JP2011199104A - Semiconductor annealing device, method of annealing semiconductor, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel semiconductor annealing device, a method of annealing a semiconductor, and a storage medium to be used when annealing the semiconductor.SOLUTION: The semiconductor annealing device includes: a first laser light source for emitting a first laser pulse; a second laser light source for emitting a second laser pulse; a composite optical system for superposing the first laser pulse and the second pulse laser pulse on the same optical axis; a processing stage for holding a processing object; a waveguide optical system for transmitting the first and second laser pulses superposed on the same optical axis in the composite optical system to the processing stage; a controller for controlling emission of the first laser pulse by the first laser light source and that of the second laser pulse by the second laser light source; and a memory for storing the data including a relationship between the depth in which silicon is melted and the delay time when two laser pulses are incident onto the silicon with a delay time interval.

Description

  The present invention relates to an apparatus and method for performing semiconductor annealing, and a storage medium that can be used when performing semiconductor annealing.

  Various inventions related to semiconductor annealing for activating a impurity by irradiating a silicon wafer to which an impurity has been added are known (see, for example, Patent Document 1). Patent Document 1 discloses an invention of a semiconductor annealing method in which two laser pulses are incident on a semiconductor substrate into which an impurity is introduced with a time difference to activate the impurity.

  Further, an invention of an epitaxial silicon wafer manufacturing method is disclosed in which a crystal defect layer is introduced directly below an epitaxial growth surface of a silicon wafer and an epitaxial layer having no crystal defects is formed on the growth surface (for example, Patent Document 2). reference).

  A technique for recovering crystal defects generated in the manufacturing process of a silicon wafer and crystal defects generated by addition of impurities is important in providing a high-quality silicon wafer. Recovery of crystal defects may be performed, for example, from the surface of the silicon wafer to a certain depth.

JP 2007-123300 A JP 2001-77119 A

  An object of the present invention is to provide a novel semiconductor annealing apparatus and method, and a storage medium that can be used when performing semiconductor annealing.

  According to one aspect of the present invention, a first laser light source that emits a first laser pulse, a second laser light source that emits a second laser pulse, the first laser pulse, and the second laser pulse A synthesis optical system for superimposing laser pulses on the same optical axis, a processing stage for holding a workpiece, and the first and second laser pulses superimposed on the same optical axis in the synthesis optical system, A waveguide optical system that propagates to the processing stage, and a control device that controls emission of the first laser pulse by the first laser light source and emission of the second laser pulse by the second laser light source And a storage device for storing data including a relationship between a melting depth at which silicon melts and the delay time when two laser pulses are incident on silicon with a delay time. It is subjected.

  According to another aspect of the present invention, (a) when two laser pulses are incident on silicon with a delay time, data including the relationship between the melting depth at which silicon melts and the delay time is prepared. There is provided a semiconductor annealing method comprising: (b) performing semiconductor annealing with reference to the data.

  Furthermore, according to another aspect of the present invention, when two laser pulses are incident on silicon with a delay time, a storage medium storing data including a relationship between a melting depth at which silicon melts and the delay time Is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the storage medium which can be used when performing a novel semiconductor annealing apparatus, method, and semiconductor annealing can be provided.

(A) is a schematic diagram showing a semiconductor annealing apparatus according to an embodiment, and (B) is a graph showing time waveforms of laser pulses 40 a and 40 b for one shot incident on a work 30. (A) and (B) show an example of the relationship between the delay time and the melting depth. (A) and (B) show other examples of data stored in the storage device 15a.

  FIG. 1A is a schematic diagram illustrating a semiconductor annealing apparatus according to an embodiment. The semiconductor annealing apparatus according to the embodiment includes laser light sources 10a and 10b, mirrors 11a to 11c, variable attenuators 12a and 12b, a combining optical system 13, a lens 14, a control device 15, and a processing stage 20. The control device 15 includes a storage device 15a which is a memory, for example, and controls the operation of the semiconductor annealing device according to the embodiment.

  In response to the trigger signal from the control device 15, the laser light sources 10a and 10b emit laser pulses (pulse laser beams) 40a and 40b having the same pulse width, for example. Each of the laser light sources 10a and 10b includes, for example, an Nd: YLF laser oscillator and a nonlinear optical crystal. Both laser pulses 40a and 40b are second harmonics of the Nd: YLF laser. The laser pulse 40b is emitted with a slight time difference (delay time) from the laser pulse 40a. The delay time can be accurately controlled by the input timing of the trigger signal given from the control device 15 to the laser light sources 10a and 10b, for example. Further, the control device 15 can change the pulse width of the laser pulses 40a and 40b by increasing or decreasing the drive current of the excitation light source of the Nd: YLF laser oscillator. The pulse widths of the laser pulses 40a and 40b may be different.

  The laser pulses 40a and 40b are reflected by the mirrors 11a and 11b and then enter the variable attenuators 12a and 12b. The variable attenuators 12a and 12b can emit the incident laser light by changing the intensity thereof. The intensity change of the laser pulses 40a and 40b is controlled by the control device 15.

  Laser pulses 40 a and 40 b whose intensities are changed by the variable attenuators 12 a and 12 b enter the combining optical system 13. The combining optical system 13 includes a beam superimposing device, for example, a polarization beam splitter, and superimposes the laser pulses 40a and 40b on the same optical axis. The superimposed laser pulses 40 a and 40 b are reflected by the mirror 11 c, collected by the lens 14, and incident on the workpiece 30 held on the processing stage 20, and semiconductor annealing processing (activation annealing) of the workpiece 30 is performed. .

  The processing stage 20 includes a stage 20a, a drive system 20b, and a joule meter 20c. The stage 20a includes a holding surface that holds a workpiece, and holds the workpiece 30, for example, a silicon wafer to which impurities are added, on the holding surface. The drive system 20b can move the stage 20a in a two-dimensional direction. The movement of the stage 20a by the drive system 20b is controlled by the control device 15.

  The joule meter 20c is fixed to the stage 20a, for example, and can be moved together with the stage 20a by the drive system 20b. The energy of the laser pulses 40a and 40b can be measured by moving the joule meter 20c by the drive system 20b and causing the laser pulses 40a and 40b to enter the joule meter 20c. Energy is measured prior to, for example, semiconductor annealing. The measured value is transmitted to the control device 15. The control device 15 controls the variable attenuators 12a and 12b based on the measured values so that the energy density of the laser pulses 40a and 40b incident on the workpiece 30 becomes a predetermined value.

  FIG. 1B is a graph showing time waveforms of laser pulses 40 a and 40 b for one shot incident on the workpiece 30. The horizontal axis of the graph indicates time, and the vertical axis indicates the intensity of the laser pulse. For convenience of display, the waveform of the laser pulse 40a and the waveform of the laser pulse 40b are shown with different zero points on the vertical axis (intensity).

  The delay time is, for example, the time from when the trigger signal is given to the laser light source 10a by the control device 15 until the trigger signal is given to the laser light source 10b. Therefore, for example, a period from the time when the laser light source 10a starts emitting the laser pulse 40a to the time when the laser light source 10b starts emitting the laser pulse 40b. Further, it is a period from the time when the laser pulse 40a is incident on the workpiece 30 to the time when the laser pulse 40b is incident. Further, for example, a period from the time when the laser pulse 40a rises to a constant intensity (intensity of 30 in FIG. 1B) to the time after the laser pulse 40b rises to the intensity. For example, the time waveform of the laser pulse 40a and that of the laser pulse 40b are the same when translated in the horizontal axis direction by the delay time.

  2A and 2B show an example of the relationship between the delay time and the melting depth.

FIG. 2A is a graph showing the relationship between the delay time and the silicon melting depth when the energy density of the laser pulses 40a and 40b on the surface of the workpiece (silicon wafer) 30 is 2.25 J / cm ² , respectively. is there. The horizontal axis of the graph represents the delay time in the unit “nsec”, and the vertical axis represents the depth (melting depth) at which the silicon melts when the laser pulses 40a and 40b are incident on the silicon (work 30). "μm". A curve a shows a relationship between the laser pulses 40a and 40b when both pulse widths are 180 nsec. A curve b displays the relationship between the laser pulses 40a and 40b when both pulse widths are 240 nsec. Curve c shows the relationship between the laser pulses 40a and 40b when the pulse widths are 130 nsec and 100 nsec, respectively. It has been clarified for the first time by the inventors' research that the melting depth can be controlled by changing (controlling) the delay time in this way. These data are determined by pre-processing before the main processing.

  The storage device 15a stores data representing the melting depth at which silicon is melted when two laser pulses enter the silicon with a delay time, using one or more parameters including the delay time. Also good. In this case, when the semiconductor annealing process is performed by irradiating the workpiece 30 with the laser pulses 40a and 40b, the data stored in the storage device 15a is referred to.

  Hereinafter, an example in which data is stored in the storage device 15a will be described.

For example, when semiconductor annealing is performed by setting the pulse width of the laser pulses 40a and 40b to 180 nsec and the energy density of the laser pulses 40a and 40b on the surface of the workpiece (silicon wafer) 30 to 2.25 J / cm ² , refer to the curve a it can. For example, when the delay times of the laser pulses 40a and 40b are 0 nsec, 100 nsec, 300 nsec, 500 nsec, and 700 nsec, the curve a is 0.51 μm, 0.53 μm, 0.43 μm, 0.41 μm, and 0.37 μm from the surface, respectively. It shows that the workpiece 30 can be melted to the depth. In addition, for example, when performing a semiconductor annealing process in which the workpiece 30 is melted to a depth of 0.45 μm from the surface, the delay time may be set to 260 nsec. Is shown.

  The control device 15 refers to the data stored in the storage device 15a, and based on this, triggers the delay time, for example, the laser light source 10a, so that the semiconductor annealing process for realizing the desired melting depth is performed. The time from the application of the signal to the application of the trigger signal to the laser light source 10b is determined. The control device 15 includes, for example, an input unit, and the required value (target value) of the melting depth is input from the input unit by an operator of the semiconductor annealing apparatus as an example.

  For example, when the melting depth required for a certain workpiece is different from that required for another workpiece, the delay time can be determined and changed for each workpiece to control the melting depth.

  Further, for example, the correspondence between the irradiation positions of the laser pulses 40a and 40b on the workpiece 30 and the required value of the melting depth was recorded so that different melting depths were realized in different parts of one workpiece 30. The table is stored in the storage device 15a, and the melting depth (required value) recorded in the table is realized while referring to both the table and data indicating the relationship between the delay time and the silicon melting depth. In addition, control for changing the delay time according to the irradiation position on the workpiece 30 may be performed.

  For example, when the control is performed with reference to the curve c, the delay time can be changed in the range of 100 nsec to 700 nsec, and the melting depth can be controlled in the range of 0.71 μm to 0.47 μm (width 0.24 μm).

  FIG. 2A shows a graph with the description of the curves a to c. For example, data having only the description of the curve a can be stored in the storage device 15a.

  FIG. 2B is an example of data in which the data shown in FIG. 2A is discretely described. The data stored in the storage device 15a is not limited to data such as graphs that continuously indicate the relationship between the delay time and the melting depth of silicon, but may be discrete data as shown in FIG. In this figure, the relationship between the delay time and the melting depth of silicon is described in increments of 100 nsec or 200 nsec, but the increment can be increased or decreased. It is also possible to store data represented by mathematical formulas, for example, a formula approximating the curve a in FIG. 2A in the storage device 15a, and calculate the delay time for realizing the required melting depth.

  Although partially overlapping with the above contents, for example, the following semiconductor annealing method can be performed using the semiconductor annealing apparatus according to the embodiment. First, the pulse widths of the laser pulses 40a and 40b and the energy density of the laser pulses 40a and 40b on the surface of the workpiece 30 are determined. Next, the control device 15 refers to data indicating the relationship between the delay time and the silicon melting depth, and based on this, the delay time for realizing a desired silicon melting depth (required value of the silicon melting depth). To decide. The control device 15 realizes the determined delay time through control of the timing of the trigger signal given to the laser light sources 10a and 10b. Then, the determined pulse width of the laser pulses 40a and 40b, the energy density of the laser pulses 40a and 40b on the surface of the work 30, and the delay time of the laser pulses 40a and 40b so that the required silicon melting depth is achieved. Then, semiconductor annealing is performed.

  In this case, if the desired silicon melt depth differs depending on the irradiation position within one work or between one work and another work, refer to the data and set the delay time according to the desired silicon melt depth. The melting depth can be controlled by determining and changing the delay time.

  That is, for example, two laser pulses are incident on the workpiece surface by a predetermined shot at a first delay time that realizes the first melting depth determined with reference to the data, and then the data is referred to. The semiconductor annealing process is performed by causing two laser pulses to be incident on the work surface with a predetermined shot at a second delay time for realizing the determined second melting depth.

  In the above example, after determining the pulse widths of the laser pulses 40a and 40b and the energy density of the laser pulses 40a and 40b on the surface of the work 30 to predetermined values, the melting time of the work 30 is changed by changing the delay time. Controlled. In order to achieve a desired melting depth in the semiconductor annealing process, the pulse width of the laser pulses 40a and 40b, the energy density of the laser pulses 40a and 40b irradiated on the surface of the workpiece 30, and the delay time of the laser pulses 40a and 40b It is also possible to decide all at once.

  3A and 3B show other examples of data stored in the storage device 15a.

  FIG. 3A is an example of a table showing the melting depth of silicon using three parameters of the pulse widths of the laser pulses 40a and 40b, the energy density on the surface of the workpiece 30, and the delay time.

For example, this table describes five combinations of pulse width, energy density, and delay time to achieve a melt depth of 0.6 μm. As an example, by setting the pulse width of the laser pulses 40a and 40b to 240 nsec, the energy density of the laser pulses 40a and 40b on the surface of the work 30 to 2.95 J / cm ² , and the delay time to 500 nsec, respectively, The semiconductor annealing process can be performed. Similarly, in this table, five combinations of pulse width, energy density, and delay time for realizing a melt depth of 0.3 μm, 0.4 μm, and 0.5 μm are described, respectively. For example, by setting the pulse width of the laser pulses 40a and 40b to 180 nsec, the energy density of the laser pulses 40a and 40b on the surface of the workpiece 30 to 1.8 J / cm ² , and the delay time to 100 nsec, respectively, the melting depth of 0.3 μm It is possible to perform the semiconductor annealing process.

  The control device 15 refers to this table, and determines the processing conditions for semiconductor annealing that achieves the required melt depth. For example, when the required value of the melt depth is 0.5 μm, one of five combinations that realize this is selected and determined as a processing condition. The control device 15 controls the pulse widths of the laser pulses 40a and 40b, the delay time, and the energy density on the surface of the work 30 so as to satisfy the processing conditions.

FIG. 3B is a graph showing the relationship between the melting depth of silicon and the energy density of the laser pulses 40a and 40b on the surface of the work 30. FIG. The horizontal axis of the graph represents the energy density of each of the laser pulses 40a and 40b in the unit “J / cm ² ”, and the vertical axis represents the silicon melting depth in the unit “μm”. A curve a shows the relationship between the energy density and the melting depth when the pulse widths of the laser pulses 40a and 40b are both 180 nsec and the delay time is 500 nsec. A curve b displays the relationship between the laser pulses 40a and 40b when the pulse widths are both 240 nsec and the delay time is 500 nsec. Curve c shows the relationship between the laser pulses 40a and 40b when the pulse widths are 130 nsec and 100 nsec, respectively, and the delay time is 500 nsec. Curves d and e show the relationship between the laser pulses 40a and 40b when the pulse width is 180 nsec and 240 nsec and the delay time is 100 nsec, respectively.

  In the storage device 15a, the melting depth of silicon as shown in FIG. 3B is indicated by using three parameters of the pulse widths of the laser pulses 40a and 40b, the energy density on the surface of the workpiece 30, and the delay time. A graph may be stored.

  In addition to the data shown in FIGS. 2A, 2B, 3A, and 3B, for example, the melting depth of silicon is used, the pulse widths of the laser pulses 40a and 40b, and the delay time. The energy density of the laser pulses 40a and 40b irradiated on the surface of the work 30 may be generated at a constant energy and stored in the storage device 15a. Further, data representing the silicon melting depth using the energy density and delay time of the laser pulses 40a and 40b applied to the surface of the workpiece 30 is created with the pulse widths of the laser pulses 40a and 40b being constant. It can also be stored in the storage device 15a. The storage device 15a stores data representing the melting depth at which silicon is melted when two laser pulses enter the silicon with a delay time, using one or more parameters including the delay time. It only has to be.

  In the above example, the control device 15 determines the processing conditions by referring to the data stored in the storage device 15a that represents the melting depth using one or more parameters including the delay time. Then, the control device 15 controlled the pulse widths of the laser pulses 40a and 40b, the delay time, and the energy density on the surface of the workpiece 30 so as to satisfy the processing conditions.

  The delay time can be controlled, for example, by adjusting the timing of the trigger signal given to the laser light sources 10a and 10b. The pulse widths of the laser pulses 40a and 40b can be controlled, for example, by increasing or decreasing the drive current of the excitation light source of the Nd: YLF laser oscillator. The energy density of the laser pulses 40a and 40b irradiated on the surface of the workpiece 30 can be controlled through intensity changes of the laser pulses 40a and 40b by the variable attenuators 12a and 12b.

  The determination of the processing conditions and the realization of the determined processing conditions (the pulse widths of the laser pulses 40a and 40b, the delay time, and the energy density on the surface of the work 30) are not necessarily functions of the control device.

  For example, the control device 15 may include a display device such as a display, and may derive processing conditions that satisfy the required value of the melting depth based on data stored in the storage device 15a and display the processing conditions on the display device. The displayed processing conditions, such as delay time, are realized by the operator of the semiconductor annealing apparatus. In addition, a printer that performs print display can be used as the display device.

  Further, the control device 15 displays on the display device data for deriving a processing condition that satisfies the required value of the melting depth, for example, the graph shown in FIG. 2A, based on the storage contents of the storage device 15a. May be. In this case, the processing conditions are determined and realized by an operator of the semiconductor annealing apparatus, for example.

  According to the semiconductor annealing apparatus according to the embodiment, the silicon melting depth in the semiconductor annealing process is controlled using data representing the melting depth of silicon using one or more parameters including a delay time. be able to. Further, the melting depth can be controlled by the delay time.

    Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto.

  For example, in the embodiment, a silicon wafer is used as the processing object. However, a workpiece whose surface is formed of silicon, such as a glass substrate having a silicon layer formed on the surface, can be used as the processing object.

  In the examples, data representing the melting depth of silicon using one or more parameters including a delay time is used, but data including a relationship between the melting depth of silicon and the delay time is widely used. can do.

  Furthermore, in the embodiment, the delay time or the like is determined based on the required value of the silicon melting depth, but it is also possible to grasp the silicon melting depth based on the delay time or the like.

  In addition, data including the relationship between the melting depth of silicon and the delay time, for example, a storage medium in which data representing the melting depth of silicon using one or a plurality of parameters including the delay time is recorded, for example, FIG. ) To 3B, the semiconductor annealing can be performed using a conventional semiconductor annealing apparatus that does not include the storage device 15a while referring to the description of paper, memory, and the like. By doing so, it is possible to determine a delay time or the like based on a desired silicon melting depth, or to implement a laser processing method for grasping the silicon melting depth based on the delay time or the like.

    It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.

  It can be used for semiconductor annealing.

10a, 10b Laser light sources 11a-11c Mirrors 12a, 12b Variable attenuator 13 Synthetic optical system 14 Lens 15 Control device 15a Storage device 20 Processing stage 20a Stage 20b Drive system 20c Joule meter 30 Work 40a, 40b Laser pulse

Claims (15)

A first laser light source emitting a first laser pulse;
A second laser light source emitting a second laser pulse;
A combining optical system that superimposes the first laser pulse and the second laser pulse on the same optical axis;
A machining stage for holding the workpiece,
A waveguide optical system for propagating the first and second laser pulses superimposed on the same optical axis in the synthesis optical system to the processing stage;
A control device for controlling emission of the first laser pulse by the first laser light source and emission of the second laser pulse by the second laser light source;
A semiconductor annealing apparatus having a storage device for storing data including a relationship between a melting depth at which silicon melts and a delay time when two laser pulses are incident on silicon with a delay time.   The semiconductor annealing apparatus according to claim 1, wherein the control device determines the delay time according to a target value of a melting depth based on data stored in the storage device.   The controller is configured to emit the second laser pulse when a delay time determined according to a target value of the melting depth has elapsed from the emission of the first laser pulse. The semiconductor annealing apparatus according to claim 2, wherein the emission of the first and second laser pulses is controlled.   The semiconductor annealing apparatus according to claim 1, wherein the data stored in the storage device is data representing the melting depth only by the delay time. Furthermore,
A first variable attenuator disposed on an optical path of the first laser pulse between the first laser light source and the combining optical system, and changing an intensity of the first laser pulse;
A second variable attenuator disposed on the optical path of the second laser pulse between the second laser light source and the combining optical system and changing the intensity of the second laser pulse;
The data stored in the storage device includes a plurality of melting depths, the delay time, and pulse energy densities of the first and second laser pulses on the surface of the workpiece to be processed held on the processing stage. Data expressed using the parameters of
The control device is configured to generate pulses of the first and second laser pulses on the surface of the workpiece held on the machining stage according to the target value of the melting depth based on the data stored in the storage device. 4. The energy density is determined, and the first and second variable attenuators are controlled to change the intensities of the first and second laser pulses so as to obtain the determined pulse energy density. The semiconductor annealing apparatus as described. The data stored in the storage device includes the melting depth, the delay time, the pulse energy density of the first and second laser pulses on the surface of the workpiece held on the processing stage, and the first Data expressed using a plurality of parameters including the pulse widths of the first and second laser pulses,
The controller determines the pulse widths of the first and second laser pulses according to the target value of the melting depth based on the data stored in the storage device, and the determined pulse width and The semiconductor annealing apparatus according to claim 5, wherein the first and second laser light sources are controlled. (A) a step of preparing data including a relationship between a melting depth at which silicon melts and the delay time when two laser pulses are incident on silicon with a delay time;
(B) A semiconductor annealing method including a step of performing semiconductor annealing with reference to the data. The step (b)
(B1) referring to the data, and determining the delay time according to the target value of the melting depth;
(B2) including two laser pulses incident on the surface of a workpiece whose surface is formed of silicon with a delay time determined in the step (b1). Semiconductor annealing method.   The semiconductor annealing method according to claim 7 or 8, wherein the data prepared in the step (a) is data representing the melting depth only by the delay time. In the step (a), preparing data representing the melting depth using a plurality of parameters including the delay time and the pulse energy density of the two laser pulses on the surface of the workpiece,
In the step (b1), referring to the data, the pulse energy density of the two laser pulses on the surface of the workpiece is determined according to the target value of the melting depth,
9. The semiconductor annealing method according to claim 8, wherein in the step (b2), the two laser pulses are made incident on the surface of the workpiece with the pulse energy density determined in the step (b1). In the step (a), a plurality of parameters including the melting depth, the delay time, the pulse energy density of the two laser pulses on the surface of the workpiece, and the pulse width of the two laser pulses are set. Prepare the data represented by using
In the step (b1), referring to the data, the pulse width of the two laser pulses is determined according to the target value of the melting depth,
The semiconductor annealing method according to claim 10, wherein in the step (b2), the two laser pulses having the pulse width determined in the step (b1) are incident on the surface of the workpiece. The step (b)
(B3) Two laser pulses are applied to the surface of the workpiece whose surface is formed of silicon, with a first delay time for realizing the first melting depth determined with reference to the data. Injecting, and
(B4) Two laser pulses are applied to the surface of the workpiece whose surface is formed of silicon with a second delay time for realizing the second melting depth determined with reference to the data. The semiconductor annealing method according to claim 7, further comprising a step of making the light incident.   13. The semiconductor annealing method according to claim 12, wherein the data prepared in the step (a) is data representing the melting depth only by the delay time.   A storage medium storing data including a relationship between a melting depth at which silicon melts when the two laser pulses are incident on silicon with a delay time and the delay time.   The storage medium according to claim 14, wherein the data is data representing the melting depth only by the delay time.

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