Halogen Lamp Intensity Control for Semiconductor Wafer Warpage Prevention
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Solution Overview
Problem
The existing flash lamp annealing process results in non-uniform temperature distribution in the susceptor, leading to uneven heating of semiconductor wafers, which can cause warpage during the preheating stage due to the susceptor's non-uniform temperature distribution.
Innovation Solution
The method involves controlling the intensity ratio of light emitted from continuous halogen lamps, initially with a lower intensity in the central portion compared to the edge portion (warpage suppressing irradiation) to prevent warpage, followed by increasing the intensity ratio to heat the semiconductor wafer uniformly (temperature increasing irradiation), and finally adjusting to ensure uniform in-plane temperature distribution (uniformizing irradiation).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the susceptor is heated by heat transfer and heat radiation from the semiconductor wafer during flash lamp annealing, then the susceptor temperature increases, but this results in non-uniform temperature distribution in the susceptor with the central portion at high temperature and edge portion at low temperature
Solution Approach 1:
The patent applies local quality by making the light intensity from the halogen lamps non-uniform across different regions. Specifically, the light intensity in the radial direction is controlled to be higher at the edge portion and lower at the central portion of the semiconductor wafer. This compensates for the non-uniform temperature distribution in the susceptor, ensuring uniform heating across the wafer surface.
Solution Approach 2:
The patent introduces asymmetry in the light intensity distribution from the halogen lamps. Instead of uniform illumination, the system deliberately creates an asymmetric intensity profile where the edge regions receive more light intensity than the central region. This asymmetric illumination pattern counteracts the symmetric but non-uniform temperature distribution in the susceptor.
2Temperature
If the semiconductor wafer is heated by light from halogen lamps when the susceptor has non-uniform temperature distribution, then the wafer temperature increases, but the central portion of the wafer is heated more strongly than the edge portion causing warpage
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for the expected non-uniform heating effect. Before the wafer heating process begins, the system is configured to emit light with a specific intensity distribution that anticipates and counteracts the non-uniform temperature distribution in the susceptor. This prevents warpage from occurring in the first place rather than correcting it afterward.
Solution Approach 2:
The patent implements local quality by varying the light intensity across different regions of the semiconductor wafer. The halogen lamps are controlled to provide higher intensity illumination at the edge portions and lower intensity at the central portion, creating a non-uniform light distribution that matches and compensates for the susceptor's temperature profile.
3Productivity
If flash lamp annealing is used to activate impurities in the semiconductor wafer surface, then the activation temperature is reached in extremely short time, but the susceptor develops significant non-uniformity in temperature distribution
Solution Approach 1:
The patent applies preliminary action by performing preheating of the semiconductor wafer using halogen lamps before the flash lamp annealing process. During this preheating stage, the light intensity is controlled to compensate for the non-uniform temperature distribution in the susceptor. This preliminary heating action ensures that when flash lamp annealing occurs, the wafer is already at a uniform temperature, preventing warpage even though the susceptor remains non-uniform.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for uniform heating of the semiconductor wafer without warpage, even when the susceptor has a non-uniform temperature distribution, ensuring efficient and consistent preheating and activation of impurities without deep diffusion.
Implementation Method 1
the temperature of the semiconductor wafer can be raised rapidly, with only a small amount of light transmitted through the semiconductor wafer
Implementation Method 2
the susceptor is also heated by heat transfer and heat radiation from the semiconductor wafer that is at an increased temperature
Implementation Method 3
the susceptor is also heated by heat transfer and heat radiation from the semiconductor wafer that is at an increased temperature
Implementation Method 4
The wavelength of light emitted from the xenon flash lamps is shorter than that of light emitted from conventional halogen lamps, and approximately coincides with a fundamental absorption band of a silicon semiconductor wafer. Thus, when a semiconductor wafer is irradiated with a flash of light emitted from the xenon flash lamps, the temperature of the semiconductor wafer can be raised rapidly
Data Source
AI summary
The temperature of a susceptor made of quartz is increased by heat transfer and heat radiation from a heated semiconductor wafer. When the treated semiconductor wafer is transported outwardly, the susceptor has a non-uniform temperature distribution in which a central portion thereof is higher in temperature than an edge portion thereof. In an early stage of preheating in which a new semiconductor wafer is held by the susceptor and starts being irradiated with light emanating from halogen lamps, an intensity ratio that is the ratio of the intensity of light emanating from a central portion of a light irradiator including an array of the halogen lamps to the intensity of light emanating from an edge portion thereof is less than 100%. Thereafter, the ratio of the intensity of light emanating from the central portion of the light irradiator to the intensity of light emanating from the edge portion thereof is increased.