Claims
- 1. A method for process monitoring, comprising:
receiving a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, following production of contact openings in the second layer by an etch process, the contact openings comprising a plurality of test openings having different, respective transverse dimensions; directing a beam of charged particles to irradiate the test openings; measuring, in response to the beam, at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample, thus producing an etch indicator signal; and analyzing the etch indicator signal as a function of the transverse dimensions of the test openings so as to assess a characteristic of the etch process.
- 2. The method according to claim 1, wherein analyzing the etch indicator signal comprises assessing a residual thickness of the dielectric layer at a bottom of the test openings as a function of the transverse dimensions.
- 3. The method according to claim 2, wherein the test openings comprise a first opening having a first transverse dimension, and at least a second opening having a second transverse dimension that is less than the first transverse dimension, and the method further comprises controlling the etch process, in response to the etch indicator signal, so that the first opening is sufficiently deep to reach the first layer, while at least the second opening is not sufficiently deep to reach the first layer.
- 4. The method according to claim 3, wherein the test openings further comprise a third opening, having a third transverse dimension intermediate the first and second transverse dimensions, and wherein analyzing the etch indicator signal comprises detecting a potential process defect when the etch indicator signal indicates that the third opening is not sufficiently deep to reach the first layer.
- 5. The method according to claim 2, wherein the sample has a barrier layer formed between the first and second layers, and wherein assessing the residual thickness comprises analyzing the etch indicator signal after etching the second layer in order to assess an integrity of the barrier layer, and then analyzing the etch indicator signal after etching the barrier layer.
- 6. The method according to claim 1, wherein analyzing the etch indicator signal comprises assessing a critical dimension of a bottom of the test openings as a function of the transverse dimensions.
- 7. The method according to claim 1, wherein analyzing the etch indicator signal comprises measuring a beam current of the beam of charged particles, and analyzing a ratio of the etch indicator signal to the beam current.
- 8. The method according to claim 1, wherein measuring at least one of the specimen current and the total yield of the electrons comprises measuring the total yield of the electrons emitted from the surface of the sample and further comprises measuring a primary current of the beam, and taking a difference between the primary current and the total yield to determine the etch indicator signal.
- 9. The method according to claim 1, wherein the plurality of test openings comprises multiple groups of the test openings in respective test areas, which are distributed in different locations across the sample, and wherein directing the beam comprises positioning at least one of the beam and the sample so as to irradiate each of at least two of the test areas in turn.
- 10. The method according to claim 9, wherein analyzing the etch indicator signal comprises evaluating a variation of the etch indicator signal across the sample so as to assess a uniformity of the etch process.
- 11. The method according to claim 1, wherein the plurality of test openings comprise at least first and second arrays of test openings, characterized by different, respective first and second spacings between the test openings in the arrays.
- 12. The method according to claim 1, wherein directing the beam comprises irradiating the test openings along a beam axis that deviates substantially in angle from a normal to a surface of the sample.
- 13. The method according to claim 12, wherein the test openings have side walls and a bottom, and wherein irradiating the test openings comprises angling the beam so that more of the charged particles strike the side walls than strike the bottom.
- 14. The method according to claim 1, wherein directing the beam comprises operating the beam so as to precharge a surface of the sample in proximity to the test openings, so as to facilitate measurement of the specimen current.
- 15. The method according to claim 14, wherein operating the beam so as to precharge the surface causes electrons to be emitted from the surface, and comprising creating an electric field in a vicinity of the surface so as to cause at least a portion of the emitted electrons to return to the surface, thereby generating a negative precharge at the surface.
- 16. The method according to claim 1, wherein the sample comprises a semiconductor wafer, and the contact openings comprise at least one of contact holes, trenches and vias.
- 17. The method according to claim 1, wherein receiving the sample comprises receiving the sample with a photoresist layer overlying the second layer, the photoresist layer having been used in etching the contact openings, and wherein analyzing the etch indicator signal comprises monitoring the etch indicator signal while irradiating the test area, prior to removing the photoresist layer.
- 18. The method according to claim 17, and comprising, if the etch indicator signal indicates that a residual thickness of the second layer at a bottom of one or more of the test openings is greater than a predetermined limit, further etching the second layer using the photoresist layer so as to increase the depth.
- 19. The method according to claim 1, wherein the sample comprises a semiconductor wafer, and wherein at least some of the contact openings not comprised in the plurality of test openings belong to multiple microelectronic circuits on the wafer, wherein the circuits are separated by scribe lines, and the test openings are located on one of the scribe lines.
- 20. The method according to claim 1, wherein analyzing the etch indicator signal comprises detecting a residue within the contact openings, and comprising irradiating the sample with the beam of charged particles so as to remove the residue.
- 21. The method according to claim 1, wherein directing the beam comprises directing a pulsed beam of the charged particles to irradiate the test openings, and wherein measuring at least one of the specimen current and the total yield of electrons comprises measuring a time variation of the specimen current by capacitive coupling to the sample.
- 22. A method for process monitoring, comprising:
receiving a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, following production of contact openings in the second layer by an etch process, the contact openings comprising at least first and second arrays of test openings, characterized by different, respective first and second spacings between the test openings in the first and second arrays; directing a beam of charged particles to irradiate the arrays of test openings; measuring, in response to the beam, at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample, thus producing an etch indicator signal; and analyzing the etch indicator signal as a function of the spacings of the arrays of the test openings so as to assess a characteristic of the etch process.
- 23. The method according to claim 22, wherein analyzing the etch indicator signal comprises assessing a residual thickness of the dielectric layer at a bottom of the test openings as a function of the spacings.
- 24. The method according to claim 23, wherein the first spacing is substantially greater than the second spacing, and the method comprises controlling the etch process, in response to the etch indicator signal, so that the test openings in the first array are sufficiently deep to reach the first layer, while the test openings in the second array are not sufficiently deep to reach the first layer.
- 25. The method according to claim 23, wherein the sample has a barrier layer formed between the first and second layers, and wherein assessing the residual thickness comprises analyzing the etch indicator signal after etching the second layer in order to assess an integrity of the barrier layer, and then analyzing the etch indicator signal after etching the barrier layer.
- 26. The method according to claim 22, wherein analyzing the etch indicator signal comprises assessing a critical dimension of a bottom of the test openings as a function of the transverse dimensions.
- 27. The method according to claim 22, wherein analyzing the etch indicator signal comprises measuring a beam current of the beam of charged particles, and analyzing a ratio of the etch indicator signal to the beam current.
- 28. The method according to claim 22, wherein measuring at least one of the specimen current and the total yield of the electrons comprises measuring the total yield of the electrons emitted from the surface of the sample and further comprises measuring a primary current of the beam, and taking a difference between the primary current and the total yield to determine the etch indicator signal.
- 29. The method according to claim 22, wherein the test openings comprise multiple arrays of the test openings having different, respective spacings in a plurality of test areas, which are distributed in different locations across the sample, and wherein directing the beam comprises positioning at least one of the beam and the sample so as to irradiate each of at least two of the test areas in turn.
- 30. The method according to claim 29, wherein analyzing the etch indicator signal comprises evaluating a variation of the etch indicator signal across the sample so as to assess a uniformity of the etch process.
- 31. The method according to claim 22, wherein directing the beam comprises irradiating the test openings along a beam axis that deviates substantially in angle from a normal to a surface of the sample.
- 32. The method according to claim 31, wherein the test openings have side walls and a bottom, and wherein irradiating the test openings comprises angling the beam so that more of the charged particles strike the side walls than strike the bottom.
- 33. The method according to claim 22, wherein directing the beam comprises operating the beam so as to precharge a surface of the sample in proximity the test openings, so as to facilitate measurement of the specimen current.
- 34. The method according to claim 33, wherein operating the beam so as to precharge the surface causes electrons to be emitted from the surface, and comprising creating an electric field in a vicinity of the surface so as to cause at least a portion of the emitted electrons to return to the surface, thereby generating a negative precharge at the surface.
- 35. The method according to claim 22, wherein the sample comprises a semiconductor wafer, and the contact openings comprise at least one of contact holes, trenches and vias.
- 36. The method according to claim 22, wherein receiving the sample comprises receiving the sample with a photoresist layer overlying the second layer, the photoresist layer having been used in etching the contact openings, and wherein analyzing the etch indicator signal comprises monitoring the etch indicator signal while irradiating the test area, prior to removing the photoresist layer.
- 37. The method according to claim 36, and comprising, if the etch indicator signal indicates that the residual thickness of the second layer at the bottom of one or more of the test openings is less than a predetermined limit, further etching the second layer using the photoresist layer so as to increase the depth.
- 38. The method according to claim 22, wherein the sample comprises a semiconductor wafer, and wherein at least some of the contact openings not comprised in the plurality of test openings belong to multiple microelectronic circuits on the wafer, wherein the circuits are separated by scribe lines, and the test openings are located on one of the scribe lines.
- 39. The method according to claim 22, wherein analyzing the etch indicator signal comprises detecting a residue within the contact openings, and comprising irradiating the sample with the beam of charged particles so as to remove the residue.
- 40. The method according to claim 22, wherein directing the beam comprises directing a pulsed beam of the charged particles to irradiate the test openings, and wherein measuring at least one of the specimen current and the total yield of electrons comprises measuring a time variation of the specimen current by capacitive coupling to the sample.
- 41. A method for monitoring a process carried out on a sample, the method comprising:
directing a beam of charged particles to irradiate the sample along a beam axis that deviates substantially in angle from a normal to a surface of the sample; measuring, in response to incidence of the beam on the sample, a specimen current flowing through the sample; and analyzing the specimen current so as to assess a characteristic of the process.
- 42. The method according to claim 41, wherein the sample has a first layer that is at least partially conductive and a second layer formed over the first layer, and wherein the process comprises an etch process, which is applied to the sample so as to produce contact openings in the second layer, and wherein directing the beam comprises irradiating the contact openings, and wherein analyzing the specimen current comprises assessing the etch process.
- 43. The method according to claim 42, wherein some of the contact holes are characterized by a tilt relative to the normal to the surface, and wherein directing the beam comprises angling the beam so as to compensate for the tilt.
- 44. The method according to claim 42, wherein the contact openings have side walls and a bottom, and wherein directing the beam comprises angling the beam so that more of the charged particles strike the side walls than strike the bottom.
- 45. The method according to claim 44, wherein the contact openings are characterized by an aspect ratio, and wherein directing the beam comprises aligning the beam axis at an angle that deviates from the normal to the surface by at least an arctangent of an inverse of the aspect ratio.
- 46. The method according to claim 42, wherein analyzing the specimen current comprises assessing whether a contaminant residue is present within the contact openings.
- 47. The method according to claim 46, and comprising irradiating the sample with the beam of charged particles along the normal to the surface so as to remove the residue.
- 48. The method according to claim 42, wherein directing the beam comprises operating the beam so as to negatively precharge the surface of the sample in proximity the contact openings, so as to facilitate measurement of the specimen current.
- 49. The method according to claim 48, wherein operating the beam so as to precharge the surface causes electrons to be emitted from the surface, and comprising creating an electric field in a vicinity of the surface, so as to cause at least a portion of the emitted electrons to return to the surface, thereby negatively precharging the surface.
- 50. The method according to claim 42, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 51. The method according to claim 42, wherein the sample has a barrier layer formed between the first and second layers, and wherein assessing the etch process comprises analyzing the specimen current after etching the second layer in order to assess an integrity of the barrier layer, and then analyzing the specimen current after etching the barrier layer.
- 52. The method according to claim 41, wherein analyzing the specimen current comprises measuring a beam current of the beam of charged particles, and analyzing a ratio of the specimen current to the beam current.
- 53. The method according to claim 41, wherein directing the beam comprises directing a pulsed beam of the charged particles to irradiate the sample, and wherein measuring the specimen current comprises measuring a time variation of the specimen current by capacitive coupling to the sample.
- 54. A method for process monitoring, comprising:
directing a beam of charged particles to irradiate a surface of a sample, whereby electrons are emitted from the surface; applying an electric field in a vicinity of the surface, so as to cause at least a portion of the emitted electrons to return to the surface, thereby generating a negative precharge at the surface; and receiving a signal produced by the sample in response to the beam and the negative precharge.
- 55. The method according to claim 54, wherein the sample has a first layer that is at least partially conductive and a second layer formed over the first layer, and wherein the negative precharge is formed on the surface of the second layer.
- 56. The method according to claim 55, wherein the second layer comprises a dielectric material.
- 57. The method according to claim 54, wherein receiving the signal comprises measuring at least one of a specimen current flowing through the sample and a total yield of electrons emitted from the surface of the sample.
- 58. The method according to claim 57, wherein the sample has a first layer that is at least partially conductive and a second layer formed over the first layer, with contact openings formed in the second layer by an etch process, and wherein receiving the signal comprises analyzing the signal so as to assess a characteristic of the etch process.
- 59. The method according to claim 58, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 60. The method according to claim 58, wherein the sample has a barrier layer formed between the first and second layers, and wherein analyzing the signal comprises analyzing the signal after etching the second layer in order to assess an integrity of the barrier layer, and then analyzing the signal after etching the barrier layer.
- 61. The method according to claim 54, wherein directing the beam comprises operating the beam during a precharging interval so as to generate the negative precharge at the surface, and then operating the beam after the precharging interval so as to generate the signal.
- 62. The method according to claim 61, wherein operating the beam during the precharging interval comprises setting the beam source so that electrons have an energy in a positive charging domain of the surface of the sample.
- 63. A method for testing a semiconductor device, comprising:
irradiating a junction in the semiconductor device with a first beam comprising electromagnetic radiation; irradiating the device with a second beam comprising charged particles, so that at least some of the charged particles are incident on the junction substantially simultaneously with the electromagnetic radiation; and measuring, in response to incidence of the first and second beams on the junction, a property of the device.
- 64. The method according to claim 63, wherein measuring the property comprises forming an electronic image of the device.
- 65. The method according to claim 63, wherein the junction comprises a semiconductor material, and wherein irradiating the junction with the first beam comprises irradiating the junction with photons having an energy greater than or equal to a bandgap of the semiconductor material.
- 66. The method according to claim 63, wherein the junction comprises a P-N junction.
- 67. The method according to claim 63, wherein measuring the property comprises measuring a current flowing through the device.
- 68. The method according to claim 67, wherein a dielectric layer is formed over the junction, and a contact hole is formed through the dielectric layer in order to contact the junction, and wherein irradiating the junction with the first and second beams comprises irradiating an interior of the contact hole, and wherein measuring the current comprises assessing a characteristic of the contact hole based on the current.
- 69. The method according to claim 68, wherein assessing the characteristic comprises assessing a suitability of the contact hole to make a conductive electrical contact with the junction.
- 70. A method for process monitoring, comprising:
receiving a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, following production of contact openings in the second layer by an etch process; directing a beam of charged particles to irradiate one or more of the contact openings; measuring a primary current of the beam and a total yield of electrons emitted from a surface of the sample in response incidence of the beam on the contact openings; and analyzing a relation between the primary current and the total yield of the electrons so as to assess a characteristic of the etch process.
- 71. The method according to claim 70, wherein analyzing the relation comprises analyzing a difference between the primary current and the total yield.
- 72. The method according to claim 70, wherein analyzing the relation comprises analyzing a ratio between the primary current and the total yield.
- 73. The method according to claim 70, wherein directing the beam comprises irradiating multiple contact openings, which are distributed in different locations across the sample, and wherein analyzing the relation comprises evaluating a variation of the relation across the sample so as to assess a uniformity of the etch process.
- 74. The method according to claim 70, wherein directing the beam comprises precharging a surface of the sample in proximity to the one or more of the contact openings, and wherein measuring the primary current and the total yield comprises measuring the total yield of the electrons emitted from the precharged surface.
- 75. The method according to claim 70, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 76. The method according to claim 70, wherein the sample has a barrier layer formed between the first and second layers, and wherein analyzing the relation comprises analyzing the relation after etching the second layer in order to assess an integrity of the barrier layer, and then analyzing the relation after etching the barrier layer.
- 77. A method for process monitoring of a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, wherein contact openings are formed in the second layer by an etch process, the method comprising:
determining, for a given set of characteristics of the contact openings, a threshold level of an etch indicator signal, which is produced by measuring at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample in response to irradiation of the contact openings by a beam of charged particles; directing the beam of charged particles to irradiate each of a plurality of the contact openings that have the given set of characteristics and are disposed at different, respective positions over a surface of the sample; determining, in response to the beam, the etch indicator signal produced at each of the respective positions of the plurality of the contact openings; and comparing the etch indicator signal produced at the respective positions to the threshold level so as to assess a characteristic of the etch process.
- 78. The method according to claim 77, wherein comparing the etch indicator signal comprises determining, if an absolute magnitude of the specimen current falls below the threshold level by more than a predetermined margin, that at least some of the contact openings are underetched.
- 79. The method according to claim 77, wherein determining the threshold level comprises finding the level of the etch indicator signal that corresponds to etching of the contact openings through the second layer to expose the first layer within the opening.
- 80. The method according to claim 79, wherein finding the level comprises calibrating the threshold level in a procedure performed on a test sample, for subsequent application in assessing the characteristic of the etch process performed on other samples.
- 81. The method according to claim 80, wherein calibrating the threshold level comprises making measurements of the etch indicator signal generated by the test sample, and comparing the measurements to at least one of a cross-sectional profile of the contact openings in the test sample and a conductivity of electrical contacts made through the contact openings in the test sample.
- 82. The method according to claim 79, wherein the sample has a barrier layer formed between the first and second layers, and wherein finding the level of the etch indicator signal comprises finding a first level that corresponds to etching of the contact openings through the second layer to expose the barrier layer, and finding a second level that corresponds to etching of the contact openings through the barrier layer to expose the first layer within the openings.
- 83. The method according to claim 82, wherein comparing the etch indicator signal comprises analyzing the etch indicator signal after etching the second layer in order to assess an integrity of the barrier layer, and then analyzing the etch indicator signal after etching the barrier layer in order to verify that at least some of the contact openings have been etched through the barrier layer to the first layer.
- 84. The method according to claim 77, and comprising evaluating a variation of the etch indicator signal across the sample so as to assess a uniformity of the etch process.
- 85. The method according to claim 84, wherein evaluating the variation comprises signaling that a process fault has occurred if the variation of the etch indicator signal across the sample is greater than a predetermined maximum.
- 86. The method according to claim 77, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 87. The method according to claim 77, wherein the sample has a photoresist layer overlying the second layer, the photoresist layer having been used in etching the contact openings, and wherein measuring the etch indicator signal comprises measuring the etch indicator signal prior to removing the photoresist layer.
- 88. The method according to claim 87, and comprising, if the etch indicator signal indicates that a depth of one or more of the contact openings is less than a predetermined limit, further etching the second layer using the photoresist layer so as to increase the depth.
- 89. The method according to claim 77, wherein determining the etch indicator signal comprises measuring a beam current of the beam of charged particles, and analyzing a ratio of at least one of the specimen current and the total yield of the electrons to the beam current.
- 90. The method according to claim 77, wherein directing the beam comprises directing a pulsed beam of the charged particles to irradiate the sample, and wherein determining the etch indicator signal comprises measuring a time variation of the specimen current by capacitive coupling to the sample.
- 91. A method for process monitoring of a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, wherein contact openings are formed in the second layer by an etch process, the method comprising:
directing a beam of charged particles to irradiate each of a plurality of the openings that share a given set of characteristics and are disposed at different, respective positions across the sample; measuring at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample in response to irradiation of the contact openings by the beam of charged particles, thus producing an etch indicator signal as a function of the respective positions of the plurality of the openings; and evaluating a variation of the etch indicator signal across the sample so as to assess a uniformity of the etch process.
- 92. The method according to claim 91, wherein evaluating the variation comprises determining that a process fault has occurred if the variation of the etch indicator signal across the sample is greater than a predetermined maximum.
- 93. The method according to claim 91, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 94. The method according to claim 91, wherein evaluating the variation of the etch indicator signal comprises measuring a beam current of the beam of charged particles, and analyzing a ratio of the etch indicator signal to the beam current.
- 95. The method according to claim 91, wherein directing the beam comprises directing a pulsed beam of the charged particles to irradiate the sample, and wherein measuring the specimen current comprises measuring a time variation of the specimen current by capacitive coupling to the sample.
- 96. Apparatus for etching a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, contact openings having been created in the second layer by an etch process, the contact openings including a plurality of test openings having different, respective transverse dimensions, the apparatus comprising:
a test station, which comprises:
a particle beam source, which is adapted to direct a beam of charged particles to irradiate the test openings; and a current measuring device, which is coupled to measure, in response to the beam, at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample, thus producing an etch indicator signal; and a controller, which is adapted to analyze the etch indicator signal as a function of the transverse dimensions of the test openings so as to assess a characteristic of the etch process.
- 97. The apparatus according to claim 96, wherein the controller is adapted to assess a residual thickness of the dielectric layer at a bottom of the test openings as a function of the transverse dimensions.
- 98. The apparatus according to claim 97, wherein the test openings comprise a first opening having a first transverse dimension, and at least a second opening having a second transverse dimension that is less than the first transverse dimension, and
wherein the controller is adapted to control the etch process, in response to the etch indicator signal, so that the first opening is sufficiently deep to reach the first layer, while at least the second opening is not sufficiently deep to reach the first layer.
- 99. The apparatus according to claim 98, wherein the test openings further comprise a third opening, having a third transverse dimension intermediate the first and second transverse dimensions, and wherein the controller is adapted to detect a potential process defect when the etch indicator signal indicates that the third opening is not sufficiently deep to reach the first layer.
- 100. The apparatus according to claim 97, wherein the sample has a barrier layer formed between the first and second layers, and wherein the controller is adapted to analyze the etch indicator signal after etching of the second layer in order to assess an integrity of the barrier layer, and to analyze the etch indicator signal after etching of the barrier layer.
- 101. The apparatus according to claim 96, wherein the controller is adapted to assess a critical dimension of a bottom of the test openings as a function of the transverse dimensions.
- 102. The apparatus according to claim 96, wherein the current measuring device is further adapted to measure a beam current of the beam of charged particles, and wherein the controller is adapted to analyze a ratio of the etch indicator signal to the beam current.
- 103. The apparatus according to claim 96, wherein the current measuring device comprises a secondary electron detector, for detecting the total yield of the electrons emitted from the surface of the sample, and a primary electron detector, for detecting a primary current of the beam, and is wherein the controller is adapted to take a difference between the primary current and the total yield in order to determine the etch indicator signal.
- 104. The apparatus according to claim 96, wherein the plurality of test openings comprises multiple groups of the test openings in respective test areas, which are distributed in different locations across the sample, and wherein the test station comprises a positioning device, which is adapted to position at least one of the beam and the sample so as to irradiate each of at least two of the test areas in turn.
- 105. The apparatus according to claim 104, wherein the controller is adapted to evaluate a variation of the etch indicator signal across the sample so as to assess a uniformity of the etch process.
- 106. The apparatus according to claim 96, wherein the plurality of test openings comprise at least first and second arrays of test openings, characterized by different, respective first and second spacings between the test openings in the arrays.
- 107. The apparatus according to claim 96, wherein the beam source is adapted to irradiate the test openings along a beam axis that deviates substantially in angle from a normal to a surface of the sample.
- 108. The apparatus according to claim 107, wherein the test openings have side walls and a bottom, and wherein the beam axis is angled so that more of the charged particles strike the side walls than strike the bottom.
- 109. The apparatus according to claim 96, wherein the beam source is adapted to precharge a surface of the sample in proximity to the test openings, so as to facilitate measurement of the specimen current by the current measuring device.
- 110. The apparatus according to claim 109, wherein the beam causes electrons to be emitted from the surface, and wherein the apparatus comprises a bias electrode, which is positioned and coupled to create an electric field in a vicinity of the surface so as to cause at least a portion of the emitted electrons to return to the surface, thereby generating a negative precharge at the surface.
- 111. The apparatus according to claim 96, wherein the sample comprises a semiconductor wafer, and the contact openings comprise at least one of contact holes, trenches and vias.
- 112. The apparatus according to claim 96, wherein the test station is adapted to receive the sample with a photoresist layer overlying the second layer, the photoresist layer having been used in etching the contact openings, so as to measure at least one of the specimen current and the total yield of the electrons while irradiating the test area with the particle beam, prior to removing the photoresist layer.
- 113. The apparatus according to claim 112, and comprising an etch station, which is adapted to form the contact openings in the second layer by the etch process, wherein the controller is adapted to control the etch process, in response to the etch indicator signal, so as to cause the etch station to further etch the second layer using the photoresist layer so as to increase a depth of the contact openings if the etch indicator signal indicates that a residual thickness of the second layer at a bottom of one or more of the test openings is greater than a predetermined limit.
- 114. The apparatus according to claim 96, wherein the sample comprises a semiconductor wafer, and wherein at least some of the contact openings not comprised in the plurality of test openings belong to multiple microelectronic circuits on the wafer, wherein the circuits are separated by scribe lines, and the test openings are located on one of the scribe lines.
- 115. The apparatus according to claim 114, wherein the controller is adapted to analyze the etch indicator signal so as to detect a residue within the contact openings, and to control the particle beam source so as to irradiate the sample with the beam of charged particles in order to remove the residue.
- 116. The apparatus according to claim 96, wherein the particle beam source is adapted to pulse the beam of the charged particles that irradiates the test openings, and wherein the current measuring device is capacitively coupled to the sample so as to measure a time variation of the specimen current.
- 117. Apparatus for etching a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, contact openings having been created in the second layer by an etch process, the contact openings including at least first and second arrays of test openings, characterized by different, respective first and second spacings between the test openings in the first and second arrays, the apparatus comprising:
a test station, which comprises:
a particle beam source, which is adapted to direct a beam of charged particles to irradiate the test openings; and a current measuring device, which is coupled to measure, in response to the beam, at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample, thus producing an etch indicator signal; and a controller, which is adapted to analyze the etch indicator signal as a function of the spacings of the arrays of the test openings so as to assess a characteristic of the etch process.
- 118. The apparatus according to claim 117, wherein the controller is adapted to assess a residual thickness of the dielectric layer at a bottom of the test openings as a function of the spacings.
- 119. The apparatus according to claim 118, wherein the first spacing is substantially greater than the second spacing, and wherein the controller is adapted to control the etch process, in response to the etch indicator signal, so that the test openings in the first array are sufficiently deep to reach the first layer, while the test openings in the second array are not sufficiently deep to reach the first layer.
- 120. The apparatus according to claim 118, wherein the sample has a barrier layer formed between the first and second layers, and wherein the controller is adapted to analyze the etch indicator signal after etching of the second layer in order to assess an integrity of the barrier layer, and to analyze the etch indicator signal after etching of the barrier layer.
- 121. The apparatus according to claim 117, wherein the controller is adapted to assess a critical dimension of a bottom of the test openings as a function of the transverse dimensions.
- 122. The apparatus according to claim 117, wherein the current measuring device is further adapted to measure a beam current of the beam of charged particles, and wherein the controller is adapted to analyze a ratio of the etch indicator signal to the beam current.
- 123. The apparatus according to claim 117, wherein the current measuring device comprises a secondary electron detector, for detecting the total yield of the electrons emitted from the surface of the sample, and a primary electron detector, for detecting a primary current of the beam, and is adapted to take a difference between the primary current and the total yield in order to determine the etch indicator signal.
- 124. The apparatus according to claim 117, wherein the test openings comprises multiple arrays of the test openings having different, respective spacings in a plurality of test areas, which are distributed in different locations across the sample, and wherein the test station comprises a positioning device, which is adapted to position at least one of the beam and the sample so as to irradiate each of at least two of the test areas in turn.
- 125. The apparatus according to claim 24, wherein the controller is adapted to evaluate a variation of the etch indicator signal across the sample so as to assess a uniformity of the etch process.
- 126. The apparatus according to claim 117, wherein the beam source is adapted to irradiate the test openings along a beam axis that deviates substantially in angle from a normal to a surface of the sample.
- 127. The apparatus according to claim 126, wherein the test openings have side walls and a bottom, and wherein the beam axis is angled so that more of the charged particles strike the side walls than strike the bottom.
- 128. The apparatus according to claim 117, wherein the beam source is adapted to precharge a surface of the sample in proximity to the test openings, so as to facilitate measurement of the specimen current by the current measuring device.
- 129. The apparatus according to claim 128, wherein the beam causes electrons to be emitted from the surface, and wherein the apparatus comprises a bias electrode, which is positioned and coupled to create an electric field in a vicinity of the surface so as to cause at least a portion of the emitted electrons to return to the surface, thereby generating a negative precharge at the surface.
- 130. The apparatus according to claim 117, wherein the sample comprises a semiconductor wafer, and the contact openings comprise at least one of contact holes, trenches and vias.
- 131. The apparatus according to claim 117, wherein the test station is adapted to receive the sample with a photoresist layer overlying the second layer, the photoresist layer having been used in etching the contact openings, so as to measure at least one of the specimen current and the total yield of the electrons while irradiating the test area with the particle beam, prior to removing the photoresist layer.
- 132. The apparatus according to claim 131, and comprising an etch station, which is adapted to form the contact openings in the second layer by the etch process, wherein the controller is adapted to control the etch process, in response to the etch indicator signal, so as to cause the etch station to further etch the second layer using the photoresist layer so as to increase a depth of the contact openings if the etch indicator signal indicates that a residual thickness of the second layer at a bottom of one or more of the test openings is greater than a predetermined limit.
- 133. The apparatus according to claim 117, wherein the sample comprises a semiconductor wafer, and wherein at least some of the contact openings not comprised in the plurality of test openings belong to multiple microelectronic circuits on the wafer, wherein the circuits are separated by scribe lines, and the test openings are located on one of the scribe lines.
- 134. The apparatus according to claim 133, wherein the controller is adapted to analyze the etch indicator signal so as to detect a residue within the contact openings, and to control the particle beam source so as to irradiate the sample with the beam of charged particles in order to remove the residue.
- 135. The apparatus according to claim 117, wherein the particle beam source is adapted to pulse the beam of the charged particles that irradiates the test openings, and wherein the current measuring device is capacitively coupled to the sample so as to measure a time variation of the specimen current.
- 136. Apparatus for monitoring a process carried out on a sample, the apparatus comprising:
a particle beam source, which is adapted to direct a beam of charged particles to irradiate the sample along a beam axis that deviates substantially in angle from a normal to a surface of the sample; a current measuring device, which is coupled to measure, in response to the beam, a specimen current flowing through the sample; and a controller, which is adapted to analyze the specimen current so as to assess a characteristic of the etch process.
- 137. The apparatus according to claim 136, wherein the sample has a first layer that is at least partially conductive and a second layer formed over the first layer, and wherein the process comprises an etch process, which is applied to the sample so as to produce contact openings in the second layer, and wherein directing the beam comprises irradiating the contact openings, and wherein the controller is adapted to assess the etch process by analyzing the specimen current.
- 138. The apparatus according to claim 137, wherein the sample has a barrier layer formed between the first and second layers, and wherein the controller is adapted to analyze the specimen current after etching of the second layer in order to assess an integrity of the barrier layer, and to analyze the specimen current after etching of the barrier layer.
- 139. The apparatus according to claim 136, wherein some of the contact holes are characterized by a tilt relative to the normal to the surface, and wherein the beam is angled so as to compensate for the tilt.
- 140. The apparatus according to claim 136, wherein the contact openings have side walls and a bottom, and wherein the beam is angled so that more of the charged particles strike the side walls than strike the bottom.
- 141. The apparatus according to claim 136, wherein the contact openings are characterized by an aspect ratio, and wherein the beam axis is aligned at an angle that deviates from the normal to the surface by at least an arctangent of an inverse of the aspect ratio.
- 142. The apparatus according to claim 136, wherein the controller is adapted to assess, based on the specimen current, whether a contaminant residue is present within the contact openings.
- 143. The apparatus according to claim 142, wherein the particle beam source is further adapted to irradiate the sample with the beam of charged particles along the normal to the surface so as to remove the residue.
- 144. The apparatus according to claim 136, wherein the particle beam is adapted to negatively precharge the surface of the sample in proximity the contact openings, so as to facilitate measurement of the specimen current by the current measuring device.
- 145. The apparatus according to claim 144, wherein the beam causes electrons to be emitted from the surface, and wherein the apparatus comprises a bias electrode, which is positioned and coupled to create an electric field in a vicinity of the surface, so as to cause at least a portion of the emitted electrons to return to the surface, thereby generating a negative precharge at the surface.
- 146. The apparatus according to claim 136, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 147. The apparatus according to claim 136, wherein the current measuring device is further adapted to measure a beam current of the beam of charged particles, and wherein the controller is adapted to analyze a ratio of the specimen current to the beam current.
- 148. The apparatus according to claim 136, wherein the particle beam source is adapted to pulse the beam of the charged particles that irradiates the test openings, and wherein the current measuring device is capacitively coupled to the sample so as to measure a time variation of the specimen current.
- 149. Apparatus for process monitoring, comprising:
a particle beam source, which is adapted to direct a beam of charged particles to irradiate a surface of a sample, whereby electrons are emitted from the surface; a bias electrode, which is adapted to apply an electric field in a vicinity of the surface, so as to cause at least a portion of the electrons emitted during the precharging interval to return to the surface, thereby generating a negative precharge at the surface; and a current measuring device, which is coupled to receive a signal produced by the sample in response to the beam and the negative precharge.
- 150. The apparatus according to claim 149, wherein the sample has a first layer that is at least partially conductive and a second layer formed over the first layer, and wherein the negative precharge is formed on the surface of the second layer.
- 151. The apparatus according to claim 150, wherein the second layer comprises a dielectric material.
- 152. The apparatus according to claim 149, wherein the current measuring device is adapted to measure at least one of a specimen current flowing through the sample and a total yield of electrons emitted from the surface of the sample.
- 153. The apparatus according to claim 152, wherein the sample has a first layer that is at least partially conductive and a second layer formed over the first layer, with contact openings formed in the second layer by an etch process, and wherein the signal is indicative of a characteristic of the etch process.
- 154. The apparatus according to claim 153, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 155. The apparatus according to claim 153, wherein the sample has a barrier layer formed between the first and second layers, and wherein the signal received by the current measuring device after etching of the second layer is indicative of an integrity of the barrier layer, and the signal received by the current measuring device after etching of the barrier layer is indicative of an extent to which the contact openings have been etched through the barrier layer to the first layer.
- 156. The apparatus according to claim 149, wherein the beam source is adjustable to produce the beam with first beam characteristics during a precharging interval so as to generate the negative precharge at the surface, and then to produce the beam after the precharging interval with second beam characteristics, so as to generate the signal.
- 157. The apparatus according to claim 156, wherein the beam source is adapted to irradiate the surface with the particles during the precharging interval with an energy in a positive charging domain of the surface of the sample,
- 158. Apparatus for testing a semiconductor device, comprising:
a radiation source, which is adapted to irradiate a junction in the semiconductor device with a first beam comprising electromagnetic radiation; a particle beam source, which is adapted to irradiate the device with a second beam comprising charged particles, so that at least some of the charged particles are incident on the junction substantially simultaneously with the electromagnetic radiation; and a measuring element, which is adapted to measure, in response to incidence of the first and second beams on the junction, a property of the device.
- 159. The apparatus according to claim 158, wherein the measuring element is adapted to form an electronic image of the device in response to incidence of the first and second beams on the junction.
- 160. The apparatus according to claim 158, wherein the junction comprises a semiconductor material, and wherein the radiation source is adapted to irradiate the junction with photons having an energy greater than or equal to a bandgap of the semiconductor material.
- 161. The apparatus according to claim 158, wherein the junction comprises a P-N junction.
- 162. The apparatus according to claim 158, wherein the measuring element comprises a current measuring element, which is adapted to measure a current flowing through the device.
- 163. The apparatus according to claim 162, wherein a dielectric layer is formed over the junction, and a contact hole is formed through the dielectric layer in order to contact the junction, and wherein the radiation source and particle beam source are respectively adapted to direct the first and second beams into the contact hole, so that the measured current is indicative of a characteristic of the contact hole.
- 164. The apparatus according to claim 163, wherein the measured current is indicative of whether the contact hole is suitable to make a conductive electrical contact with the junction.
- 165. Apparatus for monitoring an etch process applied to a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, following production of contact openings in the second layer by the etch process, the apparatus comprising:
a particle beam source, which is adapted to direct a beam of charged particles to irradiate one or more of the contact openings; a beam current detector, for detecting a primary current of the beam; a secondary electron detector, for detecting a total yield of electrons emitted from a surface of the sample in response incidence of the beam on the contact openings; and a controller, which is adapted a relation between the primary current and the total yield of the electrons so as to assess a characteristic of the etch process.
- 166. The apparatus according to claim 165, wherein the relation comprises a difference between the primary current and the total yield.
- 167. The apparatus according to claim 165, wherein the relation comprises a ratio between the primary current and the total yield.
- 168. The apparatus according to claim 165, wherein the particle beam source is adapted to irradiate multiple contact openings, which are distributed in different locations across the sample, and wherein the controller is adapted to evaluate a variation of the relation across the sample so as to assess a uniformity of the etch process.
- 169. The apparatus according to claim 165, wherein the particle beam source is adapted to precharge a surface of the sample in proximity the one or more of the contact openings, so that the secondary electron detector measures the total yield of the electrons emitted from the precharged surface.
- 170. The apparatus according to claim 165, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 171. The apparatus according to claim 165, wherein the sample has a barrier layer formed between the first and second layers, and wherein the controller is adapted to analyze the relation after etching of the second layer in order to assess an integrity of the barrier layer, and to analyze the relation after etching of the barrier layer.
- 172. Apparatus for monitoring a process applied to a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, contact openings having been created in the second layer by an etch process, the apparatus comprising:
a test station, comprising:
a particle beam source, which is adapted to direct a beam of charged particles to irradiate each of a plurality of the contact openings that are disposed at different, respective positions over a surface of the sample; and a current measuring device, which is adapted to produce an etch indicator signal by measuring, in response to irradiation of each of the plurality of the contact openings by the beam of charged particles, at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample; and a controller, which is adapted to store a calibrated threshold level of the etch indicator signal for a given set of properties of the etch process, and to compare the respective etch indicator signal produced with respect to each of the plurality of the contact openings to the threshold level so as to assess a characteristic of the etch process.
- 173. The apparatus according to claim 172, wherein the controller is adapted to determine, if an absolute magnitude of the specimen current falls below the threshold level by more than a predetermined margin, that at least some of the contact openings are underetched.
- 174. The apparatus according to claim 173, wherein the threshold level is calibrated by finding the level of the etch indicator signal that corresponds to etching of the contact openings through the second layer to expose the first layer within the opening.
- 175. The apparatus according to claim 174, wherein the threshold level is calibrated in a procedure performed on a test sample, for subsequent application in assessing the characteristic of the etch process performed on other samples.
- 176. The apparatus according to claim 175, wherein the threshold level is calibrated making measurements of the etch indicator signal generated by the test sample, and comparing the measurements to at least one of a cross-sectional profile of the contact openings in the test sample and a conductivity of electrical contacts made through the contact openings in the test sample.
- 177. The apparatus according to claim 172, wherein the controller is further adapted to analyze a variation of the etch indicator signal across the sample so as to assess a uniformity of the etch process.
- 178. The apparatus according to claim 177, wherein the controller is adapted to signal that a process fault has occurred if the variation of the etch indicator signal across the sample is greater than a predetermined maximum.
- 179. The apparatus according to claim 172, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 180. The apparatus according to claim 172, wherein the sample has a photoresist layer overlying the second layer, which is used in etching the contact openings, and wherein the test station is adapted to measure the etch indicator signal prior to removing the photoresist layer.
- 181. The apparatus according to claim 180, and comprising an etch station, which is adapted to form the contact openings in the second layer by the etch process, wherein the controller is adapted to cause the etch station to further etch the second layer using the photoresist layer so as to increase a depth of one or more of the contact openings, if the etch indicator signal indicates that the depth is less than a predetermined limit.
- 182. The apparatus according to claim 172, wherein the current measuring device is further adapted to measure a beam current of the beam of charged particles, and wherein the control is adapted to analyze a ratio of at least one of the specimen current and the total yield of the electrons to the beam current.
- 183. The apparatus according to claim 172, wherein the particle beam source is adapted to pulse the beam of the charged particles that irradiates the sample, and wherein the current measuring device is capacitively coupled to the sample so as to measure a time variation of the specimen current.
- 184. The apparatus according to claim 172, wherein the sample has a barrier layer formed between the first and second layers, and
wherein the apparatus comprises an etch station, which is adapted to form the contact openings in the second layer by the etch process and to etch the contact openings through the barrier layer, and wherein the controller is adapted to store first and second calibrated threshold levels of the etch indicator signal and to compare the respective etch indicator signal to the first calibrated threshold level after the etch station has etched the contact openings through the second layer, and to the second calibrated threshold level after the etch station has etched the contact openings through the barrier layer.
- 185. The apparatus according to claim 184, wherein the first calibrated threshold level corresponds to etching of the contact openings through the second layer to expose the barrier layer, and the second calibrated threshold level corresponds to etching of the contact openings through the barrier layer to expose the first layer within the openings, and
wherein the controller is adapted to compare the etch indicator signal to the first calibrated threshold level after etching of the second layer in order to assess an integrity of the barrier layer, and to compare the etch indicator signal to the second calibrated threshold level after etching of the barrier layer in order to verify that at least some of the contact openings have been etched through the barrier layer to the first layer.
- 186. Apparatus for monitoring a process applied to a sample having a first layer that is at least partially conductive and a second layer formed over the first layer, contact openings having been formed in the second layer by an etch process, the apparatus comprising:
a test station, which comprises:
a particle beam source, which is adapted to direct a beam of charged particles to irradiate each of a plurality of the openings that are disposed at different, respective positions across the sample; and a current measuring device, which is adapted to measure at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample in response to irradiation of the contact openings by the beam of charged particles, thus producing an etch indicator signal as a function of the respective positions of the plurality of the openings; and a controller, which is adapted to evaluate a variation of the etch indicator signal across the sample so as to assess a uniformity of the etch process.
- 187. The apparatus according to claim 186, wherein the controller is adapted to determine that a process fault has occurred if the variation of the etch indicator signal across the sample is greater than a predetermined maximum.
- 188. The apparatus according to claim 186, wherein the sample comprises a semiconductor wafer, and wherein the contact openings comprise at least one of contact holes, trenches and vias.
- 189. The apparatus according to claim 186, wherein the current measuring device is further adapted to measure a beam current of the beam of charged particles, and wherein the controller is adapted to analyze a ratio of the etch indicator signal to the beam current.
- 190. The apparatus according to claim 186, wherein the particle beam source is adapted to pulse the beam of the charged particles that irradiates the sample, and wherein the current measuring device is capacitively coupled to the sample so as to measure a time variation of the specimen current.
- 191. A method for process monitoring of a sample having a first layer that is at least partially conductive, a second, barrier layer formed over the first layer, and a third, dielectric layer formed over the second layer, the method comprising:
etching contact openings in the third layer in a first etch process; directing a beam of charged particles to irradiate the contact openings in a first monitoring step following the first etch process; measuring at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample in response to irradiation of the contact openings by the beam of charged particles in the first monitoring step, thus producing a second etch indicator signal; evaluating the first etch indicator signal to assess a first characteristic of the first etch process; further etching the contact openings from the third layer into the second layer in a second etch process; directing the beam of charged particles to irradiate the contact openings in a second monitoring step following the second etch process; measuring the at least one of the specimen current flowing through the first layer and the total yield of the electrons emitted from the surface of the sample in response to irradiation of the contact openings by the beam of charged particles in the second monitoring step, thus producing a second etch indicator signal; and evaluating the second etch indicator signal to assess a second characteristic of the second etch process.
- 192. The method according to claim 191, wherein evaluating the first etch indicator signal comprises assessing an integrity of the second layer.
- 193. The method according to claim 191, wherein evaluating the second etch indicator signal comprises verifying that at least some of the contact openings have been etched through the second layer to the first layer.
- 194. Apparatus for process monitoring of a sample having a first layer that is at least partially conductive, a second, barrier layer formed over the first layer, and a third, dielectric layer formed over the second layer, the apparatus comprising:
an etch station, which is adapted to form contact openings in the third layer in a first etch process, and subsequently to further etch the contact openings from the third layer into the second layer in a second etch process; a test station, which comprises:
a particle beam source, which is adapted to direct a beam of charged particles to irradiate the contact openings; and a current measuring device, which is adapted to measure at least one of a specimen current flowing through the first layer and a total yield of electrons emitted from a surface of the sample in response to irradiation of the contact openings by the beam of charged particles, thus producing a first etch indicator signal following the first etch process and a second etch indicator signal following the second etch process; and a controller, which is adapted to evaluate the first etch indicator signal in order to assess a first characteristic of the first etch process and to evaluate the second etch indicator signal in order to assess a second characteristic of the second etch process.
- 195. The apparatus according to claim 194, wherein the controller is adapted to assess, in response to the first etch indicator signal, an integrity of the second layer.
- 196. The apparatus according to claim 194, wherein the controller is adapted to verify, in response to the second etch indicator signal, that at least some of the contact openings have been etched through the second layer to the first layer.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 10/209087, filed Jul. 30, 2002, which is assigned to the assignee of the present patent application and is incorporated herein by reference.
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
10209087 |
Jul 2002 |
US |
Child |
10434977 |
May 2003 |
US |