EVALUATION OF AN UNDERCUT OF DEEP TRENCH STRUCTURES IN SOI WAFERS
First Claim
1. A method for evaluating an undercutting of deep trench structures in a semiconductor wafer wherein a control structure (100, 100b) is created on the semiconductor wafer, which control structure is configured such that as a result of a trench etching of a silicon layer of the semiconductor wafer, a silicon ridge (4b) is provided having a defined width between two adjacent trenches, the ridge being undermined (U) when undercuts merge into each other, wherein:
- said silicon ridge is heated after the trench etching, said undermined ridge (4b) thereby caused to move as compared to a non-undermined silicon ridge; and
said movement is registered and serves as a criterion of a ridge mobility.
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Accused Products
Abstract
A technique is provided which enables quantitative evaluation of an undercutting of deep trench structures in semiconductor wafers and, in particular, SOI wafers, by means of electrical or optical measuring. A specific control structure (100) having a defined ridge width is used which can be routinely measured in the course of the production process. The control structure comprises two adjacent trenches (5) each which are separated by a ridge having a defined ridge width. By undercutting (U) the adjacent trenches, the regions of undercutting of adjacent trenches may intersect each other starting from a specific minimum ridge width which results in a detachment of the ridge from the bottom making the ridge moveable. Mobility is determined by thermal deflection of the ridge. Arranging a plurality of control structures having various ridge widths enables determination of a quantitative amount of the undercutting.
47 Citations
33 Claims
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1. A method for evaluating an undercutting of deep trench structures in a semiconductor wafer wherein a control structure (100, 100b) is created on the semiconductor wafer, which control structure is configured such that as a result of a trench etching of a silicon layer of the semiconductor wafer, a silicon ridge (4b) is provided having a defined width between two adjacent trenches, the ridge being undermined (U) when undercuts merge into each other, wherein:
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said silicon ridge is heated after the trench etching, said undermined ridge (4b) thereby caused to move as compared to a non-undermined silicon ridge; and said movement is registered and serves as a criterion of a ridge mobility. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 31, 32, 33)
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12. A method for evaluating an undercutting of a deep trench structure in a substrate suitable for the production of a micro-structure component, comprising:
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producing a silicon ridge having a ridge width between two adjacent trenches by trench etching of a silicon layer of the substrate; generating a current flow in said silicon ridge; and assessing the amount of undercutting of said silicon ridge occurring during trench etching in a deeper region of the adjacent trenches using the generated current flow and a material loss of said ridge determined by the amount of undercutting. - View Dependent Claims (13, 14)
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15. An arrangement for evaluating an undercutting of a deep trench structure in a semiconductor wafer comprising:
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a component area for receiving micro-structure components, said area being defined by a trench structure (5A) having a given trench width; a first control structure (100) having a structure different from that of said micro-structure components and a silicon ridge formed by two adjacent trenches (5) having a certain width and being partially open between said adjacent trenches, wherein said silicon ridge is fixed at both ends thereof and comprises a contact surface for contacting by an external test probe. - View Dependent Claims (17, 18, 19, 20, 21)
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16. (canceled)
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22. An arrangement for evaluating an undercutting of a structure of deep trenches in a SOI wafer comprising:
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a component area defined by trenches having a defined width; a plurality of control structures located outside said component area, each control structure comprising one respective silicon ridge formed by adjacent trenches having a defined width, and wherein silicon ridge widths at a surface are provided with values graded in a defined manner so that said silicon ridges have various amounts of undercutting due to trench etching and thus various amounts of lateral mobility, wherein at least one contact surface for making contact with an external probe is provided in each control structure, said contact surface being connected with a respective silicon ridge. - View Dependent Claims (23, 24)
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25. (canceled)
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26. An arrangement in the form of a control structure for evaluating an undercutting of a deep trench structure in a SOI wafer, configured such that a silicon ridge having a defined ridge width is formed between two adjacent trenches extending substantially in parallel with each other in a portion of said arrangement as a result of trench etching, said silicon ridge is undermined when undercuts merge into each other and regions are formed in two portions adjacent to the ends of said silicon ridge which are not completely undermined during etching;
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wherein said trench comprises a closed trench, which encloses all three portions of said control structure; wherein contact points are provided in non-undermined portions at ends of said silicon ridge and in an adjacent non-etched semiconductor area for electric heating of said silicon ridge and for measuring a deflection thereof due to heating. - View Dependent Claims (27, 28)
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- 29. A method for evaluating an undercutting of deep trench structures in SOI wafers using a control structure created on said SOI wafers, which control structure is configured such that a silicon ridge having a defined ridge width is formed between two adjacent trenches extending in parallel with each other as a result of trench etching, which silicon ridge is undermined when undercuts merge into each other, wherein said silicon ridge is heated after trench etching, whereby said undermined silicon ridge is caused to move in comparison to a non-undermined ridge, due to expansion, said movement being registered and serving as a criterion of mobility for evaluating an amount of undercutting.
Specification