JP5717598B2 - Semiconductor manufacturing apparatus and semiconductor manufacturing method - Google Patents

Description

  Embodiments described herein relate generally to a semiconductor manufacturing apparatus and a semiconductor manufacturing method.

  In a semiconductor manufacturing process, there is microwave annealing in which annealing treatment is performed by irradiating a silicon substrate with microwaves. In this microwave annealing, annealing at a low temperature can be realized by non-thermal crystallization of silicon as compared with the case where optical annealing or the like is used.

  However, since the frequency at which the efficiency of absorbing microwaves is maximum varies depending on the crystal state of silicon, it is not easy to perform an efficient annealing process that always maximizes the absorption efficiency depending on the crystal state.

US Patent Publication No. 2009-0184399

J. N. Lee, et. Al., J. Appl. Phys., 82 (6), 15, 1997 L. Guttman, W. Y. Ching, and Jagannath Rath, PRL, vol. 44, no. 23, 1980 L. Ley, J. Reichardt, and R. L. Johnson, vol. 49, no. 22, 1982 J. H. Booske, et. Al., J. Mater. Res., Vol. 7, No. 2, 1992

  Provided are a semiconductor manufacturing apparatus and a semiconductor manufacturing method capable of performing efficient annealing.

  In the semiconductor manufacturing apparatus of the embodiment, a susceptor on which a substrate having at least a part of grains grown by microwave irradiation is placed, an irradiation unit that irradiates the substrate with microwaves, and the irradiation unit irradiates A control unit that controls the irradiation unit such that the frequency of the microwave approaches the resonance frequency of the grain.

  The semiconductor manufacturing method of the embodiment includes a step of irradiating a substrate having at least a portion of grains placed on a susceptor with microwaves, and a step of bringing the frequency of the microwaves close to the resonance frequency of the grains. Have

The block diagram of the semiconductor manufacturing apparatus which concerns on 1st embodiment. The schematic diagram explaining the crystal growth of a grain. An example of the time series data of the resonance frequency which memory memorizes. The block diagram of the semiconductor manufacturing apparatus which concerns on 2nd embodiment.

  Hereinafter, embodiments for carrying out the invention will be described.

(First embodiment)
FIG. 1 is a configuration diagram of a semiconductor manufacturing apparatus 100 according to the first embodiment.

  The semiconductor manufacturing apparatus 100 performs an annealing process by irradiating a substrate such as a wafer (hereinafter referred to as a silicon substrate 10), which is a material of the semiconductor substrate, with microwaves in a circuit manufacturing process of the semiconductor substrate.

  This annealing process is a process necessary for repairing the lattice defect of the silicon crystal lattice that occurs when the silicon substrate 10 is doped with impurities to generate semiconductor carriers. As a result, a circuit that is once electrically inactivated can be activated.

  In general, the annealing process uses light annealing (for example, RTP, FLA, LSA, etc.) that uses a halogen lamp or a xenon lamp to bring the silicon substrate 10 to a high temperature of 1000 ° C. or higher. However, under such a high temperature, the impurity in the silicon substrate 10 diffuses, resulting in an increase in circuit leakage current.

  Therefore, in the semiconductor manufacturing apparatus 100 of this embodiment, microwaves that can be annealed at a relatively low temperature of 600 ° C. or lower are used (microwave annealing). Thus, since impurity diffusion which is a problem when using optical annealing can be suppressed, the leakage current of the circuit can be reduced.

  Here, before describing the configuration of the semiconductor manufacturing apparatus 100, the relationship between microwave annealing and silicon crystallization will be described.

  In general, the degree of electrical activation of the circuit of the silicon substrate 10 by the annealing treatment is an important indicator that the regularity of the silicon crystal lattice is high. That is, in the silicon substrate 10, it is considered that the crystal lattice becomes regular and becomes an electrically active state.

  In the above carrier generation, it is considered that the silicon substrate 10 is doped with an impurity so that the crystal lattice of the silicon substrate 10 is partially in an amorphous silicon (non-crystalline) state. It is done. Specifically, the amorphous silicon is formed by collecting partially crystallized polysilicon (grains).

  In Non-Patent Document 1, it is confirmed by X-ray diffraction measurement that the regularity of the silicon crystal lattice is increased by microwave annealing. In addition, in the annealing process as described above, considering that the silicon substrate 10 is partially in an amorphous silicon state, the microwave is absorbed by at least amorphous silicon grains by performing microwave annealing. It can be considered.

  As described above, microwaves are absorbed by the grains forming the amorphous silicon in the silicon substrate 10, and the grains grow non-thermally, thereby increasing the regularity (crystallizing) of the crystal lattice of the amorphous silicon. It is considered a thing. Thereby, the activation of the circuit at a low temperature can be realized.

1 includes a susceptor 101 that supports a silicon substrate 10, a container 102 that covers the susceptor 101, an internal atmosphere is controlled, a radio wave source 103 that radiates microwaves, and a micro wave that is radiated by the radio wave source 103. A control unit 104 that controls the wave frequency and a memory 105 that stores time-series data of the microwave frequency irradiated by the radio wave source 103 are provided.

  The susceptor 101 is a base for supporting the silicon substrate 10. Circuits having various patterns are formed on the surface layer of several hundred nm on the surface of the silicon substrate 10 supported by the susceptor 101. Further, impurities are doped in the silicon substrate 10, and the silicon substrate 10 is partially in an amorphous silicon state.

  The container 102 is controlled so that the internal atmosphere (temperature, pressure, gas components, etc.) is suitable for the annealing process. In general, at the stage of annealing treatment, the temperature is preferably about 350 ° C. to 650 ° C., and the pressure is preferably atmospheric pressure. As a gas component, nitrogen gas is preferably used to prevent oxidation.

  In addition to the necessity of transmitting the microwave irradiated by the radio wave source 103 described later, it is preferable that the container is made of, for example, transparent quartz or the like because of the necessity of having a certain degree of heat resistance.

  Therefore, a gas supply device 106 is attached to a part of the container 102, and nitrogen gas is supplied from the gas supply device 106 into the container 102. Further, the container 102 is provided with a gas discharge port 107, and nitrogen gas is discharged from the gas discharge port 107. A heat source 108 such as a heater is provided in the container 102, and the temperature in the container 102 is controlled by a control unit 104 described later.

  The radio wave source 103 is provided outside the container 102 so as to face the susceptor 101. The radio wave source 103 irradiates the silicon substrate 10 supported by the susceptor 101 with microwaves. As a result, the grains for forming the amorphous silicon of the silicon substrate 10 are gradually crystallized and the amorphous silicon is crystallized for annealing.

  It is preferable that the radio wave source 103 can radiate microwaves having different frequencies in a range of about 1 GHz to 100 GHz, for example.

  The control unit 104 controls the radio wave source 103 to change the frequency of the microwave irradiated by the radio wave source 103 along the time series data of the frequency stored in the memory 105 in advance. The frequency stored in the memory 105 is a unique pattern depending on the material (silicon in this embodiment) as will be described later.

  Specifically, assuming that the annealing start time is zero, for example, the frequency of the microwave is read from the memory 105 every second, and the frequency of the microwave irradiated by the radio wave source 103 is brought closer to the frequency read from the memory 105. To control.

  The control unit 104 controls the atmosphere in the container 102. Specifically, the temperature in the container 102 is controlled by instructing the heat source 108 to generate a heat value in a direction in which the temperature in the container 102 measured by a temperature sensor (not shown) approaches a predetermined temperature. .

  In addition, the control unit 104 sets the gas supply amount to the gas supply device 106 in a direction to bring the pressure in the container 102 measured by a pressure sensor (not shown) closer to a predetermined pressure as necessary. The pressure in the container 102 can also be controlled by instructing the gas discharge port 107 for the discharge amount.

  The control unit 104 can be logically realized as a module of an arithmetic processing unit such as a CPU.

  The memory 105 stores time-series data of the microwave frequency irradiated by the radio wave source 103 at each time from the start of the annealing process. The controller 104 also stores predetermined values such as temperature and pressure used when controlling the atmosphere in the container 102.

Hereinafter, the time-series data of the microwave frequency stored in the memory 105 will be described in detail.

  According to Non-Patent Document 2 and Non-Patent Document 3, in amorphous silicon having non-uniform charge distribution due to vacancies due to crystal defects and dangling bonds, interaction with microwaves occurs and microwaves are absorbed. It is stated.

  Like the amorphous silicon, dangling bonds and vacancies exist on the surface of the grains. Accordingly, non-uniform charges exist on the grain surface, and the grain size gradually increases with time as non-thermal crystal growth proceeds by absorption of microwaves.

  In general, the amount of absorption of the microwave depends on the frequency of the microwave, and the frequency of the microwave when the amount of absorption is maximum is called the resonance frequency. This resonance frequency depends on the grain size. Therefore, in the semiconductor manufacturing apparatus 100 according to the present embodiment, by irradiating microwaves having resonance frequencies that change sequentially with grain growth, the grains are efficiently grown and lattice defects of the silicon substrate 10 are repaired. .

  Here, the relationship between the grain size and the resonance frequency will be described.

When the annealing start time t = 0 [s] and the grain size at time t [s] is a (t) [nm], a (t) uses the grain growth rate Γ [1 / s]

It is expressed. Here, with reference to Non-Patent Document 1, a value of about a grain growth rate Γ = 10 to 100 can be used.

  By the way, Non-Patent Document 4 shows that the square of the resonance frequency of microwave absorption is proportional to the non-uniform charge (excess charge or insufficient charge) of each grain and inversely proportional to the mass. However, in the case of amorphous silicon, each grain here is a lump of fine silicon crystals having a grain size on one side, and the inside thereof is crystallized. Alternatively, in a completely amorphous state, for example, silicon atoms themselves can be regarded as grains.

At this time, if the resonant frequency of the microwave is f [1 / s], the mass of the grain is M, and the non-uniform charge is q,

It becomes.

  The non-uniform charge q is considered to be proportional to the number of dangling bonds and holes present in each grain. Further, as shown in FIG. 2, as the crystallization progresses, the grains are bonded to each other, and the grain size increases. Then, dangling bonds and vacancies are mainly left on the surface of the grains. That is, it is considered that the number of dangling bonds and vacancies increases in proportion to the grain surface area as the grain size increases.

At this time, the grain non-uniform charge q is proportional to the surface area of the grain (ie, the square of the grain size a),

It becomes.

On the other hand, the mass M of the grain is proportional to the volume (that is, the cube of the grain size a) because the density of silicon is almost constant regardless of the state (amorphous, polysilicon, single crystal).

It becomes.

By substituting the above (Equation 3) and (Equation 4) into (Equation 2),

Is obtained.

From the above, the resonance frequency f (t) [1 / s] at time t [s] is obtained using the grain size a (t).

It becomes.

Further, when (Equation 1) is substituted into (Equation 6), the resonance frequency f (t) [1 / s] of microwave absorption at time t [s] is expressed by the following equation. .

As described above, the efficiency of nonthermal crystallization can be increased by setting the microwave frequency to the resonance frequency represented by (Equation 7) for each time.

In consideration of the fact that the growth rate Γ is about 10 to 100 as described above, Γt >> 1 holds when sufficient time has elapsed from the start of the annealing process, and (Expression 7) Can be approximated as follows.

Therefore, the resonance frequency f (t) [1 / s] of microwave absorption at time t [s] is strictly expressed by (Equation 7), but is squared at time t as (Equation 8). Can be considered to be included in (Equation 7) if it is a time-series change in frequency showing a tendency inversely proportional to.

  The memory 105 stores time series data (Equation 7) of the resonance frequency obtained by the above description. FIG. 3 shows an example of time series data stored in the memory 105.

Hereinafter, the operation of the semiconductor manufacturing apparatus 100 will be described.

  In the semiconductor manufacturing apparatus 100, the silicon substrate 10 is supported on the susceptor 101. In the circuit layer on the surface of the silicon substrate 10, an amorphous silicon region is formed.

  The radio wave source 103 irradiates the silicon substrate 10 with a microwave having a predetermined frequency. As a result, the amorphous silicon of the silicon substrate 10 absorbs microwaves, and non-thermal crystallization proceeds. At the same time, a part of the energy of the microwaves is heated to increase the temperature of the silicon substrate 10 (450 ° C. To about 550 ° C.).

  At this time, since the atmosphere in the container 102 is controlled by the control unit 104, the temperature of the silicon substrate 10 is also kept constant. Here, it shall be maintained at 450 ° C., for example. The temperature of the silicon substrate 10 is detected by, for example, a temperature sensor (not shown), and the time when the temperature reaches 450 ° C. is set as an initial state (time t = 0).

  The control unit 104 counts the time, for example, every second from the time t = 0, and reads the microwave frequency corresponding to the time from the time-series data of the frequency stored in the memory 105. And the control part 104 controls the radio wave source 103, and the microwave corresponding to this frequency is irradiated from the radio wave source 103.

  By absorbing the microwave and the grains gradually growing, the amorphous silicon is crystallized and the lattice defects are repaired. For example, when a predetermined time has elapsed, the control unit 104 ends the control of the radio wave source 103, and the radio wave source 103 stops the microwave irradiation.

  As a result, the silicon substrate 10 is always irradiated with microwaves having a resonance frequency, and the efficiency of non-thermal crystallization of amorphous silicon is increased. That is, the annealing time can be shortened and the temperature can be lowered. Therefore, it becomes possible to suppress the leakage current of the circuit.

  In the present embodiment, the example in which the radio wave source 103 covering the frequency region of about 1 GHz to 100 GHz is described, but a plurality of radio wave sources 103 covering different frequency regions may be provided. For example, by providing a radio wave source that can change the frequency in the range of about 1 GHz to 50 GHz and a radio wave source that can change the frequency in the range of about 50 GHz to 100 GHz, in this case, the resonance frequency is around 50 GHz. The two radio wave sources can be switched and used.

(Second embodiment)
FIG. 4 is a configuration diagram of a semiconductor manufacturing apparatus 200 according to the second embodiment. Here, the same components as those of the semiconductor manufacturing apparatus 100 of FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the semiconductor manufacturing apparatus 100 according to the first embodiment, the radio wave source 103 always uses the frequency-series data stored in the memory 105 in advance, and the radio wave source 103 generates a microwave having a frequency close to the resonance frequency with respect to the silicon substrate 10. Irradiation.

  In addition to the configuration of FIG. 1, the semiconductor manufacturing apparatus 200 according to the present embodiment includes a measuring unit 109 that measures the amount of microwave transmission that passes through the silicon substrate 10 immediately below the susceptor 101.

  When the frequency of the microwave irradiated to the silicon substrate 10 is a resonance frequency, the microwave is absorbed by the silicon substrate 10 as described above. However, most of the microwave having a frequency different from the resonance frequency passes through the silicon substrate 10 without being absorbed by the silicon substrate 10.

  Therefore, in the present embodiment, the microwave frequency is changed by using the transmission amount of the microwave.

  The control unit 104 obtains the transmission amount measured by the measurement unit 109. For example, when the transmission amount is equal to or greater than a predetermined value, the control unit 104 adjusts the microwave frequency in a direction in which the transmission amount becomes smaller than the predetermined value.

  When the transmission amount is smaller than the predetermined value, the frequency of the microwave can be controlled according to the time-series data of the frequency stored in the memory 105 as in the semiconductor manufacturing apparatus 100 according to the first embodiment.

  Thereby, even if the resonance frequency varies from the tendency of (Equation 7) due to individual differences in the silicon substrate 10 and its surface circuit, the control unit 104 can always adjust the frequency in the direction of the resonance frequency. Therefore, the efficiency of non-thermal crystallization of amorphous silicon can be further increased.

  According to the semiconductor manufacturing apparatus of at least one embodiment described above, an efficient annealing process can be performed.

These embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... Silicon substrate 100 ... Semiconductor manufacturing apparatus 101 ... Susceptor 102 ... Container 103 ... Radio wave source 104 ... Control part 105 ... Memory 106 ... Gas supply apparatus 107 ...・ Gas outlet 108 ... Heat source 109 ... Measurement unit

Claims (7)

A mounting section on which a substrate having at least a part of grains grown by microwave irradiation can be mounted;
An irradiation unit for irradiating the substrate with microwaves;
A control unit for controlling the irradiation unit so that the frequency of the microwave irradiated by the irradiation unit is close to the resonance frequency of the grain;
A storage unit for storing time series data of the resonance frequency that changes with the growth of the grains;
The said control part is a semiconductor manufacturing apparatus which obtains the said resonance frequency from the said memory | storage part, and changes with time so that the frequency of the said microwave may be approximated to the said resonance frequency. A mounting section on which a substrate having at least a part of grains grown by microwave irradiation can be mounted;
An irradiation unit for irradiating the substrate with microwaves;
A control unit that controls the irradiation unit so that the frequency of the microwave irradiated by the irradiation unit becomes the resonance frequency of the grain;
A storage unit for storing time series data of the resonance frequency that changes with the growth of the grains;
The said control part is a semiconductor manufacturing apparatus which acquires the said resonance frequency from the said memory | storage part, and controls the said irradiation part so that the frequency of the said microwave may become the said resonance frequency. The semiconductor manufacturing apparatus according to claim 1, wherein the storage unit stores the resonance frequency as time-series data represented by the following equation.

  The semiconductor manufacturing apparatus according to claim 1, wherein the control unit controls the irradiation unit such that the frequency is inversely proportional to a square root of time. Comprising a measuring unit for measuring the amount of microwaves transmitted through the substrate;
5. The semiconductor manufacturing apparatus according to claim 1, wherein when the transmission amount is equal to or greater than a predetermined value, the control unit changes the frequency in a direction to decrease the transmission amount. 6. A placement step of placing a substrate having at least a portion of grains grown by microwave irradiation;
An irradiation step of irradiating the substrate with microwaves;
The frequency of the microwave to be irradiated by said irradiation step, the control Gosuru control step so as to approach the resonance frequency of the grains,
The control step obtains the resonance frequency from a storage unit that stores time-series data of the resonance frequency that changes as the grain grows, and changes with time so that the frequency of the microwave approaches the resonance frequency. A semiconductor manufacturing method. A placement step of placing a substrate having at least a portion of grains grown by microwave irradiation;
An irradiation step of irradiating the substrate with microwaves;
The frequency of the microwave to be irradiated by said irradiation step, the control Gosuru control step so that the resonance frequency of the grains,
The control step obtains the resonance frequency from the storage unit that stores time series data of said resonant frequency varies with the growth of the grains, control the frequency of the microwave so that the resonance frequency semiconductor Production method.

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