JPH01310535A - Device for evaluating semiconductor ion implantation condition - Google Patents

Abstract

PURPOSE:To make it possible to conduct an efficient evaluation on the implantation of ions by a method wherein, when ions are implanted on a semiconductor sample substrate, an evaluation value is formed on the ion current directly corresponding to the implanted quantity of ions for every position of ion beam irradiation when ions are implanted on a semiconductor sample substrate. CONSTITUTION:In the course of a process wherein ions are implanted on a semiconductor substrate 1 by changing the position of irradiation of ion beam B, when the position designated by a position designating means 2 and the position of irradiation of the ion beam B are coincided, the ion beam current produced by ion implantation on the semiconductor sample substrate 1 is detected by a sample-holding means 3, and the detected value is retained. This disposition of the sample holding means 3 is repeated everytime the beam irradiation position is coincided with the designated position in the course of ion beam scanning operation, and in the above-mentioned process, the evaluation value making means 4 makes the evaluation value of the ion-implanted quantity at the designated position based on the beam current value retained by the sample-holding means 3 successively. As a result, the quantity of ion-implantation can be catched in the course of process of the ion implantation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a semiconductor ion implantation state evaluation device that evaluates the ion implantation state of a semiconductor sample substrate into which ions have been implanted while sequentially changing the ion beam irradiation position. .

[Prior Art] As semiconductor integrated circuits become smaller and more highly integrated, the ion implantation method is widely adopted due to the need for highly accurate impurity implantation into semiconductor substrates. In this ion implantation method, ions are sequentially implanted by scanning the semiconductor substrate while changing the irradiation position of the ion beam, but when performing such ion implantation, the amount of ions implanted within the semiconductor substrate is non-uniform. In order to prevent ion implantation defects, it is necessary to evaluate the ion implantation state.

Conventionally, the state of ion implantation in a semiconductor sample substrate has been evaluated by, for example, measuring sheet resistance at 50 to 100 points on a semiconductor sample substrate that has undergone a thermal diffusion process and associated treatments after completing a predetermined ion implantation process. This is done by determining the state of sheet resistance distribution (Solid
5tate Technology Nov, '83
pp, 101-106).

In addition, as another evaluation method, a method has been proposed in which, for example, the amount of ions implanted into a semiconductor sample substrate is evaluated by utilizing changes in the ultraviolet absorption rate of an organic photoresist irradiated with ions (SolidState Tech.
noloay Nov, '83 pp, 143-1
51).

[Problems to be Solved by the Invention] In the former evaluation described above, it is difficult to perform efficient evaluation, and it is also difficult to perform accurate evaluation for minute ion implantation.

The reason why this evaluation cannot be performed efficiently is that the final evaluation cannot be performed until after the ion implantation of the entire semiconductor sample substrate has been completed and the thermal diffusion process, etc. This is not possible because there is a limit to the accuracy of measuring sheet resistance for minute ion implantations. For example, accurate measurement is difficult unless the amount of each ion implanted is about 1×10 12 [/~] or more. Furthermore, since the evaluation is performed after the thermal diffusion process and the accompanying cleaning process, etc., the evaluation also includes failure factors in those processes, so it is not possible to evaluate the pure state of ion implantation.

On the other hand, in the method using the organic photoresist, although defective factors such as heat treatment are removed, the relationship between the change in ultraviolet absorption rate and the amount of ion implantation must be determined experimentally in advance; There is a problem that the measured value varies depending on the processing conditions of the resist (coating amount, baking conditions, etc.).

Therefore, an object of the present invention is to enable the ion implantation surroundings into a semiconductor sample substrate to be determined directly during the ion implantation process.

[Means for Solving the Problems] The present invention is based on an apparatus for evaluating the ion implantation state of a semiconductor sample substrate 1 into which ions have been implanted while sequentially changing the irradiation position of the ion beam (B). In the apparatus, technical means for solving the above problem include a position specifying means 2 for specifying a position on the semiconductor sample substrate 1;
The position specified by this position specifying means and the ion beam (
B) A sample hold means 3 that detects the ion beam current generated from the semiconductor substrate 1 by ion implantation when the irradiation position matches and holds the value, and based on the value held by the sample hold means 3. The apparatus includes an evaluation value creation means 4 for creating an evaluation value of the ion-implanted surface at the specified position.

[Semiconductor 1M while changing the irradiation position of the working coin ion unit (8)
In the process of sequentially implanting ions by scanning the plate, when the position specified by the position specifying means 2 matches the irradiation position of the ion beam (B), the sample holding means 3 at that time The ion beam current generated due to ion implantation is detected and its value is held. This processing by the sample hold means 3 is repeated every time the beam irradiation position matches a designated position in the process of ion beam scanning, but in the process, the evaluation value creation means 4 determines the beam current that is sequentially held by the sample hold means 3. An evaluation value of the ion implantation amount at the specified position is created based on the value.

The evaluation value created in this way becomes the basis for determining whether the amount of ion implantation at the specified position of the semiconductor sample substrate 1 is normal.

The evaluation value created by the evaluation value creation means 4 may be any value that reflects the ion implantation amount at that position, such as the average value of the beam current value or the integrated value within a predetermined time. It's not something you can do.

[Example] FIG. 2 is a diagram showing an example of a semiconductor ion implantation state evaluation apparatus according to the present invention. This example is applied to an electrostatic deflection type ion implantation device.

In the figure, 10 is an ion generator, 11 is an X-direction scanner, 12 is a Y-direction scanner, 15 is an X-scan oscillator, and 16 is a Y-scan oscillator, and the oscillation voltage from the X-scan oscillator 15 is By applying the oscillation voltage from the Y-scan oscillator 16 to the Y-direction scanner 12, the ion beam (B) from the ion generator 1o is
The semiconductor sample substrate 20 set on the sample stage 18 is irradiated with the beam under the unidirectional action, and the entire semiconductor substrate 20 is scanned with the beam. This is the basic configuration of an electrostatic deflection type ion implanter.

23 and 24 are comparators, and the comparator 23 outputs the oscillation voltage ■ from the X-scan oscillator 15 and the base 11! X position designation voltage created by potentiometer R1 based on power supply 21 (
When the oscillation voltage ■ becomes equal to or higher than the X position specified voltage 0, the comparison output is raised and the comparator 2
4 is the oscillation voltage ■ from the Y-scan oscillator 16 and the reference power supply 21
The oscillation voltage ■ is compared with the Y position designation voltage ■ (reference voltage) created by potentiometer R2 based on
The comparison output is set to rise when the voltage exceeds the position designation voltage ■.

Reference numeral 25 denotes a monostable multivibrator (hereinafter simply referred to as MM) which outputs a predetermined pulse signal at the rising edge of the comparator 23 and 26 at the rising edge of the comparator 24, respectively.
The output signal from each MM25.26 is AND circuit 27
It is designed to be input.

On the other hand, a beam current flowing through the sample stage 18 based on charges generated from the semiconductor sample substrate 20 by irradiation with the ion beam is further supplied to a beam current meter 30 via a resistor R3. Reference numeral 28 denotes a sample and hold circuit, which detects and holds the terminal voltage (2) of the resistor R3 as the beam current value. voltage value) is maintained. Reference numeral 29 denotes an averaging circuit, which is composed of a CR smoothing circuit and the like, and averages the sampling value ■ held in the sample hold circuit 28 over a predetermined period of time. In addition, the two outputs of the averaging circuit are connected to the voltmeter 31,
The output value I is configured to be confirmed by the voltmeter 31. 32 is an oscilloscope, to which the oscilloscope 32 has an The terminal voltage (2) of the resistor R3 corresponding to the beam current is added together via the resistor R4, and the terminal voltage (2) of the resistor R3 corresponding to the beam current is added together via the resistor R5 and connected to the same Z input (luminance modulation input) terminal. The oscilloscope 32 with each input connection as described above determines the beam irradiation point (measurement point) on the semiconductor sample substrate 20 to be evaluated.
will be displayed as a spot. Note that this measurement point can also be found by reading the outputs of the oscilloscope 32 and the potentiometers R1 and R2 with a voltmeter.

Next, the operation will be explained according to the timing chart shown in FIG.

The X-scan oscillator 15 and the Y-scan oscillator 16 each output an AC waveform voltage with its own period (see FIGS. 3(a) and 3(b)).
) see). Here, the semiconductor sample substrate 2 of the ion beam
Since the irradiation position on 0 is determined by the deflection m in the X and Y directions corresponding to the AC waveform voltage,
The output voltage value ■ from the Y-scan oscillator 16 corresponds to the ion beam irradiation position in the X direction, and the output voltage value ■ from the Y scan oscillator 16 corresponds to the ion beam irradiation position in the Y direction. Furthermore, the voltages set by the potentiometers R1 and R2 also correspond to the X position and Y position in the same coordinate system (X, Y position designating voltages). Therefore, the position on the semiconductor sample substrate 20 at which the ion implantation j is to be evaluated is set by each potentiometer R1, R2.

As described above, the ion beam from the ion generator 10 is deflected in the X and Y directions by the X and Y direction scanners 11 and 12 based on the oscillation voltages from the X and Y scan oscillators 15 and 16. The 20 surfaces of the substrate are sequentially scanned. In this process, the output of the comparator 23 rises every time the output voltage from the X-scanning oscillator 15 becomes equal to or higher than the X position designation voltage set by the potentiometer R1. Output (Figure 3 (
c), see 9). At the same time, the output of the comparator 24 rises every time the output voltage (■) from the Y-scan oscillator 16 exceeds the Y position designation voltage (■) set by the potentiometer R2, and at that rising timing, the MM26 generates a predetermined pulse signal (■). output (see Figure 3(d)). When the irradiation position of the ion beam matches the position set by each potentiometer R1, R2, a pulse signal is simultaneously output from the MM25, 26, and the output of the AND circuit 27 rises (see FIG. 3(e)). The sample and hold circuit 28 is activated at the rising edge (sampling signal) of the AND circuit 27, and the terminal voltage of the resistor R3 corresponding to the beam current value is at that point (time ti>
The instantaneous value at is held in the sample hold circuit 28 (see FIG. 3(g)). This sample hold circuit 2
The value held at 8 is the instantaneous value of the ion current generated when the position specified by the potentiometers R1 and R2 is irradiated with the ion beam, that is, it corresponds to the amount of ion implanted in one ion beam irradiation. becomes. In the process of scanning the ion beam, each time the ion beam irradiation position matches the position designated by the potentiometers R1 and R2, the new beam current value at that time is held in the sample and hold circuit 28, as described above, and the averaging circuit 29 smooths and averages the voltage values updated and held by the sample and hold circuit 28), and the value is indicated by the voltmeter 31. In addition,
A spot is displayed on the display screen of the oscilloscope 32 corresponding to the specified ion beam irradiation position.

Furthermore, the beam current value generated from the semiconductor sample substrate 20 is always indicated to the beam current meter 30 regardless of the ion beam irradiation position.

In the process of scanning the ion beam to the semiconductor sample FA substrate 20 as described above, the potentiometer R1 is turned on at predetermined intervals.
, R2 sequentially change the designated position, the average value of the beam current value at the designated position becomes the voltage g131 as above.
By observing the state, the state of ion implantation ω into the semiconductor sample substrate 20 can be determined.

For example, if the indicated value on the voltmeter 31 is lower or higher than the rated voltage value, it can be determined that the ion implantation amount at that position is poor.

Note that instead of averaging the beam current values held in the sample and hold circuit 28, it is also possible to add them sequentially. In this way, it becomes possible to directly evaluate the ion particle teeth actually accumulating at the irradiation position.

In the above embodiment, the measurement points of the ion implantation amount were changed sequentially, but for example, the measurement points (50 to 1
It is also possible to separately set up a beam current measurement system as described above for each of the points (00 points).

In this way, ion implantation at each point can be observed in parallel, and the state of the implanted amount can be determined more accurately and quickly. Moreover, if the sample values in the sample hold circuit 28 are digitized and subsequent processing is performed using a microcomputer or the like, more efficient processing becomes possible and more diverse evaluations of the ion implantation state become possible.

For example, it is also possible to directly evaluate the uniformity by calculating the deviation value of the beam current distribution at each ion beam irradiation position using a microcomputer.

Furthermore, a more useful device can be realized by adding a function to issue an alarm when the evaluation result is determined to be defective, and a function to interrupt ion implantation along with the alarm.

In addition, although the above embodiment assumes a medium-current type electrostatic deflection type ion implanter, it is also possible to use a high-current type in which the beam irradiation position is mechanically changed by electrostatic deflection and rotation of the sample stage. Even if there is one, a magnetic field deflection type can also be applied in the same way. However, the position designation method is determined based on each beam irradiation position control method.

[Effects of the Invention] As explained above, according to the present invention, an evaluation value can be created based on the ion current that directly corresponds to the ion implantation amount for each ion beam irradiation position during ion implantation into a semiconductor sample substrate. As a result, the amount of ions implanted into the semiconductor sample substrate can be determined directly during the ion implantation process. Therefore, efficient evaluation of ion implantation is possible, as well as highly accurate evaluation.

Furthermore, since evaluation can be performed during the ion implantation process, it is possible to prevent the process from being continued in a defective ion implantation state due to a failure of the ion implantation apparatus or the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a diagram showing an example of a semiconductor ion implantation state evaluation device according to the present invention, and FIG. 3 shows signal waveforms of various parts in the device shown in FIG. This is a timing chart. [Explanation of symbols] 1.2o...Semiconductor sample substrate 2...Position specifying means 3...Sample holding means 4...Evaluation value creation means 10...Ion generator 11...X direction scanning Instrument 12...Y direction scanner 15...X scan oscillator 16...Y scan oscillator 18...Sample stage 21...Reference power source 23.24...Comparator 25.26...Single Stable multivibrator (MM) 27...AND circuit 28...Sample hold circuit 29...Averaging circuit R1, R2...Potentiometer Patent applicant) Confucian Pirox Co., Ltd. Agent
Patent attorney Nakamura Konamizo (3 others) Figure 1 Figure 3

Claims (1)

[Claims] An apparatus for evaluating the ion implantation state of a semiconductor sample substrate (1) into which ions have been implanted while sequentially changing the irradiation position of the ion beam (B), the apparatus comprising: A position specifying means (2) for specifying a position, and when the position specified by the position specifying means (2) and the ion beam (B) irradiation position match, the ion beam is generated from the semiconductor sample substrate (1) by ion implantation. Sample hold means (3) that detects the ion beam current and holds its value
and an evaluation value creation means (4) for creating an evaluation value of the ion implantation amount at the specified position based on the value held by the sample hold means (3). Condition evaluation device.