JP2006100299A - Semiconductor device manufacturing method and manufacturing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that shavings occurring in a field layer during CMP process of an embedded dielectric in an element separation process using an STI method cause the occurrence of the leak current and the thinner line of a gate electrode mask, and thereby cause a decrease in yield and reliability. <P>SOLUTION: Paying attention to that the variations in the thickness of a stopper film on an element region after the CMP process depend on a height difference between a first stopper film formed on the element region and a second stopper film formed on the element separation region, the thickness of a film embedding a groove that satisfies a target value of the height difference is calculated from the depth of an etching groove, and deposition is implemented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a semiconductor device manufacturing method and system for obtaining a smooth trench groove buried surface.

According to Moore's Law, semiconductor devices have achieved four times higher speed and higher integration in about three years. Up to now, high performance and high integration of LSI devices have been ensured by miniaturization of MOS transistors. In recent years, in order to overcome the delay of electrical signals due to wiring, there is a trend toward high integration in the vertical direction while pursuing miniaturization in the horizontal direction. In the process of advancing the multilayer wiring, the most important thing is the implementation of a planarization process corresponding to the reduction in the depth of focus of lithography accompanying the miniaturization.

In semiconductor device manufacturing, a technique for forming a trench groove and planarizing a buried film is used everywhere, such as an element isolation technique and a damascene line forming technique. Element isolation is a technique for electrically isolating transistors formed on a silicon substrate.

FIG. 1 shows a trench element isolation manufacturing method. First, a silicon nitride film 103 is deposited on the silicon semiconductor substrate 101 as a pad oxide film 102 and a polishing stopper film. Next, a photoresist film is applied, and a photoresist pattern 104 is formed only in the element region by photolithography. The state at this time is shown in FIG. Then, the silicon nitride film 103 and the pad oxide film 102 are patterned using the photoresist pattern as a mask. The etching time at this time is determined by an end point detection method using a light emission monitor.
In the end point detection using the light emission monitor, a difference between the emission spectrum when the silicon nitride film or the oxide film is etched and the emission spectrum when the etching progresses and the silicon semiconductor substrate surface is deposited is detected.

Next, the photoresist pattern is removed, and the silicon semiconductor substrate 101 is anisotropically etched using the silicon nitride film 103 as a mask to form a trench groove. The state at this time is shown in FIG. In the element isolation technique, a process of forming a trench in the silicon semiconductor substrate 101 using the silicon nitride film 103 as a mask is referred to as trench etching. In trench etching of a silicon semiconductor substrate, since the same film is etched, a change in depth cannot be detected by the end point detection method using a light emission monitor, and a predetermined value is used as the etching time.

Next, an oxide film 105 is deposited by CVD (Chemical Vapor Deposition) to fill the trench. The state at this time is shown in FIG. And CMP (Ch
The planarization is performed by emical mechanical polishing (polishing) until the silicon nitride film 103 has a desired thickness. At that time, the silicon nitride film 103 is used as a CMP stopper. The state at this time is shown in FIG. Through the above processing, the element region of the silicon semiconductor substrate can be electrically isolated by the buried insulating film.

In recent years, shallow trench isolation (STI) using a trench trench is a method of selectively oxidizing a silicon opening that has been widely used in the past in order to form a silicon trench and embed an insulating film. Compared to the LOCOS (Local Oxidation of Silicon) structure that forms the structure, there is an advantage that the separation width can be narrowed. When performing multi-layer wiring, the element isolation surface is the lowest layer that can also be referred to as a reference surface. Therefore, it is necessary to reduce unevenness. However, in a wide-area opening, cutting called dishing occurs. For this reason John M. Bond and Joseph P Ellul: J. El
As shown in ectronchem.Soc., Vol.143, No.1, 3718 (1996), a method of adding a film having a slower CMP polishing rate than a buried oxide film to a wide opening is considered ( FIG. 2 (a)).
First stopper film formed in the element portion and second stopper film 201 formed in the element isolation portion
Thus, it is possible to protect the buried oxide film and obtain a smooth surface after the CMP (FIG. 2B).

  Damascene is a buried pattern forming method for forming multilayer wiring.

John M. Bond and Joseph P Ellul: J. Electronchem. Soc., Vol. 143, No. 1, 3718 (1996)

In the etching apparatus, since the apparatus state greatly affects the etching result, the etching result varies between lots and between lots due to the influence of fluctuation of the apparatus over time. Therefore, when the same film thickness is always formed in the groove formed by etching, the relative relationship between the first CMP stopper film and the insulating film embedded in the groove is not constant, and as a result, the first CMP stopper Variation occurs in the altitude difference 202 in the groove between the film and the second CMP stopper film.

On the other hand, the polishing time of CMP is calculated based on the thickness of the first stopper film and the thickness of the buried insulating film.
It is determined by calculating a condition that the remaining film thickness of the stopper film is constant. But first
The remaining amount of the stopper film depends on the difference in elevation between the first stopper film and the second stopper film, and the difference in elevation is higher, that is, the longer the time until the first stopper film is polished. The residual film thickness tends to increase. Conversely, if the elevation difference is small, the amount of remaining film is small. Further, this tendency varies depending on the pattern density of the wafer to be polished, and an appropriate altitude difference for the remaining film amount of the first stopper film to be a target value varies depending on the pattern density.

Since the remaining film thickness of the first stopper film corresponds to the difference between the silicon surface of the element region and the buried oxide film surface of the element isolation region, the element isolation region is not formed when the remaining film thickness becomes extremely thin. Causes leakage current. Therefore, the present invention provides a semiconductor device manufacturing method and a manufacturing system thereof for realizing an appropriate altitude difference in order to reduce the remaining film variation of the first stopper film.

The present invention provides a target burying amount based on an etching groove depth, an elevation difference target value between the first stopper film and the second stopper film, a manufacturing specification of the second stopper film thickness, and an oxide film thickness in the groove. A step of calculating a target film formation amount using a relational expression between an embedding amount and a film formation amount, and a film formation time for achieving the target film formation amount using a QC result of the film formation apparatus. It consists of steps to calculate.

According to the invention, since the film thickness is adjusted according to the actual groove depth value, the altitude difference between the first stopper film and the second stopper film is always kept constant regardless of the groove depth. , C caused by elevation difference
It is possible to suppress the remaining film thickness variation of the first stopper film after MP. As a result, the insulating film surface in the element isolation region can always be formed higher than the Si surface in the element region by the amount of the remaining film of the first stopper film. To do.

In addition, by arranging the second stopper film at an appropriate height above the element isolation region, dishing in a wide range of element isolation regions is suppressed, and the etching mask thinning of the gate electrode formed across the element regions is reduced. Therefore, it is possible to improve the reliability of the device by making the gate electrode width that determines the device characteristics uniform.

In addition, when there is a variation in elevation difference between the first CMP stopper film and the second CMP stopper film, it is necessary to determine the polishing conditions for each lot. In some cases, the first lot used for the condition determination is required. In some cases, the wafer must be scrapped. However, by making the altitude difference constant, it is not necessary to set the condition. Therefore, it is possible to eliminate the number of steps for setting the condition and reduce the scrap wafer.

For the measurement of the groove depth, a contact type profiler or a non-contact type Scatterometry is used. FIG. 3 shows the measurement principle of Scatterometry. In Scatterometry, light is incident on a measurement target pattern at a certain angle, and the light intensity for each wavelength of reflected light is measured (FIG. 3 (
a)) and a method of changing the incident angle to the repetitive pattern to be measured and measuring the light intensity of the reflected light with respect to the incident light angle (FIG. 3B). For example, in the method of measuring the reflected light spectrum of the repetitive pattern in FIG. 3A, a plurality of profiles having different widths, taper angles, and depths are created in the computer as shown in FIG. Each light intensity characteristic (Signature) is calculated by wave optics simulation to create a library. Then, by matching the actual signature with the signature in the library, the signature having a high degree of coincidence with the actual signature is extracted, and the width, taper angle, and depth of the measurement target pattern are calculated. With the introduction of scatterometry, the groove depth can be measured in-line without contaminating the wafer surface or damaging the wafer itself.

Example 1
FIG. 5 shows the information flow of the process cooperation control process between the etching process and the film forming process for controlling the difference in elevation between the first stopper film and the second stopper film to be constant. FIG. 12 shows a cross-sectional shape at the start of polishing. First, the groove depth 1201 after etching is measured by Scatterometry, and the result is stored in the etching result database 508. In Figure 5, Scatterometry is set to Optical Critical
It is written as OCD503, which is an abbreviation for Dimension (optical measuring device). When forming the groove filling oxide film by the film forming apparatus 504, first, the target filling amount 1202 is calculated (deposition time calculation processing 512).
(1)). The target embedding amount 1202 is an embedding amount that achieves the altitude difference target value 202 (
1) Calculated by the equation.

Target embedding amount = (groove depth + groove oxide thickness / 2)
-(Groove oxide film thickness + second stopper film thickness + elevation difference target value) (1)
Here, the oxide thickness 1203 in the trench corresponds to the thickness of the oxide film formed by oxidizing the silicon trench itself in order to improve the adhesion between the surface of the silicon trench and the buried insulating film before forming the buried insulating film, It is formed by consuming silicon that is half the thickness of the oxide film thickness 1203 in the groove defined in the manufacturing specification. For this purpose, the in-groove oxide film 1203, the buried oxide film 1202, and the second stopper film 1205 are added to a depth obtained by adding a value 1204 that is half of the in-groove oxide film thickness to the groove depth after etching.
Are sequentially formed to achieve the target altitude difference 202. Here, the altitude difference target value 202 and the second
The values stored in the manufacturing specification database 509 are used as the stopper film thickness 1205 and the in-groove oxide film thickness 1202.

The buried film thickness indicates the oxide film thickness that should be buried in the groove when CMP is performed, but the oxide film thickness actually formed by the film deposition apparatus does not directly become the buried film thickness. The film is affected by processes such as annealing, cleaning, and nitride film formation that are performed after film formation and before CMP. The relationship between the film formation amount and the embedment amount is stored in advance as the embedment characteristic 511, and the target film formation amount is calculated using this relational expression (deposition time calculation process 512 (2)).
. The relational expression is, for example, film formation amount = a1 × embedding amount + b1 (2)
The coefficient and the intercept are values obtained experimentally.

Next, a film formation time for achieving the target film formation amount is calculated (film formation time calculation process 512 (3)). The film formation time is expressed by the following equation.

Deposition time = target deposition amount / deposition rate (3)
Here, since the film formation speed varies depending on the state of the apparatus, the result of the apparatus QC is used here as a value indicating the film formation speed. The value of the device QC is acquired every time QC is performed and stored in the device QC result database 510.

FIG. 6 shows the transition of the target film formation amount calculated based on the etching groove depth. During the period to be analyzed, there was a lot whose etching groove depth was extremely shallow twice, and it was necessary to make the film thickness extremely thin for this lot.

FIG. 7 shows the result of the altitude difference control. The plot indicated by * is the transition of the elevation difference in the conventional film formation amount without giving the relationship that the altitude difference is constant between the groove depth and the film formation amount. On the other hand, the plot indicated by the saddle shape indicates an altitude difference formed when the target film formation amount shown in FIG. 6 is converted into a film formation time using QC data. The plots indicated by the black diamonds are the control results when the film formation speed shown in the equation (3) is predicted by the average value of the film formation speed actual values of the past three lots and converted into the film formation time. By setting the film formation time using the predicted value, the variation σ is reduced to about 1/10.

FIG. 8 shows a relationship 801 between the elevation difference used to determine the target elevation difference and the CMP residual film deviation amount. The CMP residual film deviation amount indicates the deviation amount from the target value of the CMP residual film thickness. The CMP residual film deviation amount shows elevation difference dependency, and the elevation difference at which the CMP residual film deviation amount becomes 0 is the elevation difference target value 802. When the variation in altitude difference is 1/10, the CMP residual film deviation amount is also reduced to 1/10, and the residual film variation is greatly improved.

(Example 2)
FIG. 9 shows the relationship between the CMP residual film shift amount and the altitude difference of the products having different element isolation region densities. When the element isolation region density is small, the area of the element isolation portion is reduced, and the surface area of the second CMP stopper film is reduced. For this reason, the polishing speed of the second CMP stopper film is higher than that of the element having a high element isolation region density. Therefore, when compared with a wafer having the same elevation difference, the wafer with a lower density has a lower density than that of the first stopper film. The time to start polishing is early, and the CMP remaining film tends to become thin. By such a mechanism, the altitude difference target value at which the CMP residual film deviation amount becomes zero differs depending on the element isolation region density, and the altitude difference target value 902 becomes large in a product having a low density.

By adopting a configuration in which the target altitude difference can be appropriately set for each element isolation region density of the starting wafer, it is possible to reduce the CMP residual film variation to 1/10 even for a low-density product type. .

(Example 3)
FIG. 10 is a block diagram showing the overall configuration of the third embodiment of the present invention. In the figure,
The film forming apparatus group 1001 includes at least one film forming apparatus 502. In addition,
The film formation apparatus 502 includes a plurality of chambers, and a film formation process can be performed in each chamber. The film forming apparatus group 1001 includes a data operation station 10 including an input / output interface 1005, a film forming time calculation processing unit 512, and a database unit 1004.
03 through an input / output interface 1005. Further, the film forming apparatus group 10
01 is connected to a manufacturing management system 1006 that manages manufacturing information and progress information of the entire semiconductor device manufacturing line. In addition, the type, process,
For example, the film forming apparatus and its chamber name, lot number / wafer number may be input by reading an identifier formed on the wafer and transmitted from the manufacturing management system 1006 to the data operation station 1003 via the network. Is possible.

The measurement device group 1002 includes at least one measurement device 505 and is connected to the data operation station 1003 and the manufacturing management system 1006. The database unit 1004 in the data operation station 1003 is an etching result database in which semiconductor device type name, process name, lot / wafer number, etching apparatus / chamber name, groove depth measurement date and time, and groove depth measurement result are accumulated. 508 and semiconductor device type, process, element isolation region density, semiconductor device standard corresponding to element isolation region density (for example, altitude difference target value, second stopper film thickness, oxide thickness in trench) Manufacturing specification database 509, film forming apparatus name / chamber name, QC result measurement date / time, film forming time, film thickness average value accumulating apparatus QC result database 510, semiconductor device type name, process name, film forming apparatus・ Embedding characteristics database in which relational expressions (for example, coefficients and intercepts) between chamber name, deposition amount and embedding amount are accumulated. Consisting of 511.

When the groove depth measurement process is performed in the measuring apparatus group 1002 after the etching process, the semiconductor device type name, process name, etching apparatus / chamber name, lot / wafer number, measurement date / time, and groove depth measurement data are displayed. The data is registered in the etching result database 508 of the database unit 1004 via the input / output interface 1005. Thereafter, in response to a data inquiry from the film formation time calculation processing unit 512, the corresponding data is searched and the corresponding data is transmitted to the film formation time calculation processing unit 512. The film formation time calculation processing unit 512 includes a database unit 1004.
Based on the data acquired from the above, a set value of the film formation time is calculated, and the calculation result is transmitted to the film formation apparatus in the film formation apparatus group 1001 via the input / output interface 1005. At this time, not only the calculation result but also a film forming process start command is transmitted to the corresponding film forming apparatus, and the film forming apparatus performs the film forming process according to the instructed film forming time.

The manufacturing management system 1006 accumulates manufacturing results (starting start date / time, starting end date / time, lot / wafer number name, manufacturing device name) in each process in manufacturing semiconductor devices, manages the manufacturing flow, and manufactures the next process. I give instructions.

FIG. 11 is a flowchart of the film formation time calculation processing unit 512. In step 1101, the type, process, lot name, wafer number, film forming apparatus, chamber information, and start date / time of the start wafer are acquired. These pieces of information can be acquired from the manufacturing management system 1006 that manages the information of the entire semiconductor device manufacturing line based on the identifier written on the wafer. Step 110
In step 2, the groove depth information of the wafer to be formed is acquired from the etching result database using the process, lot name, and wafer number as search keys. In step 1103, an altitude difference target value corresponding to the product type acquired in step 1101, a second CMP stopper film thickness,
The in-groove oxide film thickness is obtained from the manufacturing specification database 62. In step 1104, the required filling amount is calculated from the groove depth, the altitude difference target value, the second CMP stopper film thickness, and the in-groove oxide film thickness. In step 1105, a relational expression between the embedment amount and the film formation amount is acquired using the product name as a search key. The relational expression between the embedment amount and the film formation amount needs to be evaluated in advance and registered in the database unit. In step 1106, the required film formation amount is calculated using this relational expression. In step 1107, the film formation time and the film thickness average value are acquired from the apparatus QC result database using the film formation apparatus name and measurement date and time as search keys, and the film formation rate is calculated. In step 1108, the film formation time for realizing the required film formation amount is calculated using the film formation rate. In step 1109, this is set in the film forming apparatus. In step 1110, film formation is performed, and the process ends.

In the system described in this embodiment, the data calculation station 1004 is configured separately from the manufacturing management system 1006. However, the database unit 1004 and the film formation time calculation processing unit 5 are not described.
12 is incorporated in the manufacturing management system 1006, or a data operation station 1003 including a database unit 1004 and a film formation time calculation processing unit 512 is provided in each film formation apparatus 502. Even if it is the structure built in.

It is process sectional drawing which shows the element isolation method in semiconductor device manufacture. FIG. 11 is a process cross-sectional view in which two CMP stopper films are formed in the element isolation method. It is a figure which shows the signal detection method of Scatterometry. It is a figure which shows the measurement principle of Scatterometry. In Example 1, it is a figure which shows the flow of the information of a process cooperation control process. In Example 1, it is a figure which shows transition of the target film-forming amount. In Example 1, it is a figure which shows a process cooperation control result. In Example 1, it is a figure which shows the residual film deviation | shift amount suppression effect by process cooperation control. In Example 2, it is a figure which shows the residual film shift | offset | difference amount suppression effect by process cooperation control. In Example 3, it is a figure which shows the whole structure of a process cooperation control system. In Example 3, it is a flowchart of the film-forming time process part. In Example 1, it is a figure which shows the cross-section at the time of a grinding | polishing start, and each film thickness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Silicon semiconductor substrate, 102 ... Pad oxide film, 103 ... Silicon nitride film, 10
4 ... Photoresist pattern, 105 ... Oxide film, 201 ... Second CMP stopper film, 20
2 ... elevation difference 301 ... light source 302 ... detector 303 ... measurement object 304 ... diffraction grating 4
DESCRIPTION OF SYMBOLS 01 ... Profile, 402 ... Library, 403 ... Light intensity characteristic of measurement object, 404 ... Measurement result, 501 ... Processed wafer, 502 ... Etching apparatus, 503 ... Scatterome
try, 504 ... film forming apparatus, 505 ... measuring instrument, 506 ... annealing apparatus, 507 ... CMP apparatus, 508 ... etching result database, 509 ... manufacturing specification database, 510 ... apparatus QC result database, 511 ... embedding characteristic database, 512 ... Deposition time calculation processing, 801... Altitude difference dependency of CMP residual film deviation amount, 802... Altitude difference target value, 901.
Altitude difference dependency of residual film deviation amount, 902 ... Altitude difference target value, 1001 ... Film forming apparatus group, 1002 ...
Measuring device group, 1003... Data operation station, 1004.
... I / O interface, 1006 ... Manufacturing management system, 1201 ... Groove depth after etching, 1202 ... Embedded insulating film thickness, 1203 ... Oxide film thickness in groove, 1204 ... Silicon consumption during oxidation in groove, 1205 ... Second CMP stopper film thickness.

Claims (3)

In the planarization polishing method of the groove filling film,
A first polishing stopper film formed on the convex portion and a second polishing stopper film formed on the groove filling film of the concave portion;
A planarization polishing method for a groove filling film, characterized in that an elevation difference between concave portions of the first polishing stopper film and the second polishing stopper film is kept within a certain range. In an element isolation method for a semiconductor substrate,
A first nitride nitride film formed in the element region and a second nitride nitride film formed on the trench-filling insulating film in the element isolation region;
An element isolation method for a semiconductor substrate, wherein an altitude difference in an element isolation region between the first nitride nitride film and the second nitride nitride film is maintained within a certain range. Based on the depth of the groove formed on the substrate, the difference in elevation between the first polishing stopper film formed on the convex portion and the second polishing stopper film formed on the concave groove embedding film is determined by polishing. Calculating a target groove embedding amount so as to be a target value at the start,
Calculating the target film formation amount from the target groove embedding amount using the relationship between the groove embedding amount at the start of polishing and the film formation amount;
Using the film forming speed of the film forming apparatus to convert the target film forming amount into a film forming time,
A process cooperation control system for etching results and film forming conditions, wherein the film forming time is given to a film forming apparatus to perform film forming.

Images