JPH0237657A - Ion implanter for semiconductor substrate - Google Patents

Abstract

PURPOSE:To enable a dose amount to be kept constant over the whole semiconductor substrate by scanning an ion beam in such a way as to compare ion beam charge amounts supplied into respective Faraday cups with a reference value so as to detect ununiformity in the charge amounts and correct the ununiformity. CONSTITUTION:There are provided a Faraday cup group 7 comprising a plurality of Faraday cups 8-1 through 8-n arranged along the scanning direction X of an ion beam and a means 11 for comparing ion beam charge amounts supplied into the respective Faraday cups with a reference value so as to detect ununiformity in the charge amounts between the respective cups. An output from the ununiformity detecting means 11 is fed back to an ion beam scanning means 3, and thereat, the scanning means 3 scans an ion beam 5 in such a way as to correct the ununiformity. This can keep a dose amount in an ion beam scanning direction constant.

Description

[Detailed Description of the Invention] [Summary] Regarding a single-wafer type ion implantation device for a semiconductor substrate, the purpose is to make it possible to make the dose constant over the entire surface of the semiconductor substrate. In an apparatus for implanting ions into the semiconductor substrate by scanning an ion beam with an ion beam scanning means in at least one of two directions, an ion beam is scanned in at least one of two directions: A Faraday cup group consisting of a plurality of Faraday cups arranged side by side along the scanning direction of the ion beam with an opening on the same plane as the surface of the semiconductor substrate, and an amount of ion beam charge flowing into each Faraday cup. It comprises means for detecting non-uniformity in the amount of ion beam charge between each Faraday cutter 1 by comparing it with a reference value, and feeding back the output from the non-uniformity detecting means to the ion beam scanning means. An ion beam scanning means is configured to scan the ion beam so that the non-uniformity is corrected.

[Industrial application field]

The present invention relates to a single-wafer type ion implantation apparatus for semiconductor substrates.

In order to ensure that the electrical characteristics of each IC chip cut out from a semiconductor substrate are approximately equal, the ion implantation device must be configured so that the dose interval is constant over the entire surface of the conductor substrate. .

[Conventional technology]

Conventionally, there is a configuration in which a Faraday cup is arranged to monitor the irradiation state of the ion beam.

[Problems solved by the invention]

In this configuration, the VL position is simply monitored, and the scanning state of the ion beam is not changed from time to time, making it difficult to maintain a constant dose.

The present invention relates to an ion implantation apparatus for a semiconductor substrate that makes it possible to maintain a constant dose over the entire surface of the semiconductor substrate.

[Means to solve the problem]

FIG. 1 shows the original configuration of the ion implantation apparatus of the present invention.

1 is a semiconductor substrate, which is a wafer.

2 is an ion source, 3 is an X-direction scanning means, and 4 is a Y-direction scanning means. , the X direction and the Y direction are perpendicular to each other on the substrate 1. Each scanning means 3.4 is electrostatic or magnetostatic.

The ion beam 5 from the ion source 2 is transmitted to each scanning means 3.
After 4, ■→■→■...C)→■→Spit)...■→
■→■→■...
The wafer 1 is scanned in the X2 direction and then scanned in the Y+ and Y2 directions multiple times, and ions are implanted into the wafer 1 during this process. However, strictly speaking, the path ■→■, the path O→■, the path ■→O again, etc. are made so that they are crossed by only f times, so that the ion beam 5 is spread throughout the wafer 1.

The ion beam 5 extends beyond the wafer 1 and scans it. 6
is the overscan area.

7 is a group of Faraday cups in the X (generic term for X+ and X2), which includes a plurality of Faraday cups 8-1 to 8-.
η are closely aligned in the X direction and arranged in the overscan region 6 above the sea urchin box in the figure.

9 is a group of faraday cups 10-1 to 10-1 in the Y direction (general term for Y+, Y2);
10-m are closely aligned in the Y direction, and the Yerbaski [? It is placed in the control area 6.

The Faraday cup 8-+ has an opening 8 as shown in FIG.
-1a is placed on the same plane as the surface 1a of the wafer 1. Iya's Faraday Cup 8-2~8
n, 10+ to 10-m are similarly arranged.

11 is an X-direction charge non-uniformity detection means ■→■→■
The amount of charge of the ion beam flowing into each of the 71 Faraday cups 1a1 to 8-1 during the scanning process is compared with the average value from the average value forming means 12, and
The degree of non-uniformity in the amount of charge of the ion beam is detected.

The signal from the means 11 is applied to the X-direction scanning means 3 and fed back.

13 is a Y-direction charge inhomogeneity detection means ■→■...
・In the process of scanning →@, each Faraday cup 10−τ~1
The amount of charge of the ion beam flowing into 0-m is compared with the average value from the average value forming means 14 to determine the degree of non-uniformity of the amount of charge of the ion beam between each Faraday cup 10-1 to 10-m. Detect.

The signal from the means 13 is applied to the Y-direction scanning means 4 and fed back.

C Effect] The X-direction scanning means 3 is feedback-controlled, and the ion beam 5 scans in the X-direction so that non-uniformity regarding the dose M is corrected.

The Y-direction scanning means 3 is feedback controlled each time it scans in the X-direction, and the ion beam 5 is controlled in the Y-direction.
is scanned so that non-uniformities in dose are corrected.

By scanning the ion beam in this manner, ion implantation into the wafers 1 to 1 is performed such that the dose amount is constant over the entire surface of the wafer.

Note that, as shown in FIG. 3, if the Faraday cup 15 is arranged and the opening 15a is shifted from the surface 1a of the wafer 1, the ion beam 5 will be directed to the wafer surface 1.
There is a difference between the scanning speed at point a and the scanning speed at the aperture 15a, making it difficult to accurately detect the non-uniformity. However, Faraday Cup 8-1a (15
) are arranged as shown in FIG. 2, and the above-mentioned non-uniformity can be detected with high accuracy.

(Embodiment) FIG. 4 shows an ion implantation apparatus 20 for semiconductor substrates, which is an embodiment of the present invention. In the figure, parts corresponding to those shown in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted.

It is a single wafer type, and one wafer 1 is supported on a support plate 21.

First, the configuration and operation for uniformizing the dose in the X direction will be described.

Miller integration circuits 22-1 to 22-TI are connected to the Faraday cubes 8-1 to 8n, and are configured to hold integral values.

In FIG. 1, the current corresponding to the ion beam charge m flowing into each Faraday cup 8-1 to 8-1 during the scanning process of the ion beam from ■→■→■
It is output from + to 8-TI.

This is supplied to each mirror integration circuit 22-1 to 22-1, integrated and held.

23 is an amplifier with an amplification ratio of 1/n, and constitutes the average value forming means 12.

The voltages from each of the Miller integration circuits 22-1 to 22-1 are attenuated and averaged by the amplifier 23, and the average (
If voltage is output.

24-1 to 24-TI are differential amplifier circuits, and
This constitutes a load lifting non-uniformity detection means 11.

The voltages from the mirror integration circuits 22-1 to 22-η and the average voltage from the means 12 are applied to each differential amplifier circuit 24-1 to 24-1, and a voltage corresponding to the difference between the two is applied. is output to each output terminal 25-1 to 25η.

The voltage at each terminal 25-1 to 25-1 represents the non-uniformity of scanning at the position where the ion beam 5 scans each of the Faraday cups 8-+ to 8-1.

The voltage of each terminal 25-1 to 25 V is determined by the switch circuit 2.
6 and is sequentially applied to the transistor 27.

Reference numeral 28 denotes a triangular wave forming circuit for scanning in the X direction, which is composed of an integrating circuit including a transistor 27, two amplifiers, and a capacitor 30, and forms a triangular wave from a square wave.

31 is a square wave forming circuit, which forms a square wave of the X direction scanning frequency.

This square wave is supplied to a triangular wave forming circuit 28, where it is converted into a triangular wave and applied to the X-direction scanning means 3.

In this case, the time constant of the integrating circuit constituting the triangular wave forming circuit 28 is modulated by the voltage of each terminal 25-1 to 25'nl, and the circuit 28 outputs a triangular wave with a changed slope.

This gradient is a gradient in a direction that corrects the non-uniformity of scanning, and feedback is applied to the scanning means 3 so that the non-uniformity of scanning is corrected.

The X-direction scanning means 3 operates in response to a signal from the circuit 28, and the ion beam 5 scans ions at each location on the wafer 1 in the X+ and X2 directions. Scanning is performed by changing the scanning speed as appropriate so that the JI is constant. This results in
The dose amount at each portion of the upper wafer 1 in the X direction is constant.

Next, the configuration and operation for uniformizing the dose amount in the Y direction will be explained.

The structure of this part is substantially the same as the above structure, and substantially corresponding parts are given the same reference numerals with a suffix y, and their explanation will be omitted.

When the ion beam 5 completes one scan in the arrow Y+ and Y2 directions, the ion beam 5 is connected to the Faraday cup 10-+ to 10 at each output terminal 25-+V to 25-mV.
Scanning non-uniformity at the scanning position of m, i.e. Y
A voltage representing scan non-uniformity in the l and Y2 directions is output.

The square wave of the Y-direction scanning frequency from the square wave forming circuit 31y is converted into a triangular wave whose time constant is modulated by the above voltage in the triangular wave forming circuit 28y, and whose slope is changed in the direction of correcting scanning non-uniformity. , is fed back to the Y-direction scanning means 4.

The means 4 operates accordingly, and the ion beam 5 is scanned in the directions of arrows Y+ and Y2, changing the scanning speed as appropriate so that the amount of ion irradiation on each part of the wafer 1 is constant. Thereby, the dose amount at each portion of the upper wafer 1 in the Y direction is made constant.

As a result, ions are implanted into the wafer 1 in both the directions of the arrows X and Y, ie, so that the dose ω at each location on the entire surface is constant.

Therefore, the electrical characteristics of each IC chip cut out from this wafer 1 are approximately constant, and the yield of IC chips is improved.

32 is a reset terminal, to which a reset signal is applied when the wafer is replaced, and the integration circuits 22-+ to 22-T
I, 22−+ V ~ 22 mV reset.

Note that this embodiment can be applied regardless of the configuration of the scanning means 3.4, and can be applied not only to the parallel scanning method but also to the normal scanning method.

In the case of the parallel scan method, the scanning speed of the ion beam tends to fluctuate due to aberrations in the beam optical system, and the dose amount tends to change. According to the present invention, variations in the dose due to variations in the scanning speed of the ion beam are corrected.

In the case of a normal scanning method, the difference in the ion implantation angle on the wafer changes the line-of-sight area seen from the beam, the distance difference from the scanning electrode to the wafer, etc., and the dose changes due to this. Easy to do.

According to the present invention, fluctuations in the dose due to these factors are also corrected.

FIG. 5 shows a device 40 for implanting ions into a semiconductor substrate according to another embodiment of the present invention.

In this apparatus 40, the ion beam scanning means is only the X direction scanning means 3, and the wafer 1 is not mechanically moved in the Y direction. In FIG. 5, parts corresponding to those shown in FIG. 4 are given the same reference numerals, and their explanations will be omitted.

41 is a wafer movement mechanism, and 42 is a motor.

Reference numeral 43 designates one elongated Faraday cup, which is arranged in place of the Y-direction Faraday cup group 9 described above.

The scanning in the X+ and X2 directions is corrected and scanned in the same manner as in the previous embodiment.

Every time the ion beam scans the right side in the figure, a current is generated from the Faraday cup 43. This is applied to the motor 42 via the Ji ranger 44, the motor 42 rotates, the wafer moving mechanism 41 is driven, and the support plate 21 is moved together with the wafer 1 in the directions of arrows Y+ and Y2.

A current proportional to the amount of the ion beam is generated from the Faraday cup 43, and the motor 42 rotates in accordance with this current.

Therefore, the wafer 1 is moved at a speed proportional to the irradiation distance of the ion beam onto the Faraday cup 43.

As a result, the dose amount at each portion of the upper wafer 1 in the Y direction is made constant.

〔Effect of the invention〕

As explained above, according to the present invention, the ion beam can be
Scanning can be performed so that non-uniformity in the amount of ion beam charge between each Faraday cup is corrected. Thereby, ions can be implanted into the semiconductor substrate so that the dose in the ion beam scanning direction is made uniform.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the basic structure of the present invention, Fig. 2 is a drawing showing the arrangement of the Faraday cup with respect to the wafer, Fig. 3 is a drawing explaining the disadvantages when the Faraday cup is arranged behind the wafer, Fig. 4 5 is a diagram showing an ion implantation device according to one embodiment of the present invention, and FIG. 5 is a diagram showing an ion implantation device according to another embodiment of the present invention. In the figure, 1 is a wafer, 1a is a surface, 2 is an ion source, 3 is an X-direction scanning means, 5 is an ion beam, 6 is an overscan area, 7 is an X-direction Faraday cup group, 8-+ to 8-TI, 10 + ~10 m
9 is a Faraday cup group in the Y direction, 11 is an X direction charge suspension non-uniformity detection means, 12.14 is an average value forming means, 13 is a Y direction charge amount inconsistency detection means, and 20.40 is a Y direction charge amount inconsistency detection means. Ion implantation device, 21 is a support plate, 22-1 to 22T+- are Miller integration circuits, 23 is an amplifier, 24-1 to 24-η are differential amplifier circuits, 25-1 to 25 TI are output terminals, 26 is a switch circuit, 27 is a transistor, 28 is a triangular wave forming circuit for scanning in the X direction, 29 is an amplifier, 30 is a capacitor, 31 is a square wave forming means, 32 is a reset terminal, 41 is a wafer moving mechanism, 42 is a motor, 43 is an elongated Faraday cup, 44 does not show amplifier. @Figure 2 Patent applicant Fujitsu Tsusashi Co., Ltd. Figure 3

Claims (1)

[Claims] Ion beam scanning means (3
) in an apparatus for implanting ions into the semiconductor substrate by scanning an ion beam (5) with an ion beam (5), an aperture (8- A plurality of Faraday cups (8-_1 to 8-_n
), and the ion beam charge amount flowing into each Faraday cup (8-_1 to 8-_n) is compared with a reference value to determine the difference in ion beam charge amount between each Faraday cup. a means for detecting uniformity (11);
to the semiconductor substrate configured to feed back the output of ion implanter.