Charged particle beam drawing apparatus and charged particle beam drawing method

Abstract

To extend the life of a high vacuum gauge while suppressing focus deviation of a charged particle beam.SOLUTION: A charged particle beam drawing apparatus according to the present embodiment draws a pattern on a substrate to be drawn in a chamber by irradiating the substrate with a charged particle beam. The charged particle beam drawing apparatus includes a supply device that supplies a cleaning gas to the chamber, a vacuum pump that discharges gas from the chamber, a pressure sensor that detects a pressure in the chamber, and a control device that acquires a detection value of the pressure sensor and controls the supply device such that the pressure in the chamber becomes a first target value. The control device further controls the supply device such that the pressure in the chamber becomes a second target value different from the first target value when the charged particle beam with which the substrate is irradiated is adjusted.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a charged particle beam drawing apparatus and a charged particle beam drawing method. [Background technology]

[0002] As LSIs become more highly integrated, the circuit line width required for semiconductor devices is becoming finer year by year. To form the desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision original pattern (mask, or particularly one used in steppers and scanners, called a reticle) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure apparatus. The high-precision original pattern is drawn by an electron beam drawing apparatus, and so-called electron beam lithography technology is used.

[0003] In an electron beam lithography system, a pattern is drawn by irradiating a desired position with an electron beam deflected by a deflector. During use of the lithography system, hydrocarbon contaminants (contamination) adhere to the electron optical system components such as the deflector. When electric charge accumulates on the contaminants, a problem occurs in which the irradiation position of the electron beam shifts, causing a phenomenon called beam drift.

[0004] A method is known in which a cleaning gas such as ozone gas is introduced into the column of a drawing device to keep the electron optical components clean while drawing is being performed. For example, the ozone introduced into the column is collided with an electron beam to separate the ozone into oxygen and active oxygen. The separated active oxygen is reacted with pollutants to turn them into carbon monoxide gas, which is then exhausted, thereby reducing the amount of pollutants adhering to the electron optical components.

[0005] The pressure inside the column is controlled to be constant because fluctuations in the pressure inside the column due to the introduction of cleaning gas would cause the electron beam to shift from its focus. In conventional lithography systems, when gas generation from components inside the system gradually decreases with use, the amount of ozone gas introduced is gradually increased to maintain the pressure inside the column.

[0006] However, in such a conventional lithography apparatus, the pressure inside the column is always kept high, and this causes a problem in that the high vacuum gauge (pressure gauge) used for measuring the pressure quickly deteriorates. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2001-81545 A [Patent Document 2] JP 2017-41584 A [Patent Document 3] JP 2007-172862 A Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a charged particle beam drawing apparatus and a charged particle beam drawing method that can extend the life of a high vacuum gauge while suppressing focus deviation of a charged particle beam. [Means for solving the problem]

[0009] A charged particle beam drawing apparatus according to one embodiment of the present invention is a charged particle beam drawing apparatus that draws a pattern by irradiating a charged particle beam onto a substrate to be drawn in a chamber, and includes a supply device that supplies a cleaning gas to the chamber, a vacuum pump that exhausts gas from the chamber, a pressure sensor that detects the pressure in the chamber, and a control device that acquires the detection value of the pressure sensor and controls the supply device so that the pressure in the chamber becomes a first target value, and the control device further controls the supply device so that the pressure in the chamber becomes a second target value different from the first target value when adjusting the charged particle beam to be irradiated to the substrate.

[0010] A charged particle beam drawing method according to one embodiment of the present invention is a charged particle beam drawing method in which a charged particle beam is irradiated onto a substrate to be drawn in a chamber to draw a pattern, the method comprising the steps of: supplying a cleaning gas into the chamber; discharging gas from the chamber; detecting the pressure in the chamber with a pressure sensor; controlling the amount of the cleaning gas supply so that the pressure in the chamber becomes a first target value based on the detection value of the pressure sensor; and adjusting the charged particle beam irradiated onto the substrate, wherein the adjustment is performed by controlling the amount of the cleaning gas supply so that the pressure in the chamber becomes a second target value different from the first target value, and after the adjustment, the amount of the cleaning gas supply is controlled so that the pressure in the chamber becomes the second target value. Effect of the Invention

[0011] According to the present invention, it is possible to extend the life of a high vacuum gauge while suppressing defocusing of a charged particle beam. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a multi-beam writing apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of a shaping aperture array plate. [Diagram 3] 13 is a graph showing a change in internal pressure of a vacuum chamber according to a comparative example. [Figure 4] 11 is a flowchart illustrating a drawing method according to the embodiment. [Diagram 5] 4 is a graph showing an example of a change in internal pressure of a vacuum chamber. [Figure 6] FIG. 13 is a diagram showing an example of a parameter setting screen. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In the following, in the embodiment, a configuration using an electron beam as an example of a charged particle beam will be described. However, the charged particle beam is not limited to an electron beam, and a beam using charged particles such as an ion beam may be used.

[0014] FIG. 1 is a schematic diagram of a drawing apparatus according to an embodiment. As shown in FIG. 1, the drawing apparatus 100 includes a drawing unit W and a control system C. The drawing apparatus 100 is an example of a multi-charged particle beam drawing apparatus. The drawing unit W includes a vacuum chamber 60 including an electron optical lens barrel 60a and a drawing chamber 60b. The drawing chamber 60b is a rectangular hollow member, and a circular opening is formed on the upper surface. The electron optical lens barrel 60a is a cylindrical casing with the longitudinal direction in the Z-axis direction, and is inserted into an opening formed on the upper surface of the drawing chamber 60b.

[0015] An electron gun 201, an illumination lens 202, a shaping aperture array plate 203, a blanking aperture array plate 204, a reduction lens 205, a limiting aperture member 206, an objective lens 207, and a deflector 208 are arranged within the electron optical column 60a.

[0016] An XY stage 105 is disposed in the pattern writing chamber 60b. A substrate 101 to be patterned is disposed on the XY stage 105. The substrate 101 is, for example, a mask blank or a semiconductor substrate (silicon wafer).

[0017] Furthermore, a pressure sensor 50 (high vacuum gauge) is disposed in the internal space of the vacuum chamber 60. The pressure sensor 50 outputs a voltage signal having a value corresponding to the pressure inside the chamber.

[0018] The control system C has a control device 110, a stage driving device 120, a deflection control circuit 130, a memory unit 140, a cleaning gas supply device 30, a vacuum pump 40, and a touch panel 70. Drawing data is input from the outside and stored in the memory unit 140. The drawing data defines information on a plurality of graphic patterns that describe the patterns to be formed on the substrate 101. Specifically, a graphic code, coordinates, size, etc. are defined for each graphic pattern.

[0019] The control device 110 is a computer having a CPU, and controls the drawing unit W, the stage driving device 120, the deflection control circuit 130, the cleaning gas supply device 30, the vacuum pump 40, and the touch panel 70 in an integrated manner.

[0020] An electron beam 200 emitted from an electron gun 201 of the drawing unit W illuminates the entire shaping aperture array plate 203 via an illumination lens 202 .

[0021] Fig. 2 is a conceptual diagram showing the configuration of the shaping aperture array plate 203. As shown in Fig. 2, the shaping aperture array plate 203 has a plurality of apertures 203a formed in the vertical direction (y direction) and horizontal direction (x direction) at a predetermined arrangement pitch. It is preferable that each aperture 203a is formed in a rectangular or circular shape of the same dimensions. Multi-beams 20a to 20e are formed (emitted) by a portion of the electron beam 200 passing through each of the plurality of apertures 203a.

[0022] In the blanking aperture array plate 204, a passage hole is formed in accordance with the arrangement position of each opening 203a of the shaping aperture array plate 203. A blanker consisting of a pair of two electrodes is arranged in each passage hole. By grounding one electrode of the blanker to keep it at ground potential and switching the other electrode to ground potential or a potential other than ground potential, the deflection of the beam passing through the passage hole is switched on and off, thereby performing blanking control. When the blanker does not deflect the beam, the beam is turned on. When the blanker deflects the beam, the beam is turned off. In this way, the multiple blankers perform blanking deflection of the corresponding beams among the multi-beams that have passed through the multiple openings 203a of the shaping aperture array plate 203.

[0023] The multiple beams 20 a to 20 e that have passed through the blanking aperture array plate 204 are reduced in size by a reduction lens 205 and travel toward an opening formed in a limiting aperture member 206 .

[0024] Here, the beam controlled to the beam-off state is deflected by the blanker and follows a trajectory that passes outside the opening of the limiting aperture member 206, and is therefore blocked by the limiting aperture member 206. On the other hand, the beam controlled to the beam-on state is not deflected by the blanker and passes through the opening of the limiting aperture member 206. In this way, blanking control is performed by turning on / off the blanker deflection, and the beam is controlled to be turned on / off.

[0025] The multi-beams that have passed through the limiting aperture member 206 are focused by the objective lens 207 to become a pattern image with a desired reduction ratio. The beams (all of the multi-beams) that have passed through the limiting aperture member 206 are deflected together in the same direction by the deflector 208, and are irradiated onto a desired position on the substrate 101.

[0026] When the XY stage 105 is moved continuously by the stage driving device 120, at least while the beam is being irradiated onto the substrate 101, the deflector 208 controls the irradiation position of the beam so as to follow the movement of the XY stage 105. The multiple beams irradiated at one time are ideally arranged at a pitch obtained by multiplying the arrangement pitch of the multiple openings 203a of the shaping aperture array plate 203 by the desired reduction ratio described above.

[0027] The control device 110 virtually divides the drawing area of ​​the substrate 101 into a plurality of mesh areas. The size of the mesh area is, for example, approximately the same as the size of one individual beam included in the multi-beam, and each mesh area becomes a pixel (unit irradiation area). The control device 110 reads out the drawing data from the storage unit 140, and calculates the pattern area density ρ of each pixel using a pattern defined in the drawing data.

[0028] The control device 110 calculates the reference dose D 0 Multiplying by ρD, the beam irradiation dose irradiated to each pixel is 0 A correction coefficient for correcting the proximity effect and the like may be further multiplied. The control device 110 divides the irradiation amount by the current amount of each of the multiple individual beams constituting the multibeam to calculate the irradiation time of each of the multiple individual beams.

[0029] The control device 110 rearranges the irradiation time data in a shot order according to the writing sequence, generates irradiation time control data, and outputs it to the deflection control circuit 130. The deflection control circuit 130 outputs the irradiation time control data to the blanking aperture array plate 204. The input / output circuit of the blanking aperture array plate 204 transfers the irradiation time data to the corresponding blanker.

[0030] Each of the individual beams that make up the multi-beam simultaneously exposes a different pixel, and each beam is turned on for the required amount of time to provide the desired exposure for each pixel.

[0031] In multi-beam writing, beam adjustment such as focusing is important. For example, the method described in JP 2018-82120 A is used to obtain an optimal lens value (excitation current value) of the objective lens 207, and focusing is performed. The reduction magnification of the multi-beam may be adjusted using the method described in JP 2017-199758 A, or the deflection sensitivity may be adjusted using the method described in JP 10-284392 A. Beam adjustment is performed at a predetermined time interval.

[0032] The cleaning gas supply device 30 is connected to the vacuum chamber 60 via piping, and includes a cleaning gas generator and a flow rate control valve for controlling the amount of cleaning gas introduced into the vacuum chamber 60. The cleaning gas supply device 30 supplies cleaning gas into the vacuum chamber 60 at a flow rate instructed by the control device 110. The cleaning gas is, for example, ozone gas.

[0033] The vacuum pump 40 exhausts gas from the inside of the vacuum chamber 60 based on instructions from the control device 110, and maintains the inside of the vacuum chamber 60 at a predetermined pressure or less.

[0034] In order to suppress the defocusing of the multi-beam, the control device 110 acquires the measured value of the pressure sensor 50 at a predetermined period, and controls the cleaning gas supply device 30 and the vacuum pump 40 so that the internal pressure of the vacuum chamber 60 is constant. For example, the control device 110 controls the valve opening of the cleaning gas supply device 30 and the start and stop of the vacuum pump 40 based on the measured value of the pressure sensor 50. The gas generated from the components such as the blanking aperture array plate 204 in the vacuum chamber 60 gradually decreases over time. As shown in FIG. 3, when the internal pressure of the vacuum chamber 60 is controlled to a constant value P, the amount of cleaning gas introduced into the vacuum chamber 60 gradually increases, and the partial pressure of the cleaning gas in the vacuum chamber 60 gradually increases. In the graph of FIG. 3, the gray part is the partial pressure of the cleaning gas, the white part is the partial pressure of the gas generated from the components in the chamber, and the internal pressure of the chamber is the sum of these.

[0035] In a multi-beam lithography apparatus, the vacuum chamber 60 has a large number of components and generates a large amount of gas, especially at the beginning of operation, so that the initial internal pressure is high and the target value P for constant pressure control is also high. If the internal pressure of the vacuum chamber 60 remains high for a long period of time, the pressure sensor 50 will deteriorate early.

[0036] Therefore, in this embodiment, the target value of the constant pressure control is lowered at the timing of beam adjustment. When the target value of the constant pressure control is lowered, the internal pressure of the vacuum chamber 60 changes, but since the beam adjustment is performed, the focus deviation of the multi-beam is suppressed.

[0037] The multi-beam writing method according to this embodiment will be described with reference to the flowchart shown in FIG.

[0038] The control device 110 starts the vacuum pump 40 (step S1). Gas is discharged from the inside of the vacuum chamber 60, and the pressure inside the chamber decreases.

[0039] The cleaning gas supply device 30 supplies a cleaning gas into the vacuum chamber 60 (step S2).

[0040] The control device 110 controls the cleaning gas supply device 30 to adjust the gas supply amount so that the internal pressure of the vacuum chamber 60 becomes a predetermined target value (within a target range) based on the measurement value of the pressure sensor 50 (steps S3_No, S4). The target value is based on the internal pressure of the vacuum chamber 60 before the start of the cleaning gas supply. For example, it is a value obtained by adding a predetermined value to the internal pressure of the vacuum chamber 60 before the start of the cleaning gas supply, or a value obtained by multiplying it by a predetermined factor. The predetermined additional value or factor can be arbitrarily set by the user by operating the touch panel 70.

[0041] For example, a parameter setting screen as shown in Fig. 6 is displayed on the touch panel 70. The user presses the touch key 73 to set a predetermined additional value (partial pressure (B) of the cleaning gas) in advance. The internal pressure of the vacuum chamber 60 before the start of the supply of the cleaning gas is displayed in a display field 72. The target value is displayed in a display field 74.

[0042] While controlling the pressure inside the chamber to be constant at a target value, multiple beams are formed by the above-mentioned method and irradiated onto the substrate 101 to write a desired pattern (steps S3_Yes, S5). The detection value (measurement value) of the pressure sensor 50 is displayed in real time in the display field 71 of the parameter setting screen.

[0043] When the timing for beam adjustment arrives (Yes in step S6), the supply of cleaning gas from the cleaning gas supply device 30 is stopped (step S7).

[0044] The control device 110 obtains the internal pressure of the vacuum chamber 60 from the pressure sensor 50 after a predetermined time (e.g., about 3 minutes) has elapsed since the supply of the cleaning gas was stopped (step S8). At this time, the vacuum pump 40 has exhausted almost all of the cleaning gas from the vacuum chamber 60, and the internal chamber pressure measured by the pressure sensor 50 is due to gas generation from the components in the chamber (corresponding to the white part in the graph of FIG. 3).

[0045] The control device 110 calculates a new target value for the pressure in the chamber based on the pressure measured in step S8, and updates the target value (step S9). For example, the new target value is calculated by adding a predetermined value to the pressure measured in step S8, or by multiplying it by a predetermined magnification. The pressure measured in step S8 is displayed in a display field 72 of the parameter setting screen. A new target value obtained by adding the partial pressure (B) of the cleaning gas set by the touch key 73 to this measured pressure is displayed in a display field 74.

[0046] The supply of the cleaning gas is resumed (step S10), and the cleaning gas supply device 30 is controlled to adjust the gas supply amount so that the internal pressure of the vacuum chamber 60 reaches the updated target value (steps S11_No, S12).

[0047] When the pressure inside the chamber reaches the target value (step S11_Yes), beam adjustment is performed (step S13). In the beam adjustment, focusing, reduction magnification adjustment, deflection sensitivity adjustment, etc. are performed. After the beam adjustment, pattern writing is resumed.

[0048] 5 shows an example of changes in the internal pressure of the vacuum chamber 60. In this example, the initial target value for constant internal pressure control of the vacuum chamber 60 is P0. At the timing T1 for beam adjustment, the cleaning gas is exhausted, the pressure inside the chamber is measured, and the target value is updated to P1. Because the amount of gas generated from the components inside the chamber has decreased, the updated target value P1 is smaller than the target value P0 before the update.

[0049] The chamber pressure is controlled to be P1 until the next beam adjustment timing T2. At the beam adjustment timing T2, the cleaning gas is exhausted and the chamber pressure is measured and updated to a new target value P2. Because the amount of gas generated from the components in the chamber has decreased, the updated target value P2 is smaller than the target value P1 before the update.

[0050] Until the timing T3 of the next beam adjustment, the pressure inside the chamber is controlled to be P2.

[0051] In this manner, in this embodiment, the target value for constant pressure control in the vacuum chamber 60 is gradually lowered at each beam adjustment timing in accordance with the reduction in the amount of gas generated from the components in the chamber. By lowering the target value for constant pressure control, the internal pressure of the vacuum chamber 60 changes, but since beam adjustment is performed, it is possible to suppress defocusing of the multi-beam.

[0052] Since the internal pressure of the vacuum chamber 60 decreases at each beam adjustment timing, the internal pressure of the vacuum chamber 60 does not remain high for a long period of time, which suppresses deterioration of the pressure sensor 50 and extends its lifespan.

[0053] In addition, the amount of cleaning gas supplied to the vacuum chamber 60 can be reduced.

[0054] In the above embodiment, an example was described in which a predetermined value (first predetermined value) was added to the pressure inside the chamber after exhausting the cleaning gas to automatically calculate and update the target value of the constant pressure control, but if the calculated target value of the constant pressure control falls below a predetermined threshold value (second predetermined value), a value (third predetermined value) previously set by the user may be set as the new target value. This makes it possible to prevent the target value of the constant pressure control from becoming excessively low.

[0055] The user can set an arbitrary threshold value (Th) by pressing a touch key 75 on the parameter setting screen shown in Fig. 6. The user can also manually set a target value (SV_f) of the chamber internal pressure by pressing a touch key 76.

[0056] When it is time to adjust the beam, a new target value is calculated by adding the cleaning gas partial pressure (B) set by the user to the internal pressure (A) after the cleaning gas is exhausted, and is displayed in the display field 73.

[0057] If the calculated target value is less than the preset threshold value (Th), the target value for constant pressure control becomes the target value (SV_f) set by the user. After this, the automatic target value calculation and update process (steps S7 to S12) is skipped, and the target value becomes constant.

[0058] At the timing of beam adjustment, parts in the vacuum chamber 60, such as the blanking aperture array plate 204, may be replaced. In this case, the replacement of parts increases gas generation, the measured pressure in step S8 increases, and the new target value calculated by adding a predetermined value or multiplying by a predetermined magnification may be higher than the previous target value (before the part replacement).

[0059] In addition, if the previous target value was the user-set target value (SV_f) and the new target value calculated after the part replacement is also equal to or less than the user-set target value (SV_f), there is no need to change the target value (leave it as SV_f).

[0060] Although the above embodiment has been described as a multi-beam drawing apparatus, the drawing apparatus may be a single-beam drawing apparatus.

[0061] The present invention is not limited to the above-described embodiment, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0062] 30 Cleaning gas supply device 40 Vacuum Pump 50 Pressure Sensor 60 Vacuum Chamber 100 drawing device 110 Control device

Claims

1. A charged particle beam lithography apparatus that irradiates a charged particle beam onto a substrate to be lithographed in a chamber to lithograph a pattern, comprising: a supply device for supplying a cleaning gas to the chamber; a vacuum pump for exhausting gas from the chamber; a pressure sensor for detecting a pressure within the chamber; a control device that acquires a detection value of the pressure sensor and controls the supply device so that the pressure in the chamber becomes a first target value; Equipped with The control device further controls the supply device so that the pressure in the chamber becomes a second target value different from the first target value when adjusting the charged particle beam irradiated to the substrate.

2. 2. The charged particle beam drawing apparatus of claim 1, wherein the control device controls the supply device to stop the supply of the cleaning gas before adjusting the charged particle beam, and calculates the second target value by adding a predetermined value to the detection value of the pressure sensor a predetermined time after the supply of the cleaning gas is stopped.

3. 2. The charged particle beam drawing apparatus of claim 1, wherein the control device controls the supply device to stop the supply of the cleaning gas before adjusting the charged particle beam, and when a value obtained by adding a first predetermined value to the detection value of the pressure sensor a predetermined time after the supply of the cleaning gas is stopped becomes less than a second predetermined value, the control device sets a third predetermined value to the second target value.

4. A charged particle beam lithography method for irradiating a charged particle beam onto a substrate to be lithographed in a chamber to lithograph a pattern, comprising: providing a cleaning gas to the chamber; evacuating the chamber; and detecting a pressure in the chamber with a pressure sensor; controlling the supply amount of the cleaning gas based on a detection value of the pressure sensor so that the pressure in the chamber becomes a first target value; adjusting the charged particle beam irradiated onto the substrate; Equipped with performing the adjustment by controlling the supply amount of the cleaning gas so that the pressure in the chamber becomes a second target value different from the first target value; After the adjustment, the supply amount of the cleaning gas is controlled so that the pressure in the chamber becomes the second target value.

5. Stopping the supply of the cleaning gas; 5. The charged particle beam drawing method according to claim 4, further comprising the step of calculating the second target value based on a detection value of the pressure sensor a predetermined time after the supply of the cleaning gas is stopped.

6. 6. The charged particle beam drawing method according to claim 5, further comprising the step of calculating the second target value by adding a predetermined value to a detection value of the pressure sensor a predetermined time after the supply of the cleaning gas is stopped.

7. 6. The charged particle beam drawing method according to claim 5, further comprising the step of: setting a third predetermined value to the second target value when a value obtained by adding a first predetermined value to a detection value of the pressure sensor a predetermined time after the supply of the cleaning gas is stopped is less than a second predetermined value.

Images