JP5015464B2 - Ion implantation method and ion implantation apparatus - Google Patents

Description

  The present invention relates to an ion implantation method and ion implantation apparatus for performing ion implantation by relatively moving a wide ribbon beam and a substrate to be processed.

  Conventionally, in the semiconductor manufacturing field, there is an ion implantation process for doping impurity ions. In general, in the ion implantation process, in-plane uniformity of the ion implantation amount (dose amount) is required in order to prevent variations in device characteristics. Therefore, conventionally, the ion beam is electrostatically scanned with respect to a stationary wafer, or the wafer is mechanically scanned with respect to the ion beam to improve the in-plane uniformity of the dose amount.

  On the other hand, in recent years, a technique is known in which ion implantation is performed by shaping an ion beam into a wide ribbon shape or sheet shape and irradiating the wafer with this ribbon ion beam (hereinafter referred to as a “ribbon beam”). (See, for example, Patent Document 1 below). The ribbon beam is formed wider than the wafer diameter, and ions are implanted over the entire wafer surface by one-dimensional scanning of the wafer with respect to the ribbon beam.

Japanese Patent Laid-Open No. 7-90580

  However, the wide ribbon beam has a beam intensity distribution in the beam major axis direction (width direction), for example, as schematically shown in FIG. For this reason, when the wafer is one-dimensionally scanned with a ribbon beam, the beam intensity distribution is directly reflected in the in-plane dose distribution. As a result, there is a problem that it is difficult to ensure in-plane uniformity of the dose amount.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an ion implantation method and an ion implantation apparatus that can improve in-plane uniformity of a dose amount in ion implantation using a ribbon beam.

In solving the above problems, the ion implantation method of the present invention corrects the in-plane distribution of the substrate to be processed due to the intensity distribution of the ribbon beam when the substrate to be processed is scanned in at least two directions with respect to the ribbon beam. It is characterized by controlling the scanning speed.

  Controlling the scanning speed so as to correct the intensity distribution of the ribbon beam refers to changing the scanning speed in proportion to the magnitude of the beam intensity in consideration of the proportional relationship between the beam intensity and the dose. . Here, the intensity distribution of the ribbon beam is a beam distribution in the beam width direction, and the scan direction is a direction intersecting the beam width direction. Therefore, by performing scanning in at least two directions and controlling the scanning speed in consideration of the dose distribution resulting from the beam scanning in the other direction when scanning in one direction, the ribbon beam The intensity distribution can be corrected. Thereby, finally, the dose amount can be substantially uniform in the surface, and the in-plane uniformity can be improved.

  Preferably, after the intensity distribution in the major axis direction of the ribbon beam is measured, scanning in each direction is performed with the scanning speed of the ribbon beam in the plane of the substrate to be processed being proportional to the intensity distribution of the ribbon beam. The scanning direction of the ribbon beam can be two orthogonal directions.

  The ion implantation apparatus of the present invention includes a beam irradiation source for irradiating a wide ribbon beam and a support member for supporting the substrate to be processed, and the ion implantation is performed by relatively moving the ribbon beam and the substrate to be processed. In the ion implantation apparatus, the rotation mechanism unit that rotates the support member over a predetermined angle range, the movement mechanism unit that linearly moves the support member in the diameter direction, and the beam measurement unit that measures the intensity distribution in the major axis direction of the ribbon beam And a control means for controlling the rotational drive of the rotation mechanism section and the moving speed of the linear movement section.

  According to the present invention, when performing ion implantation using a ribbon beam, the scanning speed is controlled so that the scanning direction is a plurality of directions, and the intensity distribution of the ribbon beam is corrected when scanning in at least one direction. As a result, it is possible to finally perform ion implantation in which the dose is substantially uniform in the plane.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 show an ion implantation apparatus 1 according to an embodiment of the present invention. The ion implantation apparatus 1 of this embodiment includes a beam irradiation source 2 that irradiates a ribbon beam 10 and a stage 3 that supports a wafer W inside a vacuum chamber (not shown). The wafer W corresponds to the “substrate to be processed” of the present invention, and is not limited to a semiconductor wafer and may be composed of a glass substrate or the like. On the other hand, the stage 3 corresponds to the “support member” of the present invention.

  Although the beam irradiation source 2 is simply shown in the figure, the configuration is not particularly limited. For example, an ion beam consisting of only desired ions extracted from the ion source and separated by mass is shaped into a wide ribbon or sheet via a lens mechanism or slit mechanism and guided to the subsequent stage, or a grid formed from a plasma formed in a vacuum chamber It is possible to apply a configuration in which ions extracted through the electrode are shaped into a ribbon shape and guided to the subsequent stage.

  The ribbon beam 10 is preferably formed so as to be able to irradiate the entire irradiated region on the wafer W. In the present embodiment, the ribbon beam 10 is formed with a width larger than the diameter of the wafer W. Has been. When a rectangular glass substrate or the like is used as the substrate to be processed, the ribbon beam 10 is formed with a width larger than the outer dimension of the substrate.

  The stage 3 is provided with a linear movement mechanism unit 4 that linearly moves the stage 3 in the direction of arrow A in FIG. 2 and a rotation mechanism unit 5 that rotates and moves the stage 3 in the direction of arrow B in FIG. . The linear movement mechanism unit 4 and the rotation mechanism unit 5 are for causing the wafer W supported on the stage 3 to scan in different directions with respect to the ribbon beam 10 in which the beam irradiation direction is fixed.

  In the present embodiment, the wafer W is scanned in a direction (short axis direction, direction A in FIG. 2) perpendicular to the width direction (long axis direction) of the ribbon beam 10. Therefore, the linear movement mechanism unit 4 controls the scanning speed of the wafer W, and the rotation mechanism unit 5 rotates the wafer W by 90 degrees. The wafer W is irradiated with the ribbon beam 10 once in the in-plane X-axis and Y-axis directions (FIG. 2). For ease of explanation, it is assumed that the X axis and Y axis in FIG.

  The controller 7 controls the linear moving speed (scanning speed) of the wafer W by the linear moving mechanism 4 and the rotational driving of the wafer W by the rotating mechanism 5. The controller 7 controls the scanning speed of the wafer W based on the beam intensity distribution in the major axis direction of the ribbon beam 10 as will be described later. For measurement of the beam intensity distribution in the major axis direction of the ribbon beam 10, a beam intensity measuring device 6 installed so as to be movable back and forth between the beam irradiation source 2 and the stage 3 is used.

  The beam intensity measuring device 6 is composed of, for example, a Faraday cup, and can be moved in the direction of arrow F by a drive mechanism 6A. The beam intensity measuring device 6 moves over the entire beam width of the ribbon beam 10 to measure the beam intensity in the major axis direction of the ribbon beam 10 and output it to the control unit 7. The control unit 7 receives the output from the beam intensity measuring device 6 and acquires the beam intensity distribution in the major axis direction of the ribbon beam 10.

  Assume that the ribbon beam 10 has a beam intensity distribution as shown in FIG. 3, for example. As shown in FIG. 3, the beam intensity at each point is different in the major axis direction (Y-axis direction in FIG. 2) of the ribbon beam 10. Therefore, when the wafer W is scanned in the X-axis direction (A direction) in FIG. 2 with respect to the ribbon beam 10 having such a beam intensity distribution, the beam intensity is reflected as it is in the dose amount, so the scanning is completed. Sometimes a dose distribution similar to the beam intensity distribution shown in FIG. 3 occurs in the wafer plane (Y-axis direction).

Therefore, in the present embodiment, the controller 7 controls the scanning speed of the wafer W so as to correct the in-plane distribution of the substrate to be processed due to the beam intensity distribution of the ribbon beam 10. That is, the dose is adjusted by changing the scanning speed in proportion to the magnitude of the beam intensity.

  For example, when the ribbon beam 10 has the beam intensity distribution shown in FIG. 3, the beam intensity on the vertical axis is set as the scanning speed of the wafer W. That is, at the time of the first scan (injection) in the X-axis direction, the scan speed is adjusted in advance so as to correct the non-uniform injection distribution caused by the second scan (injection). In the second implantation, the wafer is rotated 90 degrees so that the Y-axis direction coincides with the scanning direction (A direction), and then the scan speed is corrected so as to correct the non-uniform implantation distribution caused by the first implantation. Is adjusted.

  As described above, when performing beam scanning in two directions, the X-axis direction and the Y-axis direction, the dose distribution resulting from the beam scanning in the Y-axis direction is taken into consideration when performing the beam scanning in the X-axis direction. On the other hand, the scanning speed is controlled, and conversely, at the time of beam scanning in the Y-axis direction, the scanning speed is controlled in consideration of the dose distribution resulting from the beam scanning in the X-axis direction. As a result, the dose distributions in the X and Y axis directions are interpolated with each other, and finally a substantially uniform dose distribution can be obtained in the plane.

  Hereinafter, a specific example will be described. For easy understanding, the beam intensity distribution in the major axis direction of the ribbon beam is represented by a linear function as shown in FIG.

  FIG. 5A shows the dose distribution obtained as a result of scanning the ribbon beam in the X-axis direction, and FIG. 5B shows an example of control of the scanning speed in the beam scanning in the X-axis direction. FIG. 6A shows a dose distribution obtained as a result of scanning the ribbon beam in the Y-axis direction, and FIG. 6B shows an example of controlling the scanning speed in the beam scanning in the Y-axis direction. 5A and 6A, the Z axis is an axis orthogonal to the X and Y axes, and represents the magnitude of the dose here. Ix and Iy indicate the beam intensity distribution (FIG. 4) of the ribbon beam at the time of beam scanning in the X-axis direction and the Y-axis direction, respectively, and when the beam intensity distribution at the time of scanning in each direction is unchanged, Ix = Iy.

  As shown in FIG. 5B, when scanning in the X-axis direction, the scanning speed V is controlled to increase in proportion to the beam intensity in the Y-axis direction. In this example, the scan speed V increases at a constant change rate α in the X-axis direction. Accordingly, when beam scanning is performed in the X-axis direction by such speed modulation control, the dose distribution in the wafer surface is as shown in FIG. 5A. As a result, in FIG. 5A, the dose amounts (relative values) at points P1, Q1, R1, and S1 are d, 2d, 4d, and 2d, respectively.

  On the other hand, as shown in FIG. 6B, when scanning in the Y-axis direction, the scanning speed V is controlled to increase in proportion to the beam intensity in the X-axis direction. In this example, the scan speed V decreases at a constant change rate α toward the Y-axis direction. Accordingly, when beam scanning is performed in the Y-axis direction by such speed modulation control, the dose distribution in the wafer surface is as shown in FIG. 6A. As a result, the doses (relative values) at points P2, Q2, R2, and S2 in FIG. 6A are 4d, 2d, d, and 2d, respectively.

The final dose amount of ions implanted into the wafer is the sum of the dose amounts in the X-axis direction and the Y-axis direction. In the case of this example, paying attention to the dose amount at P point (P1, P2), Q point (Q1, Q2), R point (R1, R2) and S point (S1, S2), the sum of the dose amount at each point Are 5d, 4d, 5d, and 4d, respectively. That is, the in-plane dose amount is in the range of 4d to 5d, and the difference between the maximum value and the minimum value of the dose amount is d.
When the ribbon beam having the beam intensity distribution shown in FIG. 4 is scanned in only one direction and the implantation is performed so that the average value of the dose amount matches, the difference between the minimum value and the maximum value of the dose amount is about In view of the fact that it spreads to 2.8 d, it can be seen that the variation in the in-plane dose can be reduced by this embodiment.

  Next, an operation example of the ion implantation apparatus 1 of the present embodiment configured as described above will be described. First, as shown in FIG. 1, the beam intensity measuring device 6 is moved in the direction of arrow F. The beam intensity distribution of the ribbon beam 10 is measured. This measurement process is performed before the start of the first scan. The control unit 7 acquires the beam intensity distribution of the ribbon beam 10 based on the output signal from the beam intensity measuring device 6, and generates a scan speed modulation signal as shown in FIGS. 5B and 6B.

  Subsequently, the beam intensity measuring device 6 is retracted to the standby position to irradiate the wafer W on the stage 3 with the ribbon beam 10, and the wafer W is scanned in the X-axis direction by driving the linear movement mechanism unit 4. This beam scanning process is not limited to a single scan in the same direction, and a reciprocating scan may be performed twice or more.

  After the beam scan in the X-axis direction is completed, the beam scan in the Y-axis direction is performed. The switching of the beam scan in the Y-axis direction is realized by rotating the stage 3 by 90 degrees by the rotation mechanism unit 5. At this time, the irradiation of the ribbon beam 10 is stopped on the beam irradiation source 2 side.

  According to the ion implantation apparatus of the present embodiment, when performing ion implantation using the ribbon beam 10, the scanning direction is set to two directions of the X-axis direction and the Y-axis direction, and the ribbon beam is used for scanning in each direction. Since the scanning speed is controlled so that the ten intensity distributions are interpolated with each other, it is possible to finally perform ion implantation in which the dose amount is substantially uniform in the plane.

  On the other hand, when ion implantation using the ribbon beam 10 is performed, the beam current of the ribbon beam 10 may fluctuate. The fluctuation of the beam current value here means a case where the intensity distribution in the beam long axis direction does not change and the beam current value fluctuates as a whole.

  Therefore, in the present embodiment, as shown in FIG. 7, the beam current of the ribbon beam 10 is monitored by the beam intensity measuring device 6 retracted to the radially outward position of the wafer 6 during ion implantation, and the beam current is measured. The scanning speed of the wafer W is controlled in accordance with the variation amount. The scanning speed control of the wafer W is performed by the control unit 7 controlling the moving speed of the linear moving mechanism unit 4 based on the output of the beam intensity measuring device 6. Specifically, when the beam current is halved, the scanning speed of the wafer W is also halved, and when the beam current is doubled, the scanning speed is also doubled.

  In this way, the fluctuation of the beam current of the ribbon beam 10 is measured in real time, and the dose amount is corrected by feeding back to the scanning speed of the wafer W, whereby the set dose amount and the actual dose amount can be matched. it can.

  Next, although the Example of this invention is described with reference to FIGS. 8-11, this invention is not limited to a following example.

Example 1
A ribbon beam having a beam intensity distribution having the shape shown in FIG. 8A is used to scan in both the X and Y axes so as to correct the in-plane distribution of the substrate to be processed due to the intensity distribution of the ribbon beam in the same manner as described above. Ion implantation was performed while controlling the speed. FIG. 8B shows the in-plane dose distribution after correction, and FIG. 8C shows the in-plane dose distribution when no correction is performed by scanning only in one direction without controlling the scan speed. 8B and 8C, the X axis represents the ribbon beam minor axis direction, Y represents the ribbon beam major axis direction, and Z represents the dose amount. The dose distribution was measured on a rectangular area formed on the wafer surface.

  A value (STD / AVE) obtained by dividing the standard deviation (STD) of the dose distribution in the measurement area by the average dose (AVE) in the measurement area is compared. While it was 1%, it was improved to 0.13% in the case with correction shown in FIG. 8B.

(Example 2)
Using a ribbon beam having a beam intensity distribution having the shape shown in FIG. 9A, scanning in both the X and Y axes is performed in a manner similar to the above to correct the in-plane distribution of the substrate to be processed due to the intensity distribution of the ribbon beam. Ion implantation was performed while controlling the speed. FIG. 9B shows an in-plane dose distribution after correction, and FIG. 9C shows an in-plane dose distribution when no correction is performed by scanning only in one direction without controlling the scan speed. 9B and 9C, the X axis represents the ribbon beam minor axis direction, Y represents the ribbon beam major axis direction, and Z represents the dose amount. The dose distribution was measured on a rectangular area formed on the wafer surface.

  A value (STD / AVE) obtained by dividing the standard deviation (STD) of the dose distribution in the measurement area by the average dose (AVE) in the measurement area is compared. Compared to 4%, in the case with correction shown in FIG. 9B, it was improved to 0.55%.

(Example 3)
A ribbon beam having a beam intensity distribution having the shape shown in FIG. 10A is used to scan in both the X and Y axes so as to correct the in-plane distribution of the substrate to be processed due to the intensity distribution of the ribbon beam in the same manner as described above. Ion implantation was performed while controlling the speed. FIG. 10B shows an in-plane dose distribution after correction, and FIG. 10C shows an in-plane dose distribution when no correction is performed by scanning only in one direction without controlling the scan speed. 10B and 10C, the X axis represents the ribbon beam minor axis direction, Y represents the ribbon beam major axis direction, and Z represents the dose amount. The dose distribution was measured on a rectangular area formed on the wafer surface.

  When a value (STD / AVE) obtained by dividing the standard deviation (STD) of the dose distribution in the measurement area by the average dose (AVE) in the measurement area is compared, the case of no correction shown in FIG. Compared to 9%, in the case with correction shown in FIG. 10B, it was improved to 0.55%.

Example 4
Using a ribbon beam having a beam intensity distribution having the shape shown in FIG. 11A, scanning is performed in both the X and Y axes so as to correct the in-plane distribution of the substrate to be processed due to the intensity distribution of the ribbon beam in the same manner as described above. Ion implantation was performed while controlling the speed. FIG. 11B shows the in-plane dose distribution after correction, and FIG. 11C shows the in-plane dose distribution in the case of no correction in which only one direction is scanned without controlling the scan speed. 11B and 11C, the X axis indicates the ribbon beam minor axis direction, Y indicates the ribbon beam major axis direction, and Z indicates the dose amount. The dose distribution was measured on a rectangular area formed on the wafer surface.

  A value (STD / AVE) obtained by dividing the standard deviation (STD) of the dose distribution in the measurement area by the average dose (AVE) in the measurement area is compared. While it was 1%, it was improved to 0.56% in the case with correction shown in FIG. 11B.

  The embodiment of the present invention has been described above. Of course, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

  For example, in the above embodiment, the substrate to be processed is scanned in two directions with respect to the ribbon beam, but the present invention is not limited to this, and three or more directions may be used. Also, the two scan directions are not limited to orthogonal directions.

  Furthermore, the scan speed control is not limited to the case where it is performed in all directions, and can be set as appropriate according to the beam intensity distribution, the existence distribution of the irradiated area (resist opening) on the wafer, etc. If speed control is sufficient, it may be performed only in the one direction.

It is a schematic block diagram of the ion implantation apparatus by embodiment of this invention. 5 is a schematic perspective view illustrating a beam scanning process for a wafer W. FIG. It is a figure which shows an example of the beam intensity distribution in the major axis direction of a ribbon beam. It is a figure which shows the other example of the beam intensity distribution in the long axis traverse of a ribbon beam. 5A and 5B are diagrams illustrating a process of scanning in the X-axis direction with a ribbon beam having the beam intensity distribution shown in FIG. 4, where A is a dose distribution after scanning, and B is an example of scan speed modulation. 5A and 5B are diagrams illustrating a process of scanning in the Y-axis direction with a ribbon beam having the beam intensity distribution shown in FIG. 4, where A is a dose distribution after scanning, and B is an example of scan speed modulation. It is explanatory drawing of 1 effect | action of the ion implantation apparatus of embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining Example 1 of this invention, A is a beam intensity distribution of a ribbon beam, B is an in-plane dose distribution which shows the result of the example of application of this invention, C shows the result of the example of application of a prior art. Each in-plane dose distribution is shown. It is a figure explaining Example 2 of this invention, A is the beam intensity distribution of a ribbon beam, B is the in-plane dose distribution which shows the result of the example of application of this invention, C shows the result of the example of application of a prior art. Each in-plane dose distribution is shown. It is a figure explaining Example 3 of this invention, A is the beam intensity distribution of a ribbon beam, B is the in-plane dose distribution which shows the result of the example of application of this invention, C shows the result of the example of application of a prior art. Each in-plane dose distribution is shown. It is a figure explaining Example 4 of this invention, A is the beam intensity distribution of a ribbon beam, B is the in-plane dose distribution which shows the result of the application example of this invention, C shows the result of the application example of a prior art. Each in-plane dose distribution is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ion implantation apparatus 2 Beam irradiation source 3 Stage (support member)
4 linear movement mechanism part 5 rotation mechanism part 6 beam intensity measuring device (measuring means)
7 Control unit (control means)
10 Ribbon beam W Wafer (Substrate to be processed)

Claims (5)

A wide ribbon beam and the target substrate, by relatively moving the first and second axes mutually orthogonal directions an ion implantation method of performing ion implantation,
Measure the intensity distribution of the ribbon beam in the beam width direction,
The beam width direction and the first axial direction are orthogonal to each other, and the substrate to be processed is scanned in the first axial direction with respect to the ribbon beam at a scanning speed proportional to the intensity distribution ,
An ion implantation method in which the beam width direction and the second axial direction are orthogonal to each other, and the substrate to be processed is scanned in the second axial direction with respect to the ribbon beam at a scanning speed proportional to the intensity distribution .   The ion implantation method according to claim 1, wherein a width of the ribbon beam is larger than a diameter or an outer dimension of the substrate to be processed. 3. The ion according to claim 2 , wherein a beam current of the ribbon beam is monitored on the outer side of the substrate to be processed at the time of ion implantation, and a scan speed of the substrate to be processed is controlled in accordance with a variation amount of the beam current. Injection method. A beam irradiation source for irradiating a wide ribbon beam;
A support member for supporting the substrate to be processed ;
A rotation mechanism that rotates the support member over a predetermined angular range;
A linear movement mechanism that linearly moves the support member in any of first and second axial directions orthogonal to each other ;
Beam measuring means for measuring the intensity distribution in the beam width direction of the ribbon beam;
Control means for controlling the rotational drive of the rotating mechanism and the moving speed of the linear moving mechanism ,
The control means includes
When scanning the ribbon beam in the first axial direction, the beam width direction and the first axial direction are orthogonal to each other, and the support member is moved to the first axis at a scanning speed proportional to the intensity distribution. Controlling the rotation mechanism unit and the linear movement mechanism unit to move in a direction ,
When scanning the ribbon beam in the second axial direction, the beam width direction and the second axial direction are orthogonal to each other, and the support member is moved to the second axis at a scanning speed proportional to the intensity distribution. An ion implantation apparatus that controls the rotation mechanism unit and the linear movement mechanism unit to move in a direction . The beam measuring means monitors the beam current of the ribbon beam on the outer side of the substrate to be processed, and the control means controls the moving speed of the linear moving mechanism based on the output of the beam measuring means. 4. The ion implantation apparatus according to 4 .