A method for measuring the transmittance of a halftone mask

Abstract

The application discloses a kind of halftone mask through rate measurement methods, on halftone mask, in one field of view, with adjacent full transparent area, non-transparent area and semi-transparent area, measurement method is: first, in the both sides of halftone mask respectively no contact setting laser transmitter and laser receiver;Then only open laser transmitter, so that the laser that laser transmitter emits passes through semi-transparent area;Then open laser receiver, laser receiver respectively obtains the laser signal that full transparent area, non-transparent area and semi-transparent area are penetrated, and respectively recorded as A, B, C;Finally, the transmittance T of semi-transparent area is calculated, and the calculation formula is: T=[(C-B) / (A-B)]×100%;The halftone mask through rate measurement method of the application is simple and fast in measurement operation, contactless measurement throughout, can satisfy the high-precision processing requirement of halftone mask.Simultaneously, measurement is carried out using photoelectric signal, and measurement precision is high, and the requirement of measurement tool and environment is lower.

Description

Technical Field

[0001] This invention belongs to the field of mask detection and measurement, and more specifically relates to a method for measuring the transmittance of halftone masks. Background Technology

[0002] Halftone masks (HTM) are masks that utilize a film with a certain optical transmittance to achieve partial light transmission. As an advanced mask material, they are mainly used in the production of TFT panels. Traditional masks only exhibit two effects: light transmission and opacity for specific wavelengths of light. Halftone masks, however, are created by repeatedly sputtering and depositing two layers—a semi-transparent film and a light-blocking film—on a glass substrate. Then, two photolithography processes are used to create a pattern structure that includes fully transparent, completely opaque, and partially transparent effects.

[0003] Transmittance is a crucial parameter for the light transmission effect of the semi-transparent area on a halftone mask, and it is also an important parameter guiding the processing of halftone masks. After processing, the transmittance of the semi-transparent area needs to be measured and verified to meet customer requirements. Current transmittance measurement methods are susceptible to environmental influences, resulting in low accuracy and large errors, which seriously affect the processing and production of halftone masks and ultimately impact their quality. Summary of the Invention

[0004] The purpose of this invention is to provide a method for measuring the transmittance of halftone photomasks. The measurement operation is simple and fast, the measurement accuracy is high, and the entire process is non-contact, which can meet the high-precision processing requirements of halftone photomasks.

[0005] The present invention provides a method for measuring the transmittance of a halftone mask, wherein the halftone mask has adjacent fully transparent, opaque, and semi-transparent areas within a field of view.

[0006] The measurement method is as follows: First, a laser emitter and a laser receiver are set up without contact on both sides of the halftone mask; then, only the laser emitter is turned on, so that the laser emitted by the laser emitter passes through the semi-transparent area; finally, the laser receiver is turned on, and the laser receiver obtains the laser signals transmitted through the fully transparent area, the opaque area, and the semi-transparent area, respectively, and denoted as A, B, and C; finally, the transmittance T of the semi-transparent area is calculated, and the calculation formula is: T = [(CB) / (AB)] × 100%;

[0007] The laser wavelength is 365nm for the I line, 405nm for the H line, or 435nm for the G line.

[0008] Preferably, a collimating lens group is provided at the front of the laser emitter; the laser emitted by the laser emitter is collimated by the collimating lens group and then passes vertically through the middle position of the semi-transparent area.

[0009] Preferably, the laser receiver is provided in three parts, which are respectively facing the fully transparent area, the opaque area and the semi-transparent area, and work simultaneously to receive laser signals passing through the fully transparent area, the opaque area and the semi-transparent area respectively.

[0010] Preferably, the laser receiver is turned on only after the energy of the laser source emitted by the laser emitter has stabilized.

[0011] The beneficial effects of the halftone mask transmittance measurement method of the present invention are: the measurement operation is simple and fast, the entire process is non-contact, and it can meet the high-precision processing requirements of halftone masks. At the same time, it uses photoelectric signals for measurement, resulting in high measurement accuracy and lower requirements for measuring tools and the environment. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the halftone mask structure of the technical solution of the present invention.

[0013] Figure 2 This is a graph showing the experimental results of halftone mask transmittance measured according to the technical solution of this invention;

[0014] in, Figure 2 The Y-axis represents the measurement results of the semi-transparent area, and the X-axis represents the number of measurements.

[0015] NO. represents the number of measurements on the X-axis; the Value in the Voltage (mV) column is the voltage signal energy C received by the laser in the semi-transparent region; and the Value in the Trans (%) column is the transmittance T of the semi-transparent region. Detailed Implementation

[0016] To facilitate understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will now be further described in conjunction with specific embodiments and the accompanying drawings.

[0017] Determined by the halftone mask itself, a halftone mask contains fully transparent, opaque, and semi-transparent areas. During measurement, it is essential to ensure that within a single field of view on the halftone mask, there are adjacent fully transparent, opaque, and semi-transparent areas. For example... Figure 1 The aforementioned area has a halftone mask 01, a fully transparent area 04, an opaque area 03, and a semi-transparent area 02.

[0018] The present invention provides a method for measuring the transmittance of a halftone photomask, the specific steps of which are as follows:

[0019] First, a laser emitter and a laser receiver are positioned on opposite sides of the halftone mask without contact. Neither the laser emitter nor the laser receiver should touch the surface of the halftone mask to avoid damage or contamination. This also prevents excessive distance between the laser emitter and receiver and the halftone mask surface, which could lead to laser energy loss. A distance of approximately 10 cm between the laser emitter and receiver and the halftone mask surface is generally considered optimal.

[0020] Then, only the laser emitter is turned on, allowing the emitted laser light to pass through the semi-transparent region. To improve measurement accuracy, a collimating lens group is placed in front of the laser emitter to collimate the emitted laser light. After being collimated by the collimating lens group, the emitted laser light passes perpendicularly through the center of the semi-transparent region. Simultaneously, to further improve measurement accuracy, measurements are performed approximately 10 minutes after the laser emitter is turned on, allowing the emitted laser energy to stabilize.

[0021] Then, after the laser energy emitted by the laser transmitter stabilizes, the laser receiver is activated. The laser receiver receives the laser signals transmitted through the fully transparent, opaque, and semi-transparent regions, denoted as A, B, and C, respectively. Finally, the transmittance T of the semi-transparent region is calculated using the formula: T = [(CB) / (AB)] × 100%. The laser receiver receives the laser light and converts the laser light signal into an electrical signal, which is then sent to the controller for calculation.

[0022] In this scheme, the transmittance of the semi-transparent area on the halftone mask is calculated by the formula T=[(CB) / (AB)]×100%, which effectively eliminates the influence of a small amount of laser light passing through the opaque area on the measurement results, resulting in high accuracy of the semi-transparent area transmittance measurement.

[0023] In this scheme, the laser wavelength is 365nm for the I line, 405nm for the H line, or 435nm for the G line.

[0024] In this scheme, to improve measurement accuracy and eliminate the influence of laser energy fluctuations from the laser emitter itself, three laser receivers can be set up, facing the fully transparent area, the opaque area, and the semi-transparent area respectively, operating simultaneously and receiving laser signals passing through the fully transparent area, the opaque area, and the semi-transparent area respectively. In this way, the three laser receivers simultaneously receive laser signals passing through the fully transparent area, the opaque area, and the semi-transparent area respectively, eliminating the influence of laser energy fluctuations during laser emitter operation and improving measurement accuracy.

[0025] To verify the above measurement method, the transmittance of several halftone masks with different transmittances was measured according to the method described above. The measurement results are as follows. Figure 2 As shown: Figure 2The Y-axis represents the transmittance measurement results of the semi-permeable area, and the X-axis represents the number of measurements.

[0026] In this experiment, five halftone masks with different transmittances were used for sequential measurements, with each halftone mask measured at least twice under identical conditions. Figure 2 In the measurement process, measurements 1, 2, and 3 are taken using the first halftone mask; measurements 4 and 5 are taken using the second halftone mask; measurements 6 and 7 are taken using the third halftone mask; measurements 8 and 9 are taken using the fourth halftone mask; and measurements 10 and 11 are taken using the fifth halftone mask. The measurement structure is as follows: Figure 2 The table on the right is shown below. In the table, NO. represents the number of measurements on the X-axis; the Voltage (mV) column represents the voltage signal energy C received by the laser in the semi-transparent region; and the Trans (%) column represents the transmittance T of the semi-transparent region. Figure 2 The measurement results show that the results of the two measurements of each mask are basically consistent, indicating high measurement accuracy.

[0027] The technical solution of the present invention has been described above by way of example in conjunction with the embodiments and accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for measuring the transmittance of a halftone photomask, characterized in that, On the halftone mask, within a single field of view, there are adjacent fully transparent, opaque, and semi-transparent areas. The measurement method is as follows: First, a laser emitter and a laser receiver are set up without contact on both sides of the halftone mask; then, only the laser emitter is turned on, so that the laser emitted by the laser emitter passes through the semi-transparent area; finally, the laser receiver is turned on, and the laser receiver obtains the laser signals transmitted through the fully transparent area, the opaque area, and the semi-transparent area, respectively, and denoted as A, B, and C; finally, the transmittance T of the semi-transparent area is calculated, and the calculation formula is: T = [(CB) / (AB)] × 100%; The laser wavelength is 365nm for the I line, 405nm for the H line, or 435nm for the G line.

2. The method for measuring the transmittance of a halftone mask according to claim 1, characterized in that, A collimating lens group is provided at the front of the laser emitter; the laser emitted by the laser emitter is collimated by the collimating lens group and then passes vertically through the middle position of the semi-transparent area.

3. The method for measuring the transmittance of a halftone mask according to claim 1, characterized in that, The laser receiver is provided in three parts, which are respectively facing the fully transparent area, the opaque area and the semi-transparent area, and work simultaneously to receive laser signals passing through the fully transparent area, the opaque area and the semi-transparent area respectively.

4. The method for measuring the transmittance of a halftone mask according to claim 1, characterized in that, The laser receiver is turned on only after the energy of the laser source emitted by the laser transmitter has stabilized.

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