Wafer Processing Equipment

Abstract

To provide a wafer processing device with a structure which inhibits thermal expansion of a fixing screw fixing a chuck to a chuck base to reduce change of axial force and thereby enable high precision processing.SOLUTION: A wafer processing device includes: a constant temperature chiller water source 23 which supplies constant temperature chiller water to a chuck table 12 to keep a chuck 15 at a substantially constant temperature; and an annular cover 27 which causes the constant temperature chiller water discharged from an outer periphery side surface of the chuck table 12 to be stored between itself and the outer periphery side surface of the chuck table 12 and supplies the constant temperature chiller water to the fixing screw 17 side and which is provided covering at least the entire outer periphery side surface of the chuck 15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wafer processing device, and more particularly to a wafer processing device capable of performing highly accurate processing such as grinding and polishing on a disk-shaped wafer held on a rotating chuck table. [Background technology]

[0002] Conventionally, as a processing device for grinding the surface of a semiconductor wafer (hereinafter simply referred to as "wafer") to make it flat, there has been known a device that includes a chuck table that suction-holds a disk-shaped wafer and a rotating processing wheel that has a grinding wheel for grinding the wafer, and that grinds the surface of the wafer with the grinding wheel.

[0003] In such grinding machines, when grinding, the heat accumulated in the grinding wheel is transferred to the chuck table via the wafer, causing thermal expansion of the chuck table, which can interfere with the processing of wafers with micron-level accuracy.

[0004] Therefore, a chuck table with a cooling function has been proposed. This chuck table is equipped with a disk-shaped chuck (suction plate) on which a wafer is placed and a cooling means on the back side of the chuck. A technology has been proposed to reduce the thermal expansion of the chuck by flowing temperature-controlled water through a flow path inside the chuck (see, for example, Patent Documents 1 and 2).

[0005] In addition, a technology has been proposed to reduce the thermal expansion of the chuck by providing a flow path on a chuck base that rotates integrally with the chuck and flowing temperature-controlled water through the flow path on the chuck base (see Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-237200 [Patent Document 2] Japanese Patent Application Publication No. 2018-27588 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-69429 Summary of the Invention [Problem to be solved by the invention]

[0007] However, while the techniques described in Patent Documents 1, 2, and 3 can reduce the thermal expansion of the chuck, the fastening members, such as the fixing screws that secure the chuck to the chuck base, are generally made of different materials. Therefore, heat is transferred from the chuck and the chuck base to the fixing screws. It takes time for the fixing screws to reach approximately the same temperature as the chuck and the chuck base, and during this time, the fixing screws undergo thermal expansion. This thermal expansion of the fixing screws changes the axial force that secures the chuck, resulting in a change in the shape of the chuck. This poses a problem: accuracy discrepancies are likely to occur between the machining of the first sheet and the machining of the Nth sheet.

[0008] Therefore, a technical problem that must be solved arises in order to provide a wafer processing device that has a structure that can reduce axial force changes and perform processing with high precision by suppressing thermal expansion of the fixing screws that secure the chuck and chuck base, and an object of the present invention is to solve this problem. [Means for solving the problem]

[0009] The present invention has been proposed to achieve the above-mentioned object, and the invention described in claim 1 provides a wafer processing apparatus having a chuck table fixed by a plurality of fixing screws between a chuck that suction-holds a wafer and a chuck base that rotates integrally with the chuck, the wafer processing apparatus comprising: a constant temperature chiller water supply means that supplies constant temperature chiller water to the chuck table to maintain the chuck at an approximately constant temperature; and an annular cover that covers at least almost the entire outer peripheral side surface of the chuck, and stores the constant temperature chiller water discharged from the outer peripheral side surface of the chuck table between the chuck table and the outer peripheral side surface and supplies it to the fixing screw side.

[0010] According to this configuration, the chuck and chuck base are maintained at a constant temperature by supplying constant-temperature chiller water from the constant-temperature chiller water supply means to the chuck table. At the same time, the constant-temperature chiller water supplied to the chuck table is discharged from the outer peripheral side surface of the chuck table and received in a gap formed between the chuck table and an annular cover that covers substantially the entire outer peripheral side surface of the chuck table. By storing a predetermined amount of constant-temperature chiller water in the gap and actively supplying the stored constant-temperature chiller water to the fixing screw side, the time it takes for the fixing screw to reach the same temperature as the chuck and chuck table can be shortened. This minimizes changes in thermal expansion of the fixing screw during processing. This suppresses changes in the axial force that secures the chuck, eliminating differences in processing accuracy from the first wafer to the Nth wafer, enabling high-precision wafer processing.

[0011] The invention described in claim 2 provides a wafer processing apparatus having the configuration described in claim 1, wherein the cover extends to approximately the same height as the head of the fixing screw, and the constant temperature chiller water can be stored up to a position where the head of the fixing screw is immersed in the constant temperature chiller water.

[0012] With this configuration, the cover extends to the height of the fixing screws, so the constant temperature chiller water received in the gap between the annular cover and the chuck table is accumulated up to a position where the heads of the fixing screws are immersed. Therefore, the constant temperature chiller water received in the gap between the annular cover and the chuck table comes into direct contact with the fixing screws through the heads of the fixing screws, allowing for active temperature regulation of the fixing screws.

[0013] The invention described in claim 3 provides a wafer processing device having the configuration described in claim 1 or 2, wherein the chuck has a slit cut out from the outer peripheral side surface of the chuck to the inner peripheral side surface of the mounting hole into which the fixing screw is attached.

[0014] With this configuration, the constant temperature chiller water received in the gap between the annular cover and the chuck table is allowed to accumulate up to the top of the fixing screw while passing through the slit and coming into direct contact with the outer peripheral side surface of the fixing screw. Therefore, the constant temperature chiller water received in the gap between the annular cover and the chuck table comes into direct contact with the fixing screw through the slit over a range from the outer peripheral side surface to the head of the fixing screw that is screwed into the screw hole, thereby enabling active temperature regulation of the fixing screw. [Effects of the Invention]

[0015] According to the present invention, constant-temperature chiller water is supplied from a constant-temperature chiller water supply means to the chuck table to maintain the chuck at a constant temperature. At the same time, the constant-temperature chiller water supplied to the chuck table is discharged from the outer peripheral side surface of the chuck table, and the discharged constant-temperature chiller water is received in a gap formed between the chuck table and an annular cover that covers substantially the entire outer peripheral side surface of the chuck table. The constant-temperature chiller water received in the gap is supplied to the fixing screw, and the temperature of the fixing screw is actively adjusted to be substantially the same as the constant-temperature chiller water. This shortens the time it takes for the fixing screw to reach the same temperature as the chuck and chuck table. Furthermore, thermal expansion changes in the fixing screw during processing can be minimized. This suppresses changes in the axial force that secures the chuck, maintaining a substantially constant chuck shape. This eliminates precision differences between the first wafer and the Nth wafer, enabling high-precision wafer processing. [Brief explanation of the drawings]

[0016] [Figure 1] 1A and 1B are schematic diagrams showing the main configuration of a rotation mechanism in a wafer processing apparatus according to an embodiment of the present invention, in which FIG. 1A is a perspective view of the rotation mechanism, and FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. [Figure 2] 10 is a structural explanatory diagram of a constant temperature control passage formed in a chuck base in the rotation mechanism of the same. FIG. [Figure 3] 2A and 2B are enlarged views of a portion of the rotation mechanism shown in FIG. 1, in which (A) is a perspective view thereof and (B) is a cross-sectional view taken along line BB in (A). [Figure 4] 4A and 4B are enlarged partial views showing a modified example of the rotation mechanism shown in FIG. 3, in which (A) is a perspective view and (B) is a cross-sectional view taken along line CC in (A). DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to achieve the object of the present invention to provide a wafer processing apparatus having a structure capable of reducing axial force changes and performing processing with high precision by suppressing thermal expansion of the fixing screws that fix the chuck and chuck base, the present invention provides a wafer processing apparatus having a chuck table that is fixed between a chuck that suction-holds a wafer and a chuck base that rotates integrally with the chuck by a plurality of fixing screws, and an annular cover that covers at least almost the entire outer peripheral side of the chuck so that the constant temperature chiller water discharged from the outer peripheral side of the chuck table is stored between the chuck table and the outer peripheral side of the chuck and supplied to the fixing screw side. [Example]

[0018] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the following embodiment, when the number, value, amount, range, etc. of components is mentioned, the number is not limited to the specific number, and may be more or less than the specific number, unless otherwise specified or when it is clearly limited to a specific number in principle.

[0019] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0020] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0021] In the following description, expressions indicating directions such as up, down, left, and right are not absolute, but are appropriate when each part of the wafer processing apparatus of the present invention is in the posture depicted, but if the posture changes, they should be interpreted accordingly. Furthermore, the same elements are given the same symbols throughout the description of the embodiments.

[0022] Hereinafter, a preferred embodiment of a wafer processing apparatus according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3, taking as an example a case where the apparatus is applied to a grinding apparatus that processes the surface of a wafer to make it flat.

[0023] 1A and 1B are schematic diagrams showing the main configuration of a rotation mechanism 10 in a wafer processing apparatus according to the present invention, with (A) being a perspective view of the rotation mechanism 10 and (B) being a cross-sectional view taken along line AA in (A). The wafer processing apparatus has the rotation mechanism 10 attached to an apparatus main body 11. The entire wafer processing apparatus is controlled in accordance with a predetermined procedure by a program in a control device 50.

[0024] The rotation mechanism 10 has a chuck table 12 that holds a wafer (not shown) and rotates horizontally. The chuck table 12 holds the wafer and is disposed below a grinding unit (not shown), and the wafer is brought into contact with a rotating grinding wheel in the grinding unit to grind the surface of the wafer.

[0025] The chuck table 12 includes a disk-shaped chuck base 14 rotatably mounted via a rotary joint 13, a similarly disk-shaped chuck 15 mounted on the chuck base 14 so as to be integrally rotatable, and a constant temperature control unit 16 provided on the chuck base 14 and positioned between the chuck 15 and the chuck base 14. The chuck 15 and the chuck base 14 are fixed together with a fixing screw 17, which is a fastening member.

[0026] The chuck 15 includes a disk-shaped suction plate 18 and a chuck side frame 19. The chuck side frame 19 surrounds the outer peripheral side and bottom surface of the suction plate 18 and is integrated with the suction plate 18. The suction plate 18 is made of a porous holding member, and its upper surface serves as an adsorption surface 18A that suction-holds the wafer. In this embodiment, the chuck side frame 19 of the chuck 15 is made of alumina (aluminum oxide), and the chuck base 14 and the fixing screw 17 are both made of stainless steel (SUS).

[0027] The chuck-side frame 19 has a plurality of mounting holes 20 (eight in this embodiment) penetrating vertically at approximately equal intervals along the circumferential direction, outside the outer periphery of the suction plate 18. On the other hand, the chuck base 14 has the same number of screw holes 33 formed therein, corresponding to the mounting holes 20 of the chuck-side frame 19. The chuck-side frame 19 is placed on the chuck base 14 with the mounting holes 20 aligned with the screw holes 33. When the chuck-side frame 19 is placed on the chuck base 14 and the fixing screws 17 are threaded through the mounting holes 20 from above the chuck-side frame 19 and screwed into the screw holes 33, the chuck 15 and the chuck base 14 are fixed together with the center O of the chuck table 12 in the same position. A counterbore 20A is provided above the mounting holes 20. A portion of the counterbore 20A is open on the outer periphery of the chuck-side frame 19, exposing the side of the fixing screw 17 on the outer periphery of the chuck-side frame 19.

[0028] The constant temperature control unit 16 is provided on the upper surface of the chuck base 14 opposite the chuck 15. The constant temperature control unit 16 is formed as a groove excavated with a U-shaped cross section, and is composed of a water channel 21 in which the upper surface of the groove is covered and closed by the lower surface (interface) of the chuck 15.

[0029] As shown in Figure 3, the water channel 21 consists of multiple (in this embodiment, four: 21A, 21B, 21C, and 21D) concentrically formed annular water channel sections 21A, 21B, 21C, and 21D, and a communicating water channel section 21E that sequentially connects each of these annular water channel sections 21A, 21B, 21C, and 21D to one another.

[0030] Furthermore, a through-hole serving as a water supply port 21F is provided in the annular water channel portion 21A provided on the central side of the chuck base 14, and a drain port 21G is provided in the annular water channel portion 21D provided on the outermost periphery of the chuck base 14. The water supply port 21F is connected to a constant temperature chiller water source 23 via a water supply pipe 22 arranged through the rotary joint 13. On the other hand, the drain port 21G opens to the outer periphery of the chuck base 14. Furthermore, a chuck pipe 24 is provided in the center of the chuck base 14. One end of the chuck pipe 24 is connected to the lower end of the suction plate 18.

[0031] The constant temperature chiller water source 23 adjusts the temperature of the constant temperature chiller water to, for example, approximately 30° C. before supplying it to the water passage 21, so that the temperature of the entire chuck 15 can be adjusted to approximately 30° C. Meanwhile, the vacuum source 25 applies a suction force by drawing a vacuum to the suction plate 18 via the chuck piping 24, so that the wafer W can be suction-held on the suction surface 18A of the suction plate 18.

[0032] A ring-shaped base-side frame 26 is attached to the outer peripheral surface of the chuck base 14. The upper surface of the base-side frame 26 is slightly lower than the upper surface of the chuck base 14 and is set at a height so as not to block the front of the drain outlet 21G of the water channel 21. Meanwhile, a labyrinth groove 26A is formed around the entire periphery of the lower surface of the base-side frame 26, cutting from the bottom to the top. A part of a labyrinth cover 30 is disposed in the labyrinth groove 26A, which seals off treated water attempting to enter the apparatus main body 11 and protects the power unit 29 including a motor 29A, a power transmission belt 29B, pulleys 29C and 29D, the rotary joint 13, etc.

[0033] The chuck-side frame 19 is provided with a ring-shaped cover 27 that covers substantially the entire outer peripheral side surface of the chuck 15. The cover 27 is made of the same alumina as the chuck-side frame 19, and the inner diameter of the main body 27A is larger than the outer diameter of the chuck 15. A gap is formed between the chuck-side frame 19 and the chuck 15, forming a constant-temperature chiller water reservoir 28 that stores constant-temperature chiller water discharged from the drain port 21G. The lower end of the main body 27A has a fixed flange 27B bent outward, and the upper end has a gap-adjusting flange 27C bent inward toward the outer peripheral side surface of the chuck 15. The fixed flange 27B is provided with a discharge port 27D that extends from the outer periphery to the inner periphery of the fixed flange 27B. The discharge port 27D is formed as a groove recessed into a substantially U-shaped cross section.

[0034] The cover 27 is fixed to the base-side frame 26 with the fixing flange 27B in close contact with the upper surface of the base-side frame 26 by the fixing screws 32. As shown in FIG. 3B, the height H of the cover 27 when fixed to the base-side frame 26 is approximately equal to the height of the heads 17A of the fixing screws 17 that attach the chuck 15 to the chuck base 14. That is, the cover 27 extends to approximately the same height as the heads 17A of the fixing screws 17. A gap δ1 is provided around the entire periphery between the inner circumferential surface of the main body 27A and the outer circumferential surface of the chuck base 14 so as not to block the drain outlet 21G of the water passage 21. A predetermined gap δ2 is also provided between the inner circumferential surface of the gap-adjusting flange 27C of the cover 27 and the outer circumferential surface of the chuck 15. The gap δ2 between the inner peripheral surface of the gap adjustment flange 27C and the outer peripheral surface of the chuck 15 has the function of making it easier for the constant temperature chiller water stored in the constant temperature chiller water storage chamber 28 to flow onto the side of the head 17A of the fixing screw 17 when the constant temperature chiller water rises, and the function of allowing the constant temperature chiller water that overflows from the constant temperature chiller water storage chamber 28 and cannot be completely discharged through the outlet 27D to escape to the outside of the cover 27 through the gap δ2.

[0035] The power unit 29 transmits the rotation of the motor 29A, which rotates under the control of the control device 50, to the chuck table 12 side via a power transmission belt 29B stretched between a pulley 29D provided on the output shaft of the motor 29A and a pulley 29C provided on the rotating part of the rotary joint 13, and also rotates the chuck table 12 at a predetermined constant speed.

[0036] Next, the operation of the processing apparatus configured as described above will be described. First, before grinding is performed, constant-temperature chiller water at approximately 30°C is flowed from constant-temperature chiller water source 23 through water supply pipe 22 toward constant-temperature control unit 16. This constant-temperature chiller water enters water passage 21 from water supply port 21F, then exits drain port 21G and is discharged into constant-temperature chiller water storage chamber 28. The amount of this constant-temperature chiller water discharged is adjusted by control device 50 so that it is slightly greater than the amount discharged from drain port 27D of cover 27. Then, the entire chuck base 14 and chuck 15 of chuck table 12 are adjusted to temperatures approaching approximately 30°C, the same as the constant-temperature chiller water.

[0037] The constant temperature chiller water discharged from drain outlet 21G accumulates in constant temperature chiller water storage chamber 28 and rises within constant temperature chiller water storage chamber 28 over time. Because cover 27 is extended to a height substantially equal to that of head 17A of fixing screw 17, the constant temperature chiller water discharged into constant temperature chiller water storage chamber 28 rises to approximately the top of head 17A of fixing screw 17. When the constant temperature chiller water rises to the side of head 17A of fixing screw 17, the side of head 17A of fixing screw 17 gradually becomes immersed in the constant temperature chiller water. This allows the heat of the constant temperature chiller water to adjust the temperature of fixing screw 17 to approximately the same as that of the constant temperature chiller water. In other words, the entire chuck table 12 is adjusted to a temperature close to that of the constant temperature chiller water (30°C).

[0038] When the entire chuck table 12, i.e., the chuck base 14, chuck 15, fixing screws 17, etc., have been adjusted to a temperature approximately equal to that of the constant-temperature chiller water, the wafer W is placed on the suction surface 18A of the suction plate 18 of the chuck 15. Then, under the control of the control device 50, the vacuum source 25 applies a negative pressure to the suction surface 18A, and the wafer W is suction-held on the suction surface 18A. Thereafter, under the control of the control device 50, the motor 29A is driven to rotate, and the driving force of the motor 29A rotates the chuck table 12. At the same time, a grinding unit (not shown) is driven to grind the surface of the wafer.

[0039] During grinding, constant-temperature chiller water at approximately 30°C flows through water supply pipe 22 from constant-temperature chiller water source 23 to constant-temperature control unit 16 in chuck base 14, maintaining chuck base 14 and chuck 15 at a constant temperature, and the constant-temperature chiller water discharged from drain outlet 21G and stored in constant-temperature chiller water storage chamber 28 soaks the side surfaces of heads 17A of fixing screws 17, and the heat of the constant-temperature chiller water adjusts fixing screws 17 to approximately the same temperature as the constant-temperature chiller water. As a result, during grinding, the entire chuck table 12, i.e., chuck base 14, chuck 15, and fixing screws 17, are each maintained at approximately the same temperature as the constant-temperature chiller water.

[0040] Therefore, in the machining apparatus of this embodiment, constant-temperature chiller water is supplied to the chuck table 12 from a constant-temperature chiller water source 23, which is a constant-temperature chiller water supply means, so that the chuck 15 and the suction plate 18 are maintained at a substantially constant temperature. Furthermore, the constant-temperature chiller water supplied to the chuck table 12 is discharged from the outer peripheral side surface of the chuck table 12, and the discharged constant-temperature chiller water is received in a constant-temperature chiller water reservoir 28, which is the gap between the chuck table 12 and an annular cover 27 that covers the entire outer peripheral side surface of the chuck table 12. The temperature of the fixing screw 17 is actively adjusted using the constant-temperature chiller water stored in the constant-temperature chiller water reservoir 28. This shortens the time it takes for the fixing screw 17 to reach the same temperature as the chuck 15 and the chuck table 12, and minimizes changes in thermal expansion of the fixing screw 17 during machining. This suppresses changes in the axial force that secures the chuck 15, thereby maintaining a substantially constant shape of the chuck 15. This eliminates the difference in processing accuracy between the first wafer and the Nth wafer, enabling high-precision processing of wafers. Also, the constant-temperature chiller water remaining in the gap between the annular cover 27 and the chuck table 12 can be discharged to the outside of the chuck table 12 through the outlet 27D provided in the cover 27 and the gap δ1 provided between the cover 27 and the chuck 15.

[0041] FIG. 4 is a partially enlarged view showing a modified example of the rotation mechanism 10 shown in FIG. 3 , where (A) is a perspective view and (B) is a cross-sectional view taken along the line CC in (A). The modified example shown in FIG. 4 has a slit 31 cut out at the mounting hole 20 on the chuck 15 side, through which the fixing screw 17 that secures the chuck 15 to the chuck base 14 passes, and the slit 31 extends from the outer peripheral side surface of the chuck 15 to the inner peripheral side surface of the mounting hole 20 and opens into the mounting hole 20. The other configurations in FIG. 4 are the same as those in FIGS. 1 to 3 . Therefore, the same components as those in FIGS. 1 to 3 are designated by the same reference numerals and their descriptions are omitted. Only the different structural components will be described. The opening width of the slit 31 is smaller than the thread diameter of the fixing screw 17 to prevent the fixing screw 17 from slipping out of the slit 31.

[0042] In the structure of the rotation mechanism 10 shown in FIG. 4, water is supplied from the constant-temperature chiller water source 23 to the constant-temperature control unit 16 to adjust the temperature of the chuck 15 and chuck base 14. The water is then discharged from the drain port 21G of the chuck base 14 and stored in the constant-temperature chiller water storage chamber 28. The water then enters the mounting hole 20 through the slit 31, immersing more of the outer peripheral surface of the fixing screw 17. This actively adjusts the fixing screw 17 to approximately the same temperature as the constant-temperature chiller water using the heat of the constant-temperature chiller water. In this case, the area of ​​the fixing screw 17 immersed in the constant-temperature chiller water is larger than in the structure shown in FIG. 3, so the time it takes for the fixing screw 17 to reach approximately the same temperature as the constant-temperature chiller water is shortened. Therefore, the temperatures of the chuck base 14, chuck 15, and fixing screw 17 of the chuck table 12 as a whole approach approximately 30°C, the same as the constant-temperature chiller water, more quickly.

[0043] The present invention can be modified in various ways without departing from the spirit of the present invention, and it goes without saying that the present invention also covers such modifications. [Explanation of symbols]

[0044] 10: Rotation mechanism 11: Device body 12: Chuck table 14: Chuck base 15: Zipper 16: Constant temperature control unit 17: Fixing screw 17A: Head 18: Suction plate 18A: Adsorption surface 20: Mounting hole 20A: Counterbore 21: Waterway 21F: Water supply outlet 21G: Drain port 22: Water supply pipe 23: Constant temperature chiller water source (constant temperature chiller water supply means) 24: Pipe for chuck 25: Vacuum source 26: Base side frame 26A: Concave groove 27: Cover 27D: Discharge port 28: Constant temperature chiller water storage room 31: Slit 33: Screw hole 50: Control device W: Wafer δ1, δ2: gap

Claims

1. A wafer processing apparatus including a chuck table fixed by a plurality of fixing screws between a chuck that suction-holds a wafer and a chuck base that rotates integrally with the chuck, a constant temperature chiller water supply means for supplying constant temperature chiller water to the chuck table to maintain the chuck at a substantially constant temperature; an annular cover provided to cover at least substantially the entire outer peripheral side surface of the chuck, which stores the constant temperature chiller water discharged from the outer peripheral side surface of the chuck table between the outer peripheral side surface of the chuck table and the chuck table, and supplies the constant temperature chiller water to the fixing screw side; Equipped with The wafer processing device is characterized in that the chuck has a slit cut out from the outer peripheral side surface of the chuck to the inner peripheral side surface of the mounting hole into which the fixing screw is attached.

2. 2. The wafer processing apparatus according to claim 1, wherein the cover extends to a height approximately equal to the head of the fixing screw and is capable of storing the constant temperature chiller water up to a position where the head of the fixing screw is immersed in the constant temperature chiller water.

Images