; etch the periphery of the mark area 2 after exposure and development, including sequential etching Chamfer layer 7 and substrate 1 to obtain non-marking area 6 and chamfer structure layer 2-1; S5, remove second photosensitive layer 8-2 to obtain target alignment mark structure.

Preparation method of the alignment mark structure: after preparing the chamfer layer 7, first etching to obtain the alignment structure 2-2, then etching to obtain the raised chamfer structure, and finally etching to obtain the non-marking area 6 and obtaining the chamfer. Structural layer 2-1, the target alignment mark structure can be obtained. The etching steps are all conventional photolithography processes, and the preparation method is simple and easy to operate.

Based on the above embodiment, S3 is followed by: S31, depositing a high reflectivity thin film layer 11 with a thickness of no more than 100 nm.

After the step of etching to obtain the raised chamfered structure and before the step of etching to obtain the non-marking area 6, a high reflectivity thin film layer 11 may be sputter-deposited in the alignment structure 2-2 to further improve the contrast of the alignment structure 2-2.

Based on the above embodiment, S5 also includes: removing the high reflectivity thin film layer 11 on the chamfer structure layer 2-1.

After depositing the high-reflectivity film layer 11 in step S31 and removing the second photosensitive layer 8-2, the residual high-reflectivity film on the upper surface of the chamfered structural layer 2-1 and the upper surface of the non-marking area 6 can also be removed at the same time. A high reflectivity film is formed on the bottom and side walls of structure 2-2.

Based on the above embodiments, the etching method in S3 is dry etching. The dry etching includes one of reactive ion etching and inductively coupled plasma etching. The etching gas includes SF ₆ and O. _2. One of N ₂ , CHF ₃ , Cl ₂ , Ar and C ₄ F ₈ ; the tilt angle of the convex chamfer structure obtained by etching is 35 to 55°.

Choosing dry etching for the chamfered structure is beneficial to protecting the steepness of the alignment structure 2-2. The inclination angle of the chamfered structure can be controlled by etching gas flow, etching time, power, chamber pressure, etc.

The alignment mark structure and its formation method of the present disclosure, on the one hand, set up a higher-height chamfer structure layer on the mark area, and set up a lower-height non-mark area on the periphery of the mark area, so that the surface of the mark area is closer The surface of the mask, rather than the non-marking area, is further away from the mask, which improves the contrast of the alignment structure; a high reflectivity film layer is also provided on the bottom and side walls of the alignment structure to enhance the reflected light intensity of the alignment structure, further The contrast of the alignment structure is improved; on the other hand, by forming a raised chamfer structure in the chamfer structure layer, it helps the multi-layer film to evenly cover the chamfer structure in the marking area, thereby making the incident light at the edge of the alignment structure It can reflect in one direction, significantly improving the edge definition of the alignment structure. Combining the above two aspects, the present disclosure reduces the distortion of the alignment structure, thereby reducing the alignment error in IC manufacturing.

The present disclosure will be further described below through specific embodiments. The above-mentioned alignment mark structure and its formation method will be described in detail in the following embodiments. However, the following examples are only for illustrating the present disclosure, and the scope of the present disclosure is not limited thereto.

The alignment mark structure of this embodiment includes a marking area 2 formed on the substrate 1 and a non-marking area 6 arranged around the marking area. The marking area 2 includes a preset alignment structure 2-2 and a chamfer structure layer 2- 1. The planar size of the alignment structure 2-2 ranges from 0.5 to 50 μm. The alignment structure is a concave structure, and its etching depth is 100 to 4000 nm; the chamfered structure layer 2-1 is a convex structure, and the chamfered structure layer The thickness of 2-1 does not exceed 100nm, and the inclination angle of the chamfer structure is 35 to 55°. The non-marking area 6 may be a zigzag area, located in the range of 1 to 1000 μm from the edge of the marking area 2 . The etching depth of the non-marking area 6 does not exceed 1/2 of the etching depth of the alignment structure 2-2, and the etching depth of the non-marking area 6 is 100-2000 nm.

The preparation method of the alignment mark structure in this embodiment includes the following steps, as shown in Figure 5:

Step (1): Prepare substrate 1;

Step (2): Prepare a chamfer layer 7 on the surface of the substrate 1. The thickness d ₁ of the chamfer layer 7 is 10 to 100 nm; equivalent to the above step S1;

Step (3): Prepare a first photosensitive layer 8-1 on the chamfered layer 7, the thickness d2 of the first photosensitive layer 8-1 is 100-1000 nm;

Step (4): Exposure and development are performed on the basis of step (3). The first mask 9-1 is an alignment mark mask, and the exposure light source 10 is above the first mask 9-1;

Step (5): Etch the pattern developed in step (4), first use the first photosensitive layer 8-1 as a mask to etch the chamfer layer 7, and etch through the chamfer layer 7;

Step (6): Based on step (5), use the first photosensitive layer 8-1 and the chamfering layer 7 as a mask to etch the substrate 1 to obtain the alignment structure 2-2. The alignment structure 2-2 The etching depth _d5 is 100~4000nm; equivalent to the above step S2;

Step (7): Etch the chamfer structure, and the inclination angle of the chamfer structure is 35 to 55°; equivalent to the above step S3;

Step (8): Remove the residual photoresist etched on the surface of chamfering layer 7;

Step (9): Optionally prepare a high reflectivity thin film layer 11, the thickness _d6 of the high reflectivity thin film layer 11 is 10 to 100 nm;

Step (10): Prepare a second photosensitive layer 8-2 on the chamfered layer 7, the thickness _d7 of the second photosensitive layer 8-2 is 100~1000nm;

Step (11): Expose and develop again based on step (10) to form the non-marking area 6;

Step (12): Carry out etching on the basis of step (11), sequentially etch the chamfer layer 7 and the substrate 1, optionally etch the high reflectivity thin film layer 11, and optionally etch the substrate 1 The depth d ₈ is 10 to 2000 nm, forming the chamfer structure layer 2-1 and the non-marking area 6; equivalent to the above step S4;

Step (13): Remove the remaining photoresist on the surface of the substrate 1, optionally, simultaneously remove the remaining high reflectivity film layer on the upper surface of the chamfered structural layer 2-1 and the upper surface of the non-marking area 6; equivalent to the above Step S5.

Wherein, the substrate 1 in the above step (1) can be a silicon-based substrate, a sapphire substrate, a silicon carbide substrate, etc.

In the above step (2), the material of the chamfer layer 7 should be a non-transparent medium that is easy to be etched and controlled, and can be one of silicon nitride, aluminum nitride, silicon carbide, and polysilicon.

The first photosensitive layer 8-1 in the above step (3) and the second photosensitive layer 8-2 in the step (10) are both prepared by the same spin coating method.

The alignment marks on the alignment mark mask in the above step (4) may include cross-shaped alignment marks, grid-type alignment marks, etc.

The exposure process of the above steps (4) and (11) can be close contact exposure, laser direct writing processing, projection lithography, etc.

The etching of the chamfer layer 7 in the above step (5) is dry etching, including ion beam etching, reactive ion beam etching or inductively coupled plasma etching. The optional gases are SF ₆ , O ₂ , and N ₂ , CHF ₃ , Cl ₂ , Ar and C ₄ F ₈ , etc.

The etching of the substrate 1 in the above step (6) is dry etching or wet etching, which may include ion beam etching, reactive ion beam etching or inductively coupled plasma etching. The optional gas is SF. _6. CHF ₃ or Ar; the solution for wet etching can be a mixed solution of KOH and IPA, a mixed solution of a certain concentration of H ₂ SO ₄ and H ₃ PO ₄ , etc.

The inclination angle of the chamfered structure in the above step (7) is 35-55°. The etching method of the chamfered structure is dry etching, including reactive ion etching and inductively coupled plasma etching, and the optional gases are _SF6 , _{O2 , N2} , _CHF3 , _Cl2 , Ar and _C4F8 .

The surface etching residual photoresist in the above steps (8) and (13) can be removed by dry method or wet method. Dry removal can use reactive ion beam etching or inductively coupled plasma etching, and the optional etching gas is O ₂ ; the solution for wet removal can be ethanol, acetone, concentrated sulfuric acid, etc.

In the above step (9), the highly reflective film is deposited on the bottom and side walls of the alignment structure 2-2.

The etching of the non-marking area 6 in the above step (11) may be dry etching or wet etching. Dry etching can include ion beam etching, reactive ion beam etching or inductively coupled plasma etching. The optional gases are SF ₆ , CHF ₃ or Ar; the wet etching solution can be a mixture of KOH and IPA. solution, mixed solution of H ₂ SO ₄ and H ₃ PO ₄ , etc.

According to the above scheme, 4 specific embodiments and 3 comparative examples are provided below.

Example 1:

As shown in Figure 2, the steps for forming the alignment mark structure in this embodiment are as follows:

The substrate 1 is a silicon-based material; the chamfer layer 7 is made of Si ₃ N ₄ with a thickness of 20 nm, and the preparation method is magnetron sputtering coating;

The first photosensitive layer 8-1 is prepared by spin coating. The material model of the first photosensitive layer 8-1 is AR-P3170 and the thickness is 100nm;

The material of the light-blocking layer on the first mask 9-1 is metal Cr, with a thickness of 100 nm, and the base is quartz; the mark pattern on the first mask 9-1 is a grating structure with a period of 20 μm, and the length of the grating is 40 μm. The area of the mark pattern is 200 μm*40 μm; there are also rough alignment marks on the first mask 9-1, the mark shape is a cross and the width is 10 μm; contact photolithography is used to expose the mark pattern on the first mask 9-1 to the first photosensitive layer 8-1;

After development, the Si ₃ N ₄ of the chamfer layer 7 is etched using reactive ion beam etching. The etching gases are SF ₆ and O ₂ , the gas flow ratio is 5:1, the cavity pressure is 1Pa, and the power is 40w. The time is 20s, the etching depth is 20nm; the alignment structure 2-2 is etched, using reactive ion beam etching, etching gases SF ₆ and CHF ₃ , the cavity pressure is 1Pa, the power is 100w, and the etching time is 10min. The etching depth is 1500nm; the Si ₃ N ₄ of the chamfer layer structure 2-1 is etched using reactive ion beam etching. The etching gases are SF ₆ , O ₂ and N ₂ , where the gas flow rates of SF ₆ and O ₂ are The ratio is 3:1, the cavity pressure is 1Pa, the power is 40w, the etching time is 10s, so that the chamfer tilt angle is about 35°;

Remove the remaining first photosensitive layer 8-1, soak the substrate with acetone until the first photosensitive layer 8-1 falls off, rinse with deionized water and dry the substrate 1;

Prepare the second photosensitive layer 8-2, spin-coat the photoresist AR-1500 with a thickness of 500nm; the pattern of the non-marking area 6 on the second mask 9-2 is a U-shaped pattern, with an inner circle area of 201μm*41μm and an outer circle area of 400μm*240μm; the second mask 9-2 also includes a cross-shaped alignment mark matching the first mask 9-1; the light-blocking material on the second mask 9-2 is metal Cr with a thickness of 100nm, and the substrate is quartz;

The non-marking area 6 on the second mask 9-2 is exposed to the second photosensitive layer 8-2 using a contact exposure process; after development, the non-marking area 6 is etched using an ion beam, the etching time is 5 minutes, and the substrate is rotated The angle is 15°. One-time etching penetrates the chamfer layer 7 and the etched part of the substrate 1 to form the chamfer structure layer 2-1 and the non-marking area 6. The etching of the non-marking area 6 (the middle part of the substrate 1) The etching depth is 500nm; remove the remaining second photosensitive layer 8-2, soak the substrate 1 with acetone until the second photosensitive layer 8-2 falls off, rinse with deionized water and dry the substrate 1.

In this embodiment, the chamfer structure 2-1 covered above the alignment structure 2-2 has an inclination angle of about 35°, the thickness of the Si ₃ N ₄ chamfer structure layer is 20 nm, and the multi-layer film 3 covers the chamfer structure. There is a gentle transition above so that the reflected light emerges from the same angle, improving the clarity of the alignment structure.

The distance between the non-marking area 6 and the upper surface of the chamfered structural layer 2-1 increases to 520nm. As shown in Figure 3, this structure increases the gap between the non-marking area 6 and the mask to a certain extent. , the reflectivity of the non-marking area 6 is reduced, and the contrast of the marking area 2 relative to the non-marking area 6 is increased. As shown in Figure 6 is the alignment mark structure obtained by using the method of this embodiment. The image under the CCD camera is clear, which proves that the method of the present disclosure is effective.

Example 2:

As shown in Figure 2, the steps for forming the alignment mark structure in this embodiment are as follows:

The substrate 1 is a silicon-based material; the material of the chamfer layer 7 is AlN, the thickness is 100nm, and the preparation method is atomic layer deposition;

The first photosensitive layer 8-1 is prepared by spin coating. The material model of the first photosensitive layer 8-1 is AR-P3170 and the thickness is 100nm. The material of the light-blocking layer on the first mask 9-1 is metal Cr. The thickness is 100nm, and the substrate is quartz; the marking pattern on the first mask 9-1 is a square checkerboard grid with a period of 10 μm, and the area of the marking pattern is 400 μm*200 μm; there is also rough alignment on the first mask 9-1 Mark, the mark shape is a cross and the width is 10 μm; use contact photolithography to expose the mark pattern on the first mask 9-1 to the first photosensitive layer 8-1;

After development, the AlN of the chamfer layer 7 is etched. The etching gases for reactive ion beam etching are Cl ₂ and Ar, the gas flow ratio is 5:1, the chamber pressure is 0.5Pa, the power is 20w, and the etching time is 100s. The etching depth is 100nm; the alignment structure 2-2 is etched, using reactive ion beam etching, etching gases SF ₆ and CHF ₃ , the cavity pressure is 1Pa, the power is 100w, the etching time is 25min, and the etching depth is 4000nm; Etch AlN with chamfer layer structure 2-1, using reactive ion beam etching, etching gases are Cl ₂ and Ar, gas flow ratio is 3:1, cavity pressure is 1Pa, power is 40w, etching time is 10s, making the chamfer tilt angle approximately 40°;

Remove the remaining first photosensitive layer 8-1, soak the substrate with acetone until the first photosensitive layer 8-1 falls off, rinse with deionized water and dry the substrate 1;

Prepare the second photosensitive layer 8-2, spin-coat photoresist AR-3100 with a thickness of 1000nm; the pattern of the non-marking area 6 on the second mask 9-2 is zigzag, the inner circle area is 401μm*201μm, and the outer circle area is 401μm*201μm. The area is 600μm*400μm; the second mask 9-2 also includes cross-shaped alignment marks that match the first mask 9-1; the light-blocking material on the second mask 9-2 is metal Cr, with a thickness of is 100nm, and the substrate is quartz; a contact exposure process is used to expose the non-marking area 6 on the second mask 9-2 to the second photosensitive layer 8-2; after development, ion beam etching is used to achieve one-time etching penetration The chamfering layer 7 and the etched part of the substrate 1, the etching time is 10 minutes, and the substrate rotation angle is 15°, forming the chamfering structure layer 2-1 and the non-marking area 6, the non-marking area 6 (the middle part of the substrate 1 ), the etching depth is 1000nm; remove the remaining second photosensitive layer 8-2, soak the substrate 1 with acetone until the second photosensitive layer 8-2 falls off, rinse with deionized water and dry the substrate 1.

In this embodiment, the chamfer structure layer 2-1 covering the alignment structure 2-2 has an inclination angle of about 40°, and the thickness of the AlN chamfer structure layer is 100 nm. When the multi-layer film 3 covers the chamfer structure, There are gentle transitions so that the reflected rays emerge from the same angle, further improving the clarity of the aligned structure. The distance between the non-marking area 6 and the upper surface of the chamfered structure layer 2-1 increases to 1100 nm. This recessed structure increases the gap between the non-marking area 6 and the mask to a certain extent, making the non-marking area 6 The reflectivity of area 6 is reduced, thereby increasing the contrast of marked area 2 relative to non-marked area 6.

Embodiment three:

As shown in FIG. 2 , the steps for forming the alignment mark structure of this embodiment are as follows:

The substrate 1 is made of sapphire material; the material of the chamfer layer 7 is SiC, the thickness is 100nm, and the preparation method is plasma enhanced atomic layer deposition;

The first photosensitive layer 8-1 is prepared by spin coating. The material model of the first photosensitive layer 8-1 is AR-P3170 and the thickness is 500nm. The material of the light-blocking layer on the first mask 9-1 is metal Cr. The thickness is 100nm, and the substrate is quartz; the marking pattern on the first mask 9-1 is a grating structure with a period of 20 μm, the length of the grating is 40 μm, and the area of the marking pattern is 200 μm*40 μm; the marking pattern on the first mask 9-1 There are also marks used for rough alignment. The mark shape is a cross and the width is 10 μm; contact photolithography is used to expose the mark pattern on the first mask 9-1 to the first photosensitive layer 8-1;

After development, the SiC of the chamfer layer 7 is etched using an inductively coupled plasma etching process. The etching gases are SF ₆ and C ₄ F ₈ , the total gas flow is 80 sccm, the upper electrode power is 500w, and the lower electrode power is 200w. The etching time is 2 minutes, the etching depth is 100nm; the alignment structure 2-2 is etched, using wet etching, and the etching solution volume ratio is V (98% H ₂ SO ₄ ): V (85% H ₃ PO ₄ )=3:1, etching time 30min, etching depth 4000nm; etching SiC with chamfer layer structure 2-1, using inductively coupled plasma etching process, etching gases are SF ₆ and C ₄ F ₈ , total gas flow rate is 80sccm, the upper electrode power is 1000w, the lower electrode power is 600w, the etching time is 30s, so that the chamfer tilt angle is about 45°;

Remove the remaining first photosensitive layer 8-1, soak the substrate with acetone until the first photosensitive layer 8-1 falls off, rinse with deionized water and dry the substrate;

Prepare the second photosensitive layer 8-2, spin-coat photoresist AR-3100 with a thickness of 1000nm; the pattern of the non-marking area 6 on the second mask 9-2 is a zigzag shape, the inner circle area is 201μm*41μm, and the outer circle area is 201μm*41μm. The area is 400μm*240μm; the second mask 9-2 also includes cross-shaped alignment marks that match the first mask 9-1; the light-blocking material on the second mask 9-2 is metal Cr, with a thickness of is 100nm, and the substrate is quartz; a contact exposure process is used to expose the non-marking area 6 on the second mask 9-2 to the second photosensitive layer 8-2; after development, ion beam etching is used to achieve one-time etching penetration The chamfering layer 7 and the etched part of the substrate 1, the etching time is 10 minutes, the substrate rotation angle is 15°, and the chamfering structure layer 2-1 and the non-marking area 6 are formed. The non-marking area 6 (the middle part of the substrate 1 ), the etching depth is 1000nm; remove the remaining second photosensitive layer 8-2, soak the substrate 1 with acetone until the second photosensitive layer 8-2 falls off, rinse with deionized water and dry the substrate 1.

In this embodiment, the chamfer structure layer 2-1 covering the alignment structure 2-2 has an inclination angle of about 45°, and the thickness of the SiC chamfer structure layer is 100 nm, so that the multi-layer film 3 covers the chamfer structure. There are gentle transitions at times so that the reflected rays emerge from the same angle, further improving the clarity of the alignment structure. The distance between the non-marking area 6 and the upper surface of the chamfered structure layer 2-1 increases to 1100 nm. This recessed structure increases the gap between the non-marking area 6 and the mask to a certain extent, making the non-marking area 6 The reflectivity of area 6 is reduced, thereby increasing the contrast of marked area 2 relative to non-marked area 6.

Embodiment 4:

As shown in Figure 2, the steps for forming the alignment mark structure in this embodiment are as follows:

The substrate 1 is a silicon-based material; the chamfer layer 7 is made of Si ₃ N ₄ with a thickness of 20 nm, and the preparation method is magnetron sputtering coating;

The first photosensitive layer 8-1 is prepared by spin coating. The material model of the first photosensitive layer 8-1 is AR-P3170 and the thickness is 100nm. The material of the light-blocking layer on the first mask 9-1 is metal Cr. The thickness is 100nm, and the substrate is quartz; the marking pattern on the first mask 9-1 is a grating with a period of 20 μm, the grating length is 40 μm, and the area of the marking pattern is 200 μm*40 μm; it is also useful on the first mask 9-1 For rough alignment marks, the mark shape is a cross-shaped alignment mark with a width of 10 μm; contact photolithography is used to expose the mark pattern on the first mask 9-1 to the first photosensitive layer 8-1;

After development, the Si ₃ N ₄ of the chamfer layer 7 is etched using reactive ion beam etching. The etching gases are SF ₆ and O ₂ , the gas flow ratio is 5:1, the cavity pressure is 1Pa, and the power is 40w. The time is 20s, the etching depth is 20nm; the alignment structure 2-2 is etched, using reactive ion beam etching, the etching gas is SF ₆ and CHF ₃ , the cavity pressure is 1Pa, the power is 100w, and the etching time is 10min , the etching depth is 1500nm; the Si ₃ N ₄ of the chamfer layer 7 is etched using reactive ion beam etching, and the etching gases are SF ₆ , O ₂ , and N ₂ , where the gas flow ratio of SF ₆ and O ₂ is 3:1, the cavity pressure is 1Pa, the power is 20w, and the etching time is 15s, so that the tilt angle of the chamfered structural layer 2-1 is approximately 55°;

Remove the remaining first photosensitive layer 8-1, soak the substrate 1 with acetone until the first photosensitive layer 8-1 falls off, rinse with deionized water and dry the substrate 1;

Prepare a high reflectivity thin film layer 11, and use magnetron sputtering to coat a layer of Ag on the surface of the substrate 1. The thickness of the Ag layer is 10 nm;

Prepare the second photosensitive layer 8-2, spin-coat photoresist AR-1500 with a thickness of 500nm; the non-marking area 6 on the second mask 9-2 has a zigzag structure, the inner circle area is 201μm*41μm, and the outer circle area is 400μm*240μm; the second mask 9-2 also includes cross-shaped alignment marks that match the first mask 9-1; the light-blocking material on the second mask 9-2 is metal Cr, with a thickness of 100nm, the substrate is quartz; a contact exposure process is used to expose the non-marking area 6 on the second mask 9-2 to the second photosensitive layer 8-2; after development, the non-marking area 6 is etched using ion beam etching. The etching time is 5 minutes, and the substrate rotation angle is 15°; this method is used to etch clean the chamfer layer 7 and the high reflectivity film layer 11 on the non-marking area 6 at one time, and then etch the non-marking layer 7 on the substrate 1. The etching depth of the marking area 6 and the non-marking area 6 (the middle part of the substrate 1) is 500nm; remove the remaining second photosensitive layer 8-2, soak the substrate with acetone until the second photosensitive layer 8-2 falls off, and remove the remaining second photosensitive layer 8-2. The remaining high reflectivity thin film layer 11 on the quasi-structure 2-2 is rinsed with deionized water and the substrate is dried.

In this embodiment, the chamfered structural layer 2-1 covering the alignment structure 2-2 has an inclination angle of about 55°. In this embodiment, in addition to the chamfered structural layer 2-1 and the non-marking area 6, The high reflectivity film 11 is added to the bottom and side walls of the alignment structure 2-2, which can further improve the contrast of the alignment structure 2-2.

Comparative Example 1:

The substrate 1 of the alignment mark structure in this comparative example is made of silicon-based material; the first photosensitive layer 8-1 is prepared by spin coating. The material model of the first photosensitive layer 8-1 is AR-P3170 and the thickness is 100nm; The material of the light-blocking layer on the first mask 9-1 is metallic Cr, with a thickness of 100 nm, and the base is quartz; the marking pattern on the first mask 9-1 is a grating with a period of 20 μm, a grating length of 40 μm, and the marking pattern The area is 200 μm*40 μm; contact photolithography is used to expose the mark pattern on the first mask 9-1 to the first photosensitive layer 8-1; after development, the alignment structure 2-2 is etched, and reactive ion beam etching is used Etching, the etching gas is SF ₆ and CHF ₃ , the cavity pressure is 1Pa, the power is 100w, the etching time is 10min, the etching depth is 1500nm; remove the remaining first photosensitive layer 8-1, soak the substrate with acetone and wait The residual glue of the first photosensitive layer 8-1 is peeled off, rinsed with deionized water and the substrate is dried.

This comparative example prepared the alignment mark structure as shown in Figure 1. After preparing the multilayer film 3 on the substrate with the alignment mark, due to the uneven thickness of the multilayer film at the edge of the alignment structure 2-2, The light reflected by illumination on the surface of the multi-layer film 5-1, the light directly reflected by the illumination on the substrate 5-2, the sum of the irregular scattered light reflections of the illumination at the edge of the marking area 5-3, the illumination multiple times inside the multi-layer film The light 5-4 reflected back into the air and incident on the edge of the alignment mark cannot be reflected vertically in one direction, resulting in unclear alignment signals.

As shown in Figure 7, it can be found that there is no non-marking area in this comparison example. As the marking area with a recessed structure has low contrast under the CCD camera, the alignment mark cannot be seen clearly; at the same time, due to the absence of a chamfered structural layer, the edge clarity of the grating mark is very low. Low, the edge of the grating mark cannot be recognized, and subsequent alignment work cannot be performed.

Comparative Example 2:

The steps for forming the alignment mark structure in this comparative example are as follows:

The substrate 1 is a silicon-based material; the chamfer layer 7 is made of Si ₃ N ₄ with a thickness of 20 nm, and the preparation method is magnetron sputtering coating;

The first photosensitive layer 8-1 is prepared by spin coating. The material model of the first photosensitive layer 8-1 is AR-P3170 and the thickness is 100nm. The material of the light-blocking layer on the first mask 9-1 is metal Cr. The thickness is 100nm, and the substrate is quartz; the marking pattern on the first mask 9-1 is a grating with a period of 20 μm, the length of the grating is 40 μm, and the area of the marking pattern is 200 μm*40 μm; contact photolithography is used to decorate the first mask The mark pattern on the template 9-1 is exposed to the first photosensitive layer 8-1;

After development, the Si ₃ N ₄ of the chamfer layer 7 is etched using reactive ion beam etching. The etching gases are SF ₆ and O ₂ , the gas flow ratio is 5:1, the cavity pressure is 1Pa, and the power is 40w. The time is 20s, the etching depth is 20nm; the alignment structure 2-2 is etched, using reactive ion beam etching, the etching gases are SF ₆ and CHF ₃ , the cavity pressure is 1Pa, the power is 100w, and the etching time is 10 minutes, the etching depth is 1500nm; the chamfer layer 7 is etched using reactive ion beam etching. The etching gases are SF ₆ , O ₂ and N ₂ , where the gas flow ratio of SF ₆ and O ₂ is 3:1. The cavity pressure is 1Pa, the power is 20w, and the etching time is 15s, so that the tilt angle of the chamfered structural layer 2-1 is about 55°; remove the remaining first photosensitive layer 8-1, soak the substrate 1 with acetone and wait for The photosensitive layer 8-1 is peeled off, rinsed with deionized water and the substrate 1 is dried.

The alignment mark structure prepared in this comparative example contains a chamfer structure layer but no non-marking area. As shown in Figure 8, it can be found that the marked area without non-marking area as a concave structure has low contrast under the CCD camera, and the alignment mark cannot be seen clearly, which in turn affects subsequent alignment work.

Comparative example three:

The steps for forming the alignment mark structure in this comparative example are as follows:

The substrate 1 is a silicon-based material; the first photosensitive layer 8-1 is prepared by spin coating. The material model of the first photosensitive layer 8-1 is AR-P3170 and the thickness is 100nm;

The material of the light-blocking layer on the first mask 9-1 is metal Cr with a thickness of 100 nm, and the base is quartz; the mark pattern on the first mask 9-1 is a grating with a period of 20 μm, the length of the grating is 40 μm, and the mark The area of the pattern is 200μm*40μm; there are also marks for rough alignment on the first mask 9-1, the shape of the marks is cross-shaped, and the width is 10μm; contact photolithography is used to remove the marks on the first mask 9-1 The pattern is exposed to the first photosensitive layer 8-1; the alignment structure 2-2 is etched, using reactive ion beam etching, the etching gas is SF ₆ and CHF ₃ , the cavity pressure is 1Pa, the power is 100w, and the etching time is 10min, etching depth is 1500nm;

Remove the remaining first photosensitive layer 8-1, soak the substrate 1 with acetone until the first photosensitive layer 8-1 falls off, rinse with deionized water and dry the substrate 1; prepare the second photosensitive layer 8-2, and spin coating Photoresist AR-P3170, thickness is 100nm; the non-marking area 6 on the second mask 9-2 has a zigzag structure, the inner ring area is 201μm*41μm, and the outer ring area is 400μm*240μm; the second mask 9- 2 also includes cross-shaped alignment marks that match the first mask 9-1 for rough alignment. The light-blocking material on the second mask 9-2 is metal Cr with a thickness of 100nm, and the base is quartz. ;

The non-marking area 6 on the second mask 9-2 is exposed to the second photosensitive layer 8-2 using a contact exposure process; after development, the non-marking area 6 is etched using reactive ion beam etching, and the etching gas is SF. ₆ and CHF ₃ , the cavity pressure is 1Pa, the power is 50w, the etching time is 3min, and the etching depth is 500nm; remove the remaining second photosensitive layer 8-2, soak the substrate 1 with acetone and wait for the second photosensitive layer 8- 2 came off, rinsed with deionized water and dried the substrate 1.

The alignment mark structure prepared in this comparative example does not include a chamfer structure layer, but only includes a non-marking area. After the multilayer film 3 is prepared on the substrate of the alignment mark structure, the light that is reflected multiple times inside the multilayer film and then back to the air cannot be reflected vertically in one direction, resulting in unclear alignment signals. As shown in Figure 9, it can be found that the edge definition of the grating mark of the alignment mark structure without a chamfered structural layer is very low, and the edge of the grating mark cannot be identified, making subsequent alignment work impossible.

By optimizing the structure and layout of the alignment marks, the present disclosure enables the alignment marks to have clear edges and contrast under the alignment detection system, thereby improving the detection capability of the alignment signals, reducing the distortion of the alignment signals, and realizing the goals in IC manufacturing. The purpose of reducing overlay errors.

The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection of the present disclosure.

Claims (11)

1. An alignment mark structure, characterized by including:

   Substrate (1);

   The marking area (2) includes an alignment structure (2-2) and a chamfer structure layer (2-1); the alignment structure (2-2) is formed in the substrate (1) and is a recessed structure ; The chamfered structural layer (2-1) is formed on the surface of the substrate (1) and is a protruding structure. The chamfered structural layer (2-1) is formed on the surface of the alignment structure (2-2). ) forms a raised chamfered structure on its edge;

   A non-marking area (6) is arranged around the periphery of the marking area (2), and the upper surface of the non-marking area (6) is lower than the chamfered structural layer (2-1) in the marking area (2). lower surface.
2. The alignment mark structure according to claim 1, characterized in that the bottom and side walls of the alignment structure (2-2) are provided with a high reflectivity film layer (11);

   The thickness of the high reflectivity thin film layer (11) does not exceed 100 nm, and its material includes one of Au, Al, and Ag.
3. The alignment mark structure according to claim 1, characterized in that the planar size of the alignment structure (2-2) ranges from 0.5 to 50 μm, and the depression depth of the alignment structure (2-2) is 100 ~4000nm.
4. The alignment mark structure according to claim 3, characterized in that the alignment structure (2-2) includes one of a cross-shaped alignment mark and a grid-type alignment mark.
5. The alignment mark structure according to claim 1, characterized in that the thickness of the chamfer structure layer (2-1) does not exceed 100 nm, and the inclination angle of the chamfer structure is 35 to 55°;

   The material of the chamfer structure layer (2-1) is a non-transparent medium that is easy to be etched and controlled, including one of silicon nitride, aluminum nitride, silicon carbide, and polysilicon.
6. The alignment mark structure according to claim 3, characterized in that the non-marking area (6) is a zigzag structure and is arranged around the periphery of the alignment structure (2-2) in a range of 1 to 1000 μm;

   The non-marking area (6) is formed in the substrate (1) by etching, and its etching depth does not exceed 1/2 of the depth of the recessed structure.
7. A method for preparing an alignment mark structure according to any one of claims 1 to 6, characterized in that it includes:

   S1, forming a chamfer layer (7) on the substrate (1);

   S2, coat the first photosensitive layer (8-1); etch the mark area (2) after exposure and development, including sequentially etching the chamfer layer (7) and the substrate (1) to obtain the alignment structure (2 -2);

   S3, etching the chamfer layer (7) at the edge of the alignment structure (2-2) to obtain a convex chamfer structure, and removing the first photosensitive layer (8-1);

   S4, coat the second photosensitive layer (8-2); after exposure and development, etch the periphery of the marking area (2), including sequentially etching the chamfer layer (7) and the substrate (1) to obtain a non- Marking area (6) and chamfering structural layer (2-1);

   S5, remove the second photosensitive layer (8-2) to obtain a target alignment mark structure.
8. The method for preparing an alignment mark structure according to claim 7, wherein after S3, it further includes:

   S31, deposit a high reflectivity thin film layer (11) with a thickness of no more than 100 nm.
9. The method for preparing an alignment mark structure according to claim 8, wherein S5 further includes:

   The high reflectivity thin film layer (11) on the chamfered structural layer (2-1) is removed.
10. The method for preparing an alignment mark structure according to claim 7, wherein the etching method in S3 is dry etching, and the dry etching includes reactive ion etching, inductively coupled plasma etching. One of the etching gases, the etching gas includes one of SF ₆ , O ₂ , N ₂ , CHF ₃ , Cl ₂ , Ar and C ₄ F ₈ ;
11. The method for preparing an alignment mark structure according to claim 7, wherein the tilt angle of the convex chamfered structure obtained by etching in S3 is 35 to 55°.

Images