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What is the TTV, Bow, Warp of silicon wafers?

2024-05-24

Latest company news about What is the TTV, Bow, Warp of silicon wafers?

Wafer surface profile parameters Bow, Warp, TTV are very important factors that must be considered in chip manufacturing. Together, these three parameters reflect the flatness and thickness uniformity of the silicon wafer and have a direct impact on many key steps in the chip manufacturing process.

latest company news about What is the TTV, Bow, Warp of silicon wafers?  0

TTV is the difference between the maximum and minimum thickness of a silicon wafer. This parameter is an important index used to measure the thickness uniformity of silicon wafers. In a semiconductor process, the thickness of the silicon wafer must be very uniform over the entire surface. Measurements are usually made at five locations on the silicon wafer and the maximum difference is calculated. Ultimately, this value is the basis for judging the quality of the silicon wafer. In practical applications, the TTV of a 4-inch silicon wafer is generally less than 2um, and that of a 6-inch silicon wafer is generally less than 3um.

latest company news about What is the TTV, Bow, Warp of silicon wafers?  1

Bow

Bow in semiconductor manufacturing refers to the bending of silicon wafers. The word probably comes from a description of the shape of an object when it is bent, like the curved shape of a bow. The Bow value is defined by measuring the maximum deviation between the center and edge of the silicon wafer. This value is usually expressed in micrometers (µm). The SEMI standard for 4-inch silicon wafers is Bow< 40um.

latest company news about What is the TTV, Bow, Warp of silicon wafers?  2

Warp

Warp is a global feature of silicon wafers, indicating the maximum distance of the wafer surface from the plane. It measures the distance between the highest and lowest points of a silicon wafer. The SEMI standard for 4-inch silicon wafers is Warp< 40um.

latest company news about What is the TTV, Bow, Warp of silicon wafers?  3

What's the difference between TTV,Bow,Warp?

  • TTV focuses on changes in thickness and is not concerned with the bending or distortion of the wafer.
  • Bow focuses on the overall bend, mainly considering the bend of the center point and the edge.
  • Warp is more comprehensive, including bending and twisting of the entire wafer surface.

Although these three parameters are related to the shape and geometric properties of the silicon wafer, they are measured and described differently, and their impact on the semiconductor process and wafer processing is also different.

latest company news about What is the TTV, Bow, Warp of silicon wafers?  4

  • Effect of TTV, Bow, Warp on semiconductor process:

First of all, the smaller the three parameters, the better. The larger the TTV, Bow, and Warp, the greater the negative impact on the semiconductor process, so if the values of the three exceed the standard, the silicon chip will be scrapped.

  • Influence on the lithography process:

Focal depth problem: During lithography, changes in focal depth may result, which affects the sharpness of the pattern.

Alignment problems: May cause the wafer to shift during alignment, further affecting the alignment accuracy between layers.latest company news about What is the TTV, Bow, Warp of silicon wafers?  5

  • Impact on chemical mechanical polishing:

Uneven polishing: May result in uneven polishing during CMP, resulting in surface roughness and residual stress.

  • Effect on film deposition:

  Uneven deposition: Convex and concave wafers may cause uneven thickness of deposited film during deposition.

  • Impact on wafer loading:

  Loading problems: Convex and concave wafers can cause damage to wafers during automatic loading.

  Finally, as semiconductor practitioners, we must realize the importance of wafer profile parameters for the entire process process, and pay attention to details when doing semiconductor processes.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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