Method for improving variation of photoetching alignment mark

Abstract

The invention provides a method for improving variation of a photoetching alignment mark. The method comprises the following steps of: forming the photoetching alignment mark on a front-layer pattern; forming a first epitaxial layer with a first thickness on the front layer pattern at a growth rate of 0.05-0.2 um / min; and forming a second epitaxial layer of a second thickness on the first epitaxial layer at a growth rate of 1.5-2.5 [mu] m / min. According to the invention, a two-step epitaxial growth method is adopted, so that a better photoetching alignment mark is obtained. A thicker epitaxial layer can be grown, and a layer of photoetching alignment mark is reduced, so that the process time is reduced.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a method for improving photolithography alignment mark variation. Background Art

[0002] The buried layer epitaxy is to perform epitaxial growth on a silicon wafer with an existing buried layer pattern (NBL / PBL). The epitaxial growth grows upward along the original lattice direction. After the epitaxial growth is completed, the same pattern as before the growth is formed on the new epitaxial layer, forming a Figure 1 When growing thicker epitaxial layers (greater than 9um), pattern drift will occur, causing the lithography alignment marks to vary, forming Figure 3 The structure shown.

[0003] See also Figure 2 During the epitaxy reaction, Si, H2, As and HCL are produced. The epitaxy process is a composite process of growth and etching. Due to the etching effect, after the epitaxy growth is completed, the new pattern will drift (distort) relative to the original pattern. The longer the epitaxy growth process, the more significant this effect will be.

[0004] Severe pattern drift will cause the lithography alignment marks after epitaxy to change, resulting in poor alignment of the subsequent layer lithography / OVL (overlay mark) deviation exceeding the specification.

[0005] In the prior art, the atmospheric buried layer epitaxial growth conditions are a process temperature of 1150+ / -50 degrees and a growth rate of 2.0+ / -0.5um / min. Under this standard process condition, when the epitaxial thickness exceeds 9-10um, serious pattern drift (distortion) will occur, and the lithography alignment mark variation after epitaxy will be caused, and the rear layer lithography alignment will be poor / OVL offset will exceed the specification. To solve this problem, epitaxy is divided into two processes, and a layer of lithography alignment marks is added in the middle.

[0006] For thicker epitaxy (8-12um), the prior art uses a normal rate (1.5-2.5um / min) to grow 4-6um epitaxy once, forms a new lithography alignment mark, and then uses a normal rate (1.5-2.5um / min) to grow 4-6um epitaxy again.

[0007] In order to solve the above problems, a new method for improving the variation of photolithography alignment marks needs to be proposed. Summary of the invention

[0008] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for improving the variation of lithography alignment marks, which is used to solve the problem of pattern drift occurring when growing a thicker epitaxial layer (greater than 9um) in the prior art, resulting in variation of lithography alignment marks.

[0009] To achieve the above objectives and other related objectives, the present invention provides a method for improving lithography alignment mark variation, comprising:

[0010] Step 1: forming a photolithography alignment mark on the front layer pattern;

[0011] Step 2: forming a first epitaxial layer of a first thickness on the front layer pattern at a growth rate of 0.05-0.2 um / min;

[0012] Step three: forming a second epitaxial layer of a second thickness on the first epitaxial layer at a growth rate of 1.5-2.5 um / min.

[0013] Preferably, the front layer pattern in step one is a substrate and a buried layer thereon.

[0014] Preferably, the photolithography alignment mark in step one is formed by photolithography and etching.

[0015] Preferably, the photolithography alignment mark in step one is a windmill-shaped groove group.

[0016] Preferably, the growth temperature of the first epitaxial layer in step 2 is 1100 to 1200 degrees Celsius.

[0017] Preferably, the thickness of the first epitaxial layer in step 2 is 10-20% of the thickness of the first and second epitaxial layers.

[0018] Preferably, the thickness of the first epitaxial layer in step 2 is 1-3 um.

[0019] Preferably, the growth temperature of the second epitaxial layer in step three is 1100 to 1200 degrees Celsius.

[0020] Preferably, the thickness of the second epitaxial layer in step three is 7-9 um.

[0021] Preferably, the method further comprises: step 4, washing and then taping out.

[0022] As described above, the method for improving the variation of lithography alignment marks of the present invention has the following beneficial effects:

[0023] The present invention adopts a two-step epitaxial growth method, thereby obtaining better photolithography alignment marks, being able to grow a thicker epitaxial layer, reducing one layer of photolithography alignment marks, and thus reducing process time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram showing a prior art method of forming the same pattern as before growth on a new epitaxial layer;

[0025] Figure 2Shown is a schematic diagram of the epitaxial reaction process of the prior art;

[0026] Figure 3 Shown is a schematic diagram of a variation of a photolithography alignment mark in the prior art;

[0027] Figure 4 Shown is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] See also Figure 4 The present invention provides a method for improving lithography alignment mark variation, comprising:

[0030] Step 1: forming a photolithography alignment mark on the front layer pattern;

[0031] In some embodiments, the front layer pattern in step 1 is a substrate and a buried layer thereon, which can be a P-type buried layer or an N-type buried layer.

[0032] In some embodiments, the photolithography alignment mark in step 1 is formed by photolithography and etching.

[0033] In some embodiments, the photolithography alignment mark in step 1 is a windmill-shaped groove group, and a current layer alignment mark will be formed on the subsequent current layer pattern to align with the photolithography alignment mark to determine whether the previous layer pattern and the current layer pattern are aligned, and the current layer pattern is filled in the center of the windmill-shaped groove group. In other embodiments, the shapes of the photolithography alignment mark and the current layer alignment mark can also be adjusted to other shapes.

[0034] Step 2: Form a first epitaxial layer of a first thickness on the front layer pattern at a growth rate of 0.05-0.2 um / min; for example, the growth rate of the first epitaxial layer may be 0.05 um / min, 0.1 um / min, 0.15 um / min, or 0.2 um / min.

[0035] In some embodiments, the growth temperature of the first epitaxial layer in step 2 is 1100 to 1200 degrees Celsius.

[0036] In some embodiments, the thickness of the first epitaxial layer in step 2 is 10-20% of the thickness of the first and second epitaxial layers.

[0037] In some embodiments, the thickness of the first epitaxial layer in step 2 is 1-3 um.

[0038] Step 3: Form a second epitaxial layer of a second thickness on the first epitaxial layer at a growth rate of 1.5-2.5um / min. For example, the growth rate of the second epitaxial layer can be 1.5um / min, 2um / min, and 2.5um / min. Pattern drift is related to the epitaxial growth rate (the faster the growth rate, the greater the pattern drift, and the more obvious the variation of the lithography alignment mark). A two-step epitaxial growth method is used to obtain better lithography alignment marks.

[0039] In some embodiments, the growth temperature of the second epitaxial layer in step 3 is 1100 to 1200 degrees Celsius. Pattern drift is related to the epitaxial growth temperature (the lower the growth temperature, the greater the pattern drift and the more obvious the variation of the lithography alignment mark). The epitaxial layer grown at this temperature can obtain better lithography alignment marks.

[0040] In some embodiments, the thickness of the second epitaxial layer in step three is 7-9 um.

[0041] In some embodiments, the method further includes: step 4, post-wafer cleaning.

[0042] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0043] In summary, the present invention adopts a two-step epitaxial growth method to obtain better photolithography alignment marks. A thicker epitaxial layer can be grown, reducing one layer of photolithography alignment marks, thereby reducing process time. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0044] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for improving lithography alignment mark variation, characterized in that: At least: Step 1: forming a photolithography alignment mark on the front layer pattern; Step 2: forming a first epitaxial layer of a first thickness on the front layer pattern at a growth rate of 0.05-0.2 um / min; Step three: forming a second epitaxial layer of a second thickness on the first epitaxial layer at a growth rate of 1.5-2.5 um / min.

2. The method for improving lithography alignment mark variation according to claim 1, characterized in that: The front layer pattern in step 1 is the substrate and the buried layer thereon.

3. The method for improving lithography alignment mark variation according to claim 1, characterized in that: The photolithography alignment mark in step one is formed by photolithography and etching.

4. The method for improving lithography alignment mark variation according to claim 1, characterized in that: The photolithography alignment mark in step 1 is a windmill-shaped groove group.

5. The method for improving lithography alignment mark variation according to claim 1, characterized in that: The growth temperature of the first epitaxial layer in step 2 is 1100 to 1200 degrees Celsius.

6. The method for improving lithography alignment mark variation according to claim 1, characterized in that: The thickness of the first epitaxial layer in step 2 is 10-20% of the thickness of the first and second epitaxial layers.

7. The method for improving lithography alignment mark variation according to claim 1, characterized in that: The thickness of the first epitaxial layer in step 2 is 1-3 um.

8. The method for improving lithography alignment mark variation according to claim 1, characterized in that: The growth temperature of the second epitaxial layer in step three is 1100 to 1200 degrees Celsius.

9. The method for improving lithography alignment mark variation according to claim 1, characterized in that: The thickness of the second epitaxial layer in step three is 7-9 um.

10. The method for improving lithography alignment mark variation according to claim 1, characterized in that: The method further comprises: step 4, washing and then taping out.

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