A DMD maskless lithography system based on two-dimensional galvanometer and a splicing lithography method

Abstract

The present invention discloses a DMD maskless lithography system based on a two-dimensional galvanometer and a splicing lithography method. The system comprises a light source system, a DMD, a deflection system, a projection system, an observation system and a sample stage, which are arranged in sequence. The exposure light source is uniformly collimated and shaped to irradiate the object surface DMD. The DMD generates a digital mask and reflects a light beam carrying graphic information into the deflection system. The light beam is deflected by the two-dimensional galvanometer and an F-Theta field lens. Finally, the light beam is imaged on a substrate coated with photoresist on the sample stage through a projection system consisting of a sleeve lens and an objective lens, thereby realizing lithography exposure. The DMD plane and the image plane are conjugately imaged. The present invention deflects the light beam on the X-axis and Y-axis through the rapid response of the two-dimensional galvanometer. In conjunction with the F-Theta field lens, the change in the light beam direction caused by the galvanometer is converted into a change in the position of the focus on the intermediate image plane by the galvanometer. The galvanometer cooperates with the galvanometer to realize aberration correction and compensate for the field curvature and distortion of the system. The F-Theta field lens provides a flat image plane with high transmittance, a large scanning range, low aberration, and low F-Theta distortion. This imaging is performed through a projection system consisting of a tube lens and an objective lens, ultimately enabling array stitching lithography exposure on a substrate. This system enables maskless stitching lithography without the need for a multi-axis precision motorized translation stage. It features high efficiency, a simple structure, strong resistance to mechanical interference, and minimal error, enabling accurate, high-precision stitching lithography.

Description

Technical Field

[0001] The present invention belongs to the field of maskless projection lithography, and more specifically relates to a DMD maskless lithography system based on a two-dimensional galvanometer and a splicing lithography method. Background Art

[0002] As a core process in the fabrication of semiconductor micro- and nano-devices, photolithography is of undeniable importance. As lithographic linewidths continue to shrink, mask production costs and processing cycles in traditional mask lithography are also increasing. To find a low-cost solution, maskless lithography has become a research hotspot.

[0003] Maskless lithography based on DMDs, with its low cost and excellent digital mask properties, has improved the flexibility of lithography and has been widely used in the field of micro-nano device processing. The DMD is a highly integrated micro-mirror array device. The light beam reflected by the on-state micromirrors carries the mask information and is collected by the subsequent projection system for exposure. The stray light reflected by the off-state micromirrors is absorbed by a specific medium. By loading different digital mask patterns, the required exposure light field can be obtained through reflection from the DMD micromirrors to complete the patterning process.

[0004] However, in high-scale DMD maskless lithography systems, the area of ​​a single exposure is limited by the size of the DMD chip. To achieve large-area lithography exposure, traditional methods include stepper lithography and scanning lithography. Stepper lithography requires a multi-axis precision motorized translation stage to move to the next position after each exposure, undergoing a stage acceleration and deceleration process in the process, resulting in high mechanical noise and low efficiency. Scanning lithography, on the other hand, requires multiple segmentation and cutting of the target pattern to generate a large sequence of sub-images. Each time the DMD refreshes a frame, the motorized translation stage must move one step in coordination, placing extremely high demands on the system's coordination capabilities.

[0005] Therefore, a two-dimensional galvanometer is used to deflect the light beam, and the F-Theta field mirror converts the change of the light beam direction caused by the galvanometer into a change of the position of the focus on the intermediate image plane. This explores a splicing lithography method for DMD maskless lithography with simple structure and high precision, which is of great significance to reducing costs and improving the efficiency of DMD maskless splicing lithography. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a DMD maskless lithography system and a stitching lithography method based on a two-dimensional galvanometer. The two-dimensional galvanometer is used to deflect the light beam, and the F-Theta field mirror converts the change in the direction of the light beam caused by the galvanometer into a change in the position of the focus on the intermediate image plane, thereby realizing stitching lithography on the substrate.

[0007] The first object of the present invention is to provide a DMD maskless lithography system based on a two-dimensional galvanometer, comprising a light source system, a DMD, a deflection system, a projection system, an observation system and a sample stage arranged in sequence. The exposure light source in the light source system is irradiated on the object plane DMD after uniform light collimation and shaping. The DMD generates a digital mask and reflects the light beam carrying graphic information into the deflection system. The two-dimensional galvanometer deflects the light beam to ensure that the F-Theta field lens converts the change in the direction of the light beam into a change in the position of the focus on the intermediate image plane. Finally, the system is imaged on a substrate coated with photoresist on the sample stage through a micro-projection system composed of a sleeve lens and an objective lens to realize lithography exposure, wherein the DMD plane and the image plane are conjugately imaged.

[0008] In one embodiment of the present invention, the light source system is composed of an exposure light source, an auxiliary focusing light source, and a uniform light collimating lens. The auxiliary focusing light source has a wavelength band that does not react with the photoresist. The two light sources are coaxial and concentric, and the incident angle irradiated to the DMD plane is twice the DMD switching state flip angle.

[0009] In one embodiment of the present invention, the flip axis of the DMD micromirror is along the diagonal direction, and the DMD needs to be rotated 45° during installation so that the DMD flip axis is vertically downward.

[0010] In one embodiment of the present invention, the deflection system is composed of a two-dimensional galvanometer and an F-Theta field mirror. The position of the two-dimensional galvanometer should satisfy that the middle plane of the two mirrors should be located at the scanning distance of the F-Theta field mirror. The F-Theta field mirror makes the angular velocity of the input light beam and the output light beam directly proportional, so that the scanning mirror can operate at a constant angular velocity. At the same time, the change of the light beam direction by the galvanometer is converted into a change in the position of the focus on the intermediate image plane, and the galvanometer is used to achieve aberration correction and compensate for the field curvature and distortion of the system. When in use, the F-Theta field mirror can provide a flat field image plane and greatly simplify the control circuit. It has the characteristics of high transmittance, large scanning range, low aberration and low F-Theta distortion.

[0011] In one embodiment of the present invention, the projection system consists of a tube lens and an objective lens, the tube lens is installed behind the F-Theta field lens, and the distance between them should satisfy the sum of the rear working distance of the F-Theta field lens and the front working distance of the tube lens, and the objective lens is installed behind the tube lens, and the distance between them satisfies the optimal working pupil distance of the tube lens.

[0012] In one embodiment of the present invention, the observation system is composed of a beam splitter, an illumination light source, an imaging lens, and a CCD camera. The illumination light source uses white light and a filter and does not react with the photoresist. The imaging lens focuses the light reflected from the substrate surface on the CCD camera plane for observing the substrate surface. The CCD camera forms a conjugate image with the substrate surface.

[0013] A second object of the present invention is to provide a DMD maskless splicing lithography method based on a two-dimensional galvanometer, wherein the method applies the DMD maskless lithography system based on a two-dimensional galvanometer, and comprises the following steps:

[0014] Step 1: Turn on the auxiliary focusing light source, the DMD generates a digital mask and reflects it into the two-dimensional galvanometer mirror with an initial angle of 45 degrees. At this time, the light beam carrying the mask information is imaged on the substrate through the projection system without deflection. Turn on the exposure light source and exposure can be performed at the initial origin of the substrate.

[0015] Step 2: Two analog voltage signals are input from the outside to drive the two-dimensional galvanometer to deflect the mechanical angles θ1 / 2 and θ2 / 2 on the X and Y axes respectively. The outgoing light beam is deflected to the optical angles θ1 and θ2 and enters the F-Theta field mirror.

[0016] Step 3: The focal length of the F-Theta field lens is f1, and the distances by which the incident light beam is deflected along the coordinate axes at the intermediate image plane satisfy the following relationship:

[0017] D i =f1×θ i (i=1, 2);

[0018] Step 4: The image at the intermediate image plane is formed on the substrate by the projection system. The zoom ratio of the combination of the focal length f2 of the tube lens and the focal length f3 of the objective lens satisfies the following relationship:

[0019] β=f3 / f2;

[0020] Step 5: The distances that the image on the substrate is deflected along the coordinate axis relative to the initial origin satisfy the following relationship:

[0021] D x =D1×β,D y =D2×β;

[0022] Step 6: The light beam carrying the mask information is deflected and imaged on the substrate through the projection system. The exposure light source is turned on, and the origin can be offset on the substrate for exposure.

[0023] Step 7: The program repeats the above steps 1 to 6, and controls the deflection angle to match the step length with the size of the single exposure format. For example, if the length of the single exposure format rectangle is L and the width is W, make Dx =L,D y =W, the stitching lithography process of the target pattern can be realized.

[0024] The present invention proposes a DMD maskless splicing lithography method by utilizing the ability of a two-dimensional galvanometer and an F-Theta field mirror to deflect light beams. The beneficial effects are as follows:

[0025] Through the rapid response of the two-dimensional galvanometer, combined with the F-Theta field lens, the galvanometer's changes in the beam direction are converted into changes in the focal position on the intermediate image plane. This synergistic effect corrects aberrations and compensates for the system's field curvature and distortion. The F-Theta field lens provides a flat image plane with high transmittance, a large scanning range, low aberrations, and low F-Theta distortion. This system eliminates the acceleration and deceleration processes associated with multi-axis motorized displacement motion and, in conjunction with the projection system, enables maskless splicing lithography. This system boasts high efficiency, a simple structure, strong resistance to mechanical interference, and minimal error, enabling accurate, high-precision splicing lithography. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a module diagram of the DMD maskless lithography system based on a two-dimensional galvanometer of the present invention;

[0027] Figure 2 This is a diagram of the components of the DMD maskless lithography system based on a two-dimensional galvanometer of the present invention;

[0028] Figure 3 This is a schematic diagram of the working principle of the F-Theta field mirror of the present invention;

[0029] Figure 4 It is a schematic diagram of splicing photolithography on a substrate according to the present invention;

[0030] Figure 5 It is a SEM scanning image of the actual array lithography of the present invention. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0032] Example 1

[0033] like Figure 1As shown, this embodiment provides a DMD maskless lithography system based on a two-dimensional galvanometer, including a light source system, a DMD, a deflection system, a projection system, an observation system and a sample stage arranged in sequence. The exposure light source in the light source system is irradiated on the object plane DMD after uniform light collimation and shaping. The DMD generates a digital mask and reflects the light beam carrying graphic information into the deflection system. The two-dimensional galvanometer deflects the light beam, and the F-Theta field lens converts the change in the direction of the light beam into a change in the position of the focus on the intermediate image plane. Finally, the micro-projection system composed of a tube lens and an objective lens is used to form an image on a substrate coated with photoresist on the sample stage to achieve lithography exposure, wherein the DMD plane and the image plane are conjugately imaged.

[0034] like Figure 2 As shown, the light source system consists of an exposure light source, an auxiliary focusing light source, and a uniform light collimating lens. The auxiliary focusing light source has a wavelength band that does not react with the photoresist. The two light sources are coaxial and concentric, and the incident angle irradiated on the DMD plane is twice the DMD switching state flip angle. The deflection system consists of a two-dimensional galvanometer and an F-Theta field lens. The position of the two-dimensional galvanometer should satisfy that the middle plane of the two reflectors should be located at the scanning distance of the F-Theta field lens. At the same time, the change in the direction of the light beam caused by the galvanometer is converted into a change in the position of the focus on the intermediate image plane. The galvanometer is used to achieve aberration correction and compensate for the field curvature and distortion of the system in cooperation with the galvanometer. The projection system consists of a tube lens and an objective lens. The tube lens is installed behind the F-Theta field lens. The distance between them should satisfy the sum of the rear working distance of the F-Theta field lens and the front working distance of the tube lens. The objective lens is installed behind the tube lens. The distance between them satisfies the optimal working pupil distance of the tube lens. The observation system consists of a beam splitter, an illumination light source, an imaging lens, and a CCD camera. The illumination light source does not react with the photoresist. The imaging lens focuses the light reflected from the substrate surface on the CCD camera plane for observing the substrate surface. The CCD camera forms a conjugate image with the substrate surface.

[0035] Example 2

[0036] This embodiment provides a DMD maskless splicing lithography method based on a two-dimensional galvanometer. The method uses a DMD maskless lithography system based on a two-dimensional galvanometer provided in the first embodiment, and includes the following steps:

[0037] Step 1: Turn on the auxiliary focusing light source, the DMD generates a digital mask and reflects it into the two-dimensional galvanometer mirror with an initial angle of 45 degrees. At this time, the light beam carrying the mask information is imaged on the substrate through the projection system without deflection. Turn on the exposure light source and exposure can be performed at the initial origin of the substrate.

[0038] Step 2: Two analog voltage signals are input from the outside to drive the two-dimensional galvanometer to deflect the mechanical angles θ1 / 2 and θ2 / 2 on the X and Y axes respectively. The outgoing light beam is deflected to the optical angles θ1 and θ2 and enters the F-Theta field mirror.

[0039] Step 3: The focal length of the F-Theta field lens is f1. The incident light beam is deflected along the X-axis and Y-axis at the intermediate image plane to satisfy the following relationship:

[0040] D i =f1×θ i (i=1, 2);

[0041] Step 4: The image at the intermediate image plane is formed on the substrate by the projection system. The zoom ratio of the combination of the focal length f2 of the tube lens and the focal length f3 of the objective lens satisfies the following relationship:

[0042] β=f3 / f2;

[0043] Step 5: The distances that the image on the substrate is deflected along the X-axis and Y-axis relative to the initial origin satisfy the following relationship:

[0044] D x =D1×β,D y =D2×β;

[0045] Step 6: The light beam carrying the mask information is deflected and imaged on the substrate through the projection system. The exposure light source is turned on, and the origin can be offset on the substrate for exposure.

[0046] Step 7: The program repeats the above steps 1 to 6, and controls the deflection angle to match the step length with the size of the single exposure format. For example, if the length of the single exposure format rectangle is L and the width is W, make D x =L,D y =W, the target pattern stitching lithography process can be realized;

[0047] like Figure 3 As shown in the figure, for a beam with an incident angle of θ, the F-Theta field mirror deflects the beam at the intermediate image plane by a displacement of D = f × θ. The F-Theta field mirror makes the angular velocities of the input and output beams directly proportional, enabling the scanning mirror to operate at a constant angular velocity. Simultaneously, the galvanometer's change in beam direction translates into a change in the focal point's position on the intermediate image plane, collaborating with the galvanometer to achieve aberration correction and compensate for the system's field curvature and distortion.

[0048] like Figure 4 As shown in the figure, the deflected light beam is imaged on a silicon substrate coated with photoresist through the projection system, and is displaced by D along the X-axis and Y-axis relative to the initial position. x With D yBy calculating the numerical relationship between the required single exposure format and the displacement step length, the corresponding deflection angle of the two-dimensional galvanometer can be calculated. The laser galvanometer is controlled by an external analog voltage input signal. Benefiting from the high precision and good mechanical stability of the galvanometer, the splicing lithography process can be accurately implemented on the substrate.

[0049] like Figure 5 As shown, this is an actual 3×3 array lithography SEM scan of this embodiment, using positive photoresist. The central rectangle is the initial origin of the substrate, and the surrounding graphics are generated by galvanometer deflection exposure. After principle verification, the image edges are clear and sharp, and lithography exposure can be achieved. The scale in the figure is 100μm.

[0050] Some steps in the embodiments of the present invention may be implemented using software, and the corresponding software program may be stored in a readable storage medium, such as a CD or a hard disk.

[0051] The above embodiments of the present invention are merely examples for more clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Any modifications, equivalent substitutions, and improvements within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A DMD maskless lithography system based on a two-dimensional galvanometer, characterized in that: The system comprises a light source system, a DMD, a deflection system, a projection system, an observation system and a sample stage, which are arranged in sequence. The exposure light source in the light source system is irradiated onto the object surface DMD after uniform light collimation and shaping. The DMD generates a digital mask and reflects the light beam carrying graphic information into the deflection system. The two-dimensional galvanometer in the deflection system deflects the light beam, ensuring that the F-Theta field mirror converts the change in the direction of the light beam into a change in the position of the focus on the intermediate image plane. Finally, the micro-projection system consisting of a sleeve lens and an objective lens forms an image on a substrate coated with photoresist on the sample stage, thereby realizing photolithography exposure. The DMD plane and the image plane are conjugate images.

2. A DMD maskless lithography system based on a two-dimensional galvanometer according to claim 1, characterized in that: The light source system consists of an exposure light source, an auxiliary focusing light source, and a uniform light collimating lens. The auxiliary focusing light source has a wavelength that does not react with the photoresist. The two light sources are coaxial and concentric, and the incident angle irradiating the DMD plane is twice the DMD switching state flip angle.

3. The DMD maskless lithography system based on a two-dimensional galvanometer according to claim 1, characterized in that: The DMD micromirror flip axis is along the diagonal direction. During installation, the DMD needs to be rotated 45° so that the DMD flip axis is vertically downward.

4. The DMD maskless lithography system based on a two-dimensional galvanometer according to claim 1, characterized in that: The deflection system consists of a two-dimensional galvanometer and an F-Theta field mirror. The position of the two-dimensional galvanometer should satisfy that the middle plane of the two mirrors should be located at the scanning distance of the F-Theta field mirror. The F-Theta field mirror makes the angular velocities of the input light beam and the output light beam directly proportional, so that the scanning mirror can operate at a constant angular velocity. At the same time, the change of the light beam direction caused by the galvanometer is converted into a change in the position of the focus on the intermediate image plane. The galvanometer cooperates with the galvanometer to achieve aberration correction and compensate for the field curvature and distortion of the system. When used, the F-Theta field mirror can provide a flat field image plane and greatly simplify the control circuit. It has the characteristics of high transmittance, large scanning range, low aberration and low F-Theta distortion.

5. The DMD maskless lithography system based on a two-dimensional galvanometer according to claim 1, characterized in that: The projection system consists of a tube lens and an objective lens. The tube lens is installed behind the F-Theta field lens, and the distance between them should meet the sum of the rear working distance of the F-Theta field lens and the front working distance of the tube lens. The objective lens is installed behind the tube lens, and the distance between them meets the optimal working pupil distance of the tube lens.

6. The DMD maskless lithography system based on a two-dimensional galvanometer according to claim 1, characterized in that: The observation system consists of a beam splitter, an illumination light source, an imaging lens, and a CCD camera. The illumination light source uses white light and a filter and does not react with the photoresist. The imaging lens focuses the light reflected from the substrate surface on the CCD camera plane for observing the substrate surface. The CCD camera forms a conjugate image with the substrate surface.

7. A splicing lithography method for a DMD maskless lithography system based on a two-dimensional galvanometer, characterized in that: A DMD maskless lithography system based on a two-dimensional galvanometer according to any one of claims 1 to 6 is applied, comprising the following steps: Step 1: Turn on the auxiliary focusing light source, the DMD generates a digital mask and reflects it into the two-dimensional galvanometer mirror with an initial angle of 45 degrees. At this time, the light beam carrying the mask information is imaged on the substrate through the projection system without deflection. Turn on the exposure light source and exposure can be performed at the initial origin of the substrate. Step 2: Two analog voltage signals are input from the outside to drive the two-dimensional galvanometer to deflect the mechanical angles θ1 / 2 and θ2 / 2 on the X and Y axes respectively. The outgoing light beam is deflected to the optical angles θ1 and θ2 and enters the F-Theta field mirror. Step 3: The focal length of the F-Theta field lens is f1. The incident light beam is deflected along the X-axis and Y-axis at the intermediate image plane to satisfy the following relationship: D i =f1×θ i (i=1,2); Step 4: The image at the intermediate image plane is formed on the substrate by the projection system. The zoom ratio of the combination of the focal length f2 of the tube lens and the focal length f3 of the objective lens satisfies the following relationship: β=f3 / f2; Step 5: The distances that the image on the substrate is deflected along the X-axis and Y-axis relative to the initial origin satisfy the following relationship: D x =D1×β,D y =D2×β; Step 6: The light beam carrying the mask information is deflected and imaged on the substrate through the projection system. The exposure light source is turned on, and the origin can be offset on the substrate for exposure. Step 7: The program repeats the above steps 1 to 6, and controls the deflection angle to match the step length with the size of the single exposure format. For example, if the length of the single exposure format rectangle is L and the width is W, make D x =L,D y =W, the stitching lithography process of the target pattern can be realized.

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