CN117261004A - Processing method of large-size photomask substrate - Google Patents

Abstract

The invention relates to a processing method, in particular to a processing method of a large-size photomask substrate. According to the processing method, the quartz mask plate semi-finished product is manufactured through cutting, detecting and polishing. According to the processing method of the large-size photomask substrate, tension, movement speed, cutting speed and spray liquid flow are determined through experiments, the flatness of the quartz plate blank body can be controlled to be 130-290 mu m during cutting, the flatness of the quartz plate blank body can be reduced to be within 50 mu m during grinding, and the processing difficulty of the semi-finished product stage to be within 20 mu m is effectively reduced. Solves the problem of high processing difficulty of semi-finished products caused by poor flatness control in the blank stage processing of the existing processing method.

Description

A method for processing large-sized photomask substrates

Technical field

The invention relates to a processing method, in particular to a processing method of a large-sized photomask substrate.

Background technique

Synthetic quartz glass is widely used in semiconductors, precision optics and other fields due to its extremely excellent optical properties, thermal shock resistance, extremely low thermal expansion coefficient and electrical conductivity. Synthetic quartz mask is a blank photomask substrate produced by processing synthetic quartz ingots. It has high chemical stability, high hardness, low thermal expansion coefficient, and high light transmittance (especially in the ultraviolet segment). It is often used as a high-performance material for IC and LSI large-scale FPDs. Photomask substrate for precision devices. At present, the flat surface processing of quartz glass is mainly completed by grinding with diamond grinding wheels. The grinding thickness is used to achieve flatness (the difference between the high points and low points of the surface). The same processing method is used for synthetic quartz masks.

The processing process of the synthetic quartz mask plate surface is divided into rough stage, semi-finished product stage and finished product stage. The rough stage is to cut the thermally modified quartz ingot into pieces, and trim the flatness and total thickness difference through cold processing while grinding the thickness to a certain value (if the cutting equipment can meet the relevant appearance and size requirements, especially roughness, If the flatness and total thickness are different, the grinding process can be omitted). In the semi-finished product stage, the flatness and total thickness difference are processed to within 20 μm and polished on both sides, and in the film-making stage, coating photolithography is performed.

The optimal cutting flatness of equipment for cutting large-size quartz sheets can only be within 100 μm, and the cutting accuracy is limited. After cutting is completed, it needs to go through a grinding process. The grinding method is to use one side as the reference plane and grind the other. The two sides are processed alternately and repeatedly. In the actual processing process, the thinner the thickness, the larger the area, and the more difficult the processing.

At present, in the actual processing process, the flatness of the quartz sheets in the rough stage after cutting and grinding is poor, and can often only be controlled at 80-90 μm. In the subsequent semi-finished product stage, the flatness of the quartz sheets needs to be controlled within 20 μm, that is, the flatness of the quartz sheets in the rough stage needs to be controlled. It is difficult to process the quartz sheet by grinding the protruding points of at least 60μm.

Therefore, it is necessary to design a processing method for large-sized photomask substrates to solve the above problems.

Contents of the invention

The object of the present invention is to provide a processing method for a large-sized photomask substrate that can promote the processing flatness of the blank stage to within 50 μm, thereby reducing the processing difficulty of processing the semi-finished product stage to within 20 μm.

The technical solution of the present invention is:

A method for processing large-sized photomask substrates, which is characterized by: including the following steps:

1) After the synthetic quartz ingot is thermally modified, select the diameter of the diamond wire used to cut the quartz sheet according to the thickness of the synthetic quartz sheet, and install the selected diamond wire on the cutting device;

2) Adjust the tension, movement speed, cutting speed (i.e., the downward speed of the diamond wire) and the spray fluid flow rate of the diamond wire according to the diameter of the diamond wire;

3) Start the cutting device to move the diamond wire to cut the quartz ingot to produce a quartz sheet body;

4) Fix the quartz sheet blank obtained in step 3) on the support tooling of the flatness testing equipment, and use compression to make the blank sheet horizontal to the detection direction and perpendicular to the fixed datum plane. Control the pressure to 0.6- through the pressure sensing device. 0.8br, so that the force of pressing the quartz sheet body will not deform the product and affect the detection value;

5) The flatness detection equipment detects the flatness of the quartz sheet body fixed on the support tooling of the flatness detection equipment, and scans the plane of the quartz sheet body at intervals of 10mm-50mm to obtain the flatness value (the flatness value is a virtual virtual machine constructed with The plane is the reference plane. Compare the sum of the highest point and the lowest point in the height fluctuation of the entire plane) and the regional distribution drawings of high and low points. When trimming the plane, use the regional distribution drawings of high and low points to determine the area where auxiliary tooling is required and the thickness of the auxiliary tooling;

6) Adjust the left and right swing speed of the working platform of the flatness detection equipment (that is, the left and right swing speed of the quartz sheet body) to 13000-20000mm/min. Set the rotation speed of the diamond grinding wheel to 1000r according to the length and size of the quartz sheet body. /min, according to the thickness of the quartz sheet body, set the up and down swing speed of the diamond grinding wheel to 150-300mm/min, set the single grinding amount to 0.001-0.05mm/time, and match the flatness value after testing to different single The amount of grinding is to grind the quartz sheet body multiple times, and produce a semi-finished synthetic quartz mask plate through multiple grinding;

7) During the second grinding, use auxiliary tooling. The auxiliary tooling is made of materials with different thicknesses, can be bent and fit on the quartz blank, and has a hardness less than quartz. It is padded between the quartz blank and the work surface of the flatness testing equipment. , Reduce the deformation of the surface caused by the extrusion of the diamond grinding wheel during the grinding process;

8) Mill and chamfer the edges of the semi-finished quartz mask plate, and conduct finished product inspection on the semi-finished quartz mask plate after milling and chamfering.

The first grinding of the quartz sheet body requires grinding both the front and back sides. The second time, an auxiliary tooling pad is used to detect the back side of the high point area. The grinding stages are set in stages during a single grinding process. The upper surface of the quartz sheet body is ground according to the cutting amount; the area padded with auxiliary tooling will be ground more, the gap from the low point will be reduced, and the flatness will become smaller and smaller.

The cutting device includes a winding drum A, a winding drum B, a wire wheel, a cutting wheel, a spray liquid outlet, a tension wheel, a reversing wheel and a diamond wire. The winding drum A and the winding sleeve B are arranged symmetrically. , there are wire pulleys inside the winding drum A and the winding sleeve B, there are cutting wheels inside the wire pulleys, and there are spray liquid outlets between the cutting wheels; there is a tension wheel above the wire pulley on the side of the winding sleeve A, There is a reversing wheel above the wire pulley on the side of the winding sleeve B; diamond wire is wound on the winding sleeve A, and the end of the diamond wire passes through the wire pulley, tension wheel, cutting wheel and the inner side of the winding drum A in sequence. The cutting wheel, reversing wheel and wire pulley inside the winding drum B are wound and connected with the winding drum B.

The diameter of the diamond wire is 0.35-0.5mm, the tension of the diamond wire is set to 110-200N, the cutting speed is set to 1-3mm/min, the movement speed is 800-1000m/min, and the spray liquid outlet and the The angle of the top end face of the synthetic quartz glass ingot is 15-60 degrees, and the flow rate of the spray liquid is set to 15-20L/h.

The beneficial effects of the present invention are:

This large-size photomask substrate processing method determines the tension, movement speed, cutting speed and spray liquid flow rate through experiments, and can control the flatness of the quartz sheet body to 130-290 μm during cutting, and can control the flatness of the quartz sheet body to 130-290 μm during grinding. The flatness of the quartz sheet body is reduced to less than 50 μm, which effectively reduces the processing difficulty of processing the semi-finished product to less than 20 μm. It solves the problem of poor flatness control in the rough stage processing of existing processing methods, which makes processing difficult in the semi-finished product stage.

Description of the drawings

Figure 1 is a schematic structural diagram of the cutting device of the present invention;

Figure 2 is a schematic diagram of the flatness range distribution of the cutting experiment of the present invention;

Figure 3 is a schematic diagram of the running trajectory of the diamond grinding wheel of the present invention;

Figure 4 is a schematic diagram of the use of the auxiliary tooling of the present invention;

Figure 5 is a schematic diagram of the flatness change of the present invention;

Figure 6 is a schematic diagram of flatness changes in existing processing methods.

In the picture: 1. Winding drum A, 2. Winding drum B, 3. Wire pulley, 4. Cutting wheel, 5. Spray liquid outlet, 6. Tension pulley, 7. Reversing pulley, 8. Diamond wire, 9. Synthetic quartz ingot, 10. On the quartz sheet body, 11. Diamond grinding wheel, 12. The upper surface of the quartz sheet body, 13. The lower surface of the quartz sheet body, 14. The work surface of the flatness testing equipment, 15. Auxiliary Tooling, 16, virtual plane.

Detailed ways

The processing method of the large-sized photomask substrate includes the following steps:

After the synthetic quartz ingot is thermally reformed, the diameter of the diamond wire of the cutting device used to cut the quartz sheet is selected according to the thickness of the synthetic quartz sheet.

The cutting device includes winding drum A, winding drum B, wire guide wheel, cutting wheel, spray liquid outlet, tension wheel, reversing wheel and diamond wire. Winding drum A and winding sleeve B are arranged symmetrically. There are wire pulleys on the inside of the drum A and the coil sleeve B, and a cutting wheel is installed on the inside of the wire pulleys. There is a spray liquid outlet between the cutting wheels; there is a tension wheel above the wire pulley on the side of the coil sleeve A, and there is a tension wheel on the coil sleeve A side. There is a reversing wheel above the wire pulley on side B; diamond wire is wound on the winding sleeve A, and the end of the diamond wire passes through the wire pulley, tension wheel, cutting wheel and winding drum inside the winding drum A in turn. The cutting wheel, reversing wheel, and wire pulley inside B are wound and connected to the winding drum B. The winding drum A and the winding sleeve B are respectively connected to the output shaft of the motor. The motor can drive the winding drum A and the winding sleeve B to rotate, thereby driving the two ends to be connected to the winding drum A and the winding sleeve B respectively. The diamond wire moves back and forth between the winding drum A and the winding sleeve B, thereby cutting the synthetic quartz ingot through the moving diamond wire. The function of the cutting wheel is to drive the diamond wire between the cutting wheels downward through the cutting wheel, thereby cutting the synthetic quartz ingot through the diamond wire between the cutting wheels. The function of the tension wheel is to tension the diamond wire through the tension wheel and adjust the tension of the diamond wire. The function of the spray liquid outlet is to spray spray liquid (cooling liquid) to the top of the synthetic quartz ingot, and the diamond wire and synthetic quartz ingot are cooled by the spray liquid flowing from the top of the synthetic quartz ingot to the diamond wire.

The diameter of the diamond wire is selected within the range of 0.35-0.5mm. After the diamond wire selection is completed, the selected diamond wire is installed on the cutting device. After the diamond wire is installed, the tension, movement speed, cutting speed (i.e., the downward speed of the diamond wire) and the spray fluid flow rate of the diamond wire are adjusted according to the diameter of the diamond wire. The tension of the diamond wire is set in the range of 110-200N, the cutting speed of the diamond wire is set in the range of 1-3mm/min, the movement speed of the diamond wire is set in the range of 800-1000m/min, and the spray liquid flow rate is set in the range of 110-200N. Set within the range of 15-20L/h. For example: when cutting a 1mm thick synthetic quartz sheet, select a 0.35mm diameter diamond wire, set the diamond wire tension to 110N, the diamond wire cutting speed to 3mm/min, the diamond wire movement speed to 1000m/min, spray The flow rate of the liquid is set to 20L/h, and the spray liquid outlet is manually adjusted so that it is aligned with the top end face of the synthetic quartz ingot, and the angle with the top end face of the synthetic quartz ingot is 15-60 degrees.

The selection and working parameters of the diamond wire are determined through experiments. The optimal parameters are obtained by statistics on the flatness of the quartz sheet bodies obtained by cutting diamond wires of different diameters under different parameters (see Figure 2). The synthesis is reduced through the optimal parameters. The flatness of quartz pieces when cut.

After the selection of the diamond wire and the setting of the working parameters are completed, the cutting device is started to move the diamond wire to cut the quartz ingot to produce a quartz sheet body. After the quartz sheet body is cut from the synthetic quartz ingot, the quartz sheet body is fixed on the support tooling of the flatness testing equipment (CMM MMZ 1 25/50/18 three-dimensional coordinate detector), and pressed tightly to promote The blank sheet is horizontal to the detection direction and perpendicular to the fixed datum plane. The pressure is controlled to 0.6-0.8br through the pressure sensing device, so that the force of pressing the quartz sheet blank will not deform the product and affect the detection value, but also the quartz can be The sheet body is fixed. After the quartz sheet body is fixed, the flatness detection equipment detects the flatness of the quartz sheet body fixed on the support tooling of the flatness detection equipment. The inspection process scans the plane of the quartz sheet body at intervals of 10mm-50mm to obtain the flatness value (the flatness value is based on the constructed virtual plane as the reference plane, and compares the sum of high points and low points in the entire plane height fluctuation) and the high and low point areas. Distribution drawing (see Figure 4). When trimming the plane of the quartz sheet body, determine the area where auxiliary tooling is required and the thickness of the auxiliary tooling through the regional distribution drawing of high and low points.

After the flatness inspection of the quartz plate body is completed, adjust the left and right swing speed of the working platform of the flatness detection equipment (that is, the left and right swing speed of the quartz plate body) to 13000-20000mm/min, according to the length and size of the quartz plate body. Set the rotation speed of the diamond grinding wheel to 1000r/min, set the up and down swing speed of the diamond grinding wheel to 150-300mm/min according to the thickness of the quartz sheet body, and set the single grinding amount (single feed amount of the diamond grinding wheel) It is 0.001-0.05mm/time, and the quartz sheet body is ground multiple times by matching the measured flatness value with different single grinding amounts. The first time the quartz sheet body is ground, both the front and back sides need to be ground. That is, one side of the quartz sheet body is used as the reference surface and the other side is ground. Then the quartz sheet body is turned over to use the polished quartz. The end surface of the sheet blank is the datum surface and the other surface is ground. When polishing for the first time, use the side with less flatness as the base surface. For the second time, use the auxiliary tooling pad on the opposite side of the high-point detection area. In the single grinding process, set the grinding amount in stages to grind the upper surface of the quartz sheet body; the area with the auxiliary tooling pad will be ground more. , the gap from the low point will be reduced, and the flatness will become smaller and smaller. Semi-finished synthetic quartz mask plates are produced through multiple grinding operations.

During the second grinding, auxiliary tooling is used. The auxiliary tooling is made of materials with different thicknesses, can be bent and fit on the quartz blank, and has a hardness less than quartz. It is padded between the quartz blank and the work surface of the flatness testing equipment to reduce The surface is deformed by the extrusion of the diamond grinding wheel during the grinding process. During the second grinding, the thickness and shape of the auxiliary tooling are selected according to the flatness distribution area and height difference in the single grinding process.

The entire grinding process is divided into three stages: The first stage: Since the flatness values of the two surfaces of the cut quartz sheet body are different, the surface with the smaller value is selected as the reference surface. The following stages need to be based on the flatness value. This surface is used as a benchmark to pad auxiliary tooling. During the initial grinding, the datum surface of the quartz sheet body directly falls on the work surface of the flatness testing equipment. The thickness and area of the auxiliary tooling are selected according to the recessed value. After grinding one side, the datum surface is directly turned over. During grinding, the up and down swing speed of the diamond grinding wheel is set to 300mm/min, the single grinding amount is 0.05mm/time, and the cumulative grinding amount is the flatness value of the quartz sheet body obtained by testing. After the first stage of processing is completed, the flatness of the quartz sheet body is tested, the flatness after the first stage of grinding is detected, and the flatness value after grinding is obtained. After the inspection, proceed to the second stage. After the first stage of processing, the high points and low points of the two surfaces will be complementary. The high and low points of the reference surface correspond to the low points of the other side, and the low points of the reference surface correspond to the high points of the other side. , the first stage is also the stage where the flatness value decreases fastest in the entire grinding process. Second stage: The auxiliary tooling is placed on the back of the high point area of the datum. The thickness of the auxiliary tooling is selected to be 70%-80% of the high point value of flatness. The area of the auxiliary tooling is the area of the product flatness area (the high point value of flatness). 50%-60% of the protruding area), the center point of the auxiliary tooling is on the midline point of the flatness area, so that the auxiliary tooling can not only support the protruding flatness area to facilitate grinding, but also will not raise the flatness. The area surrounding the highlighted area so that it does not affect the flatness of the area surrounding the highlighted area. Set the up and down swing speed of the diamond grinding wheel to 250mm/min, and the single grinding amount is 0.02mm/time for grinding. The cumulative grinding amount is the thickness of the auxiliary tooling, which is 70%-80% of the high point value of flatness. After the grinding is completed, turn over directly without changing any parameters, conduct flatness testing on the datum surface, obtain the flatness value of the datum surface and the regional distribution drawing of high and low points, and grind the datum surface again. Through repeated flipping and grinding, the up and down swing speed of the diamond grinding wheel is gradually reduced to 150mm/min according to the flatness value obtained by the test, and the single grinding amount is reduced to 0.001mm/time. When the flatness value of a surface is finally detected to be within 50 μm, release the quartz sheet body, remove the auxiliary tooling, and place the quartz body directly on the work surface of the flatness testing equipment for the third stage. The third stage: Set the up and down swing speed of the diamond grinding wheel to 250mm/min, and the single grinding amount to 0.01mm/time. Grind the entire large surface of the quartz sheet body so that the thickness of the quartz sheet body meets the process requirements. .

After the grinding is completed, the semi-finished quartz mask plate is edge milled and chamfered, and the semi-finished quartz mask plate after edge milling and chamfering is inspected for finished product.

This large-size photomask substrate processing method determines the tension, movement speed, cutting speed and spray liquid flow rate through experiments, and can control the flatness of the quartz sheet body to 130-290 μm during cutting, and can control the flatness of the quartz sheet body to 130-290 μm during grinding. The flatness of the quartz sheet body is reduced to less than 50 μm, which effectively reduces the processing difficulty of processing the semi-finished product to less than 20 μm. It solves the problem of poor flatness control in the rough stage processing of existing processing methods, which makes processing difficult in the semi-finished product stage.

Claims (3)

1. A processing method of a large-size photomask substrate is characterized in that: the method comprises the following steps:

1) After the synthetic quartz ingot is subjected to thermal modification, selecting the diameter of a diamond wire used for cutting the quartz piece according to the thickness of the cut synthetic quartz piece, and installing the selected diamond wire on a cutting device;

2) Adjusting the tension, the movement speed, the cutting speed and the spraying liquid flow of the diamond wire according to the diameter of the diamond wire;

3) Starting a cutting device to enable the diamond wire to move so as to cut the quartz ingot, and producing a quartz plate blank;

4) Fixing the quartz plate blank obtained in the step 3) on a supporting tool of flatness detection equipment, adopting a compacting mode to enable the blank plate to be horizontal to the detection direction, and controlling the pressure to be 0.6-0.8br by a pressure sensing device perpendicular to a fixed reference surface, so that the strength of compacting the quartz plate blank can not deform to influence the detection value of a product;

5) The flatness detection equipment detects the flatness of the quartz plate blank body fixed on the supporting tool of the flatness detection equipment, the flatness value and the area distribution drawing of the high points and the low points are obtained by scanning the plane of the quartz plate blank body according to the interval of 10mm-50mm, and the area needing the auxiliary tool and the thickness of the auxiliary tool are judged through the area distribution drawing of the high points and the low points when the plane is trimmed;

6) Adjusting the left-right swinging speed of a working platform of the flatness detection equipment to 13000-20000mm/min, setting the rotating speed of a diamond grinding wheel to 1000r/min according to the length dimension of a quartz plate blank, setting the up-down swinging speed of the diamond grinding wheel to 150-300mm/min according to the thickness of the quartz plate blank, setting the single grinding amount to 0.001-0.05 mm/time, matching different single grinding amounts through the detected flatness values, grinding the quartz plate blank for multiple times, and producing a synthetic quartz mask plate semi-finished product through multiple grinding;

7) During secondary grinding, an auxiliary tool is used, the auxiliary tool is made of materials which have different thicknesses, can be flexibly attached to a blank piece of the quartz piece and have hardness smaller than that of quartz, and is arranged between a quartz blank body and a working table of flatness detection equipment, so that deformation of the surface caused by extrusion of a diamond grinding wheel in the grinding process is reduced;

8) And (3) milling edges and chamfering the obtained quartz mask plate semi-finished product, and carrying out finished product inspection on the quartz mask plate semi-finished product after edge milling and chamfering.

2. The method for processing a large-sized photomask blank according to claim 1, wherein: the quartz plate blank is firstly ground into a front surface and a back surface which are both required to be ground, and the auxiliary tool pad is used for the second time on the back surface of the detection high-point area, and the grinding quantity of the stage is set in stages in the single grinding process to grind the upper surface of the quartz plate blank; the area with the auxiliary tool is ground more, the drop with the low point is reduced, and the flatness is smaller and smaller.

3. The method for processing a large-sized photomask blank according to claim 1, wherein: the diameter of the diamond wire is 0.35-0.5mm, the tension of the diamond wire is 110-200N, the cutting speed is 1-3mm/min, the moving speed is 800-1000m/min, the angle between the spray liquid outlet and the top end face of the synthetic quartz glass ingot is manually adjusted to 15-60 degrees, and the flow of the spray liquid is set to 15-20L/h.