Method of minimizing the access time in semiconductor memories

• US 6,285,621 B1
• Filed: 08/12/1999
• Issued: 09/04/2001
• Est. Priority Date: 02/12/1997
• Status: Expired due to Term

• Current Assignee: Polaris Innovations Limited (Wi-LAN Inc.)
• Original Assignee: Infineon Technologies AG
• Inventors: Beer, Leopold
• Primary Examiner(s): PHAN, TRONG Q
• Application Number:
  US09/373,476
• Time in Patent Office: 754 Days
• Field of Search: 365/185.09, 365/185.18, 365/185.21, 365/185.23, 365/185.24, 365/200, 365/201, 365/226, 365/230.03
• US Class Current: 365/226
• CPC Class Codes: G11C 11/401 forming cells needing refreshing or charge regeneration, i.e. dynamic cells
• CPC Class Codes: G11C 11/4074 Power supply or voltage generation circuits, e.g. bias voltage generators, substrate voltage generators, back-up power, power control circuits
• CPC Class Codes: G11C 2029/5004 Voltage
• CPC Class Codes: G11C 29/028 with adaption or trimming of parameters
• CPC Class Codes: G11C 29/50 Marginal testing, e.g. race, voltage or current testing
• CPC Class Codes: G11C 29/50012 of timing
• CPC Class Codes: G11C 5/145 Applications of charge pumps; Boosted voltage circuits; Clamp circuits therefor G11C5/141 takes precedence

Abstract

The dictates of production mean that the access times of semiconductor memories are subject to fluctuations, even given identical technological parameters. The fluctuations lead to a proportion of slow memory chips. The access time is shortened by raising the internal supply voltage of the slower semiconductor memories by an absolute value which is dependent on the respective semiconductor memory. The method is employed in semiconductor memories, in particular in dynamic semiconductor memories.

Claims

1. A method of minimizing access time to data of a semiconductor memory by means of a supply voltage generator for generating an internal supply voltage, which comprises the following method steps:

defining a standby current of a semiconductor memory as a parameter characterizing an access time to the semiconductor memory;

assigning a value of a boost voltage to the value of the parameter, whereby a magnitude of the boost voltage is greater than the given value of an internal supply voltage of the semiconductor memory and at which boost voltage the semiconductor memory is still functional; and

setting the internal supply voltage to the value of the boost voltage.

2. The method according to claim 1, wherein the defining step comprises determining the value of the access time characterizing parameter after applying an external supply voltage to the semiconductor memory, as soon as the semiconductor memory has reached a state of functional readiness.

3. The method according to claim 1, wherein the defining step comprises determining the value of the access time characterizing parameter during a functional test of the semiconductor memory.

4. The method according to claim 1, wherein the assigning step comprises assigning the value of the boost voltage to the value of the parameter by means of experimentally determined measurement curves.

5. The method according to claim 1, wherein the setting step comprises setting the internal supply voltage to the value of the boost voltage by blowing at least one fuse of the supply voltage generator of the semiconductor memory.

6. The method according to claim 5, wherein the step of blowing the at least one fuse is effected temporally in parallel with a blowing of any other fuses of the semiconductor memory.

7. The method according to claim 1, wherein the setting step comprises setting the internal supply voltage to the value of the boost voltage in steps.

8. The method according to claim 7, wherein the setting step comprises increasing the internal supply voltage in steps of 0.3 V.

9. A method of minimizing an access time to data of a semiconductor memory by means of a supply voltage generator for generating an internal supply voltage, which comprises the following method steps:

defining a threshold voltage of a field-effect transistor on a semiconductor memory as a parameter characterizing an access time to the semiconductor memory;

assigning a value of a boost voltage to the value of the parameter, whereby a magnitude of the boost voltage is greater than the given value of an internal supply voltage of the semiconductor memory and at which boost voltage the semiconductor memory is still functional; and

setting the internal supply voltage to the value of the boost voltage.

10. The method according to claim 9, wherein the defining step comprises determining the value of the access time characterizing parameter after applying an external supply voltage to the semiconductor memory, as soon as the semiconductor memory has reached a state of functional readiness.

11. The method according to claim 9, wherein the defining step comprises determining the value of the access time characterizing parameter during a functional test of the semiconductor memory.

12. The method according to claim 9, wherein the assigning step comprises assigning the value of the boost voltage to the value of the parameter by means of experimentally determined measurement curves.

13. The method according to claim 9, wherein the setting step comprises setting the internal supply voltage to the value of the boost voltage by blowing at least one fuse of the supply voltage generator of the semiconductor memory.

14. The method according to claim 13, wherein the step of blowing the at least one fuse is effected temporally in parallel with a blowing of any other fuses of the semiconductor memory.

15. The method according to claim 9, wherein the setting step comprises controlling the supply voltage generator by means of a control circuit, whereby the threshold voltage of the field-effect transistor is transferred to the control circuit.

16. The method according to claim 9, wherein the setting step comprises setting the internal supply voltage to the value of the boost voltage in steps.

17. The method according to claim 16, wherein the setting step comprises increasing the internal supply voltage in steps of 0.3 V.