Base Bias Circuit Isolation for Wider Plasma Process Windows
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Solution Overview
Problem
Current plasma devices in semiconductor manufacturing face issues with a narrow process window and potential wafer damage due to uncontrolled DC bias voltage, limiting the ability to meet diverse process requirements.
Innovation Solution
A base bias adjustment apparatus and method that includes positive and negative bias adjustment units, with an anti-interference unit to prevent current interference, allowing simultaneous operation and expanding the adjustment range of bias voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If only negative bias voltage is applied to the base, then ion bombardment energy is increased, but wafer damage occurs and process window is limited
Solution Approach 1:
The bias voltage control is segmented into two independent units: a negative bias adjustment unit (using RF power supply) for ion bombardment energy control, and a positive bias adjustment unit (using DC power supply) for wafer voltage control. This segmentation allows each unit to independently optimize its function without interfering with the other, resolving the contradiction between achieving high ion energy and preventing wafer damage.
Solution Approach 2:
A matcher circuit is introduced as an intermediary between the RF power supply and the base, and a DC power supply is introduced as an intermediary for positive bias. These intermediaries enable precise control and isolation of the bias voltage sources, allowing simultaneous application of positive and negative biases while preventing direct interference between the circuits, thus expanding the process window.
2Power
If RF power supply is used to increase negative DC bias voltage, then ion energy is increased, but wafer voltage forward value increases causing wafer damage
Solution Approach 1:
The control functions are segmented: the negative bias adjustment unit (RF power supply through matcher) controls ion bombardment energy, while the positive bias adjustment unit (DC power supply) independently controls wafer voltage. This segmentation allows the system to achieve high ion energy while simultaneously preventing wafer damage through positive bias control.
Solution Approach 2:
The positive bias adjustment unit applies a preliminary counteracting action by providing positive bias voltage to counterbalance the harmful effects of excessive negative bias voltage on the wafer. This preliminary anti-action prevents wafer damage before it occurs, allowing the system to operate at higher ion energies safely.
3Adaptability or versatility
If positive and negative bias adjustment units operate simultaneously, then process flexibility is improved, but current interference between circuits occurs
Solution Approach 1:
The matcher circuit serves as an intermediary that isolates the RF power supply circuit from the base, preventing current from the positive bias circuit (connected directly to base) from flowing into the negative bias circuit. This intermediary structure enables simultaneous operation of both adjustment units without mutual interference, maintaining process flexibility while managing circuit complexity.
Data Source
AI summary
A base bias adjustment apparatus includes: a positive bias adjustment unit; a negative bias adjustment unit; and an anti-interference unit. A first terminal of the positive bias adjustment unit is grounded, and a second terminal of the positive bias adjustment unit is electrically connected to a base for adjusting a bias voltage of the base to have a positive bias voltage at the base. A first terminal of the negative bias adjustment unit is grounded, and a second terminal of the negative bias adjustment unit is electrically connected to the base through the anti-interference unit for adjusting the bias voltage of the base to have a negative bias voltage at the base. The anti-interference unit is electrically connected between the negative bias adjustment unit and the base for suppressing a current from a circuit between the positive bias adjustment unit and the base.