JP3196721B2 - Semiconductor device manufacturing method and measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device, which corrects an overlay displacement between an upper layer pattern and a lower layer pattern in a photolithography process and improves a manufacturing yield. ,
The present invention relates to a measuring device for measuring a displacement in the semiconductor device.

[0002]

2. Description of the Related Art Generally, in a manufacturing process of a semiconductor device, a conductive layer and an insulating layer having a required pattern are sequentially formed on a semiconductor substrate from a lower layer to an upper layer by a photolithography process using a photomask. In this photolithography process, a photoresist is applied to the surface of the semiconductor substrate, exposed using a photomask, and the photoresist is developed to obtain a photoresist pattern. The desired pattern is obtained by etching the conductive layer and the insulating layer. For this reason, if there is a misalignment in the pattern superposition between the sequentially laminated lower layer pattern and the upper layer pattern formed thereon, it becomes difficult to obtain a semiconductor element having desired characteristics. For this reason, it is necessary to position the photomask for forming the upper layer pattern of the next step with high precision with respect to the lower layer pattern formed in the previous step, and for that purpose, exposure using the photomask of the upper layer pattern is performed. before,
It is necessary to measure the positional deviation of the upper layer pattern from the lower layer pattern and correct the positional deviation of the upper layer pattern of the photomask in the exposure apparatus.

Conventionally, as a method of measuring such a displacement, a photoresist is applied on a formed lower layer pattern, exposed with a photomask of the upper layer pattern, and the photoresist is developed by developing the photoresist. At the time of forming the pattern, a method of detecting the relative position of both patterns by measuring a dimension defined between each of the lower layer pattern and the resist pattern of the upper layer pattern, and measuring a displacement has been proposed. I have. For example, FIG.
(A) and (b) are a plan view and a cross-sectional view showing an example thereof, in which a conductive film such as polycrystalline silicon is formed on a gate insulating film 22 formed on the surface of a silicon wafer 21;
The conductive film is formed in a required pattern to form a gate electrode 23a as a lower layer pattern. After forming an interlayer insulating film 24 made of a silicon oxide film so as to cover the gate electrode 23a, a photoresist 25 is coated on the interlayer insulating film,
5, a pattern of the contact hole is exposed and developed using a photomask (not shown) for opening the contact hole as an upper layer pattern to form a photoresist pattern 25a. Then, the photoresist pattern 25a of the obtained contact hole and the gate electrode 23a
In contrast, for example, an image is taken from the surface of the semiconductor substrate using an optical measuring device such as a CCD camera having a high-magnification optical system to capture the pattern outline of the photoresist pattern 25a and the gate electrode 23a. The position of each pattern is measured by analyzing the image of the captured pattern contour,
The displacement between the two semiconductor patterns is measured based on the measurement result.

However, with the recent miniaturization and high density of semiconductor elements, when the pattern width of a semiconductor element pattern to be formed is reduced to a sub-μm or a few μm or less of a comma, the existing optical system of an image pickup apparatus is required. Is made for visible light, it is not possible to directly measure the positional deviation of each pattern. In the above example, when the pattern size of the gate electrode is about 0.25 μm, and the opening diameter of the contact hole is finer than this, and when the displacement between the two patterns is controlled within about 0.06 μm, In addition, it is extremely difficult to measure the displacement with the above-described optical imaging apparatus. For this reason, conventionally, in addition to the pattern for forming the above-described semiconductor element, a pattern for measuring the positional deviation having a size larger than that of the semiconductor element pattern of about 10 to 30 μm is formed, and this positional deviation measurement is performed. The position deviation is measured using the pattern for use. In the example shown in FIG. 5, a rectangular, for example, square frame-shaped pattern 23A is formed in a conductive film for forming a gate electrode in a region other than the element formation of the semiconductor substrate, and the above-mentioned frame-shaped pattern 23A is formed at a center position of the frame-shaped pattern 23A. A rectangular pattern 25A is formed by a part of the photoresist 25. These frame pattern 23A and rectangular pattern 25A
Is large in size with respect to the gate electrode 23a and the like, and can be measured by the above-described high-magnification optical measuring device. Based on the displacement, the displacement in the X and Y directions of the plane and the displacement in the rotation direction are calculated, and the position of the exposure apparatus is corrected based on the calculation result.

[0005]

However, according to the study by the present inventor, when an aberration occurs in the projection optical system of an exposure machine for projecting and exposing the above-mentioned pattern, a large-size pattern and a semiconductor The degree of the influence of the aberration is different from that of the micro-dimensional pattern formed by a part of the element. Therefore, the value of the positional deviation measured using the above-described positional deviation measuring pattern is the same as the positional deviation in the micro-dimensional pattern. Turned out to be inapplicable as the value of. For this reason,
Even when the positional deviation measured in the positional deviation measurement pattern is within the preset allowable dimension, it is not necessarily guaranteed that the positional deviation is within the allowable dimension in the microscopic pattern, and the positional deviation in the microscopic pattern is affected by the positional deviation. Element defects such as leaks, short circuits, and open circuits have occurred, which has been a factor in lowering the production yield of semiconductor devices.

[0006] Therefore, it is required to directly measure the displacement of a minute dimensional pattern, and as one of the methods, it is proposed to measure the displacement of a minute dimensional pattern using an SEM (scanning electron microscope). Have been. However, as is well known, the SEM is based on the principle of obtaining an image of the observed object using secondary electrons emitted from the observed object, so that the pattern observed by the SEM needs to be a conductor. For this reason, in the manufacturing process of the semiconductor device, it is not always possible to measure the displacement using the SEM. For example, in the example shown in FIG.
Since an interlayer insulating film 24 made of a silicon oxide film is formed on the upper layer to cover the same, when this silicon wafer is observed using an SEM, the pattern of the lower gate electrode 23a and the silicon wafer 21 The secondary electrons from the surface are attenuated or diffused and diffracted by the interlayer insulating film 24, so that it is difficult to obtain a clear SEM image. It becomes difficult to measure the displacement between the gate electrode 23a and the photoresist pattern 25a of the contact hole with high accuracy, and it is difficult to solve the above-mentioned problem.

SUMMARY OF THE INVENTION It is an object of the present invention to manufacture a semiconductor device capable of manufacturing a semiconductor device having a high manufacturing yield by detecting a positional shift in a minute dimension pattern with high reliability and enabling a high-precision correction in an exposure machine. It is an object of the present invention to provide a method and a measuring device for measuring a displacement in a semiconductor device.

[0008]

According to the manufacturing method of the present invention, a step of forming a lower layer pattern on a semiconductor substrate, a step of forming an insulating film covering the lower layer pattern, and forming an upper layer pattern on the insulating film are provided. A method of manufacturing a semiconductor device including a step of forming a photoresist pattern for
Apply photoresist on the surface of the conductive substrate,
Large and small dimensions for detecting a displacement between the lower layer pattern and the upper layer pattern in the photoresist using the respective photomasks for forming the lower layer pattern and the upper layer pattern with respect to the photoresist. Forming each misregistration detection pattern, observing the large-dimension misregistration detection pattern with an optical measuring instrument and measuring misregistration, and scanning the small-dimension misregistration detection pattern with a scanning type Measuring the positional deviation by observing with an electron microscope; obtaining the correlation between the positional deviations in the large and small dimensions based on the measured positional deviations of the respective positional deviation detecting patterns; and Forming a large-size misregistration detection pattern with the lower layer pattern and each part of the photoresist pattern; Measuring the positional deviation by observing the detected pattern with an optical measuring device, and comparing the positional deviation measured from the large-sized positional deviation detecting pattern of the semiconductor substrate with the calculated positional deviation correlation. Thus, the method includes a step of estimating a positional shift of the microscopic pattern formed on the semiconductor substrate, and a step of correcting an exposure position in an exposure apparatus for performing the exposure based on the estimated positional shift.

Here, the large-dimension displacement detection pattern is formed as a pattern of several μm or more, and the small-dimension displacement detection pattern is formed as a pattern of a few μm comma. The large-size and minute-size misalignment detection patterns form a part of the photoresist left by exposure and development using a photomask for forming the lower layer pattern and the upper layer pattern. Is formed as a pattern in which a part of the remaining photoresist is removed by exposure and development using a photomask for the purpose.

According to the manufacturing method of the present invention, a large-size misregistration detecting pattern is formed on a semiconductor substrate to be a product, and the misalignment is detected by an optical measuring device. A large size misalignment detection pattern and a small size misalignment detection pattern are formed, and the large size misalignment detection pattern is measured with an optical measuring instrument to detect the misalignment. The position shift detection pattern is measured by an SEM to detect the position shift, and the correlation between the position shifts in these large-size and minute-size position shift detection patterns is obtained. By applying the positional deviation measured on the substrate, the positional deviation of the semiconductor substrate, which is the product, in the micro-dimensional pattern is estimated, the positional deviation in the exposure device is corrected, and the positioning is performed with high accuracy. It is possible to manufacture a semiconductor device.

Further, the measuring apparatus of the present invention comprises a stack of two consecutive photolithography steps, each having a surface formed on a conductive substrate, for measuring the pattern displacement in the above-described manufacturing method of the present invention. An optical measuring device that measures a pattern of several μm or more for the alignment pattern,
A scanning microscope to measure the pattern of tenths of [mu] m, the scanning microscope and measured position displacement by the optical measuring instrument
Means for determining the correlation with the displacement measured by the mirror.
It is configured to be provided . Further, for a semiconductor substrate having a resist pattern for forming an upper layer pattern on an insulating film covering a lower layer pattern, a pattern of several μm or more of the resist pattern is measured, and the optical measuring device and the scanning microscope are used. And a means for estimating and displaying a pattern misalignment of a few μm in the resist pattern from the correlation between the measured values and the measured values.

[0012]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing main steps in an embodiment of the present invention. A gate insulating film 12 made of a silicon oxide film is formed on the surface of the product wafer 11A, and a conductive film 13 such as polycrystalline silicon is formed thereon to a required thickness. Then, a positive-type photoresist 14 is applied on the conductive film 13, and a gate electrode pattern is exposed to the photoresist 14 by an exposure device using a photomask for forming a gate electrode, and developed, and The photoresist is applied to the gate electrode pattern 14a.
Leave. At this time, a large-sized pattern 14A having a side of about 10 to 30 μm, here a rectangle, is formed as a part of the photoresist pattern on a part of the photoresist 14 (step S10).
1).

At this time, on the one hand, a dummy wafer 11B used only for measuring the displacement is prepared, the surface of the dummy wafer 11B is coated with the positive photoresist 14 at the same time, and the photoresist for forming the gate electrode is formed. The gate electrode pattern is similarly exposed and developed by the exposure apparatus using the mask. As a result, the photoresist in the region that is not exposed is left, and the photoresist pattern 14b of the gate electrode pattern is formed. In this state, the conductive surface of the dummy wafer 11B is exposed between the gate electrode patterns. Also,
At this time, the same photoresist pattern as the pattern 14A formed on the product wafer is formed on a part of the photoresist 14 to form a large-sized rectangular pattern 14B in the lower layer of the dummy wafer (step S102).

Then, in the product wafer 11A, the patterned photoresist 14a,
Etching the conductive film 13 using 14A as a mask,
Gate electrode 13a and large-sized rectangular pattern 13 in lower layer
Form A. Next, an interlayer insulating film 15 such as BPSG is formed on the product wafer on which the gate electrode 13a and the rectangular pattern 13A are formed. Further, a positive photoresist 16 is applied thereon. Then, one of the plurality of product wafers is selected for pilot exposure, and the photoresist is exposed to a contact hole pattern by an exposure apparatus using a photomask for forming a contact hole, and is developed. Thereby, a photoresist pattern 16a of the contact hole is formed,
A minute size pattern S1 is formed. At this time, a rectangular pattern 16A having a similar shape with a smaller planar dimension than the rectangular pattern 13A is formed as a blank pattern without the photoresist 16, and these are used to form a large-size misalignment detection pattern L1. Is formed (step S103). FIG. 2 is a plan view and a sectional view of the product wafer in this state.

On the other hand, also for the dummy wafer 11B, a contact hole pattern is exposed to the photoresist 14b remaining on the surface of the dummy wafer by an exposure device using the photomask for forming the contact hole, and develop. As a result, the photoresist 14b is exposed in a region where the contact hole is opened, and a part of the photoresist 14b is removed by development. As a result, a small-size position shift detection pattern S2 composed of the photoresist pattern 14b in a state where the conductive surface of the dummy wafer 11B is exposed in a region where the contact hole is opened is formed. At this time, a similar rectangular pattern having a smaller planar dimension is exposed at a position facing the rectangular pattern 14B, and a part of the photoresist pattern 14B of the rectangular pattern is removed in the exposed area. , The photoresist 1
A rectangular pattern 14C having a blanking structure in which no 4 is present is formed, and a large-size misregistration detecting pattern L2 exposing the conductive surface of the dummy wafer is formed with these (step S104). The dummy wafer in this state is as shown in FIG.

Then, the dummy wafer 11B is set on the optical measuring device 17, and the large-size misalignment detecting pattern L2 is imaged. Thus, the outer shape of the rectangular pattern 14B and the outer shape of the inner rectangular pattern 14C can be obtained as an imaging pattern. For example, as shown in FIG. 3, the lateral positions X11, X12 and X21, X22 of each outer side are obtained. Is measured, and the displacement of the midpoint of the position of each pattern, that is, (the midpoint of X11 and X12) and (the midpoint of X21 and X22) are calculated to measure the displacement in the X direction of both patterns. can do. Similarly, the displacement in the Y direction can be measured and calculated, and further, the displacement in the rotational direction can be calculated therefrom. From this, the displacement in the large displacement detection pattern L2 on the dummy wafer 11B is measured (step S105).

Next, the dummy wafer 11B is
18 and the dummy wafer 1 exposed between the photoresists 14b in the pattern S2 for detecting positional deviation of minute dimensions left on the dummy wafer 11B.
Observe the pattern on the conductive surface of 1B. With this observation,
The external positions x11 and x12 of the gate electrode and the external positions x21 and x22 of the contact holes are measured, respectively.
By performing the same calculation as in the case of the large displacement detection pattern, the displacement of the contact hole pattern with respect to the gate electrode pattern in the plane X direction is obtained. That is, from the positional deviation between the gate electrode pattern and the contact hole pattern, the positional deviation of the microscopic positional deviation detection pattern S2 on the dummy wafer 11B can be measured. In this measurement, the displacement in the plane X direction and Y direction and the displacement in the rotation direction in the minute dimension pattern are measured (step S106).

The displacement in the pattern S2 for detecting small-dimension displacement detected by the SEM 18 and the amount of displacement in the pattern L2 for detecting large-dimension displacement measured by the optical measuring device 17 are described below. (Step S107). FIG. 4 is a diagram showing an example of the correlation characteristic obtained by the present inventor. The horizontal axis x indicates the amount of positional deviation in a large-size pattern, the vertical axis y indicates the amount of positional deviation in a small-size pattern, and y = k · The relationship x + a is obtained. Note that the size of the minute dimension pattern is 0.25 μm.
m, the dimension of the large dimension pattern is 20 μm, the NA (numerical aperture) of the projection optical system in the exposure apparatus is 0.60, and the σ (dispersion rate) of the projection optical lens is 0.50. From this correlation characteristic, a deviation a occurs in the positional deviation between the small size pattern S2 and the large size pattern L2 due to the influence of the aberration of the projection optical system in the exposure apparatus. It is presumed that the deviation a is caused by various factors such as the NA and σ in the exposure apparatus, the size of the minute dimension pattern, the pattern position in the chip, and the like. Further, k is a count that depends on the scale accuracy of the SEM and the optical measuring instrument, but is roughly 1. In any case, from this correlation characteristic, the positional deviation in the large dimensional pattern L2 and the positional deviation in the small dimensional pattern S2 are different, and a specific correlation generated between the two is measured.

Then, the product wafer 11A formed by the pilot exposure is set on the optical measuring device 17, and a rectangular pattern 13A made of a conductive film formed on the product wafer 11A and a photoresist An image of a large-size misalignment detection pattern L1 composed of a rectangular pattern 16A formed of a blank pattern is captured, and the outer side position of the rectangular pattern 13A and the rectangular pattern 16A are captured.
Can be obtained as an imaging pattern, the X-direction position and the Y-direction position of each pattern are measured, and the misalignment of the center position of both patterns is measured. Plane X direction and Y at
The displacement in the direction and the displacement in the rotation direction can be measured (step S108).

In this case, actually, the product wafer 1 differs due to the difference in the substrate structure between the product wafer and the dummy wafer.
There may be a slight difference between the positional deviation of the large-sized pattern L1 formed on the dummy wafer 11B and the positional deviation of the large-sized pattern L1 formed on the dummy wafer 11B. In this case, the value of the positional deviation of the large dimensional pattern L1 obtained on the product wafer 11A is compared with the positional deviation correlation between the large dimensional pattern L2 and the small dimensional pattern S2 obtained on the dummy wafer 11B shown in FIG. By applying the corresponding positional deviation value of the large dimensional pattern L2, the positional deviation of the small dimensional pattern S1 on the product wafer 11A is estimated (step S109).

Therefore, by correcting the exposure device (not shown) based on the estimated positional deviation in the microscopic pattern, the positional deviation in the microscopic pattern S1 formed on the product wafer 11A in the subsequent steps is corrected. The production can be performed within the allowable range (step S11).
0). The correction of the displacement in this exposure apparatus includes:
For the projection exposure diameter, change the magnification of the lens or replace the entire lens. Alternatively, position adjustment in the plane X and Y directions of the table on which the silicon wafer to be exposed is mounted, or rotation position adjustment in the θ direction on the plane is performed. In adjusting the position of the table, the table is set to an optimum position obtained by the least square method. Thus, by performing exposure with a photomask for the contact hole on a product wafer other than the pilot exposure, a resist pattern of a contact hole positioned with high precision with respect to the gate electrode can be formed,
By etching the interlayer insulating film using this resist pattern, it is possible to open a contact hole that is not displaced from the gate electrode.

Here, in the above-described embodiment, the case where the gate electrode is used as the lower layer pattern and the case where the contact hole is opened in the interlayer insulating film as the upper layer pattern is exemplified. However, the present invention is not limited to these patterns. When the base is an insulating film at the time of formation, the manufacturing method of the present invention can be similarly applied.

[0023]

As described above, according to the present invention,
While a large-size misregistration detection pattern is formed on a semiconductor substrate as a product and the misalignment is detected by an optical measuring device,
A similar large-size misregistration detection pattern and a very small-dimension misregistration detection pattern are formed on a conductive substrate, and the large-dimension misregistration detection pattern is measured using an optical measuring instrument. On the other hand, while detecting the displacement, a pattern for detecting a small-sized positional displacement is measured by an SEM to detect the positional displacement, and a correlation between the positional deviations in the large-sized and small-sized positional deviation detecting patterns is obtained. By applying the misalignment measured on the product semiconductor substrate to this correlation, even when it is difficult to directly measure the misalignment by SEM due to the presence of an insulating film on the surface of the product semiconductor substrate. , Estimate misalignment of micro-sized patterns on semiconductor substrates to be products, correct misalignment in exposure equipment, and manufacture semiconductor devices positioned with high precision with high yield Rukoto can be realized. Further, by using the measuring apparatus of the present invention, the manufacture of the semiconductor device positioned with high precision as described above can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic process diagram for explaining main steps of a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a plan view and a cross-sectional view of a product wafer.

FIG. 3 is a plan view and a sectional view of a dummy wafer.

FIG. 4 is a diagram showing a correlation between a positional deviation in a large-size positional deviation detecting pattern and a positional deviation in a small-sized pattern.

FIG. 5 is a plan view and a cross-sectional view of a product wafer provided with a misregistration detection pattern in a conventional manufacturing method.

[Explanation of symbols]

 11A Product wafer 11B Dummy wafer 13A Rectangular pattern 13a Gate electrode 14 Photoresist 14B Rectangular pattern 14C Rectangular pattern 15 Interlayer insulating film 16 Photoresist 16A Rectangular pattern 17 Optical measuring instrument 18 Scanning electron microscope L1, L2 Pattern S1, S2 Pattern for detecting displacement of minute dimensions

Continuation of the front page (51) Int.Cl. ⁷ identification code FI H01L 21/30 564Z G01B 11/24 A (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027

Claims (7)

(57) [Claims] 1. A method comprising: forming a lower pattern on a semiconductor substrate; forming an insulating film covering the lower pattern; and forming a photoresist pattern for forming an upper pattern on the insulating film. In a method of manufacturing a semiconductor device, a photoresist is applied to a surface of a substrate having a conductive surface, and the photoresist is formed using respective photomasks for forming the lower layer pattern and the upper layer pattern on the photoresist. Forming large and small dimensional misregistration detection patterns for detecting misalignment between the lower layer pattern and the upper layer pattern, and observing the large dimensional misregistration detection pattern with an optical measuring instrument Measuring the position shift by observing the pattern for detecting the position shift of the minute dimension with a scanning electron microscope. A step of measuring the displacement; a step of calculating a correlation between the displacements in the large dimension and the small dimension based on the measured displacements of the large and small dimension displacement detection patterns; and Forming a large-size misregistration detection pattern on each part of the lower layer pattern and the photoresist pattern, and measuring the misregistration by observing the misalignment detection pattern on the semiconductor substrate with an optical measuring instrument; Estimating a positional deviation of a micro-dimensional pattern formed on the semiconductor substrate by comparing a positional deviation measured from a large-sized positional deviation detecting pattern of the semiconductor substrate with a correlation of the obtained positional deviation. Correcting the position shift in an exposure apparatus for exposing and forming the pattern based on the estimated position shift. Method of manufacturing a body apparatus. 2. The semiconductor according to claim 1, wherein the large-size misregistration detection pattern is formed as a pattern having a size of several μm or more, and the small-dimension misregistration detection pattern is formed as a pattern having a comma of several μm. Device manufacturing method. 3. The pattern for detecting displacement of large and small dimensions includes a part of the photoresist left by exposure and development using a photomask for forming the lower layer pattern and the upper layer. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the pattern is formed by removing a part of the remaining photoresist by exposure and development using a photomask for forming a pattern. 4. The lower pattern is a gate electrode made of a conductive film formed on a silicon substrate, the insulating film is an insulating film such as a silicon oxide film, and the upper pattern is formed on the interlayer insulating film. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the contact hole is a contact hole. 5. The method of manufacturing a semiconductor device according to claim 1, wherein said photoresist is of a positive type. 6. An optical measuring device for measuring a position shift in a pattern of several μm or more for a superimposed pattern of two consecutive photolithography steps formed on a conductive substrate having a surface, Contact the pattern
Measurement of in kicking a scanning microscope to measure the positional deviation, the optical measuring instrument is measured positional deviation between the scanning microscope
Means for determining the correlation with the position error
A semiconductor device measuring device , characterized in that: 7. A semiconductor substrate having a resist pattern for forming an upper layer pattern on an insulating film covering a lower layer pattern, wherein a pattern of several μm or more of the resist pattern is measured by an optical measuring device. In item 6
Estimated to display the positional deviation of the pattern of tenths of μm of the resist pattern from said correlation obtained
An apparatus for measuring a semiconductor device, comprising: