Wafer fixing method and semiconductor manufacturing apparatus

Abstract

To reduce occurrence of a defect caused by release of stress that has occurred when a wafer is removed.SOLUTION: A wafer fixture F to be used in a semiconductor manufacturing apparatus includes a mechanical clamp M and an electrostatic chuck E. When the processing temperature of a wafer W is equal to or higher than a first reference temperature T1 that is higher than room temperature, the wafer W is fixed by using only the mechanical clamp M. The semiconductor manufacturing apparatus IM also includes the wafer fixture F for fixing a wafer W using a combination of the mechanical clamp M and the electrostatic chuck E, and a control device C for controlling the fixation of the wafer W. The control device C fixes the wafer W by using only the mechanical clamp M when the processing temperature of the wafer W is equal to or higher than the first reference temperature T1 that is higher than room temperature.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a wafer fixing method that uses a mechanical clamp and an electrostatic chuck in combination, and to a semiconductor manufacturing device in which the wafer fixing method is used. [Background technology]

[0002] Some implantation processes in ion implantation equipment, which is a type of semiconductor manufacturing equipment, are performed on wafers heated to high temperatures. For example, in the case of SiC wafers, it is difficult to recover from crystal defects in the annealing process after ion implantation, so ion implantation is performed on the wafers heated to high temperatures to avoid adverse effects on device characteristics.

[0003] In ion implantation processing, the wafer is fixed by a mechanical clamp or an electrostatic chuck. For example, Patent Document 1 discloses that a mechanical clamp is used in combination with an electrostatic chuck in high-temperature implantation processing at or above a predetermined temperature in order to compensate for the decrease in the chucking force caused by the deterioration of the characteristics of the electrostatic chuck.

[0004] Moreover, Patent Document 2 discloses a method of fixing a wafer by using a mechanical clamp not equipped with a power mechanism in combination with an electrostatic chuck. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special table 2013-531374 [Patent Document 2] Patent Publication 2015-203140 Summary of the Invention [Problem to be solved by the invention]

[0006] The performance of the electrostatic chuck deteriorates in the high temperature range, but since the electrostatic chuck is configured to fix a wide area of ​​the back surface of the wafer, the entire wafer is fixed to a certain degree firmly. During high-temperature implantation, the wafer is heated by a heater or ion beam irradiation, which generates stress in the wafer if the wafer is firmly fixed.

[0007] When the wafer is removed from the wafer fixture after the high-temperature implantation process, the thermal strain suppressed during the implantation process is suddenly released as stress, resulting in defects such as the wafer cracking or the wafer bouncing off the wafer fixture.

[0008] Patent Documents 1 and 2 do not disclose any measures to address the above-mentioned problems. Furthermore, when an electrostatic chuck is used, a residual adsorptive force is generated on the wafer. When the wafer is released from the wafer fixture, complex voltage control is required to remove the residual adsorptive force.

[0009] An object of the present invention is to reduce the occurrence of problems caused by stress release that occurs when a wafer is separated. [Means for solving the problem]

[0010] The wafer fixing method is as follows: A wafer fixture used in semiconductor manufacturing equipment that has a mechanical clamp and an electrostatic chuck. The mechanical clamps alone are used to secure the wafer when the processing temperature of the wafer is at or above a first reference temperature that is greater than room temperature.

[0011] In the high temperature range where the thermal deformation of the wafer is relatively large, the wafer is fixed using only mechanical clamps, which reduces the stress released when the wafer is removed, thereby reducing the occurrence of defects caused by the stress release that occurs when the wafer is removed.

[0012] To reduce the stresses that occur when the wafer is heated, Prior to clamping the wafer, it is preferred to heat the wafer on the wafer fixture to bring the temperature of the wafer above a processing temperature.

[0013] In order to reduce the stress generated in the wafer during low temperature processing, The wafer fixing method is as follows: A wafer fixture used in semiconductor manufacturing equipment that has a mechanical clamp and an electrostatic chuck. The mechanical clamps alone are used to secure the wafer when the processing temperature of the wafer is at or below a second reference temperature that is below room temperature.

[0014] Similarly to the high-temperature processing, when the processing temperature of the wafer is equal to or lower than the second reference temperature which is lower than the room temperature, the occurrence of defects at the time of wafer removal due to stress release can be reduced by fixing the wafer using only the mechanical clamp.

[0015] Semiconductor manufacturing equipment a wafer fixture that uses a combination of a mechanical clamp and an electrostatic chuck to fix a wafer; a control device for controlling the fixing of the wafer; The controller clamps the wafer using only the mechanical clamps when the processing temperature of the wafer is equal to or greater than a first reference temperature that is higher than room temperature.

[0016] With the above-described configuration, deformation of the wafer can be tolerated, and the occurrence of problems caused by stress release when the wafer is removed can be reduced.

[0017] To reduce the stresses that occur when the wafer is heated, The controller preferably heats the wafer on the wafer fixture prior to clamping the wafer to a processing temperature.

[0018] the mechanical clamp partially fixes a peripheral edge of the wafer; It is desirable to provide a restricting member for restricting radial movement of the wafer at a peripheral edge of the wafer, at a location not fixed by the mechanical clamp.

[0019] The presence of a restraining member can more reliably prevent the wafer from falling off the mechanical clamp. Effect of the Invention

[0020] In the high temperature range where the amount of thermal deformation of the wafer is relatively large, the wafer is fixed using only mechanical clamps, which reduces the stress released when the wafer is removed, and thus reduces the occurrence of defects due to stress release. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a schematic plan view showing a configuration example of a wafer fixture; [Diagram 2] FIG. 2 is a schematic plan view showing a configuration example of a wafer fixture when viewed from the P direction in FIG. [Diagram 3] FIG. 1 is a schematic plan view showing a configuration example of an ion implantation apparatus equipped with a wafer fixing device; [Figure 4] 1 is a flowchart showing an example of a wafer fixing method. [Diagram 5] 1 is a flowchart showing another example of a wafer fixing method. [Figure 6] Flowchart showing another example of a wafer fixing method [Figure 7] Flowchart showing another example of a wafer fixing method [Figure 8] FIG. 13 is a schematic plan view showing another example of the configuration of the wafer fixture; [Figure 9] FIG. 11 is a schematic plan view showing another example of the configuration of the wafer fixture; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Fig. 1 is a schematic plan view showing a configuration example of the wafer fixture F. Fig. 2 is a schematic plan view showing a configuration example of the wafer fixture F when viewed from the P direction in Fig. 1, and for simplification of the drawing, the illustration of the restricting member 6 is omitted. An example of the configuration of the wafer fixture F will be described with reference to these figures.

[0023] The wafer fixture F includes a mechanical clamp M and an electrostatic chuck E. This wafer fixture F is used when processing a wafer W in semiconductor manufacturing equipment such as an ion implanter, an ion beam etching equipment, or a film forming equipment. The mechanical clamp M is a mechanical clamp that does not require a power mechanism, similar to, for example, Patent Document 2. By changing the inclination of the wafer fixture F, the link mechanism 3, rod 4, and pressing portion 5 are linked to realize the opening and closing operation of the jaws 1 that press the edge of the upper surface of the wafer.

[0024] The electrostatic chuck E is, for example, a bipolar electrostatic chuck equipped with a pair of electrodes 10a, 10b as shown in Fig. 2. The electrostatic chuck E attracts the wafer W by Coulomb force or Johnsen-Rahbek force by applying DC voltages of opposite polarities to the electrodes 10a, 10b.

[0025] The electrostatic chuck E is provided with a heater 11 and heats the wafer W to a predetermined processing temperature before processing. However, it is not essential that the electrostatic chuck E is provided with the heater 11, and a heating means for heating the wafer W may be provided separately from the electrostatic chuck E. For example, the temperature of the wafer W may be heated to the processing temperature before processing the wafer W using a heater made of an LED lamp that can be moved to a position facing the surface of the wafer W. Furthermore, the electrostatic chuck E may include a temperature measuring device 31 (e.g., a thermocouple) for measuring the temperature of the wafer W. In Fig. 2, the temperature of the wafer W is directly measured by the temperature measuring device 31, but the wafer temperature may be measured indirectly by measuring the temperature of another member (e.g., the temperature of the electrostatic chuck E) that can be correlated with the wafer temperature.

[0026] The support table 2 supports an electrostatic chuck E. For example, when the wafer fixture F is used in an ion implantation device, which is a semiconductor manufacturing device, the support table 2 is rotated and tilted by a driving mechanism (not shown) to adjust the irradiation angle of the ion beam with respect to a device structure formed on the wafer W.

[0027] A restricting member 6 for restricting radial movement of a circular wafer W is provided around the electrostatic chuck E. When the wafer W is placed on the electrostatic chuck E, the restricting member 6 is in contact with the peripheral edge of the wafer W or is slightly spaced apart from the peripheral edge of the wafer W. The regulating member 6 is a rod-shaped heat-resistant member, and is made of a material such as glassy carbon, SiC, sintered SiC, or tantalum.

[0028] The control device C has a memory function for storing data, a calculation function for calculating data, and a function for controlling each part based on the calculation results and input data. The control device C receives the recipe information R and compares the processing temperature of the wafer W included in the recipe information R with a reference temperature stored in the control device C. Then, based on the comparison result, it outputs a command signal I to the wafer fixture F.

[0029] 3 is a schematic plan view showing a configuration example of an ion implantation apparatus IM including a wafer fixture F. Plasma that is the source of an ion beam IB is generated in a plasma chamber 21. An extraction electrode 22 extracts the ion beam IB from the plasma generated in the plasma chamber 21.

[0030] The ion beam IB extracted from the extraction electrode 22 contains a plurality of ions. The mass analysis electromagnet 23 analyzes the ions according to their mass in order to extract desired ions from the ion beam IB. The acceleration tube 24 accelerates and decelerates the ion beam IB analyzed by the mass analysis electromagnet 23, and converts it into an ion beam IB with a desired energy.

[0031] An energy analyzing electromagnet 25 is disposed downstream of the accelerating tube 24. The energy analyzing electromagnet 25 removes ions of unnecessary energy components generated by charge exchange between the mass analyzing electromagnet 23 and the accelerating tube 24 and within the accelerating tube 24.

[0032] When the ion beam IB is cut by a plane perpendicular to the traveling direction of the ion beam IB, the cut surface of the ion beam IB extracted from the extraction electrode 22 is elliptical. Such an ion beam IB is called a spot beam. After passing through the energy analyzing electromagnet 25, the ion beam IB is periodically scanned in one direction by a scanner 26, and is converted into an ion beam that appears to be wide in the scanning direction.

[0033] The scanned ion beam IB enters the parallelizer 27, where it is converted into a parallel ion beam IB with a uniform traveling direction by magnetic deflection. The scanning width of the ion beam IB after passing through the parallelizer 27 is wider than the dimension of the wafer W in the scanning direction of the ion beam IB. The wafer W is moved in a direction parallel to the Y-axis in the figure with respect to such an ion beam IB, thereby performing an ion implantation process.

[0034] A wafer W held by a wafer fixture F is placed in the processing chamber 28. A support table 2 supporting the wafer fixture F is connected to a driving mechanism 30. The support table 2 is rotated and tilted by the driving mechanism 30, thereby adjusting the irradiation angle of the ion beam IB with respect to the device structure formed on the wafer W.

[0035] When the wafer W is transferred to the wafer fixture F, the support table 2 is rotated by about 90 degrees from the illustrated position by the drive mechanism 30. At this time, the wafer support surface of the electrostatic chuck E faces upward in the figure. When the electrostatic chuck E is in this position, the wafer W placed on the electrostatic chuck E is heated by the heater 11 to a temperature equal to or higher than the processing temperature.

[0036] A temperature measuring device 32 (for example, a radiation thermometer or a thermograph) is provided on the ceiling of the processing chamber 8. The temperature measuring device 32 is used to measure the temperature of the wafer W on the electrostatic chuck E. The number of devices for measuring the wafer temperature is not limited as long as the device can measure the wafer temperature. For example, if the electrostatic chuck E is provided with the temperature measuring device 31, the temperature measuring device 32 may be removed from the ceiling of the processing chamber 8.

[0037] Each of the illustrated XYZ axes is drawn based on the trajectory of an ideal ion beam IB entering a processing chamber 28 described later. The Z axis is parallel to the traveling direction of the ion beam IB. The X-axis and Y-axis are mutually perpendicular to the Z axis. The directions of the XYZ axes change according to the position of the ion beam IB transported through the beamline. In this ion implantation apparatus IM, the scanning direction of the ion beam IB in the scanner 26 is parallel to the X-axis. The control device C may have a function of controlling each part of the ion implantation device IM.

[0038] FIG. 4 is a flow chart showing an example of a wafer fixing method carried out by the control device C shown in FIGS. Recipe information R is input to the control device C (process S1). Next, the processing temperature of the wafer W included in the recipe information R is compared with a first reference temperature T1 higher than room temperature (approximately 25° C.) stored in the control device C (process S2). If the processing temperature is equal to or higher than the first reference temperature T1 (e.g., 300° C. or 500° C.), the wafer W is fixed using only the mechanical clamp M (process S3). Conversely, if the processing temperature is lower than the first reference temperature T1, at least the electrostatic chuck E of the wafer fixing fixture F is used to fix the wafer W (process S4).

[0039] Generally, the higher the processing temperature of the wafer W, the greater the amount of thermal deformation of the wafer W. If the wafer W is fixed so firmly that thermal deformation of the wafer W is hardly tolerated, the stress when the wafer W is released will be large, and defects such as cracking or bouncing of the wafer W will occur frequently.

[0040] Mechanical clamps used in semiconductor manufacturing equipment do not cover the entire surface of the wafer to be processed. The mechanical clamps fix the wafer W over the entire or part of the peripheral edge of the wafer W, or in the vicinity of the peripheral edge. The mechanical clamp does not fix a wide area of ​​the back surface of the wafer as the electrostatic chuck E does, and therefore can tolerate thermal deformation of the wafer W. In other words, fixing the wafer W by the mechanical clamp does not prevent the wafer W from being thermally deformed, except for some places where the wafer W is pressed.

[0041] In the flow chart of Fig. 4, in the high temperature range where the thermal deformation of the wafer W is relatively large, only the mechanical clamp M is used to fix the wafer W. This reduces the stress released when the wafer is removed, and reduces the occurrence of defects caused by the stress release that occurs when the wafer is removed. In addition, by using only the mechanical clamp M, the complicated voltage control for removing the residual adsorption force that occurs when the electrostatic chuck E is used is no longer necessary.

[0042] On the other hand, in order to perform semiconductor manufacturing processing with high precision, it is better to firmly fix the position of the wafer W. For this reason, when the processing temperature is lower than the first reference temperature T1, an electrostatic chuck E is used to fix the wafer W. In this case, a mechanical clamp M may be used in combination as necessary. Although the use of the electrostatic chuck E causes the problem of residual clamping force, if the processing temperature is lower than the first reference temperature T1, the amount of thermal deformation of the wafer W is small, and the stress released when the wafer is released is small. For this reason, it is only necessary to focus on removing the residual clamping force, which simplifies the control when the wafer is released.

[0043] Fig. 5 is a flow chart showing another example of a wafer fixing method. The same steps as those in the flow chart of Fig. 4 are given the same reference numerals and detailed explanations are omitted. The same applies to the subsequent flow charts.

[0044] The flowchart in Fig. 5 adds processes S5 and S6 to the flowchart in Fig. 4. After the wafer W is placed on the electrostatic chuck E, the wafer W is heated before being fixed (process S5). After the wafer W is heated, the wafer temperature is measured, and the measurement result is compared with the processing temperature obtained from the recipe information R (process S6). If the comparison result shows that the wafer temperature is equal to or higher than the processing temperature, the process proceeds to process S2. Conversely, if the wafer temperature is lower than the processing temperature, the process returns to process S5, and heating of the wafer W continues.

[0045] When the wafer W is heated to a processing temperature after being fixed, a large stress is generated in the wafer W. In particular, if the wafer W is warped, the amount of thermal deformation of the wafer W due to heating is large, and the stress when the wafer is released is very large. In order to reduce the occurrence of such stress, thermal deformation of the wafer W is intentionally promoted before the wafer W is fixed, and the wafer W is fixed after the thermal deformation becomes small.

[0046] The above-mentioned heating of the wafer W is performed on the wafer fixture F. However, this does not exclude preliminary heating of the wafer W at a location other than on the wafer fixture F. As long as the wafer temperature is ultimately heated on the wafer fixture F to a temperature equal to or higher than the processing temperature, preliminary heating may be performed before the wafer W is transferred to the wafer fixture F.

[0047] Moreover, the above-mentioned "on the wafer fixture F" includes the wafer fixture F and the area above the wafer fixture F. Before the wafer W is transferred to the electrostatic chuck E, the wafer W is held by the transfer arm of the transfer robot and transferred above the electrostatic chuck E provided on the wafer fixture F. In this state, the wafer temperature may be heated to a temperature equal to or higher than the processing temperature. This is because even if the wafer W is heated, the wafer temperature hardly changes because the heating position of the wafer W is close to the electrostatic chuck E.

[0048] 6 is a flow chart showing another example of a wafer fixing method. After the wafer temperature reaches or exceeds the processing temperature in step S6, the elapsed time is counted (step S7). Then, the elapsed time is compared with a predetermined set time (TM) (step S8). After the elapsed time reaches or exceeds the set time, the wafer W is fixed by a mechanical clamp M or an electrostatic chuck E. The set time is the time required for the amount of thermal deformation of the wafer W to become sufficiently small, and is a time previously obtained by an experiment or the like. The set time may be stored in advance in the control device C, and the set time may be changed as necessary. Also, a data table may be prepared for each type of wafer W and processing temperature, and the set time may be switched according to the recipe information R. By setting a set time and sufficiently heating the wafer W, it is possible to reduce the amount of thermal deformation of the wafer W after the wafer is fixed. In addition, as an additional effect, it is also possible to make the heat distribution uniform within the wafer surface.

[0049] In the above embodiments, the high-temperature processing of the wafer W has been the subject of attention. However, even in low-temperature processing, cracking or jumping of the wafer W due to stress release during the wafer removal may occur similarly. Fig. 7 is a flow chart showing an example of a wafer fixing method in a low temperature process, which differs from Fig. 4 showing an example of a wafer fixing method in a high temperature process in step S9. In process S9, the process temperature of the wafer W obtained from the recipe information R is compared with a second reference temperature lower than room temperature (e.g., about 25° C.). If the comparison result indicates that the process temperature is equal to or lower than the second reference temperature T2, the wafer W is fixed only by the mechanical clamp M.

[0050] As with high-temperature processing, when the processing temperature of the wafer W is equal to or lower than a second reference temperature T2 (e.g., −50° C.) that is lower than room temperature, the wafer can be fixed using only the mechanical clamp M, thereby reducing the occurrence of malfunctions when the wafer is removed due to stress release.

[0051] The electrostatic chuck E includes a wafer cooling means for cooling the wafer temperature instead of or in addition to the heater 11. Specific examples of the wafer cooling means include a flow path for flowing a coolant such as Galden or a Peltier element.

[0052] Fig. 8 is a schematic plan view showing another configuration example of the wafer fixture F. The difference from the wafer fixture F shown in Fig. 1 is that a regulating member 36 made of a wide arc-shaped member is used instead of a rod-shaped member. When a tilt angle is set in the ion implantation process, the ion implantation process is performed in a state in which the wafer fixture F is tilted obliquely with respect to the traveling direction of the ion beam IB. In this case, the side surface of the electrostatic chuck E will be exposed to the ion beam IB, and there is a concern that the electrostatic chuck E may be damaged if the side surface is irradiated with the ion beam IB.

[0053] Therefore, by employing an arc-shaped regulating member 36 that fits along the periphery of the electrostatic chuck E, sputtering of the electrostatic chuck E by the ion beam IB can be prevented. The height of the regulating member 36 from the support base 2 (the dimension in the front-rear direction of the paper in the figure) is greater than the height of the electrostatic chuck E (the dimension in the front-rear direction of the paper in the figure). The restricting member 36 may be provided along the entire periphery of the electrostatic chuck E except for the portion pressed by the claws 1 of the mechanical clamp M, as long as the transfer of the wafer W is not impeded.

[0054] The tip of the jaw 1 of the mechanical clamp M may be a single jaw that presses down on the edge of the wafer W, but in order to give the tip elasticity, it may be configured as a multi-branched portion that presses down on the edge of the wafer W. The material of the jaw 1 is glassy carbon, SiC, sintered SiC, tantalum, or the like, which is resistant to sputtering and does not easily scratch the wafer W, is used.

[0055] In cases where machining of the material is difficult due to the complex shape of the jaws 1, the jaws 1 may be made of multiple materials, with only the tip portions that come into contact with the wafer W being made of a material such as glassy carbon or SiC. Also, in order to provide further elasticity to the tip portions of the jaws 1, the tip portions of the jaws 1 may be made of a separate abutment member 9 to which an elastic member such as a coil spring or a leaf spring is attached. Specifically, this is the configuration shown in FIG. 9. Here, the elastic member is made of a material with excellent heat resistance, such as austenitic stainless steel, Ni-based superalloy, or Ni-Co-based superalloy.

[0056] 9, by attaching an elastic member to the contact member 9, it is possible to sufficiently tolerate deformation of the wafer W, and further reduce the stress on the wafer W. Also, instead of the configuration of FIG. 9, the contact member 9 itself may be made of an elastic member. In this case, the contact member 9 is made of a material that is unlikely to come into close contact with the wafer W and is heat resistant.

[0057] The configuration of the mechanical clamp M in the above embodiment is merely an example, and the mechanical clamp M may be configured to include a power mechanism for realizing the opening and closing operation of the claws 1. Furthermore, the fixing of the wafer W by the mechanical clamp M may be performed in all wafer processing from high temperature range to low temperature range. The portion of the wafer W pressed by the mechanical clamp M is not limited to the top surface of the wafer W, but may be the side surface.

[0058] Although the electrostatic chuck E in the above embodiment attracts the wafer W with a bipolar DC voltage, the structure and attracting method of the electrostatic chuck E are not limited to the configuration described in the above embodiment. For example, an electrostatic chuck that is provided with two or more electrodes and attracts the wafer W with a two-phase or more AC voltage, or an electrostatic chuck that attracts the wafer W using a gradient force may be used. Furthermore, the electrostatic chuck E does not need to adsorb the entire back surface of the wafer W, but may adsorb only a part of the wafer W. As long as the adsorption area of ​​the wafer W by the electrostatic chuck E is larger than the fixing area of ​​the wafer W by the mechanical clamp M, the effect of implementing the wafer fixing method according to the present invention can be obtained.

[0059] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0060] F Wafer Fixture M Mechanical Clamp E Electrostatic Chuck W wafer IM Ion Implantation Equipment T1 1st reference temperature T2 2nd reference temperature C Control device 6, 36 Regulatory members

Claims

1. A wafer fixture used in semiconductor manufacturing equipment that has a mechanical clamp and an electrostatic chuck. The wafer clamping method further comprises clamping the wafer using only the mechanical clamp when the processing temperature of the wafer is equal to or greater than a first reference temperature that is higher than room temperature.

2. 2. The method of claim 1, further comprising heating the wafer on the wafer fixture to bring the temperature of the wafer to or above a processing temperature prior to clamping the wafer.

3. A wafer fixture used in semiconductor manufacturing equipment that has a mechanical clamp and an electrostatic chuck. The method of clamping a wafer, further comprising clamping the wafer using only the mechanical clamp when the processing temperature of the wafer is equal to or lower than a second reference temperature that is lower than room temperature.

4. a wafer fixture that uses a combination of a mechanical clamp and an electrostatic chuck to fix a wafer; a control device for controlling the fixing of the wafer; The semiconductor manufacturing apparatus, wherein the control device fixes the wafer using only the mechanical clamp when a processing temperature of the wafer is equal to or higher than a first reference temperature that is higher than room temperature.

5. 5. The semiconductor manufacturing apparatus according to claim 4, wherein said control device heats said wafer on said wafer fixture before fixing said wafer to a temperature equal to or higher than a processing temperature.

6. the mechanical clamp partially fixes a peripheral edge of the wafer; 6. The semiconductor manufacturing apparatus according to claim 4, further comprising a restricting member for restricting radial movement of said wafer at a peripheral edge of said wafer at a location not fixed by said mechanical clamp.

Images