CN100405567C - Etching monitoring device and method - Google Patents

Abstract

The invention relates to an etching monitoring device, which includes a light source, a test monitoring sheet, a monochromator, a light detector and a plurality of light guide elements; the light source provides a reference light signal and a monitoring light signal, and the multiple The light guide element is used to transmit the above-mentioned reference light signal and the above-mentioned monitoring light signal. The reference light signal is transmitted to the monochromator, and a monochromatic light is selected by the monochromator to be emitted to the photodetector as a reference comparison signal; the monitoring light The signal is transmitted to the test monitoring sheet, which reflects the monitoring light signal and transmits it to the monochromator, and the monochromator selects a monochromatic light of the same wavelength to emit to the photodetector as a monitoring comparison signal. The invention can effectively eliminate the influence of stray light, vibration, etc. on the monitoring results, and improve the monitoring accuracy and stability; in addition, the use of the test monitoring sheet does not need to locate the monitoring light signal, greatly improving its response speed. The present invention also provides a monitoring method using the above etching monitoring device.

Description

Etching monitoring device and method

【Technical field】

The invention relates to a semiconductor or other wafer etching process monitoring device and monitoring method in semiconductor technology, especially a real-time etching process monitoring device and monitoring method.

【Background technique】

The manufacturing process of a semiconductor integrated circuit mainly includes four basic operations: mask making, etching, layer structure formation by deposition or growth, and doping. Among them, etching is an important part of the manufacturing process of semiconductor integrated circuits. There are two types of etching methods for semiconductor integrated circuits: wet etching and dry etching. Dry etching is usually a kind of plasma etching (PlasmaEtching), which can be divided into three categories due to different etching effects: physical etching, such as sputter etching (Sputter Etching), ion beam etching (Ion Beam Etching) ; chemical etching, such as plasma chemical etching (Plasma Chemical Etching); and physical and chemical compound etching, such as reactive ion etching (Reactive Ion Etching). Because plasma etching has the advantages of anisotropy, high surface ratio, and better etching profile, it can meet the high-precision requirements of VLSI graphics transfer.

As integrated circuit process technology develops toward micron, or even sub-micron depths, large-scale structural features such as gate oxide layers are very sensitive to slight overetching. Therefore, in the etching process of integrated circuit manufacturing, it is extremely important to control the etching rate and the end point.

A method in the prior art is to pre-etch a silicon wafer or a glass wafer in the semiconductor process, and then calculate the etching rate and the time required to complete the entire etching process according to the etching depth and etching time during the etching process. The time; then, further etching is performed according to the time required for subsequent etching to complete the entire etching process. However, in the semiconductor etching process, due to changes in factors such as pressure, gas flow, electromagnetic field, etc., it will cause an immediate change in the etching rate during the etching process. Therefore, the above etching end point control method is difficult to meet the requirement of high precision because it cannot monitor the whole etching process in real time.

Referring to Fig. 1, it is a kind of etching real-time monitoring device 30 disclosed in U.S. Patent No. 4,618,262, which is composed of laser source 33, beam splitter 34, fixed mirror 36, scanning mirror 38, focusing lens 27, wafer 15 , Etching machine 48, detector 42, signal amplifier 45, computer control system 50, linear stepping motor 40 composition. In the etching process, a beam of laser light 18 is produced by the laser source 33, and is projected onto the wafer 15 through the beam splitter 34, the fixed mirror 36, the scanning mirror 38, and the focusing lens 27, and then a detection is generated by the reflection of the wafer 15. Light beam 41, through focusing lens 27, scanning mirror 38, fixed mirror 36, beam splitter 34, is received by detector 42 and generates analog electrical signal, sent to computer control system 50 through signal amplifier 45, by computer control system 50 according to The etching rate, the current etching depth, etc. are calculated from the analog electrical signal to control the etching rate of the etching machine 48 and/or stop the etching. The linear stepper motor 40 is controlled by the computer control system 50 to change the deflection angle of the scanning mirror 38 to detect the position of the scribe line (Scribe Line) of the wafer 15, and lock the laser 18 at the position of the scribe line to realize the alignment of the wafer. 15. Etching process monitoring. The installation position and angle of each component of the etching process real-time monitoring device 30 require strict dimming alignment, so the alignment of the optical path is easily affected by vibration and other reasons during use, thereby affecting the monitoring accuracy and stability. Moreover, during the etching monitoring process, the position of the cutting line needs to be scanned first, and the laser beam is positioned at the position of the cutting line before the etching process can be monitored, which reduces its response speed.

In view of this, it is necessary to provide a real-time etching monitoring device and an etching monitoring method with high monitoring accuracy and stability and fast response speed.

【Content of invention】

The following will illustrate an etching monitoring device and monitoring method with several embodiments, which have the characteristics of high monitoring accuracy and stability, and fast response speed.

In order to achieve the above, an etching monitoring device is provided, which is used to monitor the etching thickness of the object to be etched, which includes: a light source; a test monitoring sheet; a monochromator; a light detector; and a plurality of light guide elements; The light source provides a reference light signal and a monitoring light signal, and the plurality of light guide elements are used to transmit the above-mentioned reference light signal and the above-mentioned monitoring light signal. The reference light signal is transmitted to the monochromator, and the monochromator converts it into Monochromatic light, and select a first monochromatic light to emit to the photodetector as a reference comparison signal; the monitoring light signal is transmitted to the test monitoring sheet, and the test monitoring sheet reflects the above-mentioned monitoring light signal and transmits it It is transmitted to the monochromator, and the monochromator converts it into monochromatic light, and selects a monochromatic light with the same wavelength as the first monochromatic light to emit to the photodetector as a monitoring comparison signal.

The reference light signal and the monitoring light signal are transmitted through a plurality of light guide elements.

The plurality of light guiding elements include optical fibers and light concentrating devices arranged at both ends of the optical fibers.

Preferably, the condensing device includes a condensing mirror and a double-fiber collimation device.

The test monitoring sheet and the object to be etched are set in the same etching chamber.

The ratio of the etching rate between the test monitor sheet and the object to be etched is a predetermined value.

And, provide a kind of etching monitoring method, it comprises the following steps:

providing a light source from which a reference light signal and a monitoring light signal are generated;

Transmitting the reference light signal to a monochromator, the monochromator converts it into monochromatic light, and selects a first wavelength monochromatic light to emit to a photodetector as a reference comparison signal;

The monitoring light signal is transmitted to a test monitoring piece and reflected by the test monitoring piece, the reflected monitoring light signal is transmitted to the above-mentioned monochromator, and the monochromator converts it into monochromatic light, and selects the above-mentioned The monochromatic light with the same wavelength as the first wavelength monochromatic light is emitted to the photodetector as a monitoring comparison signal, and the reference optical signal and the monitoring optical signal are transmitted through a plurality of light guide elements;

Comparing the intensity difference between the monitoring contrast signal and the reference contrast signal to calculate the etching thickness of the test monitoring sheet;

The etching thickness of the object to be etched is calculated by the ratio of the etching rate of the test monitor sheet to the object to be etched.

Compared with the prior art, the etching monitoring device provided by this technical solution uses a monochromator to suppress the interference of other stray light, greatly improving the monitoring accuracy of the etching process monitoring device; The precise alignment and adjustment of the installation position and angle between the components only needs to align the light guide element with each component, which can increase its shock resistance and improve the stability of the etching process monitoring device. In addition, it puts the test monitoring sheet and the object to be etched in the same etching chamber, which has the same etching atmosphere, and monitors the thickness change of the object to be etched through the thickness change of the test monitoring sheet. In the etching monitoring process, only the condenser lens 7122 and 7131 is well adjusted with the test monitoring sheet 72, and there is no need to locate the monitoring optical signal, which is beneficial to improving the response speed of the etching monitoring device.

【Description of drawings】

FIG. 1 is a schematic diagram of an etching monitoring device disclosed in the prior art.

FIG. 2 is a schematic diagram of an etching monitoring device according to a first embodiment of the present invention.

FIG. 3 is a schematic diagram of an etching monitoring device according to a second embodiment of the present invention.

Fig. 4 is a schematic structural diagram of a dual-fiber collimation device in the etching monitoring device according to the second embodiment of the present invention.

【Detailed ways】

The embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Referring to FIG. 2 , the etching monitoring device provided by the first embodiment of the present invention is used to monitor the real-time etching thickness of the object to be etched (a wafer 631 is used in this embodiment). The etching process monitoring device includes a light source 70, a monochromator 73, a light detector 74, a test monitoring sheet 72, and a plurality of light guide elements.

The light source 70 is usually a halogen lamp to provide light signals; the light signal emitted by the light source 70 is modulated by a light modulator (Chopper) 701 to generate two beams of light with the same light intensity (or in a fixed ratio), one of which is used as The reference light signal, another beam of light is used as the monitoring light signal.

The reference light signal emitted by the light source 70 and modulated by the optical modulator 701 passes through the condenser 7111, the optical fiber 711 and the condenser 7112 to the monochromator 73, and the monochromator 73 converts it into monochromatic light, and selects a first monochromator. The colored light is emitted to the photodetector 74 through the emission slit 731 of the monochromator 73 as a reference contrast signal. Wherein, the condenser lens 7111 and the condenser lens 7112 are used for beam convergence.

The light source 70 emits and the monitoring optical signal modulated by the light modulator 701 passes through the condenser lens 7121, the optical fiber 712, and the condenser lens 7122 is transmitted to the etching chamber 60 and is incident on the test monitoring sheet 72 located in the etching chamber 60; the test monitoring sheet 72 reflects the incident to the monitoring light signal thereon. The monitoring optical signal reflected by the test monitoring sheet 72 passes through the condenser lens 7131 successively, the optical fiber 713, and the condenser lens 7132 is transmitted to the monochromator 73, which is converted into monochromatic light by the monochromator 73, and is selected to match the above-mentioned first monochromatic light. The monochromatic light with the same wavelength (ie, the monitoring wavelength) is emitted to the photodetector 74 through the emission slit 731 of the monochromator 73 as a monitoring comparison signal. Wherein, the condenser mirrors 7121, 7122, 7131 and 7132 are used for beam convergence, and the condenser mirror 7122 and the condenser mirror 7131 form a small angle to receive the monitoring light signal incident by the condenser mirror 7122 and reflected by the test monitoring sheet 72.

In the etching chamber 60 , the test monitoring chip 72 and the wafer 631 are located on the same transparent substrate 630 , their relative positions are fixed, and the etching atmosphere is the same. The light reflectance of the transparent substrate 630 is very small, approximately zero. The wafer 631 can be a silicon wafer or a glass wafer. The etch rate relationship of wafer 631 and test monitoring sheet 72 is related to both materials; The etch rate is determined; therefore, the test monitor sheet 72 and the wafer 631 have a predetermined etch rate ratio. After this etch rate ratio is measured, it will not change with the etch environment (such as, the atmosphere concentration in the etch chamber 60) in the etch chamber 60 because the test monitor sheet 72 and the wafer 631 are in the same etch atmosphere, i.e. the etch rate ratio fixed. During the etching process, a certain amount of gas is filled into the etching chamber 60 from the gas inlet 610, and ions with a certain initial velocity and concentration are generated by the plasma generator 620, and then the gas in the etching chamber 60 is ionized to achieve wafer 631 and test the etching of monitoring sheet 72.

The light detector 74 detects the reference light signal input by the monochromator 73 and the monitoring light signal reflected by the test monitoring sheet 72 as a reference comparison signal and a monitoring comparison signal respectively, and compares the reference comparison signal and the monitoring comparison signal, and through the monitoring comparison The light intensity difference of the signal relative to the reference comparison signal is used to obtain the real-time etching thickness of the test monitor piece 72; Among them, the photodetector 74 mostly has a wide wavelength range (such as 400nm-1100nm), so as to meet the requirements of different detection wavelengths in the process.

In addition, in order to increase the service life of the test monitoring sheet 72, the test monitoring sheet 72 can be placed on a rotating carrier with multiple openings, such as a circular carrier, which has six openings or more; The transfer carrier is located on the etched side of the test monitor strip 72 . Every time etching is performed, a motor drives the gear structure on the outer ring of the circular carrier to rotate to obtain an unetched portion of the test monitoring sheet for the next etching.

The monitoring process of the etching monitoring device described above shows that the light emitted by the light source 70 is modulated by the light modulator 701, and then two beams of light are respectively derived, and the light intensity of the two beams of light is the same or has a fixed ratio. One beam of light is focused by the condenser lens 7111 and input to the monochromator 73 through the optical fiber 711 as a reference light signal to form a reference light path; the reference light signal is filtered into monochromatic light by the monochromator 73 and is input to the photodetector 74 as a reference Compare signals.

Another beam of light is focused by the condenser lens 7121 and then input into the etching chamber 60 through the optical fiber 712; Therefore, the intensity of the light beam input by the optical fiber 712 reflected by the test monitoring sheet 72 becomes smaller; the light beam reflected by the test monitoring sheet 72 is focused by the condenser lens 7131 and sent by the optical fiber 713 as a monitoring light signal. The monochromator 73 is input to form a monitoring optical path; the monitoring light signal is filtered by the monochromator 73 into monochromatic light, and input to the photodetector 74 as a monitoring comparison signal.

The reference light signal and monitoring light signal input to the monochromator 73 are respectively converted into monochromatic light by the monochromator 73, and the monochromatic light corresponding to the monitoring wavelength is selected to be emitted to the photodetector by the exit slit 731 of the monochromator 73 Then monitor the reference comparison signal and the monitoring comparison signal input by the monochromator 73 through the photodetector 74, and directly obtain the real-time etching state of the test monitoring sheet 72 according to the light intensity difference of the monitoring comparison signal relative to the reference comparison signal. Because wafer 631 and test monitor sheet 72 are etched in the same atmosphere, and relative position is fixed, it has fixed etching ratio; The purpose of monitoring the real-time etching status of the wafer 631.

Referring to Fig. 3, the etching process monitoring device provided by the second embodiment of the present invention is basically similar to the first embodiment, and it includes a light source 70, a plurality of light guide elements, a monochromator 73, a light detector 74, and A test monitoring strip 72. The difference is that a pair of optical fiber collimation devices 81 are used to replace the separated condenser lens 7122 and condenser lens 7131 in the first embodiment;

Referring to FIG. 4 , the dual-fiber collimation device 81 is taken as an example for illustration. The dual-fiber collimation device 81 includes a fiber ferrule 811 , a collimator lens 812 and a sleeve 813 . The optical fiber ferrule 811 has a through hole 8111; the optical fiber 712 and the optical fiber 713 are inserted through the above through hole 8111 and fixed in it by glue; the collimating lens 812 is used to collimate the light beam input by the optical fiber 712 and project it to the On the test monitoring sheet 72, after being reflected by the test monitoring sheet 72, it is projected to the collimating lens end face 8121 at the same angle in the opposite direction. The sleeve 813 is used to fix the fiber ferrule 811 and the collimating lens 812 .

In the etching monitoring device and method in the above embodiments, the use of the monochromator 73 can reduce the influence of stray light on the monitoring signal, and improve the monitoring accuracy of the etching process monitoring device. Moreover, the adoption of the optical fiber can avoid the interference of external ambient light on the entire test optical path, and improve the monitoring stability of the etching process monitoring device. In addition, the adoption of the test monitoring sheet 72 only needs to adjust the condenser lenses 7122 and 7131 with the test monitoring sheet 72, and there is no need to locate the monitoring light signal during the etching monitoring process, which is beneficial to improve the response speed of the etching monitoring device.

In addition, those skilled in the art can also make other changes within the spirit of the present invention, such as using other light sources for the design of the present invention. Of course, these changes made according to the spirit of the present invention should all be included within the scope of protection claimed by the present invention.

Claims (10)

1. An etching monitoring device is used to monitor the etching thickness of the object to be etched, and it includes: a light source; a test monitoring sheet; a monochromator; a light detector; and a plurality of light guide elements; the light source provides a A reference light signal and a monitoring light signal, the plurality of light guide elements are used to transmit the above-mentioned reference light signal and the above-mentioned monitoring light signal, the reference light signal is transmitted to a monochromator, and the monochromator converts it into monochromatic light, And select a first monochromatic light to emit to the photodetector as a reference comparison signal; the monitoring light signal is transmitted to the test monitoring piece, and the test monitoring piece reflects the above-mentioned monitoring light signal and transmits it to the monochromatic The monochromator converts it into monochromatic light, and selects a monochromatic light with the same wavelength as the first monochromatic light to emit to the photodetector as a monitoring comparison signal. 2 . The etching monitoring device according to claim 1 , wherein the plurality of light guiding elements comprise optical fibers and light concentrating devices arranged at both ends of the optical fibers. 3 . 3. The etching monitoring device according to claim 2, characterized in that the light concentrating device comprises a concentrating mirror and a double-fiber collimation device. 4. The etching monitoring device according to claim 1, wherein the ratio of the etching rate of the test monitoring sheet to the etching rate of the object to be etched is a predetermined value. 5. The etching monitoring device according to claim 1, characterized in that the test monitoring sheet and the object to be etched are arranged in the same etching chamber. 6. An etching monitoring method, comprising the steps of: providing a light source, generating a reference light signal and a monitoring light signal by the light source; passing the reference light signal to a monochromator, and the monochromator converts it into monochromatic light, and select a monochromatic light of the first wavelength to emit to a photodetector as a reference comparison signal; transmit the monitoring light signal to a test monitoring piece and be reflected by the test monitoring piece, and the reflected The monitoring light signal is transmitted to the above-mentioned monochromator, which converts it into monochromatic light, and selects the monochromatic light having the same wavelength as the first wavelength monochromatic light to emit to the above-mentioned photodetector as a monitoring comparison signal , the reference light signal and the monitoring light signal are transmitted through a plurality of light guide elements; comparing the intensity difference of the monitoring contrast signal with respect to the reference contrast signal to calculate the etching thickness of the test monitoring piece; through the test monitoring piece and a to-be-etched The etch thickness of the object to be etched is calculated from the ratio of the etching rate of the object to be etched. 7. The etching monitoring method according to claim 6, wherein the plurality of light guiding elements comprise optical fibers and light concentrating devices arranged at both ends of the optical fibers. 8 . The etching monitoring method according to claim 7 , wherein the focusing device comprises a focusing lens and a double fiber collimating device. 9 . 9. The etching monitoring method according to claim 6, wherein the ratio of the etching rate of the test monitoring sheet to the etching rate of the object to be etched is a predetermined value. 10. The etching monitoring method according to claim 6, characterized in that the test monitoring sheet and the object to be etched are arranged in the same etching chamber.

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