JPS61220348A - Evaluation of semiconductor treatment process and apparatus for the same - Google Patents

Abstract

PURPOSE:To realize non-contact measurement of an implanted ion quantity of low dosage implantation, an etched quantity and the like by a method wherein carriers are created near the surface of a semiconductor only and an electromagnetic wave which is influenced by the difference between the total number of carriers created continually by light application and the total number of carriers lost by recombination is detected. CONSTITUTION:A short wavelength light is applied to a treated Si wafer by a light source 1. The light is a continuous light or a pulse light whose pulse width is wider enough than the life-time of carriers of the substrate. The light passes through a chopper 2 and is divided by a half mirror 3. The separated laser beam is detected by a photodiode 7. The Si wafer 4 is so provided as to have its surface to be measured facing the light source 1 and accepting the light from the source 1. A microwave oscillator 5 and a microwave detector 6 are provided on the back side of the Si wafer 4. The microwave oscillator 5 emits the microwave against the wafer 4 and the microwave detector 6 detects the reflected wave of the microwave influenced by the excess carriers in the Si wafer 4 with a detection diode. The microwave is absorbed by the carriers in the Si wafer 4 but a degree of absorption is proportional to the carrier concentration. Therefore, the carrier concentration can be estimated by measuring the reflected light.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention measures the ion implantation amount of low-dose implantation without heat treatment, and also measures the region with the largest implantation dose by performing heat treatment. The present invention relates to a method for evaluating a semiconductor processing process that can be performed, and an apparatus for implementing the method.

In addition, this method is attracting attention as a dry process.
It can also be used to measure the amount etched by processes such as the above S i02 and S i3 N4 films.

(Prior Art) The amount of ions implanted into a semiconductor is often measured after the ion-implanted semiconductor is heat-treated.

The implantation amount that can be measured before heat treatment is 10”
-1018/cm2.

In this case, the induced photoresist film coated on the glass substrate is used as a monitor, and the amount of ion implantation is estimated from the change in color.

The photoresist film becomes graphite and darkens due to ion induction. By measuring the optical change caused by this, the total amount of implanted ions is indirectly measured.

After heat treatment, measurements are performed by contact or destructive methods.

The film thicknesses of S i02 and S 13 N4 after dry etching are measured by optical measurement.

When measuring a semiconductor wafer into which ions have been implanted after heat treatment, there are contact methods such as resistivity and CV measurement.

The method using an organic resist does not directly use a semiconductor and is only possible when implanting at 1012/cm2 or more.

5i02. Measuring the amount of plasma etching of Si3N4 etc. requires the use of a completely different device from that used to measure the amount of ion implantation.

(Problems to be Solved by the Invention) An object of the present invention is to provide a semiconductor processing process evaluation method and apparatus that can measure the amount of ions implanted in low-dose implantation, the amount of etching in a dry process, etc. in a non-contact manner. It is about providing.

(Means to solve the problem) Irradiate short wavelength light to generate carriers only near the surface of a semiconductor such as Si, and recombine the carriers by damage caused to the surface of Si in proportion to the amount of ion implantation. can be caused.

On the other hand, the surface recombination rate can be made smaller than that without a junction by forming a PN junction or a high-low junction such as p + p, n + n by ion implantation and heat treatment.

When controlling the film thickness by plasma etching of a 5i02.5L3N4 film on a St wafer, the recombination rate at the interface between the film and Si changes, resulting in the recombination with carriers that are continuously generated by light irradiation. The difference in the number of carriers lost can be detected as the magnitude of the microwave signal.

In order to achieve the above object, the semiconductor processing process evaluation method according to the present invention is a method for evaluating the processing of a semiconductor that has been subjected to a process that changes the electrical properties of the semiconductor surface by injection of carriers or the like during the semiconductor processing process. The method comprises irradiating the semiconductor with short continuous wavelength light or light with a pulse width sufficiently larger than the lifetime of carriers in the substrate to generate carriers only near the surface of the semiconductor, and irradiating the semiconductor with electromagnetic waves. It is configured to evaluate the semiconductor processing process by detecting electromagnetic waves affected by the difference between the total number of carriers continuously generated by the light irradiation and the total number of carriers lost by recombination.

Further, the apparatus for carrying out the above method is used to evaluate the processing process of a semiconductor, which carries out the above process evaluation method for a semiconductor that has been subjected to a process that changes the electrical properties of the semiconductor surface by injection of carriers or the like during the semiconductor processing process. The apparatus comprises a light source device for irradiating a processed semiconductor with light of a continuous short wavelength or a pulse width sufficiently larger than the live time of carriers on the substrate; an electromagnetic wave generator that emits electromagnetic waves towards a region, an electromagnetic wave detector that detects the level of the electromagnetic waves affected by carriers generated near the surface of the arbitrary region of the semiconductor, and an electromagnetic wave detector that detects the output of the detector. It consists of a recording device.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings and the like.

FIG. 1 is a schematic diagram showing an embodiment of a processing process evaluation apparatus for carrying out the semiconductor processing process evaluation method according to the present invention.

The light source 1 is a light source for irradiating a processed Si wafer with light of a continuous short wavelength or a pulse width sufficiently larger than the lifetime of the substrate carrier. In this embodiment, a helium neon laser oscillator with an output of about 1 mW is used.

A chopper 2 having a rotating plate with slits is rotated in front of the light source 1 to project a laser beam with a pulse width of about 5 ms.

The light transmitted through the chopper 2 is split by a half mirror 3, and a portion of the light for forming a synchronization signal is separated. The laser beam separated by the half mirror 3 is detected by a photodiode 7.

The Si wafer 4 is placed so that the surface to be measured faces the light source 1 and the light from the light source 1 enters the position to be measured.

Note that the Si wafer 4 is supported by a support device (not shown), and can be moved so that any position of the Si wafer 4 is irradiated with the laser beam.

An electromagnetic wave generator 5 and an electromagnetic wave detector 6 are placed on the back surface of the St wafer 4.

As an electromagnetic wave generator, a GaAs Gunn diode is placed inside the waveguide, and a 10MHz microwave is applied to the Si wafer 4.
is firing towards. A detection diode is used as the electromagnetic wave detection a6 to detect reflected waves of electromagnetic waves affected by excess carriers of the Si wafer 4.

The detected output of the electromagnetic wave detector 6 is amplified by a lock-in amplifier 8 with a high S/N ratio.

The output of the lock-in amplifier 8 is measured and recorded for each position irradiated by the light source using a voltage needle and a data mapping system. A plotter is used to record the correspondence with the position of the Si wafer 4.

The apparatus of the embodiment can inject carriers into the Si wafer 4 using a He--Ne optical pulse, detect, amplify, and record the carrier concentration as the magnitude of a reflected microwave wave.

The microwave is absorbed by carriers within the Si wafer 4.

Generally, absorption is performed in proportion to carrier concentration, so carrier concentration can be estimated by detecting reflected waves.

If the recombination speed of carriers in the Si wafer 4 is low, many carriers remain and the absorption amount becomes large. Figure 2 shows Si
This is a graph showing the normalized value (P) of the total number of carriers in the semiconductor under continuous light irradiation using the recombination speed (SA) on the implanted surface of wafer 4 and the recombination speed (SB) on the back surface of wafer 4. be.

This graph shows the normalized value (P) of the total number of carriers in the Si wafer 4 under irradiation with continuous light (absorption coefficient α-3800 cm-') from a He-Ne laser oscillator (light source 1).

For example, if SB = 100 cm/s, the value of (P) is 100 cm/s.
It can be seen that the speed changes within a range of about 5,000 cm/s to 5,000 cm/s.゛In Figure 3, six levels of p+ ions are implanted into the Sl wafer 4 using a sector-shaped mask, and muffing is performed by matching the output voltage detected by the device shown in Figure 1 to the implantation position of the Si wafer 4. The results are shown below.

6 levels are 0, lXl0", lx1 per unit square cm
This means that ion implantation is performed at six levels: 0t', lX10'2.1x1013.6x1013.

The output voltage is large in the part where the injection amount is 0, but when the injection amount is 101
The decrease in output is clearly seen up to 2/cm2.

FIG. 4 shows similar measurement results for a Si wafer implanted with B+ ions.

In FIG. 5, the horizontal axis represents the ion implantation amount, and the vertical axis represents the ion implantation amount.
The average value of each dose in Figure 4 is plotted, and p+,
It is shown that it is possible to measure a low dose region up to 1012/Cm2 in the case of B+ ion implantation.

Figure 6.7 shows similar measurement results from 1010 to 1012.
The figures show cases of p+ ion implantation and B+ ion implantation within the range of /'Cm2.

It is predicted that measurement can be performed with sufficiently high sensitivity even in the case of a lower dose region than 1010/Cm2. The dotted line in FIG. 6.7 indicates that a process has been applied to reduce the recombination speed on the wafer surface in order to make the effect of carrier recombination remarkable due to the introduction of defects by ion implantation.

FIG. 8 shows heat treatment (900°C) after ion implantation.

20 minutes), the microwave signal is plotted against the dose amount. As shown in Fig. 5.6.7, the sensitivity is particularly good in the implantation range of 1011/Cm2 or more, where the amount of change in the microwave signal becomes small. This can also be understood from the fact that the surface recombination rate S can be expressed as follows.

5=So XNd/ (ns+ps+2ni)So:
Surface recombination rate before ion implantation Nd: Impurity concentration of the substrate ns and ps: Concentration of N-type and P-type carriers activated by ion implantation nl: Intrinsic carrier concentration Therefore, in the case of FIG. 8, the donor corresponding to ns As the concentration increases, S becomes smaller than So, and He-N
The rate of recombination of carriers injected by the e-laser beam at the surface becomes smaller, and the microwave signal becomes larger.

5i02. formed on a Si wafer. An example will be shown in which the thickness of the etched film when a film such as Si3N4 was plasma etched was measured using the apparatus of the embodiment.

Fig. 9 shows a Si wafer with a 513N4 film coated with 2,300 layers using a mask for 7 seconds (film thickness: 2,200 layers), 14 seconds (film thickness: 2,100 layers), 21 seconds (film thickness: 2,000 layers),
The graph shows the distribution of microwave signals within the wafer measured by the above-described apparatus after plasma etching was performed at four levels for 150 seconds (film thickness: 0) and heat treatment was performed at 900°C for 20 minutes. be. The signal becomes smaller as the amount of plasma etch increases.

FIG. 10 summarizes the measurement results when the plasma etch time increases by 7 seconds. As will be seen, by monitoring the magnitude of the microwave signal, the amount of plasma etch (remaining film thickness) can be measured non-contact and non-destructively.

Figure 11 shows the relationship between plasma etch time and film thickness.

(Effects of the Invention) Since the method and apparatus of the present invention are configured as described above, a low dose ion implantation amount can be measured in a non-contact and non-destructive manner without performing wafer heat treatment.

Even if heat treatment is performed after low-dose ion implantation, the dose can be measured without contact by utilizing changes in the surface recombination rate.

Therefore, it can be widely used in semiconductor processing processes.

Low ion implantation dose (especially active layer of position sensor, C
MO3 channel doping etc. 1012tons/c
m 2 or less) in a non-contact, non-destructive, non-contaminating manner before heat treatment, in-process measurement can be performed as much as possible, and the results can be reflected in the ion implantation process.

Furthermore, the injection amount exceeds 10”7cm2 and becomes 10”7cm2.
In a range close to , the amount of implantation can be measured by applying a heat treatment after implantation and using the decrease in surface recombination rate to increase the microwave signal.

S i02 , S i3 N4 on Si, where not only the ion implantation but also the recombination rate near the wafer surface changes
By measuring the total number of carriers within the wafer in a form corresponding to the amount of dry etching of the film, etc., it is possible to measure the amount of etch (residual film thickness) of the thin film on the wafer.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a processing process evaluation apparatus for carrying out the semiconductor processing process evaluation method according to the present invention. Figure 2 shows the recombination rate (SA) of the implanted surface of the Si wafer 4.
FIG. 2 is a graph showing the normalized value (P) of the total number of carriers in a semiconductor under continuous light irradiation using the recombination speed (SB) of the back surface and FIG. 3 is a graph showing the results of ion implantation of different levels into a Si wafer and measurement and muffing using the apparatus shown in FIG. 1. FIG. 4 is a graph showing the results of ion implantation of different levels into another Si wafer, measurement and mapping using the apparatus shown in FIG. In Figure 5, the horizontal axis shows the ion implantation amount, and the vertical axis shows the ion implantation amount.
It is a graph plotting and showing the average value of each dose amount in the figure. Figure 6.7 shows similar measurement results from 1010 to 1012/
3 is a graph showing cases of p+ ion implantation and B+ ion implantation within a range of cm 2 . Figure 8 shows heat treatment (900°C, 20 minutes) after ion implantation.
It is a graph showing the results measured after applying. FIG. 9 is a graph showing the results measured using the above-mentioned apparatus after performing plasma etching at four levels and further performing heat treatment at 900° C. for 20 minutes. FIG. 10 is a graph summarizing the measurement results when the plasma etch time increases by 7 seconds. FIG. 11 is a graph showing the relationship between plasma etch time and film thickness. 1... Light source (He-Ne laser oscillator) 2... Chopper 3... Half mirror 4... Silicon wafer 5... Electromagnetic wave generator (microwave oscillator) 6... Electromagnetic wave detector (microwave oscillator) Wave detector) 7...Photodiode 8...Lock-in amplifier 9...Voltage needle and data mapping Patent applicant Hamamatsu Photonics Co., Ltd. Representative Patent attorney Hisashi Inoro 16 Figure Off Figure 28 Figure dose amount Ucw 43 Figure 9

Claims (4)

[Claims] (1) A method for evaluating the processing of a semiconductor that has been subjected to a treatment that changes the electrical properties of the semiconductor surface by injection of carriers or the like during the semiconductor processing process, the method comprising: By irradiating light with a pulse width sufficiently larger than the lifetime, carriers are generated only near the surface of the semiconductor, and by irradiating the semiconductor with electromagnetic waves, carriers are continuously generated by the light irradiation and carriers are lost by recombination. A semiconductor processing process evaluation method configured to evaluate a semiconductor processing process by detecting electromagnetic waves affected by a difference in the total number of . (2) A semiconductor processing process evaluation apparatus that carries out the above-mentioned processing evaluation method for a semiconductor that has been subjected to a process that changes the electrical properties of the semiconductor surface by carrier injection or the like during the semiconductor processing process, a light source device that irradiates the semiconductor with a short continuous wavelength or a pulse width sufficiently larger than the lifetime of carriers on the substrate; It is composed of an electromagnetic wave generator that emits, an electromagnetic wave detector that detects the level of the electromagnetic wave affected by carriers generated near the surface of the arbitrary region of the semiconductor, and a device that records the output of the detector. Semiconductor processing process evaluation equipment. (3) The semiconductor processing process evaluation device according to claim 2, wherein the light source device is a He-Ne laser oscillator. (4) The semiconductor processing process evaluation device according to claim 2, wherein the electromagnetic wave generator is a microwave generator, and the electromagnetic wave detector is a microwave detector.