JP3519892B2 - Single-wafer ion implantation apparatus adjustment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a single-wafer type ion implanter.

[0002]

2. Description of the Related Art A hybrid scan method is generally used in a single-wafer ion implantation apparatus. In this method, as shown in FIG. 6 (A), while the wafer 10 is mechanically scanned in the Y direction in the drawing at about 1 HZ, the ion beam 11 is drawn by an electromagnetic or electrostatic deflector 12 in the drawing X.
Scan in the direction of 100 to 1000 Hz. Figure 6
In (A), the dotted line shows the beam at the time of wafer left edge irradiation.
The dashed line shows the beam at the time of irradiation of the right edge of the wafer.

The ion beam amount distribution when the ion beam 11 is applied to one point on the wafer 10 is as shown in FIG. 6 (B). Half-width W that indicates the spread of the ion beam
Increases in inverse proportion to the 3/2 power of the energy E of the ion beam 11. Therefore, the lower the beam energy E is, the more the ion beam 11 is scanned along the line 13 at a constant speed, as shown in FIG. 6C.
The dose nonuniformity at the end of the scanning range of 1 becomes large.

In order to make this uniform, ion beam amount distribution uniform adjustment is performed as shown in FIG. (20)
The speed V (X) at which the deflector 12 scans the ion beam 11 in the X direction is adjusted. That is, a Faraday cup (not shown) having a receiving portion diameter smaller than the cross-sectional diameter of the ion beam 11 is arranged on the front surface of the wafer 10, and the Faraday cup is line 13 for the ion beam 11 which is reciprocally scanned at high speed as described above. The current of the ion beam 11 captured while being mechanically scanned at a constant speed along is detected, and the value obtained by integrating this current while the Faraday cup travels a unit distance is measured as the ion beam amount, and the ion beam amount along the X direction is measured. Scanning speed V (X) so that the distribution of
Adjust.

(21) The dispersion degree Dis of the ion beam amount, for example, the standard deviation σr is measured. (22) If Dis> ε, the process returns to step 20. If not, the ion beam amount distribution uniform adjustment is completed. ε is, for example, 1% when the dispersion degree Dis is the standard deviation σ. Such uniform adjustment of the ion beam amount distribution is performed by, for example, adjusting the wafer 10 to 25
It is performed every time a single ion implantation process is performed.

[0006]

However, the lower the beam energy E used, the longer the adjustment time for uniformizing the ion beam amount distribution, and at a low energy of 5 kV or less, the upper limit value (for example, 30 minutes) of the adjustment time is set. After a while
The standard deviation σ could not be reduced to 1% or less. In view of such problems, an object of the present invention is to provide a single-wafer-type ion implantation apparatus adjustment method capable of shortening the ion beam amount distribution uniform adjustment time.

Another object of the present invention is to provide a method for adjusting a single-wafer-type ion implanter capable of performing low-energy ion beam implantation at a required sheet resistance dispersion degree or less.

[0008]

According to another aspect of the present invention, there is provided a single-wafer-type ion implantation apparatus adjusting method, which is based on a ratio of a sheet resistance change amount to a dose change amount when uniformly implanting ions into an object. Then, a permissible upper limit of the degree of dispersion of the ion beam is determined, and the single-wafer ion implantation apparatus is adjusted so that the degree of dispersion of the amount of ion beam is equal to or less than the permissible upper limit.

According to this single-wafer-type ion implantation apparatus adjusting method, the smaller the absolute value of the above ratio, the larger the allowable upper limit value of the ion beam amount dispersion degree for the same required sheet resistance dispersion degree value. The effect of shortening the adjustment time for uniformizing the distribution of the amount of ion beam is shortened, and it greatly contributes to the improvement of the throughput of the ion implantation process.

Further, as described above, the allowable upper limit value of the ion beam amount dispersion degree can be made larger than in the conventional case,
It is possible to perform low-energy ion beam implantation, which was impossible in the past, at a required sheet resistance dispersion degree or less. In the method for adjusting a single-wafer-type ion implantation apparatus according to a second aspect, in the first aspect, the allowable upper limit value of the degree of dispersion is determined under the condition that the dose is substantially equal to the upper limit of the allowable value.

According to this single-wafer-type ion implantation apparatus adjusting method, the upper limit of the allowable ion beam amount dispersion degree can be further increased, so that the above effect can be enhanced. According to the single-wafer-type ion implantation apparatus adjusting method of the third aspect, the dose is set to 1 × 10 ¹⁵ cm ^-2 or more when the beam energy is 5 kV or less. In the method for adjusting a single-wafer type ion implantation apparatus according to claim 4, in any one of claims 1 to 3, the dispersion degree is a standard deviation, and the standard deviation of the sheet resistance distribution in the ion implantation region is 1% or less. The dose value is determined so that the standard deviation upper limit value of the ion beam amount is 6 to 2% with respect to the request.

In the method for adjusting a single-wafer-type ion implantation apparatus according to a fifth aspect, in any one of the first to fourth aspects, the ratio of the sheet resistance change amount to the dose change amount is the sheet resistance sensitivity S = (Δρs / ρs) / (ΔD / D), where ρs is the sheet resistance, D is the dose, and Δρs is the amount of change in the sheet resistance when the dose D is changed by ΔD under a constant beam energy.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the ion implantation apparatus, as described in the section of the related art, the ion beam amount distribution uniform adjustment is performed so that the standard deviation σr as the dispersion degree Dis of the ion beam amount distribution is, for example, 1% or less.

However, in order to reduce the variations in the characteristics of the circuit elements formed on the wafer, it is sufficient to make the sheet resistance ρs of the ion-implanted region after annealing uniform. Therefore, the relationship between the sheet resistance ρs and the dose D is calculated by a computer using the following empirical formula, and is calculated using FIGS. 3 (A), (B) and FIG.
The results shown in are obtained. ρ = 44.9 EXP (9.23 × 10 ¹⁶ / n) +47
0.5 / [1+ {n / (2.23 × 10 ¹⁷ )} ^0.719 ]
−29 / (1 + 6.1 × 10 ²⁰ / n) ² ρs = 1 / ∫ {1 / (eρn)} dZ where ρ is resistivity and impurity concentration n is activated (functions as a carrier) The impurity concentration, e is the absolute value of the electron charge amount, the Z axis is the direction perpendicular to the wafer surface (depth direction), the integral range of Z is 0 to ∞, and Z = 0 is the position on the wafer surface.

The impurity concentration n is a function of the beam energy E, the dose D and the depth Z, and is known experimentally. In FIG. 5, E = 2 kV, 5 kV, 10 kV and 50 k.
The relationship of the impurity concentration n with respect to the depth Z in the case of implanting V = 1 boron ions at D = 1 × 10 ¹⁵ cm ^-2 is shown. The impurity concentration n in FIG. 5 is a concentration that does not matter whether it is active or inactive.
The upper limit value (solid solubility) of the concentration of activated impurities differs depending on the annealing condition. When the impurity concentration n in FIG. 5 exceeds the solid solubility, the impurity concentration n in the calculation of the sheet resistance ρs is fixed. The solubility was taken.

3 (A), (B) and FIG. 4 respectively,
This is a case where boron B having a beam energy E of 20 kV, 5 kV, and 2 kV is ion-implanted by the method of FIG. 6A, and when the dose D becomes a certain value or more, the sheet resistance ρs with respect to the variation ΔD of the dose D. It can be seen that the ratio of the change amount Δρs of is small. The reason why the sheet resistance is reduced by annealing even at the same dose value is that the inactive implanted ions are activated (function as carriers) by annealing.

As the absolute value of the ratio Δρs / ΔD is smaller, the allowable upper limit value of the dose distribution with respect to the same required value of the sheet resistance dispersion is larger, so that the ion beam amount distribution uniform adjustment time in FIG. 7 is shortened. To be done. Here, the sheet resistance sensitivity S obtained by making the above ratio dimensionless is defined as S = (Δρs / ρs) / (ΔD / D). 1 (A), (B) and FIG. 2 respectively,
The sheet resistance sensitivity S is obtained based on the results shown in FIGS. 3A, 3B and 4.

For example, E = 2 kV, D = 1 × 10 ¹⁵ cm ^-2
Further, in the case of no annealing, the sheet resistance sensitivity S is as small as about 0.2 from FIG. 2, and if ΔD / D is 5% or less, Δρs / ρs can be 1% or less. Therefore, for example, in the source and drain regions of the MOSFET, E =
When forming under the condition of 2 kV and Δρs / ρs ≦ 0.01, by setting D = 1 × 10 ¹⁵ cm ⁻² , ΔD
/ D (actually, the standard deviation of the beam dose distribution, the same applies hereinafter) may be set to 5% or less, and the ion beam dose distribution uniform adjustment of FIG. 7 performed before this formation is completed in a few minutes. Conventionally, the relationship between the sheet resistance sensitivity S and the dose D defined by the present inventor was unknown, so that, for example, E
= 2 kV and ΔD / D ≦ 0.01 were required, and the ion beam amount distribution uniform adjustment in FIG. 7 could not be completed in 30 minutes.

The dose D is 10 ¹⁵ cm ^-2 as in the LDD (Lightly Doped drain) structure and the Extension structure.
If the following restrictions apply, ΔD / D is set to 1
Must be below%. Such a limitation can also be understood from the relationship between the sheet resistance sensitivity S and the dose D. The ion beam amount distribution shown in FIG. 7 was adjusted to be uniform, and boron (E) of 5 kV was implanted into the wafer by D = 1 × 10 ¹⁵ cm ^-2 by the method of FIG. 6 (A) and annealed at 850 ° C. for 30 minutes. Standard deviation σd of dose D
And the standard deviation σs of the sheet resistance ρs was measured, and the following results were obtained.

(1) σd = 1.31%, σs = 0.279%, σs / σd = 0.21 (2) σd = 7.0%, σs = 1.87%, σs / σd = 0. 27 Under the above conditions, S = −0.8 is relatively large from the calculation shown in FIG. 1 (B), but the measured value is small like the above value of σs / σd. This is D = 1 × 10 ¹⁵
Since the change in S is abrupt at cm ^-2 , it is considered that there is a large error from the actual measurement.

From the results of (1) and (2), for example, σs
The standard deviation σd when = 1% is 4% by the linear interpolation method.
And when the condition σs ≦ 1% is required, D = 1
× With 10 ^{1 5} cm ^-2, the steps of FIG. 7 22
Is set to 0.04, which shortens the ion beam amount distribution uniform adjustment time in FIG. Generally, the condition σs ≦ 1
It has been found that the dose value can be set so that σd is 6 to 2% with respect to the requirement of%.

The present invention includes various modifications other than the above. For example, the ion beam scanning method is not limited to the hybrid scanning method, and may be a method in which a wide ion beam is used and scanning in the width direction is not performed.

[Brief description of drawings]

FIG. 1 is a diagram showing calculated values of sheet resistance sensitivity to dose.

FIG. 2 is a diagram showing calculated values of sheet resistance sensitivity with respect to dose.

FIG. 3 is a diagram showing calculated values of sheet resistance with respect to dose.

FIG. 4 is a diagram showing calculated values of sheet resistance with respect to dose.

FIG. 5 is a diagram showing the beam energy dependence of the impurity concentration distribution of boron in the implantation depth direction.

FIG. 6 is an explanatory diagram of an ion beam amount distribution in ion beam irradiation.

FIG. 7 is a schematic flowchart showing a procedure for uniformizing a beam dose distribution.

[Explanation of symbols]

10 wafers 11 ion beam 12 deflector

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/265 H01J 37/317 C30B 31/22

Claims (5)

(57) [Claims] 1. A permissible upper limit of the degree of dispersion of the ion beam is determined based on the ratio of the amount of change in sheet resistance to the amount of change in dose when uniformly implanting ions into an object. A single-wafer-type ion implanter adjusting method, comprising adjusting the single-wafer-type ion implanter so as to be equal to or less than an allowable upper limit value. 2. The method for adjusting a single-wafer ion implanter according to claim 1, wherein the allowable upper limit of the dispersion degree is set under the condition that the dose is substantially equal to the upper limit of the allowable value. 3. The method for adjusting a single-wafer ion implanter according to claim 1, wherein the dose is set to 1 × 10 ¹⁵ cm ⁻² or more when the beam energy is 5 kV or less. 4. The above-mentioned dispersion degree is a standard deviation, and the dose is adjusted so that the upper limit of the standard deviation of the ion beam amount is 6 to 2% in response to the requirement that the standard deviation of the sheet resistance distribution in the ion implantation region is 1% or less. 4. The method for adjusting a single-wafer-type ion implanter according to claim 1, wherein the value of is determined. 5. The ratio of the sheet resistance change amount to the dose change amount is the sheet resistance sensitivity S = (Δρs / ρs) /
(ΔD / D), wherein ρs is a sheet resistance, D is a dose, and Δρs is a sheet resistance change amount when the dose D is changed by ΔD under a constant beam energy. The method for adjusting a single-wafer-type ion implantation apparatus according to any one of 1 to 4.