TWI694165B - Method of measuring offset of pvd material layer and calibration of offset - Google Patents

Abstract

A method of measuring offset includes providing substrate. A big trench and a small trench are embedded in the substrate. The big trench has a first vertical center line. The small trench has a second vertical center line. A first distance is between the first vertical center line and the second vertical center line. Then, a physical vapor deposition process is performed to form a material layer fills into the big trench and the small trench. The material layer in the big trench forms a first recess, and the material layer in the small trench forms a second recess. The thicknesses of the material layer on the opposing sidewalls of the big trench are different. Then, a position of a third vertical center line of the first recess and a position of a fourth vertical center line of the second recess are detected. A second distance is between the third vertical center line and the fourth vertical center line. Finally, the difference between the second distance and the first distance is calculated to get an offset.

Description

Method for measuring offset of physical vapor deposition material layer and method for correcting offset

The invention relates to a method for measuring the offset of a material layer and a method for correcting the offset, in particular to a method for measuring the offset for a physical vapor deposition material layer and a method for correcting the offset.

The manufacturing process of the integrated circuit starts from the silicon wafer and goes through a series of process steps; the oxidation process, optical development, chemical vapor deposition, ion implantation, etching, chemical mechanical polishing and other front-end processes, as well as packaging and testing and other back-end processes Just finished. In order to be able to lay out a complete electronic circuit on the die on the wafer, in the process, according to the design of the circuit, by optical development technology, ion implantation or metal wiring will be performed in the selected area, and at the same time, other exposures must be protected Surface area.

Optical development mainly includes procedures such as photoresist coating, baking, reticle alignment, exposure and development. After coating the design of the electronic circuit on the wafer with photoresist, and then through the process of photomask alignment, exposure and development, the pattern on the photomask is converted to the photoresist, so the photoresist on the wafer surface will be It has the same figure as the mask. In order to ensure that the interconnection rate between the upper film layer and the lower film layer in the semiconductor manufacturing process is correct, the alignment step between the development of the photomask is particularly important.

However, after the material layer is formed, uneven thickness of the material layer often occurs, which affects the alignment of the photomask and causes a shift in the photoresist pattern after subsequent exposure.

In view of this, the present invention provides a method of measuring the offset of the material layer and a method of correcting the offset to ensure the correctness of the position of the photoresist pattern after exposure.

According to a preferred embodiment of the present invention, a method for measuring the offset of a physical vapor deposition material layer includes: providing a first substrate, wherein at least one first large trench and at least one small trench are buried in the first substrate, The first large ditch has a first vertical centerline, and the small ditch has a second vertical centerline, wherein there is a first distance between the first vertical centerline and the second vertical centerline, and then a first physical vapor phase is performed A deposition process to form a first material layer to fill the first large trench and the small trench, wherein the first material layer forms a first groove in the first large trench, and forms a second groove in the small trench, the first A material layer has different thicknesses on two opposite sidewalls of the first large trench, and then detects the position of a third vertical centerline of the first groove and detects the position of a fourth vertical centerline of the second groove , Where there is a second distance between the third vertical centerline and the fourth vertical centerline, and finally the difference between the first distance and the second distance is calculated to obtain an offset.

In order to make the above objects, features and advantages of the present invention more obvious and understandable, the preferred embodiments are described below in conjunction with the accompanying drawings, which are described in detail below. However, the following preferred embodiments and drawings are for reference and description only, and are not intended to limit the invention

FIGS. 1 to 6 are a method for measuring the offset of the physical vapor deposition material layer and a method for correcting the offset according to the first preferred embodiment of the present invention.

As shown in FIG. 1, a first substrate 10 is provided, at least one first large trench 12 and at least one small trench 14 are buried in the first substrate 10, and the number of the first large trenches 12 may be one or more, The number of the small trenches 14 may be one or more. In the embodiment of the present invention, the number of the first large trenches 12 and the small trenches 14 is one as an example. The first substrate 10 may be a semiconductor wafer, such as a silicon wafer or a silicon germanium wafer. The first substrate 10 may also be other insulating materials, such as silicon oxide, silicon nitride, or silicon oxynitride. The first substrate 10 may be a test substrate, that is, a substrate used for testing the process before actual mass production and adjusting process parameters based on the test results to reduce the error value of the process during actual mass production. In addition, the first substrate 10 may be a substrate for production, that is, a substrate for formal production of semiconductor elements. The first large trench 12 and the small trench 14 may be disposed on the scribe line of the first substrate 10 or at a position where a grain will be formed in the future. The first large trench 12 and the small trench 14 serve as alignment marks.

Please continue to refer to FIG. 1 to measure the vertical centerline positions of the first large ditch 12 and the small ditch 14 to obtain the first vertical centerline M1 and the second vertical centerline M2. There is a first distance D1 between the first vertical centerline M1 and the second vertical centerline M2. Next, a buffer layer 16 is formed on the sidewalls and bottom of the first large trench 12 and the small trench 14. The buffer layer 16 may preferably be titanium nitride. According to another preferred embodiment of the present invention, the buffer layer 16 may not be formed. The first vertical center line M1 and the second vertical center line M2 refer to reference lines perpendicular to the bottom of the first large ditch 12 and the bottom of the small ditch 14 respectively, and bisecting the first large ditch 12 and the small ditch 14 respectively.

As shown in FIG. 2, a physical vapor deposition process 18 is performed to form a first material layer 20 to fill the first large trench 12 and the small trench 14, wherein the first material layer 20 forms a first A groove 22, forming a second groove 24 in the small trench 14, the thickness of the first material layer 20 on the two opposite sidewalls of the first large trench 12 is different, preferably the first material layer 20 is in the small trench The thickness on the opposite side walls of 14 is essentially the same. After the first material layer 20 is formed, the first groove 22 and the second groove 24 serve as alignment marks for the first material layer 20. However, the different thicknesses of the first material layer 20 on the opposite side walls may cause deviations in the positioning of the photomask later. The first material layer 20 is preferably a conductive material, such as tungsten, titanium, copper, or other conductive materials, but is not limited thereto. The first material layer 20 may be any material formed by a physical vapor deposition process, including Conductive or insulating materials are acceptable.

The thickness of the first material layer 20 is preferably 60 nm, but can be adjusted according to different requirements. In addition, the ratio of the opening width of the small trench 14 to the thickness of the first material layer 20 needs to be controlled to ensure that after the first material layer 20 fills the small trench 14, there will be grooves in the small trench 14 that can be detected later The vertical center line of the groove, the ratio of the opening width of the small trench 14 to the thickness of the first material layer 20 is preferably greater than 2.5.

The physical vapor deposition process 18 bombards the target material (that is, the material to be plated) with a high-energy ion beam or atomic beam, and then strikes the atoms on the target material and deposits them on the first substrate 10. Each atom will have various reflection angles. According to different coordinate axis positions of the first large trench 12 on the first substrate 10, the angle of the incident atoms received by the first large trench 12 may be biased. Because the target material is usually placed above the center of the first substrate 10, if the first large trench 12 is located in the center of the first substrate 10, it will receive atoms from all directions on average, so the first material layer 20 is in the first The thickness of the opposite side walls in the large trench 12 will be the same. If the first large ditch 12 is located on the left edge of the first substrate 10, it will receive more atoms incident from the right, otherwise if the first large ditch 12 is located on the right edge of the first substrate 10, it will receive more The atoms incident from the left will cause the thickness of the first material layer 20 on the opposite side walls of the first large trench 12 to be somewhat different. However, because the small trench 14 has a small opening, the difference in thickness of the first material layer 20 on both sides is so small that it can be regarded as zero in practice. According to a preferred embodiment of the present invention, the ratio of the height and width of the small trench 14 is between 0.333 and 1.066, and the ratio of the height and width of the first large trench 12 is between 0.038 and 0.123. For example, the width of the small trench 14 is preferably 150 nm, the width of the first large trench 12 is preferably 1300 nm, and the depth of the small trench 14 and the first large trench 12 are the same, preferably between 50 nm and Between 160 nanometers.

As shown in FIG. 3, the first material layer 20 is planarized so that the thickness of the first material layer 20 on the upper surface of the first substrate 10 becomes smaller, for example, after planarization, the first material layer 20 is on the substrate 10 The thickness of the surface is preferably 10 nm. Then, the position of a third vertical center line M3 of the first groove 22 and the position of a fourth vertical center line M4 of the second groove 24 are detected, wherein the third vertical center line M3 and the fourth vertical center line M4 refers to a reference line that is perpendicular to the bottom of the first groove 22 and the bottom of the second groove 24 and bisects the first groove 22 and the second groove 24, respectively. There is a second distance D2 between the third vertical center line M3 and the fourth vertical center line M4, and then the difference between the first distance D1 and the second distance D2 is calculated to obtain an offset X. In addition, the first material layer 20 has the same thickness on the sidewalls of the opposite sides of the small trench 14, so the position of the fourth vertical centerline M4 of the second groove 24 coincides with the position of the second vertical centerline M2 of the small trench 14 . Since the thickness of the first material layer 20 on both sides of the first large trench 12 is different, after the first material layer 20 is deposited, the alignment mark formed by the first groove 22 is positioned to be the same as that of the first large trench 12 The positions of the formed alignment marks are different, that is to say, the position of the third vertical center line M3 of the first groove 22 is different from the position of the first vertical center line M1, thereby causing an offset X.

As shown in FIG. 4, a second material layer 26 is selectively formed to conform to cover the first large trench 12 and the small trench 14 and fully cover the upper surface of the first substrate 10, and the second groove 24 of the small trench 14 will be The second material layer 26 is filled. The second material layer 26 is preferably a composite material layer of a magnetic tunnel junction (MTJ). For example, the second material layer 26 includes a ferromagnetic material and an insulating layer. Ferromagnetic materials are, for example, cobalt, platinum, cobalt/nickel alloy, cobalt/palladium alloy, iron/boron alloy, cobalt/platinum alloy, gadolinium/iron alloy, cobalt-iron alloy, cobalt/iron/boron alloy or tantalum/iron/ Cobalt alloy. The insulating layer may be magnesium oxide (MgO) or aluminum oxide (Al ₂ O ₃ ). However, depending on product requirements, the second material layer 26 may be other materials, such as semiconductor materials, insulating layers, or metals.

Next, a photoresist layer 28 is formed to fully cover the second material layer 26, and then the offset X is input to an exposure machine 27 to correct the position of a photomask 30, and then the photoresist layer 28 is exposed. Generally speaking, the position of the photomask 30 should be aligned with the position of the first large trench 12, but because the thickness of the first material layer 20 on both sides of the first large trench 12 is different, the first material layer 20 is superimposed on the first large trench After 12, the position of the first groove 22 formed is different from that of the first large trench 12, resulting in misalignment of the photomask 30. In addition, because the thickness of the first material layer 20 on both sides of the first large trench 12 is different, after the first material layer 20 is formed, the positions of the third vertical center line M3 and the first vertical center line M1 of the first groove 22 are different , But the second material layer 26 formed later has the same overall thickness, so the vertical centerline of the groove formed in the first large trench 12 by the second material layer 26 is the third vertical centerline M3 position. That is to say, after the second material layer 26 is formed, the exposure machine 27 will be positioned with the third vertical center line M3, but this is an incorrect position, so the present invention inputs the offset X to the exposure machine 27 After correcting the detected position of the third vertical center line M3 back to the position of the first vertical center line M1, that is, the position of the alignment mark formed by the first large trench 12, the reticle 30 can be adjusted to Correct location.

According to another preferred embodiment of the present invention, the photoresist layer 28 may be directly formed without forming the second material layer 26, and then the offset X is input to the exposure machine 27 to correct the position of the photomask 30.

As shown in FIG. 5, the photoresist layer 28 is developed to form a patterned photoresist layer 32. As shown in FIG. 6, using the patterned photoresist layer 32 as a mask, the second material layer 26, the first material layer 20 and the buffer layer 16 are etched, and finally the patterned photoresist layer 32 is removed.

As described above, the distribution of the thickness of the first material layer 20 will change because the first large trench 12 is at different positions on the first substrate 10, so the above method of obtaining the offset X can be repeated to obtain the The first large trench 12 on a substrate 10 at different coordinate axis positions undergoes different offsets after physical vapor deposition.

After the offset X is obtained from the first substrate 10, the offset X can be used for another substrate. 7 to 10 are the offset correction methods according to the second preferred embodiment of the present invention.

As shown in FIG. 7, a second substrate 50 is provided on which a second large trench 52 is provided, the first large trench 12 and the second large trench 52 are the same size and the first large trench 12 is on the first substrate 10 The coordinate axis position is the same as the coordinate axis position of the second large ditch 52 on the second substrate 50, that is to say, on the exposure machine, the first vertical center line M1 of the first large ditch 12 and the vertical center line of the second large ditch 52 (Not shown) will be considered to be in the same position by the exposure machine. The second substrate 50 and the first substrate 10 have the same size. The second substrate 50 is a substrate used for the formal production of semiconductor devices, and the small trench 14 on the first substrate 10 is not provided thereon. Next, a buffer layer 56 is formed to cover the sidewalls and bottom of the second large trench 52, and then a physical vapor deposition process 58 is performed to form a third material layer 60 to fill the second large trench 52, the third material layer 60 and the first The thickness of the material layer 20 is the same as the material, that is to say, the thickness of the third material layer 60 on the two opposite sidewalls of the second large trench 52 is also different.

As shown in FIG. 8, a fourth material layer 66 is selectively formed to conformally cover the second large trench 52 and fully cover the upper surface of the second substrate 50. The thicknesses of the fourth material layer 66 and the second material layer 26 and The material is the same. Next, a photoresist layer 68 is formed to fully cover the fourth material layer 66. Then, the offset X obtained from the first substrate 10 is input to the exposure machine 27 to correct the position of the photomask 30', and the photoresist layer 68 is exposed. As shown in FIG. 9, the photoresist layer 68 is developed to form a patterned photoresist layer 72. As shown in FIG. 10, the patterned photoresist layer 72 is used as a mask to etch the fourth material layer 66 and the third The material layer 60 and the buffer layer 56 finally remove the patterned photoresist layer 72.

FIG. 11 is a schematic diagram of the position of a patterned photoresist layer with an uncorrected offset according to a third preferred embodiment of the present invention, in which elements with the same function will continue to be used in the second preferred embodiment Component label. As shown in FIG. 11, another second substrate 50 is provided, and the third material layer 60 is filled into the second large trench 52 to form a groove 62. Since the exposure machine has no correction for the offset X, the mask The alignment position is based on the position of the groove 62 as the alignment mark, that is, based on the fifth vertical center line M5 of the groove 62 in the third material layer 60, and the fifth vertical center line M5 is the bottom of the vertical groove 62 And the reference line that divides the groove 62 right and left. Compared with the position of the patterned photoresist 72 in Fig. 9, the position of the patterned photoresist 72' after the final exposure and development in Fig. 11 is shifted.

The method for measuring the offset of the present invention is applicable to all material layers formed by a physical vapor deposition process, and is not limited to the materials mentioned above. The present invention can be applied to other trench transistors, trench capacitors, trenches, etc. As long as the manufacturing process of the insulating structure and the like is made by depositing the material formed by the trench and the physical vapor deposition process in the trench, the subsequent exposure process can be matched with the method of the present invention. The above are only the preferred embodiments of the present invention, and all changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the present invention.

10: The first base 12: The first big ditch 14: Small ditch 16: Buffer layer 18: Physical vapor deposition process 20: first material layer 22: First groove 24: second groove 26: Second material layer 27: Exposure machine 28: photoresist layer 30: Mask 30’: Mask 32: Patterned photoresist layer 50: second base 52: The second largest ditch 56: buffer layer 58: Physical vapor deposition process 60: third material layer 62: groove 66: fourth material layer 68: photoresist layer 72: Patterned photoresist 72’: Patterned photoresist D1: First distance D2: Second distance M1: first vertical centerline M2: Second vertical centerline M3: Third vertical centerline M4: Fourth vertical centerline M5: Fifth vertical centerline X: offset

FIGS. 1 to 6 are a method for measuring the offset of the physical vapor deposition material layer and a method for correcting the offset according to the first preferred embodiment of the present invention. 7 to 10 are a method for measuring the offset of the physical vapor deposition material layer and a method for correcting the offset according to the second preferred embodiment of the present invention. FIG. 11 is a schematic diagram showing that the patterned photoresist is shifted according to the third preferred embodiment of the present invention.

10: The first base

12: The first big ditch

14: Small ditch

16: Buffer layer

20: first material layer

22: First groove

24: second groove

D1: First distance

D2: Second distance

M1: first vertical centerline

M3: Third vertical centerline

M4: Fourth vertical centerline

X: offset

Claims (8)

A physical vapor deposition material layer offset measurement method and offset correction method, including: A first substrate is provided, wherein at least one first large ditch and at least one small ditch are buried in the first substrate, the first large ditch has a first vertical centerline, and the small ditch has a second vertical centerline, wherein There is a first distance between the first vertical centerline and the second vertical centerline; Performing a first physical vapor deposition process to form a first material layer to fill the first large trench and the small trench, wherein the first material layer forms a first groove in the first large trench, in A second groove is formed in the small trench, and the thickness of the first material layer on two opposite sidewalls of the first large trench is different; Detecting the position of a third vertical center line of the first groove and detecting the position of a fourth vertical center line of the second groove, wherein between the third vertical center line and the fourth vertical center line Have a second distance; and The difference between the first distance and the second distance is calculated to obtain an offset. The method for measuring the offset of the physical vapor deposition material layer and the method for correcting the offset as described in claim 1 further include: detecting the position of the third vertical centerline and the fourth vertical centerline Before the position, a planarization process is performed to remove part of the first material layer. The method for measuring the offset of the physical vapor deposition material layer and the method for correcting the offset as described in claim 1, wherein after obtaining the offset, the method further includes: Forming a second material layer to fill the first large trench and the small trench and fully cover the upper surface of the first substrate; Form a photoresist layer to fully cover the second material layer: After inputting the offset into an exposure machine to correct the position of a photomask, expose the photoresist layer; Developing the photoresist layer to form a patterned photoresist layer; and Using the patterned photoresist layer as a mask, the first material layer and the second material layer are etched. The method for measuring the offset of the physical vapor deposition material layer and the method for correcting the offset as described in claim 1, wherein after obtaining the offset, the method further includes: A second base is provided on which a second large ditch is provided, the first large ditch and the second large ditch are of the same size and the coordinate axis position of the first large ditch on the first base and the second large ditch are The coordinate axis positions on the second substrate are the same, and the second substrate and the first substrate are the same size; A second physical vapor deposition process is performed to form a third material layer to fill the second large trench, wherein the third material layer and the first material layer have the same thickness and material, and the third material layer is in the first The thickness of the two opposite side walls of the two major ditches is different; A photoresist layer is formed to fully cover the third material layer: After inputting the offset into an exposure machine to correct the position of a photomask, expose the photoresist layer; Developing the photoresist layer to form a patterned photoresist layer; and Using the patterned photoresist layer as a mask, the third material layer is etched. The method for measuring the offset of the physical vapor deposition material layer and the method for correcting the offset as described in claim 1, wherein the ratio of the opening width of the small trench to the thickness of the first material layer is preferably greater than 2.5. The method for measuring the offset of the physical vapor deposition material layer and the method for correcting the offset as described in claim 1, wherein the depths of the first large trench and the small trench are the same. The method for measuring the offset of the physical vapor deposition material layer and the method for correcting the offset as described in claim 1, wherein the ratio of the height and width of the small trench is between 0.333 and 1.066. The method for measuring the offset of the physical vapor deposited material layer and the method for correcting the offset as described in claim 1, wherein the ratio of the height and width of the first large trench is between 0.038 and 0.123.

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