Ion implantation method and ion implantation apparatus performing the same

Abstract

The present invention provides an improved ion implantation method and an ion implantation apparatus for performing the improved ion implantation method, belongs to the field of ion implantation technology, which can solve the problem of the poor stability and uniformity of the ion beam of the existing ion implantation apparatus. The improved ion implantation method of the invention comprises steps of: S1, detecting densities and beam distribution nonuniformities under various decelerating voltages; S2, determining an operation decelerating voltage based on the beam densities and the beam distribution nonuniformities; and S3, performing an ion implantation under the determined operation decelerating voltage. The present invention ensures the uniformity and stability of the ion beam, and thus ensures the uniformity of performances of the processed base materials in each batch or among various batches.

Claims

1. An ion implantation method comprising steps of: S1, detecting beam current densities and non-uniformities of beam current density distribution under various decelerating voltages; S2, determining an operation decelerating voltage based on the beam current densities and the non-uniformities of beam current density distribution; and S3, performing an ion implantation under the determined operation decelerating voltage, wherein S1 comprises steps of: S11, setting initial values of parameters, including: setting an initial value of the decelerating voltage to V.sub.0, the beam current density to .sub.0, the non-uniformity of beam current density distribution to x.sub.0, an optimization range of the decelerating voltage to V.sub.0L, a control error range of the beam current density to p, and the non-uniformity of beam current density distribution to be less than q, and S12, preliminarily determining starting points for optimization of the decelerating voltage, wherein m different decelerating voltage test points are taken within the optimization range of the decelerating voltage V.sub.0L, and beam current densities .sub.g and non-uniformities of beam current density distribution x.sub.g under the m test points are measured, respectively.

2. The ion implantation method of claim 1, wherein S2 comprises steps of: S21, filtering the starting points for optimization of the decelerating voltage, including: taking decelerating voltages at n test points, under which the beam current density .sub.g and the non-uniformity of beam current density distribution x.sub.g satisfy |.sub.g.sub.0|<p and x.sub.g<q, as a starting-point set for optimization of the decelerating voltage; and ranking the n starting points for optimization of the decelerating voltage according to an order of the non-uniformities of beam current density distribution x.sub.g from the smallest one to the biggest one, and taking them as starting points for optimization of the decelerating voltage sequentially; S22, evaluating pre-operation decelerating voltages, sequentially evaluating the starting points for optimization of the decelerating voltage, performing an ion implantation process under a decelerating voltage V.sub.i corresponding to the i-th starting point for optimization of the decelerating voltage, obtaining a non-uniformity of beam current density distribution x.sub.i corresponding to the decelerating voltage V.sub.i, detecting and recording corresponding non-uniformities of beam current density distribution every a predetermined time interval for k times, and defining the recorded non-uniformities of beam current density distribution as x.sub.ir[x.sub.i1, x.sub.i2, . . . x.sub.ik]; S23, determining an operation decelerating voltage, including: comparing an error ratio value |x.sub.irx.sub.i|/x.sub.i between x.sub.ir and x.sub.i with a control error upper limit W of the non-uniformity of beam current density distribution; when all x.sub.ir satisfy (|x.sub.irx.sub.i/x.sub.i)<W, determining the decelerating voltage V.sub.i corresponding to the i-th test point as the operation decelerating voltage; and when at least one x.sub.ir satisfies (|x.sub.irx.sub.i|/x.sub.i)W, performing S22 for the decelerating voltage V.sub.i+1.

3. The ion implantation method of claim 1, wherein p is 5%, and q is 10%.

4. The ion implantation method of claim 2, wherein p is 5%, and q is 10%.

5. The ion implantation method of claim 1, wherein m is a natural number equal to or more than 10.

6. The ion implantation method of claim 2, wherein m is a natural number equal to or more than 10.

7. The ion implantation method of claim 3, wherein m is a natural number equal to or more than 10.

8. The ion implantation method of claim 4, wherein m is a natural number equal to or more than 10.

9. The ion implantation method of claim 1, wherein L=V.sub.0/5.

10. The ion implantation method of claim 2, wherein L=V.sub.0/5.

11. The ion implantation method of claim 3, wherein L=V.sub.0/5.

12. The ion implantation method of claim 4, wherein L=V.sub.0/5.

13. The ion implantation method of claim 1, wherein them test points are uniformly distributed within the optimization range of the decelerating voltage V.sub.0L.

14. The ion implantation method of claim 2, wherein the m test points are uniformly distributed within the optimization range of the decelerating voltage V.sub.0L.

15. The ion implantation method of claim 3, wherein the m test points are uniformly distributed within the optimization range of the decelerating voltage V.sub.0L.

16. The ion implantation method of claim 2, wherein W is 3%.

17. The ion implantation method of claim 2, wherein k is a natural number equal to or more than 10.

18. The ion implantation method of claim 1, wherein S3 comprises a step of performing the ion implantation process on at least one base material under the determined operation decelerating voltage.

19. An ion implantation apparatus for performing the ion implantation method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flowchart of an ion beam control method of an ion implantation apparatus in the embodiment 1 of the present invention.

(2) FIG. 2 is a flowchart illustrating how to detect the beam current densities and the non-uniformities of beam current density distribution under various decelerating voltages in the embodiment 1 of the present invention.

(3) FIG. 3 is a flowchart illustrating how to determine the operation decelerating voltage based on the beam current densities and the non-uniformities of beam current density distribution in the embodiment 1 of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(4) In order to make persons skilled in the art better understand the solutions of the present invention, the present invention will be further described in detail below in conjunction with the drawings and embodiments.

(5) The present invention provides an improved ion implantation method, which may be used in any type of ion implantation, so that the beam current density and the non-uniformity of beam current density distribution are within a predetermined control range, so as to ensure the uniformity of performances of the substrates subjected to the ion implantation in the same batch or among various batches.

Embodiment 1

(6) As shown in FIG. 1, the invention provides an improved ion implantation method comprising steps of:

(7) step S1, detecting beam current densities and non-uniformities of beam current density distribution under various decelerating voltages; step S2, determining an operation decelerating voltage based on the beam current densities and the non-uniformities of beam current density distribution; and

(8) step S3, performing an ion implantation under the determined operation decelerating voltage.

(9) Specifically, as shown in FIG. 2, the step S1 comprises following steps.

(10) Step S11, setting initial values of parameters.

(11) Specifically, the control parameters of an ion implantation process are set as follows: setting an initial value of the decelerating voltage to V.sub.0, the beam current density to .sub.0, the non-uniformity of beam current density distribution to x.sub.0, an optimization range of the decelerating voltage to V.sub.0L, a control error range of the beam current density to p, and the non-uniformity of beam current density distribution to be less than q.

(12) Preferably, the initial value of the decelerating voltage V.sub.0 is a decelerating voltage when the former process is stable; the beam current density .sub.0 and the non-uniformity of beam current density distribution x.sub.0 are the beam current density and the non-uniformity of beam current density distribution corresponding to the decelerating voltage when the former process is stable. When an operator thinks that the ion implantation process is unstable, he/her may adjust the decelerating voltage near its initial value V.sub.0 to ensure the stability of the ion implantation process among batches.

(13) Process control parameters q, p and L of the ion implantation apparatus are set experientially depending on the performance of the ion implantation apparatus and requirements on processing of the base material. Preferably, the non-uniformity of beam current density distribution is less than 10%, namely, q is 10%; the control error range of the beam current density p is 5%. Preferably, the optimization range of the decelerating voltage V.sub.0L is V.sub.0V.sub.0/5.

(14) Step S12, preliminarily determining starting points for optimization of the decelerating voltage,

(15) wherein taking m different decelerating voltage test points within the optimization range of the decelerating voltage V.sub.0L, and measuring beam current densities .sub.g and non-uniformities of beam current density distribution x.sub.g under the m test points, respectively.

(16) Preferably, m is a natural number equal to or more than 10, and the more the test points are selected, the more accurate the decelerating voltage obtained by optimization is.

(17) Preferably, the m test points are uniformly distributed within the optimization range of the decelerating voltage V.sub.0L, so that the preferable operation decelerating voltage is not easily be omitted.

(18) It should be understood that, a method for detecting the beam current density and the non-uniformity of beam current density distribution under a specific decelerating voltage is described above, however, other similar methods in the prior art are applicable.

(19) As shown in FIG. 3, the step S2 comprises following steps.

(20) Step S21, filtering the starting points for optimization of the decelerating voltage.

(21) Decelerating voltages at n test points, under which the beam current density .sub.g and the non-uniformity of beam current density distribution x.sub.g satisfy |.sub.g.sub.0|<p and x.sub.g<q, are taken as a starting-point set for optimization of the decelerating voltage; that is, the above m test points are filtered to find out n test points as the starting point set for optimization of the decelerating voltage.

(22) Next, the filtered n starting points for optimization of the decelerating voltage are ranked according to an order of the non-uniformities of beam current density distribution x.sub.g from the smallest one to the biggest one, used as starting points for optimization of the decelerating voltage sequentially, and respectively recorded as (x.sub.g1, x.sub.g2, . . . , x.sub.gi, . . . , x.sub.gn). For a test point, the smaller the non-uniformity of beam current density distribution is, the better the quality of the ion beam thereof is, therefore, in a case that the beam current density is within a certain error range of a set target beam current density, a decelerating voltage corresponding to the test point with small non-uniformity of beam current density distribution is first selected to evaluate, wherein 1in.

(23) Step S22, evaluating pre-operation decelerating voltages.

(24) The starting points for optimization of the decelerating voltage are taken as pre-operation decelerating voltages, and the size of a fluctuation range of the non-uniformities of beam current density distribution corresponding to each pre-operation decelerating voltage at different time points is taken as a criterion for evaluating the pre-operation decelerating voltage to determine whether the pre-operation decelerating voltage is an operation decelerating voltage.

(25) Specifically, the pre-operation decelerating voltages are sequentially evaluated according to the order of the starting points for optimization of the decelerating voltage. First, the pre-operation decelerating voltage V.sub.1 determined in the step S21 corresponding to the smallest non-uniformity of beam current density distribution x.sub.g1 is evaluated. For example, the evaluating procedure of every pre-operation decelerating voltage V.sub.i is as follows: performing an ion implantation process under the decelerating voltage V.sub.i corresponding to the i-th starting point for optimization of the decelerating voltage, obtaining a non-uniformity of beam current density distribution x.sub.i corresponding to the decelerating voltage V.sub.i in the step S12, detecting and recording corresponding non-uniformities of beam current density distribution every a time period of t for k times, and defining the recorded non-uniformities of beam current density distribution as x.sub.ir[x.sub.i1, x.sub.i2, . . . x.sub.1k];

(26) Preferably, k is a natural number equal to or more than 10, and the more the test points are, the more adequate the data for optimization of the decelerating voltage is.

(27) It should be understood that, the above parameters may be adjusted depending on experience and application scene, for example, the length of the time period of t and the number k of the time periods may be combinedly adjusted.

(28) Step S23, determining an operation decelerating voltage.

(29) comparing an error ratio value |x.sub.irx.sub.i/x.sub.i between the x.sub.ir and x.sub.i with a control error upper limit W of the non-uniformity of beam current density distribution;

(30) wherein, preferably, W is 3%, which requires that the fluctuation range of corresponding non-uniformities of beam current density distribution of the pre-operation decelerating voltage at various time points is small, and of course, W may be adjusted according to a specific application scene.

(31) Specifically, when all x.sub.ir satisfy (|x.sub.irx.sub.i|/x.sub.i)<W, the decelerating voltage V.sub.i corresponding to the i-th test point is determined as the operation decelerating voltage, the step S23 of determining the operation decelerating voltage is completed, and then the step S3 is performed, that is, the ion implantation process is performed under the operation decelerating voltage.

(32) When at least one x.sub.ir satisfies (|x.sub.irx.sub.i|/x.sub.1)W, i=i+1 is performed, and the step S22 is performed, namely, the next start point for optimization of the decelerating voltage V.sub.i+1 (that is, next per-operation decelerating voltage V.sub.i+1) is evaluated, and whether the per-operation decelerating voltage is the operation decelerating voltage is determined by the step S23, if yes, the step S23 of determining the operation decelerating voltage is completed and then the step S3 is performed, namely, the ion implantation process is performed under the operation decelerating voltage V.sub.i+1; and if no, the step S22 is performed, that is, the pre-operation decelerating voltage V.sub.i+2 is evaluated, and whether the per-operation decelerating voltage is the operation decelerating voltage is determined by the step S23 to determine the operation decelerating voltage. In the present embodiment, the above operations are performed repeatedly till an operation decelerating voltage is determined.

(33) In summary, the operation decelerating voltage obtained in embodiments of the invention is acquired by sequentially evaluating the pre-operation decelerating voltages with respect to the selected starting points for optimization of the decelerating voltage in the order of the non-uniformities of beam current density distribution from the smallest one to the biggest one, that is to say, if the pre-operation decelerating voltage V.sub.1 corresponding to the smallest non-uniformity of beam current density distribution x.sub.g1 in the step S21 is determined as the operation decelerating voltage by the step S22 and the step S23, then the step S3 may be performed, namely, the ion implantation process is performed under the operation decelerating voltage V.sub.1. If the pre-operation decelerating voltage V.sub.1 corresponding to the smallest non-uniformity of beam current density distribution x.sub.g1 in the step S21 is not determined as the operation decelerating voltage by the step S22 and the step S23, then the pre-operation decelerating voltage V.sub.2 corresponding to the second smallest non-uniformity of beam current density distribution x.sub.g2 is evaluated, and so on, till an operation decelerating voltage is determined.

(34) After the operation decelerating voltage is determined by the steps S21, S22 and S23 in FIG. 3, the ion implantation process is performed on at least one base material under the determined operation decelerating voltage, preferably, the number of the base materials is 10, and of course, the number of the base materials may be increased or reduced as desired.

(35) The ion implantation apparatus performs ion implantation process on the base material under the operation decelerating voltage determined according to the embodiment of the invention, the uniformity and stability of the ion beam is ensured, and thus uniformity of performances of the processed base materials in each batch or among various batches may be ensured, therefore, uniformity of performances of semiconductor devices made of the base materials may be ensured.

(36) It should be understood that, the above embodiments are only exemplary embodiments employed to illustrate the principle of the invention, and the invention is not limited thereto. Persons skilled in the art can make various modifications and improvements without departing from the principle and substance of the invention, and these modifications and improvements should be considered to be within the protection scope of the invention.