KR20030021299A - Method For Certifying Film Thickness Standard Reference Material For Film Thickness Measuring Equipment - Google Patents

Abstract

PURPOSE: A method for certifying a film thickness standard reference material for equipment for measuring film thickness is provided to manufacture and authenticate the film thickness standard reference material, and establish an accurate management standard of metal film measuring equipment. CONSTITUTION: Identification is granted to each wafer(S10). A metal film is accumulated on the wafers as a standard reference film(S20). The thickness of the metal film of each wafer is measured by using non-destructive film thickness measuring equipment(S30). The wafers are divided into wafers for a transmission electron microscope and wafers for an SRM(Film Thickness Standard Reference Material)(S40). A polycrystal silicon film is accumulated on the wafers for a transmission electron microscope(S50). The film thickness of wafers for the transmission electron microscope is measured(S60). Correlation between the transmission electron microscope and the non-destructive film thickness measuring equipment(S70) is measured. The correlation is applied to the wafers for the SRM(S80). The metal film thickness of the wafers for the SRM obtained by the correlation is authenticated(S90). The wafers for the SRM are registered(S100). The non-destructive film thickness measuring equipment is compensated by using the metal film thickness of the authenticated wafers for the SRM(S110).

Description

Method for Certifying Film Thickness Standard Reference Material For Film Thickness Measuring Equipment}

The present invention relates to a film thickness standard reference material certification method for film thickness measurement equipment, and more specifically, to a non-destructive film thickness by authenticating a film thickness standard reference material with high accuracy of a transmission electron microscope (TEM). It relates to a film thickness standard reference material certification method for film thickness measurement equipment to improve the accuracy of the measurement equipment.

In general, manufacturing processes of semiconductor memory devices and non-memory devices include laminating an insulating film, a dielectric film, a metal film, or the like on a substrate such as a wafer made of a single crystal silicon material, and forming the stacked film in a desired pattern. Include. The thickness of the film is measured by a non-destructive film thickness measuring instrument with high accuracy immediately after the completion of the stacking of the film to check whether the film is initially laminated to a desired thickness. The film thickness measuring equipment is largely divided into non-destructive film thickness measuring equipment and destructive film thickness measuring equipment. The non-destructive film thickness measuring apparatus may be an ellipsometer or a thickness measuring apparatus using light absorption and reflectance of a laser or a lamp, for example, nanospec, optiprobe, and metapulse. ). The destructive film thickness measuring instrument includes a transmission electron microscope (TEM) and has a much higher accuracy than a non-destructive film thickness measuring instrument. However, since the wafer must be cut to measure the film thickness, It is no longer applicable to subsequent processes.

Currently, Film Thickness Certified is used for the calibration of various film thickness measuring equipment or matching and maintenance of film thickness measuring equipment during the manufacturing process of semiconductor memory devices and non-memory devices. Reference Material (hereinafter referred to as 'CRM') is used. This ensures the exact thickness of the film, thereby improving the accuracy of the quality required in the manufacturing process of the semiconductor device.

However, until now, semiconductor manufactures have been made by purchasing expensive wafers on which film thickness certification materials (CRM), that is, certified thickness films, are stacked from VLSI, an institution certified by the National Institute of Standards and Technology (NIST) in the United States. The first non-destructive film thickness measuring instruments installed on the line have been calibrated within tolerances. Then, in a semiconductor manufacturing line, it is common to measure the film thickness by the calibrated film thickness measuring devices immediately after laminating the film to a desired thickness on wafers for integrated circuit fabrication using a chemical vapor deposition apparatus or a sputtering apparatus. .

However, in order to initially calibrate the film thickness measuring equipment used in the semiconductor manufacturing line, the film thickness certification reference material (CRM) must be purchased from a foreign VLSI company. However, when the film thickness measuring instruments are used for a certain period of time, a correction of the film thickness measuring apparatuses is inevitable. At this time, the additional purchase of the CRM is a significant burden on the cost increase of the semiconductor device.

In addition, the CRM has a certain limitation in the accuracy of the film thickness because it uses the film thickness measurement results only depend on the film thickness measurement equipment using the light absorption and reflectance of the laser or lamp. In particular, in the case of metal film, there is no globally recognized CRM and the reflection of light is so severe that thickness measuring equipment using laser or lamp cannot make CRM of correct thickness.

In addition, the transmission electron microscope is not properly utilized in CRM despite the high accuracy due to the drawback that the measurement sample can no longer be used in a subsequent process by destroying the wafer as the measurement sample.

In view of this, there is an urgent need to provide a film thickness standard reference material (hereinafter referred to as 'SRM') on its own while approaching the high accuracy of the transmission electron microscope.

Accordingly, an object of the present invention is to provide a film thickness standard reference material authentication method for film thickness measurement equipment to improve the accuracy of the non-destructive film thickness measurement equipment to the high thickness accuracy of the transmission electron microscope.

It is another object of the present invention to provide a film thickness standard reference material authentication method for film thickness measurement equipment to measure the thickness of a metal film with high accuracy.

It is still another object of the present invention to provide a method for authenticating a film thickness standard reference material for a film thickness measuring apparatus, which reduces the purchase cost of CRM by authenticating the film thickness standard reference material (SRM) by itself.

1 is a flow chart showing a film thickness standard reference material authentication method for film thickness measuring equipment according to the present invention.

Figure 2 is a graph showing the correlation between the transmission electron microscope and the non-destructive thickness measurement equipment applied to the film thickness standard reference material authentication method for the film thickness measurement equipment according to the present invention.

Film thickness standard reference material authentication method for the film thickness measuring equipment according to the present invention for achieving the above object

Stacking a predetermined film for thickness measurement on wafers and measuring the film with a predetermined film thickness measuring instrument; Classifying the wafers into transmission electron microscope wafers and film thickness standard wafers; Measuring the thickness of the films of the wafers for transmission electron microscopes with a transmission electron microscope; Calculating a correlation between the transmission electron microscope and the film thickness measuring instrument with respect to the measured film thickness; Applying the correlation to the wafers for the film thickness standard reference material; Authenticating the film thickness with a value of the film thickness measuring instrument; And calibrating the film thickness measuring instrument using the certified film thickness standard reference material wafers.

Preferably, a metal film may be laminated on the wafer as a film for measuring the thickness.

Preferably, the step of measuring the thickness of the metal film with the transmission electron microscope

Further depositing a film for establishing a boundary with the metal film on the transmission electron microscope wafers; And measuring the thickness of the metal film with the transmission electron microscope.

Preferably, any one of a polysilicon film and a nitride film may be laminated on the metal film as a film for establishing a boundary with the metal film.

Hereinafter, with reference to the accompanying drawings, the film thickness standard reference material authentication method for the film thickness measuring equipment according to the present invention will be described in detail.

1 is a flowchart showing a film thickness standard reference material authentication method for the film thickness measurement equipment according to the present invention, Figure 2 is applied to the film thickness standard reference material authentication method for the film thickness measurement equipment according to the present invention, permeation This graph shows the correlation between electron microscope and nondestructive film thickness measuring instrument.

Referring to FIG. 1, in step S10, first, SRM wafers (not shown) of single crystal silicon material, in which no semiconductor manufacturing process is performed, are prepared. At this time, for example, 26 wafers are prepared for comparison between a non-destructive film thickness measuring instrument and a transmission electron microscope. After the wafers are prepared, each wafer is given an identification (hereinafter referred to as 'ID') for wafer identification. That is, a laser marking device (not shown) is used to mark IDs with mixed letters and numbers, for example, on the surfaces of the wafers.

After the ID has been assigned, in step S20, a metal film such as an aluminum film is used as a standard reference film for thickness measurement on the surfaces of the wafers using a conventional vacuum deposition apparatus or sputtering apparatus. Laminate to thickness.

After the lamination of the metal film is completed, in step S30, the metal film thickness of each of the wafers is measured by using a non-destructive film thickness measuring device (not shown), for example, metapulse. At this time, in order to confirm statistical correlation and repeatability and reproducibility of the metal film, the thickness of the metal film is measured, for example, 60 times in total over 3 days. Then, the average value and the standard deviation of the metal film thickness measured by the film thickness measuring instrument are calculated.

After the measurement of the thickness of the metal film is completed, in step S40, the wafers are transferred to the transmission electron microscope wafers and the SRM wafers in order to obtain a correlation between the film thickness measuring instrument and the transmission electron microscope. Classify in ratio of 6.

After the classification of the wafers is completed, in step S50, a polysilicon film or a nitride film is deposited on the surface of the wafers for the transmission electron microscope in order to increase the thickness of the transmission electron microscope, for example, by a chemical vapor deposition process. Laminate further to a thickness of 500Å or more. This is to establish an interface between the polysilicon film and the metal film. Of course, as long as a good interface with the metal film can be established, nitride films other than the polycrystalline silicon film can also be used.

After the lamination of the polysilicon film is completed, in step S60, the thickness of the metal film of the wafers for the transmission electron microscope is measured by a transmission electron microscope (not shown). At this time, the metal film thickness of each wafer measured by the transmission electron microscope becomes a substantial thickness. On the other hand, in order to measure the thickness of the metal film with the transmission electron microscope, the wafers must be cut, and thus the measured, cut wafers are no longer used and must be discarded.

After the measurement of the thickness of the metal film by the transmission electron microscope is completed, in step S70 to calculate the correlation between the transmission electron microscope and the film thickness measuring equipment. That is, for each wafer, the relationship between the metal film thickness measured by the transmission electron microscope and the metal film thickness previously measured by the film thickness measuring devices before the measurement by the transmission electron microscope is calculated. Make up.

More specifically, in the first transmission electron microscope wafer, when the thickness of the metal film was measured at 502 kHz by metapulse and measured at 500 kHz by transmission electron microscope, it is shown in the graph of FIG. 2. As described above, the value of 502 Hz measured by metapulse is represented by Y1 on the Y axis, and the value of 500 Hz measured by the transmission electron microscope is represented by X1 on the X axis. In this manner, for each of the wafers for transmission electron microscopes including the second wafer, the values of the thicknesses measured by the metapulse and the thicknesses measured by the transmission electron microscope are previously displayed on the Y and X axes.

Accordingly, there is a statistical correlation of Y1: Y2 = X1: X2 between the thicknesses Y1 and X1 of the first investment microscope wafer and the thicknesses Y2 and X2 of the second investment microscope wafer. Can be established. At this time, it is preferable that the difference between Y1 and Y2 is small, for example within several hundred microseconds.

After such a correlation is calculated, the correlation is applied to the wafers for SRM in step S80. Therefore, if the correlation is applied to the wafer for SRM, the value of the thickness X2 can be obtained with the accuracy of the transmission electron microscope when the thicknesses Y1, X1, and Y2 are known correctly. That is, it is possible to obtain the same high accuracy as measured by the transmission electron microscope without directly measuring the thickness of the metal films deposited on the SRM wafers by the transmission electron microscope.

After the correlation is applied to the wafers for SRM, in step S90, the metal film thickness (Xn) of the wafers for SRM obtained by the correlation is authenticated by its own equipment management department and not by an external organization. Issue a supporting certificate. Therefore, since the self-certified SRM wafer can be used again in the future when the calibration of the film thickness measuring equipment is required, it is possible to reduce the cost of purchasing expensive CRM from foreign countries for the calibration of the film thickness measuring equipment. Cost increases can be curbed.

After the thickness Xn of the metal film is authenticated, in step S100, the SRM wafer is registered as a certified SRM, which replaces expensive CRM to be purchased from a foreign country, for example, by handwriting or computerization in a register. Manage.

Once the SRM wafers are registered, in step S110, the film thickness measuring equipment is corrected using the metal film thickness Xn of the certified SRM wafers. Therefore, the film thickness measuring instrument is corrected so that the metal film can be measured by the thickness Xn after performing the correction instead of the thickness Yn measured in the state before performing the correction. Thereafter, whenever necessary, the thickness of the SRM wafer is measured by the film thickness measuring instrument to monitor the film thickness measuring instrument.

Therefore, the present invention can calculate the statistical correlation between the transmission electron microscope and the film thickness measuring equipment can be produced by itself in the SRM having the accuracy of the transmission electron microscope and can establish its own certification criteria.

In addition, the present invention can ensure the correct thickness of the metal film with high reflectivity, thereby facilitating the correction of the film thickness measuring equipment, matching and maintenance between the measuring equipment, and further improving the accuracy of the quality required in the semiconductor manufacturing process. You can.

Furthermore, the present invention can suppress the purchase of CRM from foreign countries and reduce the cost burden due to the purchase of CRM by producing the SRM by itself.

In the meantime, the present invention has been described with reference to a metal film for convenience of explanation, but the present invention may be similarly applied to an insulating film, a dielectric film, a polycrystalline silicon film, or the like other than the metal film.

As described in detail above, in the film thickness standard reference material authentication method for the film thickness measuring apparatus according to the present invention, an identification factor (ID) is assigned to wafers, and for reflecting thicknesses on the wafers, Laminating a metal film, measuring the metal film with a film thickness measuring instrument, classifying the wafers for a transmission electron microscope and a film thickness standard reference material, laminating a polysilicon film on a metal film of the wafers for transmission electron microscope, and then transmitting electrons. The thickness of the metal film was measured under a microscope, the correlation between the film thickness measuring device and the thickness of the metal film of the transmission electron microscope was calculated, and the correlation was applied to the film thickness standard reference material wafer. Self-certified metal film thickness of wafer for reference material, the film thickness standard reference material Registered in the registration colon, and the film thickness measurement device to an accuracy of correcting the transmission electron microscope.

Therefore, the present invention can make and authenticate the film thickness standard reference material by itself. In addition, since the metal film can be measured accurately, it is possible to establish accurate management standards of the metal film thickness measuring equipment. In addition, it is possible to reduce the cost of purchasing expensive certified film thickness reference material from abroad and further reduce the cost.

On the other hand, the present invention is not limited to the contents described in the drawings and detailed description, it is obvious to those skilled in the art that various modifications can be made without departing from the spirit of the invention. .

Claims (4)

Stacking a predetermined film for thickness measurement on wafers and measuring the film with a predetermined film thickness measuring instrument; Classifying the wafers into transmission electron microscope wafers and film thickness standard wafers; Measuring the thickness of the films of the wafers for transmission electron microscopes with a transmission electron microscope; Calculating a correlation between the transmission electron microscope and the film thickness measuring instrument with respect to the measured film thickness; Applying the correlation to the wafers for the film thickness standard reference material; Authenticating the film thickness with a value of the film thickness measuring instrument; And And calibrating the film thickness measurement instrument using the certified film thickness reference material wafers. The method according to claim 1, wherein a metal film is laminated on the wafer as the film for measuring the thickness. The method of claim 2, wherein the thickness of the metal film is measured by the transmission electron microscope. Further depositing a film for establishing a boundary with the metal film on the transmission electron microscope wafers; And The film thickness standard reference material authentication method for measuring the thickness of the metal film, characterized in that it comprises the step of measuring by the transmission electron microscope. 4. The method according to claim 3, wherein any one of a polysilicon film and a nitride film is laminated on the metal film as a film for establishing a boundary with the metal film. .